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Critical Reviews in Environmental Science and
Technology
ISSN: 1064-3389 (Print) 1547-6537 (Online) Journal homepage: https://www.tandfonline.com/loi/best20
Lithium iron phosphate batteries recycling: An
assessment of current status
Federica Forte, Massimiliana Pietrantonio, Stefano Pucciarmati, Massimo
Puzone & Danilo Fontana
To cite this article: Federica Forte, Massimiliana Pietrantonio, Stefano Pucciarmati, Massimo
Puzone & Danilo Fontana (2020): Lithium iron phosphate batteries recycling: An assessment of
current status, Critical Reviews in Environmental Science and Technology
To link to this article: https://doi.org/10.1080/10643389.2020.1776053
Published online: 11 Jun 2020.
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Lithium iron phosphate batteries recycling:
An assessment of current status
Federica Forte
a
, Massimiliana Pietrantonio
a
, Stefano Pucciarmati
a
,
Massimo Puzone
b
, and Danilo Fontana
a
a
ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic
Development, Department for Sustainability, Rome, Italy;
b
ENEA, Italian National Agency for New
Technologies, Energy and Sustainable Economic Development, Department for Sustainability,
Rotondella, Italy
ABSTRACT
In this paper the most recent
advances in lithium iron phosphate
batteries recycling are presented.
After discharging operations and
safe dismantling and pretreat-
ments, the recovery of materials
from the active materials is mainly
performed via hydrometallurgical
processes. Moreover, a significant
number of works are currently
being focused on direct regener-
ation processes. Both approaches
arecurrentlyappliedonlyat
laboratory scale. The main chal-
lenges to be faced when dealing
with upscaling these technologies
(for example mechanic vs manual
dismantling, valuable elements
recovery strategy vs all-compo-
nents recovery strategy) are here
presented and discussed.
Abbreviations: CO
2
e: carbon dioxide equivalent; DEC: diethyl carbonate; D2EHPA: di-2-
ethylhexyl phosphoric acid; DMAC: dimethylacetamide; DMC: dimethyl carbonate; DOD:
depth-of-discharge; EC: ethylene carbonate; EDTA-2Na: ethylenediaminetetraacetic acid
disodium salt; EEE: electrical and electronic equipment; ELV: end-of-life vehicles; EoL:
end-of-life; EVs: electric vehicles; GHG: greenhouse gas emissions; GWh: gigawatt hours;
LCA: Life cycle assessment; LCO: lithium cobalt oxide; LFP: lithium iron phosphate; LIBs:
lithium-ion batteries; LMO: lithium manganese oxide; MC: mechanochemical; NCA: lith-
ium nickel cobalt aluminum oxide; NiCd: nickel–cadmium; NiMH: nickel metal hydride;
NMC: lithium nickel manganese cobalt oxide; NMP: N-methyl-2-pyrrolidone; O/A:
organic-to-aqueous volume ratio; Pb-acid: lead acid; PCBs: printed circuit boards; PE:
polyethylene; PP: polypropylene; PVDF: polyvinylidene fluoride; S/L: solid-to-liquid; SX:
solvent extraction; UBRP: Umicore Battery Recycling Process; WEEE: waste electrical and
electronic equipment
KEYWORDS Lithium iron phosphate batteries; recycling; materials recovery
CONTACT Danilo Fontana danilo.fontana@enea.it ENEA, Italian National Agency for New Technologies,
Energy and Sustainable Economic Development, via Anguillarese 301, Rome, 00123, Italy.
ß2020 Taylor & Francis Group, LLC
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY
https://doi.org/10.1080/10643389.2020.1776053
1. Introduction
Lithium-ion batteries (LIBs) are being increasingly used in modern applica-
tions, such as portable electronic devices and electric vehicles (EVs), due to
their high energy density and long cycling life (Wang, Gaustad, et al.,
2016). The sales volume of power batteries reached 160 gigawatt hours
(GWh) worldwide in 2018 and these figures are expected to grow in the
coming years, because of the importance of the clean energy technologies
(Pillot, 2019). Due to huge increase in production, excessive end-of-life
(EoL) LIBs have been generated in the recent decades and this pose the
problem of identifying a sustainable recycling strategy (Sethurajan et al.,
2019). It is of strategic importance to develop recovery processes which are
sustainable from both an economic and an environmental point of view
and which are aimed at valorizing the whole waste, according to the princi-
ples of the Circular Economy (COM, 2019).
Olivine-type lithium iron phosphate (LiFePO
4
, LFP) batteries were first
synthesized in 1996 (Padhi et al., 1997) and have gained considerably in
importance in some applications such as energy storage, electronic equip-
ment and EVs due to their characteristics of low raw material costs, long
life span, thermal stability, non-toxicity, reduced fire hazards and excellent
electrochemical performance (Takahashi et al., 2002; Yuan et al., 2011;
Zhang et al., 2012). LFP batteries are a source of strategic materials due to
the presence of lithium, graphite and phosphorus, the latest two being
included in the list of critical raw materials by the European Commission
(SWD, 2018).
Recently Wang and Wu (2017) examined the current status of spent
LiFePO
4
batteries recycling in China, discussing the state of the art in pre-
processing and final batteries recovery, however the study is limited to a
specific geographic area. Elwert et al. (2019) addressed the recycling of LFP
batteries with focus on industry-driven approaches and only few examples
of research studies are presented.
The aim of the present work is to offer an extensive review of the most
recent advances in EoL LFP batteries processing, from the pretreatment
until the recovering of the different materials. The review took into account
a publication period between 1996 and 2020 and included scientific papers
and public information obtained from recycling plants websites. Academic
Search Engines (such as Google Scholar, ScienceDirect etc.) and online
databases (such as Web of Science) as well as direct contact with stakehold-
ers (trade associations and recycling plants managers) were used as the
main information source. This work can be used as a guidance for further
research in the field and to identify gaps and possible solutions to bring
technology close to the market.
2 F. FORTE ET AL.
2. LiFePO
4
characteristics and market share
As a general rule, LIBs are made of an anode, a cathode, current collectors,
a separator, liquid electrolyte, container and sealing parts (Gratz et al.,
2014). The anode is usually a copper foil coated with a mixture of graphite,
a conductor, polyvinylidene fluoride (PVDF) binder and the electrolyte.
The electrolyte is normally lithium hexafluorophosphate (LiPF
6
) dissolved
in an organic solvent (commonly ethylene carbonate (EC), diethyl carbon-
ate (DEC), dimethyl carbonate (DMC) or their mixture). Similarly, the
cathode is an aluminum foil coated with cathode materials, a conductor, a
PVDF binder and fluoride salt. In order to prevent a short circuit between
two electrodes, a separator made of polypropylene (PP) or polyethylene
(PE) is placed between the anode and cathode as a barrier (Zhang et al.,
2014). The structure of a Li-ion cell is shown in Figure 1 (Mancini, 2008).
Li ions move from the anode to the cathode during discharge and are
intercalated into open spaces in the voids in the cathode. The Li ions make
the reverse journey during charging. Numerous designs are possible for
assembling cells into a battery pack for an electric or hybrid vehicle
(Gaines & Cuenca, 2000). A modular design is used in most cases, with a
number of cells (typically between 6 and 12) packaged together into a unit
called a “module.”The modules can then be combined into a battery pack
sized to match the requirements of the vehicle (Figure 2). The same mod-
ules could be used in a variety of different battery packs. The shapes and
sizes of a LIB cell vary greatly and the number of individual cells in battery
packs or modules may vary from tens to thousands depending on the
applications (Huang et al., 2018).
Figure 1. LIB mechanism during charge and discharge (Mancini, 2008).
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 3
As reported in Table 1, LIBs properties mainly depend on the employed
cathode materials (Buchmann, 2001): lithium cobalt oxide (LCO, LiCoO
2
),
lithium manganese oxide (LMO, LiMn
2
O
4
), lithium nickel manganese
cobalt oxide (NMC, LiNiMnCoO
2
), lithium iron phosphate (LFP, LiFePO
4
),
lithium nickel cobalt aluminum Oxide (NCA, LiNiCoAlO
2
).
Because of their high voltages, LCO batteries were the earliest developed
LIBs in the 1990s and are widely used in consumer electronics products
(Fan et al., 2020). The LFP and LMO batteries are superior to LCO in
terms of cost and safety (Fan et al., 2020). Owing to their low cost, high
safety, and long cycle lives, LFP batteries are mainly used in EVs and elec-
trical storage system. Their typical composition is reported in Table 2
(Buchert & Sutter, 2015). NCM batteries are also widely used in EVs
because of their high energy density. NCM and NCA batteries have advan-
tages in terms of their energy density; however, demanding production
processes have limited the development of NCA batteries (Li, Lu, Chen,
et al., 2018). The low energy density and high temperature performance of
LMO batteries have led to their low market share, therefore LFP and NCM
batteries currently dominate the market (Fan et al., 2020).
The focus of this paper is on LIBs with LFP as cathodic active material.
As the major LiFePO
4
production and consumption country, China’s ship-
ment amount of LiFePO
4
reached 32400 tonnes in 2015, accounting for
65% of the worldwide market (Li, Xing, et al., 2017). The global market for
LFP cathode active materials is expected to grow from 32000 t in 2015 to
64000 t in 2025, even though the relative market share is decreasing from
23% to 16% (Table 3). The market share of the different types of LIBs is
shown in Figure 3, with a forecast up to 2030 (Pillot, 2019).
Figure 2. From Cell to Module to Battery Pack (Gaines & Cuenca, 2000).
Table 1. Types of LIBs and their main applications. (Buchmann, 2001).
Cathode type Properties Applications
LCO Voltages: 3.60 V nominal; specific
energy: 150–200 Wh/kg
Mobile phones, tablets,
laptops, cameras
LMO Voltages: 3.70 V nominal; specific
energy: 100–150 Wh/kg
Power tools, medical devices, electric
powertrains
NMC Voltages: 3.70V nominal; specific
energy: 150–220 Wh/kg
E-bikes, medical devices,
EVs, industrial
LFP Voltages: 3.20 V nominal; specific
energy: 90–120 Wh/kg
Portable and stationary needing high
load currents and endurance
NCA Voltages: 3.60 V nominal; specific
energy: 200–260 Wh/kg
Medical devices, industrial, electric
powertrain (Tesla)
4 F. FORTE ET AL.
Regarding LFP manufacturing, and in particular the synthesis of the
cathodic material, the hydrothermal method is the most promising synthe-
sis method because of its wide material sources, short processing time and
good performance of the products (Bao et al., 2017; Martins et al., 2017;
Pei et al., 2012; Xiuqin et al., 2012). During a typical hydrothermal synthe-
sis, the aqueous solutions of raw materials (i.e., FeSO
4
, LiOH, and H
3
PO
4
)
are mixed under airatmosphere; the mixture is then subjected to the hydro-
thermal process at a high temperature (>100 C) in an autoclave for a few
hours. LFP is then obtained as a solid product (Jing et al., 2019).
Safety of LFP batteries is due to the fact that LiFePO
4
has a two-phase
lithiation process at 3.5 V versus Li/Li
þ
which offers an extremely stable
voltage plateau in contrast to the single-phase intercalation process of lay-
ered oxide materials with a sloped lithiation voltage profile (Li, Lu, Chen,
et al., 2018).
The electrochemical reactions occurring at the electrode/electrolyte inter-
faces can be represented as reported in Eq. (1) and Eq. (2) (adapted from
Wang, Jiang, et al., 2016. Discharge: from left to right; charge: from right
to left):
Table 2. Generic composition of a LFP battery, wt% (adapted from Buchert & Sutter, 2015).
Battery components Materials and components Weight percentage, %
Pack þmodule Steel (including screws) 7.3
Wiring 1.1
Electrical and electronic equipment (EEE) 2.1
Plastics 5.7
Al 22.2
Cell casing Al 8.1
Anode Carbon 10.9
Cu foil 10.5
Cathode Al foil 6.1
Li 0.4
Fe 3.1
P 1.7
O 3.5
Separators Plastics 9.7
Tabs Cu 0.6
Al 0
Electrolyte Solvent 7
Table 3. Expected market volume per material type in 2015 and 2025 (adapted from
Lebedeva et al., 2017).
2015 2025 Expected grow
% kt % kt times
LCO 26 37 16 64 1.7
NMC 29 40 48 192 4.8
LFP 23 32 16 64 2.0
LMO 12 17 10 40 2.4
NCA 10 14 10 40 2.9
Total 100 140 100 400 2.9
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 5
Positive electrode LiyxFePO4þxLiþþxe$LiyFePO4(1)
Negative electrode LixC6$Li0C6þxLiþþxe(2)
3. Collection and sorting
LIBs management is gaining more and more public awareness in the
last decades. Governments are realizing the importance of setting up a
comprehensive collection system and laws relevant to the collection and
disposal of spent batteries have been constantly increasing (Lv et al., 2018).
LIB recycling is carried out in North America, Asia and Europe only
(Balasubramaniam et al., 2020). At European level, the collection of waste
batteries is organized through three main directives: the Directive 2006/66/
Figure 3. Cathode active material forecasts 2000-2030 (Pillot, 2019).
6 F. FORTE ET AL.
EC of the European Parliament and of the Council of 6 September 2006 on
batteries and accumulators and waste batteries and accumulators (European
Commission, 2006), the Directive 2012/19/EU of the European Parliament
and of the Council of 4 July 2012 on waste electrical and electronic equip-
ment (WEEE) (European Commission, 2012) and the Directive 2000/53/EC
of the European Parliament and of the Council of 18 September 2000 on
EoL vehicles (European Commission, 2000; Recharge, n.d.). The Battery
Directive regulates the waste management of any type of battery at its EoL.
The WEEE Directive regulates electrical and electronic equipment (EEE),
including batteries used in these products: when EEE become a waste and
are dismantled for further treatment, batteries are collected for separate
recycling, reuse or repurpose. Batteries installed in EVs are treated accord-
ing to the end-of-life vehicles (ELV) Directive until they are dismantled
from the vehicle; once dismantled, they are regulated by the waste manage-
ment requirements of the Battery Directive. The Battery Directive hence
applies to portable batteries, automotive batteries as well as industrial bat-
teries. However, depending on the type of battery, different waste manage-
ment obligations exist. According to the Waste Batteries Directives,
industrial and automotive batteries have to be properly collected and
recycled when no longer in service; nevertheless, more efforts are still need
to enhance the collecting efficiency and reducing landfilling and/or inciner-
ation of spent LIBs. Most European member states have met or exceeded
the 2012 target for the collection of waste portable batteries (set at 25%),
but only 14 member states have met the 2016 target (set at 45%): an esti-
mated 56.7% of all waste portable batteries are not collected annually and
this amount is hampers the achievement of the Directive’s environmental
protection objectives (SWD, 2019). The drawback of this collective recy-
cling facilities is capability of treating less than 30% of the world’s LIB pro-
duction (Balasubramaniam et al., 2020). Regarding LFP batteries, according
to a forecast of Elwert et al. (2018), annual return flows of LFP are
expected to increase from 130 t in 2017 to 310,000 t in 2025. Similar data
were also reported by Circular Energy Storage Research and Consulting
(Mellin, 2017), as shown in Figure 4.
Collection centers place LIBs, lead acid (Pb-acid) batteries, nickel–cad-
mium (NiCd) batteries, nickel metal hydride (NiMH) batteries into desig-
nated drums, sacks or boxes (Buchmann, 2001). This sorting step can be
otherwise performed directly at the treatment plant, normally by manual
sorting by experienced personnel (KMK Metals Recycling Ltd, n.d.). LIBs
are then processed as mixed feed. There are only few examples of industrial
plants where LIBs are separated by sub-chemistry (LCO, LFP, LMO etc.),
such as Accurec Recycling GmbH (Accurec Recycling GmbH, n.d.), how-
ever no information is available about the details of this sorting step.
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 7
The diversity of cathode chemistries is a challenge because they may
require different conditions for an efficient recycling process; treating them
simultaneously increase the required resources (e.g. energy and time con-
sumed by a sorting mechanism) or may have a negative impact on the
quality of the output streams (Vel
azquez-Mart
ınez et al., 2019; Wang,
Jiang, et al., 2016).
4. Treatment processes
Recycling of spent LIBs is relatively new compared to the recycling of
NiCd and Pb-acid batteries. Most of the commercial processes were not a
LIB-dedicated recycling process in their original design: the core technology
was based on pyrometallurgical methods typical of cobalt and nickel
extractive metallurgy. Through this technology only Co, Ni, and Cu could
be recovered effectively, Li and Al being lost in the slag. Therefore, most
of these companies established a process combining pyrometallurgical and
hydrometallurgical methods (Li, Lu, Zhai, et al., 2018; Li, Zhang, et al.,
2018;Liu,Lin,etal.,2019;Lvetal.,2018). The Umicore Battery
Recycling Process (UBRP), for example, was mainly developed for cobalt
and nickel containing batteries and it is not an ideal solution for LFP
cells as only copper and, potentially, lithium are recovered in form of
high-value products; other metals such as aluminum and iron are mainly
transferred to the slag fraction and end up as a low-value construction
material. Regarding the economic and environmental performance of the
recycling process, no specific information on LFP batteries is available
(Elwertetal.,2019).
Figure 4. LIBs available for recycling in 2025 (t) (Mellin, 2017).
8 F. FORTE ET AL.
The economic recycling of LFP batteries poses a challenge due to the
low content of valuable metals; nevertheless, their recycling needs to be
addressed as increasing return flows have to be expected (Elwert et al.,
2018). Furthermore, even though LiFePO
4
batteries are often referred to
as eco-friendly batteries because of their lower toxicity, they may still
cause environmental problems (Yang et al., 2018). For example, the
organic electrolytes containing toxic LiPF
6
andthemetalionswillgrad-
ually transfer to soil and groundwater when the spent LiFePO
4
batteries
are directly disposed of in landfill or recycled in improper ways (Zeng
et al., 2014).
In the following paragraphs a detailed analysis of the different EoL LFP
recycling steps (from discharging until the recovery of the valuable frac-
tions) is provided. A schematic flow-sheet the recycling chain is shown in
Figure 5. It includes the discharging and dismantling steps with the classi-
fication of the different battery components (paragraph 4.1), the separ-
ation of the LiFePO
4
active material from the Al foil through thermal/
chemical treatment, with or without a previous mechanical treatment step
(paragraph 4.2), and the actual recovery step performed on the active
material through two possible routes: hydrometallurgical methods aimed
at materials recovery (paragraph 4.3.1) and regeneration methods (para-
graph 4.3.2).
Figure 5. Recycling routes of EoL LFP batteries.
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 9
4.1. Discharging and dismantling
LIBs are not usually operated at voltages as low as 0.0 V: they have a lower
practical voltage (for example 3.0 V for LiCoO
2
batteries) and a circuit pro-
tection module is used to prevent the battery from discharging below it
(Vetter et al., 2005). In terms of cycle life, a lifetime of up to 1000 cycles at
80% depth-of-discharge (DOD) is demanded. Spent LIBs batteries have
thus a residual capacity and must be fully discharged before any other fur-
ther step to prevent short-circuiting and self-ignition, consequently to avoid
an explosion (Nie et al., 2015). This can be done by two methods: one is to
immerse the batteries in saltwater to cause them short circuit and complete
discharge, while the other is to directly use the charging and discharging
equipment to discharge the battery pack (Wang et al., 2017). To avoid self-
ignition and short-circuiting, batteries can be completely discharged by
immersing them in a 5 wt% NaCl solution (Liu, Zhong, et al., 2019; Zhong
et al., 2019; Yang et al., 2018) or discharged to a potential of 2.0 V (Chen
et al. (2016). Large-scale European processes, however, usually do not use
these stabilization techniques prior to opening the cells and opt for opening
under an inert atmosphere (Harper et al., 2019). Opening under carbon
dioxide, in particular, allows for the formation of a passivating layer of lith-
ium carbonate on any exposed Li metal.
Batteries are then subjected to a dismantling step to separate the different
components (such as plastic casing, printed circuit boards (PCBs), cables,
aluminum and copper foils, separator) for further recovery through specific
recycling routes, when available. At industrial scale, discharging is normally
followed by a mechanical treatment (crushing followed by magnetic and
mechanical separation units) aimed at separating the different components
for further recovery (Akkuser, n.d.; Fortum, n.d.; Recupyl, n.d.). Shredding
and crushing activities are sometimes performed in inert or cryogenic
atmospheres to prevent violent reactions of Li and to minimize risks from
the presence of organic solvents. A contact between metallic Li with water
or moisture results in intense exothermic reactions. Hydrogen and oxygen
are formed which leads to a high risk danger of explosion (Sonoc et al.
2015). In the Umicore process, LIBs are fed into the furnace without any
pretreatment step (Umicore, n.d.).
At laboratory scale manual dismantling is more often performed (Li, Lu,
Zhai, et al., 2018; Li, Wang, et al., 2019; Liu, Zhong, et al., 2019;; Song
et al., 2017). In the work of Song et al. (2017), for example, the discharged
LiFePO
4
batteries were dismantled by steel saw, taking out the battery core;
then the soft packing of battery core was cut with scissors, getting the
winding cathode and anode plates together and finally the cathode and
anode plates were separated using a small knife. In the work of Yang et al.
(2017), after removing the plastic cases, the steel case was removed
10 F. FORTE ET AL.
mechanically; then anode and cathode were uncurled manually and copper
and aluminum foils were collected for recycling separately. Chen et al.
(2016) separated the cathode plates, the separator and the anode plates
using special equipment; in their process, most of the operations are con-
ducted inside a sealed box, ensuring that the electrolyte exhaust gas cannot
be leaked into the environment. There are, in fact, safety hazards coming
from vapors and gases emitted by the electrolyte when exposed to air. The
electrolyte accounts for 12–14 wt% of a pouch cell used in automobile bat-
teries and is composed of a Li salt, typically LiPF
6
, dissolved in an organic
solvent (usually a mixture of ethylene carbonate and propylene carbonate).
LiPF
6
hydrolyzes in the presence of water via releasing toxic hydrogen
fluoride (HF). Ethylene carbonate and propylene carbonate are both
flammable and skin irritant. Batteries, even if fully discharged, must be
thus opened in a well-ventilated area free from sparks such that the flam-
mability and toxicity hazards posed by the electrolyte are mitigated (Sonoc
et al., 2015).
4.2. Materials separation
The separation of the different materials contained in the battery cells for
further recovery can be performed through different techniques (Table 4).
The cathode materials can be separated through chemical processes, by
soaking the Al foil in an appropriate solvent and by collecting the active
material by filtration followed by a washing step and drying. In the work
of Jiang et al. (2019), the positive plates of spent LiFePO
4
batteries, previ-
ously cut into small pieces (3 3 cm), were soaked in distilled water for
30 minutes at room temperature and stirred with a glass rod to remove the
active materials from the Al foil. The material was filtered and collected
several times with deionized water, dried at 100 C for 4 hours and ground
into powder for recovery. In the work of Li, Xing, et al. (2017), the cathode
plates were immersed in 0.4 mol L
1
NaOH solution for 30 min under
Table 4. Methods for the separation of the cathode materials.
Method Conditions Ref.
Chemical treatment distilled water, t¼4h, T¼100 C Jiang et al. (2019)
Chemical treatment N-methyl-2-pyrrolidone, t¼1h, T¼100 C Li, Lu, et al. (2018)
Chemical treatment 0.4 mol L
1
NaOH, t¼30 min, S/L ¼100 g L
1
;
ultrasonic aided
Li, Xing, et al. (2017)
Chemical treatment DMAC, t¼30 min, T¼30 C, S/L ¼50 g mL
1
Song et al. (2017)
Chemical treatment water, t¼1 h; ultrasonic aided Yang et al. (2017)
Chemical treatment 10 mol L
1
NaOH; ultrasonic aided Bian et al. (2016)
Chemical treatment diluted NaOH Chen et al. (2016)
Thermal treatment t¼1h, T¼450 C Song et al. (2020)
Thermal treatment Pyrolysis, T¼550 C; N
2
atmosphere Liu, Zhong, et al. (2019)
Thermal treatment Pyrolysis, t¼2h, T¼550 C Zhong et al. (2019)
Thermal treatment t¼1h, T¼600 C Zheng et al. (2016)
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 11
ultrasound with solid-to-liquid (S/L) ratio of 100 g L
1
to separate cathode
materials from the Al foils. After a washing step with deionized water and
desiccation at 120 C for 4 h, the cathode materials were crushed and
screened (particle size <2.5 mm) for the subsequent leaching step. Li, Lu,
Zhai, et al. (2018) used N-methyl-2-pyrrolidone (NMP) to separate the
cathode active materials from the Al foil at 100 C for 1 h; after filtration
and drying, the powder was calcined at 400 C for 1 h to remove the
impurities, such as acetylene black and PVDF binder, and then ground for
30 min in a planetary ball mill. In the work of Song et al. (2017), the cath-
ode plate was first cut into small pieces (1 1 cm) and then soaked in
dimethylacetamide (DMAC) to separate the cathode materials and Al foil
for 30 min at 30 C and S/L ratio of 1/20 g mL
1
. The black powder is then
collected after filtration and dried at 60 C for 24 h. Yang et al. (2017) sepa-
rated the cathode materials from the Al foil by ultrasonic-assisted and
mechanical enhancement technique in water after 1 h. According to Bian
et al. (2016), the cathode materials can be detached from Al foil by
immersing the cathode in 10 mol L
1
NaOH aqueous solution with ultra-
sound-assistance; the foil could be recovered in its metallic form and the
spent LiFePO
4
materials were collected through filtering, washing sequen-
tially with deionized water and ethanol and drying at 80 C in air. In the
work of Chen et al. (2016) and Li, Zhang, et al. (2017) the spent batteries
obtained after dismantling were soaked in dilute alkaline solution (pH ¼
10–11) and then plate lugs and aluminum-plastic films could be directly
recycled; the cathode plates, separator and anode plates were separated by
mechanical separation using a special equipment. By immersing the anode
plates in deionized water under ultrasound for 30 min, the anode materials
and the Cu foil could be easily separated and recycled directly.
Separation by thermal treatments is also applied and several example can
be found in the available literature. In the work of Song et al. (2019) the
cathodes were smashed, dried and heated at 450 C for 1 h in muffle to
decompose binder (PVDF) and separate the cathode powder from the Al.
In the work of Zheng et al. (2016), after collecting the electrolyte by a
supercritical method, the LiFePO
4
cathode sheets were crushed into about
2cm
2
and heated at different temperatures ranging from 450–650 C for
1 h; this treatment allowed removing the binders and the carbon in the
electrode, but also oxidized Fe(II) to Fe(III), which facilitated the subse-
quent recovery step. The powder was then separated from the Al collector
by oscillation sieving. Zhong et al. (2019) proposed a process consisting of
pyrolysis and physical separation to recycle spent LiFePO
4
batteries. About
99.91% of the organic electrolytes was recycled and LiPF
6
was disposed by
pyrolysis process. The active materials could be effectively separated from
current collectors after the pyrolysis under N
2
at T¼550 C for 2 h. The
12 F. FORTE ET AL.
pyrolytic gas was mainly composed of light alkenes and the pyrolytic tar
was mainly composed of aromatic long chain alkenes and light alcohols.
Pyrolytic residues were recycled by color sorting, high-pressure water clean-
ing and flotation processes, and about 99.34% of Al, 96.25% of Cu, and
49.67% of cathode active materials were recovered from the spent LIBs.
Liu, Zhong, et al. (2019) investigated the pyrolysis process and pyrolysis
behaviors of the main components in spent LiFePO
4
batteries using isocon-
versional method. More than 96 wt% electrolyte, about 88 wt% separator
and 50 wt% poly(vinylidene difluoride) were converted into pyrolytic gas
and oil, which were mainly composed of small molecular compounds, and
most of the fluorine was converted into HF gas, which can be adsorbed by
alkaline solution. The pyrolysis residues were mainly composed of carbon
powder, fluorocarbon, hydrocarbons, active materials, copper, and alumi-
num foils. The active materials containing LiFePO
4
and C were not
destroyed after the pyrolysis and can be reused as raw materials for pro-
ducing new batteries.
4.3. Treatment of the cathode materials
Once the cathodic powder is separated, two main routes are applicable, one
aimed at materials recovery via hydrometallurgical methods (section 4.3.1)
and the other one aimed at regenerated the active material itself
(section 4.3.2).
4.3.1. Material recovery via hydrometallurgical methods
Metal recovery is normally performed through hydrometallurgical methods
that consist in a leaching step aimed at dissolving the element of interest
followed by a separation step, which can be performed through different
techniques, such as precipitation, solvent extraction (SX), ion-exchange
etc. Normally a hydrometallurgical metal recovery is performed at low
temperature.
Sulfuric acid (H
2
SO
4
) is the most commonly used agent for the (select-
ive) leaching of LFP batteries (Table 5). The dissolution reaction (Eq. (3))
between the LFP active material and H
2
SO
4
is promoted by the addition of
an oxidizing agent such as H
2
O
2
(Larouche et al., 2020):
2LiFePO4ðsÞþH2SO4þH2O2ðaqÞ!2FePO4ðaqÞþLi2SO4ðaqÞþ2H2O (3)
Umicore patent, for example, is based a leaching step with H
2
SO
4
;an
oxidizing agent (O
2
or H
2
O
2
) is added in order to maintain a redox poten-
tial of at least 200 mV vs. Ag/AgCl, and preferably of at least 300 mV, to
minimize the leaching of iron (Schurmans and Thijs, 2012). The need for
the oxidation of Fe(II) to Fe(III) imposes a minimal oxidation power to the
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 13
Table 5. Lithium recovery from spent LFP batteries by hydrometallurgy.
Leaching
Li leaching
yield, %
Separation
step
Global recovery
yield, % Ref.
2.7 mol L
-1
H
2
O
2
,t¼4h, T¼25 C, S/L ¼200 g L
-1
95.4 ––Jing et al. (2019)
Citric acid, ball-to-powder ratio ¼25, citric acid to
LFP ratio ¼20 g g
-1
, 1.0 mL H
2
O
2
,t¼2h
99.35 precipitation with saturated
Na
2
CO
3
,T¼95 C
85.4 (being the precipitation
yield 89.95)
Li, Bian, et al. (2019)
0.28 mol L
-1
H
2
SO
4
,t¼4h, T¼85 C,
high-temperature oxidative activation
98.46 precipitation with Na
3
PO
4
84.2 (being the precipitation
yield 85.56)
Tao et al. (2019)
1.05 times theoretical amount of Na
2
S
2
O
8
,
t¼20 min, T¼25 C, S/L ¼300 g L
-1
>99 precipitation with saturated
Na
2
CO
3
,t¼2h, T¼95 C
–Zhang et al. (2019)
Synthetic chloride media –SX with 40 vol% D2EHPA in
kerosene (t¼15 min,
T¼35 C, O/A¼5), stripping
with 6 mol L
-1
HCl (t¼30 min, T¼35 C,
O/A¼10, 6 stages) ;
precipitation with Na
2
CO
3
(t¼2h, T¼80 C)
90 (as precipitation yield) Song et al. (2019)
0.3 mol L
-1
oxalic acid, t¼60 min, T¼80 C , S/L ¼60 g L
-1
98 ––Li, Lu, et al. (2018)
0.8 mol L
1
acetic acid, 6 vol% H
2
O
2
,
S/L ¼120 g L
1
,t¼30 min, T¼50 C
95.05 precipitation with saturated
Na
2
CO
3
,t¼2h, T¼95 C
84.76 Yang et al. (2018)
4 mol L
-1
HCl, calcination at T¼600 C prior to leaching precipitation with Na
3
PO
4
96 (as precipitation yield) Wang et al. (2018)
0.6 mol L
-1
H
3
PO
4
,t¼20 min, cathode powder to EDTA-2Na
ratio ¼3:1, S/L ¼50 g L
-1
), mechanochemical activation
94.29, precipitation with 5 mol L
-1
NaOH 82.55 Yang et al. (2017)
0.3 mol L
-1
H
2
SO
4
,H
2
O
2
/Li molar ratio ¼2.07, H
2
SO
4
/Li
molar ratio ¼0.57, t¼120 min, T¼60 C
96.85 precipitation with
Na
3
PO
4
,t¼2h, T¼65 C
92.5 (being the precipitation
yield 95.56)
Li, Xing, et al. (2017)
2.5 mol L
-1
H
2
SO
4
, S/L ¼100 g L
-1
,t¼4h, T¼60 C 97 precipitation with Na
2
CO
3
Zheng et al. (2016)
6.5 mol L
-1
HCl, 15 vol% H
2
O
2
,t¼2h, T¼60 C, S/L ¼200 g L
-1
92.15 precipitation with saturated
Na
3
PO
4
,T¼90 C
80.93 ± 0.16 Huang et al. (2016)
4 mol L
-1
H
2
SO
4
, 2 vol% H
2
O
2
,T¼60 C–precipitation with saturated
Na
3
PO
4
,T¼60 C
90 (as precipitation yield) Cai et al. (2014)
H
2
SO
4
þO
2
/H
2
O
2
,t¼2h, T¼80-120 C, S/L ¼100 g L
-1
>92 precipitation with Na
2
CO
3
–Schurmans and Thijs (2012)
2 mol L
-1
H
2
SO
4
,T¼80 C–precipitation with H
3
PO
4
–Tedjar and Foudraz, 2005
O/A ¼organic-to-aqueous volume ratio.
14 F. FORTE ET AL.
reaction medium, which can be achieved using oxygen, with a partial pres-
sure of at least 1 hPa. This can be realized for example by bubbling pure
oxygen at atmospheric pressure through the reaction mixture, or by using a
pressure reactor with an oxygen-bearing atmosphere. The Li-rich liquor
can be further processed for the precipitation of Li as a carbonate by add-
ition of Na
2
CO
3
. In the process patented by Recupyl, the cathode material
is leached with 2 mol L
1
H
2
SO
4
at 80 C in the presence of steel shot with
an iron/cathodic mass ratio of 0.15. The leachate is afterwards cooled to
60 C and then oxidized by means of 30 vol% H
2
O
2
at pH 3.85. Iron is
then separated in the form of oxyhydroxide of the goethite type. Li is then
recovered as Li
3
PO
4
through precipitation with H
3
PO
4
(Tedjar & Foudraz,
2005). According to Li, Zhang, et al. (2017), using 0.3 mol L
1
H
2
SO
4
and
H
2
O
2
as an oxidant, 96.85% Li could be selectively leached while Fe and P
remain in the residue as FePO
4
. Li was then recovered by precipitation
with Na
3
PO
4
. The FePO
4
was directly recovered by burning at 600 C for
4 h to remove carbon slag. Amorphous FePO
4
2H
2
O was recovered by
Zheng et al. (2016) by a dissolution-precipitation method. By using 2.5 mol
L
1
H
2
SO
4
, 98% Fe and 97% Li were leached from the mixed powder.
With PEG-6000 as a surfactant, the pH was adjusted to 2, causing precipi-
tation of FePO
4
. Li was recovered as Li
2
CO
3
by precipitation with Na
2
CO
3
.
The recovered materials (FePO
4
2H
2
O and Li
2
CO
3
) were used as raw mate-
rials to synthesize high performance LiFePO
4
/C by a carbon thermal reduc-
tion method. According to Tao et al. (2019), Li
þ
and small part of PO
4
can
be selectively leached with H
2
SO
4
after oxidative activation at 600 C under
air atmosphere. The leaching rates of Li, Fe and P were 98.46%, 0.010%,
and 26.59%, respectively, under the optimized conditions (0.28 mol L
1
H
2
SO
4
,t¼4h, T¼85 C). NaOH was added to the leachate in order
to remove the impurities (AlPO
4
,Cu
3
(PO
4
)
2
, FePO
4
) and Li was recovered
as Li
3
PO
4
by precipitation with Na
3
PO
4
. A stoichiometric amount of
H
3
PO
4
was then added into the insoluble residue in order to recover iron
as FePO
4
.
Recently, a number of works are being focusing on leaching of EoL LIBs
with organic acids, which potentially have a smaller environmental impact
that mineral acids (Lv et al., 2018; Musariri et al., 2019). Li, Lu, Zhai, et al.
(2018) employed oxalic acid as a leaching reagent to recover Li and remove
P from LFP batteries. The process occurs under conditions of a 0.3mol L
1
oxalic acid concentration, T¼80 C, t¼60 min and S/L ¼60 g L
1
. Li leach-
ing efficiency achieved up to 98%, while Fe precipitates as FeC
2
O
4
2H
2
O.
Yang et al. (2018) stated that by properly adjusting or controlling the oxida-
tive state and proton activity of the leaching solution, Li is selectively leached
against Fe and Al in the presence of acetic acid. After impurities removal, Li
is recovered as Li
2
CO
3
by precipitation with sodium carbonate.
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 15
Mechanochemical (MC) treatment has been used to process spent bat-
teries in the pretreatment stage since 1990s. MC reaction can decrease the
particle size and break the crystal structure, thus facilitating the subsequent
treatment (Yang et al., 2017). The Authors used diluted H
3
PO
4
in the pres-
ence of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) for the
leaching step, which allowed recovering 97.67% Fe and 94.29% Li. Li, Bian,
et al. (2019) used a mechanochemical treatment based on ball milling
(planetary ball mill, ball-to-powder ratio ¼25, grinding time ¼2 h, rota-
tion speed ¼300 rpm) in the presence of citric acid. The mixture was after-
wards dissolved in deionized water and filtrated. With addition of H
2
O
2
,
the extraction efficiency of Li was 99.35% with small co-extraction of Fe
(3.86%) which can be removed as Fe(OH)
3
by precipitation with NaOH. Li
is recovered as Li
2
CO
3
after reaction with saturated Na
2
CO
3
at 95 C. The
grinding and leaching were integrated in the recycling process, which is
easy to operate and thus showed great potential for industrial application.
Liu, Tan, et al. (2019) proposed an acid-free Li extraction process which
makes use of sodium chloride (NaCl) as a co-grinding reagent via a mech-
anical force-induced solid phase reaction. Li was recovered as Li
2
CO
3
by
using Na
2
CO
3
as precipitating agent, which allowed also the regeneration
of NaCl. The proposed acid-free mechanochemical process eliminated the
need for acid and alkali materials and the discharge of wastewater.
In the work of Jing et al. (2019), 95.4% Li was extracted using 2.7 mol
L
1
H
2
O
2
as an oxidant (T¼298 K, pH 7, S/L ¼200 g L
1
), while iron
remained in the residue; however it is not evident from the experimental
procedure whether H
2
O
2
is used together with an extra solvent (for example
inorganic acids usually employed for Li leaching) or alone. Olivine struc-
tured LiFePO
4
is fairly stable and the acid additions must be largely exces-
sive. Acid concentration can be decreased from 2.5 mol L
1
to 0.3 mol L
1
when oxidizing agents (such as H
2
O
2
) are added to the leaching system (Li
et al., 2017; Zheng et al., 2016). Zhang et al. (2019) proposed an innovative
process for the selective leaching of Li without the addition of acid and
alkali: the Authors employed sodium persulfate to oxidize LiFePO
4
to
FePO
4
, forcing lithium to deintercalate from the cathode. More than 99%
of Li was leached at 25 C and within 20 minutes. Li was then recovered as
Li
2
CO
3
(purity >99%) by addition of Na
2
CO
3
.
After leaching, Li is, thus, mostly recovered as carbonate or phosphate
by precipitation with Na
2
CO
3
or Na
3
PO
4
. In the work of Wang et al.
(2018), cathodic material was first calcined to oxidize ferrous iron com-
pletely. The powder was then dissolved in HCl solution adding 6 mol L
1
NH
3
water solution for pH adjustment: this allowed Fe(III) ions to
precipitate as FePO
4
. Finally, a certain amount of Na
3
PO
4
was added to
the filtrate to obtain Li
3
PO
4
. LiFePO
4
was then synthesized through
16 F. FORTE ET AL.
hydrothermal reaction by using recovered Li
3
PO
4
as Li source and
FeSO
4
7H
2
O as Fe source.
Fe impurities can be removed by precipitation with NaOH (Li, Bian,
et al., 2019; Tao et al., 2019). Some Authors focused on Fe recovery and
valorization as well. For example, in the work of Tao et al. (2019), the resi-
due obtained after selective Li leaching was treated with H
3
PO
4
through
mechanical ball mill followed by heat treatment at 600 C, which allowed
the recovery of iron as FePO
4
. For example, Yang et al. (2017) obtained
crystalline iron phosphate precipitation by refluxing air for 9 h at 90 Cso
that Fe(II) is oxidized into Fe(III) and further precipitated out from the
solution. Li, Xing, et al. (2017) treated the FePO
4
which remained in the
leaching residue by burning at 600 C for 4 h to remove carbon slag and
recover FePO
4
. In the work of Zheng et al. (2016) ammonia was added to
the leaching solution in order to adjust the pH value at 2. After filtration,
the residue was washed with deionized water and then dried at 80 C,
which gave the amorphous hydrated FePO
4
. To form FePO
4
with an alpha
quartz structure, the amorphous hydrated FePO
4
was then annealed at
700 C for 5 h. Huang et al. (2016) employed a flotation step to selectively
recover Fe as FeCl
3
from the leaching liquor. Cai et al. (2014) conducted
experiments to determine regions of phase diagram which are of interest
for Fe and Li precipitation process from H
2
SO
4
leachate, in order to iden-
tify the optimal operating conditions. The Authors found out that there is
an optimal amount of NaOH (2 mol L
1
) to be added, such that pure
FePO
4
with high yield can be recovered in the precipitation process: too lit-
tle NaOH (<7.5 mL) decreases the recovery, whereas too much NaOH
(>7.5 mL) leads to the precipitation of Fe(OH)
3
. SX with saponified di-2-
ethylhexyl phosphoric acid (D2EHPA)-kerosene system was used by Song
et al. (2019) to separate Li and P from synthetic chloride media. Li was
effectively extracted, while P remained in the raffinate. The extraction was
a process of cation-exchange between Li
þ
and Na
þ
. The stripping solution
was then precipitated with Na
2
CO
3
and the obtained product (Li
2
CO
3
) was
in accordance with the standard specifications.
Processing of LFP has been studied by some authors as a general route
that encompasses all LIB chemistries (Larouche et al., 2020). Cathode mate-
rials from EoL LIBs are normally treated in order to extract Co, Ni, Al and
Mn and LiFePO
4
is often discarded due to infeasibility of recycling
(Wang & Ma, 2018). LiFePO
4
is precipitated as FePO
4
and remains as a
by-product, along with graphite and carbon. In the work patented by
Wang and Ma (2018), FePO
4
was separated from graphite and carbon by
leaching with 5 mol L
1
HCl, to yield a solution of iron chloride and phos-
phoric acid. pH adjustment with NH
4
OH was then performed to precipi-
tate an iron phosphate precursor. LiCO
3
and a carbon source (glucose or
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 17
sucrose) were finally added to the precipitated FePO
4
under agitation and
the combined mixture is sintered to yield the cathode powders. A stepwise
leaching-flotation-precipitation process was adopted by Huang et al. (2016)
to separate and recover Li/Fe/Mn from mixed types of cathode materials
(LiFePO
4
and LiMn
2
O
4
). Leaching was performed by HCl assisted with
H
2
O
2
; Fe(III) ions were selectively floated and recovered as FeCl
3
and finally
Mn(II)/Mn(III) and Li(I) were sequentially precipitated and separated as
MnO
2
/Mn
2
O
3
and Li
3
PO
4
using saturated KMnO
4
solution and hot satu-
rated Na
3
PO
4
solution, respectively. In the work of Zou et al. (2013) mixed
cathode materials including LiFePO
4
were leached using 4 mol L
1
H
2
SO
4
and 30 wt% H
2
O
2
for 2–3h at 70–80 C. After co-precipitating Ni, Mn and
Co, the leaching solution was treated with Na
2
CO
3
solution at 40 C to pre-
cipitate Li as Li
2
CO
3
.
The advantages of hydrometallurgy are (1) the reduced gas emission,
compared for instance to thermal processes which release toxic gases (diox-
ins/furans), dust and volatile metals, (2) low dust and (3) low energy con-
sumption (Sethurajan et al., 2019). Other advantages are the high recovery
rate, no slag generation and easy working conditions. In hydrometallurgical
processes, a large amount of liquid wastes and sludge are produced and
must be disposed carefully; another drawback is represented by the slow
leaching kinetics. Cost benefit analysis and rigorous techno-economic feasi-
bility studies and demonstration are needed prior the commercial imple-
mentation. Despite a significant amount of studies are available about
materials recovery from EoL LFP batteries, most of them are only applied
at laboratory scale. This is mainly due to the fact that the economy of the
recycling processes is not compensated by the revenues of the recovered
products (Li is much less expensive than cobalt and nickel). The low value
of the elements contained in the active material of LFP electrodes makes its
recycling hardly economical (Larouche et al., 2020). However, the develop-
ment of suitable treatment process for these types of batteries should be
encouraged and promoted because of sustainability considerations which
should take into account the strategic value of LFP batteries elements (Li,
P, graphite, etc.) and the environmental hazards caused by EoL LFP
improper management.
4.3.2. Regeneration of LiFePO
4
Besides methods aimed at materials recovery via hydrometallurgical meth-
ods, a significant number of works are currently being focused on direct
regeneration of the active materials (Table 6). A full-solid route was investi-
gated by Sun et al. (2020) to resynthesize LiFePO
4
/C materials from spent
LFP batteries. The cathode powder (obtained after dismantling and binder
decomposition) was grinded and sieved through 400 mesh screen, sintered
18 F. FORTE ET AL.
Table 6. Regeneration methods for spent LFP batteries.
Method Operative conditions Effectiveness Ref.
Solid-state
regeneration methods
t¼2h, T¼800 C, ball-milling for 2 h and addition of sucrose and
Li
2
CO
3
as C and Li source.
Further heating at 350 C for 5 h and then at 650 C for 10 h in
H
2
/Ar atmosphere.
Resynthesized material meeting the
reuse requirement for LIBs.
Sun et al. (2020)
Ball-milling and addition of Li
2
CO
3
as Li source.
Further calcination at 700 C in high purity N
2
atmosphere.
Li, Wang, et al. (2019)
Heat treatment with different temperature regimes, milling for 2 h
and addition of glucose and Li
2
CO
3
as C and Li source. Further
heating up to 900 C.
Jiang et al. (2019)
t¼8h, T¼700 C, addition of new LiFePO
4
as Li source. Song et al. (2017)
t¼1h, T¼650 C in Ar/H
2
atmosphere with addition of Li
2
CO
3
as
Li source.
Li, Zhang, et al. (2017)
Heat treatment
under Ar/H
2
flow
t¼1h, T¼650 C Good discharge capacities and
specific energy densities.
Chen et al. (2016)
Liquid-state
regeneration methods
H
3
PO
4
leaching and solution refluxed for 9 h at 85 C to obtain
FePO
4
2H
2
O hierarchical micro-flowers.
Further calcination with Li
2
CO
3
and glucose in N
2
atmosphere.
Resynthesized material with
controllable morphology and good
electrochemical performances.
Bian et al. (2016)
Annealing in a box furnace, t¼10 h, T¼700 C. Dissolution in 6 mol
L
-1
HCl and addition of NH
4
OH, to obtain amorphous FePO
4
xH
2
O
powder. Milling with LiOHH
2
O and sucrose as Li and C source.
Further heat treatment at 700 C for 8 h under H
2
/Ar conditions.
Shin et al. (2015)
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 19
at 800 C for 2 h in air to remove PVDF, conductive additive and carbon
coating layers and then mixed with 20 wt% sucrose (as carbon source) and
different amount of Li
2
CO
3
(as lithium source) using planetary ball-milling
for 2 h. These mixtures were pressed into tablets and heated at 350Cfor5h
and then at 650 C for 10 h under H
2
/Ar atmosphere in the tube furnace to
resynthesize the LiFePO
4
/C materials. The Authors found out that, among
the resynthesized LiFePO
4
/C materials, the one with Li
2
CO
3
addition amount
of 1.4 wt% showed the best physical, chemical and electrochemical perform-
ances in half cell and full cell (high initial charge/discharge capacities, equal
to 185.2/154.6 mAh
1
and high initial Coulombic efficiency, equal to 84%),
meeting the reuse requirement for LIBs. A physical direct regeneration
method was studied by Li, Wang, et al. (2019) to repair spent LFP batteries
without using acid/alkaline solutions. The cathode material was mixed with
Li
2
CO
3
uniformly and subjected to ball-milling for 6 h followed by calcin-
ation at 700 C. The Authors found out that the regenerated cathode material
exhibits excellent electrochemical performance, suggesting the applicability of
the recovery method on large-scale applications. A direct regeneration of
cathode materials using a solid phase sintering method was investigated by
Song et al. (2017). The spent battery was firstly dismantled to separate the
cathode and anode plate and then the cathode plate is soaked in DMAC to
separate the cathode materials and Al foil. The spent materials were regener-
ated at different temperatures for 8 h by solid phase sintering with doping of
new LiFePO
4
at different ratios. It was found that the best performances (in
terms of battery capacities) were achieved at a doping ratio of 3:7 and at
T¼700 C. In the work of Jiang et al. (2019), the spent cathode materials,
previously ground into powder (0.2 1.1 lm), were regenerated by heat
treatment with impurity removal, to obtain products with adequate electro-
chemical performances. The Authors found out that the best electrochemical
performances (discharge specific capacity of 105.4 mAh g
1
at 0.1 C after 10
cycles) are achieved when the heat treatment and regeneration temperature
are 700 C and the lithium element volume is 5% higher than calculated. A
direct regeneration process of cathode material mixture from scrapped
LiFePO
4
batteries was developed by Li, Zhang, et al. (2017) which allowed
recovering high purity cathode materials. Dismantled batteries are first
soaked in dilute NaOH solution; LiPF
6
in the electrolyte is thus rapidly
hydrolyzed and collected through filtration, while the other electrolyte com-
ponents are separated by exploiting the different density, solubility and boil-
ing points. The recycled cathode material mixture is further directly
regenerated with Li
2
CO
3
at different temperatures: the Authors found out
that the cathode material mixture regenerated at T¼650 C displayed the
best physical, chemical and electrochemical performances, which meet the
reuse requirement for middle-end Li-ion batteries.
20 F. FORTE ET AL.
In the work of Chen et al. (2016), after discharged and dismantling oper-
ations, cathode plates were treated for 1 h under Ar/H
2
flow at different
temperatures (150–800 C). As the temperature increases from 600 Cto
800 C, all the cathode powders displayed improved tap densities and dis-
charge capacities compared with the ones treated at low temperatures.
Among them, cathode powders treated at T¼650 C showed almost the
same discharge capacities and specific energy densities as the unused ones
at high discharge current densities. Bian et al. (2016) used a liquid-state
regeneration method consisting in leaching the cathode materials with
0.5 mol L
1
H
3
PO
4
and in a subsequent heat treatment (refluxed for 9 h at
85 C) to obtain FePO
4
2H
2
O hierarchical micro-flowers. New LiFePO
4
/C
was prepared via a carbothermal reduction process, calcining the obtained
FePO
4
2H
2
O precursor with Li
2
CO
3
and glucose in N
2
atmosphere. The
resynthesized LiFePO4/C showed excellent electrochemical performance,
however, the process is very complex and can lead to fluctuation of product
quality. A liquid-state regeneration method was used also by Shin et al.
(2015) Both commercially available LiFePO
4
powder and LiFePO
4
electrode
materials obtained from spent batteries were used to prepare crystalline
FePO
4
2H
2
O and then re-synthesize LiFePO
4
/C cathode materials. LiFePO
4
powder/electrode materials were annealed at 700 C in a box furnace for
10 h. The resulting powder was dissolved in 6 mol L
1
HCl for 6 h at
120 C. After addition of 6.25% NH
4
OH, amorphous FePO
4
xH
2
O powder
was obtained. After milling with LiOHH
2
O and sucrose as lithium and
carbon sources, heat treatment was performed at 700 C for 8 h under
reducing conditions to obtain LiFePO
4
/C electrode materials. The recycled
LiFePO
4
/C exhibited a very comparable discharge capacity of about 140 mA
hg
1
at 1 C with a capacity retention of about 99%.
As in the case of the hydrometallurgical methods, the available studies
focused on cathode materials regeneration are currently applied only at
laboratory scale. However, most of these studies showed how the regener-
ated products have good electrochemical properties which meet the reuse
requirement for LFP batteries, thus suggesting the applicability of such
methods on a higher scale.
4.4. Life cycle assessment studies
Life cycle assessment (LCA) can be considered a valuable tool to assess the
benefits and burners associated with a process/product. In literature there
are several works focusing on LCA applied to LFP manufacturing (Dunn
et al., 2015; Liang et al., 2017; Oliveira et al., 2015; Xie et al., 2018).
Larouche et al. (2020) summarized these results comparing process costs
and greenhouse emissions of cathode materials production and they found
CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY 21
out that the energy impacts of the manufacturing step range from 19 to
56 MJ per kg of LFP. Ioakimidis et al. (2019) examined a number of scen-
arios that complement the primary use phase of EV LFP batteries with sec-
ondary applications in smart buildings in Spain. The results showed that
there are significant environmental benefits from reusing the existing EV
batteries in the secondary applications instead of manufacturing new ones
to be used for the same purpose and time frame.
Differently from the LIBs manufacturing, the EoL treatment stage is only
evaluated in a few studies (Ciez & Whitacre, 2019;Ellingsenetal.,2017;
Nordel€
of et al., 2019). These LCA studies showed that production of second-
ary metals from battery recycling is less energy demanding than extraction
from primary sources and that recycling is beneficial with respect to green-
house gas emissions (GHG) emissions (Ellingsen et al., 2017). However,
there is much uncertainty associated with the data and results, making it dif-
ficult to provide direction for reducing environmental impacts of LIBs. This
is due to the lack of access to industry data, which led to large uncertainty
associated with the use of materials (e.g. solvents) and energy.
Specific information on LCA applied to LFP batteries is missing. To the
best of our knowledge, the only study available is by Ciez and Whitacre
(2019), where the GHG emissions, energy inputs and costs associated with
the production and recycling of three common cathode chemistries (NMC,
NCA and LFP) were evaluated. They compared direct recycling methods
and pyro-, hydrometallurgical recovery processes and assumed that any
materials not recovered through these methods are incinerated. Regarding
LFP recycling, it was found out that direct recycling offers significant
embodied energy reductions; hydrometallurgical recycling resulted in an
increase in energy consumption, although not significant, while pyrometal-
lurgical recycling determined a net increase in energy consumption. While
pyro- and hydrometallurgical processes do not significantly reduce life-cycle
GHG emissions, direct cathode recycling has the potential to reduce emis-
sions and can be economically competitive.
More studies are thus needed which deal with the actual LFP recycling
step, in order to better evaluate the feasibility of a treatment process and
its impacts on the environment, thus facilitating the technology scale-up.
5. Conclusions and future perspectives
In the present review, the most recent advances in EoL LFP batteries proc-
essing are provided. Despite the increasing number of studies focused on
recycling and valorization, most of them are only assessed at laboratory
scale and commercial recycling processes are limited. More efforts are,
thus, needed in order to scale-up these technologies at industrial level.
22 F. FORTE ET AL.
Further research should be devoted, for example, to the very initial stages
of the batteries value chain, from the collection to the dismantling step. First
of all, it should be noticed that the lack of a proper labeling system affects
the entire value chain, because it makes impossible to identify the type of
cathode which enters the treatment plant, thus hampering the recycling effi-
ciency and the purity of the obtained products. Furthermore, most of the
technologies relies on manual dismantling of the batteries components, which
is not applicable at industrial level. Further investigations are thus required in
order to develop automatic or semi-automatic pretreatment processes.
Regarding the actual recovery step, it is evident that an all-component
integrated strategy aimed at the valorization of the whole waste fractions is
missing: the main focus is still on the recovery of Li and very few studies
involve the recovery of the other materials contained in LFP batteries. In
order to be cost-effective, a recycling chain needs to be oriented to the val-
orization of the whole waste: not only the cathode materials, but also the
anode (because of the presence of graphite) and the electrolyte should be
valorized, according to the principles of Circular Economy.
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