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SEM images of 100 ppi compressed RVC coated in polyaniline (a and b) and CF coated in polyaniline (c and d). Note the uniform coverage of polyaniline on the RVC structures, as well as some regions on the CF strands where the PA coating is not evenly distributed.
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The challenges associated with the fabrication of three-dimensional (3D) electrode and electrolyte materials for Li-ion batteries are discussed. The basic issues for achieving a solid 3D cell foundation, which can simultaneously offer sufficient electronic conductivity to enable stable cycling, as well as enough compatibility with the incorporation...
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... reaction at low potentials vs. Li + /Li. 15 3D copper structures are instead a suitable anodic current collector, where an anode electrode layer can be deposited. Considerations analogous to those mentioned above for the Al nanorods hold also in this case. Additionally, for this type of current collector the area gain can be further increased by depositing longer Cu rods, e.g. up to 8 – 9 m m, since the electrodeposition of Cu in aqueous solutions is easier and more robust than that of aluminium in ionic liquids. The excellent electronic conductivity of Cu is another essential feature that enables e ffi cient electron transfer in rods with even higher aspect ratios, provided that the thickness of the coated active layers can be limited to a few tens of nanometers. In this respect, a further down-scaling of the Cu structures does not immediately represent a limitation for the performances of the corresponding electrodes, where the width of both the sup- porting rods and the active anodic layer can simultaneously be reduced, while increasing the overall surface area. 7,8 Nonethe- less, the lack of space for the subsequent components needed in a 3D microbattery design poses the ultimate limitation for these structures when AAO templates are used, as earlier mentioned. The third type of current collector that we have explored possesses a di ff erent 3D morphology relying on reticulated carbon structures (Fig. 3a and b) and carbon felt strands (Fig. 3c and d), which can o ff er a direct route towards microbatteries with an aperiodic design. 26 These carbonaceous materials have large surface areas, due to their characteristic pores and network-like connections, which are randomly arranged. Their structures are not as ne as those of template-electrodeposited metal nanorods, yet they are still within the length scales generally considered suitable for 3D microbatteries. They intrinsically possess su ffi cient void space, so that the deposition of a rst electrode layer followed by an electrolyte and a second electrode can be envisaged. Typical area gains between 20 and 50 are observed for such substrates with a thickness of 1 mm. Dedicated electrode materials can readily be deposited on their surface using electrodeposition and other chemical methods. Whilst carbon current collectors, in principle, can be oxidised at potentials above those normally used for cathode materials, the rate of this or any other corrosion reaction has been shown to be negligible when used in combination with lithium battery electrolytes. 16,27 Furthermore, the use of carbon black additives in all conventional cathode systems likewise con rms the stability of this kind of carbon. 28 Therefore, carbon current collectors are ideally suited for con gurations where the cathode is deposited as the primary layer or when high-voltage anode materials, such as Li 4 Ti 5 O 12 or TiO 2 , are being employed. The above substrates represent solid sca ff oldings to build up 3D microbatteries, allowing various strategies to coat both cathode and anode materials via a number of suitable approaches. A number of examples of electrochemical approaches to directly deposit the active materials onto the 3D current collectors, without the addition of any binder and/or electrically conductive additive, are presented in the following subsections. We have focused on simple and low cost methods for preparing conformal cathode and anode layers on these 3D-structured substrates to advance the fabrication of microbatteries and to directly enable the following step of electrolyte deposition. 3.2.1 Positive electrodes. One possible way to proceed is to start with an initial deposition of a cathode material layer ( e.g. LiCoO 2 , 29 CuS x , 30 MnO 2 27 or LiFePO 4 31,32 on a suitable support. An interesting alternative to these active compounds is to have a polymer as a cathode material, since this can o ff er enhanced adaptability for both synthesis and assembly in a 3D cell con guration. In this respect, polyaniline (PA) is a suitable candidate, which has been used as an electrode material since the 1960s. 33 It usually operates via an anion insertion mecha- nism and has a theoretical capacity of 148 mA h g À 1 , where most of the capacity is accessed above 2.8 V vs. Li + /Li. The characteristic electronic conductivity of PA, as well as its versatility and the easy access to porous textures, makes this electro-active polymer clearly attractive in this context. Furthermore, all conventional oxide-based cathodes ( e.g. LiCoO 2 , LiFePO 4 , LiMn 2 O 4 , etc. ) su ff er from limited electrical conductivity and it is challenging to immediately synthesise and deposit them in thin layers by electrochemical routes. Here PA is used as the active cathode material prepared in conformal deposits on aperiodic carbon structures ( i.e. RVC and carbon felt (CF)) via straightforward electrodeposition. The PA deposits obtained on the RVC and CF substrates are shown in Fig. 4. The PA on the RVC surface is clearly seen as a rough layer, when compared to the previous smooth carbon surface (see Fig. 3a and b). The PA layer appears to be approximately even, with no exposed areas visible on RVC. In the case of the PA layer on the carbon felt, a rougher coverage of the CF surface can be noticed and akes of the active material can be seen crossing from one ber to another. Nevertheless, the deposits look to be reasonably conformal on both the RVC and CF supports. The corresponding voltage pro le curves of charging and discharg- ing at C/10 are shown in Fig. 5a, where the e ff ect of the increased surface area for the PA coating on the 3D substrates can be clearly observed. The capacity per foot print area observed for the PA layer on the planar stainless steel substrate was 0.01 mA h cm À 2 , whereas those obtained for the PA coatings on RVC and CF were 0.11 and 0.27 mA h cm À 2 , respectively. Despite the PA coating on RVC o ff ering reduced performances compared to its analogue on CF, these RVC structures can be more advanta- geous than CF in terms of rigidity, which helps in maintaining structural stability upon cycling and avoiding possible short- circuits. Although the capacity enhancements are signi cant, they are only about half of the values that can be expected on the basis of the theoretical increase in surface area. This may be due to electrode thinning in the centre of the structure as a result of electrolyte depletion during the electrodeposition process, though this may not be easily observed by SEM. The PA material was cycled for more than 40 cycles and did not exhibit any signi cant capacity fade (see Fig. 5b). High rate capabilities were also observed at rates of 10 C for the PA-coated CF samples, with capacities exceeding 50% of those obtained at C/10. This high performance can be explained considering the highly conductive porous layers of PA with thicknesses in the range 1 – 2 m m. Accordingly, the characteristic structure allows for good ionic conduction through the pores, as well as e ff ective electronic conduction through the polymer backbone. It is worth mentioning that this situation is o en lacking in thin lm cathodes, where binders and conductive additives are not included, thus leading to signi cant fading of both the capacity and the rate capability of such electrodes. 27 3.2.2 Negative electrodes. Another option is to begin with the deposition of an anodic material as the rst layer onto a compatible 3D substrate. In this respect, copper stands out as an optimal support, because it displays excellent electronic conductivity and does not undergo Li-alloying at low potentials vs. Li + /Li. Moreover, it is stable with respect to corrosion up to $ 3.4 V vs. Li + /Li in combination with most of the electrolytes usually employed. Accordingly, several deposition processes of active materials such as Fe 3 O 4 , 15 Sn, 17 Si, 16 Sb 34 and Bi 19 have been reported on 3D Cu current collectors. We have earlier presented how a Cu current collector can be directly employed for the synthesis of Cu 2 Sb by electro- depositing a layer of Sb. 34,35 This simple approach resulted in Cu 2 Sb electrodes with excellent adhesion to the underlying 3D Cu substrate, ensuring stable cycling behaviour 36,37 and a higher energy density 18 than that of an analogous 2D con guration. Here, we have further developed this strategy for the deposition of an alternative anode material on these 3D Cu substrates. In particular, we use the same template-electrodeposition process to form, in situ , a thin layer of Cu 2 O on the copper nanorods. The Cu 2 O deposits directly generated on the surface of the Cu structures during the template-assisted electrodeposition can be observed in Fig. 6a as roughening of the rod contours in the form of grains. The reaction of the Cu 2 O electrode is di ff erent from that of Li-alloying materials ( e.g. Cu 2 Sb), since the reduction of Cu 2 O causes the formation of copper nanoparticles embedded in a matrix of Li 2 O, due to a conversion reaction. 38 Cu 2 O nanoparticles are formed upon subsequent oxidation, while the Li 2 O matrix is dissolved. Such a process yields a surprising overall reversibility, particularly considering the dramatic structural changes involved in the reactions. Although cuprous oxide has a theoretical capacity of 375 mA h g À 1 , larger capacities can in fact be expected for 3D electrodes, as a result of the signi cant double layer charging e ff ect 39,40 at the extensive Cu/Li 2 O interfaces generated by the conversion reaction, as well as the larger surface area of the corresponding support. Conversely, capacities exceeding their theoretical values have also been explained in terms of electrolyte decomposition, yielding an organic, gel- like layer. 41 Another attractive characteristic of Cu 2 O is its small volume change ( i.e. 22%) upon lithiation and de-lithiation, which is signi cantly limited ...
Citations
... Compared to solid-state electrolytes, gel polymer based electrolytes comprising a polymer matrix and liquid electrolytes are extensively used in lithium-ion batteries. Specific properties such as higher safety concerns, excellent ionic conductivity and stretchability permit their application in lithium-ion batteries [122][123][124]. However, the traditional GPE prepared by solution casting followed by solvent evaporation limits its usage due to dimensional stability and flexibility. ...
Additive manufacturing techniques (3D printing) provide a promising solution to the complicated, expensive, and material-wasting traditional fabrication process for lithium-ion batteries (LIBs). LIBs are known for their high energy and power density, but the complex electrode architectures limit their practical applications in flexible and wearable devices. 3D printing technology allows the controllable fabrication of complex, flexible, and free-standing 3D architecture with computational stimulation, computer-aided design modeling, and machine learning, which can significantly enhance the performance of LIBs. This article reviews recent developments in 3D printing technology for the fabrication of LIBs, including printing electrode materials of different architectures, electrolyte suitability, rheological properties of inks, and their performance. The review also highlights the controllability of 3D printing on the architecture, such as interdigitated-thickness aligned structure, dimensionality, porosity, and interconnectivity of structures with the help of pre-patterned designs by CAD modeling. To overcome challenges and explore future applications, a detailed review of the intrinsic and extrinsic properties of the material, existing 3D printing techniques with their pros and cons, and their adaptability for practical applications is necessary. Finally, the challenges and possible outcomes for real-time applications of 3D printed LIBs are summarized.
... In this report focusing on diffusion-controlled Litrapping, we will, however, only discuss intercalation reactions since the capacity losses seen for conversion materials mainly are due to other effects, such as the formation of passivating surface oxides during the delithiation (i.e., oxidation) of the metal nanoparticles generated in the conversion reaction (e.g., SnO 2 + 4 Li + + 4 e − = Sn + 2 Li 2 O). [105][106][107][108] Diffusion-controlled Li-trapping effects should, nevertheless, still be possible to see for electrode materials undergoing conversion reactions providing that the capacity losses due to the abovementioned irreversible conversion reaction and the Li-trapping effects can be differentiated. The problem can be illustrated using SnO 2 as an example. ...
Rechargeable lithium‐based batteries generally exhibit gradual capacity losses resulting in decreasing energy and power densities. For negative electrode materials the capacity losses are largely attributed to the formation of a solid electrolyte interphase (SEI) layer and volume expansion effects. For positive electrode materials, the capacity losses are, instead, mainly ascribed to structural changes and metal ion dissolution. This Review focuses on another, so far largely unrecognized, type of capacity loss stemming from diffusion of lithium atoms or ions as a result of concentration gradients present in the electrode. An incomplete delithiation step is then seen for a negative electrode material while an incomplete lithiation step is obtained for a positive electrode material. Evidence for diffusion‐controlled capacity losses is presented based on published experimental data and results obtained in recent studies focusing on this trapping effect. The implications of the diffusion‐controlled Li‐trapping induced capacity losses, which are discussed using a straightforward diffusion‐based model, are compared with those of other phenomena expected to give capacity losses. Approaches that can be used to identify and circumvent the diffusion‐controlled Li‐trapping problem (e.g., regeneration of cycled batteries) are discussed, in addition to remaining challenges and proposed future research directions within this important research area. This article is protected by copyright. All rights reserved
... [60], [61] The dendrite growth has the largest impact on energy density and cyclability for all Zn batteries, as Zn dendrites (Young's modulus E = 108 GPa) [62] can easily traverse the inter-electrode space piercing existing plastic separators (Figure 2.1, A to B). Liquid organic Zn 2+ electrolytes make metal deposition on the anode more uniform and improve the reversibility of cathode chemistry, [63]- [68] however, the problem of dendrite growth persists [69], [70] and a new problem of flammability emerges. Recently, rechargeable batteries were constructed using three-dimensional (3D) electrodes [71], [72] in the form of Zn sponges, [73] Zn-on-Ni foams, [68] or carbon cloths [74] in order to alleviate the problem of anode-tocathode bridging by dendrites. While demonstrating impressive cyclability, the 3D electrodes increase the bulk of the anode and make them prone to mechanical damage, while increasing the likelihood of leakage of the liquid electrolyte. ...
Energy storage is an integral part of life. Living creatures have developed a distributed and structural energy storage system to survive under various and sometimes extreme conditions. Similarly, energy storage is critical for today's modern life to power from small biomedical instruments to large aircraft. There are still several challenges against efficient and safe energy storage utilization due to the mechanical, chemical, and physical limitations of existing materials. Inspired by biological structures, we present multifunctional nanocomposites from aramid nanofibers (ANF), a Kevlar's nanoscale version, to address the safety and efficiency of various battery chemistries and enable structural energy storage to increase energy density. High mechanical properties of ANF suppress dendrite formation, and tunability with different copolymers and fabrication methods allow ANF-based nanocomposites to meet specific needs of different battery chemistries. In the first part of this thesis, we engineered biomimetic solid electrolyte from ANF and polyethylene oxide for zinc batteries inspired by the cartilage structure. These strong nanocomposites can block stiff zinc dendrite formation and prevent short circuits over cycles. Resilience to plastic deformation and damage while having no leaking fluids or cracks is essential for the safety of, for instance, electrical vehicles employing such batteries. These load-bearing batteries can be used as a structural component and increase energy density by simply avoiding inactive parts. As a proof of concept, we utilized this battery on a commercial drone as an auxiliary energy storage unit to extend flight endurance by about 20%. In the second part of the thesis, we address a specific polysulfide shuttle problem in lithium-sulfur batteries utilizing bioinspired ANF nanocomposites. Mimicking ion channels on the cell membrane, we engineered biomimetic nanochannels (1nm diameter) for selectively allowing lithium-ion passage while physically blocking lithium polysulfide species (>2nm) on the cathode side. Selective ion transport through nanochannels is also modeled by finite element analysis, COMSOL. These ion channels allow us to reach >3500 cycles. In addition to previous solid and liquid electrolyte systems, here in the last part of the thesis, we present a tunable quasi-solid polymer electrolyte to take advantage of both electrolyte features while minimizing their individual risks and drawbacks. Similar to the kidney filtration system, specifically the glomerular basement membrane, this gel electrolyte filters ions depending on their size and charge. Selective permeability and regulated ion transport provide safe and stable charge/discharge cycles. High mechanical properties keep functionality under extreme conditions, including high temperature and nail penetration. To show practical utilization of our structural batteries, we integrated pouch cells in various prototypes, including health monitoring devices, robotic prosthetics, and electric vehicles. Taken together, mimicking structural and functional properties of multifunctional biological materials, i.e., cartilage, we present a novel multifunctional nanocomposite system that can be tailored to the specific needs of numerous structural energy storage applications.
... From Table 2, it is clear that the most widely reported 3D thin-film electrode is TiO 2 . [18,26,28,38,60,61] Due to its high theoretical volumetric capacity of 1280 mAh cm −3 , TiO 2 is an interesting candidate as it offers a small volume expansion and high cycling stability. [62,63] Furthermore, a wide range of ALD processes are available for the deposition of TiO 2 and the material is well-known from semiconductor industry. ...
... As can be seen in Table 2, most anode thin-films were deposited by ALD [18,26,38,60,61] and (low-pressure) chemical vapor deposition (LP-CVD). [28,54,64] A variety of other anode materials can be deposited by ALD, such as Li 4 Ti 5 O 12 , [65] Nb 2 O 5 , [66] and MoO 2 , [67] which, however, were not electrochemically tested as 3D TFB electrode to date. ...
The status and progress toward solid‐state 3D thin‐film Li‐ion microbatteries is reviewed. Planar thin‐film batteries (TFBs) are commercially available. A major issue with planar TFBs, however, is that the total footprint capacity is limited, as only a relatively small electrode volume is available for energy storage. Coating of the complete battery thin‐film stack, i.e., cathode/solid electrolyte/anode, over a 3D microstructured current collector substrate can provide higher footprint capacity as a result of the surface area enhancement. However, thus far, no 3D TFB with footprint capacity exceeding the limit of ≈250 µAh cm−2 are achieved. The authors provide a status of the individual components: thin‐film cathodes, anodes, and thin‐film solid electrolyte conformally coated over 3D substrates with periodic microstructures. Guidance for designing a 3D TFB with optimum capacity is also provided. 3D thin‐film batteries are solid‐state microbatteries where a thin‐film stack of cathode/solid‐electrolyte/anode is conformally coated over a 3D substrate and bottom current collector for increased footprint capacity while maintaining the high speed charging properties of thin‐film electrodes.
... SPEs generated by this scenario provide a mechanism for applying these type of electrolytes onto architecturally complex 3D electrode structures, such as in small-scale high energy density batteries where the energy per footprint area can be significantly increased by two orders of magnitudes. [14][15][16] Micro or nano scale batteries are essential for powering a range of autonomous microelectronic devices, such as medical implants and sensors. 17,18 One of the difficulties in realising this concept is the need to coat complex non-planar electrode structures with a thin contiguous SPE film or, in the case of liquid electrolytes, apply the indispensable separator membrane. ...
... Brandell and colleagues electrografted binary poly(propylene glycol)diacrylate/ lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) films of nanometer thicknesses from an ethanolic monomer solution onto Cu 2 O-coated 3D Cu nano-pillars and estimated the ionic conductivity of the resultant films to be in the order of 10 −6 Scm −1 . 14,16 Djenizian et al. demonstrated the direct electrochemical polymerization of polyethylene oxide-b-methylmethacrylate co-monomer electrolyte from 0.035 M aqueous LiTFSI solutions onto 3D nanostructured electrodes. 28,29 It should be noted that most of the electrografted films were electrochemically polymerized from monomer solutions where radicals generated from the respective solvents (or from oxygen saturation) 26 initiated the polymerization as opposed to radicalization of the unsaturated functionality of the monomer reported by Jérôme et al. 22 Herein, we present our approach for electrochemical grafting and polymerization of ultrathin polymer electrolytes (UTPE) onto 3D cylindrical micropillars and also onto planar disc electrodes from ternary monomeric electrolyte blends in the absence of sacrificial solvents. ...
Solid state microbatteries are highly sought after for emerging microsensor technologies. To overcome the problem of the dwarfing capacity resulting from the miniaturization of the battery, 3D-structured platform consisting of high surface area micropillar-shaped electrodes are used. However, applying a conformal and continuous solid polymer electrolyte films onto the intricate 3D electrodes is a crucial step toward achieving functional microbatteries. In this work, we present our approach for the development of polyethylene oxide (PEO)-acrylate based ion conducting polymer thin films which function as solid polymer electrolyte (SPE) and a separator. The SPEs were electrochemically deposited on the 3D electrodes resulting in ultrathin, continuous, conformal, and pinhole-free polymer films. The electrochemical and Li ⁺ ions transport properties of the SPEs were characterized by EIS measurements and cyclic voltammetry. Furthermore, the homogenous composition of the SPEs at various depths were confirmed by XPS depth profiling techniques.
... Liquid organic Zn 2+ electrolytes make metal deposition on the anode more uniform and improve the reversibility of cathode chemistry; 14−19 however, the problem of dendrite growth persists, 20,21 and a new problem of flammability emerges. Recently, rechargeable batteries were constructed using three-dimensional (3D) electrodes 22,23 in the form of Zn sponges, 24 Zn-on-Ni foams, 19 or carbon cloths 25 in order to alleviate the problem of anode-to-cathode bridging by dendrites. While demonstrating impressive cyclability, the 3D electrodes increase the bulk of the anode and make them prone to mechanical damage while increasing the likelihood of leakage of the liquid electrolyte. ...
... Thin-film cathodes are typically prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Since PVD methods do not provide coating of high-aspect-ratio microchannels and CVD is a relatively slow process and requires costly equipment and toxic precursors [29], the only methods which enable formation of thin-film conformal layers of active battery materials are electrochemical synthesis [1,10,13,14,16,17,21,25,26,30] and EPD. In Ref. [21] an electrophoretic-deposition method was used for the first time to prepare thin-film LiFePO 4 cathodes. ...
Miniature power sources are needed for a variety of applications, including implantable medical devices, remote microsensors and transmitters, “smart” cards, and Internet of things (IoT) systems. Today's rechargeable lithium-ion batteries - with the best performance on the subject of energy density and with a reasonably good power efficiency - dominate the consumer market. Insufficient areal energy density from thin-film planar microbatteries has inspired a search for three-dimensional microbatteries (3DMB) with the use of low cost and efficient micro- and nano-scale materials and techniques. The exclusive capabilities of the 3D-printing technology enable the design of different shapes and high-surface-area structures, which no other manufacturing method can easily do. We present a novel, quasi-solid rechargeable 3D microbattery assembled on a 3D-printed perforated polymer substrate (3DPS) with interconnected channels formed through XYZ planes. Simple and inexpensive electrophoretic-deposition routes are applied for the fabrication of all the thin-film active-material layers of the microbattery. With the advantage of thin films, which conformally follow all the contours of the 3D substrate and are composed of nanosize electrode materials, like modified Lithium Iron Phosphate (LFP, Lithium Titanate (LTO), and original polymer-in-ceramic electrolyte, our 3D microbatteries offer high reversible specific capacity and high pulse-power capability.
... [18,32,42,49,50] High energy and power densities can be achieved simultaneously with 3D architectured electrodes and due to that, more active materials can be loaded for a given footprint area and meanwhile the surface area of the electrode is significantly increased due to 3D structural designs. [51][52][53] In the following sections, we review the recent advances on microsized lithium-ion batteries with several exemplary configuration designs. Major focus is given to the discussion on the influence of the electrode structural designs on the output electrochemical performances. ...
... [113][114][115] Electrolyte: The commonly used liquid electrolyte (LiPF 6 dissolved in ethylene carbonate/dimethyl carbonate) brings potential risks for leakage and high self-discharge rate problems in micro-LIBs. An alternative choice adopting solid-state electrolytes gives rise to several other tough problems; [9,52] e.g., it brings difficulties to fully fill the micro-/ nanoscale gaps between anodes and cathodes for micro-LIBs or the possible nanostructures of the electrodes. [116] However, the merits of solid-state electrolyte are not only Small 2017, 13, 1701847 Figure 11. ...
Development of microsized on-chip batteries plays an important role in the design of modern micro-electromechanical systems, miniaturized biomedical sensors, and many other small-scale electronic devices. This emerging field intimately correlates with the topics of rechargeable batteries, nanomaterials, on-chip microfabrication, etc. In recent years, a number of novel designs are proposed to increase the energy and power densities per footprint area, as well as other electrochemical performances of microsized lithium-ion batteries. These advances may guide the pathway for the future development of microbatteries.
... To overcome the contact problem, composite cathodes containing polymer electrolytes as binder and ionic conductor have been suggested. [14][15][16] In this case, a ceramic/polymer interface is created where the ceramic electrolyte layer is in contact with the ionically conductive polymer of the composite cathode. Such three dimensionally (3D) structured cathodes might also provide higher energy densities by overcoming the limited thickness, which is due to low ionic conductivity of the cathode active materials. ...
Model systems for electrochemical impedance spectroscopy (EIS) studies of solid-state electrolytes based on ceramic lithium ion conductor Li7La3Zr2O12 (LLZO) and polymer electrolyte P(EO)20-LiClO4 are investigated for the first time. The aim of the present study is to identify and quantify the lithium ion transition resistance of the ceramic/polymer interface. Symmetrical model systems consisting of LLZO pellets with sheets of P(EO)20-LiClO4 are manufactured and investigated in detail. In such symmetric model systems we observed an additional ion-transfer process, which we attributed to the interface processes (i.e. distributed Li⁺ transition across the interface). Based on the EIS measurement data obtained above the polymer electrolyte’s melting temperature, at 70°C the interface resistance of the lithium ion transition is estimated to be ∼9 kΩ cm² and the capacitance of the process is in the order of 0.1 μF/cm². According to our investigations, it is possible to predict interface resistivity of lithium ion transport for different polymer/ceramic composite electrolytes for solid state lithium battery applications.
... The planar thin film microbattery was first introduced by Oak Ridge National Laboratory 1 where the battery capacity is determined by the battery footprint. In order to fully utilize the limited area, 3D microbattery was developed as an alternative technology for small scale energy storage, [2][3][4][5][6][7][8][9][10] where the ultimate goal is to obtain a high surface area substrate coated with thin layers of cathode, electrolyte and anode materials to enhance the energy density per footprint area. Also, the 3D architecture with a larger active surface area can facilitate the ion transfer between electrolyte and active material, thus achieving fast energy storage and release. ...
Here we demonstrate the use of projection stereo-micro-lithography as a low-cost and high-throughput method to fabricate threedimensional (3D) microbattery. An Ultraviolet (UV)-curable Poly (ethylene glycol) (PEG)-base gel polymer electrolyte (GPE) isfirst created. The GPE is then used as a resin for micro-stereolithography in order to build a 3D architecture of battery’s electrolyte.Active materials, LiFePO4(LFP) and Li4Ti5O12(LTO), are mixed with carbon black and the GPE resin, which is then flown intothe 3D structure. Aluminum (Al) foil is cut and inserted as a current collector. The GPE is characterized and the microbattery isperformed a cycling test. Results show a feasibility of microbattery fabrication using projection micro-stereolithography.
