Likun Zhu

Indiana University-Purdue University Indianapolis | IUPUI · Department of Mechanical Engineering

Green synthesis offers a superior alternative to traditional methods for producing metal and metal oxide nanoparticles. This approach is not only benign and safe but also cost-effective, scalable, and straightforward, operating under ambient conditions. Notable metals and metal oxide nanoparticles, such as manganese oxides, iron oxides, silver, and...

Green synthesis offers a superior alternative to traditional methods for producing metal and metal oxide nanoparticles. This approach is not only benign and safe but also cost-effective, scalable, and straightforward, operating under ambient conditions. Notable metals and metal oxide nanoparticles, such as manganese oxides, iron oxides, silver, and...

Surface coating has become an effective approach to improve the electrochemical performance of Ni-rich cathode materials. In this study, we investigated the nature of an Ag coating layer and its effect on electrochemical properties of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material, which was synthesized using 3 mol.% of silver nanoparticles by a...

Group IV elements and their oxides, such as Si, Ge, Sn and SiO have much higher theoretical capacity than commercial graphite anode. However, these materials undergo large volume change during cycling, resulting in severe structural degradation and capacity fading. Al2O3coating is considered an approach to improve the mechanical stability of high-c...

Transition-metal oxide anode materials have been observed to possess an intriguing surplus of capacity beyond the expected values based on conversion reaction. However, the mechanisms behind this phenomenon have remained...

Elemental doping for substituting lithium or oxygen sites has become a simple and effective technique to improve the electrochemical performance of layered cathode materials. Compared with single-element doping, this work presents an unprecedented contribution to the study of the effect of Na+/F- co-doping on the structure and electrochemical perfo...

The development of lithium-ion batteries (LIBs) based on current practice allows an energy density increase estimated at 10% per year. However, the required power for portable electronic devices is predicted to increase at a much faster rate, namely 20% per year. Similarly, the global electric vehicle battery capacity is expected to increase from a...

The increasing adoption of lithium-ion batteries (LIBs) in consumer electronics, electric vehicles, and smart grids poses two challenges: the accurate prediction of the battery health to prevent operational impairments and the development of new materials for high-performance LIBs. Characterized by their flexibility and mathematical tractability, G...

Lithium sulfur (LiS) batteries are among the next generation of rechargeable batteries offering high energy densities. Obstacles remain for their practical application, such as capacity fading and low Coulombic efficiency resulting from shuttling and reaction of polysulfides with the Li anode. A new supramolecular approach to suppress shuttling usi...

Irreversible capacity loss is a critical problem in high capacity anode materials of Li-ion batteries, such as silicon, germanium, and tin. In addition to solid electrolyte interface formation and active material loss, Li trapping in high capacity anode materials during cycling has been considered a new mechanism of capacity loss but received less...

This work is motivated by an experiment of microbubble transport in a polymer microfluidic gas generation device where coalescence-induced detachment exhibits. We numerically study three-dimensional microbubble coalescence using the graphics processing unit accelerating free energy lattice Boltzmann method with cubic polynomial boundary conditions....

The dynamic information of lithium‐ion battery active materials obtained from coin cell‐based in‐situ characterizations might not represent the properties of the active material itself because many other factors in the cell could have impacts on the cell performance. To address this problem, a single particle cell was developed to perform the in‐si...

The volume expansion of Si and SiO particles was investigated using a single-particle battery assembled with a focused ion beam and scanning electron microscopy (FIB-SEM) system. Single Si and SiO particles were galvanostatically charged and discharged as in real batteries. Microstructural changes of the particles were monitored in situ using FIB-S...

Ga-Sn liquid metal material is demonstrated as a self-healing anode system due to its fluidity via operando synchrotron-based transmission X-ray microscopy and X-ray diffraction experiments. Cracks formed due to volume expansions can be recovered by the fluidity of the liquid metals. By incorporating with a poly(ethylene oxide) (PEO)-based electrol...

Alloy-based materials are promising anodes for rechargeable batteries because of their higher theoretical capacities in comparison to graphite. Unfortunately, the huge volume changes during cycling cause serious structural degradation and undesired parasitic reactions with electrolytes, resulting in fragile solid-electrolyte interphase formation an...

To investigate the lithium transport mechanism in micrometer-sized germanium (Ge) particles, in situ focused ion beam-scanning electron microscopy was used to monitor the structural evolution of individual Ge particles during lithiation. Our results show that there are two types of reaction fronts during lithiation, representing the differences of...

Operando Investigation of Energy Storage Material by FIB-SEM System - Xinwei Zhou, Likun Zhu, Yuzi Liu

Selenium-doped germanium (GeSe) µm-sized particles have been reported with good cycling performance and rate capability due to a Li-Se-Ge network formed during the first lithiation that provides a Li ion fast pathway. To understand the effect of the Li-Se-Ge network at a high cycling rate, we monitored the morphology change of both pure Ge and GeSe...

State-of-the-art lithium-ion batteries cannot satisfy the increasing energy demand worldwide because of the low specific capacity of the graphite anode. Silicon and phosphorus both show much higher specific capacity; however, their practical use is significantly hindered by their large volume changes during charge/discharge. Although significant ef...

We systematically study the effects of liquid viscosity, liquid density, and surface tension on global microbubble coalescence using lattice Boltzmann simulation. The liquid-gas system is characterized by Ohnesorge number Oh≡ηh/ρhσrF with ηh,ρh,σ, and rF being viscosity and density of liquid, surface tension, and the radius of the larger parent bub...

To understand the effect of selenium doping on the good cycling performance and rate capability of a Ge0.9Se0.1 electrode, the dynamic morphological and phase changes of the Ge0.9Se0.1 electrode were investigated by synchrotron-based operando transmission X-ray microscopy (TXM) imaging, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XA...

Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte i...

In the past two decades, lithium-ion batteries (LIBs) have been extensively utilized in portable electronic devices as well as electric vehicles (EVs). However, conventional LIBs depending on the lithium intercalation reactions of anode and transitional metal oxide cathode materials have limited capacities and low energy densities, which prevent th...

Germanium (Ge) is a promising candidate for high-capacity Li-ion battery anode due to its high theoretical capacity of 1384 mAh/g (for the charged Li 15 Ge 4 phase), low operation voltage, fast bulk Li diffusion, and high electrical conductivity. However, the major challenge in the development of Ge anode is the large volume change involved in the...

Germanium (Ge) has been considered a promising anode active material, due to its high capacity, low voltage, fast lithium ion diffusion, and high electrical conductivity. However, Ge based anode materials suffer from pulverization due to a large volume change, up to 300%. Although pulverization issues can be alleviated by nano-structuring the Ge-ba...

The morphological evolution of tin particles with different sizes during the first lithiation and delithiation processes has been visualized by an in operando synchrotron transmission X-ray microscope (TXM). The in operando lithium ion battery cell was operated at constant current condition during TXM imaging. Two-dimensional projection images with...

Germanium has emerged as a promising high capacity anode material for lithium ion batteries. To understand the microstructure evolution of germanium under different cycling rates, we monitored single germanium particle batteries using an in situ focused ion beam-scanning electron microscope. Our results show that both lithium concentration and deli...

Selenium (Se) is a potential cathode material for high energy density rechargeable lithium batteries. In this study, a binder‐free Se‐carbon nanotube (CNT) composite electrode has been prepared by a facile chemical method. At initial state, Se is present in the form of branched nanowires with a diameter of <150 nm and a length of 1–2 μm, interwoven...

The dynamics of bubble coalescence are of importance for a number of industrial processes, in which the size inequality of the parent bubbles plays a significant role in mass transport, topological change and overall motion. In this study, coalescence of unequal-sized microbubbles captive on a solid substrate was observed from cross-section view us...

A synchrotron transmission X-ray microscopy tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source was employed to obtain three-dimensional morphology data of all-solid Li ion battery electrodes. The three-phase electrode was fabricated from a 47:47:6 (wt%) mixture of Li(Ni1/3 Mn1/3 Co1/3)O2 as active material, Li1.3Ti...

Recent experiments revealed micrometer (µm)-sized selenium (Se)-doped germanium (Ge) particles forming a network of inactive phase (Li–Ge–Se) bring superior performance in cycling stability and capacity over un-doped Ge particles. Therefore, based on two states of Li (one for diffusion and another for alloyed reaction), a phase-field model (PFM) is...

The electrode of Li-ion batteries is required to be chemically and mechanically stable in the electrolyte environment for in situ monitoring by transmission X-ray microscopy (TXM). Evidence has shown that continuous irradiation has an impact on the microstructure and the electrochemical performance of the electrode. To identify the root cause of th...

During the last decade, many research efforts have been made to develop alloy-type anode materials for lithium ion batteries (LIBs), because of their much higher storage capacity compared to graphite (372 mAh/g) (1). Sn is one of the alloy-type materials and it has theoretical capacity of 994 mAh/g (for the charged Li 4.4 Sn phase) (2). Sn is also...

Recent experiments observed micrometer (µm)-sized Selenium (Se)-doped Germanium (Ge) particles forms a network of active Ge inclusions amidst an amorphous Se-containing inactive phase during initial lithiation/delithiation cycles. Such an inactive coating phase is supposed to be responsible for the superior performance of cycling stability and capa...

Germanium (Ge) has been studied as an anode active material for high energy density lithium ion batteries (LIBs) (1, 2), due to its high volumetric capacity, low operation voltage, fast bulk Li diffusion, and high electrical conductivity. Similar to other high capacity lithium alloys (Si and Sn), Ge electrode accompanies large volume change of the...

The impact of calendering process on the geometric characteristics and electrochemical performance of LiNi1/3Mn1/3Co1/3O2 (NMC) electrode was investigated in this study. The geometric properties of NMC electrodes with different calendering conditions, such as porosity, pore size distribution, particle size distribution, specific surface area and to...

To investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomogra...

Alloy-typed materials have been studied as an anode active material to develop high energy density lithium ion batteries (LIBs). Especially, lithium alloys based on the group IV elements (Si, Ge, and Sn) are potential candidates for the anode material because of their high theoretical capacities and low operating voltages (1). Lithiation and deliti...

The energy and power capabilities of Li ion batteries (LIBs) have been considered critical factors to determine the commercial values of the LIB powered applications. Many efforts have been done to improve the energy density and rate capability of LIBs. In addition to intrinsic material properties of anode and cathode active materials, the structur...

Li dendrite formation on graphite anode electrode of Li ion batteries (LIBs) during fast charging processes is one of the significant safety concerns in the application of electric vehicles. Catastrophic failures due to thermal runaway could be triggered by the short circuit due to Li dendrite. In order to understand the mechanism and suppress the...

A multiscale platform has been developed to model lithium ion battery (LIB) electrodes based on the real microstructure morphology. This multiscale framework consists of a microscale level where the electrode microstructure architecture is modeled and a macroscale level where discharge/charge is simulated. The coupling between two scales are perfor...

In order to explore the local effects of electrode microstructural inhomogeneity, a half cell Li ion battery was built with reconstructed realistic LiCoO2 cathode electrode which was divided equally into eight subdomains. A previously developed C++ code was used to simulate the discharge and charge processes using finite volume method. The geometri...

In this article, we present a fabrication method that is capable of making (3D) microfluidic devices with multiple layers of homogeneous polystyrene (PS) film. PS film was chosen as the primary device material because of its advantageous features for microfluidics applications. Thermopress is used as a bonding method because it provides sufficient...

The performance of lithium ion battery (LIB) is limited by the inner polarization and it is important to understand the factors that affect the polarization [1]. This study focuses on the polarization analysis based on realistic 3D electrode microstructures. A c++ software was developed to rebuild and mesh the microstructure of cathode and anode el...

Fast lithium ion conducting inorganic solid materials are considered superior candidates for lithium ion batteries (LIBs) to overcome flammable characteristics, leakage, and tight electrochemical window issues of organic liquid electrolytes. Besides high ion conductivities of the inorganic materials, their wide electrochemical window and good chemi...

Heat generation is a major safety concern in the design and development of lithium ion batteries (LIBs) for large scale applications, such as electric vehicles. The total heat generation in LIBs includes entropic heat, enthalpy, reaction heat, and heat of mixing (1-3). The heat of mixing will be released during relaxation of Li ion concentration gr...

In recent years, research on all-solid lithium ion batteries (LIBs) has increased considerably due to raised concerns relating to safety hazards such as the solvent leakage and flammability of liquid electrolytes used in commercial LIBs. All-solid LIBs use fast Li ion conducting solid electrolytes that do not carry the safety burdens of liquid elec...

The microstructure of electrodes plays a critical role in determining the performance of lithium ion batteries (LIBs), because the microstructure can affect the transport and electrochemical processes within electrodes (1-3). Increasing the volume fraction of active materials in the electrode will increase the energy density. However, the electrode...

Dry film photoresists (DF PRs) are widely used to perform photolithography on non-traditional substrates such as printing circuit boards, plastic sheets, or non-planar surfaces. Commercially available DF PRs are usually in a negative tone and rather thick, limiting lithographic resolution and versatility. The relatively large pressure required for...

We report the development of a microfluidic gas generator using polymer film-based microfabrication method. The method is time and cost efficient and capable of fabricating microfluidic devices with feature resolution lower than 100 µm. Complicated 3-dimensional devices can be fabricated by aligning and stacking multiple layers of patterned polymer...

This paper reports a new type of hierarchically structured surface consisting of re-entrant silicon micropillars with silicon nanowires atop for superhydrophobic surface with extremely low hysteresis. Re-entrant microstructures were fabricated on a silicon substrate through a customized one-mask microfabrication process while silicon nanopillars we...

The realistic three dimensional (3D) microstructure of lithium ion battery (LIB) electrode plays a key role in studying the effects of inhomogeneous microstructures on the performance of LIBs. However, the complexity of realistic microstructures imposes a significant computational cost on numerical simulation of large size samples. In this work, we...

Microfluidic platforms provide elegant schemes for isolation of rare cells from the blood. Hierarchical 3-dimensional architectures with silicon nanopillar forests draw advantage of unique surface interactions with target cells to aid capture and adhesion. Microchannels with numerically optimized designs of micro post arrays maximize contact freque...

A three dimensional numerical framework with finite volume method was employed to simulate heat generation of a semi lithium ion battery (LIB) cell during isothermal galvanostatic discharge processes. The microstructure of the LIB cathode electrode was experimentally determined using X-ray nano computed tomography technology. Heat generation in the...

This study focuses on preparing a hybrid electrolyte, the combination of 90 wt% inorganic solid and 10 wt% organic liquid, for lithium based rechargeable batteries to illustrate the effect of electrode/electrolyte interfacing on electrochemical performance. The inorganic solid electrolyte selected is Li1.3Ti1.7Al0.3(PO4)3, and the Li-ion conducting...

Based on the experimentally determined microstructure of a lithium ion battery (LIB) cathode electrode using X-ray nano-CT technology, a three dimensional simulation framework of galvanostatic discharge with finite volume method is presented. The tomography data were used to evaluate the homogeneity of porosity and tortuosity of the electrode. With...

Lithium ion batteries experience diffusion-induced stresses during charge and discharge processes which can cause electrode failure in the form of fracture. Previous diffusion-induced stress models and simulations are mainly based on simple active material particle structures, such as spheres and ellipsoids. However, the simple structure model cann...

This article introduces an on-demand microfluidic hydrogen generator that can be integrated with a micro-proton exchange membrane (PEM) fuel cell. The catalytic reaction, reactant circulation, gas/liquid separation, and autonomous control functionalities are all integrated into a single microfluidic device. It generates hydrated hydrogen gas from a...

Mechanical deflections of a thin sheet metal, notional multi-lobed mixer were investigated using computational fluid dynamics (CFD) and finite element structural analysis. The computational model was set up as a steady state one-way fluid structure interaction (FSI) problem. For a typical sheet metal alloy, such as Inconel 718, the analysis was per...

An ever increasing demand for packaging more energy on-board to meet the needs of power hungry microsystems is driving the miniaturization of power generators. We report a fully integrated Power MEMS, in the 10-μL size, designed to deliver high energy and power densities. On-board hydrogen production and an efficient control scheme that facilitates...

This paper introduces a micro-hydrogen generator with self-circulation and self-regulation mechanisms for delivering alkaline sodium borohydride solution without parasitic power consumption. The self-circulation of the sodium borohydride solution was achieved by using directional growth and selective venting of hydrogen bubbles in microchannels, wh...

Micro-proton exchange membrane fuel cells are considered to be the next generation power sources for micro-scale power applications, but onboard hydrogen storage and generation with high energy density at the small scale is still a technical barrier. This paper introduces a hydrogen generation method based on an onboard hydride fuel and a byproduct...

We have developed a fully integrated micro power generator, based on a hydrogen fuel cell. Key to the power generator is an on-board hydrogen production with a passive microfluidic control valve that provides self-regulating operation. Critical integration issues are identified and regimes established for efficient power generation. Preliminary res...

This paper introduces and discusses the feasibility of millimeter scale powder packed-bed reactors using high energy density chemical hydrides for micro-PEM fuel cell applications. Two different reactors were designed and tested using LiBH4, LiAlH4, NaAlH4 and CaH2 hydride fuels. The mechanisms that limit the total yield of H2 generated and impact...

Portable devices have become much more feature packed and require much more power than before. However, they have been facing a persistent problem as rechargeable battery technology hasn't kept pace with the rapid advancements. Bridging that gap may now be possible through fuel cells, a clean energy technology that produces electricity from the ele...

Micro-power sources that are comparable to or smaller than the size of the micro-devices needing power are needed for many applications. This paper introduces an integrated millimeter scale power source based on a micro-silicon fuel cell and a MEMS hydrogen generator, with passive control. The integrated devices are fabricated from silicon wafers u...

We propose a new type of micro/nano fluidic mixer based on non-equilibrium electrokinetics and demonstrate its mixing performance. We fabricate the device with two-step reactive ion etching, one for nanochannels and one for microchannels. Mixing is achieved by strong vortex structures formed near the micro/nano channel interface. We expect the prop...

We propose a new type of micro/nano fluidic mixer based on non-equilibrium electrokinetics and demonstrate its mixing capacity. We fabricate the device with two-step reactive ion etching, one for a nanochannel and one for a microchannel. Mixing is achieved by strong vortex structures formed near the micro/nano channel interface. We expect the propo...

A fully-integrated, self-regulated micro fuel cell (FC) system is reported to power implanted, under-water, or on-flight devices in anaerobic environments. Using silicon micromachining processes, we have fabricated hydrogen and oxygen generators and demonstrated their capability to automatically deliver reactants to a μFC with self-regulation. Hyd...