Energy Density Lithium Research Articles

Preparation and Characterization of High-Voltage Cathode Material LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> for Lithium Ion Batteries

High energy density and rechargeable lithium ion batteries are attracting widely interest in renewable energy fields. The preparation of the high performance materials for electrodes has been regarded as the most challenging and innovative aspect. By utilizing a facile combustion synthesis method, pure nanostructure LiNi0.5Mn1.5O4 cathode material for lithium ion batteries were successfully fabricated. The crystal phase of the samples were characterized by X-Ray Diffraction, and micro-morphology as well as electrochemistry properties were also evaluated using FE-SEM, electrochemical charge-discharge test. The result shows the fabricated LiNi0.5Mn1.5O4 cathode materials had outstanding crystallinity and near-spherical morphologies. That obtained LiNi0.5Mn1.5O4 samples delivered an initial discharge capacity of 137.2 mAhg-1 at the 0.1 C together with excellent cycling stability and rate capability as positive electrodes in a lithium cell. The superior electrochemical performance of the as-prepared samples are owing to nanostructure particles possessing the shorter diffusion path for Li+ transport, and the nanostructure lead to large contact area to effectively improve the charge/discharge properties and the rate property. It is demonstrated that the as-prepared nanostructure LiNi0.5Mn1.5O4 samples have potential as cathode materials of lithium-ion battery for future new energy vehicles.

(Invited) Multiscale Stress-Transport-Kinetics Continuum Models for Lithium-Metal Batteries-Relevance of Richard Alkire’s Electrodeposition Legacy for Next-Generation Batteries

Multiscale is a term commonly used/abused in the literature. First, we will quantify the meaning of ‘multiscale’ models. Richard Alkire’s selected contributions in the field of electrodeposition – Multiscale models (continuum + KMC) and finite element methods for shape changes will be reviewed. The relevance of the same for the current hot-topic in the field of lithium-metal batteries – modeling, simulating and controlling the dendrite formation in lithium-metal batteries will be discussed. There is significant interest in using pressure as an external control to achieve proper cyclability and desirable deposition characteristics in high energy-density lithium metal anodes. We aim to provide useful predictions of cell-level variables by using a multiscale approach in which local electrochemical effects of pressure and mechanical coupling in the anode are coupled with macro homogeneous models of porous cathodes to study the effect of pressure on voltage response. Progress made in multiscale models coupling stress, transport and kinetic models at different length scales and our perspectives will be presented. Our interest lies in efficient (ideally real-time) simulation of the coupled models. Acknowledgements The authors would like to thank for the financial support of this work by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the DOE through the Advanced Battery Material Research (BMR) Program (Battery500 consortium) and the Clean Energy Institute (CEI) at the University of Washington and the Washington Research Foundation (WRF) for their partial monetary support during this work.

Submicro-sized porous SiO2/C and SiO2/C/graphene spheres for lithium ion batteries

In order to improve electrochemical performance of inert SiO2 anode for lithium ion batteries, submicro-sized porous SiO2/C and SiO2/C/graphene spheres with the same SiO2 content (43 wt.%) have been synthesized through a simple suspension nebulization and spray pyrolysis method followed by carbonization, where the components of the spheres are mixed uniformly. The addition of graphene results in mesoporous structure of the SiO2/C/graphene spheres. The electrochemical performances of the porous SiO2/C and SiO2/C/graphene spheres have been evaluated, which indicate that the SiO2/C/graphene spheres exhibits much higher cyclic capacity and stability than SiO2/C with reversible capacity retention of 97% over 100 cycles. The graphene additives display very strong effects in reducing charge transfer resistance and improving structural stability of the porous spheres simultaneously. The mesoporous SiO2/C/graphene spheres are promising anode candidate for high energy-density lithium ion batteries.

Bulk and Surface Modifications in High Ni Cathode Materials

High energy-density lithium ion batteries (LIBs) are in demand for portable electronic devices and electrical vehicles. Since the energy density of these batteries relies heavily on the cathode material, a great deal of attention is being focused on developing alternative materials with a higher degree of Li utilization and specific energy density [1]. In particular, layered Ni-rich oxides can deliver higher capacities at lower cost than the conventional LiCoO2(LCO). However, there are still several problems associated with their cycle life, thermal stability, and safety, which need to be solved [2]. In addition, these drawbacks increase with increasing Ni amount, and motivate major research efforts to understand, mitigate and overcome these effects. In stoichiometric layered lithium metal oxides, every vacant tetrahedral site is coordinated by either 3 lithium ions and 1 transition-metal (TM) ion, or 1 lithium ion and 3 TM ions. Effectively, only in the first case at least two Li sites are connected and can therefore sustain lithium migration. Hence, for each Li diffusion channel in the layered structure, exactly one gate site is a TM site, while the second one is a lithium site [3]. The barrier for lithium migration through such a 1-TM channel is correlated to the TM valence and the areal lithium-TM separation. The latter varies with the width of the Li layer (the distance between TM-O slabs), constraining the degree of local relaxation for the TM when lithium enters the activated state [4]. Nevertheless, the Li slab distance highly varies during discharge-charge processes and leads to cell volume fluctuation which is considered a potential source of electrode degradation, as it could favor the formation of microcracks [5]. Moreover, this fluctuation increases with increasing Ni amount. One promising approach to control the Li slab distance in high Ni materials is anionic substitution [6]. In this work, the effect of N and F dopants is evaluated and a correlation between structural parameters and electrochemical performance was established. Moreover, the effect of N and F can be restricted to the materials surface. The stabilization of surfaces in high Ni materials is a fundamental challenge in order to control the aging processes of these materials.

Ultrafine Si/C–graphite composite anode materials with improved cyclic performance

Si is of great interest as anode candidate for high energy-density lithium ion batteries. However, the rapid capacity fading and low first-cycle coulombic efficiency strongly hinder its applications. Ultrafine Si/C nanoparticles mixed graphite powders as composite anode materials have been synthesized through magnesiothermic reduction of ultrafine SiO2/C, and then mixed with graphite. Electron microscopy investigation indicates that the ultrafine Si/C particles with size ca. 10nm are attached on the graphite surface. Electrochemical evaluation demonstrates that the cyclic performance of the ultrafine Si/C-graphite composite materials has been improved compared with Si and Si/C, in which the reversible capacity can reach 662.4mAhg−1 with the first-cycle coulombic efficiency as high as 90.9%. Meanwhile, the capacity retention can reach 90.8% over 100 cycles. These ultrafine Si/C-graphite composite materials are promising anode candidate with combined electrochemical properties to meet multiple requirements of high energy-density lithium ion batteries.

Enhanced electrochemical performance of Ti-doped Li1.2Mn0.54Co0.13Ni0.13O2 for lithium-ion batteries

Lithium-rich manganese-based layer-structured oxides (xLi2MnO3⋅(1-x)LiNi1/3Co1/3Mn1/3O2) have attracted great attention for their potential applications as cathode materials of high energy-density lithium ion batteries. However, these oxides suffer from inferior cycling and poor rate capability due to presence of the Li2MnO3 phase. Herein, the Li+ ions in the Li-layer of the Li1.2Mn0.54Co0.13Ni0.13O2 (or 0.5Li2MnO3⋅0.5LiNi1/3Co1/3Mn1/3O2) are partially substituted with aliovalent Ti4+ ions to improve its long-term cycling stability and rate performance. The obtained oxide (Li1.2-xTixMn0.54Co0.13Ni0.13O2, x = 2.5%) exhibits an initial capacity of 320 mAh g−1 and a capacity retention of 71% after 300 cycles as well as good rate performance. In addition, although Ti doping cannot prevent the transformation from the layered to the spinel-like phase, it stabilizes the structure of the spinel-like phase below 3.0 V. Based on first-principles calculations and performance evaluation, these improvements are attributed to the Ti-doping induced enhancement in conductivity, diffusion, activation energy of Mn migration and TiO bonding. This novel design may furthermore open a door for the synthesis of lithium-rich materials with high rate performance.

ChemInform Abstract: Recent Advances in Composite Membranes Modified with Inorganic Nanoparticles for High‐Performance Lithium Ion Batteries

AbstractReview: 124 refs.

Density functional theory screening of gas-treatment strategies for stabilization of high energy-density lithium metal anodes

To explore the potential of molecular gas treatment of freshly cut lithium foils in non-electrolyte-based passivation of high-energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of molecular gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated.The simulations suggest that exposure to different molecular gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages ≤1 mono-layer. The substantial Li → adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.

Molybdenum substitution for improving the charge compensation and activity of Li2MnO3.

Lithium-rich layer-structured oxides xLi2 MnO3 ⋅ (1-x)LiMO2 (0<x<1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy-density lithium ion batteries. However, the characteristic charge compensation contributed by O(2-) in Li2 MnO3 leads to the evolution of oxygen during the initial Li(+) ion extraction at high voltage and voltage fading in subsequent cycling, resulting in a safety hazard and poor cycling performance of the battery. Molybdenum substitution was performed in this work to provide another electron donor and to enhance the electrochemical activity of Li2 MnO3 -based cathode materials. X-ray diffraction and adsorption studies indicated that Mo(5+) substitution expands the unit cell in the crystal lattice and weakens the LiO and MnO bonds, as well as enhancing the activity of Li2 MnO3 by lowering its delithiation potential and suppressing the release of oxygen. In addition, the chemical environment of O(2-) ions in molybdenum-substituted Li2 MnO3 is more reversible than in the unsubstituted sample during cycling. Therefore molybdenum substitution is expected to improve the performances of the Li2 MnO3 -based lithium-rich cathode materials.

Lithium Batteries in the Afterlife

Engineering![Figure][1] CREDIT: CAGAN/ISTOCKPHOTO We are accustomed to collecting single-use batteries for recycling, but what about rechargeable lithium batteries in consumer electronic products? Many of these products are disposed of in the normal rubbish with the batteries still inside. The harmful nature of this e-waste has been recognized, but previous studies have focused on the impacts of the electronic products—such as cellphones—themselves, rather than the batteries contained in them. Kang et al. have performed leaching tests and applied life-cycle impact and hazard assessment models to determine the environmental impacts and human toxicity potentials of lithium-ion batteries used in cell phones. They analyzed 16 batteries from cell phones sent for recycling, representing the three types of lithium battery that are most abundant in e-waste: lithium-ion and lithium-polymer from traditional phones and small, high–energy-density lithium batteries from smartphones. The authors show that these batteries contain several metals, including lead and cobalt, that can leach out under simulated landfill conditions at concentrations exceeding U.S. federal and state regulations. They call for regulatory efforts to increase recycling and reuse of rechargeable batteries and to reduce the levels of toxic metals in these batteries and in consumer electronics as a whole. Environ. Sci. Technol. 47 , 10.1021/es400614y (2013). [1]: pending:yes

Preparation and characterization of flake graphite/silicon/carbon spherical composite as anode materials for lithium-ion batteries

Using nano-Si, glucose and flake graphite of ∼0.5μm as raw materials, flake graphite/silicon/carbon composite is successfully synthesized via spray drying and subsequent pyrolysis. The samples are characterized by XRD, SEM, TEM and electrochemical measurements. The composite is composed of flake graphite, nano-Si and amorphous glucose-pyrolyzed carbon and presents good spherical appearance. Some micron pores arising from the decomposition of glucose exist on the surface of the composite particles. The composite has a high reversible capacity of 602.7mAh/g with an initial coulombic efficiency of 69.71%, and shows nearly the same cycleability as the commercial graphite in 20 cycles. Both the glucose-pyrolyzed carbon and the micron pores play important roles in improving the cycleability of the composite. The flake graphite/silicon/carbon composite electrode is a potential alternative to graphite for high energy-density lithium ion batteries.

Fe3O4[sbnd]C open hollow sphere assembled by nanocrystals and its application in lithium ion battery

This article reports a solvothermal method to fabricate sub-micrometer hematite α-Fe2O3 hollow sphere, and Fe3O4C sphere is obtained with further carbothermal reduction process. The key trick of the solvothermal method is to use crystal water of the raw material Fe(NO3)3·9H2O as the water phase in the water/oil “micro-reactor” system. Interestingly, one hole is found on the surface of almost each α-Fe2O3/Fe3O4 hollow sphere. The obtained material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmer–Teller analysis, elemental analysis and its electrochemical properties are also studied. This Fe3O4C composite material shows a high reversible capacity of 917.3mAhg−1 at 90mAg−1, 849.3mAhg−1 at 900mAg−1, and can be employed as excellent anode material for high energy-density lithium ion battery.

A novel carbon–silicon composite nanofiber prepared via electrospinning as anode material for high energy-density lithium ion batteries

Electrospun carbon–silicon composite nanofiber is employed as anode material for lithium ion batteries. The morphology of composite nanofiber is optimized on the C/Si ratio to make sure well distribution of silicon particles in carbon matrix. The C/Si (77/23, w/w) nanofiber exhibits large reversible capacity up to 1240 mAh g −1 and excellent capacity retention. Ex situ scanning electron microscopy is also conducted to study the morphology change during discharge/charge cycle, and the result reveals that fibrous morphology can effectively prevent the electrode from mechanical failure due to the large volume expansion during lithium insertion in silicon. AC impedance spectroscopy reveals the possible reason of unsatisfactory rate capability of the nanofiber. These results indicate that this novel C/Si composite nanofiber may has some limitations on high power lithium ion batteries, but it can be a very attractive potential anode material for high energy-density lithium-ion batteries.