Generation Lithium-ion Batteries Research Articles

Review and Stress Analysis on the Lithiation Onset of Amorphous Silicon Films

This work aims to review and understand the behavior of the electrochemical lithiation onset of amorphous silicon (a-Si) films as electrochemically active material for new generation lithium-ion batteries. The article includes (i) a review on the lithiation onset of silicon films and (ii) a mechanochemical model with numerical results on the depth-resolved mechanical stress during the lithiation onset of silicon films. Recent experimental studies have revealed that the electrochemical lithiation onset of a-Si films involves the formation of a Li-poor phase (Li0.3Si alloy) and the propagation of a reaction front in the films. The literature review performed reveals peculiarities in the lithiation onset of a-Si films, such as (i) the build-up of the highest mechanical stress (up to 1.2 GPa) during lithiation, (ii) a linear increase in the mechanical stress with lithiation which mimics the characteristics of linear elastic deformation, (iii) only a minute volume increase during Li incorporation, which is lower than expected from the number of Li ions entering the silicon electrode, (iv) the largest heat generation appearing during cycling with only a minor degree of parasitic heat contribution, and (v) an unexpected enhanced brittleness. The literature review points to the important role of mechanical stresses in the formation of the Li-poor phase and the propagation of the reaction front. Consequently, a mechanochemical model consisting of two stages for the lithiation onset of a-Si film is developed. The numerical results calculated from the mechanochemical model are in good accord with the corresponding experimental data for the variations in the volumetric change with state of charge and for the moving speed of the reaction front for the lithiation of an a-Si film of 230 nm thickness under a total C-rate of C/18. An increase in the total C-rate increases the moving speed of the reaction front, and a Li-rich phase is likely formed prior to the end of the growth of the Li-poor phase at a high total C-rate. The stress-induced phase formation of the Li-poor phase likely occurs during the lithiation onset of silicon electrodes in lithium-ion battery.

Deep eutectic solvent electrolytes based on trifluoroacetamide and LiPF6 for Li-metal batteries

New generation lithium batteries require better performances, improved safety, and sustainability. Better performances can be obtained with lithium anodes and high-voltage cathodes, which in turn pose more pressure on the electrolyte stability, which is mandatory for safety. Deep Eutectic Solvents (DESs) are promising components for safer and more environmentally sustainable electrolytes. We investigate the physico-chemical properties of DESs made with 2,2,2-trifluoroacetamide (TFA) and LiPF6. The best composition is tested against Li metal and two cathode active materials: LiFePO4 (LFP) and high voltage LiNi1-x-yMnxCoyO2 (NMC). We obtain good electrochemical performance in a Li-metal cell with LFP. Accelerated rate calorimetry shows improved thermal stability of the Li|DES|NMC cell with respect to a commercial liquid electrolyte.

Limiting Factors Affecting the Ionic Conductivities of LATP/Polymer Hybrid Electrolytes

All-Solid-State Lithium Batteries (ASSLB) are promising candidates for next generation lithium battery systems due to their increased safety, stability, and energy density. Ceramic and solid composite electrolytes (SCE), which consist of dispersed ceramic particles within a polymeric host, are among the preferred technologies for use as electrolytes in ASSLB systems. Synergetic effects between ceramic and polymer electrolyte components are usually reported in SCE. Herein, we report a case study on the lithium conductivity of ceramic and SCE comprised of Li1.4Al0.4Ti1.6(PO4)3 (LATP), a NASICON-type ceramic. An evaluation of the impact of the processing and sintering of the ceramic on the conductive properties of the electrolyte is addressed. The study is then extended to Poly(Ethylene) Oxide (PEO)-LATP SCE. The presence of the ceramic particles conferred limited benefits to the SCE. These findings somewhat contradict commonly held assumptions on the role of ceramic additives in SCE.

Grid-like Fe3O4 nanocrystals enhance the performances of glass-ceramic anodes for lithium-ion batteries

Glasses hold great promise as high-energy anode materials in next generation lithium-ion batteries (LIBs). However, the electrochemical performances of the glass anodes still need to be greatly enhanced to meet the requirement for developing high energy density LIBs. Here we show that grid-like Fe3O4 nanocrystals enable a substantial enhancement of the electrochemical performances of iron borate glass ceramic anode for LIBs. We find that both Fe2O3 and Fe3O4 crystals precipitate in the glass matrix during melt-quenching if Fe2O3 content exceeds about 20 mol%. The ferrous/ferric ion ratio increases with Fe2O3 content, and thereby significantly raises the electronic conductivity of the Fe2O3-B2O3 glass-ceramics. The 90Fe2O3–10B2O3 anode exhibits the reversible capacity of ∼ 505 mA h g−1 at 1 A g−1 after 1000 cycles. The unique architecture of this anode, which involves grid-like arrangement of Fe3O4 nanocrystals in glass phase, provides more active sites for storing Li+ ions, and enhances Li+ ions transfer kinetics. This architecture prevents the propagation of microcracks in anode during lithiation/delithiation and thereby enhances the cycling stability.

Voltage-dependent formation of cathode–electrolyte interphase with independent metallic layer in LiNi0.8Mn0.1Co0.1O2 cathode for high-energy density lithium-ion batteries

Layered LiNi0.8Mn0.1Co0.1O2 (NMC811) has emerged as the promising cathode material for next generation lithium-ion batteries owing to its high capacity. The double redox reaction between Ni2+/Ni3+ and Ni3+/Ni4+ is the major source of the large capacity, but it often leads to the formation of an unstable cathode–electrolyte interphase (CEI) layer. Herein, the correct nature of the CEI layer for the NMC811 battery has been studied with a particular attention to the voltage dependency (4.3 V vs. 4.7 V). A CEI metallic layer consisting of transition metal (TM) composites (i.e. 54.9MnOx, 54.9MnF3, 58.7NiO, 58.7NiF3, 58.9CoOx, and 58.9CoF3) has been long considered as a part of inorganic layer. However, the present study found that the metallic layer can be present as an independent CEI layer depending on the cut-off voltages. To further understand the nature of the CEI formation with the cathode material, a density-functional theory was conducted. The Fermi level with respect to the redox couples of the TMs/oxygen orbitals and their covalency not only affect the cathode stability but also modulate the CEI property. It is also proposed that the covalency of TM(3d)-O(2p) is the key factor that determines the localization of the TM metallic layer.

Silicon/Graphite/Amorphous Carbon as Anode Materials for Lithium Secondary Batteries.

Although silicon is being researched as one of the most promising anode materials for future generation lithium-ion batteries owing to its greater theoretical capacity (3579 mAh g-1), its practical applicability is hampered by its worse rate properties and poor cycle performance. Herein, a silicon/graphite/amorphous carbon (Si/G/C) anode composite material has been successfully prepared by a facile spray-drying method followed by heating treatment, exhibiting excellent electrochemical performance compared with silicon/amorphous carbon (Si/C) in lithium-ion batteries. At 0.1 A g-1, the Si/G/C sample exhibits a high initial discharge capacity of 1886 mAh g-1, with a high initial coulombic efficiency of 90.18%, the composite can still deliver a high initial charge capacity of 800 mAh g-1 at 2 A g-1, and shows a superior cyclic and rate performance compared to the Si/C anode sample. This work provides a facile approach to synthesize Si/G/C composite for lithium-ion batteries and has proven that graphite replacing amorphous carbon can effectively improve the electrochemical performance, even using low-performance micrometer silicon and large size flake graphite.

Insight into the effect of fracture surfaces in graphdiyne on the anode performance for lithium ion batteries.

Two-dimensional (2D) materials are promising anode materials for the next generation of lithium ion batteries. While the Li storage and kinetics at the surface and intercalation sites of 2D materials are widely explored, the effects of the fracture surfaces (FSs) are rarely considered despite the fact that there are numerous FSs in real 2D materials. Herein, we investigate how the FSs in graphdiyne (GDY) affect the anode performance based on first-principles calculations. Results show that both the internal and external FSs have much lower binding energies to Li atoms than perfect GDY, meaning FSs are more active in storing Li atoms. Then, the diffusion barriers of Li atoms on the internal and external FSs are only 0.42 and 0.47 eV, respectively, close to the 0.315 eV of surface sites and lower than the 0.638 eV of intercalation sites, indicating a good kinetics of Li atoms. In addition, due to the new electronic states from the C atoms with dangling bonds, the FSs convert the semiconductor characteristics of perfect GDY to metallic ones, which is helpful to the electronic conductivity. Our work demonstrates that the FSs in 2D materials are beneficial to the anode performance, which may enlighten the design of anode materials.

Synthesis of Cobalt-Free, Low-Cost Layered LiNi0.6Mn0.2Fe0.2O2 (NMF622) Cathode Electrodes for Next Generation Lithium-Ion Batteries

Synthesis of Cobalt-Free, Low-Cost Layered LiNi0.6Mn0.2Fe0.2O2 (NMF622) Cathode Electrodes for Next Generation Lithium-Ion Batteries

Thermally expanded graphite: a promising anode electrode in the current and next-generation LIBs

The interesting properties of thermally expanded graphite make it an ideal candidate for application as the anode electrode in conventional and next generation lithium-ion batteries.

Molecular dynamic study of the applicability of silicene lithium ion battery anodes: A review

Lithium-ion batteries (LIBs) are the main energy storage devices that have found wide application in the electrical, electronics, automotive and even aerospace industries. In practical applications, silicene has been put forward as an active anode material for LIBs. This is facilitated by its high theoretical capacitance, strength, and small volume change during lithiation. Thin-film materials containing two-layer silicene and intended for use in the LIB anode have been studied by the method of classical molecular dynamics. Among the important characteristics obtained is the fillability of the silicene anode (under the influence of an electric field), which was determined depending on the type of vacancy defects in silicene and the type of substrate used. Both metallic (Ag, Ni, Cu, Al) and non-metallic (graphite, silicon carbide) substrates are considered. The behavior of the self-diffusion coefficient of intercalated lithium atoms in a silicene channel as it is filled has been studied. Based on the construction of Voronoi polyhedra, the packing of lithium atoms and the state of the walls in the channel has been studied in detail. The change in the shape of silicene sheets, as well as the stresses in them caused by lithium intercalation, are analyzed. It has been established that two-layer silicene with monovacancies on a nickel substrate is the most optimum variant of the anode material. The results of this work may be useful in the development of new anode materials for new generation LIBs.

A ternary MOF derived single crystalline LiNi1/3Mn1/3Co1/3O2 as high-voltage cathodes for lithium-ion batteries

Single-crystal NCMs show properties of good cyclability and high safety, and considers as promising cathode materials for next generation lithium batteries. But industrial production of single-crystal NCMs should overcome problems of lengthy production steps, high production costs and poor consistency. In this work, a Ni-Co-Mn ternary MOF has been developed for NCM cathode materials preparation. The MOF derived precursors show high activity and can be used to prepare single-crystal NCM111 (SC-NCM) in a regular sintering process. As-prepared SC-NCM cathode materials show an average particle size of 400 nm, reveal a polyhedral structure with smooth surface, and can be applied as a high-voltage cathode with excellent cyclability and high specific capacities. Specifically, it is delivery a high discharge capacity of 172 mAh g−1 and maintains 156 mAh g−1 after 50 cycles in a large potential range of 2.8–4.6 V at a high current of 1 C; it also reveals a good capacity retention of 88.3 % after 600 cycles. The enhanced electrochemical performance can be attributed to the SC-NCM reveals a good microstructural stability, which prevents the unexpected structural degradation and microcrack generation during battery cycling. This work provides a new method to synthesis the high-quality single-crystal NCM materials with good electrochemical performance.

A holistic review on the synthesis techniques of spinel structured lithium cobalt manganese tetroxide

Spinel structured lithium cobalt manganese tetroxide (LiCoMnO4) which exhibit unrivalled reduction potential of 5.3V (vs. Li0 | Li+) was identified to be one of the potential cathode candidates for next generation lithium-ion batteries offering high voltage output and energy density. The focal point of this article is to holistically review relevant techniques established for the synthesis of LiCoMnO4 compound, particularly solid-state reaction, sol-gel synthesis, flux method and hydrothermal technology. Electrochemical performances of lithium cobalt manganese tetroxide (LiCoMnO4) synthesised via the four distinctive approaches as well as the critical process parameters will be compared and scrutinised. Adversities associated with deoxygenation in the course of synthesis process at high temperature and proposed countermeasure via fluorine-substitution will also be discussed.

A Lignin-Based Carbon Anode with Long-Cycle Stability for Li-Ion Batteries.

Due to its wide source and low cost, biomass-based hard carbon is considered a valuable anode for lithium-ion batteries (LIBs). Lignins, as the second most abundant source in nature, are being intensively studied as candidate anode materials for next generation LIBs. However, direct carbonization of pure lignin usually leads to low specific surface area and porosity. In this paper, we design a porous carbon material from natural lignin assisted by sacrificing a metal-organic framework (MOF) as the template. The MOF nanoparticles can disperse the lignin particles uniformly and form abundant mesopores in the composites to offer fast transfer channels for Li+. The as-prepared carbon anode shows a high specific capacity of 420 mAh g-1 with the capacity retention of 99% after 300 cycles at 0.2 A g-1. Additionally, it keeps the capacity retention of 85% after long cycle of 1000 cycles, indicating the good application value of the designed anode in LIBs. The work provides a renewable and low-cost candidate anode and a feasible design strategy of the anode materials for LIBs.

Development and Application of a Poly(acrylic acid)-Grafted Styrene–Butadiene Rubber as a Binder System for Silicon-Graphite Anodes in Li-Ion Batteries

Silicon anodes require polymer binder systems that are both mechanically robust and electrochemically stable, to accommodate the dramatic volume expansion experienced during cycling operation. Herein, we report the use of a poly(acrylic acid)-grafted styrene–butadiene rubber (PAA-g-SBR) with 80% partially neutralized Na-PAA as the binder system for silicon-graphite anodes. The PAA-g-SBR graft copolymer was synthesized by grafting tert-butyl acrylate onto SBR and treating the intermediate with H3PO4. The PAA-g-SBR/Na-PAA binder system was found to provide superior electrochemical performances to that of a Na-PAA/SBR system. The Na-PAA/PAA-g-SBR system had a stable capacity retention of 673 mAh g–1 for 130 cycles, while the capacity retention of the Na-PAA/SBR system was found to decline immediately. The Na-PAA/PAA-g-SBR system also displayed more preferable mechanical properties, with a lower Young’s modulus value and a larger strain at failure compared to that of the Na-PAA/SBR system. Overall, these findings indicate a promising and robust polymer binder system for the application of silicon anodes in the next generation of lithium-ion batteries.

Hierarchical micro–nano hydrangea–like NiCo2O4/V2O3 free–standing anode for high–performance lithium–ion batteries

As one of binary transition metal oxides, NiCo2O4 (NCO) suffers from several problems like self–agglomeration and drastic volume change when used as an anode for lithium–ion batteries (LIBs). Herein, we propose a facile one–step hydrothermal method combined with heat treatment to prepare a hierarchical micro–nano hydrangea–like NiCo2O4/V2O3 composite array (denoted as NCO/VO) on a nickel foam substrate as a free–standing anode for LIBs. The V2O3 is introduced to form a composite structure with NCO, improving the electronic and ionic conductivity of the electrode. The synergistic effect of porosity, composite structure and micro–nano architecture offers the electrode excellent electrochemical performance. The specific capacity of the as–prepared electrode is 1155.6 mA h g−1 after 200 cycles under the current density of 100 mA g−1, with a retention ratio of 91.02 %. When the current density rises to 1000 mA g−1, it delivers a specific capacity of 750 mA h g−1, showing excellent rate performance. This work demonstrates that NCO/VO–NF is a promising candidate anode for next–generation LIBs.

Preparation and performances of gallium-doped LLZO electrolyte with high ionic conductivity by rapid ultra-high-temperature sintering

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) for next generation lithium batteries due to its high Li+ conductivity and stability against lithium metal, especially the Li7−3xGaxLa3Zr2O12 (Ga-LLZO) is most valuable because of its high ionic conductivity (> 1 ×10−3 S cm−1). However, it is difficult to prepare high-quality Ga-LLZO by the traditional air ambient sintering. Herein, we develop a simple and efficient rapid ultra-high-temperature sintering (RUHTS) method to prepare high-conductivity Ga-LLZO ceramic SSE. It has been found that the as-prepared Ga-LLZO ceramic SSE with the composition of Li6.25Ga0.25La3Zr2O12 exhibits high relative density of 99%, good ionic conductivity of 1.48 × 10−3 S cm−1 and large critical current density of 0.5 mA cm−2 after sintering at 1200 °C for 2 min. In addition, the Ga-LLZO SSE shows good electrochemical stability and interfacial compatibility against Li metal. The assembled Li-Li symmetric cell represents a small interfacial impedance of 37 Ω cm2. In the same time, the Li/Ga-LLZO/LE+LMNCO full battery has a total impedance of 205 Ω cm2, and can deliver a first discharge capacity of 235.1 mAh g−1 at 0.5 C, and the capacity retention rate is 88.3% after 100 cycles. This indicates that the as-prepared Ga-LLZO has good application prospect in the Li-metal solid-state batteries (LMSSBs). Moreover, this method does not require the use of mother powder during preparation process, which will effectively reduce the waste of raw materials, save manufacture costs and be beneficial to quantity production of Ga-LLZO ceramic electrolyte.

Understanding the failure mechanism towards developing high-voltage single-crystal Ni-rich Co-free cathodes

Benefited from its high process feasibility and controllable costs, binary-metal layered structured LiNi0.8Mn0.2O2 (NM) can effectively alleviate the cobalt supply crisis under the surge of global electric vehicles (EVs) sales, which is considered as the most promising next-generation cathode material for lithium-ion batteries (LIBs). However, the lack of deep understanding on the failure mechanism of NM has seriously hindered its application, especially under the harsh condition of high-voltage without sacrifices of reversible capacity. Herein, single-crystal LiNi0.8Mn0.2O2 is selected and compared with traditional LiNi0.8Co0.1Mn0.1O2 (NCM), mainly focusing on the failure mechanism of Co-free cathode and illuminating the significant effect of Co element on the Li/Ni antisite defect and dynamic characteristic. Specifically, the presence of high Li/Ni antisite defect in NM cathode easily results in the extremely dramatic H2/H3 phase transition, which exacerbates the distortion of the lattice, mechanical strain changes and exhibits poor electrochemical performance, especially under the high cutoff voltage. Furthermore, the reaction kinetic of NM is impaired due to the absence of Co element, especially at the single-crystal architecture. Whereas, the negative influence of Li/Ni antisite defect is controllable at low current densities, owing to the attenuated polarization. Notably, Co-free NM can exhibit better safety performance than that of NCM cathode. These findings are beneficial for understanding the fundamental reaction mechanism of single-crystal Ni-rich Co-free cathode materials, providing new insights and great encouragements to design and develop the next generation of LIBs with low-cost and high-safety performances.

Ether-/Ester-/Fluorine-Rich Binding Emulsion Formula for Lithium-Ion Batteries

Practical application of a Si anode in a high-energy-density battery cannot be achieved due to the huge volume expansion of these anodes. Researchers have focused on binders of the anode to restrict volume expansion in order to address this issue, as the hydrogen bonds and mechanical properties of binders can be used to enhance adhesion and accommodate the volume changes of a Si anode. Herein, we comprehensively consider binders’ hydrogen bonds, mechanical properties, stability, and compatibility with the electrolyte solution, and design an ether-/ester-/fluorine-rich composite polymer, P(TFEMA-co-IBVE). The proposed binder formula possesses outstanding stability, adhesion, and mechanical strength; moreover, it can accommodate the dramatic volume changes of a Si electrode and exhibits excellent electrochemical performance, achieving a high areal capacity of about 5.4 mA∙h∙cm−2. This novel polymer design may be applied to other electrode materials in the next generation of lithium-ion batteries.

A synergetic modification approach toward high capacity Ni-rich cathode materials for next generation lithium-ion batteries

High discharge capacity and low cost of Ni-rich cathode materials make them an ideal candidate for energy storage applications. Here, we report a novel synergetic approach to modify the LiNi0.91Co0.06Mn0.03O2 cathode active material by Li+ conductive Li3BO3 coating and B3+ doping. The crystal structure of synthesized materials is analyzed by XRD and the surface by XPS, FESEM and FETEM. In rate performance test, Li+ conductive coating on modified NCM (LBO-0.05) conduces a superior discharge capacity of 88.6 mAh g−1 at 5C while pristine delivers only 45.8 mAh g−1. LBO-0.05 NCM exhibited the highest initial columbic efficiency (92%) and discharge capacity (215.3 mAh g−1) than the pristine sample (90.7%, 212.6 mAh g−1). At 2C cycling, LBO-0.05 demonstrates improved capacity retention of 79.4% as compared to pristine which shows only 67.3% after 100 cycles. The enhanced electrochemical performance of modified NCM is attributed to multifunctional Li3BO3 coating and B3+ doping.

Coal-Based Semicoke-Derived Carbon Anode Materials with Tunable Microcrystalline Structure for Fast Lithium-Ion Storage.

Fast charging capability is highly desired for new generation lithium-ion batteries used in consumer-grade electronic devices and electric vehicles. However, currently used anodes suffer from sluggish ion kinetics due to limited interlayer distance. Herein, the coal-based semicoke was chosen as precursor to prepare cost-effective carbon anodes with high-rate performance through a facile pyrolytic strategy. The evolution of microstructure and its effect on electrochemical performance are entirely studied. The results show that large number of short-ordered defective structures are generated due to the occurrence of turbostatic-like structures when pyrolyzed at 900 °C, which are propitious to large interlayer distance and developed porous structure. High accessible surface area and large interlayer spacing with short-ordered defective domains endow the sample treated at 900 °C under argon (A900) with accelerated ion dynamics and enhanced ion adsorption dominated surface-induced capacitive processes. As a result, A900 delivers high capacity (331.1 mAh g-1 at 0.1 A g-1) and long life expectancy (94.8% after 1000 cycles at 1 A g-1) as well as good rate capability (153.2 mAh g-1 at 5 A g-1). This work opens a scalable avenue to fabricating cost-effective, high-rate, and long cycling life carbon anodes.