Generation Lithium-ion Batteries Research Articles

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.

Implication of magnetic property on the degradation process of layered Ni-rich transition metal oxide cathode for high-capacity lithium-ion batteries

Layered LiNi0.8Mn0.1Co0.1O2 (NMC811) has received considerable attention as a high-energy density cathode for next generation lithium-ion batteries (LiBs). The charge compensation process underlying the achievement of high capacity is generally described by a two-stage redox reaction between Ni2+/Ni3+ and Ni3+/Ni4+. However, the increase of the Ni for the high battery capacity often leads to a significant degradation of the NMC811 material. In this study, the magnetic property of the NMC811 battery system has been compared at low (4.3 V) and high (4.7 V) cut-off voltages. There has been a notable drop in the magnetic moment from 2.33 μB (pristine) to 2.11 μB and 2.07 μB for the cathodes cycled at 4.3 V and 4.7 V, respectively. The amount of low-spin Ni4+ increased in the cathode material after the high voltage cycling. A density-functional theory (DFT) simulation has been adopted to further understand the discrepancy in the magnetic moment upon the different voltages. The local magnetic moment () of the transition metals are evaluated with different atomic environments including the Li/Ni exchange. Also, the corresponding density of states (DOS) are provided. It is shown that the electrochemical performance will significantly deteriorate when a high antiferromagnetic interaction occurs with the Li/Ni exchange.

Octahedral FeF3·0.33H2O nanocrystalline fixed on carbon fibers as the cathode of lithium-ion battery based on the “gravel and glue” strategy

Due to its high theoretical specific capacity and low cost, iron trifluoride (FeF3) is a potential cathode material for the next generation of lithium-ion batteries. However, the problems, such as poor electronic conductivity and volume change during cycling of metal fluoride, seriously hinder its practical application. To solve these problems, the FeF3·0.33H2O nanocrystalline @ Spongy Porous Carbon @ Carbon Fiber (FF@SPC@CF) composite is prepared based on the "gravel and glue" strategy. In the composite, the octahedral FeF3·0.33H2O nanocrystals (∼100 nm) coated with oligo-graphene are first uniformly embedded in the porous spongy carbon to form a mixed "mortar", which is then firmly bonded to the kapok carbon fiber. The prepared FF@SPC@CF composite offers the initial discharge capacity of 407 mAh·g−1 and remains at 108 mAh·g−1 after 400 cycles when it was used as the cathode with the voltage in the range of 1.5–4.5 V at 0.2 C (1C=237 mAh·g−1). The capacities are much better than 256 mAh·g−1 (first discharge capacity) and 8 mAh·g−1 (400 cycles later) of pure FeF3·0.33H2O electrode. Therefore, the "gravel and glue" design strategy for the carbon-supported composite material in this study offers an effective way to improve the electrochemical performance of FeF3·0.33H2O cathode material.

Development of New Borate-Based Lithium Ionic Liquid for Next Generation Lithium-Ion Battery

Solvate ionic liquids (SILs), which consist of a solvate ion and its counter ion, are expected as the electrolyte for the new generation Lithium-ion batteries [1]. Li-glymes SIL is an equimolar mixture of lithium salts and glyme of an oligoether such as triglyme and tetraglyme (Gn: CH3O-(CH2CH2O) n -CH3, n = 3 and 4). Li-glymes SIL shows favorable liquid properties like ordinary aprotic ionic liquids; negligible vapor pressure, practically non-inflammability, ionic conductivity and electrochemical stability, and so on. Watanabe et al. [2] have proposed that the specific Li+ ion hopping conduction occurs in the Li-glymes SIL. In Lithium-ion batteries with Li-glymes SIL, the desolvated Li+ ions are intercalated into graphite electrode, however, the co-intercalation of Li+ ion and glyme into the electrode occurs in the battery using the excess glyme electrolyte solution [3]. This suggests that the solvent activity affects the electrode reaction. In the present study, we prepared lithium ionic liquids with oligoether chains (Figure 1) and measured those physical and electrochemical properties.Infrared spectroscopic (IR) measurements were carried out to identify the prepared lithium ionic liquids. An intense peak, which cannot be observed in the IR spectra of the raw materials, appears in approximately 1000 cm-1. This peak is attributable to B-O vibration mode, suggesting that the lithium ionic liquids are synthesized. We here define the new lithium ionic liquids as LiB(Gn)4 (n = 3 or 4). The ionic conductivities of LiB(G3)4 and Li(B4)4 are 0.20 and 0.37 mS cm-1, respectively. In addition, Li+ ion transport number is approximately 0.5 for both LiB(G3)4 and Li(B4)4., which is higher than that of electrolyte solution used in a commercial lithium-ion battery. This suggests that Li+ ion hopping conduction may occur via the exchange among glymes which are side chain of anion.

An Effective Mixed-Salt As Electrolyte Additive to Improve Calendar Life for Si Anode in Lithium Ion Batteries

For the next generation of Lithium-ion batteries, Silicon is drawing attention as the upcoming anode materials with higher capacity than commercial graphite ( Silicon : 3590 mA h g-1vs Graphite : 375 mA h g-1). Especially, Si is suitable for long range electric vehicle from being higher theoretical capacity. However, the chronic problem of Si anode such as large expansion with fracture or pulverization has effect on the calendar life performance. In order to achieve the enhanced calendar life, we suggest that Ca and Mg mixed additive with electrolyte for Si anode in this work, based on our previous reports. In this work, analytical techniques such as NMR and Rietveld refinement was conducted to clarify effect of mixed salt. Ca and Mg inserted to bulk Si to cause formation of quaternary Li-Ca-Mg-Si phase with thermodynamic stability, and Ca salt make dense and strong CaF2 SEI layer on the Si particle, which protect the side reaction between Si particle and electrolyte in coin cell system,. The full cell with mixed additive electrolyte (called Gen FMC) shows enhanced calendar life performance with lower measured current and current leakage than that of baseline electrolyte (called Gen F), being brought by less side reaction. In adding to that, full cell with Gen FMC could delivered high specific capacity after 100 cycles with 47.4 % of retention (Gen F : 36.3%) and high columbic efficiency. We were also able to find that Gen FMC tends to have less cracking electrode surface than that of Si electrode with Gen F.

(Invited) High Throughput Solvent-Free Manufacturing of Battery Electrodes

Research into the manufacturing of LIB electrodes is constantly evolving with new active materials, improved binders, and improved drying techniques to more efficiently produce high-quality electrodes. However, the one constant in all these endeavors is that electrode research and manufacture still generally rely on a slurry-coating process, where large amounts of potentially toxic solvents are necessary for slurry production. As such, solvent-free, also known as dry-process (DP), electrode processing has been proposed to solve the conventional lithium-ion battery electrodes fabrication disadvantages, such as high equipment costs for solvent reclamation, currently seen in industry.Currently, the solvent-free, state-of-the-art electrodes use polytetrafluoroethylene (PTFE) as a binder and the PTFE is fibrillized and dispersed in the dry powder mixture using a jet mill. One key solvent-free electrode shortcoming is that PTFE is not electrochemically stable for the anode, traditionally resulting in initial capacity losses of greater than 30% and poor mechanical strength, effectively limiting solvent-free processing to cathodes. A second shortcoming is that solvent-free electrodes generally require the addition of fibrillization promoters or processing steps that add cost and detract from performance by limiting active material content in the final electrodes.In a recent development, Navitas and its internal partners of Cabot, Arkema, the University of Tennessee, Knoxville, and Oak Ridge National Laboratory have shown the capability to produce both solvent-free anodes and cathodes utilizing an advanced dry-electrode process (ADEP) that also enables high-throughput production of next generation battery electrodes. These electrodes have improved mechanical strength, sufficient to withstand roll-to-roll manufacturing, and the anodes demonstrate an initial capacity loss of less than 15%. The group has demonstrated roll-to-roll production of solvent-free electrodes at quasi-industry standard active material compositions (90-92%) without the reliance of previously used fibrillization promoters, even at reduced PTFE concentrations in the formulation. Navitas has recently demonstrated the large format lamination of the initially formed, or “free-standing,” electrodes after they have been produced in roll-to-roll manufacturing and the integration of solvent-free electrodes in dual-layer and multi-layer pouch cells using typical industry tooling and cell production techniques.Key words: solvent-free, dry-process, fibrillization, next generation lithium-ion batteries (NGLB), advanced dry-electrode process (ADEP), initial capacity loss, free-standing, roll-to-roll, pouch cell