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Thick and dense graphite anodes used in lithium‐ion batteries (LIBs) suffer from sluggish reaction kinetics at the electrode level, causing Li metal plating on their surfaces and significant capacity decay at high charging currents. Thus, it is crucial to tailor electrodes based on a comprehensive understanding of the complex reaction kinetics to realize fast‐charging LIBs. A multi‐interface strategy is proposed for electrode tailoring using Al2O3 nanoparticles to enhance fast‐charging capability while suppressing Li metal plating. Molecular dynamics simulations suggest that the incorporated Al2O3 nanoparticles perturb the charge and molecule distributions in the boundary layer, forming an "interfacial highway" for facile Li+ transport at the Al2O3/electrolyte interface. This pushes Li+ deeper into the electrode and homogenizes the Li+ flux across the electrode's top surface. A full cell assembled with the Al2O3‐decorated graphite electrode (areal capacity of 4.4 mAh cm−2) exhibits excellent cyclability with a capacity retention of 83.4% over 500 cycles even at a 2C rate without any noticeable signal for undesirable Li plating. The role of interfacial highways predicted by theoretical computations is further validated using a pouch‐type full cell (500 mAh). These findings provide insights into the interfacial and microstructural design of high‐capacity graphite electrodes for fast‐charging, long‐cycling LIBs. [ABSTRACT FROM AUTHOR]

Summary: Silicon suboxides (SiOx) are considered potential anode materials for high‐energy lithium‐ion batteries (LIBs) owing to their high specific capacity and stable cycling performance. Several structural parameters, such as chemical composition, particle size, surface area, and crystallinity, affect the electrochemical performance of SiOx. In particular, the crystallinity of the Si embedded in the SiO2 matrix significantly influences the electrochemical performance of SiOx, as it directly affects the structural stability of Si during cycling. To optimize the high‐performance synthesis of SiOx, we conduct a comparative study of the heat absorbents (KCl and NaCl) to demonstrate their critical role in determining the crystallinity of SiOx particles during the magnesiothermic reduction of SiO. The different heat capacities of these absorbents induced distinctive structural evolutions of SiO during the process, affecting the electrochemical behavior of SiOx during cycling. When KCl was present, the resulted substance has a lower crystallinity of Si, thereby offering superior electrochemical performance compared to that in the presence of NaCl. KCl‐SiOx exhibited a high reversible capacity of 1862 mAh g−1 and an initial Coulomb efficiency (ICE) of 83.0%. Moreover, a stable cycle performance of up to 200 cycles and high capacity retention of up to 89.1% at a current density of 750 mA g−1 could be achieved. Therefore, we believe that the results obtained herein will provide a basis for the development of high‐performance SiOx anode materials for commercial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defect in graphene-silicon(d-Gr/Si) composites enhances electrochemical performance. • Li adsorption energies in the d-Gr/Si were less than -0.6 eV and 0.25 eV at pristine Gr/Si. • Defected Gr/Si is more thermionically stable than pristine Gr/Si. • Charge transfer on defects improves electrical conduction and mechanical strength at interfaces. • Our analyses elucidate that defect engineering enhances Li capacity and mechanical strength. Carbon-coated silicon materials are considered as promising anode materials in high-capacity lithium-ion batteries (LIBs). Theoretically, using graphene as the anode material in the LIB would afford high electrical conductivity, mechanical stability of Si, and suppression of the unstable solid–electrolyte interface. However, its usage is hindered by its electrochemical characteristic, which is not electrochemically active when combined with lithium. Therefore, research on graphene as the anode and coated material in LIBs has been conducted using defect engineering to enhance the storage capacity of graphene. Although the electrochemical characteristics of various defects in graphene have been studied experimentally and theoretically, graphene-based composite anode materials such as graphene–silicon composite electrodes have rarely been studied from the electrochemical and mechanical perspectives. In this study, lithium adsorptions are conducted on various defected graphene and graphene–silicon composites using density functional theory calculation. The formation energies of Li on the various defected graphene are assessed, and the mechanical strengths of the graphene–silicon composites are analyzed. Our calculations validate that the defects in graphene enhance the electrochemical adsorptions and interfacial mechanical strengths of the graphene and graphene–silicon composites. During lithiation, the defects mediate greater interfacial adhesion of the silicon–graphene composite. Hence, we elucidate that defected graphene increases the electro-chemo mechanical stabilities of silicon composites in high-capacity LIBs. [ABSTRACT FROM AUTHOR]

Transition metal oxides have attracted considerable interest as promising anode materials for lithium-ion batteries (LIBs) due to their high energy densities. It is necessary, however, to resolve the foremost issue for them in terms of practical applications, relating to the large volume changes during cell operation. Herein, we report a SnO 2 anode with a hierarchical fibrous porous architecture which was fabricated by electrospinning the Sn-precursor with poly(vinylpyrrolidone) and subsequent temperature-dependent pyrolysis processes, resulting in the distinctive morphology, featuring hierarchical fibrous porous structures on the microscale with numerous primary constituent nanoparticles. The porous fibres are composed of uniform polycrystalline nanoparticles (approximately 10–50 nm in size) and abundant voids in close proximity to the constituent nanoparticles. By comparing with an anode containing commercial SnO 2 nanopowder (with a size of <100 nm), we found that the porous fibrous SnO 2 anode featured superior rate capability, long-term cycling stability, and dimensional stability, which was attributed to the distinctive structural characteristics, which offered enhanced kinetics towards electrochemical reactions with lithium ions and space for alleviating the huge volume expansion during charging/discharging. These findings would pave the way for practical applications in LIBs with high capacity and long cycle life of transition metal oxide anodes that suffer from significant volume changes during cycling. [ABSTRACT FROM AUTHOR]

Abstract: A Si–Ni alloy and graphite composite is synthesized by arc-melting followed by high-energy mechanical milling. The alloy particles consist of an electrochemically active silicon phase with inactive phases such as NiSi2 and NiSi distributed uniformly on the surface of the graphite. The inactive phases can accommodate the large volume changes of Si during cycling of the composite as an anode material for lithium batteries. The cycle-life of the composite increases with increase in Si content. A large reversible capacity (about 800mAhg−1) and good cycleability suggest that the composite may prove to be an alternative to conventional graphite-based anode materials for lithium-ion secondary batteries. [Copyright &y& Elsevier]

Abstract: Si/Ni alloy and graphite composites were synthesized using arc-melting followed by high energy mechanical milling (HEMM). Alloy particles comprising of NiSi2, NiSi and Si phases were distributed finely and uniformly on the surface of graphite in the composites obtained after HEMM. The composite containing 60wt.% of Si/Ni alloy exhibited a stable capacity of ∼780mAh/g. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that some bonds were formed between alloy and graphite after HEMM, which appeared to retain the electrical connection between alloy and graphite during cycling. X-ray diffraction (XRD) analysis indicated that NiSi2 and NiSi phases, which acted as an inactive alloy matrix remained invariant during charge and discharge. In addition to NiSi2 and NiSi phases, disordered graphite layers also played the role of media for the accommodation of large volume change of Si during cycling. The large reversible capacity and good cycleability showed that Si/Ni alloy and graphite composite could be an alternative to conventional graphite-based anode materials for lithium-ion secondary batteries. [Copyright &y& Elsevier]

[Display omitted] • Graphite anodes were surface-modified with Co 2 P nanoparticles. • The modified anodes exhibited a remarkable charging time of 16.1 min (80 % SOC). • Stable cycling performance > 300 cycles was achieved with the Co 2 P@graphite anode. • LiP and Li 3 P reduced interfacial overpotential and increased reversibility. Natural graphite (NG) is widely utilized as a practical anode in commercial lithium-ion batteries (LIBs) thanks to its high theoretical capacity and low operating voltage as well as high reversibility for Li+ storage. Recently, there has been a strong need to further enhance the fast-charging capability and reduce the charging time of NG for use in expanding electric vehicle applications. To enhance the charging performance of NG, various approaches have been explored to make its surface favorable for fast Li+ intercalation. Herein, we propose a surface modification of NG with functional cobalt phosphide (Co 2 P). Co 2 P nanoparticles can be introduced onto NG particles via a thermally induced phase transition process. Various structural and electrochemical investigations have provided insights into the crucial functions and reaction mechanisms of Co 2 P nanoparticles. We demonstrated that electrochemical conversion reactions of Co 2 P nanoparticles occurred during the first charging process, and the resulting phases induced effective surface stabilization and high-voltage operation during subsequent cycles. In particular, lithium phosphide (LiP and Li 3 P) formation is mainly responsible for reducing the overpotential for interfacial reactions between NG and the electrolyte, leading to the effective Li plating suppression and an increase in reversibility during cycles. In practice, the full-cell employing the Co 2 P@NG anode offered a superior cycling performance over 300 cycles and a charging time of 16.1 min (80 % SOC). We expect our findings make a valuable contribution to the advancement of fast-charging LIBs. [ABSTRACT FROM AUTHOR]

The thermal stability of a fully delithiated cathode, coupled with an inorganic salt, organic solvents, and electrolyte, was evaluated with differential scanning calorimetry (DSC) to address the safety issue of lithium-ion batteries. The DSC experiments revealed that vinylene carbonate (VC)-based systems exhibit decreased thermal stability compared to other coexisting systems. The DSC analysis of the cathode and electrolyte in the presence of VC, employed as additives, confirmed the reduction in thermal stability. Our results suggested that VC additives, which have been recently employed to enhance the electrochemical performance in anodes, negatively affect the thermal properties and safety characteristics of the cathode in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

LiTaO 3 has a high ionic conductivity (10−5−10−6 S cm−1), mechanical strength, and excellent moisture stability. Such characteristics would make it more valuable for reducing the interfacial resistance and promoting the surface stabilization of Li 2 NiO 2. The positive effects of the LiTaO 3 surface layer towards improving the structural stability and electrochemical performance of Li-excess Li 2 NiO 2 are demonstrated for practical use. [Display omitted] • Li 2 NiO 2 offers surplus Li+ for compensating the irreversible Li+ loss in the anode. • LiTaO 3 coating layer can suppress the formation of impurities after air exposure. • The gas evolution and mechanical cracking can be minimized during cycling. • A full-cell with LiTaO 3 @Li 2 NiO 2 shows stable cycling performance up to 200 cycles. Silicon based anodes are known to have a high specific capacity and low operating voltage (less than 0.5 V vs. Li/Li+). Even so, the solid electrolyte interphase (SEI) formation induces the severe capacity loss at the first cycle, known as a critical factor in reducing the energy density of lithium-ion batteries (LIBs). To improve the energy density by compensating the initial Li+ loss, the utilization of Li-excess cathode additives has been considered as the most practical strategy for supplying surplus Li+ during the initial charge. Li 2 NiO 2 is an ideal cathode additive thanks to its large charge capacity (≥320 mAh g−1) and low Coulombic efficiency (∼35%) at the first cycle. Surface protection of Li 2 NiO 2 is still required, however, due to its vulnerability to moisture (H 2 O) and carbon dioxide (CO 2) in the ambient atmosphere. In addition, Li 2 NiO 2 becomes more structurally unstable due to oxygen (O 2) gas evolution, leading to the formation of microcracks. Herein, we introduce a functional LiTaO 3 coating layer onto the surface of Li 2 NiO 2 for structural stabilization. The LiTaO 3 coating layer can effectively suppress the formation of impurities (i.e. , LiOH and Li 2 CO 3) after air exposure. Furthermore, the gas evolution and mechanical cracking can be minimized by enhancing the structural integrity of Li 2 NiO 2 during cycling. [ABSTRACT FROM AUTHOR]

The mechanical properties of cathode materials are among the critical factors that directly affect the lifespan of lithium-ion batteries (LIBs). However, a significant challenge remains in understanding the exact mechanism of mechanical degradation of present cathode materials that results in significant loss of performance during long-term operation. Herein, a comparative study on the correlation between mechanical strength (e.g. particle hardness) and cycle performance of the cathode materials (particularly those with layered structures) is presented. By improving the particle hardness of cathode materials via Mg doping, the formation of undesirable microcracks within the particles during cycling can be effectively suppressed, thus improving cycle performance. Structural and electrochemical analyses are performed in order to further elucidate the mechanical degradation mechanism of LIBs during repeat cycles, and identify a possible approach to the enhancement of electrochemical performance and long-term durability in present cathode materials. Image 1 • A strategy for improving the cycle performance of NCM cathode is presented. • The particle hardness of NCM can be effectively enhanced by Mg doping. • The enhanced particle hardness of Mg-NCM positively affects the cycle performance. • The formation of microcracks within Mg-NCM can be suppressed during cycles. [ABSTRACT FROM AUTHOR]

Abstract: 1,3,5-trihydroxybenzene (THB) is examined as a film-forming additive for over-lithiated layered oxide positive electrode. The surface film generated from the carbonate-based electrolyte (THB-free) is thermally/electrochemically unstable to be dissolved or decomposed during elevated-temperature cycling. Due to this instability, electric charges are consumed in every cycle for electrolyte decomposition to give a low coulombic efficiency. In contrast, the protective film that is generated by oxidative decomposition of the additive (THB) prior to the carbonate electrolyte is robust enough to remain intact. As a result, a full-cell comprising graphite/over-lithiated layered oxide gives a higher coulombic efficiency and longer life cycle. [Copyright &y& Elsevier]