Elastic <i>a</i>‑Silicon Nanoparticle Backboned Graphene Hybrid as a Self-Compacting Anode for High-Rate Lithium Ion Batteries

Although various Si-based graphene nanocomposites provide enhanced electrochemical performance, these candidates still yield low initial coloumbic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles lead to severe capacity fading and increase in internal impedance. Therefore, an innovative structure to solve these problems is needed. In this study, an amorphous (<i>a</i>) silicon nanoparticle backboned graphene nanocomposite (<i>a</i>-SBG) for high-power lithium ion battery anodes was prepared. The <i>a</i>-SBG provides ideal electrode structuresa uniform distribution of amorphous silicon nanoparticle islands (particle size <10 nm) on both sides of graphene sheetswhich address the improved kinetics and cycling stability issues of the silicon anodes. <i>a</i>-Si in the composite shows elastic behavior during lithium alloying and dealloying: the pristine particle size is restored after cycling, and the electrode thickness decreases during the cycles as a result of self-compacting. This noble architecture facilitates superior electrochemical performance in Li ion cells, with a specific energy of 468 W h kg^–1 and 288 W h kg^–1 under a specific power of 7 kW kg^–1 and 11 kW kg^–1, respectively

Additive-Derived Surface Modification of Cathodes in All-Solid-State Batteries: The Effect of Lithium Difluorophosphate- and Lithium Difluoro(oxalato)borate-Derived Coating Layers

Sulfide-based electrolytes, with their high conductivity and formability, enable the construction of high-performance, all-solid-state batteries (ASSBs). However, the instability of the cathode–sulfide electrolyte interface limits the commercialization of these ASSBs. Surface modification of cathodes using the coating technique has been explored as an efficient approach to stabilize these interfaces. In this study, the additives lithium difluorophosphate (LiDFP) and lithium difluoro­(oxalato)­borate (LiDFOB) are used to fabricate stable cathode coatings via heat treatment. The low melting points of LiDFP and LiDFOB enable the formation of thin and uniform coating layers by a low-temperature heat treatment. All-solid-state cells containing LiDFP- and LiDFOB-coated cathodes show electrochemical performances significantly better than those comprising uncoated cathodes. Among all of the as-prepared coated cathodes, LiDFP-coated cathodes fabricated using a slightly lower temperature than the phase-transition temperature of LiDFP (320 °C) show the best discharge capacity, rate capability, and cyclic performance. Furthermore, cells comprising LiDFP-coated cathodes showed significantly low impedance. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy confirm the effectiveness of the LiDFP coating. LiDFP-coated cathodes minimized side-reactions during cycling, resulting in a significantly low cathode-surface degradation. Hence, this study highlights the efficiency of the proposed coating method and its potential to facilitate the commercialization of ASSBs. Overall, this study reports an effective technique to stabilize the cathode–electrolyte interface in sulfide-based ASSBs, which could expedite the practical implementation of these advanced energy-storage devices

Stable Solid Electrolyte Interphase Layer Formed by Electrochemical Pretreatment of Gel Polymer Coating on Li Metal Anode for Lithium–Oxygen Batteries

Lithium–oxygen (Li–O2) batteries exhibit the highest theoretical specific energy density among candidates for next-generation energy storage systems, but the instabilities of Li metal anode (LMA), air electrode, and electrolyte largely limit the practical applications of these batteries. Herein, we report an effective method to protect the LMA against side reactions between the LMA and the crossover contaminants such as highly reactive oxygen moieties. A solid electrolyte interphase (SEI) layer rich in inorganic components is formed on the LMA coated with poly­(ethylene oxide) thin film through an in situ electrochemical precharging step under oxygen atmosphere. This uniformly distributed SEI layer interacts with the flexible polymer matrix and forms a submicrometer-sized gel-like polymer layer. This polymer-supported SEI layer leads to much longer cycle life (130 vs 65 cycles) as compared to that of pristine cells under the same testing conditions. It is also very effective to stabilize the LMA/electrolyte interphase with a redox mediator

Native Void Space for Maximum Volumetric Capacity in Silicon-Based Anodes

Volumetric energy density is considered a primary factor in developing high-energy batteries. Despite its significance, less efforts have been devoted to its improvement. Silicon-based materials have emerged as next-generation anodes for lithium-ion batteries due to their high specific capacity. However, their volumetric capacities are limited by the volume expansion rate of silicon, which restricts mass loading in the electrodes. To address this challenge, we introduce porous silicon templated from earth-abundant minerals with native internal voids, capable of alleviating volumetric expansion during repeated cycles. In situ transmission electron microscopy analysis allows the precise determination of the expansion rate of silicon, thus presenting an analytical model for finding the optimal content in silicon/graphite composites. The inner pores in silicon reduce problems associated with its expansion and allow higher silicon loading of 42% beyond the conventional limitations of 13–14%. Consequently, the anode designed in this work can deliver a volumetric capacity of 978 mAh cc–1. Thus, suppressing volume expansion with natural abundant template-assisted materials opens new avenues for cost-effective fabrication of high volumetric capacity batteries

Flexible High-Energy Li-Ion Batteries with Fast-Charging Capability

With the development of flexible mobile devices, flexible Li-ion batteries have naturally received much attention. Previously, all reported flexible components have had shortcomings related to power and energy performance. In this research, in order to overcome these problems while maintaining the flexibility, honeycomb-patterned Cu and Al materials were used as current collectors to achieve maximum adhesion in the electrodes. In addition, to increase the energy and power multishelled LiNi_0.75Co_0.11Mn_0.14O₂ particles consisting of nanoscale V₂O₅ and Li_<i>x</i>V₂O₅ coating layers and a Li_δNi_{0.75–<i>z</i>}Co_0.11Mn_0.14V_<i>z</i>O₂ doping layer were used as the cathode–anode composite (denoted as PNG-AES) consisting of amorphous Si nanoparticles (<20 nm) loaded on expanded graphite (10 wt %) and natural graphite (85 wt %). Li-ion cells with these three elements (cathode, anode, and current collector) exhibited excellent power and energy performance along with stable cycling stability up to 200 cycles in an in situ bending test