The uniform and smaller-sized (~3 μm) LiNi0.8Co0.1Mn0.1O2 (SNCM) particles are prepared via a fast nucleation process of oxalate co-precipitation, followed by a two-step calcination procedure. It is found that the fast nucleation by vigorous agitation enables us to produce oxalate nuclei having a uniform size which then grow into micron-particles in less than a few minutes. The impacts of solution pH, precipitation time, calcination temperature, and surface modification with ZrO2 on the structural, morphological, and electrochemical properties of SNCM are systematically examined to identify the optimal synthetic conditions. A novel bimodal cathode design has been highlighted by using the combination of the SNCM particles and the conventional large (~10 μm) LiNi0.83Co0.12Mn0.05O2 (LNCM) particles to achieve the high volumetric energy density of cathode. The volumetric discharge capacity is found to be 526.6 mAh/cm3 for the bimodal cathode L80% + S20%, whereas the volumetric discharge capacity is found to be only 480.3 and 360.6 mAh/cm3 for L100% and S100% unimodal, respectively. Moreover, the optimal bi-modal cathode delivered higher specific energy (622.4 Wh/kg) and volumetric energy density (1622.6 Wh/L) than the L100% unimodal (596.1 Wh/kg and 1622.6 Wh/L) cathode after the 100th cycle. This study points to the promising utility of the SNCM material in Li-ion battery applications.

Porous architectures for silicon/graphite (Si/Gr) composites can buffer the massive volume expansion of Si particles during electrochemical cycling. However, the large surface area derived from the high porosity leads to unavoidable side reactions at the electrode–electrolyte interface, leading to the formation of thick resistive natural solid–electrolyte interphase (SEI). Herein, a simple and scalable route is developed for coating a polymeric artificial SEI (A-SEI) inside the porous architecture for the Si/Gr composite via a facile incipient wetness impregnation (IWI) method. Cross-sectional focused ion beam microscopic results infer that the polymer coating is successful. Polymer coating for the porous matrix as A-SEI induces sufficient porosity as well as prevents excessive electrolyte penetration into the highly porous matrix. Furthermore, it prevents the direct contact of active materials with electrolytes, minimizing the parasitic reactions that form natural SEIs. Consequently, the polymer coating obtained by IWI enables remarkable enhancement in the long-cycle stability of the porous Si/Gr electrode, in contrast to the nonimpregnated electrode displaying capacity roll-over due to excessive SEI formation. Moreover, it is demonstrated that the coating effectively prevents the formation of dendritic lithium plating on the surface of the Si/Gr electrode, thereby enhancing the safety of the battery.

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Composite cathodes consisting of a LiNi0.8Co0.1Mn0.1O2 (NCM) cathode and brittle Li3InCl6 (LIC) solid‐state electrolyte (SSE) are assessed for all‐solid‐state Li‐ion battery (ASSLIB) applications under a low stacking pressure (coin‐cell configuration: ≈2.0 MPa). Herein, an investigation is conducted to understand how the internal particle morphologies of the polycrystal (PC‐)/single‐crystal (SC‐) NCM cathode materials affect the internal cracking within the composite electrodes and thereby electrode performance. Extensive debonding between NCM and LIC takes place even at a very low current density (0.03C) with high voltage (4.4 V), but substantially narrower/shorter debonding gaps are observed for SC‐NCM as compared with PC‐NCM (wider/lengthier) due to their different particle sizes. High current rates (e.g., 0.1C) bring about greater strain rates in PC‐NCM particles, resulting in widespread microcracking along the grain boundaries between primary particles and consequently creating “dead zones” that are isolated from the ionic and electronic conduction pathways. Although SC‐NCM shows microcracking within the agglomerates, individual NCM crystals remain in close contact with the SSEs because of noticeably fewer grains in the agglomerations than in the PC‐NCM secondary particles. A low‐pressure SC‐NCM ASSLIB is demonstrated with good cycle stability comparable with that of a liquid‐electrolyte cell even under stressful currents.