jwlimgroup

All-Solid-State Batteries (ASSBs)

All-solid-state batteries (ASSBs) are widely regarded as next-generation energy storage systems because of their high energy density and enhanced safety. However, the confinement of solid electrolytes and electrodes within a rigid cell architecture generates complex internal stresses that remain difficult to understand and control. Our research addresses key barriers to ASSB commercialization, including moisture instability, interfacial degradation, and low-pressure fabrication and operation. To overcome these challenges, we combine advanced characterization techniques, such as synchrotron-based X-ray analysis, with innovative manufacturing approaches including warm isostatic pressing and roll pressing. We also develop novel sulfide and halide solid electrolytes and engineered silicon-based anode materials.

Sulfide solid electrolytes

Sulfide solid electrolytes are softer than their oxide counterparts, yet they remain too rigid to enable truly low-pressure fabrication and operation. Practical sulfide-based ASSBs still rely on high external stack pressures to sustain interfacial contact, which demands bulky pressurizing hardware and lowers cell-level energy density, which is a key barrier to commercialization. Reducing the required stack pressure is therefore essential. To this end, we seek softer sulfide electrolytes that deform readily under low pressure, conforming to the cathode active material to form intimate, low-resistance interfaces and to accommodate volume changes during cycling. We synthesize these electrolytes in-house and systematically tune their composition and microstructure, correlating the resulting mechanical properties.

Halide solid electrolytes

To establish high-performance anode–SE interfaces, electrochemically stable solid electrolytes (SEs) are generally preferred. However, most highly conductive SEs, including sulfides and halides, are thermodynamically unstable at the low potentials associated with practical anodes. Sulfide SEs decompose into ionically insulating products, such as Li₂S and LiCl, resulting in increased interfacial resistance and degraded electrochemical performance. Although kinetically stabilized interphases can be achieved through carefully engineered anode–sulfide combinations, their practical applicability remains limited. Similar challenges are encountered at the cathode interface, where sulfide electrolytes often require protective coatings to mitigate oxidative decomposition beyond their electrochemical stability window.

Consequently, recent research on halide electrolytes has increasingly focused on low-potential stability, reversible lithiation behavior, dynamic interfacial evolution during cycling, and interfacial stability under low stack pressures. These efforts aim to expand the effective stability window of halide electrolytes, enabling compatibility with both low-voltage anodes and high-voltage cathodes while meeting the requirements of next-generation solid-state batteries for low-pressure operation, high energy density, and long cycle life.

Silicon anodes

As part of our research on advanced anodes for all-solid-state batteries, we study silicon-based anodes for high energy density cell. Silicon is abundant and has high capacity, but large volume changes during cycling lead to mechanical degradation and interfacial instability. Building on our work on monolithic silicon wafer anodes, we aim to stabilize silicon electrodes through electrode architecture and interface design. Current strategies include metallic buffer layers and surface coatings to accommodate volume changes, maintain solid-solid contact, and improve cycling performance.

Anode-free ASSBs

Anode-free batteries represent the ultimate anode design for ASSBs, maximizing energy density by eliminating any host or excess anode material. All lithium is supplied by the cathode, plating onto the bare current collector during charge and stripping back during discharge. This minimalist architecture not only pushes energy density to its limit but is also a promising route toward low-pressure ASSB operation. To guide uniform deposition, anode-free cells commonly adopt a thin interlayer at the current collector. Our research focuses on silver-carbon (Ag-C) interlayers, in which lithiophilic Ag forms a Li-Ag alloy that lowers the nucleation barrier and anchors plated lithium for dense, reversible cycling. We study these cells at the pouch-cell level together with synchrotron-based and operando- techniques to resolve the practical issues of Ag-C anode-free ASSBs.