Abstract All‐solid‐state batteries are emerging as potential successors in energy storage technologies due to their increased safety, stemming from replacing organic liquid electrolytes in conventional Li‐ion batteries with less flammable solid‐state electrolytes. However, all‐solid‐state batteries require precise control over cycling pressure to maintain effective interfacial contacts between materials. Traditional uniaxial cell holders, often used in battery research, face challenges in accommodating electrode volume changes, providing uniform pressure distribution, and maintaining consistent pressure over time. This study introduces isostatic pouch cell holders utilizing air as pressurizing media to achieve uniform and accurately regulated cycling pressure. LiNi 0.8 Co 0.1 Mn 0.1 O 2 | Li 6 PS 5 Cl | Si pouch cells are fabricated and tested under 1 to 5 MPa pressures, revealing improved electrochemical performance with higher cycling pressures, with 2 MPa as the minimum for optimal operation. A bilayer pouch cell with a theoretical capacity of 100 mAh, cycled with an isostatic pouch cell holder, demonstrated a first‐cycle Coulombic efficiency of 76.9% and a discharge capacity of 173.6 mAh g −1 (88.1 mAh), maintaining 83.6% capacity after 100 cycles. These findings underscore the effectiveness of isostatic pouch cell holders in enhancing the performance and practical application of all‐solid‐state batteries.

All-solid-state batteries using sulfur-based positive electrodes (cathodes) offer a cost-effective route to achieve high specific energy. However, low active material utilization and cycle life hinder performance. Here, we demonstrate a positive electrode design that employs sulfide solid-state electrolytes, where a high energy synthesis approach forms a metastable and ionically conductive interphase on the active material surface. This interphase facilitates high active material utilization and contributes capacity with cycling. We also show that tailoring active material particle sizes to the micron-scale improves rate performance and cycling stability. Structural analysis reveals that the substantial volume change of sulfur-based positive electrodes during operation can partially offset that of the negative electrodes, thereby mitigating internal mechanical stress. The combined design principles enable sulfur areal capacities up to 11 mAh cm^-2 while maintaining stable cycling at 25 °C. We further demonstrate several specific-energy-focused cell architectures, particularly a Li₂S anode-free pouch cell that operates under "low stack pressure" of 10 MPa. This work outlines practical design strategies for constructing high-specific-energy all-solid-state batteries for a broad range of emerging applications.

The development of all-solid-state batteries (ASSBs) has attracted significant interest owing to their potential to deliver high energy density, improved safety, and long cycle life. However, their practical implementation is still limited by the narrow electrochemical stability window of sulfide solid-state electrolytes, interfacial decomposition at high-voltage cathodes, and mechanically driven contact loss in composite electrodes. In this mini-review, we provide an overview of recent progress in sulfide-based solid-state electrolytes, with particular focus on interfacial degradation phenomena in composite cathodes and strategies to mitigate resistance growth through protective coatings and microstructural engineering. We also discuss the integration of high-energy-density anodes, including lithium metal, silicon-based, and anode-free designs, and examine how interlayers and stack-pressure management influence interfacial stability. Finally, we highlight the remaining challenges and outline future research directions for realizing durable, high-performance sulfide-based ASSBs.

All-solid-state batteries using Si as the anode have shown promising performance without continual solid-electrolyte interface (SEI) growth. However, the first cycle irreversible capacity loss yields low initial Coulombic efficiency (ICE) of Si, limiting the energy density. To address this, we adopt a prelithiation strategy to increase ICE and conductivity of all-solid-state Si cells. A significant increase in ICE is observed for Li₁Si anode paired with a lithium cobalt oxide (LCO) cathode. Additionally, a comparison with lithium nickel manganese cobalt oxide (NCM) reveals that performance improvements with Si prelithiation is only applicable for full cells dominated by high anode irreversibility. With this prelithiation strategy, 15% improvement in capacity retention is achieved after 1000 cycles compared to a pure Si. With Li₁Si, a high areal capacity of up to 10 mAh cm^-2 is attained using a dry-processed LCO cathode film, suggesting that the prelithiation method may be suitable for high-loading next-generation all-solid-state batteries.

Abstract All‐solid‐state batteries are emerging as potential successors in energy storage technologies due to their increased safety, stemming from replacing organic liquid electrolytes in conventional Li‐ion batteries with less flammable solid‐state electrolytes. However, all‐solid‐state batteries require precise control over cycling pressure to maintain effective interfacial contacts between materials. Traditional uniaxial cell holders, often used in battery research, face challenges in accommodating electrode volume changes, providing uniform pressure distribution, and maintaining consistent pressure over time. This study introduces isostatic pouch cell holders utilizing air as pressurizing media to achieve uniform and accurately regulated cycling pressure. LiNi 0.8 Co 0.1 Mn 0.1 O 2 | Li 6 PS 5 Cl | Si pouch cells are fabricated and tested under 1 to 5 MPa pressures, revealing improved electrochemical performance with higher cycling pressures, with 2 MPa as the minimum for optimal operation. A bilayer pouch cell with a theoretical capacity of 100 mAh, cycled with an isostatic pouch cell holder, demonstrated a first‐cycle Coulombic efficiency of 76.9% and a discharge capacity of 173.6 mAh g −1 (88.1 mAh), maintaining 83.6% capacity after 100 cycles. These findings underscore the effectiveness of isostatic pouch cell holders in enhancing the performance and practical application of all‐solid‐state batteries.