(696d) Mixed Electronic-Ionic Conductive Polymer Binder for Silicon-Based All-Solid-State Batteries

Silicon (Si) has emerged as a promising negative electrode material for high-energy-density all-solid-state batteries (ASSBs) due to its high theoretical specific capacity (~3600 mAh/g) and abundance. The application of silicon in ASSBs encounters several challenges, including substantial volumetric variation (~300%) during electrochemical cycling and poor cycling stability. In addition, the lack of liquid electrolytes in ASSBs poses a critical challenge in achieving sufficient ionic conductivity within the Si electrode. To address these challenges, various studies have explored potential solutions, including controlling the thickness of silicon anode to be below 150 nm,¹ fabricating electrodes with a combination of silicon and solid-state electrolyte (e.g, Garnet-type electrolyte² and sulfide electrolyte³, and subjecting SSBs to a high pressure (10-50 MPa)⁴.

Here, we introduce a new approach to mitigate these challenges using a mixed electronic-ionic conductive (MEIC) hierarchically ordered structure (HOS) as a polymer binder for the silicon electrode. The multifunctional HOS polymer binder effectively preserves the structural integrity of the silicon electrode, even when silicon particles experience significant volume expansion and shrinkage during the charging-discharging process. By establishing covalent bonds between the silicon surface and the polymer binder, the resulting ASSBs exhibited excellent resilience and required only minimal hand-tightening force (<1 ton) for operation. The polymer binder effectively maintained continuous electronic and ionic pathways within the silicon electrode, eliminating the need for additional additives such as carbon materials and solid-state electrolytes. Using the versatile polymer binder, the resultant ASSBs featured an outstanding cycling performance in full cells, with an average Coulombic efficiency exceeding 99.7% over 200 cycles.

Reference

1. Song, A. et al. A Review on the Features and Progress of Silicon Anodes‐Based Solid‐State Batteries. Advanced Energy Materials 13, 2301464 (2023).

2. Ping, W. et al. A silicon anode for garnet-based all-solid-state batteries: Interfaces and nanomechanics. Energy Storage Materials 21, 246-252 (2019).

3. Rana, M. et al. Toward Achieving High Areal Capacity in Silicon-Based Solid-State Battery Anodes: What Influences the Rate-Performance? ACS Energy Letters 8, 3196-3203 (2023).

4. Tan, D. H. et al. Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes. Science 373, 1494-1499 (2021).