Pressure Effects and Countermeasures in Solid-State Batteries: A Comprehensive Review

Solid-state batteries (SSBs) have garnered significant attention as promising and safe electrochemical solutions for high-energy storage. Despite their advantageous characteristics, the widespread adoption of SSBs encounters significant obstacles. Foremost among these challenges is the inadequate solid-state electrolyte (SSE)-electrode contact, particularly under typical operating conditions with moderate pressures. Consequently, substantial external pressures are conventionally applied to establish a tightly bonded and low-impedance interfacial connection. Unfortunately, high pressure concurrently precipitates detrimental effects, such as SSE structural fractures and premature short circuits. Moreover, the pressure parameters that are currently employed in laboratory-scale research lack consistency and far exceed the current industrial requirement (< 1 MPa), which undermines the objective evaluation of SSBs' actual performance and hampers the practical utilization. This review aims to construct a comprehensive perspective on the effect of pressure on SSBs, with a specific focus on decoupling the interfacial/bulk electrochemo-mechanical dynamics. In particular, the adverse consequences and fundamental causes of the highly-pressure-reliance behavior in SSBs are scrutinized, followed by a systematic summarization of the current strategies toward low-pressure SSBs. Based on these insights, it is put forth promising directions for better disentangling the electrochemo-mechanical interplay within SSBs and inspiring the development of pressure-independent SSBs.