A review of the effect of external pressure on all-solid-state batteries

As the most promising next-generation energy storage system, all-solid-state batteries (ASSBs) have the advantages of high theoretical energy density and intrinsic safety. However, the limitation of the “solid-solid” contact between the electrode and the solid electrolytes (SEs) severely hinders the interfacial charge transport. Studies have shown that the introduction of external pressure can effectively reduce the “solid-solid” contact resistance and prolong the cycle life of the battery. At the same time, the application of external pressure on the electrode materials has dramatic multiple interdisciplinary consequences. For example, a high preparation pressure on layered cathode materials may cause cracks thus having an adverse effect on the performance of ASSBs; however, a high stack pressure may suppress the chemo-mechanical failure of high energy density alloying electrodes thus reviving this class of anode materials. The external pressure induced results thus requires an urgent comprehensive review on this topic. Therefore, we provide a timely overview on the effects of external pressure on the SEs, the electrode materials and the electrode-SE interfaces by introducing the physical properties of commonly used sulfide, oxide, polymer solid electrolytes, lithium metal and alloy anodes, and layered oxide cathodes. We show that different materials and battery systems require very different external pressures. By appropriately tuning the external pressure, the performance of ASSBs can be optimized. Finally, we provide a summary and outlook on how to tailor the external pressure for high performance ASSBs developments.