Cryogenic engineering of solid polymer electrolytes for room temperature and 4 V-class all-solid-state lithium batteries

Solid polymer electrolytes (SPEs) are promising candidates for all-solid-state lithium batteries (ASSLBs) due to their advantages of good interfacial adhesion and shape flexibility. However, the low ionic conductivity at room temperature (RT) and inferior electrochemical stability at high voltages limit the practical applications of SPEs. In this work, we demonstrate a cryogenic engineering to improve PEO-based SPEs for ASSLBs operated at RT. The rapid in situ cooling process will lead to the uniform formation of PEO crystal nuclei, which can limit the PEO crystal growth in SPEs. The novel crystallization structure could promote the ionic conductivity of SPEs effectively. Such improved cryogenic SPEs display a superior ionic conductivity of 2.17 x 10(-5) S cm(-1) and a superior electrochemical stability at RT. A discharge capacity of 154.9 mAh g(-1) can be achieved at 0.1 C and RT when LiFePO4 (LFP) is used as the cathode. The discharge capacity can remain at similar to 98%, even after 100 cycles performed at 0.1 C. Notably, cryogenic SPEs can be utilized in 4 V-class ASSLBs. A high discharge capacity of 118 mAh g(-1) can be achieved at 0.2 C and RT with the LiNi0.6Co0.2Mn0.2O2 (NCM622) as the cathode and can retain a 94.1% capacity even after 100 cycles. These extraordinary performances of cryogenic SPEs break new ground for the fabrication of ASSLBs operated at RT and high voltages.

Automated summary

In this study, a cryogenic engineering approach is demonstrated to enhance the performance of PEO-based SPEs for ASSLBs operated at room temperature, resulting in improved ionic conductivity and electrochemical stability. The novel crystallization structure achieved through rapid cooling promotes the ionic conductivity effectively, leading to superior performance of the cryogenic SPEs in terms of discharge capacity and cycle stability. These advancements open up new possibilities for the fabrication of ASSLBs operated at room temperature and high voltages.