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 2.17×10^-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 ∼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 LiNi_0.6Co_0.2Mn_0.2O₂ (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.

固态聚合物电解质（SPE）具有良好的界面粘合力和形状柔韧性，是全固态锂电池（ASSLB）的有希望的候选者。但是，室温（RT）的低离子电导率和高压下的电化学稳定性差，限制了SPE的实际应用。在这项工作中，我们展示了一种低温工程技术，可以改善RT下运行的ASSLB的基于PEO的SPE。快速的原位冷却过程将导致PEO晶核的均匀形成，这会限制SPE中PEO晶体的生长。新型的结晶结构可以有效地提高固相萃取的离子电导率。此类改进的低温SPE具有2.17×10 ^-5 S cm ^-1的优异离子电导率在室温下具有出色的电化学稳定性。当LiFePO ₄（LFP）用作阴极时，在0.1 C和RT下可以达到154.9 mAh g ^-1的放电容量。即使在0.1 C下执行100次循环后，放电容量仍可保持在〜98％。值得注意的是，低温SPE可用于4 V级ASSLB。以LiNi _0.6 Co _0.2 Mn _0.2 O ₂（NCM622）为阴极，在0.2 C和RT下可获得118 mAh g ^-1的高放电容量，即使在100次循环后仍可保持94.1％的容量。低温SPE的这些非凡性能为制造在RT和高压下运行的ASSLB开辟了新天地。