Low-temperature all-solid-state lithium-ion batteries based on a di-cross-linked starch solid electrolyte

The preparation of a low-temperature solid electrolyte is a challenge for the commercialization of the all-solid-state lithium-ion battery (ASSLIB). Here we report a starch-based solid electrolyte that displays phenomenal electrochemical properties below room temperature (RT). The starch host of the electrolyte is synthesized by two cross-linking reactions, which provide sufficient and orderly binding sites for the lithium salt to dissolve. At 25 °C, the solid electrolyte has exceptional ionic conductivity (σ, 3.10 × 10^-4 S cm^-1), lithium-ion transfer number (t ⁺, 0.82) and decomposition potential (dP, 4.91 V). At -20 °C, it still has outstanding σ (3.10 × 10^-5 S cm^-1), t ⁺ (0.72) and dP (5.50 V). The LiFePO₄ ASSLIB assembled with the electrolyte exhibits unique specific capacity and long cycling life below RT, and the LiNi_0.8Co_0.1Mn_0.1O₂ ASSLIB can operate at 4.3 V and 0 °C. This work provides a solution to solve the current challenges of ASSLIBs to widen their scope of applications.