Tailoring polymer electrolyte ionic conductivity for production of low- temperature operating quasi-all-solid-state lithium metal batteries

The stable operation of lithium-based batteries at low temperatures is critical for applications in cold climates. However, low-temperature operations are plagued by insufficient dynamics in the bulk of the electrolyte and at electrode|electrolyte interfaces. Here, we report a quasi-solid-state polymer electrolyte with an ionic conductivity of 2.2 × 10^-4 S cm^-1 at -20 °C. The electrolyte is prepared via in situ polymerization using a 1,3,5-trioxane-based precursor. The polymer-based electrolyte enables a dual-layered solid electrolyte interphase formation on the Li metal electrode and stabilizes the LiNi_0.8Co_0.1Mn_0.1O₂-based positive electrode, thus improving interfacial charge-transfer at low temperatures. Consequently, the growth of dendrites at the lithium metal electrode is hindered, thus enabling stable Li||LiNi_0.8Co_0.1Mn_0.1O₂ coin and pouch cell operation even at -30 °C. In particular, we report a Li||LiNi_0.8Co_0.1Mn_0.1O₂ coin cell cycled at -20 °C and 20 mA g^-1 capable of retaining more than 75% (i.e., around 151 mAh g^-1) of its first discharge capacity cycle at 30 °C and same specific current.