Mg2+ initiated in situ polymerization of dioxolane enabling stable interfaces in solid-state lithium metal batteries

Abstract

In situ polymerized solid-state polymer electrolytes (SPEs) have attracted much attention due to their good machinability and excellent interface contact with electrodes. However, the undesirable stability to lithium metal and high-voltage electrodes hinders their application in high energy density solid-state lithium batteries. Herein, a poly(1,3-dioxolane) composite SPE possessing high interfacial stability with both a lithium metal anode and a high voltage cathode was fabricated via in situ polymerization initiated by a Mg²⁺-containing montmorillonite filler. The strong coordination between Mg²⁺ and anions of lithium salts not only improves the antioxidant stability of the polymer chains, but also optimizes the Li⁺ coordination structure and facilitates the formation of robust MgF₂-containing interphases on both the anode and the cathode. As a result, the composite SPE exhibits an improved homogeneous polymer chain distribution, a high Li⁺ transference number of 0.60 and an extended electrochemical window of 5.3 V. The Li/Li symmetric cells exhibit outstanding cycling stability for 6000 hours and the Li/LiNi_0.8Co_0.1Mn_0.1O₂ cells demonstrate excellent rate capability and cycle stability over 500 cycles. This work provides a promising pathway for SPEs toward practical high energy density solid-state batteries.