A single-ion negative-charge accelerator unlocks high-speed Li-ion transport in in situ polymerized solid-state lithium metal batteries

Abstract

In situ polymerized solid-state electrolytes (IPSEs) are promising candidates for high-performance lithium metal batteries (LMBs) due to their satisfactory interfacial compatibility and lithium salt dissociation capability, though the low ionic conductivity limits their practical application. Herein, a single-ion negative-charge accelerator was developed through interlayer cation-exchange engineering of lithium montmorillonite (LMMT) and incorporated during the in situ polymerization process to unlock fast Li-ion conduction. LMMT with edge-exposed hydroxyl (–OH) groups and intrinsic negative charges effectively anchors anions and competitively adsorbs Li ions, thus mitigating strong Li-ion coordination. Meanwhile, the interlayer single-ion channels in LMMT expedite the directional Li-ion transport. As a result, the optimized electrolyte demonstrates a high ionic conductivity of 0.5 mS cm⁻¹ at 30 °C and a Li-ion transference number of 0.81. Moreover, exceptional cycling stability in Li∥Li symmetric cells for over 1700 h at 0.2 mA cm⁻² is achieved. In addition, the assembled Li∥LiFePO₄ cells exhibit a capacity retention of 84.5% after 400 cycles at 1C. This work provides new insight into the design of high-conductivity IPSEs for safe and high-performance LMBs.