Diluent-Reorganized Solvation Structure for High-Voltage Lithium Metal Batteries

Localized high-concentration electrolytes (LHCEs) demonstrate promising performance in high-voltage lithium (Li) metal batteries. However, the understanding of Li⁺ migration kinetics and solvation configuration controlled by diluents is still lacking, limiting LHCEs’ rational design and optimization. In this study, we establish the structure–activity relationship between diluent-concentration-controlled Li⁺-solvated structures and kinetic signatures in LHCEs. Specifically, diluent concentration optimization reveals a volcano-type relationship in LHCE performance: Li⁺ transport kinetics and interfacial stability first improve (0 vol.% → 50 vol.%) due to enhanced dipole-mediated solvation reorganization and then degrade (50 vol.% → 75 vol.%) from excessive Li⁺ channel disruption. Consequently, an LHCE with 50 vol.% diluent achieves optimal kinetics and interfacial stability, enabling Li||Li cells to cycle stably over 4,500 h at 0.5 mA cm⁻² with 25-mV voltage polarization. Furthermore, 4.6-V Li||LiCoO₂ cells achieve 800 cycles at 2C (63% retention) while maintaining 129.7 mAh g⁻¹ at 5C. These findings reveal the critical role of diluents in LHCE design, highlighting the promise of LHCEs for high-voltage lithium metal battery applications.