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.

Lithium (Li) metal as an anode material for batteries has extremely high specific capacity and extremely low redox potential, which can significantly improve the energy density of the battery. However, the main problems faced by the use of Li metal anodes are Li dendrite growth, interfacial side reaction and volumetric change of electrode. Herein, a strategy to prepare the three-dimensional (3D) Li foam by combining 3D scaffold with quantitative Li was proposed to suppress Li dendrites growth and alleviate electrode volumetric change. The 3D Li foam facilitated the efficient utilization of Li metal by suppressing the Li dendrite growth, mitigating the volumetric change, and improving the rate performance. Therefore, the cycling lifetime and rate performance of the symmetric cells using the 3D Li foam were improved. The EIS results showed that the 3D Li foam reduced the charge transfer resistance of the symmetric cells. And the average discharge specific capacity of the LTO cell during 1000 cycles was enhanced from 65 mAh·g^-1 to 121 mAh·g^-1 by using the 3D Li foam.