Unified affinity paradigm for the rational design of high-efficiency lithium metal electrolytes

Electrolyte engineering breakthroughs are crucial to support extremely high-energy battery chemistries. However, the complex interplay between battery performance and electrolyte structure remains poorly understood and difficult to predict. Here we introduce the concept of ‘normalized cation/anion–solvent affinity’, which describes the critical interactions between solvents and both cations and anions. This innovative approach allows for the simultaneous and quantitative prediction of electrolyte microstructures, transport characteristics, redox behaviours and interphase characteristics. Leveraging this framework, we screened approximately 150 solvent candidates and identified electrolyte formulations that significantly improve Li metal plating/stripping Coulombic efficiency ( >99.5%). Among these, four electrolytes achieved Coulombic efficiency greater than 99.8%, while supporting the durability of aggressive high-voltage cathodes. These formulations enabled the realization of highly reversible Li metal batteries (LMBs) with a record-breaking high energy density of 600 Wh kg−1 and over 100 cycles, advancing LMBs towards practical applications. The unified affinity paradigm offers valuable insights for designing next-generation electrolytes for high-energy LMBs and other alkali-metal-ion batteries.