Synergistic solid-liquid hybrid electrolyte for cycle-stable and high-efficiency Li-CuCl2 batteries.

The escalating demand for high-energy lithium-ion batteries has intensified interest in the CuCl₂ conversion cathode, which offers exceptional theoretical energy density. However, its practical application has been severely hindered by rapid capacity decay, primarily due to active material dissolution and copper species crossover. Here, we propose a novel solid-liquid hybrid electrolyte system that integrates a solvation-tuned liquid electrolyte (8 M LiFSI/DME) with a Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) ceramic electrolyte to address these dual degradation pathways. This strategy can effectively suppress the dissolution of CuCl₂ due to confinement of solvent molecules within Li⁺ solvation sheaths coupled with physical barrier blocking, while simultaneously maintaining favorable Li⁺ transport kinetics across the solid-liquid interface. Meanwhile, the LAGP ceramic electrolyte also functions as an ion-selective barrier, effectively inhibiting Cu species migration and significantly mitigating shuttle-induced lithium corrosion. Consequently, the Li-CuCl₂ battery with this hybrid electrolyte achieves remarkable cycling stability, maintaining 77.9% capacity retention over 400 cycles at 0.5C. Additionally, it demonstrates a record-high energy efficiency of 95.8% and delivers a practical energy density of 806.6 W h kg^-1 based on the total cathode mass. The reported results demonstrate that the hybrid electrolyte is a powerful strategy for the conversion-type metal chloride to achieve excellent electrochemical performance in lithium-ion batteries.