A cost-effective all-in-one halide material for all-solid-state batteries

All-solid-state batteries require advanced cathode designs to realize their potential for high energy density and economic viability^1-3. Integrated all-in-one cathodes, which eliminate inactive conductive additives and heterogeneous interfaces, hold promise for substantial energy and stability gains but are hindered by materials lacking sufficient Li⁺/e^- conductivity, mechanical robustness and structural stability^4-14. Here we present Li_1.3Fe_1.2Cl₄, a cost-effective halide material that overcomes these challenges. Leveraging reversible Fe²⁺/Fe³⁺ redox and rapid Li⁺/e^- transport within its framework, Li_1.3Fe_1.2Cl₄ achieves an electrode energy density of 529.3 Wh kg^-1 versus Li⁺/Li. Critically, Li_1.3Fe_1.2Cl₄ shows unique dynamic properties during cycling, including reversible local Fe migration and a brittle-to-ductile transition that confers self-healing behaviour. This enables exceptional cycling stability, maintaining 90% capacity retention for 3,000 cycles at a rate of 5 C. Integration of Li_1.3Fe_1.2Cl₄ with a nickel-rich layered oxide further increases the energy density to 725.6 Wh kg^-1. By harnessing the advantageous dynamic mechanical and diffusion properties of all-in-one halides, this work establishes all-in-one halides as an avenue for energy-dense, durable cathodes in next-generation all-solid-state batteries.