Phase-junction engineering triggered built-in electric field for fast-charging batteries operated at −30°C

The high operational capability of fast-charging lithium-ion batteries (LIBs) at low temperatures (<−30°C) is essential for frequency regulation and peak-load shifting of power grids in cold regions. However, the low-temperature performance is seriously plagued by the sluggish Li+ diffusion and high-voltage polarization. Herein, the heterostructure-induced built-in electric field is constructed by selected nitriding of TiNb2O7, which demonstrates high accessibility for accelerated low-temperature dynamics. The introduced charged phase-junction interface enables promoted Li+ diffusion rates, enhanced Li+ adsorption, and reduced lattice strains. The mosaic TiNb2O7/TiNbN2 heterostructure displays an outstanding specific capacity of 241.5 mA h g−1 at −30°C, corresponding to 89% retention compared with that at 25°C. It even delivers a high-capacity retention of 96% at a 5C rate after approximately 1,000 cycles at −30°C. Our work provides new insight into structure-function relationships for developing fast-charging batteries for cold-region accumulation of electric energy.