Driving Fast‐Charging for Sodium Ion Batteries in Wide Temperature Range by Metallic 1 T Phase ReSe ₂

ABSTRACT To enable fast sodium ion battery charging in a wide temperature range, the local structures of anode materials must be optimized to reduce the Na ⁺ diffusion resistance at the interface and inside the electrode. Guided by theoretical predictions, isotropic ReSe ₂ with a 1 T phase crystal structure (1 T ReSe ₂ ) is developed herein to exhibit enhanced electrical conductivity for efficient charge transfer compared to the 1 T' ReSe ₂ phase. Enabled by its metallic characteristic and longer Re─Se bonds, 1 T ReSe ₂ achieves a lower Na ⁺ diffusion barrier and lower adsorption energy than 1 T' ReSe ₂ , facilitating faster Na ⁺ storage reaction kinetics. Operando spectroscopy characterization confirms that the 1 T ReSe ₂ electrode can directly produce Na _x ReSe ₂ without undergoing a significant phase transition. This inhibits volume expansion, leading to improved cycling stability. As a result, 1 T ReSe ₂ exhibits good fast‐charging performance in a wide temperature range. A capacity of 197 mAh g ⁻¹ @20 A g ⁻¹ is maintained after 8000 cycles at room temperature, and a capacity of 136 mAh g ⁻¹ @1 A g ⁻¹ (corresponding to a capacity retention rate of 60%) is retained after 465 cycles at −40°C.