LAUSR

Chloride ion batteries (CIBs) are a promising type of energy storage device due to their high theoretical volumetric energy density and abundant reserves of chlorine‐containing precursors. However, the unsatisfactory cycling performance and structural instability of cathode materials hinder their practical application. In this work, layered double hydroxides (LDHs), which consist of a trimetallic NiVAl hydroxide host matrix and interlayer Cl−, are demonstrated to be high‐performance cathode materials for CIBs. The Ni2V0.9Al0.1‐Cl LDH is capable of delivering a high initial capacity of 312.2 mAh g−1 at 200 mA g−1 and an ultralong life over 1000 cycles (with a capacity higher than 113.8 mAh g−1). Such a long cycling life exceeds that of any reported CIBs. The remarkable Cl−‐storage performance of the Ni2V0.9Al0.1‐Cl LDH is ascribed to the synergetic contributions from Vm+ (high redox activity), Ni2+ (favorable electronic structure), and inactive Al3+ (enhances the structural stability), which is revealed by a comprehensive study that utilizes synchrotron X‐ray absorption near‐edge structure experiments, kinetic investigations, and theoretical calculations. This study provides an effective strategy to achieve superior rechargeable batteries, which are applicable to large‐scale energy storage and power grids.