Crystal Engineering of Silica Anode Achieving Intrinsic Zero‐Strain

Abstract Si‐based anodes have large intrinsic volume expansion, which hinders their practicality and commercialization. To address this challenge, the design principle of intrinsic zero‐strain anodes (① large intracrystalline cavities and ② strong bonds) is proposed, and silica with large intracrystalline cavities (SLIC) established by strong Si─O bonds ([SiO 4 ] coordinate structures) is obtained and acts as an anode, achieving the intrinsic zero‐strain feature first in silicon‐based anodes. The phase structure of SLIC is maintained and the [SiO 4 ] coordinate structure merely shows slight disorder during cycling. The feature stems from lithiation taking place by the solid‐solution insertion reaction rather than the conventional conversion/alloying addition reactions, because the solid‐solution insertion reaction for the SLIC has the lowest change in the Gibbs free energy. The SLIC anode demonstrates excellent cycling stability and high initial Coulombic efficiency (≈85%). Moreover, owing to the low working voltage (≈0.28 V) and relatively high specific capacity, the SLIC anode presents the highest gravimetric energy density among reported zero‐/quasi‐zero‐strain anodes and high volumetric energy density (around twice as much as graphite). The universality of the designing principle is also validated. This work provides design guidelines for zero‐strain anodes in next‐generation batteries.