Long-life and high volumetric capacity Bi₂Sn₂O₇ anode with interpenetrating Bi–O and Sn–O networks

Conversion-alloying anodes possess high theoretical capacity but suffer from serious phase agglomeration-induced fast capacity fading during cycling. Here, we report that multiple intercross lithiation steps integrated into a p-block bimetal oxide anode can achieve long life and high volumetric capacity behavior. Rationally designed Bi₂Sn₂O₇, which is composed of two interpenetrating Bi−O and Sn−O networks, undergoes intercross four-step reduction-alloying reactions and constructs a mutually buffered anti-coarsening microstructure. The intermixed atom configuration of Bi₂Sn₂O₇ establishes three-dimensional (3D) electronic conductive networks, which improve the atomic diffusion barriers for each atom and lower the tendency of phase migration aggregation. Carbon-free Bi₂Sn₂O₇ with a superior tap density of 2.2 g cm⁻³ shows an exceptionally high volumetric capacity of 1,955 mA h cm⁻³ at 2 A g⁻¹ (approaching the theoretical value of Li metal) and cycled for 500 cycles without decay. This atom immobilization strategy may offer new perspectives for next-generation conversion-alloying-type lithium-ion battery anodes. © 2022 The Authors