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

Abstract

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 Bi 2 Sn 2 O 7 , 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 Bi 2 Sn 2 O 7 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 Bi 2 Sn 2 O 7 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. • Bi 2 Sn 2 O 7 is developed as lithium-ion battery anode • Carbon-free Bi 2 Sn 2 O 7 anode undergoes intercross and self-buffered reactions • Bi 2 Sn 2 O 7 with superior tap density shows ultrahigh volumetric capacity and stability Dong et al. present a rationally designed bimetal oxide Bi 2 Sn 2 O 7 , which is composed of two interpenetrating Bi−O and Sn−O networks. The carbon-free Bi 2 Sn 2 O 7 anode undergoes intercross and self-buffered reactions, showing an exceptional long-term cycling stability and ultra-high volumetric capacity approaching the theoretical value of Li metal.