Dual Buffering Inverse Design of Three-Dimensional Graphene-Supported Sn-TiO2 Anodes for Durable Lithium-Ion Batteries.

ABSTRACT

Stable battery operation involving high-capacity electrode materials such as tin (Sn) has been plagued by dimensional instability-driven battery degradation despite the potentially accessible high energy density of batteries. Rational design of Sn-based electrodes inevitably requires buffering or passivation layers mostly in a multi-stacked manner with sufficient void inside the shells. However, undesirable void engineering incurs energy loss and shell fracture during the strong calendaring process. Here, this study reports an inverse design of freestanding 3D graphene electrodes sequentially passivated by capacity-contributing Sn and protective/buffering TiO2 . Monodisperse polymer bead templates coated with inner TiO2 and outer SnO2 layers generate regular macropores and 3D interconnected graphene framework while the inner TiO2 shell turns inside out to fully passivate the surface of Sn nanoparticles during the thermal annealing process. The prepared 3D freestanding electrodes are simultaneously buffered by electronically conductive and flexible graphene support and ion-permeable/mechanically stable TiO2 nanoshells, thus greatly extending the cycle life of batteries more than 5000 cycles at 5 C with a reversible capacity of ≈520 mAh g-1 with a high volumetric energy density.