“Mobius strip-like” FeSn alloy: A novel highly-distorted 3D hierarchical porous anode for ultrafast and stable Li storage

Tin provides high specific capacity (994 mAh g−1) by forming Li4.4Sn in lithium-ion batteries (LIBs) yet exhibits poor electrochemical stability. Inspired by the miraculous "Mobius strip" with superior stress-relieving effect in the developable surface, herein, through a facile dealloying and sol-gel pyrolysis method, a "Mobius strip-like" highly-distorted C-wrapped 3D hierarchical porous FeSn integrated anode (HD-3D-HP FeSn@C) is initially designed and utilized to relieve the mechanical stress in Sn-based anode generated during lithiation-delithiation. The anodes are characteristic of highly-distorted bimodal pore-size distribution composed of microporous architecture and homogeneous nanopores on pore walls on the developable surface, which contribute to effective stress relief and rapid mass transfer. Moreover, the wrapped-C is of great significance for maintaining the anode structure and improving the stability of solid electrolyte interface (SEI). Therefore, the HD-3D-HP FeSn@C anodes display the ultrafast Li storage properties with high rate capability (0.23 mAh cm−2 at 10 mA cm−2) and good cycling stability (68.89 % of capacity retention after 1000 cycles at 1 mA cm−2, only ∼0.03 % capacity decay per cycle). This work provides a novel and universal anode design philosophy towards high-performance LIBs, which may shed light on the evolution of other secondary batteries beyond alkali metal batteries.