Self-healing Sn4P3@Hard carbon Co-storage anode for sodium-ion batteries

With a high theoretical specific and typical self-healing mechanism, Sn4P3 alloy has been widely concerned as an anode material for sodium-ion batteries (SIBs). The mechanism is attributed to a reversible conversion reaction combined with an alloy reaction. Essentially, Sn nanoparticles act as an electronic channel to activate the P component. Meanwhile, P and Na3P play a matrix to partially restore the degradation and aggregation of the alloy. Nevertheless, pure Sn4P3 inevitably shortens the cycle life due to volume expansion. Herein, the puffed rice hard carbon (HC) with loose structure within the temperature range from 800 °C to 1400 °C is used to tightly wrap the alloy via a simple ball milling. The structurally stable Sn4P3@HC composites improve the electrochemical performance of SIBs. At 1000 °C, the composites show an excellent reversible capacity of 430 mA h g−1 at 100 mA g−1 over 100 cycles, with an elevated rate capability of 260 mA h g−1 even at 3.0 A g−1, and a high capacity of 312 mA h g−1 after 400 cycles at 1.0 A g−1. This work not only testifies a superior design of HC and alloy which synergistically stabilize the electrochemical performance of SIBs, but also provides a simple, efficient, and easy-to-scale coating method for active materials.