Interfacial architectures based on a binary additive combination for high-performance Sn4P3 anodes in sodium-ion batteries

We demonstrate the important strategy to design suitable electrolyte systems that make the desirable interfacial structure to allow the reversible sodiation/desodiation of Sn4P3 anodes. Our investigation reveals that the remarkable improvement in the electrochemical performance of Sn4P3 anodes for NIBs is achieved by the combination of fluoroethylene carbonate (FEC) with tris(trimethylsilyl) phosphite (TMSP). We clearly present the unique functions of this binary additive combination to build up a protective surface film on the Sn4P3 anode against unwanted electrolyte decomposition and to prevent the formation of the Na15Sn4 phase, which is accompanied by a large volume expansion during the Na insertion (sodiation) process.