High-performance silicon diphosphideanocarbon composite anode for Li-ion batteries: Role of chemical bonding and interfaces in the establishment of cycling stability

摘要

Silicon diphosphide (SiP2), a next-generation anode material for lithium ion batteries, exhibits a high theoretical specific capacity (2900 mAh g(-1)), however, its capacity is rapidly faded due to its large volume change. An effective way to improve the electrochemical performances of SiP2 is to composite with carbon buffer. In the composite, chemical bonds of SiP2 and carbon are expected to maintain SiP2 to carbon connections during cycling, thereby, provide electron conduction pathways even under the volume change of SiP2. However, effect of the chemical bonds is not clearly understood. Thus, it is very important to distinguish contributions of the carbon buffer and chemical bonds to the electrochemical properties of SiP2. Herein, SiP2 composites with nanocarbon are prepared with and without chemical bonds between SiP2 and carbon by controlling ball milling parameter with an aim to investigate respective contribution of the carbon buffer and chemical bonds to the electrochemical properties of SiP2. The SiP2anocarbon composite with P-O-C and Si-O-C chemical bonds shows great improvement of electrode performances over the composite without the chemical bonds. Furthermore, the SiP2-nanocarbon interface is found to facilitate fast ion conduction, overcoming the issues associated with the ionically insulative LiP.