Sn4P3 Encapsulated in Carbon Nanotubes/Poly(3,4-ethylenedioxythiophene) as the Anode for Pseudocapacitive Lithium-Ion Storage

Developing lithium-ion batteries (LIBs) with higher capacity is crucial for renewable energy utilization, such as large-scale energy storage systems, as well as portable and flexible electronics. As a conversion-reaction type LIB anode material, Sn4P3 could deliver a theoretical gravimetric capacity of 1132 mA h g(-1). However, the usage of Sn4P3 in real LIB applications has been impeded by large volume expansion, low electronic conductivity, and limited Li+ charging speed upon cycling. Therefore, Sn(4)P(3 )is usually combined with carbon materials to improve its electrochemical performance. Herein, Sn(4)P(3 )nanoparticles were encapsulated inside the inner cavities of carbon nanotubes (CNTs) using a low-pressure vapor approach. This stemlike CNT network was further coated using poly(3,4-ethylenedioxythiophene) (PEDOT) as the electron-boosting buffer layer. In this special design, CNT/PEDOT bilayers could relieve the volume expansion of Sn4P3 during charge-discharge, as well as provide robust electron and ion transportation. As anode materials for LIBs, Sn4P3@CNT/PEDOT exhibits superior rate performances (reversible capability of 499 mA h g(-1) at 2000 mA g(-1)) and superior long-term cycling stability (701 mA h g(-1) after 500 cycles at 500 mA g(-1) and 1208 mA h g(-1) after 230 cycles at 100 mA g(-1)). In addition, a high pseudocapacitive contribution of 80% was delivered by Sn4P3@CNT/PEDOT, satisfying potential fast-charging demands. The present study provides a novel train of thought for improving the electrochemical performance of other conversion-reaction-type anode materials with large volume expansion.