Multi-walled carbon nanotube-wrapped SiP2 as a superior anode material for lithium-ion and sodium-ion batteries

Abstract

SiP2 has a high specific theoretical capacity of 2902 mA h g-1 as an anode material for lithium-ion batteries and 1788 mA h g-1 for sodium-ion batteries, respectively, but demonstrates very poor cycling stability in the entire voltage range (0–2 V). Here, we report high performance SiP2 anodes for lithium-ion batteries and sodium-ion batteries with good cycling stability by wrapping SiP2 with multi-walled carbon nanotube (MWCNT) on the surface of SiP2 via a ball milling prociess. MWCNT provides a robust network to connect fragment SiP2 with surrounding electrical conductor and serves as an effective conductive agent. MWCNT-wrapped SiP2 shows a reversible capacity of 1622 mA h g-1 after 100 cycles at 0.5 A g−1 in lithium-ion batteries and 925 mA h g-1 after 200 cycles at 0.2 A g−1 in sodium-ion batteries. In addition, rate capability is significantly enhanced. Furthermore, both coin-type and pouch-type full cells are assembled using SiP2 anodes which are coupled respectively with a cathode of LiFePO4 for lithium-ion batteries and a cathode of Na2/3Ni1/3Mn2/3O2 for sodium-ion batteries, and supplied as a reliable energy source for electronic uses to evaluate practical applications.