Checking the shuttle effect of lithium-sulfur batteries with TCEP shear agent

Abstract

Sulfur is widely distributed in earth and is low cost and environmentally friendly. Lithium-sulfur battery was considered to be the next generation of new energy storage systems. However, the solubility, deposition, and shuttle effect of polysulfides of lithium-sulfur (Li-S) batteries checked the practical applications owing to low coulomb efficiency and the loss of active substances. Tris (2-carboxyethyl) phosphine (TCEP) can be used as a shear agent to transfer higher order lithium-polysulfide compounds (Li2Sx, x > 6) into low-order lithium-polysulfide compounds (Li2Sx, x < 4). The dissolution and diffusion of polysulfides were checked with an increase of utilization rate of active substances. The performance of charge and discharge and cycle of lithium-sulfur battery also were improved. Multi-walled carbon nanotubes (MWCNTs) provided high conductivity and maintained structural integrity of electrode, the diameter of MWCNTs is about 80 nm, and length is about 15 μm. The electrochemical test results showed that the first discharge capacity of electrode with TCEP interlayer reached 1410 mAh/g at a rate of 0.05 C, and the utilization rate of active material was as high as 84.6%. After 10 cycles at 3 C ratio, the discharge specific capacity still reached 526 mAh/g and the coulomb efficiency remained at 90.6%. It showed good rate and cycling performance.