Multifunctional water-soluble binders for Li–S batteries

Lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical specific capacity and low price, while there are still a series of problems, such as the shuttle effect of lithium polysulfide (LiPS) and the fragility of cathode structures, which need to be addressed. In order to solve the above problems, the use of a binder is an effective approach. Therefore, in this work, poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA) and boric acid (BA) were used to jointly construct a novel polymer binder for sulfur cathodes. The designed PAA-PVA-BA copolymer binder (PPB) contains a large number of polar functional groups, which have a strong adsorption capacity for LiPS and can effectively inhibit the shuttle effect of LiPS. Meanwhile, the PPB binder also demonstrates good electrolyte compatibility and thermal stability, which provides strong support for the efficient and stable operation of Li-S batteries. Therefore, Li-S batteries with the PPB binder have excellent cycling performance, completing 200 cycles at a current density of 0.5 C with a capacity retention rate of 84.4%. The rate performance of Li-S batteries assembled with PPB as a binder was also greatly improved, maintaining a high discharge capacity of 408.1 mA h g^-1 at 2 C. This work provides a new strategy for designing advanced water-soluble multifunctional binders for improving the cycle life of Li-S batteries.