The dual actions of modified polybenzimidazole in taming the polysulfide shuttle for long-life lithium–sulfur batteries

The development of lithium–sulfur (Li–S) batteries is of practical significance to meet the rapidly escalating demand for advanced energy storage technologies with long life and high-energy density. However, the dissolution and shuttling of the intermediate polysulfides (PS) initiates the loss of active sulfur and the poisoning of the lithium anode, leading to unsatisfactory cyclability and consequently hinders the commercialization of Li–S batteries. Herein, we develop a facile strategy to tame the PS dissolution and the shuttling effect in the Li–S system by introducing a modified polybenzimidazole (mPBI) with multiple functions. As a binder, the excellent mechanical property of mPBI endows the sulfur electrode with strong integrity and, therefore, results in high sulfur loading (7.2 mg cm−2), whereas the abundant chemical interaction between mPBI and PS affords efficient PS adsorption to inhibit sulfur loss and prolong battery life. As a functional agent for the separator, the mPBI builds a PS shield onto the separator to block PS’s migration to further suppress the PS shuttling. The dual actions of mPBI confer an excellent performance of 750 mAh g−1 (or 5.2 mAh cm−2) after 500 cycles at C/5 on the Li–S battery with an ultralow capacity fading rate of 0.08% per cycle. Researchers have used a super-stable polymer to block adverse dissolution effects in energy-rich rechargeable lithium-sulfur batteries. Polybenzimidazole (PBI) polymers find use in firefighting equipment and astronaut spacesuits because of their high mechanical and thermal stability. Research team led by Shanqing Zhang from Griffith Universityin Australia and Zhoupeng Li from Zhejiang University in China now shows that PBI can make an attractive binder and separating agent for next-generation batteries. While the lithium-sulfur system has higher energy density than current lithium-ion batteries, polysulfides shuttling effect, the main technical barrier often degrades device efficiency. The team prepared a new electrode by mixing a sulfur-carbon composite with a modified form of PBI. They found battery durability improved by three to five times over typical polymer binders, while favorable binding interactions between PBI and polysulfides enhanced performance and cycling stability. A modified polybenzimidazole (mPBI) was synthesized to tame the polysulfides (PS) shuttling in Li–S batteries via dual actions. As a binder, the mPBI mechanically and chemically offers strong electrode integrity and high sulfur loading, inhibits sulfur loss and prolongs lifespan for sulfur electrode. As a functional agent, the mPBI builds a shield onto the separator to block PS migration so as to further suppress the PS shuttling. This strategy confers an excellent performance of 750 mAh g−1 (or 5.2 mAh cm−2) after 500 cycles at C/5 for the resultant Li–S battery with an ultralow capacity fading rate of 0.08% per cycle.