Creating anion defects on hollow CoxNi1-xO concave with dual binding sites as high-efficiency sulfur reduction reaction catalyst

Abstract The slow reaction kinetics of sulfur reduction leads to excess accumulation of lithium polysulfides in sulfur cathode, which exacerbates the shuttle effects and causes a series of poor performances. Herein, hollow CoxNi1-xO concave (CNCO) is synthesized and anion defects are created on its surface as high-efficiency sulfur reduction reaction (SRR) catalyst to regulate the catalytic conversion behavior of lithium polysulfides. It has been found that the CNCO has lithiophilic/sulfiphilic dual binding sites and rich oxygen vacancies, which endow the sulfur cathode with strong affinity and high-efficiency SRR catalytic activity to lithium polysulfides, and thus the cycle stability and reaction kinetics of lithium-sulfur batteries are significantly improved. As a result, lithium-sulfur battery using CNCO as an additive can deliver a high initial specific capacity of 1355 mAh g−1 at 0.1C with a low Li2S nucleation barrier and overpotential. Moreover, this battery has a stable lifespan and can keep an high reversible capacity of 925 mAh g−1 even after 100 cycles at 0.5C. Meanwhile, even with thick cathode and low electrolyte consumption, it can achieve a high areal capacity of 3.7 mAh cm−2 at 0.5C with a low fading rate of 0.056% per cycle within 170 cycles. Therefore, this work systematically explores the positive effects of a high-efficiency SRR catalyst on the catalytic mechanism and performance enhancement of lithium-sulfur battery, it will be an important step for the practical application of lithium-sulfur battery.