Full Potential Catalysis of Co_0.4Ni_1.6P–V/CNT with Phosphorus Vacancies for Li₂S_1–2 Deposition/Decomposition and S₈/Li₂S_n (3 ≤ n ≤ 8) Conversion in Li–S Batteries

The slow kinetics of polysulfide conversions hinders the commercial progress of Li–S batteries. The introduction of high-efficiency catalysts accelerates heterogeneous reactions and enhances the utilization of S. The full potential of the Co 0.4 Ni 1.6 P–V/CNT-modified separator catalyzes the all-process reactions of the S electrode and increases the rates and cycling lives of the batteries. The two-site synergistic effect of Co 0.4 Ni 1.6 P–V/CNT regulates the catalytic activity, and the phosphorus vacancies enrich the active sites. The higher electron density at the Co and Ni double sites increases chemisorption of the Co 0.4 Ni 1.6 P–V/CNT on Li 2 S n (1 ≤ n ≤ 4), stretches and breaks the Li–S and Ni–S bonds during Li 2 S decomposition, and reduces the energy barrier for Li 2 S decomposition. The cyclic voltammograms of the asymmetric batteries demonstrated that Co 0.4 Ni 1.6 P–V/CNT also catalyzed the Li 2 S n ⇌ S 8 (3 ≤ n ≤ 8) reaction, realizing the full catalytic potential of the Li–S batteries. Increased Li + diffusion/migration in the Co 0.4 Ni 1.6 P–V/CNT-modified separator ensured fast electrochemical reactions. The excellent catalytic effect of Co 0.4 Ni 1.6 P–V/CNT provided smaller polarization and superior rate performance, which led to high discharge specific capacities of 1511.9, 1172.6, 1006.0, 881.0, and 785.7 mA h g –1 at current densities of 0.1, 0.2, 0.5, 1, and 2 mA cm –2 with sulfur loadings of 7.98 mg cm –2, respectively. This approach involving simple crystal modulation and introduction of defects provides a new way to achieve the full catalytic potential of Li–S batteries.