Improved Electrochemical Performance of Lithium-Sulfur Batteries with Boron-Doped Zinc Cobalt Sulfide Catalyst-Modified Separators

Lithium-sulfur (Li-S) batteries possess considerable potential for high theoretical energy density; however, their practical implementation has been impeded by the polysulfide shuttle effect, resulting in inadequate cycling stability. This study addresses this challenge by synthesizing and applying a boron-doped zinc cobalt sulfide catalyst (B-ZnCo2S4) as a separator coating. The investigation demonstrates that B-ZnCo2S4-modified separators significantly enhance the electrochemical characteristics of Li-S batteries. The B-ZnCo2S4 and pristine ZnCo2S4 catalysts were synthesized using a solvothermal method, and their morphological disparities were analyzed via scanning electron microscopy (SEM). Characterization techniques affirm successful boron doping without altering the crystal structure. Batteries assembled with B-ZnCo2S4-modified separators exhibit superior electrochemical performance compared to those with ZnCo2S4-modified separators, as evidenced by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Linear Sweep Voltammetry (LSV). The B-ZnCo2S4 battery demonstrates higher catalytic activity, resulting in lower polarization voltage and charge transfer impedance. Furthermore, UV-Vis analysis reveals enhanced adsorption capabilities of lithium polysulfides by B-ZnCo2S4. During rate testing, the B-ZnCo2S4 battery exhibits an impressive specific capacity exceeding 500 mAh/g at 4C, while sustaining capacities above 800 and 900 mAh/g at reduced rates of 0.5C and 0.2C, respectively, indicating excellent reversibility. In extended cycling tests of 200 and 500 cycles, the battery demonstrates exceptional cycling stability, with decay rates of only 0.16% and 0.07% at 0.5C and 1C, respectively. SEM analysis further confirms the effective inhibition of lithium dendrite formation by B-ZnCo2S4. Therefore, the utilization of B-ZnCo2S4 as a catalyst holds great promise in augmenting the operational efficiency and longevity of Li-S batteries. These discoveries present encouraging prospects for the advancement of Li-S batteries, enabling enhanced performance and improved practical feasibility.