Optimizing high energy density sulfur cathodes: A multivariate approach to electrode formulation and processing

Lithium-sulfur (Li-S) batteries involve complex solid-liquid-solid phase transformations during both discharging and charging processes, where cathode materials, formulation, and structure play a crucial role. Here, a design of experiments (DoE) methodology and an empirical model are developed to systematically explore the interactions and trade-offs among cathode factors and process variables, and to obtain generalizable effects estimates for the multivariate system. Compared to the conventional one-factor-at-a-time (OFAT) approach, this work demonstrates advantages in both efficiency and accuracy by allowing the data to guide future research and decisions. Further, an optimized cathode formulation and processing parameters are predicted and validated experimentally, achieving over 1000 mAh g^-1 in discharge capacity and improved cycling under practical lean electrolyte (4 µL mg^-1 S) and high S-loading cathodes (>4 mg cm^-2) conditions. The optimized cathode was scaled up and assembled into Li-S pouch cells, achieving 316 Wh kg^-1 in cell-level energy, proving that the comprehensive and rigorous framework for optimizing complex systems with DoE leads to improved performance in a practical pouch cell system.. Authors: Spackman, Isaac [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)]; Anderson, Cassidy [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States)] (ORCID:0000000200914529); Liu, Jun [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States)]; Xiao, Jie [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States)]; Lu, Dongping [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)] (ORCID:0000000195978500). DOE Contract: AC02-98CH10886; AC05-76RL01830. Subjects: 25 ENERGY STORAGE; Design of experiments; Electrode processing; High loading electrode; Interaction effects; Lithium-sulfur batteries