Lithium Sulfur Battery: Current Status and Future Prospects

Lithium sulfur battery is a promising candidate for the next generation rechargeable battery since the negative electrode, lithium, and the cathode, sulfur, have the highest theoretical capacities of 3862 and of 1672 mAh/g, respectively, among any other active materials, e.g., graphite (372 mAh/g) or LiCoO₂ (274 mAh/g, only about 50% is practically available). However, there are several challenging issues in order to realize the use of this type of next generation battery. First, the lithium metal anode has an intrinsic safety issue, dendrite growth that can result in internal short circuit failure. Second, the sulfur cathode is a very insulating material; therefore, sulfur-based cathodes need a large amount of conducting additives, resulting in the decrease in the practically available gravimetric capacity per the unit mass of cathode composite. Third, lithium polysulfides, reduced (discharged) forms of sulfur, dissolve into an electrolyte solution, resulting in capacity fading. For realistic battery applications, these issues from both the anode and the cathode need to be solved or mitigated. To this end, we integrate three practically possible solutions: (1) manufacture-friendly pre-lithiation of anode or cathode materials, (2) practically optimal choice of conducting agent and of the method for sulfur-conductive-agent integration, and (3) stabilization of discharged forms of the cathode. In addition, we are tackling with a well-known issue among lithium sulfur battery researchers, low mass-loading of sulfur: sulfur-based cathode, 2 mg/cm²; LiCoO₂-based cathode, 20 mg/cm², graphite-based anode, 10 mg/cm². In this presentation, the current status of our research and future prospects will be introduced.