April 18, 2021

Qingdao Energy Institute successfully prepared flexible sulfur-supported body for high-performance lithium-sulfur battery

In recent years, with the promotion and application of portable electronic equipment and electric vehicles, today's society has presented new challenges for electrochemical energy storage devices. The traditional lithium-ion battery is subject to the lower theoretical capacity of the electrode material, and it is difficult to meet the requirements of high energy density energy storage systems. Lithium-sulfur batteries based on multi-electron conversion reactions are considered to be one of the most promising next-generation high-energy battery systems due to their ultra-high specific energy, abundant raw materials, low prices, and low toxicity and harmlessness. Important research directions and hot spots in the field of energy storage.

However, the inherent defects of lithium-sulfur batteries hinder their large-scale use. On the one hand, due to the low conductivity of the elemental sulfur and the reduction product polysulfide (Li2S / Li2S2), the utilization rate of the active material in the lithium-sulfur battery is low, and the rate performance is poor; Sulfur compounds will cause the "shuttle effect" to appear. Therefore, the development of cathode materials with high conductivity and strong adsorption capacity for polysulfide compounds is the key to obtaining high-performance lithium-sulfur batteries.

In response to the above problems, the Advanced Energy Storage Materials and Technology Research Group of the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, based on the modification of the positive electrode loaded sulfur body, prepared a flexible reinforced concrete body with a "reinforced concrete" structure, and Lithium-sulfur batteries have high sulfur loading, high sulfur utilization, and long cycle life. Using graphene film as the current collector, lignin fiber and carbon nanotube as the composite carrier, the flexible sulfur carrier has excellent conductivity and anchoring ability of polysulfide compounds, while combining the depolarization characteristics of graphene. The lithium-sulfur battery assembled with this current collector has a battery capacity of up to 1632.5 mAh g-1 (97.5% of theoretical capacity) at 0.1C and a capacity retention rate of 86.5% for 500 cycles at 1.0C. Even at a high sulfur load of 9.2 mg cm-2, the lithium-sulfur battery still exhibits excellent cycle stability, with a cycle capacity retention rate of 91.5% after 100 cycles at 0.5C. This work provides a new idea for improving the sulfur utilization rate and cycle life of lithium-sulfur batteries.

Related results have been published in Journal of Materials Chemistry A (Tao Liu, Jianfei Wu *, et al. Doi: 10.1039 / C8TA08521H). In addition, the research team has also made new progress in lithium-rich manganese cathode materials and sulfide solid electrolytes. The relevant results have been in Electrochimica Acta (2018, 269: 422-428), Advanced Materials Interfaces (2018: 1800783 (1-8) ), Journal of Alloys and Compounds (2018, 744: 41-50; 2017, 727: 1136-1141) and other magazines. The research results were supported by the National Natural Science Foundation of China, the "100 Persons Plan" project of the Chinese Academy of Sciences, and the Qingdao Energy Institute-Dalian Chemical Institute Fusion Project.

"Reinforced concrete-like" flexible sulfur-carrying pole piece and related structure diagram

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