The continuous progress of science and technology has put forward higher requirements for lithium-ion battery technology, especially in the field of large-scale energy storage such as electric vehicles, which has put forward higher requirements for new lithium-ion batteries with higher energy density and lower price. Among them, lithium sulfur batteries, as a multi-electron reaction lithium-ion battery, have attracted widespread attention because their energy density (2600Wh/kg) and price advantages are much higher than those of lithium iron phosphate and lithium cobalt oxide batteries currently on the market. However, there are a series of problems such as poor conductivity of singlet sulfur, intermediate polysulfide shuttle effect, and volume expansion during the charging and discharging process. At present, researchers have proposed a series of optimization strategies for the substrate materials of sulfur positive electrodes, such as improving the conductivity of sulfur positive electrodes by porous carbon and improving the adsorption of polysulfides by nitrogen doping. However, the effect achieved by various means is limited and cannot solve the problem fundamentally. Therefore, a more effective cathode matrix material combining multiple functions is needed.
A new lithium-sulfur battery material with nanocobalt porous carbon carrier has been developed at Peking University
A new lithium-sulfur battery material
Recently, a research group led by a professor from Feng New Materials Disc Clean Energy Center of Peking University Shenzhen Graduate School College a MOF material was prepared based on cobalt nanocrystals of co-responsible nitrogen-doped porous carbon cage for lithium-sulfur battery as a new host material, which was found by its excellent electrochemical performance characterization tests including XRD, SEM, TEM, XPS, and revealed by various means such as DFT The reason for the performance, the positive effect of Co nanocrystals, polysulfide adsorption kinetics on the diffusion and conversion of lithium ions was elucidated, which provides an idea for the preparation of a new type of cathode material for lithium batteries. The results were recently published in Advanced Energy Materials (2020, 10 (9), 1903550, IF=24.884), a leading journal in the field of energy materials.
The novelty of this study is that our group utilizes the high specific surface area zNCO-MOF to adsorb glucose small molecules, and during the carbonization process, the glucose is preferentially carbonized into a carbon frame with SP2 structure, which separates metallic cobalt in the MOF cavity and improves the electrical conductivity. Meanwhile, the appropriate amount of sulfur can make the active sulfur material loaded inside the carbon cage instead of the surface, so that the sulfur can maintain a strong interaction with the carbon cage skeleton. The team prepared cobalt nanocrystals with high dispersion to assume loading of nitrogen-doped porous carbon cage polysulfide active materials and intermediates with multi-functional effects, including improved electrical conductivity, high sulfur content, stress relief, accelerated diffusion kinetics of lithium ions, catalytic polysulfide fast conversion and strong polysulfide adsorption intermediates, etc. They can ensure high performance ratio and long cycle life of lithium-sulfur batteries.
A new lithium-sulfur battery material with nanocobalt porous carbon carrier developed by Peking University
Electrochemical performance of a new lithium-sulfur composite anode material
Meanwhile, a series of studies have shown that the highly dispersed Co nanocrystals carried in the skeleton can not only effectively promote the diffusion of lithium ions and the redox of polysulfides, but also further enhance the adsorption of polysulfides. This work provides a new reference for transition metals as high-performance catalysts for polysulfides in lithium-sulfur batteries.
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