A new material for ultra-thin two-dimensional pseudocapacitor cathodes was developed

Recently, the team of Wu Zhongshuai, a researcher at the Institute of Chemical Physics, Chinese Academy of Sciences, has made new progress in constructing high-performance two-dimensional pseudocapacitance multi-electron reaction lithium storage materials. The team designed and prepared a new ultra-thin two-dimensional VOPO4 pseudocapacitor cathode material, which significantly improved the kinetics of multi-electron reactions and constructed a solid-state lithium metal battery with high energy density and high power density. The results were published in Advanced Energy Materials.

Schematic diagram of ultra-thin materials. Photo courtesy of Dalian Chemical Properties

A “multi-electron reaction” is generally defined as a reaction in which more than one electron is transferred per active material molecule. As a typical class of multi-electron reaction cathode materials with multiple redox pairs, VOPO4 can provide higher energy density due to its high potential due to its negative electricity (PO4)3-anion. However, VOPO4 has a slow reaction kinetics due to the volume diffusion process and low intrinsic conductivity.

In this work, the team realized a high-rate multi-electron reaction chemical pseudocapacitor cathode by regulating the V4+ defect in VOPO4. The two-dimensional VOPO4/graphene nanosheets prepared by the team not only have an ultra-thin nanosheet structure to improve the electronic and ionic conductivity, but also effectively adjust the multi-electron reaction uniformity and reaction kinetics by controlling the content of V4+ defects, and reduce the electrode polarization.

Furthermore, the team proposed a new UV-curable solid electrolyte with room temperature ionic conductivity of 0.99mS/cm, which is significantly higher than that of polyethylene oxide solid electrolyte. The solid-state lithium metal battery assembled by the team achieves a high energy density of 85.4Wh/kg and a high power density of 2.3kW/kg, while the pouch battery shows excellent mechanical flexibility and safety.

This work provides a new way to develop multi-electron chemical two-dimensional pseudocapacitor fast charging cathode materials for high specific energy and high power lithium metal batteries. (Source: Sun Danning, China Science News)

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