High-performance multi-electron reaction lithium storage material

Recently, Wu Zhongshuai, a researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has made new progress in multi electron reaction electrode materials. By constructing two-dimensional heterostructures, the team overcame the reversibility and dynamics limitations of multi-electron reactions, and realized pseudo-capacitance multi-electron reactions with high magnification and high capacity. Relevant results were published in Energy and Environmental Science.



The theoretical capacity of the electrode material is closely related to the number of electrons transferred at each redox center. Multi-electron reaction means that a single redox center undergoes more than one electron transfer during charge storage. Multi-electron reaction can break through the bottleneck of single or less than one electron transfer in traditional battery reaction, and greatly improve the specific capacity of electrode materials. However, the complexity of thermodynamics and dynamics of multi-electron transfer process will also increase significantly, making multi-electron reaction face great challenges of poor reversibility and slow dynamics.



This work developed a two-dimensional heterostructure strategy based on graphene oxide template. The two-dimensional V2O5/graphene heterostructure prepared by the team presents ultra-thin nano-sheet morphology (2.8 nm), has rich surface active sites, and is easy to release the stress/strain during ion insertion/removal, promoting reversible structural transformation. In addition, the composite of graphene not only improves the electronic conductivity of the material, but also produces a rich heterogeneous interface with built-in electric field, which promotes the charge transfer.



Benefiting from the above advantages of morphology and structure, two-dimensional V2O5/graphene heterostructure overcomes the irreversible phase transition and kinetic constraints of vanadium oxide in multi-electron reactions, realizes the reversible multi-electron transfer lithium storage reaction led by pseudocapacitance, and shows high specific capacity and excellent magnification performance, which is superior to most reported intercalated oxide materials. In this work, by decoupling the above multi-electron reactions with high capacity and wide operating voltage window, a symmetric energy storage device with pre-lithified two-dimensional V2O5/graphene electrode as both positive and negative electrodes is constructed, which has excellent energy/power performance and ultra-long cycle stability.



This work provides a new strategy for the development of multi-electron reaction electrode materials with high capacity and high magnification, and also provides an example of constructing symmetrical energy storage devices based on multi-electron reaction.



Relevant paper information: https://doi.org/10.1039/D2EE02888C