Construction Of Three-Dimensional Carbon-Based Current Collector For Sodium Metal Anode

Sodium metal batteries provide opportunities for the development of energy storage devices with high energy density.In this system,sodium metal anode has a high theoretical specific capacity(1166 mA h g-1)and a low reduction electrochemical potential(-2.714 V vs.standard hydrogen electrode).However,it also has some problems during the cycle,such as an unstable SEI,the growth of sodium dendrite,serious volume expansion and gas generation.The occurrence of these problems will affect the performance and safe use of sodium metal anode.Recently,the design of three-dimensional carbon-based current collector was considered as an effective strategy to solve these problems.The three-dimensional structure can reduce the local current density to delay the formation of sodium dendrites,and the carbonaceous structure has the advantages of light-weight and low sodium nucleation overpotential.Herein,we constructed the ’sodiophilic’ three-dimensional carbon-based current collector by electrospinning and carried out the following research:(1)A three-dimensional uniform nitrogen-doped carbon framework was prepared by the carbonization of polyacrylonitrile film.Its specific surface area is as high as 1098 m2 g-1.And the deposition test combined with density functional theoretical calculation proved that a large amount of nitrogen doping inside the fiber can effectively reduce the sodium nucleation barrier of the surface.Meanwhile,the half-cell assembled by it achieved an ultra-stable performance of 3500 h under the conditions of 2 mA cm-2 and 2 mA h cm-2.Even at a higher current density of 4 mA cm-2,it can cycle for more than 950 h.Moreover,the stability and rate performance of the full cell assembled by matching it with Na3V2(PO4)3@C have been significantly improved.The series of results show that electrospinning has a huge potential in the design of three-dimensional carbon-based current collectors for sodium metal anode.(2)The effect of tin coating on the copper foil for sodium metal anode was investigated.As a result,the sodium nucleation overpotential on copper foil coated with commercial tin powder was greatly reduced and the stability of the half-cell under 2 mA cm-2 was improved.Furthermore,the "sodiophilic" tin was introduced into the three-dimensional uniform nitrogen-doped carbon framework to prepare a tin/nitrogendoped carbon framework.The sodium nucleation overpotential was further reduced and the performance of half-cell at 6 mA cm-2 was enhanced.In summary,the success of our strategy provides a reference for constructing a composite three-dimensional carbon-based current collector by electro spinning to improve the performance of sodium metal anode.