Study On Modification And Performance Of Three Dimensional Fluid Collector Of Lithium Metal Batteries

Lithium metal anode is an ideal anode material for lithium battery.However,due to the local polarization and the two-dimensional deposition mode of lithium metal,a large number of lithium dendrites will be generated during the cycle of lithium metal battery,and the lithium dendrites will penetrate the diaphragm,resulting in battery short circuit and safety problems.At the same time,the formation of dead lithium will also cause the loss of battery capacity,resulting in a lower Coulomb efficiency.The introduction of three-dimensional fluid collector can effectively inhibit the growth of lithium dendrite and alleviate the volume expansion of lithium metal during charging and discharging process.In this paper,nickel foam metal（NF）and 200-mesh Cu net were used as the substrate of the three-dimensional current collectors,and the modification was carried out to study the deposition behavior of lithium metal and the electrochemical performance of the current collectors.（1）The electrochemical properties of Li₂S@Ni-NF three-dimensional current collectors with ion/electron double conductivity in lithium metal batteries were investigated.Based on NF,the current collectors modified by Li₂S and Ni on NF was realized through Ni₃S₂ nanosheet modification and in situ activation process.The Li₂S@Ni-NF current collectors has a unique vertical arrangement and cross-linking structure of nanosheets.This ion/electron conductive array can not only effectively regulate the lithium ion flux,but also play a role in regulating the electric field,providing a continuous way for the rapid transmission of Li⁺ions and electrons.Therefore,the current collectors has a high diffusion coefficient and electronic conductivity of Li⁺ions,and can effectively inhibit the growth of lithium dendrites.n Li Fe PO₄|Li₂S@Ni-NF@Li battery system,when the N/P was 6.3,under 2 C ratio,the cycle after 800 cycles,the capacity is 134.36 m Ah g^-1,compared with the cycle of the highest discharge capacity,capacity retention rate is as high as 90.8%.After 700 cycles at 5 C rate and 350 cycles at 10 C rate,the capacity retention rate can reach 95.7%and86.4%,respectively.Even better,when N/P is 1.2,it has a capacity of 101.98 m Ah g^-1after 130 cycles at a rate of 0.5 C.This work provides a new idea for the development of high performance dendrite-free lithium mental anode.（2）Cu₃P-Cu three-dimensional current collectors was prepared and its electrochemical performance in half lithium metal cell was studied.The Cu net modified with Cu₃P nanorods was obtained by chemical deposition method and high temperature solid phase method.Compared with the original Cu network,the modified fluid collector has better lipophilicity.At the same time,the larger specific surface area reduces the local current density and effectively alleviates the volume expansion problem of lithium metal in the charging and discharging process.Moreover,lithium metal tends to deposit in the Cu network skeleton pores,which achieves a higher porosity utilization rate.When 5 m Ah cm^-2 lithium metal was deposited to Cu₃P-Cu@Li electrode at the current density of 0.5 m A cm^-2,no obvious lithium dendrites were observed,and Cu₃P-Cu current collectors effectively regulated the deposition behavior of lithium metal.In the half-cell system,the Coulomb efficiency of Cu₃P-Cu accumulator reaches 98.45%after 320 cycles under the condition of area current of 1m A cm^-2 and area capacity of 1 m Ah cm^-2.