Preparation And Electrochemical Performance Of Modified Separator For Lithium Metal Batteries

To keep pace with the expeditious development of electric vehicles,smart grid-level energy storage devices,and portable electronic devices,batteries with high energy density and satisfied endurance time are urgently needed.With the merits of high energy density,low work potential and low density,Li metal has been regarded as the most ideal anode.However,uncontrollable and detrimental Li dendrite growth is always impeding practical application of Li metal batteries due to uneven Li deposition and repeated destruction/reconstruction of fragile SEI,which could lead to low CE,fast decay of cyclic performance and even puncture of separator to arouse serious safety problems.To solve this problem,a simple blade coating technology was used to successfully prepare PE composite separators,and the electrochemical properties of composite separators prepared with different coating were studied.On the one hand,coating of separator can improve wettability and thermal stability of commercial PE separator;On the other hand,the interparticles of coating have micro/nano voids,which can make the Li ion flux distribution more uniform to obtain smooth Li deposition layer.The specific research contents are as follows:(1)the economic and green perovskite-type CaTiO3 is adopted as the coating of commercial PE separator,which proves that CaTiO3 has good lithiophilicity.Compared with the traditional PE separator,the composite separator improves the mechanical strength of PE separator and makes it difficult to be penetrated by sharp Li dendrites.In addition,the lithiophilic CaTiO3 coating significantly reduces the nucleation overpotential of Li,and finally obtaining a dendrite-free Li anode.The symmetrical battery with composite separator can cycle stably for 1500 h in carbonate-based electrolyte.(2)The two-dimensional siloxene was prepared by HCl-etching method,and the feasibility of using 2D material as the coating of commercial PE separator was explored.It is found that,on the one hand,2D siloxene coating notably enhances the inherent properties of common PE separator and reduces the interface contact resistance;On the other hand,2D siloxene coating and Li induces in-situ LixSi-rich passivation layer which can accelerate the transport of Li ions,guide smooth Li deposition morphology,and finally obtain a stable and long-cycle Li anode with synergistic advantages.