Study On Doping Flame Synthesis ZnMn₂O₄ Nanoparticles For Suppressing Of Dendrite Growth In Lithium Ion Batteries

In recent years,facing the dual pressure of energy and environment,lithium-ion battery has been widely used in the field of energy storage and power supply,but the related safety problems also occur frequently.Especially under the abuse behavior of long-term charge and discharge with high current,the uneven insertion of Li⁺on the graphite anode surface leads to dendrite growth or even direct connection of positive and negative electrode,which resulting in the thermal runaway of the lithium-ion battery in the end.Therefore,basing on the research ideas of enhancing the capacity of anode and guiding the uniform deposition of Li⁺on the anode,ZnMn₂O₄ with conversion reaction and alloying reaction is prepared by flame synthesis method in this paper.The effect of nanostructure ZnMn₂O₄ doping in flaky graphite on suppressing dendrite growth of lithium-ion battery anode is studied.Firstly,nanostructure ZnMn₂O₄ is synthesized through premixed stagnant planar flame.However,the crystallinity of the raw product is not satisfied.Then the nanoparticles are calcined at 600℃ for 2 h.The size and specific surface area of polycrystalline ZnMn₂O₄ is 50 nm and48.54 m²/g,respectively.The size of the calcined ZnMn₂O₄only increases 30 nm compared with that of the raw product.On the contrary,the specific surface area of ZnMn₂O₄ prepared by coprecipitation method is only 16.41 m²/g.It is obvious that flame aerosol synthesis technology has so many advantages,including simple preparation process,uniform product size distribution and highly nanoscale.Secondly,by adjusting the experimental working conditions of flame aerosol synthesis,it is found that ZnMn₂O₄ can be synthesized only by high temperature flame,while the mixture of Zn O and Mn₃O₄ can be obtained by relatively low temperature flame.Further the study on the effect of nitrate and acetate on the morphology of the products shows that only acetate can be used as the precursor to synthesize nanoscale binary composite transition metal oxides.Finally,ZnMn₂O₄ is uniformly dispersed on the surface or interlamination of graphite by ultrasonic mixing method.Compared with pure graphite,the capacity,rate performance and cycle stability of the anode are significantly improved by doping 40%wt nanostructure ZnMn₂O₄.The specific capacity maintains at 498.4 m Ah/g after 100 cycles.The charge transfer impedance of the anode doped with 40%wt nano-ZnMn₂O₄ is stable at 64.49Ω,which is far lower than that of graphite anode.The porous structure of the anode by doping 40%wt nanostructure ZnMn₂O₄,the alloying reaction between Zn and Li and the low charge transfer resistance together make Li⁺uniformly deposite on the anode surface,which can reduce the side reaction of Li⁺deposition during charge discharge with high current.In summary,nanostructure ZnMn₂O₄ doped in graphite plays an important role in suppressing dendrite growth and improving the safety and stability of the lithium-ion battery.