Preparation And Properties Of Special Structure Spinel Manganese-based Materials

Li-ion batteries are used as a prospective chemical energy storage device in electric vehicles?EVs?,hybrid electric vehicles?HEVs?and plug-in hybrid electric vehicles?PHEVS?,owing to high power and energy density,excellent rate capability,superior cyclability and so on.Spinel manganese-based materials have aroused extremely widespread interest because of its low cost,abundance,safety,environmental benignity.In view of this,the development of spinel manganese-based cathode materials with superior performance have very profound practical significance.In this paper,in order to meet the development of the next generation lithium-ion battery,LiMn₂O₄ and LiNi_0.5Mn_1.5O₄intergrown cathode and excellent nanostructures of LiMn₂O₄ are studied.5V hierarchical hollow porous cube-shaped spinel manganese-based intergrown cathode materials are synthesized by an impregnation method with cube-shaped MnO₂ as self-template and manganese source.And then equal proportion of LiNi0.5Mn1.5O4 and LiMn₂O₄(LMO/LNMO-1/1,LiMn_1.75Ni_0.25O₄)intergrown cathode materials exhibit the most excellent electrochemical performance.This is because a homogeneous intergrown structure tunes the concentration of Mn³⁺to some extent,optimizes the distribution of Mn and Ni ions and regularly stabilizes LiNi_0.5Mn_1.5O₄ and LiMn₂O₄.The initial discharge capacity and energy density are as high as 141.7 mAh g^-1 and 627.8 Wh Kg^-1 at 1 C.At 5 C,the first discharge capacity of LMO/LNMO-1/1 yields 121.8 mAh g^-1 with 88.8%capacity retention up to 100 cycles,What's more,even though cells are performed at elevated temperature and encounter with intermittent high rate load,considerably superior cycle stabilities still are retained.The LMO/LNMO-1/1 yields the primal discharge capacity of142.5 mAh g^-1 and 140.8 mAh g^-1,with 93.1%and 92.9%capacity retention up to 50cycles at 55°C and subjecting to intermittent 5 C discharge or 5 C charge load every five cycles,respectively.Hierarchical porous LiMn₂O₄ nanosheets cathode is prepared via an impregnation method with ultra-thin MnO₂ nanosheets as self-template and manganese source,which improves dramaticlly the rate capability and cyclic perpormance of lithium ion batteries.At5 C,25°C,the initial discharge capacity of LiMn₂O₄ is 109.8 mAh g^-1,with 98.3%capacity retention up to 500 cycles;At 5 C,55°C,the primal discharge capacity of 115.1mAh g^-1 is delivered,with capacity retention of 96%by the end of 100 cycles,which shows a good cycle stability and high temperature stability.Most importantly,at 10 C,after 600cycles,the correspondingly capacity retentions of 99.1%is retained.The superior rate capacity,high temperature performance and cyclability of LiMn₂O₄ can be attributed to the unique hierarchical porous nanosheets structure,which not only reduces the Li⁺ions diffusion distance,is conducive to the full infiltration of electrolyte and improve the reaction kinetics;but also can supply interior space to accommodate the resulting volume strain and lattice stress arising from repetitive Li⁺ions de-/intercalation processes.