Controllable Synthesis Of One-Dimensional Hierarchical LiNi_1/3Co_1/3Mn_1/3O₂ And Its Electrochemical Performance

Lithium-ion batteries are favored by researchers because of their high energy density,long cycle life,high operating voltage and no memory effect.Cathode materials are the key factors to determine the electrochemical performance and cost of lithium-ion batteries.The hierarchical LiNi_1/3Co_1/3Mn_1/3O₂ materials are considered to be the most promising cathode materials for lithium-ion batteries,owing to the high specific capacity,wide voltage range,low toxicity,good safety and low price under the synergistic action of Ni,Co and Mn.However,LiNi_1/3Co_1/3Mn_1/3O₂ materials still have some shortcomings of cationic mixing and low electronic conductivity,which affect the cyclic and rate performance.To deal with these problems,the electrochemical properties are usually improved by means of the control of morphological structure,element doping and surface modification.In this paper,the preparation of LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials with one-dimensional structure is taken as the main route,which shows high electrode-electrolyte contact area,short Li⁺transmission pathway and effective buffering effect.In order to obtain LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials with higher specific capacity and longer cycle life,different preparation processes are used to control the morphology and structure,and element doping modification is introduced.The main contents and results are as follows.?1?Single crystal LiNi_1/3Co_1/3Mn_1/3O₂ nanorods?NR-LNCM?cathode materials have been successfully synthesized via a facile template method followed with heat-treatment,using single crystal?-MnO₂ nanorods as self-template and Mn source.The NR-LNCM cathode materials exhibit better electrochemical performance than the bulk LNCM materials?B-LNCM?prepared by the traditional coprecipitation method in the paper.The NR-LNCM electrode delivers a high initial discharge specific capacity is 189.0 mAh g^-1and remains 170.5 mAh g^-1after 200cycles at 0.5 C,with a high retention rate of 90.2%.In addition,good structural reversibility and stability of the NR-LNCM materials are proved by the ex-situ XRD test during the first charge-discharge process.?2?LiNi_1/3Co_1/3Mn_1/3O₂?LNCM?hollow fibers composed of ultra-thin flake have been synthesized by wet spinning method,using sodium alginate gel as spinning solution and transition metal salt solution as coagulating bath.The LNCM hollow fibers have a lower degree of cation mixing,obvious layered structure,uniform particle size and more pores under the calcination condition of 750^oC for 12h.When the precursors are pressed into sheets,LNCM electrodes deliver a high discharge specific capacity of 173.5 mAh g^-1and remain a high capacity retention of143.3 mAh g^-1after 200 cycles at 0.5 C.?3?Mg-doped LiNi_1/3Co_1/3Mn_1/3O₂?Mg-LNCM?hollow fibers are prepared by wet spinning method using the solution of transition metal salt and Mg salt as coagulating bath.The effect of Mg doping on the electrochemical properties of LNCM is investigated and the results show that the Mg-LNCM materials exhibit better electrochemical performance than LNCM.The Mg-LNCM electrode delivers a higher initial discharge specific capacity of 202.7 mAh g^-1and the specific discharge capacity could maintain 180.5 mAh g^-1after 200 cycles at 0.5 C.