【作者】 沙鸥；

【导师】 唐致远；

【作者基本信息】 天津大学 ， 应用化学， 2012， 博士

【摘要】 本论文主要对尖晶石型高压正极材料LiNi_0.5Mn_1.5O₄的制备与改性以及层状正极材料LiNi_1/3Co_1/3Mn_1/3O₂的制备进行了系统研究，并初步探究了LiNi_0.5Mn_1.5O₄/Li₄Ti₅O₁₂和LiNi_1/3Co_1/3Mn_1/3O₂/Li₄Ti₅O₁₂全电池的电化学性能。以NiCO₃·2Ni（OH）₂·4H₂O为镍源，采用球磨固相法在最佳工艺条件（800℃，20h）下得到了电化学性能较好的LiNi_0.5Mn_1.5O₄正极材料，其在1C倍率下的放电比容量为105.6mAh·g^-1，循环100圈后的容量保持率为89.7%。通过优化的溶胶-凝胶法探究了低温退火处理对LiNi_0.5Mn_1.5O₄正极材料的结构和电化学性能的影响。结果显示，低温退火处理降低了材料中Mn³⁺的含量，提高了产物的纯度和电化学性能，使其在1C倍率下的放电比容量达到125.0mAh·g^-1，循环100圈后的容量保持率高达97.6%。成功制备了Cu²⁺掺杂的LiNi_0.45Cu_0.05Mn_1.5O₄正极材料，发现Cu²⁺掺杂能有效抑制电极极化，改善材料的高倍率和高温循环性能：在20C倍率下循环150圈后的放电比容量达到首次(114.2mAh·g^-1)的95.7%，高温（55℃）且5C放电倍率下的容量仍有127.3mAh·g^-1，循环100圈后容量仅衰减2.0%。首次报道了多元离子掺杂的LiNi0.475Al0.01Cr0.04Mn1.475O₃.95F0.05正极材料，其在0.2C，1C，5C，10C，15C和20C倍率下的放电比容量分别可以达到136.6，134.0，129.0，119.9，104.5和86.4mAh·g^-1，在高温（55℃）且1C和10C倍率下循环100圈后容量仅衰减0.3%和4.4%。多元离子掺杂提高了材料的电化学反应活性及循环可逆性，使其具有更加优异的大电流充放电性能。首次提出了采用廉价且无毒的尿素辅助溶胶-凝胶法制备LiNi_0.5Mn_1.5O₄正极材料，所制备的材料在1C，3C和5C倍率下的放电比容量最高可达到132.1,123.3和113.0mAh·g^-1。另外，在探究LiNi_0.5Mn_1.5O₄/Li₄Ti₅O₁₂全电池的电化学性能时发现，采用正极过量匹配的全电池在0.5C倍率下循环200圈后仍可达到98.7mAh·g-1，库伦效率均在99%左右，具有良好的循环寿命和循环可逆性。以LiOH·H₂O和Ni_1/3Co_1/3Mn_1/3（OH）₂为原料，采用高温固相法制备了性能较好的LiNi_1/3Co_1/3Mn_1/3O₂正极材料，其与Li₄Ti₅O₁₂负极材料相匹配组装的全电池(LiNi_1/3Co_1/3Mn_1/3O₂/Li₄Ti₅O₁₂)在0.2C，1C，5C和10C倍率下的首次放电比容量分别可达到147.3，139.2，119.6和86.0mAh·g^-1，且在5C倍率下循环1000圈后的容量保持率仍有83.7%，具有优异的大电流充放电性能和循环寿命。更多还原

【Abstract】 The preparation and modification of spinel high-voltage cathode materialLiNi_0.5Mn_1.5O₄and layered cathode material LiNi_1/3Co_1/3Mn_1/3O₂weresystematacially studied in this paper. The electrochemical properties ofLiNi_0.5Mn_1.5O₄/Li₄Ti₅O₁₂and LiNi_1/3Co_1/3Mn_1/3O₂/Li₄Ti₅O₁₂full cells were alsodiscussed preliminarily.With NiCO₃·2Ni（OH）₂·4H₂O as Ni source, LiNi_0.5Mn_1.5O₄cathode materialsynthesized by ball-milling solid state method under the optimal process conditions（800℃,20h）, could reach a discharge capacity of105.6mAh·g^-1at the rate of1Cwith the capacity retention of89.7%after100cycles.The effect of low-temperature annealing treatment on the structure andelectrochemical performance of spinel LiNi_0.5Mn_1.5O₄cathode material was studiedby the optimized sol-gel method. The results showed that the content of Mn³⁺in theproduct was decreased and highly purity product was obtained after annealingtreatment. The annealed material with good electrochemical performance could reacha discharge capacity of125.0mAh·g^-1at the rate of1C with the capacity retention of97.6%after100cycles.The Cu²⁺doped LiNi_0.45Cu_0.05Mn_1.5O₄cathode material had been preparedsuccessfully. It was found that doping with Cu²⁺could reduce the electrodepolarization and ameliorate the cycle performance of the spinel at high rate and hightemperature. The LiNi_0.45Cu_0.05Mn_1.5O₄cathode material could reserve95.7%of theinitial discharge capacity (114.2mAh·g^-1) after150cycles at the discharge rate of20C, and could deliver127.3mAh·g^-1at high temperature （55℃） and5C with acapacity fading rate of2.0%after100cycles.Multiple ion doped LiNi0.475Al0.01Cr0.04Mn1.475O₃.95F0.05cathode material wasfirstly reported, which could achieve136.6,134.0,129.0,119.9,104.5and86.4mAh·g^-1at0.2C,1C,5C,10C,15C and20C, respectively. In addition, whencycled at55℃for100cycles, the capacity fading rates were only0.3%and4.4%at1C and10C, respectively. After multiple ion doping, the electrochemical reaction activity and cycle reversibility of the material had been improved, promoting theenhancement of its charge-discharge performance at high current.A cheap and nontoxic urea-based sol-gel method for the synthesis ofLiNi_0.5Mn_1.5O₄cathode material was proposed for the first time. The obtainedmaterial could achive132.1,123.3and113.0mAh·g^-1at1C,3C and5C,respectively. In addition, in the research of the electrochemical performance ofLiNi_0.5Mn_1.5O₄/Li₄Ti₅O₁₂full cell, the cell designed by some excess positive capacityshowed preferable cycle life and reversibility, which could achive98.7mAh·g^-1after200cycles at0.5C and the coulombic efficiencies were around99%.Layered LiNi_1/3Co_1/3Mn_1/3O₂cathode material was synthesized by hightermperature solid state method with LiOH·H₂O and Ni_1/3Co_1/3Mn_1/3（OH）₂as rawmaterials. The full cell (LiNi_1/3Co_1/3Mn_1/3O₂/Li₄Ti₅O₁₂) matched with Li₄Ti₅O₁₂anodematerial could reach the discharge capacity of147.3,139.2,119.6and86.0mAh·g^-1at0.2C,1C,5C and10C, respectively. Besides, it also could reserve83.7%after1000cycles at the rate of5C, revealing excellent charge-discharge performance andcycle life at high current.更多还原