【作者】 高军；

【导师】 赵景茂；

【作者基本信息】 北京化工大学 ， 材料学， 2007， 硕士

【摘要】 尖晶石型锰酸锂具有无毒、能量密度高等特点，是下一代锂离子电池最有前途的正极材料之一。但在充放电循环过程中，由于锰的溶解、电解液分解以及Jahn-Teller效应等原因，尖晶石型锰酸锂的比容量衰减较快。本文主要研究了锂离子电池正极材料尖晶石型锰酸锂的离子掺杂改性，以改善材料的结构和电化学性能。（1）采用离子半径比Mn³⁺大，但有着比Mn-O键强很多的金属—氧键和更强八面体场择位能的La³⁺和Sm³⁺对尖晶石锰酸锂进行单一元素掺杂改性。比较分析了La³⁺和Sm³⁺不同浓度掺杂所得LiMn_2-xM_xO₄（M为所掺杂的离子）尖晶石锰酸锂的结构特征和电化学性能。实验表明，通过选择适量的离子掺杂，可以使掺杂后的锰酸锂结构更加稳定，电化学循环性能提高，但是掺杂离子的量不能太多，对于本文所选用的两种掺杂元素，掺杂的量都应该控制在x=0.02以下。比较发现，所得材料中，电化学循环性能最好的是：LiMn_1.98La_0.02O₄和LiMn_1.99Sm_0.01O₄，首次充放电容量分别为120mAh·g^-1和118.8mAh·g^-1，50次充放电循环之后放电容量仍保持在105.7mAh·g^-1和107mAh·g^-1。（2）合成了二元掺杂的锂离子电池正极材料LiM1_xM2_yMn_2-x-yO₄（M1=Ni，Al，Co；M2=La，Sm）。使用X-射线衍射光谱（XRD）和扫描电镜（SEM）分析了正极材料的结构和形貌，实验结果表明：所合成的产物呈现出良好的尖晶石型结构，颗粒分布均匀；充放电测试表明：掺杂不同元素对锰酸锂电化学性能影响很大，对比发现LiCo_0.08La_0.02Mn_1.9O₄在3.0～4.3V电压区间内，电化学性能最好，首次放电容量达120mAh·g^-1，50次充放电循环后放电容量为mAh·g^-1，容量衰减为7％。更多还原

【Abstract】 The spinel manganic acid lithium is promising to be cathodes forLi-ion battery, due to its relatively high energy density and low toxicity.However, the capacity of spinel manganic acid lithium fades rapidly inthe charge-discharge cycle process. It has been suggested that thecapacity fading is due to Jahn-Teller distortion, dissolution of manganeseinto the electrolyte and decomposition of the electrolyte. This dissertationis intending to investigate the modification of spinel lithium manganesecathode material for lithium-ion batteries by ion doping, so as to improveits electrochemical performance.（1） The lanthanide ion La³⁺ or Sm³⁺, which has the much larger ionicradius than Mn³⁺, and has much stronger Mn-O bond energy and higheroctahedral site preference, were introduced to modify spinel lithiummanganese. Analysis the structure and electrochemical characterization ofLiMn_2-xMO₄（ M represents the doping element ） spinel lithiummanganese cathode doped with La³⁺ and Sm³⁺.The experiment resultsshowed that the structure was more steady and the cycling performance was better than pure lithium manganese cathode by doping someelements. X in LiMn_2-xM_xO₄ must be under 0．02 otherwise the structurewould be changed at the same time discharge capacity decayed. Bycomparison, LiMn₁．98La₀．02O₄ and LiMn₁．99Sm₀．01O₄ show the bettercharacterization in cycle performance. The first discharge capacity is120mAh·g^-1 and 118．8 mAh·g^-1 , the capacity still keep 105．7 mAh·g^-1 and107 mAh·g^-1 after 50 cycle.（2） The cathode materials, LiM1_xM2_yMn_2-x-yO₄ （M1= Ni, Al, Co;M2=La, Sm） , for Lithium-ion battery doped with two elements weresynthesized by high temperature solid-state reaction method. X-raydiffraction and SEM showed that the material had a better spinel structureand the particle size were narrowly distributed, and the electrochemicaltest showed a great difference among the materials doped with differentelements. LiCo_0．08 La_0．02 Mn_1．9 O₄ has the best performance compared to theothers in the range of 3．0-4．3V. The first discharging capacity reached120mA·h/g, and the capacity still kept at 109mA·h/g after 50 cycles,which decayed only 7%.更多还原