A doping-coating surface modification method was used to improve the cycle performance of the lithium-ion battery cathode material spinel LiMn2O4. Al was chosen as the doping element and AI(NO3)3 as the raw material. We investigated Al3* doping of 7.1%(atomic fraction) at the temperatures of 300,400, 500, 600, 700, 750, and 800 ℃. It was found that at increasing temperatures, the maximum specific capacity of the modified samples first increased and then decreased, with a maximum at 700 ℃. The fading rate increased initially with temperature as well, and then decreased, followed by a small rise with temperature. This is because the coated layer gradually reacted with the LiMnzO4 granule at elevated temperatures and became a completely solid solution layer by 750 ℃. The fading rate reached the minimum at the same time. Subsequently, the solid solution layer diffused into the LiMn2O4 granule, weakening the granule protection so that the fading rate slightly increased. Among these samples, the maximum specific capacity (133.6 mAh ·g-1) was for the sample treated at 700 ℃ for 5 h, and the fading rate was 3.4% after 50 cycles. It is shown that doping-coating surface modification with Al3+ may enable the commercial application of spinel LiMn2O4 cathode material for lithium-ion batteries.%采用表面掺杂包覆改性的方法对LiMn2O4尖晶石型锂离子电池正极材料进行改性.以Al为表面掺杂元素,Al(NO3)3为原料,研究了Al3+掺杂量为7.1％(原子分数)时不同温度(300、400、500、600、700、750、800℃)下的改性效果.研究发现,随着热处理温度的升高,改性样品的最大比容量先升高后降低,在700 ℃达到最大值；循环衰减先增大后降低再增大；这是由于随着热处理温度的升高,包覆层逐渐分解并与LiMn2O4颗粒反应固溶,在750℃完全固溶,衰减达到极小值,而后固溶层向颗粒内部扩散,导致包覆层对颗粒免受电解液溶解的保护能力变弱,因而容量衰减增大.其中700℃热处理5h的样品最大比容量为133.6 mAh·g-1,循环50周衰减3.4％研究表明Al3+表面掺杂包覆改性有利于促进LiMn2O4尖晶石型锂离子电池正极材料的商业化生产,具有大规模应用的前景.
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