非计量化合物LiMn_1-XM_xO_2-YF_Y的固相合成及其电化学性能测试

【作者】 刘冬如；

【导师】 黄可龙；

【作者基本信息】 中南大学 ， 应用化学， 2005， 硕士

【摘要】 本文在详细评述了锂离子电池及其正极材料研究进展的基础上,选取层状LiMnO2为研究对象,对其合成和掺杂改性进行了详细研究。 研究了以一水氢氧化锂、四水草酸锰、三氧化二钼为合成原料,采用高温固相分段加热法合成LiMn_0.9Mo_0.1O₂。其首次充电容量为160mAh·g^-1,放电容量为158mAh·g^-1。经10次充放电循环后,其充电容量为156mAh·g^-1,放电容量为155mAh·g^-1。Mo³⁺的掺杂降低了LiMnO₂的容量,但提高了其循环扫描稳定性和充放电稳定性,且其晶型致密细小均匀。 研究了以一水氢氧化锂、电解二氧化锰EMD、三氧化二铬为原料,直接高温固相合成LiMn_0.85Cr_0.15O₂。其首次充电容量为149mAh·g^-1,放电容量为150mAh·g^-1。经10次充放电循环后,其充电容量为148mAh·g^-1,放电容量为148mAh·g^-1。所合成的试样循环稳定性、充放电稳定性好。 研究了一水氢氧化锂、电解二氧化锰EMD、三氧化二铬、活性碳C、氟化锂为原料,采用中温固相法,利用活性碳C的还原性,合成LiMn_0.85Cr_0.15O_1.95F_0.05。常温下（25℃）,其首次充电容量为168mAh·g^-1,放电容量为210mAh·g^-1;经18次充放电循环后,其充电容量为186mAh·g^-1,放电容量为163mAh·g^-1。高温下（55℃）,其首次充电容量为194mAh·g^-1,放电容量为174mAh·g^-1:经9次充放电循环后,其充电容量为193mAh·g^-1,放电容量为151mAh·g^-1。充放电容量高,循环稳定性和充放电稳定性好。经XRD检测,它主要为o-LiMnO₂ Mo³⁺、Cr³⁺的掺杂,提高了LiMnO₂的循环和充放电的稳定性。Cr³⁺、F^-阴阳离子共掺杂,既提高了LiMnO₂的容量,又提高了其循环和充放电的稳定性。更多还原

【Abstract】 On the base of reviewing the development of lithium ion battery and its cathode materials in detail, layered LiMnO₂ were chosen and their synthesis and modification procedures were studied.Lithium hydroxide, manganese oxalate and molybdenum trioxide were used as raw materials, LiMno.9Moo.1O2 were synthesized by solid state synthesis method at high temperature. At C/10 rate, the fist charge capacity was 160 mAh.g^-1, and the fist discharge capacity was 158 mAh.g^-1 at 25℃（vs Li metal, voltage window 2.0⁴.3V）, and the last charge and discharge capacities were 156 mAh.g^-1 and 155 mAh.g^-1. Its stability of cycling scanning and charge-discharge was very choiceness, and the size of crystal were tuniformity.LiMn₀.85Cr₀.15O₂ was synthesized with lithium hydroxide, electrolyte manganese dioxide, chromium trioxide by solid state synthesis method at high temperature. At C/10 rate, the fist charge capacity was 149 mAh.g^-1, and the fist discharge capacity was 150 mAh.g^-1 at 25℃（vs Li metal, voltage window 2.0⁴.3V）, and the last charge and discharge capacities were 148 mAh.g^-1 and 148 mAh.g^-1. And its efficiency of charge-discharge was very high. Its stability of cycling scanning and charge-discharge was very choiceness.LiMn₀.85Cr₀.15O₁.95F₀.05 was synthesized with lithium hydroxide, electrolyte manganese dioxide, chromium trioxide, carbon, lithium fluoride by solid state synthesis method at middle temperature. At C/18 rate, the fist charge capacity was 168 mAh.g^-1, and the fist discharge capacity was 210 mAh.g^-1 at 25℃（vs Li metal, voltage window 2.0⁴.3V）, and the last charge and discharge capacities were 186 mAh.g^-1 and 163mAh.g^-1. At C/9 rate, the fist charge capacity was 194 mAh.g^-1, and the fist discharge capacity was 174 mAh.g^-1 at 55℃（vs Li metal, voltage window 2.0⁴.3V）, and the last charge and discharge capacities were 193 mAh.g^-1 and 151 mAh.g^-1. Its capacity of charge-discharge was very high, and its stability of cycling scanning and charge-discharge was very choiceness. Its components were mostly o-LiMnO₂ compound by XRD.The stability of cycling scanning and charge-discharge are improved dopingCr3+ separately. The stability of cycling scanning and charge-discharge and its capacity are improved simultaneity doping Cr3+ and F".更多还原