【作者】 曾曦；

【导师】 李奇；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2007， 硕士

【摘要】 以锂钴氧和锂镍钴锰氧分别作为正极活性物质,中间相炭微球为负极制备了高容量18650锂离子二次电池。研究了工艺条件对电池性能的影响并探讨了电池容量衰减的部分原因。试验结果表明电池的充放电制度对电池的性能有很大的影响,当电池的充放电范围的电压上限过高(超过4.2V)时,电极材料的克容量会在循环中降低。此外,预充时如果电极活化不完全,电池要在几个甚至十几个循环后才能达到最大容量。电极的面密度越大,首次充放电效率越低。当注液量不足时,会使电极浸润不够,电池的充电过程中恒压充电的比率会增大,电极材料的利用率会降低。同时由于离子迁移路径减少使得电池的内阻增大,从而降低电池循环寿命。当注液量达到一定程度时,各项指标会稳定下来,一般来说以每100mAh容量注0.3g为宜。正负极的配比对电池的实际容量的发挥有重要影响,在设计电池时,应该让负极稍微过量为宜,但也不可过量太多,否则过多的碳负极及其与电解质的界面(SEI)膜的形成会消耗的锂离子。此外,正负极的配比过低还会影响电池的循环性能,当正负极配比达到一定比例以后,电池循环性能便不再受影响。电池的内阻会随着循环的进行而增大,由于正极的晶体颗粒粉化导致与电解液的界面阻抗增大。极片的厚度不均匀时会使电池的局部正极活性物质过剩,从而使锂离子沉积,导致容量衰减。更多还原

【Abstract】 In this paper, we used LixCoO2 and LiNixCoyMn1-x-yO2 as cathode active materials, carbonaceous mesophase spherules (CMS) as anode active material to prepare 18650 lithium-ion second batteries. The influence on properties of batteries due to change of technological conditions were studied, and reasons for capacity fade were investigated as well.The results show that the properties of batteries are mainly influenced by charge/discharge schedule. When the top limit of charge voltage is too high, the capacity per gram of electrode material decreases suddenly with the cycling. Besides, if not activated during the initial charge period, the capacity of battery comes to the maximum value after several cycles. Larger the density per area, lower the initial charge/discharge efficiency. When electrolytes is not enough, the constant voltage charge period take a longer time. The utility ratio of electrode materials decreases as well. At the same time, the battery resistance increases and the cycle life decreases due to the decrease of the paths of Li-ion transportation. The properties of batteries come to a stable state when appropriate electrolytes are injected into batteries. In our experiment, 0.3g electrolytes per 100mAh is the best. The capacity of batteries is related to the ratio of cathode and anode closely. During the battery design, the designed capacity of anode should be larger than that of cathode, but not too much, since the forming of excess SEI membrane consumes a large number of lithium-ions. The cycle life is also influenced by the ratio between cathode and anode capacity. The resistance of the batteries increases with the cycling due to the interface resistance between the particles of cathode materials and electrolytes increases. The unlevelness of thickness of the electrode makes partial cathode active materials surplus, and results in capacity fade.更多还原