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Crystal structure Control and Development of functional electrode using Low-expanding Composite Spinel Oxides

低膨胀复合尖晶石氧化物晶体结构控制与功能电极开发

基本信息

批准号：
07455336
负责人：
WAKIHARA Masataka
金额：
$ 4.99万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455336/
关键词：
Lithium secondary battery Lithium manganese oxide spinel Low-expansion Control of crystal structure Charge-discharge cycling Diffusion coefficient of lithium スピネル型酸化物酸素分圧制御

项目摘要

Lithium secondary batteries using lithium-cobalt oxide, LiCoO_2 as the cathode, and carbon materials as the anode (so called "lithium ion batteries") have been commercialized, and the production is rapidly expanding. However, the natural resources for cobalt is so limited (less than 9 million tons) that new cathode materials which replace cobalt are strongly expected. Manganese is one of the abundant elements, and lithium-manganese spinel oxide, LiMn_2O_4 can also successfully work as the reversible cathode of lithium secondary batteries, however, the stability of this compound in a long term charge-discarge cycling is not satisfactory when it is compared with LiCoO_2. In the present project, we have focused our efforts on the stabilization of the LiMn_2O_4 crystal lattice by substituting other metal elements for a part of manganese ion in LiMn_2O_4, i.e., LiM_yMn_<2-y>O_4. As the M elements, such metals that have stronger affinities to oxide ions compared to that of Mn-O have been chosen, e.g., Cr, Ni, Co.Notable improvement in the charge-discharge cycling properties have been observed for LiM_yMn_<2-y>O_4. Especially, when y=1/6 and M=Co, more than 90% of the initial discharge capcity of 115 mAh/g was maintained even after 200 cycle, while in the case of LiMn_2O_4, the discharge capacity after the same cycle number was almost 60% of the initial capacity. When M=Ni, although the initial capacity was not large (95mAh/g), reduction in the cycling capacity was also small. Variation of the diffusion coefficient of lithium (D_<Li>) with the lithium content x in LiM_yMn_<2-y>O_4 were also measured. It was also found by using CPR method that the D_<Li> value at x=0.5 was higher by two orders of magnitude (10^<-7.5>cm^2s^<-1>) compared with those in other x region, where lithium ions were expected to be arranged in a ordered form.

以锂钴氧化物、LiCoO_2为正极、碳材料为负极的锂二次电池(即所谓的锂离子电池)已经商业化，并且产量正在迅速扩大。然而，钴的自然资源非常有限(不到900万吨)，因此人们强烈期待新的正极材料来取代钴。锰是锂的丰富元素之一，锂锰尖晶石氧化物LiMn_2O_4也可以成功地作为锂二次电池的可逆正极，但与LiCoO_2相比，这种化合物在长期充放电循环中的稳定性并不令人满意。作为M元素，选择了与氧化物离子亲和力强的金属，如铬、镍、钴等。LiM_yMn_2-y&GT；O_4的充放电循环性能有了明显的改善。特别是当y=1/6和M=Co时，即使在200次循环后，初始放电容量仍保持在115mAh/g的90%以上，而对于LiMn_2O_4，相同循环次数后的放电容量几乎是初始容量的60%。当M=Ni时，虽然初始容量不大(95mAhg)，但循环容量的降低也很小。还测量了LiMyMnLt；2-y&gt；O4中锂的扩散系数D<Li>随锂含量x的变化。用CPR方法还发现，在x=0.5处的D<li>值比其他x区的值高两个数量级(10^&lt；-7.5&gt；cm^2s^&lt；-1&gt；)，其他x区的锂离子可能是有序排列的。