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Crystal structure Control and Application to electrode materials of Low-expanding Composite Oxides

低膨胀复合氧化物晶体结构控制及其在电极材料中的应用

基本信息

批准号：
07505029
负责人：
WAKIHARA Masataka
金额：
$ 1.41万
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 (A)
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-07505029/
关键词：
Lithium secondary battery Lithium manganese oxide spinel Low-expansion Control of crystal structure Charge-discharge cycling Diffusion coefficient of lithium スピネル型酸化物正極

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 repidly 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 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（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，钴的天然资源是如此有限（少于900万吨），以致于强烈期望替代钴的新阴极材料。锰是一种丰富的金属元素，尖晶石型锂锰氧化物LiMn_2O_4也可以作为锂二次电池的可逆正极材料，但其长期充放电循环稳定性不如LiCoO_2。在本课题中，我们的研究重点是用其它金属元素取代LiMn_2O_4中的部分锰离子，LiM_yMn_<2-y>O_4。作为M元素，选择了与Mn-O相比对氧化物离子具有更强亲和力的金属，例如，Cr、Ni、Co的掺杂，LiM_yMn_ O_4的充放电循环性能得到显著改善<2-y>。特别是当y=1/6，M=Co时，200次循环后仍能保持90%以上的首次放电容量（115 mAh/g），而LiMn_2O_4在相同循环次数后的放电容量仅为初始容量的60%左右。当M=Ni时，虽然初始容量不大（95 mAh/g），但循环容量的降低也很小。同时还测量了锂在LiM_yMn_ O_4中的扩散系数（D_<Li>）随锂含量x<2-y>的变化。用CPR方法还发现，<Li>x=0.5时的D_值比其它x区域的D_值高两个数量级（10^<-7.5>cm ^2·s ^<-1>），而其它x区域的D_值可能是锂离子有序排列的结果。