Electrochemical and ex situ XRD investigations on (1- x)LiNiO 2 xLi 2TiO 3 (0.05= x=0.5)
Electrochemical and ex situ XRD investigations on (1- x)LiNiO 2 xLi 2TiO 3 (0.05= x=0.5)
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DOI：
10.1016/j.electacta.2004.03.002
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发表时间：
2004-08
期刊：
影响因子：
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通讯作者：
Lianqi Zhang;Xiaoqing Wang;H. Noguchi;M. Yoshio;K. Takada;T. Sasaki
中科院分区：
文献类型：
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作者：
Lianqi Zhang;Xiaoqing Wang;H. Noguchi;M. Yoshio;K. Takada;T. Sasaki
尝试了解 (1−x)LiNiO2·xLi2TiO3(0.05≤x≤0.5) 中不寻常的电化学行为，即当 x 达到 0.075 时，初始充电容量超过过渡金属氧化至 +4，并伴随出现不可逆的初始充电平台。与充电至 4.4V 相比，充电至 4.6 和 4.8V 后充放电极化降低，并且在 x=0.1 和 0.2 时充电至 4.6V 后库伦可逆性增加，这表明过量的初始充电容量可能并非主要来自电解质分解；而x=0.2的样品的异位XRD结果证实Li+确实在充电平台阶段被提取出来，排除了电解质分解主要导致异常电化学行为的可能性。考虑到Ni4+和Ti4+一般不可能被氧化到更高的价态，因此推断这些材料中负责对过剩电荷容量进行电荷补偿的物质一定是氧离子。各种电化学循环实验表明，从应用角度观察到的容量和循环性能，x=0.05的样品具有高耐高电压和高温度的能力，是非常有前途的正极材料。
An attempt to understand the unusual electrochemical behaviors in (1−x)LiNiO2·xLi2TiO3(0.05≤x≤0.5), an excess initial charge capacity exceeding the oxidation of transitional metal to +4 accompanying the appearance of an irreversible initial charge plateau when x reached 0.075, was performed. The decreased charge–discharge polarization after charging to 4.6 and 4.8V and increased columbic reversibility after charging to 4.6V typically for x=0.1 and 0.2, in contrast to charging to 4.4V, suggested that the excess initial charge capacity possibly did not come mainly from electrolyte decomposition; while ex situ XRD results in the sample with x=0.2 confirmed that Li+were really extracted at the stage of the charge plateau, ruling out the possibility that electrolyte decomposition mainly accounted for the unusual electrochemical behaviors. It was inferred that the species responsible for charge compensation for the excess charge capacity must be oxygen ions in these materials, considering that Ni4+and Ti4+are generally impossible to be oxidized to a higher valence. Various electrochemical cycling experiments demonstrated that the sample for x=0.05 with high resistant ability to high voltage and temperature is very promising cathode material in view of observed capacity and cycleability from a viewpoint of application.