Investigations on synthesis and electrochemical performance of high performance LiNi0.8Co0.1Mn0.1O2 cathode material
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摘要: 通过改变煅烧过程中的气氛条件,以简单的固相法合成工艺获得了优异性能的LiNi0.8Co0.1Mn0.1O2(NCM811)材料,并探究了不同O2流量对样品的结构和电化学性能的影响。结果表明,当O2流量为0.1 L/min时,所合成的LiNi0.8Co0.1Mn0.1O2样品具有最低的阳离子混乱程度和较大的晶面间距。该样品在1 C、4.3 V下循环100次后的放电容量为174 mA·h·g−1,容量保持率高达98.3%;在更高的2 C倍率下循环100次后的保持率也达96.8%,并在高截止电压条件下表现良好。从实验结果还可得出,过低的O2流量不利于Ni2+转化为Ni3+,从而造成较高的阳离子混排度,而过高的O2流量则会使所合成LiNi0.8Co0.1Mn0.1O2材料的晶胞体积减小,不利于Li+的脱嵌。
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关键词:
- 锂离子电池 /
- 正极材料 /
- LiNi0.8Co0.1Mn0.1O2 /
- O2气氛 /
- 阳离子混排
Abstract: A facie solid-state route has been employed to synthesize LiNi0.8Co0.1Mn0.1O2 material with superior electrochemical performance by varying the oxygen flow rate during the calcination process, and the effect of different oxygen flow rates on the structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 has also been investigated. It reveals that the LiNi0.8Co0.1Mn0.1O2 material synthesized under a flow rate of 0.1 L/min has the lowest degree of cation mixing among all samples and large d-space. The 0.1 L/min sample shows a discharge capacity of 174 mA·h·g−1 after 100 cycles at 1 C, corresponding to the capacity retention rate of 98.3%. A retention rate as high as 96.8% is achieved at 2 C, and good performance is also obtained in high cut-off votage test. Moreover, we confirm that low oxygen-flow rate can lead to high degree of cation mixing because of high content of Ni2+, and high oxygen-flow rate can decrease the d-spacing of LiNi0.8Co0.1Mn0.1O2 material, thereby being harmful for the Li+ intercalation/deintercalation.-
Key words:
- lithium ion battery /
- cathode material /
- LiNi0.8Co0.1Mn0.1O2 /
- O2 atmorsphere /
- cation mixing
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图 6 LiNi0.8Co0.1Mn0.1O2在3~4.5 V下的循环性能 (a),LiNi0.8Co0.1Mn0.1O2-0.05 (b)、LiNi0.8Co0.1Mn0.1O2-0.1 (c) 第1次、第50次和第100次充放电的dQ·dV-1曲线
Figure 6. Cycling performance of LiNi0.8Co0.1Mn0.1O2 tested in the voltage range of 3-4.5 V (a), and the dQ·dV
−1 curves of the 1 st, 50 th and 100 th cycles for LiNi0.8Co0.1Mn0.1O2-0.05 (b) and LiNi0.8Co0.1Mn0.1O2-0.1 (c) 图 7 LiNi0.8Co0.1Mn0.1O2-0.05和LiNi0.8Co0.1Mn0.1O2-0.1样品第1圈 (a)、第50圈 (b) 的电化学阻抗图谱
Figure 7. Electrochemical impedance spectra of the LiNi0.8Co0.1Mn0.1O2-0.05 and LiNi0.8Co0.1Mn0.1O2-0.1 samples after 1 st cycle (a) and 50 th cycle (b)
Rs—Solution resistance; Rct—Charge transfer resistance; Q—Constant phase angle element
表 1 不同O2流量合成的LiNi0.8Co0.1Mn0.1O2的晶胞参数
Table 1. Cell parameters of LiNi0.8Co0.1Mn0.1O2 synthesized under different O2-flow rates
Sample a/nm c/nm c/a V/(10−3nm3) I(003)/I(104) O2-flow rates/(L·min−1) LiNi0.8Co0.1Mn0.1O2−0.05 0.28670 1.41621 4.9397 100.81 1.61 0.05 LiNi0.8Co0.1Mn0.1O2−0.1 0.28665 1.41649 4.9416 100.79 1.99 0.1 LiNi0.8Co0.1Mn0.1O2−0.2 0.28620 1.40917 4.9238 99.96 1.79 0.2 LiNi0.8Co0.1Mn0.1O2−0.3 0.28621 1.40874 4.9220 99.94 1.75 0.3 Notes: a,c—Cell parameters; V—Cell volume; I(003)/I(104)—Intensity ratio of peak (003) to peak (104). 表 2 LiNi0.8Co0.1Mn0.1O2-0.05和LiNi0.8Co0.1Mn0.1O2-0.1样品拟合后的EIS参数
Table 2. EIS parameters of the LiNi0.8Co0.1Mn0.1O2-0.05 and LiNi0.8Co0.1Mn0.1O2-0.1 samples after fitting
Sample Cycle Rs/Ω Rsf/Ω Rct/Ω LiNi0.8Co0.1Mn0.1O2-0.05 1 5.126 8.634 4.725 50 3.77 53.56 113.7 LiNi0.8Co0.1Mn0.1O2-0.1 1 6.104 7.314 5.192 50 4.71 17.09 53.67 Note: Rsf—Surface film resistance. -
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