Commercially available 18650 Li-ion batteries are considered for high-energy-density storage and usage in mobile applications as well as to store energy from intermittent energy sources. This has triggered intense research for suitable electrode and electrolyte materials, while their current state-of-the-art, temperature-dependent performance is hardly described in detail. The fatigue process in two brands of rechargeable commercial high-energy Li-ion batteries (18650-type, 3500 mAh LiNi_0.83Mn_0.07Co_0.11O₂ (NMC-811) and LiNi_0.86Co_0.11Al_0.03O₂ (NCA)) as a function of cycling temperature has been investigated using in situ neutron powder diffraction (NPD) and electrochemical impedance spectroscopy (EIS). The batteries (∼140) were cycled at conditions specified by the manufacturer and simulated realistic user conditions with good statistics. Cycling temperature (25, 35, and 45 °C) had a significant influence on capacity fade, with 35 °C showing the highest capacity retention. The NCA cells reached the end-of-life condition of 70% of the initial capacity after only 200 cycles when cycling at 25 °C and 1/0.5C discharging/charging rates. EIS showed that the largest increase in impedance came from the charge-transfer resistance for both cell brands, while one brand also showed a sudden increase in the ohmic resistance, which coincides with a sudden capacity drop. From in situ NPD, the decrease in Li content in the cathode and the anode could be traced as a function of cycle number, and this was found to correlate well with the observed discharge capacity. In addition, Rietveld refinement allowed for the detection of changes in the lattices of the anode and cathode, which were linked to trapping of Li ions in the electrodes.

中文翻译：

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在标准条件下循环时，高能商业锂电池的疲劳：原位中子粉末衍射研究

考虑将市售的18650锂离子电池用于高能量密度存储和在移动应用中的使用，以及存储间歇性能源的能量。这已经触发了对合适的电极和电解质材料的深入研究，而几乎没有详细描述它们当前最新的，与温度相关的性能。两个品牌的可充电商业高能锂离子电池（18650型，3500 mAh的LiNi _0.83 Mn _0.07 Co _0.11 O ₂（NMC-811）和LiNi _0.86 Co _0.11 Al _0.03 O ₂（NCA）作为循环温度的函数，已经使用原位中子粉末衍射（NPD）和电化学阻抗谱（EIS）进行了研究。在制造商指定的条件下对电池（约140个）进行循环，并模拟具有良好统计数据的实际用户条件。循环温度（25、35和45°C）对容量衰减有显着影响，其中35°C显示最高的容量保持率。当在25°C和1 / 0.5C放电/充电速率下循环时，仅200个循环后，NCA电池就达到了初始容量的70％的寿命终止条件。EIS显示，两个品牌电池的阻抗最大增加都来自电荷转移电阻，而一个品牌电池的欧姆电阻也突然增加，这与容量突然下降相符。从原位NPD，阴极和阳极中Li含量的下降可以追溯到循环次数的函数，并且发现这与所观察到的放电容量密切相关。此外，Rietveld精修技术可以检测阳极和阴极晶格中的变化，这些变化与锂离子在电极中的捕获有关。