Wu Zhen, Cheng Yaxin, Shi Yuhang, Xia Meng, Zhang Yuhan, Hu Xuechen, Zhou Xiaojin, Chen Yuanzhen, Sun Junjie, Liu Yongning
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, PR China.
Qingdao Industrial Energy Storage Research Institute, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101, PR China; School of Future Technology, University of Chinese Academy of Sciences, Beijing 101408, PR China.
J Colloid Interface Sci. 2022 Aug 15;620:57-66. doi: 10.1016/j.jcis.2022.03.101. Epub 2022 Mar 25.
Li-rich layered oxides are recognized as promising candidates for next-generation Li-ion batteries owing to the high capacity of >250 mAh g, but the severe voltage fade has prevented their commercialization. It is widely known that high-voltage charge processes result in layered-to-spinel structural evolution and voltage fade in Li-rich layered oxides. This work emphasizes that limiting the low-voltage reduction can maintain the structure and voltage stability of Li-rich layered oxides after the 4.6 V high-voltage charge processes. A strategy of limiting the low-voltage (<2.8 V) reduction by cycling at 4.6-2.8 V was performed in traditional LiNiMnCoO and high-Ni LiNiMnCoO. After 300 cycles, traditional LiNiMnCoO and high-Ni LiNiMnCoO cycling at 4.6-2 V showed midpoint discharge voltages of 2.83 V and 2.97 V with high voltage fade rates of 2.25 mV/cycle and 2.24 mV/cycle, respectively. While the two materials cycling at 4.6-2.8 V can maintain discharge midpoint voltages of 3.34 V and 3.49 V, with low voltage decay rates of 0.692 mV/cycle and 0.632 mV/cycle, respectively. To better understand the voltage performance, their electric structures were calculated by density functional theory. Physical characterizations were also used to analyze their differences in structural evolution. The results suggested that limiting low-voltage reduction in Li-rich layered oxides is highly necessary for maintaining their structure and voltage stability.
富锂层状氧化物因其大于250 mAh g的高容量而被认为是下一代锂离子电池的有前景的候选材料，但严重的电压衰减阻碍了它们的商业化。众所周知，高压充电过程会导致富锂层状氧化物中发生从层状到尖晶石的结构演变和电压衰减。这项工作强调，限制低电压还原可以在4.6 V高压充电过程后维持富锂层状氧化物的结构和电压稳定性。在传统的LiNiMnCoO和高镍LiNiMnCoO中实施了通过在4.6 - 2.8 V循环来限制低电压（<2.8 V）还原的策略。300次循环后，在4.6 - 2 V循环的传统LiNiMnCoO和高镍LiNiMnCoO的中点放电电压分别为2.83 V和2.97 V，电压衰减率分别高达2.25 mV/循环和2.24 mV/循环。而在4.6 - 2.8 V循环的这两种材料可以分别维持3.34 V和3.49 V的放电中点电压，电压衰减率分别为0.692 mV/循环和0.632 mV/循环。为了更好地理解电压性能，通过密度泛函理论计算了它们的电子结构。还使用物理表征来分析它们在结构演变方面的差异。结果表明，限制富锂层状氧化物中的低电压还原对于维持其结构和电压稳定性非常必要。
