Achieving stable anionic redox chemistry in Li-excess O2-type layered oxide cathode via chemical ion-exchange strategy
Achieving stable anionic redox chemistry in Li-excess O2-type layered oxide cathode via chemical ion-exchange strategy
复制标题
DOI：
10.1016/j.ensm.2021.02.047
复制
发表时间：
2021-03-05
影响因子：
20.4
通讯作者：
Zhou, Haoshen
中科院分区：
文献类型：
--
作者：
Cao, Xin;Li, Haifeng;Zhou, Haoshen
引发氧氧化还原活性被认为是提高Li/Na离子电池正极材料输出容量的一种有前途的策略。然而，晶格氧的不可逆损失导致结构畸变为尖晶石相，这导致严重的电压衰减和容量退化。在此，通过化学离子交换过程，P2型氧化物前体的碱金属层内的钠已被Li取代，同时过渡金属层可以被很好地保留，导致形成Li过量的O2型层状氧化物阴极Li-0.66[Li0.12Ni0.15Mn0.73]O-2。通过系统的原位/非原位和表面/体相表征（硬X射线吸收光谱、操作拉曼/XRD和差示电化学质谱等），氧化还原可逆性和结构稳定性已经得到了全面的证明。此外，从相同的钠基前体演化而来，通过电化学离子交换过程产生的类似O2型化合物在结构和氧化还原过程上都呈现严重的不可逆行为。这些发现阐明了化学离子交换策略可以被视为设计具有稳定的阴离子/阳离子氧化还原活性和增强的结构稳定性的高容量阴极候选物的有效方法。
Triggering oxygen redox activity has been regarded as a promising strategy to boost the output capacity of cathode materials for Li/Na-ion batteries. However, irreversible loss of lattice oxygen aggravates a structural distortion to a spinel phase, which leads to severe voltage decay and capacity degeneration. Herein, via chemical ion exchange procedure, the sodium within the alkali metal layer of a P2-type oxide precursor has been substituted by Li while the transition metal layer can be well preserved, resulting in the formation of a Li-excess O2-type layered oxide cathode, Li-0.66[Li0.12Ni0.15Mn0.73]O-2. Through systematic in/ex-situ and surface/bulk characterization (hard X-ray absorption spectroscopy, operando Raman/XRD and differential electrochemical mass spectroscopy, etc.), the redox reversibility and structural stability has been comprehensively demonstrated. Moreover, being evolved from the same sodium-based precursor, a similar O2-type compound generated by electrochemical ion exchange procedure presents severely irreversible behavior on both structural and redox processes. These findings elucidated that the chemical ion exchange strategy can be regarded as an efficient way to design high- capacity cathode candidates possessing stable anionic/cationic redox activities and enhanced structural stability.