Effects of cation superstructure ordering on oxygen redox stability in O2-type lithium-rich layered oxides

Abstract

Archetypical layered oxide with oxygen redox capability bears additional lithium ion in transition metal layer, and its local coordination with oxygen is crucial in triggering the oxygen redox activity. These...

Inconsistency between superstructure stability and long-term cyclability of oxygen redox in Na layered oxides

“…For instance, Kang and coworkers reported that the destruction of the honeycomb superstructure in pristine O2-type Li-/Mn-rich layered oxides makes the structure more susceptible to in-plane/out-of-plane TM migrations over cycling and leads to a gradual loss of OAR activity; by contrast, the preservation of the honeycomb superstructure successfully refrains the pernicious TM migrations and achieves a stable OAR activity. 26 In terms of Na layeredoxides, Chueh and others substantiated that the characteristic ffiffi ffi 7 p  ffiffi ffi 7 p superstructure originating from the in-plane &/Mn ordering in Na 2 Mn 3 O 7 (Na 4/7 [& 1/7 Mn 6/7 ]O 2 where & represents TM vacancies) can disfavor O-O dimerization and stabilize the hole polarons on O, which is beneficial to the reversibility of the OAR. [27][28][29] Bruce and colleagues firstly proposed that the ribbon superstructure in P2-Na 0.6 Li 0.2 Mn 0.8 O 2 can hinder the in-plane Mn migration and helps in suppressing the first-cycle voltage hysteresis with respect to the honeycomb superstructure in P2-Na 0.75 Li 0.25 Mn 0.75 O 2 .…”

Oxygen vacancy chemistry in oxide cathodes

“…18b. 82 In addition, the spatial distribution of anionic redoxmediated OVs can also be indirectly imaged by detecting the spatial distribution of TM chemical states in cathode particles. 52,202 However, the widespread use of STXM is limited due to the following shortcomings: long imaging time, imaging in a vacuum, and narrow imaging field.…”

“…The strategy of regulating the oxygen framework is widely regarded as a potential solution for addressing the failure of anionic redox reactions. 80–83 In this approach, the O2-type structure, characterized by oxygen atoms arranged in a stacking mode of ABCBA, is utilized to prevent the migration of transition metal ions and associated structural failures. 84 This allows for the achievement of reversible electrochemistry in Li-rich oxide cathodes.…”

“…199 Although the low-energy soft X-ray limits the maximum detection depth of the sample, it provides STXM with high sensitivity to light elements such as Li, O, and C. Based on the absorption intensity difference of O K-edge at 530.6 eV, this feature allows STXM to visualize the redox degree of lattice oxygen in different regions and the spatial distribution of anionic redox-mediated OVs in oxide cathode particles. 82,200,201 Fig. 18a demonstrates that lattice oxygen redox is partially irreversible in O2-type Li-rich oxide Li x [Li 0.25 Co 0.25 Mn 0.5 ]O 2 during the initial charge–discharge process.…”

Correlating concerted cations with oxygen redox in rechargeable batteries

“…147 Although trivalent ions may have a weaker impact compared to divalent ions, it has been demonstrated that Co 3+ reduces the electrostatic energy of Li + –Mn 6 4+ ordering by in-plane geometrical frustration. 148 The superstructure can seriously affect the cycle life of the material; it has been shown that even for the same elemental species, different ratios will significantly affect the electrochemical behavior. This is the impact of the control of cation ordering.…”