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Oxygen loss is a serious problem of lithium‐rich layered oxide (LLO) cathodes, as the high capacity of LLO relies on reversible oxygen redox. Oxygen release can occur at the surface leading to the formation of spinel or rock salt structures. Also, the lattice oxygen will usually become unstable after long cycling, which remains a major roadblock in the application of LLO. Here, it is shown that Zr doping is an effective strategy to retain lattice oxygen in LLO due to the high affinity between Zr and O. A simple sol‐gel method is used to dope Zr4+ into the LLOs to adjust the local electronic structure and inhibit the diffusion of oxygen anions to the surface during cycling. Compared with untreated LLOs, LLO–Zr cathodes exhibit a higher cycling stability, with 94% capacity retention after 100 cycles at 0.4 C, up to 223 mAh g−1 at 1 C, and 88% capacity retention after 300 cycles. Theoretical calculations show that due to the strong Zr–O covalent bonding, the formation energy of oxygen vacancies has effectively increased and the loss of lattice oxygen under high voltage can be suppressed. This study provides a simple method for developing high‐capacity and cyclability Li‐rich cathode materials for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides are promising cathode materials for lithium-ion batteries due to their high reversible capacities (more than 250 mAh g−1). Nevertheless, in operation, the oxygen lattice would be transformed into O 2 gas with phase transformation. Thus, to suppress O 2 gas, it is necessary to pre-generate the oxygen vacancies in the surface of materials. Herein, for facile and scalable pre-generation of oxygen vacancies, pristine Li 2 MnO 3 ·LiNi 1/3 Co 1/3 Mn 1/3 O 2 oxide (PLR-NCM) is treated directly by CO 2 gas just at the room temperature. The modified material (MLR-NCM), with rich oxygen vacancies in the surface and no obvious structural change inside, shows a discharge capacity of 321 mAh g−1 based on half-cells at 55 °C and 0.1 C (1.0 C = 250 mA g−1), and 240 mAh g−1 as full cells at the room temperature. In addition, it also exhibits high cycling and rate performance owing to the significantly improved lithium ion and electron diffusion efficiencies. Importantly, by real-time monitoring of structural evolution using in situ XRD technique, we find that the O 2 gas release of the modified material is successfully suppressed. This facile method proposed in our work provides a new strategy for greatly improving the performance of lithium-ion batteries. Image 1 • Modified Li-rich layered materials (MLR-NCM) with rich oxygen vacancies are prepared. • Oxygen vacancies in MLR-NCM are formed by facile and scalable direct CO 2 treatments. • MLR-NCM show high Li-storage capacity, cycling and rate performances. • In situ XRD technique is used to confirm that oxygen vacancies suppress O 2 release. • Full cells with MLR-NCM perform excellent Li-storage performance at room temperature. [ABSTRACT FROM AUTHOR]

Doping is a very effective way to optimize the electrochemical performance of electrodes by tuning the electron configurations on an atomic scale. Here, to obtain excellent Co 3 O 4 electrodes for lithium ion storage, a meaningful defect-engineering of carbon-doping Co 3 O 4 microrods strongly coupling with nitrogen-doped carbon (C–Co 3 O 4 @N–C) is designed and validated. Compared with unmodified Co 3 O 4 microrods, the defect-rich C–Co 3 O 4 @N–C microrod electrode features a remarkably high initial Coulombic efficiency of 84.5% and specific capacity of 1130 mAh g−1 at 0.2 A g−1, excellent cycling stability (1265 and 1036 mAh g−1 capacity retention after 110 and 500 cycles at 0.2 A g−1 and 1 A g−1, respectively) and superior rate capacity (452 mAh g−1 capacity retention after 3000 cycles at 5 A g−1). These results demonstrate that introducing rich defects by carbon dopants and nitrogen-doping carbon can effectively modulate the electron structure and accelerate the carrier transport of materials. This valid stratagem greatly elevates lithium-ion battery performance and can be further extended to other transition metal oxides and fields. Image 1 • Carbon doping effectively tunes electron configurations of Co 3 O 4 , improving electron conductivity. • Unique microrod structures can self-adapt to volume expansion during cycles. • Ultralow nitrogen-doped carbon accelerates carrier diffusion of Co 3 O 4 electrodes. • Coupling nitrogen-doped carbon with carbon doped Co 3 O 4 features high Li-storage properties. [ABSTRACT FROM AUTHOR]