Although the lithium-rich cathode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 , as a promising cathode material, has a high specific capacity, it suffers from capacity decay and discharge voltage decay during cycling. In this work, the specific capacity and discharge voltage of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 are stabilized by surface-functionalized LiCeO 2 coating. We have conducted LiCeO 2 coating via a mild synchronous lithium strategy to protect the electrode surface from electrolyte attack. This optimized LiCeO 2 coating has high Li + conductivity and abundant oxygen vacancies. The results demonstrate that 3% LiCeO 2 -coated Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 exhibits the highest capacity retention rate at 1, 2, and 5 C after 200 cycles, which were 84.3%, 85.4%, and 86.3%, respectively. The discharge specific capacity was almost 1.3, 1.4, and 1.4 times that of the pristine electrode. In addition, the 3% LiCeO 2 electrode exhibited the least voltage decay of 0.409, 0.497, and 0.494 V at 1, 2, and 5 C, which was only about half of the pristine electrode. It should not be overlooked that the 3% LiCeO 2 electrode still exhibits a high capacity at high current densities of 1250 mA g −1 (5 C) and 2500 mA g −1 (10 C), and its specific discharge capacities are 190.5 and 160.6 mAh g −1 , respectively. These outstanding electrochemical properties benefit from surface-functionalized LiCeO 2 coatings. To better understand the mechanism of oxygen loss of lithium-rich materials, we propose the lattice oxygen migration path of the LiCeO 2 -coated electrodes during the cycle. Our research provides a possible solution to the poor rate capability and cycle performance of cathode materials through surfacefunctionalized coatings.

A gentle method is used to treat the precursor to induce the doping of SO4 2– and Ni2+. The doped SO4 2– induces the formation of oxygen vacancies and defects, which are beneficial for inhibition of the loss of O2–, stabilization of the structure, and amelioration of voltage decay, and the doped Ni2+ increases the degree of lithium nickel mixing and significantly increases the midvoltage. After modification, the specific discharge capacity reaches 305.20 mAh g–1, with a Coulombic efficiency of 86.20% (the specific discharge capacity and Coulombic efficiency of the original material are only 276.50 mAh g–1 and 77.30%, respectively). In addition, the cycle performance is also significantly improved, and the discharge midvoltage is dramatically increased from 2.74 to 3.00 V after 350 cycles at a large current density of 1C due to the dual-ion synergistic effect. In summary, these results show that the materials exhibit not only a more stable structure but also better electrochemical performance after modification.

Anion energy storage provides the possibility to achieve higher specific capacity in lithium‐ion battery cathode materials, but the problems of capacity attenuation, voltage degradation, and inconsistent redox behavior are still inevitable. In this paper, a novel O2‐type manganese‐based layered cathode material Lix[Li0.2Mn0.8]O2 with a ribbon superlattice structure is prepared by electrochemical ion exchange, which realizes the highly reversible redox of anions and excellent cycle performance. Through low‐voltage pre‐cycling treatment, the specific capacity of the material can reach 230 mAh g−1 without obvious voltage attenuation. During the electrochemical ion exchange, the precursor with P2 structure transforms into Lix[Li0.2Mn0.8]O2 with O2 structure through the slippage and shrink of adjacent slabs, and the special superlattice structure in Mn slab is still retained. Simultaneously, a certain degree of lattice mismatch and reversible distortion of the MnO6 octahedron occur. In addition, the anion redox catalyzes the formation of the solid electrolyte interface, stabilizing the electrode/electrolyte interface and inhibiting the dissolution of Mn. The mechanism of electrochemical ion exchange is systematically studied by comprehensive structural and electrochemical characterization, opening an attractive path for the realization of highly reversible anion redox.

Lithium-rich layered oxides exhibit a superior specific capacity more than 280 mAh g -1 in the range of 2.0-4.8 V. Meanwhile, capacity attenuation and voltage decay are also caused by such a wide voltage range. The structure evolution and electrochemical properties of materials at different voltage regulation systems have been studied. Complex phase transition and interplanar spacing increase can be blocked under the lower voltage cycle and the diffusion ability of Li + has been significantly improved after pre-cycling treatment, especially at the condition of 4.5 V. Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 exhibits excellent capacity retention of 92.77% with slight voltage attenuation of 0.3731 V compared to 55.74% and 0.7883 V at high voltage after 200 cycles under the synergistic effect of pre-cycling and lower voltage operation. Such superior electrochemical performance is attributed to that: (1) pre-cycling can gentle the activation process and rationalize the intercalation/deintercalation interval of Li + ; (2) the lower voltage operation will restrain the release of oxygen in high voltage region to stabilize the phase structure and inhibit the decomposition of electrolyte. The rational voltage regulation system can improve the reversibility of anion redox and maintain excellent cycle performance.

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