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Manganese‐based layered oxides are currently of significant interest as cathode materials for sodium‐ion batteries due to their low toxicity and high specific capacity. However, the practical applications are impeded by sluggish intrinsic Na+ migration and poor structure stability as a result of Jahn–Teller distortion and complicated phase transition. In this study, a high‐entropy strategy is proposed to enhance the high‐voltage capacity and cycling stability. The designed P2‐Na0.67Mn0.6Cu0.08Ni0.09Fe0.18Ti0.05O2 achieves a deeply desodiation and delivers charging capacity of 158.1 mAh g−1 corresponding to 0.61 Na with a high initial Coulombic efficiency of 98.2 %. The charge compensation is attributed to the cationic and anionic redox reactions conjunctively. Moreover, the crystal structure is effectively stabilized, leading to a slight variation of lattice parameters. This research carries implications for the expedited development of low‐cost, high‐energy‐density cathode materials for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb‐layered‐oxides (HLOs) manifest outstanding structural stability, high redox potential, and long‐life electrochemistry. Here, recent progress on HLOs as well as Na3Ni2SbO6 and Na3Ni2BiO6 as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state‐of‐the‐art sodium‐ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure–property relationship, and inspire more interest in high output voltage, long lifespan sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Cation migration often occurs in layered oxide cathodes of lithium‐ion batteries due to the similar ion radius of Li and transition metals (TMs). Although Na and TM show a big difference of ion radius, TMs in layered cathodes of sodium‐ion batteries (SIBs) can still migrate to Na layer, leading to serious electrochemical degeneration. To elucidate the origin of TM migration in layered SIB cathodes, we choose NaCrO2, a typical layered cathode suffering from serious TM migration, as a model material and find that the TM migration is derived from the random desodiation and subsequent formation of Na‐free layer at high charge potential. A Ru/Ti co‐doping strategy is developed to address the issue, where the doped active Ru is first oxidized to create a selective desodiation and the doped inactive Ti can function as a pillar to avoid complete desodiation in Ru‐contained TM layers, leading to the suppression of the Na‐free layer formation and subsequent enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries are commonly regarded as a promising candidate in large‐scale energy storage. Layered iron/manganese oxide cathodes receive extensive attentions due to the element abundance and large theoretical capacity. However, these materials usually undergo obvious degradation of electrochemical performance due to the tendency of Mn dissolution and Fe migration during continuous sodium release and uptake. Herein, a strategy of anion–cation synergetic redox is proposed to suppress the structural deterioration originated from overusing the electrochemical activity of transition‐metal ions, and decreased lattice strain as well as superior electrochemical performance are realized simultaneously. Results show that the Na0.8Li0.2Fe0.2Mn0.6O2 (NLFM) electrode is highly resistant to the erosion of moisture that is distinct from the traditional Mn/Fe‐based electrodes. Moreover, the NLFM electrode demonstrates solid solution behavior without phase transition during cycles. The ultra‐small volume change of 0.85% is ascribed to the negligible manganese dissolution and invisible transition‐metal migration. The high‐stable layered structure assures superior reversible capacity of ≈165 mA h g–1, excellent rate capability, and splendid capacity retention of over 98.3% with 100 cycles. The findings deepen the understanding of the synergy between anion and cation redox and provide new insights to design the high‐stable layered cathode for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

All‐solid‐state batteries (ASSBs), particularly those with Li‐free anodes or even anode‐free configurations, have attracted extensive attention due to high safety and energy density. However, chemical‐mechanical degradation typically deteriorates the cycle life and energy of Li‐free anode ASSBs with the absence of Li inventory. Here, the prelithiation agent Li5FeO4 (LFO) coated Ni‐rich layered oxide is developed as the cathode for Li‐free anode ASSBs. The coated LFO acts as an interfacial protective layer to prevent the highly oxidizing Ni‐rich cathode from reacting with sulfide solid‐state electrolytes (SSEs), mitigating the structural degradation of Ni‐rich cathodes and the decomposition of SSE, resulting in excellent cycle life. Beneficial from the coated LFO in the cathode of the Li‐free anode ASSBs, the reversible capacity improves from 174.7 mAh g−1 to 199.7 mAh g−1, and the capacity retention is enhanced from 33.8 % to 84.8 % after 100 cycles. Additionally, an ultrahigh energy density of 440 Wh kg−1, based on the mass of the composite cathode, Li‐free anode, and SSE, is obtained in a Li‐free anode all‐solid‐state pouch cell equipped with the LFO‐coated cathode. [ABSTRACT FROM AUTHOR]

Molten-carbonate fuel cells (MCFCs) are high-temperature fuel cell systems that typically operate at approximately 650 °C. Due to their high operating temperature, the thermal degradation of MCFC components limits the lifetime of the MCFC. Therefore, lowering the operating temperature is an effective way to reduce thermal degradation. However, the electrochemical reaction on the cathode also becomes slower as the operational temperature decreases. To improve the performance and stability, atomic layer deposition (ALD) of ZrO 2 on the cathode is proposed. ALD produces a uniform, thin coating with precise thickness control. Therefore, nano-coating can be performed via ALD without affecting the porous structure of the cathode. The uniform ZrO 2 coating donates electrons to NiO due to the low electronegativity of Zr. The electron-rich environment of NiO improves the cell performance by providing electrons for the oxygen reduction reaction. Also, the single cell using ZrO 2 -coated cathode demonstrates improved stability compared to the uncoated cathode cell due to the inhibition of NiO sintering by the ZrO 2 coating layer. • A coating of ZrO 2 is prepared by atomic layer deposition (ALD) on the cathode. • The oxygen reduction reaction is improved by the ZrO 2 coating on the cathode. • The ZrO 2 -coated cathode cell shows a higher voltage than the uncoated cathode cell. • The ZrO 2 coating on the cathode prevents the sintering of NiO at 600 °C. • The ZrO 2 -coated cathode cell has improved stability by the prevention of sintering. [ABSTRACT FROM AUTHOR]

The Li‐rich Mn‐based cathode materials (LMRs) deliver excellent energy density and exhibit low cost, which are considered as the most promising cathode materials for the next generation lithium‐ion batteries. However, the irreversible redox reaction of the oxygen atoms directly leads to release oxygen and intensifies phase transformation. Besides, the local stress and strain will be generated due to the unit‐cell volume difference between R‐3m and C2/m phases, which continuously aggravates the collapse of secondary particles. Herein, the strong Nb4d−O2p−Li2s configurations at the Li1 sites of the TM‐layer in the C2/m phase and secondary particles with the radial arrangement of refined primary particles are designed to inhibit oxygen release and relieve lattice stress by Nb2O5 treatment. Meanwhile, the preferential growth of the active {010} planes is presented to obtain an excellent transmission rate of Li+. As a result, the designed LMR delivers remarkable electrochemical properties with high discharge capacity and initial coulomb efficiency of 276 mAh g−1 and 85 % at 0.1 C, outstanding cycling retention rate of 81 % after 300 cycles. This novel crystal structure combining oxygen coordination regulation and micro‐nano scale design provides inspiration for the design of high‐performance LMRs. [ABSTRACT FROM AUTHOR]