Li-richl ayered oxides with high capacity are expected to be the next generation of cathode materials. However,t he irreversible and sluggish anionic redox reaction leads to the O 2 loss in the surface as well as the capacity and voltage fading.I nt he present study,asimple gas-solid treatment with ferrous oxalate has been proposed to uniformly coat at hin spinel phase layer with oxygen vacancy and simultaneously realize Fe-ion substitution in the surface.T he integration of oxygen vacancy and spinel phase suppresses irreversible O 2 release,p revents electrolyte corrosion, and promotes Li-ion diffusion. In addition, the surface doping of Fe-ion can further stabilizet he structure.A ccordingly,t he treated Feox-2 %c athode exhibits superior capacity retention of 86.4 %a nd 85.5 %a t1Ca nd 2C to that (75.3 %a nd 75.0 %) of the pristine sample after 300 cycles,r espectively. Then, the voltage fading is significantly suppressed to 0.0011 V per cycle at 2Cespecially.T he encouraging results may play asignificant role in paving the practical application of Li-rich layered oxides cathode.

Increasing the nickel content and broadening the voltage window are important means for LiNi x Co y Mn 1−x−y O 2 layered cathodes with low cost and high energy density, but these nickel-rich cathodes often suffer from structural instability and unsatisfactory cyclic performance. The systematic and detailed degradation mechanism especially under a high voltage is still unclear, which hinders the further development of nickel-rich cathodes. Our results show that due to the migration of high valence nickel ions to lithium sites, especially upon the deep removal of Li + ions, the nickel-rich cathode undergoes an irreversible phase transformation from a layered structure to a spinel or even rocksalt phase. Such irreversible phase transitions within a wide voltage window would cause insufficient lithium utilization and voltage decay, finally deteriorating the electrochemical performance of nickel-rich cathodes. In a narrow voltage range of 3.0−4.3 V, the capacity retention of the Ni-rich cathode is 93.4%, and the voltage fading is only 40 mV after 250 cycles. However, the cathode only exhibits a capacity retention of 77.4% with a significant voltage decay over 180 mV, as the voltage range further extends to 3.0−4.6 V. Furthermore, various characterizations and electrochemical performances demonstrate that the strengthened metal−oxygen bonds in the transition layer can produce stable structures and suppress phase transitions, thereby displaying superior electrochemical performance in the widened voltage window. As a result, the cycling retention of a Zr-doped cathode reaches 84.5%, and the voltage decay is only 50 mV after 250 cycles at 3.0−4.6 V, which exhibits excellent long-term cycle performance. These insights provide guidance for understanding the electrochemical mechanism and the design of high-voltage cathode materials.

Li- and Mn-rich layered oxide (LMR) materials are a promising candidates for next-generation Li-ion battery (LIB) anode materials because of their high specific capacity. However, their low initial Coulombic efficiency, voltage decay, and irreversible phase transition during cycling are the fatal drawbacks of LMR materials. This work reports on a cobalt-free LMR material composed of primary particles with a boron-induced exposed long- strip-like {010} plane. Because of this unique structure, the long strip-like cathode exhibits excellent electrochemical performance with a discharge capacity of 202 mAh g–1 at 1 C and a retention rate of 95.2% after 200 cycles. In addition, it is found that this long strip-like structure can modulate the redox of oxygen and enhance the reversibility. The irreversible phase transition process from the layered to a spinel and then to a rock-salt phase during cycling is also significantly suppressed. This work provides a feasible method for regulating the exposed {010} plane and a new idea for the structural design of LMR materials.

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A series of alkyl sulphobetaine Gemini surfactants Cn‐GSBS (n = 8, 10, 12, 14, 16) was synthesized, using aliphatic amine, cyanuric chloride, ethylenediamine, N,N′‐dimethyl‐1,3‐propyldiamine and sodium 2‐chloroethane sulfonate as main raw materials. The chemical structures were confirmed by FT‐IR, 1H NMR and elemental analysis. The Krafft points differ markedly with different carbon chain length, for C8‐GSBS, C10‐GSBS and C12‐GSBS are considered to be below 0 °C and C14‐GSBS, C16‐GSBS are higher than 0 °C but lower than room temperature. Surface‐active properties were studied by surface tension and electrical conductivity. Critical micelle concentrations were much lower than dodecyl sulphobetaine (BS‐12) and decreased with increasing length of the carbon chain from 8 to 16, and can reach a minimum as low as 5 × 10−5 mol L−1 for C16‐GSBS. Effects of carbon chain length and concentration of Cn‐GSBS on crude oil emulsion stability were also investigated and discussed.