Triggering the anionic redox reactions at high voltage is an effective approach to boost the capacity of Li-rich layered oxides. However, the irreversible lattice oxygen release at high voltage and sluggish ion kinetics remain conundrums. Herein, a surface modifying coupling defect engineering strategy is proposed to improve the reversibility of anionic redox reactions and ion diffusion efficiency in Li-rich layered oxides. A LiNbO₃ surface modification acts as an effective physical barrier to suppress lattice oxygen release, thereby improving cycling stability of Li-rich layered oxide. Furthermore, the oxygen vacancies in the LiNbO₃ coating enhance the ion transport kinetics, strengthening the rate capability. After 500 cycles, a high capacity retention of 83.3% can be achieved for the obtained cathode materials (the oxygen-deficient LiNbO₃-coated Li-rich layered oxide (CV-LLO)) at 5 C, much higher than that of the pristine materials (LLO, 52.3%). Moreover, CV-LLO delivers a capacity of 169.9 mAh·g⁻¹ at 5 C, which was 65.1% of the capacity at 0.2 C, much higher than that of the pristine LLO (85.6 mAh·g⁻¹, 33.7%). This study provides insights into the construction of Li-rich layered oxide cathode with highly reversible anionic redox reaction and highly cycling stability for Lithium storage.

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are generally catalyzed by precious metals (Pt) and metal oxides (IrO₂) which still have many shortages including expensive price, poor selectivity and undesirable stability. In this work, we report a Mn⁰-doped CoN_x on N-doped porous carbon (Mn-CoN_x/N-PC) composite from carbonizing metal-organic framework (MOF) derivative as the dual-functional catalyst to boost both the ORR and OER performances. Owing to the strong coordination effect between nitrogen and metal elements, the introduction of N can obviously improve the content of Co-N-C active sites for ORR. Meanwhile, the Mn-doping significantly regulates the electronic structure of the Co element and increases the content of Co⁰ which provide efficient OER active sites. Mn-CoN_x/N-PC catalyst delivers super dual-functional activity with a half-wave potential of 0.85 V, better than the 20% Pt/C catalyst (0.82 V). When used in Zn-air batteries for testing, Mn-CoN_x/N-PC electrocatalyst shows a high power density (145 mW·cm⁻²) and good cycle performance.

It is of vital importance to design efficient and low-cost bifunctional catalysts for the electrochemical water splitting under alkaline and neutral pH conditions. In this work, we report an efficient and stable NiCo₂S₄/N, S co-doped reduced graphene oxide (NCS/NS-rGO) electrocatalyst for water splitting, in which NCS microspheres are composed of one-dimentional (1D) nanorods grown homogeneously on the surface of NS-rGOs). The synergetic effect, abundant active sites, and hybridization of NCS/NS-rGO endow their outstanding electrocatalytic performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both alkaline and neutral conditions. Furthermore, NCS/NS-rGO employed as both anode and cathode in a two-electrode alkaline and neutral system electrolyzers deliver 10 mA/cm² with the low cell voltage of 1.58 V in alkaline and 1.91 V in neutral condition. These results illustrate the rational design of carbon-supported nickel-cobalt based bifunctional materials for practical water splitting over a wide pH range.