High-voltage medium-nickel low-cobalt lithium layered oxide cathode materials are becoming a popular development route for high-energy lithium-ion batteries due to their relatively high capacity, low cost, and improved safety. Unfortunately, capacity fading derived from surface lithium residue, electrode-electrolyte interfacial side reactions, and bulk structure degradation severely limits large-scale commercial utilization. In this work, an ultrathin and uniform NASICON-type Li₃V₂(PO₄)₃ (LVP) nanoscale functional coating is formed in situ by utilizing residual lithium to enhance the lithium storage performance of LiNi_0.6Co_0.05Mn_0.35O₂ (NCM) cathode. The GITT and ex-situ EIS and XPS demonstrate exceptional Li⁺ diffusion and conductivity and attenuated interfacial side reactions, improving the electrode-electrolyte interface stability. The variable temperature in-situ XRD demonstrates delayed phase transition temperature to improve thermal stability. The battery in-situ XRD displays the single-phase H1-H2 reaction and weakened harmful H3 phase transition, minimizing the bulk mechanical degradation. These improvements are attributed to the removal of surface residual lithium and the formation of NASICON-type Li₃V₂(PO₄)₃ functional coatings with stable structure and high ionic and electronic conductivity. Consequently, the obtained NCM@LVP delivers a higher capacity retention rate (97.1% vs. 79.6%) after 150 cycles and a superior rate capacity (87 mAh·g^–1 vs. 58 mAh·g^–1) at a 5 C current density than the pristine NCM under a high cut-off voltage of 4.5 V. This work suggests a clever way to utilize residual lithium to form functional coatings in situ to improve the lithium storage performance of high-voltage medium-nickel low-cobalt cathode materials.

Aqueous zinc-based battery is usually plagued by serious dendrites and side reactions including Zn corrosion and water decomposition on the anode. To address the drawbacks, constructing coating layers with high conductivity and anti-catalytic effects on hydrogen evolution reaction has been considered as an efficient strategy. Herein, cheap and abundant two-dimensional (2D) conductive graphite (KS-6) coating layer with high electronic conductivity (~ 10⁶ S·m⁻¹) could directly form strong bonding with Zn foil due to high zincophilicity, which correspondingly protects Zn metal from liquid electrolyte to inhibit parasitic hydrogen evolution and guide uniform Zn electrodeposition during cycling. The KS-6 layer owns a profitable charge redistribution effect to endow Zn anode with a lower nucleation energy barrier and a more uniformly distributed electric field compared with bare Zn. Therefore, such integrated Zn anode exhibits low voltage hysteresis (~ 38 mV) and excellent cycling stability with dendrite-free behaviors (1 mA·cm⁻² and 2 mAh·cm⁻²) over 2,000 h, far outperforming many reported Zn metal anodes in aqueous systems. Encouragingly, in light of the superior Zn@KS-6 anode, VNO_x powders and Prussian blue analogs Mn₂Fe(CN)₆ are applied as the cathode materials to assemble full batteries, which show remarkable cycling stabilities and high Coulombic efficiencies (CEs) over 200 cycles with capacity retention of 81.5% for VNO_x//Zn@KS-6 battery and over 400 cycles with capacity retention of 94.6% for Mn₂Fe(CN)₆//Zn@KS-6 battery, respectively.