Li–O2 batteries have aroused considerable interest in recent years, however they are hindered by high kinetic barriers and large overvoltages at cathodes. Herein, a step‐scheme (S‐scheme) junction with hematite on carbon nitride (Fe2O3/C3N4) is designed as a bifunctional catalyst to facilitate oxygen redox for a visible‐light‐involved Li–O2 battery. The internal electric field and interfacial Fe−N bonding in the heterojunction boost the separation and directional migration of photo‐carriers to establish spatially isolated redox centers, at which the photoelectrons on C3N4 and holes on Fe2O3 remarkably accelerate the discharge and charge kinetics. These enable the Li–O2 battery with Fe2O3/C3N4 to present an elevated discharge voltage of 3.13 V under illumination, higher than the equilibrium potential 2.96 V in the dark, and a charge voltage of 3.19 V, as well as superior rate capability and cycling stability. This work will shed light on rational cathode design for metal–O2 batteries.

Hard carbon (HC) is a promising anode material for sodium‐ion batteries, yet still suffers from low initial Coulombic efficiency (ICE) and unstable solid electrolyte interphase (SEI). Herein, sodium diphenyl ketone (Na‐DK) is applied to realize dual‐function presodiation for HC anodes. It compensates the irreversible Na uptake at the oxygen‐containing functional groups and reacts with carbon defects of five/seven‐membered rings for quasi‐metallic sodium in HC. The as‐formed sodium induces robust NaF‐rich SEI on HC in 1.0 M NaPF6 in diglyme, favoring the interfacial reaction kinetics and stable Na+ insertion and extraction. This renders the presodiated HC (pHC) with high ICE of ≈100 % and capacity retention of 82.4 % after 6800 cycles. It is demonstrated to couple with Na3V2(PO4)3 cathodes in full cells to show high capacity retention of ≈100 % after 700 cycles. This work provides in‐depth understanding of chemical presodiation and a new strategy for highly stable sodium‐ion batteries.

Two-phase transformation reaction is ubiquitous in solid-state electrochemistry; however, it usually involves inferior structure rearrangement upon extraction and insertion of large-sized Na + , thus leading to severe local strain, cracks, and capacity decay in sodium-ion batteries (SIBs). Here, a homeostatic solid solution reaction is reported in the layered cathode material P′2-Na 0.653 Ni 0.081 Mn 0.799 Ti 0.120 O 2 during sodiation and desodiation. It is induced by the synergistic incorporation of Ni and Ti for the reinforced O(2p)-Mn(3d-e g *) hybridization, which leads to mitigated Jahn−Teller distortion of MnO 6 octahedra, contracted transition-metal oxide slabs, and enlarged Na layer spacings. The thermodynamically favorable solid solution pathway rewards the SIBs with excellent cycling stability (87.2% capacity retention after 500 cycles) and rate performance (100.5 mA h g −1 at 2500 mA g −1 ). The demonstrated reaction pathway will open a new avenue for rational designing of cathode materials for SIBs and beyond.

Network-like mesoporous NiCo 2 O 4 arrays were grown on flexible carbon cloth via a hydrothermal method first assisted by polyethylene oxidepolypropylene oxidepolyethylene oxide and ethylene glycol followed by thermal treatment. These arrays were made up of nanoflakes (thickness varies from 5 to 15 nm) and multilevel pores, giving a vast specific surface area of 130.2 m 2 g À1 . The as-prepared products were fabricated into electrodes to conduct electrochemical experiments. The results showed a high capacitance of 1843.3 F g À1 (volume capacitance of 33.8 F cm À3 ) at 1 A g À1 , satisfied constant rate performance of 80% shifting from 1 to 32 A g À1 (1481 F g À1 ), and only a 10% loss of its capacitance even after 4000 recycles at a consistent current density of 10 A g À1 . A symmetric supercapacitor based on NWM NiCo 2 O 4 was assembled and it exhibited a high specific capacitance of 269 F g À1 at 1 A g À1 and a preferable energy density of 38.3 W h kg À1 at a power density of 396 W kg À1 . The optimum overall performance of both high rate capability and cycle stability make the network-like mesoporous NiCo 2 O 4 the prime candidate for application in electrochemical supercapacitors. Electronic supplementary information (ESI) available: XRD patterns of a bare CC substrate, the EDS spectrum and SEM images of NWM NiCo 2 O 4 , supplementary BET and BJH of NiO NS samples, supplementary data of the electrochemical performance of a bare CC substrate and the compared NiO NSs are presented. A table comparing SC, capacitance retention and rate capability of NWM NiCo 2 O 4 prepared in this work and of some previously reported nanostructured spinel materials and a comparison of certain related parameters in EIS of samples are shown here. See