We present ac oral-like FePc omposite with FeP nanoparticles anchored and dispersed on anitrogen-doped 3D carbon framework (FeP@NC). Due to the highly continuous N-doped carbon framework and as pring-buffering graphitized carbon layer around the FePnanoparticle,asodium-ion battery with the FeP@NC composite exhibits an ultra-stable cycling performance at 10 Ag À1 with ac apacity retention of 82.0 %i n1 0000 cycles.A lso,p article refinement leads to ac apacity increase during cycling. The FePn anoparticles go through arefining-recombinationprocess during the first cycle and present aglobal refining trend after dozens of cycles,which results in ag radually increase in graphitization degree and interface magnetization, and further provides more active sites for Na + storage and contributes to ar ising capacity with cycling. The capacity ascending phenomenon can also extend to lithium-ion batteries.

Hollow SnS/TiO2@C nanospheres with high-performance originating from the built-in electric field introduced by SnS/TiO2 heterostructures for fast ion diffusion.

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Hierarchical CoFeO (CFO) hollow spheres were successfully synthesized via solvothermal method and calcination treatment. The obtained CFO completely inherited the hollow structure and spherical morphology of its precursor of cobalt-based ferrocenyl coordination polymers (Co-Fc-CPs). The three-dimensional (3D) porous hierarchical hollow structure can not only promote the permeation of electrolyte and shorten the lithium-ion transfer distance but also provide a cushion for the volume change during insertion/extraction of lithium ions. To improve the electrochemical properties, the CFO was combined with two forms of carbonaceous materials to controllably obtain 3D CoFeO@C (CFO@C) and CoFeO@reduced graphene oxide (CFO@rGO) composites. Compared with bare CFO and CFO@C, CFO@rGO exhibited a superior electrochemical performance, achieving a high specific capacity of 933.1 mA h g at a current density of 100 mA g after 100 cycles and showing an outstanding cycling life with a capacity of 615.6 mA h g at 1000 mA g after 600 cycles. In situ X-ray diffraction technique was applied to investigate the lithium storage mechanism during discharge/charge processes. This work provides a new approach to prepare hierarchical hollow bimetallic oxides composites for lithium-ion anode materials.

NaVPO4F is regarded as one of the most competitive cathodes in high performance sodium ion batteries (SIBs). Two polymorphs with the tetragonal and monoclinic NaVPO4F have been reported, while the true presentation of the fluorophosphates is still poorly understood. Herein, fluorophosphates with a molar ratio of 1:1:1:1 for Na, V, P, F are fabricated at different temperatures. The presentation of tetragonal and monoclinic NaVPO4F is strikingly confirmed. For the first time, the accurate atomic arrangement in the crystal, and the irreversible phase transition from tetragonal to monoclinic with temperature variation are unveiled by combining series of advanced in/ex situ characterizations. From both the thermodynamic and kinetic perspectives, the sodium storage behavior and the electron/Na+ conduction, contributing to notably different electrochemical performance for the two fluorophosphates, are elaborately studied based on experimental and density functional theory calculations. The comprehensive expositions indicate that the tetragonal and monoclinic NaVPO4F have the potential to be employed as high‐energy‐density and high‐power‐density cathodes, respectively. This research answers the question of the true state of the fluorophosphates and reveals some of their previously unexplored mysteries, which provides an instructive selection principle for NaVPO4F compounds for serving in well‐defined application scenarios and is expected to become an accelerator for the next generation of high‐performance SIBs.

We present a coral‐like FeP composite with FeP nanoparticles anchored and dispersed on a nitrogen‐doped 3D carbon framework (FeP@NC). Due to the highly continuous N‐doped carbon framework and a spring‐buffering graphitized carbon layer around the FeP nanoparticle, a sodium‐ion battery with the FeP@NC composite exhibits an ultra‐stable cycling performance at 10 A g−1 with a capacity retention of 82.0 % in 10 000 cycles. Also, particle refinement leads to a capacity increase during cycling. The FeP nanoparticles go through a refining–recombination process during the first cycle and present a global refining trend after dozens of cycles, which results in a gradually increase in graphitization degree and interface magnetization, and further provides more active sites for Na+ storage and contributes to a rising capacity with cycling. The capacity ascending phenomenon can also extend to lithium‐ion batteries.

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