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Transition metal oxide (TMO)‐based anodes attract much attention for lithium storage due to the merits of high theoretical capacity, facile synthesis, and easy scale‐up. Moreover, the increased working potential avoids the issue of lithium dendrites formation and thus improves battery safety. Herein, we propose a route to significantly improve the electrochemical performance of TMO anodes through configurational entropy optimization. For example, high‐entropy oxide (FeCoNiCrCu)3O4 is synthesized by carefully selecting metal elements. The (FeCoNiCrCu)3O4 electrode ensures not only low potential but also holds high capacity. In the half‐cell configuration, the (FeCoNiCrCu)3O4 electrode provides a specific capacity of 575.7 mAh g−1 after 200 cycles at 0.2 A g−1. More importantly, the electrode showed a relatively low discharge voltage of 0.39 V at 0.5 A g−1, which is caused by the configuration entropy optimization. The assembled (FeCoNiCrCu)3O4//LCO coin‐type full cell exhibits a high capacity of 266.3 mAh g−1 after 100 cycles at 0.2 A g−1 and an operating voltage up to 3.9 V. [ABSTRACT FROM AUTHOR]

In recent years, Nb-based oxides, especially Nb2O5, due to their unique structural advantages, have stimulated scholars' extensive research enthusiasm in the field of energy storage systems including lithium ion batteries (LIBs) and sodium ion batteries (SIBs), excellent chemical stability and outstanding rate capability dominated by pseudocapacitive nature. In addition, Nb-based oxides usually have a higher operating voltage (> 1.0 V vs Li+/Li), which can effectively prevent the decomposition of organic electrolytes and the formation of solid electrolyte interface films in batteries. This review systematically summarizes the different crystal structures of Nb2O5 and the lithium storage mechanism based on theoretical calculations, as well as the comparison of various synthesis strategies. In addition, the advanced research progress of niobium-based oxides as anode materials in LIBs and SIBs is summarized from the perspective of nanostructure control engineering that affects electrochemical performance. It also puts forward reasonable cognition and challenges for future research, which is conducive to the design of energy storage equipment that meets the needs of sustainable development. The design and optimization of various synthesis methods facilitate the formation of a variety of heterogeneous nanostructures, leading to reversible storage of Li and Na ions. [ABSTRACT FROM AUTHOR]

Transition metal oxide nanostructures are drawing much attention as promising electrodes for advanced rechargeable batteries. However, due to the intrinsic low electronic conductivity and substantial volume change during cycling, the electrodes usually show low rate capability and poor cycling life. Herein, we report a route combining surface/interface engineering and defect chemistry to tune the lithium storage properties in nanoscale cubic Co3O4 crystallites. The Co3O4 crystallites were annealed in an inert atmosphere by carefully controlling the temperature, which induces the conformal formation of CoO layers with a tunable thickness on the surface of initial cubes. Microstructural characterizations and electrochemical measurements indicate that the optimized sample possesses a CoO thickness of ∼1.1 nm and shows a reversible lithium storage capacity of 1069.4 mAh·g–1 after 100 cycles of a current density of 0.1 A·g–1. A capacity of 807.9 mAh·g–1 can be obtained at a rate of 5 A·g–1. The improved lithium storage performance is attributed to the unique CoO–Co3O4 interface structure and defect chemistry, which induces a strong electric field at the sharp Co3O4–CoO interface according to density functional theory calculations. The optimized sample also shows it improved sodium storage properties. This work thus provides an effective strategy for the design and synthesis of advanced electrode materials for energy applications. [ABSTRACT FROM AUTHOR]

Uniform Fe 3 O 4 microflowers assembled with porous nanoplates were successfully synthesized by a solvothermal method and subsequent annealing process. The structural and compositional analysis of the Fe 3 O 4 microflowers were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The Bruauer–Emmett–Teller (BET) specific surface area was calculated by the nitrogen isotherm curve and pore size distribution of Fe 3 O 4 microflowers was determined by the Barret–Joyner–Halenda (BJH) method. When evaluated as anode material for lithium-ion batteries, the as-prepared Fe 3 O 4 microflowers electrodes delivered superior capacity, better cycling stability and rate capability than that of Fe 3 O 4 microspheres electrodes. The improved electrochemical performance was attributed to the microscale flowerlike architecture and the porous sheet structural nature. [ABSTRACT FROM AUTHOR]

[Display omitted] Graphite is a widely used anode material in commercial lithium-ion batteries (LIBs), but its low theoretical specific capacity and extremely low redox potential limit its application in high-performance lithium-ion batteries. However, developing lithium-ion battery anode with high specific capacity and suitable working potential is still challenging. At present, conductive polymers with excellent properties and graphite-like structures are widely used in the field of electrochemistry, but their Li+ storage mechanism and kinetics are still unclear and need to be further investigated. Therefore, we synthesized the conducting polymer Fe 3 (2, 3, 6, 7, 10, 11-hexahydroxytriphenylene) 2 (Fe-CAT) by the liquid phase method, in which the d-π conjugated structure and pores facilitate electron transfer and electrolyte infiltration, improving the comprehensive electrochemical performance. The Fe-CAT electrode displays a high capacity of 950 mA h g−1 at 200 mA g−1. At the current density of 5.0 A g−1, the electrode shows a reversible capacity of 322 mA h g−1 after 1000 cycles. The average lithiation voltage plateau is ∼ 0.79 V. The combination of ex-situ characterization techniques and electrochemical kinetic analysis reveals the source of the excellent electrochemical performance of Fe-CAT. During the charging/discharging process, the aromatic ring in the organic ligand is involved in the redox reaction. Such results will provide new insights for the design of next-generation high-performance electrode materials for LIBs. [ABSTRACT FROM AUTHOR]

Transition metal oxides have attracted considerable attention as possible electrode materials for lithium-ion batteries. However, poor electrical conductivity and volume change during cycling result in low rate capacity and rapid capacity fading, which hinder the practical applications of those electrodes. In this work, we report a facile approach to modify Co 3 O 4 nanoparticles (NPs) by laser irradiation treatment. The structural and composition of the samples were studied by different techniques. The results show that the surface of the as-prepared particles transforms to a thin CoO layer, and oxygen vacancies are generated after the laser treatment. Compared to the as-prepared Co 3 O 4 NPs, the laser treated sample shows a higher reversible capacity of 833.4 mAhg −1 after 100 cycles at a current density of 0.1 Ag -1 . A capacity of 348.4 mAhg −1 can be obtained at a rate of 5 Ag -1 . The unique microstructure that induced by laser irradiation in the Co 3 O 4 NPs is responsible for the improved lithium storage properties. [ABSTRACT FROM AUTHOR]

Transition metal oxide (TMO) anodes show promising applications in energy storage due to the unique physical and chemical properties and high theoretical capacity to storage ions. Their practical usages are restricted by low intrinsic electronic conductivity, sluggish ionic diffusion, and large volume change during continuous cycling. In this work, we propose a strategy of selective solution-phase reduction on specific crystalline planes to generate the defect chemistry and thus improve the intrinsic electronic conductivity. Taking Co 3 O 4 electrode as a typical example, we prepared the structures with different exposed planes, which were then subjected to solution-phase reduction at room temperature. When used as the electrodes for lithium ion batteries, the optimized material possesses a high reversible capacity of 873.5 mAh g−1 at a current of 0.1 A g−1, even at a large current density of 5 A g−1, a remarkable discharge capacity of 569.1 mA h g−1 can still be achieved. The improved performance is attributed to the synergistic effects of the optimized amount of Co2+ species and oxygen vacancies. The current strategy can be extended to other TMO electrodes, paving an alternative way to optimize the electrochemical performance for different applications. Selective solution-phase reduction on specific exposed crystalline planes generates defect structures and thus improves the lithium storage properties in a given material. Image 1 • Exposed crystalline planes are selective reduced in solution. • Defect structures can be generated. • The optimized sample exhibits enhanced lithium storage properties. [ABSTRACT FROM AUTHOR]

We report a facile method to synthesise and modify porous Co 3 O 4 nanosheets. The nanosheets are prepared by hydrothermal reaction and calcination, then reduced with an H 2 /Ar mixed gas at 250 °C within 1 min. The modification treatment generates oxygen vacancies and Co 3 O 4 /CoO interface structure. Electrochemical measurements show that the nanosheets (Co 3 O 4 -30) reduced for 30 s have excellent electrochemical performance. After the Co 3 O 4 -30 electrode was cycled 200 times under 0.5 Ag-1, the reversible capacity was 892 mAh g−1. A reversible capacity of 250 mAh g−1 can be achieved even at a higher current density of 5.0 Ag-1. The good lithium storage performance is attributed to oxygen vacancies and appropriate Co 3 O 4 /CoO interface structure. This study provides a facile strategy to construct improved transition metal oxide electrodes for energy storage and conversion. Rapid annealing in H 2 /Ar mixed gas at low temperature provides a facile approach to generate oxygen vacancies and Co 3 O 4 /CoO interface in porous Co 3 O 4 nanosheets, which show excellent electrochemical properties when used as the anodes for lithium ion batteries. Image 1 • Porous Co 3 O 4 nanosheets are modified by rapid reduction in H 2 /Ar at 250 °C. • Oxygen vacancies and Co 3 O 4 /CoO interface are generated by the reduction. • The optimised sample exhibits good lithium storage properties. [ABSTRACT FROM AUTHOR]