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The zinc–air battery with FeS2/NiS2 HDSNRs prepared by a one-step hydrothermal self-template process and high-temperature sulfurization process exhibits long-term stability for 480 h, and was well observed by in situ XRD.

A well-designed Co–Mo–P active site allows electron transport between Co and MoP, which will reduce the absorption free energy of the intermediates and improve the electrocatalytic activity of the hybrid.

The yolk–shell structure, realized by various synthesis methods, exhibits unique morphology and structural properties, which is currently undergoing a transition from material production technology to energy storage applications. To design an anode for lithium ion batteries (LIBs), a buffer space is designedly built between the Sb2Se3 nanorod yolk and the mesoporous carbon shell to obtain a novel yolk–shell structure (i.e., Sb2Se3@void@C). The confined void space is created by using a sacrificial template (such as silica) and the mesoporous carbon shell is obtained from the pyrolysis of phenolic resin, which effectively improves the electrical conductivity and structural stability of Sb2Se3 anode materials for LIB. Both the void space in the yolk–shell structure and the mesoporous carbon shell can efficiently buffer the volume expansion during the repeated discharge–charge processes, and further maintain the structural integrity. Besides, the permeable mesoporous carbon shell facilitates the electrolyte infiltration into the void space to ensure enough contact area between the Sb2Se3 and electrolyte, which benefits the shortening of the diffusion paths of Li+ ions. As a result, the Sb2Se3@void@C anode exhibits a high reversible specific capacity of 404.8 mA h g−1 at a rate of 1.0 A g−1 for at least 200 cycles, and maintains an average capacity of 594.7 at a rate of 3.0 A g−1. To further establish the detailed lithium storage behavior, in situ XRD is conducted to reveal the conversion reaction and alloying/dealloying reaction mechanisms. This research sheds light on yolk–shell structure designs with various morphologies to improve the electrochemical performance of energy storage materials.

Herein, we report a post-assembly strategy by growing bimetallic Co/Zn zeolitic imidazolate frameworks (BIMZIF) on the surface of customized Mo metal–organic frameworks (MOFs) (Mo-MOFs) to prepare core–shell structured Mo-MOF@BIMZIF, which results in a porous Co–MoO2 polyhedral nanocage (Co–MoO2-NC) structure and abundant Co–Mo–O active sites after high temperature pyrolysis. Co–MoO2-NC-900 which was obtained by pyrolysis at 900 °C displays a low overpotential (370 mV) for the oxygen evolution reaction (OER) and a half-wave potential (E1/2 ≈ 0.89 V) for the oxygen reduction reaction (ORR), exhibiting bifunctional features. A Zn–air battery with Co–MoO2-NC-900 shows a high power density of 176.5 mW cm−2 at 217.1 mA cm−2, which is better than that of reference Pt/C + Ir/C electrocatalysts, and is capable of exhibiting a smaller discharge–charge overpotential (0.85 V) and excellent stability (1145 h). Density functional theory calculations and experiments reveal that the structure and electron transfer between the Co and MoO2 components reduce the free energy of the intermediates, resulting in bifunctional electrocatalytic activity.

The development of high-efficiency and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts as air cathodes is still a challenge in energy storage and conversion. In this work, we report two-dimensional (2D) ultra-thin Co9S8/MnS sulfur/nitrogen co-doped carbon nanosheets (Co9S8/MnS-USNC) with outstanding ORR and OER activities as well as remarkable stability in alkaline media. Benefiting from the accessible functional surface and active sites of the 2D structure and adjustment of the electronic structure by the synergetic effect, Co9S8/MnS-USNC possesses a half-wave potential of 0.90 V for the ORR and a low overpotential of 360 mV for the OER at a current density of 10 mA cm−2. The aqueous zinc–air batteries displayed a maximum power density of 146 mW cm−2 and superior durability of 600 hours, and those of all-solid-state zinc–air batteries are 79 mW cm−2 and 18 hours respectively. The reaction mechanism of the Co9S8/MnS-USNC catalyst as the air cathode was also verified by in situ Raman spectroscopy.

Electrochemical deionization is an emerging desalination technique with great promise for production of fresh water, but its widespread application is still hindered by the low desalination capacity of the conventional carbonaceous electrodes. Herein, we constructed a novel dual-ion electrochemical deionization (DEDI) system using two types of faradaic material that accommodate specifically Cl− and Na+ as the electrodes, i.e. NiVAl trimetallic layered double hydroxides as the anode and a Na super ionic conductor Na3Fe2(PO4)3 as the cathode, to remove NaCl from saline water. Both faradaic materials were incorporated with a carbon support to prevent aggregation of the active materials as well as to enhance the electrical conductivity. The DEDI system allowed a high operation voltage due to the large gap of the redox potential between the two faradaic materials, and thus delivered an extraordinary NaCl adsorption capacity of 105.5 mg g−1 at 1.6 V. It also exhibited excellent cycling stability, with the adsorption capacity even increased by 148.3% after 100 cycles of charge and discharge. Furthermore, the excellent electrical conductivity, good electrochemical stability and high voltage endow the system with a high efficiency for energy recovery, with 56.2% of the energy consumed for deionization recoverable during discharging.

Herein, a uniformly distributed SnS2/Co3S4 heterostructure nanosheet array was grown on carbon cloth (CC) fibers by a simple solvothermal method and an oil bath method. When the hierarchical SnS2/Co3S4@CC nanoarray composite is used as a binder-free anode for sodium-ion batteries, its charge and discharge capacity is stabilized at 910.1 mA h g−1 at a current density of 0.5 A g−1 after 100 cycles. Even under a high current density of 2 A g−1, after 760 long-term cycles, the reversible capacity is stable at 637.2 mA h g−1, and still has excellent cycle stability with capacity retention of 87.3%. This excellent performance can be attributed to the reasonable design of the arrayed-electrode structure and the in situ growth of Co3S4 nanoparticles on the heterointerface of matrix SnS2 nanosheets: the well-defined array structure can shorten the diffusion path of Na+ ions and effectively alleviates volume expansion under long-cycle performance; the hierarchical heterostructure of SnS2/Co3S4 nanosheets can expand the interface contact area, provide more active sites and effectively enhance the electrochemical kinetics for sodium storage. The excellent electrochemical performance brought by the rational design of the heterogeneous nanostructure arrays provides new possibilities for the practical application of energy storage in the future.

Solid-state electrolytes (SSEs) are promising alternatives to traditional liquid electrolytes because of their safety issues. However, polymer SSEs have low ionic conductivity and weak mechanical strength, and inorganic SSEs are very brittle and unstable to lithium metal and atmospheric moisture, which restricts their practical applications. To avoid these disadvantages, it is essential to develop polymer–inorganic composite SSEs. In this work, we for the first time construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) (PVDF-HFP) blended with Li1.3Al0.3Ti1.7(PO4)3 and flower-like CeO2 particles enriched with oxygen vacancies as inorganic fillers. The composite SSEs exhibit a wide electrochemical window of 5.1 V (vs. Li/Li+) and high ionic conductivity of 1.66 × 10−3 S cm−1 at room temperature. The conductivity enhancement originates from the oxygen vacancies associated with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for releasing more lithium ions, and CeO2 is also beneficial for the suppression of Li dendrites. The solid-state LiFePO4/SSE/Li cell exhibits superior electrochemical performance at room temperature, the capacity is as high as 166.6 mA h g−1 at 0.1C, and the cell can sustain 83.1 mA h g−1 at 2C after 1000 cycles.

Correction for ‘Tuning and understanding the electronic effect of Co–Mo–O sites in bifunctional electrocatalysts for ultralong-lasting rechargeable zinc–air batteries’ by Yi Guan et al., J. Mater. Chem. A, 2021, 9, 21716–21722, https://doi.org/10.1039/D1TA04408G.

In this study, FeOx and CoOx thin films were successively and uniformly coated on high-surface-area carbon nanotubes by plasma-enhanced atomic layer deposition, which formed a heterojunction of the two oxides. As an electrocatalyst in the oxygen evolution reaction (OER), CoOx/FeOx/CNTs showed excellent electrocatalytic performance in terms of catalytic activity and stability. The overpotential of CoOx/FeOx/CNTs in OER was only 308 mV at 10 mA cm−2, which was lower than those of the pure oxides: CoOx/CNTs (392 mV) and FeOx/CNTs (406 mV). The as-prepared electrocatalyst also displayed better stability than the reference RuO2 material, with almost no attenuation of current density in contrast to the 10% loss seen with RuO2. The OER performance of CoOx/FeOx/CNTs was superior to those of its oxide components due to the formation of heterojunction, which led to a smoother reaction path and a lower overpotential for OER compared to pure oxides, as supported by the density-functional theory (DFT) calculations. These results provide a new direction for the preparation of electrocatalysts for metal–air batteries and water splitting reactions.

In this work, we propose to bind carbon nanofibrous networks onto a carbon felt substrate via the self-assembly process of polyaniline for vanadium redox flow batteries. The binder-free carbon nano-network wrapped carbon felt has a specific surface area of 161 m2 g−1, which is one hundred times higher than that of pristine carbon felt (0.4 m2 g−1) and thermally treated carbon felt (1.0 m2 g−1). Besides, the surface compositions of carbon nanofibers are also optimized by sulfur and nitrogen co-doping to selectively catalyze vanadium redox reactions with low parasitic reaction activity. It was found that the optimized N–S co-doping and the hierarchically porous structure collaboratively provide abundant active sites and an efficient mass transfer pathway, promoting the advection–diffusion–reaction process. Meanwhile, the nanofiber network also improves the interconnectivity among the micron-scale fibers of carbon felt, reducing the cell internal resistance. As a result, the present electrode exhibits an encouraging energy efficiency of 82.4% at a remarkably high current density of 320 mA cm−2 in a vanadium redox flow battery system, as compared to that obtained by the thermally treated carbon felt (66.8%). Furthermore, the carbon nano-network wrapped carbon felt also demonstrates a superior long-term stability over 1000 cycles, showing great promise in practical flow battery applications.

A novel free-standing and binder-free air electrode with excellent electrochemical performance was designed for highly reversible Li–O2 batteries. The 3D hierarchically N, S co-doped macro–mesoporous carbon (NSMmC) was deposited on carbon paper (CP) via a template method, and then uniformly decorated with PdNi nanoparticles. The macropores of the porous carbon can provide enough space to accommodate discharge products, while the interconnected pores and channels efficiently facilitate oxygen and electrolyte diffusion. The introduction of PdNi nanoparticles greatly reduce the charge transfer resistance, resulting in the improvement of electron mobility of the whole cathode. Compared with Pd–NSMmC/CP and NSMmC/CP cathodes, the PdNi–NSMmC/CP cathode shows considerable enhancement of Li–O2 battery performance. The ultrafine and evenly distributed PdNi nanoparticles can not only provide enough catalytic sites, but can also tailor the discharge products into a cage-like morphology, which provides enough channels for electron and lithium ion transport. Moreover, the smaller size of the cage-like Li2O2 makes it decompose more easily, resulting in lower charge overpotential. This study provides a promising strategy to design 3D structured air cathodes for Li–O2 batteries with high electrocatalytic performance.

Herein, an electrocatalyst consisting of iron and nitrogen co-doped porous carbon (Fe–N/C) was prepared by catalytic carbonization of chitin with the assistance of FeCl3 and ZnCl2. The catalytic activity of Fe–N/C towards the oxygen reduction reaction (ORR) in both acidic and alkaline electrolytes was significantly enhanced by air-plasma etching for only 120 s, showing a four-electron ORR process with an onset potential and limiting current comparable to those of Pt catalysts. This performance enhancement originated from the removal of less stable sp3 and amorphous sp2 carbons which would expose more active catalytic FeN4 centers, as well as the transformation of a small fraction of iron-based nanoparticles into FeN4 species.

Correction for ‘Enhanced structural stability and overall conductivity of Li-rich layered oxide materials achieved by a dual electron/lithium-conducting coating strategy for high-performance lithium-ion batteries’ by Dan Gao et al., J. Mater. Chem. A, 2019, 7, 23964–23972, DOI: 10.1039/C9TA04551A.

Herein, we propose a novel post-modification synthesis strategy to prepare M-doped (M = Fe, Co, Mo, etc.) transition metal phosphides (TMPs) composed of Co and MoP embedded in nitrogen-doped carbon nanospheres (denoted as Co–Mo–P@NCNS-600). Through engineering of the anion chemistry of cobaltosic oxide nanoparticles to adjust the composition, morphology and crystallographic orientation of the Mo-based metal–organic frameworks (MOFs), and then a pyrolysis–phosphidation process, the Co–Mo–P@NCNS-600 electrocatalyst exhibits excellent electrocatalytic performance (overpotentials (η10) of 270 mV for the oxygen evolution reaction and 62 mV for the hydrogen evolution reaction), benefiting from the well-designed structure and the electronic state control. Furthermore, when the Co–Mo–P@NCNS-600 is used in a water-splitting device, it can reach a 10 mA cm−2 current density at low potential (1.58 V), and exhibits excellent stability for 380 000 s (105.6 h). Density functional theory (DFT) results indicate that the successful construction of the Co–Mo–P active site will effectively modulate the intrinsic electronic properties and improve the electrochemical performance.