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To make supercapacitors a viable commercial product, it is necessary to increase the mass loading (ML) of the electrodes. However, current research on high ML MXene electrodes mainly focuses on internal structure optimization, often neglecting the importance of surface texture in the electrodes, which plays a crucial role in mediating interactions between the internal structure and the electrolyte. This study reports on a simple ion‐intercalation process that can reduce charge transfer resistance and improve cycling stability. Through the integration of 3D visualization models and wide‐angle X‐ray scattering techniques, a comprehensive investigation of the electrode's surface structure and MXene flake arrangement is conducted. The results showed that pre‐oriented aggregates induced by ion‐intercalation create a sophisticated surface structure with rich hills and valleys, promoting electrolyte permeation and ion exchange. This work highlights the significance of surface texture in films and electrodes, guiding the design of high‐performance materials. [ABSTRACT FROM AUTHOR]

Silicon-based electrodes offer a high theoretical capacity and a low cost, making them a promising option for next-generation lithium-ion batteries. However, their practical use is limited due to significant volume changes during charge/discharge cycles, which negatively impact electrochemical performance. This study proposes a practical method to increase silicon content in lithium-ion batteries with minimal changes to the manufacturing process by using dual-layer electrodes (DLEs). These DLEs are fabricated with two slurries containing silicon and graphite as active materials. Notably, the electrode with the silicon as the outermost layer on top of the graphite layer (Si-on-top) demonstrated a superior initial capacity of 935 mAh/g and retained 70% of its capacity (537 mAh/g) after 100 cycles at 0.5 C. In contrast, a single-layered electrode (SLE) with a silicon–graphite mixture retained only 50.3% of its capacity (370 mAh/g) under the same conditions. These findings suggest that DLEs, particularly with the silicon layer located on top, effectively increase silicon content in the negative electrode while remaining compatible with existing manufacturing processes. This approach offers a realistic strategy for enhancing the performance of lithium-ion batteries without significant process modifications. [ABSTRACT FROM AUTHOR]

Recently, strategies of optimizing cathode/electrolyte interphase (CEI) have been applied to enhance the durability of LiCoO2 (LCO) at high voltages (≥4.55 V vs Li/Li+) and high temperatures (≥45 °C), but the underlying mechanism is still in debate. Herein, a durable CEI on LCO that operates at 45 °C is achieved via tuning the chemical and morphological properties at the surface. Specifically, an artificial CEI layer composing of island‐shaped AlPO4/Li3PO4 deposits is constructed on LCO surface, i.e., AP‐LCO. Upon cycle, a progressive chemical evolution from AlPO4 to Li3AlF6/Li3PO4 takes place, and a robust CEI enriching with ion‐conductive Li3AlF6 species is formed, leading to a uniform and compact CEI to provide a comprehensive coverage on LCO surface. Therefore, the AP‐LCO displays outstanding improvements in the resistance to HF corrosion, the suppression of surface degradation, and the kinetics of Li+ transport, along with an unprecedentedly high thermal stability. Benefited from the above advantages, the Li||AP‐LCO cell shows high capacity retention of 84.0% in 500 cycles at 45 °C and 4.6 V. This work provides a new insight into the role of robust CEI for high‐temperature durability of LCO cathodes. [ABSTRACT FROM AUTHOR]

As the energy storage sector gains prominence, sodium batteries have garnered attention due to their affordability and the abundance of raw materials. Among the methods aimed at enhancing sodium battery performance, electrolyte additives are notably cost‐effective. Despite typically comprising no more than 5% of the components, these additives play a crucial role in improving battery cycle life and overall functionality. This review begins by analyzing the factors propelling the development of sodium batteries and the diverse roles of additives, extensively examines the roles of common functional groups (fluorine(F)‐containing, sulfonyl, sulfoxide, phosphate ester, nitrogenous, boron, silyl groups, etc.) in additives. Furthermore, it categorizes the latest functional electrolyte additives into five distinct types. Lastly, the review provides an overview of the potential for designing additives that are both sustainable and efficient. This comprehensive review aims to be a valuable resource for informing the strategic selection and enhancement of electrolyte additives, thereby facilitating future progress in the field. [ABSTRACT FROM AUTHOR]

Non‐aqueous lithium‐oxygen batteries (LOBs) have emerged as a promising candidate due to their high theoretical energy density and eco‐friendly cathode reaction materials. However, LOBs still suffer from high overpotential and poor cycling stability resulting from difficulties in the decomposition of discharge reaction Li2O2 products. Here, a 3D open network catalyst structure is proposed based on highly‐thin and porous multi‐metal oxide nanofibers (MMONFs) developed by a facile electrospinning approach coupled with a heat treatment process. The developed hierarchically interconnected 3D porous MMONFs catalyst structure with high specific surface area and porosity shows the enhanced electrochemical reaction kinetics associated with Li2O2 formation and decomposition on the cathode surface during the charge and discharge processes. The uniquely assembled cathode materials with MMONFs exhibit excellent electrochemical performance with energy efficiency of 82% at a current density of 50 mA g−1 and a long‐term cycling stability over 100 cycles at 200 mA g−1 with a cut‐off capacity of 500 mAh g−1. Moreover, the optimized cathode materials exhibit a remarkable energy density of 1013 Wh kg−1 at the 100th discharge and charge cycle, which is nearly four times higher than that of C/NMC721, which has the highest energy density among the cathode materials currently used in electric vehicles. [ABSTRACT FROM AUTHOR]

Medium-nickel cobalt-free cathode materials have attracted much attention in recent years for their low cost and high energy density. However, the structural stability of nickel-based cathode materials becomes compromised when accompanied by the increasing of voltage, leading to poor cycling performance and, thus, hindering their widespread industrial application. In this work, we investigated the optimal charge cut-off voltage for the nickel-based cathode material LiNi0.6Mn0.4O2 (NM64). Within the voltage range of 3.0 to 4.5 V, the electrode energy density reached 784.08 Wh/kg, with an initial Coulombic efficiency of 84.49%. The reversible specific capacity at 0.1 C reached 197.84 mAh/g, and it still maintained a high reversible specific capacity of nearly 150 mAh/g, with a capacity retention rate of 86% after 150 cycles at 1 C. Furthermore, NM64 exhibited an intact morphological structure without noticeable cracking after 150 cycles, indicating excellent structural stability. This study emphasizes the relationship between the stability of NM64 cathodes and different operating voltage ranges, thereby promoting the development of high-voltage layered nickel-based cathode materials. [ABSTRACT FROM AUTHOR]

Superabsorbent starch (SS) was coated on Zn foil by a simple scratch coating method to form an artificial interface protection layer, which inhibited the formation of dendrites by guiding the uniform deposition of Zn2+. In addition, SS coating contains a large amount of OH–, which can promote the desolvation process of hydrated Zn2+ and inhibit the side reaction. [Display omitted] Aqueous zinc ion batteries (AZIBs) have attracted much attention for their safety, low cost and high theoretical capacity. Nevertheless, Zn dendrites and the adverse reactions such as corrosion, hydrogen evolution and passivation on the anode affect the cycle life and stability of AZIBs. Herein, superabsorbent starch (SS) was employed on Zn foil to form an artificial interface protection layer, which inhibited the formation of dendrites by guiding the uniform deposition of Zn2+. SS with a large amount of oxygen-containing functional group is superabsorbent, which can attract the active water around the hydrated Zn2+, promoting the desolvation process of the hydrated Zn2+ and significantly inhibiting the occurrence of hydrogen evolution reaction. In addition, the inherent pore structure of the SS artificial interfacial layer can induce uniform nucleation of Zn2+ and inhibit the dendrites growth. Moreover, compared to bare Zn//MnO 2 cell (44.1 %), the capacity retention of Zn@SS//MnO 2 cell remained as high as 87.8 % after 1000 cycles at 1.5 A g−1. The simple method provided a new method for the rapid development of AZIBs. [ABSTRACT FROM AUTHOR]

Hexagonal MnMX-based (M = Co or Ni, X = Si or Ge) alloys exhibit giant reversible barocaloric effects. However, giant volume expansion would result in the as-cast MnMX ingots fragmenting into powders, and inevitably bring the deterioration of mechanical properties and formability. Grain fragmentation can bring degradation of structural transformation entropy change during cyclic application and removal of pressure. In this paper, giant reversible barocaloric effects with high thermal cycle stability can be achieved in the epoxy bonded (MnCoGe)0.96(CuCoSn)0.04 composite. Giant reversible isothermal entropy change of 43.0 J∙kg−1∙K−1 and adiabatic temperature change from barocaloric effects (ΔTBCE) of 15.6 K can be obtained within a wide temperature span of 30 K at 360 MPa, which is mainly attributed to the integration of the change in the transition temperature driven by pressure of −101 K∙GPa−1 and suitable thermal hysteresis of 11.1 K. Further, the variation of reversible ΔTBCE against the applied hydrostatic pressure reaches up to 43 K∙GPa−1, which is at the highest level among the other reported giant barocaloric compounds. More importantly, after 60 thermal cycles, the composite does not break and the calorimetric curves coincide well, demonstrating good thermal cycle stability. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries are anticipated to be the next generation of important energy storage devices to replace lithium‐ion batteries due to the ongoing use of lithium resources and the safety hazards associated with organic electrolytes in lithium‐ion batteries. Manganese‐based compounds, including MnOx materials, have prominent places among the many zinc‐ion battery cathode materials. Additionally, Cu doping can cause the creation of an oxygen vacancy, which increases the material's internal electric field and enhances cycle stability. MnOx also has great cyclic stability and promotes ion transport. At a current density of 0.2 A g−1, the Cu/MnOx nanocomposite obtained a high specific capacitance of 304.4 mAh g−1. In addition, Cu/MnOx nanocomposites showed A high specific capacity of 198.9 mAh g−1 after 1000 cycles at a current density of 0.5 A g−1. Therefore, Cu/MnOx nanocomposites are expected to be a strong contender for the next generation of zinc‐ion battery cathode materials in high energy density storage systems. [ABSTRACT FROM AUTHOR]

In this paper, we design a binder GG-CA-GLY (abbreviation: GGC) for silicon negative electrode by guar gum as the backbone chain with self-healing function, combing and straightening the guar molecular chain of guar gum through the plasticizing effect of glycerol. The condensation reactions between the exposed hydroxyl sites of guar gum and the carboxyl groups of citric acid create a stronger hydrogen bond, so as to achieve the effect of self-healing and cope with the serious volume expansion effect of silicone-based materials. [Display omitted] • A easy polycondensation reaction is used to create a mechanically strong self-healing polymer (GGC). • GGC adhesives have excellent mechanical properties and facilitate rapid self-healing. • GGC@Si electrodes were prepared with excellent rate capability and higher cycling stability. • GGC adhesives have the ability to repair cracks and other damage on prepared silicon anodes, returning them to their original state. Silicon is a promising anode material for lithium-ion batteries with its superior capacity. However, the volume change of the silicon anode seriously affects the electrode integrity and cycle stability. The waterborne guar gum (GG) binder has been regarded as one of the most promising binders for Si anodes. Here, a unique steric molecular combing approach based on guar gum, glycerol, and citric acid is proposed to develop a self-healing binder GGC, which would boost the structural stability of electrode materials. The GGC binder is mainly designed to weaken van der Waals' forces between polymers through the plasticizing effect of glycerol, combing and straightening the guar molecular chain of GG, and exposing the guar hydroxyl sites of GG and the carboxyl groups of citric acid. The condensation reaction between the hydroxyl sites of GG and the carboxyl groups of citric acid forms stronger hydrogen bonds, which can help achieve self-healing effect to cope with the severe volume expansion effect of silicone-based materials. Silicon electrode lithium-ion batteries prepared with GGC binders exhibit outstanding electrochemical performance, with a discharge capacity of up to 1579 mAh/g for 1200 cycles at 1 A/g, providing a high capacity retention rate of 96%. This paper demostrates the great potential of GGC binders in realizing electrochemical performance enhancement of silicon anode. [ABSTRACT FROM AUTHOR]

This study reports the development of a new Ti-Zr-Mn-based AB 2 type hydrogen storage alloys for a two-stage metal hydride hydrogen compressor (MHHC). The hydrogen storage alloys are designed to compress hydrogen from 35 to 865 bar within a temperature difference of 115 °C. High-pressure PCT measurements up to 700 bar were carried out to test the performance of the alloys. The alloys' hysteresis and the plateau slope were reduced by optimizing the composition. The introduction of fugacity correction into the Van't hoff equation reduces the deviation between calculation and actual pressure to 24 bar at a pressure above 350 bar. A precise relation between the Ti/Zr ratio and the desorption pressure is described and helps make a correct design of the alloy composition. The designed alloy shows looses less than 1% of the capacity over 3000 full cycles. The desorption plateau pressure of the alloy is constant within 92% during the whole cycling process. A 2 stages compressor working with two types of alloys offers compression with a temperature range between -20 and 95 °C for the refueling hydrogen vehicles up to 865 bar. • The alloys for 2-stage hydrogen compressor compress H 2 from 35 to 865 bar. • The improved calculated plateau pressure match well with the 700 bar PCT test. • The alloy shows excellent cyclability, after 3000 cycles without degradation. [ABSTRACT FROM AUTHOR]

Supercapacitors are prospective energy storage devices for electronic devices due to their high power density, rapid charging and discharging, and extended cycle life. Materials with limited conductivity could have low charge-transfer ions, low rate capability, and low cycle stability, resulting in poor electrochemical performance. Enhancement of the device's functionality can be achieved by controlling and designing the electrode materials. Graphene oxide (GO) has emerged as a promising material for the fabrication of supercapacitor devices on account of its remarkable physiochemical characteristics. The mechanical strength, surface area, and conductivity of GO are all quite excellent. These characteristics make it a promising material for use as electrodes, as they allow for the rapid storage and release of charges. To enhance the overall electrochemical performance, including conductivity, specific capacitance (Cs), cyclic stability, and capacitance retention, researchers concentrated their efforts on composite materials containing GO. Therefore, this review discusses the structural, morphological, and surface area characteristics of GO in composites with metal oxides, metal sulfides, metal chalcogenides, layered double hydroxides, metal–organic frameworks, and MXene for supercapacitor application. Furthermore, the organic and bacterial functionalization of GO is discussed. The electrochemical properties of GO and its composite structures are discussed according to the performance of three- and two-electrode systems. Finally, this review compares the performance of several composite types of GO to identify which is ideal. The development of these composite devices holds potential for use in energy storage applications. Because GO-modified materials embrace both electric double-layer capacitive and pseudocapacitive mechanisms, they often perform better than pristine by offering increased surface area, conductivity, and high rate capability. Additionally, the density functional theory (DFT) of GO-based electrode materials with geometrical structures and their characteristics for supercapacitors are addressed. [ABSTRACT FROM AUTHOR]

A novel electrolyte additive, 3, 3, 3‐trifluoropropylmethyldimethoxysilane (TFPMDS), is first proposed to modify both the cathode and the anode of lithium‐ion batteries at the same time. Charging/discharging tests demonstrate that the electrolyte with 1 wt% TFPMDS not only greatly improves the capacity retention of LiNi0.5Mn1.5O4 (LNMO)//Li cell (29.6%→90.8%) and graphite//Li cell (68.1%→98.3%), but also successfully ensures the long‐term cycle stability of LNMO//graphite pouch cell at 4.9 V. Further electrochemical measurements combining with spectroscopic characterization and theoretical calculations indicate that TFPMDS additive displays three principal functions: 1) Be preferentially oxidized to build a robust cathode electrolyte interphase (CEI) enriched in F/Si species with F‐rich nature of strong oxidation‐resistance. 2) Be able to scavenge the hazardous HF, F−, and H+ through its strong binding with these species and thus to protect LNMO at high‐voltage. 3) Be preferentially adsorbed on the graphite surface to form a "framework", and to co‐construct an elastic solid electrolyte interphase (SEI) after the reduction of ethylene carbonate. Importantly, the Si─O group within TFPMDS is especially important for constructing a "molecular bridge" at the CEI/SEI interphase coupling the inorganic and organic species to improve its compatibility, stability, and elasticity. [ABSTRACT FROM AUTHOR]

The pursuit of high energy densities propels the design of next‐generation nickel‐based layered oxide cathodes. The utilization of low‐cobalt, ultrahigh‐nickel layered oxide cathodes, and the extension of operating voltages promise enhanced energy density. However, stability and safety face challenges associated with nickel content, including structural degradation, lattice oxygen evolution, and thermal instability. In this study, a promising strategy of Al and Nb dual‐bulk‐doping is presented in high‐Ni cathode materials of LiNi0.96Co0.04O2 (NC) to stabilize the bulk structure, suppress oxygen release, and attain superior electrochemical performance at high voltages. The introduction of Al and Nb effectively raises the migration energy of Ni2+ into Li sites and stabilizes lattice oxygen through strengthened Al─O and Nb─O bonds. Furthermore, the substitution of high‐valence Nb ions reduces the charge depletion of lattice oxygen and induces an ordered microstructure. The Al and Nb dual‐bulk‐doping strategy mitigates strain and stress associated with the H2↔H3 phase transition, reducing the generation and propagation of microcracks. The resulting Li(Ni0.96Co0.04)0.985Al0.01Nb0.005O2 (NCAN) cathode exhibits superior cycling stability, with a capacity retention of 77.8% after 300 cycles, even when operating at a high‐voltage of 4.4 V, outperforming the NC (48.5%). This work provides a promising perspective for developing high‐voltage and high‐Ni cathode materials. [ABSTRACT FROM AUTHOR]

Currently, the major challenge in terms of research on K‐ion batteries is to ensure that they possess satisfactory cycle stability and specific capacity, especially in terms of the intrinsically sluggish kinetics induced by the large radius of K+ ions. Here, we explore high‐performance K‐ion half/full batteries with high rate capability, high specific capacity, and extremely durable cycle stability based on carbon nanosheets with tailored N dopants, which can alleviate the change of volume, increase electronic conductivity, and enhance the K+ ion adsorption. The as‐assembled K‐ion half‐batteries show an excellent rate capability of 468 mA h g−1 at 100 mA g−1, which is superior to those of most carbon materials reported to date. Moreover, the as‐assembled half‐cells have an outstanding life span, running 40,000 cycles over 8 months with a specific capacity retention of 100% at a high current density of 2000 mA g−1, and the target full cells deliver a high reversible specific capacity of 146 mA h g−1 after 2000 cycles over 2 months, with a specific capacity retention of 113% at a high current density of 500 mA g−1, both of which are state of the art in the field of K‐ion batteries. This study might provide some insights into and potential avenues for exploration of advanced K‐ion batteries with durable stability for practical applications. [ABSTRACT FROM AUTHOR]

Rechargeable Li‐O2 batteries (LOBs) are regarded as promising candidates for the next generation of energy storage devices. One of the major impediments is the poor cycle stability resulting from unreliable cathode catalysts and serious corrosion of Li anode, hindering the commercial application of LOBs. Herein, a synergetic strategy is proposed, including the design of a stable Co3Ru cathode catalyst via d‐band center modulation and the construction of a robust LiF/Sn/Li5Sn2‐PFDTMS hybrid protective layer on Li anode. Theoretical calculations reveal that the negative shift of the d‐band center provides a dominant descriptor for improving the catalysis activity and stability of Ru‐based catalysts. In situ construction of the PFDTMS‐enhanced LiF/Sn/Li5Sn2 hybrid layer possesses excellent mechanical stability and toughness, which can effectively shield the Li anode from corrosive reaction and ensure good Li+ transport. Consequently, the LOBs exhibit a long cycle life of 990 cycles (≈1980 h). This work confers the concept for high‐performance LOBs via rationally constructing stable catalysts and Li anodes. [ABSTRACT FROM AUTHOR]

Ultra-thin and porous MgCo2O4 nanowires with larger specific surface area was successfully synthesized on Ni foam by hydrothermal method with surfactant sodium dodecylsulphate. It showed that MgCo2O4 nanowires exhibited a dense interwoven and transparent net-like structure with a high specific capacitance of 2128 F/g at a current of 5 A/g. After 6000 cycles under the condition of 40 A/g, 98.4% of initial capacitance was retained. Additionally, asymmetric supercapacitor was assembled with this nanowires as binder-free positive electrode and activated carbon as negative electrode respectively, which displayed a specific capacitance of 65.32 F/g and energy density of 20.41 Wh/kg under the power density of 338.95 W/kg. The above results show that the asymmetric supercapacitor is a good energy storage device which has good potential in practical applications. [ABSTRACT FROM AUTHOR]

In recent years, the remarkable energy density of high-nickel ternary materials has captured considerable attention. Nevertheless, the high-nickel ternary cathode material encounters several challenges, including cationic mixing, microcrack formation, poor cycling capability, and limited thermal stability. Coating, as a viable approach, proves to be effective in enhancing the material properties. In this study, the LiNi0.8Co0.1Mn0.1O2 (NCM811) sample underwent a dry grinding process, followed by Y2O3 coating and subsequent sintering at varying temperatures. The microstructure, morphology, and electrochemical properties of the materials were meticulously examined, and the underlying mechanism of coating modification was meticulously explored. The outcomes demonstrate the attainment of dual coating and doping effects through Y2O3 modification. Y2O3 coating mitigates the direct interaction between the NCM811 surface and the electrolyte, thereby inhibiting undesired side reactions at the interface. Moreover, the Y element infiltrates the crystal structure, imparting stability at elevated sintering temperatures. Remarkably, the Y2O3-coated cathode materials exhibit significantly enhanced cycling stability, discharge capacity, and rate performance. These findings can provide novel insights that can be harnessed to improve the energy density cathode material of NCM811. [ABSTRACT FROM AUTHOR]

Molybdate intercalation significantly reduces the thickness of cobalt–nickel layered hydroxide, greatly increases its specific surface area, regulates its pore distribution, increases the crystal plane spacing, promotes the diffusion rate of hydroxide in it, and increases its specific capacity. Meanwhile, the bilayered MCN-LDH@CP electrode significantly improved the areal energy density and peak power density and cycle stability of the CoNi//Zn battery. The quasi-solid-state MCN-LDH@CP//Zn battery can still charge a mobile phone even when hammered and pierced, showing excellent safety and reliability. [Display omitted] Seeking cathode materials with high areal capacity and excellent cycling tolerance is a key step to develop aqueous rechargeable zinc-based alkaline batteries with high energy density, power density and excellent stability. Here, the bilayered cathode composite (MCN-LDH@CP) of molybdate intercalated cobalt–nickel layered hydroxide nanosheets (MCN-LDH) grown on cobalt phosphate octahydrate microsheet (CP) was prepared by a two-step hydrothermal process. Molybdate intercalation significantly reduces the thickness of cobalt–nickel layered hydroxide, greatly increases its specific surface area, regulates its pore distribution, increases the crystal plane spacing, promotes the diffusion rate of hydroxide in it, and increases its specific capacity. Meanwhile, the bilayered MCN-LDH@CP electrode significantly improved the areal energy density (2.89 mWh/cm2) and peak power density (111.22 mW/cm2) and cycle stability (97.8 % after 7000 cycles) of the CoNi//Zn battery. The excellent stability is mainly due to the fact that the MCN-LDH overlay inhibits the loss of P element of CP and improves the structural stability of the sample. The quasi-solid-state MCN-LDH@CP//Zn battery can still charge a mobile phone even when hammered and pierced, showing excellent safety and reliability. This work opens a new avenue to develop CoNi//Zn batteries with high energy density, power density and excellent tolerance. [ABSTRACT FROM AUTHOR]

Micro-sized single-crystalline Ni-rich cathodes are emerging as prominent candidates owing to their larger compact density and higher safety compared with poly-crystalline counterparts, yet the uneven stress distribution and lattice oxygen loss result in the intragranular crack generation and planar gliding. Herein, taking LiNi0.83Co0.12Mn0.05O2 as an example, an optimal particle size of 3.7 µm is predicted by simulating the stress distributions at various states of charge and their relationship with fracture free-energy, and then, the fitted curves of particle size with calcination temperature and time are further built, which guides the successful synthesis of target-sized particles (w-NCM83) with highly ordered layered structure by a unique high-temperature short-duration pulse lithiation strategy. The W-NCM83 significantly reduces strain energy, Li/O loss, and cationic mixing, thereby inhibiting crack formation, planar gliding, and surface degradation. Accordingly, the m-NCM83 exhibits superior cycling stability with highly structural integrity and dual-doped m-NCM83 further shows excellent 88.1% capacity retention. [ABSTRACT FROM AUTHOR]

[Display omitted] • pH buffer KH 2 PO 4 were added to the electrolyte of Zn/γ-MnO 2 with proton reaction mechanism. • The rate performance and cycle stability at high current densities were greatly enhanced by the additional KH 2 PO 4. • The KH 2 PO 4 can service as a new proton source and reduce the formation of zinc hydroxide sulfate. • The electrochemical reaction kinetics of Zn/γ-MnO 2 battery have been significantly improved by the additional pH buffers KH 2 PO 4. Zinc-ion batteries (ZIBs) are rapidly emerging as safe, cost-effective, nontoxic, and environmentally friendly energy storage systems. However, mildly acidic electrolytes with depleted protons cannot satisfy the huge demand for proton reactions in MnO 2 electrodes and also cause several issues in ZIBs, such as rapidly decaying cycling stability and low reaction kinetics. Herein, we propose a pH-buffering strategy in which KH 2 PO 4 is added to the electrolyte to overcome the problems caused by low proton concentrations. This strategy significantly improves the rate and cycle stability performance of zinc–manganese batteries, delivering a high capacity of 122.5 mAh/g at a high current density of 5 A/g and enabling 9000 cycles at this current density, with a remaining capacity of 70 mAh/g. Ex-situ X-ray diffraction and scanning electron microscopy analyses confirmed the generation/dissolution of Zn 3 PO 4 ·4H 2 O and Zn 4 (OH) 6 (SO 4)·5H 2 O, byproducts of buffer products and proton reactions. In-situ pH measurements and chemical titration revealed that the pH change during the electrochemical process can be adjusted to a low range of 2.2–2.8, and the phosphate distribution varies with the pH range. Those results reveal that H 2 PO 4 − provides protons to the cathode through the chemical balance of HPO 4 2−, HPO 4 2–, and Zn 3 PO 4 ·4H 2 O. This study serves as a guide for studying the influences and mechanisms of buffering additives in Zn–MnO 2 batteries. [ABSTRACT FROM AUTHOR]

Among the electrode materials for supercapacitors (SCs), metal-organic framework (MOFs) is attracting huge research interest as a new type of energy storage electrode materia. However, due to their poor conductivity and stability, the practical application of original MOFs in the field of energy storage has been greatly hindered. Here, we demonstrate a special core-shell structure, which the synergistic action of NiCo2O4 and Ni-MOF forms a tight conductive network that speeds up electron transport and larger specific surface area, more active sites were obtained and mechanical stability that indicates its outstanding long life. The test results show that it has a high specific capacity of 4.23 F cm–2 at 5 mA cm–2, and the capacity retention rate is maintained at 97.5% after 8000 cycles. In addition, an asymmetric supercapacitor device, using NiCo2O4@Ni-MOF and activated carbon (AC) as anode and cathode, has a high specific capacity of 3.21 F cm–2 at 5 mA cm–2 and excellent cycling performance (83.8% retention over 8000 cycles at 10 mA cm–2). Our work demonstrates the possibility of using novel structured Ni-MOF-based hybrid arrays as electrodes for SCs with enhanced electrochemical performance compared to Ni-MOF and NiCo2O4, providing a reliable prospect for flexible energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract Currently, the major challenge in terms of research on K‐ion batteries is to ensure that they possess satisfactory cycle stability and specific capacity, especially in terms of the intrinsically sluggish kinetics induced by the large radius of K+ ions. Here, we explore high‐performance K‐ion half/full batteries with high rate capability, high specific capacity, and extremely durable cycle stability based on carbon nanosheets with tailored N dopants, which can alleviate the change of volume, increase electronic conductivity, and enhance the K+ ion adsorption. The as‐assembled K‐ion half‐batteries show an excellent rate capability of 468 mA h g−1 at 100 mA g−1, which is superior to those of most carbon materials reported to date. Moreover, the as‐assembled half‐cells have an outstanding life span, running 40,000 cycles over 8 months with a specific capacity retention of 100% at a high current density of 2000 mA g−1, and the target full cells deliver a high reversible specific capacity of 146 mA h g−1 after 2000 cycles over 2 months, with a specific capacity retention of 113% at a high current density of 500 mA g−1, both of which are state of the art in the field of K‐ion batteries. This study might provide some insights into and potential avenues for exploration of advanced K‐ion batteries with durable stability for practical applications.

With the advantages of being cheap, safe, and environmentally friendly, aqueous Zn-ion batteries (AZIBs) show promise in large-scale energy storage and smart wearables. Moreover, with the expansion of the field of flexible electronics, the huge demand potential of wearable smart electronic devices is increasingly being underscored, which proposes higher requirements for the structural and electrochemical stability of energy storage devices and device safety in physical deformation processes. Aqueous electrolyte-based AZIBs are prone to interface separation during bending, which affects battery stability and makes it difficult to realize further practical applications in flexible electronics. Unlike aqueous electrolytes, hydrogel electrolytes are flexible and foldable, assuring the structural and performance stability of flexible energy storage devices under the action of external impacts. Particularly, polyacrylamide (PAM)-based hydrogels are the preferred materials for preparing hydrogel electrolytes due to their better ionic conductivity, strain, and stability. Herein, montmorillonite–PAM hydrogel (MMT–PAM) electrolytes with a three-dimensional network structure were produced by a two-step process using two-dimensional layered montmorillonite and acrylamide monomer. The addition of montmorillonite provides adsorption sites for the in situ polymerization of acrylamide monomer to enhance the mechanical properties of the hydrogel and facilitates the rapid transport of Zn2+ through the abundant negative charge on the MMT surface, increasing its ionic conductivity (34 mS∙cm−1 at room temperature is much higher than that of the PAM hydrogel electrolyte (17 mS∙cm−1)) to obtain MMT–PAM hydrogel electrolytes with better electrochemical properties. The MMT–PAM hydrogel electrolyte-based Zn–MnO2 batteries –demonstrated a specific capacity of 289 mA·h∙g−1 at a current density of 0.2 A∙g−1 and could be stably cycled for 2000 cycles, whereas the PAM hydrogel electrolyte-based Zn–MnO2 batteries only cycled for hundreds of cycles at the same current density before short-circuiting, thus demonstrating the long battery cycle life of the MMT–PAM hydrogel electrolyte-based Zn–MnO2 batteries. The MMT–PAM-based batteries maintained a high specific capacity even at a high current density of 4 A∙g−1. Furthermore, flexible batteries based on MMT–PAM hydrogel electrolytes could still work properly under different external impacts, such as cutting and piercing. The prepared flexible batteries were folded and immersed in aqueous solution to provide stable voltage and remarkable water resistance, demonstrating their possible application in flexible electronics. Therefore, this work sheds light on the possibility of further application of hydrogel electrolytes in aqueous Zn–MnO2 batteries and the further development of flexible energy storage devices based on hydrogel electrolytes.

Silicon-based electrodes offer a high theoretical capacity and a low cost, making them a promising option for next-generation lithium-ion batteries. However, their practical use is limited due to significant volume changes during charge/discharge cycles, which negatively impact electrochemical performance. This study proposes a practical method to increase silicon content in lithium-ion batteries with minimal changes to the manufacturing process by using dual-layer electrodes (DLEs). These DLEs are fabricated with two slurries containing silicon and graphite as active materials. Notably, the electrode with the silicon as the outermost layer on top of the graphite layer (Si-on-top) demonstrated a superior initial capacity of 935 mAh/g and retained 70% of its capacity (537 mAh/g) after 100 cycles at 0.5 C. In contrast, a single-layered electrode (SLE) with a silicon–graphite mixture retained only 50.3% of its capacity (370 mAh/g) under the same conditions. These findings suggest that DLEs, particularly with the silicon layer located on top, effectively increase silicon content in the negative electrode while remaining compatible with existing manufacturing processes. This approach offers a realistic strategy for enhancing the performance of lithium-ion batteries without significant process modifications.

MCS-x materials, synthesized through a straightforward stirring and carbonization process using a solvent-induced self-assembly technique, exhibit ultra-long cycle stability in their application to sodium-ion batteries (SIBs). [Display omitted] Mesoporous carbon nanospheres (MCSs) are extensively employed in energy storage applications due to their ordered pore size, large specific surface area (SSA), and abundant active sites, resulting in excellent electrochemical performance for sodium storage. However, challenges persist in achieving precise structural control and stable synthesis reactions for these MCSs. Additionally, employing MCSs with a larger SSA in sodium storage applications can lead to increased side reactions and potential structural instability. To address these issues, we propose a solvent-induced self-assembly method for obtaining high nitrogen-containing multi-cavity MCSs with reduced SSA. The morphology and SSA of the nanospheres can be precisely adjusted by regulating the reaction time. Introducing an amine-phenol bridging structure into the polymer system significantly bolsters the structural and morphological stability of the mesoporous materials. The performance of these novel nanospheres in sodium-ion batteries (SIBs) is remarkable, exhibiting excellent sodium storage capability and exceptional ultra-long cycle stability. At a rate of 0.1 A g−1, the nanospheres achieved a high reversible capacity of 252 mAh g−1, and even after 20,000 cycles at 5 A g−1, a specific capacity of 136 mAh g−1 was retained. In summary, our study presents a novel approach for synthesizing mesoporous carbon materials and offers valuable insights for sodium storage research, opening new possibilities for enhancing energy storage applications. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (ZIBs) have significant potential for large energy storage systems because of their high energy density, cost-effectiveness and environmental friendliness. However, the limited voltage window, poor reaction kinetics and structural instability of cathode materials are current bottlenecks which contain the further development of ZIBs. In this work, we rationally design a Ni-doped V2O5@3D Ni core/shell composite on a carbon cloth electrode (Ni-V2O5@3D Ni@CC) by growing Ni-V2O5 on free-standing 3D Ni metal nanonets for high-voltage and high-capacity ZIBs. Impressively, embedded Ni doping increases the interlayer spacing of V2O5, extending the working voltage and improving the zinc-ion (Zn302+) reaction kinetics of the cathode materials; at the same time, the 3D structure, with its high specific surface area and superior electronic conductivity, aids in fast Zn302+ transport. Consequently, the as-designed Ni-V2O5@3D Ni@CC cathodes can operate within a wide voltage window from 0.3 to 1.8 V vs. Zn30/Zn302+ and deliver a high capacity of 270 mAh g−1 (~1050 mAh cm−3) at a high current density of 0.8 A g−1. In addition, reversible Zn2+ (de)incorporation reaction mechanisms in the Ni-V2O5@3D Ni@CC cathodes are investigated through multiple characterization methods (SEM, TEM, XRD, XPS, etc.). As a result, we achieved significant progress toward practical applications of ZIBs. [ABSTRACT FROM AUTHOR]

Nickel-rich cathode LiNi0.83Co0.11Mn0.06O2 (NCM) has a high specific discharge capacity and low cost, and is a very promising cathode material. However, NCM exhibits poor structural and chemical stability, resulting in poor cycle stability. Surface coating can maintain structural stability, isolate cathode materials and electrolytes, and effectively improve the cycle stability of NCM. The mixed ion–electron conductor Li7.3La3Zr1.7Co0.3O12 (LZC) was coated on the surface of NCM using an anhydrous co-precipitation method, with a coating thickness of 2% (molar ratio), which promotes the conduction of electrons and ions. The coated positive electrode material was prepared into a liquid electrolyte half battery. After 200 cycles at 1 C between 2.8 and 4.5 V, the capacity retention of NCM is only 62.2%, while the capacity retention of the most excellent coating sample increased to 79.2%. [ABSTRACT FROM AUTHOR]

The present investigation involves two synthesis methods, autocombustion (Co3O4-AC) and sol–gel (Co3O4-SG), for producing nearly spherical-shaped and polygonal shaped nanomaterials of spinel cobalt oxide (Co3O4) respectively as electrode materials. TEM image analysis unveiled distinct particle morphologies for the two samples. The Co3O4-AC particles exhibited a nearly spherical shape, whereas the Co3O4-SG particles displayed a polygonal shape. The phase purity of the Co3O4 samples were confirmed via XRD patterns analysis and the crystallite size was calculated to be 44 nm for Co3O4-AC and 36 nm for Co3O4-SG. The surface area, estimated via BET experiments, of Co3O4-AC was found to be 15 m2/g, while Co3O4-SG exhibited a slightly lower surface area of 11 m2/g. Co3O4-AC exhibited a higher specific capacitance (Cs) of 162 F/g at 0.25 A/g, indicating its superior energy storage capability. On the other hand, Co3O4-SG shows a Cs of 98 F/g, indicating slightly lower performance compared to Co3O4-AC. Both nanomaterials exhibited better stability, with more than 85% capacity retention after 5000 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Cobalt‐free ultrahigh‐nickel layered oxide cathodes hold great promise for reducing the cost and enhancing the energy density of Li‐ion batteries. However, the increasing Ni content and the elimination of Co could cause severe interfacial and structural degradation, leading to poor electrochemical performance of ultrahigh‐nickel layered oxide cathodes. Here, a Co‐free oxide, LiNi0.96Al0.03Ca0.01O2 (NAC), where Ca acts as pillar ions at the surface and Al works as an oxygen stabilizer across the bulk, is presented. An epitaxial layer rich in segregated Ca can effectively inhibit adverse surface reconstruction at high states of charge, together with the oxygen stabilization of bulk phase by doping Al, significantly reinforcing the structural rigidity of the layered oxide during cycling. The fabricated NAC cathode material exhibits exceptional electrochemical performance in terms of high cycling stability with 93% capacity retention over 500 cycles and a material‐level energy density of ~800 Wh kg−1. This study provides an efficient and feasible strategy to design and stabilize ultrahigh‐nickel oxides for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Sodium–potassium (NaK) liquid alloy is a promising candidate for use as an anode material in sodium batteries because of its fluidity, which effectively suppresses the growth of sodium or potassium dendrites. However, the poor wettability of NaK alloy on conventional metal substrates is unfavorable for cell fabrication due to its strong surface tension. In this paper, low-density and low-cost fluorinated aluminum foam is used as a substrate support material for NaK liquid alloy. By combining low-surface-tension NaKC with fluorinated aluminum foam, we obtain a uniformly distributed and structurally stable electrode material. The composite electrode has a cycling stability of more than 3000 h in a symmetrical cell. Furthermore, when coupled with a sulfurized polyacrylonitrile cathode in carbonate electrolyte, it maintains excellent stability even after 800 cycles, with 72% of capacity retention. [ABSTRACT FROM AUTHOR]

A composite material of alginate and CaCl2 was tested in a laboratory reactor (1 L) for its ability to thermochemically store heat. The material was exposed to air at 25 °C and 25% RH to prevent the salt from dissolving, and the heat evolution was observed over a period of 15 cycles. To evaluate the changes in the material, samples were taken after 5, 10 and 15 cycles and the material properties and calorimetric characteristics were examined. A change of the material in favor of the heat release was determined, so that an increase of the heat storage capacity from 1.28 kJ∙cm−3 to 2.11 kJ∙cm−3 was detected, with a simultaneous steep decrease of the pore volume in the range from 0.01 to 10 μm. The temperature lift of the reactor showed a significant increase, with the first cycle showing the smallest amount. [ABSTRACT FROM AUTHOR]

[Display omitted] Lithium metal batteries have garnered significant attention as a promising energy storage technology, offering high energy density and potential applications across various industries. However, the formation of lithium dendrites during battery cycling poses a considerable challenge, leading to performance degradation and safety hazards. This study aims to address this issue by investigating the effectiveness of a protective layer on the lithium metal surface in inhibiting dendrite growth. The hypothesis is that continuous lithium consumption during battery cycling is a primary contributor to dendrite formation. To test this hypothesis, a protective layer of Li 3 Bi/Li 2 O was applied to the lithium foil through immersion in a BiN 3 O 9 solution. Experimental techniques including kelvin probe force microscopy (KPFM) and density functional theory (DFT) calculations were employed to analyze the structural and electronic properties of the Li 3 Bi/Li 2 O layer. The findings demonstrate successful doping of Bi into the Li coating, forming Bi-Bi and Bi-O bonds. KPFM measurements reveal a higher work function of Li 3 Bi/Li 2 O, indicating its potential as an effective protective layer. DFT calculations further support this observation by revealing a greater adsorption energy of lithium on the Li 3 Bi/Li 2 O layer compared to the bulk material. Charge density analysis suggests that the adsorption of Li atoms onto the Li 3 Bi/Li 2 O layer induces a redistribution of charge, resulting in increased electron availability on the surface and preventing electrode–electrolyte contact. This study provides insights into the role of the Li 3 Bi/Li 2 O protective layer in inhibiting dendrite growth in lithium metal batteries. By mitigating dendrite formation, the protective layer holds promise for enhancing battery performance and longevity. These findings contribute to the development of strategies for improving the stability and reliability of lithium metal batteries, facilitating their wider adoption in energy storage applications. [ABSTRACT FROM AUTHOR]

Hydrogen has enormous commercial potential as a secondary energy source because of its high calorific value, clean combustion byproducts, and multiple production methods. Electrocatalytic water splitting is a viable alternative to the conventional methane steam reforming technique, as it operates under mild conditions, produces high‐quality hydrogen, and has a sustainable production process that requires less energy. Electrocatalysts composed of precious metals like Pt, Au, Ru, and Ag are commonly used in the investigation of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Nevertheless, their limited availability and expensive cost restrict practical use. In contrast, electrocatalysts that do not contain precious metals are readily available, cost‐effective, environmentally friendly, and possess electrocatalytic performance equal to that of noble metals. However, considerable research effort must be devoted to create cost‐effective and high‐performing catalysts. This article provides a comprehensive examination of the reaction mechanism involved in electrocatalytic water splitting in both acidic and basic environments. Additionally, recent breakthroughs in catalysts for both the hydrogen evolution and oxygen evolution reactions are also discussed. The structure‐activity relationship of the catalyst was deep‐going discussed, together with the prospects of current obstacles and potential for electrocatalytic water splitting, aiming at provide valuable perspectives for the advancement of economical and efficient electrocatalysts on an industrial scale. [ABSTRACT FROM AUTHOR]

A composite material of alginate and CaCl2 was tested in a laboratory reactor (1 L) for its ability to thermochemically store heat. The material was exposed to air at 25 °C and 25% RH to prevent the salt from dissolving, and the heat evolution was observed over a period of 15 cycles. To evaluate the changes in the material, samples were taken after 5, 10 and 15 cycles and the material properties and calorimetric characteristics were examined. A change of the material in favor of the heat release was determined, so that an increase of the heat storage capacity from 1.28 kJ∙cm−3 to 2.11 kJ∙cm−3 was detected, with a simultaneous steep decrease of the pore volume in the range from 0.01 to 10 μm. The temperature lift of the reactor showed a significant increase, with the first cycle showing the smallest amount.

Medium-nickel cobalt-free cathode materials have attracted much attention in recent years for their low cost and high energy density. However, the structural stability of nickel-based cathode materials becomes compromised when accompanied by the increasing of voltage, leading to poor cycling performance and, thus, hindering their widespread industrial application. In this work, we investigated the optimal charge cut-off voltage for the nickel-based cathode material LiNi0.6Mn0.4O2 (NM64). Within the voltage range of 3.0 to 4.5 V, the electrode energy density reached 784.08 Wh/kg, with an initial Coulombic efficiency of 84.49%. The reversible specific capacity at 0.1 C reached 197.84 mAh/g, and it still maintained a high reversible specific capacity of nearly 150 mAh/g, with a capacity retention rate of 86% after 150 cycles at 1 C. Furthermore, NM64 exhibited an intact morphological structure without noticeable cracking after 150 cycles, indicating excellent structural stability. This study emphasizes the relationship between the stability of NM64 cathodes and different operating voltage ranges, thereby promoting the development of high-voltage layered nickel-based cathode materials.

Supercapacitors are prospective energy storage devices for electronic devices due to their high power density, rapid charging and discharging, and extended cycle life. Materials with limited conductivity could have low charge-transfer ions, low rate capability, and low cycle stability, resulting in poor electrochemical performance. Enhancement of the device’s functionality can be achieved by controlling and designing the electrode materials. Graphene oxide (GO) has emerged as a promising material for the fabrication of supercapacitor devices on account of its remarkable physiochemical characteristics. The mechanical strength, surface area, and conductivity of GO are all quite excellent. These characteristics make it a promising material for use as electrodes, as they allow for the rapid storage and release of charges. To enhance the overall electrochemical performance, including conductivity, specific capacitance (Cs), cyclic stability, and capacitance retention, researchers concentrated their efforts on composite materials containing GO. Therefore, this review discusses the structural, morphological, and surface area characteristics of GO in composites with metal oxides, metal sulfides, metal chalcogenides, layered double hydroxides, metal–organic frameworks, and MXene for supercapacitor application. Furthermore, the organic and bacterial functionalization of GO is discussed. The electrochemical properties of GO and its composite structures are discussed according to the performance of three- and two-electrode systems. Finally, this review compares the performance of several composite types of GO to identify which is ideal. The development of these composite devices holds potential for use in energy storage applications. Because GO-modified materials embrace both electric double-layer capacitive and pseudocapacitive mechanisms, they often perform better than pristine by offering increased surface area, conductivity, and high rate capability. Additionally, the density functional theory (DFT) of GO-based electrode materials with geometrical structures and their characteristics for supercapacitors are addressed.

Rapid development of electronic technology put forward high requirements for sustainable energy storage systems, and fiber supercapacitors have been considered as one of the prospective research fields. Herein, five metal oxides of Al2O3, Fe2O3, MoO2, NiO and ZnO are chosen as electrochemical active materials to prepare fiber electrodes as well as parallel fiber supercapacitors, respectively. According to the test results, ZnO fiber supercapacitor exhibits the optimal electrochemical performance among them, achieving 1.19 μF·cm−1 at the current density of 0.25 μA·cm−1. In addition, the electrochemical performance of parallel and twisted ZnO fiber supercapacitors are compared systematically so as to illustrate the effect of device structures on their electrochemical performance, and the twisted ZnO fiber supercapacitor shows higher capacitance retention and energy density than the parallel fiber device. Furthermore, the electrochemical cycling stability of parallel as well as twisted ZnO fiber supercapacitors are studied after 10,000 galvanostatic charge–discharge cycles, and parallel ZnO fiber supercapacitor presents better cycle stability owing to the simpler device structure. This work would provide effective evidence for the design and development of high-performance metal oxide-based fiber supercapacitors in the future.

Rapidly increasing demand for energy density in consumer electronics is eager for developing high‐voltage LiCoO2 (LCO). However, some great challenges such as severe phase transition and surface instability negate the cycle life of LCO operated at high‐voltages (≥4.6 V). Herein, a chemical reconstruction strategy is proposed to form a collective surface of LCO through an interdiffusion reaction of MgHPO4·3H2O (MP) so as to extend the cycle life of high‐voltage LCO. The collective surface renders a three‐layer configuration that demonstrates an amorphous Li3PO4 outmost layer, a spinel‐like layer beneath, and a Mg diffusion layer within LCO bulk. MP with relatively low hardness enables the uniform precoating via mechanical mixing, followed by a sintering process to undergo an interdiffusion reaction. Li3PO4 is an intrinsic electrochemical stabilizer against interfacial side reactions. The spinel‐like compounds build a high‐voltage‐stable surface against irreversible O2 release. In addition, Mg diffuses into the bulk lattice to suppress irreversible phase transition during the deep delithiation of LCO. Therefore, such modified LCO with a collective surface exhibits ultralong life with capacity retention of 82% after 1000 cycles at 1 C within 3.0–4.6 V and stable operating at 4.7 V or elevated temperature (45 °C). [ABSTRACT FROM AUTHOR]

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NaCrO2 is a promising cathode for Na-ion batteries. However, further studies of the mechanisms controlling its specific capacities and cycle stability are needed for real-world applications in the future. This study reveals, for the first time, that the typical specific capacity of ~110 mAh/g reported by many researchers when the charge/discharge voltage window is set between 2.0 and 3.6 V vs. Na/Na+ is actually controlled by the low electronic conductivity at the electrode/electrolyte interface. Through wet solution mixing of NaCrO2 particles with carbon precursors, uniform carbon coating can be formed on the surface of NaCrO2 particles, leading to unprecedented specific capacities at 140 mAh/g, which is the highest specific capacity ever reported in the literature with the lower and upper cutoff voltages at the aforementioned values. However, such carbon-coated NaCrO2 with ultrahigh specific capacity does not improve cycle stability because with the specific capacity at 140 mAh/g the Na deintercalation during charge is more than 50% Na ions per formula unit of NaCrO2 which leads to irreversible redox reactions. The insights from this study provide a future direction to enhance the long-term cycle stability of NaCrO2 through integrating carbon coating and doping. [ABSTRACT FROM AUTHOR]

In this paper, [Ni0.9Co0.1](OH)2 precursor is used to dope H3BO3 to synthesize positive electrode material when mixing lithium in wet method, and to explore the best doping by testing the microscopic morphology and electrochemical performance of the positive electrode material amount and calcination temperature. After doping with B, the microstructure of the material is improved, and the primary crystal grains are oriented and agglomerated into a needle shape. This good crystal structure can slow down the generation of grain microcracks and mechanical fracture, and improve the cycle stability of the positive electrode material. After doping B, the discharge specific capacity was slightly improved. When the calcination temperature is 750 °C and the doping amount of B is 1.0 mol%, the first discharge specific capacity reaches 223 mAh g−1. More importantly, the capacity retention rate of the battery after 100 cycles has been greatly improved, from 74 % without doping B to 87 %. [ABSTRACT FROM AUTHOR]

Aiming to elucidate the hydrogen absorption/desorption cycling properties of Mg-based alloys with in-situ formed Mg2Ni and LaHx (x = 2, 3) nanocrystallines, the hydrogen storage cycle stability, hydriding/dehydriding cycling kinetics and thermodynamic stability of the experimental alloys have been investigated in detail. The results show that the Mg-Ni-La alloys exhibit improved hydrogen storage cycling properties and can remain storage hydrogen above 5.5 wt% after 200 cycles. With the increase of cycling numbers, the dehydrogenation rates of the experimental samples increase firstly and then gradually decrease, and eventually maintain relative stable state. Microstructure observation reveals that powders sintering and hydrogen decrepitation both exist during hydrogen absorption/desorption cycles due to repeated volume expansion and contraction. Meanwhile, the in-situ formed LaHx (x = 2, 3) and Mg2Ni nanocrystallines stabilize the microstructures of the particles and hinder the powders sintering. After 200 cycles, the average particle size of the experimental samples decreases and the specific surface area apparently increases, which leads to the decomposition temperatures of MgH2 and Mg2NiH4 slightly shift to lower temperatures. Moreover, Mg2Ni and LaHx (x = 2, 3) have been proven to be stable catalysts during long-term cycling, which can still uniformly distribute within the powders after 200 cycles.