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Transition metal phosphides, especially bimetallic phosphides, are promising noble-metal-free electrocatalysts for hydrogen evolution reaction (HER). However, their inferior charge transfer ability constrains further performance improvement. In this work, a facile strategy is reported to fabricate Co

In this work, nitrogen and fluorine co-doped porous carbon nanosheets (NFPCNS) were fabricated from pharmaceutical drug residues derived from the fermentation synthesis of lincomycin hydrochloride via high-temperature pyrolysis and subsequent KOH activation without adding any nitrogen and fluorine reagents. The obtained NFPCNS exhibits an optimized integration of three dimensional interconnected nanosheet structure, large specific surface area of 2912 m

Hypothesis One prevailing method to construct excellent temperature tolerance/long-lasting moisture hydrogels is to couple the original hydrogel networks with freezing-tolerant/moisture retaining agents, including ionic liquids, inorganic salts, zwitterionic osmolytes, and polyhydric alcohols. Among them, organohydrogels have shed new light on the development of ionic skins with long-term usability and stable sensing performance at subzero temperatures due to their long-lasting water retention and anti-freezing capability. Experiments We report a dual network organohydrogel by doping conductive ZnSO4 into the double network hydrogel of polyvinyl alcohol-polyacrylamide (PVA-PAM) with subsequent immersing in a mixed solvent of ethylene glycol (EG) and H2O. The anti-freezing and moisture retaining abilities of the PVA/PAM/Zn/EG (PPZE) organohydrogel were studied and the sensing performances of the PPZE organohydrogel-based ionic skin were investigated. Findings The organohydrogel exhibits a high conductivity (0.44 S m−1), excellent fatigue resistance and exceptional moisture retaining ability with more than 99.3% of the initial weight retention after 31 days storage at ambient temperature. Importantly, the PPZE organohydrogel-based ionic skin shows an ultra-low temperature anti-freezing ability and remains flexibility and sensing capability with a high sensitivity (signal response time ∼ 0.23 s) even at -50 °C. The PPZE organohydrogel demonstrates a tremendous potential in artificial skin and health monitoring.

Metal sulfides are recognized as potential candidates for the anode materials of lithium ion batteries (LIBs) because of their high theoretical capacity. However, the low reaction kinetics of metal sulfides leads to their poor cycle life and rate performance, which limits their practical application in the field of energy storage. In this work, we synthesized a self-assembled carbon-free vanadium sulfide (V3S4) nanosheet via a facile and efficient method. The unique mesoporous nanostructure of V3S4 can not only accelerate the migration of ions/electrons, but also alleviate the volume expansion during the lithium ion insertion/extraction process. When used as the anode material of LIBs, the carbon-free V3S4 electrode exhibits remarkable electrochemical performance with ultra-high charge capacity (1099.3 mAh g-1 at 0.1 A g-1), superior rate capability (668.8 mAh g-1 at 2 A g-1 and 588.8 mAh g-1 at 5 A g-1) and impressive cycling ability (369.6 mAh g-1 after 200 cycles at 10 A g -1), which is very competitive compared with those of most metal sulfides-based anode materials reported so far. The strategy in this work provides inspiration for the rational design of advanced nanostructured electrode materials for energy storage devices.

Rational construction of hybrid materials integrating the collective virtues of individual building blocks has spurred significant interest in electrode materials for energy storage. Herein, a smart hybrid was fabricated via in-situ assembling of the few-layered MoS2 (f-MoS2) coated on the multi-layered Ti3C2 MXene decorated with the TiO2 nanoparticles by the scalable hydrothermal and annealing approaches. In the unique architecture, the multi-layered Ti3C2 with the expanded interspaces as the conductive backbone can facilitate the electron transport, provide adequate space to facilitate the infiltration of organic electrolyte into the interior of electrode, and inhibit the aggregation of MoS2 nanosheets, while the f-MoS2 with enlarged interlayer can be beneficial for the lithium-ion diffusion and prevent the multi-layered Ti3C2from restacking. Moreover, the TiO2 decorated on the Ti3C2 can effectively inhibit the instability of long-chain lithium polysulfides dissolved in organic electrolyte to improve the cycling stability. Thanks to the synergistic effect of the building blocks, the Ti3C2/TiO2@f-MoS2 hybrid employed as lithium storage anode delivers an extraordinary endurable ability with a high storage capacity of 403.1 mA h g−1 after 1200 cycles at 2 A g−1. Importantly, the smart hybridization strategy in this work paves an efficient way to explore the high-performance MXene-based hybrid materials in energy storage fields.

Transition metal sulfides, as an important class of inorganics, have been shown to be potential high-performance electrode candidates for lithium-ion batteries (LIBs) in account of their high activity towards lithium storage, rich types and diverse structures. Despite these advantages, structure degradation related with volume variations upon electrochemical cycling restricts their further development. In this present study, a unique hybrid structure with ultrafine heazlewoodite nanoparticles (less than 10 nm) in-situ confined in nitrogen and sulfur dual-doped carbon (Ni3S2@NSC) was constructed though a facile pyrolysis process, using a novel Ni-based metal chelates as the precursor. Specifically, enhanced structure stability, shortened Li+ migration distance and improved reaction dynamics can be obtained simultaneously in the designed structure, thereby allowing to realize high lithium storage performance. Consequently, a remarkable reversible capacity of 955.9 mAh g−1 (0.1 A g−1 after 100 cycles) and a superior long-term cycling stability up to 1200 cycles (863.7 mAh g−1 at 1.0 A g−1) are obtained. Importantly, the fundamental understanding on the improved lithium storage of Ni3S2@NSC based on the synergistic coupling reveals that the combination between Ni3S2 and NSC at the hetero-interface through the doped sulfur atoms contributes to the integrity of electrode and improved kinetics.

Zinc-based energy storage systems (zinc-air, zinc-nickel and zinc-ion batteries and zinc-ion hybrid supercapacitors (ZHSs) are considered as promising power sources for wide applications from personal electronic devices to electric vehicles. However, these systems, especially the Zn-based hybrid supercapacitors, display unsatisfying power density and energy density, which should be enhanced for their large-scale applications. In this work, aqueous alkaline zinc-carbon hybrid supercapacitors (A-ZCHS) were designed, consisting of B, N dual doped carbon cathode, Zn anode and KOH electrolyte. The B, N dual doped carbon was prepared via thermal treatment of metal-organic frameworks and boric acid, which exhibits abundant hierarchical pore structure (micropore, mesopore and macropore) and suitable defect construction, promoting ion diffusion/charge transfer and providing more rapid surface pseudocapacitance reaction. More obviously, when the optimized B, N dual doped carbon was used as cathode in A-ZCHS and ZHS, more capacitive charge storage and rapider electrochemical kinetics can be observed in A-ZCHS than in ZHS. Therefore, the optimized A-ZCHS displays a high energy density of 115.7 Wh kg−1 at the power density of 711.6 W kg−1 with excellent stability, which is much better than most of ZHSs reported previously. The A-ZCHS should be a promising candidate for energy storage applications.

Although widely used as hybrid capacitive deionization (HCDI) electrode material, the low intrinsic conductivity of metal hexacyanometalate (MHCF) severely hinders the fast insertion/extraction of Na

Ignited by the concept of bionics, hydrogel-based bionic skin sensors have received more and more attention and been widely used in health monitoring, robots, implantable prostheses and human-machine interfaces. However, there still remain some challenges to be urgently solved for hydrogel-based bionic skin sensors, such as the water evaporation and the defects of single conductive mechanism of electronic skin or ionic skin. Herein, we prepared a polyvinyl alcohol/polyacrylamide/CaCl

The parasitic reactions leading to capacity fading and charge loss remain a serious issue for capacitive deionization (CDI). NaTi2(PO4)3 (NTP) has recently emerged as a promising faradaic cathode in hybrid CDI (HCDI) with high Na+ uptake capacity and good Na+ selectivity, but it is still challenged by serious parasitic reactions. Although the irreversible faradaic reactions on carbon electrode are raising growing attention in CDI research field, the parasitic reactions on faradaic materials are seldom studied in HCDI by now. In this work, we evaluated the parasitic reactions of NTP-reduced graphene oxide (rGO) electrode in both three-electrode mode and full-cell HCDI mode. By using deaired electrolyte, the coulombic efficiency of NTP-rGO is significantly enhanced from 75.0% to 98.2% in 3rd cycle, and the capacity retention rate is promoted from 37.5% to 80.3% at the low current density of 0.1 mA g−1 in 100 cycles, suggesting that electrochemical reduction of oxygen and its derived reactions are the main parasitic reactions in NTP-based HCDI. In full-cell HCDI desalination tests, by introducing cation exchange membrane to block the penetration of dissolved oxygen, the parasitic reactions and pH fluctuations are successfully suppressed. The study here provides an insight into understanding and suppressing the parasitic reactions in HCDI, and should be of value to the development of efficient and stable HCDI for practical applications.

Mass loading and potential plateau are the two most important issues of potassium (K)-ion batteries (KIBs), but they have long been ignored in previous studies. Herein, we report a simple and scala...

As one of the low‐cost energy storage systems, Na‐ion batteries (NIBs) have received tremendous attention. However, the performance of current anode materials still cannot meet the requirements of NIBs. In our work, we obtain sulfur‐doped interconnected carbon microspheres (S‐CSs) via a simple hydrothermal method and subsequent sulfurizing treatment. Our S‐CSs exhibit an ultrahigh reversible capacity of 520 mAh g–1 at 100 mA g–1 after 50 cycles and an excellent rate capability of 257 mAh g–1, even at a high current density of 2 A g–1. The density functional theory calculations demonstrate that sulfur doping in carbon favors the adsorption of Na atom during the sodiation process, which is accountable for the performance enhancement. Furthermore, we also utilize operando Raman spectroscopy to analyze the electrochemical reaction of our S‐CSs, which further highlights the sulfur doping in improving Na‐ion storage performance.

Here, we introduce a new strategy using urea for the synthesis of carbon-incorporated 2D Fe3O4 (2D-Fe3O4/C) nanoflakes under solvothermal conditions with the following pyrolysis process under an inert atmosphere. Thanks to the structural advantages of 2D-Fe3O4/C, including 2D flakes providing a larger accessible surface area and exposing more active sites, as well as carbon incorporation promoting electrical conductivity for faster charge transfer, the 2D-Fe3O4/C displays a high specific capacitance of 386 F g−1 at 1 A g−1 in a three-electrode system. More importantly, when further assembled into a hybrid supercapacitor with pre-synthesized NiCo-layered double hydroxides as positive electrodes, the assembled supercapacitor device delivers a high-energy density of 32.5 W h kg−1 at 400 W kg−1 and little capacitance loss with bending angles ranging from 0° to 180°. As another capacitive application in desalination, 2D-Fe3O4/C also shows a high desalination capacity of 28.5 mg g−1 over 7.5 min, which suggests a very high mean desalination rate of 3.8 mg g−1 min−1. Our results not only highlight the significance of 2D metal oxide nanosheets/nanoflakes, but also hold great potential for high-performance capacitive applications in supercapacitors and desalination.

The development of high-performance carbon-based anode materials is still a significant challenge for K-ion storage. In our work, we designed reduced graphene oxide coating carbon sub-microspheres hierarchical nanostructure (CS@RGO) hierarchical nanostructure via a simple freeze-drying and subsequent pyrolysis as anode for K-ion batteries (KIBs), which presented an excellent electrochemical performance for K-ion storage, with a reversible specific capacity of 295 mAh g

Cobalt phosphides, as low cost and abundant non-noble materials for hydrogen evolution reaction (HER), are always constrained by their inferior charge transfer and sluggish intrinsic electrocatalytic kinetics. In this work, carbon-incorporated Co/Co2P microspheres (Co/Co2P@C) as a novel Mott–Schottky catalyst were synthesized successfully via carbonization and gradual phosphorization of Co based metal-organic frameworks. The unique merits, including Mott-Schottky effect at the interface formed between metal Co and semiconductor Co2P, the incorporated carbon-layer on the surface and the spherical structure endow Co/Co2P@C with favorable electrical conductivity, preferable kinetics and long-term stability when it was evaluated as electrocatalyst for HER in wide-pH range. As a result, the Co/Co2P@C with the optimized phosphorization degree delivers a benchmark current density of 10 mA cm−2 at the low overpotential of 192 and 158 mV in acidic and alkaline electrolytes, respectively, with a remarkable stability (CV cycling for 3000 cycles and continuous electrolysis at the overpotential of 200 mV for 48 h). Therefore, the as-designed Co/Co2P@C should be one of the most promising catalysts for HER application.

Supercapacitors, also known as electrochemical capacitors, are attracting much research attention owing to their high power density, long-term cycling stability, as well as exceptional safety compared with rechargeable batteries, although the globally accepted quantitative benchmarks on the power density, cycling stability, and safety are yet to be established. However, it should be noted that the supercapacitors generally exhibit low energy density, which cannot satisfy the demands where both high energy density and power density are needed. To date, various methods have been employed to improve the electrochemical performances of supercapacitors. Among them, introducing redox additives (or redox mediators) into conventional aqueous electrolyte is regarded as one of the most promising strategies. The redox additives in aqueous electrolyte are widely demonstrated to be able to increase the charge storage capability via redox transformation and thus enhance the electrochemical performances. Herein, we present a brief review on the classification, state-of-the-art progress, challenges, and perspectives of the redox additives in aqueous electrolyte for high performance supercapacitors.

Mn-based oxides are efficient pseudocapacitive electrode materials and have been investigated for capacitive deionization (CDI). However, their poor conductivity seriously affects their desalination performance. In this work, polyaniline coated Mn

The design of high-performance electrode materials with excellent desalination ability has always been a research goal for efficient capacitive deionization (CDI). Herein, a hybrid architecture with Cu/Cu

Rocking-chair capacitive deionization (RCDI), as the next generation technique of capacitive deionization, has thrived to be one of the most promising strategies in the desalination community, yet was hindered mostly by its relatively low desalination rate and stability. Motivated by the goal of simultaneously enhancing the desalination rate and structural stability of the electrode, this paper reports an anion-driven flow-through RCDI (AFT-RCDI) system equipped with BiOCl nanostructure coated carbon sponge (BiOCl@CS for short; its backbone is derived from commercially available melamine foam with minimum capital cost) as the flow-through electrode. Owning to the rational design of the composite electrode material with minimum charge transfer resistance and ultrahigh structure stability as well as the superior flow-through cell architecture, the AFT-RCDI displays excellent desalination performance (desalination capacity up to 107.33 mg g-1; desalination rate up to 0.53 mg g-1s-1) with superior long-term stability (91.75 % desalination capacity remained after 30 cycles). This work provides a new thought of coupling anion capturing electrode with flow-through cell architecture and employing a low-cost BiOCl@CS electrode with commercially available backbone material, which could shed light on the further development of low-cost electrochemical desalination systems.

Highlights The iron selenide composite with ether-based electrolyte presents excellent potassium storage performance.We develop in situ visualization technique to monitor the potassiation–depotassiation process.Iron selenide composite in ether-based electrolyte presents a homogeneous electrochemical reaction, resulting in a stable potassium-ion storage. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00708-1., As one of the promising anode materials, iron selenide has received much attention for potassium-ion batteries (KIBs). Nevertheless, volume expansion and sluggish kinetics of iron selenide result in the poor reversibility and stability during potassiation–depotassiation process. In this work, we develop iron selenide composite matching ether-based electrolyte for KIBs, which presents a reversible specific capacity of 356 mAh g−1 at 200 mA g−1 after 75 cycles. According to the measurement of mechanical properties, it is found that iron selenide composite also exhibits robust and elastic solid electrolyte interphase layer in ether-based electrolyte, contributing to the improvement in reversibility and stability for KIBs. To further investigate the electrochemical enhancement mechanism of ether-based electrolyte in KIBs, we also utilize in situ visualization technique to monitor the potassiation–depotassiation process. For comparison, iron selenide composite matching carbonate-based electrolyte presents vast morphology change during potassiation–depotassiation process. When changing to ether-based electrolyte, a few minor morphology changes can be observed. This phenomenon indicates an occurrence of homogeneous electrochemical reaction in ether-based electrolyte, which results in a stable performance for potassium-ion (K-ion) storage. We believe that our work will provide a new perspective to visually monitor the potassium-ion storage process and guide the improvement in electrode material performance. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00708-1.

Antimony-based oxides (SbxOy) have been considered as promising candidate anode materials for lithium ion batteries (LIBs). However, the poor electrical conductivity and huge volume change of SbxOy during lithium insertion and extraction hinder its lithium-storage performance. In this work, Sb2O5/Co-containing carbon polyhedra (SCCP) were prepared through a galvanic replacement reaction accompanied by oxidation process. Sb2O5 possesses high theoretical capacity and carbon not only effectively improves the charge transport ability but also accommodates the volume change of Sb2O5 during charge/discharge process. Besides, the inner metallic Co further enhances the electrical conductivity of the composite. Furthermore, the dominated capacitive contribution of SCCP electrode can also improve its lithium-storage performance. Benefiting from the synergetic effects of these factors, when used as anode material for LIBs, SCCP demonstrates an ultrahigh specific capacity of 1009 mA h g−1 at 100 mA g−1 after 100 cycles. Even at a high current density of 1000 mA g−1, a reversible capacity of 462.8 mA h g−1 is still achieved after 700 cycles. SCCP should be a promising anode material for next generation LIBs.

Transition metal oxide electrodes, with rational structure as well as component design and combination with carbonaceous conductive support, are widely used in high-performance lithium-ion batteries (LIBs). Herein, NiMoO4 nanowires in situ decorated on reduced graphene oxide (NiMoO4/rGO) were synthesized through a facile hydrothermal and subsequent annealing method. Due to the enhanced electrical conductivity and buffering matrix provided by rGO and the synergistic effect between NiMoO4 and rGO, the resultant NiMoO4/rGO exhibits short ion transport pathways and improved diffusion kinetics. The results reveal that NiMoO4/rGO hybrid shows much improved lithium storage performances compared with pure NiMoO4 nanowires including a high specific capacity (1212.4 mAh g−1 after 100 cycles at 0.2 A g−1), high rate capability (988.6 mAh g−1 at 2 A g−1 and 928.1 mAh g−1 at 4 A g−1) and excellent cycling performance at high current density (1007.6 mAh g−1 after 1000 cycles at 1 A g−1) when applied as anode material for LIBs, outperforming most of the reported metal molybdates-based electrodes. Besides, such excellent lithium storage performance, combined with the simple hydrothermal-annealing synthesis strategy, makes the NiMoO4/rGO a promising anode material for high-performance LIBs.

Utilizing renewable and abundant biomass waste to prepare hierarchically porous carbons (HPC) materials with large surface area and good electrical conductivity have received considerable attention recently. In this work, a novel 3D HPC was prepared by a low-cost and facile hydrothermal process, carbonization, and chemical activation from Huiyuan® fruit grain orange (FGO) with expired deadline for the first time. The obtained HPC exhibits a high specific surface area of 2149 m2 g−1 and facilitated charge transfer ability offered by its hierarchical structure. When used as electrodes for supercapacitor, HPC displays a maximum specific capacitance of 452.7 F g−1 at 1 A g−1 in 1 M H2SO4, which is one of the highest values reported for biomass-derived carbons. Remarkably, the all-solid-state symmetric supercapacitor based on HPC-4 exhibits a high energy density of 14.1 Wh kg−1 at a power density of 140 W kg−1 and outstanding cycling stability (90% capacitance retention after 6000 charge/discharge cycles at 10 A g−1). HPC-4 should be a promising electrode material for all-solid-state supercapacitor application.

Wasted coffee grounds (WCGs) were activated by a pyrolysis process using KOH, where the porosity increased with temperature, exhibiting a micropore-dominant structure. WCGs upon an activation temperature of 800 °C (AWCG800) showed a surface area up to 1856 m2 g−1 and a specific capacitance of 180.3 F g−1 in 1 M NaCl solution at a scan rate of 10 mV s−1. The AWCG800 electrodes showed an electrosorption capacity up to 12.50 and 16.50 mg g−1 in NaCl solution at cell voltages of 1.2 and 1.4 V, respectively, with an initial concentration of 5 mM. X-ray photoelectron spectroscopy analysis indicated that AWCG800 maintained a high carbon content of 87 at% upon the activation process. The study suggests a practical way for converting WCGs into mesoporous and microporous carbons with large surface area and pore volume, high carbon component, and good wettability to water, which is promising for capacitive deionization application.

In this work, we developed bismuth oxychloride anchoring on graphene nanosheets (BiOCl/G) composite via a simple one-step hydrothermal process for KIBs’ anode, which delivers a high reversible specific capacity of 251 mAh g−1 at 50 mA g−1 after 50 cycles. Meanwhile, our BiOCl/G composite also exhibits a low voltage plateau during potassiation-depotassiation process, and such low voltage plateau in anode is helpful to improve the energy density of the full battery. In addition, we also provide the energy changes for migration of K-ion of our composite according to the density functional theory calculation and the result shows that the introduction of graphene in BiOCl can reduce the adsorption energy variation, which is in favor of K-ion intercalation process. In consideration of low potential plateau of our composite, we also introduce a new evaluation method, relative energy density (ER), which not only includes the specific capacity, but also combines the potential plateau of the anode materials during potassiation-depotassiation process. According to the calculation, our BiOCl/G composite obtain an ultra-high ER of 541 Wh kg−1 at 50 mA g−1 after 50 cycles with a relative energy conversion efficiency of 81%.

Faradic electrochemical deionization (EDI), as the next generation of capacitive deionization (CDI), was considered one of the most promising solutions to address the global fresh-water shortage, while rationalizing its cell architecture and developing suitable electrode material are of equal importance to the desalination performance of EDI. In this work, chloride pre-intercalated CoFe-layered double hydroxides (LDH) (CoFeCl-LDHs) were fabricated through coprecipitation and further used as Cl- capturing electrodes for rocking-chair CDI (RCDI) system. By coupling the advantages of both rational cell architecture (symmetric RCDI system with balanced ion storage) and suitable electrode material (reversible Cl- intercalation and fast charge transfer), the CoFeCl-LDH-based RCDI system exhibits an ultrahigh desalination capacity (100.2 mg g-1) and fast desalination rate (0.38 mg g-1 s-1), which outpperform those of the other LDH-based CDI systems. The outstanding desalination performance of the CoFeCl-LDH-based RCDI further demonstrates the critical importance of both electrode material and cell architecture to the EDI system, which could shed light on the future design of highly efficient EDI systems.

The parasitic reactions leading to capacity fading and charge loss remain a serious issue for capacitive deionization (CDI). NaTi

Aqueous zinc-ion batteries (ZIBs) have been considered to be potential energy storage devices because of their cost-effectiveness and environmental friendliness. However, most of the cathode materials reported in ZIBs exhibit poor electrochemical performances like capacity fading during cycling and inferior performance at high current densities, which significantly hinder the further development of ZIBs. Here, we reported a novel three-dimensional hydrated vanadium pentoxide (V2O5·nH2O)/MXene composite via a simple one-step hydrothermal method. Owing to the unique structure and high electrical conductivity of MXene, V2O5·nH2O/Ti3C2Tx MXene shows a remarkable electrochemical performance with a reversible capacity of 323 mAh g-1 at 0.1 A g-1 and exceptional rate capability (262 mAh g-1 at 1 A g-1 and 225 mAh g-1 at 2 A g-1) when used as the cathode for aqueous ZIBs. This work offers a new insight into fabricating novel vanadium oxide-based cathode material for aqueous ZIBs.

Nickel sulfide based anode materials, featuring rich types, high specific capacities and favorable conversion kinetics, have been proved to be promisingly applied in high-performance sodium-ion batteries (SIBs). Unfortunately, the poor electronic/ionic conductivity, together with the structure change induced degraded capacity upon cycling, restricts their further development. In this work, heazlewoodite nanoparticles decorated on nitrogen doped reduced graphene oxide (Ni3S2/NrGO) were fabricated via a facile combined approach with freeze-drying and subsequent in-situ sulfidation. In the obtained hybrid structure, the synergistic effect between Ni3S2 and NrGO endows the composite with highly conductive pathways, thus accelerating the charge transfer. Benefitting from the buffering matrix offered by NrGO as well as the tight combination between Ni3S2 and NrGO, this novel Ni3S2/NrGO demonstrates satisfying sodium storage performance, with a stable reversible capacity of 299.2 mAh g−1 up to 100 cycles (0.1 A g−1) and a high initial Coulombic efficiency of 76.8%. Importantly, the rational structure design and synthesis method, as well as the insights on the improved electrochemical performance reported in this work, should be helpful for the development of new-type host materials with high performance for SIBs.