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Lithium–sulfur batteries are widely considered as promising next generation energy storage devices due to their high energy density and low cost. However, the shuttle effect and sluggish kinetics of polysulfide conversion are still key challenges for practical application. Herein, we designed hierarchical nitrogen-doped carbon nanotubes/ultrathin molybdenum disulfide nanosheets in a core–shell architecture (denoted as NC@MoS2) to alleviate the shuttle effect and propel redox reaction kinetics, thereby improving the electrochemical performance of lithium–sulfur batteries. Both experimental investigations and theoretical studies reveal that MoS2 nanosheets can chemically immobilize lithium polysulfides and catalyze the conversion of polysulfides. Moreover, this unique core–shell architecture could facilitate rapid electrical transport and favorable electrolyte infiltration. We have demonstrated that the obtained S–NC@MoS2 cathodes exhibit excellent rate capability (516 mA h g−1 at 5C) and superior cycle stability (only 0.049% capacity decay per cycle up to 1000 cycles at 2C). Remarkably, the composite cathode with a high sulfur loading of 3.6 mg cm−2 still maintains high rate capability and stable cycling performance over 300 cycles. This work offers a new strategy to develop high-performance lithium–sulfur batteries through the exploration of two-dimensional mediator catalysts.

Lithium metal is strongly recognized as a promising anode material for next-generation high-energy-density systems. However, unstable solid electrolyte interphase and uncontrolled lithium dendrites growth induce severe capacity decay and short cycle life accompanied by high security risks. Here, we propose a simple method for constructing an artificial solid electrolyte interphase layer on the surface of lithium metal through spontaneous reaction, where ammonium persulfate and lithium nitrate are exploited as oxidants. The satisfactory artificial protective layer with uniform and dense morphology is composed of mixed lithium compounds, mainly including Li xSO y and Li xNO y species, which could effectively stabilize the interphase between electrolyte and lithium metal anode and restrain the "shuttle effect" of polysulfides. By employing the premodified lithium metal as anodes for lithium-sulfur batteries, the resulting cells exhibit excellent cycle stability (capacity decay of 0.09% per cycle over 300 cycles at 1 C and Coulombic efficiency of over 98%) and outstanding rate capability (850.8 mAh g-1 even at 4 C). Hence, introducing a stable artificial protective layer to protect lithium anode delivers a new strategy for solving the issues related to lithium-metal batteries.

It is a huge challenge to design and develope a highly active and stable non-noble metal electrocatalyst for hydrogen evolution reaction (HER) in alkaline solution. Increasing the active sites and improving conductivity of catalysts are the effective ways to enhance the catalytic performance. Here, nanoparticle-stacked porous NiCoO2@C microflakes arrays grown on Ni foam (NiCoO2@C-NF) was synthesized through a simple high temperature heat treatment reaction of the corresponding NiCo2O4-NF. The nanoparticle-stacked porous microflakes arrays provide a large amount of exposed active sites. Thus, NiCoO2@C-NF with 0.072 g of glucose used for their preparation exhibits remarkable performance with −10 and −100 mA cm−2 for HER at overpotentials of −128 and −184 mV in 1.0 M NaOH solution, respectively. It is much better than that of NiCo2O4-NF (a η10 of −221 mV and η100 of −379 mV).

Ni-based compounds are being explored as an alternative for Pt in hydrogen evolution reactions. In this work, phenylhydrazine-4-sulfonic acid is utilized in the reduction of graphene oxide to synthesize novel hydrophilic graphene, and electrodeposition is used to synthesize Ni–HG/NF composite cathodes from a nickel sulphamate bath containing suspended-sized hydrophilic graphene. The Ni–HG0.5/NF composite coatings reveal prominent activity on the hydrogen evolution reaction in alkaline solutions with a high exchange current density of 5.012 mA cm–2, a low Tafel slope of 81 mV dec–1, and small overpotentials of 30 and 140 mV to obtain current densities of 10 and 100 mA cm–2. These results are attributed to hydrophilic reform of hydrophilic graphene, enhanced charge transfer between Ni and hydrophilic graphene, and the strong intensity of Ni(111) of Ni–HG0.5/NF catalyst.

La2O3-coated LiNi1/3Mn1/3Co1/3O2 has been successfully synthesized via a wet chemical process followed. The 3 wt% La2O3-coated LiNi1/3Mn1/3Co1/3O2 illustrated highest rate capability, lowest voltage decay, outstanding cycling performance, and excellent energy density at the range of 2.5–4.5 V. The discharge capacity of LiNi1/3Mn1/3Co1/3O2 at a 5C rate increases from 86.9 to 137.5 mA h g−1 upon coating with La2O3 particles. The decrements of the average discharge voltages for 3 wt% La2O3-coated LiNi1/3Mn1/3Co1/3O2 electrode is 10.3 mV over 100th cycle and 26.9 mV over 200th cycle compared to 407 mV over 100th cycle for bare nickel cobalt manganese. The energy densities retention of 3 wt% La2O3-coated LiNi1/3Mn1/3Co1/3O2 is 96.5% after 100 cycles and 89.7% after 200 cycles compared to 34.5% after 100 cycles for bare LiNi1/3Mn1/3Co1/3O2. Universal but efficient, it can also be suitable to coat other layered cathode materials to ameliorate their electrochemical properties.

MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g−1 at 100 and 1000 mA g−1, respectively. The capacity is 792.2 mAh g−1 after long cycle at a current density of 1000 mA g−1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.

A highly cross-linked three-dimensional (3D) hierarchical porous NiCo2O4 nanosheet@MnO2 nanosheet arrays (NNAs) on Ni foam is fabricated by a facile and stepwise hydrothermal approach. The NiCo2O4@MnO2 hybrid electrode demonstrates excellent electrochemical properties with high area capacitance of 5.3 F cm-2 at 1 mA cm−2, tremendous rate performance (68.9% with current density increased to 20 mA cm−2), and outstanding cycling stability (90.1% capacitance retention over 5000 cycles at 20 mA cm−2). The intriguing performance is related to unique cross-linked porous heterostructure with open geometry that provides large surface areas and superb channels for the electrolyte penetration and ion diffusion. Besides, by analyzing non-faradaic capacitive current upon repeated potential cycling, this honor attributes to not only sufficient Faraday reactions, but also a worthy electrochemical double-layer capacitance (EDLC) contribution with an electrochemical surface area (ESA) value of 616 mF cm−2 (220 F g−1 with a mass loading of 2.8 mg cm−2), which approximates to that of porous carbon.

It is highly desirable to improve the high voltage stabilities of cathode materials for Li-ion battery materials since it can deliver a higher reversible capacity at high cutoff voltage. Herein, we propose a novel facile strategy to generate La2O3-modified LiNi1/3Co1/3Mn1/3O2 with superior electrochemical performance in the voltage range of 2.5–4.5 V via a solid-state method. It can be observed that La2O3-modified LiNi1/3Co1/3Mn1/3O2 can greatly enhance the electrochemical performance due to the synergistic effect of ion doping and surface-modifying. La ions doping can alleviate the Li+/Ni2+ mixing, and substantially enhance the structure stability of LiNi1/3Co1/3Mn1/3O2 during charge/discharge cycles at high cutoff voltage. LaNi0.4Co0.6O3/LaMnO3.26 spreading on the surface layer is very useful in improving the diffusion of Li+ and inhibiting the particles from reacting with the electrolyte, enhancing the high voltage stabilities of the interface between electrode and electrolyte. The capacity retention of 0.7% (molar fraction) La2O3-modified LiNi1/3Co1/3Mn1/3O2 is 79.0% after 300 cycles compared to 61.7% for bare LiNi1/3Co1/3Mn1/3O2. And its discharge capacity at 10 C is 141.7 mAh g−1 in the voltage range of 2.5–4.5 V, which is higher than those of other samples. This work not only offers a facile novel strategy to achieve superior electrochemical performances of cathode materials but also presents some new insights into the stabilization mechanism of modified cathode materials during charge/discharge cycles or long-term storage at high cutoff voltage.

A novel 3 dimensional (3D) heterostructure that is composed of exfoliated Ni-Al layered double hydroxide nanosheet and reduced graphene oxide (Ni-Al LDH/rGO) is synthesized by adopting a simple and feasible solution-phase technique. The unique hierarchical heterostructure has a stable layered structure, more active sites and fast electron transport channels, which play an important role for improving the cycle stability and rate capacity performance. The prepared Ni-Al LDH/rGO electrode exhibits excellent performance with a capacitance of 629.8 C g−1 at 1 A g−1, and a high specific capacitance of 471.6 C g−1 even at a high current density of 20 A g−1. The asymmetric supercapacitor (ASC) fabricated by using the Ni-Al LDH/rGO as the positive electrode and using active carbon (AC) as the negative electrode, which exhibits a high energy density of 58.6 Wh kg−1 at the power density of 359 W kg−1 and remains good cycle stability. The superior electrochemical properties are due to the 3D heterostructure, where the large specific surface area of rGO nanosheets serve as a conductive 2D backbone successfully offset structure limitation by the potential synergistic effect. The exfoliated ultrathin Ni-Al LDH nanosheets with only a few atomic layers in this architecture are expected to provide large reactive active sites for fast charge transfer. Therefore, the unique 3D heterostructure is favorable for stabilizing crystal structure and enhancing capability and cycling stability for pseudocapacitors during the charge−discharge process.

Two-dimensional layered sulfide (MoS2, VS2, WS2) has aroused intense scholarly interest, and its fascinating chemical properties and physical structure provide the possibility of further triggering the catalytic activity of the Ni. In this paper, we chose Ni and MoS2, which are both commonly used in electrocatalytic water splitting, to prepare the hybrid and then used it as a template to study the origin activity. With the method of experimental and theoretical reciprocal verification, it was discovered that the strong binding energy of Ni to MoS2 enables Ni to grow flat along the MoS2 surface to facilitate the Ni particles refinement and dispersion. Besides, the weakening of Ni H bond demonstrated the subsequent recombination and release process of H in Ni-MoS2 catalyst is relatively easy. We hope this study may be extended to other two-dimensional transitional metal dichalcogenides based interface engineering to filtrate logical HER catalysts in alkaline media, and stimulate the rational design of the Ni-based materials as well as other transition metal catalysts.

The industrialization of fuel cells is coming. Non-noble metals with carbonaceous coatings, as cathodic catalysts for fuel cells, expected to replace platinum for catalyzing the oxygen reduction reaction (ORR), have attracted the attention of researchers. This is mainly due to the low price, easy availability, high stability, and gratifying catalytic activity of these materials. However, the high density and uniform dispersion of coated particles still face a challenge. In view of this, we prepared Fe3C/Fe@G catalysts with a structure of nitrogen-doped multilayer graphene uniformly coated on iron and iron carbide (Fe3C/Fe) in a very simple way. The half wave potential of Fe3C/Fe@G-800 is comparable to that of commercial Pt/C, and it also highlights the excellent stability that is a benefit of the complete coating of graphene layers to internal particles; highly dispersed Fe3C/Fe nanoparticles with small size in the graphene layer; the equilibrium degree of graphitization and the defect density.

Phosphorus-doped three-dimensional hierarchical porous carbons (P-3DHPCs) have been synthesized by direct pyrolysis of mixture containing glucose, manganese nitrate and sodium hypophosphite without any hard templates. Glucose and sodium hypophosphite are used as carbon and phosphorus source in the facile template-free strategy, respectively. The P-3DHPCs not only possess favorable hierarchical pore structure which is beneficial to ion adsorption and transportation, but also acquire effective heteroatoms doping, further improving the capacitive performance. More importantly, the amount of sodium hypophosphite plays a critical role in textural properties and phosphorus content of P-3DHPCs. The results demonstrate that P-3DHPC-0.2 shows the best electrochemical performance compared to the other samples. High specific capacitance (367 F g −1 at 0.3 A g −1 ) is obtained in 6 M KOH, and the capacitance still maintains 319 F g −1 when tested at 20 A g −1 (ca.88% capacitance retention). Moreover, the P-3DHPC-0.2 also possesses good cycling stability with only a loss of 3.5% after 10000 cycles at 3 A g −1 . The facile preparation method and good electrochemical performance render P-3DHPCs to be a promising candidate for supercapacitor application.

Orthorhombic vanadium pentoxide (V2O5) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process. The effect of disodium citrate dosage on the crystallinity, morphology and electrochemical properties of the products was analyzed. Experimental results indicate that orthorhombic V2O5 nanowires with high crystallinity and diameter of about 20 nm can be obtained at 180 °C for 24 h when the dosage of disodium citrate is 0.236 g. Furthermore, the prepared V2O5 nanowires demonstrate a high specific capacitance of 528.2 F g−1 at 0.5 A g−1 and capacitance retention of 85% after 1000 galvanostatic charge/discharge cycles at 1 A g−1 when used as supercapacitors electrode in 0.5 M K2SO4.

The synthesis of nickel cobalt sulfide is well-established because of its good electrical conductivity and great structural flexibility with low cost. It is extremely challenging to fabricate a unique structure with high tap density to improve its volumetric energy density and practical application. Here, we report a simple one-step hydrothermal method to synthesize micron-sized Ni–Co mixed sulfide solid spheres (1–2 μm in diameter). Because of the high tap density of more than 1.0 g cm–3 and the unique structure, the Ni–Co mixed sulfides demonstrate exceptional energy-storage performance. When acting as an electrode material for supercapacitors, these Ni–Co solid spheres can deliver a specific capacitance of 1492 F g–1 at a current density of 1.0 A g–1, and a retention of 76% at 10 A g–1 after 10 000 cycles. An asymmetric supercapacitor based on these solid spheres exhibits a high energy density of 48.4 W h kg–1 at a power density of 371.2 W kg–1 with excellent long-term cycling performance (91% retentio...

The development of cost-effective and high-efficiency electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) still remains highly challenging. Exposing as many active sites as possible is the key method to improve activity of HER and OER performance. In this communication, we demonstrate a novel 3D hierarchical network NiCo 2 S 4 nanoflake grown on Ni foam (NiCo 2 S 4 -NF) as a highly efficient and stable electrochemical catalyst. The NiCo 2 S 4 -NF exhibits overpotentials as low as 289 and 409 mV at 100 mA cm −2 , superior long-term durability during a 20 h measurement, and a low Tafel slope of 89 and 91 mV dec −1 for HER and OER in 1.0 M NaOH solution. The outstanding performance is owe to the inherent activity of ultrathin NiCo 2 S 4 nanoflakes and the special structure of NiCo 2 S 4 -NF that can provide a huge number of exposed active sites, accelerate the transfer of electrons, and facilitate the diffusion of electrolyte simultaneously.

In this work, preparing three nickel-based carbon composite catalysts (Ni-OCNT, Ni-ONC and Ni-rGO) by supergravity field electrodeposition for hydrogen evolution reaction (HER) from nickel sulfamate bath containing suspended nano-sized carbon materials. The crystal structure, morphology and chemical compositions of the composite catalysts were characterized by XRD and SEM measurements. The electrochemical activity of composite coatings for HER was determined by polarization measurement and electrochemical impedance spectroscopy in 1.0 M NaOH solution. The prepared nickel-based carbon composite catalysts exhibit a significant enhancement in electrocatalytic activity for HER compared with pure Ni electrode. In addition, the Ni-rGO, Ni-ONC, Ni-OCNT catalysts prepared under supergravity field demand overpotentials of 245, 177, 91 mV and 286, 224, 154 mV and 330, 286, 222 mV to drive current densities of 80, 30, 10 mA cm−2, respectively. Ni-rGO cathode presents excellent HER activity with lowest overpotentials.

We report a novel and simple approach to synthesis highly efficient and stable electrochemical catalyst of Ni-(MoS 2 /GO) composite coatings by electrodeposition from aqueous solution with the nickel sulphamate precursor. Depositing under supergravity fields has been applied to scatter more MoS 2 /GO hybrids in the coatings and decrease the size of nickel particles as far as possible and increase large amount of exposed active sites. In 1.0 M NaOH solution, Ni-(MoS 2 /GO) only needs overpotentials as low as −33 mV and −132 mV at a current density of −10 mA cm −2 and −100 mA cm −2 , respectively. The behavior of Ni-(MoS 2 /GO) exceeds most of the same reported HER catalysts in previously literature. In addition, we also synthesized Ni-MoS 2 , Ni-GO and pure Ni catalysts use the same method. The results show that Ni-(MoS 2 /GO) exhibited better HER activity at a current density of −100 mA cm −2 than these catalysts. In the future research field of HER catalysis materials, the development of this material may be not limited to nickel based materials, also will be used in Fe, Co and other non noble metal based materials, outlining a general approach for the synthesis of nanostructured M-(MoS 2 /GO) as a class of new catalyst with efficient HER activity.

Exploiting high-efficiency catalysts toward hydrogen evolution reaction (HER) is a significant assignment nowadays. We find a quick and straightforward means to produce large-scale g-C3N4, which does not use template and easily obtains uniform nanostructures. And, we fabricate one-step preparation of a non-noble-metal catalyst, consisting of carbon material and transition metal only, by coupling graphitic carbon nitride (g-C3N4) with Ni. The results show that Ni/C3N4 composite catalyst possesses coral-like structure and its unique morphology is in favor of electrochemical activity for HER. Simultaneously, the Ni/C3N4 composite catalyst presented prominent activity on HER with a high exchange current density of 1.91 × 10–4 A cm–2, a low Tafel slope of 128 mV dec–1 and small overpotentials of 356 and 222 mV to reach current densities of 100 and 10 mA cm–2, which are superior to those of the state-of-the-art HER-active Ni-based compositions, as well as majority other metal-free catalysts, and even rivaled th...

This work report the synthesis of porous carbon with hierarchical pore structure and uniform nitrogen-sulfur-oxygen doping. The favorable pore structure (micro-, meso-, and macro-pores) is beneficial to ion adsorption and transportation, and the doping heteroatoms can introduce electrochemical active sites which contribute to additional pseudocapacitance. Therefore, the carbon material shows good electrochemical performance when employed as supercapacitor electrode. High specific capacitance (367 F g−1 at 0.3 A g−1), good rate performance and stable cycling characteristics are obtained in 6 M KOH. In addition, when tested in 1 M H2SO4, a higher specific capacitance (382 F g−1 at 0.3 A g−1) is delivered. Furthermore, the assembled symmetric cell yields a maximum specific energy of 35.3 W h kg−1 in 1 M TEABF4/AN, significantly improving the specific energy of carbon-based supercapacitors.

Owing to the scarcity of platinum resources and their visible flaw with poor durability and severe anode methanol crossover, Pt-based catalysts for catalyzing ORR have been experiencing some problems lately. Hence, nonprecious metal catalysts which are expected to replace platinum-based catalysts have become popular green sustainable development topics. We chose a facile pyrolysis method for the synthesis of this material, making the resulting coating material present a state of effectively encapsulating all cobalt nanoparticles into slim nitrogen-doped carbon nanotubes after process optimization, and the cobalt content even reached 20.9 wt %. In the catalytic aspect, the optimized Co@NSCNTs show a half wave potential equivalent to Pt/C in alkaline medium. Then, better durability (after 60,000 s chronoamperometry, the current retention still remains 95%) and commendable resistance to methanol crossover performed than the literature confirmed. All these characteristics superior to Pt/C should be ascribed t...

Metal Ni is a plentiful resource that can actively split water toward hydrogen evolution reaction (HER) in alkaline solution, but exploiting high-efficiency Ni-based composite catalysts is still a significant assignment. Therefore, we design a catalytic material with one-step approach to co-electrodeposit Ni nanoparticles and reduced graphene oxide (rGO) sheets on a three-dimensional Ni foam. When the carbon content existed in Ni-rGO composite catalyst is 3.335 at%, the catalyst exhibits excellent activity on HER with a low Tafel slope (b = 77 mV dec −1 ), a high exchange current density (j 0 = 3.408 mA cm −2 ), small overpotentials of only 36, 129, and 183 mV to drive 10, 60, and 100 mA cm −2 respectively, and high stability under the different current densities. Such remarkable hydrogen evolution performance is attributed to good electrical conductivity, large specific surface area and harmonious synergistic effect between Ni particles and rGO sheets. In addition, density functional theory (DFT) calculations explain that Ni-rGO composite material presents superior interfacial activity in adsorption/desorption of H* compared with pure Ni and rGO sheet.

It remains an important project for the development of water splitting electrolyze to design and synthesis of more efficient non-noble metal catalyst. In this work, a structured Ni–MoS 2 composite coating has been synthesized under supergravity fields with nickel sulphamate bath containing suspended MoS 2 submicro-flakes. X-ray diffraction patterns indicate that the MoS 2 submicro-flakes have been successfully incorporated into the Ni matrix. Additionally, SEM shows that the prepared Ni–MoS 2 composite coatings display finer grain size than the pure Ni coatings, which can increase the electrochemistry surface area and the active site of hydrogen evolution reaction. Therefore, due to the synergistic effect of molybdenum disulfide and nickel, the Ni–MoS 2 composite coatings are directly used as binder-free electrode, which exhibits outstanding electrocatalytic activity for HER in 1.0 M NaOH solution at room temperature. The Ni–MoS 2 composite coatings demonstrated an outstanding performance toward the electrocatalytic hydrogen production with low overpotential (100 mA cm −2 at η = 207 mV), a Tafel slope as small as 65 mV dec −1 , and stable cycling performance (1200 cycles). The preeminent HER performance of this catalyst suggests that it may hold great promise for practical applications.

A lithium metal anode is regarded as the most promising anode material for the next generation of high-energy density batteries because of its high specific capacity and low reduction potential. However, dendritic deposition and severe side reactions in continuous Li plating/stripping inevitably hinder the practical application of Li metal batteries. A solid polymer electrolyte protective layer with synergistic Li3PO4/polyvinyl alcohol (PVA) features is in situ constructed on a lithium metal anode to obtain a stable interface during charge/discharge cycles. The protective layer can adapt to volume changes and inhibit lithium dendrites. The in situ reaction guaranteed the uniformity of ion transport and a tight interface between the protective layer and the lithium metal, so that the lithium deposition behavior was effectively regulated. The PP-Li anode presented a stable Li plating/stripping for 1000 h in a symmetrical cell system and exhibited an enhanced performance of the lithium titanium oxide cell. The in situ Li3PO4/PVA solid polymer electrolyte protective layer provided a promising strategy to tackle the challenges raised by the intrinsic properties of the lithium metal anode.

LaMnO3 perovskite is one of the most promising catalysts for oxygen reduction reaction (ORR) in metal-air batteries and can be compared to Pt/C. However, the low catalytic activity toward oxygen evolution reaction (OER) limits its practical application in rechargeable metal-air batteries. In this work, the MnO2/La0.7Sr0.3MnO3 hierarchical core-shell composite materials with a special interface structure have been designed via the selective dissolution method. The core of La0.7Sr0.3MnO3 particles is wrapped by the porous and loose MnO2 nanoparticles. The as-prepared MnO2/La0.7Sr0.3MnO3 materials have excellent catalytic activity toward ORR/OER and are used as bifunctional oxygen electrocatalysts for metal-air batteries. Based on results of transmission electron microscopy, X-ray photoelectron spectroscopy, valence-band spectroscopy, and O2 temperature-programmed desorption analysis, we conclude that the bifunctional catalytic activity of the MnO2/La0.7Sr0.3MnO3 materials can be effectively promoted due to the specific interface structure between the La1-xSrxMnO3 core and the MnO2 shell. This can be attributed to three aspects: (a) the electronic conductivity, which is beneficial for providing the faster charge-transfer paths and kinetics at the oxide/solution interface than that of the MnO2 sample; (b) the enhancement of oxygen adsorption capacity due to surface defects (oxygen vacancies) and chemical adsorption, which is helpful to improve the reaction kinetics during the process of oxygen catalysis; and (c) the tuning of oxygen adsorption ability via the moderate Mn-O bond strength, which may be conducive to getting for obtain an enhanced Mn-O bond strength on the surfaces for ORR and a weakened Mn-O bond in the lattice for OER.

The shuttle effect of dissolved polysulfides migrating to and depositing on anodes often leads to low round-trip efficiency and short cycle life for lithium-sulfur (Li-S) batteries. Herein, we report the rational design of cobalt-embedded nitrogen-doped hollow carbon microspheres (Co@N-HCMSs) as a multifunctional sulfur host for Li-S batteries. The hollow carbon microspheres exhibit large central cavities wrapped by a hierarchically porous shell, showing a large surface area of 1954 m2 g−1. Furthermore, the carbon shells display a unique porous architecture, in which small pores are scattered on the outside and large pores are inside, thereby functioning as a selection barrier to confine polysulfides and diffuse Li+ simultaneously. Moreover, the highly dispersed cobalt nanoparticles in the porous shell activate the surrounding N-doped carbon layer, which not only promote chemical adsorption of polysulfides but also catalyze polysulfide conversion. This facilitation effect has been confirmed by Bader charge and density function theory (DFT) calculations. When applied in Li-S batteries, the sulfur-impregnated Co@N-HCMSs cathode material exhibits excellent electrochemical performances, especially with a high sulfur content of 90.5 wt% and a high areal sulfur loading of 5.1 mg cm−2.

Nickel metal hydride (MH-Ni) batteries are widely used in hybrid electric vehicles (HEVs). Estimating a battery's state of charge (SOC) remains challenging in practical applications, and it is also the core technology. Because MH-Ni batteries exhibit high rates of self-discharge and have flat and broad charge-discharge voltage plateaus, the estimation of their SOC through their voltage, current, internal resistance, and temperature is not accurate and has a large cumulative error. In this study, a new method for estimating SOC based on battery's stable internal pressure is proposed using the one-to-one correspondence between the hydrogen equilibrium pressure and the reversible hydrogen-storage capacity described by the pressure–concentration–isotherm (P-C-T) curves of hydrogen storage alloys. The actual SOC and the stable internal pressure of the battery have a one-to-one correspondence after the battery was stored at different temperatures and SOCs, and this relationship is maintained after different cycling number and after four years of storage.

At present, a lot of attention has been paid to the reasonable design and synthesis of materials with core shell structure for high-performance supercapacitors. Herein, the Co3O4@MnO2 core shell arrays on nickel foam are successfully synthesized via a facile and effective hydrothermal method followed with annealing process. The sample was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrochemical performance of the Co3O4@MnO2 material was studied using cyclic voltammetry, charge/discharge cycling, and electrochemical impedance measurements in 6 mol L−1 KOH aqueous electrolyte. The results indicated that the Co3O4@MnO2 material presented excellent electrochemical performance in terms of specific capacitance, cyclic stability, and charge/discharge stability.

© 2017 The Royal Society of Chemistry. Ni-reduced graphene oxide (rGO) composite cathodes were successfully prepared by composite electrodeposition under supergravity fields. The synthesized composite cathodes exhibit unique hierarchical structure with large numbers of Ni nanoparticles anchoring on the rGO surface. Specifically, the sample prepared from the electrolyte containing 0.7 g L-1 GO at rotational speed 3000 rpm displays a favorable activity toward the hydrogen evolution reaction (HER) in 1 M NaOH solution with a high exchange current density of 741.3 μA cm-2 and a low Tafel slope of 120 mV dec-1. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) tests demonstrate that the superior catalytic activity should be ascribed to the enhanced active surface area and the improved intrinsic activity. Furthermore, the morphology and microstructure properties of Ni-rGO cathodes synthesized from various GO concentrations and supergravity fields are systematically investigated.

The ultrathin porous carbon shell with the thickness of about 10 nm has been fabricated by a facile method using sodium citrate as carbon precursor without any activation. The electric conductivity of the material is as high as 7.12 S/cm, which contributes to a good rate performance for supercapacitor electrode without any conductive additive. When tested in 6 M KOH by three-electrode system, the C-700 sample exhibits specific capacitance of 251 F g −1 at 1 A g −1 , high rate capability with the specific capacitance of 228 F g −1 at 20 A g −1 , only a loss of 3% after 10000 cycles at a current density of 3 A g −1 . Non aqueous performance was tested in 1 M TEA-BF 4 /acetonitrile, the material can deliver an energy density of 12–17 Wh kg −1 in a two-electrode system. Apparently, the porous carbon with ultrathin structure can provide low-resistant pathways and short ion diffusion channels for energy storage. Therefore, the ultrathin porous carbon shell would be a promising material particularly for applications where high power output performances are required.

Ni–S/CeO 2 composite materials for hydrogen evolution reaction (HER) have been prepared by an electrodeposition method under supergravity field from nickel sulfamate. With the different mass concentrations of CeO 2 , the morphology and X-ray diffraction patterns of Ni–S/CeO 2 are diverse. Apparently, the CeO 2 contents of Ni–S/CeO 2 composite electrodes under supergravity fields are higher than that under normal gravity field. In addition, the HER catalytic activity of Ni–S/CeO 2 composite electrodes can be measured in 1.0 M NaOH at 298 K. The results show that overpotential of Ni–S/CeO 2 electrode of 7 g/L CeO 2 under 3000 rpm is the least, suggesting perhaps too much content of CeO 2 hinder the desorption of H ads , or too little CeO 2 can not play palpable roles in improving the catalytic activity and increasing oxygen vacancies. And the exchange current density j 0 value of Ni–S/CeO 2 composite electrode prepared under the speed of 3000 rpm, which is 1.16 times larger than the Ni–S/CeO 2 of 0 g/L CeO 2 , is 1.9 times higher than that under normal gravity field. EIS results suggest that there exists a synergetic effect on HER between CeO 2 and Ni–S alloy matrix.

A novel sandwiched gel polymer electrolyte (GPE) was prepared using a facile method as separator solely for rechargeable Lithium–Sulfur batteries. As a result of the strong physical shielding and chemical absorption of GPE, the separator can not only suppress shuttle effect in ether-based electrolyte, but also improve utilization of sulfur significantly resulting in a high capacity. The PVDF layers could absorb ether-based electrolyte largely and then enhance Li + transfer; the PMMA layer can be utilized to trap the dissolved polysulfides. Lithium–Sulfur batteries with the sandwiched GPE separator shows an encouraging electrochemical performance. A high initial discharge capacity of 1711.8 mAh g −1 is obtained, and the capacity retains at 1145.3 mAh g −1 after 50 cycles at 200 mA g −1 , which is higher than that of the cell with the commercial separator. These results indicate that the appropriate GPE separator is more suitable in Lithium−Sulfur batteries applications.

In this work, supergravity fields are performed to prepare Ni-CNTs composite cathodes with wool-ball-like morphology from the Watts bath containing well-distributed functionalized CNTs. The prepared Ni-CNTs composite cathodes are used as noble metal-free electrocatalyst with favorable electrocatalytic activity for hydrogen evolution reaction (HER) in alkaline solutions. The crystal structure and morphology of the composite cathodes are characterized by XRD and SEM measurements. The electrochemical activities of the cathodes are characterized through Tafel polarization measurement, electrochemical impedance spectroscopy and cyclic voltammetric study in 1.0 M NaOH solution. The results indicate that catalytic activities of the Ni-CNTs cathodes prepared under supergravity fields are enhanced significantly, and the sample prepared at rotating speed 3000 rpm from the bath containing 1 g dm −3 CNTs exhibits the highest HER activity with smallest Tafel slope and largest exchange current density of 823.9 μA cm −2 . Furthermore, the effects of both the CNTs concentrations and the intensities of supergravity fields on the properties of the Ni-CNTs cathodes are investigated.

Two-dimensional cobalt–manganese binary metal oxides (Co1.5Mn1.5O4) porous nanosheets have been successfully synthetized via a simple liquid phase precipitation method. This thin nanosheet structure can shorten the electrolyte ion diffusion distance. Meanwhile, the abundant mesoporous provides more electrochemical active sites, facilitates ion diffusion, and reduces the volume expansion in the charge/discharge cycling processes. Furthermore, there is a synergistic effect on the electrochemical reaction of Co1.5Mn1.5O4. Owe to the high electrical conductivity, cobalt can decrease the impedance and expedite charge transfer. In return, manganese contributes more capacitance in the binary metal oxides. As a result, the as-prepared Co1.5Mn1.5O4 porous nanosheets exhibit outstanding electrochemical performances, such as a specific capacitance of as high as 472.5 F g−1 at 0.5 A g−1, excellent rate capability of 338.5 F g−1 at 10 A g−1 which is equivalent to about 71.6 % of the capacitance at 0.5 A g−1, and long-term cyclability of almost 100 % capacity retention after 1000 cycles.

Al-doped ZnO (AZO) thin films were prepared on glass substrates with different atomization interval times by aerosol-assisted chemical vapor deposition method. The structure, morphology, and optical and electrical properties were investigated by X-ray diffractometer, atomic force microscope, UV-vis double beam spectrophotometer and 4 point probe method. ZnO thin films exhibited strong growth orientation along the (002) plane and the crystalline was affected by the atomization interval time. All the films had high transmittance and the films with interval times of 2 min and 4 min had good haze values for the transparent conducting oxide silicon solar cell applications. The AZO thin film had the best optical and electrical properties when the atomization interval time was 4 min. This is very important for the optoelectronic device applications. The surface morphology of AZO films depended on the atomization interval time.

The critical challenges hindering the commercialization of Li-rich cathodes are their rapid-decaying capacity and voltage during cycling, originating from the degradation of lattice structure and interface side reaction between electrode and electrolyte. Surface engineering is considered to be an effective strategy to mitigate these disadvantages. Herein, an in-situ self-reconstruction strategy is proposed and developed to simultaneously optimize surface chemical composition and local structure of Li-rich cathodes. Specifically, the multifunction protective layer consisting of cation disorder phase and LiTMPO4-like (TM: Ni, Co, Mn) phase is produced by a simple PH3 gas treatment. LiTMPO4 featuring the ability against high potential is responsible for preventing interface side reaction and further reduce the dissolution of Mn. Both LiTMPO4-like phase and surface cation disorder phase contribute to stabilizing surface oxygen structure and limiting surface O2 release. Compared to the pristine one, better integrity of chemical phases and higher oxidation state of TM cations after long-term cycling are confirmed in the modified sample by synchrotron-based scanning transmission X-ray microscopy, highlighting the key roles of the multifunction protective layer in stabilizing the capacity and voltage during cycling. This surface self-reconstruction strategy provides a new path for guiding the interface design of high energy density cathodes.

Lithium cobalt oxides are widely investigated as promising bifunctional catalysts for metal-air batteries in recent years. Generally, the promotion of catalytic activity of LiCoO2-based materials is mainly due to the ultra-thin layer structure with thickness of several atomic layers. Herein, a series of nanosheets are obtained from layered LiCoO2 material treated by nitric acid. More unexpectedly, although the specific surface area of the samples increases dramatically due to ultrathin nanosheets, the catalytic activities almost are not improved compared with that of bulk LiCoO2 material. After annealing process, these samples exhibit superior catalytic performance in alkaline solutions. Based on X-ray diffraction spectra, raman spectra, X-ray photoelectron spectroscopy, and O2 temperature-programmed desorption analysis, the results indicate that metastable Li1-x-yHyCoO2 nanosheets are obtained from bulk LiCoO2 material treated by acid. They transform into main phase of spinel-type Li1-xCoO2-δ material with more oxygen vacancies after annealing process. The great difference in electrochemical performances between the two-type materials is attributed to the crystal structures, the exposure of Co–O octahedral sites in the plane of spinel-type Li1-xCoO2-δ, the coexistence of valence state of Con+ and oxygen vacancy.

Developing sufficient resources, low prices and easy availability non-noble metal-based catalysts for the oxygen reduction reaction (ORR) to substitute Pt-based materials is extremely desirable but still a grand challenge.Notably, a facile and cost-efficient pyrolysis strategy is demonstrated to fabricate a three-dimensional (3D) structural ORR electrocatalyst (denoted as Fe@N–CNS/CNTS)based on Fe/N Co-doped carbon nanotubes (NCNT) with ultra-thin porous carbon nanosheets (NCNS) via a ZnCl2-assisted approach. The ZnCl2 play a crucial role in creating the 3D porous structure which is more beneficial for enhancing specific surface area and exposing sufficient active sites. Anecdotally, the rationally designed catalysts have multifactorial synergistic function of ultra-thin porous NCNS, NCNTS with iron carbide and oxide (Fe3C,Fe2O3). The prepared optimal Fe@N-CNS/CNTS-0.5 revealed catalytic performance with onset potential of 0.983V (vs RHE) and relatively small Tafel slope of 63 mV dec−1 in 0.1 M KOH solution. More importantly, after 25,000s chronoamperometry, the as-prepared electrocatalyst possessed excellent durability with only 7% current decay surpassing that of the 20% Pt/C (17%), which is also further evaluated in realistic quasi-solidstate flexible Zn-air batteries. As a consequence, this strategy provided a universal approach for future development of the multifunctional cathode catalysts.

Li metal has been regarded as the most promising anode material for next-generation high-energy-density batteries. However, the growth of lithium dendrites caused by non-uniform deposition brings many obstacles to the commercialization process of metallic Li anodes. An effectively designed 3D current collector can significantly suppress the lithium dendrites growth and related issues. Herein, we develop a 3D conductive skeleton that hierarchical copper fibers grown vertically on the copper foam skeleton (HCF/CF) by a rational strategy. The Cu fiber with numerous protuberances secondary structure can provide the electrochemical active sites, which sever as charge centers to induce Li uniform nucleation and deposition on HCF/CF skeleton. Furthermore, the abundant porous structure of HCF/CF current collector can alleviate the volume change during repeated Li plating/striping. Comparison with Cu foam, the HCF/CF skeleton reveals an observably improved Li plating/striping behavior and a high Coulombic efficiency (98% retention after 200 cycles). The Li anode based on HCF/CF current collector can run for 820 h at a current density of 1 mA cm−2 without evident voltage fluctuation. The full cells of Li@HCF/CF|LFP exhibit a superior cycling and rate performance. The strategy for modifying foam copper has effectively improved the deposition behavior of lithium as well as enhanced the electrochemical performance of lithium anode.

Carbon materials have unique stability and controllable structure for all-carbon lithium-ion capacitors (LICs) electrode materials. In this paper, we used chitosan as a carbon source and self-doped nitrogen source, zinc nitrate as a templating agent. Hierarchical porous carbon nanosheets (PCNS) materials with graphene-like structure and abundant nitrogen doping were prepared through a one-step carbonization process. The PCNS materials were used as both capacitor-type cathode and battery-type anode for LICs. Due to the multi-mesoporous and ultrathin nanosheets structure, a large specific surface area (1321.3 m2 g−1) was obtained of PCNS materials, which ensures a high specific discharge capacity of 65.8 mAh g−1 at 3 A g−1 for the capacitor-type cathode. The interconnected graphene-like structure not only provides a large adsorbable area but also reduces the diffusion distannce of ions between the surface of the electrode and electrolyte. When the PCNS materials used as an anode for LIC, it also appeared a high specific discharge capacity of 285.0 mAh g−1 at a big current density of 20 A g−1. Finally, all-carbon symmetric LIC with a broad voltage window of 0.01–4.5 V was constructed successfully. The symmetric LIC shows a high energy density of 146 Wh kg−1 (at a power density of 1125 W kg−1) and an excellent capacity retention rate of 84.5% (10,000 cycles at 5 A g−1).

The application of SiO anodes in Li-ion batteries is greatly restricted by its low initial coulombic efficiency (ICE). Usually, a pre-lithiation procedure is necessary to improve the ICE, but the available technologies are associated with safety issues. Metal (M)-mixed SiO shows great promise to address these issues by reactivating Li

A stable MnO

Spinel LiNi0.5Mn1.5O4 (LNMO) is a competitive cathode material for the next generation high energy density lithium ion batteries (LIBs) because of its high potential (4.7 V) and acceptable theoretical capacity (146.7 mAh g−1). Nevertheless, it suffers from severe capacity decay during cycling, especially at elevated temperatures. Herein, we propose an integrated modification strategy combing Li+-conductive Li2ZrO3 coating layer with superficial Zr-doping. The coating layer of Li2ZrO3 avoids the direct contact between the cathode material and electrolyte, and favors Li+ transport kinetics and interface stability, superficial Zr-doping can greatly improve electron conductivity by inducing an appropriate amount of Mn3+. Electrochemical measurements demonstrate that desirable capacity retention of 82.4% can be obtained for 2 wt% Li2ZrO3-surface modified LNMO at 25 °C for 5 C rate after 1000 cycles, significantly higher than that of 66.1% for the pristine sample. Notably, the capacity retention of 2 wt% Li2ZrO3-coated LNMO sample can maintain up to 83.5% at 1 C rate after 200 cycles at 55 °C. This integrated modification strategy of synergistic coating and doping is regarded as a promising and useful choice for elevating the performance of LIBs.

Development of highly-active and noble-metal-free electrocatalysts for hydrogen evolution reactions is a challenge, and optimizing the structure and the composition of the relative materials is critical to obtain the high-quality catalysts. Ni-based compounds are being explored as noble-metal-free electrocatalysts in hydrogen evolution reactions but the Ni-based needs to be modified effectively. In this work, we co-electrodeposited Ni nanoparticles, hydrophilic graphene and graphene oxide layers on Ni foam to synthesize Ni-HG-rGO/NF catalysts. It was presented a Datura-like shape allowing for high performance with current densities of −10 and −100 mA cm−2 for HER at overpotentials of −50 and −132 mV, a low Tafel slope of −48 mV dec−1 and excellent long-term stability in 1.0 M NaOH solution. These results demonstrate that the Ni-HG-rGO/NF electrode can be a competitive electrode materials for HER in alkaline conditions.

Herein we report an in-situ strategy for synthesizing NiO foamed sheet on Ni foam substrate which could achieve great improvement on the areal performance of battery-type supercapacitors. The anchored NiO foamed sheets are synthesized via a precursor growth step by hydrothermal oxidation, and followed by a pore-inducing step through heat treating. The physical characterizations indicate that this film product has a multi-level pore structure with high active surface area. As for electrode material, the anchored sheets could ensure excellent conductivity at the film/substrate interface, and the porous structure could form high free electron/ionic diffusion routes which facilitates the redox reactions for reversible energy storage. The electrochemical measurements show that the areal capacity of as-synthesized electrode could achieve 4.31–3.39 C cm−2 at a wide current range of 10–200 mA cm−2. The single supercapacitor device exhibits a high areal energy density of 9.84–9.45 W h m−2 at a wide power density of 100–2000 W m−2.

A novel acetylene black/sulfur@graphene composite (AB/S@G) with unique three-dimensional sandwich structure was successfully prepared via an in situ sulfur deposition strategy and self-assembly. Acetylene black as conductive carbon skeleton and graphene nanosheets as physical shields played an extremely important role for improving the electrochemical performances of the AB/S@G cathode. Compared with the AB/S cathode, the AB/S@G cathode with a sulfur content of 54 wt% exhibited a high utilization of sulfur, an enhanced cyclical stability, and an excellent rate capability. The AB/S@G cathode came true a high sulfur utilization of 95.73% after undergoing a high initial discharge capacity of 1603.5 mAh g −1 at a current density of 200 mA g −1 , much higher than that (71.78%) of the AB/S cathode. The excellent electrochemical performances were principally attributed to the combined effect of graphene nanosheets and acetylene black, which provided an improved electrical conductivity for the sulfur cathode, effective restraining for soluble polysulfides, and powerful buffer for the volume changes of sulfur during cycling.