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Antimony (Sb) and its oxides, as promising electrode materials, have attracted much attention because of their low cost, environmental friendliness, and high theoretical capacity. Herein, boron doped flower-cluster-like Sb/SbO2@reduced graphene oxide (rGO) composites are synthesized for use as sodium-ion battery anode materials using a solvothermal strategy. The contents of Sb and antimony oxide (SbO2) are controlled by adding different contents of NaBH4. Meanwhile, the introduction of NaBH4 successfully realizes boron doping and enlarges the lattice spacing of the SbO2, improving its conductivity and Na+ transport. As a result, optimal Sb/SbO2@rGO-10 composites display a desirable capacity of 346 mAh g−1 at 50 mA g−1 after 100 cycles with a capacity retention of 106%. Even at high current densities, a capacity of 236 mAh g−1 is achieved, demonstrating a satisfactory rate capacity. Moreover, the Sb/SbO2@rGO-10 electrode shows satisfactory Na storage performance at low temperatures. In addition, sodium-ion full cells are assembled using an Sb/SbO2@rGO-10 anode and a Na3V2(PO4)2O2F cathode, with which a satisfactory electrochemical performance of 102 mAh g−1 after 50 cycles at 50 mA g−1 is achieved, showing their high practical potential.

Room-temperature sodium metal batteries with metallic Na anodes and flammable organic solvent-based electrolytes are breeding severe safety concerns. Herein, by introducing non-flammable, highly-fluorinated ethers as bridge solvents, we enable superior miscibility of an all-fluoride fire extinguishant into fluorinated carbonate electrolytes. Besides the intrinsic non-flammability of the designed electrolyte, the embedded PFMP extinguishant further enhances the battery safety by its efficacy to in situ dissipate the internal heat at an elevated temperature (ΔH = +88.1 J g−1). Moreover, the cyclability is greatly improved by using such an electrolyte. The Na/Na symmetrical cells can cycle for 1100 h at 1.0 mA h cm−2 and more than 800 h at 5.0 mA h cm−2. Paired with a high voltage Na3V2(PO4)2O2F cathode, the full cell exhibits a high initial coulombic efficiency of 94.7% and a capacity retention of 87.1% after 1000 cycles at 0.5C, which is mainly ascribed to the thin F-rich interphases established on both the Na metal anode and the cathode.

Herein, we develop a Co3O4-based anode material with a hierarchical structure similar to that of a lotus pod, where single yolk–shell-structured Co3O4@Co3O4 nanospheres are well embedded in a nitrogen-doped carbon (N–C) conductive framework (Co3O4@Co3O4/N–C). This distinctive architecture contains multiple advantages of both the yolk–shell structure and conductive N–C framework to improve the Li ion storage performance. Especially, the doping of the N atom in N–C increases the interaction between the carbon and adsorbents, which is confirmed by the theoretical calculations in this work, making the carbon framework much more electrochemically active. As a result, the Co3O4@Co3O4/N–C exhibits fast surface-controlled kinetics, which corroborate the high counterion mobility and the ultrafast electron-transfer kinetics of the electrode. Due to these synergetic effects, desired capacity stability (1169.6 mAh g–1 at 200 mA g–1 after 100 cycles) and superior rate performance (633.4 mAh g–1 at 10 A g–1) have been ...

In this work, carbon-free, porous, and micro/nanostructural Zn2GeO4 nanofibers (p-ZGONFs) have been prepared via a dissolution-recrystallization-assisted electrospinning technology. The successful electrospinning to fabricate the uniform p-ZGONFs mainly benefits from the preparation of completely dissolved solution, which avoids the sedimentation of common Ge-containing solid-state precursors. Electrochemical tests demonstrate that the as-prepared p-ZGONFs exhibit superior Li-storage properties in terms of high initial reversible capacity of 1075.6 mA h g–1, outstanding cycling stability (no capacity decay after 130 cycles at 0.2 A g–1), and excellent high-rate capabilities (e.g., still delivering a capacity of 384.7 mA h g–1 at a very high current density of 10 A g–1) when used as anode materials for lithium ion batteries (LIBs). All these Li-storage properties are much better than those of Zn2GeO4 nanorods prepared by a hydrothermal process. The much enhanced Li-storage properties should be attributed t...

The synergistic design of cathode region was conducted to minimize the shuttle effect of polysulfides and decrease the loading of inactive components in order to acquire high-energy-density lithium–sulfur (Li–S) batteries. The well-designed cathode region presented two special characteristics: one was the intertwined nanofibers interlayer based on ultrafine TiO2 nanocrystal uniformly embedded within N-doping porous carbon; the other was the lightweight and three-dimensional current collector of fibrous cellulose paper coated by reduced graphene oxide. In consequence, the decent reversible capacity of 874.8 mA h g–1 was acquired at 0.1 C with a capacity retention of 91.83% after 100 cycles. Besides, the satisfactory capacity of 670 mA h g–1 was delivered after 300 cycles at 1 C with the small decay rate of only 0.08%. Because of higher capacity and lower loading of inactive component in cathode region, the energy density of cell increased more than five times compared with unmodified cell. Moreover, to fur...

To make alloying anodes be practicability for lithium-ion batteries, graphene-incorporation has been demonstrated as one of the most effective strategies. However, successive lithiation/delithiation would usually lead to the detachment and self-aggregation of active alloying nanoparticles and graphene. Herein, an oxygen-bonds-bridging (Sn–O–C) Sn/graphene (Sn–O–G) micro/nanocomposite, in which Sn particles are in the ultrasmall scale of

A novel kind of MnCO 3 nanoplatelets-reduced graphene oxide (RGO) composites, as an anode material in rechargeable Li-ion battery, was prepared by a simple low temperature reaction route. The graphene not only provided an avenue for the transport of Li-ion, but also buffered the volume expansion of MnCO 3 nanoplatelets during charge and discharge. Compared to pure MnCO 3 nanoplatelets, MnCO 3 -RGO composites presented the improved electrochemical performances. At a low current density of 100 mA g −1 , MnCO 3 -RGO composites delivered a desired performance of 849.1 mAh g −1 after 200 cycles. When at a high current density of 500 mA g −1 , the discharge capacity still maintained at 810.9 mAh g −1 after 700 cycles. Our experimental results suggest that this composite will be a candidate as a novel anode material for the power batteries of electric vehicles and the energy storage batteries of smart grids in the future.

Metallic antimony (Sb) is one promising candidate as anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity of 660 mAh/g. However, the electrochemical formation of Na 3 Sb alloy makes it will suffer from tremendous volume variation during Na-uptake/release cycling and hence poor practical Na-storage properties. The incorporation of reduced graphene oxide (rGO) should be one effective strategy to overcome this issue. Herein, it is excitingly discovered that in-situ preparation micro/nanocomposite composed of Sb and rGO has played an effective role on improving Na-storage performance, especially fast energy storage and cycle life. The in-situ -prepared micro/nanocomposite (I-Sb/rGO) can deliver a superior capacity of 112 mAh/g even at an ultrahigh current density of 6 A/g compared to the ex-situ -prepared one (E-Sb/rGO). And it also exhibits outstanding cycle life with a residual capacity of 173 mAh/g after 150 cycles at current density of 0.5 A/g, much higher than that (36 mAh/g) of the ex-situ one. Those enhanced performance can be attributed to the advanced in-situ -prepared process.

A facile and effective approach to prepare Co 3 O 4 /CoFe 2 O 4 hollow cubes with uniform size and complex interior architectures is proposed via annealing of metal-cyanide-bridged hybrid coordination polymers (HCPs). The synergistic effect of the hybrid metal oxides and the rational design of the architecture endow these heterostructures with good lithium storage property and charge carrier transfer kinetics. In the hybrid materials, CoFe 2 O 4 offers high theoretical capacity and Co 3 O 4 provides stability at high current densities, leading to the significant enhancement in lithium storage properties comparing to the pure CoFe 2 O 4 . For example, Co 3 O 4 /CoFe 2 O 4 heterostructures annealed at 800 °C exhibit a high capacity of 511 mA h g −1 at a current density of 8.0 A g −1 and a reversible capacity of 515 mA h g −1 during the 500th cycle at a current density of 5.0 A g −1 .

As is well known, a gradual increase in capacity during cycling is a common phenomenon in previously reported oxide-based anodes for lithium-ion batteries. However, not only may this be superfluous for practical applications, but it may also imply the presence of some electrochemical instabilities and side reactions. To achieve ultrastable Li storage without such a gradual increase in capacity, the mechanism of this increase by using a MnO/graphene-based nanohybrid (MnO@C/RGO) as an example was comprehensively explored. Then, the gradual increase behavior of the specific capacity was effectively restrained by rationally optimizing the cutoff voltage, which resulted in the MnO@C/RGO electrode maintaining a nearly constant capacity during cycling at different current densities. Taking the high current density of 2 A g−1 as an example, there was no clear capacity change (increase/attenuation) even over 2000 cycles with stable coulombic efficiencies of around 99.7 %. This ultrastable Li-storage capability should mainly benefit from rational testing parameters and an optimal 3D conductive network. More importantly and interestingly, full cells were also assembled and tested by coupling MnO@C/RGO and commercial LiFePO4 as the anode and cathode materials, respectively. The full cells impressively exhibited superior rate performance and excellent cycling stability.

Inspired by the preparation of the hierarchically-porous carbon (HPC) derived from metal organic frameworks (MOFs) for energy storage, in this work, a simple iron-based metal- organic complex (MOC), which was simpler and cheaper compared with the MOF, was selected to achieve versatile energy storage. The intertwined 1 D nanospindles and enriched-oxygen doping of the HPC was obtained after one-step carbonization of the MOC. When employed in lithium-ion batteries, the HPC exhibited reversible capacity of 778 mA h g(-1) after 60 cycles at 50 mA g(-1) . Moreover, the HPC maintained a capacity of 188 mA h g(-1) after 400 cycles at 100 mA g(-1) as the anode material in a sodium-ion battery. In addition, the HPC served as the cathode matrix for evaluation of a lithium-sulfur battery. The general preparation process of the HPC is commercial, which is responsible for the large-scale production for its practical application.

In this work, the low-cost hierarchically porous nitrogen-doped carbon nanosheets (PNCNs) were prepared via one-step carbonization and KOH activation process of grapefruit peels. The prepared PNCNs exhibit higher specific surface area due to the inducement of the KOH-assisted carbonization compared to directly carbonized grapefruit peels (DCGPs). The PNCNs exhibit excellent electrochemical performances with high specific capacitance up to 311 F g−1, superior cycling stability over 10000 cycles with only 5.95 % capacitance degradation, high energy density of 17.7 W h kg−1 and power density of 1100 W kg−1 in 1 mol L−1 H2SO4 electrolyte. All these electrochemical data are significantly better than the comparative DCGPs material. Moreover, the assembled symmetric supercapacitor in 1 mol L−1 Na2SO4 aqueous electrolyte exhibits a high energy density of 34.05 W h kg−1 at a power density of 180 W kg−1 and retains 14.25 W h kg−1 even at 5400 W kg−1.

Layered compounds LiNi 1/3 Co 1/3 Mn 1/3 O 2 have recently received much attention as they have been regarded as a promising cathode materials for industrial application. However, its fast energy density decay and poor rate performance which originate from structure disruption especially at high rate and high cut-off voltage limit its large-scale application. Here, a novel designed concept and facile method were firstly used to fabricate (PO 4 ) 3− polyanions doped layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LNMC-(PO 4 ) 0.015 -O 1.94 ) structure, which could offer more stable high-voltage cycling performance and high rate capability. We attribute this improved performance to the robust P tet -O covalence, which will stabilize the oxygen close-packed structure during repeated cycling. Moreover, our stepwise pre-cycling treatments could effectively restrain the formation of micro-cracks and non-crystallization defects, and significantly improve cyclic durability with high charge voltage of 4.7V. The LNMC-(PO 4 ) 0.015 -O 1.94 electrode can still delivers capacity retention of 81% after 200 cycles at a current density of 300mA g −1 . The preliminary results reported here manifest that this novel-designed LNMC-(PO 4 ) 0.015 -O 1.94 material represents an attractive alternative to ultrafast-rate, long-life and high-voltage electrode material for lithium ion batteries.

Graphene incorporation should be one effective strategy to develop advanced electrode materials for a sodium-ion battery (SIB). Herein, the micro/nanostructural Sb/graphene composite (Sb-O-G) is successfully prepared with the uniform Sb nanospheres (∼100 nm) bound on the graphene via oxygen bonds. It is revealed that the in-situ-constructed oxygen bonds play a significant role on enhancing Na-storage properties, especially the ultrafast charge/discharge capability. The oxygen-bond-enhanced Sb-O-G composite can deliver a high capacity of 220 mAh/g at an ultrahigh current density of 12 A/g, which is obviously superior to the similar Sb/G composite (130 mAh/g at 10 A/g) just without Sb-O-C bonds. It also exhibits the highest Na-storage capacity compared to Sb/G and pure Sb nanoparticles as well as the best cycling performance. More importantly, this Sb-O-G anode achieves ultrafast (120 C) energy storage in SIB full cells, which have already been shown to power a 26-bulb array and calculator. All of these superior performances originate from the structural stability of Sb-O-C bonds during Na uptake/release, which has been verified by ex situ X-ray photoelectron spectroscopies and infrared spectroscopies.

Lithium-ion capacitors (LICs) are hybrid energy storage devices that have the potential to bridge the gap between conventional high-energy lithium-ion batteries and high-power capacitors by combining their complementary features. The challenge for LICs has been to improve the energy storage at high charge−discharge rates by circumventing the discrepancy in kinetics between the intercalation anode and capacitive cathode. In this article, the rational design of new nanostructured LIC electrodes that both exhibit a dominating capacitive mechanism (both double layer and pseudocapacitive) with a diminished intercalation process, is reported. Specifically, the electrodes are a 3D interconnected TiC nanoparticle chain anode, synthesized by carbothermal conversion of graphene/TiO2 hybrid aerogels, and a pyridine-derived hierarchical porous nitrogen-doped carbon (PHPNC) cathode. Electrochemical properties of both electrodes are thoroughly characterized which demonstrate their outstanding high-rate capabilities. The fully assembled PHPNC//TiC LIC device delivers an energy density of 101.5 Wh kg−1 and a power density of 67.5 kW kg−1 (achieved at 23.4 Wh kg−1), and a reasonably good cycle stability (≈82% retention after 5000 cycles) within the voltage range of 0.0−4.5 V.

Dual-carbon enhanced Si-based composite (Si/C/G) has been prepared via employing the widely distributed, low-cost and environmentally friendly Diatomite mineral as silicon raw material. The preparation processes are very simple, non-toxic and easy to scale up. Electrochemical tests as anode material for lithium ion batteries (LIBs) demonstrate that this Si/C/G composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pristine Si material as well as both single-carbon modified composites. Specifically for the Si/C/G composite, it can still deliver a high specific capacity of about 470 mAh g−1 at an ultrahigh current density of 5 A g−1, and exhibit a high capacity of 938 mAh g−1 at 0.1 A g−1 with excellent capacity retention in the following 300 cycles. The significantly enhanced Li-storage properties should be attributed to the co-existence of both highly conductive graphite and amorphous carbon in the Si/C/G composite. While the former can enhance the electrical conductivity of the obtained composite, the latter acts as the adhesives to connect the porous Si particulates and conductive graphite flakes to form robust and stable conductive network.

Two-dimensional (2D) graphene oxide/polypyrrole (GO/PPy) hybrid materials derived from in-situ polymerization are used as precursors for constructing functionalized three-dimensional (3D) porous nitrogen-doped carbon nanosheet frameworks (FT-PNCNFs) through a one-step activation strategy. In the formation process of FT-PNCNFs, PPY is directly converted into hierarchical porous nitrogen-doped carbon layers, while GO is simultaneously reduced to become electrically conductive. The complementary functions of individual components endow the FT-PNCNFs with excellent properties for both supercapacitors (SCs) and sodium ion batteries (SIBs) applications. When tested in symmetrical SC, the FT-PNCNFs demonstrate superior energy storage behaviour. At an extremely high scan rate of 3000 mV s −1 , the cyclic voltammetry (CV) curve retains an inspiring quasi-rectangle shape in KOH solution. Meanwhile, high capacitances (∼247 F g −1 at 10 mV s −1 ; ∼146 F g −1 at 3000 mV s −1 ) and good cycling stability (∼95% retention after 8000 cycles) are achieved. In addition, an attractive SIB anode performance could be achieved. The FT-PNCNFs electrode delivers a reversible capacity of 187 mAh g −1 during 160th cycle at 100 mA g −1 . Its reversible capacity retains 144 mAh g −1 after extending the number of cycles to 500 at 500 mA g −1 .

Presently, graphene incorporation is one of the most effective strategies to develop superior electrode materials for sodium-ion batteries (SIBs). Herein, it is excitingly found that an incorporated graphene nanosheet in the preparation processes can not only completely protect all the Sb nanoparticles in an Sb/C composite from being inactivated, but also suppresses their growth to undesirable micrometer size. While there are still many exposed Sb particulates on the surface of pristine Sb/C microplates, the graphene-incorporated Sb/C/G nanocomposite consists of uniform Sb nanoparticles of 20–50 nm, all of which have been protected by and wrapped in the mixed carbon network. When used as anode materials for SIBs, the Sb/C/G nanocomposite exhibits the best Na-storage properties in terms of the highest reversible capacity (650 mA h g−1 at 0.025 A g−1), fastest Na-storage ability (290 mA h g−1 at a high current density of 8 A g−1), and optimal cycling performance (no capacity decay after 200 cycles), in comparison to pristine Sb/C and pure Sb. It is further revealed that the much enhanced performance should originate from the improvement of Na-storage kinetics and increase of electronic conductivity via comparing the electrochemical impedance spectra, and cyclic voltammetry profiles, as well as the polarization variation along with current densities.

In this paper, gelatin as a natural biomass was selected to successfully prepare an oxygen-enriched carbon with layered sedimentary rocks structure, which exhibited ultrahigh-rate performance and excellent cycling stability as supercapacitors. The specific capacitance reached 272.6 F g(-1) at 1 A g(-1) and still retained 197.0 F g(-1) even at 100 A g(-1) (with high capacitance retention of 72.3%). The outstanding electrochemical performance resulted from the special layered structure with large surface area (827.8 m(2) g(-1)) and high content of oxygen (16.215 wt %), which effectively realized the synergistic effects of the electrical double-layer capacitance and pseudocapacitance. Moreover, it delivered an energy density of 25.3 Wh kg(-1) even with a high power density of 34.7 kW kg(-1) and ultralong cycling stability (with no capacitance decay even over 10,000 cycles at 2 A g(-1)) in a symmetric supercapacitor, which are highly desirable for their practical application in energy storage devices and conversion.

A dissolution–recrystallization method was developed to prepare flexible paper electrodes constructed of Zn2GeO4 nanofibers anchored with amorphous carbon (ZGO/C-P) for high energy and power Li-ion batteries. The ZGO/C-P exhibits superior long-term cycle stability (up to 2000 cycles at 1 A g−1) and excellent rate capability.

In this manuscript, graphene-encapsulated porous cobalt oxide cubes (Co3O4@G) are fabricated through a facile precipitation reaction with subsequent calcination and a self-assembly process. The synthesized porous Co3O4 cubes anchored in the conductive graphene network can realize superior electrical conductivity, withstand volume variation upon prolonged cycling and shorten the diffusion path of lithium ions. When evaluated as anode materials, the Co3O4@G electrode shows excellent electrochemical properties in terms of both stable cycling performance and good rate capabilities. For example, a reversible discharge capacity of 980 mA h g(-1) is delivered after 80 cycles at a current density of 200 mA g(-1). Introducing a conductive graphene network to modify other metal oxides with poor electric conductivity and large volume excursions is of great interest in the development of lithium ion battery technologies.

In recent years, metal-organic compounds have been considered as ideal sacrificial templates to obtain transition metal oxides for electrochemical applications due to their diverse structures and tunable properties. In this work, a new kind of cobalt-based metal organic compound with a layered structure was designed and prepared, which was then transformed into ultrafine cobalt oxide (Co3O4) nanocrystallites via a facile annealing treatment. The obtained Co3O4 nanocrystallites further assembled into a hierarchical shale-like structure, donating extremely short ion diffusion pathway and rich porosity to the materials. The special structure largely alleviated the problems of Co3O4 such as inferior intrinsic electrical conductivity, poor ion transport kinetics and large volume changes during the redox reactions. When evaluated as anode materials for lithium-ion batteries, the shale-like Co3O4 (S-Co3O4) exhibited superior lithium storage properties with a high capacity of 1045.3 mA h g−1 after 100 cycles at 200 mA g−1 and good rate capabilities up to 10 A g−1. Moreover, the S-Co3O4 showed decent electrochemical performance in sodium-ion batteries due to the above-mentioned comprehensive merits (380 and 153.8 mA h g−1 at 50 and 5000 mA g−1, respectively).

Over the past years, the biomass-derived materials are receiving more and more attention as high-performance and low-cost anodes for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). Herein, the hard carbon derived from unburned charcoal (UC-x) is prepared by acid and heat treatment. And it is inferred from morphological characterization that the unique net structure is favorable for electrolyte permeation and charge transfer for Na+/Li+. As a result, the UC-x electrode as an anode shows high specific capacity (150 m Ah g − 1 for SIBs and 350 m A h g − 1 for LIBs at 0.1 A g − 1) and enhanced cycling stability (250 mA h g − 1 after 300 cycles for LIBs and 273 mA h g − 1 after 200 cycles for SIBs). In addition, UC-1200 possesses fast electrochemical kinetics for Na+/Li+ (1–6 × 10−10 cm2 s − 1 for Na+ and 1–2.5 × 10−10 cm2 s − 1 for Li+) and the dominated electrode reaction is mainly controlled by pseudocapacitance. In a word, this work provides a kind of unique biomass material as anodes for SIBs/LIBs from the reutilization of the waste and promotes the development of carbonaceous electrode materials.

Currently, rechargeable sodium-ion batteries (SIBs) with high voltage and high energy density have attracted considerable attention. However, compared with lithium-ion batteries (LIBs), there are many urgent challenges that need to be solved to achieve the practical application of SIBs. Due to the similar physicochemical properties of sodium and lithium, the study of SIBs is based on LIBs. However, the radius of Na+ is larger than that of Li+, a limited number of LIBs electrode materials can be used in SIBs, especially anode materials. Graphite can store sodium ions if an ether-based electrolyte is being used. The storage capacity of graphite for sodium is low (∼35 mAh g−1) when traditional carbonate-based electrolyte is used. Therefore, it is vital that anode materials with splendid rate capability, outstanding cycling performance and low cost are developed rapidly. Among all types of anode materials, metal sulfides (MSx) with higher theoretical specific capacity and lower cost are an ideal practical anode material. Here, a summaryof the recent research advances on MSx of SIBs is provided. The crystal structures, sodium storage mechanism and optimization strategies for high performance batteries are summarized. this paper hopes to provide inspiration for the development of MSx to assist the development of the next generation of rechargeable battery applications.

The development of new and efficient anode materials for lithium-ion batteries (LIBs) has attracted considerable attention. Herein, a new polyoxometalate-based metal-organic framework (POMOF), [Mn4(L)(SiW12O40)·(DMF)2·(H2O)6]·4OH·4DMF·7H2O (1), was prepared with a resorcin [4]arene-based ligand (L), Keggin-type [SiW12O40]4- anion and Mn(II) cation (DMF = N,N′-dimethylformamide). Compound 1 has a layer structure sandwiched by [SiW12O40]4- anions. The high specific capacity and excellent cycling stability are achieved by using 1 as an anode material for LIBs. The high electrochemical performance of compound 1 is attributed to the good electron storage and reversible multi-electron redox properties of [SiW12O40]4- anions within the framework.

As a member of Na-super-ionic conductor (NASICON) family, Na3(VO)2(PO4)2F (NVPF) is reported to possess higher redox potential and larger specific capacity than its analogue Na3V2(PO4)3 (NVP). However, the rate and cycling performance of NVPF is significantly lower than that of NVP. Moreover, almost reported NVPF materials are bulk-type powders, which can not satisfy the requirement of flexible energy-storage devices. Herein, NVPF nanoparticles are uniformly encapsulated into the carbon nanofiber (CNF) by a simple electrospinning & annealing strategy. In the CNF@NVPF architecture, the CNF framework can provide structurally stable hosts for fast Na+ extraction/insertion and effective electron-transport channels. As a result, mechanical flexibility (multiple bending, rolling and twisting) and high Na-storage properties such as superior rate capability (20C) and high cycle stability (96% retention after 2000 cycles), are achieved. By employing CNF@NVPF as the battery-type cathode and ZnO-activated porous carbon nanofiber (pCNF) as the capacitor-type anode, a novel sodium-ion capacitor (SIC) is constructed with both high energy and powder densities (182.8 Wh kg−1 at 340 W kg−1 and 85.3 Wh kg−1 at 5898 W kg−1 based on the total mass of both electrodes), apparently superior to recently SIC counterparts in literature. Furthermore, the satisfactory mechanical flexibility and the low self-discharge rate are demonstrated in the pouch cell.

Recently, NiMoO4 has attracted much interest because of its high theoretical capacity and redox activity as lithium-ion batteries (LIBs). However, its applications are limited by its poor cycling stability and rate performance. In this paper, NiMoO4 nanofibers (NiMoO4-NFs) were fabricated via scalable electrospinning technique. The prepared NiMoO4-NFs were directly used as electrode materials without any current collector. Electrochemical tests demonstrated that the NiMoO4-NFs exhibited desired electrochemical performance including high reversible capacity (892.7 mA h g−1), superior long-term cycle stability and rate capacity (511 mA h g−1 at 1 A g−1 after 500 cycles). The electrochemical reaction mechanism was explored by using ex situ transmission electron microscopy. A two-phase reaction process was confirmed in the electrochemical reaction. The desired electrochemical properties made NiMoO4-NFs appropriate for the next generation of LIBs.

In this paper, broccoli-like multichannel FeCO3 microspheres were synthesized via one-pot hydrothermal process at low temperature. Then, a successful phase and morphology transformation from FeCO3 to Fe3O4 was realized to form the Fe3O4-RGO composites via a low temperature hydrolysis reaction in the presence of graphene and hydrazine. The multichannel structure of FeCO3 microspheres benefits for the permeation of alkaline solution, improves the dispersion of Fe2+ and further makes Fe3O4 homogeneously anchored on RGO sheets. Therefore, the Fe3O4-RGO composites show a satisfied property of 925.3 mAh g−1 at 100 mA g−1. Moreover, this anode material still delivers capacity of 636.1 mAh g−1 after 1000 cycles at 500 mA g−1. This work provides a new route for synthesizing metal oxide and their composites, which will find potential application in the field of energy storage.

Metallic selenides have been widely investigated as promising electrode materials for metal-ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger-sized Na+ /K+ greatly hamper their application. Herein, a bimetallic selenide (MoSe2 /CoSe2 ) encapsulated in nitrogen, sulfur-codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K-ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g-1 at 10 A g-1 in NIBs and 310 mAh g-1 at 5 A g-1 in KIBs. A combination of ex situ X-ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na+ /K+ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K+ diffusion kinetics than that of Na+ . More significantly, it shows excellent energy storage properties in Na/K-ion full cells when coupled with Na3 V2 (PO4 )2 O2 F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high-performance energy storage devices.

A three-dimensional hierarchical Ni3Se2 nanorod array (NA) grown in situ on foam Ni is the first to act as a carbon/binder-free electrode of SIBs via a one-step reversible conversion reaction. By a special decomposition-fusion process, the morphology and composition of the NA are regulated to obtain ultrahigh areal capacity, which is three times greater than that reported for other metal selenides.

Due to the Earth's scarcity of lithium, replacing lithium with earth-abundant and low-cost sodium for sodium-ion batteries (SIBs) has recently become a promising substitute for lithium-ion batteries. However, the shortage of appropriate anode materials limits the development of SIBs. Here, a dual-carbon conductive network enhanced GeP

Solid-state lithium metal batteries have emerged as a promising alternative to existing liquid Li-ion batteries and can power the future storage market considering their higher energy outputs and better safety. Among various solid electrolytes, polymer electrolytes have received more attention due to their potential advantages, including wide electrochemical windows, ease of processing, low interface impedance and low cost. Polymeric electrolytes based on poly(ethylene oxide) (PEO) as a well-known polymer matrix have been extensively studied because of their highly flexible EO segments in the amorphous phase that can provide channels for lithium ion transport. However, obtaining a PEO-based solid electrolyte with high Li ion conductivity and without sacrificing mechanical strength is still a huge challenge. In this study, polymethylhydrogen-siloxane (PMHS) with low glass transition temperature and good flexibility was blended into the PEO to optimize ion transportation by the solution casting technique. The hybrid electrolyte membrane with 40% PMHS exhibited high ionic conductivity (2.0 × 10-2 S cm-1 at 80 °C), large electrochemical windows (5.2 V), a high degree of flexibility, and thermal stability. When assembling a Li/LiFePO4 battery, a reversible capacity close to 140 mA h g-1 (0.1 C) at 60 °C was delivered. In addition, a cell with this polymer electrolyte exhibits excellent stability. These results demonstrate that solid polymer electrolyte systems are eligible for next-generation high energy density all-solid-state lithium ion batteries.

As a promising cathode material of sodium-ion battery, P2-type Na

As important anodes in lithium-ion batteries, graphene is always faced with the aggregation problem that makes most of the active sites lose their function at high current densities, resulting in low Li-ion intercalation capacity and poor rate performance. To address this issue, a layered g-C

In order to develop promising anode materials for sodium-ion batteries (SIBs), a novel pie-like FeS@C (P-FeS@C) nanohybrid, in which all ultrasmall FeS nanocrystals (NCs) are completely embedded into the carbon network and sealed by a protective carbon shell, has been prepared. The unique pie-like structure can effectively speed up the kinetics of electrode reactions, while the carbon shell stabilizes the FeS NCs inside. Studies show that the electrochemical reaction processes of P-FeS@C electrodes are dominated by the pseudocapacitive behavior, leading to an ultrafast Na+-insertion/extraction reaction. Hence, the prepared P-FeS@C nanohybrid exhibits superior Na-storage properties especially high rate capability in half cells. For example, it can deliver reversible capacities of 555.1 mA h g−1 at 0.2 A g−1 over 150 cycles and about 60.4 mA h g−1 at 80 A g−1 (an ultrahigh current density even higher than that of the capacitor test). Furthermore, an advanced P-FeS@C//Na3V2(PO4)2O2F full cell has been assembled out, which delivers a stable specific capacity of 441.2 mA h g−1 after 80 cycles at 0.5 A g−1 with a capacity retention of 91.8%.

F-Doped MnWO4 nano-particles were synthesized by a one-pot hydrothermal reaction. When evaluated as an electrode material for a Li ion battery, the F-doped nano-MnWO4 delivers a theoretical capacity of 708 mA h g-1 and a long cycle life, as demonstrated by more than 85% capacity retention when cycled for 150 cycles.

A new hexadecahedron assembled by core-shell CoS

In this work, the chemical interaction of cathode and lithium polysulfides (LiPSs), which is a more targeted approach for completely preventing the shuttle of LiPSs in lithium-sulfur (Li-S) batteries, has been established on the electrode level. Through simply posttreating the ordinary sulfur cathode in atmospheric environment just for several minutes, the Au nanoparticles (Au NPs) were well-decorated on/in the surface and pores of the electrode composed of commercial acetylene black (CB) and sulfur powder. The Au NPs can covalently stabilize the sulfur/LiPSs, which is advantageous for restricting the shuttle effect. Moreover, the LiPSs reservoirs of Au NPs with high conductivity can significantly control the deposition of the trapped LiPSs, contributing to the uniform distribution of sulfur species upon charging/discharging. The slight modification of the cathode with3 wt % Au NPs has favorably prospered the cycle capacity and stability of Li-S batteries. Moreover, this cathode exhibited an excellent anti-self-discharge ability. The slight decoration for the ordinary electrode, which can be easily accessed in the industrial process, provides a facile strategy for improving the performance of commercial carbon-based Li-S batteries toward practical application.

Polypyrrole nanospheres were embedded in graphene layers (rGCP) to successfully form three-dimensional hierarchical cross-linking structure through simple hydrothermal method. The structure of rGCP composite mainly resulted from the synergistic effect of cetyltrimethyl ammonium bromide and crumpled graphene layers, which was beneficial for achieving large surface area, short ion diffusion pathway, excellent rate performance and cycling stability. As a result, the hybrid rGCP composite exhibited excellent electrochemical performance with a specific capacitance of almost 400 F g −1 at the scan rate of 1 mV s −1 . Furthermore, even at the high current density of 10 A g −1 , it still retained the capacitance of 243.2 F g −1 , and excellent cycling stability (91.8% capacitance retention even after 5000 cycles). The as-prepared hierarchical hybrid composite has promising potential in electrochemical energy storage.

LiNi 1/3 Co 1/3 Mn 1/3 O 2 is successfully coated with MnO 2 by a chemical deposition method. The X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) results demonstrate that MnO 2 forms a thin layer on the surface of LiNi 1/3 Co 1/3 Mn 1/3 O 2 without destroying the crystal structure of the core material. Compared with pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , the MnO 2 -coated sample shows enhanced electrochemical performance especially the rate capability. Even at a current density of 750 mA g −1 , the discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 is 155.15 mAh g −1 , while that of the pristine electrode is only 132.84 mAh g −1 in the range of 2.5–4.5 V. The cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) curves show that the MnO 2 coating layer reacts with Li + during cycling, which is responsible for the higher discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Electrochemical impedance spectroscopy (EIS) results confirmed that the MnO 2 coating layer plays an important role in reducing the charge transfer resistance on the electrolyte–electrode interfaces.

A superior Na3 V2 (PO4 )3 -based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most-common chelator, disodium ethylenediamintetraacetate [Na2 (C10 H16 N2 O8 )], as both sodium and nitrogen-doped carbon sources for the first time. 2D-reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium-ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high-rate capabilities and prolonged cycling life compared to the pristine NVP and single-carbon-modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g(-1) , which is obviously higher than 106 and 112.3 mAh g(-1) for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g(-1) even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP-based cathodes including the apparent Na diffusion coefficients and charge-transfer resistances.

In recent years, graphene-incorporated micro-/nanocomposites represent one of the hottest developing directions for the composite materials. However, a large number of active nanoparticles (NPs) are still in the unprotected state in most constructed graphene-containing designs, which will seriously impair the effects of the graphene additives. Here, a fully protected Fe3O4-based micro-/nanocomposite (G/Fe3O4@C) is rationally developed by carbon-boxing the common graphene/Fe3O4 microparticulates (G/Fe3O4). The processes and results of full protection are tracked in detail and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen absorption–desorption isotherms, as well as scanning and transition electron microscopy. When used as the anode for lithium-ion batteries, the fully protected G/Fe3O4@C exhibits the best lithium-storage properties in terms of the highest rate capabilities and the longest cycle life compared to the common G/Fe3O4 composites and commercial Fe3O4 products. These much improved properties are mainly attributed to its novel structural features including complete protection of active Fe3O4 nanoparticles by the surface carbon box, a robust conductive network composed of nitrogen-doped graphene nanosheets, ultra-small Fe3O4 NPs of 4–5 nm, abundant mesopores to accommodate the volume variation during cycling, and micrometer-sized secondary particles.

We have developed a facile and mass-producible strategy named electric discharge method to successfully improve the surface properties of Cu foils with rough carbon layer. Electrochemical tests in half-cells demonstrate that the coated carbon layer can significantly reduce the polarization resistance and enhance the reversible capacity of graphite anode when utilizing the Cu foils as current collector for lithium ion batteries. More importantly, the developed carbon coated Cu anode current collector can also improve the overall performances of LiFePO 4 full cells in terms of enhanced rate capability (from 887.9 to 946.3 mAh at 4C rate), reduced polarization voltage (11.7 mV lower at 4C rate), longer cycle life (about 650 increased cycles if taking 80 % capacity retention as the end of cycle life when used at 1 C rate) as well as improved low-temperature performance (capacity retention: 42.87% vs. 38.85% at -20 °C).

Recently, room temperature sodium ion batteries (SIBs) have been considered as one of the optimal alternatives for lithium ion batteries although there are still many challenges to be solved. At the present stage, the research priorities for SIBs still focus on the development of various electrode materials to meet the applicability. In this communication, we have controllably prepared a superior anode material (disodium terephthalate, Na 2 C 8 H 4 O 4 ) with nanosheet-like morphology, which exhibits much improved electrochemical properties in terms of larger reversible capacity (248 mA h/g vs. 199 mA h/g), higher rate capabilities (for instance, 1.55 times the bulk material at 1250 mA/g) and better cycling performance (105 mA h/g vs. 60 mA h/g after 100 cycles at 250 mA/g) in comparison with the bulk one prepared at the similar system without the addition of polar solvent dimethylformamide. More importantly, it is further disclosed that, these enhanced performances could be mainly due to the new one-step desodiation mechanism and optimized ionic/electronic transfer pathways in the nanosheet system through the analyses of ex-situ infrared spectra, cyclic voltammogram, galvanostatic curves, scanning electron microscope images and electrochemical impedance spectroscopy.

It can clear the various economic factors in the process of the implementation of the small towns heating to establish small town heating economic model. It comes down to the total economic cost of small towns heating under the condition of different fuel types to analyze the parameters in the mode with different fuels according to the heating process. When some kind of fuel is used, by calculating we can conclude that the lowest heating cost contributes to use of economical fuels in the region.

Mesoporous SiO2 nanospheres (MSNs) and carbon nanocomposite with dual-porosity structure (DMSNs/C) were synthesized via a straightforward approach. Both MSNs and DMSNs/C showed uniform pore size distribution, high specific surface area, and large pore volume. When evaluated as an anode material for lithium ion batteries (LIBs), the DMSNs/C nanocomposite not only delivered an impressive reversible capacity of 635.7 mAh g–1 (based on the weight of MSNs in the electrode material) over 200 cycles at 100 mA g–1 with Coulombic efficiency (CE) above 99% but also exhibited excellent rate capability. The significant improvement of the electrochemical performance was attributed to synergetic effects of the dual-mesoporous structure and carbon coating layer: (i) the dual-porosity structure could increase the contact area and facilitate Li+ diffusion at the interface between the electrolyte and active materials, as well as buffer the volume change of MSNs, and (ii) the homogeneous carbon coating represented an excell...