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To significantly improve the electrochemical performance of tin-based materials as anodes for lithium ion batteries, hybridizing tin-based nanomaterials with carbon is an effective way. This is due to carbon materials serving not only as conductive networks to increase the electrical conductivity, but also as construct void to buffer volume expansion. However, the use of excess carbon in hybrids and the low lithium storage ability of the carbon could lead to the reduced total capacity of the electrode. Herein, we develop a simple and effective approach to the synthesis of EG/SnO2-x in which SnO2 nanoparticles are tightly anchored on the surface of expanded graphite (EG) with well-defined expanded structures and highly conductive frameworks. Benefiting from the rational mass loading of SnO2, as well as the high conductivity and strong lithium storage characteristic of EG, the EG/SnO2-3 hybrid displays outstanding electrochemical performance with excellent rate capability (e.g., 406.3 mAh g–1 at 1 A g−1) and long cycling stability (e.g., 262.7 mAh g−1 over 500 cycles). In particular, the large proportion of capacity secured from a narrow voltage range of 0.01–0.3 V, corresponding to a low average working potential, is vital for the hybrids applied in high voltage full-cell LIBs.

Rational design of carbon materials for electrochemical devices has attracted great attentions over the past decades. Doping carbon with heteroatoms has been widely proven to be an effective way to improve the physical and electrochemical properties of carbon. The selective types and doping level of heteroatoms, as well as simple and green doping routes, are keys to the development of heteroatoms doped carbon. Due to a strong synergistic effect generated by the co-doping of boron (B) and nitrogen (N), B, N co-doped carbon materials have been demonstrated to be promising catalysts for multiple electrochemical devices. Herein, we report an eco-friendly and one-step approach to synthesis of B, N co-doped graphene (B, N-G) using BN as B and N doping resources. The decomposition of BN under a controlled flow of water steam at high temperature not only enables a high-level B and N co-doping into carbon but also facilitates the formation of highly active catalytic sites. Benefiting from high co-doping level of heteroatoms and highly active catalytic sites (e.g., BC2O), the B, N-G as cathode for rechargeable lithium oxygen batteries displays outstanding lithium storage properties with an ultrahigh specific capacity of 18222 mAh g−1 at 100 mA g−1 and good cycling stability with a limited specific capacity of 1000 mAh g−1 over 120 cycles at 1 A g−1.

The big challenge for practical lithium metal batteries is how to make full and reversible utilization of lithium anode. The preformed three-dimensional (3D) porous framework with numerous lithium nucleation sites is able to guide the lithium deposition in the cavity of 3D framework, suppressing the dendrite growth and dimensional change. Herein, we design a nanocapsule structure for lithium metal anodes consisting of 3D graphene with MgxLiy seeds inside. The 3D composite anode not only can be prepared in a simple and scalable process, but also can meet the requirements for both high energy density and long cycle life in the practical cells. During the observation of lithium deposition by transmission electron microscope, it was found that lithium metal was mainly deposited around the MgxLiy seeds within 3D graphene. Thereafter, when the composite anodes are well paired with the commercial LiFePO4 cathodes in coil cells and NCM811 (LiNi0.8Co0.1Mn0.1O2) cathodes in pouch batteries, they are able to deliver the energy density exceeding 350 ​Wh·kg−1 and long cycle life (>150 cycles) with high energy retention (>85%). The 3D lithium metal/graphene composite anode in the present work provides a promising new avenue for the fabrication of high energy density Li-metal batteries.

Although lithium ion batteries (LIBs) hold great promise as a next generation power supply, the poor rate capability of the graphite that is mainly used as the battery anode limits high-performance LIBs. Compared to other reported carbon-based materials, however, its relatively low average working voltage still makes it attractive. Herein, we were able to introduce carbon disulfide (CS2) at the edges of graphene nanoplatelets (GnPs) with rich –C=S/-C-S bonds via ball-milling graphite in the presence of CS2. The resultant edge-thionic acid-functionalized GnPs (TAGnPs) exhibited a larger accessible surface area and smaller particle size than pristine graphite. Importantly, the TAGnPs retained a long-range-ordered layered structure similar to pristine graphite. When the TAGnPs were used as anode materials for LIBs, they displayed superior rate capability (e.g., high average reversible capacities of 228.3, 208.1, 141.0 and 80.6 mAh g−1 at 0.5, 1, 2 and 5 A g−1, respectively) compared to pristine graphite and the reference edge-hydrogenated GnPs (HGnPs), which mainly have -C-H bonds at their edges. Theoretical calculations also indicated that the presence of –C=S/-C-S bonds at the edges of TAGnPs enabled stronger Li+ adsorption capability.

This paper reports the rational design and synthesis of a novel electron-withdrawing building block, thiazole flanked naphthalene diimide (TzNDI), which offers a coplanar conformation and deep-lying highest-occupied molecular orbitals energy level in resulting conjugated polymers. A series of conjugated polymers (PTzNDI-2FT, PTzNDI-T, PTzNDI-Se, and PTzNDI-2T) consisting of TzNDI and different donor units were synthesized and characterized. The polymers all possess a high molecular weight and excellent thermal property. Their intense light absorption in low energy bands suggests an enhanced intramolecular charge transfer. The organic field-effect transistors (OFETs) based on these polymers exhibit unipolar n-type transport characteristics with low off current and high on–off current ratio. More importantly, all the devices exhibit near ideal transfer curves with kink-free transfer characteristics. Among these polymers, PTzNDI-2FT exhibits the highest electron mobility (μe) of 0.57 cm2 V–1 s–1, outperformi...

A (MoS2/carbon fiber (CF))@MoS2@C hybrid has been prepared by an efficient method combining the electrospinning, hydrothermal and annealing techniques. Coupled with graphite as cathode, the hybrid enables the full cell (i.e., dual ion batteries) to deliver a high initial discharge capacity of 112.3 mAh g−1 at 0.2 A g−1 and maintain a high reversible capacity of 90.5 mAh g−1 at 0.5 A g−1 after 500 cycles. These remarkable sodium storage properties of (MoS2/CF)@MoS2@C are mainly attributed to its three-dimensional framework with its highly conductive, cross-linked structure, which effectively increases the conductivity of the hybrid and the mass loading of MoS2. Moreover, the MoS2 nanoplates embedded inside CF, as well as being sandwiched between the CF/MoS2 and a thin carbon layer, also can effectively buffer the pulverization and aggregation of the electrode, and thus maintain the structural integrity of (MoS2/CF)@MoS2@C during the charge-discharge process.

Heteroatoms doped carbon based materials with enhanced catalytic properties hold great potential in energy storage applications, including rechargeable lithium oxygen batteries (LOBs). However, large-scale production of heteroatoms co-doped carbon with high-level dopants as well as the precise control of uniformly distributed dopant location remain challenges. Holey graphene as an emerging carbon based material has attracted increased attention as cathode for LOBs due to its nanoholes through the graphene nanosheet basal plane. Apart from the given rapid diffusion channels for mass (e.g., O2 and Li+ ), the nanoholes also provide rich egdes for the mass adsorption and storage as well as the heteroatoms doping. Herein, we report an environment-friendly and simple approach to mass production of hG with abundant in-plane nanoholes via direct oxidation of reduced graphene oxides (rG) by a controlled flow gas of H2O. Based on the obtained hG, 3.0 at.% B and 2.1 at.% N atoms are further co-doped into the hG to form B, N-hG. Benefiting from its holey structures and the synergistic effect of B and N, the B, N-hG as cathode for LOBs displays promising properties with a maximum discharge capacity of 15340 mAh g−1 and long cycling stability over 117 cycles.

Sodium ion batteries (SIBs) have attracted increasing attention as one of the most promising candidates for cost-effective, high-energy rechargeable batteries. Owing to their high theoretical capacity and energy density, and rich electrochemical interaction with Na+ (V2+–V5+), a large number of vanadium(V)-based cathode materials, including vanadium oxides (e.g., V2O5 and VO2), vanadium bronzes (e.g., NaxVO2, NaV3O8, NaV6O15 and δ-NH4V4O10), V-based phosphates (e.g., Na3V2(PO4)3, VOPO4, NaVOPO4, Na7V3(P2O7)4 and Na2(VO)P2O7) and F-containing V-based polyanions (e.g., NaVPO4F, Na3V2(PO4)2F3 and Na3(VOx)2(PO4)2F3−2x), have been explored for SIBs. In this review, we mainly summarize the basic structures, modified/optimized structures, synthetic methods and morphology control of V-based cathode materials for SIBs. Additionally, major drawbacks, emerging challenges and some perspectives on the development of V-based cathode materials for SIBs are also discussed.

Lithium iodide (LiI) as cathode for lithium-iodine (Li-I 2 ) batteries hold great promise compared to I 2 mainly owing to its greater merits, including its potential pairing with a lithium-metal-free anode and only ~5% decrease in theoretical capacity. LiI confined within the meso-micro porous carbon polyhedrons (LiI@MCP) as cathode for Li-I 2 batteries has been studied for the first time. Benefiting from the rich meso-/micro-porous structures and highly conductive frameworks of MCP, the LiI@MCP with uniform distribution of LiI displays high reversible capacity, good rate abilities and superior long cycling life at 2C over 800 cycles with a low capacity decaying rate (0.021% per cycle). This work will open a new paradigm for the use of LiI as cathode for high-performance Li-I 2 batteries.

Solar-driven photoelectrochemical (PEC) water splitting is a clean and powerful approach for renewable hydrogen production. The PEC performance of hematite (α-Fe 2 O 3 ) is largely limited by its short hole diffusion length, which imposes restrictions on increasing the thickness for enough light absorption. In this work, we report a well-engineered three-dimensional (3D) Fe 2 O 3 /NTO (Nb-doped SnO 2 ) nanobowl heterojunction for PEC electrode, driven by a high-photovoltage perovskite solar cell (PSC), has boosted the efficiency greatly. The 3D heterojunction is made of an ultrathin Ti-doped hematite layer deposited on a periodic NTO nanobowl array. This PEC electrode, not only significantly improves the light absorption of the ultrathin hematite, but also enhances the interface contact. As a result, it exhibits ∼3.16 mA cm −2 photocurrent at 1.23 V vs the reversible hydrogen electrode with the Co–Pi cocatalyst. The tandem cell self-biased with a high-photovoltage PSC delivers up to 3.25% solar-to-hydrogen conversion efficiency, higher than those of state-of-the-art hematite-based PEC cells.

Metal-air batteries, especially Li-air batteries, have attracted significant research attention in the past decade. However, the electrochemical reactions between CO2 (0.04 % in ambient air) with Li anode may lead to the irreversible formation of insulating Li2CO3, making the battery less rechargeable. To make the Li-CO2 batteries usable under ambient conditions, it is critical to develop highly efficient catalysts for the CO2 reduction and evolution reactions and investigate the electrochemical behavior of Li-CO2 batteries. Here, we demonstrate a rechargeable Li-CO2 battery with a high reversibility by using B,N-codoped holey graphene as a highly efficient catalyst for CO2 reduction and evolution reactions. Benefiting from the unique porous holey nanostructure and high catalytic activity of the cathode, the as-prepared Li-CO2 batteries exhibit high reversibility, low polarization, excellent rate performance, and superior long-term cycling stability over 200 cycles at a high current density of 1.0 A g−1. Our results open up new possibilities for the development of long-term Li-air batteries reusable under ambient conditions, and the utilization and storage of CO2.

A highly efficient and continuous high-pressure homogenization (HPH) approach is developed for scalable production of graphene sheets and sandwich-structured α-Fe2O3/graphene hybrids by liquid-phase exfoliation of stage-1 FeCl3-based graphite intercalation compounds (GICs). The enlarged interlayer spacing of FeCl3-GICs facilitates their efficient exfoliation to produce high-quality graphene sheets. Moreover, sandwich-structured α-Fe2O3/few-layer graphene (FLG) hybrids are readily fabricated by thermally annealing the FeCl3 intercalated FLG sheets. As an anode material of Li-ion battery, α-Fe2O3/FLG hybrid shows a satisfactory long-term cycling performance with an excellent specific capacity of 1100.5 mA h g–1 after 350 cycles at 200 mA g–1. A high reversible capacity of 658.5 mA h g–1 is achieved after 200 cycles at 1 A g–1 and maintained without notable decay. The satisfactory cycling stability and the outstanding capability of α-Fe2O3/FLG hybrid are attributed to its unique sandwiched structure consisti...

Phosphorus has recently received extensive attention as a promising anode for lithium ion batteries (LIBs) due to its high theoretical capacity of 2,596 mAh·g–1. To develop high-performance phosphorus anodes for LIBs, carbon materials have been hybridized with phosphorus (P-C) to improve dispersion and conductivity. However, the specific capacity, rate capability, and cycling stability of P-C anodes are still less than satisfactory for practical applications. Furthermore, the exact effects of the carbon support on the electrochemical performance of the P-C anodes are not fully understood. Herein, a series of xP-yC anode materials for LIBs were prepared by a simple and efficient ball-milling method. 6P-4C and 3P-7C were found to be optimum mass ratios of x/y, and delivered initial discharge capacities of 1,803.5 and 1,585.3·mAh·g–1, respectively, at 0.1 C in the voltage range 0.02–2 V, with an initial capacity retention of 68.3% over 200 cycles (more than 4 months cycling life) and 40.8% over 450 cycles. The excellent electrochemical performance of the 6P-4C and 3P-7C samples was attributed to a synergistic effect from both the adsorbed P and carbon.

Li–air batteries represent cutting edge electrochemical energy storage devices, but their practical applications have been precluded by the high cathode cost, the low discharge/charge efficiency, and/or the short battery lifetime. Here, we developed a low-cost, but very efficient, air electrode from porous nitrogen-doped holey graphene for rechargeable nonaqueous Li–O2 cells. The resultant Li–O2 cell can deliver a high round-trip efficiency (85%) and a long cycling life (>100 cycles) under controlled discharge/charge depths or a high capacity of 17 000 mAh/g under the full discharge/charge condition, superior to most other carbonaceous air cathodes. The observed superb performance for the air electrode based on the nitrogen-doped holey graphene can be attributed to its efficient metal-free catalytic activity and three-dimensional mass transport pathway. Therefore, this work represents a new approach to low-cost, efficient, metal-free, binder-free, and hierarchically porous air electrodes useful for energy...

Three-dimensional heterostructured NiCo2O4@MnMoO4 nanocolumn arrays (NCAs) on Ni foam were first fabricated through an improved two-step hydrothermal process associated with a successive annealing treatment. The hybrid NiCo2O4@MnMoO4 electrode exhibited remarkable pseudocapacitor property with high initial mass specific capacitance of 1705.3 F g(-1) at 5 mA cm(-2), and retained 92.6% after 5000 cycles, compared to the bare NiCo2O4 electrode with 839.1 F g(-1) and 90.9%. The excellent capacitive property of the NiCo2O4@MnMoO4 hydrid was attributed to its high-electron/ion-transfer rate, large electrolyte infiltrate area, and more electroactive reaction sites.

Electrocatalysts for the oxygen reduction reaction (ORR) play a crucial role in renewable-energy technologies, including metal-air batteries and fuel cells. However, development of novel catalysts with high activity and low cost remains a great challenge. Here, we present hierarchical MnO 2 /reduced graphene oxide (MnO 2 /rGO) hybrid nanosheets by using a facile method and study its electrocatalytic performance. Cyclic voltammograms, and rotating disk electrode and rotating ring/disk electrode measurements demonstrate that the hierarchical MnO 2 /rGO hybrid nanosheets exhibit excellent electrocatalytic activity for the ORR in an alkaline medium, as evidenced by their higher cathodic current density, more positive onset potential, lower H 2 O 2 yield, and higher electron transfer number compared to pure rGO. The excellent catalytic activity of the MnO 2 /rGO hybrid nanosheets highlights the importance of the synergetic chemical coupling effect between the ultrathin MnO 2 nanosheets and the graphene layer.

Carbon materials as promising anodes for lithium ion batteries (LIBs) have attracted great attentions owing to their high theoretical capacities and rich natural resources. To improve anode performance of carbon, several common strategies have been developed, such as the fabrication of carbon with various nanostructures and modification of carbon frameworks by heteroatoms doping. Besides, the introduction of transition metal single atom or atom clusters embedded in nitrogen-doped carbon frameworks is also a feasible route. Herein, we report a simple and effective approach for synthesis of Con@N-C hybrids (i.e., Co@N-C-0, Con@N-C-1 and Con@N-C-2) with interconnected porous carbon nanostructures and numerous active sites (e.g., Co-N-C). When it was measured as anode for LIBs, the Con@N-C-1 hybrid displayed outstanding lithium storage properties with a high initial reversible capacity of 1587 mAh g−1 at 0.1 C and maintained a high reversible capacity of 1000 mAh g−1 at 5 C after 800 cycles. Both experimental and theoretical results reveal that Co-N-C with high specific activity along with interconnected porous carbon nanostructures synergistically promote the transportation and storage of Li+.

3d transition metals have been investigated as active centers in Ni(OH)2 to catalyze oxygen evolution reaction (OER), while conflicts of mechanism still exist. Herein, we studied how Ni, Co and Fe determine the OER activity in atomically thin Ni(OH)2 via experiments and theoretical calculations. The results show that both Co and Fe, with enhanced density of states near the Fermi level, decrease the overpotential by increasing the binding energy of O* and consequently exhibit higher catalytic activities than Ni. In particular, Fe, with nearly optimal O* binding energy, exhibits the lowest overpotential of 181 mV to reach 50 mA cm-2. In the case of CoFe co-doping, Co alters the electronic states of Fe, which weakens the Fe-OOH bond and slightly increases the overpotential. Based on the calculated activities, an overpotential contour plot is constructed, providing guidance for rational catalyst design via modulating electronic structures and intermediate binding energies.

Electrochemical and photocatalytic water splitting provide great opportunities to meet the increasing demands of energy and, also environmental concerns. Efficiency of the two systems is highly dependent on the electrocatalysts and photocatalysts. Carbon-based materials that own unique advantages including diversity of structure, good electrical conductivity, and a combination of mechanical strength and lightness have been widely investigated in water splitting. In this chapter, we review the recent development in this research field. We start with the introduction of fundamentals of electrochemical and photoelectrochemical water splitting (e.g., photoexcitation process, hydrogen evolution reaction, and oxygen evolution reaction), followed by surveying various forms of carbon-based materials and their applications in electrochemical and photoelectrochemical water splitting. In particular, we analyze the performance enhancement mechanisms to elicit fundamental insights. Additionally, we briefly outline the challenges and prospects of this research field.

Antimony- (Sb) based materials have been considered as one of promising anodes for sodium ion batteries (SIBs) owing to their high theoretical capacities and appropriate sodium inserting potentials. So far, the reported energy density and cycling stability of the Sb-based anodes for SIBs are quite limited and need to be significantly improved. Here, we develop a novel Sb/C hybrid encapsulating the Sb nanorods into highly conductive N and S codoped carbon (Sb@(N, S–C)) frameworks. As an anode for SIBs, the Sb@(N, S–C) hybrid maintains high reversible capacities of 621.1 mAh g–1 at 100 mA g–1 after 150 cycles, and 390.8 mAh g–1 at 1 A g–1 after 1000 cycles. At higher current densities of 2, 5, and 10 A g–1, the Sb@(N, S–C) hybrid also can display high reversible capacities of 534.4, 430.8, and 374.7 mAh g–1, respectively. Such impressive sodium storage properties are mainly attributed to the unique cross-linked carbon networks providing highly conductive frameworks for fast transfer of ions and electrons, a...

Amorphous nitrogen-doped carbon nanosheets was synthesized through thermal decomposition of ethylenediaminetetraacetic acid manganese disodium salt hydrate (C 10 H 12 N 2 O 8 MnNa 2 ⿿2H 2 O). The as-synthesized nitrogen-doped carbon nanosheets were characterized by X-ray diffraction, scanning electron microscopy, transition electron microscopy and X-ray photoelectron spectroscopy. The N content of the as-synthesized carbon nanosheets could reach as high as 11.77 at.%, with an especially high total of 7.94 at.% pyridinic N pluspyrrolic N. When tested as anode material for lithium ion batteries, the optimized carbon nanosheets exhibited high capacity, excellent rate capability, and stable cyclability over 600 cycles. The specific capacity was still as high as 465.8 mAh g ⿿1 at 0.5 C after 600 cycles,with a capacity decay from the 2nd cycle of 0.05% per cycle over 599 cycles. The excellent performance of C-600 is attributed to a synergistic effect of high surface area, numerous nanopores, high thermal stability, and low charge transfer resistance.

Sb/Cu2Sb/C composites are synthesized via a thermolysis approach with copper citrate and antimony acetate as precursors, respectively. The as-synthesized composites display an initial reversible capacity of 602 mA h g−1 and maintain 461 mA h g−1 after 60 cycles. The excellent electrochemical performance of the Sb/Cu2Sb/C composites can be ascribed to the presence of Sb/Cu2Sb and amorphous carbon layers. The amorphous carbon layers could prevent the damage of electrodes that resulted from large volume expansion. The Sb/Cu2Sb improves their electronic conductivity.

Nitrogen-doped holey graphene (N-hG) as an anode material for lithium-ion batteries has delivered a maximum volumetric capacity of 384 mAh cm(-3) with an excellent long-term cycling life up to 6000 cycles, and as an electrochemical capacitor has delivered a maximum volumetric energy density of 171.2 Wh L(-1) and a volumetric capacitance of 201.6 F cm(-3) .

Graphene-like nanomaterials have received tremendous research interest due to their atomic thickness and fascinating properties. Previous studies mainly focus on the modulation of their electronic structures, which undoubtedly optimizes the electronic properties, but is not the only determinant of performance in practical applications. Herein, we propose a generalized strategy to incrementally manipulate the architectures of several atomically thin transition metal (hydr)oxides, and study their effects on catalytic water oxidation. The results demonstrate the obvious superiority of a wrinkled nanosheet architecture in both catalytic activity and durability. For instance, wrinkled Ni(OH)2 nanosheets display a low overpotential of 358.2 mV at 10 mA cm–2, a high current density of 187.2 mA cm–2 at 500 mV, a small Tafel slope of 54.4 mV dec–1, and excellent long-term durability with gradually optimized performance, significantly outperforming other nanosheet architectures and previously reported catalysts. Th...

Numerous efforts have been devoted to developing high-performance graphene-based electrodes for application in advanced electrochemical energy storage systems (e.g., lithium ion batteries (LIBs) and sodium ion batteries (SIBs)), including modified graphene with various structures and types of heteroatom doping, as well as their related composite-/hybridized-electrode materials. Owing to their outstanding characteristics (large surface area, high electronic conductivity, high charge carrier mobility, great mechanical strength, and high theoretical capacity), graphene-based electrodes have been widely demonstrated to show improved and diverse properties for LIBs and SIBs in terms of high specific capacity, high rate capability, long cycling life, and flexible-battery structures. In this chapter, we briefly provide an overview of the significant progress achieved on graphene-based electrodes (including both cathodes and anodes) for application in LIBs and SIBs over the past decade. Moreover, despite the impressive improved electrochemical performance reported for LIBs and SIBs, emerging challenges and some perspectives on the use of graphene-based electrodes for future LIB and SIB applications are also presented in this chapter.

Edge-selectively fl uorinated graphene nanoplatelets (FGnPs) are prepared by mechanochemically driven reaction between fl uorine gas (20 vol% in argon) and activated carbon species from graphitic C‐C bonds unzipped by high-speed stainless steel balls with a high kinetic energy. The fl uorination at edges of the unzipped graphene nanoplatelets (GnPs) is confi rmed by various analytical techniques while the content of flin FGnPs is determined to be 3.0 and 3.4 at% by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy, respectively. Because of the large difference in electronegativity between carbon ( χ = 2.55) and fl uorine ( χ = 3.98) and the strong C‐F bond, the edge-fl uorination of GnPs can provide the maximized charge polarization with an enhanced chemical stability. Thus, electrodes based on the resultant FGnPs demonstrate superb electrochemical performance with excellent stability/cycle life in dye-sensitized solar cells (FF: 71.5%; J sc : 14.44 mA cm −2 ; V oc : 970 mV; PCE: 10.01%) and lithium ion batteries (650.3 mA h g −1 at 0.5 C, charge retention of 76.6% after 500 cycles).

In this work, amorphous carbon very thin layers coated on a Nb2O5 nanosheet flexible composite have been successfully synthesized. The composite delivers a discharge capacity of 396 mA h g−1 after 100 cycles at a current density of 100 mA g−1, which is very much higher than for bare Nb2O5 nanosheets.

Layered MoS2 has attracted much attention as a promising anode material for lithium ion batteries. The intrinsically poor electrical/ionic conductivity, volume expansion and pulverization, stress accumulation and unstable solid–electrolyte interface formation within MoS2 electrodes during the lithiation–delithiation process significantly result in their fast capacity fading, poor rate capability and cycle life. To address these critical issues, a novel nanobowl structure for MoS2 with a carbon coating (MoS2@C-400, 500, 600) is successfully fabricated by a facile solvothermal method, followed by a post-annealing process. The fabricated MoS2@C-600 and MoS2@C-500 exhibited high reversible capacities of 1164.4 and 1076.4 mA h g−1 at 0.2C, and maintained high capacity retention of 72.1% and 78.4% over 150 cycles, respectively. Such remarkable lithium storage properties are attributed to the unique nanobowl structure, which provides a large accessible surface area and high pore volume, and flexible carbon film coating, allowing for easy diffusion of electrolyte, alleviation of volume expansion, formation of stable solid electrolyte interfaces and fast diffusion of lithium ions.

MoO3@C nanofibers have been successfully synthesized by electrospinning the Mo precursor with polyvinyl pyrrolidone (PVP), followed by annealing. When tested as an anode material, the as-synthesized MoO3@C nanofibers could deliver a high discharge capacity of 623 mA h g−1 after 100 cycles at 500 mA g−1, and 502 mA h g−1 even at 1000 mA g−1.

Novel layered 2D frameworks (C3N and C2N-450) with well-defined crystal structures are explored for use as anode materials in lithium-ion batteries (LIBs) for the first time. As anode materials for LIBs, C3N and C2N-450 exhibit unusual electrochemical characteristics. For example, C2N-450 (and C3N) display high reversible capacities of 933.2 (383.3) and 40.1 (179.5) mAh g−1 at 0.1 and 10 C, respectively. Furthermore, C3N shows a low hypothetical voltage (≈0.15 V), efficient operating voltage window with ≈85% of full discharge capacity secured at >0.45 V, and excellent cycling stability for more than 500 cycles. The excellent electrochemical performance (especially of C3N) can be attributed to their inherent 2D polyaniline frameworks, which provide large net positive charge densities, excellent structural stability, and enhanced electronic/ionic conductivity. Stable solid state interface films also form on the surfaces of the 2D materials during the charge/discharge process. These 2D materials with promising electrochemical performance should provide insights to guide the design and development of their analogues for future energy applications.

Lithium‐ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium‐ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated‐graphite for LIBs, but also an effective strategy to develop diverse high‐energy batteries for stationary energy storage in the future.

Edge-selectively halogenated graphene nanoplatelets (XGnPs, X = Cl, Br, or I) are prepared by a simple mechanochemical ball-milling method, which allows low-cost and scalable production of XGnPs as highly stable anode materials for lithium-ion batteries.

A series of Li 2 Fe 1-3 x /2 V x P 2 O 7 ( x = 0, 0.025, 0.05, 0.075, and 0.1) cathode materials for LIBs were prepared by the sol-gel method. Structural characterization of Li 2 Fe 1-3 x /2 V x P 2 O 7 ( x = 0, 0.025, 0.05, 0.075, and 0.1) samples was conducted by synchrotron X-ray diffraction. The morphology and oxidation states of Fe 2+ and V 3+ in the Li 2 Fe 1-3 x /2 V x P 2 O 7 samples were confirmed by scanning electron microscopy and magnetic susceptibility measurements, respectively. The electrochemical measurements indicated that Li 2 Fe 1-3 x /2 V x P 2 O 7 ( x = 0.025) delivered the higher reversible capacity of 79.9 mAh g −1 at 1 C in the voltage range of 2.0 - 4.5 V with higher 77.9% capacity retention after 300 cycles than those of Li 2 FeP 2 O 7 (48.9 mAh g −1 and 72.6%). Moreover, the rate capability of Li 2 Fe 1-3 x /2 V x P 2 O 7 ( x = 0.025) were also significantly enhanced through vanadium substitution to iron of Li 2 Fe 1-3 x /2 V x P 2 O 7 . The vanadium substituted to Fe2 site of Li 2 FeP 2 O 7 decreases Li occupying the Li5 position in the FeO 5 unit, leading to a low degree exchange between Li and Fe in the MO 5 (M = Li and Fe). The low degree cation disorder was beneficial to lithium-ion extraction/insertion during the charge-discharge process and hence enhances the capacity and rate capability.

A series of nitrogen-containing polymer and carbon spheres were obtained by the sol–gel method. In particular, the nitrogen-rich carbon spheres were prepared by one-pot hydrothermal synthesis in the presence of resorcinol/formaldehyde as carbon precursors and ethylenediamine (EDA) as both a base catalyst and nitrogen precursor, followed by carbonization in nitrogen and activation with CO2. The introduction of EDA to the sol–gel system resulted in structurally bonded nitrogen-containing carbon spheres. The nitrogen doping level and the particle size can be tuned by varying the EDA amount in the reaction mixture. The maximum nitrogen doping level of 7.2 wt % in carbon spheres could be achieved without sacrificing the spherical morphology. The diameter of these carbon spheres (CS) can be tuned in the rage of 50–1200 nm by varying the EDA amount. N2 adsorption analysis showed that the aforementioned activated carbon spheres exhibited high surface area reaching up to1224 m2/g. Ultra high CO2 adsorption capacit...

The improvement of the high-efficiency electrode materials for lithium ion batteries is one of the research priorities. The research on the carbon with M − N active sites (M-N-C) as anodes for lithium ion batteries is still quite rare. Herein, we report a series of highly crystalline M@C2N hybrids in which the metal (M = Ru, Pd and Co) are uniformly embedded in the two-dimensional C2N networks. Together with the unique structural features (e.g., uniform two-dimensional nanohole structure, high surface area and enlarged distance between C2N nanosheets), rich N-M coordination homogenously distributing through the M@C2N structure are favorable for the brisk infiltration of electrolyte, swift transportation of Li+/electrons and more storage of Li+, thereby leading to the superior lithium storage properties.

A high performance Li3V2(PO4)3 cathode material for lithium ion batteries was synthesized by the microwave-assisted hydrothermal method followed by a post annealing process. The synchrotron X-ray diffraction analysis results confirmed that single-phase Li3V2(PO4)3 with monoclinic structure was obtained. Scanning electron microscope and transmission electron microscope images revealed that the as-prepared Li3V2(PO4)3 was composed of nanowires and microsized particles. Electrochemical results demonstrated that the Li3V2(PO4)3 electrode measured at 10 C after 500 cycles can deliver discharge capacities of 85.4 mAh g−1 and 103.4 mAh g−1, with a capacity retention of 99.3% and 95.9%, in the voltage ranges of 3.0–4.3 V and 3.0–4.8 V, respectively, indicating good cycling stability. Furthermore, the electrochemical performance of Li3V2(PO4)3 in ionic liquid electrolytes between 3.0 V and 4.8 V was also measured.

The recent progress and future development of cathode materials for lithium ion batteries have been critically reviewed in this article. We have given some critical opinions and rational ideas regarding the development of cathode materials to dramatically reduce the cost and increase the efficiency of future lithium ion batteries, which will revolutionize the way for transportation and affect many aspects of our lives.

A hybrid electrolyte energy storage system combining the features of supercapacitors and lithium batteries has been constructed. It consists of MnO2 nanoflakes in 1 M Li2SO4 aqueous electrolyte as the cathode and lithium foil in ionic liquid (1 M lithium bis(trifluoromethanesulfonyl)imide (LiNTf2) in N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)imide ([C3mpyr][NTf2])) electrolyte as the anode, separated by a lithium super ionic conductor glass ceramic film (LiSICON). This system shows the advantages of both a supercapacitor (long cycle life) and a lithium battery (high energy), as well as low cost and improved safety due to the combination of ionic liquid and ceramic solid state electrolyte in lithium side, which can reduce the formation and prevent the penetration of lithium dendrites. The specific energy for the cathode materials in the hybrid electrolyte system is 170 Wh kg−1 with more than 85% retention up to 2400 cycles. This system is a great candidate for stationary batteries storing solar and wind energy. Keywords: Hybrid electrolyte, Supercapacitor, Lithium battery, MnO2, Ionic liquid, LiSICON

LiNi1/3Mn1/3Co1/3O2 (NMC) as a cathode material for lithium ion batteries has been synthesized by the sol–gel method. The X-ray diffraction Rietveld refinement results indicated that single-phase NMC with hexagonal layered structure was obtained. Scanning electron microscope images revealed well crystallized NMC with uniform particle size in the range of 100–200 nm. The performance of the NMC electrodes with sodium carboxylmethyl cellulose (CMC), poly(vinylidene fluoride) (PVDF), and alginate from brown algae as binders was compared. Constant current charge–discharge test results demonstrated that the NMC electrode using CMC as binder had the highest rate capability, followed by those using alginate and PVDF binders, respectively. Electrochemical impedance spectroscopy test results showed that the electrode using CMC as the binder had lower charge transfer resistance and lower apparent activation energy than the electrodes using alginate and PVDF as the binders. The apparent activation energies of NMC electrodes using CMC, alginate, and PVDF as binders were calculated to be 27.4 kJ mol−1, 33.7 kJ mol−1, and 36 kJ mol−1, respectively.

Porous metal oxide architectures coated with a thin layer of carbon are attractive materials for energy storage applications. Here, a series of porous metal oxide (e.g., vanadium oxides, molybdenum oxides, manganese oxides) foams with/without nitrogen-doped carbon (N-C) coating have been synthesized via a general surfactant-assisted template method, involving the formation of porous metal oxides coated with 1-hexadecylamine (HDA) and a subsequent thermal treatment. The presence of HDA is of importance for the formation of a porous structure, and the successive pyrolysis of such a nitrogen-containing surfactant generates nitrogen-doped carbon (N-C) coated on the surface of metal oxides, which also provides a facile way to adjust the valence states of metal oxides via the carbothermal reduction reaction. When used as electrode materials, the highly porous metal oxides with N-C coating exhibited enhanced performance for lithium ion storage, thanks to the unique 3D structures associated with highly porous structure and thin N-C coating. Typically, the porous metal oxides (V2O5, MoO3, MnO2) exhibited discharge capacities of 286, 303, and 463 mAh g(-1) at current densities of 30 and 100 mA g(-1), respectively. In contrast, the metal oxides with low valences and carbon coating (VO2@N-C, MoO2@N-C, and MnO@N-C) exhibited improved capacities of 461, 613, and 892 mAh g(-1). The capacity retentions of about 87.5, 80.2, and 85.0% for VO2@N-C, MoO2@N-C, and MnO@N-C were achieved after 600 cycles, suggesting the acceptable cycling stability. The present strategy would provide general guidance for preparing porous metal oxide foams with enhanced lithium storage performances.

The compound Li9Cr3(P2O7)3(PO4)2 has been successfully synthesized using sol–gel method. X-ray diffraction Rietveld refinement analysis indicates that single phase Li9Cr3(P2O7)3(PO4)2 can be obtained under air condition and high purity nitrogen atmosphere. Scanning electron microscopy indicates that nanowires with lengths ranging from several to tens micrometers and diameters varying from 100nm to 500nm can be obtained in the Li9Cr3(P2O7)3(PO4)2 compound heated under air condition. The electrochemical properties of Li9Cr3(P2O7)3(PO4)2 sintered under N2 as cathode material is reported for the first time. The XRD patterns of the electrodes before and after 30 cycles indicate that the Li9Cr3(P2O7)3(PO4)2 keeps its original monodiphosphate structure.

Layered monodiphosphate Li9V3(P2O7)3(PO4)2 can be synthesized by direct solid-state reaction using either hydrogen or carbon as the reducing agent at the sintered temperature of 750 °C. When the temperature is higher than 800 °C, Li9V3(P2O7)3(PO4)2 begins to decompose into Li3V2(PO4)3 and Li4P2O7. The measurement results of electronic conductivity, magnetization, and electrochemical impedance spectroscopy are reported for the first time. After carbon coating, the electronic conductivity comes to 2.07 × 10−3 S cm−1, which is the same order of magnitude as that of carbon-coated LiFePO4 and Li3V2(PO3)4. Li-ion diffusion coefficient (4.19 × 10−10 cm2 s−1) for carbon-uncoated Li9V3(P2O7)3(PO4)2 is close to that of LiCoO2 and much higher than that of LiFePO4. Li9V3(P2O7)3(PO4)2 exhibits a paramagnetic behavior in the temperature range of 5−300 K, which is consistent with the result from our X-ray photoelectron spectroscopy analysis where the oxidation state of vanadium is +3 in the Li9V3(P2O7)3(PO4)2 compound. ...

Since the discovery of graphene in 2004, research on 2D materials has grown rapidly. Compared to their bulk counterparts, 2D atomically thin, layered transition-metal dichalcogenides (TMDCs or MX2) nanosheets exhibit excellent electronic and optical properties, outstanding mechanical flexibility, and exceptional catalytic performance. As a representative of 2D materials, MX2 holds great promise in many potential applications, especially in energy-related applications. Here, a brief overview of atomically thin layered MX2 nanosheets applied in energy storage and conversion systems is presented. Firstly, the crystal structures and phases, morphologies, and synthesis methods of MX2 are discussed. Sequentially, the achieved progress on atomically thin MX2 in energy-related applications (i.e., the hydrogen-evolution reaction, oxygen-evolution reaction, CO2 electrochemical reduction, electrochemical capacitors, lithium-ion batteries, sodium-ion batteries, and lithium–sulfur batteries) is systematically discussed. Finally, the conclusions and some prospects regarding atomically thin MX2 for applications in the field of energy-storage systems are provided.

The rapid increase of the CO2 concentration in the Earth's atmosphere has resulted in numerous environmental issues, such as global warming, ocean acidification, melting of the polar ice, rising sea level, and extinction of species. To search for suitable and capable catalytic systems for CO2 conversion, electrochemical reduction of CO2 (CO2 RR) holds great promise. Emerging heterogeneous carbon materials have been considered as promising metal-free electrocatalysts for the CO2 RR, owing to their abundant natural resources, tailorable porous structures, resistance to acids and bases, high-temperature stability, and environmental friendliness. They exhibit remarkable CO2 RR properties, including catalytic activity, long durability, and high selectivity. Here, various carbon materials (e.g., carbon fibers, carbon nanotubes, graphene, diamond, nanoporous carbon, and graphene dots) with heteroatom doping (e.g., N, S, and B) that can be used as metal-free catalysts for the CO2 RR are highlighted. Recent advances regarding the identification of active sites for the CO2 RR and the pathway of reduction of CO2 to the final product are comprehensively reviewed. Additionally, the emerging challenges and some perspectives on the development of heteroatom-doped carbon materials as metal-free electrocatalysts for the CO2 RR are included.

With the large-scale applications of electric vehicles in recent years, future batteries are required to be higher in power and possess higher energy densities, be more environmental friendly, and have longer cycling life, lower cost, and greater safety than current batteries. Therefore, to develop alternative electrode materials for advanced batteries is an important research direction. Recently, the Chevrel phase Mo6 T8 (T = S, Se) has attracted increasing attention as electrode candidate for advanced batteries, including monovalent (e.g., lithium and sodium) and multivalent (e.g., magnesium, zinc and aluminum) ion batteries. Benefiting from its unique open crystal structure, the Chevrel phase Mo6 T8 cannot only ensure rapid ion transport, but also retain the structure stability during electrochemical reactions. Although the history of the research on Mo6 T8 as electrodes for advanced batteries is short, there has been significant progress on the design and fabrication of Mo6 T8 for various advanced batteries as above mentioned. An overview of the recent progress on Mo6 T8 electrodes applied in advanced batteries is provided, including synthesis methods and diverse structures for Mo6 T8 , and electrochemical mechanism and performance of Mo6 T8 . Additionally, a briefly conclusion on the significant progress, obvious drawbacks, emerging challenges and some perspectives on the research of Mo6 T8 for advanced batteries in the near future is provided.

Recent advances and achievements in emerging Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries with promising cathode materials open up new opportunities for the development of high-performance lithium-ion battery alternatives. In this review, we focus on an overview of recent important progress in the design of advanced cathode materials and battery models for developing high-performance Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries. We start with a brief introduction to explain why Li-X batteries are important for future renewable energy devices. Then, we summarize the existing drawbacks, major progress and emerging challenges in the development of cathode materials for Li-O2 (S) batteries. In terms of the emerging Li-X (Se, Te, I2 , Br2 ) batteries, we systematically summarize their advantages/disadvantages and recent progress. Specifically, we review the electrochemical performance of Li-Se (Te) batteries using carbonate-/ether-based electrolytes, made with different electrode fabrication techniques, and of Li-I2 (Br2 ) batteries with various cell designs (e.g., dual electrolyte, all-organic electrolyte, with/without cathode-flow mode, and fuel cell/solar cell integration). Finally, the perspective on and challenges for the development of cathode materials for the promising Li-X (X = O2 , S, Se, Te, I2 , Br2 ) batteries is presented.