High Pseudocapacitance Research Articles

Confined Assembly of Hydrated Vanadium Oxide into Hollow Mesoporous Carbon Nanospheres for Fast and Stable K+ Storage Capability.

The rational structural design of the electrode materials is significant to enhance the electrochemical performance for potassium ion storage, benefiting from the shortened ion diffusion distance, increased conductivity, and pseudo-capacitance promotion. Herein, hydrated vanadium oxide (HVO) nanosheets with enriched oxygen defects are well confined into hollow mesoporous carbon spheres (HMCS), producing Od -VOH@C nanospheres through one-step hydrothermal reaction. Attributed to the restricted growth in the HMCS, the HVO nanosheets are loosely packed, generating abundant interfacial boundaries and large specific areas. As a result, Od -VOH@C nanospheres show increased reaction kinetics and well buffer the volume effects for the K+ storage. Od -VOH@C delivers stable capacities of 138 mAh g-1 at 2.0 A g-1 over 10000 cycles in half-cells attributed to the high pseudo-capacitance contribution. The K+ storage mechanism of insertion and conversion reaction is confirmed by ex situ X-ray diffraction, Raman, and X-ray photoelectron spectroscopy analyses. Moreover, the symmetric potassium-ion capacitors of Od -VOH@C//Od -VOH@C deliver a high energy density of 139.6Wh kg-1 at the power density of 948.3W kg-1 .

Interface Density Engineering on Heterogeneous Molybdenum Dichalcogenides Enabling Highly Efficient Hydrogen Evolution Catalysis and Sodium Ion Storage.

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO2 /MoS2 heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO2 /MoS2 @NSC) by controllable sulfidation. MoO2 and MoS2 are coupled intimately at atomic level, forming the MoO2 /MoS2 heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO2 /MoS2 heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS2 nanorods counterpart (η10 : 156mV vs 232mV) and most of the MoS2 -based heterostructures reported recently. First-principles calculation deciphers that MoO2 /MoS2 heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O-Mo-S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant "ion reservoir"-like channels, and low Na+ diffusion barrier appended by high-density MoO2 /MoS2 heterointerfaces, the material delivers high specific capacity of 888 mAh g-1 , remarkable rate capability and cycling stability of 390 cycles at 0.1 A g-1 as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.

Compacted mesoporous titania nanosheets anode for pseudocapacitance‐dominated, high‐rate, and high‐volumetric sodium‐ion storage

AbstractSurface‐redox pseudocapacitive nanomaterials show promise for fast‐charging energy storage. However, their high surface area usually leads to low density, which is not conducive to achieving both high volumetric capacity and high‐rate capability. Herein, we demonstrate that TiO2 nanosheets (meso‐TiO2‐NSs) with densely packed mesoporous are capable of fast pseudocapacitance‐dominated sodium‐ion storage, as well as high volumetric and gravimetric capacities. Through compressing treatment, the compaction density of meso‐TiO2‐NSs is up to ~1.6 g/cm3, combined with high surface area and high porosity with mesopore channels for rapid Na+ diffusion. The compacted meso‐TiO2‐NSs electrodes achieve high pseudocapacitance (93.6% of total charge at 1 mV/s), high‐rate capability (up to 10 A/g), and long‐term cycling stability (10,000 cycles). More importantly, the space‐efficiently packed structure enables high volumetric capacity. The thick‐film meso‐TiO2‐NSs anode with the mass loading of 10 mg/cm2 delivers a gravimetric capacity of 165 mAh/g and a volumetric capacity of 223 mAh/cm3 at 5 mA/cm2, much higher than those of commercial hard carbon anode (80 mAh/g and 86 mAh/cm3). This work highlights a pathway for designing a dense nanostructure that enables fast charge kinetics for high‐density sodium‐ion storage.

Construction of Phthalocyanine-Titanium Dioxide/Graphene/Polyaniline Composite Electrodes by Electrochemical Method for Supercapacitor Applications

Supercapacitors (SCs) are the most interesting alternative energy storage and conversion systems to successfully overcome the global energy problem for future generations. A lot of work has been done to improve the capacitive performance of an electrode and to achieve high power and energy density. Herein, for the first time in the literature, we prepared hybrid composite materials consisting of metallo phthalocyanine doped-titanium dioxide (MPc-TiO2) and high conductivity graphene (Gr) and polyaniline (PANI) in a one-step on pencil graphite electrode (PGE) using the cyclic voltammetry method. The microscopic and structural characteristics of the synthesized MPc-TiO2/Gr/PANI/PGE (M=Cu and Co) are analyzed by various spectroscopic and analytical techniques. As a result, the optimized CoPc-TiO2/Gr/PANI/PGE as the electrode shows a highly specific capacitance of 401.5 F g−1 at 5 A g−1 and excellent cyclic stability up to 1000 cycles. The good electrochemical performance could be attributed to the synergistic effect of the high pseudocapacitance and good conductivity of CoPc-TiO2 as well as the capacitive contribution and conductivity of Gr and PANI. Our strategy provides a new avenue to develop high-performance SCs via rational integration of MPc-TiO2 with Gr and PANI.

Heterostructures of MoO3 nanobelts assembled on delaminated V4C3Tx MXene nanosheets for supercapacitors with excellent room/high temperature performance

A novel flexible delaminated vanadium carbide MXene (d-V4C3Tx) and molybdenum trioxide (MoO3) are promising electrode materials. However, the re-stacking of the d-V4C3Tx nanosheets and the poor conductivity and cyclic stability of MoO3 seriously restrict their development for supercapacitors application. Constructing heterostructures to obtain a synergistic property enhancement is an effective strategy to solve it. Herein, the free-standing d-V4C3Tx/MoO3 heterostructure composite films are fabricated by combining hydrothermal, electrostatic assembly with vacuum-assisted filtration methods, and the energy storage mechanism is dominated by diffusion-controlled process. Results indicate that the as-prepared composite film electrode has high specific capacity of 645 0 C g−1 at current density of 1 A g−1. Even at 40 °C, it also has 639.2 C g−1 at a scan rate of 2 mV s−1. This impressive electrochemical performance can be attributed to the enhanced conductivity and high pseudocapacitance offered by the heterostructures. The as-fabricated asymmetric supercapacitor (ASC), in which the d-V4C3Tx/MoO3 composite film is used as negative electrode and the active carbon (AC) is used as positive electrode, exhibits maximum energy density of 22.2 Wh kg−1 and maximum power density of 5289.9 W kg−1, and the capacity retention rate can still up to 97.0% even after 10,000 cycles at a current density of 10 A g−1. Furthermore, the assembled ASC device successfully drives the small alarm clock and lights the light emitting diode (LED), which facilitates the development of applications for such high-performance supercapacitors.

Sodium alginate-based gel electrodes without binder for high-performance supercapacitors

Binder use results in an expansion of the dead volume of the active material and a decline in the active sites, which will lead to a decrease in the electrochemical activity of the electrode. Therefore, the construction of electrode materials without the binder has been the research focus. Here, a novel ternary composite gel electrode without the binder (reduced graphene oxide/sodium alginate/copper cobalt sulfide, rGSC) were designed using a convenient hydrothermal method. Benefiting from the dual-network structure of rGS via the hydrogen bonding between rGO and sodium alginate not only better encapsulates CuCo2S4 with high pseudo-capacitance, but also simplifies the electron transfer path, and reduces the electron transfer resistance, which leads to a remarkable enhanced electrochemical performance. The rGSC electrode exhibits a specific capacitance of up to 1600.25 F g−1 when the scan rate is 10 mV s−1. The asymmetric supercapacitor was constructed with rGSC and activated carbon as the positive and negative electrode in a 6 M KOH electrolyte. It has a large specific capacitance and high energy/power density (10.7 Wh kg−1/1329.1 W kg−1). This work proposes a promising strategy for designing gel electrodes for higher energy density and larger capacitance without the binder.

Incorporating α-Al2O3 Nanodots into Expanded Graphite Anodes toward Stable Fast Charging for Lithium-Ion Batteries

High-power lithium-ion batteries place high demands on the fast charging ability of electrode materials, while for the current graphite anode, it suffers from anisotropic and sluggish Li+ transport due to its small interlayer spacing. In addition, the large polarization at low lithiation potential at a high rate leads to Li+ deposition and side reactions of Li with the electrolyte. In this work, α-Al2O3 nanodots incorporated into aggregates of thin-layer graphite have been developed by facile high-energy ball milling of graphite and layer-structured pseudo-boehmite. By optimization, the ball-milled graphite/Al2O3 (BG/Al2O3) manifests a high reversible capacity of 344 mAh g–1 higher than the 98.7 mAh g–1 of graphite after 500 cycles at 1 A g–1 (∼2.7C) and 200 mAh g–1 higher than the 59.6 mAh g–1 of raw graphite at 3 A g–1 after 500 cycles. The wrinkled edges and expanded interlayer spacing generated by high-energy ball milling optimize the Li+ transport and accelerate reaction kinetics, contributing high pseudocapacitance and enabling fast charging ability. The α-Al2O3 nanodots can decrease the side reactions between the electrolyte and graphite electrode, contributing high cyclic stability. This study lays a foundation for the one-step mechanical force chemistry method to prepare highly stable fast-charging graphite anode materials for lithium-ion batteries.

Electrostatic Interfacial Cross-Linking and Structurally Oriented Fiber Constructed by Surface-Modified 2D MXene for High-Performance Flexible Pseudocapacitive Storage.

Fiber supercapacitors are promising power supplies suitable for wearable electronics, but the internally insufficient cross-linking and random structure of fiber electrodes restrict their performance. This study describes how interfacial cross-linking and oriented structure can fabricate an MXene fiber with high flexibility and electrochemical performance. The continuous and highly oriented macroscopic fibers were constructed by 2D MXene sheets via a liquid-crystalline wet-spinning assembly. The oxyanion-enriched terminations of surface-modified MXene in situ could reinforce the interfacial cross-linking by electrostatic interactions while mediating the sheet-to-sheet lamellar structure within the fiber. The resultant MXene fiber exhibits high electrical conductivity (3545 S cm-1) and mechanical strength (205.5 MPa) and high pseudocapacitance charge storage capability up to 1570.5 F cm-3. Notably, the assembled fiber supercapacitor delivers an energy density of 77.6 mWh cm-3 at 401.9 mW cm-3, exceptional flexibility and stability exhibiting ∼99.5% capacitance retention under mechanical deformation, and can be integrated into commercial textiles to power microelectronic devices. This work provides insight into the fabrication of an advanced MXene fiber and the development of high-performance flexible fiber supercapacitors.

Space stability by incorporating iron atoms into the cobalt structure enabling capacitive deionization stability possible

Exploring and designing high performance pseudocapacitance electrode materials is of great significance in enhancing the desalination performance of capacitive deionization (CDI). Transition metal cobalt is considered a prospective electrode material for CDI because of its abundance and high theoretical capacity, which can produce a higher salt removal capacity than pure capacitive materials in the CDI process. However, due to the collapse and loss of the active electrode crystal matrix, the cobalt electrode exhibits poor electrochemical performance. In this work, we used a second metal element, Fe, introduced by ion exchange pyrolysis to regulate the leaching effect and optimize the ion matching for cobalt to protect the electrode structure. In addition, the interconnected external carbon layers form a robust matrix for enhanced electrical conductivity with ion transport. Thanks to the synergistic effect of the cobalt‑iron (Co3Fe7@C) electrode structure and surface engineering, the adsorption capacity reached 72.29 mg·g−1, achieving 110 % capacity retention in 100 cycles of chlorine removal. As a result, the carbon-coated cobalt‑iron bimetallic electrode exhibits excellent dechlorination capabilities in capacity, cycle life and rate capability. This study provides a promising avenue for the design of stable electrode materials for capacitive deionization electrodes.

Recent advances in the utilization of covalent organic frameworks (COFs) as electrode materials for supercapacitors.

Due to their excellent stability, ease of modification, high specific surface area, and tunable redox potentials, covalent organic frameworks (COFs) as potential electrodes in supercapacitors (SCs) have raised much research interest because these materials can enable the achievement of high electric double-layer supercapacitance and high pseudocapacitance. Here, the design strategies and SC applications of COF-based electrode materials are summarized. The detailed principles are introduced first, followed by discussions on strategies with diverse examples. The updated advances in design and applications are also discussed. Finally, in the outlook section, we provide some guidelines on the rational design of COF-based electrode materials for high-performance SCs, which we hope will inspire novel concepts for COF-based supercapacitors.

In situ Cu doping of ultralarge CoSe nanosheets with accelerated electronic migration for superior sodium-ion storage.

The progress of sodium-ion batteries is currently confronted with a noteworthy obstacle, specifically the paucity of electrode materials that can store large quantities of Na+ in a reversible fashion while maintaining competitiveness. Herein, ultrafast and long-life sodium storage of metal selenides is rationally demonstrated by employing micron-sized nanosheets (Cu-CoSe@NC) through electron accumulation engineering. The nanosheet structure proves to be effective in reducing the transport distance of sodium ions. Furthermore, the addition of Cu ions enhances the electron conductivity of CoSe and accelerates charge delocalization. As an anode for sodium-ion batteries, Cu-CoSe@NC exhibits a noticeably enhanced specific capacity of 527.2 mA h g-1 at 1.0 A g-1 after 100 cycles. Additionally, Cu-CoSe@NC maintains a capacity of 428.5 mA h g-1 at 5.0 A g-1 after 800 cycles. It is possible to create sodium-ion full batteries with a high energy density of 101.1 W h kg-1. The superior sodium storage performance of Cu-CoSe@NC is attributed to the high pseudo-capacitance and diffusion control mechanisms, as evidenced by theoretical calculations and ex situ measurements.

High Power-Density WO3-x–Grafted Corannulene-Modified graphene nanostructures for Micro-Supercapacitors

• Micro-supercapacitors (MSCs) with reduced graphene oxide (rGO) were designed. • Restocking of rGO nanosheets was prevented with corannulene Bucky-bowls. • rGO nanosheets were modified by grafted intercalation WO 3 nanoparticles. • Double-layer capacitance of rGO nanosheets was augmented with WO 3 pseudocapacitance. • High energy-density and high power-density of MSCs were achieved. The emergence of nanotechnology and development of new methods of nanoengineering novel materials have enabled to design supercapacitors, new devices filling the niche between the high energy-density electrochemical batteries and the high power-density dry capacitors. Thanks to the nanoengineering, new devices combining the unique properties of electrochemical double-layer capacitance with high storage capability of pseudocapacitance materials could became a reality. A special niche in these applications is for micro-supercapacitors, which can drive miniature sensors and implantable biodevices, requiring fast remote charging and high energy density packed in a small volume. In this work, the micro-supercapacitors were fabricated using WO 3-x nanoparticles immobilized on rGO nanosheets to increase the carbon nanoform double-layer capacitance by adding very high pseudocapacitance of WO 3-x . To improve the attachment of WO 3 to the carbon support and enhance the graphene matrix conductance, grafting of WO 3 nuclei onto the GO defect sites was employed by electrochemical processing and nanoparticle growth, followed by the electroreduction of unprotected oxidation sites of GO to form a highly-conductive reduced graphene oxide (rGO) support. Further protection of rGO nanosheets from stacking interactions was also necessary. It was achieved by modifying graphene sheets with corannulene (CORA) which is a C 20 H 10 polyaromatic hydrocarbon (PAH) molecule forming a cup (or: Bucky bowl) structure. We have found that corannulene can efficiently separate the rGO nanosheets in more hydrophobic locations of rGO where WO 3-x nanoforms are missing. The chemical structure, morphology, and electrochemical properties of hybrid materials used for designing the micro-supercapacitor devices were characterized by Raman spectroscopy (RS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infra-red spectroscopy (FTIR), electrochemical quartz crystal nanogravimetry (EQCN), cyclic voltammetry (CV), as well as potential-pulse and current-pulse charging/discharging characteristics. The supercapacitor properties of the proposed WO 3 ,CORA/rGO devices were favorable compared with those for mono plate graphene (MPG) and laser-induced graphene (LIG) MSCs.

Synthesis by adding CTAB and characterization of Ag@CuO@rGO nanocomposite with a novel core-shell crystal sugar structure and its application in supercapacitors.

In this study, we successfully synthesized Ag@CuO@rGO (rGO wrapped around Ag/CuO) nanocomposites using AgNO3, Cu(NO)32, and NaOH as raw materials and particularly treated CTAB as a template by chemical precipitation, hydrothermal synthesis, and subsequent high-temperature calcination processes. In addition, transmission electron microscopy (TEM) images revealed that the prepared products appeared to have a mixed structure. The results indicated that the best choice was CuO wrapped around Ag nanoparticles to form a core-shell crystal structure, and the crystal particles were arranged similarly to form an icing sugar block structure and were tightly wrapped by rGO. Moreover, the electrochemical test results demonstrated that Ag@CuO@rGO composite electrode material exhibited high pseudocapacitance performance; the material had a high specific capacity of 1453 F g-1 at a current density of 2.5 mA cm-2, and the charging and discharging cycles remained constant up to 2000 times, indicating that the introduction of Ag improved the cycling stability and reversibility of the CuO@rGO electrode material and increased its specific capacitance, leading to the increase in the specific capacitance of supercapacitors. Therefore, the above results strongly support the application of Ag@CuO@rGO in optotronic devices.

Thickness‐Independent Capacitive Performance of Holey Ti3C2Tx Film Prepared through a Mild Oxidation Strategy

The Ti3 C2 Tx film with metallic conductivity and high pseudo-capacitance holds profound promise in flexible high-rate supercapacitors. However, the restacking of Ti3 C2 Tx sheets hinders ion access to thick film electrodes. Herein, a mild yet green route has been developed to partially oxidize Ti3 C2 Tx to TiO2 /Ti3 C2 Tx by introducing O2 molecules during refluxing the Ti3 C2 Tx suspension. The subsequent etching away of these TiO2 nanoparticles by HF leaves behind numerous in-plane nanopores on the Ti3 C2 Tx sheets. Electrochemical impedance spectroscopyshows that longer oxidation time of 40min yields holey Ti3 C2 Tx (H-Ti3 C2 Tx ) with a much shorter relax time constant of 0.85s at electrode thickness of 25 µm, which is 89times smaller than that of the pristineTi3 C2 Tx film (75.58s). Meanwhile, H-Ti3 C2 Tx film with 25min oxidation exhibits less-dependent capacitive performance in film thickness range of 10-84 µm (1.63-6.41mgcm-2 ) and maintains around 60% capacitance as the current density increases from 1to 50Ag-1 . The findings clearly demonstrate that in-plane nanopores not only provide more electrochemically active sites, but also offer numerous pathways for rapid ion impregnation across the thick Ti3 C2 Tx film. The method reported herein would pave way for fabricating porous MXene materials toward high-rate flexible supercapacitor applications.

Layered manganese phosphorus trisulfides for high‐performance lithium‐ion batteries and the storage mechanism

AbstractAlthough advanced anode materials for the lithium‐ion battery have been investigated for decades, a reliable, high‐capacity, and durable material that can enable a fast charge remains elusive. Herein, we report that a metal phosphorous trichalcogenide of MnPS3 (manganese phosphorus trisulfide), endowed with a unique and layered van der Waals structure, is highly beneficial for the fast insertion/extraction of alkali metal ions and can facilitate changes in the buffer volume during cycles with robust structural stability. The few‐layered MnPS3 anodes displayed the desirable specific capacity and excellent rate chargeability owing to their good electronic and ionic conductivities. When assembled as a half‐cell lithium‐ion battery, a high reversible capacity of 380 mA h g−1 was maintained by the MnPS3 after 3000 cycles at a high current density of 4 A g−1, with a capacity retention of close to or above 100%. In full‐cell testing, a reversible capacity of 450 mA h g−1 after 200 cycles was maintained as well. The results of in‐situ TEM revealed that MnPS3 nanoflakes maintained a high structural integrity without exhibiting any pulverization after undergoing large volumetric expansion for the insertion of a large number of lithium ions. Their kinetics of lithium‐ion diffusion, stable structure, and high pseudocapacitance contributed to their comprehensive performance, for example, a high specific capacity, rapid charge–discharge, and long cyclability. MnPS3 is thus an efficient anode for the next generation of batteries with a fast charge/discharge capability.

Organic Supercapacitors as the Next Generation Energy Storage Device: Emergence, Opportunity, and Challenges.

Harnessing new materials for developing high-energy storage devices set off research in the field of organic supercapacitors. Various attractive properties like high energy density, lower device weight, excellent cycling stability, and impressive pseudocapacitive nature make organic supercapacitors suitable candidates for high-end storage device applications. This review highlights the overall progress and future of organic supercapacitors. Sustainable energy production and storage depend on low cost, large supercapacitor packs with high energy density. Organic supercapacitors with high pseudocapacitance, lightweight form factor, and higher device potential are alternatives to other energy storage devices. There are many recent ongoing research works that focus on organic electrolytes along with the material aspect of organic supercapacitors. This review summarizes the current research status and the chemistry behind the storage mechanism in organic supercapacitors to overcome the challenges and achieve superior performance for future opportunities.

Freestanding vanadium nitride nanowire/nitrogen-doped graphene paper with hierarchical pore structure for asymmetric supercapacitor anode

Vanadium nitride (VN) is a promising anode material for asymmetric supercapacitors (ASCs) owing to its high theoretical pseudocapacitance and high electrical conductivity. However, the instability of VN in aqueous electrolytes hinders practical applications. In this study, VN nanowires (VNNWs) were hybridized with nitrogen-doped graphene (NG) to fabricate a freestanding VNNW/NG porous paper electrode. The prepared paper electrode exhibited excellent electrochemical performance with an outstanding specific capacitance of 244.7 F·g−1 at 0.5 A·g−1 and a rate capability of 70.7% capacitance retention as the current density increased from 1 to 10 A·g−1. Moreover, the VNNW/NG anode presented remarkable cycling stability of 87% capacitance retention over 10,000 cycles at 5 A·g−1. Encapsulation with NG significantly improved the stability of VNNWs, overcoming their major drawbacks (i.e., low cycling stability). Also, the hierarchical pore structure of the VNNG/NG could facilitate high energy and power density capabilities. An ASC assembled with VNNW/NG anode and nickel oxide/reduced graphene oxide (NiO/rGO) cathode presented high energy density of 20.2 Wh·kg−1 at power density of 850.0 W·kg−1. Thus, we suggest that the design strategy of the fabricated porous paper electrode could be utilized to produce high-performance anode materials for application in supercapacitors.

Tracking the pyrolysis process from 2D Mn2n polymer to high-rate anode materials for lithium ion batteries

By manipulating the pyrolysis of multidimensional precursors, excellent energy storage materials can be obtained. On the molecular level, however, the pyrolysis tracking and evolution of two-dimensional (2D) precursors require additional study. Here, we designed a 2D layered Mn-based polymer (Mn2n, [Mn2L2(CH3OH)2]n, L = 3-ethoxylsalicylate iso-nicotinyl hydrazone) bridged with L as a precursor, and obtained a 2D porous nanosheet N-doped carbon skeleton embedded with Mn2+O (Mn2+O/NC) through controlled pyrolysis under an inert atmosphere. The pyridine nitrogen coordination of isoniazid is astonishingly essential for the formation of 2D layered Mn2n polymers. The formation of Mn-N(pyridine) bonds serves as a bridge between the basic units of Mn2. Thermogravimetric mass spectrometry (TG-MS) could track the pyrolysis process and provide a potential evolutionary from a 2D Mn2n precursor to a 2D porous nanosheet Mn2+O/NC structure. The specific capacity of Mn2+O/NC-800 electrode reaches up to 614.1 mAh g−1 after 600 cycles at 200 mA g−1 current density when the pyrolysis product is used as the anode material of lithium ion battery. Dynamic analysis indicates that the 2D porous nanosheet structure of Mn2+O/NC has a high pseudocapacitance contribution and charge transfer efficiency, which effectively improves the performance of lithium ion batteries. This work will provide a useful guidance for the design of new electrode materials.

Oxygen vacancy engineering boosted manganese vanadate toward high stability aqueous zinc ion batteries

Aqueous zinc-ion batteries (AZIBs) are attractive alternatives to conventional battery technologies owing to their low-cost, safety and environmental friendliness. The development of AZIBs has thus far proceeded rapidly; however, finding suitable materials for AZIB cathodes with high capacity, long-cycle stability, fast reaction kinetics has proved challenging. In this study, a manganese vanadate precursor (Mn 0.04 V 2 O 5 ·1.17 H 2 O; MVO) was prepared using a simple hydrothermal method and calcined at a low temperature (250 °C) to generate oxygen vacancies (Mn 0.04 V 2 O 5−x ·0.64 H 2 O; MVO-250). The presence of oxygen vacancies effectively provide active sites, increase surface reactivity to improve zinc-ion storage, and inhibit the dissolution of electrode materials in the electrolyte. Consequently, MVO-250 exhibits a superior specific capacity and long-cycle performance to MVO. Moreover, after 4000 cycles at 5 A g −1 , the discharge specific capacity of the MVO-250 electrode remain at 150 mA h g −1 , while that of MVO is only (76 mA h g −1 ). Owing to its high pseudocapacitance (90.5%) at 1.0 mV s −1 , MVO-250 has a higher zinc ion diffusion coefficient than MVO (77.2%). This research demonstrates the diverse potential applications prospect of the modification of AZIBs cathode materials with oxygen vacancies. • Oxygen vacancies were formed in manganese vanadate by a simple low-temperature heat treatment in air. • The presence of oxygen vacancies was proven through various characterization techniques. • Superior specific capacity and excellent long-cycle stability were obtained at high current density. • Fast reaction kinetics were achieved owing to the effect of the oxygen vacancies.

N, P co-doped pitch derived soft carbon nanoboxes as high-performance anodes for sodium-ion batteries

Carbonaceous materials have been regarded as promising materials for sodium-ion batteries (SIBs), owing to their high electrical conductivity and stable chemical properties. High-performance sodium-ion batteries need high quality carbon materials as anodes with low cost. Herein, we report a facile method of preparing N/P co-doped soft carbon nanoboxes (NPSC) using petroleum pitch as raw material. Benefitting from the nanobox-like morphology, expanded graphitic layer spacing and excellent electrical conductivity, the NPSC anodes show fast sodium-ion diffusion and high pseudo capacitance ratio, as a result, excellent rate capability and cycling performance can be achieved. The NPSC can deliver a high reversible capacity of 162 mAh g −1 over 3000 cycles at high current density of 1 A g −1 . DFT calculations reveal that N, P co-doping carbon has more electrons near fermi level, thus facilitating electron transport. This work puts forward a convenient method to prepare carbon based anode for high performance SIBs with low cost petroleum pitch. • Petroleum pitch derived carbon was applied as high performance anode for sodium-ion batteries. • The special nanobox-like structures were constructed by a recrystallized NaCl template. • A high reversible capacity of 162 mAh g −1 was achieved at high current density of 1 A g −1 for over 3000 cycles.