Poor Intrinsic Electronic Conductivity Research Articles

Construction of a bi-continuous charge transport network towards high-performance vanadium-based phosphate cathode materials for potassium ion batteries

As one class of most promising cathode materials for potassium ion batteries (KIBs), polyanionic compounds still suffer from unsatisfactory effective capacity and rate performance due to their poor intrinsic electronic conductivity. In this paper, nanoscale K3V3(PO4)4 (KVP) particles with a bi-continuous charge transport network (denote as KVP-S) are designed and prepared. Carbon nanotubes (CNTs) play a crucial role in this design, not only effectively inhibiting the aggregation and growth of particles, but also providing a three-dimensional (3D) electron conductive network. Benefiting from the advantages of nanoscale particle size and bi-continuous charge transport network, the KVP-S electrode exhibits a high capacity (118mAh g−1 at 20 mA g−1), outstanding rate performance (102 mAh g−1 at 0.5 C; 66 mAh g−1 at 5 C) and excellent cycling stability (94 % retention after 50 cycles at 1 C). Even at a higher rate of 5 C, it still maintains a high capacity retention of 92 % after 300 cycles. More importantly, the capacity can maintain 80 mAh g−1 at 1 C when the mass loading is extended to 4 mg cm−2, In addition, in-situ X-ray diffraction (XRD) and ex-situ X-ray photoelectron spectroscopy (XPS) analyses reveal that the potassium storage mechanism of KVP-S is two single-phase solid solution reactions, involving V2+/V3+/V4+ three-electron redox conversions with a total volume change of 5.5 %. This study provides a new way to rationally design nanoscale particle electrodes with highly conductive charge transport networks.

Tailoring of High-Valent Sn-Doped Porous Na3V2(PO4)3/C Nanoarchitechtonics: An Ultra High-Rate Cathode for Sodium-Ion Batteries.

NASICON structured Na3V2(PO4)3 (NVP) has captured enormous attention as a potential cathode for next-generation sodium-ion batteries (SIBs), owing to its sturdy crystal structure and high theoretical capacity. Nonetheless, its poor intrinsic electronic conductivity has led to inferior electrochemical performance in terms of rate capability and long cycling performance. To address this problem, a combined strategy is adopted, such as (1) carbon coating and (2) high valent Sn4+ ion doping in the lattice site of vanadium in the NVP cathode. Carbon coating can effectively enhance the surface electronic conductivity, wherein high-valent Sn4+ improves the bulk intrinsic electronic conductivity of the materials. Moreover, Sn is a well-known alloying/dealloying type anode for SIBs; thus, doping of such metal in cathode materials will assume the role of structure stabilizing pillars and establishing high-performing cathode materials. Herein, Na3V2-xSnx(PO4)3/C (denoted as Sn(x)-NVP/C, where x = 0.00, 0.03, 0.05, 0.07, 0.1) were synthesized via sol-gel route, followed by calcination at 800 °C. XRD, Raman, XPS, and electron microscopy data confirmed the high purity of the synthesized cathode. The optimized Sn(0.07)-NVP/C exhibited excellent electrochemical performance in terms of high rate capability and long cycling performance, a high appreciable capacity of 98 mAh g-1 with capacity retention of 85% after 500 cycles. Similarly, at a high current of 20C, it is still able to deliver a stable capacity of 76 mAh g-1 with 85% capacity retention after 3000 cycles. The rate capability study indicates the high current tolerance of Sn(0.07)-NVP/C up to 70 C with a capacity delivery of 55 mAh g-1. It is worth mentioning that CV and EIS analysis for Sn(0.07)-NVP/C cathode displayed minimum voltage polarization and enhanced diffusion coefficient. Moreover, DFT calculation also proved that the electronic and ionic conductivity of NVP is promoted by Sn doping. Hence, the present results demonstrated that Sn(0.07)-NVP/C is considered a promising cathode for sodium-ion battery application.

Improved cycle stability and high-rate capability of LiNbO3-coated Li3VO4 as anode material for lithium-ion battery

Lithium vanadate (Li3VO4) has garnered considerable attention as an alternative negative electrode material for non-aqueous lithium-ion batteries due to its high capacity, energy efficiency, and stable discharge voltage. Nonetheless, the Li3VO4 material displays a low rate capability, attributed mainly to its poor intrinsic electronic conductivity. Here, we report the synthesis of lithium niobate LiNbO3-coated Li3VO4 (LVO@LNO) using a one-pot sol-gel method. The resulting LVO@LNO demonstrates a high reversible capacity of approximately 530 mAh/g, which is more than double that of free Li3VO4. To explore the effect of the LNO coating process on the morphological and structural properties, Raman, XRD, operando XRD, XPS, SEM and HTEM analyses were conducted. To explain the enhancement of electronic conductivity in our modified material after a LiNbO3 coating, we conducted an Ex-Situ electrochemical impedance (EIS) and Density Functional Theory (DFT) computational study. Additionally, we designed a full cell utilizing a 1 wt% LNO-coated LVO anode and NMC-811 cathode. The cell yielded an output voltage of approximately 2.8 V with a high initial specific capacity of 350 mAh/g versus to the anode, at 1C with a capacity retention of 85 % after 100 cycles.

Enabling Electron Delocalization by Conductor Heterostructure for Highly Reversible Sodium Storage

AbstractNiobium oxides have fascinated numerous interests for ultrafast sodium‐ion batteries due to their impressive stability, fast pseudocapacitive kinetics, and high safety features. However, the poor intrinsic electronic conductivity and unrevealed mechanisms largely limit their further applications. Here, inspired by density functional theory (DFT) calculations, the introduction of conductor heterostructure (Nb2O5/NbSe2) can largely decrease the bulk phase inserted energy of Na+ from 9.88 to −3.54 eV, as well as promote the delocalization of electron, greatly improving the electrical conductivity of Nb2O5. As expected, the as‐obtained orthorhombic niobium pentoxide (T‐Nb2O5‐x‐NbSe2@C) delivers a high conductivity of 3.69 S cm−1, exhibiting a great improvement of four orders magnitude than that of the parent Nb2O5 (1.87 × 10−4 S cm−1). Impressively, T‐Nb2O5‐x‐NbSe2@C possesses a high reversible capacity of 249 mAh g−1 at 0.1 A g−1, as well as excellent rate performance of 63 mAh g−1 at 5.0 A g−1, nearly twins the capacity of parent porous Nb2O5. Furthermore, the periodic evolutions of the main peaks for targeted electrodes during repeated charging/discharging processes have been further revealed by in situ XRD, demonstrating a highly reversible inserted/extracted storage mechanism of Na+. This work provides a novel method to improve the conductivity of materials by constructing conductor heterojunction.

Emerging Amorphous to Crystalline Conversion Chemistry in Ca-Doped VO2 Cathodes for High-Capacity and Long-Term Wearable Aqueous Zinc-Ion Batteries.

Amorphous transition metal oxides have attracted significant attention in energy storage devices owing to their potentially desirable electrochemical properties caused by abundant unsaturated dangling bonds. However, the amorphization further amplifies the shortcoming of the poor intrinsic electronic conductivity of the metal oxides, resulting in unsatisfying rate capability and power density. Herein, freestanding amorphous Ca-doped V2 O5 (a-Ca-V2 O5 ) cathodes are successfully prepared via in situ electrochemical oxidation of Ca-doped VO2 nanoarrays for wearable aqueous zinc-ion batteries. The doping of Ca and construction of freestanding structure effectively uncover the potential of amorphous V2 O5 , which can make full use of the abundant active sites for high volumetric capacity and simultaneously achieve fast reaction kinetics for excellent rate performance. More importantly, the introduction of Ca can notably reduce the formation energy of VO2 according to theoretical calculation results and realizes amorphous to crystalline reversible conversion chemistry in the charge/discharge procedure, thereby facilitating the reversible capacity of the newly developed a-Ca-V2 O5 . This work provides an innovative design strategy to construct high-rate capacity amorphous metal oxides as freestanding electrodes for low-cost and high-safe wearable energy-storage technology.

Sn3O4 nanosheets with N-doped carbon coating for high performance lithium storage

Tin-based oxides are promising anode materials for lithium ion batteries (LIBs) in virtue of their many advantages including high capacity, abundant reserves and environmental friendliness. Yet, previous studies mainly focus on the SnO2-based anodes for lithium storage. Considering that the mixed valence and layered crystal structure of Sn3O4 may lead to better lithium storage properties, Sn3O4-based anode material is designed and synthesized through a facile hydrothermal method in this work. The as-prepared Sn3O4 nanosheets are coated with N-doped carbon layers (∼15 nm) on both sides through dopamine polymerization and subsequent polydopamine carbonization to solve the issues of poor intrinsic electronic conductivity and drastic volume change during LiSn alloying/dealloying, which have hindered their application in LIBs. With the structural and composition advantages brought by the thick N-doped carbon layers, the Sn3O4@NC nanosheets delivered a remarkable reversible capacity (1222 mAh g−1 after 50 cycles at 200 mA g−1) and excellent rate performance when applied in LIB as anode material, owing to the improved electrical conductivity and strengthened structure stabilities. Importantly, we demonstrate a convenient strategy to realize carbon coating in the fabrication of Sn3O4-based anode materials, which could inspire the development of other Sn3O4-based anode materials with excellent lithium storage properties.

Insight into the Li-Storage Property of Surface-Modified Ti2Nb10O29 Anode Material for High-Rate Application.

Ti-based anode materials are considered to be an alternative to graphite anodes to accomplish high-rate application requirements. Ti2Nb10O29 (TNO15) has attracted much attention due to its high lithium storage capacity through the utilization of multiple redox couples and a suitable operating voltage window of 1.0 to 2.0 V vs Li/Li+. However, poor intrinsic electronic conductivity has limited the futuristic applicability of this material to the battery anode. In this work, we report the modification of TNO15 by introducing oxygen vacancies and using few-layered carbon and copper coatings on the surface to improve its Li+ storage property. With the support of the galvanostatic intermittent titration technique (GITT), we found that the diffusion coefficient of carbon/copper coated TNO15 is 2 orders of magnitude higher than that of the uncoated sample. Here, highly conductive copper metal on the surface of the carbon-coated oxygen-vacancy-incorporated TNO15 increases the overall electronic and ionic conductivity. The prepared TNO15-800-C-Cu-700 half-cell shows a significant rate capability of 92% when there is a 10-fold increase in the current density. In addition, the interconnected TNO15 nanoparticles create a porous microsphere structure, which enables better Li-ion transportation during charge/discharge process, and experiences an enhancement after the carbon and copper coating on the surface of the primary TNO15 nanocrystallites.

Mechanistic exploration of Co doping in optimizing the electrochemical performance of 2H-MoS2/N-doped carbon anode for potassium-ion battery

The 2H-MoS2/nitrogen-doped carbon (2H-MoS2/NC) composite is a promising anode material for potassium-ion batteries (PIBs). Various transition metal doping has been adopted to optimize the poor intrinsic electronic conductivity and lack of active sites in the intralayer of 2H-MoS2. However, its optimization mechanisms have not been well probed. In this paper, using Cobalt (Co) as an example, we aim to investigate the influence of transition metal doping on the electronic and mechanical properties and electrochemical performance of 2H-MoS2/NC via first-principles calculation. Co doping is found to be effective in improving the electronic conductivity and the areas of active sites on different positions (C surface, interface, and MoS2 surface) of 2H-MoS2/NC. The increased active sites can optimize K adsorption and diffusion capability/processes, where general smaller K adsorption energies and diffusion energy barriers are found after Co doping. This helps improve the rate performance. Especially, the pyridinic N (pyN), pyrrolic N (prN), and graphitic N (grN) are first unveiled to respectively work best in K kinetic adsorption, diffusion, and interfacial stability. These findings are instructive to experimental design of high rate 2H-MoS2/NC electrode materials. The roles of different N types provide new ideas for optimal design of other functional composite materials.

A high-energy-density NASICON-type Na3V1.25Ga0.75(PO4)3 cathode with reversible V4+/V5+ redox couple for sodium ion batteries

The stable three-dimensional framework and high operating voltage of sodium superionic conductor (NASICON)-type Na3V2(PO4)3 has the potential to work with long cycle life and high-rate performance; however, it suffers from the poor intrinsic electronic conductivity and low energy density. Herein, Ga3+ is introduced into Na3V2(PO4)3 to activate the V4+/V5+ redox couple at a high potential of 4.0 V for enhancing energy density of the materials (Na3V2-xGax(PO4)3). After the partial substitution of Ga3+ for V3+, three redox couples (V2+/V3+, V3+/V4+ and V4+/V5+) of V are reversibly converted in the voltage range of 1.4–4.2 V, suggesting multi-electrons (>2e−) involved in the reversible reaction, and simultaneously the electronic conductivity of the materials is effectively enhanced. As a result, the cathode with x = 0.75 exhibits excellent electrochemical properties: in the voltage range of 2.2–4.2 V, delivering an initial capacity of 105 mAh/g at 1C with a capacity retention rate of 92.3% after 400 cycles, and providing a stable reversible capacity of 88.3 mAh/g at 40C; and in the voltage range of 1.4–4.2 V, presenting the reversible capacity 152.3 mAh/g at 1C (497.6 Wh kg−1), and cycling stably for 1000 cycles at 20C with a capacity decay of 0.02375% per cycle. It is found that the Na3V2-xGax(PO4)3 cathodes possess the sodium storage mechanism of single-phase and bi-phase reactions. This investigation presents a useful strategy to enhance the energy density and cycling life of NASICON-structured polyanionic phosphates by activating high-potential V4+/V5+ redox couple.

Suppresses Dissolution and Enhanced Conductivity in Core–Shell VO2@Ni3N as a High‐Capacitance and Improved Cycling Anode Materials for Supercapacitor

Vanadium dioxide, as one of superior pseudocapacitive electrode candidates in supercapacitors, suffers from the detrimental dissolution in aqueous electrolytes and poor intrinsic electronic conductivity. Herein, an ultrathin Ni3N shell is deposited on the VO2 surfaces (VO2@Ni3N) to inhibit the inevitable dissolution during charge/discharge processes. Meanwhile, the Ni3N coating layer also provides sufficient electron transport pathways for the rapid surface faradic reactions of VO2, promoting the electrochemical reaction kinetics. The designed VO2@Ni3N anode exhibits significant energy storage ability, especially at large current density (2058 F g−1 at 1 A g−1, 711 F g−1 at 7 A g−1), and the considerable cycling lifespans (capacitance retention of 91.3% after 5000 cycles). The asymmetric supercapacitor presents an energy density of 41.73 Wh kg−1 at a power density of 1176.7 W kg−1. This study may enlighten the design of advanced pseudocapacitive materials for practical electrochemical energy storage technologies.

High-Energy-Density Cathode Achieved via the Activation of a Three-Electron Reaction in Sodium Manganese Vanadium Phosphate for Sodium-Ion Batteries.

Sodium superionic conductor (NASICON)-type Na3 V2 (PO4 )3 has attracted considerable interest owing to its stable three-dimensional framework and high operating voltage; however, it suffers from a low-energy density due to the poor intrinsic electronic conductivity and limited redox couples. Herein, the partial substitution of Mn3+ for V3+ in Na3 V2 (PO4 )3 is proposed to activate V4+ /V5+ redox couple for boosting energy density of the cathodes (Na3 V2- x Mnx (PO4 )3 ). With the introduction of Mn3+ into Na3 V2 (PO4 )3 , the band gap is significantly reduced by 1.406eV and thus the electronic conductivity is greatly enhanced. The successive conversions of four stable oxidation states (V2+ /V3+ , V3+ /V4+ , and V4+ /V5+ ) are also successfully achieved in the voltage window of 1.4-4.0V, corresponding to three electrons involved in the reversible reaction. Consequently, the cathode with x = 0.5 exhibits a high reversible discharge capacity of 170.9 mAh g-1 at 0.5 C with an ultrahigh energy density of 577Wh kg-1 . Ex-situ x-ray diffraction (XRD) analysis reveals that the sodium-storage mechanism for Mn-doped Na3 V2 (PO4 )3 consists of single-phase and bi-phase reactions. This work deepens the understanding of the activation of reversible three-electron reaction in NASICON-structured polyanionic phosphates and provides a feasible strategy to develop high-energy-density cathodes for sodium-ion batteries.

Construction of highly conductive MoS2/MoO2/reduced graphene oxide nanocomposites for ultralong-life hybrid Mg2+/Li+ batteries

Hybrid Mg2+/Li+ batteries (MLIBs) are a promising battery system that combines the advantages of fast lithium-ion kinetics and dendrite-free magnesium deposition. Layered molybdenum disulfide (MoS2) has gained increasing interest due to larger layer spacing and weak van der Waals forces in MLIBs. However, poor intrinsic electronic conductivity hinders its practical application. Here, a highly conductive MoS2/MoO2/reduced graphene oxide (MoS2/MoO2/rGO) composite synthesized via a facile hydrothermal method is employed as a high-performance cathode material for MLIBs. The high electrical conductivity (7.5 ×10−3 S cm−1) and large specific surface area of MoS2/MoO2/rGO facilitate the rapid transport of interfacial electrons and provide abundant active sites for Mg2+/Li+ storage. The optimized MoS2/MoO2/rGO composite exhibits a high discharge capacity (297.3 mAh g−1) and excellent rate performance. Moreover, the composite electrode delivers ultra-long cycle life over 5000 cycles at 1000 mA g−1, with a capacity degradation rate of only 0.007 % per cycle. The results offer valuable insights for the development of highly conductive MoS2-based composites.

2D coordination unsaturated Ni-MOFs hierarchical nanosheets with internal electric fields for high-performance hybrid supercapacitors

The poor intrinsic electronic conductivity and low-exposure electroactive sites of MOFs limit their practical application in energy storage. Herein, the coordination unsaturated nickel-based metal organic frameworks (Ni-MOFs) were prepared by one-step solvothermal method via adjusting the molar ratio of metal salts to organic ligands (RM/L). The coordination unsaturated degree and morphology of the materials can be controlled by adjusting RM/L. When the RM/L is 2, the obtained Ni-MOF 2:1 is a two-dimensional (2D) hierarchical nanosheets made of interwoven ultra-thin nanoribbons. The 2D hierarchical nanosheets structure of Ni-MOF 2:1 can not only expose more electroactive sites, but also promote ions diffusion. The density functional theory (DFT) simulations reveal that the coordination unsaturated centers can narrow the band gap, thus resetting the internal electric field and improving the conductivity of Ni-MOF 2:1. Benefit from abundant electroactive sites, rapid ions diffusion and improved electrical conductivity, the Ni-MOF 2:1 shows a high specific capacity of 746 C g−1 at 1 A g−1 and excellent cycling stability of 89.7 % capacity retention after 10,000 cycles at 10 A g−1. The hybrid supercapacitor (HSC) assembled with Ni-MOF 2:1 as cathode and activated carbon (AC) as anode has a maximum energy density of 53.1 Wh Kg−1 at 799.9 W Kg−1. This work provides a promising strategy for the rational design of MOFs-based electrode materials for high performance HSC. Moreover, compared with the studies using MOFs derivatives as electrode materials, the direct use of Ni-MOFs as electrode materials in this study is of great significance to avoid energy waste and maintain the inherent advantages of MOFs.

Ultrafast Charge-Discharge Capable and Long-Life Na3.9 Mn0.95 Zr0.05 V(PO4 )3 /C Cathode Material for Advanced Sodium-Ion Batteries.

Na4 MnV(PO4 )3 /C (NMVP) has been considered an attractive cathode for sodium-ion batteries with higher working voltage and lower cost than Na3 V2 (PO4 )3 /C. However, the poor intrinsic electronic conductivity and Jahn-Teller distortion caused by Mn3+ inhibit its practical application. In this work, the remarkable effects of Zr-substitution on prompting electronic and Na-ion conductivity and also structural stabilization are reported. The optimized Na3.9 Mn0.95 Zr0.05 V(PO4 )3 /C sample shows ultrafast charge-discharge capability with discharge capacities of 108.8, 103.1, 99.1, and 88.0 mAh g-1 at 0.2, 1, 20, and 50 C, respectively, which is the best result for cation substituted NMVP samples reported so far. This sample also shows excellent cycling stability with a capacity retention of 81.2% at 1 C after 500 cycles. XRD analyses confirm the introduction of Zr into the lattice structure which expands the lattice volume and facilitates the Na+ diffusion. First-principle calculation indicates that Zr modification reduces the band gap energy and leads to increased electronic conductivity. In situ XRD analyses confirm the same structure evolution mechanism of the Zr-modified sample as pristine NMVP, however the strong ZrO bond obviously stabilizes the structure framework that ensures long-term cycling stability.

Synthesis of Co3O4@CNTs with oxygen vacancies on nickel foam for improved performance of asymmetric supercapacitor electrode

Metal oxide Co3O4 is regarded as a promising pseudocapacitance material due to its high theoretical specific capacitance and excellent reversible ability. While its poor intrinsic electronic conductivity and low activity sites limit its supercapacitor performance. Herein, oxygen vacancy-abundant Co3O4 nanowire assembly coupling with carbon nanotubes (CNTs) has been synthesized on nickel foam (Co3O4@CNTs@NF). The introduction of CNTs and oxygen vacancies provides enhanced electrical conductivity, more available active sites, and fast faradic redox reactions to the Co3O4@CNTs composite. The strong binding force between Co3O4@CNTs and nickel foam gives excellent capacitive property and remarkable cyclic durability. The Co3O4@CNTs@NF electrode exhibits a high specific capacitance of 1291 F g−1 at 5 mA/cm2 and a capacitance retention rate of 106% after 5000 cycles at 30 mA g−1. It can be used as the anode to assemble an asymmetric supercapacitor using active carbon loaded on NF (AC@NF) as the cathode. The Co3O4@CNTs@NF//AC@NF device exhibits a high energy density of 57.6 Wh/kg at 273.4 W/kg. This work provides deep insights into the development of excellent electrode materials for the next generation of supercapacitors.

Interface and Structure Engineering of Tin‐Based Chalcogenide Anodes for Durable and Fast‐Charging Sodium Ion Batteries

AbstractTransition metal dichalcogenides with high theoretical capacity usually suffer from poor intrinsic electronic conductivity and drastic volumetric change upon cycling, degrading their attractiveness for electrochemical high‐power and long‐term applications. Herein, a high‐efficiency and extensible synthetic strategy for in situ encapsulating nanostructured SnSe0.5S0.5 into N‐doped graphene (SnSe0.5S0.5 @ NG) by robust interfacial CSeSn bonds with formation of 3D porous network nanohybrids, is reported. Systematic electrochemical studies indicate that interface and structure engineering on SnSe0.5S0.5, including defects implantation, chemical bonding interaction, and nanospace confinement design, endow it with robust structural stability, ultrafast Na+ storage kinetics, and highly reversible redox reaction. In addition, the introduction of foreign Se ligand not only facilitates the transport of electrons/ions by enhancing the conductivity and decreasing the diffusion energy barrier but also generates more reactivity sites, as demonstrated by density functional theory calculations. By virtue of these superiorities, the SnSe0.5S0.5 @ NG exhibits superior sodium storage performance with high‐rate capability and long durability over 2000 cycles at 2 A g−1. Impressively, the full battery, when coupling SnSe0.5S0.5 @ NG anode with Na3V2(PO4)3/C cathode, can deliver high energy density of 213 Wh kg−1. This work provides an effective structural engineering strategy to design advanced electrode material with potential application for sodium‐ion batteries.

Applications of Soft Dendritic Colloids in Li-Ion Batteries with Advanced Structure-Derived Performance

Adoption of electric vehicles and increasing demands of consumer electronics require electrochemical energy storage devices with high capacity and rate capabilities. Supply-chain and material-cost concerns as well as charge-rate limitations associated with irreversible lattice changes motivates the replacement of mixed-metal oxide cathodes in lithium-ion batteries (LIBs). Electrochemically active polymeric materials have emerged as promising candidates to replace metal oxides due to their high tunability and increased capacity. However, many of these materials suffer from poor intrinsic electronic conductivity and may be soluble into the electrolyte, causing irreversible capacity fade. Nanostructuring and composite formation are two polymer processing methods that can be leveraged to combat these drawbacks. The introduction of new nanostructured and nanocomposite cell components can decrease diffusion length scales, increase mechanical stability, and allow for higher electronic conductivity in polymer electrodes. Herein, we utilize a new class of polymeric materials called soft dendritic colloids (SDCs) as a platform for creating such nanocomposites. These fibrillar polymeric particles, formed via turbulent solvent-nonsovent induced phase separation, have hierarchical morphology, large aspect ratios and demonstrate pronounced adhesion and network-forming behavior. SDC-based materials have shown impressive results as nonwoven polyvinylidene difluoride separators in Li-ion batteries. Herein, we propose and present their use as Li-ion battery electrodes with advanced structural properties, derived from electroactive polymeric materials.

Tuning the electronic properties of NiO anode by in-situ introducing metallic Cu for high capacity and long life-span lithium-ion batteries

Over the years, nickel oxides-based anodes have attracted extensive attention for their high theoretical capacity with the rapid development of lithium-ion batteries (LIBs). However, the poor intrinsic electronic conductivity and the electrode pulverization phenomenon seriously hamper their commercial application. Herein, a unique N-doped carbon-coated Cu/NiO composite (Cu/[email protected]) is constructed via one step carbothermic reaction. The experiment results and density functional theory (DFT) calculations evidence that the well-conductive Cu nanoparticles evenly dispersing in the nickel oxide phase can effectively enhance the electronic conductivity and improve the lithium-ion adsorption capacity of hetero-interfaces, resulting in fast reaction kinetics of the electrode. Besides, the covalent characteristic interaction between Cu-Ni atoms also inhibits the volume expansion of the NiO phase during cycling. Additionally, the N-doped carbon coating layer further improves the reaction reversibility and stability of the electrode as a conductive matrix. Therefore, when serving as the anode for LIB, the Cu/[email protected] performs outstanding cycling reversibility with a high specific capacity retention of 92.1 % at 1000 mA g−1, and even reserves a high specific capacity of 882 mAh g−1 at 2000 mA g−1 after 1000 repeated long-term cyclic tests. This facile strategy would shed some lights on modifying various transition-metal oxides with adjustable electrochemical performance.

Facile Synthesis of SnNb2 O6 @C Composite with Ultrathin Carbon Layer as Anode Materials for High-Performance Sodium-Ion Batteries.

Niobium-based oxides have attracted a lot of attention as anode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, excellent rate capability and exceptional safety. However, their poor intrinsic electronic conductivity and sluggish sodium ions diffusion kinetics severely hinder their practical applicability. Here, SnNb2 O6 @C was successfully prepared by a simple solid-state reaction technique coupled with carbon coating. HRTEM images show that the SnNb2 O6 @C particles are covered with uniformly ultrathin amorphous carbon layer of about 1.8 nm, thus improving the electronic conductivity and diffusion coefficient of sodium ions. As anode for SIBs, the as-obtained SnNb2 O6 @C material exhibits excellent specific capacity (369 mAh g-1 at a current density of 50 mA g-1 ) and remarkable rate performance (177 mAh g-1 at 1000 mA g-1 ), which indicates its good prospect in practical application.

Enhanced electrochemical performances of FeS/PC composites as anode materials for lithium-ion batteries

• FeS@PC anode material where FeS nanoparticles embedded in the porous carbon was synthesized by two-step in-situ immersion/calcination method. • The electrochemical properties of the FeS@PC anode material are evaluated. • The material achieves a high initial discharge capacity of 1397.3 mAh/g and reversible capacities of 592 mAh/g at a current density of 0.1 C after 65 cycles. Due to the various micro/nanostructures and high theoretical specific capacities, transition-metal compounds are attractive anodes for next-generation lithium-ion batteries (LIBs). The practical use of transition metal oxides as anode materials for commercial LIBs is hindered by their limited long-term stability and poor intrinsic electronic conductivity. Here we present the realization of embedded ferrous sulfide (FeS) nanoparticles in the porous carbon (PC) by a two-step in-situ immersion/calcination method. The electrochemical properties are evaluated by cyclic voltammogram, electrochemical impedance and discharge-charge galvanostatic (constant current) tests. By optimizing the reaction conditions, the LIBs achieves a high initial discharge capacity of 1397.3 mAh/g and reversible capacities of 592 mAh/g at a current density of 0.1 C after 65 cycles. With these promising results, the FeS/PC composites exhibit considerable potential applications for lithium-ion batteries.