THE ELECTROCHEMICAL BEHAVIOUR OF THE NEW VANADIUM BRONZE (Li_3V_5O_(15)) CATHODE IN SECONDARY LITHIUM BATTERY

A new kind of vanadium bronze with rich lithium (Li_5V_5O_(15))was prepared from Li_2CO_3 and V_2O_5 at 680℃ for 24 hrs. The charge and discharge curves of bronze electrode were determined in organic electrolyte. One mole of this material could be incorporated up to 4 mole lithium at 0.2mA/cm^2 and 1.0V cut-off voltage, corresponding capacity about 340Ah/kg. Compared with the cell of Li/Li_(1+x)V_3O_5 the cell of Li/new bronze had higher capacity, smoother discberge curve, but lower plateau voltage (about 1.8V). The cycling behaviour of this material was good. The electrode insertion reaction was controlled by the lithium diffusion process in the bronze. This new bronze could be used for low voltage rechargeable lithium battery.

Syntheses and Application of All-lithium Salts of Heteropolyacid as Electrolyte of Lithium-ion Battery

The all-lithium salts of heteropoly acid Li_xXM_ 12O_ 40(HPA-Li)(X=P, Si; M=Mo, W) were obtained via ion exchange and characterized by means of IR and UV spectroscopies, TG and elemental analyses. The conductivity of the electrolytic solution consisting of Li_3PW_ 12O_ 40 and PC/DME mixing solvent(1/2.5, volume ratio) is up to 7.2×10 -2 S/cm, being higher than that of LiClO_4 as the electrolyte. The all-lithium salts were used as electrolytes in secondary lithium-ion batteries. The discharge capacity of the PAS/Li batteries with Li_3PW_ 12O_ 40 electrolyte solutions reaches to 148 (mA·h)/g and the cyclic life is up to 380 times, much better than those of commercialized products with LiClO_4 and LiAsF_6 as electrolytes.

A Novel Application of Lithium Heteropoly Blue as Non-aqueous Electrolyte in Polyacenic Semiconductor-Li Secondary Batteries

Lithium heteropoly blue(Li 5PW Ⅵ 10 W Ⅴ 2O 40 ) was used as a non aqueous electrolyte in the polyacenic semiconductor (PAS) Li secondary battery instead of LiClO 4. The properties of the PAS Li secondary battery, especially the effect of Li 5PW Ⅵ 10 W Ⅴ 2O 40 on the capacity, the cycle property and the self discharging of the battery have been investigated. The results indicate that not only Li 5PW Ⅵ 10 W Ⅴ 2O 40 can overcome the disadvantages of LiClO 4, which is apt to explode when heated or rammed, but also the PAS Li secondary battery assembled with the novel electrolyte has a larger capacity and smaller self discharging than that assembled with LiClO 4. Therefore, it is believed that lithium heteropoly blue is a better and novel electrolyte for the PAS secondary battery and exhibits significant and practical application.

Study on stabilities and electrochemical behavior of V(V) electrolyte with acid additives for vanadium redox flow battery

Several acid compounds have been employed as additives of the V(V) electrolyte for vanadium redox flow battery(VRB) to improve its stability and electrochemical activity. Stability of the V(V) electrolyte with and without additives was investigated with ex-situ heating/cooling treatment at a wide temperature range of-5 ?C to 60 ?C. It was observed that methanesulfonic acid, boric acid, hydrochloric acid, trifluoroacetic acid,polyacrylic acid, oxalic acid, methacrylic acid and phosphotungstic acid could improve the stability of the V(V) electrolyte at a certain range of temperature. Their electrochemical behaviors in the V(V) electrolyte were further studied by cyclic voltammetry(CV), steady state polarization and electrochemical impedance spectroscopy(EIS). The results showed that the electrochemical activity, including the reversibility of electrode reaction, the diffusivity of V(V) species, the polarization resistance and the flexibility of charge transfer for the V(V) electrolyte with these additives were all improved compared with the pristine solution.

Study of lithium/polypyrrole secondary batteries with Lithium as cathode and polypyrrole anode

Lithium/polypyrrole （Li/PPy） batteries were fabricated using lithium sheet as cathode, PPy as anode, microporous membrane polypropylene/polyethylene/polypropylene （PP/PE/PP） composite as separator and LiPF6/ethylene carbonate-dimethyl carbonate-methyl ethyl carbonate （EC-DMC-EMC） as electrolyte. Polypyrrole was prepared by chemical polymerization. Certain fundamental electrochemical performances were investigated. Properties of the batteries were characterized and tested by SEM, galvanostatic charge/discharge tests, cyclic voltammetry （CV）, and a.c. impedance spectroscopy. The influences of separator, morphology, and conductivity of PPy anode, cold-molded pressure, and electric current on the performances of the batteries were studied. Using PP/PE/PP membranes as separator, the battery showed good storage stability and cycling property. The conductivity of materials rather than morphology affected the behavior of the battery. The higher the conductivity, the better performances the cells had. Proper cold-molded pressure 20 MPa of the anode pellet would make the properties of the cells good and the fitted charge/discharge current was 0.1 mA. The cells showed excellent performance with 97%-100% coulombic efficiency. The highest discharge capacity of 95.2 mAh/g was obtained.

Functional porous carbon-based composite electrode materials for lithium secondary batteries

The synthetic routes of porous carbons and the applications of the functional porous carbon-based composite electrode materials for lithium secondary batteries are reviewed. The synthetic methods have made great breakthroughs to control the pore size and volume, wall thickness, surface area, and connectivity of porous carbons, which result in the development of functional porous carbon-based composite electrode materials. The effects of porous carbons on the electrochemical properties are further discussed. The porous carbons as ideal matrixes to incorporate active materials make a great improvement on the electrochemical properties because of high surface area and pore volume, excellent electronic conductivity, and strong adsorption capacity. Large numbers of the composite electrode materials have been used for the devices of electrochemical energy conversion and storage, such as lithium-ion batteries （LIBs）, Li-S batteries, and Li-O2 batteries. It is believed that functional porous carbon-based composite electrode materials will continuously contribute to the field of lithium secondary batteries.

Ni0.85 Se hexagonal nanosheets as an advanced conversion cathode for Mg secondary batteries

Mg secondary batteries are promising scalable secondary batteries for next-generation energy storage.However,Mg-storage cathode materials are greatly demanded to construct high-performance Mg batteries.Electrochemical conversion reaction provides plenty of cathode options,and strategy for cathode selection and performance optimization is of special significance.In this work,Ni0.85Se with nanostructures of dispersive hexagonal nanosheets(D-Ni0.85Se)and flower-like assembled nanosheets(F-Ni0.85Se)is synthesized and investigated as Mg-storage cathodes.Compared with F-Ni0.85Se,D-Ni0.85Se delivers a higher specific capacity of 168 mAh g^-1 at 50 mA g^-1 as well as better rate performance,owing to its faster Mg^2+-diffusion and lower resistance.D-Ni0.85Se also exhibits a superior cycling stability over 500cycles.An investigation on mechanism indicates an evolution of Ni0.85Se towards NiSe with cycling,and the Mg-storage reaction occurs between NiSe and metallic Ni^0.The present work demonstrates that advanced conversion-type Mg battery cathode materials could be constructed by soft selenide anions,and the electrochemical properties could be manipulated by rational material morphology optimization.

Lignin-based materials for electrochemical energy storage devices

Lignin is the most abundant aromatic polymer in nature,which is rich in a large number of benzene ring structures and active functional groups.The molecular structure of lignin has unique designability and controllability,and is a class of functional materials with great application prospects in energy storage and conversion.Here,this review firstly focuses on the concept,classification,and physicochemical property of lignin.Then,the application research of lignin in the field of electrochemical storage materials and devices are summarized,such as lignin-carbon materials and lignin-carbon composites in supercapacitors and secondary batteries.Finally,this review points out the bottlenecks that need to be solved urgently and the prospects for future research priorities.

Three-in-one fire-retardant poly(phosphate)-based fast ion-conductor for all-solid-state lithium batteries

The development of flame retardant or nonflammable electrolytes is the key to improve the safety of lithium batteries,owing to inflammable organic solvents and polymer matrix in common liquid and polymer electrolytes regarded as the main cause of battery fire.Herein,a series of solid-state polyphosphate oligomers(SPPO)as a three-in-one electrolyte that integrated the roles of lithium salt,dissociation matrix,and flame retardant were synthesized.The well-designed SPPO electrolytes showed an optimal ionic conductivity of 5.5×10^(-4)S cm-1at 30℃,an acceptable electrochemical window up to 4.0 V vs.Li/Li+,and lithium ion transference number of 0.547.Stable Li-ion stripping/plating behavior for 500 h of charge-discharge cycles without internal short-circuit in a Li|SPPO|Li cell was confirmed,together with outstanding interface compatibility between the SPPO electrolyte and lithium foil.The optimal Li|SPPO|LiFePO4cell presented good reversible discharge capacity of 149.4 mA h g-1at 0.1 C and Coulombic efficiency of 96.4%after 120 cycles.More importantly,the prepared SPPO cannot be ignited by the lighter fire and show a limited-oxygen-index value as high as 35.5%,indicating splendid nonflammable nature.The SPPO could be a promising candidate as a three-in-one solid-state electrolyte for the improved safety of rechargeable lithium batteries.

Recent progresses in the suppression method based on the growth mechanism of lithium dendrite

Lithium secondary batteries（LSBs） with high energy densities need to be further developed for future applications in portable electronic devices, electric vehicles, hybrid electric vehicles and smart grids. Lithium metal is the most promising electrode for next-generation rechargeable batteries. However, the formation of lithium dendrite on the anode surface leads to serious safety concerns and low coulombic efficiency.Recently, researchers have made great efforts and significant progresses to solve these problems. Here we review the growth mechanism and suppression method of lithium dendrite for LSBs’ anode protection. We also establish the relationship between the growth mechanism and suppression method. The research direction for building better LSBs is given by comparing the advantages and disadvantages of these methods based on the growth mechanism.

Charactering and optimizing cathode electrolytes interface for advanced rechargeable batteries:Promises and challenges

With the advancement of secondary batteries,interfacial properties of electrode materials have been recognized as essential factors to their electrochemical performance.However,the majority of investigations are devoted into advanced electrode materials synthesis,while there is insufficient attention paid to regulate their interfaces.In this regard,the solid electrolyte interphase(SEI)at anode part has been studied for 40 years,already achieving remarkable outcomes on improving the stability of anode candidates.Unfortunately,the study on the cathode electrolyte interfaces(CEI)remains in infancy,which constitutes a potential restriction to the capacity contribution,stability and safety of cathodes.In fact,the native CEI generally possesses unfavorable characteristics against structural and compositional stability that requires demanding optimization strategies.Meanwhile,an in-depth understanding of the CEI is of great significance to guide the optimization principles in terms of composition,structure,growth mechanism,and electrochemical properties.In this literature,recent progress and advances of the CEI characterization methods and optimization protocols are summarized,and meanwhile the mutually-reinforced mechanisms between detection and modification are explained.The criteria and the potential development of the CEI characterization are proposed with insights of novel optimization directions.

Electocbemical Process of Ti-Ni Alloy Electrodes by Cyclic Voltammetry

The electrochemical process of Ti-Ni alloy electrode was studied by using cyclic voltammetry. The hydrogen-absorbing electrode could be approximately regarded as a reversible hydrogen elecrede. The con- trolling steps of the discharging process varying with the anodic overpotentials were investigated and the effect ofelecrode constituent modification or Zr adulteation on the electrochemical behavior was also studied.

Nanocarbons and their hybrids as catalysts for non-aqueous lithium–oxygen batteries

Rechargeable lithium-oxygen (Li–O2) batteries have been considered as the most promising candidates for energy storage and conversion devices because of their ultra high energy density. Until now, the critical scientific challenges facing Li–O2batteries are the absence of advanced electrode architectures and highly efficient electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which seriously hinder the commercialization of this technology. In the last few years, a number of strategies have been devoted to exploring new catalysts with novel structures to enhance the battery performance. Among various of oxygen electrode catalysts, carbon-based materials have triggered tremendous attention as suitable cathode catalysts for Li–O2batteries due to the reasonable structures and the balance of catalytic activity, durability and cost. In this review, we summarize the recent advances and basic understandings related to the carbon-based oxygen electrode catalytic materials, including nanostructured carbon materials (one-dimensional (1D) carbon nanotubes and carbon nanofibers, 2D graphene nanosheets, 3D hierarchical architectures and their doped structures), and metal/metal oxide-nanocarbon hybrid materials (nanocarbon supporting metal/metal oxide and nanocarbon encapsulating metal/metal oxide). Finally, several key points and research directions of the future design for highly efficient catalysts for practical Li–O2batteries are proposed based on the fundamental understandings and achievements of this battery field. ? 2016 Science Press

In-situ/operando characterization techniques in lithium-ion batteries and beyond

Nowadays,in-situ/operando characterization becomes one of the most powerful as well as available means to monitor intricate reactions and investigate energy-storage mechanisms within advanced batteries.The new applications and novel devices constructed in recent years are necessary to be reviewed for inspiring subsequent studies.Hence,we summarize the progress of in-situ/operando techniques employed in rechargeable batteries.The members of this large family are divided into three sections for introduction,including bulk material,electrolyte/electrode interface and gas evolution.In each part,various energy-storage systems are mentioned and the related experimental details as well as data analysis are discussed.The simultaneous strategies of various in-situ methods are highlighted as well.Finally,current challenges and potential solutions are concluded towards the rising influence and enlarged appliance of in-situ/operando techniques in the battery research.

Improved electrochemical hydrogen storage properties of Mg-Y thin films as a function of substrate temperature

Pd-capped Mg78Y22 thin films have been prepared by direct current magnetron co-sputtering system at different substrate temperatures and their electrochemical hydrogen storage properties have been investigated.It is found that rising substrate temperature to 60 ℃ can coarsen the surface of thin film,thus facilitating the diffusion of hydrogen atoms and then enhancing its discharge capacity to 1725 mAh·g-1.Simultaneously,the cyclic stability is effectively improved due to the increased adhesion force between film and substrate as a function of temperature.In addition,the specimen exhibits a very long and flat discharge plateau at about —0.67 V,at which nearly 60%of capacity is maintained.The property is favorable for the application in metal hydride/nickel secondary batteries.The results indicate that rising optimal substrate temperature has a beneficial effect on the electrochemical hydrogen storage of Mg-Y thin films.

Architectural design and electrochemical performance of MOF-based solid-state electrolytes for high-performance secondary batteries

Nowadays solid-state batteries have become a hot spot in the research of batteries and a significant candidate for commercial batteries for the increasing demands for good safety and excellent energy density.Metal-organic frameworks(MOFs)have been considered as suitable materials for solid-state electrolytes(SSEs)for the merits of regular channels and large specific surface areas,which can provide a promising structural platform for fast-ion conduction.Therefore,numerous kinds of MOF-based SSEs with enhanced electrochemical performance have been successfully synthesized and studied in recent years.In this review,the recent progress(synthesis methods,physical and chemical characteristics)of MOF-based SSEs for secondary batteries have been summarized.Finally,the challenges and opportunities faced by the future development in this field are put forward,hoping to provide some enlightenment for the synthesis of MOF-based SSEs,so as to create more efficient,long-lasting,and safe SSE-based secondary batteries.

High‑Mass‑Loading Electrodes for Advanced Secondary Batteries and Supercapacitors

The growing demand for advanced electrochemical energy storage systems(EESSs)with high energy densities for electric vehicles and portable electronics is driving the electrode revolution,in which the development of high-mass-loading electrodes(HMLEs)is a promising route to improve the energy density of batteries packed in limited spaces through the optimal enlargement of active material loading ratios and reduction of inactive component ratios in overall cell devices.However,HMLEs face significant challenges including inferior charge kinetics,poor electrode structural stability,and complex and expensive production processes.Based on this,this review will provide a comprehensive summary of HMLEs,beginning with a basic presentation of factors influencing HMLE electrochemical properties,the understanding of which can guide optimal HMLE designs.Rational strategies to improve the electrochemical performance of HMLEs accompanied by corresponding advantages and bottlenecks are subsequently discussed in terms of various factors ranging from inactive component modification to active material design to structural engineering at the electrode scale.This review will also present the recent progress and approaches of HMLEs applied in various EESSs,including advanced secondary batteries(lithium-/sodium-/potassium-/aluminum-/calcium-ion batteries,lithium metal anodes,lithium-sulfur batteries,lithium-air batteries,zinc batteries,magnesium batteries)and supercapacitors.Finally,this review will examine the challenges and prospects of HMLE commercialization with a focus on thermal safety,performance evaluation,advanced characterization,and production cost assessment to guide future development.

Multi-electron Reaction Materials for High-Energy-Density Secondary Batteries:Current Status and Prospective

To address increasing energy supply challenges and allow for the effective utilization of renewable energy sources,transformational and reliable battery chemistry are critically needed to obtain higher energy densities.Here,significant progress has been made in the past few decades in energetic battery systems based on the concept of multi-electron reactions to overcome existing barriers in conventional battery research and application.As a result,a systematic understanding of multi-electron chemistry is essential for the design of novel multi-electron reaction materials and the enhancement of corresponding battery performances.Based on this,this review will briefly present the advancements of multi-electron reaction materials from their evolutionary discovery from lightweight elements to the more recent multi-ion effect.In addition,this review will discuss representative multi-electron reaction chemistry and materials,including ferrates,metal borides,metal oxides,metal fluorides,lithium transition metal oxides,silicon,sulfur and oxygen.Furthermore,insertion-type,alloy-type and conversion-type multi-electron chemistry involving monovalent Li^(+) and Na^(+) cations,polyvalent Mg^(2+) and Al^(3+) cations beyond those of alkali metals as well as activated S^(2−) and O^(2−) anions are introduced in the enrichment and development of multi-electron reactions for electrochemical energy storage applications.Finally,this review will present the ongoing challenges and underpinning mechanisms limiting the performance of multi-electron reaction materials and corresponding battery systems.

Amorphous carbon-based materials as platform for advanced highperformance anodes in lithium secondary batteries

The growing concern for the exhaustion of fossil energy and the rapid revolution of electronics have created a rising demand for electrical energy storage devices with high energy density,for example,lithium secondary batteries(LSBs).With high surface area,low cost,excellent mechanical strength,and electrochemical stability,amorphous carbon-based materials(ACMs)have been widely investigated as promising platform for anode materials in the LSBs.In this review,we firstly summarize recent advances in the synthesis of the ACMs with various morphologies,ranging from zero-to three-dimensional structures.Then,the use of ACMs in Li-ion batteries and Li metal batteries is discussed respectively with the focus on the relationship between the structural features of the as-prepared ACMs and their roles in promoting electrochemical performances.Finally,the remaining challenges and the possible prospects for the use of ACMs in the LSBs are proposed to provide some useful clews for the future developments of this attractive area.

Engineering sphere-like porous FeF3@C cathode with rational interfacial designing towards high-power batteries

Due to the high theoretical capacity and energy density,conversion-type metal fluorides have captured plenty of attentions but still suffer from the inferior kinetic behaviors and serious capacity fading.For addressing the issues above,the strategies of surface/interface engineering are utilized for the preparation of sphere-like porous FeF3@C materials,where the as-resulted sample displays the uniform particle size(~150 nm in radii)and the ultrathin carbon layers(thickness of~10 nm).Significantly,benefitting from the rich oxygen of precursor,the interfacial chemical bonds Fe-O-C are successfully constructed between carbon matrix and FeF3 materials,accompanying by the enhancements of ions/electrons(e-)conductivity and stability.When used as Li-storage cathodes,the initial lithium-ions storage capacity could reach up to~400mAh·g^(-1) at 0.1 A·g^(-1).Even at 1.0 A·g^(-1),the capacity could be still remained at about 210 mAh·g^(-1),with the retention of 85%after 400 cycles.Assisted by the detailed kinetic behaviors,the considerable electrochemical properties come from the enhanced diffusion-controlled contributions,whilst the segregation of Fe with LiF is effectively alleviated by unique architecture.Moreover,during cycling,solid electrolyte interface film is reversibly formed/decomposed.Thus,this work is expected to offer rational exterior/interfacial designing strategies for metalbased samples.