Enabling High-Performance Sodium Battery Anodes by Complete Reduction of Graphene Oxide and Cooperative In-Situ Crystallization of Ultrafine SnO_(2)Nanocrystals

The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few-layer graphene sheets loaded with ultrafine SnO_(2)nanocrystals,using short exposure of microwave to xerogel of graphene oxide(GO)and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO(RGO).The resultant nanocomposites(SnO_(2)@MWG)enabled significantly quickened redox processes as SIB anode,which led to remarkable full anode-specific capacity reaching 538 mAh g^(−1)at 0.05 A g^(−1)(about 1.45 times of the theoretical capacity of graphite for the LIB),in addition to outstanding rate performance over prolonged charge–discharge cycling.Anodes based on the optimized SnO_(2)@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g^(−1),and capacity retention of over 70.4%was maintained at a high areal loading of 3.4 mg cm^(−2),highly desirable for high energy density SIBs to rival the current benchmark LIBs.

Facile preparation of core-shell Si@Li4Ti5O12 nanocomposite as large-capacity lithium-ion battery anode

As a promising alternative anode material,silicon(Si)presents a larger capacity than the commercial anode to achieve large capacity lithium-ion batteries.However,the application of pure Si as anode is hampered by limitations such as volume expansion,low conductivity and unstable solid electrolyte interphase.To break through these limitations,the core-shell Si@Li4Ti5O12nanocomposite,which was prepared via in-situ self-assembly reaction and decompressive boiling fast concentration method,was proposed in this work.This anode combines the advantages of nano-sized Si particle and pure Li4Ti5O12(LTO)coating layer,improving the performance of the lithium-ion batteries.The Si@Li4Ti5O12 anode displays a high initial discharge/charge specific capacity of 1756/1383 m Ahg^-1 at 500 mAg^-1(representing high initial coulombic efficiency of 78.8%),a large rate capability(specific capacity of 620 mAhg^-1 at4000 mAg^-1),an outstanding cycling stability(reversible specific capacity of 883 mAhg^-1 after 150 cycles)and a low volume expansion rate(only 3.3% after 150 cycles).Moreover,the synthesis process shows the merits of efficiency,simplicity,and economy,providing a reliable method to fabricate large capacity Si@Li4Ti5O12nanocomposite anode materials for practical lithium-ion batteries.

Monoclinic Cu_(3)(OH)_(2)V_(2)O_(7)·2H_(2)O nanobelts/reduced graphene oxide:A novel high-capacity and long-life composite for potassium-ion battery anodes

Developing suitable anode materials for potassium-ion batteries(PIBs)remains a great challenge owing to the limited theoretical capacity of active materials and large radius of K+ion(1.38?).To solve these obstacles,by integrating the principles of multielectron transfer and rational porous crystal framework,we creatively propose the monoclinic Cu_(3)(OH)_(2)V_(2)O_(7)·2H_(2)O(CVO)as a novel anode for PIBs.Furthermore,inspired by the metastable nature of CVO under high temperature/pressure,we skillfully design a facile hydrothermal recrystallization strategy without the phase change and surfactants addition.Thus,for the first time,the porous composite of Cu_(3)(OH)_(2)V_(2)O_(7)·2H_(2)O nanobelts covered in situ by reduced graphene oxide(CVO NBs/r GO)was assembled,greatly improving the deficiencies of CVO.When used as a novel anode for PIBs,CVO NBs/r GO delivers large specific capacity(up to 551.4 m Ah g^(-1)at 50 m A g^(-1)),high-rate capability(215.3 m Ah g^(-1)at 2.5 A g^(-1))and super durability(203.6 m Ah g^(-1)at 500 m A g^(-1)even after 1000 cycles).The outstanding performance can be ascribed to the synergistic merits of desirable structural features of monoclinic CVO nanobelts and the highly conductive graphene 3D network,thus promoting the composite material stability and electrical/ionic conductivity.This work reveals a novel metal vanadate-based anode material for PIBs,would further motivate the subsequent batteries research on M_(3)(OH)_(2)V_(2)O_(7)-n H_(2)O(M;Co,Ni,Cu,Zn),and ultimately expands valuable fundamental understanding on designing other high-performance electrode materials,including the combined strategies of multielectron transfer with rational porous crystal framework,and the composite fabrication of 1D electrode nanostructure with conductive carbon matrix.

Electrochemically exfoliated WS_(2)in molten salt for sodium-ion battery anode

The poor crystallinity and unstable crystal structure of tungsten disulfide(WS2)limit its application in practice.In this paper,a molten salt electrolysis method is proposed to intercalate metal ions into the interlayers of layered WS2 to obtain few-layer sheetlike structures.The effect of the molten salt system,applied constant current and electrolysis duration on the exfoliation degree of WS2 bulk has been investigated.The results show that the products electrolyzed in molten LiCl-NaCl-KCl and NaClKCl salts under 25 mA were more transparent and thinner flakes sheets due to the uniform intercalation of Li^+and Na^+with smaller size.The exfoliated WS_(2)was used as an anode material for sodium-ion batteries with a potential of 0.01-2.50 V.In comparison,the WS_(2)-NaCl-25 mA electrode displays a high reversible capacity of 373 mAh·g^(-1)at0.1 A·g^(-1)after cycling for 100 cycles at the same time showing great rate and cycle performance.It also presents a high capacitive ratio of 90.65%at 1.0 mV·s^(-1).The molten salt electrolysis provides a new perspective on the exfoliation of layered material,while demonstrating the great potential of WS2 as an anode material for sodium-ion battery.

In-situ encapsulation ofα-Fe_(2)O_(3) nanoparticles into ZnFe_(2)O_(4) micro-sized capsules as high-performance lithium-ion battery anodes

Transition metal oxides as anode materials for high-performance lithium-ion batteries suffer from severe capacity decay,originating primarily from particle pulverization upon volume expansion/shrinkage and the intrinsically sluggish electron/ion transport.Herein,in-situ encapsulation ofα-Fe_(2)O_(3) nanoparticles into micro-sized ZnFe_(2)O_(4) capsules is facilely fulfilled through a co-precipitation process and followed by heat-treatment at optimal calcination temperature.The porous ZnFe_(2)O_(4) scaffold affords a synergistic confinement effect to suppress the grain growth ofα-Fe2 O3 nanocrystals during the calcination process and to accommodate the stress generated by volume expansion during the charge/discharge process,leading to an enhanced interfacial conductivity and inhibit electrode pulverization and mechanical failure in the active material.With these merits,the preparedα-Fe_(2)O_(3)/Fe_(2)O_(4) composite delivers prolonged cycling stability and improved rate capability with a higher specific capacity than soleα-Fe_(2)O_(3) and Fe_(2)O_(4).The discharge capacity is retained at 700 mAh g-1 after 500 cycles at 200 mA g^(-1) and 940 mAh g^(-1) after 50 cycles at 100 m A g^(-1).This work provides a new perspective in designing transition metal oxides for advanced lithium-ion batteries with superior electrochemical properties.

Facile fabrication of ZnO-CuO porous hybrid microspheres as lithium ion battery anodes with enhanced cyclability

ZnO–CuO porous hybrid microspheres were successfully produced through a facile aging process of zinc citrate solid microspheres in copper sulfate solution combined with the subsequent annealing treatment in air atmosphere. The electrochemical performance investigation suggests that the harvested ZnO–CuO porous hybrid microspheres illustrate much higher specific capacity and better cycling stability than single ZnO counterparts. A reversible capacity of 585 mAh·g^-1 can be acquired for ZnO–CuO porous hybrid microspheres after cycling 500 times at a current density of 200 mA·g^-1. The porous configuration and the incorporation of CuO are responsible for the enhanced lithium storage properties of ZnO–CuO hybrids.

Scalable Synthesis of Hierarchical Antimony/Carbon Micro-/Nanohybrid Lithium/Sodium-Ion Battery Anodes Based on Dimethacrylate Monomer

A facile scalable synthesis of hierarchical Sb/C micro-/nanohybrid has been addressed in this work, which possesses the advantages of both micrometer and nanometer scale structures as lithium-ion battery anode. Difunctional methacrylate monomers are used as solvent and carbon source as well. Liquid precursor of antimony（III） n-butoxide is dissolved in the resin monomer solution, and further incorporated into the cross-linking polymer network via photo polymerization. Through calcination in argon/hydrogen atmosphere, antimony nanoparticles are in situ formed by carbothermal reduction, and homogeneously embedded in the in situ formed micrometer sized carbon matrix. The morphology, structure, crys- tallinity, spatial dispersion, composition, and electrochemical performance of the Sb/C micro-/nanohybrid are systemati- cally investigated. The cyclic and rate performance of the Sb/C micro-/nanohybrid anode have been effectively improved compared to the pure carbon anode. A reversible capacity of 362 mAh g-1 is achieved with a reasonable mass loading density after 300 cycles at 66 mA g-1, corresponding to capacity retention of 79%. With reducing mass loading density, the reversible capacity reaches 793 mAh g-1 after 100 cycles. Moreover, the electrochemical performance of Sb/C micro-/nanohybrid as sodium-ion battery anode is also investigated in this study.

Biomass seaweed-derived n itrogen self-doped porous carb on anodes for sodium-ion batteries:Insights into the structure and electrochemical activity

Sustainable transformation and efficient utilization of biomasses and their derived materials are environ-mentally as well as economically compliant strategies.Biomass seaweed-derived nitrogen self-doped porous carbon with tailored surface area and pore structures are prepared through carb on izatio n and activation.The in fluence of carb on ization temperature on morphology,surface area,and heteroatom dopants are investigated to optimize sodium-ion storage capability.Seaweed-derived nitrogen selfdoped activated carbon(SAC)as anode materials for sodium-ion batteries exhibits remarkable reversible capacity of 303/192 mAh g^(-1) after 100/500 cycles at current densities of 100/200 mA g^(-1) respectively,and a good rate capability.The interconnected and porous conducting nature along with the heteroatom dopant role in creating defective sites and charge stabilization are favorable for ion storage and diffusion and electron transport,indicating the electrodes can offer improved electrochemical performances.In addition,post-mortem analysis of the cycled carbon electrodes through ex-situ tools demonstrates the sodium-ion storage mechanism.

Understanding the Li diffusion mechanism and positive effect of current collector volume expansion in anode free batteries

In anode free batteries(AFBs), the current collector acts as anode simultaneously and has large volume expansion which is generally considered as a negative effect decreasing the structural stability of a battery. Moreover, despite many studies on the fast lithium diffusion in the current collector materials of AFB such as copper and aluminum, the involved Li diffusion mechanism in these materials remains poorly understood. Through first-principles calculation and stress-assisted diffusion equations, here we study the Li diffusion mechanism in several current collectors and related alloys and clarify the effect of volume expansion on Li diffusion respectively. It is suggested that due to the lower Li migration barriers in aluminum and tin, they should be more suitable to be used as AFB anodes, compared to copper, silver, and lead. The Li diffusion facilitation in copper with a certain number of vacancies is proposed to explain why the use of copper with a thickness≤100 nm as the protective coating on the anode improves the lifetime of the batteries. We show that the volume expansion has a positive effect on Li diffusion via mechanical–electrochemical coupling. Namely, the volume expansion caused by Li diffusion will further induce stress which in turn affects the diffusion. These findings not only provide in-depth insight into the operating principle of AFBs, but also open a new route toward design of improved anode through utilizing the positive effect of mechanical–electrochemical coupling.

Improvement on electrochemical performances of nanoporous titania as anode of lithium-ion batteries through annealing of pure titanium foils

The effect of annealing of Ti foils before anodization on the morphology and electrochemical performance of resultant nanoporous anatase TiO2 （np-TiO2） as anode in rechargeable lithium-ion batteries （LIBs） was investigated. The np-TiO2 anode fabricated from annealed Ti foils exhibited higher specific surface area and reduced pore diameter compared to np-TiO2 electrode fabricated from as-received Ti foils. The highly porous np-TiO2 anode fabricated from annealed Ti foils exhibited 1st discharge capacity of 453.25 mAh/g and reduced to 172.70 mAh/g at 1 C current rate after 300 cycles; whilst the np-TiO2 electrode fabricated from the as-received Ti foils exhibited 1st discharge capacity of 213.30 mAh/g and reduced to 160.0 mAh/g at 1 C current rate after 300cycles. Even after 400cycles, such np-TiO2 electrode exhibited a reversible capacity of 125.0 mAh/g at 2.5 C current rate. Compared to the untreated Ti foils, the enhanced electro- chemical performance of np-TiO2 anode fabricated from annealed Ti foils was ascribed to the annealing- induced removal of residual stress among the Ti atoms. The benefit of annealing process can reduce pore size of as-fabricated np-TiO2.

Experimental Investigation to Evaluate LiFePO4Batteries Anode and Cathode Elastic Properties under Cyclic Temperature Loading Conditions

Experimental investigations and associated methods are provided to characterize the mechanical properties of a lithium-ion battery accounting for operating temperature variation and thermal effects. Material properties for LiFeP04 cathode and anode samples taken from an off-the-shelf battery are evaluated in new and fatigued （subjec- ted to charging and discharging cycles） conditions.

Development and prospects of degradable magnesium alloys for structural and functional applications in the fields of environment and energy

Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.

Molten salt synthesis,morphology modulation,and lithiation mechanism of high entropy oxide for robust lithium storage

High entropy oxides(HEOs)with ideal element tunability and enticing entropy-driven stability have exhibited unprecedented application potential in electrochemical lithium storage.However,the general control of dimension and morphology remains a major challenge.Here,scalable HEO morphology modulation is implemented through a salt-assisted strategy,which is achieved by regulating the solubility of reactants and the selective adsorption of salt ions on specific crystal planes.The electrochemical properties,lithiation mechanism,and structure evolution of composition-and morphology-dependent HEO anode are examined in detail.More importantly,the potential advantages of HEOs as electrode materials are evaluated from both theoretical and experimental aspects.Benefiting from the high oxygen vacancy concentration,narrow band gap,and structure durability induced by the multi-element synergy,HEO anode delivers desirable reversible capacity and reaction kinetics.In particular,Mg is evidenced to serve as a structural sustainer that significantly inhibits the volume expansion and retains the rock salt lattice.These new perspectives are expected to open a window of opportunity to compositionally/morphologi cally engineer high-performance HEO electrodes.

Anodes for low-temperature rechargeable batteries

Rechargeable alkali metal ion(Li^(+),Na^(+),K^(+))batteries have shown great success in room-temperature energy storage.However,their low-temperature(subzero temperature)applications are still severely restricted,and the poor electrochemical performance of the anode materials at low temperature serves as a critical obstacle.Therefore,it is urgent to obtain a comprehensive understanding towards the key effects of low temperatures on the performance of the anodes and overview the related improving strategies.In this work,the effects that temperature would impose on electrode performance are firstly discussed.Next,the progress in low-temperature anodes of alkali metal ion batteries is reviewed,by the classification of the reaction types of the anode materials,including intercalation-type anodes,conversion-type anodes,alloy anodes and alkali metal anodes,and corresponding strategies to improve the performance of the anodes are summarized as well.At last,some promising research directions in this field are proposed.This work is intended to shed some light on future exploitation of high-performance low-temperature anode materials.

Re-evaluating the nano-sized inorganic protective layer on Cu current collector for anode free lithium metal batteries

Anode free lithium metal batteries(AF-LMBs)have conspicuous advantages both in energy density and the compatibility of battery manufacturing process.However,the limited cycle life of AF-LMBs is a crucial factor hindering its practical application.Fluorinated or nitride artificial inorganic solid electrolyte interphase(SEI)has been found as an effective method to prolong the lifespan of AF-LMBs.Herein,by investigating the impact of nano-sized inorganic gradient layers(LiF or Li3N)on initial Li deposition behavior,we notice that the Li^(+) diffusion barrier and the deposition morphology are highly depended on the thickness of inorganic layers.Thicker protective layers cause larger overpotential as well as more aggregated Li^(+) distribution.This study reveals that the ideal SEI should be synthesized thin and uniformly enough and uncontrollable artificial SEI can cause damage to the lifespan of AF-LMBs.

Metallurgical pyrolysis toward Co@Nitrogen-doped carbon composite for lithium storage

Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.

Interconnected Bi_(5)Nb_(3)O_(15)@CNTs network as high-performance anode materials of Li-ion battery

In this work,the facile carbon nanotubes(CNTs) modulation strategy was successfully used to fabricate Bi_(5) Nb_(3) O_(15)@CNTs composites as anode materials for lithium-ion battery by a simple solid-state route.The introduction of CNTs does not change the structure of the Bi_(5) Nb_(3) O_(15) materials,the Bi_(5) Nb_(3) O_(15) particles are decorated on a three-dimensional CNTs network,and the high conductive network promotes transfer of electron/ion and relieve the volume change of Bi_(5) Nb_(3) O_(15).The Bi_(5) Nb_(3) O_(15)@CNTs(8 wt%) electrode shows a superior rate capability with charge(discharge) capacities of 490(898.7),379.1(401.6),311.3(326.9),276.5(285.5) and 243.4(252)mAh·g^(-1) at 50,100,200,300 and 500 mA·g^(-1),respectively.However,the Bi_(5) Nb_(3) O_(15) only shows charge(discharge) capacities of 431(772.6),278.6(309.9),193.1(213.7),160.8(171.1),129.9(139.1) mAh·g^(-1) at the corresponding rates,respectively.The excellent rate capability of Bi_(5) Nb_(3) O_(15)@CNTs can be ascribed to the homogeneous distribution of Bi_(5) Nb_(3) O_(15) particles in the CNTs conductive network and the enhancement of conductivity.Hence,the CNTs modulation can be considered as an effective strategy to enhance electrochemical performances of Bi_(5) Nb_(3) O_(15) materials.

Coupling Co_(3)[Co(CN)_(6)]_(2) nanocubes with reduced graphene oxide for high-rate and long-cycle-life potassium storage

As one of prussian blue analogues,Co_(3)[Co(CN)_(6)]_(2) has been explored as a promising anode material for potassium-ion batteries(PIBs) owing to its high potassium storage capacity.Unfortunately,Co_(3)[Co(CN)_(6)]_(2) possesses low electronic conductivity and its structure collapses easily during potassiation and depotassiation,resulting in poor rate performance and cyclic stability.To solve these problems,we develop a facile multi-step method to successfully combine uniformCo_(3)[Co(CN)_(6)]_(2) nanocubes with rGO by C-O-Co bonds.As expected,these chemcial bonds shorten the distance betweenCo_(3)[Co(CN)_(6)]_(2) and rGO to the angstrom meter level,which significantly improve the electronic conductivity ofCo_(3)[Co(CN)_(6)]_(2).Besides,the complete encapsulation ofCo_(3)[Co(CN)_(6)]_(2) nanocubes by rGO endows the structure ofCo_(3)[Co(CN)_(6)]_(2) with high stability,thus withstanding repeated insertion/extraction of potassium-ions without visible morphological and structural changes.Benefiting from the abovementioned structural advantages,the CO3 [Co(CN)6]2/rGO nanocomposite exhibits a high reversible capacity of 400.8 mAh g^(-1) at a current density of 0.1 A g^(-1),an exceptional rate capability of 115.5 mAh g^(-1) at 5 A g^(-1), and an ultralong cycle life of 231.9 mAh g^(-1) at 0.1 A g^(-1) after 1000 cycles.Additionally,the effects of different amounts of rGO and different sizes ofCo_(3)[Co(CN)_(6)]_(2) nanocubes on the potassium storage performance are also studied.This work offers an ideal route to significantly enhance the electrochemical properties of prussian blue analogues.

Fabrication and application of hierarchical mesoporous MoO2/Mo2C/C microspheres

Hierarchical mesoporous MoO2/Mo2C/C microspheres,which are composed of primary nanoparticles with a size of about 30 nm,have been designed and synthesized through polymer regulation and subsequent carbonization processes.The as-synthesized microspheres were characterized by XRD,Raman,SEM,TEM,XPS measurements and so on.It was found that polyethylene glycol acted as a structure-directing agent,mild reducing agent and carbon source in the formation of these hierarchical mesoporous Mo O2/Mo2C/C microspheres.Moreover,the electrochemical property of the microspheres was also investigated in this work.Evaluated as an anode material for lithium ion batteries,the hierarchical mesoporous Mo O2/Mo2C/C electrode delivered the discharge specific capacities of 665 and 588 m Ah/g after 100 cycles at current densities of 100 and 200 m A/g,respectively.The satisfactory cycling performance and controllable process facilitate the practical applications of the hierarchical mesoporous Mo O2/Mo2C/C as a potential anode material in high-energy density lithium-ion batteries.

Fabrication of Nb2O5/C nanocomposites as a high performance anode for lithium ion battery

Nb_2O_5/C nanosheets are successfully prepared through a mixing process and followed by heating treatment.Such Nb_2O_5/C based electrode exhibits high rate performance and remarkable cycling ability,showing a high and stable specific capacity of ~380mAhg^（-1） at the current density of 50 mAg^（-1）（much higher than the theoretical capacity of Nb_2O_5）.Further more,at a current density of 500mAg^（-1）,the nanocomposites electrode still exhibits a specific capacity of above 150 mAh g^（-1） after 100 cycles.These results suggest the Nb_2O_5/C nanocomposite is a high performance anode material for lithium-ion batteries.