Crystalline and amorphous metal sulfide composite electrode materials with long cycle life:Preparation and performance of hybrid capacitors

Crystalline@amorphous NiCo_(2)S_(4)@MoS_(2)(v-NCS@MS)nanostructures were designed and constructed via an ethylene glycol-induced strategy with hydrothermal synthesis and solvothermal method,which simultaneously realized the defect regulation of crystal NiCo_(2)S_(4) in the core.Taking advantage of the flexible protection of an amor-phous shell and the high capacity of a conductive core with defects,the v-NCS@MS electrode exhibited high specif-ic capacity(1034 mAh·g^(-1) at 1 A·g^(-1))and outstanding rate capability.Moreover,a hybrid supercapacitor was assembled with v-NCS@MS as cathode and activated carbon(AC)as anode,which can achieve remarkably high specific energy of 111 Wh·kg^(-1) at a specific power of 219 W·kg^(-1) and outstanding capacity retention of 80.5%after 15000 cycling at different current densities.

Ultralong cycle life enabled by in situ growth of CoMo_(1-x)P/Mo heterostructure for lithium-sulfur batteries

Lithium-sulfur batteries(Li-S batteries) are considered as promising new-generation electrochemical energy storage devices due to their extremely high theoretical energy density(2600 Wh kg-1) and theoretical specific capacity(1675 m Ah g^(-1)). However, numerous problems such as poor conductivity and the shuttle effect during discharge-charge process limit the practical application of lithium-sulfur batteries. In this work, porous tubular Co Mo_(1-x)P/Mo constructed by in situ growth of metal Mo was designed as the sulfur host for lithium-sulfur batteries. The introduction of Mo modulated the electronic structure of Co Mo P to improve the conductivity of cathode and facilitate the redox kinetics, as well as the Co Mo_(1-x)P/Mo heterostructure was beneficial to inhibit the shuttle effect through the interaction with lithium polysulfides, which improved cycling stability. As a result, Co Mo_(1-x)P/Mo/S cathode had a low-capacity decay rate of only 0.029% per cycle after 2000 cycles at 0.5 C. This work provided a new perspective for the further design of high-performance lithium-sulfur battery cathode materials.

Amorphous phosphorus chalcogenide as an anode material for lithiumion batteries with high capacity and long cycle life

The ever-increasing demands for modern energy storage applications drive the search for novel anode materials of lithium(Li)-ion batteries(LIBs) with high storage capacity and long cycle life, to outperform the conventional LIBs anode materials. Hence, we report amorphous ternary phosphorus chalcogenide(aP_(4)SSe_(2)) as an anode material with high performance for LIBs. Synthesized via the mechanochemistry method, the a-P_(4)SSe_(2) compound is endowed with amorphous feature and offers excellent cycling stability(over 1500 mA h g^(-1) capacity after 425 cycles at 0.3 A g^(-1)), owing to the advantages of isotropic nature and synergistic effect of multielement forming Li-ion conductors during battery operation. Furthermore,as confirmed by ex situ X-ray diffraction(XRD) and transmission electron microscope(TEM), the a-P_(4)SSe_(2)anode material has a reversible and multistage Li-storage mechanism, which is extremely beneficial to long cycle life for batteries. Moreover, the autogenous intermediate electrochemical products with fast ionic conductivity can facilitate Li-ion diffusion effectively. Thus, the a-P_(4)SSe_(2)electrode delivers excellent rate capability(730 mA h g^(-1)capacity at 3 A g^(-1)). Through in situ electrochemical impedance spectra(EIS) measurements, it can be revealed that the resistances of charge transfer(R_(SEI)) and solid electrolyte interphase(R_(Ct)) decrease along with the formation of Li-ion conductors whilst the ohmic resistance(R_(Ω)) remains unchanged during the whole electrochemical process, thus resulting in rapid reaction kinetics and stable electrode to obtain excellent rate performance and cycling ability for LIBs. Moreover, the formation mechanism and electrochemical superiority of the a-P_(4)SSe_(2)phase, and its expansion to P_(4)S_(3-x)Se_(x)(x = 0, 1, 2, 3) family can prove its significance for LIBs.

High-modulus solid electrolyte interphase layer with gradient composition enables long-cycle all-solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur batteries(ASSLSBs) have become one of the most potential candidates for the next-generation high-energy systems due to their intrinsic safety and high theoretical energy density.However, PEO-based ASSLSBs face the dilemma of insufficient Coulombic efficiency and long-term stability caused by the coupling problems of dendrite growth of anode and polysulfide shuttle of cathode. In this work, 1,3,5-trioxane(TOX) is used as a functional additive to design a PEO-based composite solidstate electrolyte(denoted as TOX-CSE), which realizes the stable long-term cycle of an ASSLSB. The results show that TOX can in-situ decompose on the anode to form a composite solid electrolyte interphase(SEI) layer with rich-organic component. It yields a high average modulus of 5.0 GPa, greatly improving the mechanical stability of the SEI layer and thus inhibiting the growth of dendrites. Also,the robust SEI layer can act as a barrier to block the side reaction between polysulfides and lithium metal.As a result, a Li-Li symmetric cell assembled with a TOX-CSE exhibits prolonged cycling stability over 2000 h at 0.2 m A cm^(-2). The ASSLSB also shows a stable cycling performance of 500 cycles at 0.5 C.This work reveals the structure–activity relationship between the mechanical property of interface layer and the battery's cycling stability.

A three-dimensional co-continuous network structure polymer electrolyte with efficient ion transport channels enabling ultralong-life all solid-state lithium metal batteries

Solid polymer electrolytes(SPEs)have emerged as one of the most promising candidates for the construction of solid-state lithium batteries due to their excellent flexibility,scalability,and interface compatibility with electrodes.Herein,a novel all-solid polymer electrolyte(PPLCE)was fabricated by the copolymer network of liquid crystalline monomers and poly(ethylene glycol)dimethacrylate(PEGDMA)acts as a structural frame,combined with poly(ethylene glycol)diglycidyl ether short chain interspersed serving as mobile ion transport entities.The preparaed PPLCEs exhibit excellent mechanical property and out-standing electrochemical performances,which is attributed to their unique three-dimensional cocontinuous structure,characterized by a cross-linked semi-interpenetrating network and an ionic liquid phase,resulting in a distinctive nanostructure with short-range order and long-range disorder.Remarkably,the addition of PEGDMA is proved to be critical to the comprehensive performance of the PPLCEs,which effectively modulates the microscopic morphology of polymer networks and improves the mechanical properties as well as cycling stability of the solid electrolyte.When used in a lithiumion symmetrical battery configuration,the 6 wt%-PPLCE exhibites super stability,sustaining operation for over 2000 h at 30 C,with minimal and consistent overpotential of 50 mV.The resulting Li|PPLCE|LFP solid-state battery demonstrates high discharge specific capacities of 160.9 and 120.1 mA h g^(-1)at current densities of 0.2 and 1 C,respectively.Even after more than 300 cycles at a current density of 0.2 C,it retaines an impressive 73.5%capacity.Moreover,it displayes stable cycling for over 180 cycles at a high current density of 0.5C.The super cycle stability may promote the application for ultralong-life all solid-state lithium metal batteries.

Mesoporous Mn-Sn bimetallic oxide nanocubes as long cycle life anodes for Li-ion half/full cells and sulfur hosts for Li-S batteries

Mesoporous Mn-Sn bimetallic oxide （BO） nanocubes with sizes of 15-30 run show outstanding stable and reversible capacities in lithium ion batteries CLIBs）, reaching 856.8 mAh.g-1 after 400 cycles at 500 mA·g^-1 and 506 mAh·g^-1 after 850 cycles at 1,000 mA·g^-1. The prelimLnary investigation of the reaction mechanism, based on X-ray diffraction measurements, indicates the occurrence of both conversion and alloying-dealloying reactions in the Mn-Sn bimetallic oxide electrode. Moreover, Mn-Sn BO//LiCoO2 Li-ion full cells were successfully assembled for the first time, and found to deliver a relatively high energy density of 176.25 Wh·kg^-1 at 16.35 W·kg^-1 （based on the total weight of anode and cathode materials）. The superior long-term stability of these materials might be attributed to their nanoscale size and unique mesoporous nanocubic structure, which provide short Li^＋ diffusion pathways and a high contact area between electrolyte and active material. In addition, the Mn-Sn BOs could be used as advanced sulfur hosts for lithium-sulfur batteries, owing to their adequate mesoporous structure and relatively strong chemisorption of lithium polysulfide. The present results thus highlight the promising potential of mesoporous Mn-Sn bimetallic oxides for application in Li-ion and Li-S batteries.

Synthesis of Co-Ni oxide microflowers as a superior anode for hybrid supercapacitors with ultralong cycle life

Li-ion hybrid capacitors（LIHCs）,composing of a lithium-ion battery（LIB） type anode and a supercapacitor（SC） type cathode,gained worldwide popularity due to harmonious integrating the virtues of high energy density of LIBs with high power density of SCs.Herein,nanoflakes composed microflower-like Co-Ni oxide（CoNiO） was successfully synthesized by a simple co-precipitation method.The atomic ratio of as-synthesized CoNiO is determined to be 1：3 through XRD and XPS analytical method.As a typical battery-type material,CoNiO and capacitor-type activated polyanilinederived carbon（APDC） were used to assemble LIHCs as the anode and cathode materials,respectively.As a result,when an optimized mass ratio of CoNiO and APDC was 1：2,CoNiO//APDC LIHC could deliver a maximum energy density of 143 Wh kg^-1 at a working voltage of 1-4 V.It is worth mentioning that the LIHC also exhibits excellent cycle stability with the capacitance retention of -78.2%after 15,000 cycles at a current density of 0.5 A g^-1.

Disjoint long cycles in a graph

We prove that ifG is a graph of order at least 2k with k≥9 and the minimum degree of G is at least k + 1,then G contains two vertex-disjoint cycles of order at least k.Moreover,the condition on the minimum degree is sharp.

Universal organic anodes enable safe low-cost aqueous rechargeable batteries with long cycle life,high capacity, and fast kinetics

Future battery advances and economies of scale will help scrub CO2emissions from transportation and the grid.Economical energy storage lets battery-powered electric vehicles replace internal combustion engines in the transportation sector,which now accounts for the plurality of CO2emissions.For grid-scale applications,the benefits of adding storage are many and well documented[1–2].Beyond increased penetration of intermittent renewable energy generated from such as solar panels

Lignin derived hierarchical porous carbon with extremely suppressed polyselenide shuttling for high-capacity and long-cycle-life lithium-selenium batteries

Lithium-selenium(Li-Se)batteries have attracted considerable attentions for next-generation energy storage systems owing to high volumetric capacity of 3265 m Ah cm^(-3) and excellent electronic conductivity(~10^(-5)S cm^(-1))of selenium.However,the shuttling effect and capacity fading prevent their wide applications.Herein we report a low-cost strategy for scalable fabrication of lignin derived hierarchical porous carbon(LHPC)as a new high-loading Se host for high-capacity and long-term cycling Li-Se batteries in carbonate electrolyte.The resulting LHPC exhibits three-dimensional(3D)hierarchically porous structure,high specific surface area of 1696 m^(2) g^(-1),and hetero-atom doping(O,S),which can effectively confine the Se particles into the micropores,and meanwhile,offer effective chemical binding sites for selenides from hetero-atoms(O,S).As a result,our Li-Se batteries based on Se@LHPC demonstrate high capacity of 450 m Ah g^(-1) at 0.5 C after 500 cycles,with a low capacity fading rate of only 0.027%.The theoretical simulation confirmed the strong affinity of selenides on the O and S sites of LHPC effectively mitigating the Se losing.Therefore,our strategy of using lignin as the low-cost precursor of hierarchically porous carbon for high-loading Se host offers new opportunities for high-capacity and long-life Li-Se batteries.

Engineering molecular regulation for SiO_(x) with long-term stable cycle and high Coulombic efficiency as lithium-ion battery anodes

In the current situation where the practical application of silicon anode materials encounters great challenges,silicon oxide(SiO_(x),0≤x≤2)has attracted the attention of researchers due to its relatively small volume expansion,stable cycling performance,and low cost,which is possible to realize commercial applications earlier than silicon anode.However,it remains a challenge to prepare SiO_(x)materials with long-term stable cycling performance and high Coulombic efficiency using low-cost methods.In this work,SiO_(x)anode material with high Coulombic efficiency and good long-term cycling stability was prepared at a low cost by hydrolysis of siloxane and in situ polymerization of phenolic resin.The hydrolysis of siloxane was further regulated by different silane coupling agents to regulate the size and microstructure of prepared SiO_(x)materials,which displayed the substantially improved electrochemical performance.The excellent electrochemical performance of SiO_(x)prepared by regulated hydrolysis of siloxane with silane coupling agents is attributed to the effect of silane coupling agent on size and microstructure of SiO_(x),revealing that the strategy of modulating the hydrolysis of siloxane by silane coupling agent is a potential method to prepare high-performance SiO_(x)materials.

Electrolyte design strategies towards long-term Zn metal anode for rechargeable batteries

Rechargeable Zinc(Zn)batteries exhibit great potentials as alternative energy storage devices due to their high safety,low cost,and environmental friendliness.However,the long-standing issues of low Coulombic efficiency(CE)and poor cycle stability of Zn anode,derived from dendrite,H_(2)evolution,and passivation are directly related to their thermodynamic instability in aqueous electrolyte,severely shorten the battery's cycle life.Recently reported electrolyte design strategies,which have made great progress to address Zn metal anode problems,are summarized into two categories,that is,aqueous electrolytes about cation-water interaction controlling and interface adjusting,and novel types of electrolytes towards less water,non-aqueous solvents,even no solvents.The final section shows the brief comparisons,including failure mechanisms of electrolyte exhaustion and short circuit for aqueous and nonaqueous electrolyte based full cells respectively,and possible perspectives for future research.

A cation-dipole-reinforced elastic polymer electrolyte enabling long-cycling quasi-solid-state lithium metal batteries

The application of ionic liquids(IL)in polymer electrolytes represents a safer alternative to the currently used organic solvents in lithium batteries due to their nonflammability and thermal stability.However,as a plasticizer,it is generally agreed that the introduction of ionic liquid usually leads to a trade-off between ion transport and mechanical properties of polymer electrolyte.Here we report the synthesis of an IL-embedded polymer electrolyte with both high ionic conductivity(2.77×10^(-4)S cm^(-1)at room temperature)and excellent mechanical properties(high tensile strength up to 11.4 MPa and excellent stretchability of 387%elongation at break)achieved by strong ion–dipole interactions between polymer electrolyte components,which was unveiled by the DFT calculation.Moreover,this polymer electrolyte also exhibits nonflammability,good thermal stability and the ability to recover reversibly from applied stress,i.e.,excellent elasticity.This highly viscoelastic polymer electrolyte enables tight interfacial contact and good adaptability with electrodes for stable lithium stripping/plating for 2000 h under a current density of 0.1 mA cm^(-2).By coupling with this polymer electrolyte,the LiFePO_(4)/Li cells exhibit outstanding cycling stability at room temperature as well as the reliability under extreme environmental temperature or being abused.

KOH-assisted aqueous synthesis of bimetallic metal-organic frameworks and their derived selenide composites for efficient lithium storage

To solve low efficiency,environmental pollution,and toxicity for synthesizing zeolitic imidazolate frameworks(ZIFs)in organic solvents,a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons,which are used as precursors to prepare bimetallic selenide and N-doped carbon(NC)composites.Among them,Fe–Co–Se/NC retains the three-dimensional(3D)polyhedrons with mesoporous structure,and Fe–Co–Se nanoparticles are uniform in size and evenly distributed.When assessed as anode material for lithium-ion batteries,Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 m Ah·g^(-1)at 1.0 A·g^(-1),and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 m Ah·g^(-1)after 550 cycles.It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites,the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte,and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.

KOH-assisted aqueous synthesis of ZIF-67 with high-yield and its derived cobalt selenide/carbon composites for high-performance Li-ion batteries

To solve the environmental pollution and low yield during the sythesis of zeolitic imidazolate frameworks(ZIFs)and their derived materials,a KOH-assisted aqueous strategy is proposed to synthesize cobalt zeolitic imidazolate framework(ZIF-67)polyhedrons,which are used as precursors to prepare cobalt selenide/carbon composites with different crystal phases(Co_(0.85)Se,CoSe_2).When evaluated as anode material for lithium ion batteries,Co_(0.85)Se/C composites deliver a reversible capacity of 758.7 m A·h·g^(-1)with a capacity retention rate of 90.5%at 1.0 A·g^(-1)after 500 cycles,and the superior rate capability is 620 m A·h·g^(-1)at 2.0 A·g^(-1).The addition of KOH accelerates the production of ZIF-67 crystals by boosting deprotonation of dimethylimidazole,resulting in rapid growth and structures transition from two-dimensional to three-dimensional of ZIF-67 in aqueous solution,which greatly promotes the application of MOFs in the field of energy storage and conversion.

Manipulating Horizontal Zn Deposition with Graphene Interpenetrated Zn Hybrid Foils for Dendrite-Free Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries(ZIBs)with intrinsic safety have great potentials in portable devices,but suffer from limited cycling life mainly caused by serious dendrite growth and unavoidable side reactions of Zn anodes.Herein,graphene interpenetrated Zn(GiZn)hybrid foils are developed for dendrite-free and long-term Zn anodes for high-performance ZIBs.The GiZn anode is prepared by interfacial assembly of reduced graphene oxide(rGO)on the skeletons of zinc foams,followed by mechanical compression into hybrid foils and drying process.The presence of the rGO nanosheets in the GiZn hybrid foils provides abundant zincophilic sites to induce horizontal Zn deposition for Zn metal anodes without the growth of dendrites.Meanwhile,the uniform distribution of rGO nanosheets endows the hybrid foils with superior conductivity and wetting ability with electrolytes for reduced interfacial resistances.As a result,GiZn-based symmetric cells exhibit a small voltage hysteresis of 30.4 mV and remarkable areal capacity of 30 mAh cm^(-2)at 0.5 mA cm^(-2).Further,GiZn anodes also enable the corresponding aqueous Zn||MnO_(2)batteries with high capacity of 168.5 mAh g^(-1)at 8 C,superior to the counterpart with pure Zn foil anodes(72.7 mAh g^(-1)).Therefore,GiZn hybrid foil anodes will shed light on the rational construction of 2D material-interpenetrated Zn hybrid foil anodes for high-performance ZIBs.

Intrinsic lithiophilic carbon host derived from bacterial cellulose nanofiber for dendrite-free and long-life lithium metal anode

Although lithium metal is considered a promising anode for advanced Li-S and Li-air batteries,the uncontrolled dendrite growth and infinite volume change impede its practical application.Herein,we report an ideal framework composed of carbonized bacterial cellulose(CBC)nanofibers,which shows intrinsic lithiophilicity to molten lithium without any lithiophilic surface modification.The wetting behavior of molten lithium can be significantly improved because its surface functional groups provide thermodynamical driving force,and the high surface roughness derived from nanocracks leads to rapid infusion in kinetics.The hybrid anode exhibits long cycle life up to 2000 h and excellent deep stripping-platting capacity up to 20 mAh·cm^(-2).When the anode is assembled with LiFePO_(4) cathode,the full cell delivers a good cycling stability up to 700 cycles.This is attributed to the intrinsic lithiophilic scaffold,which can not only lower the nucleation barrier of Li and provide uniform nucleation sites for stable Li stripping/plating,but also offer interspace to accommodate volume fluctuation of lithium during long cycling.This work provides a new manner to achieve a series of intrinsic lithiophilic carbon skeletons based on the large family of biomass materials and organic materials.

Nb_2O_5-carbon core-shell nanocomposite as anode material for lithium ion battery

Nb2O5-carbon nanocomposite is synthesized through a facile one-step hydrothermal reaction from sucrose as the carbon source, and stuclled as an anode material for high-performance lithium ion battery. The structural characterizations reveal that the nanocomposite possesses a core-shell structure with a thin layer of carbon shell homogeneously coated on the Nb2O5 nanocrystals. Such a unique structure enables the composite electrode with a long cycle life by preventing the Nb2O5 from volume change and pulverization during the charge-discharge process. In addition, the carbon shell efficiently improves the rate capability. Even at a current density of 500 mA.g-1, the composite electrode still exhibits a specific capacity of ~100 mAh.g-1. These results suggest the possibility to utilize the Nb2O5-carbon core-shell composite as a high performance anode material in the practical application of lithium ion battery.

Nitrogen-doped carbon stabilized Li Fe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries

Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices.Herein,we report an interface engineered Li Fe0.5Mn0.5PO4/rGO@C cathode material by the synergistic effects of r GO and polydopamine-derived N-doped carbon.The well-distributed Li Fe0.5Mn0.5PO4nanoparticles are tightly anchored on r GO nanosheet benefited by the coating of N-doped carbon layer.The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li+transfer path.Meantime,the high-speed conducting network has been constructed by r GO and N-doped carbon,which exhibits the face-to-face contact with Li Fe0.5Mn0.5PO4nanoparticles,guaranteeing the rapid electron transfer.These profits endow the Li Fe0.5Mn0.5PO4/rGO@C hybrids with a fast charge-discharge ability,e.g.a high reversible capacity of 105 m Ah·g^-1at 10 C,much higher than that of the Li Fe0.5Mn0.5PO4@C nanoparticles(46 mA·h·g^-1).Furthermore,a 90.8%capacity retention can be obtained even after cycling 500 times at 2 C.This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-power Li-ion batteries.

Layered barium vanadate nanobelts for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries(ZIBs)are deemed as the idea option for large-scale energy storage systems owing to many alluring merits including low manufacture cost,environmental friendliness,and high operations safety.However,to develop high-performance cathode is still significant for practical application of ZIBs.Herein,Ba_(0.23)V_(2)O_(5)·1.1H_(2)O(BaVO)nanobelts were fabricated as cathode materials of ZIBs by a typical hydrothermal synthesis method.Benefiting from the increased interlayer distance of 1.31 nm by Ba2+ and H2O pre-intercalated,the obtained BaVO nanobelts showed an excellent initial discharge capacity of 378 mAh·g^(-1) at 0.1 A·g^(-1),a great rate performance(e.g.,172 mAh·g^(-1) at 5 A·g^(-1)),and a superior capacity retention(93% after 2000 cycles at 5 A·g^(-1)).