Interfacial engineering of perfluoroalkyl functionalized covalent organic framework achieved ultra-long cycled and dendrite-free lithium anodes

The finite lithium-ion utilization,short cycling life,and lower capacity retention caused by irreversible dendrite growth become the maximum dilemma in lithium metal batteries’(LMBs’)commercialization.Herein,a perfluoroalkyl-functionalized covalent organic framework(COF-F6)equipped with high stability and supernal proton conduction is introduced as an artificial solid electrolyte interface to stable the lithium metal anode.Benefiting from the strong electron-withdrawing effect of perfluoroalkyl,Li^(+)will be freed more by the competition of electronegative fluorine(F)and bis(trifluoromethanesulphonyl)imide anion(TFSI^(-)).The dissociation of LiTFSI and process of Li^(+)desolvation are easier to achieve.In addition,high electronegative fluorine can also regulate local electron-cloud density to induce the fast immigration of Li^(+).All the above roles contribute to improving the Li^(+)transfer number(0.7)and achieving the goal of inhibiting Li dendrite.As a result,the perfluoroalkyl COF-F6 modified LMB presents outstanding cycling stability.The symmetric batteries accomplish an overlong life-span of more than 5000 h with a lower hysteresis voltage(11 mV)at 5 mA·cm^(-2).Also,no dendrites are observed when using an in-situ optical microscope to learn the process of Li deposition.Therefore,this dendrite-free protection tactic holds broad prospects for the practical application of Li metal anodes.

Mitigated reaction kinetics between lithium metal anodes and electrolytes by alloying lithium metal with low-content magnesium

Lithium(Li)metal is regarded as a promising anode candidate for high-energy-density rechargeable batteries.Nevertheless,Li metal is highly reactive against electrolytes,leading to rapid decay of active Li metal reservoir.Here,alloying Li metal with low-content magnesium(Mg)is proposed to mitigate the reaction kinetics between Li metal anodes and electrolytes.Mg atoms enter the lattice of Li atoms,forming solid solution due to the low amount(5 wt%)of Mg.Mg atoms mainly concentrate near the surface of Mg-alloyed Li metal anodes.The reactivity of Mg-alloyed Li metal is mitigated kinetically,which results from the electron transfer from Li to Mg atoms due to the electronegativity difference.Based on quantitative experimental analysis,the consumption rate of active Li and electrolytes is decreased by using Mgalloyed Li metal anodes,which increases the cycle life of Li metal batteries under demanding conditions.Further,a pouch cell(1.25 Ah)with Mg-alloyed Li metal anodes delivers an energy density of 340 Wh kg^(-1)and a cycle life of 100 cycles.This work inspires the strategy of modifying Li metal anodes to kinetically mitigate the side reactions with electrolytes.

Design of multifunctional polymeric binders in silicon anodes for lithium‐ion batteries

Silicon(Si)is a promising anode material for lithium‐ion batteries(LIBs)owing to its tremendously high theoretical storage capacity(4200 mAh g−1),which has the potential to elevate the energy of LIBs.However,Si anodes exhibit severe volume change during lithiation/delithiation processes,resulting in anode pulverization and delamination with detrimental growth of solid electrolyte interface layers.As a result,the cycling stability of Si anodes is insufficient for commercialization in LIBs.Polymeric binders can play critical roles in Si anodes by affecting their cycling stability,although they occupy a small portion of the electrodes.This review introduces crucial factors influencing polymeric binders'properties and the electrochemical performance of Si anodes.In particular,we emphasize the structure–property relationships of binders in the context of molecular design strategy,functional groups,types of interactions,and functionalities of binders.Furthermore,binders with additional functionalities,such as electrical conductivity and self‐healability,are extensively discussed,with an emphasis on the binder design principle.

A layered multifunctional framework based on polyacrylonitrile and MOF derivatives for stable lithium metal anode

Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.

Hard-carbon hybrid Li-ion/metal anode enabled by preferred mesoporous uniform lithium growth mechanism

To achieve high energy density in lithium batteries,the construction of lithium-ion/metal hybrid anodes is a promising strategy.In particular,because of the anisotropy of graphite,hybrid anode formed by graphite/Li metal has low transport kinetics and is easy to causes the growth of lithium dendrites and accumulation of dead Li,which seriously affects the cycle life of batteries and even causes safety problems.Here,by comparing graphite with two types of hard carbon,it was found that hybrid anode formed by hard carbon and lithium metal,possessing more disordered mesoporous structure and lithophilic groups,presents better performance.Results indicate that the mesoporous structure provides abundant active site and storage space for dead lithium.With the synergistic effect of this structure and lithophilic functional groups(–COOH),the reversibility of hard carbon/lithium metal hybrid anode is maintained,promoting uniform deposition of lithium metal and alleviating formation of lithium dendrites.The hybrid anode maintains a 99.5%Coulombic efficiency(CE)after 260 cycles at a specific capacity of 500 m Ah/g.This work provides new insights into the hybrid anodes formed by carbon-based materials and lithium metal with high specific energy and fast charging ability.

3D Free-Standing Carbon Nanofibers Modified by Lithiophilic Metals Enabling Dendrite-Free Anodes for Li Metal Batteries

Li metal with high-energy density is considered as the most promising anode for the next-generation rechargeable Li metal batteries;however,the growth of Li dendrites seriously hinders its practical application.Herein,3D free-standing carbon nanofibers modified by lithiophilic metal particles(CNF/Me,Me=Sn,Fe,Co)are obtained in situ by the electrospinning method.Benefiting from the lithophilicity,the CNF/Me composite may effectively prevent the formation of Li dendrites in the Li metal batteries.The optimized CNF/Sn–Li composite electrode exhibits a stable cycle life of over 2350 h during Li plating/stripping.When matched with typical commercial LiFePO_(4)(LFP)cathode,the LFP//CNF/Sn–Li full cell presents a high initial discharge specific capacity of 139 mAh g^(−1)at 1 C,which remains at 146 mAh g^(−1)after 400 cycles.When another state-of-the-art commercial LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM(811))cathode is used,the assembled NCM//CNF/Sn–Li full cell shows a large initial specific discharge capacity of 206 mAh g^(−1)at substantially enhanced 10 C,which keeps at the good capacity of 99 mAh g^(−1)after 300 cycles.These results are greatly superior to the counterparts with Li as the anodes,indicating the great potential for practical utilization of the advanced CNF/Sn–Li electrode.

Boosting Zn^(2+)kinetics via the multifunctional pre-desolvation interface for dendrite-free Zn anodes

Aqueous zinc ion batteries(AZIBs)are an advanced secondary battery technology to supplement lithiumion batteries.It has been widely concerned and developed recently based on the element abundance and safety advantages.However,AZIBs still suffer from serious problems such as dendrites Zn,hydrogen evolution corrosion,and surface passivation,which hinder the further commercial application of AZIBs.Herein,an in-situ ZnCr_(2)O_(4)(ZCO)interface endows AZIBs with dendrite-free and ultra-low polarization by realizing Zn^(2+)pre-desolvation,constraining H2O-induced corrosio n,and boosting Zn^(2+)transport/deposition kinetics.The ZCO@Zn anode harvests an ultrahigh cumulative capacity of~20000 mA h cm^(-2)(cycle time:over 4000 h)at a high current density of 10 mA cm^(-2),indicating excellent reversibility of Zn deposition,Such superior performance is among the best cyclability in AZIBs.Moreover,the multifunctional ZCO interface improves the Coulombic efficiency(CE)to 99.7%for more than 2600 cycles.The outstanding electrochemical performance is also verified by the long-term cycle stability of ZCO@Zn//α-MnO_(2) full cells.Notably,the as-proposed method is efficient and low-cost enough to enable mass production.This work provides new insights into the uniform Zn electrodeposition at the scale of interfacial Zn^(2+)predesolvation and kinetics improvement.

Recent Progress and Prospects on Dendrite-free Engineerings for Aqueous Zinc Metal Anodes

Rechargeable zinc-ion batteries with mild aqueous electrolytes are one of the most promising systems for large-scale energy storage as a result of their inherent safety,low cost,environmental-friendliness,and acceptable energy density.However,zinc metal anodes always suffer from unwanted dendrite growth,leading to low Coulombic efficiency and poor cycle stability and during the repeated plating/stripping processes,which substantially restrict their further development and application.To solve these critical issues,a lot of research works have been dedicated to overcoming the drawbacks associated with zinc metal anodes.In this overview,the working mechanisms and existing issues of the zinc metal anodes are first briefly outlined.Moreover,we look into the ongoing processes of the different strategies for achieving highly stable and dendrite-free zinc metal anodes,including crystal engineering,structural engineering,coating engineering,electrolyte engineering,and separator engineering.Finally,some challenges being faced and prospects in this field are provided,together with guiding significant research directions in the future.

Porous LiF layer fabricated by a facile chemical method toward dendrite-free lithium metal anode

Lithium metal is supposed to be critical material for constructing next-generation batteries due to extremely high capacity and ultralow redox potential. However, the perplexing issue of lithium dendrite growth impedes the commercial application. The initial nucleation and low Li ions diffusion rate in the electrolyte/electrode interface dominate the deposition behavior. Therefore, a uniform and flexible interface is urgently needed. Here, a facile method is proposed to prepare a thin and porous LiF-rich layer (TPL) by the in-situ reaction of small amount of ammonium hydrogen difluoride (NH4HF2) and Li metal. The deposition morphology on Li metal anode with LiF layer is significantly flat and homogeneous owning to low lateral diffusion barrier on LiF crystals and the porous structure of TPL film. Additionally, the symmetrical cells made with such TPL Li anodes show significantly stable cycling over 100 cycles at high current density of 6 mA/cm^2. The TPL Li|LiFePO4 full cells keep over 99% capacity retention after 100 cycles at 2.0 C. This approach serves as a facile and controllable way of adjusting the protective layer on Li metal.

ZnCo2O4/ZnO induced lithium deposition in multi-scaled carbon/nickel frameworks for dendrite-free lithium metal anode

Lithium metal attracts growing attention as an ideal anode candidate for next generation lithium battery systems owing to its high capacity,low density,and low working potential.However,the volume expansion of the bulk and dendrite growth on the surface of lithium anode limits its practical application.Herein,we fabricate a composite lithium host featuring both multiple scaled structure and lithiophilic property to address obstacles at both aspects of bulk and surface simultaneously.In which,the multiple scaled structure provides void space to accommodate lithium volume change while zinc and cobalt oxides sites derived from Zeolitic Imidazolate Frameworks can react with lithium and form a stable solid electrolyte interphase,leading to a stable cycling of lithium symmetrical cell for more than 500 cycles with voltage hysteresis of only 88 mV at 2 mAcm^-2 and 5 mAh cm^-2.Moreover,full cells paired with LiFePO4 cathode can realize 500 cycles with 99.2%capacity retention,showing great potential for practical applications.The excellent electrochemical performance of the composite lithium anode proves the effectiveness of our anode design with multiple scaled structure and lithiophilic feature,which can be also expanded to other metal anodes for batteries.

Mesoporous Graphene Hosts for Dendrite-Free Lithium Metal Anode in Working Rechargeable Batteries

Lithium(Li) metal anode has received extensive attentions due to its ultrahigh theoretical capacity and the most negative electrode potential. However, dendrite growth severely impedes the practical applications of the Li metal anode in rechargeable batteries. In this contribution, a mesoporous graphene with a high specific surface area was synthesized to host the Li metal anode. The mesoporous graphene host(MGH) has a high specific surface area(2090 m^2/g), which affords free space and an interconnected conductive pathway for Li plating and stripping, thus alleviating the volume variation and reducing the generation of dead Li during repeated cycles. More importantly, the high specific surface area of MGH efficiently reduces the local current density of the electrode, which favors a uniform Li nucleation and plating behavior, rendering a dendritefree deposition morphology at a low overpotential. These factors synergistically boost the Li utilization(90.1% vs. 70.1% for Cu foil) and life span(150 cycles vs. 100 cycles for Cu foil) with a low polarization of MGH electrode at an ultrahigh current of 15.0 mA/cm^2. The as-prepared MGH can provide fresh insights into the electrode design of the Li metal anode operating at high rates.

Redistribution of Li-ions using covalent organic frameworks towards dendrite-free lithium anodes:a mechanism based on a Galton Board

Because of its high theoretical specific capacity and low reduction potential,Li metal is considered to be key to reaching high energy density in rechargeable batteries.In this context,most of the research has focused on suppressing dendrite formation during Li deposition to improve the cycling reversibility and safety of the batteries.Here,covalent organic framework(COF)film coating on a commercial polypropylene separator is applied as an ion redistributor to eliminate Li dendrites.The COF crystallites consist of ordered nanochannels that hinder the movement of anions while allowing Li-ions to transport across,leading to a high Li-ion transference number of 0.77±0.01.The transport of Li-ions across the COF film can be considered to be analogous to beads passing through a Galton Board,a model that demonstrates a statistical concept of a normal distribution.Thus,an even distribution of Li-ions is obtained at the COF/Li metal interface.The controlled Li-ion flux yields a smooth Li metal surface after 1,000 h(500 times)of cycling,leading to a significantly improved cycling stability and reversibility,as demonstrated by Cu||Li half cells,Li||Li symmetric cells,and Li Fe PO4||Li full cells.These results suggest that,following the principle of a Galton Board,nanopore insulators such as COF-based materials are effective ion distributors for the different energy storage or conversion systems.

Self-assembled, highly-lithiophilic and well-aligned biomass engineered MXene paper enables dendrite-free lithium metal anode in carbonate-based electrolyte

Lithium metal anode is the ideal candidate for high-energy–density rechargeable batteries.However,uncontrolled dendrite growth hampers its commercialization.Herein,a dendrite-free composite Li metal anode is realized by a flexible,freestanding,well-aligned and highly-lithiophilic MXene paper designed by a facile electrostatic self-assembly of the exfoliated MXene nanosheets and natural polysaccharidechitosan (MX@CS).The MX@CS paper gets a well-aligned layered-3D structure with a micro-crumpled surface that can effectively decrease the local current density,guide even Li plating and suppress dendritic Li growth.More importantly,surface-adsorbed chitosan endows enhanced lithiophilicity for MXene substrate and thus reduces the Li nucleation overpotential,which is confirmed by the density functional theory calculations.Abundant lithiophilic groups on MX@CS surface provide highconcentration Li^(+)anchoring site promoting Li nucleation and laterally inducing uniform Li deposition,which effectively avoids the formation of dendritic Li.As a result,the MX@CS-Li anode with a dendrite-free Li morphology shows a significantly improved cycling life in commercial carbonatebased electrolyte.When coupled with LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode,the full cell exhibits a low capacity decay and steady ultrahigh Coulombic efficiency of 99.6%at a current density of 5C.These findings develop a new approach for designing high-performance metal-based rechargeable batteries.

Freestanding polypyrrole nanotube/reduced graphene oxide hybrid film as flexible scaffold for dendrite-free lithium metal anodes

Lithium metal anode is the most potential anode material for the next generation high-energy rechargeable batteries owing to its highest specific capacity and lowest redox potential.Unfortunately,the uneven deposition of Li during plating/stripping and the formation of uncontrolled Li dendrites,which might cause poor battery performance and serious safety problems,are demonstrating to be a huge challenge for its practical application.Here,we show that a flexible and free-standing film hybriding with polypyrrole(PPy) nanotubes and reduced graphene oxide(rGO) can significantly regulate the Li nucleation and deposition,and further prohibit the formation of Li dendrites,owing to the large specific surface area,rich of nitrogen functional groups and porous structures.Finally,the high Coulombic efficiency and stable Li plating/stripping cycling performance with 98% for 230 cycles at 0.5 mA cm^(-2) and more than 900 hours stable lifespan are achieved.No Li dendrites form even at a Li deposition capacity as high as4.0 mA h cm^(-2).Besides,the designed PPy/rGO hybrid anode scaffold can also drive a superior battery performance in the lithium-metal full cell applications.

A two-dimension laminar composite protective layer for dendrite-free lithium metal anode

Lithium(Li)metal anodes with the high theoretical specific capacity(3860 mAh g^(-1))and most negative reduction potential(-3.04 V vs.standard hydrogen electrode)have been considered as an ultimate choice for energy storage devices with high energy density[1-4].However,the practical applications of Li metalbased batteries(LMBs)are confronted with two tough issues:Li dendrite growth induced by uneven Li depositions and unstable solid electrolyte interphase(SEI)(Fig.1a)[5,6].

A flexible artificial solid-electrolyte interlayer supported by compactness-tailored carbon nanotube network for dendrite-free lithium metal anode

A dendrite-free lithium metal anode requires a stable interface designed for efficient and reversible lithium plating and stripping. In this work, we have devised a mechanically flexible artificial Li_(3)N solid-electrolyte interlayer supported by a dual-layer compactness-tailored carbon nanotube fiber network. The more compact side of the network ensures a full coverage of Li_(3)N, which prevents the reaction between electrolyte and lithium. The other side, with sparsely distributed nanotube fibers, provides mechanical flexibility for the film, and induces three-dimensional lithium deposition along its structure without any dendrite formation. The resulting full cell with NCM811 cathode has a high capacity retention of 95.1% for 160 cycles compared with less than 80% for the control.

Powder metallurgical 3D nickel current collectors with plasma-induced Ni3N nanocoatings enabling long-life and dendrite-free lithium metal anode

Building three-dimensional(3D) current collectors is a promising strategy to surmount the bottlenecks of lithium metal anodes(LMAs), but the regulation methodology of a 3D current collector has seldom been considered comprehensively concerning both skeleton architectures and surface coatings. Herein, a robust porous 3D nickel skeleton(NS) with lithiophilic NiN nanocoatings(NiN@NS) is synthesized via an integrative route of powder metallurgy/plasma-enhanced nitridation technics. The facile powder metallurgical method facilitates the adjustment of NS architectures toward sufficient electrolyte adsorption and even current density distribution, while the followed plasma-enhanced chemical vapor deposition(PECVD) method can induce compact NiN nanocoatings on NS, which reduces the Li nucleation overpotential, accelerates the Li-ion transfer, and facilitates a highly reversible oriented texture of Li deposition morphology owing to the dense and homogenous deposition of Li into the pores. The optimized NiN@NS current collector shows a high averaged Coulombic efficiency(CE) of 98.8% over 350cycles, a prolonged lifespan of 1000 h(at 2 mA cm^(-2)) in symmetrical cells, together with the significant performance in full cells. The ingenious methodology reported in this work can also be broadly applicable for the controllable production of other 3D skeletons with nitride nanocoatings for various applications.

A review on anode materials for lithium/sodium-ion batteries

Since lithium-ion batteries(LIBs) have been substantially researched in recent years, they now possess exceptional energy and power densities, making them the most suited energy storage technology for use in developed and developing industries like stationary storage and electric cars, etc. Concerns about the cost and availability of lithium have prompted research into alternatives, such as sodium-ion batteries(SIBs), which use sodium instead of lithium as the charge carrier. This is especially relevant for stationary applications, where the size and weight of battery are less important. The working efficiency and capacity of these batteries are mainly dependent on the anode, cathode, and electrolyte. The anode,which is one of these components, is by far the most important part of the rechargeable battery.Because of its characteristics and its structure, the anode has a tremendous impact on the overall performance of the battery as a whole. Keeping the above in view, in this review we critically reviewed the different types of anodes and their performances studied to date in LIBs and SIBs. The review article is divided into three main sections, namely:(i) intercalation reaction-based anode materials;(ii) alloying reaction-based anode materials;and(iii) conversion reaction-based anode materials, which are further classified into a number of subsections based on the type of material used. In each main section, we have discussed the merits and challenges faced by their particular system. Afterward, a brief summary of the review has been discussed. Finally, the road ahead for better application of Li/Na-ion batteries is discussed, which seems to mainly depend on exploring the innovative materials as anode and on the inoperando characterization of the existing materials for making them more capable in terms of application in rechargeable batteries.

The etching strategy of zinc anode to enable high performance zinc-ion batteries

Zinc-ion batteries(ZIBs)are considered to be one of the most promising candidates to replace lithium-ion batteries(LIBs)due to the high theoretical capacity,low cost and intrinsic safety.However,zinc dendrites,hydrogen evolution reaction,surface passivation and other side reactions will inevitably occur during the charging and discharging process of Zn anode,which will seriously affect the cycle stability of the battery and hinder its practical application.The etching strategy of Zn anode has attracted wide attention because of its simple operation and broad commercial prospects,and the etched Zn anode can effectively improve its electrochemical performance.However,there is no comprehensive review of the etching strategy of Zn anode.This review first summarizes the challenges faced by Zn anode,then puts forward the etching mechanisms and properties of acid,salt and other etchants.Finally,based on the above discussion,the challenges and opportunities of Zn anode etching strategy are proposed.

In Situ Reaction Fabrication of a Mixed-Ion/Electron-Conducting Skeleton Toward Stable Lithium Metal Anodes

Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.