Molecule‑Level Multiscale Design of Nonflammable Gel Polymer Electrolyte to Build Stable SEI/CEI for Lithium Metal Battery

The risk of flammability is an unavoidable issue for gel polymer electrolytes(GPEs).Usually,flameretardant solvents are necessary to be used,but most of them would react with anode/cathode easily and cause serious interfacial instability,which is a big challenge for design and application of nonflammable GPEs.Here,a nonflammable GPE(SGPE)is developed by in situ polymerizing trifluoroethyl methacrylate(TFMA)monomers with flame-retardant triethyl phosphate(TEP)solvents and LiTFSI–LiDFOB dual lithium salts.TEP is strongly anchored to PTFMA matrix via polarity interaction between-P=O and-CH_(2)CF_(3).It reduces free TEP molecules,which obviously mitigates interfacial reactions,and enhances flame-retardant performance of TEP surprisingly.Anchored TEP molecules are also inhibited in solvation of Li^(+),leading to anion-dominated solvation sheath,which creates inorganic-rich solid electrolyte interface/cathode electrolyte interface layers.Such coordination structure changes Li^(+)transport from sluggish vehicular to fast structural transport,raising ionic conductivity to 1.03 mS cm^(-1) and transfer number to 0.41 at 30℃.The Li|SGPE|Li cell presents highly reversible Li stripping/plating performance for over 1000 h at 0.1 mA cm^(−2),and 4.2 V LiCoO_(2)|SGPE|Li battery delivers high average specific capacity>120 mAh g^(−1) over 200 cycles.This study paves a new way to make nonflammable GPE that is compatible with Li metal anode.

Constructing Donor–Acceptor‑Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li^(+)Migration in Quasi‑Solid‑State Battery

Regulation the electronic density of solid-state electrolyte by donor–acceptor(D–A)system can achieve highly-selective Li^(+)transportation and conduction in solid-state Li metal batteries.This study reports a high-performance solid-state electrolyte thorough D–A-linked covalent organic frameworks(COFs)based on intramolecular charge transfer interactions.Unlike other reported COFbased solid-state electrolyte,the developed concept with D–A-linked COFs not only achieves electronic modulation to promote highly-selective Li^(+)migration and inhibit Li dendrite,but also offers a crucial opportunity to understand the role of electronic density in solid-state Li metal batteries.The introduced strong electronegativity F-based ligand in COF electrolyte results in highlyselective Li^(+)(transference number 0.83),high ionic conductivity(6.7×10^(-4)S cm^(−1)),excellent cyclic ability(1000 h)in Li metal symmetric cell and high-capacity retention in Li/LiFePO_(4)cell(90.8%for 300 cycles at 5C)than substituted C-and N-based ligands.This is ascribed to outstanding D–A interaction between donor porphyrin and acceptor F atoms,which effectively expedites electron transferring from porphyrin to F-based ligand and enhances Li^(+)kinetics.Consequently,we anticipate that this work creates insight into the strategy for accelerating Li^(+)conduction in high-performance solid-state Li metal batteries through D–A system.

Atomistic understanding of capacity loss in LiNiO_(2)for high-nickel Li-ion batteries:First-principles study

Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formation energy of Li_(x)NiO_(2).Meanwhile,the voltage profile is simulated and the ordered phases of lithium vacancies corresponding to concentrations of 1/4,2/5,3/7,1/2,2/3,3/4,5/6,and 6/7 are predicted.To understand the capacity decay in the experiment during the charge/discharge cycles,deoxygenation and Li/Ni antisite defects are calculated,revealing that the chains of oxygen vacancies will be energetically preferrable.It can be inferred that in the absence of oxygen atom in high delithiate state,the diffusion of Ni atoms is facilitated and the formation of Li/Ni antisite is induced.

A Solvent-Free Covalent Organic Framework Single-Ion Conductor Based on Ion-Dipole Interaction for All-Solid-State Lithium Organic Batteries

Single-ion conductors based on covalent organic frameworks(COFs)have garnered attention as a potential alternative to currently prevalent inorganic ion conductors owing to their structural uniqueness and chemical versatility.However,the sluggish Li+conduction has hindered their practical applications.Here,we present a class of solvent-free COF single-ion conductors(Li-COF@P)based on weak ion-dipole interaction as opposed to traditional strong ion-ion interaction.The ion(Li+from the COF)-dipole(oxygen from poly(ethylene glycol)diacrylate embedded in the COF pores)interaction in the Li-COF@P promotes ion dissociation and Li+migration via directional ionic channels.Driven by this single-ion transport behavior,the Li-COF@P enables reversible Li plating/stripping on Li-metal electrodes and stable cycling performance(88.3%after 2000 cycles)in organic batteries(Li metal anode||5,5’-dimethyl-2,2’-bis-p-benzoquinone(Me2BBQ)cathode)under ambient operating conditions,highlighting the electrochemical viability of the Li-COF@P for all-solid-state organic batteries.

Influences of transition metal on structural and electrochemical properties of Li[Ni_xCo_yMn_z]O_2(0.6≤x≤0.8) cathode materials for lithium-ion batteries

Li[NixCoyMn2]O2（0.6≤x≤0.8） cathode materials with a typical hexagonal α-NaFeO2 structure were prepared utilizing a co-precipitation method.It is found that the ratio of peak intensities of（003） to（104） observed from X-ray diffraction（XRD）increases with decreasing the Ni content or increasing the Co content.The scanning electron microscopy（SEM） images reveal that the small primary particles are agglomerated to form the secondary ones.As the Mn content increases,the primary and secondary particles become larger and the resulted particle size for the Li[Ni（0.6）Co（0.2）Mn（0.2）]O2 is uniformly distributed in the range of100-300 nm.Although the initial discharge capacity of the Li/Li[NixCoyMn2]O2 cells reduces with decreasing the Ni content,the cyclic performance and rate capability are improved with higher Mn or Co content.The Li[Ni（0.6）Co（0.2）Mn（0.2）]O2 can deliver excellent cyclability with a capacity retention of 97.1%after 50 cycles.

Synthesis of nanostructured Li_2FeSiO_4/C cathode for lithium-ion battery by solution method

Nanosphere-like Li2FeSiO4/C was synthesized via a solution method using sucrose as carbon sources under a mild condition of time-saving and energy-saving, followed by sintering at high temperatures for crystallization. The amount of carbon in the composite is less than 10% （mass fraction）, and the X-ray diffraction result confirms that the sample is of pure single phase indexed with the orthorhombic Pmn21 space group. The particle size of the Li2FeSiO4/C synthesized at 700 °C for 9 h is very fine and spherical-like with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, were tested. The cell of this sample can deliver a discharge capacity of 166 mA-h/g at C/20 rate in the first three cycles. After 30 cycles, the capacity decreases to 158 mA-h/g, and the capacity retention is up to 95%. The results show that this method can prepare nanosphere-like Li2FeSiO4/C composite with good electrochemical performance.

Preparation and electrochemical performance of 2LiFe_(1-x)Co_xPO_4-Li_3V_2(PO_4)_3/C cathode material for lithium-ion batteries

2LiFe1-xCoxPO4-Li3V2（P04）3/C was synthesized using Fel-2xCo2xVO4 as precursor which was prepared by a simple co-precipitation method. 2LiFej-xCoxPO4-Li3V2（PO4）3/C samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. All 2LiFel-xCoxPOa-Li3V2（PO4）3/C composites are of the similar crystal structure. The XRD analysis and SEM images show that 2LiFe0.96Co0.04PO4-Li3V2（PO4）3/C sample has the best-ordered structure and the smallest particle size. The charge-discharge tests demonstrate that these powders have the best electrochemical properties with an initial discharge capacity of 144.1 mA.h/g and capacity retention of 95.6% after 100 cycles when cycled at a current density of 0.1C between 2.5 and 4.5 V.

Lithium-Ion Charged Polymer Channels Flattening Lithium Metal Anode

The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein,we construct a lithium nitrate(LiNO_(3))-implanted electroactiveβphase polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)crystalline polymorph layer(PHL).The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels.These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes,decreasing the growth of lithium dendrites.The stretched molecular channels can also accelerate the transport of Li ions.The combined effects enable a high Coulombic efficiency of 97.0%for 250 cycles in lithium(Li)||copper(Cu)cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm^(-2)with ultrahigh Li utilization of 50%.Furthermore,the full cell coupled with PHL-Cu@Li anode and Li Fe PO_(4) cathode exhibits long-term cycle stability with high-capacity retention of 95.9%after 900 cycles.Impressively,the full cell paired with LiNi_(0.87)Co_(0.1)Mn_(0.03)O_(2)maintains a discharge capacity of 170.0 mAh g^(-1)with a capacity retention of 84.3%after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83.This facile strategy will widen the potential application of LiNO_(3)in ester-based electrolyte for practical high-voltage LMBs.

Synthesis, characterization and electrochemical performance of AlF_3-coated Li_(1.2)(Mn_(0.54)Ni_(0.16)Co_(0.08))O_2 as cathode for Li-ion battery

Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), and high resolution transmission electron microscope(HRTEM). XRD results show that the bare and AlF3-coated samples have typical hexagonal α-Na Fe O2 structure, and AlF3-coated layer does not affect the crystal structure of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2. Morphology measurements present that the AlF3 layer with a thickness of 5-7 nm is coated on the surface of the Li1.2(Mn0.54Ni0.16Co0.08)O2 particles.Galvanostatic charge-discharge tests at various rates show that the AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 has an enhanced electrochemical performance compared with the bare sample. At 1C rate, it delivers an initial discharge capacity of 208.2 m A·h/g and a capacity retention of 72.4% after 50 cycles, while those of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2 are 191.7 m A·h/g and 51.6 %, respectively.

Trend of Developing Aqueous Liquid and Gel Electrolytes for Sustainable,Safe,and High‑Performance Li‑Ion Batteries

Current lithium-ion batteries(LIBs)rely on organic liquid electrolytes that pose significant risks due to their flammability and toxicity.The potential for environmental pollution and explosions resulting from battery damage or fracture is a critical concern.Water-based(aqueous)electrolytes have been receiving attention as an alternative to organic electrolytes.However,a narrow electrochemicalstability window,water decomposition,and the consequent low battery operating voltage and energy density hinder the practical use of aqueous electrolytes.Therefore,developing novel aqueous electrolytes for sustainable,safe,high-performance LIBs remains challenging.This Review first commences by summarizing the roles and requirements of electrolytes–separators and then delineates the progression of aqueous electrolytes for LIBs,encompassing aqueous liquid and gel electrolyte development trends along with detailed principles of the electrolytes.These aqueous electrolytes are progressed based on strategies using superconcentrated salts,concentrated diluents,polymer additives,polymer networks,and artificial passivation layers,which are used for suppressing water decomposition and widening the electrochemical stability window of water of the electrolytes.In addition,this Review discusses potential strategies for the implementation of aqueous Li-metal batteries with improved electrolyte–electrode interfaces.A comprehensive understanding of each strategy in the aqueous system will assist in the design of an aqueous electrolyte and the development of sustainable and safe high-performance batteries.

From Liquid to Solid‑State Lithium Metal Batteries:Fundamental Issues and Recent Developments

The widespread adoption of lithium-ion batteries has been driven by the proliferation of portable electronic devices and electric vehicles,which have increasingly stringent energy density requirements.Lithium metal batteries(LMBs),with their ultralow reduction potential and high theoretical capacity,are widely regarded as the most promising technical pathway for achieving high energy density batteries.In this review,we provide a comprehensive overview of fundamental issues related to high reactivity and migrated interfaces in LMBs.Furthermore,we propose improved strategies involving interface engineering,3D current collector design,electrolyte optimization,separator modification,application of alloyed anodes,and external field regulation to address these challenges.The utilization of solid-state electrolytes can significantly enhance the safety of LMBs and represents the only viable approach for advancing them.This review also encompasses the variation in fundamental issues and design strategies for the transition from liquid to solid electrolytes.Particularly noteworthy is that the introduction of SSEs will exacerbate differences in electrochemical and mechanical properties at the interface,leading to increased interface inhomogeneity—a critical factor contributing to failure in all-solidstate lithium metal batteries.Based on recent research works,this perspective highlights the current status of research on developing high-performance LMBs.

Branch-Chain-Rich Diisopropyl Ether with Steric Hindrance Facilitates Stable Cycling of Lithium Batteries at-20℃

Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT),leading to low coulombic efficiency and limited cycle stability.Thus,it is essential to opti-mize the solvation structure thereby achieving a rapid desolvation process in LMBs at LT.Herein,we introduce branch chain-rich diisopropyl ether(DIPE)into a 2.5 M Li bis(fluorosulfonyl)imide dipropyl ether(DPE)elec-trolyte as a co-solvent for high-performance LMBs at-20℃.The incorporation of DIPE not only enhances the disorder within the electrolyte,but also induces a steric hindrance effect form DIPE’s branch chain,excluding other solvent molecules from Li+solvation sheath.Both of these factors contribute to the weak interactions between Li^(+)and solvent molecules,effectively reducing the desolvation energy of the electrolyte.Consequently,Li(50μm)||LFP(mass loading~10 mg cm^(-2))cells in DPE/DIPE based electrolyte demonstrate stable performance over 650 cycles at-20℃,delivering 87.2 mAh g^(-1),and over 255 cycles at 25℃ with 124.8 mAh g^(-1).DIPE broadens the electrolyte design from molecular structure considera-tions,offering a promising avenue for highly stable LMBs at LT.

Electrolyte Design for Low‑Temperature Li‑Metal Batteries:Challenges and Prospects

Electrolyte design holds the greatest opportunity for the development of batteries that are capable of sub-zero temperature operation.To get the most energy storage out of the battery at low temperatures,improvements in electrolyte chemistry need to be coupled with optimized electrode materials and tailored electrolyte/electrode interphases.Herein,this review critically outlines electrolytes’limiting factors,including reduced ionic conductivity,large de-solvation energy,sluggish charge transfer,and slow Li-ion transportation across the electrolyte/electrode interphases,which affect the low-temperature performance of Li-metal batteries.Detailed theoretical derivations that explain the explicit influence of temperature on battery performance are presented to deepen understanding.Emerging improvement strategies from the aspects of electrolyte design and electrolyte/electrode interphase engineering are summarized and rigorously compared.Perspectives on future research are proposed to guide the ongoing exploration for better low-temperature Li-metal batteries.

Dual Additives for Stabilizing Li Deposition and SEI Formation in Anode-Free Li-Metal Batteries

Anode-free Li-metal batteries are of significant interest to energy storage industries due to their intrinsically high energy.However,the accumulative Li dendrites and dead Li continuously consume active Li during cycling.That results in a short lifetime and low Coulombic efficiency of anode-free Li-metal batteries.Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase(SEI)stability for anode-free Li-metal batteries.Herein,we reveal that introducing dual additives,composed of LiAsF6 and fluoroethylene carbonate,into a low-cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC‖Cu anode-free Li-metal batteries.The NMC‖Cu anode-free Li-metal batteries with the dual additives exhibit a capacity retention of about 75%after 50 cycles,much higher than those with bare electrolytes(35%).The average Coulombic efficiency of the NMC‖Cu anode-free Li-metal batteries with additives can maintain 98.3%over 100 cycles.In contrast,the average Coulombic efficiency without additives rapidly decline to 97%after only 50 cycles.In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition.The dual additives significantly suppress the Li dendrite growth,enabling stable SEI formation on anode and cathode surfaces.Our results provide a broad view of developing low-cost and high-effective functional electrolytes for high-energy and long-life anode-free Li-metal batteries.

Thin polymer electrolyte with MXene functional layer for uniform Li^(+) deposition in all-solid-state lithium battery

Solid polymer electrolyte(SPE) shows great potential for all-solid-state batteries because of the inherent safety and flexibility;however, the unfavourable Li+deposition and large thickness hamper its development and application. Herein, a laminar MXene functional layer-thin SPE layer-cathode integration(MXene-PEO-LFP) is designed and fabricated. The MXene functional layer formed by stacking rigid MXene nanosheets imparts higher compressive strength relative to PEO electrolyte layer. And the abundant negatively-charged groups on MXene functional layer effectively repel anions and attract cations to adjust the charge distribution behavior at electrolyte–anode interface. Furthermore,the functional layer with rich lithiophilic groups and outstanding electronic conductivity results in low Li nucleation overpotential and nucleation energy barrier. In consequence, the cell assembled with MXene-PEO-LFP, where the PEO electrolyte layer is only 12 μm, much thinner than most solid electrolytes, exhibits uniform, dendrite-free Li+deposition and excellent cycling stability. High capacity(142.8 mAh g-1), stable operation of 140 cycles(capacity decay per cycle, 0.065%), and low polarization potential(0.5 C) are obtained in this Li|MXene-PEO-LFP cell,which is superior to most PEO-based electrolytes under identical condition. This integrated design may provide a strategy for the large-scale application of thin polymer electrolytes in all-solid-state battery.

Microwave synthesis of Li_2FeSiO_4 cathode materials for lithium-ion batteries

A novel synthetic method of microwave processing to prepare Li2FeSiO4 cathode materials is adopted. The Li2FeSiO4 cathode material is prepared by mechanical ball-milling and subsequent microwave processing. Olivin-type Li2FeSiO4 sample with uniform and fine particle sizes is successfully and fast synthesized by microwave heating at 700 ℃ in 12 rain. And the obtained Li2FeSiO4 materials show better electrochemical performance and microstructure than those of Li2FeSiO4 sample by the conventional solidstate reaction. ？2009 Yan Bing Cao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Recent progress on the recycling technology of Li-ion batteries

Lithium-ion batteries(LIBs)have been widely applied in portable electronic devices and electric vehicles.With the booming of the respective markets,a huge quantity of spent LIBs that typically use either LiFePO_(4) or Li N_(x)Co_(y)Mn_(z)O_(2) cathode materials will be produced in the very near future,imposing significant pressure for the development of suitable disposal/recycling technologies,in terms of both environmental protection and resource reclaiming.In this review,we firstly do a comprehensive summary of the-state-of-art technologies to recycle Li N_(x)Co_(y)Mn_(z)O_(2) and LiFePO_(4)-based LIBs,in the aspects of pretreatment,hydrometallurgical recycling,and direct regeneration of the cathode materials.This closed-loop strategy for cycling cathode materials has been regarded as an ideal approach considering its economic benefit and environmental friendliness.Afterward,as for the exhausted anode materials,we focus on the utilization of exhausted anode materials to obtain other functional materials,such as graphene.Finally,the existing challenges in recycling the LiFePO_(4) and Li N_(x)Co_(y)Mn_(z)O_(2) cathodes and graphite anodes for industrial-scale application are discussed in detail;and the possible strategies for these issues are proposed.We expect this review can provide a roadmap towards better technologies for recycling LIBs,shed light on the future development of novel battery recycling technologies to promote the environmental benignity and economic viability of the battery industry and pave way for the large-scale application of LIBs in industrial fields in the near future.

Electrochemical Studies of Lithium Intercalation into Graphite Film Electrode for Li^+-ion Batteries

To study the electrochemical kinetic properties of the Li/Graphite system, cycle voltammerty (CV), ac-impedance and chro- noamperometry (CA) techniques have been used. The results showed that the diffusion of lithium ions in Li_xC_6 is the rate-determining step. The chemical diffusion coefficients of lithium (D_Li) have been estimated for different x values. As for the same material, the value of D_Li was calculated in order to compare the differences among the three techniques.

Battery Separators Functionalized with Edge-Rich MoS2/C Hollow Microspheres for the Uniform Deposition of Li2S in High-Performance Lithium-Sulfur Batteries

As promising energy storage systems,lithium-sulfur(Li-S)batteries have attracted significant attention because of their ultra-high energy densities.However,Li-S battery suffers problems related to the complex phase conversion that occurs during the charge-discharge process,particularly the deposition of solid Li2S from the liquid-phase polysulfides,which greatly limits its practical application.In this paper,edge-rich MoS2/C hollow microspheres(Edg-MoS2/C HMs)were designed and used to functionalize separator for Li-S battery,resulting in the uniform deposition of Li2S.The microspheres were fabricated through the facile hydrothermal treatment of MoO3-aniline nanowires and a subsequent carbonization process.The obtained Edg-MoS2/C HMs have a strong chemical absorption capability and high density of Li2S binding sites,and exhibit excellent electrocatalytic performance and can effectively hinder the polysulfide shuttle effect and guide the uniform nucleation and growth of Li2S.Furthermore,we demonstrate that the Edg-MoS2/C HMs can effectively regulate the deposition of Li2S and significantly improve the reversibility of the phase conversion of the active sulfur species,especially at high sulfur loadings and high C-rates.As a result,a cell containing a separator functionalized with Edg-MoS2/C HMs exhibited an initial discharge capacity of 935 mAh g-1 at 1.0 C and maintained a capacity of 494 mAh g-1 after 1000 cycles with a sulfur loading of 1.7 mg cm-2.Impressively,at a high sulfur loading of 6.1 mg cm-2 and high rate of 0.5 C,the cell still delivered a high reversible discharge capacity of 478 mAh g-1 after 300 cycles.This work provides fresh insights into energy storage systems related to complex phase conversions.

Spinel lithium titanate (Li_4Ti_5O_(12)) as novel anode material for room-temperature sodium-ion battery

This is the first time that a novel anode material, spinel Li4Ti5O12 which is well known as a ＂zero-strain＂ anode material for lithium storage, has been introduced for sodium-ion battery. The Li4Ti5O12 shows an average Na storage voltage of about 1.0 V and a reversible capacity of about 145 mAh/g, thereby making it a promising anode for sodiumion battery. Ex-situ X-ray diffraction （XRD） is used to investigate the structure change in the Na insertion/deinsertion process. Based on this, a possible Na storage mechanism is proposed.