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.

Mechanical reliable,NIR light-induced rapid self-healing hydrogel electrolyte towards flexible zinc-ion hybrid supercapacitors with low-temperature adaptability and long service life

Hydrogel electrolytes hold great potential in flexible zinc ion supercapacitors(ZICs)due to their high conductivity,good safety,and flexibility.However,freezing of electrolytes at low temperature(subzero)leads to drastic reduction in ionic conductivity and mechanical properties that deteriorates the performance of flexible ZICs.Besides,the mechanical fracture during arbitrary deformations significantly prunes out the lifespan of the flexible device.Herein,a Zn^(2+)and Li^(+)co-doped,polypyrrole-dopamine decorated Sb_(2)S_(3)incorporated,and polyvinyl alcohol/poly(N-(2-hydroxyethyl)acrylamide)double-network hydrogel electrolyte is constructed with favorable mechanical reliability,anti-freezing,and self-healing ability.In addition,it delivers ultra-high ionic conductivity of 8.6 and 3.7 S m^(-1)at 20 and−30°C,respectively,and displays excellent mechanical properties to withstand tensile stress of 1.85 MPa with tensile elongation of 760%,together with fracture energy of 5.14 MJ m^(-3).Notably,the fractured hydrogel electrolyte can recover itself after only 90 s of infrared illumination,while regaining 83%of its tensile strain and almost 100%of its ionic conductivity during−30–60°C.Moreover,ZICs coupled with this hydrogel electrolyte not only show a wide voltage window(up to 2 V),but also provide high energy density of 230 Wh kg^(-1)at power density of 500 W kg^(-1)with a capacity retention of 86.7%after 20,000 cycles under 20°C.Furthermore,the ZICs are able to retain excellent capacity even under various mechanical deformation at−30°C.This contribution will open up new insights into design of advanced wearable flexible electronics with environmental adaptability and long-life span.

Incombustible solid polymer electrolytes:A critical review and perspective

Since the advent of the solid-state batteries,employing solid polymer electrolytes(SPEs)to replace routine flammable liquid electrolytes is regarded to be one of the most promising solutions in pursing highenergy-density battery systems.SPEs with superior thermal stability,good processability,and high mechanical modulus obtain increasing attentions.However,SPE-based batteries are not impenetrable due to their decomposition and combustibility under extreme conditions.Researchers believe incorporating appropriate flame-retardant additives/solvents/fragments into SPEs can intrinsically reduce their flammability to solve the battery safety issues.In this review,the recent research progress of incombustible SPEs,with special emphasis on flame-retardant structural design,is summarized.Specifically,a brief introduction of flame-retardant mechanism,evaluation index for safety of SPEs,and a detailed overview of the latest advances on diverse-types SPEs in various battery systems are highlighted.The deep insight into thermal ru naway process,the free-standing incombustible GPEs,and the ratio nal design of pouch cell structures may be the main directions to motivate revolutionary next-generation for safety batteries.

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.

PDOL-Based Solid Electrolyte Toward Practical Application:Opportunities and Challenges

Polymer solid-state lithium batteries(SSLB)are regarded as a promising energy storage technology to meet growing demand due to their high energy density and safety.Ion conductivity,interface stability and battery assembly process are still the main challenges to hurdle the commercialization of SSLB.As the main component of SSLB,poly(1,3-dioxolane)(PDOL)-based solid polymer electrolytes polymerized in-situ are becoming a promising candidate solid elec-trolyte,for their high ion conductivity at room temperature,good battery elec-trochemical performances,and simple assembly process.This review analyzes opportunities and challenges of PDOL electrolytes toward practical application for polymer SSLB.The focuses include exploring the polymerization mechanism of DOL,the performance of PDOL composite electrolytes,and the application of PDOL.Furthermore,we provide a perspective on future research directions that need to be emphasized for commercialization of PDOL-based electrolytes in SSLB.The exploration of these schemes facilitates a comprehensive and profound understanding of PDOL-based polymer electrolyte and provides new research ideas to boost them toward practical application in solid-state batteries.

Unique double-layer solid electrolyte interphase formed with fluorinated ether-based electrolytes for high-voltage lithium metal batteries

Li metal batteries using high-voltage layered oxides cathodes are of particular interest due to their high energy density.However,they suffer from short lifespan and extreme safety concerns,which are attributed to the degradation of layered oxides and the decomposition of electrolyte at high voltage,as well as the high reactivity of metallic Li.The key is the development of stable electrolytes against both highvoltage cathodes and Li with the formation of robust interphase films on the surfaces.Herein,we report a highly fluorinated ether,1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane(TTME),as a cosolvent,which not only functions as a diluent forming a localized high concentration electrolyte(LHCE),but also participates in the construction of the inner solvation structure.The TTME-based electrolyte is stable itself at high voltage and induces the formation of a unique double-layer solid electrolyte interphase(SEI)film,which is embodied as one layer rich in crystalline structural components for enhanced mechanical strength and another amorphous layer with a higher concentration of organic components for enhanced flexibility.The Li||Cu cells display a noticeably high Coulombic efficiency of 99.28%after 300 cycles and Li symmetric cells maintain stable cycling more than 3200 h at 0.5 mA/cm^(2) and 1.0m Ah/cm^(2).In addition,lithium metal cells using LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) and Li CoO_(2) cathodes(both loadings~3.0 m Ah/cm^(2))realize capacity retentions of>85%over 240 cycles with a charge cut-off voltage of 4.4 V and 90%for 170 cycles with a charge cut-off voltage of 4.5 V,respectively.This study offers a bifunctional ether-based electrolyte solvent beneficial for high-voltage Li metal batteries.

A multifunctional electrolyte additive for zinc-ion capacitors with low temperature resistant and long lifespan

Aqueous zinc-ion capacitors (ZICs) are considered as potential candidates for next generation electrochemical energy storage devices due to their high safety and low cost.However,the existing aqueous ZICs usually have the problems of zinc dendrite growth and unsatisfactory performance at low temperature.Herein,an erythritol (Eryt) additive with inhibition of zinc dendrites and anti-freezing capability was introduced into the ZnSO4electrolyte.The experimental characterization and theoretical calculation confirm that the Eryt adsorbed on the surface of zinc anodes regulates the deposition orientation of Zn^(2+) and inhibits the formation of dendrites.It also reconstructs the solvation structure in the electrolyte to reduce water activity,enabling the electrolyte to have a lower freezing point for operation at low temperature.With the assistance of Eryt,the Zn||Zn symmetric cell exhibits a long cycle life of 2000 h,while the ZIC assembled with activated carbon (AC) cathode and zinc anode (Zn||AC) maintains a capacity retention of 98.2% after 30,000 cycles at a current density of 10 A g^(-1)(even after 10,000 cycles at-20°C,the capacity retention rate reached 94.8%.).This work provides a highly scalable,low-cost and effective strategy for the protection of the anodes of low-temperature aqueous ZICs.

Effect of the anionic composition of sulfolane based electrolytes on the performances of lithium-sulfur batteries

In lithium-sulfur batteries,cell design,specifically electrolyte design,has a key impact on the battery performance.The effect of lithium salt anion donor number(DN)(DN[PF_(6)]^(-)=2.5,DN[N(SO_(2)CF_(3))_(2)]^(-)=5.4,DN[ClO_(4)]^(-)=8.4,DN[SO_(3)CF_(3)]^(-)=16.9,and DN[NO_(3)]^(-)=21.1)on the patterns of lithium-sulfur batteries and lithium metal electrode performances with sulfola ne-based electrolytes is investigated.An increase in DN of lithium salt anions leads to an increase in the depth and rate of electrochemical reduction of sulfur and long-chain lithium polysulfides and to a decrease in those for medium-and short-chain lithium polysulfides.DN of lithium salt anions has weak effect on the discharge capacity of lithium-sulfur batteries and the Coulomb efficiency during cycling,with the exception of LiSO_(3)CF_(3)and LiNO_(3).An increase in DN of lithium salt anions leads to an increase in the cycling duration of lithium metal anodes and to a decrease in the presence of lithium polysulfides.In sulfolane solutions of LiNO_(3)and LiSO_(3)CF_(3),lithium polysulfides do not affect the cycling duration of lithium metal anodes.

Long‐life lithium batteries enabled by a pseudo‐oversaturated electrolyte

The specific energy of Li metal batteries(LMBs)can be improved by using high‐voltage cathode materials;however,achieving long‐term stable cycling performance in the corresponding system is particularly challenging for the liquid electrolyte.Herein,a novel pseudo‐oversaturated electrolyte(POSE)is prepared by introducing 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether(TTE)to adjust the coordination structure between diglyme(G2)and lithium bis(trifluoromethanesulfonyl)imide(LiTFSI).Surprisingly,although TTE shows little solubility to LiTFSI,the molar ratio between LiTFSI and G2 in the POSE can be increased to 1:1,which is much higher than that of the saturation state,1:2.8.Simulation and experimental results prove that TTE promotes closer contact of the G2 molecular with Li^(+)in the POSE.Moreover,it also participates in the formation of electrolyte/electrode interphases.The electrolyte shows outstanding compatibility with both the Li metal anode and typical high‐voltage cathodes.Li||Li symmetric cells show a long life of more than 2000 h at 1 mA cm^(−2),1 mAh cm^(−2).In the meantime,Li||LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)cell with the POSE shows a high reversible capacity of 134.8 mAh g^(−1 )after 900 cycles at 4.5 V,1 C rate.The concept of POSE can provide new insight into the Li^(+)solvation structure and in the design of advanced electrolytes for LMBs.

Challenges in Li-ion battery high-voltage technology and recent advances in high-voltage electrolytes

The electrolyte directly contacts the essential parts of a lithium-ion battery,and as a result,the electrochemical properties of the electrolyte have a significant impact on the voltage platform,charge discharge capacity,energy density,service life,and rate discharge performance.By raising the voltage at the charge/discharge plateau,the energy density of the battery is increased.However,this causes transition metal dissolution,irreversible phase changes of the cathode active material,and parasitic electrolyte oxidation reactions.This article presents an overview of these concerns to provide a clear explanation of the issues involved in the development of electrolytes for high-voltage lithium-ion batteries.Additionally,solidstate electrolytes enable various applications and will likely have an impact on the development of batteries with high energy densities.It is necessary to improve the high-voltage performance of electrolytes by creating solvents with high thermal stabilities and high voltage resistance and additives with superior film forming performance,multifunctional capabilities,and stable lithium salts.To offer suggestions for the future development of high-energy lithium-ion batteries,we conclude by offering our own opinions and insights on the current development of lithium-ion batteries.

Interpenetrating network-reinforced gel polymer electrolyte for ultra-stable lithium−iodine batteries

Li-I2 batteries have attracted much interest due to their high capacity,exceptional rate performance,and low cost.Even so,the problems of unstable Li anode/electrolyte interface and severe polyiodide shuttle in Li-I2 batteries need to be tackled.Herein,the interfacial reactions on the Li anode and I2 cathode have been effectively optimized by employing a well-designed gel polymer electrolyte strengthened by cross-linked Ti-O/Si-O(GPETS).The interpenetrating network-reinforced GPETS with high ionic conductivity(1.88×10^(-3)S cm^(-1)at 25℃)and high mechanical strength endows uniform Li deposition/stripping over 1800 h(at 1.0mA cm^(-2),with a plating capacity of 3.0mAh cm^(-2)).Moreover,the GPETS abundant in surface hydroxyls is capable of capturing soluble polyiodides at the interface and accelerating their conversion kinetics,thus synergistically mitigating the shuttle effect.Benefiting from these properties,the use of GPETS results in a high capacity of 207 mAh g^(-1)(1 C)and an ultra-low fading rate of 0.013%per cycle over 2000 cycles(5 C).The current study provides new insights into advanced electrolytes for Li-I2 batteries.

Rational manipulation of electrolyte to induce homogeneous SEI on hard carbon anode for sodium-ion battery

Sodium-ion batteries (SIBs) have great potential to be the next major energy storage devices due to their obvious advantages and developing advanced electrodes and electrolytes is urgently necessary to promote its future industrialization.However,hard carbon as a state-of-the-art anode of SIBs still suffers from the low initial Coulomb efficiency and unsatisfactory rate capability,which could be improved by forming desirable solid electrolyte interphases (SEI) to some extent.Indeed,the chemistry and morphology of these interfacial layers are fundamental parameters affecting the overall battery operation,and optimizing the electrolyte to dictate the quality of SEI on hard carbon is a key strategy.Hence,this review summarizes the recent research on SEI design by electrolyte manipulation from solvents,salts,and additives.It also presents some potential mechanisms of SEI formation in various electrolyte systems.Besides,the current advanced characterization techniques for electrolyte and SEI structure analyses have been comprehensively discussed.Lastly,current challenges and future perspectives of SEI formation on hard carbon anode for SIBs are provided from the viewpoints of its compositions,evolution processes,structures,and characterization techniques,which will promote SEI efficient manipulation and improve the performance of hard carbon,and further contribute to the development of SIBs.

Asymmetric Electrolytes Design for Aqueous Multivalent Metal Ion Batteries

With the rapid development of portable electronics and electric road vehicles,high-energy-density batteries have been becoming front-burner issues.Traditionally,homogeneous electrolyte cannot simultaneously meet diametrically opposed demands of high-potential cathode and low-potential anode,which are essential for high-voltage batteries.Meanwhile,homogeneous electrolyte is difficult to achieve bi-or multi-functions to meet different requirements of electrodes.In comparison,the asymmetric electrolyte with bi-or multi-layer disparate components can satisfy distinct requirements by playing different roles of each electrolyte layer and meanwhile compensates weakness of individual electrolyte.Consequently,the asymmetric electrolyte can not only suppress by-product sedimentation and continuous electrolyte decomposition at the anode while preserving active substances at the cathode for high-voltage batteries with long cyclic lifespan.In this review,we comprehensively divide asymmetric electrolytes into three categories:decoupled liquid-state electrolytes,bi-phase solid/liquid electrolytes and decoupled asymmetric solid-state electrolytes.The design principles,reaction mechanism and mutual compatibility are also studied,respectively.Finally,we provide a comprehensive vision for the simplification of structure to reduce costs and increase device energy density,and the optimization of solvation structure at anolyte/catholyte interface to realize fast ion transport kinetics.

Acetic acid additive in NaNO_(3)aqueous electrolyte for long-lifespan Mg-air batteries

Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environmental sustainability,and cost-effectiveness.However,the fast hydrogen evolution reaction(HER)in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity,low energy density,and low utilization.Thus,the conventionally used NaCl solute was proposed to be replaced by NaNO_(3)and acetic acid additive as a corrosion inhibitor,therefore an electrolyte engineering for long-life time Mg-air batteries is reported.The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching~1.8 V for initial 5 h at a current density of 0.5 mA/cm^(2) and significantly prolonged cells'operational lifetime to over 360 h,in contrast to only~17 h observed in NaCl electrolyte.X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition.The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries.

Dilute Aqueous-Aprotic Electrolyte Towards Robust Zn-Ion Hybrid Supercapacitor with High Operation Voltage and Long Lifespan

With the merits of the high energy density of batteries and power density of supercapacitors,the aqueous Zn-ion hybrid supercapacitors emerge as a promising candidate for applications where both rapid energy delivery and moderate energy storage are required.However,the narrow electrochemical window of aqueous electrolytes induces severe side reactions on the Zn metal anode and shortens its lifespan.It also limits the operation voltage and energy density of the Zn-ion hybrid supercapacitors.Using'water in salt'electrolytes can effectively broaden their electrochemical windows,but this is at the expense of high cost,low ionic conductivity,and narrow temperature compatibility,compromising the electrochemical performance of the Zn-ion hybrid supercapacitors.Thus,designing a new electrolyte to balance these factors towards high-performance Zn-ion hybrid supercapacitors is urgent and necessary.We developed a dilute water/acetonitrile electrolyte(0.5 m Zn(CF_(3)SO_(3))_(2)+1 m LiTFSI-H_(2)O/AN)for Zn-ion hybrid supercapacitors,which simultaneously exhibited expanded electrochemical window,decent ionic conductivity,and broad temperature compatibility.In this electrolyte,the hydration shells and hydrogen bonds are significantly modulated by the acetonitrile and TFSI-anions.As a result,a Zn-ion hybrid supercapacitor with such an electrolyte demonstrates a high operating voltage up to 2.2 V and long lifespan beyond 120,000 cycles.

Study of the Relationship Between New Ionic Interaction Parameters and Salt Solubility in Electrolyte Solutions Based on Molecular Dynamics Simulation

Studying the relationship between ionic interactions and salt solubility in seawater has implications for seawater desalination and mineral extraction.In this paper,a new method of expressing ion-to-ion interaction is proposed by using molecular dynamics simulation,and the relationship between ion-to-ion interaction and salt solubility in a simulated seawater water-salt system is investigated.By analyzing the variation of distance and contact time between ions in an electrolyte solution,from both spatial and temporal perspectives,new parameters were proposed to describe the interaction between ions:interaction distance(ID),and interaction time ratio(ITR).The best correlation between characteristic time ratio and solubility was found for a molar ratio of salt-to-water of 10:100 with a correlation coefficient of 0.96.For the same salt,a positive correlation was found between CTR and the molar ratio of salt and water.For type 1-1,type 2-1,type 1-2,and type 2-2 salts,the correlation coefficients between CTR and solubility were 0.93,0.96,0.92,and 0.98 for a salt-to-water molar ratio of 10:100,respectively.The solubility of multiple salts was predicted by simulations and compared with experimental values,yielding an average relative deviation of 12.4%.The new ion-interaction parameters offer significant advantages in describing strongly correlated and strongly hydrated electrolyte solutions.

An intrinsically self-healing and anti-freezing molecular chains induced polyacrylamide-based hydrogel electrolytes for zinc manganese dioxide batteries

The anti-freezing strategy of hydrogels and their self-healing structure are often contradictory,it is vital to break through the molecular structure to design and construct hydrogels with intrinsic anti-freezing/self-healing for meeting the rapid development of flexible and wearable devices in diverse service conditions.Herein,we design a new hydrogel electrolyte(AF/SH-Hydrogel)with intrinsic anti-freezing/self-healing capabilities by introducing ethylene glycol molecules,dynamic chemical bonding(disulfide bond),and supramolecular interaction(multi-hydrogen bond)into the polyacrylamide molecular chain.Thanks to the exceptional freeze resistance(84%capacity retention at-20℃)and intrinsic self-healing capabilities(95%capacity retention after 5 cutting/self-healing cycles),the obtained AF/SH-Hydrogel makes the zinc||manganese dioxide cell an economically feasible battery for the state-of-the-art applications.The Zn||AF/SH-Hydrogel||MnO_(2)device offers a near-theoretical specific capacity of 285 m A h g^(-1)at 0.1 A g^(-1)(Coulombic efficiency≈100%),as well as good self-healing capability and mechanical flexibility in an ice bath.This work provides insight that can be utilized to develop multifunctional hydrogel electrolytes for application in next generation of self-healable and freeze-resistance smart aqueous energy storage devices.

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.

Regulating solid electrolyte interphase film on fluorinedoped hard carbon anode for sodium-ion battery

For the performance optimization strategies of hard carbon,heteroatom doping is an effective way to enhance the intrinsic transfer properties of sodium ions and electrons for accelerating the reaction kinetics.However,the previous work focuses mainly on the intrinsic physicochemical property changes of the material,but little attention has been paid to the resulting interfacial regulation of the electrode surface,namely the formation of solid electrolyte interphase(SEI)film.In this work,element F,which has the highest electronegativity,was chosen as the doping source to,more effectively,tune the electronic structure of the hard carbon.The effect of F-doping on the physicochemical properties of hard carbon was not only systematically analyzed but also investigated with spectroscopy,optics,and in situ characterization techniques to further verify that appropriate F-doping plays a positive role in constructing a homogenous and inorganic-rich SEI film.The experimentally demonstrated link between the electronic structure of the electrode and the SEI film properties can reframe the doping optimization strategy as well as provide a new idea for the design of electrode materials with low reduction kinetics to the electrolyte.As a result,the optimized sample with the appropriate F-doping content exhibits the best electrochemical performance with high capacity(434.53 mA h g^(-1)at 20mA g^(-1))and excellent rate capability(141 mAh g^(-1)at 400 mA g^(-1)).

Mechanism of high Li-ion conductivity in poly(vinylene carbonate)-poly(ethylene oxide)cross-linked network based electrolyte revealed by solid-state NMR

Solid polymer electrolytes(SPEs)have become increasingly important in advanced lithium-ion batteries(LIBs)due to their improved safety and mechanical properties compared to organic liquid electrolytes.Cross-linked polymers have the potential to further improve the mechanical property without trading off Li-ion conductivity.In this study,focusing on a recently developed cross-linked SPE,i.e.,the one based on poly(vinylene carbonate)-poly(ethylene oxide)cross-linked network(PVCN),we used solid-state nuclear magnetic resonance(NMR)techniques to investigate the fundamental interaction between the chain segments and Li ions,as well as the lithium-ion motion.By utilizing homonuclear/heteronuclear correlation,CP(cross-polarization)kinetics,and spin-lattice relaxation experiments,etc.,we revealed the structural characteristics and their relations to lithium-ion mobilities.It is found that the network formation prevents poly(ethylene oxide)chains from crystallization,which could create sufficient space for segmental tumbling and Li-ion co nductio n.As such,the mechanical property is greatly improved with even higher Li-ion mobilities compared to the poly(vinylene carbonate)or poly(ethylene oxide)based SPE analogues.