Ethylene Carbonate Research Articles

A high-voltage and low-solvating electrolyte towards promising micro-Si/Ni-rich NMC full cells

A full cell via pairing high-capacity silicon anode with high-voltage NMC cathode (Li(Ni0.83Co0.12Mn0.05)O2) holds great promise as a high-energy battery system for practical applications. Nevertheless, this potential has been hindered by challenges in terms of the pulverization of Si particles, unstable electrode/electrolyte interface, and severe dissolution of transition metals at high voltage. Herein, we present a novel high-voltage and weakly solvating electrolyte, consisted of lithium bis(fluorosulfonyl)imide in mixed solvent of diethyl carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, which effectively enables the remarkable cycling stability of both micron silicon anode (a high reversible capacity of 1667 mAh g−1 after 200 cycles) and Ni-rich cathode (a notable capacity retention of 83% after 140 cycles at an ultrahigh cut-off voltage of 4.9 V). It is revealed that the tailored electrolyte leads to the formation of a robust and reinforced concrete-like solid electrolyte interphase, characterized by a distinctive vertical side-by-side columnar structure comprised of LiF and sulfide on the micro-silicon anode. Meanwhile, a uniform and thin cathode-electrolyte interphase is observed on the surface of NMC particles when cycled in the designed electrolyte. Furthermore, coupled with high-capacity micro-Si and high-voltage NMC, this designed electrolyte endows a remarkable full-cell with high energy density (475 Wh kg−1), excellent rate capability, and high-voltage cycling stability. This research contributes a pioneering approach to enabling the utilization of micron-sized silicon anodes and Ni-rich cathodes for next-generation high-energy lithium-ion batteries.

Flexible Composite Electrolyte Membranes with Fast Ion Transport Channels for Solid-State Lithium Batteries.

Numerous endeavors have been dedicated to the development of composite polymer electrolyte (CPE) membranes for all-solid-state batteries (SSBs). However, insufficient ionic conductivity and mechanical properties still pose great challenges in practical applications. In this study, a flexible composite electrolyte membrane (FCPE) with fast ion transport channels was prepared using a phase conversion process combined with in situ polymerization. The polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) polymer matrix incorporated with lithium lanthanum zirconate (LLZTO) formed a 3D net-like structure, and the in situ polymerized polyvinyl ethylene carbonate (PVEC) enhanced the interface connection. This 3D network, with multiple rapid pathways for Li+ that effectively control Li+ flux, led to uniform lithium deposition. Moreover, the symmetrical lithium cells that used FCPE exhibited high stability after 1200 h of cycling at 0.1 mA cm-2. Specifically, all-solid-state lithium batteries coupled with LiFePO4 cathodes can stably cycle for over 100 cycles at room temperature with high Coulombic efficiencies. Furthermore, after 100 cycles, the infrared spectrum shows that the structure of FCPE remains stable. This work demonstrates a novel insight for designing a flexible composite electrolyte for highly safe SSBs.

Decoupling the Kinetic Essence of Iron‐Based Anodes through Anionic Modulation for Rational Potassium‐Ion Battery Design

AbstractPotassium‐ion batteries (PIBs) have favorable characteristics in terms of cell voltage and cost efficiency, making them a promising technology for grid‐scale energy storage. The rational design of suitable electrode materials on a theoretical basis, aiming at high power and energy density, is of paramount importance to bring this battery technology to the practical market. In this paper, a series of iron‐based compounds with different non‐metal anions are selectively synthesized to investigate the nature of kinetic differences induced by anionic modulation. A combination of experimental characterization and theoretical calculation reveals that iron phosphide, with its moderate adsorption energy (Ea) and lowest diffusion barrier (Eb), exhibits the best cycling and rate properties at low electrochemical polarization, which is related to the narrow Δd‐p band center gap that facilitates ion transfer. In addition, the optimization of the electrolyte formula results in the carbon‐supported iron phosphide anode running stably over 2000 cycles at 0.5 A g−1 and exhibiting a high rate capacity of 81.1 mAh g−1 at 2 A g−1. The superior electrochemical properties are attributed to the robust KF‐rich solid electrolyte interphase formed by the highly compatible KFSI in ethylene carbonate (EC)/diethyl carbonate (DEC) configuration.

Revolutionizing C–H Activation Reactions: Harnessing Green Solvents for Sustainable Catalysis

AbstractThis short review showcases the developing field of C–H activation reactions, with a particular focus on green catalysis through the use of environmentally friendly solvents. It evaluates the effects of these solvents on reaction outcomes, environmental aspects and general efficacy, highlighting their advantages that lead to greater selectivity, lower levels of toxicity and enhanced reaction rates. Water and biobased alternatives such as polyethylene glycols, glycerol, 2-methyltetrahydrofuran, γ-valerolactone, methanol, ethanol, p-cymene and diethyl carbonate are representative examples of such solvents. The scope of this short review encompasses studies of different methodologies, catalysts, and reaction conditions that help to develop C–H activation reactions utilizing green solvents.1 Introduction2 Water3 Polyethylene Glycols (PEGs)4 Glycerol5 2-Methyltetrahydrofuran (2-MeTHF)6 γ-Valerolactone (GVL)7 Methanol8 Ethanol9 p-Cymene10 Diethyl Carbonate11 Conclusion

Stabilizing cathode-electrolyte interphase by localized high-concentration electrolytes for high-voltage sodium-ion batteries

Sodium-ion batteries (SIBs) operating under high-voltages suffer from unstable cathode-electrolyte interphase (CEI) formed on the cathode surface, resulting in continuous electrolyte decomposition, surface reconstruction, transition metal dissolution, and eventually capacity decay. Therefore, designing high-voltage electrolyte and constructing the robust CEI are critical for high-energy SIBs. Herein, a localized high-concentration electrolyte (LHCE) is fabricated by dissolving sodium hexafluorophosphate in methyl ethyl carbonate, fluorinated ethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, which demonstrates oxidative stability exceeding 6 V relative to Na+/Na. The dense and homogeneous inorganics-rich CEIs are generated by the preferential decomposition of PF6− anions during the electrochemical charge to 4.4 V, which lower interface impedance, facilitate Na+ transportation and suppress subsequent side reactions. Consequently, the cell integrating high-voltage P2-Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2 cathode and Na anode exhibits a capacity retention of 87.3% after 200 cycles and a high-rate discharge capacity of 84 mA h g−1 at 20 C under a high cut-off voltage of 4.4 V. This work offers a feasible pathway to tailor electrolyte chemistry and interphase properties for practical next generation high-voltage SIBs.

Competitive Coordination of Sodium Ions for High-Voltage Sodium Metal Batteries with Fast Reaction Speed.

The unstable electrode-electrolyte interface and the narrow electrochemical window of normal electrolytes hinder the potential application of high-voltage sodium metal batteries. These problems are actually related to the solvation structure of the electrolyte, which is determined by the competition between cations coordinated with anions or solvent molecules. Herein, we design an electrolyte incorporating ethyl (2,2,2-trifluoroethyl) carbonate and fluoroethylene carbonate, which facilitates a pronounced level of cation-anion coordination within the solvation sheath by enthalpy changes to reduce the overall coordination of cation-solvents and increase sensitivity to salt concentration. Such an electrolyte regulated by competitive coordination leads to highly reversible sodium plating/stripping with extended cycle life and a high Coulombic efficiency of 98.0%, which is the highest reported so far in Na||Cu cells with ester-based electrolytes. Moreover, 4.5 V high-voltage Na||Na3V2(PO4)2F3 cells exhibit a high rate capability up to 20 C and an impressive cycling stability with an 87.1% capacity retention after 250 cycles with limited Na. The proposed strategy of solvation structure modification by regulating the competitive coordination of the cation provides a new direction to achieve stable sodium metal batteries with high energy density and can be further extended to other battery systems by controlling enthalpy changes of the solvation structure.

Ferroelectric BaTiO3 Regulating the Local Electric Field for Interfacial Stability in Solid-State Lithium Metal Batteries.

Solid-state Li metal batteries (SSLMBs) are widely investigated since they possess promising energy density and high safety. However, the poor interfacial compatibility between the electrolyte and electrodes limits their promising development. Herein, a robust composite electrolyte (poly(vinyl ethylene carbonate) electrolyte with 3 wt % of BaTiO3, PVEC-3BTO) with excellent interfacial performance is rationally designed by incorporating ferroelectric BaTiO3 (BTO) nanoparticles into the poly(vinyl ethylene carbonate) (PVEC) electrolyte matrix. Benefiting from the high dielectric constant and ferroelectric properties of BTO, the interfacial compatibility between electrolytes and electrodes was significantly improved. The enhanced Li+ transference number (0.64) of solid electrolyte and in situ generated BaF2 inorganic interphase contribute to the enhanced cycling stability of PVEC-3BTO based Li//Li symmetrical batteries. Furthermore, the antioxidation ability of PVEC-3BTO has also been enhanced by modulating the local electric field for good pairing with high-voltage LiCoO2 material. Therefore, in this work, the mechanism of BTO for improving interfacial compatibility is revealed, and also useful methods for addressing the interface issues of SSLMBs have been provided.

A compatibility study of protective coatings for temperature sensor integration into sodium-ion battery cells

Instrumented battery cells (i.e. those containing sensors) and smart cells (with integrated control and communication circuitry) are essential for the development of the next-generation battery technologies, such as Sodium-ion Batteries (SIBs). The mapping and monitoring of parameters, for example the quantification of temperature gradients, helps improve cell designs and optimise management systems. Integrated sensors must be protected against the harsh cell electrolytic environment. State-of-the-art coatings include the use of Parylene polymer (our reference case).We applied three new types of coatings (acrylic, polyurethane and epoxy based) to thermistor arrays mounted on flexible printed circuit board (PCBs). We systematically analyse the coatings: (i) PCB submersion within electrolyte vials (8 weeks); (ii) analysis of sample inserted into coin cell; (iii) analysis of sensor and cell performance data for 1Ah pouch SIBs. Sodium-based liquid electrolyte was selected, consisting of a 1 M solution of sodium hexafluorophosphate (NaPF6) dissolved in a mixture of ethylene carbonate and diethylene carbonate in a ratio of 3:7 (v/v%). Our novel experiments revealed that the epoxy based coated sensors offered reliable temperature measurements; superior performance observed compared to the Parylene sensors (erroneous results from one sample were reported, under 5 d submersed in electrolyte).Nuclear magnetic resonance (NMR) spectroscopy revealed in the case of most coatings tested, formation of additional species occurred during exposure to the different coatings applied to the PCBs. The epoxy-based coating demonstrated resilience to the electrolytic-environment, as well as minimal effect on cell performance (capacity degradation compared to unmodified-reference, within 2% for the coin cell, and within 3.4% for pouch cell). The unique methodology detailed in this work allows sensor coatings to be trialled in a realistic and repeatable cell environment. This study demonstrated for the first time that this epoxy-based coating enables scalable, affordable, and resilient sensors to be integrated towards next-generation Smart SIBs.

Experimental Investigations on Highly Conducting Solid Bio‐Polymer Electrolytes Based on Latex of Calotropis gigantea Plant

AbstractThe study has prepared highly conducting polymer electrolyte films using solution cast technique with poly(vinylidene fluoride‐co‐hexafluoropropylene) PVDF‐HFP, mixture of ethylene carbonate (EC), and propylene carbonate (PC) as plasticizer and latex of Calotropis gigantea (CGL) as an ionic source. In this study, four films are prepared using PVDF‐HFP:CGL in ratio 1:1 with the increasing concentration of EC+PC as 1, 2, 3, and 4 M named as 1:1:1, 1:1:2, 1:1:3, 1:1:4. The prepared polymer electrolyte is examined by polarized optical microscopy (POM), elemental dispersive X‐ray technique (EDX), and complex impedance spectroscopy. EDX and POM are studied for the surface morphology of all prepared samples and to investigate the porous nature of films. The enhancement in ionic conductivity occurs due to CGL and increasing amount of EC‐PC. Conductivity of highest composition (1:1:4) polymer electrolyte film is found to be ≈10−3 S cm−1. The optimized polymer electrolyte film is considered as a promising candidate for application in supercapacitors.

Product Yield Increasing More Than 20 Times Achieved by Reducing Water Poisoning for Direct Diethyl Carbonate Synthesis.

Diethyl carbonate (DEC) synthesis from CO2 and ethanol is a typical green chemical route for sustainable development and cleaner production. However, the bottleneck problem of a low DEC yield is still not solved at present. The DEC yield still maintains 0.5-5.0% unless expensive third additives are added. Compared to the cheap price of DEC, the third additives are generally more expensive. It is not advisible to use expensive chemicals to prepare cheap chemicals. In this work, the (ZrO2)1.0/(Fe2O3)1.0 catalyst was prepared by a novel template-precipitation method and the DEC yield of the DEC direct synthetic reaction only from CO2 and ethanol without third additives obtained 1.95%. After a series of supported catalysts were prepared, the DEC yield reached up to 46.1% for the (ZrO2)1.0/(Fe2O3)1.0@3A-CaO-CaC2 catalyst. This carrier can also be applied to other catalyst systems. CO2-TPD, NH3-TPD, and XRD were measured to analyze the microstructure and catalytic mechanism. Active center site theory was proposed to explain the intrinsic mechanism of catalyst activity. This new discovery of the mechanism and the DEC yield removed obstacles for the application of this reaction.

Room-Temperature Smart Sensor Based on Indium Acetate-Functionalized Perovskite CsPbBr3 Nanocrystals for Monitoring Electrolyte in Lithium-Ion Batteries.

Monitoring electrolyte components is an effective means of determining the safety status of lithium-ion batteries. In this study, indium acetate was taken as a ligand to functionalize perovskite CsPbBr3 nanocrystals, and then the room-temperature electrolyte sensor based on CsPbBr3 nanocrystals with ligand indium acetate was prepared. The sensor offers high response, long-term stability (21 days), and low detection limits for ethyl methyl carbonate (10 ppm), diethyl carbonate (10 ppm), and ethyl butyrate (1 ppm) gases at room temperature and boasts a fast response/recovery time (1500 ppm, 58.27/103.82 s, 33.58/40.62 s, and 45.05/103.08 s, respectively). Density functional theory results show that the gas sensitivity comes from the adsorption of an electrolyte, which changes the density-of-state distribution so that the electrical response curve changes. And using computational fluid dynamics simulation, it was found that the time required for gas detection by the built-in sensor (3.1 s) was 8.7 times shorter than that of the implantable sensor. This work provides inspiration and rationale for embedding and integrating room-temperature sensors into lithium-ion batteries to monitor safety and health conditions.

Deciphering the Formation and Accumulation of Solid-Electrolyte Interphases in Na and K Carbonate-Based Batteries.

The continuous solid-electrolyte interphase (SEI) accumulation has been blamed for the rapid capacity loss of carbon anodes in Na and K ethylene carbonate (EC)/diethyl carbonate (DEC) electrolytes, but the understanding of the SEI composition and its formation chemistry remains incomplete. Here, we explain this SEI accumulation as the continuous production of organic species in solution-phase reactions. By comparing the NMR spectra of SEIs and model compounds we synthesized, alkali metal ethyl carbonate (MEC, M = Na or K), long-chain alkali metal ethylene carbonate (LCMEC, M = Na or K), and poly(ethylene oxide) (PEO) oligomers with ethyl carbonate ending groups are identified in Na and K SEIs. These components can be continuously generated in a series of solution-phase nucleophilic reactions triggered by ethoxides. Compared with the Li SEI formation chemistry, the enhancement of the nucleophilicity of an intermediate should be the cause of continuous nucleophilic reactions in the Na and K cases.

Selective synthesis of methyl ethyl carbonate intensified by reactive distillation from consecutive transesterification of methyl carbonate and ethanol

Reactive distillation (RD) can be effectively used to improve the selectivity of the intermediate product for complex multi-reaction schemes, which involves using distillation to manipulate the column profiles in the RD column (RDC) to attribute the desired reaction and the manipulating reactions to facilitate separation. As the demand for ethyl methyl carbonate (EMC) has increased significantly due to its structural characteristics, the selective synthesis of EMC from the consecutive transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of azeotropes between reactants and products was studied as featured reaction schemes. The basic resin catalyst KC161 is utilized to build the kinetic reaction model and supplement the primary data for the process design. The pilot-scale RD experiments are explored to verify the feasibility and the reliability of the model. The impact of critical operation and structure parameters on the conversion and selectivity of the reaction and the azeotropes formed in the system were analyzed. A hybrid distillation process containing an RDC, pressure-swing distillation columns, and a regular distillation column, was designed and optimized based on minimized total annual cost (TAC) using a sequential iterative algorithm. 0. 9997 (mole purity) EMC and 0. 9999 (mole purity) diethyl carbonate (DEC) were obtained with EMC selectivity up to 0.863%.

Enhanced charge capacity and stability of Germanium(IV) Sulfide-Based anodes through Triton X100-Assisted synthesis and polysulfide shuttle mitigation

Highly soluble germanium oxide,an amorphous macroreticular form of germanium oxide, was used as a precursor for the deposition of GeS2on reduced graphene oxide (rGO) through a low-temperature, wet-chemistry process. Thermal treatment of the solid provided an ultrathin rGO – supported amorphous GeS2coating. The GeS2@rGO composite was tested as a lithium ion battery (LIB) anode. Leveraging the versatility of wet chemistry processing, we employed strategies initially developed for mitigating polysulfide shuttle effects in lithium-sulfur batteries to enhance anode performance. The anode exhibited exceptional stability, surpassing 1000 cycles, with charge capacities exceeding 1220 and 870 mAh.g−1 at rates of 2 and 5 A.g−1, respectively. Performance improvements were achieved by minimizing GeS2 grain size using the non-ionic surfactant Triton X-100 during synthesis and preventing polysulfide shuttle effects through a negatively charged thick glass fiber separator, fluoroethylene carbonate additive (FEC) in EC:DEC (ethylene carbonate: diethyl carbonate) solvent, and a polyacrylic acid (PAA) binder. These cumulative modifications more than tripled the charge capacity of the germanium sulfide LIB anode. Feasibility was further demonstrated through full cell studies using a LiCoO2 counter electrode.

Heteropoly acid catalysis in the valorization of bio-renewables: Acetylation of 1,4-cineole and 1,8-cineole (eucalyptol) in green solvents

In this work, a novel synthesis of monoterpenic acetate esters potentially valuable as flavoring agents was developed. It involves the reactions of 1,4-cineole and 1,8-cineole with acetic anhydride giving the desired products in 80–88 % total yields. The process is performed under ambient conditions in green solvents such as methyl isobutyl ketone, methyl ethyl ketone, dimethyl carbonate or diethyl carbonate in the presence of acidic cesium salt of phosphotungstic acid, Cs2.5H0.5PW12O40, as an efficient solid acid catalyst. The catalyst is stable toward leaching in the reaction system and can be reused. The process produces mixtures of acetate esters with different flavor bouquets which can be used directly as ingredients in fragrance compositions without separating individual compounds.

Effect of Temperature and Alkali Solution to Activate Diethyl Carbonate for Improving Rheological Properties of Modified Hydroxyethyl Methyl Cellulose.

The applications of cellulose ethers in the petroleum industry represent various limitations in maintaining their rheological properties with an increase in both concentration and temperature. This paper proposed a new method to improve the rheological properties of hydroxyethyl methyl cellulose (HEMC) by incorporating diethyl carbonate (DEC) as a transesterification agent and alkali base solutions. Fourier transform infrared (FTIR) analysis confirmed the grafting of both composites onto the HEMC surface. The addition of sodium hydroxide (NaOH) improved the stability of the polymeric solution as observed from ζ-potential measurement. Shear viscosity and frequency sweep experiments were conducted at concentrations of 0.25-1 wt % at ambient and elevated temperatures ranging from 80-110 °C using a rheometer. In the results, the increase in viscosity at specific times and temperatures indicated the activation of DEC through the saponification reactions with alkali solutions. All polymeric solutions exhibited shear-thinning behavior and were fitted well by the Cross model. NaOH-based modified solution exhibited low shear viscosity compared to the DEC-HEMC solution at ambient temperature. However, at 110 °C, its viscosity exceeded that of the DEC-HEMC solution due to the activation of DEC. In frequency sweep analysis, the loss modulus (G″) was greater than the storage modulus (G') at lower frequencies and vice versa at higher frequencies. This signifies the viscoelastic behavior of modified solutions at 0.50 wt % and higher concentrations. The flow point (G' = G″) shifted to a low frequency, indicating the increasing dominance of elastic behavior with the rising temperature. At 110 °C, the NaOH-based modified solution exhibited both viscous and elastic behavior, confirming the solution's thermal stability and flowability. In conclusion, modified HEMC solution was found to be effective in controlling viscosity under ambient conditions, enhancing solubility, and improving thermal stability. This modified composite could play a significant role in optimizing viscoelastic properties and fluid performance under challenging wellbore conditions.

Anion Intercalation into Graphite Electrode from Ethylene Carbonate Solutions Dissolving both Lithium Hexafluorophosphate and Lithium Bis(trifluoromethanesulfonyl)imide

Anion Intercalation into Graphite Electrode from Ethylene Carbonate Solutions Dissolving both Lithium Hexafluorophosphate and Lithium Bis(trifluoromethanesulfonyl)imide

Composition Analysis of the Solid Electrolyte Interface of NaK Anodes in Na-Ion Batteries.

Sodium-ion batteries have emerged as a promising alternative to Li-ion batteries due to the abundance of sodium. However, anodes in Na-ion batteries face challenges such as dendrite formation and an unstable solid electrolyte interface layer. To address these challenges, NaK liquid metal alloy anodes have been proposed as an alternative because they do not form dendrites. In our study, we demonstrate that the NaK alloy anode interacts with the commonly used ethylene carbonate and dimethyl carbonate electrolyte, leading to a continuously growing unstable SEI layer, evidenced by cycling failures under 100 cycles and an increasing charge transfer resistance in electrochemical impedance spectroscopy studies. In situ surface-enhanced Raman spectroscopy and X-ray photoelectron spectroscopy reveal that over the course of cycling the surface of the NaK anode becomes increasingly sodium-rich. After 30 cycles, XPS analysis detects only trace amounts of potassium on the NaK anode surface. When the electrolyte is analyzed postcycling using inductively coupled plasma optical emission spectroscopy, there is a noticeable increase in potassium levels, suggesting that potassium metal dissolves into the electrolyte. The introduction of a 10 wt % fluoroethylene carbonate additive can mitigate this problem to some extent, enabling an enhanced cycling performance of up to 800 cycles at 1C. Nevertheless, the dissolution of K metal is still evident in the XPS results, albeit to a lesser degree. These discoveries provide valuable insights for designing a more robust SEI layer for the NaK anode.

Biphasic solvents based on dual-functionalized ionic liquid for enhanced post-combustion CO2 capture and corrosion inhibition during the absorption process

To reduce the energy consumption for solvent regeneration and mitigate the corrosiveness of saturated solvents, dual-functionalized ionic liquid (IL) [DMAPA][TZ] was synthesized as a primary absorbent, and mixed with a phase separation accelerator poly (ethylene glycol) dimethyl ether (NHD) or propylene carbonate (PC) as biphasic solvents, to achieve high efficiency, energy savings, and corrosion inhibition of post-combustion CO2 capture. The results demonstrated a transition from a homogeneous solvent to a biphasic system upon CO2 absorption, with the majority of CO2 being concentrated in the rich phase, which is related to the formation of hydrogen bonds. Molecular dynamics analysis showed that interaction between the IL and PC is significantly stronger than that with NHD, resulting in a reduced absorption capacity of IL-PC relative to IL-NHD, while NHD effectively suppressed the formation of HCO3−/CO32−. At 373 K, both solvents exhibited efficient regeneration of their respective rich phases within 10 min. The calculated absorption enthalpies for IL-NHD and IL-PC are remarkably low at 0.662 and 0.772 GJ·t−1, respectively, and the regeneration energy consumption of IL-NHD was lower to 1.387 GJ·t−1. Notably, the phase separation accelerator exerts a significant influence on the phase-transition behavior and absorption products of biphasic solvents. Furthermore, ILs effectively inhibited corrosion through the adsorption-passivation mechanism; specifically, the corrosion rate of the CO2-rich phase in IL-NHD relative to 20# carbon steel was only 0.1896 mpy, which is only 1/865 of the rate of the saturated 5 M MEA solution.

Multifunctional Silane Additive Enhances Inorganic–Organic Compatibility with F‐rich Nature of Interphase to Support High‐Voltage LiNi0.5Mn1.5O4//graphite Pouch Cells

AbstractA novel electrolyte additive, 3, 3, 3‐trifluoropropylmethyldimethoxysilane (TFPMDS), is first proposed to modify both the cathode and the anode of lithium‐ion batteries at the same time. Charging/discharging tests demonstrate that the electrolyte with 1 wt% TFPMDS not only greatly improves the capacity retention of LiNi0.5Mn1.5O4 (LNMO)//Li cell (29.6%→90.8%) and graphite//Li cell (68.1%→98.3%), but also successfully ensures the long‐term cycle stability of LNMO//graphite pouch cell at 4.9 V. Further electrochemical measurements combining with spectroscopic characterization and theoretical calculations indicate that TFPMDS additive displays three principal functions: 1) Be preferentially oxidized to build a robust cathode electrolyte interphase (CEI) enriched in F/Si species with F‐rich nature of strong oxidation‐resistance. 2) Be able to scavenge the hazardous HF, F−, and H+ through its strong binding with these species and thus to protect LNMO at high‐voltage. 3) Be preferentially adsorbed on the graphite surface to form a “framework”, and to co‐construct an elastic solid electrolyte interphase (SEI) after the reduction of ethylene carbonate. Importantly, the Si─O group within TFPMDS is especially important for constructing a “molecular bridge” at the CEI/SEI interphase coupling the inorganic and organic species to improve its compatibility, stability, and elasticity.