WO2016085666A1 - Additifs de suppression de film d'interphase électrolyte solide - Google Patents

Additifs de suppression de film d'interphase électrolyte solide Download PDF

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WO2016085666A1
WO2016085666A1 PCT/US2015/060406 US2015060406W WO2016085666A1 WO 2016085666 A1 WO2016085666 A1 WO 2016085666A1 US 2015060406 W US2015060406 W US 2015060406W WO 2016085666 A1 WO2016085666 A1 WO 2016085666A1
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Prior art keywords
carbonate
electrolyte composition
graphite
additive
mixture
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PCT/US2015/060406
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English (en)
Inventor
Wu Xu
Hongfa Xiang
Jiguang Zhang
Ruiguo Cao
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Battelle Memorial Institute
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Priority claimed from US14/595,065 external-priority patent/US9865900B2/en
Application filed by Battelle Memorial Institute filed Critical Battelle Memorial Institute
Publication of WO2016085666A1 publication Critical patent/WO2016085666A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H01G11/64—Liquid electrolytes characterised by additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • Lithium-ion batteries have been developed as a promising power source for electric vehicles because of their high energy density and long lifetime.
  • Graphite is widely used as an anode electrode material in the state-of-the-art LIBs.
  • a graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte.
  • EC ethylene carbonate
  • PC propylene carbonate
  • the graphite anode may suffer from a substantial exfoliation problem during the initial lithium intercalation step.
  • additives mainly include some functional groups such as vinylene or cyclic unsaturated group.
  • vinylene carbonate (VC), vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC) have been widely studied and used as SEI film-formation additives for PC-based electrolyte
  • compositions play an important role in the protection of the structure of the graphitic anode from destruction by PC.
  • SEI film-formation additives also are needed for some functional electrolyte systems, e.g., flame-retarded electrolytes or ionic liquid-based electrolytes.
  • an energy storage device comprising:
  • an energy storage device comprising:
  • an energy storage device comprising:
  • an energy storage device comprising:
  • an additive comprising a metal (M) salt that contains a M+ cation, wherein the M+ cation has a stronger solvation ability with ethylene carbonate compared to polyethylene carbonate;
  • Fig. 1 depicts initial voltage profiles of the Lilgraphite half-cells with various electrolytes
  • baseline 1.0 mole/liter LiPFe in EC+PC+EMC (5:2:3, wt.)
  • B-FEC baseline + 2 wt.
  • FEC and B-Cs baseline + 0.05 mole/liter LiCsPF6 additive.
  • Figs. 2A-2D are a comparison of the scanning electron microscopy (SEM) (FIGS. 2A, 2B) and the transmission electron microscopy (TEM) (FIGS. 2C, 2D) images of the surface morphologies of the graphite electrodes after the Lilgraphite half-cells were charged to 0.3 V at C/20 rate in the BCs electrolyte (FIGS. 2A, 2C) and the B-FEC electrolyte (FIGS. 2B, 2D).
  • SEM scanning electron microscopy
  • TEM transmission electron microscopy
  • Figs. 3A-3B show the cycling performance at room temperature (RT) and 60°C, respectively of the graphitelNCA full-cells with various electrolytes.
  • Fig. 3C shows the rate capability at RT of the graphitelNCA full-cells with various electrolytes.
  • Figs. 3D and 3E show SEM images of the surface morphologies of the graphite electrodes taken from the full-cells after 100 cycles at 60°C using B-Cs (FIG. 3D) and B-FEC electrolytes (FIG. 3E), respectively.
  • Figs. 4A-4B show the first-cycle voltage profiles of the Lilgraphite half-cells (FIG. 4A) and the graphitelNCA full-cells (FIG. 4B) with various PC-based electrolytes at room temperature.
  • the electrolytes include 1.0 mole/liter LiPFe in EC-PC-EMC (3:1:6, wt.) without and with 0.05 mole/liter CsPFe, and 1.0 mole/liter LiPFe in EC-PC-EMC (2:1:7, wt.) without and with 0.05 mole/liter CsPF 6 .
  • Figs. 5A-5B show the first-cycle voltage profiles of the Lilgraphite half-cells (FIG. 5A) and the graphitelNCA full-cells (FIG. 5B) with non-PC-based electrolytes at room temperature.
  • the electrolytes are 1.0 mole/liter LiPF 6 in EC-EMC (3:7, wt.) without and with 0.05 mole/liter CsPF 6 .
  • Anode An electrode in an electrochemical cell through which the electric charge flows into a polarized electrical device leading the anode active material or more precisely the anode active element in the anode to a higher valence. At the same time, negatively-charged anions move toward the anode and/or positively-charged cations move away from it to balance the electrons arriving from external circuitry. In a discharging battery, such as the disclosed lithium-ion battery or a galvanic cell, the anode is the negative terminal where electrons flow out. If the anode is composed of a metal, electrons that it gives up to the external circuit are accompanied by the formation of metal cations and their moving away from the electrode and into the electrolyte.
  • Anode active material A material that is included in an anode and produces the electrons that flow out of the anode in a discharging battery.
  • a cell refers to an electrochemical device used for generating a voltage or current from an electrochemical reaction, or the reverse in which an electrochemical reaction is induced by a current. Examples include voltaic cells, electrolytic cells, redox flow cells, and fuel cells, among others.
  • a battery includes one or more cells. The terms “cell” and “battery” are used interchangeably only when referring to a battery containing a single cell.
  • Coin cell A small, typically circular-shaped, or button-like, battery. Coin cells are characterized by their diameter and thickness. For example, a type 2325 coin cell has a diameter of 23 mm and a height of 2.5 mm.
  • Intercalation A term referring to the insertion of a material (e.g. , an ion, molecule, or group) between the atoms, molecules, or groups of another material.
  • a material e.g. , an ion, molecule, or group
  • lithium ions can insert, or intercalate, into graphite (C) to form lithiated graphite (LiC 6 ).
  • Specific capacity A term that refers to capacity per unit of mass. Specific capacity may be expressed in units of mAh/g, and often is expressed as mAh/g carbon when referring to a carbon- based electrode.
  • Batteries such as LIBs, typically comprise three components: an anode, and electrolyte and a cathode.
  • the anode and the cathode participate in electrochemical reactions to produce energy.
  • LIBs produce energy through electrochemical reactions occurring between the anode and cathode.
  • both the anode and cathode are made of materials into which, and from which, lithium ions can intercalate and de-intercalate.
  • lithium ions de-intercalate from the anode material and migrate through the electrolyte to the cathode into which they insert.
  • lithium ions are extracted from the cathode material and migrate through the electrolyte back to the anode where they reinsert.
  • Graphite anodes in LIBs are susceptible to exfoliation based on the electrolytes used.
  • appropriate compounds such as EC have to be used in the electrolyte composition in LIB systems to form a stable SEI film on the graphite anode surface, which only allows the insertion or deintercalation of Li + .
  • the compounds coordinated with Li + will co- intercalate into graphite layers of the anode and "exfoliate" the graphite structure leading to quick degradation and not allowing significant (greater than 50 cycles) battery or capacitor cycling without significant loss in specific capacity such that the device is not useful and/or economically useful as an energy storage device or system.
  • PC-based electrolytes could enable wide-temperature-range (-40 ⁇ +60°C) application of LIBs.
  • film-formation additives are widely used to improve cell performances in the battery industry.
  • the novel systems and compositions disclosed herein provide a more effective surface chemistry on graphite anode than the commonly used SEI film formation additives.
  • the additives disclosed herein can effectively build up an ultrathin but compact and stable SEI layer on graphite anode, therefore significantly improving the rate capability and cycling stability at elevated temperatures (such as up to +60°C).
  • the low-temperature performance of LIBs using such additives will be improved (such as down to -40°C).
  • the conventional SEI film- formation additive can form a thick SEI layer on the graphite surface by sacrificial reduction to protect the graphite anode from exfoliation, such an SEI layer usually increases the interfacial impedance especially at low temperatures and also has poor stability under thermal or high current density conditions.
  • the SEI layer built by the additive(s) disclosed herein is so thin and compact that the graphite exfoliation in a PC-containing electrolyte composition may be effectively suppressed and also exhibit enhanced rate capability (up to 5C or even IOC rate), cycling stability (for more than 1000 cycles) and low temperature performance (down to -40°C).
  • Electrolyte additives that can effectively reduce the SEI film formation and enhance the compatibility between graphite anode and non-aqueous electrolytes, especially for (PC)-containing electrolyte compositions are provided.
  • the additive is a metal (M) salt that contains M + cations.
  • M + cations have a stronger coordinating ability with EC compared to PC and other solvents, which preferentially results in the formation of a thin and stable SEI layer on the graphite prior to PC reductive decomposition.
  • graphite electrochemical exfoliation in the PC-containing electrolyte compositions can be suppressed effectively.
  • SEI film- formation additives such as fluoroethylene carbonate (FEC)
  • FEC fluoroethylene carbonate
  • the thickness of the ultrathin film is less than 3 nm, but that formed by the commonly used SEI film-formation additives is thicker than 3 nm. Additionally, there are some particles with the size of 30-50 nm embedded in the SEI layer built by FEC. Thus, the LIBs using the SEI film- suppression additives exhibit better rate capability and cycling stability at an elevated temperature and even lower temperature than those using the common film-formation additives.
  • cations in the context of the metal (M) salt refer to atoms or molecules having a net positive electrical charge.
  • the total number of electrons in the atom or molecule can be less than the total number of protons, giving the atom or molecule a net positive electrical charge.
  • Cations are not limited to the +1 oxidation state in any particular instance.
  • a cation can be generally represented as X + , which refers generally to any oxidation state, not just +1.
  • SEI film- suppression additive examples include, but are not limited to,
  • the SEI film-suppression additive can comprise an anion that includes, but is not limited to, PF 6 -, BF 4 -, AsFe “ , N(S0 2 CF 3 )2 " , N(S0 2 F) 2 -, CF3SO3-, C10 4 " , bis(oxalato)borate (BOB ), difluoro oxalato borate (DFOB ), ⁇ , CI " , NO3 " , S0 4 2” and combinations thereof.
  • the anion comprises PF6 " .
  • the SEI film- suppression additive is cesium hexafluorophosphate (CsPF 6 ), rubidium hexafluorophosphate (RbPF 6 ), strontium
  • the cations of the SEI film-suppression additive are not chemically or electrochemically reactive with respect to the Li cations of the lithium salt. Accordingly, the SEI film-suppression additive is not necessarily consumed during electrodeposition or during operation of an energy storage device.
  • the electrolyte composition also includes at least one organic carbonate solvent.
  • the solvent is propylene carbonate (PC).
  • the solvent is ethylene carbonate (EC).
  • Other carbonate solvents include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).
  • Optional co-solvents include methyl butyrate (MB), ethyl propionate (EP), trimethyl phosphate (TMPa), triethyl phosphate (TEPa), tris(2,2,2-trifluoroethyl) phosphate (TTFEPa), tributyl phosphate (TBPa), trimethyl phosphite (TMPi), triethyl phosphite (TEPi), tris(2,2,2-trifluoroethyl) phosphite (TTFEPi), triphenyl phosphite (TPPi), dimethyl methylphosphate (DMMP), or a mixture or combination thereof.
  • MB butyrate
  • EP ethyl propionate
  • TMPa trimethyl phosphate
  • TEP trimethyl phosphate
  • TEP trimethyl phosphate
  • TEP triethyl phosphate
  • TFEPa triethyl phosphate
  • TFEPa
  • the additional co-solvents may be used for overcharge protection or flame-retarding purposes.
  • the only solvent present in the electrolyte composition is propylene carbonate.
  • the solvent comprises, or consists of, propylene carbonate and ethylene carbonate.
  • the electrolyte composition includes at least 5 weight , more particularly at least 8 weight , PC, based on the total amount of all the components of the electrolyte composition.
  • the electrolyte composition includes 0 to 50 weight , more particularly at least 0 to 5 weight , PC, based on the total amount of all the components of the electrolyte composition.
  • the electrolyte composition includes 5 to 50 weight , more particularly 8 to 20 weight , PC, and 5 to 60 weight , more particularly 15 to 40 weight , EC based on the total amount of all the components of the electrolyte composition.
  • the electrolyte composition further includes a Li salt.
  • Li salt Illustrative examples include LiPF 6 , LiBF 4 , L1CIO4, LiAsFe, LiSbF 6 , L1CF3SO3, LiN(S0 2 F) 2 , LiN(S0 2 CF 3 ) 2 , LiN(S0 2 C 2 F 5 ) 2 ,
  • Lithium hexafluorophosphate (LiPF 6 ) is preferred.
  • the SEI film- suppression additive is present in an amount of 0.001 to 0.2 mole/liter, and the Li salt is present in an amount of 0.5 to 3.5 mole/liter.
  • the electrolyte composition does not include 4,5-dichloroethylene carbonate, vinyl ethylene carbonate (VEC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC).
  • an additive metal (M) salt is included in the PC-containing electrolyte composition which also includes a main Li salt and a solvent that includes PC, and optionally at least one co-solvent such as EC or other co-solvents such as such as DMC, DEC and EMC.
  • M + cation has a lower solvation number with solvents compared to Li + , so that the M + -solvate molecular has the fast transport ability because of its small size.
  • the composition of the ultrathin SEI layer is mainly Li 2 C0 3 and lithium alkyl carbonates.
  • the concentration of SEI film- suppression additive cations is less than, or equal to, 20 weight % of that of the Li cations of the Li salt. In another, the concentration of SEI film-suppression additive cations is less than, or equal to, 10 weight % of that of the Li cations of the Li salt. In another, the concentration of SEI film-suppression additive cations is less than, or equal to, 5 weight % of that of the Li cations of the Li salt. In yet another, the
  • concentration of SEI film- suppression additive cations is less than, or equal to, 2 weight % of that of the Li cations of the Li salt.
  • the graphite anode comprises, consists essentially of, or consists of, a graphite-material based anode, such as a pure or substantially pure graphite material anode or a graphite composite-based anode, such as a mixture of graphite, carbon conductors such as carbon black, carbon nanotubes, carbon nanofiber, graphene, or reduced graphene oxide and a binder such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), or Li-polyacrylic acid (Li-PAA), or a mixture of the binders.
  • PVDF polyvinylidene fluoride
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Li-PAA Li-polyacrylic acid
  • the carbon conductor and binder are used to prepare the anode but do not contribute to the capacity of the graphite anode and as such may be considered along with other common additives as components described by the language “consisting essentially of.”
  • graphite anode For ease of discussion, certain embodiments are disclosed using the language “graphite anode” but should be understood to include the graphite-mixed anode materials noted above unless the terms “pure graphite” or “substantially pure graphite” are used.
  • a “pure graphite” anode refers to those made essentially exclusively or exclusively of graphite, to the ability for conventional means to produce the same, but does not include the graphite-mixed anode materials alternatives noted above or other conventional materials added to graphite anodes.
  • the cathode comprises a lithium intercalation compound.
  • M + cations of the additive salt disclosed herein will significantly enhance the film-formation ability of EC, even in a quite low content of EC in the electrolyte composition (e.g. 0.05 mole/liter).
  • the salt additives can effectively build up an ultrathin but stable SEI layer on the graphite anode, therefore having advantages in improving the rate capability and cycling stability at elevated temperatures over the commonly used SEI film-formation additives.
  • the additive disclosed herein suppresses graphite exfoliation without altering the bulk graphite.
  • LiPF 6 , CsPF 6 , PC, EC and EMC were acquired commercially in battery grade. Electrolytes were prepared inside a glove box filled with purified argon, where the moisture and oxygen content was less than 1 ppm. An electrolyte (B-Cs) comprising 0.05 mole/liter CsPF 6 (as the SEI film suppression additive) and 1.0 mole/liter LiPF 6 in a solvent mixture of EC-PC-EMC (5:2:3, wt.) was prepared and used to conduct electrochemical tests.
  • B-Cs electrolyte
  • a graphite electrode consisting of 92 wt.% MAG10 graphite particles (Hitachi Powdered Metals Co. Ltd.) and 8 wt.% poly(vinylidene fluoride) (PVDF) and a positive electrode consisting of 84 wt.% LiNio.sCoo.15Alo.05O2 (NCA), 4 wt.% SFG-6, 4 wt.% Super P and 8 wt.% PVDF were made on copper foil and aluminum foil, respectively.
  • the mass loading of MAG10 and NCA in the above composite electrodes was controlled at about 5 mg/cm 2 and 10 mg/cm 2 , respectively.
  • CR2032-type coin cells were assembled in the glove box and then tested on an Arbin BT- 2000 battery tester at room temperature or at 60°C in an environmental chamber (SPX Thermal Product Solutions, USA).
  • the graphitelNCA full-cells were cycled between 2.5 and 4.3 V at C/3 for charge and 1C for discharge at room temperature or at C/2 for charge-discharge at 60°C.
  • the full-cells were charged at C/5 and discharged at different rates. Before all the tests of both the half-cells and full-cells, two formation cycles were conducted in advance at a C/20 rate.
  • the graphite electrodes were obtained from the half-cells or full-cells after cell disassembly, and washed thoroughly with DMC for three times to thoroughly remove residual electrolytes and evacuated to remove DMC. Then the surface morphologies of the graphite electrodes were analyzed by scanning electron microscopy (SEM, JEOL 5900) and high resolution transmission electron microscopy (HRTEM, JEOL 2010).
  • FIG. 1 compares the initial voltage profiles of the Lilgraphite half-cells with various electrolytes.
  • the plateau at above 0.5 V clearly indicates that serious PC reduction decomposition and graphite exfoliation happen.
  • B- FEC After 2 wt. FEC is introduced (B- FEC), this plateau is significantly suppressed, but not completely.
  • B-Cs the baseline electrolyte
  • CE Coulombic efficiency
  • FIGS. 2A-2D compare the SEM and TEM images of the surface morphologies of the graphite electrodes after the Lilgraphite half-cells were charged to 0.3 V at C/20 rate in the B-Cs electrolyte (FIGS. 2A, 2C) and the B-FEC electrolyte (FIGS. 2B, 2D). It is clearly seen from FIGS. 2A and 2C that graphite in the B-Cs electrolyte is quite clean. There is an ultrathin ( ⁇ 2 nm thick) and uniform SEI layer at least detected (FIG. 2C). However, the graphite in the B-FEC electrolyte have some spots on the surface of the graphite (FIG. 2B) and the clear, non-uniform SEI layer on the graphite particle has the thickness of >3 nm observed in FIG. 2D. That is, more effective CsPF 6 additive functions in an SEI-film-suppression mechanism.
  • FIGS. 3A-3C show the cell performance of the graphitelNCA full-cells using various electrolytes.
  • the baseline electrolyte gives very low discharge capacity and fails to cycle well even at room temperature owing to its incompatibility with graphite anode.
  • CsPF 6 or FEC is introduced into the baseline electrolyte
  • the graphitelNCA full-cells with both electrolytes can be cycled stably for over 250 cycles and the B-Cs electrolyte exhibits the higher discharge capacity and better capacity retention than the B-FEC electrolyte.
  • FIG. 3B shows the cycling stability of the graphitelNCA full-cells at 60°C. It is distinct that the B-Cs electrolyte has the advantages on specific capacity and capacity retention over the B-FEC electrolyte. As for the rate capability in FIG. 3C, the B-Cs electrolyte has slightly higher capacity than the B-FEC electrolyte at low current rates ( ⁇ 2C), but the former is much better than the latter at high current rates (3C and 5C in this test).
  • the SEM images (FIGS. 3D and 3E) of the cycled graphite electrodes indicate that the graphite surface cycled in the B-Cs electrolyte is still clean (FIG.
  • the CsPF6-containing electrolytes have significantly improved Coulombic efficiency over the related control electrolytes without CsPF 6 additive, 90% vs. 58% for electrolytes of 1.0 mole/liter LiPF 6 in EC-PC-EMC (3:1:6, wt.) with and without 0.05 mole/liter CsPF 6 , and 89% vs. 74% for electrolytes of 1.0 mole/liter LiPF 6 in EC-PC-EMC (2:1:7, wt.) with and without 0.05 mole/liter CsPF 6 .
  • the electrolytes with CsPF 6 additive also show higher Coulombic efficiency than the control electrolytes although the improvement is not as large as in the half-cells (FIG. 4B).
  • LiPF 6 in a solvent mixture of EC-EMC (3:7 by wt.) with and without 0.05 mole/liter CsPF 6 (as the SEI film-suppression additive) were prepared and used to conduct electrochemical tests in

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Abstract

Dispositif de stockage d'énergie comprenant : (A) une anode comprenant du graphite; et (B) une composition d'électrolyte comprenant : (i) au moins un solvant carbonate; (ii) un additif choisi parmi CsPF6, RbPF6, Sr(PF6)2, Ba(PF6)2, ou un mélange de ceux-ci; et (iii) un sel de lithium.
PCT/US2015/060406 2014-11-26 2015-11-12 Additifs de suppression de film d'interphase électrolyte solide WO2016085666A1 (fr)

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Application Number Priority Date Filing Date Title
US201462085199P 2014-11-26 2014-11-26
US62/085,199 2014-11-26
US14/595,065 US9865900B2 (en) 2012-02-07 2015-01-12 Solid electrolyte interphase film-suppression additives
US14/595,065 2015-01-12

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* Cited by examiner, † Cited by third party
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EP4312298A4 (fr) * 2022-06-07 2024-06-12 Contemporary Amperex Technology Co., Ltd. Électrolyte non aqueux et son procédé de préparation, batterie secondaire le comprenant, et dispositif électrique

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EP4312298A4 (fr) * 2022-06-07 2024-06-12 Contemporary Amperex Technology Co., Ltd. Électrolyte non aqueux et son procédé de préparation, batterie secondaire le comprenant, et dispositif électrique

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