WO2024012244A1 - 局部高浓度电解液、二次电池、电子设备和移动装置 - Google Patents

局部高浓度电解液、二次电池、电子设备和移动装置 Download PDF

Info

Publication number
WO2024012244A1
WO2024012244A1 PCT/CN2023/104406 CN2023104406W WO2024012244A1 WO 2024012244 A1 WO2024012244 A1 WO 2024012244A1 CN 2023104406 W CN2023104406 W CN 2023104406W WO 2024012244 A1 WO2024012244 A1 WO 2024012244A1
Authority
WO
WIPO (PCT)
Prior art keywords
local high
secondary battery
concentration
electrolyte
hydrogen
Prior art date
Application number
PCT/CN2023/104406
Other languages
English (en)
French (fr)
Inventor
范修林
马强
张海阔
洪响
Original Assignee
华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Publication of WO2024012244A1 publication Critical patent/WO2024012244A1/zh

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C309/00—Sulfonic acids; Halides, esters, or anhydrides thereof
    • C07C309/63—Esters of sulfonic acids
    • C07C309/64—Esters of sulfonic acids having sulfur atoms of esterified sulfo groups bound to acyclic carbon atoms
    • C07C309/65—Esters of sulfonic acids having sulfur atoms of esterified sulfo groups bound to acyclic carbon atoms of a saturated carbon skeleton
    • C07C309/66—Methanesulfonates
    • 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
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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

Definitions

  • Embodiments of the present application relate to the field of battery technology, and in particular to a local high-concentration electrolyte, secondary batteries, electronic equipment and mobile devices.
  • high-concentration electrolytes concentration of electrolyte salts are usually >3 mol/L
  • low-concentration electrolytes concentration of electrolyte salts are usually ⁇ 1.5 mol/L
  • Embodiments of the present application provide a local high-concentration electrolyte, a secondary battery, an electronic device, and a mobile device.
  • This local high-concentration electrolyte adds hydrogen-free polyhalogen substituted alkyl compounds and/or phenyl trifluoromethanesulfonate as diluents to reduce the viscosity of the electrolyte and improve the wettability of the pole pieces, thereby improving the Coulombic performance of the secondary battery.
  • Efficiency and cycle performance are conducive to meeting the needs of high-voltage operation of secondary batteries.
  • a local high-concentration electrolyte including an electrolyte salt, an organic solvent and a diluent, the diluent including at least one of a hydrogen-free polyhalogen substituted alkane compound and phenyl trifluoromethanesulfonate.
  • the high-concentration electrolyte can be reduced by adding a hydrogen-free polyhalogen substituted alkane compound and/or phenyl trifluoromethanesulfonate as a diluent into the high-concentration electrolyte to form a local high-concentration electrolyte.
  • the total salt concentration and viscosity of the liquid can improve the wettability of the electrode piece, which will in turn help improve the Coulombic efficiency and cycle performance of the secondary battery, and help meet the needs of high-voltage operation of the secondary battery.
  • hydrogen-free polyhalogen substituted alkyl compounds and phenyl trifluoromethanesulfonate have lower molecular polarity, so the electrolyte salt can have less or no solubility in the diluent, which is beneficial to local high-concentration electrolysis.
  • the local coordination environment of high-concentration salt-solvent clusters possessed by high-concentration electrolytes can be retained in the liquid.
  • the lower molecular polarity is also conducive to making the diluent compatible with the organic solvent, thereby avoiding phase separation of the diluent and the organic solvent to obtain a clear and uniform local high-concentration electrolyte.
  • the molecular structure of the hydrogen-free polyhalogen-substituted alkane compound does not contain hydrogen elements, so it can avoid hydrogen transfer reactions on the surface of the positive electrode to suppress oxidative decomposition caused by the contact between the electrolyte and the surface of the positive electrode under high voltage. In turn, the high-voltage resistance of the local high-concentration electrolyte can be improved, which is beneficial to obtaining secondary batteries with higher energy density.
  • hydrogen-free polyhalogen-substituted alkane compounds can also decompose on the surface of the negative electrode to form a stable interface film rich in fluorides (such as lithium fluoride compounds), which is beneficial to reducing side reactions between local high-concentration electrolytes and the negative electrode and inhibiting branching. This can prevent dendrites from growing to a certain extent and penetrating the separator and triggering the battery circuit, which is beneficial to improving the safety, Coulombic efficiency and cycle performance of secondary batteries.
  • phenyl trifluoromethanesulfonate can form an interface film containing sulfide components (for example, phenyl trifluoromethanesulfonate can be decomposed into lithium sulfide and lithium alkyl sulfonate), because sulfide has a relatively high
  • the high ionic conductivity can improve the ionic conductivity of the interface film, thereby improving the rate performance of the secondary battery.
  • the molecular polarity index MPI of the hydrogen-free polyhalogen substituted alkane compound Satisfy the following formula:
  • MPI 1 is the MPI of the hydrogen-free polyhalogen substituted alkane compound
  • S pole 1 is the molecular polar surface area of the hydrogen-free polyhalogen substituted alkane compound
  • S total 1 is the hydrogen-free polyhalogen substituted alkane compound. Total surface area of molecules
  • MPI 2 is the MPI of the phenyl trifluoromethanesulfonate
  • S pole 2 is the molecular polar surface area of the phenyl trifluoromethanesulfonate
  • S total 2 is the phenyl trifluoromethanesulfonate. The total surface area of the acid ester molecule
  • the molecular polarity of the hydrogen-free polyhalogen substituted alkane compound and phenyl trifluoromethanesulfonate can be controlled, which is beneficial to controlling the solubility of the electrolyte salt in the diluent. Or without solubility, it is also helpful to control the compatibility of diluents and organic solvents.
  • the preset condition is the value of the MPI of the hydrogen-free polyhalogen substituted alkane compound and the value of the MPI of the phenyl trifluoromethanesulfonate. The value is 5 ⁇ 10.
  • the MPI of the hydrogen-free polyhalogen-substituted alkane compound is less than 5, the compatibility of the hydrogen-free polyhalogen-substituted alkane compound with the organic solvent is poor, so there may be delamination or delamination between the diluent and the organic solvent.
  • the phenomenon of turbidity results in the inability to form a clear and uniform local high-concentration electrolyte.
  • the MPI of the hydrogen-free polyhalogen-substituted alkane compound is greater than 10
  • the solubility of the electrolyte salt in the hydrogen-free polyhalogen-substituted alkane compound is high, so it may not be possible to generate a local coordination environment of high-concentration salt-solvent clusters, resulting in the inability to form a local Highly concentrated electrolyte.
  • the hydrogen-free polyhalogen substituted alkane compound and phenyl trifluoromethanesulfonate that meet the above preset conditions can have appropriate molecular polarity, and further can have appropriate solubility to form a local high-concentration electrolyte.
  • the hydrogen-free polyhalogen substituted alkane compound has an asymmetric structure.
  • the hydrogen-free polyhalogen substituted alkane compound by setting the hydrogen-free polyhalogen substituted alkane compound to have an asymmetric structure, it is beneficial to ensure that the hydrogen-free polyhalogen substituted alkane compound has molecular polarity, which is beneficial to controlling the phase relationship between the hydrogen-free polyhalogen substituted alkane compound and the organic solvent. Capacity.
  • the solubility of the electrolyte salt in the hydrogen-free polyhalogen substituted alkane compound and the phenyl trifluoromethanesulfonate is less than or equal to 0.1 mol/ L, the hydrogen-free polyhalogen substituted alkane compound and the phenyl trifluoromethanesulfonate are soluble in the organic solvent.
  • n 1 to 20.
  • the number of carbon atoms in the hydrogen-free polyhalogen substituted alkane compound may be 1 to 20.
  • the obtained hydrogen-free polyhalogen substituted alkane compound may have appropriate molecular polarity.
  • the mass percentage of the diluent in the local high-concentration electrolyte is 10% to 90%.
  • the viscosity of the local high-concentration electrolyte is less than or equal to 8 mPa ⁇ s, and the conductivity of the local high-concentration electrolyte is greater than or equal to 2.5 mS/cm.
  • the electrolyte salt includes lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt and at least one kind of aluminum salt.
  • the corresponding electrolyte salt can be flexibly set according to the system of the secondary battery used in the local high-concentration electrolyte solution.
  • the electrolyte salt includes MClO 4 , MBF 4 , MPF 6 , MAsF 6 , MPF 2 O 2 , MCF 3 SO 3 , MTDI, MB(C 2 O 4 ) 2 , MBF 2 C 2 O 4 , M[(CF 3 SO 2 ) 2 N], M[(FSO 2 ) 2 N], M[(C m F 2m+1 SO 2 )(C t F 2t +1 SO 2 )N] at least one,
  • M is Li, Na or K, and m and t are integers greater than or equal to 0.
  • the molar concentration of the electrolyte salt in the local high-concentration electrolyte solution is 1 mol/L to 8 mol/L.
  • the organic solvent includes at least one of a carbonate solvent, a carboxylate solvent, and an ether solvent.
  • the local high-concentration electrolyte further includes additives
  • the additives include vinylene carbonate, trifluoromethylethylene carbonate, ethylene vinylene carbonate, 1,3-propanesultone, 1,4-butanesultone, vinyl sulfate, vinyl sulfite, methylene methane disulfonate, succinonitrile, adiponitrile, 1,2-bis At least one of (2-nitrileethoxy)ethane, 1,3,6-hexanetrinitrile, biphenyl or fluorobenzene.
  • additives with different functional effects can be added to the local high-concentration electrolyte according to actual performance requirements.
  • a second aspect provides a secondary battery, including a positive electrode, a negative electrode, a separator, and a local high-concentration electrolyte as described in any one of the above-mentioned first aspects.
  • the secondary battery includes a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, or an aluminum secondary battery. Secondary battery.
  • an electronic device including a housing, a display screen contained in the housing, a circuit board assembly, and a secondary battery according to any one of the above second aspects, the secondary battery being Provide power to the circuit board assembly.
  • a fourth aspect provides a mobile device including the secondary battery according to any one of the above second aspects.
  • FIG. 1 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
  • Figure 2 is a schematic diagram of the working principle of a secondary battery provided by an embodiment of the present application.
  • Figure 3 is a linear sweep voltammetry (LSV) curve diagram of the electrolyte provided in Example 1 and Comparative Example 2 of the present application.
  • Figure 4 is a charge-discharge curve diagram of the battery provided in Embodiment 1 of the present application.
  • Figure 5 is a charge and discharge curve of the battery provided in Comparative Example 2 of the present application.
  • Figure 6 is a cycle performance curve diagram of the battery provided in Examples 1-3 and Comparative Examples 1-2 of the present application.
  • Figure 7 is a cycle performance curve diagram of the battery provided in Example 10 and Comparative Example 3 of the present application.
  • a and/or B can mean: A exists alone, A and B exist simultaneously, and B exists alone, Where A and B can be singular or plural.
  • the character "/" generally indicates that the related objects are in an "or” relationship.
  • the weight of the relevant components mentioned may not only refer to the specific content of each component, but also the proportional relationship between the weights of each component. Therefore, as long as it is relevant in accordance with the embodiment description of this application
  • the content of the components can be scaled up or down within the range disclosed in the examples of this application.
  • the mass described in the embodiments of this application may be mass units well known in the chemical industry such as ⁇ g, mg, g, kg, etc.
  • Primary cell It can refer to a device that converts chemical energy into electrical energy.
  • the primary cell uses the potential difference between the positive and negative electrodes to allow electrons to flow between the positive and negative electrodes.
  • Positive electrode can refer to the electrode with a higher potential in the primary battery.
  • current can flow out from the positive electrode, and the positive electrode can obtain electrons and perform reduction effects.
  • current can flow to the positive electrode, and the positive electrode can lose electrons and oxidize.
  • Negative electrode can refer to the electrode with a lower potential in the primary battery. During the discharge process, current can flow to the negative electrode, and the negative electrode can lose electrons and undergo oxidation. During the charging process, current can flow out from the negative electrode, and the negative electrode can obtain electrons and perform a reducing effect.
  • Electrolyte can refer to the medium that provides ion exchange between the positive and negative electrodes of the battery.
  • Separator It can refer to the medium used to separate the positive and negative electrodes of the battery and prevent the positive and negative electrodes from being in direct contact and causing a short circuit.
  • the separator also has the function of allowing electrolyte ions to pass through.
  • Solid electrolyte interphase (SEI) film It can refer to the passivation layer covering the surface of the electrode material formed by the reaction between the electrode material and the electrolyte at the solid-liquid interface during the first charge and discharge process of the liquid lithium-ion battery. layer.
  • the SEI film is an interface layer that has the characteristics of a solid electrolyte. It is an electronic insulator, but it is also an excellent conductor of Li + . Li + can be freely inserted and extracted through the SEI film.
  • Secondary battery also known as rechargeable battery or storage battery, can refer to a battery that can be activated by charging to continue to use the active material after the battery is discharged.
  • High concentration electrolyte It can refer to when the concentration of electrolyte salt in the electrolyte increases to the point where the solution contains almost no free solvent molecules, the anions of the electrolyte salt enter the solvation sheath, and interact with the cations and solvent molecules mainly in the form of aggregates and contact ions. to the electrolyte present in the form. That is, there is a local coordination environment with high concentrations of salt-solvent clusters in highly concentrated electrolytes. Compared with commonly used low-concentration electrolytes (concentration of electrolyte salts ⁇ 1.5mol/L), the concentration of electrolyte salts in high-concentration electrolytes is usually >3mol/L.
  • Electronic devices may be, for example, terminal consumer products or 3C electronic products (computer, communication, consumer electronic products), such as mobile phones, mobile power supplies, portable machines, tablet computers, e-readers, Laptop computers, digital cameras, wearable devices, vehicle terminals, headphones and other equipment.
  • 3C electronic products computer, communication, consumer electronic products
  • mobile phones such as mobile phones, mobile power supplies, portable machines, tablet computers, e-readers, Laptop computers, digital cameras, wearable devices, vehicle terminals, headphones and other equipment.
  • the mobile device may be, for example, a vehicle, an electric skateboard, or an electric bicycle.
  • FIG. 1 is a schematic structural diagram of an electronic device 100 provided by an embodiment of the present application. The embodiment shown in FIG. 1 is explained by taking the electronic device 100 as a mobile phone as an example.
  • the electronic device 100 may include a housing 10 , a display screen 20 , and a circuit board assembly 30 .
  • the housing 10 may include a frame and a back cover.
  • the frame surrounds the periphery of the display screen 20 and the back cover.
  • the cavity formed between the display screen 20 , the frame, and the back cover can be used to place the circuit board assembly 30 .
  • both the display screen 20 and the circuit board assembly 30 may be disposed on the housing 10 .
  • Electronic device 100 may also include a secondary battery 40 for powering circuit board assembly 30 .
  • the secondary battery 40 may be, for example, a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, an aluminum secondary battery, or the like.
  • FIG. 2 is a working principle diagram of a secondary battery 40.
  • the core components of the secondary battery 40 may include the positive electrode 101, the negative electrode 102, the electrolyte 103 and the separator 104 (corresponding communication accessories, circuits, etc. are not shown).
  • the positive electrode 101 and the negative electrode 102 can deintercalate metal ions (such as lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions or aluminum ions, etc.) to achieve energy storage and release. As shown in Figure 2, Li + moves to the left (positive electrode 101) as energy is released. Process, Li + moves to the right (negative electrode 102) as an energy storage process.
  • the electrolyte 103 may be a transport carrier for metal ions between the positive electrode 101 and the negative electrode 102 .
  • the positive electrode 101 and the negative electrode 102 are the main energy storage parts of the secondary battery 40 and can reflect the energy density, cycle performance and safety performance of the secondary battery 40 .
  • the separator 104 can pass metal ions, but the separator 104 itself is not conductive, so the separator 104 can separate the positive electrode 101 and the negative electrode 102 to prevent short circuit between the positive electrode 101 and the negative electrode 102 .
  • the cathode 101 may include a cathode active material capable of reversibly intercalating/deintercalating metal ions.
  • the positive active material may include but is not limited to lithium composite metal oxides (such as lithium nickel cobalt manganate (LiNi 0.8 Co 0.1 Mn 0.1 ), lithium iron phosphate (LiFePO 4 ), lithium cobalt oxide ( LiCoO 2 ), etc.), polyanionic lithium compound LiM i (PO 4 ) j (M is Ni, Co, Mn, Fe, Ti, V, 0 ⁇ i ⁇ 5, 0 ⁇ j ⁇ 5), etc.
  • lithium composite metal oxides such as lithium nickel cobalt manganate (LiNi 0.8 Co 0.1 Mn 0.1 ), lithium iron phosphate (LiFePO 4 ), lithium cobalt oxide ( LiCoO 2 ), etc.
  • polyanionic lithium compound LiM i (PO 4 ) j M is Ni, Co, Mn, Fe, Ti, V, 0 ⁇ i ⁇
  • the negative electrode 102 may include one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a phosphorus-based negative electrode, lithium titanate, a lithium negative electrode, a sodium negative electrode, a magnesium negative electrode, a zinc negative electrode, and an aluminum negative electrode.
  • the carbon-based negative electrode can be, for example, graphite, hard carbon, soft carbon or graphene.
  • the silicon-based negative electrode can be, for example, silicon, silicon carbon, silicon oxygen or silicon metal compound.
  • the tin-based negative electrode can be, for example, tin, tin carbon, tin oxide or tin metal compound.
  • the phosphorus-based negative electrode can be, for example, red phosphorus, black phosphorus or phosphide.
  • the lithium negative electrode, the sodium negative electrode, the magnesium negative electrode, the zinc negative electrode and the aluminum negative electrode may be corresponding metal elements or alloys, or they may be a current collector and a corresponding metal element or alloy disposed on the current collector.
  • the lithium negative electrode may be metallic lithium or a lithium alloy, or may be a current collector and metallic lithium or a lithium alloy disposed on the current collector.
  • the lithium alloy may specifically be at least one of lithium silicon alloy, lithium aluminum alloy, lithium tin alloy, and lithium indium alloy.
  • the separator 104 may include, for example, but is not limited to, single-layer polyethylene (PE), single-layer polypropylene (PP), double-layer PE/PP, double-layer PP/PP, and triple-layer PP/PE/PP membranes.
  • PE single-layer polyethylene
  • PP single-layer polypropylene
  • PP double-layer PE/PP
  • PP/PP double-layer PP/PP
  • triple-layer PP/PE/PP membranes for example, but is not limited to, single-layer polyethylene (PE), single-layer polypropylene (PP), double-layer PE/PP, double-layer PP/PP, and triple-layer PP/PE/PP membranes.
  • the electrolyte solution 103 may include electrolyte salts and organic solvents.
  • the electrolyte salt and organic solvent can be determined according to the system of the secondary battery 40 .
  • the electrolyte salt is usually lithium hexafluorophosphate (LiPF 6 )
  • the organic solvent is usually a carbonate solvent.
  • the concentration of the electrolyte salt LiPF 6 in the electrolyte 103 is usually low (generally less than 1.5 mol/L)
  • the formation process of the SEI membrane is also mainly controlled by the reduction or oxidation of solvent molecules.
  • the current market requirements for the energy density of secondary batteries are getting higher and higher.
  • One way to improve the energy density of the secondary battery 40 is to increase the battery operation of the secondary battery 40 .
  • the working voltage of the secondary battery 40 is high (for example, the working voltage is greater than 4.2V)
  • the carbonate electrolyte is prone to irreversible oxidation and decomposition, making it difficult for the secondary battery 40 to maintain a stable cycle under high voltage.
  • embodiments of the present application provide a local high-concentration electrolyte that reduces the The viscosity of the electrolyte improves the wettability of the pole pieces, which in turn can improve the Coulombic efficiency and cycle performance of the secondary battery, which is beneficial to meet the needs of high-voltage operation of the secondary battery.
  • the local high-concentration electrolyte provided by the embodiment of the present application may be the electrolyte 103 shown in FIG. 2 .
  • the embodiment of the present application provides a local high-concentration electrolyte solution.
  • the local high-concentration electrolyte solution may include electrolyte salts, organic solvents, and diluents.
  • the diluent may include at least one of a hydrogen-free polyhalogen substituted alkane compound and phenyl trifluoromethanesulfonate.
  • the local high-concentration electrolyte provided by the embodiments of the present application is formed by adding a hydrogen-free polyhalogen substituted alkane compound and/or phenyl trifluoromethanesulfonate as a diluent into the high-concentration electrolyte. , which can reduce the total salt concentration and viscosity of the high-concentration electrolyte, improve the wettability of the pole pieces, and thus help improve the Coulombic efficiency and cycle performance of the secondary battery, and help meet the needs of high-voltage operation of the secondary battery.
  • hydrogen-free polyhalogen substituted alkyl compounds and phenyl trifluoromethanesulfonate have lower molecular polarity, so the electrolyte salt can have less or no solubility in the diluent, which is beneficial to local high-concentration electrolysis.
  • the electrolyte salt can have less or no solubility in the diluent, which is beneficial to local high-concentration electrolysis.
  • Highly concentrated electrolytes possess local coordination environments of highly concentrated salt-solvent clusters.
  • the lower molecular polarity also helps to make the diluent compatible with the organic solvent, thereby avoiding phase separation of the diluent and the organic solvent to obtain a clear and uniform local high-concentration electrolyte.
  • the molecular structure of the hydrogen-free polyhalogen-substituted alkane compound does not contain hydrogen elements, so it can avoid hydrogen transfer reactions on the surface of the positive electrode to suppress oxidative decomposition caused by the contact between the electrolyte and the surface of the positive electrode under high voltage.
  • the high-voltage resistance of the local high-concentration electrolyte can be improved, which is beneficial to obtaining secondary batteries with higher energy density.
  • hydrogen-free polyhalogen-substituted alkane compounds can also decompose on the surface of the negative electrode to form a stable interface film rich in fluorides (such as lithium fluoride compounds), which is beneficial to reducing side reactions between local high-concentration electrolytes and the negative electrode and inhibiting branching. This can prevent dendrites from growing to a certain extent and penetrating the separator and triggering the battery circuit, which is beneficial to the safety, Coulombic efficiency and cycle performance of the secondary battery.
  • phenyl trifluoromethanesulfonate can form an interface film containing sulfide components (for example, phenyl trifluoromethanesulfonate can be decomposed into lithium sulfide and lithium alkyl sulfonate, etc.), because sulfide has Higher ionic conductivity can improve the ionic conductivity of the interface film, thereby improving the rate performance of the secondary battery.
  • Phenyl trifluoromethanesulfonate and hydrogen-free polyhalogen substituted alkane compounds are described in detail below.
  • the phenyl group in phenyl trifluoromethanesulfonate can be a phenyl group substituted by halogen or unsubstituted.
  • the molecular structure of phenyl trifluoromethanesulfonate can be shown as general formula (I):
  • R 1 to R 5 can each independently select any one of a hydrogen atom, a fluorine atom, a chlorine atom and a bromine atom.
  • phenyl trifluoromethanesulfonate is a phenyl group substituted by a fluorine atom
  • phenyl trifluoromethanesulfonate can also decompose on the surface of the negative electrode to form a substance rich in fluoride (such as lithium fluoride
  • the stable interface film of the compound can reduce the side reaction between the local high-concentration electrolyte and the negative electrode and inhibit the growth of dendrites.
  • the value of n may be 1 to 20. That is, the number of carbon atoms in the hydrogen-free polyhalogen substituted alkane compound may be 1 to 20. More preferably, the value of n can be 1-10, and further preferably, the value of n can be 2-6.
  • the obtained hydrogen-free polyhalogen substituted alkane compound may have appropriate molecular polarity.
  • the hydrogen-free polyhalogen-substituted alkane compound can have an asymmetric structure, which is beneficial to ensuring that the hydrogen-free polyhalogen-substituted alkane compound has molecular polarity, which is beneficial to controlling the compatibility of the hydrogen-free polyhalogen-substituted alkane compound with organic solvents. .
  • the hydrogen-free polyhalogen substituted alkane compound may be linear or branched, which is not limited in this application.
  • the molecular polarity index (MPI) of each of the hydrogen-free polyhalogen substituted alkane compound and the phenyl trifluoromethanesulfonate ester can be calculated by the following formula (1) and formula (2), To characterize the molecular polarity of each hydrogen-free polyhalogen substituted alkane compound and phenyl trifluoromethanesulfonate. It should be noted that the larger the MPI value, the greater the polarity of the corresponding molecule.
  • the MPI of hydrogen-free polyhalogen substituted alkane compounds can be calculated by formula (1):
  • MPI 1 is the MPI of the hydrogen-free polyhalogen substituted alkane compound
  • S pole 1 is the molecular polar surface area of the hydrogen-free polyhalogen substituted alkane compound
  • S total 1 is the total molecular surface area of the hydrogen-free polyhalogen substituted alkane compound.
  • the MPI of phenyl trifluoromethanesulfonate can be calculated by formula (2):
  • MPI 2 is the MPI of phenyl trifluoromethanesulfonate
  • S pole 2 is the molecular polar surface area of phenyl trifluoromethanesulfonate
  • S total 2 is the total molecular surface area of phenyl trifluoromethanesulfonate.
  • S pole 1 in formula (1) and S pole 2 in formula (2) can be calculated by the following method:
  • the molecular structure of hydrogen-free polyhalogen substituted alkane compounds and phenyl trisulfide were analyzed at the 6-311+G(d,p) basis set level.
  • the molecular structure of fluoromethanesulfonate is optimized to obtain the stable molecular configuration corresponding to the respective molecular structure.
  • the molecular surface electrostatic potential (ESP) analysis is performed on the respective molecular stable configurations.
  • the area where the molecular surface ESP is greater than the preset threshold is defined as a polar surface.
  • the surface area corresponding to the polar surface is the corresponding molecular pole. sexual surface area.
  • the preset threshold can be set according to actual application requirements, for example, it can be 13kcal/mol, 15kcal/mol, 17kcal/mol or 20kcal/mol, etc. This application does not limit this.
  • the MPI value of the hydrogen-free polyhalogen substituted alkane compound and the MPI value of the phenyl trifluoromethanesulfonate calculated according to formula (1) and formula (2) can be further set to satisfy the predetermined value.
  • the conditions are set so that a hydrogen-free polyhalogen substituted alkane compound and/or phenyl trifluoromethanesulfonate with suitable molecular polarity can be selected as the diluent according to the preset conditions.
  • the specific settings of the preset conditions can be determined based on the above-mentioned preset threshold.
  • the above-mentioned preset threshold can be 15kcal/mol.
  • the preset condition can be that the MPI value of the hydrogen-free polyhalogen substituted alkane compound and the MPI value of the phenyl trifluoromethanesulfonate are 5 to 10, more preferably 5 to 9, even more preferably 6 to 8.
  • the solubility of the electrolyte salt in the hydrogen-free polyhalogen-substituted alkane compound may be higher, so it may not be possible to generate a local coordination environment of high-concentration salt-solvent clusters, resulting in the inability to form a local coordination environment.
  • Highly concentrated electrolyte When the MPI of the hydrogen-free polyhalogen-substituted alkane compound is greater than 10, the solubility of the electrolyte salt in the hydrogen-free polyhalogen-substituted alkane compound may be higher, so it may not be possible to generate a local coordination environment of high-concentration salt-solvent clusters, resulting in the inability to form a local coordination environment. Highly concentrated electrolyte.
  • the numerical values of the above-mentioned preset thresholds and preset conditions are only examples and are not limitations of the present application.
  • the above preset threshold can be 13kcal/mol.
  • the preset conditions can be the value of MPI of the hydrogen-free polyhalogen substituted alkane compound and the value of phenyl trifluoromethanesulfonate.
  • the value of MPI is 4 to 11, which is not limited in this application.
  • the solubility of the electrolyte salt in the hydrogen-free polyhalogen substituted alkane compound and/or phenyl trifluoromethanesulfonate may be less than or equal to 0.1 mol/L. Fluoromethanesulfonate is soluble in organic solvents.
  • the percentage content of the diluent in the local high-concentration electrolyte is 10% to 90%, more preferably 15% to 80%, and further preferably 20% to 50%.
  • the viscosity of the local high-concentration electrolyte solution may be less than or equal to 8 mPa ⁇ s, and the conductivity of the local high-concentration electrolyte solution may be greater than or equal to 2.5 mS/cm.
  • composition of the diluent in the local high-concentration electrolyte solution has been introduced above.
  • the electrolyte salt and organic solvent included in the local high-concentration electrolyte solution will be introduced in detail below.
  • the electrolyte salt may be a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt or an aluminum salt, etc.
  • the lithium salt, sodium salt, and potassium salt may respectively include MClO 4 , MBF 4 , MPF 6 , MAsF 6 , MPF 2 O 2 , MCF 3 SO 3 , MTDI, MB(C 2 O 4 ) 2 , MBF 2 C 2 O 4 , M[(CF 3 SO 2 ) 2 N], M[(FSO 2 ) 2 N], M[(C m F 2m+1 SO 2 )(C t F 2t+1 SO 2 ) N], where M is Li, Na or K, m and t are integers greater than or equal to 0.
  • the magnesium salt, zinc salt or aluminum salt may be a salt substance formed by magnesium ions, zinc ions, aluminum ions and the anions in the above-mentioned lithium salt, sodium salt and potassium salt.
  • the molar concentration of the electrolyte salt in the local high-concentration electrolyte solution can be 1 mol/L to 8 mol/L, and further can be 2mol/L ⁇ 7mol/L, 2mol/L ⁇ 5mol/L or 3mol/L ⁇ 6mol/L, this application does not limit this.
  • the organic solvent may include at least one of carbonate solvents, carboxylate solvents, and ether solvents.
  • the above solvents can be mixed in any proportion to form an organic solvent, which is not limited in this application.
  • the carbonate solvent may include cyclic carbonate and/or chain carbonate.
  • Cyclic carbonates may include, for example, but are not limited to at least one of the following: ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), ⁇ -butanol Lactone (gamma-butyrolactone, GBL), butylene carbonate (BC).
  • Chain carbonates may include, for example, but are not limited to at least one of the following: dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid At least one of dipropyl carbonate (DPC).
  • Carboxylic acid solvents may include, for example, but are not limited to at least one of the following: methyl acetate (MA), ethyl acetate (EA), propyl acetate, butyl acetate, propyl propionate (n- propyl propionate (PP), butyl propionate.
  • MA methyl acetate
  • EA ethyl acetate
  • PP propyl propionate
  • PP propyl propionate
  • Ether solvents may include cyclic ethers and/or chain ethers.
  • Cyclic ethers may include, for example, but are not limited to at least one of the following: 1,3-dioxopentane, 1,4-dioxane, crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2- CH 3 -THF), 2-trifluoromethyltetrahydrofuran (2-CF 3 -THF).
  • Chain ethers may include, for example, but are not limited to at least one of the following: dimethoxymethane (DMM), ethylene glycol dimethoxy ether (DME), and diglyme.
  • additives may also be included in the local high-concentration electrolyte according to actual application requirements. Specifically, there are many types of additives that can be added to the local high-concentration electrolyte, and different additives can have different effects.
  • the additives may include at least one of film-forming additives, high-voltage additives, anti-overcharge additives, interface wetting agents, etc., which is not limited in this application.
  • film-forming additives can form a film on the surface of the negative electrode material prior to organic solvents, which is beneficial to improving the cycle performance and life of the battery.
  • film-forming additives may include, but are not limited to, vinylene carbonate, trifluoromethylethylene carbonate, ethylene vinylene carbonate, 1,3-propanesultone, 1,4-butanesultone , at least one of vinyl sulfate and vinyl sulfite.
  • High-voltage additives can preferentially decompose under high voltage to form a positive electrode protective film, which can stabilize the interface between the positive electrode and the electrolyte and help improve the cycle performance and life of the battery.
  • high voltage additives may include, but are not limited to, methylene methane disulfonate, succinonitrile, adiponitrile, 1,2-bis(2-nitrileethoxy)ethane, 1,3,6- At least one of hexanetrinitriles.
  • Anti-overcharge additives can prevent battery overcharging and help improve battery safety performance.
  • the anti-overcharge additive may be biphenyl.
  • the interface wetting agent can improve the wettability of the local high-concentration electrolyte to the electrode piece, which is beneficial to reducing the interface resistance of the battery and improving the rate performance, discharge capacity and service life of the battery.
  • the interfacial wetting agent may be fluorobenzene.
  • the mass percentage of the additive in the local high-concentration electrolyte can be 0.1% to 10%, and further can be 0.5% to 9%, 1% to 6%, or 2% to 7%, as discussed in this application. No restrictions.
  • adding an appropriate amount of additives to the local high-concentration electrolyte will not only help the additives function and improve the performance of the secondary battery, but also help avoid excessive viscosity of the local high-concentration electrolyte due to excessive additive content. Large, thus causing the problem of reduced Coulombic efficiency and cycle performance of the secondary battery.
  • the embodiment of the present application provides a method for preparing a local high-concentration electrolyte, which includes the following steps:
  • the local high-concentration electrolyte also includes additives, they can be added together with the diluent.
  • the local high-concentration electrolyte provided in Example 1 may include a lithium salt (lithium bis(fluorosulfonyl)imide, LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (1 -Chlorononafluorobutane).
  • a lithium salt lithium bis(fluorosulfonyl)imide, LiFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent (1 -Chlorononafluorobutane
  • the mass ratio of DME and 1-chlorononafluorobutane is 50:50
  • the concentration of lithium salt (LiFSI) is 1.5 mol/L.
  • PVDF adhesive polyvinylidene difluoride
  • conductive agent such as superconducting carbon black, super P, SP
  • active material lithium nickel cobalt manganate LiNi 0.8 Co 0.1 Mn 0.1 , NCM
  • NMP solvent N-methyl-2-pyrrolidone
  • the above-prepared positive electrode sheet, metallic lithium negative electrode sheet and commercial PE separator are made into a battery core, which is packaged with polymer, and filled with the local high-concentration electrolyte prepared in Example 1 of the present application, and is made after chemical formation and other processes.
  • Soft pack lithium secondary battery is made into a battery core, which is packaged with polymer, and filled with the local high-concentration electrolyte prepared in Example 1 of the present application, and is made after chemical formation and other processes.
  • the local high-concentration electrolyte provided in Example 2 may include a lithium salt (lithium bisfluorosulfonyl imide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (1,1-dichlorotetrafluoroethyl alkyl).
  • a lithium salt lithium bisfluorosulfonyl imide LiFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent (1,1-dichlorotetrafluoroethyl alkyl
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 3 may include a lithium salt (lithium bisfluorosulfonyl imide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (1,1,1-trichlorotrifluoroethylene). Fluoroethane). Among them, the mass ratio of DME and 1,1,1-trichlorotrifluoroethane is 50:50, and the concentration of lithium salt (LiFSI) is 1.5 mol/L.
  • LiFSI lithium bisfluorosulfonyl imide
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 4 may include a lithium salt (lithium bisfluorosulfonimide LiFSI), an organic solvent (formed by mixing ethylene glycol dimethyl ether DME and fluoroethylene carbonate FEC), and a diluent (1-chlorononafluorobutane).
  • a lithium salt lithium bisfluorosulfonimide LiFSI
  • an organic solvent formed by mixing ethylene glycol dimethyl ether DME and fluoroethylene carbonate FEC
  • a diluent (1-chlorononafluorobutane).
  • the mass ratio of DME, FEC and 1-chlorononafluorobutane is 50:10:40
  • the concentration of lithium salt (LiFSI) is 2.0 mol/L.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 5 may include a lithium salt (lithium bis-trifluorosulfonyl imide LiTFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (1-chlorononafluorobutane ).
  • a lithium salt lithium bis-trifluorosulfonyl imide LiTFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent (1-chlorononafluorobutane .
  • the mass ratio of DME and 1-chlorononafluorobutane is 50:50
  • the concentration of lithium salt (LiTFSI) is 1.5 mol/L.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 6 may include a lithium salt (lithium bisfluorosulfonyl imide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (phenyl trifluoromethanesulfonate). .
  • a lithium salt lithium bisfluorosulfonyl imide LiFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent phenyl trifluoromethanesulfonate
  • the mass ratio of DME and phenyl trifluoromethanesulfonate is 50:50
  • the concentration of lithium salt (LiFSI) is 1.5 mol/L.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 7 may include a lithium salt (lithium bisfluorosulfonimide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (composed of 1-chlorononafluorobutane and 1,1,1-trichlorotrifluoroethane mixture).
  • a lithium salt lithium bisfluorosulfonimide LiFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent composed of 1-chlorononafluorobutane and 1,1,1-trichlorotrifluoroethane mixture.
  • the mass ratio of DME, 1-chlorononafluorobutane and 1,1,1-trichlorotrifluoroethane is 40:30:30
  • the concentration of lithium salt (LiFSI) is 1.5 mol/L.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 8 may include a lithium salt (mixed from lithium bisfluorosulfonimide LiFSI and lithium difluoro(oxalato)borate (LiDFOB)), an organic solvent (ethylene glycol di Methyl ether (DME), and diluent (1-chlorononafluorobutane).
  • a lithium salt mixed from lithium bisfluorosulfonimide LiFSI and lithium difluoro(oxalato)borate (LiDFOB)
  • an organic solvent ethylene glycol di Methyl ether (DME)
  • 1-chlorononafluorobutane diluent
  • the mass ratio of DME and 1-chlorononafluorobutane is 50:50
  • the concentration of lithium bisfluorosulfonyl imide LiFSI is 1.5 mol/L
  • the concentration of lithium difluoroxalate borate LiDFOB is 0.1 mol/L
  • Example 8 of the present application In a glove box filled with argon, dissolve fully dry LiFSI and LiDFOB in the organic solvent DME, stir and mix to form a homogeneous solution, then add 1-chlorononafluorobutane to the above homogeneous solution, stir and mix again, The local high-concentration electrolyte provided in Example 8 of the present application was obtained.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 9 may include a lithium salt (lithium bisfluorosulfonimide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), a diluent (1-chlorononafluorobutane), and additives Ethylene sulfate (abbreviated as DTD).
  • a lithium salt lithium bisfluorosulfonimide LiFSI
  • an organic solvent ethylene glycol dimethyl ether DME
  • a diluent (1-chlorononafluorobutane) ethylene glycol dimethyl ether
  • Ethylene sulfate abbreviated as Ethylene sulfate
  • the mass ratio of DME and 1-chlorononafluorobutane is 50:50
  • the concentration of lithium salt (LiFSI) is 1.5 mol/L
  • the mass percentage of vinyl sulfate DTD is 2%.
  • Example 9 In a glove box filled with argon, dissolve fully dry LiFSI in the organic solvent DME, stir and mix to form a homogeneous solution, then add 1-chlorononafluorobutane and DTD to the above homogeneous solution, stir and mix again, The local high-concentration electrolyte provided in Example 9 of the present application was obtained.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the local high-concentration electrolyte provided in Example 10 may include a lithium salt (lithium bisfluorosulfonimide LiFSI), an organic solvent (formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC), and a diluent (1 -Chlorononafluorobutane).
  • a lithium salt lithium bisfluorosulfonimide LiFSI
  • an organic solvent formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC
  • a diluent (1 -Chlorononafluorobutane
  • the mass ratio of DMC, FEC and 1-chlorononafluorobutane is 50:10:40
  • the concentration of lithium salt (LiFSI) is 2.0 mol/L.
  • the adhesive polyvinylidene fluoride PVDF, the conductive agent SP and the active material lithium cobalt oxide (LiCoO 2 ) are fully stirred and mixed evenly in the solvent NMP at a mass percentage ratio of 2%:2%:96% to form Positive electrode slurry; the positive electrode slurry is evenly coated on the aluminum foil current collector through coating equipment, and dried in an oven to remove the NMP solvent; finally, the dried electrode piece is subjected to cold pressing, slitting and other processes to obtain the positive electrode piece.
  • CMC carboxymethyl cellulose
  • SBR polymerized styrene butadiene rubber
  • acetylene black and graphite at a mass percentage ratio of 1.5%:2.5%:1%:96%.
  • CMC carboxymethyl cellulose
  • SBR polymerized styrene butadiene rubber
  • acetylene black and graphite at a mass percentage ratio of 1.5%:2.5%:1%:96%.
  • deionized water stir thoroughly and mix evenly to form a mixed negative electrode slurry; then use coating equipment to evenly coat the negative electrode slurry on the copper foil current collector, and dry it in an oven; finally, the coated electrode
  • the sheets undergo processes such as cold pressing and slitting to obtain negative electrode sheets, which are then dried, cold pressed, and cut to obtain negative electrode sheets.
  • the positive electrode sheet, negative electrode sheet and commercial PE separator prepared above are made into an electric core, which is packaged with polymer, and filled with the local high-concentration electrolyte prepared in Example 10 of the present application, and then made into a soft package after chemical formation and other processes.
  • Lithium secondary battery Lithium secondary battery.
  • the local high-concentration electrolyte provided in Example 11 may include lithium salt (lithium bisfluorosulfonyl imide LiFSI), organic solvent (formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC), diluent (formed by 1 - Formed by mixing chlorononafluorobutane and phenyltrifluoromethanesulfonate).
  • lithium salt lithium bisfluorosulfonyl imide LiFSI
  • organic solvent formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC
  • diluent formed by 1 - Formed by mixing chlorononafluorobutane and phenyltrifluoromethanesulfonate.
  • the mass ratio of DMC, FEC, 1-chlorononafluorobutane and phenyltrifluoromethanesulfonate is 50:10:20:20
  • concentration of lithium salt (LiFSI) is 2.0 mol/L.
  • the preparation of lithium secondary battery is the same as in Example 10.
  • the lithium secondary battery electrolyte provided in Comparative Example 1 includes lithium salt (LiPF 6 ) and an organic solvent (formed by mixing ethylene carbonate EC, dimethyl carbonate DMC and fluorinated ethylene carbonate FEC), where EC, DEC and The mass ratio of FEC is 30:60:10, and the concentration of lithium salt (LiPF 6 ) is 1.0 mol/L.
  • lithium salt LiPF 6
  • organic solvent formed by mixing ethylene carbonate EC, dimethyl carbonate DMC and fluorinated ethylene carbonate FEC
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the lithium secondary battery electrolyte provided in Comparative Example 2 includes a lithium salt (lithium bisfluorosulfonyl imide LiFSI), an organic solvent (ethylene glycol dimethyl ether DME), and a diluent (1,1,2,2-tetrahydrofuran).
  • LiFSI lithium bisfluorosulfonyl imide
  • DME ethylene glycol dimethyl ether
  • a diluent 1,1,2,2-tetrahydrofuran
  • Fluoroethyl-2,2,3,3-tetrafluoropropyl ether where DME and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether are The mass ratio is 50:50, and the concentration of lithium salt (LiFSI) is 1.5mol/L.
  • the preparation of lithium secondary battery is the same as in Example 1.
  • the lithium secondary battery electrolyte provided in Comparative Example 3 includes a lithium salt (lithium bisfluorosulfonyl imide LiFSI), an organic solvent (formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC), and a diluent (1 ,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether), among which, DMC, FEC and 1,1,2,2-tetrafluoroethyl-2,2, The mass ratio of 3,3-tetrafluoropropyl ether is 50:10:40, and the concentration of lithium salt (LiFSI) is 2mol/L.
  • LiFSI lithium bisfluorosulfonyl imide
  • organic solvent formed by mixing dimethyl carbonate DMC and fluoroethylene carbonate FEC
  • a diluent (1 ,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether
  • the preparation of lithium secondary battery is the same as in Example 10.
  • Stainless steel/lithium battery performance test Assemble the stainless steel positive electrode, metallic lithium negative electrode and separator into a button battery, and drop 100uL of the local high-concentration electrolyte obtained in the above-mentioned Examples 1-11 and Comparative Examples 1-3 respectively. Lithium secondary battery electrolyte. Then the obtained button battery was tested from the open circuit voltage to 6.0V at a speed of 1mV/s. The test results are shown in Table 1 and Figure 3. Table 1 shows the decomposition potential of the stainless steel/lithium batteries corresponding to Examples 1-11 and Comparative Examples 1-3, and Figure 3 is the LSV curve of the stainless steel/lithium batteries corresponding to Example 1 and Comparative Example 2.
  • the initial charge and discharge current density is 0.5mA/cm 2
  • the initial deposition amount is 4.0mAh/cm 2
  • the cyclic discharge current density is 0.5mA/cm 2
  • the cyclic charging current density is 1.5mA/cm 2
  • the cyclic deposition amount is 1.0mAh. /cm 2
  • the cycle number is 50 cycles.
  • CE avg is the average Coulomb efficiency of the battery
  • Q c is the cycle charging capacity of the battery
  • Q s is the last charging capacity of the battery
  • Q T is the first discharge capacity of the battery
  • g is the number of charge and discharge cycles of the battery.
  • Lithium secondary battery performance test Charge and discharge cycle tests were performed on the lithium secondary batteries assembled in Examples 1-11 and Comparative Examples 1-3 at a charge and discharge rate of 0.2C/0.5C. The voltage range of the battery was set to 3.0V ⁇ 4.4V, and the capacity retention rate of the lithium secondary battery after 100 cycles was recorded. The test results are shown in Table 1 and Figure 4-Figure 7. Table 1 shows the capacity retention rate of the lithium secondary batteries provided in Examples 1-11 and Comparative Examples 1-3 after 100 cycles. Figure 4 is a charge-discharge curve of the lithium secondary battery provided in Example 1.
  • Figure 5 is a charge and discharge curve of the lithium secondary battery provided in Comparative Example 2
  • Figure 6 is a cycle performance curve of the lithium secondary battery provided in Example 1-3 and Comparative Example 1-2
  • Figure 7 is an embodiment 10 and Comparative Example 3 provide cycle performance graphs of lithium secondary batteries.
  • the capacity retention rate of the lithium manganate/lithium secondary battery after 100 cycles and the average Coulombic efficiency of the copper/lithium battery in Examples 1-9 after 50 cycles are also higher than the copper/lithium battery in Comparative Example 1 after 50 cycles.
  • the average Coulombic efficiency of the cycle Further according to the cycle performance curves shown in Figures 4 and 5, it can be seen that the charge and discharge curve of the lithium nickel cobalt manganate/lithium secondary battery in Example 1 is relatively stable and the polarization is small, while the charge and discharge curve of the lithium nickel cobalt manganate/lithium secondary battery in Comparative Example 2 The charge and discharge curve of lithium nickel cobalt manganate/lithium secondary battery has a large polarization, and the polarization continues to increase.
  • Examples 1-9 add hydrogen-free polyhalogen substituted alkane compounds (such as 1-chlorononafluorobutane, 1,1-dichlorotetrafluoroethane or 1,1,1-trichloro Trifluoroethane) or phenyl trifluoromethanesulfonate as diluent.
  • hydrogen-free polyhalogen substituted alkane compounds such as 1-chlorononafluorobutane, 1,1-dichlorotetrafluoroethane or 1,1,1-trichloro Trifluoroethane
  • phenyl trifluoromethanesulfonate as diluent.
  • the above-mentioned hydrogen-free polyhalogen substituted alkane compounds and phenyl trifluoromethanesulfonate have good compatibility with organic solvents and can reduce the electrolyte
  • the total salt concentration and viscosity can improve the wettability of the electrode piece, thereby reducing the polarization of the charge and discharge curve of the secondary battery and improving the cycle performance of the secondary battery.
  • hydrogen-free polyhalogen-substituted alkyl compounds can decompose on the surface of lithium metal anode to form a stable interface film rich in lithium fluoride compounds to reduce side reactions between the electrolyte and the anode, inhibit the growth of lithium dendrites, and thus improve Safety, Coulombic efficiency and cycle performance of secondary batteries.
  • the molecules of the hydrogen-free polyhalogen substituted alkane compounds (such as 1-chlorononafluorobutane, 1,1-dichlorotetrafluoroethane and 1,1,1-trichlorotrifluoroethane) provided by the embodiments of the present application
  • the structure does not contain hydrogen elements, which can effectively avoid hydrogen transfer reactions on the surface of the positive electrode, inhibit oxidative decomposition caused by the contact of the electrolyte with the surface of the positive electrode under high pressure, improve the high-voltage resistance of the electrolyte, and thus improve the cycle of secondary batteries. performance.
  • hydrogen-free polyhalogen-substituted alkyl compounds can decompose on the surface of the graphite negative electrode to form a stable interface film rich in lithium fluoride compounds, which can reduce side reactions between the electrolyte and the negative electrode, inhibit the growth of lithium dendrites, and thus improve the secondary Safety, Coulombic efficiency and cycle performance of secondary batteries.
  • the molecular structure of the hydrogen-free polyhalogen-substituted alkane compounds used in Examples 10 and 11 does not contain hydrogen elements, which can effectively avoid hydrogen transfer reactions on the surface of the cathode, which is beneficial to improving the high-voltage resistance of the electrolyte, and thus The cycle performance of secondary batteries can also be improved.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Secondary Cells (AREA)

Abstract

本申请实施例提供了一种局部高浓度电解液、二次电池、电子设备和移动装置。局部高浓度电解液包括电解质盐、有机溶剂和含有无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯的稀释剂。其中，无氢多卤素取代烷化合物的通式为Cn(FxCly)，n、x和y为大于或等于1的整数，且n、x和y满足x+y＝2n+2。本申请实施例提供的局部高浓度电解液、二次电池、电子设备和移动装置，通过添加稀释剂以降低电解液粘度，提高极片浸润性，进而可以提高二次电池的库伦效率和循环性能，有利于满足二次电池高电压工作的需求。

Description

局部高浓度电解液、二次电池、电子设备和移动装置
本申请要求于2022年07月15日提交中国专利局、申请号为202210832834.3、申请名称为“局部高浓度电解液、二次电池、电子设备和移动装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及电池技术领域，尤其涉及一种局部高浓度电解液、二次电池、电子设备和移动装置。
背景技术
随着经济和科技发展，大部分电子行业(例如电子消费产品、新能源汽车、电动无人机等)对二次电池能量密度的要求越来越高。当前，使用高比能电极材料以及提高电池工作电压是提高二次电池能量密度的主要途径。
高浓度电解液(电解质盐的浓度通常>3mol/L)作为高压二次电池体系的研究热点，不仅可以改善目前常用的低浓度电解液(电解质盐的浓度通常<1.5mol/L)耐高压性较差的问题，而且具有与电极相容性好、离子载体密度高等优势。
但在目前的实际应用中，高浓度电解液仍然存在着粘度较大、与极片浸润性不佳等缺陷，导致二次电池的库伦效率偏低、循环性能较差，无法有效满足二次电池高电压工作的需求。
发明内容
本申请实施例提供一种局部高浓度电解液、二次电池、电子设备和移动装置。该局部高浓度电解液通过添加无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯作为稀释剂，以降低电解液粘度，提高极片浸润性，进而可以提高二次电池的库伦效率和循环性能，有利于满足二次电池高电压工作的需求。
第一方面，提供了一种局部高浓度电解液，包括电解质盐、有机溶剂和稀释剂，所述稀释剂包括无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯中的至少一种，
所述无氢多卤素取代烷化合物的通式为Cn(FxCly)，其中，n、x和y为大于或等于1的整数，且所述n、x和y满足公式x+y＝2n+2。
在本申请中，通过将无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯作为稀释剂添加到高浓度电解液中，以形成局部高浓度电解液，从而可以降低高浓度电解液的总盐浓度和粘度，提高极片浸润性，进而有利于提高二次电池的库伦效率和循环性能，有利于满足二次电池高电压工作的需求。其中，无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯具有较低的分子极性，因此电解质盐可以在稀释剂中的溶解度较小或没有溶解度，进而有利于使局部高浓度电解液中可以保留高浓度电解液所具有的高浓度盐-溶剂簇的局部配位环境。较低的分子极性也有利于使稀释剂与有机溶剂相容，进而可以避免稀释剂和有机溶剂出现相分离，以获得澄清、均匀的局部高浓度电解液。
除此之外，无氢多卤素取代烷化合物的分子结构中不包含氢元素，因此能够避免在正极表面发生氢转移反应，以抑制电解液在高电压下与正极表面接触所引起的氧化分解，进而可以提高局部高浓度电解液的耐高压能力，有利于获得较高能量密度的二次电池。另外，无氢多卤素取代烷化合物还可以在负极表面分解，形成富含氟化物(例如氟化锂化合物)的稳定界面膜，有利于减小局部高浓度电解液与负极的副反应，抑制枝晶生长，从而可以防止枝晶生长到一定程度而穿透隔膜，引发电池电路，有利于提高二次电池的安全性、库伦效率以及循环性能。
不仅如此，苯基三氟甲烷磺酸酯的分解可以形成包含硫化物成分的界面膜(例如苯基三氟甲烷磺酸酯可以分解为硫化锂和烷基磺酸锂)，由于硫化物具有较高的离子电导率，因此可以提高界面膜的离子电导率，进而能够提高二次电池的倍率性能。
结合第一方面，在第一方面的某些实现方式中，所述无氢多卤素取代烷化合物的分子极性指数MPI 满足以下公式：
其中，MPI1为所述无氢多卤素取代烷化合物的MPI，S极1为所述无氢多卤素取代烷化合物的分子极性表面积，S总1为所述无氢多卤素取代烷化合物的分子总表面积；
所述苯基三氟甲烷磺酸酯的MPI满足以下公式：
其中，MPI2为所述苯基三氟甲烷磺酸酯的MPI，S极2为所述苯基三氟甲烷磺酸酯的分子极性表面积，S总2为所述苯基三氟甲烷磺酸酯的分子总表面积；
且所述无氢多卤素取代烷化合物的MPI的取值和所述苯基三氟甲烷磺酸酯的MPI的取值满足预设条件。
在本申请中，通过设置合适的预设条件，可以控制无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯的分子极性，进而有利于控制电解质盐在稀释剂中的溶解度较小或没有溶解度，也有利于控制稀释剂和有机溶剂相容。
结合第一方面，在第一方面的某些实现方式中，所述预设条件为所述无氢多卤素取代烷化合物的MPI的取值和所述苯基三氟甲烷磺酸酯MPI的取值为5～10。
在一种可能的情况下，当无氢多卤素取代烷化合物的MPI小于5时，无氢多卤素取代烷化合物与有机溶剂的相容性较差，因此稀释剂与有机溶剂可能存在分层或浑浊的现象，从而导致无法形成澄清、均匀的局部高浓度电解液。当无氢多卤素取代烷化合物的MPI大于10时，电解质盐在无氢多卤素取代烷化合物中的溶解度较高，因此可能无法产生高浓度盐-溶剂簇的局部配位环境，导致无法形成局部高浓度电解液。
因此，满足上述预设条件的无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯能够具有合适的分子极性，进而可以具有合适的溶解度，以形成局部高浓度电解液。
结合第一方面，在第一方面的某些实现方式中，所述无氢多卤素取代烷化合物为不对称结构。
在本申请中，通过设置无氢多卤素取代烷化合物为不对称结构，有利于确保无氢多卤素取代烷化合物具有分子极性，进而有利于控制无氢多卤素取代烷化合物与有机溶剂的相容性。
结合第一方面，在第一方面的某些实现方式中，所述电解质盐在所述无氢多卤素取代烷化合物和所述苯基三氟甲烷磺酸酯中的溶解度小于或等于0.1mol/L，所述无氢多卤素取代烷化合物和所述苯基三氟甲烷磺酸酯可溶于所述有机溶剂。
在本申请中，通过合理设置电解质盐在无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯中的溶解度，有利于使局部高浓度电解液中可以保留高浓度电解液所具有的高浓度盐-溶剂簇的局部配位环境。通过控制稀释剂与有机溶剂相容，有利于避免稀释剂和有机溶剂出现相分离，从而可以获得澄清、均匀的局部高浓度电解液。
结合第一方面，在第一方面的某些实现方式中，所述n的取值为1～20。
在本申请中，无氢多卤素取代烷化合物中的碳原子数可以为1～20。碳原子数量在上述范围内时，得到的无氢多卤素取代烷化合物可以具有合适的分子极性。
结合第一方面，在第一方面的某些实现方式中，所述稀释剂在所述局部高浓度电解液中的质量百分含量为10％～90％。
在本申请中，稀释剂的含量在上述范围内时，除了有利于使稀释剂能够在局部高浓度电解液中发挥作用以外，也有利于避免由于稀释剂含量过高，导致电解质盐析出所造成的局部高浓度电解液的电化学性能下降的问题出现。
结合第一方面，在第一方面的某些实现方式中，所述局部高浓度电解液的粘度小于或等于8mPa·s，所述局部高浓度电解液的电导率大于或等于2.5mS/cm。
在本申请中，通过设置合适的局部高浓度电解液的粘度和电导率范围，有利于提高极片浸润性，进而有利于提高二次电池的库伦效率、倍率性能以及循环性能。
结合第一方面，在第一方面的某些实现方式中，所述电解质盐包括锂盐、钠盐、钾盐、镁盐、锌盐 和铝盐中的至少一种。
在本申请中，根据局部高浓度电解液所应用的二次电池的体系不同，可以灵活设置对应的电解质盐。
结合第一方面，在第一方面的某些实现方式中，所述电解质盐包括MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2、MBF2C2O4、M[(CF3SO2)2N]、M[(FSO2)2N]、M[(CmF2m+1SO2)(CtF2t+1SO2)N]中的至少一种，
其中，M为Li、Na或K，m和t为大于或等于0的整数。
结合第一方面，在第一方面的某些实现方式中，所述电解质盐在所述局部高浓度电解液中的摩尔浓度为1mol/L～8mol/L。
在本申请中，通过设置合适的电解质盐的摩尔浓度，有利于形成具有高浓度盐-溶剂簇的局部配位环境的局部高浓度电解液，进而有利于获得具有较高能量密度的二次电池。
结合第一方面，在第一方面的某些实现方式中，所述有机溶剂包括碳酸酯类溶剂、羧酸酯类溶剂和醚类溶剂中的至少一种。
结合第一方面，在第一方面的某些实现方式中，所述局部高浓度电解液还包括添加剂，所述添加剂包括碳酸亚乙烯酯、三氟甲基碳酸乙烯酯、碳酸乙烯亚乙烯酯、1，3-丙磺酸内酯、1,4-丁磺酸内酯、硫酸乙烯酯、亚硫酸乙烯酯、甲烷二磺酸亚甲酯、丁二腈、己二腈、1,2-二(2-腈乙氧基)乙烷、1,3,6-己烷三腈、联苯或氟苯中的至少一种。
在本申请中，可以根据实际性能需求，在局部高浓度电解液中加入具有不同功能作用的添加剂。
第二方面，提供了一种二次电池，包括正极、负极、隔膜和如上述第一方面中任一项所述的局部高浓度电解液。
结合第二方面，在第二方面的某些实现方式中，所述二次电池包括锂二次电池、钾二次电池、钠二次电池、镁二次电池、锌二次电池、或铝二次电池。
第三方面，提供了一种电子设备，包括壳体、以及收容于所述壳体内的显示屏、电路板组件和上述第二方面中任一项所述的二次电池，所述二次电池为所述电路板组件供电。
第四方面，提供了一种移动装置，所述移动装置包括如上述第二方面中任一项所述的二次电池。
其中，第二方面至第四方面的有益效果，请参见第一方面的有益效果，在此不重复赘述。
附图说明
图1是本申请实施例提供的一种电子设备的结构示意图。
图2是本申请实施例提供的一种二次电池的工作原理示意图。
图3是本申请实施例1和对比例2提供的电解液的线性扫描伏安(linear sweep voltammetry，LSV)曲线图。
图4是本申请实施例1提供的电池的充放电曲线图。
图5是本申请对比例2提供的电池的充放电曲线图。
图6是本申请实施例1-3和对比例1-2提供的电池的循环性能曲线图。
图7是本申请实施例10和对比例3提供的电池的循环性能曲线图。
具体实施方式
下面将结合附图，对本申请中的技术方案进行描述。显然，所描述的实施例仅仅是本申请的一部分实施例，而不是全部的实施例。
以下实施例中所使用的术语只是为了描述特定实施例的目的，而并非旨在作为对本申请的限制。如在本申请的说明书和所附权利要求书中所使用的那样，单数表达形式“一个”、“一种”、“所述”、“上述”、“该”和“这一”旨在也包括例如“一个或多个”这种表达形式，除非其上下文中明确地有相反指示。还应当理解，在本申请以下各实施例中，术语“至少一种”、“一种或多种”是指一种、两种或两种以上。“以下至少一项(种)”或其类似表达，是指的这些项中的任意组合，包括单项(一种)或复数项(种)的任意组合。术语“和/或”，用于描述关联对象的关联关系，表示可以存在三种关系；例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A、B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
在本申请的描述中，所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小都在本申请实施例说明书公开的范围之内。具体地，本申请实施例所述的质量可以是μg、mg、g、kg等化工领域公知的质量单位。
本申请中被描述为“示例性的”，“示例”，“例如”，“可选地”或者“在某些实现方式中”的任何实施例或设计方案都不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用这些词旨在以具体方式呈现相关概念。
在本说明书中描述的参考“一个实施例”或“一些实施例”等意味着在本申请的一个或多个实施例中包括结合该实施例描述的特定特征、结构或特点。由此，在本说明书中的不同之处出现的语句“在一个实施例中”、“在一些实施例中”、“在其他一些实施例中”、“在另外一些实施例中”等不是必然都参考相同的实施例，而是意味着“一个或多个但不是所有的实施例”，除非是以其他方式另外特别强调。术语“包括”、“包含”、“具有”及它们的变形都意味着“包括但不限于”，除非是以其他方式另外特别强调。
在介绍本申请实施例之前，先阐述本申请中出现的技术术语。
原电池(primary cell):可以指将化学能转变成电能的装置，原电池利用正极和负极的电势差，使电子在正极和负极之间流动。
正极(cathode):可以指原电池中电极电势较高的一极。在放电过程中，电流可以从正极流出，正极可以得到电子、起还原作用。在充电过程中，电流可以流向正极，正极可以失去电子、起氧化作用。
负极(anode)：可以指原电池中电极电势较低的一极。在放电过程中，电流可以流向负极，负极可以失去电子、起氧化作用。在充电过程中，电流可以从负极流出，负极可以得到电子、起还原作用。
电解质(electrolyte)：可以指在电池正负极之间提供离子交换的媒介。
隔膜(separator)：可以指用于分隔电池的正极和负极、防止正负极直接接触而短路的介质。隔膜还具有可以使电解质离子通过的功能。
固体电解质界面(solid electrolyte interphase，SEI)膜：可以指在液态锂离子电池首次充放电过程中，电极材料与电解液在固液界面上发生反应所形成的一层覆盖于电极材料表面的钝化层。SEI膜是一种界面层，具有固体电解质的特征，是电子绝缘体，但也是Li+的优良导体，Li+可以经过SEI膜自由的嵌入和脱出。
二次电池(rechargeable battery)又称为充电电池或蓄电池，可以指在电池放电后可通过充电的方式使活性物质激活而继续使用的电池。
高浓度电解液：可以指当电解液中电解质盐的浓度增大到溶液中几乎不含有自由溶剂分子时，电解质盐的阴离子进入溶剂化鞘层，与阳离子和溶剂分子主要以聚集体和接触离子对形式存在的电解液。也就是说，高浓度电解液中具有高浓度盐-溶剂簇的局部配位环境。相比于常用的低浓度电解液(电解质盐的浓度<1.5mol/L)，高浓度电解液中电解质盐的浓度通常>3mol/L。
本申请实施例提供的方案可以应用于电子设备或移动装置。
电子设备例如可以是终端消费产品或3C电子产品(计算机类(computer)、通信类(communication)、消费类(consumer)电子产品)，如手机、移动电源、便携机、平板电脑、电子阅读器、笔记本电脑、数码相机、可穿戴设备、车载终端、耳机等设备。
移动装置例如可以是车辆、电动滑板、或电动自行车等。
图1是本申请实施例提供的一种电子设备100的结构示意图。图1所示实施例以电子设备100是手机为例进行说明。
电子设备100可以包括壳体10、显示屏20和电路板组件30。具体地，壳体10可以包括边框和后盖。边框环绕在显示屏20的外周且环绕在后盖外周。显示屏20、边框、后盖之间形成的空腔可以用于放置电路板组件30。在一个示例中，显示屏20和电路板组件30都可以被设置在壳体10上。电子设备100还可以包括用于为电路板组件30供电的二次电池40。二次电池40例如可以是锂二次电池、钾二次电池、钠二次电池、镁二次电池、锌二次电池或铝二次电池等。
图2是一种二次电池40的工作原理图。
二次电池40的核心部件可以包括正极101、负极102、电解液103和隔膜104(相应的连通辅件和回路等未示出)。正极101、负极102可以脱嵌金属离子(例如锂离子、钠离子、钾离子、镁离子、锌离子或铝离子等)，以实现能量的存储和释放。如图2所示，Li+向左(正极101)移动为能量释放过 程，Li+向右(负极102)移动为能量存储过程。电解液103可以是金属离子在正极101和负极102之间的传输载体。正极101和负极102是二次电池40的主体储能部分，可以体现二次电池40的能量密度、循环性能及安全性能。隔膜104可通过金属离子，但隔膜104本身不导电，从而隔膜104可以将正极101和负极102隔开，以防止正极101和负极102之间短路。
正极101可以包括能够可逆地嵌入/脱嵌金属离子的正极活性材料。以锂二次电池为例，正极活性材料可以包括但不限于锂的复合金属氧化物(如镍钴锰酸锂(LiNi0.8Co0.1Mn0.1)、磷酸铁锂(LiFePO4)、钴酸锂(LiCoO2)等)、聚阴离子锂化合物LiMi(PO4)j(M为Ni、Co、Mn、Fe、Ti、V，0≤i≤5，0≤j≤5)等。
负极102可以包括碳基负极、硅基负极、锡基负极、磷基负极、钛酸锂、锂负极、钠负极、镁负极、锌负极和铝负极中的一种或多种。其中，碳基负极例如可以是石墨、硬碳、软碳或石墨烯等。硅基负极例如可以是硅、硅碳、硅氧或硅金属化合物等。锡基负极例如可以是锡、锡碳、锡氧或锡金属化合物等。磷基负极例如可以是红磷、黑磷或磷化物等。锂负极、钠负极、镁负极、锌负极和铝负极例如可以是对应的金属单质或合金，或者也可以是集流体和设置在集流体上的对应的金属单质或合金。例如，锂负极可以是金属锂或锂合金，或者也可以是集流体和设置在集流体上的金属锂或锂合金。锂合金具体可以是锂硅合金、锂铝合金、锂锡合金、锂铟合金中的至少一种。
隔膜104例如可以包括但不限于单层聚乙烯(polyethylene，PE)、单层聚丙烯(polypropylene，PP)、双层PE/PP、双层PP/PP和三层PP/PE/PP等隔膜。
电解液103可以包括电解质盐和有机溶剂。其中，电解质盐和有机溶剂可以根据二次电池40的体系确定。以二次电池40是锂二次电池为例，在电解液103中，电解质盐通常为六氟磷酸锂(LiPF6)，有机溶剂通常为碳酸酯类溶剂。并且由于电解质盐LiPF6在电解液103中的浓度通常较低(一般小于1.5mol/L)，因此电解液103中存在大量自由溶剂分子，且Li+通常可以与3～4个溶剂分子配位，并以分离离子对的形式存在，SEI膜的形成过程也主要是由溶剂分子的还原或氧化控制。
目前市场对二次电池40能量密度的要求越来越高。一种有利于提升二次电池40能量密度的方式是提高二次电池40的电池工作。但是由于碳酸酯类溶剂的氧化电位较低，高压下容易发生氧化分解，导致上述碳酸酯类电解液具有较差的耐高压性。当二次电池40的工作电压较高时(例如工作电压大于4.2V)，碳酸酯类电解液容易发生不可逆的氧化分解，造成二次电池40很难在高压下维持稳定循环。
基于此，当前提出了电解质盐的浓度大于3mol/L的高浓度电解液。在高浓度电解液中，几乎不含有自由溶剂分子，电解质盐的阴离子与阳离子和溶剂分子主要以聚集体和接触离子对形式存在，SEI膜也主要由锂盐阴离子的分解产物组成。可见，相比于上述低浓度的碳酸酯类电解液，高浓度电解液中自由溶剂分子浓度和溶剂化结构都发生明显改变。这不仅可以改善低浓度的碳酸酯类电解液耐高压性较差的问题，也可以使高浓度电解液具有与电极相容性好、离子载体密度高等优势。
但在目前的实际应用中，由于电解质盐的浓度相对较大，高浓度电解液仍然存在着粘度较大、与极片浸润性不佳等缺陷，导致二次电池40的库伦效率偏低、循环性能较差，无法有效满足二次电池40高电压工作的需求。
有鉴于此，本申请实施例提供一种局部高浓度电解液，该局部高浓度电解液通过添加包括无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯的稀释剂，以降低电解液粘度，提高极片浸润性，进而可以提高二次电池的库伦效率和循环性能，有利于满足二次电池高电压工作的需求。
可以理解，本申请实施例提供的局部高浓度电解液可以是图2所示的电解液103。
本申请实施例提供一种局部高浓度电解液。该局部高浓度电解液可以包括电解质盐、有机溶剂和稀释剂。
其中，稀释剂可以包括无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯中的至少一种。具体地，无氢多卤素取代烷化合物的通式可以为Cn(FxCly)，其中，n、x和y为大于或等于1的整数，且n、x和y满足：x+y＝2n+2。
本申请实施例提供的局部高浓度电解液，通过将无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯作为稀释剂添加到高浓度电解液中，以形成局部高浓度电解液，这可以降低高浓度电解液的总盐浓度和粘度，提高极片浸润性，进而有利于提高二次电池的库伦效率和循环性能，有利于满足二次电池高电压工作的需求。其中，无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯具有较低的分子极性，因此电解质盐可以在稀释剂中的溶解度较小或没有溶解度，进而有利于使局部高浓度电解液中可以保留 高浓度电解液所具有的高浓度盐-溶剂簇的局部配位环境。较低的分子极性也有利于使稀释剂与有机溶剂相容，从而能够避免稀释剂和有机溶剂出现相分离，以获得澄清、均匀的局部高浓度电解液。
除此之外，无氢多卤素取代烷化合物的分子结构中不包含氢元素，因此能够避免在正极表面发生氢转移反应，以抑制电解液在高电压下与正极表面接触所引起的氧化分解，进而可以提高局部高浓度电解液的耐高压能力，有利于获得较高能量密度的二次电池。另外，无氢多卤素取代烷化合物还可以在负极表面分解，形成富含氟化物(例如氟化锂化合物)的稳定界面膜，有利于减小局部高浓度电解液与负极的副反应，抑制枝晶生长，从而可以防止枝晶生长到一定程度而穿透隔膜，引发电池电路，有利于二次电池的安全性、库伦效率以及循环性能。
不仅如此，苯基三氟甲烷磺酸酯的分解能够形成包含硫化物成分(例如苯基三氟甲烷磺酸酯可以分解为硫化锂和烷基磺酸锂等)的界面膜，由于硫化物具有较高的离子电导率，因此可以提高界面膜的离子电导率，进而能够提高二次电池的倍率性能。
以下对苯基三氟甲烷磺酸酯和无氢多卤素取代烷化合物和进行详细阐述。
在一些实施例中，苯基三氟甲烷磺酸酯中的苯基可以为被卤素取代或未取代的苯基。具体地，苯基三氟甲烷磺酸酯的分子结构可以如通式(Ⅰ)所示：
其中，R1～R5可以分别各自独立地选择氢原子、氟原子、氯原子和溴原子中的任意一种。
可以理解，若苯基三氟甲烷磺酸酯中的苯基为被氟原子取代的苯基，苯基三氟甲烷磺酸酯也可以在负极表面分解，形成富含氟化物(例如氟化锂化合物)的稳定界面膜，从而可以减小局部高浓度电解液与负极的副反应，抑制枝晶生长。
在一些实施例中，在无氢多卤素取代烷化合物的通式Cn(FxCly)中，n的取值可以为1～20。也就是说，无氢多卤素取代烷化合物中的碳原子数可以为1～20。更优选地，n的取值可以为1～10，进一步优选地，n的取值可以为2～6。
可以理解，碳原子数量在上述范围内时，得到的无氢多卤素取代烷化合物可以具有合适的分子极性。
可选地，无氢多卤素取代烷化合物可以为不对称结构，有利于确保无氢多卤素取代烷化合物具有分子极性，进而有利于控制无氢多卤素取代烷化合物与有机溶剂的相容性。
可选地，无氢多卤素取代烷化合物可以是直链的，也可以是支链的，本申请对此不作限制。
在一些实施例中，可以通过下列公式(1)和公式(2)计算无氢多卤素取代烷化合物的和苯基三氟甲烷磺酸酯各自的分子极性指数(molecular polarity index，MPI)，以表征无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯各自的分子极性大小。需要说明的是，MPI取值越大，对应的分子极性就越大。
具体地，无氢多卤素取代烷化合物的MPI可以通过公式(1)进行计算得到：
其中，MPI1为无氢多卤素取代烷化合物的MPI，S极1为无氢多卤素取代烷化合物的分子极性表面积，S总1为无氢多卤素取代烷化合物的分子总表面积。
苯基三氟甲烷磺酸酯的MPI可以通过公式(2)进行计算得到：
其中，MPI2为苯基三氟甲烷磺酸酯的MPI，S极2为苯基三氟甲烷磺酸酯的分子极性表面积，S总2为苯基三氟甲烷磺酸酯的分子总表面积。
示例性的，公式(1)中的S极1和公式(2)中的S极2可以通过下述方法计算：
首先通过密度泛函理论(density functional theory，DFT)中的B3LYP泛函，在6-311+G(d,p)基组水平上分别对无氢多卤素取代烷化合物的分子结构和苯基三氟甲烷磺酸酯的分子结构进行优化，以得到各自分子结构对应的分子稳定构型。然后对各自的分子稳定构型进行分子表面静电势(electrostatic potential，ESP)分析，将分子表面ESP大于预设阈值的区域定义为极性表面，极性表面对应的表面积即为各自对应的分子极性表面积。
可以理解，该预设阈值可以根据实际应用需求设置，例如可以是13kcal/mol、15kcal/mol、17kcal/mol或20kcal/mol等，本申请对此不作限制。
在一些实施例中，可以进一步设置根据公式(1)和公式(2)计算得到的无氢多卤素取代烷化合物的MPI的取值和苯基三氟甲烷磺酸酯的MPI的取值满足预设条件，从而可以根据预设条件选择分子极性合适的无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯作为稀释剂。这有利于控制无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯的溶解度，从而有利于控制电解质盐在稀释剂中的溶解度较小或没有溶解度，也有利于控制稀释剂和有机溶剂相容。
需要说明的是，预设条件的具体设置可以根据上述预设阈值确定。例如，上述预设阈值可以为15kcal/mol，在这种情况下，预设条件可以为无氢多卤素取代烷化合物的MPI的取值和苯基三氟甲烷磺酸酯的MPI的取值为5～10，更优选为5～9，进一步优选为6～8。
在上述预设阈值和预设条件下，当无氢多卤素取代烷化合物的MPI小于5时，无氢多卤素取代烷化合物与有机溶剂的相容性可能较差，因此稀释剂与有机溶剂可能存在分层或浑浊的现象，从而导致无法形成澄清、均匀的局部高浓度电解液。当无氢多卤素取代烷化合物的MPI大于10时，电解质盐在无氢多卤素取代烷化合物中的溶解度较高，因而可能无法产生高浓度盐-溶剂簇的局部配位环境，导致无法形成局部高浓度电解液。
可以理解，上述预设阈值和预设条件的数值仅是示例，并非是对本申请的限制。在一个可能的示例中，上述预设阈值可以为13kcal/mol，在这种情况下，预设条件可以为无氢多卤素取代烷化合物的MPI的取值和苯基三氟甲烷磺酸酯的MPI的取值为4～11，本申请对此不作限制。
在一些实施例中，电解质盐在无氢多卤素取代烷化合物和/或苯基三氟甲烷磺酸酯中的溶解度可以小于或等于0.1mol/L，无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯可溶于有机溶剂。
通过合理设置电解质盐在无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯的溶解度，有利于使局部高浓度电解液中可以保留高浓度电解液所具有的高浓度盐-溶剂簇的局部配位环境。通过控制稀释剂与有机溶剂相容，有利于避免稀释剂和有机溶剂出现相分离，从而可以获得澄清、均匀的局部高浓度电解液。
在一些实施例中，稀释剂在局部高浓度电解液中的百分含量为10％～90％，更优选为15％～80％，进一步优选为20％～50％。
需要说明的是，局部高浓度电解液中添加适当含量的稀释剂，除了有利于稀释剂在局部高浓度电解液中发挥作用以外，也有利于避免由于稀释剂含量过高，导致电解质盐析出所造成的局部高浓度电解液的电化学性能下降的问题出现。
在一些实施例中，局部高浓度电解液的粘度可以小于或等于8mPa·s，局部高浓度电解液的电导率可以大于或等于2.5mS/cm。通过设置局部高浓度电解液的粘度和电导率满足上述范围，有利于提高极片的浸润性，进而有利于提高二次电池的库伦效率、倍率性能以及循环性能。
以上介绍了局部高浓度电解液中的稀释剂的组成，以下具体介绍局部高浓度电解液中包括的电解质盐和有机溶剂。
在一些实施例中，根据不同的二次电池体系，电解质盐可以是锂盐、钠盐、钾盐、镁盐、锌盐或铝盐等。
在一个示例中，锂盐、钠盐、钾盐可以分别包括MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2、MBF2C2O4、M[(CF3SO2)2N]、M[(FSO2)2N]、M[(CmF2m+1SO2)(CtF2t+1SO2)N]中的至少一种，其中，M为Li、Na或K，m和t为大于或等于0的整数。
在另一个示例中，镁盐、锌盐或铝盐可以是由镁离子、锌离子、铝离子与上述锂盐、钠盐、钾盐中的阴离子所形成的盐类物质。
可选地，电解质盐在局部高浓度电解液中的摩尔浓度可以为1mol/L～8mol/L，进一步可以为 2mol/L～7mol/L、2mol/L～5mol/L或3mol/L～6mol/L，本申请对此不作限制。
在一些实施例中，有机溶剂可以包括碳酸酯类溶剂、羧酸酯类溶剂和醚类溶剂中的至少一种。可选地，上述溶剂可以按照任意比例混合以形成有机溶剂，本申请对此不作限制。
其中，碳酸酯类溶剂可以包括环状碳酸酯和/或链状碳酸酯。环状碳酸酯例如可以包括但不限于以下至少一种：碳酸乙烯酯(ethylene carbonate，EC)、碳酸丙烯酯(propylene carbonate，PC)、氟代碳酸乙烯酯(fluoroethylene carbonate，FEC)、γ-丁内酯(gamma-butyrolactone，GBL)、碳酸亚丁酯(butylene carbonate，BC)。链状碳酸酯例如可以包括但不限于以下至少一种：碳酸二甲酯(dimethyl carbonate，DMC)、碳酸甲乙酯(ethyl methyl carbonate，EMC)、碳酸二乙酯(diethyl carbonate，DEC)、碳酸二丙酯(dipropyl carbonate，DPC)中的至少一种。
羧酸类溶剂例如可以包括但不限于以下至少一种：乙酸甲酯(methyl acetate，MA)、乙酸乙酯(ethyl acetate，EA)、乙酸丙酯、乙酸丁酯、丙酸丙酯(n-propyl propionate，PP)、丙酸丁酯。
醚类溶剂可以包括环状醚和/或链状醚。环状醚例如可以包括但不限于以下至少一种：1,3-二氧戊烷、1,4-二氧惡烷、冠醚、四氢呋喃(tetrahydrofuran，THF)、2-甲基四氢呋喃(2-CH3-THF)、2-三氟甲基四氢呋喃(2-CF3-THF)。链状醚例如可以包括但不限于以下至少一种：二甲氧基甲烷(dimethoxymethane，DMM)、乙二醇二甲醚(ethylene glycol dimethoxy ether，DME)、二甘醇二甲醚。
在一些实施例中，根据实际应用需求，局部高浓度电解液中还可以包括添加剂。具体地，局部高浓度电解液中可以加入的添加剂种类众多，不同的添加剂可以有着不同的作用。示例性的，添加剂可以包括成膜添加剂、高电压添加剂、防过充添加剂和界面润湿剂等中的至少一种，本申请对此不作限制。
其中，成膜添加剂可以优先于有机溶剂在负极材料表面成膜，有利于提高电池的循环性能和寿命。示例性的，成膜添加剂可以包括但不限于碳酸亚乙烯酯、三氟甲基碳酸乙烯酯、碳酸乙烯亚乙烯酯、1，3-丙磺酸内酯、1,4-丁磺酸内酯、硫酸乙烯酯和亚硫酸乙烯酯中的至少一种。
高压添加剂可以在高电压下优先分解形成正极保护膜，能够稳定正极和电解液之间的界面，有利于提高电池的循环性能和寿命。示例性的，高电压添加剂可以包括但不限于甲烷二磺酸亚甲酯、丁二腈、己二腈、1,2-二(2-腈乙氧基)乙烷、1,3,6-己烷三腈中的至少一种。
防过充添加剂可以防止电池过充电，有利于提高电池的安全性能。示例性的，防过充添加剂可以是联苯。
界面浸润剂可以提高局部高浓度电解液对极片的浸润性，有利于减小电池的界面电阻，提高电池的倍率性能、放电容量和使用寿命。示例性的，界面浸润剂可以是氟苯。
可选地，添加剂在局部高浓度电解液中的质量百分含量可以为0.1％～10％，进一步可以为0.5％～9％、1％～6％或2％～7％，本申请对此不作限制。
需要说明的是，局部高浓度电解液中加入适量含量的添加剂，除了有利于添加剂发挥作用，提高二次电池的性能以外，也有利于避免由于添加剂含量过高导致局部高浓度电解液的粘度过大，从而造成二次电池的库伦效率和循环性能下降的问题出现。
本申请实施例提供一种局部高浓度电解液的制备方法，包括以下步骤：
在惰性环境或密闭环境(例如填充氩气的手套箱)中，将充分干燥的电解质盐溶于有机溶剂中，搅拌混合成均匀溶液，然后将稀释剂加入到上述均匀溶液中，再次搅拌混合均匀，得到局部高浓度电解液。
上述制备方法中的各操作可以根据现有常规电解液制备工艺实施。其中，关于电解质盐、有机溶剂和稀释剂等原料的具体说明可以参照上文所述实施例，在此就不再赘述。
此外，当局部高浓度电解液中还包括添加剂时，可以与稀释剂一同加入。
下面通过多个实施例和多个对比例，阐述本申请实施例提供的技术方案的效果。
[实施例1]
实施例1提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂，lithium bis(fluorosulfonyl)imide，LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1-氯九氟丁烷)。其中，DME和1-氯九氟丁烷的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然 后将1-氯九氟丁烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例1提供的局部高浓度电解液。
锂二次电池的制备：
将粘接剂聚偏二氟乙烯(polyvinylidene difluoride，PVDF)、导电剂(如超导炭黑，super P，SP)和活性材料镍钴锰酸锂(LiNi0.8Co0.1Mn0.1，NCM)，以2％:2％:96％的质量百分含量比在溶剂N-甲基吡咯烷酮(N-methyl-2-pyrrolidone，NMP)中充分搅拌混合均匀，形成正极浆料；通过涂布设备将正极浆料均匀涂布在铝箔集流体上，并经烘箱烘干去除NMP溶剂；最后将烘干后的极片经过冷压、分切等工序，得到正极极片。
将上述制备的正极极片、金属锂负极极片和商用PE隔膜制成电芯，采用聚合物包装，并灌注本申请实施例1制备得到的局部高浓度电解液，经化成等工序后制成软包锂二次电池。
[实施例2]
实施例2提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1,1-二氯四氟乙烷)。其中，DME和1,1-二氯四氟乙烷的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1,1-二氯四氟乙烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例2提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例3]
实施例3提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1,1,1-三氯三氟乙烷)。其中，DME和1,1,1-三氯三氟乙烷的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1,1,1-三氯三氟乙烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例3提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例4]
实施例4提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(由乙二醇二甲醚DME和氟代碳酸乙烯酯FEC混合形成)、以及稀释剂(1-氯九氟丁烷)。其中，DME、FEC和1-氯九氟丁烷的质量比为50:10:40，锂盐(LiFSI)的浓度为2.0mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将DME和FEC混合形成有机溶剂，再将充分干燥的LiFSI溶解于上述有机溶剂中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例4提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例5]
实施例5提供的局部高浓度电解液可以包括锂盐(双-三氟磺酰亚胺锂LiTFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1-氯九氟丁烷)。其中，DME和1-氯九氟丁烷的质量比为50:50，锂盐(LiTFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiTFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例5提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例6]
实施例6提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(苯基三氟甲烷磺酸酯)。其中，DME和苯基三氟甲烷磺酸酯的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将苯基三氟甲烷磺酸酯加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例6提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例7]
实施例7提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(由1-氯九氟丁烷和1,1,1-三氯三氟乙烷混合)。其中，DME、1-氯九氟丁烷和1,1,1-三氯三氟乙烷的质量比为40:30:30，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷和1,1,1-三氯三氟乙烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例7提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例8]
实施例8提供的局部高浓度电解液可以包括锂盐(由双氟磺酰亚胺锂LiFSI和二氟草酸硼酸锂(lithium difluoro(oxalato)borate，LiDFOB)混合)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1-氯九氟丁烷)。其中，DME和1-氯九氟丁烷的质量比为50：50，双氟磺酰亚胺锂LiFSI的浓度为1.5mol/L，二氟草酸硼酸锂LiDFOB的浓度为0.1mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI和LiDFOB溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例8提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例9]
实施例9提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、稀释剂(1-氯九氟丁烷)以及添加剂硫酸乙烯酯(ethylene sulfate，简写为DTD)。其中，DME和1-氯九氟丁烷的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L，硫酸乙烯酯DTD的质量百分含量为2％。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷和DTD加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例9提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[实施例10]
实施例10提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(由碳酸二甲酯DMC和氟代碳酸乙烯酯FEC混合形成)、以及稀释剂(1-氯九氟丁烷)。其中，DMC、FEC和1-氯九氟丁烷的质量比为50:10:40，锂盐(LiFSI)的浓度为2.0mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将DMC和FEC混合形成有机溶剂，再将充分干燥的LiFSI溶解于上述有机溶剂中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例10提供的局部高浓度电解液。
锂二次电池的制备：
将粘接剂聚偏二氟乙烯PVDF、导电剂SP和活性材料钴酸锂(LiCoO2)，以2％:2％:96％的质量百分含量比在溶剂NMP中充分搅拌混合均匀，形成正极浆料；通过涂布设备将正极浆料均匀涂布在铝箔集流体上，并经烘箱烘干去除NMP溶剂；最后将烘干后的极片经过冷压、分切等工序，得到正极极片。
将羧甲基纤维素钠(carboxymethyl cellulose，CMC)、丁苯橡胶(polymerized styrene butadiene rubber，SBR)、乙炔黑和石墨，以1.5％:2.5％:1％:96％的质量百分含量比，依次加入到去离子水中，充分搅拌混合均匀，形成混合负极浆料；然后采用涂布设备将负极浆料均匀涂布在铜箔集流体上，并经烘箱烘干；最后将涂布后的极片经过冷压、分切等工序，得到负极极片然后烘干、冷压、分切制得负极极片。
将上述制备的正极极片、负极极片和商用PE隔膜制成电芯，采用聚合物包装，并灌注本申请实施例10制备得到的局部高浓度电解液，经化成等工艺后制成软包锂二次电池。
[实施例11]
实施例11提供的局部高浓度电解液可以包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(由碳酸二甲酯DMC和氟代碳酸乙烯酯FEC混合形成)、稀释剂(由1-氯九氟丁烷和苯基三氟甲烷磺酸酯混合形成)。其中，DMC、FEC、1-氯九氟丁烷和苯基三氟甲烷磺酸酯的质量比为50:10:20:20，锂盐(LiFSI)的浓度为2.0mol/L。
本实施例的局部高浓度电解液的制备：
在填充氩气的手套箱中，将DMC和FEC混合形成有机溶剂，将充分干燥的LiFSI溶解于上述有机溶剂中，搅拌混合成均匀溶液，然后将1-氯九氟丁烷和苯基三氟甲烷磺酸酯加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请实施例11提供的局部高浓度电解液。
锂二次电池的制备：
锂二次电池的制作同实施例10。
[对比例1]
对比例1提供的锂二次电池电解液包括锂盐(LiPF6)、有机溶剂(由碳酸乙烯酯EC、碳酸二甲酯DMC和氟代碳酸乙烯酯FEC混合形成)，其中，EC、DEC和FEC的质量比为30:60:10，锂盐(LiPF6)的浓度为1.0mol/L。
本实施例的锂二次电池电解液的制备：
在填充氩气的手套箱中，将EC、DEC和FEC混合形成有机溶剂，再将充分干燥的LiPF6溶解于上述有机溶剂中，搅拌混合成均匀溶液，得到本申请对比例1提供的锂二次电池电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[对比例2]
对比例2提供的锂二次电池电解液包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(乙二醇二甲醚DME)、以及稀释剂(1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚)，其中，DME和1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚的质量比为50:50，锂盐(LiFSI)的浓度为1.5mol/L。
本实施例的锂二次电池电解液的制备：
在填充氩气的手套箱中，将充分干燥的LiFSI溶解于有机溶剂DME中，搅拌混合成均匀溶液，然后将1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请对比例2提供的锂二次电池电解液。
锂二次电池的制备：
锂二次电池的制作同实施例1。
[对比例3]
对比例3提供的锂二次电池电解液包括锂盐(双氟磺酰亚胺锂LiFSI)、有机溶剂(由碳酸二甲酯DMC和氟代碳酸乙烯酯FEC混合形成)、以及稀释剂(1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚)，其中，DMC、FEC和1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚的质量比为50:10:40，锂盐(LiFSI)的浓度为 2mol/L。
本实施例的锂二次电池电解液的制备：
在填充氩气的手套箱中，将DMC和FEC混合形成有机溶剂，将充分干燥的LiFSI溶解于上述有机溶剂中，搅拌混合成均匀溶液，然后将1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚加入到上述均匀溶液中，再次搅拌混合均匀，得到本申请对比例3提供的锂二次电池电解液。
锂二次电池的制备：
锂二次电池的制作同实施例10。
计算本申请实施例1-11和对比例1-3中稀释剂包括的各组分的MPI，计算结果如表1所示。
对本申请实施例1-11和对比例1-3中得到的电解液和锂二次电池进行以下电化学性能测试：
(1)不锈钢/锂电池性能测试：将不锈钢正极、金属锂负极和隔膜组装成纽扣电池，分别滴加100uL上述实施例1-11中得到的局部高浓度电解液和对比例1-3中得到的锂二次电池电解液。然后对得到的纽扣电池按照1mV/s的速度从开路电压扫到6.0V进行测试。测试结果如表1和图3所示。其中，表1示出了实施例1-11和对比例1-3对应的不锈钢/锂电池的分解电位，图3是实施例1和对比例2对应的不锈钢/锂电池的LSV曲线图。
(2)铜/锂电池性能测试：将铜片正极、金属锂负极和隔膜组装成纽扣电池，分别滴加100uL上述实施例1-11中得到的局部高浓度电解液和对比例1-3中得到的锂二次电池电解液。
然后按照如下测试流程设置对得到的纽扣电池进行测试：
首次充放电电流密度为0.5mA/cm2，首次沉积量为4.0mAh/cm2，循环放电电流密度为0.5mA/cm2，循环充电电流密度为1.5mA/cm2，循环沉积量为1.0mAh/cm2，循环周数为50周。
基于上述测试结果，根据公式(3)计算纽扣电池的平均库伦效率，计算结果如表1所示。
其中，CEavg为电池的平均库伦效率，Qc为电池的循环充电容量，Qs为电池的末次充电容量，QT为电池的首次放电容量，g为电池充放电循环周数。
(3)锂二次电池性能测试：以0.2C/0.5C充放电倍率对实施例1-11中和对比例1-3中组装得到的锂二次电池进行充放电循环测试，其中锂二次电池的电压范围设置为3.0V～4.4V，并记录锂二次电池循环100周后的容量保持率。测试结果如表1和图4-图7所示。其中，表1示出了实施例1-11和对比例1-3提供的锂二次电池循环100周后的容量保持率，图4是实施例1提供的锂二次电池的充放电曲线图，图5是对比例2提供的锂二次电池的充放电曲线图，图6是实施例1-3和对比例1-2提供的锂二次电池的循环性能曲线图，图7是实施例10和对比例3提供的锂二次电池的循环性能图。
表1

从表1可以看出，实施例1-9中的不锈钢/锂电池的分解电位都高于对比例2中的不锈钢/锂电池的分解电位。进一步根据图3所示的LSV曲线，也可以表明实施例1中的不锈钢/锂电池的分解电位高于对比例2中的不锈钢/锂电池的分解电位。此外，从表1也可以看出，实施例1-9中的镍钴锰酸锂/锂二次电池在循环100周后的容量保持率都高于对比例1和对比例2中的镍钴锰酸锂/锂二次电池循环100周后的容量保持率，实施例1-9中的铜/锂电池50周循环的平均库伦效率也都高于对比例1中的铜/锂电池50周循环的平均库伦效率。进一步根据图4和图5所示的循环性能曲线图可以看出，实施例1中的镍钴锰酸锂/锂二次电池充放电曲线比较稳定，极化较小，而对比例2中的镍钴锰酸锂/锂二次电池充放电曲线极化较大，并且极化不断增大。
这主要是因为实施例1-9中的电解液添加无氢多卤素取代烷化合物(例如1-氯九氟丁烷、1,1-二氯四氟乙烷或1,1,1-三氯三氟乙烷)或苯基三氟甲烷磺酸酯作为稀释剂，上述无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯都与有机溶剂的相容性较好，可以降低电解液的总盐浓度和粘度，提高极片浸润性，进而可以减小二次电池的充放电曲线极化，提高二次电池的循环性能。另外，无氢多卤素取代烷化合物可以在锂金属负极表面分解，形成富含氟化锂化合物的稳定界面膜，以减小电解液与负极的副反应，抑制锂枝晶生长，进而也可以提高二次电池的安全性、库伦效率和循环性能。
虽然对比例2中的电解液也加入了稀释剂，但对比例2中的稀释剂1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚的分子结构中含有氢元素，高电压时容易在正极表面发生氢转移反应，导致电解液发生不可逆的氧化分解，从而造成二次电池的高电压循环性能不佳。而本申请实施例提供的无氢多卤素取代烷化合物(例如1-氯九氟丁烷、1,1-二氯四氟乙烷和1,1,1-三氯三氟乙烷)的分子结构中不含氢元素，可以有效避免在正极表面发生氢转移反应，抑制电解液在高压下与正极表面接触所引起的氧化分解，提高电解液的耐高压能力，进而可以提高二次电池的循环性能。
从表1和图7可以看出，实施例10和实施例11中的不锈钢/锂电池的分解电位都高于对比例3中的不锈钢/锂电池的分解电位，实施例10和实施例11中的钴酸锂/石墨二次电池在循环100周后的容量保持率都高于对比例3中的钴酸锂/石墨二次电池循环100周后的容量保持率。
这主要是因为实施例10和实施例11中添加无氢多卤素取代烷化合物(例如1-氯九氟丁烷)和/或苯基三氟甲烷磺酸酯作为稀释剂，这可以降低电解液的总盐浓度和粘度，提高极片浸润性，进而可以提高二次电池的循环性能。另外，无氢多卤素取代烷化合物可以在石墨负极表面分解，形成富含氟化锂化合物的稳定界面膜，这可以减小电解液与负极的副反应，抑制锂枝晶生长，进而可以提高二次电池的安全性、库伦效率和循环性能。
并且，实施例10和实施例11中采用的无氢多卤素取代烷化合物的分子结构中不含氢元素，可以有效避免在正极表面发生氢转移反应，有利于提高电解液的耐高压能力，进而也可以提高二次电池的循环性能。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以该权利要求的保护范围为准。

Claims (17)

  1. 一种局部高浓度电解液，其特征在于，包括电解质盐、有机溶剂和稀释剂，所述稀释剂包括无氢多卤素取代烷化合物和苯基三氟甲烷磺酸酯中的至少一种；
    其中，所述无氢多卤素取代烷化合物的通式为Cn(FxCly)，其中，n、x和y为大于或等于1的整数，且所述n、x和y满足：x+y＝2n+2。
  2. 根据权利要求1所述的局部高浓度电解液，其特征在于，所述无氢多卤素取代烷化合物的分子极性指数MPI满足以下公式：
    其中，MPI1为所述无氢多卤素取代烷化合物的MPI，S极1为所述无氢多卤素取代烷化合物的分子极性表面积，S总1为所述无氢多卤素取代烷化合物的分子总表面积；
    所述苯基三氟甲烷磺酸酯的MPI满足以下公式：
    其中，MPI2为所述苯基三氟甲烷磺酸酯的MPI，S极2为所述苯基三氟甲烷磺酸酯的分子极性表面积，S总2为所述苯基三氟甲烷磺酸酯的分子总表面积；
    且所述无氢多卤素取代烷化合物的MPI的取值和所述苯基三氟甲烷磺酸酯的MPI的取值满足预设条件。
  3. 根据权利要求2所述的局部高浓度电解液，其特征在于，所述预设条件为所述无氢多卤素取代烷化合物的MPI的取值和所述苯基三氟甲烷磺酸酯的MPI的取值为5～10。
  4. 根据权利要求1至3中任一项所述的局部高浓度电解液，其特征在于，所述无氢多卤素取代烷化合物为不对称结构。
  5. 根据权利要求1至4中任一项所述的局部高浓度电解液，其特征在于，所述电解质盐在所述无氢多卤素取代烷化合物中的溶解度和在所述苯基三氟甲烷磺酸酯中的溶解度小于或等于0.1mol/L，所述无氢多卤素取代烷化合物和所述苯基三氟甲烷磺酸酯可溶于所述有机溶剂。
  6. 根据权利要求1至5中任一项所述的局部高浓度电解液，其特征在于，所述n的取值为1～20。
  7. 根据权利要求1至6中任一项所述的局部高浓度电解液，其特征在于，所述稀释剂在所述局部高浓度电解液中的质量百分含量为10％～90％。
  8. 根据权利要求1至7中任一项所述的局部高浓度电解液，其特征在于，所述局部高浓度电解液的粘度小于或等于8mPa·s，所述局部高浓度电解液的电导率大于或等于2.5mS/cm。
  9. 根据权利要求1至8中任一项所述的局部高浓度电解液，其特征在于，所述电解质盐包括锂盐、钠盐、钾盐、镁盐、锌盐和铝盐中的至少一种。
  10. 根据权利要求9所述的局部高浓度电解液，其特征在于，所述电解质盐包括MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2、MBF2C2O4、M[(CF3SO2)2N]、M[(FSO2)2N]、M[(CmF2m+1SO2)(CtF2t+1SO2)N]中的至少一种，
    其中，M为Li、Na或K，m和t为大于或等于0的整数。
  11. 根据权利要求1至10中任一项所述的局部高浓度电解液，其特征在于，所述电解质盐在所述局部高浓度电解液中的摩尔浓度为1mol/L～8mol/L。
  12. 根据权利要求1至11中任一项所述的局部高浓度电解液，其特征在于，所述有机溶剂包括碳酸酯类溶剂、羧酸酯类溶剂和醚类溶剂中的至少一种。
  13. 根据权利要求1至12中任一项所述的局部高浓度电解液，其特征在于，所述局部高浓度电解液还包括添加剂，
    所述添加剂包括碳酸亚乙烯酯、三氟甲基碳酸乙烯酯、碳酸乙烯亚乙烯酯、1，3-丙磺酸内酯、1,4-丁磺酸内酯、硫酸乙烯酯、亚硫酸乙烯酯、甲烷二磺酸亚甲酯、丁二腈、己二腈、1,2-二(2-腈乙氧基)乙烷、1,3,6-己烷三腈、联苯和氟苯中的至少一种。
  14. 一种二次电池，其特征在于，包括正极、负极、隔膜和如权利要求1至13中任一项所述的局部高浓度电解液。
  15. 根据权利要求14所述的二次电池，其特征在于，所述二次电池为锂二次电池、钾二次电池、钠二次电池、镁二次电池、锌二次电池、或铝二次电池。
  16. 一种电子设备，其特征在于，包括壳体、以及收容于所述壳体内的显示屏、电路板组件和如权利要求14或15所述的二次电池，所述二次电池为所述电路板组件供电。
  17. 一种移动装置，其特征在于，所述移动装置包括如权利要求14或15所述的二次电池。
PCT/CN2023/104406 2022-07-15 2023-06-30 局部高浓度电解液、二次电池、电子设备和移动装置 WO2024012244A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202210832834.3 2022-07-15
CN202210832834.3A CN117438648A (zh) 2022-07-15 2022-07-15 局部高浓度电解液、二次电池、电子设备和移动装置

Publications (1)

Publication Number Publication Date
WO2024012244A1 true WO2024012244A1 (zh) 2024-01-18

Family

ID=89535567

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2023/104406 WO2024012244A1 (zh) 2022-07-15 2023-06-30 局部高浓度电解液、二次电池、电子设备和移动装置

Country Status (2)

Country Link
CN (1) CN117438648A (zh)
WO (1) WO2024012244A1 (zh)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101842349A (zh) * 2007-11-01 2010-09-22 宇部兴产株式会社 磺酸苯酯化合物、使用它的非水电解液及锂电池
CN103827416A (zh) * 2011-04-11 2014-05-28 巴斯夫公司 非水电解液和包含其的电化学电池
JP2017091806A (ja) * 2015-11-10 2017-05-25 旭化成株式会社 非水電解液、リチウムイオン二次電池
CN109755635A (zh) * 2019-01-18 2019-05-14 杉杉新材料（衢州）有限公司 一种兼顾高低温性能的电池电解液添加剂、电解液及高镍三元锂离子电池
CN112242562A (zh) * 2019-07-16 2021-01-19 东莞市杉杉电池材料有限公司 一种阻燃型锂离子电池电解液及含该电解液的锂离子电池

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101842349A (zh) * 2007-11-01 2010-09-22 宇部兴产株式会社 磺酸苯酯化合物、使用它的非水电解液及锂电池
CN103827416A (zh) * 2011-04-11 2014-05-28 巴斯夫公司 非水电解液和包含其的电化学电池
JP2017091806A (ja) * 2015-11-10 2017-05-25 旭化成株式会社 非水電解液、リチウムイオン二次電池
CN109755635A (zh) * 2019-01-18 2019-05-14 杉杉新材料（衢州）有限公司 一种兼顾高低温性能的电池电解液添加剂、电解液及高镍三元锂离子电池
CN112242562A (zh) * 2019-07-16 2021-01-19 东莞市杉杉电池材料有限公司 一种阻燃型锂离子电池电解液及含该电解液的锂离子电池

Also Published As

Publication number Publication date
CN117438648A (zh) 2024-01-23

Similar Documents

Publication Publication Date Title
US11177507B2 (en) Electrolyte for lithium secondary battery and lithium secondary battery including the same
TWI384668B (zh) 電解質、電池及形成鈍化層的方法
WO2021208955A1 (zh) 电解液添加剂、二次电池电解液、二次电池和终端
CN110176630B (zh) 电解液和使用其的电化学装置
TW201523966A (zh) 電池用非水電解液，及鋰二次電池
WO2021047500A1 (zh) 电解液、包含该电解液的锂离子电池、电池模块、电池包及装置
CN114583270B (zh) 一种锂离子电池
US9711825B2 (en) Lithium ion secondary battery
JP2004022336A (ja) 二次電池用電解液およびそれを用いた二次電池
JP4797403B2 (ja) 非水系電解液二次電池及び非水系電解液二次電池用電解液
WO2023124604A1 (zh) 二次电池
CN110943251A (zh) 一种低温型锂离子电解液及由其制备的锂离子电池
US20230327210A1 (en) Battery electrolytic solution, secondary battery, and terminal
WO2023207369A1 (zh) 锂离子电池
JP5654191B2 (ja) 非水系電解液及びそれを用いた非水系電解液二次電池
CN113140797B (zh) 一种具有多腈类化合物的非水电解液及锂离子电池
CN112786967B (zh) 非水性电解液及含其的锂金属二次电池与锂离子二次电池
WO2024012244A1 (zh) 局部高浓度电解液、二次电池、电子设备和移动装置
CN110797573B (zh) 锂二次电池
CN114464892A (zh) 电解液及非水锂离子电池
CN111864266B (zh) 一种高电压锂离子电池电解液添加剂及其电解液
JP4872207B2 (ja) 非水系電解液二次電池及び非水系電解液二次電池用電解液
KR20150071973A (ko) 리튬 이차전지 전해액 및 이를 포함하는 리튬 이차전지
CN112886062B (zh) 电解液、电化学装置及电子设备
KR101797273B1 (ko) 전해질 및 이를 포함하는 이차 전지

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23838736

Country of ref document: EP

Kind code of ref document: A1