WO2022133961A1 - 锂二次电池及含有其的电池模块、电池包和用电装置 - Google Patents

锂二次电池及含有其的电池模块、电池包和用电装置 Download PDF

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WO2022133961A1
WO2022133961A1 PCT/CN2020/139182 CN2020139182W WO2022133961A1 WO 2022133961 A1 WO2022133961 A1 WO 2022133961A1 CN 2020139182 W CN2020139182 W CN 2020139182W WO 2022133961 A1 WO2022133961 A1 WO 2022133961A1
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lithium
active material
secondary battery
electrode active
positive electrode
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PCT/CN2020/139182
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English (en)
French (fr)
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陈兴布
孙信
陈晓
陈政伦
谢浩添
王帮润
李庚�
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宁德时代新能源科技股份有限公司
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Priority to EP20966531.4A priority Critical patent/EP4075558A4/en
Priority to CN202080102371.4A priority patent/CN115917816A/zh
Priority to PCT/CN2020/139182 priority patent/WO2022133961A1/zh
Publication of WO2022133961A1 publication Critical patent/WO2022133961A1/zh
Priority to US17/874,548 priority patent/US11605816B2/en

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    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
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    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • 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
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    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • 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
    • H—ELECTRICITY
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    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic 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

  • the present application belongs to the technical field of lithium secondary batteries, and relates to a lithium secondary battery, in particular to a lithium secondary battery containing a lithium compensator in a positive electrode active material layer, and a battery module provided with the lithium secondary battery, Battery packs and electrical devices.
  • Lithium secondary batteries have the advantages of high energy density, long cycle life and no memory effect and are widely used in many consumer electronic products. In recent years, with the continuous development of electric vehicles and energy storage systems, the requirements for the energy density of lithium secondary batteries are also increasing.
  • silicon material has become a potential anode material for lithium secondary batteries with high energy density due to its ultra-high theoretical specific capacity.
  • the solid electrolyte interface film SEI formed on the electrode surface is continuously broken and repaired, which consumes more lithium, thus making the cycle life of lithium secondary batteries worse.
  • Li 5 FeO 4 is currently the most studied lithium supplement in terms of cathode lithium supplementation. This type of lithium-rich material has a high theoretical specific capacity, but other metal ions (such as iron ions) generated after delithiation will shuttle. to the negative electrode for reduction. Iron precipitation is easy to damage the SEI film, and it will further pierce the separator to cause a short circuit of the battery, and the safety is low. In addition, Li 5 FeO 4 will also release oxygen after delithiation, resulting in the oxidation of the electrolyte and the attenuation of the battery capacity.
  • the present application is made in view of the above-mentioned technical problems, and its purpose is to provide a lithium secondary battery, comprising: a positive electrode, a negative electrode and an electrolyte; wherein,
  • the positive electrode includes a positive electrode active material layer, the positive electrode active material layer contains a lithium compensator, and the molecular formula of the lithium compensator is Li x Ni a Cu 1-ab M b O 2 , where 1 ⁇ x ⁇ 2, 0 ⁇ a ⁇ 1,0 ⁇ b ⁇ 0.1, M is selected from one or more of Zn, Sn, Mg, Fe and Mn;
  • the negative electrode includes a negative electrode active material layer, the negative electrode active material layer contains a first negative electrode active material and a second negative electrode active material, the first negative electrode active material is graphite, and the second negative electrode active material is selected from Si, SiO One or more of n (0 ⁇ n ⁇ 2) and SiC;
  • the electrolyte contains fluoroethylene carbonate (FEC);
  • the lithium secondary battery satisfies: 0.2 ⁇ W Si ⁇ W FEC ⁇ 7.5%-0.6 ⁇ W L , wherein W FEC is the mass ratio of the FEC in the electrolyte, and W Si is the second The mass ratio of the silicon element in the negative electrode active material in the negative electrode active material layer, and W L is the mass ratio of the lithium compensator in the positive electrode active material layer.
  • the lithium consumed for forming and repairing the solid electrolyte interface film SEI can be compensated by the lithium compensator Li x Ni a Cu 1-ab M b O 2 , and since the lithium compensator does not contain Fe, iron precipitation can be avoided And destroy the SEI film.
  • the fluorinated ethylene carbonate (FEC) contained in the electrolyte can form a dense SEI film, which makes it difficult to rupture the SEI film, so that the cycle can maintain a slow capacity decay rate and obtain a better charge-discharge ratio. capacity.
  • the lithium secondary battery of the present invention by controlling the mass ratio of fluoroethylene carbonate (FEC), silicon element, and lithium compensator within the above range, the loss of active lithium in the silicon negative electrode can be effectively compensated, and the cycle can be maintained relatively
  • the slow capacity decay rate improves the cycle life, obtains better charge-discharge specific capacity, and can reduce the amount of battery self-discharge.
  • the W L and the W Si satisfy the condition: -2.2% ⁇ W L -W Si ⁇ 2.5 %.
  • the first coulombic efficiency (ratio of first discharge capacity to charge capacity) of the secondary battery with silicon anode is low, if the silicon content increases, more lithium compensator is required to supplement the active lithium.
  • the mass ratio of silicon element and lithium compensator is within the above range, active lithium can be effectively supplemented for the silicon negative electrode, so that the cycle and storage can maintain a slow capacity decay rate, improve the cycle life and storage life, and obtain a better charge. discharge capacity.
  • W L ⁇ W Si -2.2% the lithium compensator can supplement enough active lithium for the silicon negative electrode secondary battery; at the same time, when W L ⁇ W Si +2.5%, the amount of lithium removal from the negative electrode active material is equal to that of the negative electrode active material.
  • the positive electrode of the lithium compensator has a moderate amount of lithium intercalation and vacancy, thereby further improving the discharge specific capacity of the battery.
  • the W L is 0.1% to 10%, optionally, the W L is 0.2% to 9%, and further optionally, the W L is 0.3% to 8%.
  • the addition amount of the lithium compensator is within the above range, it can supplement the lithium loss in the film formation and cycle process of the positive and negative electrodes, and supplement enough active lithium to ensure that the ratio of the negative electrode active material to the positive electrode lithium vacancy of the lithium compensator is moderate. Thereby, the discharge specific capacity of the secondary battery is further improved.
  • the W Si is 0.5 wt % to 10 wt %, optionally, the W Si is 1 wt % to 8 wt %, and further optionally, the W Si is 1.5 wt % to 6 wt %.
  • the cycle life and storage life can be improved by adding a lithium compensator effectively, and a better charge-discharge specific capacity can be obtained.
  • the Si content in the negative electrode sheet is within the above range, on the one hand, the energy density of the secondary battery can be improved; at the same time, the amount of the required lithium compensation agent L can be controlled, and the cycle and storage life of the secondary battery can be improved. and self-discharge problems.
  • the W FEC is 0.1 wt % to 7.5 wt %, optionally, the W FEC is 0.5 wt % to 6 wt %, and further optionally, the W FEC is 1 wt % to 5 wt % .
  • the specific surface area BET L value of the lithium compensator is 0.3 m 2 /g to 10 m 2 /g, and optionally, the BET L is 0.6 m 2 /g to 3.5 m 2 /g.
  • the specific surface area BET L value of the lithium compensator when the specific surface area BET L value of the lithium compensator is within the above range, problems such as gelation during the preparation of the positive electrode sheet can be avoided, thereby avoiding the decrease in cycle characteristics and discharge capacity ratio.
  • the lithium compensator when the specific surface area BET L of the lithium compensator is within the above range, on the one hand, the lithium compensator does not agglomerate, which improves the problem that the positive electrode slurry is prone to gel, and improves the battery cycle life and charge-discharge specific capacity; , it can also improve the matching degree with the positive active material, and improve the capacity of the lithium compensator, which is conducive to further exerting the contribution of the lithium compensator to the charge-discharge capacity ratio.
  • the volume average particle diameter D v 50 L of the lithium compensator is 1 ⁇ m ⁇ 20 ⁇ m, and optionally, the D v 50 L is 3 ⁇ m ⁇ 13 ⁇ m.
  • the volume average particle diameter D v 50 L of the lithium compensator is within the above range, problems such as gelation during the preparation of the positive electrode sheet can be avoided, thereby avoiding the decrease in cycle characteristics and discharge capacity ratio.
  • the lithium compensator is not likely to agglomerate, so that the positive electrode slurry is not easily gelled, and the cycle life of the battery is reduced and the charge-discharge specific capacity is improved.
  • it can also improve the matching degree with the positive active material, improve the capacity of the lithium compensator, and help further exert the contribution of the lithium compensator to the charge-discharge capacity ratio.
  • the positive electrode further includes a positive electrode active material, and the positive electrode active material includes at least one of the compounds represented by formula (I) to formula (III):
  • M' is Mn, Fe, One or more of Cr, Ti, Zn, V, Al, Zr and Ce, A includes one or more of S, N, F, Cl, Br and I; optional, 0.5 ⁇ a1 ⁇ 1, 0 ⁇ b1 ⁇ 0.5, 0.7 ⁇ a1+b1 ⁇ 1, 0 ⁇ y ⁇ 0.1, M is one or both of Mn and Al, and A is one or both of S or F;
  • M includes Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and One or more of Ce, A' including one or more of S, N, F, Cl, Br and I;
  • M"' is selected from one or more of transition metal elements and non-transition metal elements except Fe and Mn;
  • the positive active material includes at least the compound represented by formula (I).
  • the above-mentioned lithium compensator can be used in combination with various positive electrode active materials, both of which can improve cycle life and storage life, obtain better charge-discharge specific capacity, and reduce the amount of battery self-discharge.
  • the positive electrode further includes a positive electrode active material
  • the positive electrode active material includes a lithium transition metal oxide having a layered structure
  • the volume average particle size D v 50 L of the lithium compensator is the same as the The volume average particle size D v 50 N of the lithium transition metal oxide satisfies: 0.3 ⁇ D v 50 L /D v 50 N ⁇ 3.6, optionally, 0.7 ⁇ D v 50 L /D v 50 N ⁇ 3.
  • the particle size ratio of the lithium compensator to the lithium transition metal oxide having a layered structure is within the above range, the slurry of the positive electrode active material is not easily gelled, and the stability is good, and the lithium compensator has an effect on the charge-discharge capacity. contribution is also higher.
  • the positive electrode material is less likely to gel, which is beneficial to improve the cycle life and charge-discharge specific capacity of the secondary battery; At the same time, it can also improve the matching degree with the positive electrode active material, which is beneficial to the capacity of the lithium compensator and improves the contribution of the lithium compensator to the charge-discharge capacity ratio.
  • the positive electrode further includes a positive electrode active material
  • the positive electrode active material includes a lithium phosphate having an olivine structure
  • the volume average particle size D v 50 L of the lithium compensator is the same as the The volume average particle diameter D v 50 P of the lithium phosphate of the stone structure satisfies: 1 ⁇ D v 50 L /D v 50 P ⁇ 15, optionally, 2.5 ⁇ D v 50 L /D v 50 P ⁇ 11.
  • the particle size ratio of the lithium compensator to the lithium phosphate having an olivine structure is within the above range, the slurry of the positive electrode active material is not easily gelled, the stability is good, and the contribution of the lithium compensator to the capacity is relatively high. high.
  • a second aspect of the present application provides a battery module including the secondary battery according to the first aspect of the present application.
  • a third aspect of the present application provides a battery pack including the battery module according to the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device comprising at least one of the secondary battery according to the first aspect of the present application, the battery module according to the second aspect of the present application, or the battery pack according to the third aspect of the present application .
  • the battery module, battery pack and electrical device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an apparatus in which a secondary battery according to an embodiment of the present application is used as a power source.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range that is not expressly recited.
  • Embodiments of the first aspect of the present application provide a secondary battery.
  • the secondary battery includes a positive electrode sheet, a negative electrode sheet and an electrolyte.
  • active ions are inserted and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode active material may include, but is not limited to, graphite and silicon-based materials.
  • the above-mentioned graphite may include artificial graphite, natural graphite, or a mixture thereof.
  • the silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compounds (eg, silicon oxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. These materials are all commercially available.
  • the negative electrode active material layer may contain a first negative electrode active material and a second negative electrode active material, the first negative electrode active material is graphite, and the second negative electrode active material is selected from Si, SiO n (0 ⁇ n ⁇ 2), one or more of SiC.
  • the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is provided on either or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates).
  • PP polypropylene
  • PET polyethylene terephthalic acid ethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode film layer usually contains negative electrode active material and optional binder, optional conductive agent and other optional auxiliary agents, and is usually formed by coating and drying the negative electrode slurry .
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), One or more of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • auxiliary agents are, for example, thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.
  • the positive active material may include at least one of the compounds represented by formula (I) to formula (III):
  • M' is Mn, Fe, One or more of Cr, Ti, Zn, V, Al, Zr and Ce, A includes one or more of S, N, F, Cl, Br and I; optional, 0.5 ⁇ a1 ⁇ 1, 0 ⁇ b1 ⁇ 0.5, 0.7 ⁇ a1+b1 ⁇ 1, 0 ⁇ y ⁇ 0.1, M is one or both of Mn and Al, and A is one or both of S or F;
  • M includes Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and One or more of Ce, A' including one or more of S, N, F, Cl, Br and I;
  • 0 ⁇ x3 ⁇ 1, 0 ⁇ y3 ⁇ 0.1, and M"' is selected from one or more of transition metal elements and non-transition metal elements except Fe and Mn.
  • the positive electrode plate also includes a lithium compensator L, and the molecular formula of the lithium compensator L is Li x Ni a Cu 1-a- b M b O 2 , where 1 ⁇ x ⁇ 2, 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.1, M is selected from one or more of Zn, Sn, Mg, Fe and Mn.
  • the lithium compensator L may be a metal oxide mainly composed of lithium, nickel, and copper, and one or more of Zn, Sn, Mg, Fe, and Mn may be added in a small amount.
  • the positive electrode current collector has two opposite surfaces in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • Composite current collectors can be formed by metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates).
  • the positive electrode film layer also optionally includes a conductive agent.
  • a conductive agent is not specifically limited, and those skilled in the art can select them according to actual needs.
  • the conductive agent for the positive electrode film layer may be one or more selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared according to methods known in the art.
  • the positive electrode active material, conductive agent and binder of the present application can be dispersed in a solvent (such as N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector On the fluid, after drying, cold pressing and other processes, the positive pole piece is obtained.
  • NMP N-methylpyrrolidone
  • the type of electrolyte is not specifically limited, and can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolyte and liquid electrolyte (ie, electrolyte).
  • the electrolyte is an electrolyte.
  • the electrolyte includes an electrolyte lithium salt and a solvent.
  • the lithium salt can be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonimide (LiFSI), Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Trifluoromethanesulfonate (LiTFS), Lithium Difluorooxalate Borate (LiDFOB), Lithium Dioxalate Borate (LiBOB), Lithium Difluorophosphate (LiPO) 2 F 2 ), one or more of lithium difluorobisoxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium per
  • the solvent contains fluoroethylene carbonate (FEC), and fluoroethylene carbonate (FEC) can strengthen the negative electrode film formation and form a dense solid electrolyte interface film (SEI film).
  • FEC fluoroethylene carbonate
  • SEI film dense solid electrolyte interface film
  • the solvent may also contain ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), carbonic acid Dipropyl (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Methyl Formate (MF), Methyl Acetate (MA), Ethyl Acetate (EA) ), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1 , One or more of 4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).
  • EC ethylene
  • additives are also optionally included in the electrolyte.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, and additives to improve battery low temperature performance. additives, etc.
  • the lithium secondary battery satisfies: 0.2 ⁇ W Si ⁇ W FEC ⁇ 7.5%-0.6 ⁇ W L , wherein W FEC is the mass ratio of the FEC in the electrolyte, and W Si is The mass ratio of the silicon element in the second negative electrode active material in the negative electrode active material layer, W L is the mass ratio of the lithium compensator L in the positive electrode active material layer.
  • lithium consumed for forming and repairing the solid electrolyte interface film SEI can be compensated by the lithium compensator Li x Ni a Cu 1-ab M b O 2 , and since the lithium compensator does not contain Fe, It is possible to avoid iron precipitation and damage to the SEI film.
  • the fluorinated ethylene carbonate (FEC) contained in the electrolyte can form a dense SEI film, which makes it difficult to rupture the SEI film, so that the cycle can maintain a slow capacity decay rate and obtain a better charge-discharge ratio. capacity.
  • the fluoroethylene carbonate (FEC) is less than 0.2 ⁇ W Si , the film formation of the negative electrode is insufficient, and the cycle life cannot be improved. If the fluoroethylene carbonate (FEC) is greater than 7.5%-0.6 ⁇ W L , the transition metal ions in the lithium compensator L are excessively precipitated at the negative electrode, resulting in the problem of battery self-discharge.
  • the mass ratio of the FEC in the electrolyte, W FEC can be determined by using a testing method known in the art.
  • a testing method known in the art.
  • the gas chromatograph Agilgent 7890B can be used to measure the electrolyte to be injected or the electrolyte obtained by centrifuging the finished cell.
  • the mass ratio W Si of the silicon element in the second negative electrode active material in the negative electrode active material layer can be measured by a testing method known in the art.
  • the following method can be used to perform the test: select a plasma emission spectrometer with the model ICAP7400 of Thermo Fisher Scientific Company of the United States, and use the ICP method to measure.
  • the test sample can be a negative electrode piece that has been coated and cold-pressed, or a negative electrode piece that has been disassembled from the battery cell (leave the battery cell at 25°C for 30 minutes; The core discharge termination voltage, then stand for 30 minutes to fully discharge, then disassemble the battery core, take out the negative pole piece, properly rinse with DMC solution, and dry it for use).
  • the mass ratio W L of the lithium compensator L in the positive electrode active material layer can be measured by a testing method known in the art.
  • the following method can be used for testing: for the mixed pole piece of the positive active material that does not contain Ni and Cu elements, such as lithium compensator L and lithium iron phosphate, ICP (for example, the model of Thermo Fisher Scientific in the United States is ICAP7400) can be used.
  • ICP for example, the model of Thermo Fisher Scientific in the United States is ICAP7400
  • the Ni/Cu ratio and the mass ratio of the lithium compensator L were obtained by the plasma emission spectrometer) test.
  • ICP plasma emission spectrometer of Thermo Fisher Scientific company model ICAP7400 in the United States
  • the mass ratio of Ni, Co, Mn, Cu and other elements and then combined with EDS (OXFORD EDS X-max-50mm 2 ) to carry out Mapping test on the surface or cross-section of the positive pole piece to find the copper-rich area (corresponding to the lithium compensator L ) and then narrow the range, test the Ni/Cu ratio of the copper-rich area, which is the Ni/Cu ratio of the lithium compensator L, and then test the mass ratio of each element by ICP to obtain the mass ratio of the L material.
  • EDS OXFORD EDS X-max-50mm 2
  • W L and W Si satisfy the condition: -2.2% ⁇ W L -W Si ⁇ 2.5 %.
  • the silicon content increases, and more lithium compensator L is required to supplement the active lithium.
  • the mass ratio of silicon element and lithium compensator L is within the above range, the loss of active lithium in the silicon negative electrode can be effectively compensated, so that the cycle and storage can maintain a slow capacity decay rate, thereby improving the cycle life and storage life, and obtaining better Charge and discharge specific capacity.
  • the lithium compensator can supplement enough active lithium for the silicon negative electrode secondary battery; at the same time, when W L ⁇ W Si +2.5%, the negative electrode active material and lithium-containing compensation
  • the positive electrode lithium intercalation vacancy ratio of the agent is moderate, thereby further improving the discharge specific capacity of the battery.
  • W L is 0.1% to 10%, optionally, the W L is 0.2% to 9%, and further optionally, the W L is 0.3% to 8%.
  • the addition amount of the lithium compensator is within the above range, it can provide enough active lithium for the film formation of the positive and negative electrodes, and at the same time ensure that the ratio of the negative electrode active material to the positive electrode lithium-intercalation vacancy containing the lithium compensator is moderate, thereby further improving the secondary battery.
  • the discharge specific capacity decreases.
  • W Si is 0.5 wt % to 10 wt %, optionally, the W Si is 1 wt % to 8 wt %, and further optionally, the W Si is 1.5 wt % to 6 wt %.
  • the Si content in the negative electrode sheet is within the above range, on the one hand, the energy density, cycle and storage life of the secondary battery can be improved, and at the same time, the amount of the required lithium compensator L can be controlled to improve the performance of the secondary battery. Self-discharge problem.
  • the W FEC is 0.1 wt % to 7.5 wt %, optionally, the W FEC is 0.5 wt % to 6 wt %, and further optionally, the W FEC is 1 wt % to 5 wt %.
  • FEC fluoroethylene carbonate
  • the reason may be that when the content of fluoroethylene carbonate (FEC) in the electrolyte is within the above range, a dense SEI film can be formed on the surface of the negative electrode (especially the silicon particles), which can effectively improve the interface between the silicon particles and the electrolyte. reaction, thereby improving the cycle life of the secondary battery; at the same time, it can also reduce the dissolution of the copper element in the lithium compensation agent, and improve the problem of increased self-discharge rate of the secondary battery.
  • the specific surface area BET L value of the lithium compensator L is 0.3 m 2 /g to 10 m 2 /g, optionally, the BET L is 0.6 m 2 /g to 3.5 m 2 /g.
  • Lithium compensator L contains a lot of lithium, has strong alkalinity, high activity, large particles and is sensitive to water. Problems such as gelation are prone to occur during the preparation of positive electrode pieces, resulting in poor stability of the positive electrode slurry and greatly reducing the yield. .
  • the BET L value of the specific surface area of the lithium compensator is within the above range, less gel can be obtained, the cycle life can be further improved, and a better charge-discharge specific capacity can be obtained.
  • the specific surface area of the lithium compensator L can be measured by a testing method known in the art.
  • test methods and steps please refer to the standard: GB/T 19587-2004 "Determination of specific surface area of solid substances by gas adsorption BET method".
  • the instrument model NOVA 2000e can be used, and the test can be performed using the following procedure: (1) take a certain amount of sample (eg, 2.0-15.0g); (2) put the sample into a sample tube and put it into a heating pack , carry out degassing treatment (the degassing condition is 200°C, 2 hours); (3) After the degassing is completed, when the temperature of the degassing station drops to normal temperature, remove the sample tube from the degassing station, weigh and calculate the total sample (4) Put the sample tube into the test filling rod to test the specific surface area of the sample.
  • the volume average particle size D v 50 L of the lithium compensator is 1 ⁇ m ⁇ 20 ⁇ m, and optionally, the D v 50 L is 3 ⁇ m ⁇ 13 ⁇ m.
  • the volume average particle size of the lithium compensator is within the above range, less gel can be obtained, the cycle life can be ensured, and a better charge-discharge specific capacity can be obtained.
  • the volume average particle size D v 50 L of the lithium compensator L can be measured by a testing method known in the art.
  • the following method can be used for testing: refer to GB/T 19077-2016 particle size distribution laser diffraction method, and use a laser particle size analyzer (eg, Malvern Mastersizer 2000E, UK) to measure.
  • a laser particle size analyzer eg, Malvern Mastersizer 2000E, UK
  • For the positive pole piece that has been mixed with the lithium compensator L, scanning electron microscopy (SEM, ZEISS SEM Sigma 300) and ion polishing cross-sectional topography (CP) can also be used to select multiple regions (for example, more than 20 regions). ), measure the visible maximum particle size of the lithium compensator L respectively, and obtain the average value to characterize the volume average particle size D v 50 L of the lithium compensator L.
  • SEM scanning electron microscopy
  • CP ion polishing cross-sectional topography
  • the positive electrode active material includes a lithium transition metal oxide having a layered structure, and the volume average particle diameter of the lithium compensator is D v 50 L and the volume average particle diameter D of the lithium transition metal oxide.
  • v 50 N satisfies: 0.3 ⁇ D v 50 L /D v 50 N ⁇ 3.6, optional, 0.7 ⁇ D v 50 L /D v 50 N ⁇ 3.
  • the ratio of the volume average particle size of the lithium compensator to the volume average particle size of the lithium transition metal oxide is within the above range, less gelation can be achieved, cycle life can be ensured, and better charge-discharge specific capacity can be obtained.
  • the positive electrode material is less likely to gel, which is beneficial to improve the cycle life and charge-discharge specific capacity of the secondary battery; At the same time, it can also improve the matching degree with the positive electrode active material, which is beneficial to the capacity of the lithium compensator and improves the contribution of the lithium compensator to the charge-discharge capacity ratio.
  • the particle size ratio D v 50 L /D v 50 N of the volume average particle diameter D v 50 L of the lithium compensator L and the volume average particle diameter D v 50 N of the lithium transition metal oxide may be Assays are performed using test methods known in the art. As an example, the following method can be used for testing: for the powder level, the lithium compensator L can be measured by a laser particle size analyzer (for example, Malvern Mastersizer 2000E, UK) with reference to GB/T 19077-2016 particle size distribution laser diffraction method, respectively. and the D v 50 of the positive electrode active material, and then obtain the particle size ratio.
  • a laser particle size analyzer for example, Malvern Mastersizer 2000E, UK
  • the D v 50 of the positive electrode active material and then obtain the particle size ratio.
  • SEM scanning electron microscopy
  • CP ion polishing cross-sectional topography
  • the positive active material includes a lithium phosphate having an olivine structure
  • the volume average particle diameter of the lithium compensator is D v 50 L and the volume average particle diameter of the lithium phosphate having an olivine structure.
  • D v 50 P satisfies: 1 ⁇ D v 50 L /D v 50 P ⁇ 15.
  • the particle size ratio D v 50 L /D v 50 P of the volume average particle diameter D v 50 L of the lithium compensator L and the volume average particle diameter D v 50 P of the lithium transition metal oxide may be Refer to the test method for D v 50 L /D v 50 P above.
  • a separator is further included in the secondary battery.
  • the separator is arranged between the positive pole piece and the negative pole piece, and plays the role of isolation.
  • the type of separator for the secondary battery of the present application is not particularly limited, and any well-known porous structure separator for secondary batteries can be selected.
  • the release film can be selected from glass fiber film, non-woven film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and one or more multilayer composite films comprising one or more of them. species or several.
  • the secondary battery may include an outer package.
  • the outer packaging is used to encapsulate the positive pole piece, the negative pole piece and the electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
  • the outer package of the secondary battery may also be a soft package, such as a pouch-type soft package.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • the secondary battery can be prepared using methods known in the art.
  • the positive pole piece, the separator and the negative pole piece are formed into an electrode assembly by a winding process or a lamination process, wherein the separator is placed between the positive pole piece and the negative pole piece to isolate the electrode assembly; the electrode assembly is placed outside In the package, an electrolyte solution was injected and sealed to obtain a secondary battery.
  • FIG. 1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a accommodating cavity.
  • the housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the receiving cavity.
  • the electrolyte solution is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 may be one or several, and may be adjusted according to requirements.
  • the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • the plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed with fasteners.
  • the battery module 4 may further include a housing having an accommodating space in which the plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case.
  • the battery box includes an upper box body 2 and a lower box body 3 .
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • the plurality of battery modules 4 may be arranged in the battery case in any manner.
  • the secondary battery can be used as a power source of the electrical device, and can also be used as an energy storage unit of the electrical device.
  • the electrical device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric vehicles, etc.) Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electrical device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electric device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the mass ratio of graphite, silicon oxide (silicon element in the negative active material layer is 3%), binder styrene-butadiene rubber (SBR), and thickener sodium carbon methyl cellulose (CMC) is 94:3:2:1 Fully stir and mix in deionized water to form a uniform negative electrode slurry; coat the negative electrode slurry on the surface of the negative electrode current collector copper foil, dry, cold-press, slit and cut Cut to get a negative pole piece.
  • the mass ratio of the material layer is 3%, the specific surface area is 0.99m 2 /g, the average particle size D v 50 is 8 ⁇ m), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 93.5: 3:2:1.5
  • Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50, and then LiPF 6 was uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF 6 was 1.1 mol/L.
  • a fluoroethylene carbonate (FEC) additive with a mass ratio of 0.6% was added to the electrolyte.
  • the positive pole piece, the separator, and the negative pole piece are stacked in sequence, so that the separator is in the middle of the positive and negative poles to play a role of isolation, and is wound to obtain a bare cell. Put the bare cell in the outer package, inject the prepared electrolyte and seal it.
  • Examples 2 to 6 and Comparative Examples 1 to 4 are similar to the preparation methods of Example 1, but the positive active material (Lithium Iron 1.2 ⁇ m), the content of lithium compensator, the Si content of the negative electrode and the product parameters of the FEC content in the electrolyte, see Table 1 for different product parameters.
  • the positive active material Lithium Iron 1.2 ⁇ m
  • the content of lithium compensator the content of lithium compensator
  • the Si content of the negative electrode the product parameters of the FEC content in the electrolyte
  • a laser particle size analyzer for example, Malvern Mastersizer 2000E, UK
  • the instrument model is NOVA 2000e, and the test is carried out using the following procedure: (1) Take a certain amount of sample (eg, 2.0-15.0g); (2) Put the sample into the sample tube, put it into a heating pack, and carry out degassing treatment (The degassing condition is 200°C, 2 hours); (3) After the degassing is completed, when the temperature of the degassing station drops to normal temperature, the sample tube is removed from the degassing station, and the total mass of the sample is calculated by weighing; (4) Put the sample tube into the test fill rod to test the specific surface area of the sample.
  • the charge-discharge specific capacity of the battery in the example table is calculated according to the following formula:
  • the battery was charged to 3.85V at a constant current rate of 0.33C at room temperature, and then charged to a rate of 0.05C at a constant voltage of 3.85V, and then left at room temperature for 2 days to test the open circuit voltage V2 of the battery after two days.
  • the battery is charged to 4.25V at a constant current rate of 0.33C at room temperature, then charged to a rate of 0.05C at a constant voltage of 4.25V, and then discharged to a rate of 2.8V at a constant current rate of 0.33C. This is one cycle. Repeat the above cycle test until the discharge capacity decays to 80% of the initial capacity and stop the test to obtain the number of cycles.
  • Step 2 Full charge: The battery is charged to 4.25V with a constant current of 0.33C at room temperature, and then charged to a rate of 0.05C with a constant voltage of 4.25V;
  • Step 14 Capacity test: Fully charge the battery according to step 2, and then discharge it to 2.8V at a rate of 0.33C. The measured reversible capacity is recorded as C n , and the initial capacity is recorded as C 0 .
  • Step 3 Place the fully charged battery in a 60°C incubator, and take out the battery to test the reversible capacity every 15 days or 30 days.
  • Lithium compensator L and active material LFP or NCM
  • conductive agent acetylene black conductive agent acetylene black
  • binder polyvinylidene fluoride PVDF
  • the secondary batteries of Examples 1 to 6 satisfy: 0.2 ⁇ W Si ⁇ W FEC ⁇ 7.5%-0.6 ⁇ W L , where W FEC is the FEC in the electrolyte solution W Si is the mass ratio of the silicon element in the second negative electrode active material in the negative electrode active material layer, W L is the mass ratio of the lithium compensator in the positive electrode active material layer Compare.
  • the 2-day storage voltage drop (mV/h) self-discharge was kept at a low level, the cycle life was kept at a high level, and a high charge-discharge could be obtained Specific capacity.
  • the secondary batteries satisfying the above relational expressions can achieve good self-discharge characteristics, high cycle life and Higher charge-discharge specific capacity.
  • the lithium compensator Li x Ni a Cu 1-ab M b O 2 can compensate for the lithium consumed by the formation and repair of the solid electrolyte interface film SEI, and since the lithium compensator does not contain Fe, it can avoid iron precipitation. Destroy the SEI film.
  • the fluorinated ethylene carbonate (FEC) contained in the electrolyte can form a dense SEI film, which makes it difficult to rupture the SEI film, so that the cycle can maintain a slow capacity decay rate and obtain a better charge-discharge ratio. capacity.
  • FEC fluorinated ethylene carbonate
  • too much fluoroethylene carbonate (FEC) will worsen gas production, lead to expansion of the pole piece, and lead to the dissolution of metallic copper in the lithium compensator L, which will worsen the self-discharge of the system.
  • the battery self-discharge problem caused by the precipitation of transition metal ions in the lithium compensator in the negative electrode can be reduced.
  • Comparative Example 1 the content of FEC in the electrolyte was too small, which made it difficult to form a dense SEI film on the negative electrode, resulting in a decrease in cycle life and discharge specific capacity.
  • Comparative Example 2 the content of FEC in the electrolyte is too large, which leads to the precipitation of transition metal ions in the lithium compensator at the negative electrode, resulting in an excessive 2-day storage voltage drop, causing self-discharge problems, and low charge-discharge specific capacity. .
  • Examples 7 to 18 are similar to the preparation method of Example 1, but the product parameters of the content of lithium compensator, the content of negative electrode Si and the content of FEC in the electrolyte are adjusted. See Table 3 for different product parameters.
  • the secondary batteries of Examples 7 to 16 satisfy: -2.2% ⁇ W L -W Si ⁇ 2.5 %. And satisfy: W L is 0.1% - 10%; W Si is 0.5wt% - 10wt%.
  • W L and W Si satisfy the above-mentioned relational expressions, better storage life and cycle life can be obtained. This is because the first coulombic efficiency (the ratio of the first discharge capacity to the charge capacity) of the secondary battery with the silicon negative electrode is low, and if the silicon content increases, more lithium compensator is required to supplement the active lithium.
  • the mass proportion of silicon element and lithium compensator is within the above range, the loss of active lithium in the silicon negative electrode can be effectively compensated, so that the cycle and storage can maintain a slow capacity decay rate, thereby improving the cycle life and storage life, and obtaining a better charge. discharge capacity.
  • the specific charge capacity tends to increase.
  • the discharge specific capacities of Examples 14 to 16 only decreased slightly due to the presence of the lithium compensator L in a content satisfying the above relationship.
  • Example 19 The preparation methods of Examples 19 to 24 are similar to those of Example 2, but the product parameters of the specific surface area and D v 50 particle size of the lithium compensator are adjusted. For details of different product parameters, see Table 5.
  • the BET L value is 0.5 m 2 /g to 8 m 2 /g
  • the volume average particle diameter D v 50 L is 1.3 ⁇ m to 16 ⁇ m
  • the positive electrode slurry is 1.3 ⁇ m to 16 ⁇ m. No gel or slight gel occurs, and better cycle life and charge-discharge specific capacity can be obtained. This is because the lithium compensator within the above range is less likely to agglomerate, and the slurry stability is good.
  • the obtained secondary battery can obtain excellent cycle life and charge-discharge specific capacity.
  • the volume average particle diameter D v 50 L of the lithium compensator and the volume average particle diameter D v 50 N of the lithium transition metal oxide satisfy: 0.3 ⁇ D v 50 L /D v 50 N ⁇ 3.6.
  • the particle size ratio is within the above range, the slurry of the positive electrode active material is not easily gelled, has good stability, and the lithium compensator has a high contribution to the charge-discharge capacity, so that excellent cycle life and charge-discharge specific capacity can be obtained.
  • Example 25 The preparation methods of Examples 25 to 30 are similar to those of Example 5, but the product parameters of the specific surface area of the lithium compensation agent and the particle size of D v 50 are adjusted. For details of different product parameters, see Table 7.
  • the volume average particle diameter D v 50 L of the lithium compensator and the volume average particle diameter D v 50 P of the lithium phosphate having an olivine structure satisfy: 1 ⁇ D v 50 L /D v 50 P ⁇ 15.
  • the particle size ratio is within the above range, the slurry of the positive electrode active material is not easily gelled, has good stability, and the lithium compensator has a high contribution to the charge-discharge capacity, so that excellent cycle life and charge-discharge specific capacity can be obtained.

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Abstract

本申请公开了一种二次电池、含有该二次电池的电池模块、电池包和装置。正极包括正极活性物质层，该正极活性物质层含有锂补偿剂，锂补偿剂的分子式为Li xNi aCu 1-a-bM bO 2，其中1≤x≤2，0<a<1，0≤b＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。负极活性物质包括石墨和硅材料。电解液中含有氟代碳酸乙烯酯(FEC)。锂补偿剂、负极硅含量、以及氟代碳酸乙烯酯(FEC)的质量占比满足0.2×W Si≤W FEC≤7.5％-0.6×W L。由此，能够提高循环寿命，并获得较佳的充放电比容量，而且能够降低电池自放电的量。

Description

锂二次电池及含有其的电池模块、电池包和用电装置 技术领域
本申请属于锂二次电池技术领域，涉及一种锂二次电池，特别涉及一种在正极活性物质层中含有锂补偿剂的锂二次电池、以及具备所述锂二次电池的电池模块、电池包和用电装置。
背景技术
锂二次电池具有高能量密度、长循环寿命和无记忆效应等优点被广泛应用于众多消费电子产品中。近年来，随着电动汽车和储能系统的不断发展，对锂二次电池的能量密度的要求也不断在提高。
同时，硅材料由于具有超高的理论比容量，已成为极具潜力的具有高能量密度的锂二次电池的负极材料。但由于纯硅材料的导电性差，且体积膨胀高达300％，故导致在电极表面形成的固体电解质界面膜SEI不断破裂修复，消耗更多的锂，从而使得锂二次电池循环寿命变差。
为了补偿所消耗的锂，对正极补锂是一种有效的应用方法。在正极补锂方面，目前研究较多的补锂剂是Li 5FeO 4，这类富锂材料具有较高的理论比容量，但是在脱锂后生成的其他金属离子(如铁离子)会穿梭到负极进行还原。铁析出容易破坏SEI膜，也会进一步刺穿隔膜造成电池的短路，安全性较低。除此之外，Li 5FeO 4在脱锂后也会释放出氧气，造成电解液的氧化和电池容量的衰减。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种锂二次电池，包括：正极、负极和电解液；其中，
所述正极包括正极活性物质层，所述正极活性物质层含有锂补偿剂，所述锂补偿剂的分子式为Li xNi aCu 1-a-bM bO 2，其中1≤x≤2，0<a<1，0≤b＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种；
所述负极包括负极活性物质层，所述负极活性物质层含有第一负极活性物质以及第二负极活性物质，所述第一负极活性物质为石墨，所述第二负极活 性物质选自Si、SiO n(0<n<2)、SiC中的一种或多种；
所述电解液中含有氟代碳酸乙烯酯(FEC)；
所述锂二次电池满足：0.2×W Si≤W FEC≤7.5％-0.6×W L，其中，W FEC为所述FEC在所述电解液中的质量占比，W Si为所述第二负极活性物质中的硅元素在所述负极活性物质层中的质量占比，W L为所述锂补偿剂在所述正极活性物质层的质量占比。
根据上述的结构，通过锂补偿剂Li xNi aCu 1-a-bM bO 2能够补偿形成和修复固态电解质界面膜SEI所消耗的锂，并且，由于锂补偿剂不含Fe，能够避免铁析出而破坏SEI膜。另外，通过电解液中所含的氟代碳酸乙烯酯(FEC)能够形成致密的SEI膜，使SEI膜难以破裂，从而可以使循环保持较慢的容量衰减率，并获得较佳的充放电比容量。但是，氟代碳酸乙烯酯(FEC)过多，会恶化产气，导致极片膨胀，并且会导致锂补偿剂L中的金属铜溶出，恶化体系自放电。在此，通过控制氟代碳酸乙烯酯(FEC)以及锂补偿剂的含量，能够减少锂补偿剂中过渡金属离子在负极析出而出现的电池自放电问题。根据本发明的锂二次电池，通过将氟代碳酸乙烯酯(FEC)、硅元素、锂补偿剂的质量占比控制在上述范围内，可有效地弥补硅负极活性锂损失，使循环保持较慢的容量衰减率而提高循环寿命，并获得较佳的充放电比容量，而且能够降低电池自放电的量。
在任意实施方式中，所述W L与所述W Si满足条件：-2.2％≤W L-W Si≤2.5％。
由于硅负极的二次电池的首次库伦效率(首次放电容量与充电容量之比)低，如果硅含量增加，则需要更多的锂补偿剂来补充活性锂。通过硅元素、锂补偿剂的质量占比在上述范围内，可有效为硅负极补充活性锂，使循环及存放保持较慢的容量衰减率而提高循环寿命和存储寿命，并获得较佳的充放电比容量。其中，当W L≥W Si-2.2％时，锂补偿剂可以为硅负极二次电池补充足够的活性锂；同时，当W L≤W Si+2.5％时，则负极活性物质脱锂量与锂补偿剂的正极嵌锂空位配比量适中，从而进一步提升电池的放电比容量。
在任意实施方式中，所述W L为0.1％～10％，可选的，所述W L为0.2％～9％，进一步可选的，所述W L为0.3％～8％。锂补偿剂添加量在上述范围内时，可以为正负极成膜和循环过程的锂损耗，补充足够的活性锂，保证负极活性物质与含锂补偿剂的正极嵌锂空位配比量适中，从而进一步提升二次电池的放电比容量。
在任意实施方式中，所述W Si为0.5wt％～10wt％，可选的，所述W Si为 1wt％～8wt％，进一步可选的，所述W Si为1.5wt％～6wt％。
由此，通过硅含量在上述范围内，才能有效通过添加锂补偿剂，来提高循环寿命和存储寿命，并获得较佳的充放电比容量。本申请中，负极极片中Si含量在上述范围内时，一方面可以提升二次电池的能量密度；同时，还可以控制所需锂补偿剂L的用量，改善二次电池的循环、存储寿命及自放电问题。
在任意实施方式中，所述W FEC为0.1wt％～7.5wt％，可选的，所述W FEC为0.5wt％～6wt％，进一步可选的，所述W FEC为1wt％～5wt％。
由此，通过氟代碳酸乙烯酯(FEC)含量在上述范围内，能够提高循环寿命，并降低自放电的量。猜测其原因可能是，当电解液中氟代碳酸乙烯酯(FEC)含量在上述范围内时，能够在负极(尤其硅颗粒)表面形成致密的SEI膜，有效改善硅颗粒与电解液的界面副反应，从而提高二次电池的循环寿命；同时，限制氟代碳酸乙烯酯(FEC)含量上限，还可以降低锂补偿剂中的铜元素的溶出，改善二次电池的自放电率增高的问题。
在任意实施方式中，所述锂补偿剂的比表面积BET L值为0.3m 2/g～10m 2/g，可选的，所述BET L为0.6m 2/g～3.5m 2/g。
由此，通过锂补偿剂的比表面积BET L值在上述范围内，能够避免正极极片制备时发生凝胶等问题，从而避免循环特性和放电容量比的下降。本申请中，锂补偿剂的比表面积BET L在上述范围内时，一方面，锂补偿剂不发生团聚，改善正极浆料容易发生凝胶的问题，提升电池循环寿命以及充放电比容量；同时，还可以提高与正极活性物质的匹配度，提升锂补偿剂的容量发挥，有利于进一步发挥锂补偿剂对充放电容量比的贡献。
在任意实施方式中，所述锂补偿剂的体积平均粒径D v50 L为1μm～20μm，可选的，所述D v50 L为3μm～13μm。
由此，通过锂补偿剂的体积平均粒径D v50 L在上述范围内，能够避免正极极片制备时发生凝胶等问题，从而避免循环特性和放电容量比的下降。本申请中，锂补偿剂的体积平均粒径D v50 L在上述范围内时，锂补偿剂不容易发生凝聚，使正极浆料不容易发生凝胶，提升电池循环寿命降低以及充放电比容量；同时，还可以提高与正极活性物质的匹配度，提升锂补偿剂的容量发挥，有利于进一步发挥锂补偿剂对充放电容量比的贡献。
在任意实施方式中，所述正极还包括正极活性物质，所述正极活性物质包括式(I)～式(III)所示化合物中的至少一种：
Li 1+x1Ni a1Co b1M’ 1-a1-b1O 2-y1A y1       (I)；
Li 1+x2Mn a2M” 2-a2O 4-dA’ d        (II)；
LiFe (1-x3-y3)Mn x3M”’ y3PO 4            (III)；
其中，所述式(I)中，-0.1≤x1≤0.2，0<a1<1，0≤b1≤1，0<a1+b1<1，0≤y1<0.2，M’为Mn、Fe、Cr、Ti、Zn、V、Al、Zr及Ce中的一种或多种，A包括S、N、F、Cl、Br及I中的一种或多种；可选的，0.5≤a1<1，0<b1<0.5，0.7≤a1+b1<1，0≤y<0.1，M为Mn及Al中的一种或两种，A为S或F中的一种或两种；
其中，所述式(II)中，-0.1≤x2≤0.2，0<a2≤2，0≤d<1，M”包括Ni、Fe、Cr、Ti、Zn、V、Al、Mg、Zr及Ce中的一种或多种，A’包括S、N、F、Cl、Br及I中的一种或多种；
其中，所述式(III)中，0≤x3≤1，0≤y3≤0.1，M”’选自除Fe、Mn外的过渡金属元素以及非过渡金属元素中的一种或几种；
可选的，所述正极活性物质至少包括式(I)所示化合物。
由此，上述的锂补偿剂能够与各种正极活性物质配合使用，均能够提高循环寿命和存储寿命，并获得较佳的充放电比容量，而且能够降低电池自放电的量。
在任意实施方式中，所述正极还包括正极活性物质，所述正极活性物质包括具有层状结构的锂过渡金属氧化物，且所述锂补偿剂的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 N满足：0.3≤D v50 L/D v50 N≤3.6，可选的，0.7≤D v50 L/D v50 N≤3。
由此，通过锂补偿剂与具有层状结构的锂过渡金属氧化物的粒径比在上述范围内，正极活性物质的浆料不容易凝胶，稳定性较好，锂补偿剂对充放电容量的贡献也较高。本申请中，当补锂剂与具有层状结构的锂过渡金属氧化物的粒径比在上述范围内时，正极材料不易发生凝胶，有利于提升二次电池循环寿命以及充放电比容量；同时，还可以提高与正极活性物质的匹配度，有利于锂补偿剂的容量发挥，提升锂补偿剂对充放电容量比的贡献。
在任意实施方式中，所述正极还包括正极活性物质，所述正极活性物质包括具有橄榄石结构的锂磷酸盐，且所述锂补偿剂的体积平均粒径D v50 L与所述具有橄榄石结构的锂磷酸盐的体积平均粒径D v50 P满足：1≤D v50 L/D v50 P≤15，可选的，2.5≤D v50 L/D v50 P≤11。
由此，通过锂补偿剂与具有橄榄石结构的锂磷酸盐的粒径比在上述范围内，正极活性物质的浆料不容易凝胶，稳定性较好，锂补偿剂对容量的贡献也较高。
本申请第二方面提供一种电池模块，其包括根据本申请第一方面的二次电池。
本申请第三方面提供一种电池包，其包括根据本申请第二方面的电池模块。
本申请第四方面提供一种用电装置，其包括根据本申请第一方面的二次电池、根据本申请第二方面的电池模块、或根据本申请第三方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的装置的示意图。
附图标记说明：
1电池包
2上箱体
3下箱体
4电池模块
5二次电池
51壳体
52电极组件
53顶盖组件
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合附图对申请的实施例进行详细的描述。然而，本领域的普通技术人员应当理解，这些实施例仅用于阐述本申请的技术方案而非限制。
为了简明，本申请具体地公开了一些数值范围。然而，任意下限可以 与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种及两种以上。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
二次电池
本申请第一方面的实施方式提供一种二次电池。该二次电池包括正极极片、负极极片和电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。
[负极极片]
本申请的负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性物质。
在本申请的二次电池中，所述负极活性物质可以包括，但不限于，石墨和硅基材料。上述石墨可以包括人工石墨、天然石墨或它们的混合物。所述硅基材料可选自单质硅、硅氧化合物(例如氧化亚硅)、硅碳复合物、硅氮复合物、硅合金中的一种或几种。这些材料均可以通过商业途径获得。具体而言，负极活性物质层含可以有第一负极活性物质以及第二负极活性物质，所述第一负极活性物质为石墨，所述第二负极活性物质选自Si、SiO n(0<n<2)、SiC中的一种或多种。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
本申请的二次电池中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料 (铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
本申请的二次电池中，所述负极膜层通常包含负极活性材料以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种以上。
其他可选助剂例如是增稠剂(如羧甲基纤维素钠(CMC-Na))等。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性物质。
所述正极活性物质可以包括式(I)～式(III)所示化合物中的至少一种：
Li 1+x1Ni a1Co b1M’ 1-a1-b1O 2-y1A y1     (I)；
Li 1+x2Mn a2M” 2-a2O 4-dA’ d      (II)；
LiFe (1-x3-y3)Mn x3M”’ y3PO 4        (III)；
其中，所述式(I)中，-0.1≤x1≤0.2，0<a1<1，0≤b1≤1，0<a1+b1<1，0≤y1<0.2，M’为Mn、Fe、Cr、Ti、Zn、V、Al、Zr及Ce中的一种或多种，A包括S、N、F、Cl、Br及I中的一种或多种；可选的，0.5≤a1<1，0<b1<0.5，0.7≤a1+b1<1，0≤y<0.1，M为Mn及Al中的一种或两种，A为S或F中的一种或两种；
其中，所述式(II)中，-0.1≤x2≤0.2，0<a2≤2，0≤d<1，M”包括Ni、Fe、Cr、Ti、Zn、V、Al、Mg、Zr及Ce中的一种或多种，A’包括S、N、F、Cl、Br及I中的一种或多种；
其中，所述式(III)中，0≤x3≤1，0≤y3≤0.1，M”’选自除Fe、Mn外的过渡金属元素以及非过渡金属元素中的一种或几种。
正极极片中还包括锂补偿剂L，所述锂补偿剂L的分子式为Li xNi aCu 1-a- bM bO 2，其中1≤x≤2，0<a<1，0≤b＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的 一种或几种。具体而言，锂补偿剂L可以为以锂、镍、铜为主成分的金属氧化物，还可以少量添加Zn、Sn、Mg、Fe和Mn中的一种或几种。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
本申请的二次电池中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
正极膜层还可选地包括导电剂。但对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极膜层的导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
本申请中可按照本领域已知的方法制备正极极片。作为示例，可以将本申请的正极活性材料、导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮(NMP))中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
[电解质]
在本申请的二次电池中，对电解质的种类没有具体的限制，可根据需求进行选择。所述电解质可以选自固态电解质、液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。所述电解液包括电解质锂盐和溶剂。
可选的，锂盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
溶剂中含有氟代碳酸乙烯酯(FEC)，氟代碳酸乙烯酯(FEC)可以加强负极成膜，形成致密的固体电解质界面膜(SEI膜)。
可选的，溶剂还可以包含碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[正极锂补偿剂、电解液、与负极硅含量之间的关系]
在一些实施方式中，锂二次电池满足：0.2×W Si≤W FEC≤7.5％-0.6×W L，其中，W FEC为所述FEC在所述电解液中的质量占比，W Si为所述第二负极活性物质中的硅元素在所述负极活性物质层中的质量占比，W L为所述锂补偿剂L在所述正极活性物质层的质量占比。
根据上述的锂离子二次电池，通过锂补偿剂Li xNi aCu 1-a-bM bO 2能够补偿形成和修复固态电解质界面膜SEI所消耗的锂，并且，由于锂补偿剂不含Fe，能够避免铁析出而破坏SEI膜。另外，通过电解液中所含的氟代碳酸乙烯酯(FEC)能够形成致密的SEI膜，使SEI膜难以破裂，从而可以使循环保持较慢的容量衰减率，并获得较佳的充放电比容量。但是，氟代碳酸乙烯酯(FEC)过多，会恶化产气，并且会导致锂补偿剂L中的金属铜溶出，恶化体系自放电。通过控制氟代碳酸乙烯酯(FEC)以及锂补偿剂的含量，能够减少锂补偿剂中过渡金属离子在负极析出而出现的电池自放电问题。根据上述的锂二次电池，通过氟代碳酸乙烯酯(FEC)、硅元素、锂补偿剂的质量占比在上述范围内，可有效弥补硅负极活性锂损失，使循环保持较慢的容量衰减率而提高循环寿命，并获得较佳的充放电比容量，而且能够降低电池自放电的量。如果氟代碳酸乙烯酯(FEC)小于0.2×W Si，则负极成膜不足，不能改善循环寿命。如果氟代碳酸乙烯酯(FEC)大于7.5％-0.6×W L，则锂补偿剂L中过渡金属离子在负极过度地析出，从而产生电池自放电的问题。
本申请中，所述FEC在所述电解液中的质量占比W FEC可以采用本领域公知的测试方法进行测定。具体可参考GB/T 9722-2006化学试剂气相色谱法 通则进行测试。作为示例的，可以采用气相色谱仪Agilgent 7890B对待注入电解液、或者成品电芯经离心分离得到的电解液进行测定。
本申请中，所述第二负极活性物质中的硅元素在所述负极活性物质层中的质量占比W Si可以采用本领域公知的测试方法进行测定。作为示例的，可以采用如下方法进行测试：选用美国Thermo Fisher Scientific公司型号为ICAP7400的等离子体发射光谱仪，用ICP方法进行测量。测试样品可以是涂布且经冷压后的负极极片、或者是从电芯中拆解得到的负极极片(将电芯在25℃下静置30分钟；以0.33C恒流放电至电芯放电终止电压，之后静置30分钟进行满放，然后拆解电芯，取出负极极片，用DMC溶液进行适当冲洗，烘干待用)。
本申请中，所述锂补偿剂L在所述正极活性物质层的质量占比W L可以采用本领域公知的测试方法进行测定。作为示例的，可以采用如下方法进行测试：对于锂补偿剂L和磷酸铁锂等不含Ni和Cu元素的正极活性物质的混合极片，可以采用ICP(如，美国Thermo Fisher Scientific公司型号为ICAP7400的等离子体发射光谱仪)测试，获得Ni/Cu比值及锂补偿剂L的质量占比。对于锂补偿剂L和镍钴锰酸锂等含Ni元素的正极活性物质的混合极片，可以采用ICP(美国Thermo Fisher Scientific公司型号为ICAP7400的等离子体发射光谱仪)，先测试获得正极极片中Ni、Co、Mn、Cu等多种元素的质量占比，再结合EDS(OXFORD EDS X-max-50mm 2)对正极极片表面或断面进行Mapping测试，找到富铜区域(对应锂补偿剂L)后缩小范围，测试该富铜区域的Ni/Cu比值，即为锂补偿剂L的Ni/Cu比值，再根据ICP测试各元素质量占比得出L材料的质量占比。
在一些实施方式中，W L与W Si满足条件：-2.2％≤W L-W Si≤2.5％。
由于硅负极的二次电池的首次库伦效率(首次放电容量与充电容量之比)低，硅含量增加，需要更多的锂补偿剂L来补充活性锂。通过硅元素、锂补偿剂L的质量占比在上述范围内，可有效弥补硅负极活性锂损失，使循环及存放保持较慢的容量衰减率而提高循环寿命和存储寿命，并获得较佳的充放电比容量。其中，当W L≥W Si-2.2％时，锂补偿剂可以为硅负极二次电池补充足够的活性锂；同时，当W L≤W Si+2.5％时，则负极活性物质与含锂补偿剂的正极嵌锂空位配比量适中，从而进一步提升电池的放电比容量较高。
在一些实施方式中，W L为0.1％～10％，可选的，所述W L为0.2％～9％，进一步可选的，所述W L为0.3％～8％。锂补偿剂添加量在上述范围内时，可以 为正负极成膜提供足够的活性锂，同时保证负极活性物质与含锂补偿剂的正极嵌锂空位配比量适中，从而进一步提升二次电池的放电比容量降低。
在一些实施方式中，W Si为0.5wt％～10wt％，可选的，所述W Si为1wt％～8wt％，进一步可选的，所述W Si为1.5wt％～6wt％。通过硅含量在上述范围内，能够提高循环寿命和存储寿命，并获得较佳的充放电比容量。本申请中，负极极片中Si含量在上述范围内时，一方面可以提升二次电池的能量密度、循环及存储寿命，同时，可以控制所需锂补偿剂L的用量，改善二次电池的自放电问题。
在一些实施方式中，W FEC为0.1wt％～7.5wt％，可选的，所述W FEC为0.5wt％～6wt％，进一步可选的，所述W FEC为1wt％～5wt％。通过氟代碳酸乙烯酯(FEC)含量在上述范围内，能够提高循环寿命，并降低自放电的量。猜测其原因可能是，当电解液中氟代碳酸乙烯酯(FEC)含量在上述范围内时，能够在负极(尤其硅颗粒)表面形成致密的SEI膜，有效改善硅颗粒与电解液的界面副反应，从而提高二次电池的循环寿命；同时，还可以降低锂补偿剂中的铜元素的溶出，改善二次电池的自放电率增高的问题。
[锂补偿剂L]
在一些实施方式中，锂补偿剂L的比表面积BET L值为0.3m 2/g～10m 2/g，可选的，所述BET L为0.6m 2/g～3.5m 2/g。
锂补偿剂L含有较多的锂，碱性强、活性高、颗粒较大且对水敏感，正极极片制备时容易发生凝胶等问题，造成正极浆料稳定性变差，大大降低优率。通过锂补偿剂的比表面积BET L值在上述范围内，能够较少凝胶，进一步提升循环寿命，获得较佳的充放电比容量。
本申请中，所述锂补偿剂L的比表面积可以采用本领域公知的测试方法进行测定。具体测试方法及步骤可参考标准：GB/T 19587-2004《气体吸附BET法测定固态物质比表面积》。作为示例的，可使用仪器型号为NOVA 2000e，采用如下流程进行测试：(1)取一定量的样品(如，2.0-15.0g)；(2)将样品放入样品管，放入加热包中，进行脱气处理(脱气条件为200℃，2小时)；(3)脱气完成后，等脱气站温度降到常温时，将样品管从脱气站卸下，称量计算样品总质量；(4)将样品管放入测试填充棒，进行样品的比表面积测试。
在一些实施方式中，所述锂补偿剂的体积平均粒径D v50 L为1μm～20μm，可选的，所述D v50 L为3μm～13μm。通过锂补偿剂的体积平均粒径在上述范围内，能够较少凝胶，保证循环寿命，获得较佳的充放电比容量。
本申请中，所述锂补偿剂L的体积平均粒径D v50 L可以采用本领域公知的测试方法进行测定。作为示例的，可以采用如下方法进行测试：参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)进行测量。对于已混入所述锂补偿剂L的正极极片，也可以采用扫描电子显微镜(SEM，ZEISS SEM Sigma 300)和离子抛光断面形貌分析(CP)，选取多个区域(例如，20个区域以上)，分别测量所述锂补偿剂L的可视最大粒径，求得平均值后以此表征所述锂补偿剂L的体积平均粒径D v50 L。
在一些实施方式中，正极活性物质包括具有层状结构的锂过渡金属氧化物，且所述锂补偿剂的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 N满足：0.3≤D v50 L/D v50 N≤3.6，可选的，0.7≤D v50 L/D v50 N≤3。通过锂补偿剂的体积平均粒径与所述锂过渡金属氧化物的体积平均粒径之比在上述范围内，能够较少凝胶，保证循环寿命，获得较佳的充放电比容量。本申请中，当补锂剂与具有层状结构的锂过渡金属氧化物的粒径比在上述范围内时，正极材料不易发生凝胶，有利于提升二次电池循环寿命以及充放电比容量；同时，还可以提高与正极活性物质的匹配度，有利于锂补偿剂的容量发挥，提升锂补偿剂对充放电容量比的贡献。
本申请中，所述锂补偿剂L的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 N的粒径比D v50 L/D v50 N可以采用本领域公知的测试方法进行测定。作为示例的，可以采用如下方法进行测试：对于粉料层级，可以分别参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)分别测定锂补偿剂L和正极活性物质的D v50，再求得粒径比。对于已混入所述锂补偿剂L的正极极片，也可以采用扫描电子显微镜(SEM，ZEISS SEM Sigma 300)和离子抛光断面形貌分析(CP)，选取多个区域(例如，20个区域以上)，分别测量所述锂补偿剂L和正极活性物质的可视最大粒径，各自求得平均值后，再求粒径比以此表征所述锂补偿剂L的体积平均粒径D v50 L与所述正极活性物质的体积平均粒径D v50 N的粒径比D v50 L/D v50 N。
在一些实施方式中，正极活性物质包括具有橄榄石结构的锂磷酸盐，且所述锂补偿剂的体积平均粒径D v50 L与所述具有橄榄石结构的锂磷酸盐的体积平均粒径D v50 P满足：1≤D v50 L/D v50 P≤15。可选的， 2.5≤D v50 L/D v50 P≤11。通过锂补偿剂的体积平均粒径在上述范围内，能够较少凝胶，保证循环寿命，获得较佳的充放电比容量。
本申请中，所述锂补偿剂L的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 P的粒径比D v50 L/D v50 P可以参照上述D v50 L/D v50 P的测试方法进行测定。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请的二次电池对隔离膜的种类没有特别的限制，可以选用任意公知的用于二次电池的多孔结构隔离膜。例如，隔离膜可选自玻璃纤维薄膜、无纺布薄膜、聚乙烯薄膜、聚丙烯薄膜、聚偏二氟乙烯薄膜、以及包含它们中的一种或两种以上的多层复合薄膜中的一种或几种。
在一些实施方式中，二次电池可包括外包装。外包装用于封装正极极片、负极极片和电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
可以采用本领域公知的方法制备二次电池。例如，将正极极片、隔离膜及负极极片经卷绕工艺或叠片工艺形成电极组件，其中隔离膜处于正极极片与负极极片之间起到隔离的作用；将电极组件置于外包装中，注入电解液并封口，得到二次电池。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在一些实施例中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
本申请的另一方面提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池可以用作所述用电装置的电源，也可以作为所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。本发明实施例中各成分的含量，如果没有特别说明，均以质量计。
实施例1：
负极极片的制备
将石墨、氧化亚硅(硅元素在负极活性物质层中的质量占比为3％)、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按质量比为94:3:2:1在去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔的表面上，经干燥、冷压、分条、裁切，得到负极极片。
正极极片的制备
将正极活性材料锂镍钴锰氧化物LiNi 0.8Co 0.1Mn 0.1O 2(NCM811，平均粒径D v50为4.3μm)、补锂添加剂LiNi 0.4Cu 0.55Mg 0.05O 2(锂补偿剂在正极活性物质层的质量占比为3％，比表面积为0.99m 2/g，平均粒径D v50为8μm)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比93.5:3:2:1.5混合在溶剂NMP中充分搅拌混合，使其形成均匀的正极浆料；将正极浆料涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。
电解液的制备
将碳酸乙烯酯(EC)和碳酸二乙酯(DEC)以50:50的质量比混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1.1mol/L。在电解液中加入质量占比为0.6％的氟代碳酸乙烯酯(FEC)添加剂。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入配好的电解液并封装。
(实施例2～6和对比例1～4)
实施例2～6和对比例1～4与实施例1的制备方法相似，但是调整了正极活性物质(实施例3～5、对比例3～4中为磷酸铁锂，平均粒径D v50为1.2μm)、锂补偿剂的含量、负极Si含量和电解液中FEC含量的产品参数， 不同的产品参数详见表1。
测试部分
1.粉体材料体积平均粒径Dv50的测量：
参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)进行测量。
2.粉体材料比表面积的测量：
参考标准：GB/T 19587-2004《气体吸附BET法测定固态物质比表面积》。使用仪器型号为NOVA 2000e，采用如下流程进行测试：(1)取一定量的样品(如，2.0-15.0g)；(2)将样品放入样品管，放入加热包中，进行脱气处理(脱气条件为200℃，2小时)；(3)脱气完成后，等脱气站温度降到常温时，将样品管从脱气站卸下，称量计算样品总质量；(4)将样品管放入测试填充棒，进行样品的比表面积测试。
3.充放电比容量测试：
电池组装完成后，在常温下以0.05C、0.1C、0.33C梯度增加的倍率充电至4.25V，再以4.25V恒压充电至0.05C倍率，记录电池的首次充电容量；然后再以0.33C倍率恒流放电至2.8V，记录电池的放电容量。
实施例表中电池的充放电比容量根据下述公式计算所得：
Figure PCTCN2020139182-appb-000001
4. 2天存储电压降测试：
电池在常温下以0.33C倍率恒流充电至3.85V，再以3.85V恒压充电至0.05C倍率，然后在常温下静置2天，测试两天后电池的开路电压V2。
根据下述公式计算电池每小时的电压降：
Figure PCTCN2020139182-appb-000002
5.循环寿命测试：
电池在常温下以0.33C倍率恒流充电至4.25V，再以4.25V恒压充电至0.05C倍率，然后以0.33C倍率恒流放电至2.8V，以此为一次循环。重复以上循环测试，直至放电容量衰减为初始容量的80％时停止测试，得到循环次数。
6.存储寿命测试：
存储寿命测试流程：①初始容量测试→②满充→③60℃存储→④容量测试→⑤重复第3、4步直至可逆容量衰减为初始容量的80％，即为存储寿命天数。
步骤②(满充)：电池在常温下以0.33C倍率恒流充电至4.25V，再以4.25V恒压充电至0.05C倍率；
步骤①④(容量测试)：将电池按步骤②满充，然后以0.33C倍率放电至2.8V，测得可逆容量记为C n，初始容量记为C 0。
步骤③(60℃存储)：将满充状态的电池放置于60℃恒温箱中，每隔15天或30天，将电池取出测试可逆容量。
根据下述公式计算电池在60℃下存储后的容量保持率：
Figure PCTCN2020139182-appb-000003
7.浆料凝胶测试：
将不同D v50 L的锂补偿剂L和活性物质(LFP或NCM)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)，按适当的重量比在N-甲基吡咯烷酮溶剂(NMP)体系中充分搅拌混合均匀后，用保鲜膜密封好，静置一天，然后观察浆料是否凝胶。
对实施例1～6、比较例1～4进行上述测试，将评价结果综合示于表2中。
Figure PCTCN2020139182-appb-000004
从表1、2可知，实施例1～6的二次电池中，满足：0.2×W Si≤W FEC≤7.5％-0.6×W L，其中，W FEC为所述FEC在所述电解液中的质量占比，W Si为所述第二负极活性物质中的硅元素在所述负极活性物质层中的质量占比，W L为所述锂补偿剂在所述正极活性物质层的质量占比。在实施例1～6的二次电池中，2天存储电压降(mV/h)(自放电)保持在较低的水平，循环寿命保持在较高的水平，并且能够获得较高的充放电比容量。并且，通过实施例1～6的可知，无论正极活性物质是锂镍钴锰氧化物还是磷酸铁锂，满足上述关系式的二次电池均能够取得良好的自放电特性、较高的循环寿命以及较高的充放电比容量。这是由于，通过锂补偿剂Li xNi aCu 1-a-bM bO 2能够补偿形成和修复固态电解质界面膜SEI所消耗的锂，并且，由于锂补偿剂不含Fe，能够避免铁析出而破坏SEI膜。另外，通过电解液中所含的氟代碳酸乙烯酯(FEC)能够形成致密的SEI膜，使SEI膜难以破裂，从而可以使循环保持较慢的容量衰减率，并获得较佳的充放电比容量。但是，氟代碳酸乙烯酯(FEC)过多，会恶化产气，导致极片膨胀，并且会导致锂补偿剂L中的金属铜溶出，恶化体系自放电。通过控制氟代碳酸乙烯酯(FEC)以及锂补偿剂的含量，能够减少锂补偿剂中过渡金属离子在负极析出而出现的电池自放电问题。
相对于此，对比例1中，FEC在电解液中的含量过少，难以在负极形成致密的SEI膜，导致循环寿命和放电比容量降低。在对比例2中，FEC在电解液中的含量过多，导致锂补偿剂中过渡金属离子在负极析出，导致2天存储电压降过大，产生自放电问题，并且充放电比容量也较低。在正极活性物质采用磷酸锂铁的对比例3、4中，也产生相同的问题。
(实施例7～18)
实施例7～18与实施例1的制备方法相似，但是调整了锂补偿剂的含量、负极Si含量和电解液中FEC含量的产品参数，不同的产品参数详见表3。
对实施例7～18进行上述测试，将评价结果综合示于表4中。
Figure PCTCN2020139182-appb-000005
从表3、4可知，实施例7～16的二次电池中，满足：-2.2％≤W L-W Si≤2.5％。并且满足：W L为0.1％～10％；W Si为0.5wt％～10wt％。通过使W L、W Si满足上述关系式，能够得到较佳的存储寿命和循环寿命。这是由于，硅负极的二次电池的首次库伦效率(首次放电容量与充电容量之比)低，如果硅含量增加，则需要更多的锂补偿剂来补充活性锂。通过硅元素、锂补偿剂的质量占比在上述范围内，可有效弥补硅负极活性锂损失，使循环及存放保持较慢的容量衰减率而提高循环寿命和存储寿命，并获得较佳的充放电比容量。此外，随着锂补偿剂L的含量增加，充电比容量有增加的倾向。另外，随着Si含量的增加，由于存在满足上述关系的含量的锂补偿剂L，实施例14～16的放电比容量仅有小幅下降。
(实施例19～24)
实施例19～24与实施例2的制备方法相似，但是调整了锂补偿剂的比表面积、D v50粒径的产品参数，不同的产品参数详见表5。
对实施例19～24进行上述测试，将评价结果综合示于表6中。
Figure PCTCN2020139182-appb-000006
从表5、6可知，实施例19～22的二次电池中，BET L值为0.5m 2/g～8m 2/g，体积平均粒径D v50 L为1.3μm～16μm，正极浆料不凝胶或发生轻微凝胶，并且能够得到较佳的循环寿命和充放电比容量。这是由于，上述范围内的锂补偿剂不容易发生团聚，浆料稳定性佳。所得到的二次电池能够获得优异的循环寿命以及充放电比容量。此外，实施例19～22的二次电池中，锂补偿剂的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 N满足：0.3≤D v50 L/D v50 N≤3.6。通过粒径比在上述范围内，正极活性物质的浆料不容易凝胶，稳定性较好，锂补偿剂对充放电容量的贡献也较高，能够获得优异的循环寿命以及充放电比容量。
(实施例25～30)
实施例25～30与实施例5的制备方法相似，但是调整了锂补偿剂的比表面积、D v50粒径的产品参数，不同的产品参数详见表7。
对实施例25～30进行上述测试，将评价结果综合示于表8中。
Figure PCTCN2020139182-appb-000007
从表7、8可知，实施例25～28的二次电池中，锂补偿剂的体积平均粒径D v50 L与具有橄榄石结构的锂磷酸盐的体积平均粒径D v50 P满足：1≤D v50 L/D v50 P≤15。通过粒径比在上述范围内，正极活性物质的浆料不容易凝胶，稳定性较好，锂补偿剂对充放电容量的贡献也较高，能够获得优异的循环寿命以及充放电比容量。
本领域普通技术人员应当理解，上述各实施例仅是实现本发明的部分具体实施例，而在实际应用中，可以在形式上和细节上对其作各种改变和修改，均落入本申请的保护范围内。

Claims (13)

  1. 一种锂二次电池，包括：正极、负极和电解液；其中，
    所述正极包括正极活性物质层，所述正极活性物质层含有锂补偿剂，所述锂补偿剂的分子式为Li xNi aCu 1-a-bM bO 2，其中1≤x≤2，0<a<1，0≤b＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种；
    所述负极包括负极活性物质层，所述负极活性物质层含有第一负极活性物质以及第二负极活性物质，所述第一负极活性物质为石墨，所述第二负极活性物质选自Si、SiO n(0<n<2)、SiC中的一种或多种；
    所述电解液中含有氟代碳酸乙烯酯(FEC)；
    所述锂二次电池满足：0.2×W Si≤W FEC≤7.5％-0.6×W L，其中，W FEC为所述FEC在所述电解液中的质量占比，W Si为所述第二负极活性物质中的硅元素在所述负极活性物质层中的质量占比，W L为所述锂补偿剂在所述正极活性物质层的质量占比。
  2. 根据权利要求1所述的锂二次电池，其中，所述W L与所述W Si满足条件：-2.2％≤W L-W Si≤2.5％。
  3. 根据权利要求1所述的锂二次电池，其中，所述W L为0.1％～10％，可选的，所述W L为0.2％～9％，进一步可选的，所述W L为0.3％～8％。
  4. 根据权利要求1～3中任一项所述的锂二次电池，其中，所述W Si为0.5wt％～10wt％，可选的，所述W Si为1wt％～8wt％，进一步可选的，所述W Si为1.5wt％～6wt％。
  5. 根据权利要求1～4中任一项所述的锂二次电池，其中，所述W FEC为0.1wt％～7.5wt％，可选的，所述W FEC为0.5wt％～6wt％，进一步可选的，所述W FEC为1wt％～5wt％。
  6. 根据权利要求1～5中任一项所述的锂二次电池，其中，所述锂补偿剂的比表面积BET L值为0.3m 2/g～10m 2/g，可选的，所述BET L为0.5m 2/g～8m 2/g，进一步可选的，所述BET L为0.6m 2/g～3.5m 2/g。
  7. 根据权利要求1～6中任一项的锂二次电池，其中，所述锂补偿剂的体积平均粒径D v50 L为1μm～20μm，可选的，所述D v50 L为1.3μm～16μm，进一步可选的，所述D v50 L为3μm～13μm。
  8. 根据权利要求1～7中任一项所述的锂二次电池，其中，所述正极还 包括正极活性物质，所述正极活性物质包括式(I)～式(III)所示化合物中的至少一种：
    Li 1+x1Ni a1Co b1M’ 1-a1-b1O 2-y1A y1    (I)；
    Li 1+x2Mn a2M” 2-a2O 4-dA’ d     (II)；
    LiFe (1-x3-y3)Mn x3M”’ y3PO 4     (III)；
    其中，所述式(I)中，-0.1≤x1≤0.2，0<a1<1，0≤b1≤1，0<a1+b1<1，0≤y1<0.2，M’为Mn、Fe、Cr、Ti、Zn、V、Al、Zr及Ce中的一种或多种，A包括S、N、F、Cl、Br及I中的一种或多种；可选的，0.5≤a1<1，0<b1<0.5，0.7≤a1+b1<1，0≤y<0.1，M为Mn及Al中的一种或两种，A为S或F中的一种或两种；
    其中，所述式(II)中，-0.1≤x2≤0.2，0<a2≤2，0≤d<1，M”包括Ni、Fe、Cr、Ti、Zn、V、Al、Mg、Zr及Ce中的一种或多种，A’包括S、N、F、Cl、Br及I中的一种或多种；
    其中，所述式(III)中，0≤x3≤1，0≤y3≤0.1，M”’选自除Fe、Mn外的过渡金属元素以及非过渡金属元素中的一种或几种；
    可选的，所述正极活性物质至少包括式(I)所示化合物。
  9. 根据权利要求1～8中任一项所述的锂二次电池，其中，所述正极还包括正极活性物质，所述正极活性物质包括具有层状结构的锂过渡金属氧化物，且所述锂补偿剂的体积平均粒径D v50 L与所述锂过渡金属氧化物的体积平均粒径D v50 N满足：0.3≤D v50 L/D v50 N≤3.6，可选的，0.7≤D v50 L/D v50 N≤3。
  10. 根据权利要求1～9中任一项所述的锂二次电池，其中，所述正极还包括正极活性物质，所述正极活性物质包括具有橄榄石结构的锂磷酸盐，且所述锂补偿剂的体积平均粒径D v50 L与所述具有橄榄石结构的锂磷酸盐的体积平均粒径D v50 P满足：1≤D v50 L/D v50 P≤15，可选的，2.5≤D v50 L/D v50 P≤11。
  11. 一种电池模块，包括如权利要求1-10任一项所述的锂二次电池。
  12. 一种电池包，包括如权利要求1-10任一项所述的锂二次电池，或者如权利要求11所述的电池模块。
  13. 一种用电装置，包括如权利要求1-10任一项所述的锂二次电池，或者如权利要求11所述的电池模块，或者如权利要求12所述的电池包； 其中，所述锂二次电池、所述电池模块，或者所述电池包用作所述用电装置的电源。
PCT/CN2020/139182 2020-12-24 2020-12-24 锂二次电池及含有其的电池模块、电池包和用电装置 WO2022133961A1 (zh)

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