WO2020207368A1 - 一种补锂层及其负极极片和锂离子电池及装置 - Google Patents

一种补锂层及其负极极片和锂离子电池及装置 Download PDF

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WO2020207368A1
WO2020207368A1 PCT/CN2020/083448 CN2020083448W WO2020207368A1 WO 2020207368 A1 WO2020207368 A1 WO 2020207368A1 CN 2020083448 W CN2020083448 W CN 2020083448W WO 2020207368 A1 WO2020207368 A1 WO 2020207368A1
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lithium
layer
pole piece
battery
surface layer
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PCT/CN2020/083448
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English (en)
French (fr)
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陈仕通
谢斌
龚志杰
胡招
马林
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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 US17/057,290 priority Critical patent/US11777085B2/en
Priority to EP20788415.6A priority patent/EP3787094A4/en
Publication of WO2020207368A1 publication Critical patent/WO2020207368A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/26—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/249—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders specially adapted for aircraft or vehicles, e.g. cars or trains
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

  • This application belongs to the technical field of lithium ion batteries, and more specifically relates to a negative electrode lithium supplement layer and its negative electrode pole piece, lithium ion battery and device.
  • Lithium-ion batteries are widely used in the field of portable power supplies due to their high energy density and long cycle life.
  • the development of higher energy density lithium-ion batteries is a major issue that needs to be solved urgently.
  • the solid electrolyte membrane layer (SEI) formed on the surface of the negative electrode consumes a large amount of lithium source and converts lithium into inactive lithium-containing compounds such as lithium carbonate, lithium fluoride, and lithium alkyl.
  • the loss of recyclable lithium reduces the coulombic efficiency and battery capacity in the first lap of the battery.
  • the first coulombic efficiency is about 90%.
  • high-volume anode materials such as alloys (silicon, tin, aluminum), oxides (silicon oxide, tin oxide, titanium oxide) and amorphous carbon anodes are used, the consumption of lithium sources is further increased.
  • the purpose of this application is to provide a lithium-ion battery pole piece replenishment layer and its negative pole piece and lithium ion battery and device.
  • the lithium replenishment layer needs to both improve the replenishment of the lithium ion battery.
  • the heating problem of the lithium pole piece and the formation of a protective layer on the surface of the SEI film of the active material layer of the pole piece can prevent the SEI film of the active material layer from rupturing and improve the performance of the lithium ion battery.
  • the inventor provides a lithium-supplementing layer, including a transition layer, an oxide layer, and a surface layer that are connected in sequence, wherein the surface layer is a layered covering or dotted Covering, and the surface layer includes organic materials and fillers.
  • the inventor provides a lithium-supplemented negative pole piece, including: a current collector; a diaphragm, located on the current collector and including an active material, a binder, and a conductive agent; and the present application
  • the lithium supplement layer of the first aspect wherein the transition layer in the lithium supplement layer is connected to the diaphragm.
  • the inventor provides a lithium-ion battery supplemented with lithium, including: the negative pole piece, the positive pole piece, the electrolyte and the separator described in the second aspect of the present application.
  • the inventor provides a device including the lithium ion battery of the third aspect of the present application.
  • the lithium-supplementing layer of the present application is formed by connecting a transition layer, an oxide layer and a surface layer in sequence.
  • the surface layer contains an appropriate amount of organic materials and fillers, which can reduce the winding temperature of the negative pole piece and supplement the oxide layer in the lithium layer.
  • the material is used to provide an additional lithium source. After the injection, it can continue to replenish the lithium source during the cycle and improve the activity of the lithium layer.
  • the filling material contained in the surface layer can effectively restrain the expansion of the active material and improve Battery cycle performance
  • the material components in the transition layer can be used as an inorganic SEI film to inhibit the consumption of lithium source caused by the expansion of active materials.
  • FIG. 1 is a schematic diagram of a pole piece covered with a lithium supplementary layer in a specific embodiment
  • FIG. 2 is a schematic diagram of a pole piece covered with a lithium supplementary layer in a dot shape according to the specific embodiment
  • FIG. 3 is a SEM scanning electron micrograph of a cross-section of a pole piece with lithium supplementation after formation of a lithium ion battery cell containing the lithium supplement layer according to the specific embodiment
  • FIG. 4 is a schematic diagram of an embodiment of a lithium ion battery
  • Fig. 5 is a schematic diagram of an embodiment of a battery module
  • Fig. 6 is a schematic diagram of an embodiment of a battery pack
  • Figure 7 is an exploded view of Figure 6;
  • FIG. 8 is a schematic diagram of an embodiment of a device in which a lithium ion battery is used as a power source
  • the reference signs are described as follows: 1-battery pack, 2-upper box, 3-lower box, 4-battery module, 5-lithium ion battery.
  • the following describes in detail the lithium-supplementing layer, the lithium-supplemented negative pole piece, the lithium ion battery and the device of the present application.
  • the lithium supplement layer of the first aspect of the present application including a transition layer, an oxide layer, and a surface layer that are connected in sequence, wherein the surface layer is layered or dotted, and the surface layer includes organic materials and Filling material.
  • “connected” here can be understood as overlapping in the thickness direction.
  • the transition layer in the lithium-supplementing layer is a side reaction between the active material and the lithium-supplementing layer, which can be regarded as an additional inorganic SEI film produced in the lithium-supplement pole piece, which can affect the SEI film formed by the active material itself.
  • the protective effect can effectively suppress the problem of consuming lithium ions in the electrolyte due to expansion and fragmentation during the circulation of the active material.
  • the oxide layer is mainly composed of lithium metal and its oxides, nitrides and hydroxides.
  • the oxide layer is used to provide an additional lithium source. After injection, the lithium source can be continuously supplemented during the cycle to improve the cycle performance of the battery.
  • the layer material can also provide a part of the material to form the transition layer, that is, an additional layer of inorganic SEI film is formed to improve battery cycle performance, and the oxide layer material can form a dense or loose isolation layer on the surface of the pole piece to further improve the lithium supplement pole piece Because the lithium foil reacts with the air/active material, it causes the problem of heating up the pole piece winding.
  • the organic materials in the surface layer mainly use alcohols, esters and fatty acids, and their main functions are: as a carrier of the filling material, form a slurry and coat it on the surface of the lithium foil as the surface layer of the lithium supplement layer
  • the film-forming substance enables the surface layer to be formed into a film or evenly distributed on the surface of the transition layer and the oxide layer of the lithium supplement layer.
  • the filling material in the lithium replenishing layer can be used to improve the internal resistance of the cell caused by the side reaction of the organic material and the electrolyte.
  • the filling material can form a network structure or a film structure with the organic material, which can prevent the active material from circulating The problem of pole piece expansion in the process.
  • the distribution form of the surface layer on the oxide layer can be uniform layered coverage or dotted coverage.
  • the organic material is selected from stearic acid, 12-hydroxystearic acid, fatty acid metal salt, polyglycol, polyhydrocarbon cyclopentane, polyisobutyl methacrylate, phosphate, paraffin, polyurea, A mixture of one or more of poly-a-olefin, alkylnaphthalene, and polydimethylsiloxane, and the filler is selected from graphite, graphene, aluminum oxide, sodium hydroxide, and lithium hydroxide , Calcium hydroxide and molybdenum disulfide one or more of the composition of the mixture.
  • the transition layer is selected from Li oxide or lithium embedded compound, for example, a mixture of one or more selected from Li 2 O, Li x C and Li x1 Si y , where 0 ⁇ x ⁇ 2, 0 ⁇ x1 ⁇ 4.4, 0 ⁇ y ⁇ 2.
  • the lithium embedded silicide is selected, it can generally be Li x1 Si, and x1 can be 4.4, 3.75, 3.25, 2.33, etc.
  • the oxide layer is selected from a mixture of one or more of Li metal, Li 2 O, LiF, LiOH, Li 3 N, and Li 2 CO 3 .
  • the content of the organic material and the filling material in the surface layer of the lithium supplement layer and the ratio of the two have a certain influence on the performance of the pole piece and its lithium ion battery.
  • the proportion of organic materials in the surface layer is high, although it helps to form an isolation layer on the surface of the lithium supplement layer, thereby reducing the winding temperature of the lithium supplement pole piece and increasing the activity of the lithium supplement layer, an excessively high proportion of organic materials may cause: a The isolation layer formed by the lithium supplementary layer is too dense, which affects the lithium ion transmission efficiency, increases the internal resistance of the battery, and affects the battery performance; b.
  • the lithium supplementary layer contains alcohols and other substances. If the ratio of organic materials is too high, it will easily be mixed with the electrolyte. The reaction forms by-products, which affects battery performance; c. There are too few filling materials to restrain the expansion of active materials during the cycle, thereby affecting battery performance.
  • the content of the organic material is 10%-97%, preferably 20%-80%; the content of the filler material is 3%-90%, preferably 20%. %-80%.
  • the thickness of the surface layer is too small.
  • the thickness of the surface layer is 0 ⁇ m-0.1 ⁇ m, although it can also have a certain isolation effect.
  • this kind of surface layer cannot form an effective isolation layer on the surface of the lithium replenishment layer, resulting in an increase in the reaction area of the lithium layer with air and a faster reaction.
  • the temperature in the winding process of the replenishment pole piece exceeds the standard, causing production safety risks. At the same time, too high temperature of the pole piece will reduce the activity of the lithium layer.
  • the thickness of the surface layer is too thick, such as the thickness of the surface layer is greater than 15 ⁇ m, although the thick surface layer can form a good isolation layer from the air on the surface of the lithium supplement layer, the winding temperature of the lithium supplement pole piece is effectively reduced, but the surface If the layer is too thick, it will directly affect the transmission efficiency of lithium ions. The internal resistance of the resulting cell will increase, and its cycle performance will also decrease.
  • the surface layer of the lithium supplementation layer When the thickness of the surface layer of the lithium supplementation layer is in the range of 0.1 ⁇ m-15 ⁇ m, the surface layer can form an isolation layer between the lithium supplementation layer and the air, and will not significantly affect the transmission efficiency of lithium ions, because the lithium supplement pole piece is wound.
  • the temperature is controllable, and the activity of the lithium replenishment layer can be guaranteed to provide capacity and improve the performance of lithium-ion batteries.
  • the thickness of the surface layer is 0.1 ⁇ m-15 ⁇ m, preferably 1 ⁇ m-8 ⁇ m.
  • the transition layer is too thin, that is, the inorganic SEI film formed on the lithium supplement pole piece is too thin. Although the performance of the pole piece can be improved to a certain extent, it cannot really protect the expansion of the active material layer itself and improve the performance of the battery cell. Not obvious. While the transition layer is too thick, although it can play a good protective effect on the expansion of the active material layer, it may affect the direct transmission efficiency of lithium ions between the positive and negative pole pieces, thereby affecting the battery performance.
  • the thickness of the transition layer is 0.01 ⁇ m-1 ⁇ m, preferably 0.05 ⁇ m-0.7 ⁇ m.
  • the inventor further researched and found that if the thickness of the oxide layer is too thin, that is, the lithium layer is pressed to the thinnest under the same amount of replenishing lithium, it can be considered that most of the lithium layer is directly pressed into the active material layer. In this case, extremely The active material of the film reacts violently with the material in the lithium supplement layer, heating is more obvious, and the temperature rise of the pole piece winding is large, which affects the safety of production. At the same time, the increase of the winding temperature of the pole piece directly affects the material of the oxide layer. Activity affects battery cycle performance. On the contrary, if the thickness of the oxide layer is too thick, that is, under the same lithium supplement, the lithium layer has little contact with the surface active material of the pole piece.
  • the winding temperature of the lithium pole piece decreases; at the same time, because the thickness of the oxide layer is too thick, it will directly affect the efficiency of the oxide layer of the lithium supplement layer to insert the active material, even in the case of liquid injection, due to the ion between the oxide layer and the active material layer There are too few channels and electron channels (the contact area between the oxide layer and the active material layer is small), and the contact area between the oxide layer and the active material layer is small. As a result, the thickness of the transition layer in the lithium replenishment layer is difficult to achieve the optimal window. Affect battery cycle performance.
  • the thickness of the oxide layer is 0.5 ⁇ m-20 ⁇ m, preferably 0.8 ⁇ m-10 ⁇ m.
  • a lithium-supplemented negative pole piece including: a current collector; a diaphragm, located on the current collector and including an active material, a binder and a conductive agent; and the first aspect of the application
  • the lithium supplementary layer wherein the transition layer in the lithium supplementary layer is connected to the diaphragm.
  • the third aspect of the present application proposes a lithium-ion battery supplemented with lithium, including the negative pole piece, the positive pole piece, the electrolyte and the separator as described in the second aspect of the present application.
  • Fig. 4 shows a lithium ion battery 5 with a square structure as an example.
  • lithium ion batteries can be assembled into battery modules, and the number of lithium ion batteries contained in the battery modules can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • Fig. 5 is a battery module 4 as an example.
  • a plurality of lithium ion batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of lithium ion batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a containing space, and a plurality of lithium ion batteries 5 are contained in the containing space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained 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 box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • a device in the fourth aspect of the present application, includes the lithium ion battery of the third aspect of the present application.
  • the lithium ion battery provides power for the device, and can also be used as an energy storage unit of the device.
  • the 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 golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a lithium ion battery (Cell), a battery module (Module) or a battery pack (pack) according to its usage requirements.
  • Cell lithium ion battery
  • Module battery module
  • pack battery pack
  • Fig. 8 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device usually requires light and thin, and can use lithium-ion batteries as a power source.
  • the batteries of Examples 1-28 and Comparative Examples 1-4 were prepared according to the following methods.
  • the lithium foil tape with a thickness of 5000 ⁇ m is rolled through two rolling rolls to obtain ultra-thin lithium foil tapes with different thicknesses, and then the ultra-thin lithium foil tapes with different thicknesses are in accordance with the parameters shown in Table 1.
  • the active material-coated pole piece is simultaneously rolled by two calendering rolls, and ultra-thin lithium foil tapes with different thicknesses are adhered to the surface of the pole piece by rolling, thereby obtaining transition layers of different thicknesses, and then the ultra-thin
  • the surface of the pole piece of the lithium foil tape is uniformly coated, oxide layer (none in Comparative Example 2) and surface layer (none in Comparative Example 1) in sequence according to the parameters shown in Table 1.
  • the weight of the lithium supplement layer is: 10mg/1540 ⁇ 25mm 2-sided active material surface, i.e. the double-sided surface active substance 20mg / 1540 ⁇ 25mm 2.
  • Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7 to obtain an organic solvent, and then fully dried LiPF 6 is dissolved in the mixed organic solvent to prepare a concentration of 1 mol/L Of electrolyte.
  • Cycle test use lithium ion charge and discharge equipment: Xinwei mobile power product special tester (6V4A) repeatedly charge and discharge the battery until the capacity attenuation rate reaches 80%.
  • the battery capacity above is 4.2Ah, and 1C is used
  • the current rate that is, the current is 4.2Ah
  • the charge and discharge are recorded as One cycle; when the cell capacity decays to 3.36Ah, stop the test and record the number of repeated charge and discharge, which is the cycle performance data of the cell.
  • the number of cycles is qualified: ⁇ 700 times.
  • Example 1 sample Pole piece heating temperature (°C) Internal resistance (mOHM) Cycle performance (circle)
  • Example 2 43 5.68 725
  • Example 3 41 5.71 730
  • Example 4 41 5.75 730
  • Example 5 39 5.80 725
  • Example 6 37 5.91 710
  • Example 7 40 5.75 735
  • Example 8 41 5.90 720
  • Example 9 42 5.77 725
  • Example 10 40 5.81 740
  • Example 12 39 5.78 725
  • Example 13 39 5.82 730
  • Example 14 38 5.76 740
  • Example 15 39 5.84 715
  • Example 16 41 5.78 725
  • Example 17 44 5.68 720
  • Example 18 43 5.72 740
  • Example 19 41 5.81 720
  • Example 20 36 5.96 705
  • Example 21 41 5.78 720
  • Example 22 40 5.75 730 Example 23 38 5.85 710 Example 24 45 5.71 705 Example 25 44 5.73 715 Example 26 42 5.82 725 Example 27 38 5.89 705 Example 28 34 5.96 700 Comparative example 1 101 5.60 600 Comparative example 2 twenty one 5.80 420 Comparative example 3 37 6.10 650 Comparative example 4 45 5.64 660
  • the conventional lithium supplement layer contains a transition layer and an oxide layer. Because there is no surface layer to block the oxide layer material in the lithium supplement layer from air Continue the reaction, which is an exothermic reaction, which leads to production safety problems such as high temperature of the lithium supplement pole piece during the winding process; at the same time, the temperature of the pole piece is too high, which will directly affect the activity of the lithium layer and ultimately affect the electrical performance; There is a surface layer in the layer (Example 5), which forms a barrier between the lithium supplement layer and the air without significantly affecting the transmission efficiency of lithium ions. Furthermore, because the winding temperature of the lithium supplement pole piece is controllable, the lithium supplement The activity of the layer can be guaranteed to provide capacity and improve the performance of lithium-ion batteries.
  • the isolation layer formed by the surface layer is too dense, Affect the lithium ion transmission efficiency, increase the internal resistance of the battery, and affect the battery performance; b.
  • the surface layer contains organic substances such as alcohols. If the proportion of organic materials is too high, it will easily react with the electrolyte to form by-products, increase the internal resistance of the battery, and affect Battery performance; c.
  • the filling material is too small to restrain the expansion of the active material during the cycle, thus affecting the battery performance.
  • the organic material content of the surface layer of the lithium supplement layer is between 10%-97%, it is more conducive to ensure that the coating provides an isolation layer, reduce the winding temperature of the lithium supplement pole piece, increase the activity of the lithium layer, and the filling material can be It effectively restrains the expansion of active materials and ultimately improves battery performance.
  • Example 5 and Examples 7-10 organic materials of alcohols, esters and fatty acids are mainly used.
  • the main function is: as a carrier of the filling material, forming a slurry and coating on the surface of the lithium supplement layer as the surface of the lithium supplement layer.
  • the film-forming substance of the layer enables the surface layer to be formed into a film or evenly distributed on the surface of the transition layer and the oxide layer of the lithium supplement layer.
  • the type of filling material in the surface layer of the lithium supplementation layer functions, and the filling material can be used to improve the internal resistance of the cell caused by the side reaction of the organic material and the electrolyte.
  • the filling material can form a network structure or a film-forming structure with organic substances, which can inhibit the expansion of the active material during the cycle.
  • the oxide layer material in the lithium replenishment layer is used to provide additional lithium source, which can meet the requirements in the circulation process after injection. Continue to replenish the lithium source to improve battery cycle performance.
  • the oxide layer material can provide a part of the material to form the transition layer, that is, an additional layer of inorganic SEI is formed to improve the battery cycle performance.
  • the oxide layer material can form a dense (Li 2 O ) Or a sparse (Li 3 N) isolation layer, to further improve the problem of the temperature of the pole piece winding and heating due to the reaction of the lithium layer and the air/active material.
  • the thickness of the lithium supplement surface layer is too thick, such as the thickness of the surface layer> 15 ⁇ m, because the thick surface layer can form an isolation layer from the air on the surface of the lithium supplement layer, so the winding temperature of the lithium supplement pole piece is reduced, but the surface layer is too thick, It directly affects the transmission efficiency of lithium ions. It can be clearly seen that the thicker the coating thickness, the greater the internal resistance of the cell, and during the cycle, as the transmission efficiency of lithium ions deteriorates, the cycle performance will be significantly affected.
  • the surface layer of the lithium supplement layer When the thickness of the surface layer of the lithium supplement layer is in the range of 0.1 ⁇ m-15 ⁇ m, the surface layer can form a barrier between the lithium supplement layer and the air without significantly affecting the transmission efficiency of lithium ions, due to the winding temperature of the lithium supplement pole piece Controllable, the activity of the replenishing lithium layer can be guaranteed to provide capacity, thereby improving the performance of the lithium ion battery.
  • Example 5 and Examples 21-23 in Table 1 and Table 2 it can be seen that the transition layer is too thin ( ⁇ 10nm), and the inorganic SEI film formed is too thin to protect the active material layer itself from swelling. , The improvement of electrical performance is not obvious, and if the transition layer is too thick, it will directly affect the direct transmission efficiency of lithium ions in the cathode and anode electrodes, thereby affecting battery performance.
  • Example 5 and Examples 24-28 in Table 1 and Table 2 it can be seen that the thickness of the oxide layer is too thin ( ⁇ 0.5 ⁇ m), that is, the lithium layer is pressed to the thinnest under the same amount of lithium supplementation. It is believed that most of the lithium layer is directly pressed into the active material layer. In this case, the active material of the pole piece and the substance in the lithium supplement layer have a violent reaction, and the heat is large, and the temperature rise of the pole piece is relatively large, which affects production Safe; at the same time, the high winding temperature of the pole piece directly affects the activity of the oxide layer material and affects the battery cycle performance.
  • the oxide layer is too thick (>20 ⁇ m), that is, under the same lithium supplement, the lithium layer has little contact with the surface active material of the pole piece.
  • the winding temperature of the lithium supplement pole piece is reduced; at the same time, because the thickness of the oxide layer is too thick, it will directly affect the efficiency of the oxide layer of the lithium supplement layer to insert the active material, even in the case of liquid injection, due to the gap between the oxide layer and the active material layer.
  • There are too few ion channels and electron channels (the contact area between the oxide layer and the active material layer is small), which will affect the cycle performance of the battery to a certain extent. If the oxide layer is too thick and the contact area between the oxide layer and the active material layer is small, the thickness of the transition layer in the lithium supplementation layer is difficult to achieve the optimal window, which also has a certain impact on the electrical performance.
  • FIG. 2 This application also provides a schematic diagram of a pole piece covered with a lithium supplementary layer in dots.
  • the production of the pole piece is the same as that of the negative electrode pole piece containing the lithium supplementary layer of Examples 1-28 and Comparative Examples 1-4.
  • the manufacturing method is similar, but the difference is that when coating the surface layer, uniform spot coating is used to make the surface layer appear dot-like coverage on the oxide layer.
  • FIG. 3 shows a SEM scanning electron microscope image of a cross-section of a pole piece for lithium supplementation after formation of a lithium ion battery cell containing the lithium supplementation layer described in this application.
  • the electron microscope picture shows the microscopic morphology of the pole piece of the lithium ion battery cell produced in Example 22. It can be seen that there is a transition layer on the upper surface of the active material layer.
  • the main layer of the transition layer is Li 2 O;
  • the upper surface of the transition layer is an oxide layer, and the surface layer (organic + inorganic particles) presents dot coverage on the oxide layer; the thickness of the oxide layer is ⁇ 2 ⁇ m, and the thickness of the surface layer is ⁇ 4 ⁇ m.

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Abstract

本申请属于锂离子电池技术领域，更具体地涉及一种补锂层及其负极极片和锂离子电池及装置，该补锂层由过渡层、氧化层及表面层依序连接而成，该表面层包含适量的有机材料和填充物质，能够降低负极极片的收卷温度，补锂层中的氧化层物质用于提供额外的锂源，注液后可满足在循环过程中持续补充锂源，提高锂层活性，同时，表面层中含有的填充物质可有效对活性物质的膨胀起到束缚作用，改善电池循环性能。

Description

一种补锂层及其负极极片和锂离子电池及装置
本申请要求于2019年4月11日提交中国专利局、申请号为201910287520.8、申请名称为“一种补锂层及其负极极片和锂离子电池”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
本申请属于锂离子电池技术领域，更具体地涉及一种负极补锂层及其负极极片和锂离子电池及装置。
背景技术
锂离子电池由于其高能量密度、长循环寿命等优点广泛的应用于便携式电源领域。然而，随着电动车、无人机等应用大型移动电源的领域的发展，开发更高能量密度的锂离子电池是目前急需解决的重大课题。
在电池的首次充电过程中，负极表面形成的固态电解质膜层(SEI)会消耗大量的锂源，将锂转化为非活性的含锂化合物如碳酸锂、氟化锂和烷基锂，从而造成可循环锂的损失，降低电池首圈库伦效率和电池容量。在使用石墨负极的电池体系中，首次充电会消耗约10％的锂源，首次库伦效率约为90％。当采用高比容的负极材料，如合金类(硅、锡、铝)，氧化物(氧化硅，氧化锡，氧化钛)和无定型碳负极时，锂源的消耗进一步加剧。
因此，为进一步提高锂离子电池的能量密度，通过预锂化等技术来改善循环性能以及提高电池能量密度是常见的做法。目前的补锂方式是将锂箔通过轧制方式压薄附着在极片表面，但这种工艺会导致两个问题：1、锂层轧制后附着在极片(负极/正极)表面，由于嵌入极片活性物的副反应物与空气中氧气发生放热反应，导致在电极制造过程极片温度升高，造成生产安全风险；2、针对硅基/锡基等新型活性物质材料制作成的极片，由于本身硅基在循环过程中膨胀，SEI膜不稳定，导致循环性能较差。
发明内容
鉴于背景技术中存在的上述问题，本申请的目的在于提供一种锂离子电池极片补锂层及其负极极片和锂离子电池及装置，该补锂层需兼具能改善锂离子电池补锂极片的发热问题，以及在极片的活性物质层SEI膜表面形成保护层，抑制活性物质层的SEI膜破裂，改善锂离子电池的性能。
为实现上述目的，在本申请的第一方面，发明人提供了一种补锂层，包括依序连接的过渡层、氧化层及表面层，其中，所述表面层为层状覆盖或点状覆盖，且所述表面层包含有机材料和填充物质。
在本申请的第二方面，发明人提供了一种补锂的负极极片，包括：集流体；膜片，位于所述集流体上且包括活性物质、粘接剂和导电剂；以及本申请的第一方面所述的补锂层，其中，所述补锂层中的过渡层与膜片相连接。
在本申请的第三方面，发明人提供了一种补锂的锂离子电池，包括：本申请第二方面所述的负极极片、正极极片、电解液和隔膜。
在本申请的第四方面，发明人提供一种装置，所述装置包括本申请第三方面的锂离子电池。
相比于现有技术，本申请至少包括如下所述的有益效果：
本申请的补锂层由过渡层、氧化层及表面层依序连接而成，该表面层包含适量的有机材料和填充物质，能够降低负极极片的收卷温度，补锂层中的氧化层物质用于提供额外的锂源，注液后可满足在循环过程中持续补充锂源，提高锂层活性，同时，表面层中含有的填充物质可有效对活性物质的膨胀起到束缚作用，改善电池循环性能，过渡层中的物质成分可以当作无机SEI膜，抑制活性物质膨胀带来的锂源消耗。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为具体实施方式所述一种层状覆盖补锂层的极片示意图；
图2为具体实施方式所述一种点状覆盖补锂层的极片示意图；
图3为具体实施方式所述一种含有所述补锂层的锂离子电芯化成后极片补锂断面的SEM扫描电镜图；
图4是锂离子电池的一实施方式的示意图；
图5是电池模块的一实施方式的示意图；
图6是电池包的一实施方式的示意图；
图7是图6的分解图；
图8是锂离子电池用作电源的装置的一实施方式的示意图；
其中，附图标记说明如下：1-电池包，2-上箱体，3-下箱体，4-电池模块，5-锂离子电池。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
下面详细说明本申请的补锂层、补锂的负极极片以及锂离子电池及装置。
首先说明本申请第一方面的补锂层，包括依序连接的过渡层、氧化层及表面层，其中，所述表面层为层状覆盖或点状覆盖，且所述表面层包含有机材料和填充物质。一般地，此处的“连接”可以理解为沿厚度方向叠合。
所述补锂层中的过渡层为活性物质与补锂层之间的副反应物，可视为补锂极片中额外产生的无机SEI膜，其可对活性物质本身形成的SEI膜起到保护作用，可以有效抑制活性物质循环过程中因膨胀破碎而消耗电解液中锂离子的问题。
所述氧化层成分主要为锂金属及其氧化物，氮化物和氢氧化物，氧化层用于提供额外的锂源，注液后可在循环过程中持续补充锂源，改善电池 循环性能，氧化层物质还可以提供一部分物质用于形成过渡层，即额外形成一层无机的SEI膜，改善电池循环性能，氧化层物质可在极片表面形成致密或者稀松的隔离层，进一步改善补锂极片因为锂箔和空气/活性物质反应导致极片收卷升温的问题。
所述表面层中的有机材料主要使用醇类、酯类和脂肪酸类，其主要作用在于：作为填充材料的载体，形成浆料形式涂覆在锂箔表面，作为所述补锂层表面层的成膜物质，使表面层能成膜或者均匀分布在补锂层过渡层和氧化层表面。补锂层中的填充材料可用于改善因有机材料与电解液发生副反应导致的电芯内阻恶化的问题，填充材料可与有机物质形成网状结构或成膜结构，可抑制活性物质在循环过程中的极片膨胀问题。表面层在氧化层面上的分布形式可以是均匀的层状覆盖，也可以是点状覆盖。
优选地，所述有机材料选自硬脂酸、12-羟基硬脂酸、脂肪酸金属盐、聚二醇、多烃环戊烷、聚甲基丙烯酸异丁酯、磷酸酯、石蜡、聚脲、聚a-烯烃、烷基萘和聚二甲基硅氧烷中的一种或多种组成的混合物，所述填充物质选自石墨、石墨烯、三氧化二铝、氢氧化钠、氢氧化锂、氢氧化钙和二硫化钼中的一种或多种组成的混合物。
优选地，所述过渡层选择Li的氧化物或锂的嵌入式化合物，例如，选自Li 2O、Li xC和Li x1Si y中的一种或多种组成的混合物，其中0<x≤2，0<x1≤4.4，0<y≤2。若选择锂的嵌入式硅化物，一般可以是Li x1Si，x1可以是4.4、3.75、3.25、2.33等。更加优选地，所述氧化层选自Li金属、Li 2O、LiF、LiOH、Li 3N和Li 2CO 3中的一种或多种组成的混合物。
进一步地，补锂层的表面层中有机材料和填充物质的含量及二者比例对极片及其锂离子电池的性能具有一定影响。当表面层中有机材料比例高时，虽然有助于在补锂层表面形成隔离层，进而降低补锂极片收卷温度，提高补锂层活性，但有机材料比例过高可能会导致：a.补锂层形成的隔离层过于致密，影响锂离子传输效率，导致电池内阻增加，影响电池性能；b.补锂层中含有醇类等物质，如果有机材料比例过高，易与电解液反应形成副产物，影响电池性能；c.填充物质过少，无法在循环过程对活性物质的膨胀起到束缚作用，从而影响电池性能。
优选地，以所述表面层的质量为基准，所述有机材料的含量为 10％-97％，优选为20％-80％；所述填充物质的含量为3％-90％，优选为20％-80％。
在相同补锂层表面层有机材料和填充材料比例下，即有机材料与填充比例相同情况下，表面层厚度过小，如表面层厚度在0μm-0.1μm，虽然也可以起到一定的隔离效果，但此种表面层无法在补锂层表面形成有效的隔离层，导致锂层与空气反应面积增加、反应加快，补锂极片收卷过程温度超标，引起生产安全风险。同时，极片温度过高会降低锂层的活性，在高温条件下有部分锂层会形成死锂，无法用于提供容量，导致对电性能有明显影响，降低循环性能。另一方面，当表面层厚度过厚，如表面层厚度大于15μm，虽然厚的表面层可以在补锂层表面形成与空气的优良隔离层，补锂极片收卷温度得到有效降低，但是表面层过厚，会直接影响锂离子的传输效率，由此得到的电芯内阻增大，其循环性能也会降低。当补锂层表面层厚度在0.1μm-15μm范围内时，表面层既可在补锂层和空气间形成隔离层，同时也不会明显影响锂离子的传输效率，由于补锂极片收卷温度可控，补锂层的活性可以保证用于提供容量，改善锂离子电池性能。
优选地，所述表面层的厚度为0.1μm-15μm，优选为1μm-8μm。
过渡层过薄，即补锂极片上形成的无机SEI膜过薄，虽然一定程度上可以改善极片的性能，但无法对活性物质层本身的膨胀起到真正的保护作用，对电芯性能改善不明显。而过渡层过厚，虽然可以对活性物质层的膨胀起到很好的保护作用，但有可能会影响锂离子在正负极极片直接的传输效率，进而影响电池性能。
优选地，所述过渡层的厚度为0.01μm-1μm，优选为0.05μm-0.7μm。
发明人进一步研究发现，若氧化层厚度过薄，即在相同补锂量下，锂层被压到最薄，可认为大部分锂层被直接压入活性物质层内，这种情况下，极片活性物质与补锂层中的物质发生剧烈反应，发热较明显，极片收卷温升较大，影响生产制造安全，同时，极片收卷温度的升高，直接影响该氧化层物质的活性，影响电池循环性能。相反，若氧化层厚度过厚，即在相同补锂下，锂层与极片表面活性物质接触很少，在这种情况下，由于补锂层的氧化层很少与活性物质发生反应，补锂极片收卷温度降低；同时，由于氧化层厚度过厚，会直接影响补锂层的氧化层嵌入活性物质的效率，即 使在注液情况下，由于氧化层与活性物质层之间的离子通道和电子通道太少(氧化层与活性物质层接触面积小)，氧化层与活性物质层接触面积小，导致补锂层中的过渡层厚度很难做到优选窗口，从而在一定程度上会影响电池循环性能。
优选地，所述氧化层的厚度为0.5μm-20μm，优选为0.8μm-10μm。
其次说明本申请第二方面的一种补锂的负极极片，包括：集流体；膜片，位于所述集流体上且包括活性物质、粘接剂和导电剂；以及本申请第一方面所述的补锂层，其中，所述补锂层中的过渡层与膜片相连接。
本申请第三方面提出一种补锂的锂离子电池，包括：本申请第二方面所述的负极极片、正极极片、电解液和隔膜。
本申请对锂离子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4是作为一个示例的方形结构的锂离子电池5。
在一些实施例中，锂离子电池可以组装成电池模块，电池模块所含锂离子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5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个锂离子电池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锂离子电池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壳体，多个锂离子电池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6和图7是作为一个示例的电池包1。参照图6和图7，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。
在本申请的第四方面提供一种装置，所述装置包括本申请第三方面的锂离子电池。所述锂离子电池为所述装置提供电源，也可以作为所述装置的能量存储单元。所述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。
所述装置可以根据其使用需求来选择锂离子电池(Cell)、电池模块(Module)或电池包(pack)。
图8是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子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。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂离子电池作为电源。
为详细说明技术方案的技术内容、构造特征、所实现目的及效果，以下结合具体实施例并配合附图详予说明。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1-28和对比例1-4的电池均按照下述方法进行制备。
(1)含补锂层负极极片的制作方法
请参阅图1，将厚度为5000μm的锂箔带，通过两个轧制辊辊压得到厚度不同的超薄锂箔带，再将厚度不同的超薄锂箔带按照表1中所示的参数和涂布有活性物质的极片同时通过两个压延辊辊压，将厚度不同的超薄锂箔带通过辊压黏附在极片表面，从而得到不同厚度的过渡层，然后在黏附有超薄锂箔带的极片表面按照表1所示的参数依次均匀涂布、氧化层(对比例2无)和表面层(对比例1无)，补锂层补锂重量为：10mg/1540·25mm 2单面活性物质表面，双面活性物质表面即20mg/1540·25mm 2。
(2)正极极片的制作方法
将正极活性材料LiNi 1/3Co 1/3Mn 1/3O 2、导电剂Super-P、粘结剂PVDF按质量比94:3:3进行混合，加入溶剂NMP，在真空搅拌机作用下搅拌至体系呈均一状，获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔的两个表面上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切得到正极极片。
(3)电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)按照按体积比3:7进行混合得到有机溶剂，接着将充分干燥的LiPF 6溶解于混合后的有机溶剂中，配制成浓度1mol/L的电解液。
(4)隔离膜的制备
选PE/PP/PE三层多孔聚合薄膜作为隔离膜。
(5)锂离子电池的制备
将上述正极极片、隔离膜、含有补锂层负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到裸电芯；将裸电芯置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得锂离子电池。
接下来说明补锂极片温度的测试方法和锂离子电池的内阻和循环性能测试方法。
(1)极片温度测试，为补锂极片用6英寸卷筒收卷1000m，在收卷500m处插入感温线测试极片温度，测温仪器为：测温仪：SKF TKDT 10，温度规格为：≤60℃。
(2)电池内阻测试：即交流电阻，交流内阻设备：Itech公司IT5100系列电池内阻测试仪，测试方法：对测试电芯加固定频率1KHz,固定电流50mA,对电压采样，经整流仪器可计算出阻值。
(3)循环测试：使用锂离子充放电设备：新威移动电源成品专用测试仪(6V4A)对电池重复进行充放电，直至容量衰减率达到80％，如上述电芯容量为4.2Ah，用1C电流倍率(即电流为4.2Ah)重复对电芯进行充放电，以1C电流倍率对电芯充电至电压4.2V，然后再以1C电流倍率对电芯放电至电压2.5V，该充电放电记录为一次循环；当电芯容量衰减至3.36Ah时，停止测试，记录重复充放电的次数，即为电芯的循环性能数据，循环次数合格规格：≥700次。
实施例1-28和对比例1-4提供的补锂层相关参数见表1，实施例1-28和对比例1-4制备的锂离子电池的性能测试结果见表2。
表1实施例1-28和对比例1-4提供的补锂层相关参数
Figure PCTCN2020083448-appb-000001
Figure PCTCN2020083448-appb-000002
表2实施例1-28和对比例1-4提供的电池发热温度、内阻和循环性能测试结果
样品 极片发热温度(℃) 内阻(mOHM) 循环性能(圈)
实施例1 45 5.64 700
实施例2 43 5.68 725
实施例3 41 5.71 730
实施例4 41 5.75 730
实施例5 39 5.80 725
实施例6 37 5.91 710
实施例7 40 5.75 735
实施例8 41 5.90 720
实施例9 42 5.77 725
实施例10 40 5.71 740
实施例11 40 5.84 715
实施例12 39 5.78 725
实施例13 39 5.82 730
实施例14 38 5.76 740
实施例15 39 5.84 715
实施例16 41 5.78 725
实施例17 44 5.68 720
实施例18 43 5.72 740
实施例19 41 5.81 720
实施例20 36 5.96 705
实施例21 41 5.78 720
实施例22 40 5.75 730
实施例23 38 5.85 710
实施例24 45 5.71 705
实施例25 44 5.73 715
实施例26 42 5.82 725
实施例27 38 5.89 705
实施例28 34 5.96 700
对比例1 101 5.60 600
对比例2 21 5.80 420
对比例3 37 6.10 650
对比例4 45 5.64 660
由表1、表2数据可知：补锂层中没有表面层(对比例1)，即常规补锂层包含有过渡层和氧化层，由于没有表面层阻隔补锂层中的氧化层物质与空气继续反应，该反应为放热反应，导致补锂极片在收卷过程出现温度过高等生产安全问题；同时，极片温度过高，会直接影响锂层的活性，最终影响电性能；补锂层中存在表面层(实施例5)，在补锂层和空气间形成隔层，同时不会较明显影响锂离子的传输效率；再则，由于补锂极片收卷温度可控，补锂层的活性可以保证用于提供容量，改善锂离子电池性能。
同样地，由表1、表2数据可知：补锂层中只有表面层(对比例2)，即不存在过渡层和氧化层，即极片表面并无用于提供容量的锂层，无法在循环过程中提供额外的锂离子，从而影响锂离子电池的循环电性能；没有过渡层/氧化层和空气以及活性物质反应的现象，极片收卷并无出现升温现象。
通过观察表1和表2中对比例1-4、实施例1-6的数据可知：有机材料和填充物质之间的配比关系对电池性能具有一定影响。
当涂层中有机材料比例过小(填充物质比例过大)，比如有机材料：填充物质比例0:100(对比例4)，这会引起以下不良影响：a.有机物质太少或者没有，对浆料加工是挑战，过多的填充物质较难完全溶于/悬浮于有机材料中，难以形成浆料形式；b.过多的填充物质，特别是石墨类填充材料，在充放电过程中，正极上的锂离子有部分会嵌入补锂表面层中的石墨类填充物，直接导致可用于循环的锂离子减少，最终影响电池性能；当补锂层的表面层中有机材料比例过高，虽然可以有助于表面层在补锂层表面形成隔离层，进而降低补锂极片收卷温度，提高锂层活性；但有机材料比 例过高会导致：a.表面层形成的隔离层过于致密，影响锂离子传输效率，导致电池内阻增加，影响电池性能；b.表面层中含有醇类等有机物质，如果有机材料比例过高，易与电解液反应形成副产物，增加电池内阻，影响电池性能；c.填充物质过少，无法在循环过程对活性物质的膨胀起到束缚作用，从而影响电池性能。当补锂层表面层有机材料的含量在10％-97％之间时，更利于得到既能保证涂层提供隔离层，降低补锂极片收卷温度，提高锂层活性，同时填充物质可有效对活性物质的膨胀起到束缚作用，最终提高电池性能。
从表1和表2数据可知，补锂层表面层中的有机材料类型作用。通过实施例5、实施例7-10主要使用醇类，酯类和脂肪酸类有机材料，主要作用在于：作为填充材料的载体，形成浆料形式涂覆在补锂层表面，作为补锂层表面层的成膜物质，使表面层能成膜或者均匀分布在补锂层过渡层和氧化层表面。
由表1和表2中实施例5、实施例11-13数据可知，补锂层表面层中的填充材料类型作用，填充材料可用于改善因有机材料与电解液副反应导致的电芯内阻恶化的问题，填充材料可与有机物质形成网状结构或成膜结构，可抑制活性物质在循环过程中的极片膨胀问题。
通过表1和表2中实施例5、实施例14-16可知，氧化层的主要作用在于：补锂层中的氧化层物质用于提供额外的锂源，注液后可满足在循环过程中持续补充锂源，改善电池循环性能，氧化层物质可提供一部分物质用于形成过渡层，即额外形成一层无机SEI，改善电池循环性能，氧化层物质可在极片表面形成致密(Li 2O)或者稀松(Li 3N)隔离层，进一步改善补锂极片因为锂层和空气/活性物质反应导致极片收卷升温的问题。
通过表1和表2中实施例5、实施例17-20可以明显看出，涂层厚度越厚，电芯内阻越大，而在循环过程中，随着锂离子的传输效率变差，循环性能会受到明显影响。补锂层表面层厚度在0.1μm-15μm范围内时，表面层既可在补锂层和空气间形成隔层，同时不会较明显影响锂离子的传输效率，由于补锂极片收卷温度可控，补锂层的活性可以保证用于提供容量，从而改善锂离子电池性能。
通过表1和表2中实施例5、实施例17-20可知，在相同补锂层表面 层有机材料和填充材料比例下：即有机材料与填充比例相同情况下，如果表面层厚度过小，比如，当表面层厚度为0μm-0.1μm时，无法在补锂层表面形成有效的隔离层，导致锂层与空气反应面积增加，反应加快，补锂极片收卷过程温度超标，引起生产安全风险。同时，极片温度过高会降低锂层的活性，在高温条件下有部分锂层会形成死锂，无法用于提供容量，导致对电性能有明显影响，降低循环性能。
补锂表面层厚度过厚，如表面层厚度＞15μm，由于厚的表面层可以在补锂层表面形成与空气的隔离层，所以补锂极片收卷温度降低，但是表面层过厚，会直接影响锂离子的传输效率，可以明显看出，涂层厚度越厚，电芯内阻越大，而在循环过程中，随着锂离子的传输效率变差，循环性能会受到明显影响。
补锂层表面层厚度在0.1μm-15μm范围内时，表面层即可在补锂层和空气间形成隔层，同时不会较明显影响锂离子的传输效率，由于补锂极片收卷温度可控，补锂层的活性可以保证用于提供容量，从而改善锂离子电池性能。
通过表1和表2中对比例2、实施例5和实施例21-23可知，过渡层过薄(＜10nm)，形成的无机SEI膜过薄，无法对活性物质层本身膨胀起到保护作用，对电性能改善不明显，过渡层过厚，则会直接影响锂离子在阴阳极极片直接的传输效率，进而影响电池性能。
通过表1和表2中对比例2、实施例5和实施例24-28可知，氧化层厚度过薄(＜0.5μm)，即在相同补锂量下，锂层被压到最薄，可认为大部分锂层被直接压入活性物质层内，这种情况下，极片活性物质与补锂层中的物质发生剧烈反，发热较大，极片收卷温升较大，影响生产制造安全；同时，极片收卷温度高，直接影响氧化层物质的活性，影响电池循环性能。氧化层厚度过厚(＞20μm)，即在相同补锂下，锂层与极片表面活性物质接触很少，在这种情况下，由于补锂层的氧化层很少与活性物质发生反应，补锂极片收卷温度降低；同时，由于氧化层厚度过厚，会直接影响补锂层的氧化层嵌入活性物质的效率，即使在注液情况下，由于氧化层与活性物质层之间的离子通道和电子通道太少(氧化层与活性物质层接触面积小)，从而在一定程度上会影响电池循环性能。氧化层过厚，氧化层与活性物质 层接触面积小，会导致补锂层中的过渡层厚度很难做到优选窗口，对电性能同样有一定影响。
此外，请参阅图2，本申请还提供了一种点状覆盖补锂层的极片示意图，该极片的制作与实施例1-28和对比例1-4的含补锂层负极极片的制作方法相似，不同之处在于，涂布表面层时，采用均匀点沾式涂布，使表面层在氧化层上呈现点状覆盖。
请参阅图3，该图显示的是含有本申请所述补锂层的锂离子电芯化成后极片补锂断面的SEM扫描电镜图。该电镜图为实施例22制作的锂离子电芯完成化成后的极片微观形貌，可以看到在活性物质层上表面存在一层过渡层，通过成分分析，该过渡层主要层为Li 2O；在过渡层上表面为氧化层，表面层(有机+无机颗粒)在氧化层上呈现点状覆盖；氧化层厚度≈2μm，表面层厚度≈4μm。
需要说明的是，尽管在本文中已经对上述各实施例进行了描述，但并非因此限制本申请的专利保护范围。因此，基于本申请的创新理念，对本文所述实施例进行的变更和修改，或利用本申请说明书及附图内容所作的等效结构或等效流程变换，直接或间接地将以上技术方案运用在其他相关的技术领域，均包括在本申请的专利保护范围之内。

Claims (12)

  1. 一种补锂层，其中，包括依序连接的过渡层、氧化层及表面层，所述表面层为层状覆盖或点状覆盖，且所述表面层包含有机材料和填充物质。
  2. 根据权利要求1所述的补锂层，其中，所述有机材料选醇类、酯类和脂肪酸类中的至少一种。
  3. 根据权利要求1或2所述的补锂层，其中，所述有机材料选自硬脂酸、12-羟基硬脂酸、脂肪酸金属盐、聚二醇、多烃环戊烷、聚甲基丙烯酸异丁酯、磷酸酯、石蜡、聚脲、聚a-烯烃、烷基萘和聚二甲基硅氧烷中的一种或多种组成的混合物；和/或，
    所述填充物质选自石墨、石墨烯、三氧化二铝、氢氧化钠、氢氧化锂、氢氧化钙和二硫化钼中的一种或多种组成的混合物。
  4. 根据权利要求1-3任一项所述的补锂层，其中，所述过渡层选自Li 2O、Li xC和Li x1Si y中的一种或多种组成的混合物，其中0<x≤2，0<x1≤4.4，0<y≤2。
  5. 根据权利要求1-4任一项所述的补锂层，其中，所述氧化层选自Li金属、Li 2O、LiF、LiOH、Li 3N和Li 2CO 3中的一种或多种组成的混合物。
  6. 根据权利要求1-5任一项所述的补锂层，其中，以所述表面层的质量为基准，所述有机材料的含量为10％-97％，优选为20％-80％；
    所述填充物质的含量为3％-90％，优选为20％-80％。
  7. 根据权利要求1-6任一项所述的补锂层，其中，所述表面层的厚度 为0.1μm-15μm，优选为1μm-8μm。
  8. 根据权利要求1-7任一项所述的补锂层，其中，所述过渡层的厚度为0.01μm-1μm，优选为0.05μm-0.7μm。
  9. 根据权利要求1-8任一项所述的补锂层，其中，所述氧化层的厚度为0.5μm-20μm，优选为0.8μm-10μm。
  10. 一种补锂的负极极片，包括：
    集流体；
    膜片，位于所述集流体上且包括活性物质、粘接剂和导电剂；
    以及，其中，还包括：
    根据权利要求1-9中任一项所述的补锂层，所述补锂层中的过渡层与膜片相连接。
  11. 一种补锂的锂离子电池，包括：
    根据权利要求10所述的负极极片；
    正极极片；
    电解液和隔膜。
  12. 一种装置，其中，所述装置包括权利要求11所述的锂离子电池。
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