CN114709564A - Battery diaphragm and preparation method and application thereof - Google Patents
Battery diaphragm and preparation method and application thereof Download PDFInfo
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- CN114709564A CN114709564A CN202210378892.3A CN202210378892A CN114709564A CN 114709564 A CN114709564 A CN 114709564A CN 202210378892 A CN202210378892 A CN 202210378892A CN 114709564 A CN114709564 A CN 114709564A
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- 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
Abstract
The invention discloses a battery diaphragm and a preparation method and application thereof, and relates to the technical field of lithium batteries. The battery diaphragm comprises a base film, wherein a lithium supplement coating is arranged on the surface of at least one side of the base film in a stacking mode, the material of the lithium supplement coating comprises a lithium supplement material, the lithium supplement material comprises lithium powder and a passivation layer coated on the lithium powder, and the passivation layer is arranged to be broken under the action of external force to expose the lithium powder. The invention prepares the lithium supplement material by wrapping the passivation layer on the outer surface of the lithium powder, and the battery diaphragm is prepared by bonding the lithium supplement material on the basement membrane. Along with the continuous circulation of battery, its thickness and internal pressure increase gradually, increase to the passivation lithium powder on the certain degree extrusion battery diaphragm, mend the lithium to the battery after the passivation shell breaks, this application realizes mending lithium to the full life cycle's of lithium cell accuracy, and to a great extent increases the electric capacity of battery, prolongs the life of lithium cell.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a battery diaphragm and a preparation method and application thereof.
Background
Lithium ion batteries are widely used because of their advantages of high energy density, good cycle performance, no pollution, etc. However, with the rapid development of electric vehicles, smart grids, and energy storage systems, higher requirements are placed on the energy density of lithium ion batteries, and therefore, the application of lithium supplement technology is particularly important. Lithium batteries consume active lithium during the first charge to form a passivation film (also referred to as SEI film) on the surface of the negative electrode, the main components of the film being organic salts, inorganic salts, oxides, etc. of lithium, resulting in a loss of battery capacity. Therefore, the negative electrode lithium supplement technology comes along, and the modes comprise lithium in a lithium belt, lithium in lithium powder, lithium in a negative electrode material and the like, but the methods supplement the lithium lost in the first charging process of the battery, and the accurate lithium supplement of the whole life cycle of the lithium battery cannot be realized; meanwhile, in the battery circulation process, a large amount of active lithium is lost due to the generation of lithium byproducts, the loss of positive and negative electrode capacities and the like, so that the capacity of the battery cell is reduced until the battery cell is invalid, and the service life of the lithium battery is shortened.
Disclosure of Invention
The invention mainly aims to provide a battery diaphragm and a preparation method and application thereof, aiming at realizing accurate lithium supplement in the whole life cycle of a lithium battery so as to prolong the service life of the lithium battery.
In order to achieve the purpose, the invention provides a battery diaphragm which comprises a base film, wherein a lithium supplement coating is stacked on at least one side surface of the base film, the material of the lithium supplement coating comprises a lithium supplement material, the lithium supplement material comprises lithium powder and a passivation layer coated on the lithium powder, and the passivation layer is set to be broken under the action of external force so as to expose the lithium powder.
Optionally, the material of the passivation layer includes a metal inorganic salt.
Optionally, the passivation layer is made of lithium fluoride.
Optionally, the thickness of the passivation layer is 10-800 nm; and/or the presence of a gas in the gas,
the average particle diameter of the lithium powder is 20-80 μm.
Optionally, the lithium supplement coating has a thickness of 25-100 μm.
Optionally, the mass ratio of the lithium powder to the passivation layer is 100: (0.5-5).
The invention further provides a preparation method of the battery diaphragm, which comprises the following steps:
coating a passivation layer on the surface of the lithium powder to obtain a lithium supplement material;
and uniformly mixing the lithium supplement material, the binder and the solvent to obtain slurry, attaching the slurry to one side surface of the base film, and drying to prepare the battery diaphragm.
Optionally, the binder comprises at least one of polytetrafluoroethylene, polyacrylate, polyurethane, polyethylene glycol, polyethylene oxide, and epoxy.
Optionally, coating a passivation layer on the surface of the lithium powder to obtain a lithium supplement material, including:
uniformly mixing lithium powder and a solvent, heating to 82-88 ℃, adding a fluorine source, sealing, stopping heating, continuously stirring for 2-2.5h, filtering, and repeatedly washing with ethanol to obtain a lithium supplement material;
wherein the solvent comprises at least one of hexadecene, toluene, triethylene glycol dimethyl ether and N, N-dimethylformamide; and/or the presence of a gas in the atmosphere,
the fluorine source comprises at least one of perfluoroethane, perfluoropropane, perfluorobutane, perfluorobutylsulfonyl fluoride, perfluoroethylsulfonyl fluoride, perfluorooctylsulfonyl fluoride, perfluorooctanoic acid, perfluoroheptanoic acid, perfluorononanoic acid, ethyl trifluoroacetate, methyl trifluoroacetate, trifluoroethyl methacrylate and ethyl pentachloropropionate.
In addition, the invention also provides a lithium battery, which comprises a positive electrode, a negative electrode and a battery diaphragm positioned between the positive electrode and the negative electrode, wherein the battery diaphragm is the battery diaphragm.
According to the technical scheme, the passivation layer is coated outside the lithium powder to prepare the lithium supplement material, and the passivation layer is arranged to break under the action of external force to expose the lithium powder, so that the lithium supplement of the battery is realized. The metal lithium powder has high activity, can react with water and is easy to oxidize, and the passivation layer is coated on the outer surface of the metal lithium powder, so that the safety and the stability of the metal lithium powder can be greatly improved; the passivation layer is set to be breakable, and when stabilizing the lithium powder, also can realize supplementing lithium to the battery accurately. The lithium supplement material is bonded on the battery diaphragm through the adhesive, so that the lithium supplement material is prevented from falling off, the lithium ions are conducted while the anode and the cathode are prevented from contacting, the lithium supplement efficiency of the battery is improved, the positive effect on the wide use of the lithium battery is achieved, and the service life of the lithium battery is prolonged.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments.
It should be noted that those whose specific conditions are not specified in the examples were performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Lithium ion batteries are widely used due to their advantages of high energy density, good cycle performance, no pollution, etc. However, with the rapid development of electric vehicles, smart grids, and energy storage systems, higher requirements are placed on the energy density of lithium ion batteries, and therefore, the application of lithium supplement technology is particularly important. Lithium batteries consume active lithium during the first charge to form a passivation film (also referred to as SEI film) on the surface of the negative electrode, the main components of the film are organic salts, inorganic salts, oxides, and the like of lithium, which causes a loss of battery capacity. Therefore, the negative electrode lithium supplement technology is developed at the same time, and the modes comprise lithium ribbon, lithium powder and negative electrode material lithium supplement and the like, but the methods supplement lithium lost in the first charging process of the battery, and accurate lithium supplement of the whole life cycle of the lithium battery cannot be realized; meanwhile, in the battery circulation process, a large amount of active lithium is lost due to the generation of lithium byproducts, the loss of positive and negative electrode capacities and the like, so that the capacity of a battery cell is reduced until the battery cell is invalid, the service life of the lithium battery is shortened, and the wide use of the lithium battery is limited. Therefore, the battery diaphragm is improved and designed, the lithium is supplemented to the battery accurately in the whole life cycle, the energy density of the battery is increased, and the service life of the lithium battery is prolonged.
The invention provides a battery diaphragm which comprises a base film, wherein a lithium supplement coating is stacked on at least one side surface of the base film, the material of the lithium supplement coating comprises a lithium supplement material, the lithium supplement material comprises lithium powder and a passivation layer coated on the lithium powder, and the passivation layer is broken under the action of external force to expose the lithium powder.
Lithium is a high-reactivity alkali metal, can react with oxygen and water to cause oxidation and even ignition of lithium powder, and is coated by a passivation layer, so that the stability of the lithium powder is improved to a great extent, potential safety hazards are reduced, and the operability is improved. The passivation layer breaks under the exogenic action and can release the lithium powder of parcel, the battery is at continuous endless in-process, battery thickness can increase gradually, its internal pressure also increases gradually along with it, when battery internal pressure reached the ruptured threshold value of lithium powder passivation layer, can lead to the passivation layer to break, inside active lithium powder releases mends lithium to the battery, the electric capacity of increase lithium cell that can be fine, realize accurate and full life cycle's the benefit lithium, the life of very big degree extension battery. The lithium supplement material composed of the lithium powder and the passivation layer is arranged on at least one side of the battery diaphragm base film, so that the lithium supplement of the positive electrode or the negative electrode can be realized, and the application range of the lithium supplement technology of the lithium battery is expanded.
Optionally, the passivation layer may be made of a metal inorganic salt, such as lithium carbonate, lithium fluoride, and the like, and the inorganic salt has a wide source and a simple manufacturing process, and can form an effective coating effect on the surface of the lithium powder.
Preferably, the passivation layer is made of lithium fluoride which is insoluble in organic solvents, has high melting point, is high temperature resistant and corrosion resistant, is coated on the surface of the active lithium powder, is beneficial to the stability of the lithium powder, and can not react with other components inside the battery such as electrolyte when being used in the battery, thereby reducing the potential safety hazard of lithium powder exposure.
In an embodiment of the present invention, the average particle size of the lithium powder is 20 to 80 μm, the particle size of the lithium powder is too small, which increases the coating effect of the lithium powder and reduces the stability and manufacturability of the lithium powder slurry, and the particle size of the lithium powder is too large, which affects the release rate of the lithium powder, thereby reducing the actual utilization rate of the lithium powder, so that the preferred average particle size of the lithium powder is 20 to 80 μm, in this range, the lithium powder has strong operability of preparing a lithium supplement material, and the migration rate of lithium ions is good, and the lithium supplement effect of the lithium supplement coating on the battery is also better.
The thickness of the passivation layer cannot be too thin, the passivation layer is easy to break due to the fact that the passivation layer is too thin, lithium powder is exposed, and safety accidents are further caused, the dissolution efficiency of the lithium powder is reduced due to the fact that the thickness of the passivation layer is too large, the effect of improving the lithium supplement efficiency of the battery is not obvious, in one embodiment of the invention, the thickness of the passivation layer is preferably 10-800nm, such as 10nm, 50nm, 100nm, 150nm, 200nm and the like.
At least one side surface of the base film is laminated with a lithium supplement coating, in another embodiment of the scheme, the thickness of the lithium supplement coating is 25-100 μm, for example, 25 μm, 50 μm, 75 μm or 100 μm, the lithium supplement coating is too thin, the lithium supplement effect on the battery is not obvious, the lithium supplement coating is too thick, excessive lithium powder cannot play a lithium supplement role, meanwhile, the elemental lithium reacts with the electrolyte to form a byproduct, the electrolyte is consumed, the impedance of the battery is increased, and preferably, the thickness of the lithium supplement coating is set to be 25-100 μm optimally.
Correspondingly, the mass ratio of the lithium powder to the passivation layer is 100: (0.5-5), the passivation layer mainly plays a role in wrapping active lithium powder, and on the basis, the mass of the passivation layer is not required to be excessive and is excessive, so that the occupation ratio of effective lithium powder is reduced, the volume energy density and the weight energy density of the battery are influenced, and meanwhile, the cost of the passivated lithium powder is increased and the use value of the passivated lithium powder is reduced due to the excessive inorganic salt passivation layer; the passivation layer quality is too little, can lead to the passivation layer too thin, does not play fine guard action to active lithium powder, influences the stability of active lithium powder, may have the potential safety hazard, when the lithium powder with the quality ratio of passivation layer is 100: (0.5-5), the lithium supplement effect is good, and the passivation layer can also well play a role in stabilizing the lithium powder.
The invention further provides a preparation method of the battery diaphragm, which comprises the following steps:
coating a passivation layer on the surface of the lithium powder to obtain a lithium supplement material;
and uniformly mixing the lithium supplement material, the binder and the solvent to obtain slurry, attaching the slurry to one side surface of the base film, and drying to prepare the battery diaphragm.
The active lithium powder has high reaction activity, and a passivation layer needs to be coated on the outer surface of the active lithium powder, so that the active lithium powder is stabilized, and meanwhile, when the active lithium powder needs to be released to supplement lithium for the battery, the passivation layer can be broken under the action of external force. Therefore, the first step in obtaining a lithium supplement material is to coat the surface of the lithium powder with a coating layer that can be broken by an external force. The lithium supplement material is bonded on the base film through the binder to obtain the battery diaphragm, on one hand, the base film can well fix the lithium supplement material, the lithium supplement material is prevented from falling off to influence the use of the battery, and on the other hand, the internal short circuit caused by the contact of the anode and the cathode of the battery is prevented. Because of the electrolyte composition in the battery, the diaphragm needs organic solvent resistance, can select materials such as polypropylene, polyethylene or non-woven fabrics for use, and these several materials are used extensively, and corrosion resisting property is good, has good tensile properties and high temperature resistance, is used in the battery diaphragm, guarantees that the battery performance is more stable.
In preparing the battery separator, the binder in a preferred embodiment of the present scheme includes at least one of tetrafluoroethylene, polyacrylate, polyurethane, polyethylene glycol, polyethylene oxide, and epoxy resin. The materials have good cohesiveness, are resistant to organic solvents, have no influence on electrolyte in the battery, can not react with lithium powder, have good high-temperature resistance, and are preferred binder components.
Preferably, an embodiment of the present invention provides a method for preparing a lithium supplement material in which the passivation layer is lithium fluoride. The method comprises the following steps: uniformly mixing lithium powder and a solvent, heating to 82-88 ℃, adding a fluorine source, sealing, stopping heating, continuously stirring for 2-2.5h, filtering, and repeatedly washing with ethanol to obtain a lithium supplement material;
wherein the solvent comprises at least one of hexadecene, toluene, triethylene glycol dimethyl ether and N, N-dimethylformamide; and/or the presence of a gas in the gas,
the fluorine source comprises at least one of perfluoroethane, perfluoropropane, perfluorobutane, perfluorobutylsulfonyl fluoride, perfluoroethylsulfonyl fluoride, perfluorooctylsulfonyl fluoride, perfluorooctanoic acid, perfluoroheptanoic acid, perfluorononanoic acid, ethyl trifluoroacetate, methyl trifluoroacetate, trifluoroethyl methacrylate and ethyl pentachloropropionate.
In one embodiment of the invention, the lithium powder is dispersed in the organic solvent, heated to 82-88 ℃, added with the fluorine source while stirring, and then sealed, and stirred for 2-2.5h until the reaction is completed. Because the lithium powder has high reaction activity, the reaction needs to be carried out in a glove box or in an inert gas atmosphere, so that safety accidents are prevented from being caused while the lithium powder is prevented from being consumed by other side reactions; continuously stirring to ensure that the fluorine source is fully contacted and reacted with the lithium powder, and forming a passivation layer with uniform thickness on the surface of the lithium powder; and controlling the stirring time to ensure that the thickness of the passivation layer is in a proper range, obtaining solid lithium powder after complete reaction, filtering the solid lithium powder, washing the filtered solid lithium powder with ethanol, washing an organic solvent or an excessive fluorine source on the surface, and drying the washed solid lithium powder to obtain the passivated lithium powder.
The application also provides a lithium ion battery, lithium ion battery includes positive pole, negative pole and is located the battery diaphragm between positive pole and the negative pole, the battery diaphragm is the above-mentioned battery diaphragm that this application provided. The structure of the lithium ion battery provided by the application is the prior art in the field, and the lithium ion battery comprises a cylindrical battery, a square aluminum shell battery and a soft package battery, the manufacturing process of the lithium ion battery comprises winding, a lamination form and the like, wherein the positive electrode and the negative electrode are conventional positive and negative electrode plates in the field, and are not described herein any more, and the diaphragm is the diaphragm provided by the application.
According to the preparation method, the passivation layer is coated on the outer surface of the lithium powder to prepare the lithium supplement material, and the prepared lithium supplement material is bonded on the surface of the base film through the adhesive to prepare the battery diaphragm. The passivation lithium powder is coated on the diaphragm, so that the goodness of the pole piece is not affected, and the production cost can be reduced. The lithium cell is at the cyclic process of charge-discharge, because the accessory substance, the positive negative pole capacity loss of production lithium, the inside thickness of battery increases gradually, and in-service use can restrict the thickness of battery to lead to electric core internal pressure to increase gradually, when battery internal pressure increases to the threshold value of lithium powder passivation layer breakdown pressure, the passivation layer shell breaks, and inside active lithium powder can release, thereby mends lithium to the battery, increases the electric capacity of lithium cell in good time. The thickness through adjusting the passivation layer can change the cracked threshold value of passivation layer casing to carry out accurate benefit lithium to the lithium cell as required, compare in prior art and all once only mend lithium in the lithium cell first charge, the scheme of this application has more the advantage, the life of extension lithium cell that moreover can be fine.
The technical solutions of the present invention are further described in detail with reference to the following specific examples, which should be understood as merely illustrative and not limitative.
Comparative example 1
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane, 100Ah soft package battery is manufactured through lamination process, the battery size is 35 x 170 x 220, and the battery product D10 is obtained.
Example 1
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has a 0.05um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the size of the battery is 35 × 170 × 220, so that the battery product S10 is obtained.
Example 2
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has a 0.1um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the size of the battery is 35 × 170 × 220, so that the battery product S20 is obtained.
Example 3
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has 0.15um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S30 is obtained.
Example 4
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has 0.2um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S40 is obtained.
Example 5
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has 0.25um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S50 is obtained.
Example 6
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has 0.3um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S60 is obtained.
Example 7
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has a 0.35um passivation layer made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the size of the battery is 35 × 170 × 220, so that the battery product S70 is obtained.
Example 8
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (100 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder has 0.4um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S80 is obtained.
Example 9
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (the passivation lithium powder with the thickness of 200um is coated on the diaphragm by adopting a transfer coating mode, the outer layer of the lithium powder is provided with a 0.05um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured by a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S90 is obtained.
Example 10
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basal membrane + passivation lithium powder coating (the passivation lithium powder with the thickness of 300um is coated on the diaphragm by adopting a transfer coating mode, the outer layer of the lithium powder is provided with a 0.05um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured by a lamination process, and the battery size is 35 x 170 x 220, so that the battery product S100 is obtained.
Example 11
The positive electrode adopts lithium iron phosphate, the negative electrode adopts artificial graphite, the electrolyte adopts commercial electrolyte (30% EC: EMC 30%: DMC 20%: VC 2%: FEC 2%: LiPF 616%), the battery diaphragm adopts 14um PP basement membrane + passivation lithium powder coating (400 um passivation lithium powder is coated on the diaphragm in a transfer coating mode, the outer layer of the lithium powder is provided with a 0.05um passivation layer, the passivation layer is made of lithium fluoride), the 100Ah soft package battery is manufactured through a lamination process, and the size of the battery is 35 x 170 x 220, so that the battery product S110 is obtained.
Performance testing
1. Battery charge and discharge capacity test
The cell is limited and clamped by using the steel clamping plate before testing, the initial pressure is 200N, and the patch type pressure sensor is arranged between the battery and the clamping plate. And carrying out 1C/1C charge-discharge cycle test on the battery cell at a constant temperature of 25 ℃, wherein the cycle test voltage range is 2.5-3.65V. When the battery capacity attenuation curve is suddenly changed, the pressure value of the battery cell at the inflection point of the curve is recorded, and the pressure is calculated and used as the rupture pressure threshold of the passivation layer.
And (4) before testing, the electric core is limited and clamped by using a steel clamping plate, and the initial pressure is 200N. At 25 +/-2 ℃ environment:
1) standing for 30 min;
2) discharging the battery by 100A current, and cutting off the voltage by 2.5V;
3) standing for 30 min;
4) charging the battery by 100A current, and cutting off the voltage by 3.65V;
5) standing for 30 min;
6) and (5) cycling the steps 2-5 until the discharge capacity of the battery is reduced to be less than 70% of the initial discharge capacity, and stopping testing.
Table 1 example and comparative example battery charge and discharge capacity test
As can be seen from the charge and discharge capacity tests of the batteries of the examples and comparative examples in table 1, in examples 1 to 8, when the internal pressure of the battery reaches the threshold of the rupture pressure of the passivation layer, the lithium powder is released to supplement lithium, and the cycle tendency of the battery is obviously changed. When the thickness of the lithium fluoride passivation layer is gradually increased, the threshold value of the rupture pressure of the passivation layer is higher, so that the time points of lithium supplement action are different, and the effect of accurately supplementing lithium at fixed cycle turns can be achieved according to the adjustment of the thickness of the passivation layer. It can be seen from examples 1 and 9-11 that, when the thicknesses of the passivation layers are the same, the rupture pressure thresholds of the passivation layers are the same, the time points of the lithium supplement effect are also the same, and when the thicknesses of the lithium supplement coatings are thicker and thicker, the charge-discharge capacity retention rate of the battery is higher and higher, which proves that the lithium supplement coatings exert obvious effects on increasing the electric capacity of the battery and prolonging the service life of the battery.
To sum up, the technical scheme of this application is through at lithium powder surface cladding passivation layer, and the lithium material is mended in the preparation, will mend the lithium material and bond on the basement membrane surface, forms the battery diaphragm, and then prepare into the lithium cell. The inside pressure that produces of battery can cause the passivation layer to break and release lithium powder wherein, and then mend the lithium to the battery, compares in prior art and only once only mends lithium in charging for the first time, and the scheme of this application can realize the accurate lithium of meneing to the battery full life cycle, and fine increase battery capacity prolongs the life of battery, and reduction in production cost has enlarged the application range of lithium cell, provides more references to the wide use of lithium cell.
The above are only preferred embodiments of the present invention, and do not limit the scope of the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (10)
1. The battery diaphragm is characterized by comprising a base film, wherein a lithium supplement coating is arranged on at least one side surface of the base film in a stacking mode, the lithium supplement coating is made of a lithium supplement material, the lithium supplement material comprises lithium powder and a passivation layer coated on the lithium powder, and the passivation layer is arranged to break under the action of external force to expose the lithium powder.
2. The battery separator of claim 1, wherein the material of the passivation layer comprises a metal inorganic salt.
3. The battery separator of claim 2 wherein the passivation layer is lithium fluoride.
4. The battery separator of claim 1, wherein the thickness of the passivation layer is 10-800 nm; and/or the presence of a gas in the gas,
the average particle diameter of the lithium powder is 20-80 μm.
5. The battery separator of claim 1 in which the lithium supplement coating has a thickness of 25 to 100 μm.
6. The battery separator according to claim 1, wherein the mass ratio of the lithium powder to the passivation layer is 100: (0.5-5).
7. A method for preparing a battery separator as claimed in any one of claims 1 to 6, comprising the steps of:
coating a passivation layer on the surface of the lithium powder to obtain a lithium supplement material;
and uniformly mixing the lithium supplement material, the binder and the solvent to obtain slurry, attaching the slurry to one side surface of the base film, and drying to prepare the battery diaphragm.
8. The method of making a battery separator according to claim 7, wherein the binder comprises at least one of polytetrafluoroethylene, polyacrylate, polyurethane, polyethylene glycol, polyethylene oxide, and epoxy.
9. The method for preparing a battery separator according to claim 7, wherein the step of coating a passivation layer on the surface of the lithium powder to obtain the lithium supplement material comprises:
uniformly mixing lithium powder and a solvent, heating to 82-88 ℃, adding a fluorine source, sealing, stopping heating, continuously stirring for 2-2.5 hours, filtering, and repeatedly washing with ethanol to obtain a lithium supplement material;
wherein the solvent comprises at least one of hexadecene, toluene, triethylene glycol dimethyl ether and N, N-dimethylformamide; and/or the presence of a gas in the gas,
the fluorine source comprises at least one of perfluoroethane, perfluoropropane, perfluorobutane, perfluorobutylsulfonyl fluoride, perfluoroethylsulfonyl fluoride, perfluorooctylsulfonyl fluoride, perfluorooctanoic acid, perfluoroheptanoic acid, perfluorononanoic acid, ethyl trifluoroacetate, methyl trifluoroacetate, trifluoroethyl methacrylate and ethyl pentachloropropionate.
10. A lithium battery comprising a positive electrode, a negative electrode, and a battery separator between the positive electrode and the negative electrode, wherein the battery separator is the battery separator according to any one of claims 1 to 6.
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