CN115395081A - Secondary battery and power utilization device - Google Patents

Secondary battery and power utilization device Download PDF

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Publication number
CN115395081A
CN115395081A CN202211076998.4A CN202211076998A CN115395081A CN 115395081 A CN115395081 A CN 115395081A CN 202211076998 A CN202211076998 A CN 202211076998A CN 115395081 A CN115395081 A CN 115395081A
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pole piece
positive
secondary battery
positive electrode
active material
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游坤
华秉杨
邹武元
焦叶辉
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
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    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
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    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
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    • 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
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • 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

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Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a secondary battery which comprises a positive pole piece and a negative pole piece, wherein the positive pole piece comprises a positive active substance, the positive active substance is of an olivine structure, and the positive pole piece and the negative pole piece meet the relation: 0.25-plus PDc-Tc-plus-0.42; 0.1-plus PDa-plus Ta-plus 0.2;0.75< (CB-1.1)/VC <1.5; wherein, PDc is the compacted density of the positive pole piece; PDa is the compacted density of the negative pole piece; tc is the thickness of the positive pole piece; ta is the thickness of the positive pole piece; CB is the excess ratio of the negative electrode capacity to the positive electrode capacity per unit area; VC is the content of vinylene carbonate in the electrolyte as film forming additive of lithium battery electrolyte. The design of the positive and negative pole pieces and the addition of VC are controlled, so that the lithium iron phosphate battery has high energy density, long cycle life and long service life.

Description

Secondary battery and power utilization device
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a secondary battery and an electric device.
Background
The lithium ion battery has the outstanding advantages of high energy density, long cycle life, high working voltage, low self-discharge rate, environmental friendliness and the like, and can be used as an ideal power supply for multipurpose power supply. The lithium iron phosphate battery is a mainstream lithium battery, and has more prominent cost advantage, more excellent safety performance and longer cycle life compared with lithium batteries adopting other anode materials, such as ternary lithium batteries and lithium cobalt oxide batteries. The lithium iron phosphate battery has wide application due to the outstanding advantages, when the lithium iron phosphate battery is used for a passenger vehicle, the designed pole piece and the battery prepared by controlling the VC content can meet the use requirement of the passenger vehicle for 8 to 10 years only by the cycle life of 2000 to 3000 times, and the lithium battery of the passenger vehicle needs higher energy density, so the balance of the energy density and the cycle life is always considered in the pole piece design and the VC addition.
Because of its outstanding cost advantage, lithium iron phosphate batteries are also used in the fields of energy storage and construction vehicles, commercial vehicles, etc., which are prioritized in that cost recovery or even profit is achieved in the whole battery life cycle, and therefore a 10-15 year life cycle and a 4000-6000 or even higher cycle life are often required, and these existing lithium iron phosphate batteries cannot have both high cycle life and energy density, and therefore a decision scheme is urgently needed.
Disclosure of Invention
The invention aims to: in view of the deficiencies of the prior art, a secondary battery having excellent energy density, cycle life and service life is provided.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a secondary battery, includes positive pole piece and negative pole piece, positive pole piece includes anodal active material, anodal active material is the olivine structure, positive pole piece and negative pole piece satisfy following relational expression:
0.25<PDc*Tc<0.42；0.1<PDa*Ta<0.2；0.75<(CB-1.1)/VC<1.5；
wherein, the PDc is the compacted density of the positive pole piece;
wherein PDa is the compacted density of the negative pole piece;
wherein Tc is the thickness of the positive pole piece;
wherein Ta is the thickness of the negative pole piece;
wherein CB is an excess ratio of the negative electrode capacity to the positive electrode capacity per unit area;
wherein VC is the content of vinylene carbonate serving as a film forming additive of the lithium battery electrolyte in the electrolyte.
Preferably, the positive electrode piece comprises a positive electrode current collector and a positive electrode active coating arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active coating comprises a positive electrode active substance, a conductive agent, a binder and a dispersing agent, and the weight part ratio of the positive electrode active substance to the conductive agent to the dispersing agent is (80-99).
Preferably, the chemical formula of the cathode active material is LiFe x M 1-x PO 4 Wherein M is one or a combination of more of Mg, ni, V and Mn, and x is more than 0 and less than 1.
Preferably, the surface of the positive electrode active material is coated with a carbon coating layer, and the particle size distribution of the positive electrode active material satisfies the following relation: 0.5 μm < Dc50<5 μm,1< (Dc 90-Dc 10)/Dc 50<8.
Preferably, the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active coating comprises a negative electrode active material, a conductive agent, a binder and a dispersing agent, and the weight part ratio of the negative electrode active material to the conductive agent to the dispersing agent is 85-99.
Preferably, the negative active material includes at least one of artificial graphite, natural graphite, a silicon simple substance, silicon oxide, a tin simple substance, and lithium titanate.
Preferably, the negative electrode active material is artificial graphite, and the particle size distribution satisfies the following relational expression: 3 μm < Da50<30 μm,0.5< (Da 90-Da 10)/Da 50<3.
Preferably, the secondary battery further comprises a separation film, electrolyte and a shell, wherein the separation film is used for separating the positive pole piece and the negative pole piece, and the shell is used for installing and packaging the positive pole piece, the negative pole piece, the separation film and the electrolyte.
Preferably, the compacted density PDc of the positive pole piece ranges from 2.2g/cm 3 <PDc<2.4g/cm 3 . The value range of the thickness Tc of the positive pole piece is 0.065mm<Tc<0.185mm。
Preferably, the value range of the compacted density PDa of the negative pole piece is 1.45g/cm 3 <PDa<1.6g/cm 3 The value range of the thickness Ta of the negative pole piece is 0.065mm<Ta<0.185mm。
Preferably, the value range of the CB is 1.12 < CB < 1.2.
Preferably, the value range of VC is 2% less than 8%.
The second purpose of the invention is: aiming at the defects of the prior art, the electric device is provided, and has good quality and service life.
In order to achieve the purpose, the invention adopts the following technical scheme:
an electric device includes the secondary battery.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, through controlling the design of the positive and negative pole pieces and the addition amount of VC, the lithium iron phosphate battery has longer cycle life and service life, and has the advantage of high energy density, so as to meet the increasing needs in the fields of energy storage, engineering vehicles, commercial vehicles and the like.
Detailed Description
The utility model provides a secondary battery, includes positive pole piece and negative pole piece, positive pole piece includes positive active material, positive active material is the olivine structure, positive pole piece and negative pole piece satisfy following relational expression:
0.25<PDc*Tc<0.42；0.1<PDa*Ta<0.2；0.75<(CB-1.1)/VC<1.5；
wherein, PDc is the compacted density of the positive pole piece;
wherein PDa is the compacted density of the negative pole piece;
wherein Tc is the thickness of the positive pole piece;
wherein Ta is the thickness of the negative pole piece;
wherein CB is an excess ratio of the negative electrode capacity to the positive electrode capacity per unit area;
wherein VC is the content of vinylene carbonate serving as a film forming additive of the lithium battery electrolyte in the electrolyte.
According to the invention, the design of the positive and negative pole pieces and the addition amount of VC are controlled, so that the lithium iron phosphate battery has longer cycle life and service life. The invention discloses a pole piece design of a lithium iron phosphate battery, which selects a lower compaction density, so that the structure of positive and negative pole pieces is more complete, a higher liquid retaining amount is ensured, the thicknesses of the corresponding positive and negative pole pieces are also in a preferred range, meanwhile, the design of a high CB value can ensure that the capacity is not reduced too early due to lithium precipitation in the circulation process, the film forming integrity of an SEI film in the circulation period is influenced due to too low VC content, so that the circulation performance is influenced, the negative graphite is excessively consumed due to too high VC content, so that the lithium precipitation is caused by the excessive and insufficient negative pole in the circulation period, the circulation life is also influenced, and therefore, the VC content under a specific CB value is also controlled in a reasonable range. Within the limited range, the battery has excellent cycle performance and can meet the increasingly high cycle requirements of energy storage, engineering vehicles and commercial vehicles.
Wherein, the thickness of the pole piece represented by Tc and Ta is the total thickness of the double-sided active substance coating layer after the thickness of the foil is removed.
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active coating disposed on at least one surface of the positive electrode current collector, and the positive electrode active coating includes a positive electrode active material, a conductive agent, a binder, and a dispersant. The weight part ratio of the positive electrode active material to the conductive agent binder to the dispersant is 80-99. Preferably, the weight ratio of the positive electrode active material, the conductive agent, the binder and the dispersant is 80-99. The conductive agent comprises one or more of Ketjen black, mesocarbon microbeads, activated carbon, graphite, conductive carbon black, acetylene black, carbon fibers, carbon nanotubes, graphene and the like; the binder comprises one or more of vinylidene fluoride, hexafluoropropylene, pentafluoropropene, tetrafluoropropene, trifluoropropene, perfluorobutene, hexafluorobutadiene, hexafluoroisobutylene, trifluoroethylene, chlorotrifluoroethylene and tetrafluoroethylene; the dispersant comprises one or more of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch and casein.
In some embodiments, the positive active material has a chemical formula of LiFe x M 1-x PO 4 Wherein M is one or a combination of more of Mg, ni, V and Mn, and x is more than 0 and less than 1. The lithium iron phosphate is subjected to element doping, so that the structural stability of the iron phosphate can be improved, the performance of the positive active material is improved, and the high cycle life is realized.
In some embodiments, the surface of the positive electrode active material is coated with a carbon coating layer, and the particle size distribution of the positive electrode active material satisfies the following relationship: 0.5 μm < Dc50<5 μm,1< (Dc 90-Dc 10)/Dc 50<8.
In the positive electrode active material D 50 If the porosity of the pole piece is too large, the compaction density is too low, and the capacity density is too low; d 50 If the porosity of the pole piece is too small, the compaction density is too high, the liquid retention performance of the pole piece is poor, the dynamic performance is poor, and the high-rate performance is poor; d 50 The pole piece in the range can simultaneously meet the requirements of high energy density and high rate performance. (Dc) 90 -Dc 10 )/Dc 50 Reacting positive active materialThe dispersion degree of the particle size distribution can influence the uniformity of the pores of the positive pole piece; if the particle size distribution of the positive electrode meets the relational expression, the pore size distribution of the positive electrode plate is more uniform, the battery consistency is better, and the electrochemical performance and the safety performance are good; if the particle size distribution of the positive electrode does not satisfy the relational expression, the pore size distribution of the positive electrode plate is uneven, the consistency of the battery is poor, and the electrochemical performance and the safety performance are poor. The carbon coating layer is arranged on the surface of the positive active material, so that the conductivity of the positive active material can be improved, and the particle size of the positive active material has certain fineness, so that the positive active material can be uniformly distributed in the positive plate, and the performance of the positive plate is better.
In some embodiments, the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active coating comprises a negative electrode active material, a conductive agent, a binder and a dispersing agent, and the weight ratio of the negative electrode active material, the conductive agent, the binder and the dispersing agent is 85-99. Preferably, the weight ratio of the negative electrode active material, the conductive agent, the binder and the dispersant is 80-99. The conductive agent comprises one or more of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube and graphene; the binder comprises one or more of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon; the dispersant comprises one or more of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch and casein.
In some embodiments, the negative active material includes at least one of artificial graphite, natural graphite, elemental silicon, silicon oxide, elemental tin, lithium titanate.
In some embodiments, the negative active material is artificial graphite, and the particle size distribution satisfies the following relationship: 3 μm < Da50<30 μm,0.5< (Da 90-Da 10)/Da 50<3.
In the negative electrode active material D 50 If the porosity of the pole piece is too large, the compaction density is too low, and the capacity density is too low; d 50 If the porosity of the pole piece is too small, the compaction density is too high, the liquid retention performance of the pole piece is poor, the dynamic performance is poor, and the high-rate performance is poor; d 50 The pole piece in the range can simultaneously meet the requirements of high energy density and high rate performance. (Da) 90 -Da 10 )/Da 50 The reaction is the dispersion degree of the particle size distribution of the negative active material, and the dispersion degree of the particle size distribution can influence the uniformity of the pores of the negative pole piece; if the particle size distribution of the negative electrode meets the relational expression, the pore size distribution of the pressure pole piece is more uniform, the battery consistency is better, and the electrochemical performance and the safety performance are good; if the particle size distribution of the negative electrode does not meet the relational expression, the pore size distribution of the negative electrode pole piece is uneven, the consistency of the battery is poor, and the electrochemical performance and the safety performance are poor.
In some embodiments, the secondary battery further includes a separator for separating the positive electrode sheet and the negative electrode sheet, an electrolyte, and a case for housing and encapsulating the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte. Wherein, the barrier film is one of polypropylene barrier film and polybutylene barrier film. The preparation method of the electrolyte comprises the steps of mixing EC, PC and DEC (1 6 Mixing uniformly, wherein LiPF 6 The concentration of (2) is 1.15mol/L. Fluoroethylene carbonate was added to the electrolyte in an amount of 3% based on the total weight of the electrolyte. The shell is made of stainless steel or aluminum plastic films.
In some embodiments, the compacted density PDc of the positive electrode sheet ranges from 2.2g/cm 3 <PDc<2.4g/cm 3 . The value range of the compacted density PDc of the positive pole piece can be 2.2g/cm 3 <PDc<2.4g/cm 3 、2.2g/cm 3 <PDc<2.25g/cm 3 、2.25g/cm 3 <PDc<2.4g/cm 3 。
In some embodiments, the compacted density of the negative electrode sheet, PDa, ranges from 1.45g/cm 3 <PDa<1.6g/cm 3 . The value range of the compacted density PDa of the negative pole piece is 1.45g/cm 3 <PDa<1.5g/cm 3 、1.5g/cm 3 <PDa<1.55g/cm 3 、1.55g/cm 3 <PDa<1.6g/cm 3 。
In some embodiments, the thickness Tc of the positive pole piece ranges from 0.065mm and Tc plus 0.185mm. The value range of the thickness Tc of the positive pole piece is 0.065mm & lt Tc 0.090mm, 0.090mm & lt Tc & lt 0.100mm and 0.100mm & lt Tc & lt 0.185mm.
In some embodiments, the thickness Ta of the negative electrode sheet ranges from 0.065mm and Ta < -0.185mm. The value range of the thickness Ta of the negative pole piece is 0.065mm-Ta-less 0.090mm, 0.090mm-Ta-less 0.100mm and 0.100mm-Ta-less 0.185mm.
In some embodiments, the value range of the CB is 1.12 < CB < 1.2. The value range of the CB is less than 1.12, 1.15 and 1.16, and less than 1.18 and 1.18, respectively.
In some embodiments, the VC range is less than 2% and less than 8%. The value ranges of VC are 2% of VC < 4%, 4% of VC < 6% and 6% of VC < 8%.
In some embodiments, the value of PDc is 2.2g/cm 3 、2.23g/cm 3 、2.25g/cm 3 、2.28g/cm 3 、2.29g/cm 3 、2.3g/cm 3 、2.35g/cm 3 、2.37g/cm 3 、2.39g/cm 3 、2.4g/cm 3 The value of PDa is 1.45g/cm 3 、1.48g/cm 3 、1.49g/cm 3 、1.52g/cm 3 、1.53g/cm 3 、1.57g/cm 3 、1.59g/cm 3 、1.6g/cm 3 (ii) a Tc is 0.065mm, 0.068mm, 0.072mm, 0.085mm, 0.091mm, 0.098mm, 0.1mm, 0.13mm, 0.15mm, 0.16mm, 0.17mm, 0.175mm, 0.18mm, 0.185mm. Taking of TaThe values are 0.065mm, 0.068mm, 0.072mm, 0.085mm, 0.091mm, 0.098mm, 0.1mm, 0.13mm, 0.15mm, 0.16mm, 0.17mm, 0.175mm, 0.18mm, 0.185mm. The values of CB are 1.122, 1.124, 1.126, 1.128 and 1.129.VC is selected from 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.075, 0.078 and 0.079.
In some embodiments, the separator may be any material suitable for use in lithium ion battery separators in the art, for example, may be a combination including, but not limited to, one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte 6 And/or LiBOB; or LiBF used in low-temperature electrolyte 4 、LiBOB、LiPF 6 At least one of (a); also can be LiBF adopted in anti-overcharging electrolyte 4 、LiBOB、LiPF 6 At least one of LiTFSI; may also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, controlling H in electrolytes 2 At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
An electric device includes the secondary battery. The power utilization devices of the present application may include, but are not limited to: a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting apparatus, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, a lithium ion capacitor, or the like.
The present invention will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
1. Preparing a positive plate: mixing the positive electrode material powder, the conductive carbon black, the binder and the dispersant PVDF in a ratio of 97. Coating the slurry on a current collector, carrying out air-blast drying at the temperature of 80-120 ℃, and finally carrying out cold pressing and slitting to obtain the positive pole piece for later use.
2. Preparing a negative plate: mixing artificial graphite powder, conductive carbon black, a binder SBR and a dispersant CMC according to a ratio of 96.7. Coating the slurry on a current collector, carrying out air-blast drying at 80-120 ℃, and finally carrying out cold pressing and slitting to obtain a negative pole piece for later use.
3. Preparing an electrolyte:
mixing lithium hexafluorophosphate (LiPF) 6 ) The electrolyte solution was dissolved in a mixed solvent of dimethyl carbonate (DEC), ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC) (the mass ratio of the three was 3.
4. Preparing a battery: the positive plate, the polypropylene isolating film and the negative plate are wound together to form a winding core, wherein the isolating film can completely wrap the positive electrode or the negative electrode so as to prevent the positive electrode or the negative electrode from being in direct contact with each other to cause short circuit. And (4) wrapping the winding core by using an aluminum plastic film, and injecting electrolyte into the winding core. And finally, obtaining the battery product after the processes of formation, capacity grading and the like and complete sealing.
The positive electrode sheet and the negative electrode sheet were prepared according to example 1 and the raw materials with different material characteristics in the following table 1, and set with different porosities and thicknesses to obtain examples 2 to 21, and the gram capacity test of the sheet and the cycle number test of the full cell 2C charge/2C discharge charge/discharge cycle were performed, and the test results are recorded in table 2.
TABLE 1
D50/μm (D90-D10)/D50
Lithium iron phosphate 1 1.08 1.83
Lithium iron phosphate 2 1.14 1.96
Lithium iron phosphate 3 1.59 2.64
Artificial graphite 1 12.31 1.36
Artificial graphite 2 10.88 1.25
Artificial graphite 3 14.97 1.68
The cycle test method is to prepare a soft package lithium ion battery with the capacity of 10Ah for test, carry out charge-discharge cycle with the current of 10A charge/10A discharge in the voltage range of 2.5V-3.65V, and count the cycle number when the capacity retention rate of the battery is reduced to 80%.
TABLE 2
Figure BDA0003831931240000091
Figure BDA0003831931240000101
As can be seen from table 2, the lithium iron phosphate battery has the advantages of longer cycle life and service life by controlling the design of the positive and negative electrode plates and the addition of VC, and has high energy density, so as to meet the increasing needs of the fields of energy storage, engineering vehicles, commercial vehicles, and the like. Specifically, as a result of comparison in examples 1 to 9, when the positive electrode active material was lithium iron phosphate 1 and the negative electrode active material was artificial graphite 1/2/3, the secondary battery satisfied the following relationship: 0.25 plus PDc plus Tc plus 0.42; 0.1-plus PDa-plus Ta-plus 0.2;0.75< (CB-1.1)/VC <1.5, and the values of (CB-1.1)/VC are all 1, the number of cycle turns obtained by the cyclic electric test is more than 4321 turns, the highest cycle turn is embodiment 4, and is as high as 4566 turns, and the cycle performance is better. From comparison of examples 10 to 12, it can be seen from examples 11 and 12 that when the value (CB-1.1)/VC does not satisfy the relationship, the cycle performance of the secondary battery is affected, and the number of cycles is reduced; further, as can be seen from example 10, when the content of vinylene carbonate as a film-forming additive was as low as 0.01 and the value (CB-1.1)/VC does not satisfy the relationship, the cycle performance of the manufactured secondary battery was worse, the content of vinylene carbonate as a film-forming additive was insufficient, resulting in instability of SEI film, and it was easy to break and damage lithium after many cycles, thereby affecting cycle life. As can be seen from examples 13 to 15, the secondary battery using lithium iron phosphate 2 for the positive electrode and artificial graphite 2 for the negative electrode has better performance, and the average number of cycles is 6400 cycles, which is advantageous over using lithium iron phosphate 1 for the positive electrode. From examples 17 and 18, it can be seen that when the (CB-1.1)/VC value does not satisfy the relationship, and lithium iron phosphate 3 is used for the positive electrode and artificial graphite 3 is used for the negative electrode, the performance of the prepared secondary battery is reduced; from example 16, it can be seen that when the excess ratio CB of the negative electrode capacity per unit area to the positive electrode capacity is not in the range of 1.12 to 1.2 and the (CB-1.1)/VC value does not satisfy the relational expression, the performance of the prepared secondary battery is worse and the cycle life is reduced to 3614 cycles. From examples 19 to 21, it was found that when lithium iron phosphate 3 was used for the positive electrode and artificial graphite 3 was used for the negative electrode, the prepared secondary battery had better cycle performance, and the cycle number was as high as 5387 cycles.
Variations and modifications to the above-described embodiments may become apparent to those skilled in the art to which the invention pertains based upon the disclosure and teachings of the above specification. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious modifications, substitutions or alterations based on the present invention will fall within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (13)

1. The utility model provides a secondary battery, its characterized in that includes positive pole piece and negative pole piece, positive pole piece includes positive active material, positive active material is olivine structure, positive pole piece and negative pole piece satisfy following relational expression:
0.25<PDc*Tc<0.42；0.1<PDa*Ta<0.2；0.75<(CB-1.1)/VC<1.5；
wherein, PDc is the compacted density of the positive pole piece;
wherein PDa is the compacted density of the negative pole piece;
wherein Tc is the thickness of the positive pole piece;
wherein Ta is the thickness of the negative pole piece;
wherein CB is an excess ratio of the negative electrode capacity to the positive electrode capacity per unit area;
wherein VC is the content of vinylene carbonate serving as a film forming additive of the lithium battery electrolyte in the electrolyte.
2. The secondary battery according to claim 1, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active coating disposed on at least one surface of the positive electrode current collector, the positive electrode active coating comprises a positive electrode active material, a conductive agent, a binder and a dispersing agent, and the weight parts ratio of the positive electrode active material, the conductive agent, the binder and the dispersing agent is (80-99).
3. The secondary battery according to claim 1, wherein the chemical formula of the positive electrode active material is LiFe x M 1-x PO 4 Wherein M is one or a combination of more of Mg, ni, V and Mn, and x is more than 0 and less than 1.
4. The secondary battery according to claim 1, wherein the surface of the positive electrode active material is coated with a carbon coating layer, and the particle size distribution of the positive electrode active material satisfies the following relationship: 0.5 μm < Dc50<5 μm,1< (Dc 90-Dc 10)/Dc 50<8.
5. The secondary battery of claim 1, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating disposed on at least one surface of the negative electrode current collector, the negative electrode active coating comprises a negative electrode active material, a conductive agent, a binder and a dispersing agent, and the weight ratio of the negative electrode active material, the conductive agent, the binder and the dispersing agent is 85-99.
6. The secondary battery according to claim 5, wherein the negative electrode active material includes at least one of artificial graphite, natural graphite, elemental silicon, silicon oxide, elemental tin, and lithium titanate.
7. The secondary battery according to claim 5, wherein the negative electrode active material is artificial graphite, and a particle size distribution satisfies the following relational expression: 3 μm < Da50<30 μm,0.5< (Da 90-Da 10)/Da 50<3.
8. The secondary battery of claim 1, further comprising a separator for separating the positive electrode sheet from the negative electrode sheet, an electrolyte, and a case for housing and encapsulating the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte.
9. The secondary battery according to claim 1, wherein the compacted density PDc of the positive electrode sheet has a value in a range of 2.2g/cm 3 <PDc<2.4g/cm 3 The value range of the thickness Tc of the positive pole piece is 0.065mm<Tc<0.185mm。
10. The secondary battery of claim 1, wherein the compacted density of the negative electrode sheet, PDa, ranges from 1.45g/cm 3 <PDa<1.6g/cm 3 The value range of the thickness Ta of the negative pole piece is 0.065mm<Ta<0.185mm。
11. The secondary battery of claim 1, wherein the value range of the CB is less than 1.12 < CB < 1.2.
12. The secondary battery of claim 1, wherein the value range of VC is less than 2% in VC < 8%.
13. An electric device comprising the secondary battery according to any one of claims 1 to 12.
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