CN111463433B - Ultrahigh-rate lithium iron phosphate battery and preparation method thereof - Google Patents

Ultrahigh-rate lithium iron phosphate battery and preparation method thereof Download PDF

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CN111463433B
CN111463433B CN202010287491.8A CN202010287491A CN111463433B CN 111463433 B CN111463433 B CN 111463433B CN 202010287491 A CN202010287491 A CN 202010287491A CN 111463433 B CN111463433 B CN 111463433B
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iron phosphate
lithium iron
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battery
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CN111463433A (en
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邓亚凯
李亚玲
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Luoyang Chaote Power Technology Co ltd
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Luoyang Chaote Power Technology 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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • 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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • 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
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to an ultra-high-rate lithium iron phosphate battery and a preparation method thereof. The ultra-high-rate lithium iron phosphate battery comprises at least two monomer battery cells which are connected in parallel and/or in series, wherein the monomer battery cells are all-lug winding type battery cells, positive active substances of the monomer battery cells are nano lithium iron phosphate, negative active substances of the monomer battery cells are intermediate-phase graphite and soft carbon coated graphite, and the mass ratio of the intermediate-phase graphite to the soft carbon coated graphite is (2.5-3.5) - (6.5-7.5). The lithium iron phosphate battery has the energy density of over 85Wh/Kg on the premise of ensuring safety and stability, and can continuously discharge at the ultrahigh discharge rate of 10-40C under the safe working condition and perform pulse cycle discharge at the ultrahigh discharge rate of 40-70C.

Description

Ultrahigh-rate lithium iron phosphate battery and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to an ultra-high-rate lithium iron phosphate battery and a preparation method thereof.
Background
The lithium ion battery has high specific energy and specific power and high response speed, and is widely applied to the fields of electric automobiles, electronic equipment and the like. High-power equipment often needs the power supply system of high-rate discharge in the operation process, but lithium ion battery in traditional battery energy storage system all has the problem that the rate of discharge is lower. Therefore, in order to meet the use requirements of high-power equipment, a large number of lithium ion batteries are required to be connected in series and in parallel for use, so that the volume and the weight of the storage battery energy storage system are increased, and the production and transportation costs of the storage battery energy storage system are improved. Meanwhile, due to the individual difference of the lithium ion batteries, the electrical properties of the lithium ion batteries are not uniform, and the voltage difference between the lithium ion batteries is larger and larger in the continuous charging and discharging process when a large number of lithium ion batteries are connected in series and in parallel for use, so that the charging and discharging properties of the storage battery energy storage system are influenced, and the service life of the storage battery energy storage system is shortened.
Disclosure of Invention
The invention aims to provide an ultra-high-rate lithium iron phosphate battery which has higher discharge rate.
The invention also aims to provide a preparation method of the ultrahigh-rate lithium iron phosphate battery.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides an ultra-high magnification lithium iron phosphate battery, includes two at least parallelly connected and/or monomer electric cores of establishing ties, monomer electric core is full utmost point ear coiling formula electricity core, the anodal active material of monomer electric core is nanometer lithium iron phosphate, and the negative pole active material is mesophase graphite and soft carbon cladding graphite, and the mass ratio of mesophase graphite and soft carbon cladding graphite is (2.5 ~ 3.5): (6.5-7.5).
The invention optimizes the discharge rate performance of the lithium ion battery by optimizing the structure of the lithium iron phosphate battery and the positive and negative active substances. The lithium iron phosphate battery has the energy density of over 85Wh/Kg on the premise of ensuring safety and stability, and can continuously discharge at the ultrahigh discharge rate of 10-40C under the safe working condition and perform pulse cycle discharge at the ultrahigh discharge rate of 40-70C. When the lithium iron phosphate battery is used as an energy storage system of high-power equipment, the requirement of the energy storage system on discharge power under the constraints of volume and weight is met.
The ultrahigh-rate lithium iron phosphate battery comprises a positive pole column and a negative pole column, wherein the positive pole column and the negative pole column are connected with positive and negative full lugs of a single battery cell through connecting sheets. Preferably, the connecting sheet connected with the positive pole post and the positive full pole lug of the monomer battery cell is an aluminum current collector with the thickness of 1-1.5 mm and the width of 8-12 mm, and the connecting sheet connected with the negative pole post and the negative full pole lug of the monomer battery cell is a copper current collector with the thickness of 0.8-1.2 mm and the width of 8-12 mm. The connecting sheet has a larger cross-sectional area and stronger overcurrent capacity.
The connecting sheet is U-shaped, the U-shaped connecting sheet has an opening, the full pole ear of the single battery cell is inserted into the U-shaped connecting sheet through the opening, the single battery cell is divided into two groups, and the two groups of single battery cells are respectively connected with the inner side surfaces of the corresponding U-shaped connecting sheets. When the single battery cores are divided into two groups, the single battery cores are grouped according to the number of the single battery cores, and the single battery cores can be grouped in an average mode or can be grouped randomly.
The weight of the battery is further controlled by controlling the number of the single battery cores, preferably, the number of the single battery cores is four, and the two groups are formed after two single battery cores are connected in parallel. The concrete connection mode is as follows: firstly, connecting two of 4 single battery cores in parallel to form two groups of large battery cores, and then respectively connecting the two large battery cores with the inner side surfaces of the connecting pieces, namely connecting the two large battery cores in parallel through the connecting pieces.
Preferably, the connection mode is high-molecular diffusion welding. Researches show that the mode of adopting high-molecular diffusion welding is firm and reliable, and the internal resistance can be reduced, so that the temperature rise in the charging and discharging process is reduced while the multiplying power performance of the lithium iron phosphate battery is ensured. Tests show that the temperature rise of the shell of the lithium iron phosphate battery is less than 25 ℃ when 55C pulse discharge occurs.
In the lithium iron phosphate battery, a single battery cell comprises a diaphragm, and the diaphragm is a diaphragm commonly used for lithium ion batteries. Preferably, the separator used is a polystyrene separator or a polypropylene separator provided with a coating. Wherein the porosity of the diaphragm is 40-50%, and the thickness is 12-16 μm. The coating is one or more of a ceramic coating, a water-based coating and a polyvinylidene fluoride coating.
The lithium iron phosphate battery also comprises electrolyte, wherein the electrolyte comprises a flame retardant such as trifluoroethyl phosphite (TFEP), vinylidene carbonate and the like so as to ensure the safety of the battery, and the mass of the flame retardant is 0.2-0.5% of the mass of the electrolyte. The electrolyte comprises a substance capable of improving the cycle performance of the battery, such as Vinylene Carbonate (VC) and LiPO2F2Etc., the mass of which is 0.2 to 1% of the mass of the electrolyte.
The lithium salt in the electrolyte is LiPF6、LiBF4、LiBOB、LiODFB、LiTFSI、Li2One or more of DFB, LiFSI and the like, and the concentration of lithium salt in the electrolyte is 0.6-1.5M. The solvent in the electrolyte is one or more of Ethylene Carbonate (EC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC) and Ethyl Propionate (EP).
Preferably, the preparation method of the lithium iron phosphate battery adopts the technical scheme that:
the preparation method of the ultra-high-rate lithium iron phosphate battery comprises the following steps:
winding the diaphragm, the positive plate and the negative plate into a monomer battery cell in a full-tab winding manner; the positive plate is prepared by the following method: mixing a conductive agent and a dispersing agent in a first solvent to obtain first premixed conductive slurry; mixing the first conductive slurry with a positive active substance to obtain positive slurry; then coating the positive electrode slurry on the surface of a positive electrode base material to obtain the positive electrode slurry; the negative plate is prepared by the following method: mixing a conductive agent and a dispersing agent in a second solvent to obtain second premixed conductive slurry; mixing the second conductive slurry with a negative electrode active material to obtain negative electrode slurry; and coating the negative electrode slurry on the surface of a negative electrode substrate to obtain the negative electrode material.
The positive plate and the negative plate are prepared by mixing the conductive agent and the dispersing agent to form premixed slurry, so that the conductive agent is more uniformly dispersed in the positive plate and the negative plate, a complete and uniform conductive network can be formed, and the rate capability of the battery is improved.
In the preparation method of the ultra-high-rate lithium iron phosphate battery, the winding mode of winding the full tabs is that the two sides of the positive plate and the negative plate are left blank to be used as the tabs, and the tabs are not cut before winding.
The performance of the lithium iron phosphate battery is optimized by adjusting the content of active substances in the positive plate, and preferably, the mass of the positive active substances in the positive slurry accounts for 92-94% of the total mass of the positive active substances, the conductive agent and the dispersing agent. Preferably, the particle size of the positive electrode active material is 150 to 200 nm. The positive active substance is prepared by a hydrothermal method and then crushed.
Preferably, the mass percentage of the negative electrode active material in the solid components contained in the negative electrode slurry is 92-96%, and the solid components include the negative electrode active material, a conductive agent and a dispersing agent.
In the lithium iron phosphate battery, the first solvent and the second solvent used in the preparation process of the anode slurry and the cathode slurry are common solvents in the prior art. Preferably, the first solvent is N-methylpyrrolidone (NMP) and the second solvent is water.
In order to improve the uniform mixing degree of the conductive agent and the dispersing agent, the mass ratio of the conductive agent to the dispersing agent is preferably (3-4): 1. The conductive agent is one or more of carbon black, carbon nano tubes, carbon fibers and graphene. The used dispersant is a dispersant commonly used in the preparation of anode and cathode slurry in the prior art.
In the lithium iron phosphate battery, the anode substrate used by the anode plate is an aluminum foil with a functional coating, such as a carbon-coated aluminum foil, and the cathode substrate used by the cathode plate is a copper foil with a functional coating.
Drawings
Fig. 1 is a schematic structural front view of an ultra-high rate lithium iron phosphate battery according to embodiment 1 of the present invention;
fig. 2 is a schematic structural side view of an ultra-high rate lithium iron phosphate battery according to example 1 of the present invention;
FIG. 3 is a graph of capacity retention ratio versus voltage of batteries of example 1 and comparative example 2 of the present invention;
FIG. 4 is a graph of discharge cutoff voltage during a 55C rate pulse duty cycle for a battery of example 1 of the present invention;
fig. 5 is a case temperature curve during pulse discharge at 55C rate for the battery of example 1 of the present invention;
reference numerals: 1-flame-retardant plastic cover plate, 2-aluminum pole, 3-polymer diffusion welding area, 4-positive pole connecting sheet, 5-negative pole connecting sheet, 6-battery core, 7-shell, 8-positive pole lug and 9-negative pole lug.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
Embodiment of ultra-high rate lithium iron phosphate battery
Example 1
The ultra-high-rate lithium iron phosphate battery of the embodiment has a structure as shown in fig. 1, and includes a casing 7 with openings at two ends, flame-retardant plastic cover plates 1 respectively arranged at two ends of the casing 7 and used for sealing the openings, and a battery core 6, a positive connecting sheet 4, a negative connecting sheet 5 and electrolyte arranged in the casing 7.
The battery cell 6 is composed of 4 single battery cells, each single battery cell is formed by winding a full lug, and the 4 single battery cells are connected in parallel to form two groups of large battery cells.
The positive connecting sheet 4 and the negative connecting sheet 5 are both U-shaped and provided with an opening end and a closing end, the connecting sheets are inserted into full lugs of the battery cell 5 from the opening end, positive lugs 8 of two groups of large battery cells forming the battery cell 5 are respectively welded with corresponding inner side surfaces of the positive connecting sheet 4 (the structure that the positive lugs 8 of the battery cell are welded with the positive connecting sheet 4 is shown in figure 2), and negative lugs 9 are respectively welded with corresponding inner side surfaces of the negative connecting sheet 5, so that a rectangular welding area 3 is formed; the closed end of the connecting sheet is welded with the positive and negative aluminum poles 2 arranged on the flame-retardant plastic cover plate 1, and the welding adopts macromolecule diffusion welding. The positive connecting sheet 4 welded to the positive tab 8 of the battery cell 6 is made of aluminum (with a width of 12mm and a thickness of 1.5mm), the negative connecting sheet 5 welded to the negative tab of the battery cell 6 is made of copper (with a width of 12mm and a thickness of 1.2mm), and the width of the connecting sheet is greater than that of the tab.
The monomer battery core is formed by winding a positive plate, a diaphragm and a negative plate in a full-lug mode, wherein the positive active material is nano lithium iron phosphate, the negative active material is intermediate phase graphite and soft carbon coated artificial graphite (wherein the soft carbon coated artificial graphite is purchased from fir company Limited, model CP7-M), and the mass ratio of the intermediate phase graphite to the soft carbon coated graphite is 3: 7; the separator was a PP separator 12 μm thick coated on both sides with a ceramic coating of 2 μm, wherein the separator thickness did not include the coating thickness.
The solvent of the electrolyte in the ultra-high-rate lithium iron phosphate battery comprises the following components in percentage by volume: 20% EC, 20% DMC, 30% EMC and 30% EP; the lithium salt being LiPF6(concentration 1.4M). TFEP with the mass percent of 0.5% and VC with the mass percent of 1% are added into the electrolyte.
Second, example of method for manufacturing ultra-high rate lithium iron phosphate battery
Example 2
The battery prepared by the method for preparing the ultra-high-rate lithium iron phosphate battery corresponds to the lithium battery in the embodiment 1, and specifically comprises the following steps:
(1) dispersing 700g of carbon nano tube, 300g of SP and 250g of PVDF in 10kg of solvent NMP, stirring at a rotation speed of 4000r/min for 3h to obtain a first premixed conductive slurry, and then mixing the first conductive slurry with lithium iron phosphate and PVDF serving as dispersing agents, wherein the particle sizes of the lithium iron phosphate, the dispersing agents and the PVDF serving as conductive agents are 150-200 nm, so as to obtain anode slurry (in the total mass of the lithium iron phosphate, the dispersing agents and the conductive agents, the proportion of the lithium iron phosphate is 93%, the proportion of the conductive agents is 4%, and the proportion of the dispersing agents is 3%); coating the positive electrode slurry on the surface of a positive electrode substrate (the positive electrode substrate is an aluminum foil with the thickness of 20 microns, carbon layers with the thickness of 1 micron are coated on both sides of the positive electrode substrate, the thickness of the aluminum foil does not include the thickness of the carbon layers), leaving white at one end during coating, and drying to obtain a positive electrode plate;
(2) the negative plate is prepared by the following method: dispersing 700g of carbon nanotubes, 300g of SP and 250g of CMC in 10kg of water, stirring for 3 hours at the rotating speed of 4000r/min to obtain a first premixed conductive slurry, and then stirring and mixing a second conductive slurry with a negative electrode active substance (a mixture of mesophase graphite and soft carbon coated artificial graphite, the ratio of which is 3:7), a dispersant CMC, a binder SBR and solvent water to obtain a negative electrode slurry (in the total amount of the negative electrode active substance, the dispersant, the binder and the conductive agent, the proportion of the negative electrode active substance is 94%, the proportion of the conductive agent is 3%, the proportion of the dispersant is 1%, and the proportion of the binder is 2%); coating the negative electrode slurry on the surface of a negative electrode substrate (the negative electrode substrate is a copper foil with the thickness of 10 microns, both sides of the negative electrode substrate are coated with carbon layers with the thickness of 1 micron, and the thickness of the copper foil does not include the thickness of the carbon layers), and leaving white one end when coating to obtain a negative electrode sheet;
(3) winding a diaphragm, a positive plate, a diaphragm and a negative plate in sequence to form a single cell, and preparing 4 single cells (wherein a positive blank part and a negative blank part are respectively a positive lug and a negative lug); then welding the blank parts of the positive plates of the two monomer battery cores together in a polymer diffusion welding mode, and welding the blank parts of the negative plates together in a polymer diffusion welding mode to obtain a large battery core; welding the other two single battery cores together in the same way to obtain another large battery core;
(4) welding the tops of the positive and negative U-shaped connecting sheets with the lower parts of the positive and negative poles respectively in a polymer diffusion welding mode, welding the positive and negative full lugs of the two large cells with the positive and negative connecting sheets hanging down from the cover plate respectively in a polymer diffusion welding mode to obtain a complete cell, performing insulation protection treatment on the outer layer of the cell, then filling the cell into a shell, connecting the shell with the gap of the cover plate together in a laser welding mode, injecting electrolyte into the obtained semi-finished battery, forming the battery into a constant volume, and finally coating a layer of insulation protection film on the outer layer of the shell to obtain the battery.
Third, comparative example section
Comparative example 1
The lithium ion battery of the comparative example is basically the same as the ultra-high-rate lithium iron phosphate battery in example 1, and the difference is only that: the welding method is ultrasonic welding.
Comparative example 2
The lithium ion battery of the comparative example is basically the same as the ultra-high-rate lithium iron phosphate battery in example 1, and the difference is only that: the preparation method of the positive pole piece comprises the steps of directly stirring and mixing SP, a carbon nano-tube, lithium iron phosphate, PVDF and a solvent NMP to obtain positive pole slurry, coating the positive pole slurry on a positive pole substrate, and drying to obtain the positive pole piece; the preparation method of the negative pole piece comprises the steps of directly stirring and mixing SP, a carbon nano-tube, a negative active substance (the mesophase graphite and the soft carbon coated graphite are mixed according to the mass ratio of 3:7), CMC, SBR and solvent water to obtain negative pole slurry, coating the negative pole slurry on a negative pole base material, and drying to obtain the negative pole piece.
Fourth, test example
Test example 1
In the experimental example, simulation thermal imaging comparison is performed on the ultra-high-rate lithium iron phosphate battery in example 1 and the lithium ion battery in comparative example 1 under a 40C continuous discharge condition, wherein the temperature of the pole of the ultra-high-rate lithium iron phosphate battery in example 1 is about 47 ℃, and the temperature of the pole of the lithium ion battery in comparative example 1 is about 53 ℃. The result shows that the temperature rise of the lithium ion battery is lower, and the heat generation quantity is lower than that of the traditional welding mode.
Test example 2
In the test example, the performance of the lithium iron phosphate battery with ultrahigh multiplying power in example 1 and the performance of the lithium ion battery in comparative example 2 were tested, and the specific test method was as follows: the battery is subjected to continuous discharge test at 40C current, and the discharge voltage range is 3.65V-2.5V. The relationship between the capacity retention ratio and the voltage is shown in FIG. 3. In fig. 3, the discharge using the premixed conductive paste battery 40C is the capacity retention ratio-voltage relationship curve of the battery of example 1 of the present invention, and the discharge using the conventional conductive agent battery 40C is the capacity retention ratio-voltage relationship curve of the battery of comparative example 2. As can be seen from fig. 3, the discharge voltage of the ultra-high rate lithium iron phosphate battery of the present invention is higher than that of the lithium ion battery of comparative example 2, and the rate performance is more excellent.
Test example 3
In the test example, the discharge voltage of the ultra-high-rate lithium iron phosphate battery in example 1 in the 55C-rate pulse duty cycle process is recorded, and the discharge cut-off voltage is shown in fig. 4. After 50 working condition cycles, the discharge voltage of the ultra-high rate lithium iron phosphate battery is always maintained above 2.7V.
Test example 4
In this test example, the case temperature of the ultra-high-rate lithium iron phosphate battery in example 1 was measured at 55C rate during pulse discharge, and the test environment temperature was 25 ℃. The test results are shown in fig. 5, where the maximum temperature rise of the shell is less than 25 ℃.
According to the test results of the test examples 1-4, the lithium iron phosphate battery disclosed by the invention has excellent power output performance, the internal resistance is below 1Ohm, the ultrahigh-rate continuous discharge of more than 40C can be realized, the discharge cut-off voltage is more than 2.7V during 55C pulse cycle discharge, and the temperature rise of a shell is lower than 25 ℃. The lithium iron phosphate battery has low temperature rise under the condition of high-rate discharge, and the safety performance of the battery is superior; the lithium iron phosphate battery provided by the invention is resistant to overcharge, overdischarge, needling, short circuit and extrusion, and does not catch fire or explode at high temperature.

Claims (8)

1. The utility model provides an ultra-high magnification lithium iron phosphate battery, its characterized in that includes at least two parallelly connected and/or the monomer electric core of establishing ties, the monomer electric core is full utmost point ear coiling formula electricity core, the anodal active material of monomer electric core is nanometer lithium iron phosphate, and the negative pole active material is mesophase graphite and soft carbon cladding graphite, and the mass ratio of mesophase graphite and soft carbon cladding graphite is (2.5 ~ 3.5): (6.5-7.5); the lithium iron phosphate battery with ultrahigh multiplying power comprises a positive pole and a negative pole, wherein the positive pole and the negative pole are respectively connected with a positive full lug and a negative full lug of a single battery cell through connecting sheets; the connection mode is macromolecule diffusion welding.
2. The ultra-high-rate lithium iron phosphate battery as claimed in claim 1, wherein the connecting sheet is U-shaped, the U-shaped connecting sheet has an opening, the full tabs of the individual cells are inserted into the U-shaped connecting sheet through the opening, the individual cells are divided into two groups, and the two groups of individual cells are respectively connected with the inner side surfaces of the corresponding U-shaped connecting sheets.
3. The ultra-high-rate lithium iron phosphate battery as claimed in claim 2, wherein the number of the single battery cells is four, and the two single battery cells are connected in parallel to form the two groups.
4. The ultra-high-rate lithium iron phosphate battery according to any one of claims 1 to 3, wherein the lithium iron phosphate battery comprises an electrolyte, and the electrolyte comprises a flame retardant, and the mass of the flame retardant is 0.2-0.5% of the mass of the electrolyte.
5. The preparation method of the ultra-high-rate lithium iron phosphate battery as claimed in any one of claims 1 to 3, comprising the following steps: winding the diaphragm, the positive plate and the negative plate into a monomer battery cell in a full-tab winding manner; the positive plate is prepared by the following method: mixing a conductive agent and a dispersing agent in a first solvent to obtain first premixed conductive slurry; mixing the first conductive slurry with a positive active substance to obtain positive slurry; then coating the positive electrode slurry on the surface of a positive electrode base material to obtain the positive electrode slurry; the negative plate is prepared by the following method: mixing a conductive agent and a dispersing agent in a second solvent to obtain second premixed conductive slurry; mixing the second conductive slurry with a negative electrode active material to obtain negative electrode slurry; and coating the negative electrode slurry on the surface of a negative electrode substrate to obtain the negative electrode material.
6. The method for preparing the ultra-high-rate lithium iron phosphate battery according to claim 5, wherein the mass of the positive electrode active material in the positive electrode slurry accounts for 92-94% of the total mass of the positive electrode active material, the conductive agent and the dispersing agent.
7. The method for preparing the ultra-high-rate lithium iron phosphate battery according to claim 5, wherein the mass percentage of a negative active material in solid components contained in the negative electrode slurry is 92-96%, and the solid components comprise the negative active material, a conductive agent and a dispersing agent.
8. The preparation method of the ultra-high-rate lithium iron phosphate battery as claimed in claim 5, wherein the mass ratio of the conductive agent to the dispersing agent is (3-4): 1.
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CN117276768B (en) * 2023-11-20 2024-02-20 江苏中兴派能电池有限公司 Cylindrical battery and preparation method thereof

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CN105449162A (en) * 2015-01-28 2016-03-30 万向A一二三***有限公司 Anode material for lithium-ion battery and negative plate of anode material
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