CN116895825A - Lithium ion battery - Google Patents
Lithium ion battery Download PDFInfo
- Publication number
- CN116895825A CN116895825A CN202311082897.2A CN202311082897A CN116895825A CN 116895825 A CN116895825 A CN 116895825A CN 202311082897 A CN202311082897 A CN 202311082897A CN 116895825 A CN116895825 A CN 116895825A
- Authority
- CN
- China
- Prior art keywords
- active layer
- particle active
- active material
- lithium ion
- particle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 62
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 61
- 239000002245 particle Substances 0.000 claims abstract description 244
- 239000011149 active material Substances 0.000 claims abstract description 113
- 230000000694 effects Effects 0.000 claims abstract description 91
- 239000003792 electrolyte Substances 0.000 claims abstract description 7
- 239000006258 conductive agent Substances 0.000 claims description 48
- 239000011230 binding agent Substances 0.000 claims description 42
- 239000011248 coating agent Substances 0.000 claims description 36
- 238000000576 coating method Methods 0.000 claims description 36
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 28
- 239000008187 granular material Substances 0.000 claims 6
- 238000003756 stirring Methods 0.000 description 41
- 239000002002 slurry Substances 0.000 description 27
- 210000004027 cell Anatomy 0.000 description 18
- 238000002360 preparation method Methods 0.000 description 16
- 239000002033 PVDF binder Substances 0.000 description 15
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 15
- 238000000034 method Methods 0.000 description 14
- 239000011267 electrode slurry Substances 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 102220043159 rs587780996 Human genes 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000011888 foil Substances 0.000 description 7
- 239000003292 glue Substances 0.000 description 7
- 239000012528 membrane Substances 0.000 description 7
- 238000005096 rolling process Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 5
- 239000006229 carbon black Substances 0.000 description 4
- 239000001768 carboxy methyl cellulose Substances 0.000 description 4
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 4
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000004913 activation Effects 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 238000003475 lamination Methods 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 206010001497 Agitation Diseases 0.000 description 1
- 210000003771 C cell Anatomy 0.000 description 1
- NCZYUKGXRHBAHE-UHFFFAOYSA-K [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] Chemical compound [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] NCZYUKGXRHBAHE-UHFFFAOYSA-K 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000006257 cathode slurry Substances 0.000 description 1
- 239000008199 coating composition Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention belongs to the field of lithium ion batteries, and discloses a lithium ion battery. The lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive pole piece and the negative pole piece, the lithium ion battery is characterized in that the number of the positive pole pieces is at least 2, the positive pole pieces comprise at least 1 low-activity positive pole piece and at least 1 high-activity positive pole piece, the low-activity positive pole piece comprises a first current collector and a large-particle active layer arranged on the surface of the first current collector, the large-particle active layer comprises a large-particle active material, the high-activity positive pole piece comprises a second current collector and a small-particle active layer arranged on the surface of the second current collector, and the small-particle active layer comprises a small-particle active material. Not only can effectively solve the low-temperature performance problem of the battery, but also can ensure that the battery has high energy density.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and relates to a lithium ion battery, in particular to a low-temperature lithium iron phosphate lithium ion battery.
Background
With the development of new energy technology, lithium ion batteries are increasingly widely used in the fields of electric automobiles, mobile phones, computers, aerospace and the like due to the advantages of high energy density, long cycle life, safety in use and the like, and meanwhile, people also put higher requirements on the lithium ion batteries, such as high performance exertion in extreme environments of low temperature or high temperature and the like.
Taking lithium iron phosphate as an example, since the olivine structure of lithium iron phosphate determines that lithium ions can only be deintercalated in a single direction in the charge and discharge process, the conductivity is poor, and polarization is too large to discharge at low temperature. In order to improve the low-temperature performance of the lithium iron phosphate battery, many solutions adopt the mixing of large and small particles, and the characteristics of high activity of the small particles and easiness in reaction and heat release are adopted, so that the temperature of the battery cell is improved, and the large particles are heated and activated, so that the overall low-temperature performance of the battery cell is promoted.
However, the particle size of lithium iron phosphate is usually varied from several hundred nanometers to several ten micrometers, and small particles are mostly nano-sized, and their own dispersion ability is relatively poor. And because of the difficulty of processing, in order to better disperse the small particles, a higher dispersing capacity of the equipment, a higher rotation speed or a longer homogenization time is required, which undoubtedly increases the cost of processing.
Other prior art use external heating's mode to preheat the electric core, promote electric core temperature. The heating device is needed to be added on the surface of the battery cell, the temperature is slowly increased, the internal and external temperature of the battery cell is unevenly distributed, and the internal reaction of the battery cell is seriously uneven, so that the service life of the battery cell is influenced.
Therefore, providing a simple and easy solution to improve the low temperature performance of the battery is an urgent problem to be solved.
Disclosure of Invention
The invention aims to provide a lithium ion battery. Not only can effectively solve the low-temperature performance problem of the battery, but also can ensure that the battery has high energy density.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate, the number of the positive electrode plates is at least 2, the positive electrode plate comprises at least 1 positive electrode plate with low activity and at least 1 positive electrode plate with high activity, the positive electrode plate with low activity comprises a first current collector and a large particle active layer arranged on the surface of the first current collector, the large particle active layer comprises a large particle active material, the positive electrode plate with high activity comprises a second current collector and a small particle active layer arranged on the surface of the second current collector, and the small particle active layer comprises a small particle active material.
The following preferred technical solutions are used as the present invention, but not as limitations on the technical solutions provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solutions.
As a preferable technical scheme of the lithium ion battery, the thickness of the first current collector is 10 μm-15 μm.
As a preferable technical scheme of the lithium ion battery, the large-particle active layer is arranged on two side surfaces of the first current collector.
As a preferable technical scheme of the lithium ion battery, the coating surface density of the large-particle active layer is 50mg/cm 2 -70mg/cm 2 。
As a preferable technical scheme of the lithium ion battery, the compacted density of the large-particle active layer is 2.5-2.7g/cm 3 。
As a preferred embodiment of the lithium ion battery of the present invention, the particle diameter D50 of the large-particle active material is 4 mu-7 mu m.
As a preferred technical scheme of the lithium ion battery, the 1C gram capacity of the large-particle active material is more than 150mAh/g.
As a preferable technical scheme of the lithium ion battery, the thickness of the second current collector is 10 μm-15 μm.
As a preferable technical scheme of the lithium ion battery, the small particle active layer is arranged on two side surfaces of the second current collector.
As a preferable technical scheme of the lithium ion battery, the coating surface density of the small particle active layer is 30mg/cm 2 -40mg/cm 2 。
As a preferable technical scheme of the lithium ion battery, the compaction density of the small particle active layer is 2.1-2.3g/cm 3 。
As a preferred embodiment of the lithium ion battery of the present invention, the particle diameter D50 of the small-particle active material is 500nm to 2 μm.
As a preferred embodiment of the lithium ion battery according to the invention, the 1C gram capacity of the small-particle active material is >145mAh/g.
As a preferable technical scheme of the lithium ion battery, when the particle size D50 of the large-particle active material is 6 mu-7 mu m, the low-activity positive electrode plates and the high-activity positive electrode plates are alternately arranged.
As a preferable technical scheme of the lithium ion battery, when the particle size D50 of the large-particle active material is more than or equal to 4 mu m and less than 6 mu m, 1 or more high-activity positive electrode plates are arranged on each of the low-activity positive electrode plates at intervals.
As a preferable technical scheme of the lithium ion battery, the large-particle active layer further comprises a first conductive agent and a first binder, wherein the mass ratio of the large-particle active material is 93% -98%, the mass ratio of the first conductive agent is 1% -4%, and the mass ratio of the first binder is 1% -3% based on 100% of the total mass of the large-particle active layer.
As a preferred technical scheme of the lithium ion battery, the small particle active layer further comprises a second conductive agent and a second binder, wherein the mass ratio of the small particle active material is 93% -98%, the mass ratio of the second conductive agent is 1% -4%, and the mass ratio of the second binder is 1% -3% based on 100% of the total mass of the large particle active layer.
As a preferable technical scheme of the lithium ion battery, the large-particle active material and the small-particle active material are both lithium iron phosphate.
Compared with the prior art, the invention has the following beneficial effects:
according to the embodiment of the invention, the characteristic that the small-particle active material has high activity is utilized to prepare the positive electrode plate with the small-particle active layer, the characteristic that the large-particle active material has high energy density is utilized to prepare the positive electrode plate with the large-particle active layer (serving as an energy layer), the two positive electrode plates are matched in the battery, the small-particle active material is rapidly activated at the initial stage of discharging of the battery core, more heat is released, and the heat is indirectly transferred to the large-particle active material to activate the large-particle active material, so that the low-temperature performance of the battery can be solved, and the high energy density can be obtained. Meanwhile, the preparation method is compatible with the existing preparation process and has good processability.
Drawings
Fig. 1 is a positional relationship diagram of a positive electrode tab, a negative electrode tab, and a separator in a lithium ion battery of the first embodiment.
Fig. 2 is a graph of-20 ℃ energy retention of lithium ion batteries of examples one-nine and comparative example one.
Fig. 3 is a-20 ℃ discharge Wen Shengtu of the lithium ion batteries of examples one-nine and comparative example one.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.
The invention provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate, the number of the positive electrode plates is at least 2, at least 1 low-activity positive electrode plate and at least 1 high-activity positive electrode plate are included in the positive electrode plate, the low-activity positive electrode plate comprises a first current collector and a large-particle active layer arranged on the surface of the first current collector, the large-particle active layer comprises a large-particle active material, the high-activity positive electrode plate comprises a second current collector and a small-particle active layer arranged on the surface of the second current collector, and the small-particle active layer comprises a small-particle active material.
According to the embodiment of the invention, the characteristic that the small-particle active material has high activity is utilized to prepare the positive electrode plate with the small-particle active layer, the characteristic that the large-particle active material has high energy density is utilized to prepare the positive electrode plate with the large-particle active layer (serving as an energy layer), the two positive electrode plates are matched in the battery, the small-particle active material is rapidly activated at the initial stage of discharging of the battery core, more heat is released, and the heat is indirectly transferred to the large-particle active material to activate the large-particle active material, so that the low-temperature performance of the battery can be solved, and the high energy density can be obtained. Meanwhile, the preparation method is compatible with the existing preparation process and has good processability.
In one embodiment, the first current collector has a thickness of 10 μm to 15 μm, for example 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm or 15 μm, etc.
In one embodiment, the large particle active layer is disposed on both side surfaces of the first current collector.
In one embodiment, the large particle active layer has a coating surface density of 50-70mg/cm 2 . The large-particle active layer has large coating surface density, and the large active material loading can greatly improve the duty ratio of the active material, so that the energy density of the battery cell is improved. In addition, after the large-particle active material is gradually activated, the large active material loading is beneficial to releasing more heat, and the low-temperature performance of the battery is improved.
In the case where the large-particle active layer is provided on both side surfaces of the first current collector, the coating area density refers to the total coating area density of both sides.
In one embodiment, the bulk active layer has a compacted density of 2.5g/cm 3 -2.7g/cm 3 For example 2.5g/cm 3 、2.55g/cm 3 、2.6g/cm 3 、2.65g/cm 3 Or 2.7g/cm 3 Etc.
In one embodiment, the large particle active material has a particle size D50 of 4 μm to 7 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, or the like.
In one embodiment, the large particle active material has a 1C gram capacity >150mAh/g.
In an embodiment of the present invention, 1C gram capacity refers to the discharge capacity of a button cell made of an active material at 1C rate.
In one embodiment, the thickness of the second current collector is 10 μm to 15 μm, for example 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm or 15 μm, etc.
In one embodiment, the small particle active layer is disposed on both side surfaces of the second current collector.
In one embodiment, the small particle active layer has a coated surface density of 30mg/cm 2 -40mg/cm 2 For example 30mg/cm 2 、31mg/cm 2 、32mg/cm 2 、33mg/cm 2 、34mg/cm 2 、35mg/cm 2 、36mg/cm 2 、37mg/cm 2 、38mg/cm 2 、39mg/cm 2 Or 40mg/cm 2 Etc. The small particle active layer is small in coating surface density, so that the transmission path of electrons and lithium ions is shortened, the deintercalation of lithium ions is accelerated, the reaction rate of active materials at high multiplying power and low temperature is improved, the heat released by the reaction is conducted to the large particle active layer, the reaction of the large particle active layer is accelerated, the capacity of the whole battery cell is driven to be fully exerted, and the energy density of the battery cell is improved.
In the case where the small particle active layer is provided on both side surfaces of the second current collector, the coating areal density refers to the total coating areal density of both sides.
In one embodiment, the small particle active layer has a compacted density of 2.1 to 2.3g/cm 3 For example 2.1g/cm 3 、2.13g/cm 3 、2.15g/cm 3 、2.16g/cm 3 、2.18g/cm 3 、2.2g/cm 3 Or 2.3g/cm 3 Etc.
In one embodiment, the small particle active material has a particle size D50 of 500nm-2 μm, such as 500nm, 600nm, 700nm, 800nm, 1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.7 μm, 1.8 μm, or 2 μm, etc.
In one embodiment, the small particle active material has a 1C gram capacity >145mAh/g.
In one embodiment, when the particle diameter D50 of the large-particle active material is 6 μm to 7 μm, the low-activity positive electrode sheet and the high-activity positive electrode sheet are alternately arranged. When the particle size of the large-particle active material is larger, the polarization is larger, and the effect of full activation can be achieved by adopting the mode.
The above-mentioned "the low-activity positive electrode sheet and the high-activity positive electrode sheet are alternately arranged" means that the positive electrode sheets of different kinds are alternately arranged, and the two are not actually adjacent. In the battery, the positive pole piece and the negative pole piece are provided with diaphragms for isolating the positive pole and the negative pole, and avoiding the short circuit problem.
In one embodiment, the low-activity positive electrode sheet and the high-activity positive electrode sheet, the negative electrode sheet and the separator are arranged in the following manner: … …, low-activity positive pole piece, diaphragm, negative pole, diaphragm, high-activity positive pole piece, diaphragm, negative pole, diaphragm, low-activity positive pole piece, diaphragm, negative pole, … …, high-activity positive pole piece, diaphragm, negative pole, diaphragm, low-activity positive pole piece, diaphragm, negative pole, … ….
In one embodiment, when the particle diameter D50 of the large-particle active material is 4 μm or more and less than 6 μm, 1 or more high-activity positive electrode sheets are provided per interval of the plurality of low-activity positive electrode sheets. The high-activity positive electrode plates can be adjacent or spaced apart by the low-activity positive electrode plates.
The large-particle active material has moderate particle size and easier polarization, and can be used for activating a plurality of layers of low-activity positive pole pieces by inserting one layer or a plurality of layers of high-activity positive pole pieces. Illustratively, the high-activity positive electrode sheet is denoted as a, the low-activity positive electrode sheet is denoted as B, and the optional arrangement manner may be: b- … -B … B-A-B- … -B …, or B-B-B- … -B … -A-B … -B-B …, or B-B-B … -B … -ase:Sub>A-ase:Sub>A-B- … -B-B. The writing is abbreviated in that the negative electrode and the separator are omitted, and in practice, B-B, A-A or a-B and the like do not represent that they are adjacent to each other. In the battery, the positive pole piece and the negative pole piece are provided with diaphragms for isolating the positive pole and the negative pole, and avoiding the short circuit problem.
In one embodiment, the large particle active layer further comprises a first conductive agent and a first binder, wherein the mass ratio of the large particle active material is 93% -98%, such as 93%, 94%, 94.5%, 95%, 96%, 97% or 98%, etc., based on 100% of the total mass of the large particle active layer; the mass ratio of the first conductive agent is 1% -4%, such as 1%, 2%, 2.5%, 3%, 3.5% or 4%; the first binder is present in a mass ratio of 1% -3%, for example 1%, 2%, 2.5% or 3% etc.
In one embodiment, the first conductive agent includes at least one of carbon black, carbon nanotubes, or graphene, but is not limited to the above-listed species, and other conductive agents commonly used in the art are also suitable for the present invention.
In one embodiment, the first binder is polyvinylidene fluoride (PVDF) and when used, PVDF is prepared as a glue solution having a concentration of 4-8%.
In one embodiment, the small particle active layer further comprises a second conductive agent and a second binder, wherein the mass ratio of the small particle active material is 93% -98%, such as 93%, 94%, 94.5%, 95%, 96%, 97% or 98%, etc., based on 100% of the total mass of the large particle active layer; the mass ratio of the second conductive agent is 1% -4%, such as 1%, 2%, 2.5%, 3%, 3.5% or 4%; the mass ratio of the second binder is 1% -3%, for example 1%, 2%, 2.5% or 3% etc.
In one embodiment, the second conductive agent includes at least one of carbon black, carbon nanotubes, or graphene, but is not limited to the above-listed species, and other conductive agents commonly used in the art are also suitable for the present invention.
In one embodiment, the second binder is polyvinylidene fluoride (PVDF) and when used, PVDF is prepared as a glue solution with a concentration of 4-8%.
In one embodiment, the large particle active material and the small particle active material are both lithium iron phosphate.
The preparation methods of the positive electrode plate and the negative electrode plate are not limited in the embodiment of the invention, and for example, electrode slurry can be prepared, the electrode slurry is coated on a corresponding current collector, and after drying, a corresponding active layer is formed on the current collector to obtain the electrode plate.
In one embodiment, the method for preparing the positive electrode sheet comprises the following steps:
s101, dispersing a positive electrode raw material in a solvent to obtain a positive electrode slurry, wherein the positive electrode raw material comprises an active material.
In one embodiment, the positive electrode material further includes a conductive agent and a binder.
And S201, coating the positive electrode slurry on a current collector, drying and rolling to obtain a positive electrode plate.
In the embodiment of the invention, for the case that the active material is a large-particle active material, the obtained positive electrode slurry is a large-particle slurry, and the prepared positive electrode plate is a low-activity positive electrode plate; in the case that the active material is a small-particle active material, the obtained positive electrode slurry is a small-particle slurry, and the prepared positive electrode plate is a high-activity positive electrode plate.
In one embodiment, the large particle active material has a specific surface area of 10m 2 /g-12m 2 /g, e.g. 10m 2 /g、10.5m 2 /g、11m 2 /g、11.5m 2 /g or 12m 2 /g, etc.
In one embodiment, the small particle active material has a specific surface area of 13m 2 /g-15m 2 /g, e.g. 13m 2 /g、13.5m 2 /g、14m 2 /g、14.5m 2 /g or 15m 2 /g, etc.
In one embodiment, the method of preparing the positive electrode slurry includes the steps of: adding the solvent, the glue solution and the conductive agent into a planetary stirring device, stirring once, adding the active material into the stirring device at least twice, stirring after adding the active material each time, and regulating the viscosity to obtain the anode slurry.
In one embodiment, the solvent is NMP.
In one embodiment, the gum solution is an NMP solution of PVDF.
In one embodiment, the revolution speed of the primary stirring is 35rpm or less, for example 35rpm, 33rpm, 30rpm, 25rpm, 20rpm, 15rpm, or the like.
In one embodiment, the spin speed of the primary agitation is 3500rpm or less, such as 3500rpm, 3250rpm, 3000rpm, 2500rpm, 2000rpm, 1500rpm, 1000rpm, or the like.
In one embodiment, the time of one stirring is 60min-90min, such as 60min, 65min, 70min, 75min, 80min, 85min, or 90min, etc.
In one embodiment, the active material is added to the stirring apparatus at least twice, and stirring is performed for a period of 20min to 40min (e.g., 20min, 22min, 25min, 28min, 30min, 35min, 40min, etc.) after each addition of the active material, except for the last time, at a revolution speed of 35rpm or less (e.g., 35rpm, 33rpm, 30rpm, 25rpm, 20rpm, 15rpm, etc.), and at a rotation speed of 3500rpm or less (e.g., 3500rpm, 3250rpm, 3000rpm, 2500rpm, 2000rpm, 1500rpm, 1000rpm, etc.). Stirring for at least 60min and at least 120min (e.g. 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min or 115min, etc.) after adding active material for the last time; the revolution speed of the stirring is not more than 35rpm (for example, 35rpm, 33rpm, 30rpm, 25rpm, 20rpm, 15rpm, etc.), and the rotation speed is not more than 3500rpm (for example, 3500rpm, 3250rpm, 3000rpm, 2500rpm, 2000rpm, 1500rpm, 1000rpm, etc.).
In one embodiment, the remaining solvent is added to adjust the viscosity, stirring is completed for 30 minutes each time, stirring speed is not more than 35rpm, and dispersing speed is not more than 3500rpm.
In one embodiment, the viscosity is adjusted to 4500.+ -. 1000mPa.s, i.e., 3500mpa.s-5500mpa.s, e.g., 3500mpa.s, 3700mpa.s, 4000mpa.s, 4200mpa.s, 4500mpa.s, 4800mpa.s, 5000mpa.s, 5500mpa.s, etc.
In one embodiment, the fineness of the positive electrode slurry is controlled to be < 20 μm, for example, 19 μm, 18 μm, 16 μm, 15 μm, 14 μm, 12 μm, 10 μm, 8 μm, 5 μm, or the like.
In one embodiment, the step of evacuating is performed after the viscosity is adjusted, preferably to-0.095 MPa, for 30min.
Example 1
The embodiment provides a lithium ion battery, which comprises positive pole pieces, negative pole pieces 3, a diaphragm and electrolyte, wherein the diaphragm 2 is positioned between the positive pole pieces and the negative pole pieces 3, the position relationship between the positive pole pieces, the negative pole pieces and the diaphragm is shown in fig. 1, the number of the positive pole pieces is 2, and the diaphragm 2 is positioned between the positive pole pieces and the negative pole pieces 3 to separate the positive pole pieces from the negative pole pieces to avoid short circuits; the positive electrode plate comprises 1 low-activity positive electrode plate 11 and 1 high-activity positive electrode plate 12, and the low-activity positive electrode plate 11 and the high-activity positive electrode plate 12 are alternately arranged;
the low-activity positive electrode piece 11 comprises a first current collector and large-particle active layers arranged on the two side surfaces of the first current collector, wherein the large-particle active layers comprise large-particle active materials, conductive agents and binders, the high-activity positive electrode piece 12 comprises a second current collector and small-particle active layers arranged on the two side surfaces of the second current collector, and the small-particle active layers comprise small-particle active materials, conductive agents and binders;
wherein the large-particle active material is lithium iron phosphate with the particle size d50=6.3 mu m, the small-particle active material is lithium iron phosphate with the particle size d50=0.76 mu m, the first current collector and the second current collector are aluminum foils with the thickness of 13 mu m, the types of conductive agents and binding agents in the large-particle active layer and the small-particle active layer are the same, the conductive agent is Super P, the binding agent is PVDF, and the proportion of each component in the large-particle active layer is as follows: the active material of the large particles accounts for 95 percent, the conductive agent accounts for 3 percent, the binder accounts for 2 percent, and the active layer of the small particles comprises the following components in percentage: the small particle active material accounts for 95%, the conductive agent accounts for 3%, and the binder accounts for 2%.
The coating surface density of the large-particle active layer is 60mg/cm 2 The compacted density of the large-particle active layer was 2.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coating surface density of the small particle active layer is 35mg/cm 2 The compacted density of the small particle active layer was 2.2g/cm 3 。
The embodiment also provides a preparation method of the lithium ion battery, which comprises the following steps:
first, d50=0.76 μm and d50=6.3 μm lithium iron phosphate active materials, each of which was dispersed in NMP with a conductive agent, a binder in a certain weight ratio, were prepared as a slurry, which was denoted as a first slurry and a second slurry.
The preparation methods of the two slurries are the same: adding PVDF glue solution (NMP as solvent with solid content of 6%), conductive agent and part of NMP into stirring equipment, and rotating at 30rpm and 3100rpm for 75min; then adding the active material into the stirring equipment for two times, wherein the first stirring time is 30min, the revolution speed is 30rpm, the self-rotation speed is 3100rpm, and the second stirring time is 100min; revolution speed 30rpm, rotation speed 3100rpm; next, the remaining NMP was added and viscosity was adjusted, and stirring was completed for 30 minutes each time, revolution speed was 30rpm, rotation speed was 3000rpm, viscosity was controlled to 4500.+ -. 1000mPa.s, fineness was < 20. Mu.m. Vacuumizing to-0.095 MPa, and maintaining for 30min. The slurry preparation is completed.
Uniformly coating the prepared first slurry and second slurry on the two side surfaces of an aluminum foil with the thickness of 13 mu m respectively, rolling the fully dried pole pieces, and forming active layers on the two side surfaces of a current collector to obtain corresponding positive pole pieces, wherein the positive pole pieces prepared by adopting a D50=0.76 mu m lithium iron phosphate active material are marked as high-activity positive pole pieces, and the active layers in the positive pole pieces are small-particle active layers; the positive electrode sheet prepared by adopting the D50=6.3 μm lithium iron phosphate active material is marked as a low-activity positive electrode sheet, and an active layer in the positive electrode sheet is a large-particle active layer.
And a lamination process is adopted, the lithium ion battery is assembled by using the positive pole piece, and the diaphragm is positioned between the positive pole piece and the negative pole piece. N/p=1.1 was designed and the negative electrode of the appropriate areal density was selected according to the lamination mode.
The preparation method of the negative electrode plate comprises the following steps:
dissolving carboxymethyl cellulose (CMC) in water to obtain CMC solution with solid content of 1.6%, adding part of water, part of CMC solution and Super P into stirring equipment, stirring, and rotating at 35rpm and 3200rpm for 30min; then, the graphite as the negative electrode active material was added to the stirring apparatus twice for stirring, the stirring time for the first graphite addition was 30 minutes, the revolution speed was 30rpm, the rotation speed was 3200rpm, the stirring time for the second graphite addition was 60 minutes, the revolution speed was 35rpm, and the rotation speed was 3200rpm. Adding the rest water and the rest CMC solution, regulating the viscosity, stirring for 30min, wherein the revolution speed is 35rpm, the rotation speed is 3500rpm, and regulating the viscosity to 2900 Pa.s and the fineness to 20 mu m; finally, adding all the binder SBR, wherein the revolution speed is 30rpm, the rotation speed is 300rpm, stirring for 60min, vacuumizing to-0.095 MPa, and preparing the cathode slurry;
wherein, the mass ratio of graphite, SP, SBR and CMC is 96 percent to 1 percent to 1.5 percent.
Uniformly coating the prepared negative electrode slurry on the two side surfaces of the copper foil by using a transfer coater, coating different coating surface densities according to the design of N/P=1.1, rolling the coated and fully dried pole piece, and compacting the pole piece to a density of 1.6g/cm 3 And obtaining a negative electrode plate, wherein the negative electrode plate comprises a copper foil and negative electrode active layers positioned on the surfaces of two sides of the copper foil.
In this example, the coating composition was coated with a large particle active layer (coating surface density 60mg/cm 2 ) The coated surface density of the opposite anode active layer was 30.2mg/cm 2 With a small particle active layer (coating surface density 35mg/cm 2 ) The coated surface density of the opposite anode active layer was 17.6mg/cm 2 。
In the lithium ion batteries of the remaining examples and comparative examples, N/p=1.1, the coated surface densities of the negative electrode active layers opposite thereto were determined according to the coated surface densities of the large particle active layers and the small particle active layers. The areal density relationship of the opposing positive electrode active layer (large particle active layer or small particle active layer) and negative electrode active layer is shown in table 1 below.
TABLE 1
Example two
The difference from example one is that the small-particle active material is replaced by lithium iron phosphate having a particle diameter d50=0.72 μm, and the coating surface density of the large-particle active layer is 60mg/cm 2 The compacted density of the large-particle active layer was 2.65g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coated surface density of the small particle active layer was 33mg/cm 2 The compacted density of the small particle active layer was 2.18g/cm 3 。
Example III
The difference from example one is that the small-particle active material is replaced by lithium iron phosphate having a particle diameter d50=1.23 μm, and the coating surface density of the large-particle active layer is 60mg/cm 2 The compacted density of the large-particle active layer was 2.65g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coating surface density of the small particle active layer was 34mg/cm 2 The compacted density of the small particle active layer was 2.25g/cm 3 。
Example IV
The difference from example one is that the small-particle active material is replaced by lithium iron phosphate having a particle diameter d50=0.61 μm, and the coating surface density of the large-particle active layer is 60mg/cm 2 The compacted density of the large-particle active layer was 2.65g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coating surface density of the small particle active layer is 35mg/cm 2 The compacted density of the small particle active layer was 2.15g/cm 3 。
Example five
The difference from example one is that the small-particle active material is replaced by lithium iron phosphate having a particle diameter d50=1.23 μm, and the coating surface density of the large-particle active layer is 63mg/cm 2 The compacted density of the large-particle active layer was 2.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coated surface density of the small particle active layer was 33mg/cm 2 The compacted density of the small particle active layer was 2.25g/cm 3 。
Example six
The embodiment provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate, the position relationship between the positive electrode plate, the negative electrode plate and the diaphragm is shown in figure 1, and the diaphragm is positioned between the positive electrode plate and the negative electrode plate, so that the positive electrode plate and the negative electrode plate are separated, and short circuit is avoided; the positive pole piece comprises 4 low-activity positive pole pieces and 1 high-activity positive pole piece, wherein the arrangement sequence of the low-activity positive pole pieces, the high-activity positive pole pieces, the diaphragm and the negative pole pieces is as follows: the negative electrode plate, the diaphragm, the low-activity positive electrode plate, the diaphragm, the negative electrode plate, the diaphragm, the high-activity positive electrode plate, the diaphragm, the negative electrode plate, the diaphragm, the low-activity positive electrode plate, the diaphragm and the negative electrode plate;
the low-activity positive electrode plate comprises a first current collector and large-particle active layers arranged on the surfaces of two sides of the first current collector, wherein the large-particle active layers comprise large-particle active materials, conductive agents and binders, the high-activity positive electrode plate comprises a second current collector and small-particle active layers arranged on the surfaces of two sides of the second current collector, and the small-particle active layers comprise small-particle active materials, conductive agents and binders;
the large-particle active material is lithium iron phosphate with the particle size d50=5.5 mu m, the small-particle active material is lithium iron phosphate with the particle size d50=1.0 mu m, the first current collector and the second current collector are aluminum foils with the thickness of 12 mu m, the types of conductive agents and binding agents in the large-particle active layer and the small-particle active layer are the same, the conductive agent is carbon black, the binding agent is PVDF, and the proportion of each component in the large-particle active layer is as follows: the large-particle active material accounts for 96 percent, the conductive agent accounts for 2 percent, the binder accounts for 2 percent, and the small-particle active layer comprises the following components in percentage: the small particle active material accounts for 95%, the conductive agent accounts for 3%, and the binder accounts for 2%.
The coating surface density of the large-particle active layer was 63mg/cm 2 The compacted density of the large-particle active layer was 2.65g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coating surface density of the small particle active layer is 35mg/cm 2 Small particlesThe active layer had a compacted density of 2.23g/cm 3 。
The embodiment also provides a preparation method of the lithium ion battery, which comprises the following steps:
first, d50=1.0 μm and d50=5.5 μm lithium iron phosphate active materials, each of which was dispersed in NMP with a conductive agent, a binder in a certain weight ratio, were prepared as a slurry, which was denoted as a first slurry and a second slurry.
The preparation methods of the two slurries are the same: adding PVDF glue solution, conductive agent and part of NMP into stirring equipment, and enabling revolution speed to be 25rpm, rotation speed to be 2000rpm and time to be 80min; then adding the active material into the stirring equipment for two times, wherein the first stirring time is 20min, the revolution speed is 30rpm, the rotation speed is 2500rpm, and the second stirring time is 75min; revolution speed 30rpm, rotation speed 2500rpm; next, the remaining NMP was added and viscosity was adjusted, and stirring was completed for 30 minutes each time, revolution speed was 30rpm, rotation speed was 3000rpm, viscosity was controlled to 4500.+ -. 1000mPa.s, fineness was < 20. Mu.m. Vacuumizing to-0.095 MPa, and maintaining for 30min. The slurry preparation is completed.
Uniformly coating the prepared first slurry and second slurry on the two side surfaces of an aluminum foil with the thickness of 12 mu m respectively, rolling the fully dried pole pieces, and forming active layers on the two side surfaces of a current collector to obtain corresponding positive pole pieces, wherein the positive pole pieces prepared by adopting a D50=1.0 mu m lithium iron phosphate active material are marked as high-activity positive pole pieces, and the active layers in the positive pole pieces are small-particle active layers; the positive electrode sheet prepared by adopting the D50=5.5 μm lithium iron phosphate active material is marked as a low-activity positive electrode sheet, and an active layer in the positive electrode sheet is a large-particle active layer.
A negative electrode tab was prepared and a lithium ion battery was assembled in the same manner as in example one.
Example seven
The embodiment provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate, the position relationship between the positive electrode plate, the negative electrode plate and the diaphragm is shown in figure 1, and the diaphragm is positioned between the positive electrode plate and the negative electrode plate, so that the positive electrode plate and the negative electrode plate are separated, and short circuit is avoided; the positive pole piece comprises 4 low-activity positive pole pieces and 3 high-activity positive pole pieces, and the arrangement sequence of the low-activity positive pole pieces, the high-activity positive pole pieces, the diaphragm and the negative pole pieces is as follows: the membrane comprises a negative electrode pole piece, a membrane, a low-activity positive electrode pole piece, a membrane, a negative electrode pole piece, a membrane, a high-activity positive electrode pole piece, a membrane, a negative electrode pole piece, a membrane, a low-activity positive electrode pole piece, a membrane and a negative electrode pole piece;
the low-activity positive electrode plate comprises a first current collector and large-particle active layers arranged on the surfaces of two sides of the first current collector, wherein the large-particle active layers comprise large-particle active materials, conductive agents and binders, the high-activity positive electrode plate comprises a second current collector and small-particle active layers arranged on the surfaces of two sides of the second current collector, and the small-particle active layers comprise small-particle active materials, conductive agents and binders;
the large-particle active material is lithium iron phosphate with the particle size D50=6.8 mu m, the small-particle active material is lithium iron phosphate with the particle size D50=0.5 mu m, the first current collector and the second current collector are aluminum foils with the thickness of 12 mu m, the types of conductive agents and binding agents in the large-particle active layer and the small-particle active layer are the same, the conductive agent is carbon black, the binding agent is PVDF, and the proportion of each component in the large-particle active layer is as follows: the large-particle active material accounts for 96 percent, the conductive agent accounts for 2 percent, the binder accounts for 2 percent, and the small-particle active layer comprises the following components in percentage: the small particle active material accounts for 95%, the conductive agent accounts for 3%, and the binder accounts for 2%.
The coating surface density of the large-particle active layer is 60mg/cm 2 The compacted density of the large-particle active layer was 2.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The coating surface density of the small particle active layer is 35mg/cm 2 The compacted density of the small particle active layer was 2.14g/cm 3 。
The embodiment also provides a preparation method of the lithium ion battery, which comprises the following steps:
first, d50=0.5 μm and d50=6.8 μm lithium iron phosphate active materials, each of which was dispersed in NMP with a conductive agent, a binder in a certain weight ratio, were prepared as a slurry, which was denoted as a first slurry and a second slurry.
The preparation methods of the two slurries are the same: adding PVDF glue solution, conductive agent and part of NMP into stirring equipment, and enabling revolution speed to be 25rpm, rotation speed to be 1800rpm and time to be 90min; then adding the active material into the stirring equipment for two times, wherein the first stirring time is 25min, the revolution speed is 25rpm, the rotation speed is 2750rpm, and the second stirring time is 90min; revolution stirring speed is 30rpm, rotation speed is 2200rpm; next, the remaining NMP was added and viscosity was adjusted, and stirring was completed for 25 minutes each time at a revolution speed of 30rpm and a rotation speed of 2500rpm, and the viscosity was controlled to 4500.+ -. 1000mPa.s, and the fineness was < 20. Mu.m. Vacuumizing to-0.095 MPa, and maintaining for 30min. The slurry preparation is completed.
Uniformly coating the prepared first slurry and second slurry on the two side surfaces of an aluminum foil with the thickness of 12 mu m respectively, rolling the fully dried pole pieces, and forming active layers on the two side surfaces of a current collector to obtain corresponding positive pole pieces, wherein the positive pole pieces prepared by adopting a D50=0.5 mu m lithium iron phosphate active material are marked as high-activity positive pole pieces, and the active layers in the positive pole pieces are small-particle active layers; the positive electrode sheet prepared by adopting the D50=6.8 μm lithium iron phosphate active material is marked as a low-activity positive electrode sheet, and an active layer in the positive electrode sheet is a large-particle active layer.
A negative electrode tab was prepared and a lithium ion battery was assembled in the same manner as in example one.
Example eight
The difference from the seventh embodiment is that the number of the low-activity positive electrode pieces is 4, the number of the high-activity positive electrode pieces is 1, the negative electrode pieces, the diaphragm, the low-activity positive electrode pieces, the diaphragm, the negative electrode pieces, the diaphragm, the high-activity positive electrode pieces, the diaphragm, the negative electrode pieces, the diaphragm, the low-activity positive electrode pieces, the diaphragm and the negative electrode pieces.
Example nine
The difference from example one is that the coated surface density of the small particle active layer is 50mg/cm 2 The coating surface density of the large-particle active layer is 50mg/cm 2 。
Comparative example one
First, d50=0.76 μm lithium iron phosphate active material (denoted as material 1) and d50=6.3 μm lithium iron phosphate active material (denoted as material 2), conductive agent Super P, and binder PVDF were dispersed in NMP at a certain weight ratio to prepare a slurry. Wherein d50=0.76 μm and d50=6.3 μm of active material each account for 47.5%, the conductive agent accounts for 3%, and the binder accounts for 2%.
When the slurry is prepared, PVDF glue solution (the solvent is NMP, the solid content is 6%), the conductive agent and part of NMP are added into stirring equipment, the revolution speed is 30rpm, the rotation speed is 3100rpm, and the time is 75min; then, the active material 1 and the active material 2 are respectively added into the stirring equipment for two times, wherein the first stirring time is 30min, the revolution speed is 30rpm, the self rotation speed is 3100rpm, and the second stirring time is 100min; revolution speed 30rpm, rotation speed 3100rpm; next, the remaining NMP was added and viscosity was adjusted, and stirring was completed for 30 minutes each time, revolution speed was 30rpm, rotation speed was 3000rpm, viscosity was controlled to 4500.+ -. 1000mPa.s, fineness was < 20. Mu.m. Vacuumizing to-0.095 MPa, and maintaining for 30min. The slurry preparation is completed.
Uniformly coating the prepared slurry on an aluminum foil with the thickness of 13 mu m, rolling the fully dried pole piece to form an active layer on a current collector, wherein the coating surface density of the active layer is 50mg/cm 2 Compact density 2.5g/cm 3 。
A negative electrode tab was prepared and a lithium ion battery was assembled in the same manner as in example one.
And (3) testing:
the lithium ion batteries provided in each example and comparative example were subjected to a low-temperature performance test, and the test method was as follows:
after constant-current and constant-voltage charging at 25 ℃ to 3.65V, standing for 8h at 25 ℃ and-20 ℃ respectively, and discharging at 1C to 2V.
-20 ℃ discharge energy retention = -20 ℃ discharge energy/25 ℃ discharge energy.
-20 ℃ cell temperature rise = maximum temperature- (-20 ℃).
The results are shown in fig. 2, 3 and table 2.
Fig. 2 is a graph of the energy retention rate at-20 ℃ for the lithium ion batteries of examples one-nine and comparative example one, showing that the activation effect of the small-particle active material is significantly better than that of the larger particles, and the effect of alternating the high-active material layer and the low-active material layer (here, the separator-negative electrode separator-separator between the default two positive electrode sheets) is better than that of inserting one high-active material layer into the multi-layer low-active material layer, but is greatly improved compared with the size particle blending mode, indicating that the small-particle active material layer has a significant effect of improving the low-temperature performance of the battery cell.
Fig. 3 shows the-20 ℃ discharge Wen Shengtu of the lithium ion batteries of examples one-nine and comparative example one, and shows that the small particle active layer has a significant effect on the increase of the cell temperature, the temperature increase range is within the safety range, taking example seven with the largest temperature increase as an example, the temperature increase is 13.6 ℃ under the-20 ℃ condition, namely the cell temperature is-7.4 ℃, and the cell has no thermal runaway risk.
In conclusion, the introduction of the high-activity small-particle material layer can improve the low-temperature performance of the battery cell, and the safety performance of the battery cell is not affected.
TABLE 2
The low temperature performance of example nine is inferior to that of example one, probably due to the excessive density of the coated surface of the small particle active layer, which increases the electron and lithium ion transport paths, and is disadvantageous for the rapid conduction of the heat released by the reaction to the large particle active layer.
The first comparative example adopts the mixing homogenate of large and small particles, the specific surface of the small particles is larger, the agglomeration phenomenon is easy to occur, the small particles and the conductive agent and the binder are locally agglomerated together, on one hand, the conductive agent and the binder cannot be uniformly dispersed around the large particles to exert the heating effect, on the other hand, the agglomeration of the small particles and the binder influences the conductive performance around the large particles, so that the polarization around the large particles is further increased, and the exertion of the capacity of the large particles is influenced. The main reason for improving the low-temperature performance of the battery cell by respectively homogenizing and coating the large and small particles is that the two particles can be uniformly mixed with the conductive agent and the adhesive, the heat generated by the small particle reaction of the small particle active layer is uniformly transmitted to the large particle active layer, the large particles are heated and activated, the capacities of the two materials are fully exerted, the low-temperature performance of the battery cell is improved, and the high energy density is also maintained.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
The applicant states that the detailed method of the present invention is illustrated by the above examples, but the present invention is not limited to the detailed method described above, i.e. it does not mean that the present invention must be practiced in dependence upon the detailed method described above. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (10)
1. The utility model provides a lithium ion battery, includes positive pole piece, negative pole piece, diaphragm and electrolyte, the diaphragm is located positive pole piece with between the negative pole piece, its characterized in that, the quantity of positive pole piece is at least 2, including at least 1 low activity positive pole piece and at least 1 high activity positive pole piece in the positive pole piece, wherein, low activity positive pole piece include first electric current collector with set up in the big granule active layer on first electric current collector surface, big granule active layer includes big granule active material, high activity positive pole piece include the second electric current collector with set up in the little granule active layer on second electric current collector surface, little granule active layer includes little granule active material.
2. The lithium ion battery of claim 1, wherein the first current collector has a thickness of 10 μιη to 15 μιη;
preferably, the large particle active layer is disposed on both side surfaces of the first current collector;
preferably, the large particle active layer has a coating surface density of 50mg/cm 2 -70mg/cm 2 ；
Preferably, the bulk active layer has a compacted density of 2.5 to 2.7g/cm 3 。
3. The lithium ion battery according to claim 1 or 2, wherein the particle size D50 of the large-particle active material is 4 μ -7 μm;
preferably, the large particle active material has a 1C gram capacity >150mAh/g.
4. A lithium ion battery according to any of claims 1-3, wherein the thickness of the second current collector is 10 μm-15 μm;
preferably, the small particle active layer is disposed on both side surfaces of the second current collector;
preferably, the small particle active layer has a coating surface density of 30mg/cm 2 -40mg/cm 2 ；
Preferably, the small particle active layer has a compacted density of 2.1-2.3g/cm 3 。
5. The lithium ion battery of any of claims 1-4, wherein the small particle active material has a particle size D50 of 500nm-2 μιη;
preferably, the small particle active material has a 1C gram capacity >145mAh/g.
6. The lithium ion battery of any of claims 1-5, wherein the low-activity positive electrode sheet and the high-activity positive electrode sheet are alternately arranged when the particle diameter D50 of the large-particle active material is 6 μ -7 μm.
7. The lithium ion battery according to any one of claims 1 to 5, wherein when the particle diameter D50 of the large-particle active material is 4 μm or more and less than 6 μm, 1 or more high-activity positive electrode sheets are provided per a plurality of low-activity positive electrode sheets at intervals.
8. The lithium ion battery of any of claims 1-7, wherein the large particle active layer further comprises a first conductive agent and a first binder, wherein the mass ratio of the large particle active material is 93% -98%, the mass ratio of the first conductive agent is 1% -4%, and the mass ratio of the first binder is 1% -3% based on 100% of the total mass of the large particle active layer.
9. The lithium ion battery of any of claims 1-8, wherein the small particle active layer further comprises a second conductive agent and a second binder, the mass ratio of the small particle active material is 93% -98%, the mass ratio of the second conductive agent is 1% -4%, and the mass ratio of the second binder is 1% -3% based on 100% of the total mass of the large particle active layer.
10. The lithium ion battery of any of claims 1-9, wherein the large particle active material and the small particle active material are both lithium iron phosphate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311082897.2A CN116895825A (en) | 2023-08-25 | 2023-08-25 | Lithium ion battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311082897.2A CN116895825A (en) | 2023-08-25 | 2023-08-25 | Lithium ion battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116895825A true CN116895825A (en) | 2023-10-17 |
Family
ID=88310983
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311082897.2A Pending CN116895825A (en) | 2023-08-25 | 2023-08-25 | Lithium ion battery |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116895825A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117423802A (en) * | 2023-12-18 | 2024-01-19 | 天津容百斯科兰德科技有限公司 | Positive plate and application thereof |
-
2023
- 2023-08-25 CN CN202311082897.2A patent/CN116895825A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117423802A (en) * | 2023-12-18 | 2024-01-19 | 天津容百斯科兰德科技有限公司 | Positive plate and application thereof |
| CN117423802B (en) * | 2023-12-18 | 2024-04-16 | 天津容百斯科兰德科技有限公司 | Positive plate and application thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112038574B (en) | Pole piece film and preparation method and application thereof | |
| CN113948673B (en) | Lithium ion battery positive plate, preparation method thereof and lithium ion battery | |
| CN101174685A (en) | Anode or cathode pole piece of lithium ion battery and coating method thereof | |
| CN112289976A (en) | Positive electrode material layer, preparation method thereof, positive plate and battery | |
| CN104241696A (en) | Lithium ion battery with high energy density and preparation method of lithium ion battery with high energy density | |
| CN113540399B (en) | Water system negative plate for high-power lithium ion battery and preparation method thereof | |
| CN110247009A (en) | A kind of anti-overcharge diaphragm and preparation method thereof and lithium ion battery | |
| CN112151745A (en) | Positive electrode material layer for semi-solid battery, preparation method of positive electrode material layer, positive plate and semi-solid battery | |
| CN113013414B (en) | Cobalt-free positive electrode slurry, preparation method thereof, positive plate and lithium ion battery | |
| CN116895825A (en) | Lithium ion battery | |
| CN112331818A (en) | Positive plate, preparation method thereof and lithium ion battery | |
| CN113422049A (en) | Lithium iron phosphate positive pole piece and preparation method and application thereof | |
| CN113054157A (en) | Double-composite modified spinel lithium manganate positive plate, preparation method thereof and lithium ion battery | |
| CN113991058A (en) | Negative pole piece, solid-state battery and preparation method thereof | |
| CN114156431A (en) | Positive electrode homogenizing method, positive electrode slurry and application thereof | |
| CN114242936B (en) | Electrode assembly and application thereof | |
| CN116387509A (en) | Composite positive electrode for lithium metal battery and preparation method thereof | |
| CN114497508A (en) | Power type artificial graphite composite material and preparation method thereof | |
| US20210143483A1 (en) | Method and system for a battery electrode having a solvent level to facilitate peeling | |
| CN117525297A (en) | Preparation method of dry electrode | |
| CN111554881B (en) | MXene-based flexible self-supporting electrode material and preparation method thereof | |
| CN220821623U (en) | Positive plate and lithium ion battery | |
| CN115632105B (en) | Porous negative pole piece, preparation method thereof and lithium ion battery | |
| CN114725389B (en) | Long-life power lithium battery and preparation method thereof | |
| CN117594749B (en) | Silicon-based negative plate and preparation method and application thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| TA01 | Transfer of patent application right | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20240812 Address after: 313100 Green Intelligent Manufacturing Industrial Park, South Taihu industrial cluster, Changxing County Development Zone, Huzhou City, Zhejiang Province Applicant after: Jiewei Power (Changxing) Co.,Ltd. Country or region after: China Address before: No.11, Kaiyuan Road, Xiqing automobile industrial zone, Xiqing District, Tianjin 300380 Applicant before: TIANJIN EV ENERGIES Co.,Ltd. Country or region before: China |