CN117832432A - Positive electrode plate, preparation method of positive electrode plate and lithium ion battery - Google Patents
Positive electrode plate, preparation method of positive electrode plate and lithium ion battery Download PDFInfo
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- CN117832432A CN117832432A CN202311792366.2A CN202311792366A CN117832432A CN 117832432 A CN117832432 A CN 117832432A CN 202311792366 A CN202311792366 A CN 202311792366A CN 117832432 A CN117832432 A CN 117832432A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 239000007774 positive electrode material Substances 0.000 claims abstract description 57
- 239000002245 particle Substances 0.000 claims abstract description 27
- 238000009826 distribution Methods 0.000 claims abstract description 11
- 230000001186 cumulative effect Effects 0.000 claims abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 10
- 239000011267 electrode slurry Substances 0.000 claims description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 14
- 239000011248 coating agent Substances 0.000 claims description 13
- 238000000576 coating method Methods 0.000 claims description 13
- 239000006258 conductive agent Substances 0.000 claims description 12
- 239000000853 adhesive Substances 0.000 claims description 9
- 230000001070 adhesive effect Effects 0.000 claims description 9
- 239000003792 electrolyte Substances 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
- 238000003825 pressing Methods 0.000 claims description 7
- 239000002033 PVDF binder Substances 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims description 4
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 4
- 239000006229 carbon black Substances 0.000 claims description 4
- 239000004917 carbon fiber Substances 0.000 claims description 4
- 239000002041 carbon nanotube Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 4
- 229910021389 graphene Inorganic materials 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 239000003273 ketjen black Substances 0.000 claims description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 4
- 239000000661 sodium alginate Substances 0.000 claims description 4
- 235000010413 sodium alginate Nutrition 0.000 claims description 4
- 229940005550 sodium alginate Drugs 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 3
- 239000006183 anode active material Substances 0.000 claims description 2
- 239000006256 anode slurry Substances 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 11
- 238000012360 testing method Methods 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000011356 non-aqueous organic solvent Substances 0.000 description 3
- 238000004806 packaging method and process Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- UHOPWFKONJYLCF-UHFFFAOYSA-N 2-(2-sulfanylethyl)isoindole-1,3-dione Chemical compound C1=CC=C2C(=O)N(CCS)C(=O)C2=C1 UHOPWFKONJYLCF-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the technical field of batteries, in particular to a positive electrode plate, a preparation method of the positive electrode plate and a lithium ion battery. Aiming at the problem of poor multiplying power performance of the existing lithium ion battery, the adopted improvement is as follows: the positive pole piece and the positive pole material layer meet the relation of 3.0 < eta.D 50 < 10, wherein η is the porosity of the positive electrode sheet, D 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer was 50%. Through the improvement, the positive pole piece has higher multiplying power performance and longer cycle life.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a positive electrode plate, a preparation method of the positive electrode plate and a lithium ion battery.
Background
With the development of technology, tool electromotive has become a trend. Among these are travel tools such as electric bicycles, electric vehicles, and developing electric airplanes. The cruising ability is one of important performance indexes of the travel tool, and determines the time or distance that the travel tool can travel after being charged once. The stronger the cruising ability, the greater the range of use and convenience of the travel tool.
However, to achieve a strong cruising ability, great challenges are faced in the rate capability and cycle performance of lithium ion batteries. Obviously, the rate performance of the existing lithium ion battery still needs to be improved.
Disclosure of Invention
The invention provides a positive electrode plate, a preparation method of the positive electrode plate and a lithium ion battery, so as to improve the rate performance of the battery.
In order to achieve the above object, a first aspect of the present invention provides a positive electrode sheet, including a positive electrode current collector and a positive electrode material layer; at least one surface of the positive electrode current collector is coated with the positive electrode material layer; the positive electrode plate and the positive electrode material layer satisfy the relation 3.0 < eta eta.eta.D 50 Wherein eta is the porosity of the positive electrode plate and D is less than 10 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer of 50%.
In some embodiments, η ranges from 20% to 60%.
In some embodiments, D 50 The range of the value of (C) is 8-20 μm.
In some embodiments, the positive electrode material layer on the positive electrode current collector further satisfies 2.0mg/dm 2 ≤ρ≤3.5mg/dm 2 Wherein ρ is the coating weight of the positive electrode material layer per unit area.
In some embodiments, the positive electrode sheet also satisfies 3.3g/cm 3 ≤PD≤3.5g/cm 3 And PD is the compacted density of the positive electrode plate.
In some embodiments, the positive electrode material layer has the chemical formula of Li a Ni x Co y M 1-x-y O 2 Wherein M comprises Mn and/or Al,0.8 < a < 1.5,0 < x < 1,0 < y < 1,0 < x+y < 1.
In some embodiments, the positive electrode material layer includes a positive electrode conductive agent; the positive electrode conductive agent comprises at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene and ketjen black.
In some embodiments, the positive electrode material layer includes an adhesive; the adhesive comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate and polyvinyl alcohol.
The second aspect of the invention provides a preparation method of a positive electrode plate, comprising the following steps:
mixing an anode active material, auxiliary materials and a solvent to obtain anode slurry;
coating at least one surface of a positive electrode current collector with the positive electrode slurry;
drying and cold pressing the positive electrode current collector coated with the positive electrode slurry in sequence to convert the positive electrode slurry into a positive electrode material layer;
the positive electrode current collector coated with the positive electrode material layer is striped, and a positive electrode plate is obtained; wherein the positive electrode plate and the positive electrode material layer satisfy the relation 3.0 < eta.D 50 < 10, eta is the porosity of the positive electrode plate, D 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer of 50%.
The third aspect of the invention provides a lithium ion battery, which comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte; the positive electrode plate is the positive electrode plate.
The porosity of the positive electrode plate and the particle size of the positive electrode material layer provided by the invention need to meet the same relational expression, are limited in a proper numerical range, have strong synergistic relationship, and can jointly improve the multiplying power performance and the cycle life of the positive electrode plate, so that the positive electrode plate has higher multiplying power performance and longer cycle life.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
[ term interpretation ]
Positive pole piece: as the battery charges and discharges, channels for electron migration are provided, while collecting and conducting current. The positive electrode active material mainly comprises a positive electrode active material, a positive electrode conductive agent, a positive electrode current collector and an adhesive.
Positive electrode current collector: a metal foil, which acts as a conductive skeleton, can help collect and transport current.
Positive electrode material layer: is converted from the positive electrode slurry. After the positive electrode slurry is coated on the positive electrode current collector, drying and cold pressing are sequentially required, the drying is for removing the solvent in the positive electrode slurry, the conductivity and the structural stability of the electrode are improved, the cold pressing is for enhancing the compactness of the electrode, the contact between the positive electrode active material and the positive electrode current collector is improved, and the electrical property of the electrode is further enhanced.
Splitting: the method is used for cutting the coated pole piece to obtain the pole piece with the specified length, and is convenient for subsequent assembly and battery manufacturing.
Porosity: is an overall statistics of various pores in the pole piece material, including pores, capillary pores, controlled pores, etc.
Cumulative particle size distribution: also known as cumulative particle size distribution/cumulative distribution, is a statistical method used to describe the distribution of particulate matter according to different particle sizes.
Compaction density: and (3) after the active material, the adhesive and the like are prepared into pole pieces, compacting the pole pieces to obtain the density.
Positive electrode active material: is a main component of the positive pole piece and can provide energy for the battery.
Positive electrode conductive agent: helping to transfer charge.
An adhesive: for bonding the positive electrode active material and the positive electrode conductive agent together, and also can increase the mechanical strength of the electrode.
The embodiment of the invention provides a positive pole piece, which comprises a positive current collector and a positive material layer; at least one surface of the positive electrode current collector is coated with a positive electrode material layer; the positive pole piece and the positive pole material layer meet the relation of 3.0 < eta.D 50 < 10, wherein η is the porosity of the positive electrode sheet, D 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer was 50%. The porosity of the positive electrode plate and the particle size of the positive electrode material layer need to meet the same relation, are limited in a proper numerical range, have strong synergistic relation, and can jointly improve the multiplying power performance and the cycle life of the positive electrode plate, so that the positive electrode plate has higher multiplying power performance and longer cycle life.
In some embodiments, η ranges from 20% to 60%. If the porosity is too large, the compacted density becomes low, the membrane structure is liable to be broken, the effective reaction area of the electrolyte and the positive electrode active material increases, and the migration efficiency of lithium ions increases, but the contact between active particles in unit volume is small, and the discharge capacity of the battery gradually decreases. If the porosity is too small, the diffusion resistance of lithium ions increases, which results in a decrease in the rate performance, and thus, a suitable porosity is a key for the battery cell to have high rate performance and long cycle life.
In some embodiments, D 50 The range of the value of (C) is 8-20 μm. In the value range, the particle size of the positive electrode material layer is kept moderate, the positive electrode slurry is difficult to disperse and coat during homogenate, the particle size is not too large, and the rate performance of the battery cell during charge and discharge is reduced.
In some embodimentsThe positive electrode material layer on the positive electrode current collector also satisfies 2.0mg/dm 2 ≤ρ≤3.5mg/dm 2 Where ρ is the coating weight of the positive electrode material layer per unit area. If the coating weight is too light, it may result in too thin a layer of positive electrode material, which may not provide sufficient capacity and energy, thereby affecting the performance of the battery. If the coating weight is too heavy, it may cause an excessively thick layer of the positive electrode material, increase the resistance of the electrode, and also affect the rate performance of the battery. Therefore, in order to obtain good rate performance, an appropriate coating weight needs to be selected.
In some embodiments, the positive electrode sheet also satisfies 3.3g/cm 3 ≤PD≤3.5g/cm 3 Wherein PD is the compacted density of the positive pole piece. The compacted density can influence the electrochemical performance of the positive electrode plate, and the too high compacted density can lead to the gap between electrode materials to be smaller, limit the transmission path of lithium ions, reduce the ion diffusion efficiency and further influence the rate capability of the battery. Too low a compaction density may result in too large gaps between the electrode materials, making the electrode structure unstable, and also reducing the capacity utilization rate of the electrode materials, thereby affecting the rate capability of the battery.
In some embodiments, the positive electrode material layer has the formula Li a Ni x Co y M 1-x-y O 2 Wherein M comprises Mn and/or Al,0.8 < a < 1.5,0 < x < 1,0 < y < 1,0 < x+y < 1. Li in the chemical formula is lithium, ni is nickel, co is cobalt, M is a single element or a combination of multiple elements, mn is manganese, al is aluminum, and O is oxygen.
In some embodiments, the positive electrode material layer includes a positive electrode conductive agent; the positive electrode conductive agent comprises at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene and ketjen black.
In some embodiments, the positive electrode material layer includes a binder; the adhesive comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate and polyvinyl alcohol.
The embodiment of the invention also provides a preparation method of the positive plate, which comprises the following steps:
step S1: and mixing the positive electrode active material, auxiliary materials and a solvent to obtain positive electrode slurry.
In this step, optionally, the auxiliary material includes at least a positive electrode conductive agent and a binder. Optionally, the positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene, and ketjen black. Optionally, the adhesive comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate and polyvinyl alcohol.
Step S2: and coating at least one surface of the positive electrode current collector with positive electrode slurry.
Step S3: and (3) sequentially drying and cold pressing the positive electrode current collector coated with the positive electrode slurry to convert the positive electrode slurry into a positive electrode material layer.
In this step, the positive electrode material layer has the chemical formula of Li a Ni x Co y M 1-x-y O 2 Wherein M comprises Mn and/or Al,0.8 < a < 1.5,0 < x < 1,0 < y < 1,0 < x+y < 1.
Step S4: dividing the positive electrode current collector coated with the positive electrode material layer into strips to obtain a positive electrode plate; wherein, the positive pole piece and the positive pole material layer satisfy the relation 3.0 < eta.D 50 < 10, eta is the porosity of the positive pole piece, D 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer was 50%.
In this step, the value of η is optionally within the range of 20% to 60%. Alternatively, D 50 The range of the value of (C) is 8-20 μm. Optionally, the positive electrode material layer on the positive electrode current collector further satisfies 2.0mg/dm 2 ≤ρ≤3.5mg/dm 2 Wherein ρ is the coating weight of the positive electrode material layer per unit area. Optionally, the positive electrode plate also satisfies 3.3g/cm 3 ≤PD≤3.5g/cm 3 And PD is the compacted density of the positive electrode plate.
According to the preparation method, the porosity of the positive electrode plate and the particle size of the positive electrode material layer are required to meet the same relational expression, the positive electrode plate and the particle size of the positive electrode material layer are limited in a proper numerical range, the synergistic relationship is strong, the multiplying power performance and the cycle life of the positive electrode plate can be improved together, and the prepared positive electrode plate has higher multiplying power performance and longer cycle life.
An example of preparing a lithium ion battery is also provided herein, only to explain a preparation method of the lithium ion battery. The preparation method of the lithium ion battery comprises the following steps:
preparing a positive electrode plate: the preparation method is the same as that of the positive pole piece;
preparing a negative electrode plate: fully stirring and uniformly mixing artificial graphite, acetylene black, styrene-butadiene rubber and sodium carboxymethyl cellulose in a deionized water solvent system according to the mass ratio of 96:1:1.5:1.5 to obtain negative electrode slurry; coating the negative electrode slurry on a Cu foil, and drying, cold pressing and slitting to obtain a negative electrode plate;
preparing a separation film: preparing a separation membrane by adopting a porous polyethylene material;
preparing an electrolyte: the lithium salt LiPF6 and a nonaqueous organic solvent are prepared into a solution according to the mass ratio of 8:92 to be used as electrolyte of a lithium ion battery; wherein the nonaqueous organic solvent consists of ethylene carbonate, diethyl carbonate, propylene carbonate, propyl propionate and ethylene carbonate in the mass ratio of 20:30:20:28:2;
winding: sequentially stacking the positive pole piece, the isolating film and the negative pole piece, wherein the isolating film is positioned between the positive pole piece and the negative pole piece; winding the positive electrode plate, the isolating film and the negative electrode plate to obtain an electrode assembly;
and (3) packaging: and placing the electrode assembly in a packaging shell, injecting electrolyte and packaging to obtain the lithium ion battery.
According to the preparation method, in the step of (1) preparing the negative electrode plate, the negative electrode slurry with uniform components and stable performance can be obtained through reasonable proportion and full stirring and mixing, and a good foundation is provided for subsequent coating and plate preparation. (2) In the step of preparing the electrolyte, the electrolyte with uniform components and stable performance can be obtained through reasonable proportion, and good guarantee is provided for the performance and stability of the lithium ion battery; and, the nonaqueous organic solvent can provide good solubility and chemical stability, and can ensure high conductivity and high ion mobility of the electrolyte.
Examples of some of the preparation of lithium ion batteries are also provided herein for the purpose of demonstrating D 50 A number of options for η, and examples of these are reasonable matches consistent with the present invention.
Example 1
The lithium ion battery is prepared according to the scheme, wherein the method for preparing the positive electrode plate in the example comprises the following steps: and (3) fully and uniformly stirring and mixing the positive electrode active material (NCM), the conductive agent (acetylene black) and the binder (polyvinylidene fluoride (PVDF)) in an N-methylpyrrolidone solvent system according to the mass ratio of 95:3:2, coating the mixture on an Al foil of a positive electrode current collector, and drying, cold pressing and slitting the mixture to obtain the positive electrode plate. The positive electrode sheet of this example had a compacted density PD of 3.5g/cm 3 ，D 50 15um, ρ of 2.5mg/dm 2 Eta is 40%, eta is D 50 ＝6。
Example 2
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only D 50 Is 8um, eta 50 ＝3.2。
Example 3
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only D 50 20um, 50% eta, eta.D 50 ＝10。
Example 4
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only that η is 20%, η is D 50 ＝3。
Example 5
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only that η is 60%, η is D 50 ＝9。
Some examples of making lithium ion batteries are also provided herein, employing an unreasonable collocation contrary to the present invention, for comparison with examples 1-5.
Comparative example 1
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only D 50 Is 6um, eta 50 ＝2.4。
Comparative example 2
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only D 50 Is 30um, eta 50 ＝12。
Comparative example 3
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only D 50 Is 6um, eta is 15 percent, eta is D 50 ＝0.9。
Comparative example 4
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only that η is 70%, η is D 50 ＝10.5。
Comparative example 5
In comparison with the lithium ion battery preparation example proposed in example 1 above, the difference is only that η is 15%, η is D 50 ＝2.25。
ρ, PD, D corresponding to examples 1 to 5 and comparative examples 1 to 5 50 、η、η*D 50 As shown in the table below.
To learn the performance of the lithium ion batteries prepared in examples 1-5 and comparative examples 1-5, the following tests were performed:
(1) Rate capability test
And (3) fully charging the lithium ion batteries prepared in examples 1-5 and comparative examples 1-5 with xC, fully discharging with 1C, repeating the fully charging and fully discharging for 10 times, fully charging the lithium ion battery with xC, disassembling the negative electrode plate, and observing the lithium precipitation condition on the surface of the negative electrode plate. If the lithium is not separated out from the surface of the negative electrode, the test is performed again by taking 0.1C as gradient increment on the basis of the charging multiplying power xC until the lithium is separated out from the surface of the negative electrode plate, namely, the test is stopped, and the charging multiplying power (x-0.1) C at the moment is the maximum charging multiplying power of the battery, and the test result is shown in the following table.
(2) Cycle performance test
The lithium ion batteries were repeatedly charged and discharged by taking 5 lithium ion batteries prepared in examples 1 to 5 and comparative examples 1 to 5, respectively, and the cyclic capacity retention rate of the lithium ion batteries was calculated by the following steps.
First, in an environment of 25 ℃, performing first charge and discharge, performing constant current and constant voltage charge at a charge current of 0.1C (i.e., a current value that completely discharges a theoretical capacity within 10 hours) until an upper limit voltage is 4.3V;
then, constant current discharge is carried out under the discharge current of 1C until the final voltage is 3V, and the discharge capacity of the first cycle is recorded;
then, 100 charge and discharge cycles were performed, and the discharge capacity at the 100 th cycle was recorded.
Finally, according to the formula: cycle capacity retention= (discharge capacity of the 100 th cycle/discharge capacity of the first cycle) ×100%, the cycle capacity retention was calculated.
The cycle performance test data are shown in the following table.
Wherein the cyclic capacity retention is the average. From the test data of comparative examples 1 to 5 and comparative examples 1 to 5, it is understood that when the porosity of the positive electrode sheet and the particle diameter D of the positive electrode material layer 50 Satisfy the relation 3.0 < eta.D 50 The battery core has higher multiplying power performance and longer cycle life, and the reasonable collocation of the porosity and the particle size is proved, so that the porosity and the particle size can be cooperated to improve the multiplying power performance and the cycle performance of the positive pole piece.
Those skilled in the art may combine and combine the features of the different embodiments or examples described in this specification and of the different embodiments or examples without contradiction.
The above description of the preferred embodiments of the invention is intended to cover all modifications of the invention, including the equivalent structures shown in the written description or used in the direct or indirect connection, or any other suitable application in the field of technology.
Claims (10)
1. A positive electrode plate comprises a positive electrode current collector and a positive electrode material layer; at least one surface of the positive electrode current collector is coated with the positive electrode material layer; the method is characterized in that: the positive electrode plate and the positive electrode material layer satisfy the relation 3.0 < eta.D 50 Wherein eta is the porosity of the positive electrode plate and D is less than 10 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer of 50%.
2. The positive electrode sheet according to claim 1, wherein η is in the range of 20% to 60%.
3. The positive electrode sheet according to claim 1, wherein D 50 The range of the value of (C) is 8-20 μm.
4. The positive electrode sheet according to claim 1, wherein the positive electrode material layer on the positive electrode current collector further satisfies 2.0mg/dm 2 ≤ρ≤3.5mg/dm 2 Wherein ρ is the coating weight of the positive electrode material layer per unit area.
5. The positive electrode sheet according to claim 1, further satisfying 3.3g/cm 3 ≤PD≤3.5g/cm 3 And PD is the compacted density of the positive electrode plate.
6. The positive electrode sheet according to claim 1, wherein the positive electrode material layer has a chemical formula of Li a Ni x Co y M 1-x-y O 2 Wherein M comprises Mn and/or Al,0.8 < a＜1.5，0＜x＜1，0＜y＜1，0＜x+y＜1。
7. The positive electrode sheet according to claim 1, wherein the positive electrode material layer includes a positive electrode conductive agent; the positive electrode conductive agent comprises at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene and ketjen black.
8. The positive electrode sheet according to claim 1, wherein the positive electrode material layer includes an adhesive; the adhesive comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate and polyvinyl alcohol.
9. The preparation method of the positive plate is characterized by comprising the following steps:
mixing an anode active material, auxiliary materials and a solvent to obtain anode slurry;
coating at least one surface of a positive electrode current collector with the positive electrode slurry;
drying and cold pressing the positive electrode current collector coated with the positive electrode slurry in sequence to convert the positive electrode slurry into a positive electrode material layer;
the positive electrode current collector coated with the positive electrode material layer is striped, and a positive electrode plate is obtained; wherein the positive electrode plate and the positive electrode material layer satisfy the relation 3.0 < eta.D 50 < 10, eta is the porosity of the positive electrode plate, D 50 The particle size corresponding to the cumulative particle size distribution of the positive electrode material layer of 50%.
10. A lithium ion battery comprises a positive pole piece, a negative pole piece, an isolating film and electrolyte; the positive electrode plate is characterized by being as claimed in any one of claims 1 to 8.
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