CN221102165U - Lithium ion battery - Google Patents
Lithium ion battery Download PDFInfo
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- CN221102165U CN221102165U CN202322535327.6U CN202322535327U CN221102165U CN 221102165 U CN221102165 U CN 221102165U CN 202322535327 U CN202322535327 U CN 202322535327U CN 221102165 U CN221102165 U CN 221102165U
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 99
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 99
- 239000011248 coating agent Substances 0.000 claims abstract description 117
- 238000000576 coating method Methods 0.000 claims abstract description 117
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 20
- 238000005070 sampling Methods 0.000 claims abstract description 14
- 239000002245 particle Substances 0.000 claims abstract description 12
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 claims description 4
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 2
- 229910002102 lithium manganese oxide Inorganic materials 0.000 claims description 2
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 25
- 230000008021 deposition Effects 0.000 abstract description 14
- 229910052751 metal Inorganic materials 0.000 abstract description 10
- 239000002184 metal Substances 0.000 abstract description 10
- 238000012360 testing method Methods 0.000 description 25
- 239000011247 coating layer Substances 0.000 description 20
- 239000003792 electrolyte Substances 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 18
- 238000002360 preparation method Methods 0.000 description 15
- 239000000463 material Substances 0.000 description 11
- 238000011112 process operation Methods 0.000 description 11
- 230000001105 regulatory effect Effects 0.000 description 11
- 230000005540 biological transmission Effects 0.000 description 10
- 238000005056 compaction Methods 0.000 description 9
- 239000006258 conductive agent Substances 0.000 description 9
- 239000011148 porous material Substances 0.000 description 9
- 239000011267 electrode slurry Substances 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 6
- 239000007774 positive electrode material Substances 0.000 description 5
- 238000007599 discharging Methods 0.000 description 4
- 239000011888 foil Substances 0.000 description 4
- 239000012528 membrane Substances 0.000 description 4
- 238000001764 infiltration Methods 0.000 description 3
- 230000008595 infiltration Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229910002991 LiNi0.5Co0.2Mn0.3O2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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- Secondary Cells (AREA)
Abstract
The utility model provides a lithium ion battery, which comprises a positive plate and a negative current collector, wherein the positive plate comprises a positive current collector and a positive active coating arranged on the surface of the positive current collector, the positive active coating comprises positive active particles, and the thickness consistency of the positive active coating is delta D: And delta D is more than or equal to 0.12 mu m and less than or equal to 2.5 mu m; in the general formula of delta D, i represents the number of sampling points, i=1 to n, n is a positive integer greater than 1, D i is the distance between any sampling point and the positive current collector, Average of all d i, i.eThe lithium ion battery provided by the utility model has good cycle characteristics, and in the working process, a uniform metal lithium deposition layer can be formed on the surface of the negative electrode current collector.
Description
Technical Field
The utility model belongs to the technical field of batteries, and particularly relates to a lithium ion battery.
Background
The novel cathode-free lithium ion battery adopts a current collector as a cathode to replace a traditional graphite cathode, so that the use of a cathode active material is omitted, the energy density of the battery can be improved, the production cost of the battery can be reduced, and the novel cathode-free lithium ion battery is an ideal high-energy density system. During the charging process of the battery, lithium ions are extracted from the positive electrode, deposited on the negative electrode current collector in the form of metal lithium, and during the discharging process, the metal lithium is reformed to form lithium ions to be inserted back into the positive electrode. However, since the negative side of the non-negative lithium ion battery does not have stable protection of the negative active material or compensation of excessive active lithium, metallic lithium is easily unevenly deposited on the surface of the negative current collector during the cycle, resulting in a cycle life of the lithium ion battery facing a great challenge.
Therefore, how to realize uniform deposition of lithium ions to improve the cycle performance of a non-negative electrode lithium ion battery system becomes an important research direction in the field.
Disclosure of utility model
The utility model aims to provide a lithium ion battery, which can form a uniform metal lithium deposition layer on the surface of a negative current collector in the working process, so that the lithium ion battery has good cycle performance.
According to one aspect of the present utility model, there is provided a lithium ion battery comprising a positive electrode sheet and a negative electrode current collector, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active coating layer provided on a surface of the positive electrode current collector, the positive electrode active coating layer comprising positive electrode active particles, wherein the thickness uniformity of the positive electrode active coating layer is Δd: And delta D is more than or equal to 0.12 mu m and less than or equal to 2.5 mu m; in the general formula of Δd, i represents the number of sampling points selected on the first surface of the positive electrode active coating, the first surface refers to a surface far away from the positive electrode current collector in the thickness direction of the positive electrode active coating, i=1 to n, n is a positive integer greater than 1, D i is the distance between any sampling point and the positive electrode current collector, and v is the distance between any sampling point and the positive electrode current collector Average of all d i, i.e
In the lithium ion battery provided by the utility model, the adopted positive electrode active coating of the positive electrode plate has specific thickness consistency, and the positive electrode active coating has proper porosity, so that the balance of lithium ion transmission and electron conduction of the electrode plate is facilitated in the charge and discharge process, thereby inducing uniform deposition and compact growth of metallic lithium on the surface of the negative electrode plate, and improving the structural stability and the cycling stability of the prepared negative electrode-free lithium ion battery system. If the delta D is too large, the surface of the positive electrode active coating is rough and uneven, more pores exist, so that the porosity of the positive electrode plate is larger, the content of electrolyte filled in the pores of the positive electrode plate is more, the volume fraction of the electrolyte is high, the volume fraction of the conductive agent is low, and the conductive agent is not beneficial to the conduction of electrons, so that the electron transmission efficiency is lower than that of lithium ions; if delta D is too small, the surface of the positive electrode active coating is smooth, but the porosity of the positive electrode plate is small, so that the liquid absorption capacity of the positive electrode active coating is reduced, the infiltration of electrolyte to the positive electrode plate is not facilitated, the content of the electrolyte filled in the pores of the positive electrode plate is small in the working process of the lithium ion battery, the volume fraction of the electrolyte in the positive electrode plate is low, the volume fraction of the conductive agent is high, and the electron transmission efficiency is higher than that of lithium ions. Both of the above conditions are unfavorable for the balance of lithium ion and electron transport, making the cycle characteristics of lithium ion batteries poor.
Drawings
Fig. 1 is a schematic diagram of bare cell structures included in lithium ion batteries prepared in examples 1 to 10 and comparative examples 1 to 2.
In the above figures, the corresponding relationship between the technical features and the reference numerals is: 1. the negative electrode current collector, the separator, the positive electrode active coating and the positive electrode current collector are respectively arranged on the positive electrode current collector and the negative electrode current collector.
Detailed Description
The utility model provides a lithium ion battery, which comprises a positive plate and a negative current collector 1, wherein the positive plate comprises a positive current collector 4 and a positive active coating 3 arranged on the surface of the positive current collector 4, the positive active coating 3 comprises positive active particles, and the thickness consistency of the positive active coating 3 is delta D: And delta D is more than or equal to 0.12 mu m and less than or equal to 2.5 mu m; in the general formula of Δd, i represents the number of sampling points selected on the first surface of the positive electrode active coating 3, the first surface refers to a surface far away from the positive electrode current collector 4 in the thickness direction of the positive electrode active coating, i=1 to n, n is a positive integer greater than 1, D i is the distance between any sampling point and the positive electrode current collector 4, and v > Average of all d i, i.e
In the lithium ion battery provided by the utility model, the adopted positive electrode active coating 3 of the positive electrode plate has specific thickness consistency, the positive electrode active coating 3 has proper porosity, positive electrode active particles in the positive electrode active coating 3 are uniformly distributed, and balance of lithium ion transmission and electron conduction is facilitated to be achieved in the process of charging and discharging the electrode plate, so that uniform deposition and compact growth of metal lithium on the surface of the negative electrode plate are induced, and the structural stability and the cyclic stability of the prepared non-negative electrode lithium ion battery system are improved. If the delta D is too large, the surface of the positive electrode active coating 3 is rough and uneven, and more pores exist, so that the porosity of the positive electrode plate is larger, the content of electrolyte filled in the pores of the positive electrode plate is more, the volume fraction of the electrolyte is high, the volume fraction of the conductive agent is low, and the conductive agent is not beneficial to the conduction of electrons, so that the electron transmission efficiency is lower than that of lithium ions; if Δd is too small, the surface of the positive electrode active coating 3 is smooth, the porosity of the positive electrode sheet is small, so that the liquid absorbing capability of the positive electrode active coating 3 is reduced, the infiltration of electrolyte to the positive electrode sheet is not facilitated, the content of electrolyte filled in the pores of the positive electrode sheet is small in the working process of the lithium ion battery, the volume fraction of the electrolyte in the positive electrode sheet is low, the volume fraction of the conductive agent is high, and therefore the electron transmission efficiency is higher than that of lithium ions. Both of the above conditions are unfavorable for the balance of lithium ion and electron transport, making the cycle characteristics of lithium ion batteries poor.
Preferably, 0.3 μm.ltoreq.ΔD.ltoreq.0.5 μm.
Preferably, the thickness of the positive electrode active coating layer 3 is 100 to 300 μm. If the thickness of the positive electrode active coating 3 is too thick, the surface of the pole piece is uneven, the consistency of the thickness of the pole piece is difficult to ensure, and the uniform deposition of the metallic lithium in the circulation process is not facilitated; if the thickness of the positive electrode active coating layer 3 is too thin, the capacity of the battery system is adversely affected. Therefore, by making the thickness of the positive electrode active coating layer 3 satisfy the above-described specific range, it is easy to obtain a positive electrode active coating layer 3 suitable for the thickness uniformity Δd.
Preferably, the width of the positive electrode active coating layer 3 is 80 to 600mm. By defining the width of the positive electrode active coating 3, it is advantageous to control the thickness uniformity Δd along the width edge position of the positive electrode sheet, thereby more easily achieving uniformity and compactness of metal lithium deposition. Specifically, the length dimension > the width dimension of the positive electrode active coating layer 3.
Preferably, the positive electrode active particles are lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese oxide, or lithium cobalt oxide.
Preferably, the negative electrode current collector 1 is a copper current collector.
Preferably, the positive electrode current collector 4 is an aluminum current collector.
Preferably, the areal density of the positive electrode active coating layer 3 is 300 to 800g/m 2.
If the surface density of the positive electrode active coating 3 is larger, the positive electrode active coating 3 is thicker, so that the surface of the positive electrode plate is uneven, and uniform deposition of metal lithium in the circulation process is not facilitated; if the areal density is small, the positive electrode active coating 3 is thin, which is not favorable for the energy density of the battery system. Therefore, the above scheme can control the flatness of the positive plate while guaranteeing the energy density of the battery system by controlling the surface density of the positive active coating 3 within a specific range, so as to realize the compactness and uniformity of the deposition of the metallic lithium on the surface of the negative electrode.
Preferably, the porosity of the positive electrode active coating layer 3 is 10 to 40%.
The porosity of the positive plate is controlled in the range, so that the lithium ion battery can be promoted to reach the balance state of lithium ion transmission and electron conduction in the working process, and the cycle performance of the lithium ion battery is optimized.
Preferably, the porosity of the positive electrode active coating layer 3 is 15 to 18%.
The technical features of the technical solution provided in the present utility model will be further clearly and completely described in connection with the detailed description below, and it is obvious that the described embodiments are only some embodiments of the present utility model, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
Example 1
The embodiment provides a lithium ion battery, and the preparation method thereof comprises the following steps:
(1) Selection of positive electrode active material
Positive electrode active particles lithium nickel cobalt manganese oxide LiNi 0.5Co0.2Mn0.3O2 (NCM 523) were purchased according to particle size requirements, and in the following examples and comparative examples, the particle size d50=12 μm of NCM523 was used.
(2) Preparation of positive plate
Mixing the positive electrode active particles, the conductive agent acetylene black and the binder PVDF according to the mass ratio of 96:2:2, adding the solvent NMP, and stirring under the action of a vacuum stirrer until the system is uniform to obtain positive electrode slurry; and uniformly coating the anode slurry on two surfaces of an aluminum foil of the anode current collector 4, airing at room temperature, transferring to an oven, and continuously drying to form an anode active coating 3. Wherein, the surface density of the positive electrode active coating 3 is 500g/m 2 by adjusting the gap of a coating scraper of a coating machine for coating positive electrode slurry; the width of the positive electrode active coating 3 is controlled to be 235mm by selecting the width of the coating gasket to be 235mm; then, the positive electrode active coating 3 was cold-pressed to adjust the compacted density to 3.49, and the thickness of the positive electrode active coating 3 was 143 μm. And finally, a positive plate is obtained through a slitting process.
(3) Preparation of separator
The membrane 2 was selected from commercial PE polyethylene membranes, the membrane 2 thickness was 15 μm and the membrane 2 porosity was 30%.
(4) Preparation of negative electrode sheet
And cutting the photo-copper foil to obtain a negative current collector 1, and taking the negative current collector 1 as a negative plate.
(5) Preparation of electrolyte
The Ethylene Carbonate (EC) and the dimethyl carbonate (DMC) were mixed at a volume ratio of 1:1 to obtain an organic solvent, and then a sufficiently dried lithium salt LiPF 6 was dissolved in the mixed organic solvent to prepare an electrolyte having a concentration of 1 mol/L.
In practical application, electrolyte with other formulas can be selected according to specific situations.
(6) Preparation of lithium ion batteries
Sequentially stacking the positive plate, the diaphragm 2 and the negative plate, enabling the diaphragm 2 to be positioned between the positive plate and the negative plate to play a role of isolation, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging shell, drying, injecting electrolyte, and vacuum packaging and standing for 24 hours for later use.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 2
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the compaction density of the positive electrode active coating 3 is regulated to be 2.85, and the thickness of the positive electrode active coating 3 is 175 mu m. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 3
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the compaction density of the positive electrode active coating 3 is regulated to be 3.73, and the thickness of the positive electrode active coating 3 is 134 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 4
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the compaction density of the positive electrode active coating 3 is regulated to be 3.38, and the thickness of the positive electrode active coating 3 is 148 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 5
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the compaction density of the positive electrode active coating 3 is regulated to be 3.45, and the thickness of the positive electrode active coating 3 is 145 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 6
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the gap of a coating scraper of a coating machine for coating positive electrode slurry is adjusted to obtain the positive electrode active coating 3 with the areal density of 900g/m 2; the compaction density of the positive electrode active coating 3 was regulated to 2.86, and the thickness of the positive electrode active coating 3 was 315 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 7
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive electrode active material, the width of the positive electrode active coating 3 is controlled to be 650mm by selecting the width of the coating gasket to be 650mm; the compacted density of the positive electrode active coating 3 was regulated to 3.29, and the thickness of the positive electrode active coating 3 was 152 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 8
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the gap of a coating scraper of a coating machine for coating positive electrode slurry is adjusted to obtain the surface density of the positive electrode active coating 3 of 300g/m 2; the compaction density of the positive electrode active coating 3 was regulated to 2.88, and the thickness of the positive electrode active coating 3 was 104 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 9
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the gap of a coating scraper of a coating machine for coating positive electrode slurry is adjusted to obtain the positive electrode active coating 3 with the surface density of 800g/m 2; the compaction density of the positive electrode active coating 3 was regulated to 3.48, and the thickness of the positive electrode active coating 3 was 230 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Example 10
This example makes reference to example 1 for the preparation of a lithium ion battery, which differs from example 1 in that: in the process of preparing the positive plate, the gap of a coating scraper of a coating machine for coating positive electrode slurry is adjusted to obtain the surface density of the positive electrode active coating 3 of 200g/m 2; the compacted density of the positive electrode active coating 3 was regulated to 2.66, and the thickness of the positive electrode active coating 3 was 75 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this embodiment is shown in fig. 1, and the structure of the bare cell sequentially includes a negative current collector 1, a separator 2, a positive active coating 3, and a positive current collector 4 in the thickness direction.
Comparative example 1
Comparative example a lithium ion battery was prepared with reference to example 1, the comparative example differing from example 1 in that: in the process of preparing the positive electrode active material in this example, the compaction density of the positive electrode active coating 3 was regulated to 2.84, and the thickness of the positive electrode active coating 3 was 176 μm. Except for the above differences, the materials used in this comparative example and the process operation were strictly identical to those of example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this comparative example is shown in fig. 1, and the structure thereof sequentially includes a negative electrode current collector 1, a separator 2, a positive electrode active coating 3, and a positive electrode current collector 4 in the thickness direction.
Comparative example 2
Comparative example a lithium ion battery was prepared with reference to example 1, the comparative example differing from example 1 in that: in the process of preparing the positive electrode active material in this example, the compaction density of the positive electrode active coating 3 was regulated to 5.20, and the thickness of the positive electrode active coating 3 was obtained to be 96 μm. Except for the above differences, the materials used in this comparative example and the process operation were strictly identical to those of example 1.
The structure of the bare cell included in the lithium ion battery manufactured in this comparative example is shown in fig. 1, and the structure thereof sequentially includes a negative electrode current collector 1, a separator 2, a positive electrode active coating 3, and a positive electrode current collector 4 in the thickness direction.
Test case
1. Reference subject
The lithium ion batteries produced in examples 1 to 10 and comparative examples 1 to 2 were used as the subjects of the present test example.
2. Test item
(1) Thickness uniformity Δd of positive plate: taking i sampling points on the surface of the positive electrode active coating of the positive electrode plate, adopting an HPW-2002QCSX ray on-line thickness detector, directly reading the thickness of the sampling points on the surface of the positive electrode active coating through a software program, and calculating the thickness consistency of the positive electrode plate according to the following formula: Wherein d i represents the distance between any sampling point and the positive electrode current collector, and is/is The average value of the distances between i sampling points and the positive electrode current collector is represented, and n represents the number of sampling points.
(2) Thickness, width of positive electrode active coating: and disassembling the battery, and measuring the thickness and the width of the positive active coating of the positive plate by using a micrometer.
(3) Areal density of positive electrode active coating: cutting a positive plate wafer with radius r=2cm and an aluminum foil with radius 2cm, weighing the mass M1 of the positive plate and the mass M2 of the optical aluminum foil by using an electronic balance, and calculating the surface density of the positive plate according to the following formula: areal density= (M1-M2) w/(3.14 xr 2), wherein M1 represents the mass (mg) of the positive electrode sheet, M2 represents the mass (mg) of the aluminum foil, w represents the mass fraction (%) of the positive electrode active material, r represents the radius (cm) of the positive electrode sheet;
(4) Porosity of the positive electrode active coating: testing the porosity of the positive electrode active coating of the positive electrode plate according to GB/T21650.1-2008/ISO 15901-1:2005 by using a mercury porosimeter;
(5) Thickness of negative electrode deposited lithium: disassembling the battery after the cyclic test, and measuring the thickness of the deposited lithium of the negative electrode by using a micrometer;
(6) Capacity retention rate for 50 cycles: and (3) using the LAND system to charge the reference battery to 4.25V at a constant current of 0.2C, discharging the reference battery to 2.0V at a constant current of 0.33C, and taking the reference battery off the charging device for standby. Then, the above battery was subjected to a normal temperature cycle test using a LAND system, and the charge/discharge rate was 0.2C/0.33C, and the cycle was 50 weeks. And after the test is finished, processing the cycle data, and calculating the battery capacity retention rate after 50 cycles.
3. Test results
Table 1 results of performance tests of lithium ion batteries of examples 1 to 10 and comparative examples 1 to 2
The test results of this test example are shown in Table 1. Among the test subjects of the present test examples, the lithium ion batteries provided in examples 1 to 10 were able to achieve a higher cycle capacity retention in the cycle test of the present test example, however, the cycle 50 cycle capacity retention measured for the lithium ion batteries provided in comparative examples 1, 2 was significantly lower than those of the test subjects. In the lithium ion batteries prepared in examples 1 to 10 and comparative examples 1 and 2, the surface of the positive electrode current collector 4 was coated with the positive electrode active coating layer 3, respectively, except that the thickness uniformity Δd of the positive electrode active coating layer 3 was different. In the lithium ion batteries provided in examples 1 to 10, the uniformity of the thickness of the positive electrode active coating 3 of the positive electrode sheet adopted satisfies 0.12 μm and Δd and is less than or equal to 2.5 μm, and in this range, the positive electrode active coating 3 has a suitable porosity, and positive electrode active particles in the positive electrode active coating 3 are uniformly distributed, so that the balance of lithium ion transmission and electron conduction in the charging and discharging process of the electrode sheet is facilitated, and the uniform deposition and compact growth of metallic lithium on the surface of the negative electrode sheet are induced, so that the lithium ion battery has good cycle characteristics. In the lithium ion battery provided in comparative example 1, Δd is greater than 2.5 μm, the surface of the positive electrode active coating 3 is rough and uneven, and many pores exist, so that the porosity of the positive electrode sheet is larger, the content of electrolyte filled in the pores of the positive electrode sheet is large, the volume fraction of the electrolyte is high, the volume fraction of the conductive agent is low, the conduction of electrons is not facilitated, the electron transmission efficiency is lower than that of lithium ions, and thus the uniformity and compactness of the deposition of negative electrode metallic lithium are poor, and the cycle performance of the lithium ion battery is poor. In the lithium ion battery provided in comparative example 2, Δd is less than 0.12 μm, the surface of the positive electrode active coating 3 is smooth, the porosity of the positive electrode sheet is small, the liquid absorption capability of the positive electrode active coating 3 is reduced, the infiltration of electrolyte to the positive electrode sheet is not facilitated, the content of electrolyte filled in the pores of the positive electrode sheet is small in the working process of the lithium ion battery, the volume fraction of the electrolyte in the positive electrode sheet is low, the volume fraction of the conductive agent is high, and the transmission efficiency of electrons is higher than that of lithium ions. Both of the above conditions are unfavorable for the balance of lithium ion and electron transport, making the cycle characteristics of lithium ion batteries poor. In the lithium ion batteries provided in examples 1 to 10, the capacity retention rates measured corresponding to the lithium ion batteries of examples 1, 4, 5 and 8 were higher than those of the test objects provided in other examples, so that experiments prove that the lithium ion battery provided by the utility model has better cycle performance when meeting the conditions that Δd is less than or equal to 0.3 μm and less than or equal to 0.5 μm.
In the test object of the present test example, the positive electrode active coating layer 3 of example 6 had a thickness of > 300 μm and an areal density of > 800 μm, while the positive electrode active coating layer 3 of example 9 had a thickness of 100 to 300 μm and an areal density of 300 to 800 μm, and it was found from the test result that the cycle performance of example 6 was lower than that of example 9. The reason is that the thickness of the positive active coating 3 of the lithium ion battery prepared in example 6 is too thick, which easily causes uneven surface of the pole piece, and it is difficult to ensure thickness uniformity of the pole piece, so that uniformity and compactness of metal lithium deposition are difficult to realize, and cycle performance of the lithium ion battery is reduced. In addition, in the test object of the present test example, the positive electrode active coating layer 3 of example 10 had a thickness of < 100 μm and an areal density of < 300 μm, whereas the positive electrode active coating layer 3 of example 3 had a thickness of 100 to 300 μm and an areal density of 300 to 800 μm, and it was found from the test result that the cycle performance of example 10 was lower than that of example 3. The reason is that the thickness of the positive active coating 3 of the lithium ion battery prepared in example 10 is too thin to be advantageous for the capacity of the battery system, resulting in degradation of the cycle performance of the lithium ion battery. Therefore, in the lithium ion battery provided by the utility model, the thickness of the positive electrode active coating 3 is enabled to be 100-300 mu m, so that the lithium ion battery with proper thickness consistency delta D is obtained, and the lithium ion battery has good cycle characteristics.
In the test object of the present test example, the width of the positive electrode active coating layer 3 of example 7 was > 600 μm, while the width of the positive electrode active coating layer 3 of example 9 satisfied 80 to 600 μm, and it can be seen from the test results that the cycle capacity retention rate of example 7 was lower than that of example 9. Therefore, the width of the positive electrode active coating 3 is limited, so that the thickness consistency delta D along the width edge position of the positive electrode plate is favorably controlled, the uniformity and compactness of metal lithium deposition are more easily realized, the deposition thickness of the negative electrode metal lithium is reduced, and the cycle performance of the lithium ion battery is improved.
The above embodiments are only for illustrating the technical solution of the present utility model and not for limiting the scope of the present utility model, and although the present utility model has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present utility model, but these modifications or substitutions are all within the scope of the present utility model.
Claims (10)
1. The lithium ion battery is characterized by comprising a positive plate and a negative current collector, wherein the positive plate comprises a positive current collector and a positive active coating arranged on the surface of the positive current collector, and the positive active coating comprises positive active particles, wherein the thickness consistency of the positive active coating is delta D: the said And delta D is more than or equal to 0.12 mu m and less than or equal to 2.5 mu m;
In the general formula of Δd, i represents the number of sampling points selected on a first surface of the positive electrode active coating, where the first surface refers to a surface far away from the positive electrode current collector in a thickness direction of the positive electrode active coating, i=1 to n, n is a positive integer greater than 1, D i is a distance between any one of the sampling points and the positive electrode current collector, and Is the average of all said d i.
2. The lithium-ion battery of claim 1, wherein Δd is 0.3 μm or less and 0.5 μm or less.
3. The lithium-ion battery of claim 1, wherein the positive electrode active coating has a thickness of 100 to 300 μm.
4. The lithium-ion battery of claim 1, wherein the positive electrode active coating has a width of 80 to 600mm.
5. The lithium-ion battery of claim 1, wherein the positive electrode active particles are lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese oxide, or lithium nickelate.
6. The lithium-ion battery of claim 1, wherein the negative current collector is a copper current collector.
7. The lithium-ion battery of claim 1, wherein the positive current collector is an aluminum current collector.
8. The lithium-ion battery of claim 1, wherein the positive electrode active coating has an areal density of 300 to 800g/m 2.
9. The lithium-ion battery of any of claims 1-8, wherein the positive electrode active coating has a porosity of 10-40%.
10. The lithium-ion battery of claim 9, wherein the positive electrode active coating has a porosity of 15 to 18%.
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