CN115275105B - Silicon-based negative electrode plate, secondary battery and power utilization device - Google Patents
Silicon-based negative electrode plate, secondary battery and power utilization device Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 34
- 239000010703 silicon Substances 0.000 title claims abstract description 30
- 239000011248 coating agent Substances 0.000 claims abstract description 54
- 238000000576 coating method Methods 0.000 claims abstract description 54
- 239000000463 material Substances 0.000 claims abstract description 24
- 125000004430 oxygen atom Chemical group O* 0.000 claims abstract description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 20
- 239000003792 electrolyte Substances 0.000 claims description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 13
- 229910003002 lithium salt Inorganic materials 0.000 claims description 11
- 159000000002 lithium salts Chemical class 0.000 claims description 11
- 239000003960 organic solvent Substances 0.000 claims description 11
- 239000000654 additive Substances 0.000 claims description 10
- 230000000996 additive effect Effects 0.000 claims description 9
- 239000007774 positive electrode material Substances 0.000 claims description 9
- 229910002804 graphite Inorganic materials 0.000 claims description 8
- 239000010439 graphite Substances 0.000 claims description 8
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 5
- 238000004806 packaging method and process Methods 0.000 claims description 4
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 claims description 3
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 3
- 239000003575 carbonaceous material Substances 0.000 claims description 3
- 239000002131 composite material Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 229910021382 natural graphite Inorganic materials 0.000 claims description 3
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 abstract description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 13
- 229910052744 lithium Inorganic materials 0.000 abstract description 13
- 238000001556 precipitation Methods 0.000 abstract description 10
- 230000008859 change Effects 0.000 abstract description 6
- 239000010410 layer Substances 0.000 description 41
- 239000011247 coating layer Substances 0.000 description 39
- 239000011149 active material Substances 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 15
- 238000000926 separation method Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 239000006183 anode active material Substances 0.000 description 6
- 238000007600 charging Methods 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 125000004122 cyclic group Chemical group 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 238000013461 design Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 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 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010280 constant potential charging Methods 0.000 description 2
- 238000010277 constant-current charging Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
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- 238000012986 modification Methods 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- 229910013716 LiNi Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 229910020169 SiOa Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000000296 active ion transport Effects 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
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- 230000008439 repair process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
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- 238000004804 winding Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative 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
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- 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)
- Secondary Cells (AREA)
Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a silicon-based negative electrode plate, a secondary battery and an electric device. The silicon-based negative electrode plate comprises a negative electrode current collector and an active coating arranged on at least one surface of the negative electrode current collector, wherein the active coating comprises an inner coating and an outer coating, and the following relation is satisfied: a/b is more than or equal to 0.3 and less than or equal to 1; c/d is more than or equal to 1.2 and less than or equal to 3, wherein a is the number of oxygen atoms in the silicon oxygen material in the inner coating, and a is more than or equal to 0.6 and less than or equal to 1.3; b is the number of oxygen atoms in the silicon oxygen material in the outer coating, and a is more than or equal to b and less than or equal to 2; c is the thickness of the inner coating, and c is more than or equal to 50 microns and less than or equal to 150 microns; d is the thickness of the outer coating, and d is more than or equal to 25 μm and less than or equal to 100 μm. The silicon-based negative electrode plate has the characteristics of high specific energy, small change of charge and discharge volume, difficult lithium precipitation and long cycle life due to different silicon-oxygen atom proportions in the inner coating and the outer coating.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a silicon-based negative electrode plate, a secondary battery and an electric device.
Background
With the progress of battery technology in recent years, the specific capacity of the traditional graphite cathode has been improved to be close to the theoretical value (372 mAh/g), and the continuous upward improvement is difficult. To break this bottleneck, new anode materials need to be developed. Compared with a graphite cathode, the silicon material has higher gram capacity (4200 mAh/g), so that the energy density of the battery can be greatly improved, and the higher and higher energy requirements are met. And the storage is abundant, the cost is low, and the method is suitable for mass production. However, the silicon cathode has large charge and discharge volume change, so that the problems of overlarge cyclic expansion, lithium precipitation and the like of the battery are caused. Therefore, a solution to the above-mentioned problems is needed.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the silicon-based negative electrode plate is provided, an inner coating layer and an outer coating layer are arranged on the surface of a negative electrode current collector, and the silicon-oxygen atom proportion in the inner coating layer and the silicon-oxygen atom proportion in the outer coating layer are different, so that the negative electrode plate has the characteristics of high specific energy, small change of charge and discharge volume, difficult lithium precipitation and long cycle life.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a silicon-based negative electrode sheet, comprising a negative electrode current collector and an active coating layer arranged on at least one surface of the negative electrode current collector, wherein the active coating layer comprises an inner coating layer and an outer coating layer, and the inner coating layer and the outer coating layer satisfy the following relation: a/b is more than or equal to 0.3 and less than or equal to 1; c/d is more than or equal to 1.2 and less than or equal to 3, wherein,
a is the number of oxygen atoms in the silicon oxygen material in the inner coating, and a is more than or equal to 0.6 and less than or equal to 1.3;
b is the number of oxygen atoms in the silicon oxygen material in the outer coating, and a is more than or equal to b and less than or equal to 2;
c is the thickness of the inner coating, and c is more than or equal to 50 microns and less than or equal to 150 microns;
d is the thickness of the outer coating, and d is more than or equal to 25 μm and less than or equal to 100 μm.
Preferably, the value range of a is more than or equal to 0.9 and less than or equal to 1.1.
Preferably, the value range of c is 80 μm.ltoreq.c.ltoreq.120 μm.
Preferably, d is in the range of 40 μm.ltoreq.d.ltoreq.80 μm.
Preferably, 0.3.ltoreq.a/b.ltoreq.1, and 1.2.ltoreq.c/d.ltoreq.3.
The second object of the present invention is: aiming at the defects of the prior art, the secondary battery has high specific capacity, long cycle rate and good safety.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the secondary battery comprises a positive electrode plate, a negative electrode plate, a separation membrane, electrolyte and a shell, wherein the separation membrane is used for separating the positive electrode plate from the negative electrode plate, the shell is used for packaging the positive electrode plate, the negative electrode plate, the separation membrane and the electrolyte, and the negative electrode plate is the silicon-based negative electrode plate.
Preferably, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises one or more of nickel-cobalt-manganese ternary materials and iron-lithium materials.
Preferably, the positive electrode active material layer further includes a carbon-based material including one or more of natural graphite, artificial graphite, composite graphite, and graphene.
Preferably, the electrolyte comprises the following raw materials in parts by weight: 6 to 30 parts of lithium salt, 60 to 90 parts of organic solvent and 2 to 12 parts of additive.
The third object of the present invention is to: aiming at the defects of the prior art, the electric device is provided with good service life and safety.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
an electric device comprises the secondary battery.
Compared with the prior art, the invention has the beneficial effects that: according to the silicon-based negative electrode plate, the inner coating and the outer coating are arranged on the surface of the negative electrode current collector, and the silicon-oxygen atom proportion in the inner coating is different from that in the outer coating, so that the negative electrode plate has the characteristics of high specific energy, small change of charge and discharge volume, difficult lithium precipitation and long cycle life.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-based negative electrode sheet according to the present invention.
Fig. 2 is a second schematic structural view of a silicon-based negative electrode sheet according to the present invention.
1, a negative electrode current collector; 2. an inner coating; 3. and (5) an outer coating.
Detailed Description
The invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
A silicon-based negative electrode plate, comprising a negative electrode current collector 1 and an active coating layer arranged on at least one surface of the negative electrode current collector 1, wherein the active coating layer comprises an inner coating layer 2 and an outer coating layer 3, and the inner coating layer 2 and the outer coating layer 3 meet the following relation: a/b is more than or equal to 0.3 and less than or equal to 1; c/d is more than or equal to 1.2 and less than or equal to 3, wherein,
a is the number of oxygen atoms in the silicon oxygen material in the inner coating 2, and a is more than or equal to 0.6 and less than or equal to 1.3;
b is the number of oxygen atoms in the silicon oxygen material in the outer coating 3, and a is more than or equal to b and less than or equal to 2;
c is the thickness of the inner coating 2, and c is more than or equal to 50 μm and less than or equal to 150 μm;
d is the thickness of the outer coating 3, and d is more than or equal to 25 μm and less than or equal to 100 μm.
According to the silicon-based negative electrode plate, the inner coating and the outer coating are arranged on the surface of the negative current collector 1, and the silicon-oxygen atom proportion in the inner coating 2 is different from that in the outer coating 3, so that the negative electrode plate has the characteristics of high specific energy, small change of charge and discharge volume, difficult lithium precipitation and long cycle life.
The invention designs a coating of the silicon oxide double-layer anode active material containing different silicon-oxygen atom ratios, improves the cycle life and reduces the cycle expansion rate through the outer layer with higher oxygen atom ratio, and simultaneously ensures the high energy density of the battery through the inner layer active material with high silicon atom ratio. The invention improves the safety performance, the cycle performance and the gram capacity of the battery, can replace the traditional single-layer silicon cathode to meet the requirement on high energy density, and is beneficial to promoting the further development and the application of the silicon-based battery. The anode active material coating may be disposed on one side of the anode current collector 1 as shown in fig. 1, or the anode active material coating may be disposed on the other side of the anode current collector 1 as shown in fig. 2.
Under the same chemical preparation and dispersion process, the higher the oxygen atom proportion in the silicon oxide SiOx is, the smaller the volume change of the negative electrode deintercalation lithium is, the SEI film is less prone to rupture in the expansion and contraction process, and the probability that the unpassivated negative electrode active Si directly contacts and reacts with the electrolyte is also reduced, so that the irreversible consumption of the electrolyte and lithium ions is reduced, and the cycle performance of the battery is enhanced. The reduction of the volume expansion of the silicon anode is also beneficial to reducing the pulverization of the anode material and reducing the separation phenomenon between the active material layer and the current collector caused by interface stress. However, the high atomic ratio of oxygen also causes the negative electrode to generate more inactive substances during the charge-discharge reaction, thereby reducing the specific capacity of the battery. Therefore, the second active material of the battery anode surface coating selects SiOx with high oxygen atom content to form a stable SEI film, so that the active material in the battery is not excessively lost in long-term circulation; in order to balance the high energy density, the first active material coated on the negative electrode inner layer of the battery is provided with SiOx having a high silicon content.
The inventor of the invention finds that the thinner the thickness of the outer coating layer is, the more favorable the conductive ions are for quickly establishing a transport channel fully penetrating into the inner layer, the more uniform the conductivity inside the battery is, and the lower the lithium precipitation risk is. Thinning the outer active material layer also improves the SiO of Si in the double layers X Is advantageous for the high energy density and the first coulombic efficiency of the battery. However, if the overcoat layer 3 is too thin, it may cause the SEI film formed on the surface thereof to be too brittle and too thin, and not well resist the volumetric effect of the inner high silicon atom coating layer, and the continuous rupture repair affects the cycle life and capacity retention rate of the battery. It is therefore necessary to design the relative thickness of the outer active material layer to be within the lower limit that ensures long cycle life.
Through a great deal of researches, the inventor designs the negative electrode plate into a double-layer structure, and the negative electrode plate simultaneously meets the following relationship by adjusting the proportion of silicon oxygen atoms in the inner layer and the outer layer and the thickness of the coating: a/b is more than or equal to 0.3 and less than or equal to 1, and c/d is more than or equal to 1.2 and less than or equal to 3, so that the battery has higher energy density and better cycle performance and stability.
In the negative electrode plate designed by the invention, the silicon-oxygen atom proportion of the outer active material is low, and the electrolyte cannot react with the outer active material in a large amount irreversibly, so that the service life of the battery is damaged. If b is less than 0.6, consumption reaction of active silicon and other substances may occur after repeated charge and discharge of SEI film rupture, affecting the capacity of the battery; too low b increases the expansion ratio of the battery and affects the cycle life of the battery. The value of the inner layer a of the negative electrode plate ranges from 0.6 to 1.3, the stability of the inner active material coating can be ensured, the energy density of a battery is not influenced by excessive inactive materials, the expansion rate of SiOa can be controlled within a range without damaging, and the coating on a current collector is prevented from being demolding due to interface stress or SEI film on an outer coating 3 from being broken. Because b is less than or equal to 2, if a/b is less than 0.3, a is less than 0.6 and is lower than a given lower limit range, the expansion rate of SiOA is too high, the structure of the battery can be irreversibly damaged in the continuous charge and discharge process, the lithium separation risk is increased, and the cycle life is shortened; if a/b >1, the oxygen atom content of the outer layer is lower than that of the inner layer, the expansion rate and the safety are poorer than those of the inner layer, the effects of protecting and improving the performance cannot be achieved, and the design is ineffective; when a is more than 1.3, the total oxygen content of the inner layer and the outer layer is higher, and the energy density of the battery is obviously reduced.
In the negative electrode plate designed by the invention, the ratio of the thickness c of the inner active material coating to the thickness d of the outer active material coating is not less than 1 and not more than 3, and the range can promote active ions to be embedded into the inner layer material more quickly in the circulation process, so that lithium precipitation caused by ion accumulation is avoided, and meanwhile, an SEI film which is not easy to damage is generated to protect the inside active Si from excessive participation in electrochemical reaction. If c/d <1.2, the inner layer coating thickness ratio is too small, the high energy density performance of the battery will not be satisfied. If d is more than 100 mu m, the ion diffusion speed of the inner layer is affected, the interface of the negative electrode is uneven after long-term cyclic charge and discharge, and the lithium precipitation risk is increased; if c/d >3, the SEI film generated on the surface of the negative electrode may collapse under the substantial expansion and contraction of the inner layer, resulting in the exposure and irreversible consumption of the inner coating 2, affecting the safety and cycle of the battery.
In some embodiments, the value of a is in the range of 0.9.ltoreq.a.ltoreq.1.1. Preferably, 0.9.ltoreq.a.ltoreq.1, specifically, a is 0.9, 0.95, 0.98, 1, 1.1.
In some embodiments, the value of c ranges from 80 μm.ltoreq.c.ltoreq.120 μm. Preferably, the value of c is in the range of 80 μm.ltoreq.c.ltoreq.90 μm, 90 μm.ltoreq.c.ltoreq.100 μm, 110 μm.ltoreq.c.ltoreq.120 μm, specifically, the value of c is 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm.
In some embodiments, d has a value in the range of 40 μm.ltoreq.d.ltoreq.80 μm. Preferably, d has a value in the range of 40 μm.ltoreq.d.ltoreq.50 μm, 50 μm.ltoreq.d.ltoreq.60 μm, 60 μm.ltoreq.d.ltoreq.70 μm, 70 μm.ltoreq.d.ltoreq.80 μm, specifically, d is 40 μm, 45 μm, 48 μm, 50 μm, 52 μm, 56 μm, 58 μm, 60 μm, 62 μm, 65 μm, 68 μm, 70 μm, 75 μm, 78 μm, 80 μm.
In some embodiments, 0.3.ltoreq.a/b.ltoreq.1, and 1.2.ltoreq.c/d.ltoreq.3. Preferably, 0.4.ltoreq.a/b.ltoreq.0.8, and 1.5.ltoreq.c/d.ltoreq.2.6.
A secondary battery having a high specific capacity, a long cycle rate and good safety.
The secondary battery comprises a positive electrode plate, a negative electrode plate, a separation membrane, electrolyte and a shell, wherein the separation membrane is used for separating the positive electrode plate from the negative electrode plate, the shell is used for packaging the positive electrode plate, the negative electrode plate, the separation membrane and the electrolyte, and the negative electrode plate is the silicon-based negative electrode plate.
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, where the positive electrode active material layer includes one or more of a nickel-cobalt-manganese ternary material and an iron-lithium material.
In some embodiments, the positive electrode active material layer further comprises a carbon-based material comprising one or more of natural graphite, artificial graphite, composite graphite, graphene.
In some embodiments, the electrolyte comprises the following raw materials in parts by weight: 6 to 30 parts of lithium salt, 60 to 90 parts of organic solvent and 2 to 12 parts of additive. Preferably, the electrolyte comprises the following raw materials in parts by weight: 8-25 parts of lithium salt, 65-82 parts of organic solvent and 4-10 parts of additive, and specifically, the electrolyte comprises the following raw materials in parts by weight: 8 parts of lithium salt, 68 parts of organic solvent and 6 parts of additive; 10 parts of lithium salt, 82 parts of organic solvent and 7 parts of additive; 12 parts of lithium salt, 86 organic solvent and 7 parts of additive; 14 parts of lithium salt, 90 parts of organic solvent and 8 parts of additive; 12 parts of lithium salt, 90 organic solvents and 8 parts of additives; 15 parts of lithium salt, 90 parts of organic solvent and 10 parts of additive.
An electric device has good service life and safety.
An electric device comprises the secondary battery.
The power utilization device of the present application includes, but is not limited to: notebook computer, pen-input computer, mobile computer, electronic book player, portable telephone, portable facsimile machine, portable copying machine, portable printer, headset, video recorder, liquid crystal television, portable cleaner, portable CD player, mini-compact disc, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, stand-by power supply, motor, automobile, motorcycle, moped, bicycle, lighting fixture, toy, game machine, clock, electric tool, flash, camera.
Example 1
Positive pole piece: active material LiNi 0.85 Co 0.1 Mn 0.05 O 2 The conductive agent CNT and the binder PVDF are prepared according to the weight ratio of 97.2:1.8: and 1, fully stirring and uniformly mixing the materials in an NCM solvent system, coating the materials on an aluminum foil, drying, cold pressing and cutting the aluminum foil to obtain the positive electrode plate.
Negative pole piece: the first negative electrode active material (see table 1 for details, silicon to carbon ratio 5:95), super P, sodium carboxymethyl cellulose, SBR emulsion was prepared according to 97:0.8:1.0:1.2, preparing a first anode active material slurry, and coating the slurry on two surfaces of a copper foil to obtain a first active material layer, namely an inner coating layer 2; the second negative electrode active material (see table 1 for details, silicon to carbon ratio 5:95), superP, sodium carboxymethylcellulose, SBR emulsion were mixed according to 97:0.8:1.0:1.2 to prepare a second anode active material slurry, and coating the second anode active material slurry on the first active material layer to obtain a second active material layer, namely an outer coating layer 3. And then drying, cold pressing and cutting to prepare the negative electrode plate, as shown in figure 1.
Isolation film: PE porous polymeric film is used as a isolating film.
Electrolyte solution: ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed according to a volume ratio of 3:5:2 and then mixing the fully dried lithium salt LiPF 6 Dissolving in a mixed organic solvent according to a proportion of 1.2mol/L to prepare electrolyte.
Full cell preparation: and arranging the positive pole piece, the isolating film and the negative pole piece in sequence, placing a layer of isolating film between each pair of positive and negative poles, and winding to obtain the bare cell. And placing the bare cell in an outer packaging shell, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping and other procedures to obtain the lithium ion secondary battery.
The batteries of examples 2 to 10 and comparative examples 1 to 5 were similar to the preparation method of example 1, and specific parameters are shown in table 1.
TABLE 1
The performance test was performed on the above examples 1 to 10 and comparative examples 1 to 5, and the test results are recorded in table 2. And (5) testing the performance of the battery.
Discharge energy & cycle performance test: the full cell discharge energy and cycle performance tests of each example and comparative example were performed as follows: performing primary charging and discharging at 25 ℃, performing constant-current and constant-voltage charging at a charging current of 1.0C (i.e. a current value which completely discharges theoretical capacity within 1 hour), charging cutoff voltage of 4.25V, then performing constant-current discharging at a current of 1.0C, discharging cutoff voltage of 2.5V, and recording the discharge capacity of the primary cycle; and then continuously charging and discharging. Gram capacity=discharge capacity/anode coating quality, cyclic capacity retention= (discharge capacity of 500 th cycle/discharge capacity of first cycle) ×100.
And (II) testing the cyclic expansion rate: performing first charge and discharge at 45 ℃ and constant current and constant voltage charge at a charge current of 1.0C (i.e., a current value at which theoretical capacity is completely discharged within 1 hour) until an upper limit voltage is 4.25V, then performing constant current discharge at a discharge current of 1.0C and a discharge cutoff voltage of 2.5V, and recording the discharge capacity of the first cycle; and stopping the test after continuously charging and discharging until 500 times. The charging test was performed at a temperature of 25C, and constant-current charging was continued at a current of 1.0C (i.e., a current value at which the theoretical capacity was completely discharged in 1 hour) to a voltage of 4.25V, and constant-voltage charging was continued to a current of 0.05C. The negative electrode tab of the full charge core is taken out and the thickness T500 of the negative electrode tab is measured. 500 cycle expansion = [ (T500-T0)/(T1-T0) -1] ×100%. Wherein: t0 is the thickness of the copper foil, and T1 is the thickness of the pole piece after the first cycle. The cycle, discharge energy and 500-cycle expansion rate performance of each of the example and comparative example batteries were measured in accordance with the above-described method.
The test results of each example and comparative example are detailed in table 2. Table 2 shows the results of the performance tests of examples 1 to 10 and comparative examples 1 to 5.
TABLE 2
As can be seen from the above tables 1 and 2, the secondary batteries prepared according to the present invention have a good high specific capacity, a longer cycle life and a lower expansion ratio than those of the secondary batteries of comparative examples 1 to 5, the gram capacity is up to 392mAh/g, the retention rate of 500 cycles capacity is maintained at 92.8%, and the expansion ratio of 500 cycles is as low as 37.3%.
As a result of comparison of examples 1 to 10, when both of the inner coating layer 2 and the outer coating layer 3 were made of silica and graphite as the active materials, the amount of oxygen atoms in the silica material in the inner coating layer 2 was 0.9, the amount of oxygen atoms in the silica material in the outer coating layer 3 was 1.8, the thickness of the inner coating layer 2 was 100. Mu.m, and the thickness of the outer coating layer 3 was 40. Mu.m, the secondary battery obtained had a good capacity retention rate and a capacity protection rate was 92.8%. As a result of comparison of examples 1 to 10, when both of the inner coating layer 2 and the outer coating layer 3 were made of silicon oxide and graphite as active materials, the number of oxygen atoms in the silicon oxygen material in the inner coating layer 2 was 0.9, the number of oxygen atoms in the silicon oxygen material in the outer coating layer 3 was 0.9, the thickness of the inner coating layer 2 was 100 μm, and the thickness of the outer coating layer 3 was 80 μm, the secondary battery obtained had a good gram capacity as high as 392mAh/g. As a result of comparison of examples 1 to 10, when both of the inner coating layer 2 and the outer coating layer 3 were made of silica and graphite as the active materials, the number of oxygen atoms in the silica material in the inner coating layer 2 was 0.9, the number of oxygen atoms in the silica material in the outer coating layer 3 was 2.0, the thickness of the inner coating layer 2 was 100. Mu.m, and the thickness of the outer coating layer 3 was 40. Mu.m, the secondary battery obtained had a low expansion ratio, which was as low as 37.3%.
In comparative example 1, in which a had a value of 0.9 and b had a value of 0.7, the battery was not within the range given for a/b, a/b was higher than the upper limit of the range given, and c/d was within the range given, the cycle life of the battery was deteriorated, as compared with examples 1 to 10. In comparative example 1, the oxygen atom content of the negative electrode outer layer active material is not in the range of a-2, the proportion is too low, the silicon atom content is high, the cyclic expansion rate is high, the interface wrinkling after the cycle is obvious, and the SEI film is continuously destroyed and repaired during charge and discharge, so that the capacity of the battery is attenuated, and the cycle life of the battery is shortened. In comparative example 2, when c has a value of 200 μm, i.e., the thickness of the inner coating layer 2 is 200 μm, i.e., c >150 is not within the defined range, the degree of swelling is greater than that of the outer layer and the electrolyte of the inner layer is difficult to infiltrate, the active ion transport resistance increases, the battery polarization increases, and interfacial wrinkling and lithium precipitation are easily caused to affect the cycle life and safety performance of the battery.
In comparative example 3, both a/b and c/d of comparative example 3 are within the given ranges, but a is not within the selected range of 0.6 to 1.3, a >1.3, which results in a higher total oxygen content of the inner and outer layers, a significantly lower energy density of the battery, a lower silicon atom ratio of the first active material, and a significantly reduced capacity of the battery, which does not meet the high energy density requirement, although the expansion ratio is improved.
In comparative example 4, d has a value of 20 μm, i.e., the thickness of the overcoat layer 3 is 20 μm, i.e., d <25 μm is outside the defined range, a/b of comparative example 4 is within the selected range, but the overcoat active material is above the upper limit of 100 μm and c/d is below the lower limit requirement. The active material having a relatively low silicon content is excessively thick, the capacity of the battery is reduced, and the distance and resistance of active ions entering the inner layer are increased, which is liable to cause precipitation of lithium and degradation of cycle performance.
In comparative example 5, when d has a value of 20 μm, that is, the thickness of the overcoat layer 3 is 20 μm, that is, d <25 μm is not in the defined range, and a/b and c/d are in the given ranges, but c is the selected minimum value, there are problems in that the charge-discharge expansion rate of the inner layer is excessively high, the outer SEI film is repeatedly broken, the cycle life is low, the lithium deposition safety at the negative electrode interface is poor, and the like.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (10)
1. The silicon-based negative electrode plate is characterized by comprising a negative electrode current collector and an active coating arranged on at least one surface of the negative electrode current collector, wherein the active coating comprises an inner coating and an outer coating, and the inner coating and the outer coating meet the following relation: a/b is more than or equal to 0.3 and less than or equal to 1; c/d is more than or equal to 1.2 and less than or equal to 3, wherein,
a is the number of oxygen atoms in the silicon oxide material in the inner coating, and a is more than or equal to 0.6 and less than or equal to 1.3;
b is the number of oxygen atoms in the silicon oxide material in the outer coating, and a is more than or equal to b and less than or equal to 2;
c is the thickness of the inner coating, and c is more than or equal to 50 microns and less than or equal to 150 microns;
d is the thickness of the outer coating, and d is more than or equal to 25 μm and less than or equal to 100 μm.
2. The silicon-based negative electrode plate according to claim 1, wherein the value range of a is 0.9-1.1.
3. The silicon-based negative electrode plate according to claim 1, wherein the value range of c is 80 μm or less and c is 120 μm or less.
4. The silicon-based negative electrode plate according to claim 1, wherein d has a value range of 40 μm or less and d 80 μm or less.
5. The silicon-based negative electrode plate according to claim 1, wherein a/b is 0.4-0.8 and c/d is 1.3-2.8.
6. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and a case, wherein the separator is used for separating the positive electrode sheet from the negative electrode sheet, the case is used for packaging the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte, and the negative electrode sheet is the silicon-based negative electrode sheet according to any one of claims 1 to 5.
7. The secondary battery according to claim 6, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises one or more of a nickel-cobalt-manganese ternary material and an iron-lithium material.
8. The secondary battery according to claim 7, wherein the positive electrode active material layer further comprises a carbon-based material including one or more of natural graphite, artificial graphite, composite graphite, and graphene.
9. The secondary battery according to claim 6, wherein the electrolyte comprises the following raw materials in parts by weight: 6-30 parts of lithium salt, 60-90 parts of organic solvent and 2-12 parts of additive.
10. An electric device comprising the secondary battery according to any one of claims 6 to 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1787253A (en) * | 2004-12-16 | 2006-06-14 | 松下电器产业株式会社 | Negative electrode for lithium ion secondary battery, production method thereof and lithium ion secondary battery comprising the same |
| CN111261834A (en) * | 2020-03-25 | 2020-06-09 | 宁德新能源科技有限公司 | Negative pole piece, electrochemical device and electronic device |
| EP3968407A1 (en) * | 2020-04-30 | 2022-03-16 | Contemporary Amperex Technology Co., Limited | Secondary battery and fabrication method therefor, and apparatus containing secondary battery |
| WO2022140964A1 (en) * | 2020-12-28 | 2022-07-07 | 宁德新能源科技有限公司 | Negative electrode material, electrode plate comprising the negative electrode material, and electrochemical device |
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| CN1787253A (en) * | 2004-12-16 | 2006-06-14 | 松下电器产业株式会社 | Negative electrode for lithium ion secondary battery, production method thereof and lithium ion secondary battery comprising the same |
| CN111261834A (en) * | 2020-03-25 | 2020-06-09 | 宁德新能源科技有限公司 | Negative pole piece, electrochemical device and electronic device |
| EP3968407A1 (en) * | 2020-04-30 | 2022-03-16 | Contemporary Amperex Technology Co., Limited | Secondary battery and fabrication method therefor, and apparatus containing secondary battery |
| WO2022140964A1 (en) * | 2020-12-28 | 2022-07-07 | 宁德新能源科技有限公司 | Negative electrode material, electrode plate comprising the negative electrode material, and electrochemical device |
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