CN114899360A - 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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- 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
-
- 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 provides a silicon-based negative pole piece which comprises a negative pole current collector, a first active material layer and a second active material layer; the first negative electrode active material in the first active material layer includes a first silicon-based material and a first carbon-based material; the second anode active material in the second active material layer includes a second silicon-based material and a second carbon-based material; the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material is 1.1-4, and the particle size D50 of the second carbon-based material is larger than the particle size D50 of the second silicon-based material; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.1-5; the ratio of the area density of the first active material layer to the area density of the second active material layer is 0.5 to 6. Compared with the prior art, the secondary battery containing the negative pole piece has high energy density and good quick charge performance and cycle performance.
Description
Technical Field
The invention relates to the field of secondary batteries, in particular to a silicon-based negative electrode plate, a secondary battery and an electric device.
Background
The new energy automobile is an industry which is vigorously developed in the automobile industry in the future. The secondary battery is widely applied to the new energy automobile industry due to the advantages of high energy density, no memory effect, long service life and the like. However, as the demand for the mileage of a new energy automobile increases, higher energy density is required for distribution to a battery. Therefore, new anode and cathode materials of the lithium ion battery are urgently needed to be developed, and the anode material commonly used in the market at present is a graphite anode. The theoretical gram capacity of the graphite is 372mAh/g, and with the increasing maturity of industrial processes, the current high-end graphite can reach 360-365mAh/g and is very close to the theoretical capacity. However, due to the fact that the material limits the energy density to 280Wh/kg, the material is close to the limit, and the ever-increasing demand for higher energy density is difficult to meet. And the theoretical gram capacity of the silicon material is 4200mAh/g, the lithium removal phase is relatively low (0.4V), the environment is friendly, the resources are rich, and the like, so that the silicon material is considered to be a next-generation high-energy-density lithium ion battery cathode material with great potential.
Many manufacturers have begun to use a blended system of silicon oxide (SiO) and graphite as a high energy density lithium ion battery negative electrode material. However, SiO also has more problems in the use process, and the SiO used as a negative active material only expands by 180% in volume when the battery is fully charged. Various material self-direction solutions such as nano silicon, carbon coating, metal doping, core-shell structure and the like are provided for improving the expansion problem of the silicon-based material, and the solution is matched with systems such as a conductive agent, an electrolyte, a binder and the like, so that the expansion is improved to a certain extent. On the premise of ensuring the energy density, the quick charging performance is poorer, and the higher the energy density is, the poorer the quick charging performance is. Some proposals use a small-particle-size D50 SiO material, but although the small-particle-size SiO material can improve the rapid charging capability, the particle expansion side reaction is more in the later charging and discharging process, the cycle performance and other performances are seriously reduced, and the material cannot be used as a negative electrode.
In view of the above, it is necessary to provide a technical solution to the above problems.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the silicon-based negative pole piece is provided, and the secondary battery has high energy density and excellent quick charging performance and cycle performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a silicon-based negative electrode tab, comprising:
a negative current collector;
a first active material layer coated on at least one surface of the negative electrode current collector and including a first negative electrode active material; the first negative active material includes a first silicon-based material and a first carbon-based material;
the second active material layer is coated on one surface, far away from the negative current collector, of the first active material layer and comprises a second negative active material; the second negative active material includes a second silicon-based material and a second carbon-based material;
wherein the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material is 1.1-4, and the particle size D50 of the second carbon-based material is larger than the particle size D50 of the second silicon-based material; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.1-5; the ratio of the surface density of the first active material layer to the surface density of the second active material layer is 0.5-6.
Preferably, the ratio of the grain diameter D50 of the first silicon-based material to the grain diameter D50 of the second silicon-based material is 1.5-2.5; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.2-3; the ratio of the surface density of the first active material layer to the surface density of the second active material layer is 1-4.
Preferably, the particle size D50 of the first silicon-based material is 9-14 μm, the particle size D50 of the second silicon-based material is 4-8 μm, and the particle size D50 of the second carbon-based material is 8-14 μm.
Preferably, the particle size D10 of the first silicon-based material is 3-5 μm, the particle size D10 of the second silicon-based material is 1-4 μm, and the particle size D10 of the second carbon-based material is 2-4 μm.
Preferably, the surface density of the first active material layer is 0.007 to 0.025g/cm 2 (ii) a The surface density of the second active material layer is 0.007-0.025 g/cm 2 。
Preferably, the first silicon-based material has a concentration of particle size N 1 0 to 2, the particle size concentration ratio N of the second silicon-based material 2 Is 0 to 2.
Preferably, the specific surface area of the first silicon-based material is 0.8-2 m 2 The specific surface area of the second silicon-based material is 1.5-3.5 m 2 /g。
Preferably, the mass of the first silicon-based material is 3-80% of that of the first negative electrode active material; the mass of the second silicon-based material is 3-80% of that of the second negative electrode active material.
Preferably, the first and second silicon-based materials are each independently selected from the group consisting of SiO x SiO containing lithium x Magnesium-containing SiO x X is more than 0 and less than or equal to 2; wherein SiO containing lithium x The mass ratio of the medium lithium is 0-15%, and the magnesium-containing SiO x The mass percentage of the medium magnesium is 0-15%; the first carbon-based material and the second carbon-based material are each independently selected from at least one of artificial graphite, natural graphite, hard carbon, graphene, and soft carbon.
The second purpose of the invention is to provide a secondary battery, which comprises a positive pole piece, a negative pole piece and a diaphragm arranged between the positive pole piece and the negative pole piece, wherein the negative pole piece is the silicon-based negative pole piece.
It is a further object of the present invention to provide an electric device including the above-described secondary battery.
Compared with the prior art, the invention has the beneficial effects that: according to the silicon-based negative electrode piece, the design of the double coating layers is adopted, the first active material layer and the second active material layer both contain silicon-based materials and carbon-based materials, on one hand, the silicon-based materials guarantee the high energy density performance of the battery, on the other hand, the silicon-based materials and the carbon-based materials with the grain diameters meeting the requirements are screened to serve as the negative electrode active materials, meanwhile, the surface density setting between the two coating layers is regulated, and the quick charging performance and the cycle performance of the battery are guaranteed. The second active material layer of the negative pole piece has high porosity, ions in the battery can quickly go into the first active material layer through the second active material layer to generate lithium intercalation reaction in the charging and discharging process, and the silicon-based material in the second active material layer can bear the ions which cannot be completely reacted in the first active material layer under the charging condition of higher multiplying power, so that the metal precipitation condition under the current of high multiplying power is avoided, and the quick charging performance of the battery is ensured; meanwhile, the carbon-based material in the second active material layer can also play a role in inhibiting the expansion of the small-particle silicon-based material, so that the long cycle performance of the battery is ensured.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-based negative electrode tab according to the present invention.
Fig. 2 is a second schematic structural diagram of the silicon-based negative electrode plate of the present invention.
In the figure: 1-negative current collector; 2-a first active material layer; 3-a second active material layer.
Detailed Description
1. Silicon-based negative pole piece
The invention provides a silicon-based negative electrode plate, which can be shown in fig. 1-2 and comprises a negative electrode current collector 1, a first active material layer 2 coated on at least one surface of the negative electrode current collector 1, and a second active material layer 3 coated on one surface of the first active material layer 2 far away from the negative electrode current collector 1.
As shown in fig. 1, the negative electrode sheet includes a negative electrode current collector 1, a first active material layer 2, and a second active material layer 3 in this order. The coating may be at least one of extrusion coating, transfer coating, spray coating. Preferably, the coating is carried out using a transfer coater.
In the second coating method, as shown in fig. 2, the negative electrode plate sequentially includes a second active material layer 3, a first active material layer 2, a negative electrode current collector 1, a first active material layer 2, and a second active material layer 3. The coating may be at least one of extrusion coating, transfer coating, spray coating. Preferably, the coating is carried out using a transfer coater.
Wherein the first active material layer 2 includes a first anode active material; the first negative active material includes a first silicon-based material and a first carbon-based material; the mass of the first silicon-based material is 3-80% of that of the first negative electrode active material, specifically 3-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70% or 70-80%, and preferably, the content is 5-50%; the mass of the corresponding first carbon-based material is 20-97% of the mass of the first anode active material, and the specific content of the first carbon-based material can be selected according to the actually required energy density and the like. In addition, the first active material layer 2 further includes a conductive agent and a binder, which are mixed with the first negative electrode active material in a solvent to form a slurry, and then the slurry is coated on the surface of the negative electrode current collector 1, and the first active material layer 2 is obtained after drying. The mass ratio of the first negative electrode active material to the conductive agent to the binder is (93-98): (1-4): (1-4).
The second active material layer 3 includes a second anode active material; the second negative active material includes a second silicon-based material and a second carbon-based material; the mass of the second silicon-based material is 3-80% of that of the second negative electrode active material, specifically 3-5%, 5-10%, 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70% or 70-80%, and compared with the content of the first silicon-based material, the second silicon-based material is arranged on the second active material layer 3 and is positioned on the outer layer of the negative electrode pole piece, the content of the second silicon-based material is smaller than that of the first silicon-based material, namely, the content of the second carbon-based material is larger, and thus, the expansion of the outer silicon-based material can be inhibited to a certain extent. The mass of the corresponding second carbon-based material is 20-97% of the mass of the second anode active material, and the specific content of the second carbon-based material and the second anode active material can be selected according to the actually required energy density and the like. The second active material layer 3 also includes a conductive agent and a binder, and the conductive agent and the second negative electrode active material are mixed in a solvent to form a slurry, applied to the surface of the first active material layer 2, and dried to obtain the second active material layer 3. The mass ratio of the second negative electrode active material to the conductive agent and the binder in the layer is (93-98): (1-4): (1-4).
Specifically, the first silicon-based material and the second silicon-based material are respectively and independently selected from SiO x SiO containing lithium x Magnesium-containing SiO x X is more than 0 and less than or equal to 2; wherein SiO containing lithium x The mass percentage of the medium lithium is 0-15%, and the mass percentage of the medium lithium is SiO containing magnesium x The mass percentage of the medium magnesium is 0-15%; the first carbon-based material and the second carbon-based material are each independently selected from at least one of artificial graphite, natural graphite, hard carbon, graphene, and soft carbon. SiO as described above x Can be SiO or SiO 2 。
The SiO containing lithium x That is, the pre-lithiated silicon-based negative electrode material, since the silicon-based material consumes a large amount of lithium to form an SEI film during the first charge, the first cycle efficiency of the battery is reduced, and the possibility of deintercalating lithium is reduced. By pre-lithiation of the silicon-based material, i.e., lithium is supplemented at the material end, the lithium is consumed by subsequent SEI film formation, thereby improving the first efficiency of the battery. Also in SiO x Magnesium is contained, so that the effect of improving the first cycle efficiency of the silicon-based battery can be achieved, and the expansion and conductivity of the battery can be improved to a certain extent. Preferably, SiO containing lithium x The mass ratio of the medium lithium is 0.1-8%; SiO containing magnesium x The mass percentage of the medium magnesium is 0.1-8%.
In addition, the silicon-based negative pole piece at least meets the following requirements: the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material is 1.1-4, and the particle size D50 of the second carbon-based material is larger than the particle size D50 of the second silicon-based material; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.1-5; the ratio of the surface density of the first active material layer 2 to the surface density of the second active material layer 3 is 0.5 to 6.
Wherein, the particle size D50 refers to the particle size of less than 50% of the total. The particle diameter D10 means that particles smaller than this diameter account for 10% of the total. The particle size D90 means that particles smaller than this size account for 90% of the total. The D10, D50 and D90 in each material can be measured and screened by methods known in the art, for example, by a laser particle size analyzer and by screens of different mesh sizes.
Specifically, the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material may be 1.1 to 1.5, 1.5 to 1.8, 1.8 to 2.0, 2.0 to 2.3, 2.3 to 2.5, 2.5 to 2.8, 2.8 to 3.0, 3.0 to 3.3, 3.3 to 3.5, or 3.5 to 4.0, and the D50 of the second silicon-based material is smaller than the particle size D50 of the second carbon-based material when selected, so that the second carbon-based material can play a certain role when the first silicon-based material is pressed to expand; on the other hand, the second silicon-based material can also play a role of inhibiting the second silicon-based material from swelling when the second silicon-based material receives unreacted ions of the first silicon-based material; the quick charging performance of the battery is ensured, and the subsequent long-cycle performance is also ensured. Compared with the negative pole piece with the outer layer only covered by the carbon-based material, the negative pole piece disclosed by the invention has the advantages that the quick charging performance of the silicon-based battery is effectively ensured, and the lithium precipitation problem of charging under a high multiplying power is avoided. Compared with a single-layer coating system in which a silicon-based material and a carbon-based material are mixed, the negative pole piece disclosed by the invention not only effectively ensures the quick charging performance, but also has better energy density and cycle life. Preferably, the ratio of the grain diameter D50 of the first silicon-based material to the grain diameter D50 of the second silicon-based material is 1.5-2.5. The ratio of the two is preferably avoided from being too large, and the lithium intercalation connectivity of the first silicon-based material and the second silicon-based material can be further ensured.
Further specifically, the particle size D50 of the first silicon-based material is 9-14 μm, specifically 9-10 μm, 10-11 μm, 11-12 μm, 12-13 μm or 13-14 μm; the particle size D50 of the second silicon-based material is 4-8 μm, specifically 4-5 μm, 5-6 μm, 6-7 μm or 7-8 μm; the particle size D50 of the second carbon-based material is 8-14 μm, specifically 8-9 μm, 9-10 μm, 10-11 μm, 11-12 μm, 12-13 μm or 13-14 μm. In addition, the particle diameter D50 of the first carbon-based material is also 8-14 μm, specifically 8-9 μm, 9-10 μm, 10-11 μm, 11-12 μm, 12-13 μm or 13-14 μm.
The ratio of the particle size D10 of the first silicon-based material to the particle size D10 of the second silicon-based material can be 1.1-1.5, 1.5-1.8, 1.8-2.0, 2.0-2.3, 2.3-2.5, 2.5-2.8, 2.8-3.0, 3.0-3.3, 3.3-3.5, 3.5-4.0 or 4.0-5.0. The same value of the second silicon-based material D10 remained smaller than that of the first silicon-based material D10, ensuring not only that the first silicon-based material in the first active material layer 2 was large-grained but also that the second silicon-based material in the second active material layer 3 was small-grained as a whole; and the distribution uniformity of the particles of each coating is better. Preferably, the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.2-3.
Further specifically, the particle size D10 of the first silicon-based material is 3-5 μm, and specifically can be 3-4 μm or 4-5 μm; the particle size D10 of the second silicon-based material is 1-4 μm, and specifically can be 1-2 μm, 2-3 μm or 3-4 μm; the particle size D10 of the second carbon-based material is 2-4 μm, and specifically 2-3 μm or 3-4 μm. In addition, the particle diameter D10 of the first carbon-based material is also 2 to 4 μm, specifically 2 to 3 μm or 3 to 4 μm.
The second carbon-based material under the particle size is larger than the particle size of the second silicon-based material on the whole, the second carbon-based material can be considered as large particles, the second silicon-based material is small particles, the second carbon-based material and the second silicon-based material are mixed to form the second negative electrode active material, the porosity is higher, ions can be kept to rapidly pass through the second active material layer 3, the pores can also play a role in relieving expansion of the first silicon-based material, the second active material layer 3 forms an extrusion effect when the ions expand, the compaction density of the second active material layer 3 is improved along with the second carbon-based material, the subsequent excitable capacity of the second negative electrode active material is larger, and the energy density of the battery is further improved.
The first carbon-based material and the first silicon-based material under the particle size are similar in particle size, so that the first negative electrode active material particles formed by mixing are distributed more uniformly, and the embedding of ions are more stable. In addition, although the first silicon-based material particles expand with the increase of the number of charging and discharging times, the particle sizes of the first silicon-based material particles and the first carbon-based material particles are also enlarged, certain gaps are still provided for the embedding of ions, and the reduction of the cycle life caused by the expansion is relieved to a certain extent.
The ratio of the area density of the first active material layer 2 to the area density of the second active material layer 3 may be 0.5 to 0.8, 0.8 to 1.1, 1.1 to 1.5, 1.5 to 1.8, 1.8 to 2.0, 2.0 to 2.3, 2.3 to 2.5, 2.5 to 2.8, 2.8 to 3.0, 3.0 to 3.3, 3.3 to 3.5, 3.5 to 4.0, 4.0 to 5.0, or 5.0 to 6.0. Preferably, the ratio of the area density of the first active material layer 2 to the area density of the second active material layer 3 is 1 to 4. The surface density between the two layers is synchronously controlled, so that on one hand, the situation that the porosity of the first active material layer 2 is too small due to the fact that the surface density of the first active material is far larger than that of the second active material layer 3, ions cannot be rapidly embedded into the first active material layer 2, meanwhile, electrolyte cannot enter the first active material layer 2 easily, and the first circulation efficiency is too low is avoided; on the other hand, the surface density of the first active material layer 2 is prevented from being much lower than that of the second active material layer 3, so that not only is the volumetric energy reduced, but also the quick-charging performance is also affected. According to the double-layer silicon-based negative pole piece provided by the invention, the particle sizes of the silicon-based material and the carbon-based material of the two coatings and the surface density of the two coatings are synchronously controlled, so that the obtained secondary battery has high energy density and excellent rapid charging performance and cycle performance.
More preferably, the first active material layer 2 has an areal density of 0.007 to 0.025g/cm 2 (ii) a The surface density of the second active material layer 3 is 0.007-0.025 g/cm 2 . In this area density range, the ratio of the area density of the first active material layer 2 to the area density of the second active material layer 3 may satisfy the above range, and preferably, the area densities of the two layers are close to each other, thereby ensuring the cycle performance and rate performance of the battery.
More preferably, the second active material layer 3 has a porosity of 38 to 43%, and the first active material layer 2 has a porosity of 20 to 30%. Guarantee that the porosity of second active material layer 3 is greater than the porosity of first active material layer 2, the ion more can enter into first active material layer 2 through second active material layer 3 fast and take place to inlay the lithium reaction, and the inside of pole piece is also infiltrated more easily to electrolyte, reduces the resistance of battery, and the conductivity is bigger, and first cycle efficiency also can promote.
Further, in some embodiments, the first silicon-based material has a particle size concentration, N 1 0 to 2, the particle size concentration ratio N of the second silicon-based material 2 Is 0 to 2. The concentration ratio referred to herein as (D90-D10)/(D50) is the particle size concentration N of the first silicon-based material 1 (particle size of the first silicon-based material D90-particle size of the first silicon-based material D10) ÷ particle size of the first silicon-based material D50; similarly, the concentration of the second silicon-based material N 2 (particle size of second silicon-based material D90-particle size of second silicon-based material D10) ÷ particle size of second silicon-based material D50. Preferably, N 1 0.5 to 1.5, N 2 0.5 to 1.5. The invention continuously regulates and controls the particle size concentration of the silicon-based material, so that the particle size is more concentrated, the adverse effect caused by the side reaction generated by the contact of excessive fine powder and electrolyte is avoided, and the long-term cycle life and the rate capability of the battery are further improved. In addition, the difference between D90 and D10 is small in a certain concentration ratio, the distribution of each particle size is more uniform, and the coating consistency is better. Preferably, the first silicon-based material has a concentration of particle size N 1 Greater than the particle size concentration N of the second silicon-based material 2 。
In some embodiments, the specific surface area of the first silicon-based material is 0.8-2 m 2 A specific value of 0.8 to 1.0 m/g 2 /g、1.0～1.2m 2 /g、1.2～1.4m 2 /g、1.4～1.6m 2 /g、1.6～1.8m 2 A/g or 1.8 to 2.0m 2 (ii)/g; the specific surface area of the second silicon-based material is 1.5-3.5 m 2 A specific value of 1.5 to 1.8 m/g 2 /g、1.8～2.0m 2 /g、2.0～2.2m 2 /g、2.2～2.4m 2 /g、2.4～2.6m 2 /g、2.6～2.8m 2 /g、2.8～3.0m 2 /g、3.0～3.2m 2 (ii)/g or 3.2 to 3.5m 2 (ii) in terms of/g. Preference is given toThe specific surface area of the first silicon-based material is less than the specific surface area of the second silicon-based material. The suitable specific surface area is larger, the silicon-based materials are more in contact with the electrolyte, the conductivity is higher, and the specific surface area of the second silicon-based material is kept larger than that of the first silicon-based material, so that the second silicon-based material can be further ensured to be in a small particle state, and the first silicon-based material is in a large particle state, so that the quick charging performance and the cycle performance of the battery are further ensured.
2. Secondary battery
The second aspect of the invention aims to provide a secondary battery, which comprises a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are arranged between the positive pole piece and the negative pole piece, and the negative pole piece is any one of the silicon-based negative pole pieces.
In some embodiments, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder, and the mass ratio of the positive electrode active material to the conductive agent to the binder is (93-98): (1-4): (1-4).
The positive active material may be of a chemical formula including but not limited to Li c Ni h Co y M z O 2-b N b (wherein c is more than or equal to 0.95 and less than or equal to 1.2, h>0, y is more than or equal to 0, z is more than or equal to 0, h + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), and the positive electrode active material can also be selected from one or more of LiCoO and the like 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material can be modified to perform positive electrode active materialMethods of modification treatment should be known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, etc., and the material used for modification treatment may be one or a combination of more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc., but is not limited thereto. The positive electrode current collector may be any material suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, an aluminum foil, and the like.
And the separator may be various materials suitable for a lithium ion battery separator in the art, for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like, which include but are not limited thereto.
The secondary battery further includes an electrolyte including an organic solvent, an electrolytic lithium salt, and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte 6 And/or LiBOB; or LiBF used in low-temperature electrolyte 4 、LiBOB、LiPF 6 At least one of; or LiBF used in anti-overcharge electrolyte 4 、LiBOB、LiPF 6 At least one of, LiTFSI; may also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte 2 At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
3. Electric device
A third aspect of the present invention is directed to an electric device including the secondary battery described above.
The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool and the like. The vehicle can be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or a range-extended vehicle and the like; spacecraft include aircraft, rockets, space shuttles, and spacecraft, among others; electric toys include stationary or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric airplane toys, and the like; the electric power tools include metal cutting electric power tools, grinding electric power tools, assembly electric power tools, and electric power tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planers.
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Example 1
A silicon-based negative electrode plate comprises a negative electrode current collector 1, a first active material layer 2(S1) coated on two surfaces of the negative electrode current collector 1, and a second active material layer 3(S2) coated on the surface of the first active material layer 2. The first active material layer 2 includes a first anode active material including a first silicon-based material and a first carbon-based material, a conductive agent, and a binder; the second active material layer 3 includes a second anode active material; the second negative active material includes a second silicon-based material and a second carbon-based material.
Wherein the first silicon-based material is SiO, the grain diameter D50 is 10.5 μm, and the grain diameter D10 is 3.2 μm; the second silicon-based material is SiO, the particle size D50 is 5.8 mu m, and the particle size D10 is 1.6 mu m; the first carbon-based material is graphite, the particle size D50 is 12 mu m, and the particle size D10 is 3 mu m; the second carbon-based material is graphite, the particle size D50 is 12 mu m, and the particle size D10 is 3 mu m; areal density (CW) of the first active material layer 2 1 ) Is 0.02g/cm 2 (ii) a Areal density (CW) of the second active material layer 3 2 ) Is 0.01g/cm 2 (ii) a In the first active material layer 2, the ratio of SiO is 10%, and the ratio of graphite is 90%; in the second active material layer 3, the ratio of SiO was 10%, and the ratio of graphite was 90%.
Calculating that the ratio of the grain diameter D50 of the first silicon-based material to the grain diameter D50 of the second silicon-based material is 1.8; the ratio of the grain size D10 of the first silicon-based material to the grain size D10 of the second silicon-based material is 2; particle size concentration N of first silicon-based material 1 1, particle size concentration N of the second silicon-based material 2 Is 1; the ratio of the area density of the first active material layer 2 to the area density of the second active material layer 3 is 2.
The preparation method of the negative pole piece comprises the following steps: respectively preparing first active material slurry and second active material slurry, mixing a negative active material mixed with SiO and graphite with conductive carbon Super-P, a conductive carbon tube CNT, a binder carboxymethylcellulose sodium CMC and a binder styrene butadiene rubber SBR according to a mass ratio of 95:1.5:1.4:0.1:2, adding deionized water, and stirring in vacuum to obtain uniform slurry; first active material slurry is evenly coated on a copper foil and dried to obtain a first active material layer 2; and then coating the second active material slurry on the surface of the first active material layer 2, and drying to obtain the silicon-based negative electrode plate.
The obtained silicon-based negative pole piece is applied to a secondary battery, and the preparation method comprises the following steps:
1) preparing a positive plate:
mixing a positive electrode main material NCM811, a conductive agent (Super P), a binder (PVDF) and the like according to a ratio of 97.5: 1.4: mixing according to the proportion of 1.2, adding a solvent (NMP), and uniformly stirring and mixing under the action of a vacuum stirrer to obtain anode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, and then baking, cold pressing and die cutting to obtain the positive electrode piece.
2) Preparing an electrolyte:
ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then a well-dried lithium salt LiPF was added 6 Dissolving the electrolyte into a mixed organic solvent according to the proportion of 1mol/L to prepare the electrolyte.
3) Preparing a diaphragm:
the single side of the polyethylene diaphragm with the diameter of 9 mu m is coated with ceramic.
4) Assembling the battery:
stacking the positive pole piece, the diaphragm and the negative pole piece in sequence to enable the diaphragm to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and then winding to obtain a 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 processes to obtain the secondary battery.
Comparative example 1
The difference from example 1 is the arrangement of the negative electrode tab.
The negative pole piece of this comparison example includes negative pole mass flow body 1, coat in the active material layer of the both surfaces of negative pole mass flow body 1, and this active material layer includes negative pole active material, conducting agent and binder, negative pole active material includes SiO and graphite, and SiO accounts for 10%, and graphite accounts for 90%. Wherein the grain diameter D50 of SiO is 12.4 μm, the grain diameter D10 is 3.8 μm, and the concentration ratio N is 1; the particle size D50 of the graphite is 12 μm, and the particle size D10 is 3 μm; the surface density of the active material layer was 0.015g/cm 2 。
The rest of the configuration is the same as that of embodiment 1, and the description thereof is omitted.
Comparative example 2
The difference from example 1 is the arrangement of the negative electrode tab.
The negative pole piece of this comparison example includes negative pole mass flow body 1, coat in the active material layer of the both surfaces of negative pole mass flow body 1, and this active material layer includes negative pole active material, conducting agent and binder, negative pole active material includes SiO and graphite, and SiO accounts for 10%, and graphite accounts for 90%. Wherein the grain diameter D50 of SiO is 6.2 μm, the grain diameter D10 is 1.5 μm, and the concentration ratio N is 1; the particle size D50 of the graphite is 12 μm, and the particle size D10 is 3 μm; the surface density of the active material layer was 0.015g/cm 2 。
The rest of the configuration is the same as that of embodiment 1, and the description thereof is omitted.
In addition, the negative electrode sheet and the secondary battery of examples 2 to 21 were prepared by the arrangement and preparation method of example 1, and the differences between the examples are as described in table 1 below.
TABLE 1
The performance of the lithium ion batteries prepared in the above-mentioned examples 1 to 21 and comparative examples 1 to 2 was tested.
And (3) performance testing:
1) dynamic performance test
At 25 ℃, the batteries prepared in the examples and the comparative examples are fully charged with x C and fully discharged with 1C for 10 times, then the batteries are fully charged with x C, then the negative pole piece is disassembled, and the lithium precipitation condition on the surface of the negative pole piece is observed. And if no lithium is separated from the surface of the negative electrode, gradually increasing the charging rate x C by taking 0.1C as a gradient, and testing again until lithium is separated from the surface of the negative electrode, and stopping testing, wherein the charging rate (x-0.1) C at the moment is the maximum charging rate of the battery. The value of x can be determined according to parameters such as an actual system, areal density and the like.
2) Cycle performance test
The lithium ion batteries 1C prepared in examples and comparative examples were charged at 25 ℃, discharged at 1C rate, and subjected to full charge discharge cycle test, and the recording capacity retention rate after 500 cycles was obtained.
The test results are shown in table 2 below.
TABLE 2
| Group of | Maximum chargingRate of change of electricity | Capacity retention ratio/%) |
| Example 1 | 2.2C | 92％ |
| Example 2 | 2.1C | 90％ |
| Example 3 | 2.2C | 91％ |
| Example 4 | 2.3C | 85％ |
| Example 5 | 2.2C | 88％ |
| Example 6 | 2.2C | 91％ |
| Example 7 | 2.0C | 81％ |
| Example 8 | 2.3C | 91％ |
| Example 9 | 2.2C | 91％ |
| Example 10 | 2.2C | 82％ |
| Example 11 | 2.2C | 91％ |
| Example 12 | 2.2C | 81％ |
| Example 13 | 2.1C | 80％ |
| Example 14 | 2.2C | 88％ |
| Example 15 | 2.2C | 94％ |
| Example 16 | 2.1C | 93％ |
| Example 17 | 2.2C | 90％ |
| Example 18 | 2.1C | 91％ |
| Example 19 | 2.2C | 88％ |
| Example 20 | 2.3C | 94％ |
| Example 21 | 2.2C | 91％ |
| Comparative example 1 | 1.4C | 90％ |
| Comparative example 2 | 2.3C | 81％ |
It can be seen from comparison of comparative examples 1-2 that although the small-particle-size silicon-based material has good rate charging performance, the small-particle SiO expands and breaks during long-term circulation, consuming a large amount of electrolyte, and cannot maintain good long-term circulation performance, as in comparative example 2. However, as in comparative example 1, the silicon-based particles with larger particle size can maintain a certain cycle performance, but the charge-discharge rate is low, and the requirement of rapid charging cannot be met. As can be seen from the comparison of examples 1 to 16, the silicon-based negative electrode plate disclosed by the invention adopts double-layer coating, the silicon-based material and the carbon-based material with specific particle sizes are screened, and the surface density of the two-layer coating is limited during coating.
Specifically, as can be seen from the comparison of examples 1 to 13, the secondary battery containing the silicon-based negative electrode plate has good rate capability and cycle capability by adjusting D50 and D10 within the limited range. The rate capability exceeding the above range is good, but the cycle performance is deteriorated, mainly because the silicon-based material and the carbon-based material exceeding the above range cannot withstand charging at a high rate, the expansion of SiO is increased, and the side reactions are also increased. In particular, as in examples 12 to 13, the particle size D50 of the second carbon-based material is ensured to be larger than the particle size D50 of the second silicon-based material, so that the battery can maintain a better cycle performance.
In addition, it can be seen from the comparative examples of examples 9, 14 to 16 that CW is laminated with S1 1 /S2 layer CW 2 The ratio of (A) is increased, the rate performance of the battery is similar, but the cycle performance shows a trend of increasing firstly and then decreasing, which shows that the influence of the surface density ratio on the performance is gradually shown along with the consumption of the electrolyte in the cycle process, and experiments show that the CW 1 /CW 2 The ratio of (A) is superior in performance in the vicinity.
Furthermore, it can be seen from a comparison of examples 15 and 17 to 21 that the particle size concentration N of SiO also affects the rate capability and cycle performance of the battery. Concentration ratio N of SiO in a certain range 1 、N 2 The capacity retention rate of the battery can be further ensured mainly because the particle size can be more concentrated within the concentration range, and the influence of fine powder particles can be further reduced. In particular as N 1 Greater than N 2 And the rate capability and the cycle performance of the battery can be ensured.
In conclusion, the silicon-based negative electrode plate and the secondary battery containing the same have high energy density, and simultaneously have good quick charge performance and cycle performance.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (11)
1. A silicon-based negative electrode plate, comprising:
a negative current collector;
a first active material layer coated on at least one surface of the negative electrode current collector and including a first negative electrode active material; the first negative active material includes a first silicon-based material and a first carbon-based material;
the second active material layer is coated on one surface, far away from the negative current collector, of the first active material layer and comprises a second negative active material; the second negative active material includes a second silicon-based material and a second carbon-based material;
wherein the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material is 1.1-4, and the particle size D50 of the second carbon-based material is larger than the particle size D50 of the second silicon-based material; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.1-5; the ratio of the area density of the first active material layer to the area density of the second active material layer is 0.5 to 6.
2. The silicon-based negative electrode plate as claimed in claim 1, wherein the ratio of the particle size D50 of the first silicon-based material to the particle size D50 of the second silicon-based material is 1.5-2.5; the ratio of the grain diameter D10 of the first silicon-based material to the grain diameter D10 of the second silicon-based material is 1.2-3; the ratio of the surface density of the first active material layer to the surface density of the second active material layer is 1-4.
3. The silicon-based negative electrode plate as claimed in claim 1 or 2, wherein the particle size D50 of the first silicon-based material is 9-14 μm, the particle size D50 of the second silicon-based material is 4-8 μm, and the particle size D50 of the second carbon-based material is 8-14 μm.
4. The silicon-based negative electrode plate as claimed in claim 1 or 2, wherein the particle size D10 of the first silicon-based material is 3-5 μm, the particle size D10 of the second silicon-based material is 1-4 μm, and the particle size D10 of the second carbon-based material is 2-4 μm.
5. The silicon-based negative electrode plate as claimed in claim 1 or 2, wherein the first active material layer has an areal density of 0.007 to 0.025g/cm 2 (ii) a The surface density of the second active material layer is 0.007-0.025 g/cm 2 。
6. The silicon-based negative electrode plate according to claim 1 or 2, wherein the particle size concentration ratio N of the first silicon-based material 1 0 to 2, the particle size concentration ratio N of the second silicon-based material 2 Is 0 to 2.
7. The silicon-based negative electrode plate as claimed in claim 1 or 2, wherein the specific surface area of the first silicon-based material is 0.8-2 m 2 The specific surface area of the second silicon-based material is 1.5-3.5 m 2 /g。
8. The silicon-based negative electrode plate as claimed in claim 1 or 2, wherein the mass of the first silicon-based material is 3-80% of the mass of the first negative electrode active material; the mass of the second silicon-based material is 3-80% of that of the second negative electrode active material.
9. The silicon-based negative electrode plate according to claim 8, wherein the first silicon-based material and the second silicon-based material are each independently selected from SiO x SiO containing lithium x Magnesium-containing SiO x X is more than 0 and less than or equal to 2; wherein SiO containing lithium x The mass ratio of the medium lithium is 0-15%, and the magnesium-containing SiO x The mass percentage of the medium magnesium is 0-15%; the first and second carbon-based materials are each independently selected from the group consisting of synthetic stoneAt least one of ink, natural graphite, hard carbon, graphene, and soft carbon.
10. A secondary battery, comprising a positive pole piece, a negative pole piece and a diaphragm which is arranged between the positive pole piece and the negative pole piece, wherein the negative pole piece is the silicon-based negative pole piece of any one of claims 1 to 9.
11. An electric device comprising the secondary battery according to claim 10.
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| CN115911259A (en) * | 2022-11-21 | 2023-04-04 | 江苏正力新能电池技术有限公司 | Battery pole group and secondary battery |
| CN116885104A (en) * | 2023-03-13 | 2023-10-13 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, secondary battery and electricity utilization device |
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| CN111916667A (en) * | 2020-07-27 | 2020-11-10 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery comprising same |
| CN113488637A (en) * | 2021-06-18 | 2021-10-08 | 东莞塔菲尔新能源科技有限公司 | Composite negative electrode material, negative plate and lithium ion battery |
| CN114256501A (en) * | 2021-12-17 | 2022-03-29 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery containing same |
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| CN111916667A (en) * | 2020-07-27 | 2020-11-10 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery comprising same |
| CN113488637A (en) * | 2021-06-18 | 2021-10-08 | 东莞塔菲尔新能源科技有限公司 | Composite negative electrode material, negative plate and lithium ion battery |
| CN114256501A (en) * | 2021-12-17 | 2022-03-29 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery containing same |
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| CN115911259A (en) * | 2022-11-21 | 2023-04-04 | 江苏正力新能电池技术有限公司 | Battery pole group and secondary battery |
| CN116885104A (en) * | 2023-03-13 | 2023-10-13 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, secondary battery and electricity utilization device |
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