Silicon-doped negative electrode active layer, negative electrode plate, battery cell and electric equipment

Abstract

The utility model provides a silicon-doped negative electrode active layer. The silicon-doped negative electrode active layer comprises particulate matters, the particulate matter comprises an inner core and a flexible binder outer layer; the outer surface of the inner core is fully wrapped or semi-wrapped by the flexible binder outer layer; the inner core comprises graphite particles, silicon negative electrode particles and a conductive agent; and the graphite particles, the silicon negative electrode particles and the conductive agent are connected through a rigid binder. Compared with the prior art, the positive design that the binders are hard inside and soft outside is adopted, the rigid binder on the inner layer firstly dissipates most internal stress caused by volume change in the expansion process of silicon negative electrode particles, and the flexible binder on the outer layer serves as a buffer layer to absorb residual stress; through the design of the double-layer binder which is hard inside and soft outside, the stress release in the negative electrode circulation process is effectively relieved, the stability of a negative electrode interface is ensured, and the cycle life of the battery cell is prolonged.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a silicon-doped negative electrode active layer, a negative electrode sheet, a battery cell, and an electrical device. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density and long cycle life, making them stand out among various electrochemical energy storage devices and currently widely used in portable electronic devices and electric vehicles. With the increasing demand for energy, traditional graphite anodes can no longer meet the higher energy density requirements, thus necessitating the development of novel anode materials. SiO materials, due to their ultra-high specific capacity (SiO - 1713.2 mAh / g Vs graphite - 372 mAh / g), are gradually gaining favor in the industry. However, their high volumetric expansion rate (~160%) inevitably leads to structural collapse during long cycles, resulting in pulverization, failure, and deterioration of cycle performance, thus limiting their application.

[0003] Currently, methods to address the volume expansion problem of silicon anodes mainly include carbon coatings and pore structure design. However, these methods are difficult to commercialize due to complex synthesis processes, cumbersome steps, and high costs. Chinese patent CN116470054A uses a supramolecular binder with certain mechanical strength and viscosity to ensure electrode structure stability. Chinese patent CN117050679A uses a triple crosslinking binder to construct an artificial protective layer on the current collector in situ, which can suppress silicon expansion and ensure the integrity of the silicon anode. However, since their mechanism is to alleviate structural collapse by relieving stress release, these measures all rely on a certain level of mechanical strength. Based on the electrode failure process, how to efficiently release stress is key to solving this problem, but relevant forward designs are still lacking. Utility Model Content

[0004] In view of this, the technical problem to be solved by this application is to provide a silicon-doped anode active layer, anode sheet, battery cell and electrical device that can improve the stability of the anode interface.

[0005] This application provides a silicon-doped anode active layer, the silicon-doped anode active layer comprising particulate matter; the particulate matter comprising a core and a flexible binder outer layer; the flexible binder outer layer fully or partially encapsulating the outer surface of the core; the core comprising graphite particles, silicon anode particles, and a conductive agent; the graphite particles, silicon anode particles, and conductive agent are connected by a rigid binder.

[0006] Preferably, the graphite particles have a particle size of 10–20 μm; the silicon anode particles have a particle size of 5–15 μm.

[0007] Preferably, the outer surface of the core is a rigid adhesive layer.

[0008] Preferably, the thickness of the outer layer of the flexible adhesive is 20–50 nm.

[0009] Preferably, the silicon-doped anode active layer comprises a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together;

[0010] The first silicon-doped anode active sublayer includes a core; the cores are connected to each other by a rigid binder;

[0011] The second silicon-doped anode active sublayer includes a core and a flexible binder outer layer; the flexible binder outer layer partially wraps around the outer surface of the core.

[0012] Preferably, the thickness ratio of the first silicon-doped anode active sublayer to the first silicon-doped anode active sublayer is 1:(0.001~0.002).

[0013] This application also provides a negative electrode sheet, including a current collector and the aforementioned silicon-doped negative electrode active layer; the silicon-doped negative electrode active layer is disposed on at least one side surface of the current collector.

[0014] Preferably, the silicon-doped anode active layer comprises a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together; the first silicon-doped anode active sublayer is in contact with the current collector.

[0015] This application also provides a battery cell, including the aforementioned silicon-doped negative electrode active layer or the aforementioned negative electrode sheet.

[0016] Preferably, the battery cell further includes a positive electrode and a separator; the separator is disposed between the negative electrode and the positive electrode.

[0017] This application also provides an electrical device, including the aforementioned negative electrode or the aforementioned battery cell.

[0018] This application provides a silicon-doped anode active layer, comprising particulate matter; the particulate matter comprises a core and a flexible binder outer layer; the flexible binder outer layer fully or partially encapsulates the outer surface of the core; the core comprises graphite particles, silicon anode particles, and a conductive agent; the graphite particles, silicon anode particles, and conductive agent are connected by a rigid binder. Compared with the prior art, this application, through a positive design of a rigid inner binder and a flexible outer binder, firstly dissipates most of the internal stress caused by the volume change during the expansion of the silicon anode particles, while the flexible outer binder acts as a buffer layer to absorb residual stress. This dual-layer binder design effectively alleviates stress release during the anode cycling process, ensures the stability of the anode interface, and is beneficial to improving the cycle life of the battery cell. Attached Figure Description

[0019] Figure 1A schematic diagram of the first structural representation of particulate matter provided in this application;

[0020] Figure 2 A schematic diagram of a second structural representation of particulate matter provided in this application;

[0021] Figure 3 This is a schematic diagram of the negative electrode sheet provided in this application.

[0022] Figure description: 1 is graphite particle, 2 is silicon anode particle, 3 is conductive agent, 4 is rigid binder layer, 5 is flexible binder layer, 6 is second silicon-doped anode active sublayer, 7 is first silicon-doped anode active sublayer, and 8 is current collector. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] This application provides a silicon-doped anode active layer; the silicon-doped anode active layer includes particulate matter; the particulate matter includes a core and a flexible binder outer layer; the flexible binder outer layer fully or partially encapsulates the outer surface of the core; the core includes graphite particles, silicon anode particles and a conductive agent; the graphite particles, silicon anode particles and the conductive agent are connected by a rigid binder.

[0025] In one specific embodiment provided in this application, the outer surface of the core is a rigid adhesive layer; that is, the rigid adhesive not only bonds the graphite particles, silicon anode particles and conductive agent together, but also wraps around the graphite particles, silicon anode particles and conductive agent; the outer surface of the core being a rigid adhesive layer can better dissipate the stress generated during the expansion of the silicon anode particles.

[0026] See Figure 1 and Figure 2 , Figure 1 and Figure 2 The diagram shows the structure of the particulate matter provided in this application, where 1 is a graphite particle, 2 is a silicon anode particle, 3 is a conductive agent, 4 is a rigid binder layer, and 5 is a flexible binder layer.

[0027] In one specific embodiment provided in this application, the core comprises graphite particles, silicon anode particles, and a conductive agent; the particle size of the graphite particles is 10–20 μm; optionally, the particle size of the graphite particles is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any two of the above values; the graphite particles can be any type of graphite particles known to those skilled in the art, and no special type is required. The graphite degree of the graphite particles described in this application is preferably 95% to 96%; the mass of the graphite particles is preferably 90% to 92% of the mass of the silicon-doped anode active layer; optionally, the mass of the graphite particles is 90%, 91%, 92% of the mass of the silicon-doped anode active layer or any two of the above values; the particle size of the silicon anode particles is preferably 5 to 15 μm; optionally, the particle size of the silicon anode particles is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, ... The particle size of the silicon anode particles is 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any two of the above values. In some embodiments provided in this application, the particle size of the silicon anode particles is 8–9 μm. The silicon anode particles can be any silicon anode particles well known to those skilled in the art, without any special limitations. They can be silicon-oxygen anode particles or silicon-carbon anode particles, and more specifically, pre-lithiated SiOx or SiC. The mass of the silicon anode particles is preferably 3%–5% of the mass of the silicon-doped anode active layer. Optionally, the mass of the silicon anode particles is 3%, 4%, 5% of the mass of the silicon-doped anode active layer, or any two of the above values. The conductive agent can be any anode conductive agent well known to those skilled in the art, without any special limitations. Specifically, it can be conductive carbon. The mass of the conductive agent is preferably 1%–3% of the mass of the silicon-doped anode active layer. Optionally, the mass of the conductive agent is 1%, 1.5%, 2%, 2.5%, 3% of the mass of the silicon-doped anode active layer, or any two of the above values.

[0028] In one specific embodiment provided in this application, the core further includes a dispersant; by adding the dispersant, the graphite particles, silicon anode particles, and conductive agent can be fully mixed; the dispersant may be carboxymethyl cellulose (CMC) and / or lithium-modified carboxymethyl cellulose (CMC-Li); the mass of the dispersant is preferably 0.1% to 0.3% of the mass of the silicon-doped anode active layer; optionally, the mass of the dispersant is 0.1%, 0.2%, 0.3% of the mass of the silicon-doped anode active layer, or a range between any two of the above values.

[0029] In one specific embodiment provided in this application, the Young's modulus of the rigid adhesive is preferably not less than 8 GPa, more preferably 8-12 GPa, and even more preferably 8-10 GPa; the type of rigid adhesive is any adhesive known to those skilled in the art that meets the above requirements for Young's modulus, and there are no special restrictions. Adhesives that meet the above Young's modulus generally have a rigid polymer backbone or a covalent 3D network crosslinking configuration, including but not limited to polyacrylic acid (PAA) adhesives, styrene-butadiene adhesives, etc.; the swelling of the polyacrylic acid (PAA) adhesive is preferably not more than 10%; the swelling of the styrene-butadiene adhesive is preferably 15%-25%; the mass of the rigid adhesive is preferably 1.35%-2% of the mass of the silicon-doped anode active layer; optionally, the mass of the rigid adhesive is 1.35%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% of the mass of the silicon-doped anode active layer, or a range between any two of the above values.

[0030] In one specific embodiment provided in this application, the flexible adhesive outer layer fully or partially encloses the outer surface of the core, and more specifically, encloses or partially encloses the surface of the rigid adhesive layer; the thickness of the flexible adhesive layer is preferably 20-50 nm; optionally, the thickness of the flexible adhesive layer is 20 nm, 25 nm, 30 nm, 35 nm, 36 nm, 38 nm, 40 nm, 42 nm, 45 nm, 46 nm, 48 nm, 50 nm, or any two of the above values; the Young's modulus of the flexible adhesive layer is preferably not higher than 3 GPa, more preferably 1-3 GPa, even more preferably 2-3 GPa, and most preferably 2.05-2.88 GPa; the flexible adhesive layer comprises a flexible adhesive. The flexible adhesive typically has soft polymer chains, including but not limited to styrene-acrylic adhesives, SBR adhesives, and polyurethane adhesives. The Young's modulus of the flexible adhesive can be adjusted by using soft ether polyethylene glycol during the synthesis process. The swelling of the styrene-acrylic adhesive should be no less than 80%; the swelling of the SBR adhesive should be no less than 45%; and the swelling of the polyurethane adhesive should be no less than 60%. The mass of the flexible adhesive layer is preferably 0.5% to 1.5% of the mass of the silicon-doped anode active layer, more preferably 0.8% to 1.4%. Optionally, the mass of the flexible adhesive layer is 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% of the mass of the silicon-doped anode active layer, or a range between any two of the above values. In a specific embodiment provided in this application, the flexible adhesive outer layer completely encapsulates the outer surface of the core. The flexible adhesive layer is bonded to the internal rigid adhesive through bonding mechanisms such as ester bonds, hydrogen bonds, and physical cross-linking, while the outer side consists of hydrophilic polar groups to ensure the directional arrangement of the adhesive.

[0031] In one specific embodiment provided in this application, the silicon-doped anode active layer includes a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together; the first silicon-doped anode active sublayer includes a core; the cores are connected by a rigid adhesive; the second silicon-doped anode active sublayer includes particulate matter; the particulate matter includes a core and a flexible adhesive outer layer; the flexible adhesive outer layer partially wraps around the outer surface of the core. The core and particulate matter are as described above and will not be repeated here.

[0032] The silicon-doped anode active layer comprises a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together. The first silicon-doped anode active sublayer can contact the current collector via a rigid binder. The rigid binder bonds to the current collector surface through hydrogen bonds, which is beneficial for material dispersibility and slurry stability, while ensuring a certain level of adhesion. It can also form adhesion by combining with silicon oxide through covalent ester bonds (COO-Si), thereby improving the stability of the anode sheet formed with the current collector.

[0033] In one specific embodiment provided in this application, the thickness ratio of the first silicon-doped anode active sublayer to the second silicon-doped anode active sublayer is 1:(0.001~0.002).

[0034] In one specific embodiment of this application, the first silicon-doped anode active sublayer is composed of a core, which includes graphite particles, silicon anode particles, and a conductive agent. The graphite particles, silicon anode particles, and conductive agent are connected by a rigid binder, that is, the graphite particles, silicon anode particles, and conductive agent are encapsulated by the rigid binder. In another specific embodiment of this application, the flexible binder outer layer of the second silicon-doped anode active sublayer is located on the surface of the particles away from the first silicon-doped anode active sublayer. The surface of the particles is a rigid binder, which can be bonded to the external flexible binder layer through bonding mechanisms such as covalent ester bonds, hydrogen bonds, and physical crosslinking.

[0035] In one specific embodiment provided in the application, the areal density of the silicon-doped negative electrode active layer is preferably 60–100 g / m². 2 Optionally, the areal density of the silicon-doped anode active layer is preferably 60 g / m². 2 70g / m 2 80g / m 2 90g / m 2 100g / m 2 Or the range between any two of the above values.

[0036] In one specific embodiment provided in this application, the compaction density of the silicon-doped anode active layer is preferably 1.5–1.65 g / cm³. 3 Optionally, the compaction density of the silicon-doped anode active layer is 1.5 g / cm³.3 1.55g / cm 3 1.65g / cm 3 1.65g / cm 3 Or the range between any two of the above values.

[0037] In this application, the silicon-doped anode active layer can be prepared according to methods well known to those skilled in the art, specifically according to the following two methods:

[0038] The first method: When the flexible binder completely coats the outer surface of the core, the silicon-doped negative electrode active layer is prepared according to the following method: graphite particles, silicon negative electrode particles, conductive agent and rigid binder are mixed evenly in a solvent, and after stabilization, the flexible binder is added under stirring to obtain a slurry; the slurry is coated into a film and dried to obtain the silicon-doped negative active layer; the solid content of the slurry is preferably 43% to 50%; the drying is preferably vacuum drying; the drying temperature is preferably 110℃ to 130℃, more preferably 120℃.

[0039] The second method: When the silicon-doped anode active layer comprises a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together, the silicon-doped anode active layer can be prepared by the following method: graphite particles, silicon anode particles, conductive agent and rigid binder are mixed evenly in a solvent to obtain a slurry; the slurry is coated into a film, dried, and then a flexible binder solution is spin-coated onto the surface and dried further to obtain the silicon-doped anode active layer; the solid content of the slurry is preferably 43% to 50%; the mass concentration of the flexible binder solution is preferably 10% to 20%; the diameter of the spin-coating disk is preferably 100 to 200 mm; the spin-coating speed is preferably 3000 to 5000 rpm; the spin-coating method can improve the uniformity of the flexible binder, which is beneficial to the stability of mass production; both the drying and the continued drying are preferably vacuum drying; the drying and the continued drying temperatures are each preferably 110℃ to 130℃, more preferably 120℃; the continued drying time is preferably 4 to 6 hours.

[0040] This application also provides a negative electrode sheet, the negative electrode sheet including a current collector and the above-mentioned silicon-doped negative electrode active layer, the silicon-doped negative electrode active layer being disposed on at least one side surface of the current collector.

[0041] In one specific embodiment provided in this application, the negative electrode sheet includes a current collector and a silicon-doped negative electrode active layer disposed on at least one side of the current collector; the silicon-doped negative electrode active layer includes particulate matter; the particulate matter includes a core and a flexible binder outer layer; the flexible binder outer layer completely covers the outer surface of the core.

[0042] In one specific embodiment provided in this application, the negative electrode sheet includes a current collector and a silicon-doped negative electrode active layer disposed on at least one side surface of the current collector; the silicon-doped negative electrode active layer includes a first silicon-doped negative electrode active sublayer and a second silicon-doped negative electrode active sublayer stacked thereon; the first silicon-doped negative electrode active sublayer is in contact with the current collector; the first silicon-doped negative electrode active sublayer includes a core; the cores are connected to each other by a rigid adhesive; the second silicon-doped negative electrode active sublayer includes particulate matter; the particulate matter includes a core and a flexible adhesive outer layer; the flexible adhesive outer layer partially wraps around the outer surface of the core.

[0043] See Figure 3 , Figure 3 This is a schematic diagram of the structure of the negative electrode sheet provided in this application, wherein 6 is the second silicon-doped negative electrode active sublayer, 7 is the first silicon-doped negative electrode active sublayer, and 8 is the current collector.

[0044] This application also provides a battery cell, including the aforementioned silicon-doped negative electrode active layer or the aforementioned negative electrode sheet.

[0045] In one specific embodiment provided in this application, the battery cell further includes a positive electrode and a separator; the separator is disposed between the negative electrode and the positive electrode.

[0046] This application also provides an electrical device including the aforementioned battery cell.

[0047] In specific applications, electrical equipment can include laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0048] Specifically, the vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.

[0049] To further illustrate this application, the following describes in detail, with reference to embodiments, a silicon-doped anode active layer, anode sheet, battery cell, and electrical device provided in this application.

[0050] All reagents used in the following examples are commercially available.

[0051] Example 1

[0052] This embodiment provides a negative electrode slurry with a composite binder, and the components and their mass percentages are as follows:

[0053] Graphite:Silicon oxide:Conductive carbon:Rigid binder:Flexible binder:Dispersant = 91.2%:4.8%:1.5%:1.5%:0.8%:0.2%.

[0054] (The graphite particle size is 13 μm, the degree of graphitization is 95-96%, the silicon particle size is 8-9 μm, the type is pre-lithiated SiOx or SiC, and the dispersant is conventional CMC or lithiated CMC-Li)

[0055] The rigid adhesive (PAA) has a Young's modulus of 9.68 GPa and a swelling of 8%, while the flexible adhesive (polyurethane-crosslinked polyurethane PU-BASF PU-X30) has a Young's modulus of 2.38 GPa and a swelling of 80%. The two are linked by physical crosslinking and covalent ester bonds.

[0056] The negative electrode slurry is obtained through a single process: graphite, silicon oxide, conductive carbon, rigid binder, and dispersant are added sequentially and mixed evenly in deionized water. A flexible binder is then added, and after the slurry stabilizes, it is coated onto copper foil (area density 80 g / m²). 2 The electrode is vacuum dried at 120℃, and then held at a pressure of 5MPa for 30s under an electrode roller press to obtain the desired negative electrode.

[0057] Example 2

[0058] This embodiment provides a negative electrode slurry with a composite binder, and the components and their mass percentages are as follows:

[0059] Graphite:Silicon oxide:Conductive carbon:Rigid binder:Flexible binder:Dispersant = 91.2%:4.8%:1.5%:1.5%:0.8%:0.2%.

[0060] The rigid adhesive (PAA) has a Young's modulus of 9.08 GPa and a swelling of 10%, while the flexible adhesive (polyurethane-waterborne polyurethane WPU-Kejing WPU-601) has a Young's modulus of 2.5 GPa and a swelling of 65%. The two are linked by physical crosslinking and covalent ester bonds.

[0061] The negative electrode slurry is obtained through a two-stage process: graphite, silicon oxide, conductive carbon, rigid binder, and dispersant are added sequentially and mixed evenly in deionized water. After the slurry stabilizes, it is evenly coated onto Cu foil. After the negative electrode sheet is completely dry, a 15% flexible binder solution is coated onto the dried electrode in a specific ratio. After drying, the electrode is held at a pressure of 5 MPa for 30 seconds under an electrode roll press. The composite binder electrode is then vacuum dried at 120°C.

[0062] Example 3

[0063] This embodiment provides a negative electrode slurry with a composite binder, and the components and their mass percentages are as follows:

[0064] Graphite:Silicon oxide:Conductive carbon:Rigid binder:Flexible binder:Dispersant = 88.35%:6.86%:1.8%:1.5%:1%:0.7%.

[0065] The rigid binder (styrene-butadiene emulsion type Reion BM451B) has a Young's modulus of 8.35 GPa and a swelling of 22%, while the flexible binder (SBR type emulsion type Reion BAP-S401) has a Young's modulus of 2.88 GPa and a swelling of 50%. The two binders are linked by hydrogen bonds and covalent ester bonds.

[0066] The preparation process of the negative electrode slurry is as described in Example 1.

[0067] Example 4

[0068] This embodiment provides a negative electrode slurry with a composite binder, and the components and their mass percentages are as follows:

[0069] Graphite:Silicon oxide:Conductive carbon:Rigid binder:Flexible binder:Dispersant = 91.2%:4.8%:1.5%:1.15%:1.15%:0.2%.

[0070] The rigid binder (styrene-butadiene emulsion type Ruwen BM451B) has a Young's modulus of 8.05 GPa and a swelling of 24%, while the flexible binder (styrene-propanediol-Yanyi BAP-S1) has a Young's modulus of 2.05 GPa and a swelling of 120%. The two binders are linked through hydrogen bonds, covalent ester bonds, and physical crosslinking.

[0071] The preparation process of the negative electrode slurry is as described in Example 1.

[0072] Comparative Example 1

[0073] This comparative example provides a negative electrode slurry for a conventional binder, and the components and their mass percentages are as follows:

[0074] Graphite:Silicon oxide:Conductive carbon:Binder (rigid binder styrene-butadiene emulsion type Reion BM451B, Young's modulus is 8.5 GPa):Dispersant = 91.2%:4.8%:1.5%:2.3%:0.2%.

[0075] Graphite, silicon oxide, conductive carbon, binder, and dispersant are mixed in deionized water according to a certain ratio. After stirring evenly, Cu foil is used as the negative electrode current collector. The mixture is then coated, cold-pressed, cut, and slit to prepare the negative electrode sheet.

[0076] Comparative Example 2

[0077] This comparative example provides a negative electrode slurry for a conventional binder, and the components and their mass percentages are as follows:

[0078] Graphite: Silicon oxide: Conductive carbon: Binder (SBR type - emulsion type Reon BAP-S401, Young's modulus is 2.8 GPa): Dispersant = 91.2%: 4.8%: 1.5%: 2.3%: 0.2%.

[0079] Graphite, silicon oxide, conductive carbon, binder, and dispersant were mixed in deionized water according to a certain ratio and stirred evenly. Using Cu foil as the negative electrode current collector, the mixture was coated, cold-pressed, cut, and slit to prepare the negative electrode sheet.

[0080] Electrochemical performance:

[0081] The battery is assembled using coin cells, and the negative electrode current collector is made of Cu foil with an areal density of 80 g / m³. 2 Load capacity ~10mg, compaction density 1.5g / cm³ 3 The positive electrode current collector uses Al foil with an areal density of 150 g / m³. 2 Load capacity ~20mg, compaction density 3.5g / cm³ 3 The positive electrode is composed of active material: PVDF: conductive carbon SP = 97%: 1%: 2%, where the active material is the conventional ternary positive electrode material Ni68. The separator is composed of PP / PE / PP. The electrolyte solvent is ethylene carbonate (EC) and ethyl methyl carbonate (EMC), with an EMC content of 15%. The lithium salt is LiPF6 (concentration 1.0 mol / L), and the additives include 3% fluoroethylene carbonate (FEC). The battery was subjected to 1C1C cycling (charge and discharge at 1C current) within a voltage range of 2.5 to 4.4V, and the results are shown in Table 1.

[0082] Table 1. Results of Battery Electrochemical Performance Testing

[0083] Group Number of cycles @ 80% SOH Comparative Example 1 754 Comparative Example 2 822 Example 1 1226 Example 2 1154 Example 3 1038 Example 4 994

[0084] In Table 1, SOH represents the battery health status, SOH = (Qn / Qd) × 100%, Qn represents the rated capacity of the new battery, Qd represents the current actual capacity of the battery, and cycle count @ 80% SOH refers to the number of cycles when the battery capacity drops to 80%.

[0085] As shown in Table 1, the cycle life of the silicon-doped anode active layer provided in this application is significantly improved, which fully demonstrates that the design of the double-layer binder can effectively alleviate stress release during the anode cycling process and ensure the stability of the anode interface.

[0086] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A silicon-doped anode active layer, characterized in that, The silicon-doped anode active layer comprises particulate matter; the particulate matter comprises a core and a flexible binder outer layer; the flexible binder outer layer fully or partially encapsulates the outer surface of the core; the core comprises graphite particles, silicon anode particles, and a conductive agent; the graphite particles, silicon anode particles, and conductive agent are connected by a rigid binder.

2. The silicon-doped anode active layer according to claim 1, characterized in that, The graphite particles have a particle size of 10–20 μm; the silicon anode particles have a particle size of 5–15 μm.

3. The silicon-doped anode active layer according to claim 1, characterized in that, The outer surface of the core is a rigid adhesive layer.

4. The silicon-doped anode active layer according to claim 1, characterized in that, The thickness of the outer layer of the flexible adhesive is 20–50 nm.

5. The silicon-doped anode active layer according to claim 1, characterized in that, The silicon-doped anode active layer includes a first silicon-doped anode active sublayer and a second silicon-doped anode active layer stacked together. The first silicon-doped anode active sublayer includes a core; the cores are connected to each other by a rigid binder; The second silicon-doped anode active sublayer includes a core and a flexible binder outer layer; the flexible binder outer layer partially wraps around the outer surface of the core.

6. The silicon-doped anode active layer according to claim 5, characterized in that, The thickness ratio of the first silicon-doped anode active sublayer to the second silicon-doped anode active sublayer is 1:(0.001~0.002).

7. A negative electrode sheet, characterized in that, It includes a current collector and a silicon-doped anode active layer as described in any one of claims 1 to 6, wherein the silicon-doped anode active layer is disposed on at least one side surface of the current collector.

8. The negative electrode sheet according to claim 7, characterized in that, The silicon-doped anode active layer includes a first silicon-doped anode active sublayer and a second silicon-doped anode active sublayer stacked together; the first silicon-doped anode active sublayer is in contact with the current collector.

9. A battery cell, characterized in that, It includes the silicon-doped anode active layer as described in any one of claims 1 to 6 or the anode sheet as described in claim 7 or 8.

10. An electrical appliance, characterized in that, This includes the negative electrode sheet as described in claim 7 or 8, or the battery cell as described in claim 9.

Images