A negative electrode, a preparation method therefor, and an application thereof

Abstract

The application relates to a negative electrode, comprising: a plurality of negative electrode units and a plurality of conductive units for connecting the plurality of negative electrode units; wherein the negative electrode unit comprises: negative electrode particles and a polydopamine layer coated on the surface of the negative electrode particles; wherein the polydopamine layer has a plurality of primary amine structures and a plurality of secondary amine structures; the conductive unit comprises: conductive particles and a plurality of active groups formed on the surface of the conductive particles; wherein the active groups have activity of forming hydrogen bonds with the primary amine structures or / and the secondary amine structures. In the negative electrode of the application, the surface of the negative electrode particles is coated with the polydopamine layer, the surface of the conductive particles has the active groups, the active groups attract each other to form hydrogen bonds, and in the process of the silicon negative electrode cycle, the probability of the contact between the negative electrode particles and the conductive particles being destroyed is reduced, and in the case that the conductive path is damaged, as long as the negative electrode particles and the conductive particles are in contact again, the hydrogen bonds can be reformed, so that the process of the silicon negative electrode cycle is effectively maintained.

Description

Technical Field

[0001] This invention relates to the field of chemical battery technology, and in particular to a negative electrode, its preparation method, and its application. Background Technology

[0002] With the rapid development of energy storage and power energy, the demand for battery energy density is gradually increasing. Currently, graphite is still the main anode material. In order to further increase battery energy density, silicon anodes (silicon or silicon suboxide) are gradually gaining attention. However, the volume expansion and pulverization of silicon anodes during application may cause the anode structure to collapse, resulting in it peeling off from the conductive foil, destroying the conductive network, and thus leading to poor battery cycle performance.

[0003] Existing technologies generally involve increasing the content of adhesives, developing adhesives with high bonding performance, adding graphite for mixing, or nano-sized negative electrode particles, but there are no technologies for modifying negative electrode particles or / and conductive particles.

[0004] Therefore, there is an urgent need for a negative electrode, its preparation method, and its application. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a negative electrode, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention is to provide a negative electrode, comprising: a plurality of negative electrode units and a plurality of conductive units for connecting the plurality of negative electrode units; wherein,

[0008] The negative electrode unit includes: negative electrode particles and a polydopamine layer covering the surface of the negative electrode particles; wherein the polydopamine layer has a plurality of primary amine structures and a plurality of secondary amine structures;

[0009] The conductive unit includes: conductive particles and a plurality of active groups formed on the surface of the conductive particles; wherein the active groups are active in forming hydrogen bonds with the primary amine structure and / or the secondary amine structure.

[0010] Preferably, the negative electrode further includes an adhesive mixed with the negative electrode unit and the conductive unit.

[0011] Preferably, the negative electrode particles comprise at least one of silicon or silicon suboxide.

[0012] Preferably, the particle size of the negative electrode particles is 0.01 μm to 50 μm.

[0013] Preferably, the thickness of the polydopamine layer is 1 nm to 100 nm.

[0014] Preferably, the conductive particles include at least one of Super-P, Ketjen Black, acetylene black, furnace black, lamp black, graphite, graphene, carbon fiber, or carbon nanotubes.

[0015] Preferably, the active group includes a carbonyl group.

[0016] Preferably, the content of the active group in the conductive unit is not less than 10%. -8 mol / g.

[0017] A second aspect of the present invention is to provide a method for preparing a negative electrode as described above, comprising the steps of:

[0018] S1. Provide a negative electrode particle, and coat the surface of the negative electrode particle with a layer of polydopamine to obtain the negative electrode unit;

[0019] S2. Provide a conductive particle, and form a plurality of active groups on the surface of the conductive particle to obtain the conductive unit;

[0020] S3. The negative electrode unit and the conductive unit are subjected to a first mixing treatment, in which the active group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure;

[0021] After adding the binder, the process involves a second mixing treatment, coating treatment, drying treatment, and rolling treatment to obtain the negative electrode.

[0022] A third aspect of the present invention is to provide a chemical battery comprising: a negative electrode as described above.

[0023] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0024] During cycling, silicon anodes undergo volume expansion and pulverization, which causes the separation between anode particles and conductive particles, resulting in the destruction of the conductive path. Furthermore, since neither anode particles nor conductive particles contain polar groups, the conductive path is difficult to repair once it is destroyed.

[0025] In the negative electrode of this invention, the surface of the negative electrode particles is coated with a polydopamine layer, and the surface of the conductive particles has active groups. Thus, when the negative electrode particles and conductive particles are mixed, particles containing the same functional groups repel each other, which is beneficial for dispersion and formation of a uniform conductive path; while particles containing different functional groups attract each other to form hydrogen bonds. This reduces the probability of the contact between the negative electrode particles and conductive particles being disrupted during the cycling process of the silicon negative electrode. At the same time, if the conductive path is disrupted due to volume expansion or pulverization, as long as the negative electrode particles and conductive particles come into contact again, the hydrogen bonds can be reformed, thereby repairing the damaged conductive path and effectively maintaining the cycling process of the silicon negative electrode. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of step S2 in the method for preparing the negative electrode in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram illustrating the principle of hydrogen bonding between the active group and the primary amine structure and / or secondary amine structure in an embodiment of the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below.

[0029] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] The word "a" or similar terms used in the specification and claims of this patent application do not indicate a limitation on quantity, but rather indicate the presence of at least one. The word "comprising" or similar terms mean that the items preceding "comprising" cover the items listed after "comprising" or their equivalents, and do not exclude other items.

[0031] The numerical values ​​mentioned in this invention include all values ​​increasing one unit at a time from low to high, assuming that there is at least a two-unit interval between any lower and higher value. For example, if it is said that a component quantity or a physical quantity is better from 1 to 100, 10 to 90, and 20 to 80, it means that values ​​such as 5 to 95, 14 to 76, 23 to 67, 32 to 58, and 41 to 49 are clearly listed in this specification; for values ​​less than 1, 0.0001, 0.001, 0.01, or 0.1 are considered to be a suitable unit. The foregoing examples are for illustrative purposes only; in practice, all combinations of values ​​between the lowest and highest listed values ​​are considered to be clearly listed in this specification in a similar manner.

[0032] It should be further noted that the term "primary amine structure" used in the specification and claims of this patent application refers to a group with the chemical structural formula -NH2.

[0033] It should be further noted that the term "secondary amine structure" used in the specification and claims of this patent application refers to a group with the chemical structural formula -NH-.

[0034] It should be further noted that the term "active group" used in the specification and claims of this patent application refers to a group with the chemical structural formula -C=O, or other groups capable of forming hydrogen bonds with primary amine structures and / or secondary amine structures.

[0035] It should be further noted that the term "active" used in the specification and claims of this patent application refers to the ability to form hydrogen bonds through chemical reactions.

[0036] This embodiment provides a negative electrode and its preparation method, wherein...

[0037] The negative electrode comprises: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive mixed with the negative electrode units and the conductive units; wherein...

[0038] The negative electrode unit includes: negative electrode particles and a polydopamine layer covering the surface of the negative electrode particles; wherein the polydopamine layer has a plurality of primary amine structures and a plurality of secondary amine structures;

[0039] The conductive unit includes: conductive particles and a plurality of active groups formed on the surface of the conductive particles; wherein the active groups have the activity of forming hydrogen bonds with the primary amine structure and / or the secondary amine structure;

[0040] The steps of the method for preparing the negative electrode include:

[0041] S1. Provide a negative electrode particle, and coat the surface of the negative electrode particle with a layer of polydopamine to obtain the negative electrode unit;

[0042] S2, such as Figure 1 As shown, a conductive particle is provided, and a plurality of active groups are formed on the surface of the conductive particle to obtain the conductive unit;

[0043] S3, such as Figure 2 As shown, the negative electrode unit and the conductive unit are subjected to a first mixing treatment, in which the active group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure;

[0044] After adding the binder, the process involves a second mixing treatment, coating treatment, drying treatment, and rolling treatment to obtain the negative electrode.

[0045] In some preferred embodiments, the negative electrode particles comprise at least one of silicon or silicon suboxide.

[0046] In some preferred embodiments, the particle size of the negative electrode particles is 0.01 μm to 50 μm.

[0047] In some preferred embodiments, the thickness of the polydopamine layer is 1 nm to 100 nm.

[0048] In some preferred embodiments, the conductive particles include at least one of Super-P, Ketjen Black, acetylene black, furnace black, lamp black, graphite, graphene, carbon fiber, or carbon nanotubes.

[0049] In some preferred embodiments, the active group includes a carbonyl group.

[0050] In some preferred embodiments, the content of the active group in the conductive unit is not less than 10. - 8 mol / g.

[0051] Example 1

[0052] In this embodiment, the negative electrode particles are elemental silicon with a particle size of 100 nm, the polydopamine layer has a thickness of 2 nm, the conductive particles are Super-P, and the carbonyl content in the conductive unit is 5 × 10⁻⁶. -8 mol / g.

[0053] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0054] The negative electrode unit includes: silicon with a particle size of 100 nm and a polydopamine layer with a thickness of 2 nm covering the surface of the silicon.

[0055] The conductive unit includes: Super-P, and a content of 5×10 on the surface of the Super-P. - 8 carbonyl groups in mol / g;

[0056] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0057] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0058] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 2 nm thickness: At room temperature, 1 part by mass of Tris solution and 2 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of elemental silicon (particle size of 100 nm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0059] S2, Forming a concentration of 5×10 on the surface of the conductive particles. -8 mol / g carbonyl group: At room temperature, 50 parts by mass of concentrated H2SO4 solution and 50 parts by mass of 30% H2O2 were mixed, and 1 part by mass of Super-P was added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0060] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 95:4:1, and then coated, dried, and rolled in sequence.

[0061] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0062] Example 2

[0063] In this embodiment, the negative electrode particles are silicon suboxide with a particle size of 200 nm, the polydopamine layer has a thickness of 3 nm, the conductive particles are Ketjen Black, and the carbonyl content in the conductive unit is 2 × 10⁻⁶. -8 mol / g.

[0064] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0065] The negative electrode unit includes: silicon suboxide with a particle size of 200 nm and a polydopamine layer with a thickness of 3 nm covering the surface of the silicon suboxide;

[0066] The conductive unit comprises: Ketjen black, and a content of 2×10⁻⁶ on the surface of the Ketjen black. -8 carbonyl groups in mol / g;

[0067] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0068] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0069] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 3 nm thickness: At room temperature, 1 part by mass of Tris solution and 2 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon suboxide (particle size of 200 nm) are added. After stirring for 12 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0070] S2, Forming a content of 2×10 on the surface of the conductive particles. -8 mol / g carbonyl group: At room temperature, 20 parts by mass of concentrated H2SO4 solution and 80 parts by mass of 30% H2O2 were mixed, and 1 part by mass of Ketjen black was added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0071] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 95:3:2, and then coated, dried, and rolled in sequence.

[0072] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0073] Example 3

[0074] In this embodiment, the negative electrode particles are elemental silicon with a particle size of 5 μm, the polydopamine layer has a thickness of 10 nm, the conductive particles are acetylene black, and the carbonyl content in the conductive unit is 3 × 10⁻⁶. -7 mol / g.

[0075] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0076] The negative electrode unit includes: silicon with a particle size of 5 μm, and a polydopamine layer with a thickness of 10 nm covering the surface of the silicon.

[0077] The conductive unit includes: acetylene black, and a content of 3×10 on the surface of the acetylene black. -7 carbonyl groups in mol / g;

[0078] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0079] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0080] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 10 nm thickness: At room temperature, 1 part by mass of Tris solution and 3 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon (particle size of 5 μm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0081] S2, Forming a concentration of 3×10 on the surface of the conductive particles. -7 mol / g carbonyl group: Acetylene black was washed 5 times with deionized water and 2 times with methanol, dried under vacuum at 80°C for 12 h, and then treated with oxygen plasma under vacuum at room temperature for 12 h to obtain the conductive unit.

[0082] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 92:3:5, and then coated, dried, and rolled in sequence.

[0083] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0084] Example 4

[0085] In this embodiment, the negative electrode particles are silicon suboxide with a particle size of 20 nm, the polydopamine layer has a thickness of 30 nm, the conductive particles are furnace black, and the carbonyl content in the conductive unit is 7 × 10⁻⁶. -8 mol / g.

[0086] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0087] The negative electrode unit includes: silicon suboxide with a particle size of 20 nm, and a polydopamine layer with a thickness of 30 nm coated on the surface of the silicon suboxide;

[0088] The conductive unit includes: furnace black, and a content of 7×10 on the surface of the furnace black. -8 carbonyl groups in mol / g;

[0089] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0090] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0091] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 30 nm thickness: At room temperature, 1 part by mass of Tris solution and 4 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon suboxide (particle size of 20 nm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0092] S2, Forming a concentration of 7×10 on the surface of the conductive particles. -8 mol / g carbonyl group: At room temperature, 50 parts by mass of concentrated H2SO4 solution and 50 parts by mass of 30% H2O2 were mixed, and 1 part by mass of furnace black was added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0093] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 94:1:5, and then coated, dried, and rolled in sequence.

[0094] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0095] Example 5

[0096] In this embodiment, the negative electrode particles are silicon suboxide with a particle size of 200 nm, the polydopamine layer has a thickness of 3 nm, the conductive particles are lampblack, and the carbonyl content in the conductive unit is 3 × 10⁻⁶. -8 mol / g.

[0097] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0098] The negative electrode unit includes: silicon suboxide with a particle size of 200 nm and a polydopamine layer with a thickness of 3 nm covering the surface of the silicon suboxide;

[0099] The conductive unit includes: lamp black, and a content of 3×10 on the surface of the lamp black.-8 carbonyl groups in mol / g;

[0100] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0101] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0102] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 3 nm thickness: At room temperature, 1 part by mass of Tris solution and 2 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon suboxide (particle size of 200 nm) are added. After stirring for 12 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0103] S2, Forming a concentration of 3×10 on the surface of the conductive particles. -8 mol / g carbonyl group: At room temperature, 20 parts by mass of concentrated HNO3 solution and 80 parts by mass of 30% H2O2 were mixed, and 1 part by mass of lamp black was added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0104] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 95:3:2, and then coated, dried, and rolled in sequence.

[0105] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0106] Example 6

[0107] In this embodiment, the negative electrode particles are silicon suboxide with a particle size of 200 nm, the polydopamine layer has a thickness of 3 nm, the conductive particles are graphite, and the carbonyl content in the conductive unit is 8 × 10⁻⁶. -8 mol / g.

[0108] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0109] The negative electrode unit includes: silicon suboxide with a particle size of 200 nm and a polydopamine layer with a thickness of 3 nm covering the surface of the silicon suboxide;

[0110] The conductive unit comprises: graphite, and a content of 8×10⁻⁶ on the surface of the graphite. -8 carbonyl groups in mol / g;

[0111] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0112] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0113] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 3 nm thickness: At room temperature, 1 part by mass of Tris solution and 2 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon suboxide (particle size of 200 nm) are added. After stirring for 12 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0114] S2, forming a content of 8×10 on the surface of the conductive particles. -8 mol / g carbonyl group: At room temperature, 20 parts by mass of concentrated HNO3 solution and 80 parts by mass of 30% H2O2 were mixed, and 1 part by mass of graphite was added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0115] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 95:3:2, and then coated, dried, and rolled in sequence.

[0116] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0117] Example 7

[0118] In this embodiment, the negative electrode particles are elemental silicon with a particle size of 5 μm, the polydopamine layer has a thickness of 10 nm, the conductive particles are graphene, and the carbonyl content in the conductive unit is 2 × 10⁻⁶. -7 mol / g.

[0119] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0120] The negative electrode unit includes: silicon with a particle size of 5 μm, and a polydopamine layer with a thickness of 10 nm covering the surface of the silicon.

[0121] The conductive unit comprises: graphene, and a content of 2×10⁻⁶ elements formed on the surface of the graphene. -7 carbonyl groups in mol / g;

[0122] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0123] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0124] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 10 nm thickness: At room temperature, 1 part by mass of Tris solution and 3 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon (particle size of 5 μm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0125] S2, Forming a content of 2×10 on the surface of the conductive particles. -7 mol / g carbonyl group: Graphene was washed 5 times with deionized water and 2 times with methanol, dried under vacuum at 80°C for 12 h, and then treated with oxygen plasma under vacuum at room temperature for 12 h to obtain the conductive unit.

[0126] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 92:3:5, and then coated, dried, and rolled in sequence.

[0127] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0128] Example 8

[0129] In this embodiment, the negative electrode particles are elemental silicon with a particle size of 5 μm, the polydopamine layer has a thickness of 10 nm, the conductive particles are carbon fibers, and the carbonyl content in the conductive unit is 2 × 10⁻⁶. -8 mol / g.

[0130] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0131] The negative electrode unit includes: silicon with a particle size of 5 μm, and a polydopamine layer with a thickness of 10 nm covering the surface of the silicon.

[0132] The conductive unit comprises: carbon fiber, and a content of 2×10⁻⁶ on the surface of the carbon fiber. -8 carbonyl groups in mol / g;

[0133] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0134] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0135] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 10 nm thickness: At room temperature, 1 part by mass of Tris solution and 3 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 50 parts by mass of silicon (particle size of 5 μm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0136] S2, Forming a content of 2×10 on the surface of the conductive particles. -8 mol / g carbonyl: The carbon fiber was washed 5 times with deionized water and 2 times with methanol, dried under vacuum at 80°C for 12 h, and then treated with oxygen plasma under vacuum at room temperature for 12 h to obtain the conductive unit.

[0137] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 92:3:5, and then coated, dried, and rolled in sequence.

[0138] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0139] Example 9

[0140] In this embodiment, the negative electrode particles are elemental silicon with a particle size of 100 nm, the polydopamine layer has a thickness of 2 nm, the conductive particles are carbon nanotubes, and the carbonyl content in the conductive unit is 1 × 10⁻⁶. -6 mol / g.

[0141] Specifically, in this embodiment, the negative electrode includes: a plurality of negative electrode units, a plurality of conductive units for connecting the plurality of negative electrode units, and an adhesive PAA mixed with the negative electrode units and the conductive units; wherein,

[0142] The negative electrode unit includes: silicon with a particle size of 100 nm and a polydopamine layer with a thickness of 2 nm covering the surface of the silicon.

[0143] The conductive unit comprises: carbon nanotubes, and a content of 1×10⁻⁶ on the surface of the carbon nanotubes. - 6 carbonyl groups in mol / g;

[0144] The carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0145] Specifically, in this embodiment, the steps of the method for preparing the negative electrode include:

[0146] S1. Coating the surface of the negative electrode particles with a polydopamine layer of 2 nm thickness: At room temperature, 1 part by mass of Tris solution and 2 parts by mass of dopamine are dispersed in 1000 parts by mass of methanol, and 25 parts by mass of silicon (particle size of 100 nm) are added. After stirring for 24 h in a pure O2 atmosphere, the mixture is filtered and washed 5 times with methanol, and dried under vacuum at 80 °C for 12 h to obtain the negative electrode unit.

[0147] S2, Forming a concentration of 1×10 on the surface of the conductive particles. -6 mol / g carbonyl group: At room temperature, 50 parts by mass of concentrated H2SO4 solution and 50 parts by mass of 30% H2O2 were mixed, and 1 part by mass of carbon nanotubes were added. After stirring for 12 h, the mixture was filtered and washed 5 times with deionized water and 1 time with methanol. After drying under vacuum at 80 °C for 12 h, it was treated at 400 °C for 12 h under Ar(g) atmosphere to obtain the conductive unit.

[0148] S3. The negative electrode unit, the conductive unit, and the binder PAA are mixed in a mass ratio of 95:4:1, and then coated, dried, and rolled in sequence.

[0149] In the premixing process of the negative electrode unit and the conductive unit, the carbonyl group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure of the polydopamine layer.

[0150] Comparative Example

[0151] This comparative example provides another method for preparing a negative electrode, the steps of which include:

[0152] Silicon (particle size 100nm) is mixed with conductive agent Super-P and binder PAA in a mass ratio of 92:3:5, and then coated, dried and rolled in sequence to obtain the negative electrode.

[0153] Detection Examples

[0154] The negative electrodes prepared in Examples 1-9 and the comparative example were assembled with NCM811 to form full cells. The electrolytes were 1M LiPF6, EC / DMC (1:1V / V), 2% EC and 2% FEC, and the cycle performance was tested. The results are shown in the table below:

[0155] First effect Cycle number Capacity maintenance rate Example 1 90.2％ 1200 87％ Example 2 89.3％ 1100 90％ Example 3 91.5％ 1000 85％ Example 4 89.5％ 2100 91％ Example 5 90.7％ 1500 82％ Example 6 90.1％ 1700 87％ Example 7 92.1％ 1900 81％ Example 8 91.9％ 1300 85％ Example 9 91.7％ 1700 87％ Comparative Example 83.7％ 900 71％

[0156] As can be seen, the comparative silicon anode undergoes volume expansion and pulverization during cycling, which causes the anode particles and conductive particles to peel off, thereby disrupting the conductive path. Furthermore, since neither the anode particles nor the conductive particles contain polar groups, the conductive path is difficult to repair once it is disrupted.

[0157] In the negative electrode of this invention, the surface of the negative electrode particles is coated with a polydopamine layer, and the surface of the conductive particles has active groups. Thus, when the negative electrode particles and conductive particles are mixed, particles containing the same functional groups repel each other, which is beneficial for dispersion and formation of a uniform conductive path. Meanwhile, particles containing different functional groups attract each other to form hydrogen bonds. This reduces the probability of the contact between the negative electrode particles and conductive particles being disrupted during the silicon negative electrode cycling process. At the same time, if the conductive path is disrupted due to volume expansion or pulverization, the hydrogen bonds can be reformed as long as the negative electrode particles and conductive particles come into contact again, thereby repairing the damaged conductive path and effectively maintaining the cycling process of the silicon negative electrode.

[0158] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative electrode, characterized in that, include: A plurality of negative electrode units, and a plurality of conductive units for connecting the plurality of negative electrode units; wherein, The negative electrode unit includes: negative electrode particles and a polydopamine layer covering the surface of the negative electrode particles; wherein the polydopamine layer has a plurality of primary amine structures and a plurality of secondary amine structures; The conductive unit includes: conductive particles and a plurality of active groups formed on the surface of the conductive particles; wherein the active groups have the activity of forming hydrogen bonds with the primary amine structure and / or the secondary amine structure; Wherein, the active group is a carbonyl group; The active group in the conductive unit contains not less than 10%. -8 mol / g.

2. The negative electrode according to claim 1, characterized in that, The negative electrode also includes an adhesive mixed with the negative electrode unit and the conductive unit.

3. The negative electrode according to claim 1, characterized in that, The negative electrode particles include at least one of silicon or silicon suboxide.

4. The negative electrode according to claim 1, characterized in that, The particle size of the negative electrode particles is 0.01 μm to 50 μm.

5. The negative electrode according to claim 1, characterized in that, The thickness of the polydopamine layer is 1 nm to 100 nm.

6. The negative electrode according to claim 1, characterized in that, The conductive particles include at least one of the following: Super-P, Ketjen Black, acetylene black, furnace black, lamp black, graphite, graphene, carbon fiber, or carbon nanotubes.

7. A method for preparing a negative electrode as described in any one of claims 1 to 6, characterized in that, step include: S1. Provide a negative electrode particle, and coat the surface of the negative electrode particle with a layer of polydopamine to obtain the negative electrode unit; S2. Provide a conductive particle, and form a plurality of active groups on the surface of the conductive particle to obtain the conductive unit; S3. The negative electrode unit and the conductive unit are subjected to a first mixing treatment, in which the active group forms hydrogen bonds with the primary amine structure and / or the secondary amine structure; After adding the binder, the process involves a second mixing treatment, coating treatment, drying treatment, and rolling treatment to obtain the negative electrode.

8. A chemical battery, characterized in that, include: The negative electrode as described in any one of claims 1 to 6.

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