Battery monomer, battery device and power utilization device

Abstract

The invention relates to the technical field of batteries, in particular to a battery monomer, a battery device and a power utilization device.A negative electrode piece of the battery monomer comprises a negative electrode active material, and the negative electrode active material comprises a negative electrode active base material and a coating layer arranged on at least part of the surface of the negative electrode active base material; the coating layer comprises a polymer; the polymer comprises a polyether-containing structural unit as shown in a formula (1-a), a biphenyl or dibenzofuran-containing structural unit as shown in a formula (1-b) and a disulfide bond-containing structural unit as shown in a formula (1-c). The coating layer containing the polymer can inhibit the expansion of the negative electrode active base material, so that the negative influence caused by the expansion and shrinkage of the negative electrode active material is improved, and the cycle capacity retention ratio of the battery is favorably optimized.

Description

A battery cell, a battery device, and an electrical device. Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, with the increasingly wide range of applications of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] During the charging and discharging process of a secondary battery, the insertion and extraction of active ions cause the expansion and contraction of the negative electrode active material, thereby damaging the structure of the negative electrode sheet and degrading the battery's cycle performance. This problem is particularly severe for silicon-based materials, leading to a rapid decline in battery capacity during cycling. Summary of the Invention

[0004] The purpose of this application is to provide a battery cell, a battery device, and an electrical device, wherein the battery cell uses a modified negative electrode active material that is not easily expanded during charging and discharging, thereby optimizing the capacity retention rate during battery cycling.

[0005] Therefore, the first aspect of this application provides a battery cell, including a positive electrode, a separator, and a negative electrode;

[0006] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector; the negative electrode material layer includes a negative electrode active material;

[0007] The negative electrode active material includes a negative electrode active substrate and a coating layer disposed on at least a portion of the surface of the negative electrode active substrate; the coating layer includes a polymer; the polymer includes structural units shown in formulas (1-a), (1-b), and (1-c):

[0008]

[0009] in,

[0010] R1 is selected from substituted or unsubstituted C1-C6 alkylene groups; the average molecular weight of the structural unit shown in formula (1-a) is 600-5000;

[0011] A r Selected from substituted or unsubstituted diphenyl, substituted or unsubstituted dibenzofuranyl;

[0012] R2 and R3 are each independently selected from directly bonded, substituted or unsubstituted C1 to C6 alkylene groups.

[0013] In the aforementioned polymer materials, the structural unit of Formula 1-a exhibits good flexibility, possessing a certain compressible and stretchable free volume. When the negative electrode active substrate expands (or contracts), the structural unit of Formula 1-a can act as a buffer by compressing (or stretching) its own volume, thereby reducing the stress generated during the expansion (or contraction) of the negative electrode active substrate. Thus, on the one hand, it makes the negative electrode active substrate less prone to breakage; on the other hand, it reduces the force exerted by the negative electrode active substrate on the SEI film during expansion (or contraction), making the SEI film less prone to breakage. The structural unit of Formula 1-b possesses π-π bonds, exhibiting a certain degree of rigidity. Furthermore, the hydrogen bonds and π-π stacking present in the system form a supramolecular non-covalent synergistic effect, improving the stability of the coating layer formed by the polymer. This, in turn, enhances the mechanical strength of the negative electrode active material, making it easier to maintain structural integrity during the expansion (or contraction) of the negative electrode active substrate.

[0014] The disulfide bond in the structural unit of Formula 1-c is a reversible dynamic chemical bond. During the dynamic process of expansion and contraction of the negative electrode active substrate, if the volume change is too large, the disulfide bond in the polymer can break; when the volume of the negative electrode active substrate gradually recovers, the disulfide bond can automatically re-bond. Therefore, even if the negative electrode active substrate undergoes excessive expansion in certain situations, it will not damage the polymer coating layer formed on its surface. This coating layer can still provide a buffer and inhibit the expansion or contraction of the negative electrode active substrate in subsequent cycles, thereby improving the battery's cycle capacity retention. Through the combined effect of the structural units of Formula 1-a, Formula 1-b, and Formula 1-c, the negative effects of expansion and contraction of the negative electrode active substrate are significantly reduced, improving the battery's capacity retention during cycling.

[0015] In some embodiments, the polymer contains structural units of Formula 1-a, Formula 1-b, and Formula 1-c in a ratio of 1:1 to 3:1 to 2.

[0016] The structural unit of Formula 1-b mainly provides a certain degree of rigidity and participates in the formation of supramolecular non-covalent synergistic effects. When it has the above-mentioned proportion, it can provide good mechanical strength for the polymer coating layer without negatively affecting ionic conductivity. When the structural unit of Formula 1-c has the above-mentioned proportion, it further facilitates the reconnection of disulfide bonds after breakage, allowing the polymer coating layer to quickly recover to a more complete structure.

[0017] In some embodiments, the structural unit shown in Formula 1-a is connected to the negative electrode active substrate by chemical bonds.

[0018] When the negative electrode active substrate and the chain polyether structure in the polymer are chemically bonded, the connection between the two is tighter, and the coating layer formed by the polymer has a stronger inhibitory effect on the expansion of the negative electrode active substrate.

[0019] In some embodiments, the structural unit shown in equation (1-a) includes structural units selected from the group consisting of:

[0020]

[0021] Wherein, the average molecular weight of the structural unit shown in formula (1-a) is 1000–3000; and / or,

[0022] The structural unit shown in equation (1-b) includes structural units selected from the following group:

[0023]

[0024] And / or,

[0025] The structural unit shown in equation (1-c) includes structural units selected from the following group:

[0026]

[0027]

[0028] In some embodiments, the connection between the structural units of Formula 1-a, Formula 1-b, and Formula 1-c includes direct bonding or connection through the following linking groups: ester bond, amide bond, and carbamate bond.

[0029] The above-mentioned connection methods exhibit good stability in the battery anode system and do not affect the polymer's role in buffering and inhibiting the expansion of the anode active substrate. When ester bonds, amide bonds, or urethane bonds are used, they also have the advantage of being easy to prepare.

[0030] In some embodiments, the polymer has a structural formula comprising at least one selected from the group consisting of:

[0031] (Equation 1-a)-L1-(Equation 1-c)-L2-(Equation 1-b);

[0032] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b);

[0033] (Equation 1-a)-L1-(Equation 1-c)-L2-(Equation 1-b)-L3-(Equation 1-c)-L4-(Equation 1-b);

[0034] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b)-L4-(Equation 1-c);

[0035] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b)-L4-(Equation 1-c)-L5-(Equation 1-b);

[0036] Among them, L1, L2, L3, L4, and L5 are each independently selected from direct bonding or linking groups.

[0037] In some embodiments, the negative electrode active material satisfies at least one of the following conditions (i) to (iii):

[0038] (i) The polymer accounts for 5 wt% to 15 wt% of the mass of the negative electrode active material;

[0039] (ii) The coating layer is composed of the polymer;

[0040] (iii) The thickness of the coating layer is 5 nm to 20 nm.

[0041] When the negative electrode active material meets at least one of the above conditions, the proportion of polymer and / or coating layer in the negative electrode active material is more reasonable. This can better suppress the expansion effect of the negative electrode active substrate without affecting the ion transport performance, thereby further improving the battery performance.

[0042] In some embodiments, the negative electrode active substrate includes at least one of a carbon substrate and a silicon substrate.

[0043] When carbon-based and / or silicon-based substrates are coated and modified as described above, they can both suppress expansion and improve the battery cycle capacity retention rate.

[0044] In some embodiments, the negative electrode active substrate includes a silicon substrate, specifically including silicon oxide materials and / or silicon carbon materials.

[0045] For silicon substrates, the expansion phenomenon is more severe. The above-mentioned coating modification has a more significant effect on improving the performance of batteries that use silicon-oxygen materials and / or silicon-carbon materials as negative electrode active materials.

[0046] In some embodiments, the silicon-oxygen material satisfies at least one of the following:

[0047] In the aforementioned silicon-oxygen material, the mass percentage of silicon element is 10% to 50%.

[0048] The particle size Dv50 of the silicon-oxygen material is 3-15 μm;

[0049] The BET specific surface area of ​​the silicon-oxygen material is 0.2–8 m². 2 / g;

[0050] The compaction density (TD) of the silicon-oxygen material is 0.8–1.2 g / cm³. 3 .

[0051] In some embodiments, the silicon-carbon material satisfies at least one of the following:

[0052] In the silicon-carbon material, the mass percentage of silicon is 50% to 80%.

[0053] The particle size Dv50 of the silicon carbide material is 3–20 μm;

[0054] The BET specific surface area of ​​the silicon-carbon material is 0.5–5 m². 2 / g;

[0055] The compaction density (TD) of the silicon-carbon material is 1.5–2.0 g / cm³. 3 .

[0056] When silicon-oxygen materials and / or silicon-carbon materials meet at least one of the above conditions, the technical effect of inhibiting expansion is more significantly improved after the above-mentioned coating layer modification.

[0057] A second aspect of this application provides a battery device comprising the battery cell described in the first aspect of this application.

[0058] A third aspect of this application provides an electrical device comprising a single battery cell as described in the first aspect of this application, or a battery device as described in the second aspect of this application.

[0059] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, the following lists specific embodiments of this application. Attached Figure Description

[0060] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. In the drawings:

[0061] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0062] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0063] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0064] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0065] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4;

[0066] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0067] Explanation of reference numerals in the attached figures:

[0068] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0069] Exemplary embodiments of this disclosure will now be described in more detail. It should be understood that this disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0070] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0072] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0073] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0074] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0075] Rechargeable batteries have seen widespread application in recent years, but this has also placed higher demands on their performance. During charging and discharging, the insertion and extraction of active ions cause the expansion and contraction of the negative electrode active material, thereby damaging the structure of the negative electrode and degrading the battery's cycle performance. This problem is particularly severe for silicon-based materials, leading to a rapid decline in battery capacity during cycling.

[0076] This application mainly modifies the negative electrode active material by coating it with a polymer having three functional structural units, thereby suppressing the expansion effect of the negative electrode active material and improving the battery cycle capacity retention rate.

[0077] The solutions described in the embodiments of this application are applicable to battery cells, battery devices using the battery cells, and electrical devices using the battery cells or battery devices.

[0078] battery cell

[0079] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0080] The battery cells can be lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, etc.

[0081] [Electrode Assembly]

[0082] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0083] [Negative electrode plate]

[0084] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector; the negative electrode material layer includes a negative electrode active material;

[0085] The negative electrode active material includes a negative electrode active substrate and a coating layer disposed on at least a portion of the surface of the negative electrode active substrate; the coating layer includes a polymer; the polymer includes structural units shown in formulas (1-a), (1-b), and (1-c):

[0086]

[0087] in,

[0088] R1 is selected from substituted or unsubstituted C1-C6 alkylene groups; the average molecular weight of the structural unit shown in formula (1-a) is 600-5000;

[0089] A r Selected from substituted or unsubstituted diphenyl, substituted or unsubstituted dibenzofuranyl;

[0090] R2 and R3 are each independently selected from directly bonded, substituted or unsubstituted C1 to C6 alkylene groups.

[0091] In the aforementioned polymer materials, the structural unit of Formula 1-a exhibits good flexibility, possessing a certain compressible and stretchable free volume. When the negative electrode active substrate expands (or contracts), the structural unit of Formula 1-a can act as a buffer by compressing (or stretching) its own volume, thereby reducing the stress generated during the expansion (or contraction) of the negative electrode active substrate. Thus, on the one hand, this makes the negative electrode active substrate less prone to breakage; on the other hand, it reduces the force exerted by the negative electrode active substrate on the SEI film during expansion (or contraction), making the SEI film less likely to break.

[0092] The structural unit of Formula 1-b has π-π bonds and has a certain rigidity. Furthermore, the hydrogen bonds and π-π stacking in the system form a supramolecular non-covalent synergistic effect, which improves the stability of the coating layer formed by the polymer. This improves the mechanical strength of the negative electrode active material, making it easier to maintain structural integrity during the expansion (or contraction) of the negative electrode active substrate.

[0093] The disulfide bond in the structural unit of Formula 1-c is a reversible dynamic chemical bond. During the dynamic process of expansion and contraction of the negative electrode active substrate, if the volume change is too large, the disulfide bond in the polymer can break; when the volume of the negative electrode active substrate gradually recovers, the disulfide bond can automatically re-bond. Therefore, even if the negative electrode active substrate undergoes excessive expansion in certain situations, it will not damage the polymer coating layer on its surface. This coating layer can still provide a buffer and suppress the expansion and contraction of the negative electrode active substrate in subsequent cycles, thereby helping to improve the cycle capacity retention rate of the battery.

[0094] By leveraging the combined effects of the structural units in Formulas 1-a, 1-b, and 1-c, the negative effects of expansion and contraction of the negative electrode active substrate are significantly reduced, thereby improving the capacity retention rate of the battery during cycling.

[0095] As mentioned in this article, C1 to C6 alkylene refers to alkylene with 1 to 6 carbon atoms, such as -CH2-, -(CH2)2-, -(CH2)3-, -CH2-CH(CH2)-, -(CH2)4-, -CH2-CH(CH2)-CH2-, -(CH2)2-CH(CH2)-, -(CH2)5-, -CH2-C(CH2)2-CH2-, -(CH2)6-, -(CH2)3-CH(CH2)-CH2-, -(CH2)2-C(CH2)2-CH2-, etc.

[0096] As used herein, substitution refers to the replacement of a hydrogen atom with another atom or group of atoms. In the embodiments of this application, the structural unit of Formula 1-a is mainly used to provide a buffer space, the structural unit of Formula 1-b increases mechanical strength and stability, and the structural unit of Formula 1-c provides dynamic breaking and bonding functions. Therefore, there are no particular requirements or limitations on the substituents; for example, they can be selected from halogens, C1-C6 alkyl groups, etc.

[0097] In some embodiments, the average molecular weight of the structural unit shown in formula (1-a) is 600 to 5000; for example, it can be about 600, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, etc.

[0098] In some embodiments, the ratio of the structural units of Formula 1-a, Formula 1-b, and Formula 1-c in the polymer is 1:1 to 3:1 to 2; for example, the ratio can be 1:1:1, 1:1:2, 1:2:1, 1:2:2, 1:3:1, 1:3:2, etc.

[0099] The structural unit of Formula 1-b mainly provides a certain degree of rigidity and participates in the formation of supramolecular non-covalent synergistic effects. When it has the above-mentioned proportion, it can provide good mechanical strength for the polymer coating layer without negatively affecting ionic conductivity. When the structural unit of Formula 1-c has the above-mentioned proportion, it further facilitates the reconnection of disulfide bonds after breakage, allowing the polymer coating layer to quickly recover to a more complete structure.

[0100] In some embodiments, the structural unit represented by Formula 1-a is chemically bonded to the negative electrode active substrate. For example, the structural unit represented by Formula 1-a can be directly bonded to the negative electrode active substrate; or, the structural unit represented by Formula 1-a can be connected to the negative electrode active substrate via a linking group. In some embodiments, the linking group can be selected from ester bonds, amide bonds, urethane bonds, etc. For example, the surface of the negative electrode active substrate can be aminated first, and then the structural unit represented by Formula 1-a can be connected via an amide bond.

[0101] When the negative electrode active substrate and the chain polyether structure in the polymer are chemically bonded, the connection between the two is tighter, and the coating layer formed by the polymer has a stronger inhibitory effect on the expansion of the negative electrode active substrate.

[0102] In some embodiments, the structural unit shown in equation (1-a) includes structural units selected from the group consisting of:

[0103]

[0104]

[0105] The average molecular weight of the structural unit shown in formula (1-a) is 1000 to 3000.

[0106] In some embodiments, the structural unit shown in equation (1-b) includes structural units selected from the group consisting of:

[0107]

[0108] In some embodiments, the structural unit shown in formula (1-c) includes structural units selected from the group consisting of:

[0109]

[0110] In some embodiments, the connection between the structural units of Formula 1-a, Formula 1-b, and Formula 1-c includes direct bonding or connection through the following linking groups: ester bond, amide bond, and carbamate bond.

[0111] The above-mentioned connection methods exhibit good stability in the battery anode system and do not affect the polymer's role in buffering and inhibiting the expansion of the anode active substrate. When ester bonds, amide bonds, or urethane bonds are used, they also have the advantage of being easy to prepare.

[0112] In some embodiments, the polymer has a structural formula comprising at least one selected from the group consisting of:

[0113] (Equation 1-a)-L1-(Equation 1-c)-L2-(Equation 1-b);

[0114] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b);

[0115] (Equation 1-a)-L1-(Equation 1-c)-L2-(Equation 1-b)-L3-(Equation 1-c)-L4-(Equation 1-b);

[0116] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b)-L4-(Equation 1-c);

[0117] (Equation 1-a)-L1-(Equation 1-b)-L2-(Equation 1-c)-L3-(Equation 1-b)-L4-(Equation 1-c)-L5-(Equation 1-b);

[0118] Wherein, L1, L2, L3, L4, and L5 are each independently selected from direct bonding or linking groups. In some embodiments, the linking group may be selected from ester bonds, amide bonds, carbamate bonds, etc.

[0119] In some embodiments, the polymer has the following structural formula:

[0120]

[0121] In this context, * indicates direct connection to the negative electrode active substrate, or connection via a linking group.

[0122] In some embodiments, the polymer has the following structural formula:

[0123]

[0124] In this context, * indicates direct connection to the negative electrode active substrate, or connection via a linking group.

[0125] In some embodiments, the negative electrode active material satisfies at least one of the following conditions (i) to (iii):

[0126] (i) The polymer accounts for 5 wt% to 15 wt% of the mass of the negative electrode active material;

[0127] (ii) The coating layer is composed of the polymer;

[0128] (iii) The thickness of the coating layer is 5 nm to 20 nm.

[0129] When the negative electrode active material meets at least one of the above conditions, the proportion of polymer and / or coating layer in the negative electrode active material is more reasonable. This can better suppress the expansion effect of the negative electrode active substrate without affecting the ion transport performance, thereby further improving the battery performance.

[0130] In some embodiments, the negative electrode active substrate includes at least one of a carbon substrate and a silicon substrate. In some embodiments, the carbon substrate may be selected from, for example, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, etc.; the silicon substrate may be selected from, for example, silicon, silicon-oxygen materials, silicon-carbon materials (i.e., silicon-carbon composites), etc. Furthermore, the negative electrode active substrate may also include other negative electrode active materials known in the art for use in secondary batteries (e.g., lithium-ion batteries), such as Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 Li-Al alloys, etc.

[0131] When carbon-based and / or silicon-based substrates undergo the aforementioned coating modifications, they can both suppress expansion and improve battery cycle capacity retention. This is especially true for silicon-based substrates, where expansion is more severe; therefore, the coating modifications have a more significant effect on improving the performance of batteries using silicon-based anode active materials.

[0132] In some embodiments, the negative electrode active substrate comprises a silicon-oxygen material, wherein the silicon-oxygen material satisfies at least one of the following:

[0133] In the aforementioned silicon-oxygen material, the mass percentage of silicon element is 10% to 50%.

[0134] The particle size Dv50 of the silicon-oxygen material is 3-15 μm;

[0135] The BET specific surface area of ​​the silicon-oxygen material is 0.2–8 m². 2 / g;

[0136] The compaction density (TD) of the silicon-oxygen material is 0.8–1.2 g / cm³. 3 .

[0137] In some embodiments, the negative electrode active substrate comprises a silicon-carbon material, wherein the silicon-carbon material satisfies at least one of the following:

[0138] In the silicon-carbon material, the mass percentage of silicon is 50% to 80%.

[0139] The particle size Dv50 of the silicon carbide material is 3–20 μm;

[0140] The BET specific surface area of ​​the silicon-carbon material is 0.5–5 m². 2 / g;

[0141] The compaction density (TD) of the silicon-carbon material is 1.5–2.0 g / cm³. 3 .

[0142] When silicon-oxygen materials and / or silicon-carbon materials meet at least one of the above conditions, the improvement in the effect of inhibiting expansion after modification with the above-mentioned coating layer is more significant. For example, the higher the silicon content in the substrate, the stronger its expansion effect. When the silicon content is moderate, the coating layer plays a better role in inhibiting its expansion. The particle size and specific surface area of ​​the substrate affect the force of the coating layer on a unit mass of substrate. Generally speaking, the smaller the particle size or the larger the specific surface area, the greater the force of the coating layer on a unit mass of substrate. When the above-mentioned appropriate range values ​​are adopted, the force of the coating layer on the substrate is more reasonable, which is conducive to better inhibiting its expansion.

[0143] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0144] In some embodiments, the negative electrode material layer may optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting of: styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0145] In some embodiments, the negative electrode material layer may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0146] In some embodiments, the negative electrode material layer may also optionally include other additives. For example, other additives may be thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0147] In some embodiments, the negative electrode active material can be prepared by: providing a negative electrode active substrate, providing a polymer, and coating the polymer onto at least a portion of the surface of the negative electrode active substrate; or,

[0148] A negative electrode active substrate is provided, and monomers corresponding to the structural units of the polymer are provided, so that the monomers are polymerized in situ on the surface of the negative electrode active substrate to form a coating layer.

[0149] In some embodiments, a negative electrode active substrate is provided, and its surface is modified by amylation. A first structural unit with carboxyl groups at both ends is added, and the first structural unit is connected to the surface of the negative electrode active substrate through a condensation reaction. Then, a second structural unit with amino groups at both ends is provided and subjected to a condensation reaction to connect it to the first structural unit. Then, a third structural unit with carboxyl groups at both ends is provided and subjected to a condensation reaction to connect it to the second structural unit. The first, second, and third structural units are each independently selected from the structural units shown in Formula 1-a, Formula 1-b, and Formula 1-c, and the three are not the same. Optionally, in some embodiments, other steps are included after the above steps to connect more structural units. The specific method can refer to the above description, that is, providing groups with both ends suitable for condensation reactions with end groups in the polymer, and connecting them to the main chain of the polymer through a condensation reaction.

[0150] In some embodiments, the method for surface amination modification of the negative electrode active substrate includes: surface amination modification of the silicon substrate using an aminosilane coupling agent. For example, a solution containing an aminosilane coupling agent (e.g., silane coupling agent KH550) is provided, and silicon substrate powder is added to it for reaction. In some embodiments, the solvent of the solution is a mixture of water and an alcohol (e.g., methanol, ethanol, isopropanol, etc.), and the volume ratio of the aminosilane coupling agent, alcohol, and water can be approximately 10–30:70–80:5–10. The mass-volume percentage of the silicon substrate and the solution containing the aminosilane coupling agent can be, for example, 40%, 50%, 60%, 70%, etc.

[0151] In some embodiments, the polymer with the structural formula 2-1 is used as an example for illustration.

[0152]

[0153] S1. Provide a negative electrode active substrate and modify its surface with amination to obtain a negative electrode active substrate with surface amination modification;

[0154] S2. Dissolve polyethylene glycol diacetate (average molecular weight 600-5000) in an organic solvent, mix it with the surface-aminated modified negative electrode active substrate, stir and disperse until the reaction is complete, and obtain a flexible layer-coated modified negative electrode active substrate.

[0155] S3. Add benzidine to the system prepared in S2, stir and disperse until the reaction is complete, then add 2-carboxyethyl disulfide, stir and disperse until the reaction is complete, then add benzidine again, stir and disperse until the reaction is complete, then centrifuge and dry to obtain the negative electrode active material.

[0156] In some embodiments, the negative electrode sheet can be prepared by dispersing the components of the above-mentioned negative electrode material layer, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0157] [Positive electrode plate]

[0158] In some embodiments, the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector; the positive electrode material layer contains a positive electrode active material.

[0159] In some embodiments, the positive current collector may be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals may be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0160] In some embodiments, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0161] In some embodiments, the positive electrode material layer may optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting of: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0162] In some embodiments, the positive electrode material layer may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned positive electrode active material, as well as optional conductive agents, binders and any other components in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0164] [Electrolytes]

[0165] In some embodiments, the battery cell further includes an electrolyte; the electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0166] Liquid electrolytes include electrolyte salts and solvents.

[0167] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0168] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0169] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0170] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0171] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0172] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0173] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0174] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0175] [Isolation Component]

[0176] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0177] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0178] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0179] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0180] [Structure of the electrode assembly]

[0181] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0182] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0183] In some implementations, the electrode assembly is a stacked structure.

[0184] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0185] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0186] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0187] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0188] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0189] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0190] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0191] [shell]

[0192] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0193] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations. For example, Figure 1 shows a prismatic battery cell 5 as an example.

[0194] In some embodiments, referring to FIG2, the housing includes an end cap 53 and a housing 51. The housing 51 has an opening, and the end cap 53 covers the opening. The housing 51 may have one or more openings. The end cap 53 may also be provided one or more times. The positive electrode, the negative electrode, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within a receiving cavity formed by the housing 51 and the end cap 53. The electrolyte is immersed in the electrode assembly 52.

[0195] [Electrode terminals]

[0196] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0197] [Pressure relief mechanism]

[0198] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0199] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0200] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0201] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0202] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0203] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0204] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0205] Battery device

[0206] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0207] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0208] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties. Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other arbitrary way.

[0209] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0210] As an example, the battery cell assembly can be a battery module, which can be housed within a housing by fixing the battery module within the housing. Figures 4 and 5 show an example battery pack 1. Referring to Figures 4 and 5, the battery pack 1 can include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery housing.

[0211] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0212] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0213] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0214] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0215] Electrical appliances

[0216] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft. Figure 6 shows an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0217] Example 1

[0218] This embodiment provides a lithium-ion battery cell, the preparation method of which is as follows, and the relevant parameters and test results are shown in Table 1:

[0219] (1) Positive electrode plate

[0220] Lithium nickel cobalt manganese oxide (LiNi) will be used as the positive electrode active material. 0.9 Co 0.05 Mn 0.05O2), conductive carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder are dispersed in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 90:4:6. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil, followed by drying, rolling, and slitting to obtain the positive electrode sheet.

[0221] (2) Negative electrode plate

[0222] Modified anode active materials were prepared according to the following method:

[0223] S1. Aminoation modification of silicon-based material surface: Prepare a solution by mixing 20 ml of silane coupling agent KH550, 72 ml of ethanol, and 8 ml of water. Disperse the solution by stirring at 400 rpm in a three-necked flask. Gradually add 100 g of silicon oxide material powder (the silicon oxide material has a Si content of 20%, Dv50 of 8 μm, and BET of 4 μm) while stirring. 2 / g, TD is 1.0g / cm 3 After heating to 70°C and refluxing for 5 hours, the reaction was completed and then centrifuged and dried to obtain silicon-based material powder with surface amination modification.

[0224] S2. Add 2g of polyethylene glycol diacetate (Mw is 1000) to 100ml of chloroform and stir to dissolve. Then add 100g of the surface-aminated modified silicon-based material powder prepared in step S1 to the above solution and stir to disperse for 2h to obtain a mixed liquid system containing silicon-based material powder coupled with carboxyl-terminated polyethylene glycol.

[0225] S3. Add 2g of benzidine to the mixture obtained in S2, stir and disperse for 3 hours, then add 2g of 2-carboxyethyl disulfide, stir and disperse for 3 hours, then add another 2g of benzidine and stir for 3 hours. After centrifugation and drying, the modified silicon-based anode material is obtained and used as the modified anode active material. The surface of this anode active material has a polymer coating layer with a thickness of 8nm, and the polymer accounts for 10% of the mass of the anode active material.

[0226] The above-mentioned modified negative electrode active material and graphite mixture (the mass ratio of modified negative electrode active material to graphite is 15:85), polyvinylidene fluoride (PVDF) as a binder, and carbon nanotubes (CNT) as a conductive agent are dispersed in deionized water at a mass ratio of 94:2.5:3.5 and mixed evenly to prepare a negative electrode slurry. Then, the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, dried to obtain a negative electrode film, and then rolled and slit to obtain a negative electrode sheet.

[0227] (3) Preparation of electrolyte

[0228] Ethylene carbonate, diethylene carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L.

[0229] (4) Preparation of the isolation membrane: A polyethylene membrane with a 1 μm ceramic layer on each side (base membrane thickness of 9 μm) was used as the isolation membrane.

[0230] (5) Preparation of lithium-ion batteries

[0231] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound up to obtain an electrode assembly. The electrode assembly is placed in a soft-pack aluminum-plastic film, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0232] Perform the following tests:

[0233] 1. Electrode thickness expansion rate test before and after charging

[0234] At 25℃, the lithium-ion battery is charged at a constant current of 0.5C to a voltage of 4.25V, and then charged at a constant voltage until the current is ≤0.02C to obtain a fully charged battery. The fully charged battery is disassembled, and the thickness h2 of its negative electrode sheet is measured and compared with the thickness h1 of the negative electrode sheet after rolling. The expansion rate of the electrode sheet thickness before and after charging is calculated. The expansion rate of the electrode sheet thickness before and after charging is obtained by the following formula: Expansion rate of electrode sheet thickness before and after charging = (h2-h1) / h1×100%.

[0235] 2. Cyclic performance test

[0236] The lithium-ion battery was placed in the electrochemical test channel and charged at a rate of 0.5C and discharged at a rate of 1C. The charge and discharge voltage range was 2.4 to 4.25V. The battery was cycled for 40 times at room temperature (25°C). The capacity value C40 was read and compared with the initial first-cycle capacity C1. The cycle capacity retention rate can be obtained by using the formula: Capacity retention rate = C40 / C1 × 100%.

[0237] Comparative Example 1

[0238] Except for replacing the modified negative electrode active material with the unmodified silicon-based material, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 1.

[0239] Comparative Example 2

[0240] Except for the following differences, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 1.

[0241] Step S3 is skipped; centrifugal drying is performed directly after step S2.

[0242] Comparative Example 3

[0243] Except for the following differences, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 1.

[0244] Step S3: Add 2g of benzidine to the mixture obtained in S2, stir and disperse for 3 hours, and then centrifuge and dry.

[0245] Examples 2-4

[0246] Except for the average molecular weight Mw of polyethylene glycol diacetate, which is shown in Table 1, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 1.

[0247] Table 1

[0248]

[0249]

[0250] Example 5

[0251] Except for the following differences, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 2.

[0252] In S3, after the final addition of benzidine, 2g of 2-carboxyethyl disulfide was added, stirred and dispersed for 3 hours, and then centrifuged and dried.

[0253] Example 6

[0254] Except for the following differences, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 2.

[0255] In S3, the final benzidine is not added.

[0256] Table 2

[0257] Full charge expansion rate % Capacity retention rate after 40 cycles % Example 1: 21.99 3.73 Example 5: 22.39 3.98 Example 6: 23.59 4.01 surface

[0258] Examples 7-8

[0259] The main method was to adjust the amount of each coating monomer to adjust the mass ratio of the polymer in the negative electrode active material, as shown in Table 3. Otherwise, the preparation and testing were carried out in the same manner as in Example 1, and the test results are shown in Table 3.

[0260] Table 3

[0261]

[0262]

[0263] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode, a separator, and a negative electrode. The negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material. The negative electrode active material includes a negative electrode active substrate and a coating layer disposed on at least a portion of the surface of the negative electrode active substrate. The coating layer includes a polymer. The polymer includes structural units shown in formulas (1-a), (1-b), and (1-c). Wherein, R1 is selected from substituted or unsubstituted C1-C6 alkylene groups; the average molecular weight of the structural unit shown in formula (1-a) is 600-5000; A r R2 and R3 are each independently selected from directly bonded, substituted or unsubstituted C1 to C6 alkylene groups.

2. The battery cell as described in claim 1, characterized in that, In the polymer, the ratio of the number of structural units of Formula 1-a, Formula 1-b, and Formula 1-c is 1:1 to 3:1 to 2.

3. The battery cell as described in claim 1 or 2, characterized in that, The structural unit shown in Formula 1-a is connected to the negative electrode active substrate by chemical bonds.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The structural unit shown in equation (1-a) includes structural units selected from the following group: Wherein, the average molecular weight of the structural unit shown in formula (1-a) is 1000 to 3000; and / or, the structural unit shown in formula (1-b) includes structural units selected from the following group: And / or, the structural unit shown in equation (1-c) includes structural units selected from the following group:

5. The battery cell according to any one of claims 1 to 4, characterized in that, The connection between the structural units of Formula 1-a, Formula 1-b, and Formula 1-c includes direct bonding or connection through the following linking groups: ester bond, amide bond, and carbamate bond.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The polymer's structural formula includes at least one selected from the group consisting of: (Formula 1-a)-L1-(Formula 1-c)-L2-(Formula 1-b); (Formula 1-a)-L1-(Formula 1-b)-L2-(Formula 1-c)-L3-(Formula 1-b); (Formula 1-a)-L1-(Formula 1-c)-L2-(Formula 1-b)-L3-(Formula 1-c)-L4-(Formula 1-b); (Formula 1-a)-L1-(Formula 1-c)-L2-(Formula 1-b)-L3-(Formula 1-c)-L4-(Formula 1-b); (Formula 1-b)-L2-(Formula 1-c)-L3-(Formula 1-c)-L4-(Formula 1-b); (Formula 1-b)-L2-(Formula 1-c)-L2-(Formula 1-b)-L3-(Formula 1-c)-L4-(Formula 1-b); (Formula 1-b)-L2-(Formula 1-c)-L2-(Formula 1-b)-L2-(Formula 1-c ...)-L -a)-L1-(Formula 1-b)-L2-(Formula 1-c)-L3-(Formula 1-b)-L4-(Formula 1-c); (Formula 1-a)-L1-(Formula 1-b)-L2-(Formula 1-c)-L3-(Formula 1-b)-L4-(Formula 1-c)-L5-(Formula 1-b); wherein, L1, L2, L3, L4, and L5 are each independently selected from directly bonded or linking groups.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The negative electrode active material satisfies at least one of the following conditions (i) to (iii): (i) the polymer accounts for 5 wt% to 15 wt% of the mass of the negative electrode active material; (ii) the coating layer is composed of the polymer; (iii) the thickness of the coating layer is 5 nm to 20 nm.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The negative electrode active substrate includes at least one of carbon substrate and silicon substrate.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The negative electrode active substrate includes a silicon substrate, which includes silicon-oxygen materials and / or silicon-carbon materials.

10. The battery cell as described in claim 9, characterized in that, The silicon-oxygen material satisfies at least one of the following: the mass percentage of silicon in the silicon-oxygen material is 10% to 50%; the particle size Dv50 of the silicon-oxygen material is 3 to 15 μm; the BET specific surface area of ​​the silicon-oxygen material is 0.2 to 8 m². 2 / g; the compaction density TD of the silicon-oxygen material is 0.8–1.2 g / cm³. 3 .

11. The battery cell as described in claim 9 or 10, characterized in that, The silicon-carbon material satisfies at least one of the following: the mass percentage of silicon in the silicon-carbon material is 50% to 80%; the particle size Dv50 of the silicon-carbon material is 3 to 20 μm; the BET specific surface area of ​​the silicon-carbon material is 0.5 to 5 m². 2 / g; the compaction density TD of the silicon-carbon material is 1.5~2.0g / cm³. 3 .

12. A battery device, characterized in that, Includes the battery cell according to any one of claims 1 to 11.

13. An electrical appliance, characterized in that, It includes the battery cell according to any one of claims 1 to 11, or the battery device according to claim 12.

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