Negative pole piece, battery, energy storage device and electric equipment

Abstract

The invention provides a negative electrode piece, a battery, an energy storage device and electric equipment, the negative electrode piece comprises a negative electrode current collector, at least one surface of the negative electrode current collector is provided with a negative electrode material layer, and the negative electrode material layer comprises a negative electrode material and a negative electrode binder; the negative electrode binder comprises modified styrene-butadiene rubber particles formed by a styrene-butadiene rubber main chain, long-chain unsaturated fatty acid with the carbon chain length of C14-C24 and an anhydride compound; the average particle size of the modified styrene butadiene rubber particles is D50, and D50 is larger than or equal to 190 nm and smaller than or equal to 210 nm.

Description

Technical Field

[0001] This application relates to the technical field of energy storage, and particularly to a negative electrode plate, a battery, an energy storage device, and an electrical device. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have advantages such as high energy density, low self-discharge, and light weight, and are thus widely used in fields such as energy storage devices.

[0003] The negative electrode plate is one of the main structures of a secondary battery. The negative electrode binder therein, on the one hand, binds the negative electrode materials together, and on the other hand, binds the negative electrode material layer to the negative electrode current collector, which is crucial for the performance of the negative electrode plate and even the secondary battery. Summary of the Invention

[0004] In order to solve the above technical problems, this application discloses a negative electrode plate, a battery, an energy storage device, and an electrical device to improve the binding performance of the negative electrode binder, thereby improving the rate performance of the battery and reducing the DC impedance of the battery.

[0005] In a first aspect, this application provides a negative electrode plate, including a negative electrode current collector, at least one side of the negative electrode current collector having a negative electrode material layer, the negative electrode material layer including a negative electrode material and a negative electrode binder, wherein the negative electrode binder includes modified styrene-butadiene rubber particles formed by a styrene-butadiene rubber main chain, a long-chain unsaturated fatty acid with a carbon chain length of C 14 ~C 24 and an acid anhydride compound; the average particle size of the modified styrene-butadiene rubber particles is D50, and 190 nm ≤ D50 ≤ 210 nm.

[0006] In some embodiments of this application, 195 nm ≤ D50 ≤ 205 nm.

[0007] In some embodiments of this application, the modified styrene-butadiene rubber particles have unsaturated double bonds and styrene units, and the molar ratio of the unsaturated double bonds to the styrene units is 1∶(1.2~1.8).

[0008] In some embodiments of this application, it includes at least one of the following features: a) The long-chain unsaturated fatty acid includes at least one of linoleic acid, oleic acid, and linolenic acid; b) The acid anhydride compound includes at least one of maleic anhydride, phthalic anhydride, and trimellitic anhydride.

[0009] In a second aspect, this application provides a preparation method of the negative electrode plate as described in the first aspect, including the following steps: Styrene monomer, butadiene monomer, a first dispersant and a first initiator are added to water, and a seed emulsion containing a styrene-butadiene rubber main chain is formed by reaction; A long-chain unsaturated fatty acid with a carbon chain length of C 14 ~C 24 , an acid anhydride compound, a second dispersant and a second initiator are mixed with the seed emulsion, and modified styrene-butadiene rubber particles are obtained after modification. The stirring speed during the modification process is 400 rpm to 600 rpm, and the reaction temperature is 45 °C to 75 °C; A negative electrode material, a conductive agent, the modified styrene-butadiene rubber particles and a solvent are mixed to form a negative electrode paste, and the negative electrode paste is coated on at least one surface of a negative electrode current collector to form a negative electrode material layer.

[0010] In some embodiments of the present application, based on the content of the styrene-butadiene rubber main chain, the addition amount of the long-chain unsaturated fatty acid is a, 2% ≤ a ≤ 5%, and the addition amount of the acid anhydride compound is b, 0.5% ≤ b ≤ 1.5%.

[0011] In some embodiments of the present application, 3% ≤ a ≤ 4%, and 1% ≤ b ≤ 1.5%.

[0012] In some embodiments of the present application, it includes at least one of the following features: a), the first dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether, and the first initiator includes ammonium persulfate; b), the second dispersant includes nonylphenol polyoxyethylene ether, and the second initiator includes azobisisobutyronitrile.

[0013] In a third aspect, the present application provides a battery, including the negative electrode tab of the first aspect, or including the negative electrode tab prepared by the preparation method of the second aspect.

[0014] In a fourth aspect, the present application provides an energy storage device, including a box body and at least one battery of the third aspect, and the battery is housed in the box body.

[0015] In a fifth aspect, the present application provides an electrical equipment, including the energy storage device of the fourth aspect, and the energy storage device supplies power to the electrical equipment.

[0016] Compared with the prior art, the present application has at least the following beneficial effects: A negative electrode tab, a battery, an energy storage device and an electrical equipment provided by the present application, wherein the negative electrode material layer includes a negative electrode material and a negative electrode binder, the negative electrode binder includes modified styrene-butadiene rubber particles, and the modified styrene-butadiene rubber particles include a styrene-butadiene rubber main chain and a carbon chain length of C 14 ~C24 Modified styrene-butadiene rubber particles formed by long-chain unsaturated fatty acids and acid anhydride compounds, and the average particle size range of the modified styrene-butadiene rubber particles is 190nm ≤ D50 ≤ 210nm. The negative electrode tab of the present application contains the above-mentioned negative electrode binder, which can reduce the occurrence of the problem of negative electrode material peeling during the charge and discharge process of the battery, improve the rate performance of the battery and reduce the DC impedance of the battery, thereby improving the stability and service life of the battery, and being beneficial to improving the operation stability and service life of the energy storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic structural diagram of a household energy storage system according to an implementation scheme of the present application; Figure 2 It is a schematic structural diagram of a commercial energy storage system according to an implementation scheme of the present application.

[0019] Description of reference numerals: 1 - energy storage device, 2 - power conversion device, 3 - first user load, 4 - second user load, 400 - commercial energy storage system, 410 - high-voltage cable, 420 - first power conversion device, 430 - second power conversion device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0021] In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation.

[0022] Moreover, in addition to being used to indicate orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0023] In addition, the terms "mounted", "arranged", "provided with", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can be internal communication between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, components, or parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components, or parts. Unless otherwise specified, the meaning of "a plurality of" is two or more.

[0025] It should be noted that in the content of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application, but the secondary battery of this application is not limited to lithium-ion batteries.

[0026] This application provides a negative electrode tab, which includes a negative electrode current collector, at least one surface of the negative electrode current collector has a negative electrode material layer, and the negative electrode material layer includes a negative electrode material and a negative electrode binder. Among them, the negative electrode binder includes a styrene-butadiene rubber main chain, and the carbon chain length is C 14 ~C 24Modified styrene-butadiene rubber particles formed from long-chain unsaturated fatty acids and acid anhydride compounds, wherein the average particle size of the modified styrene-butadiene rubber particles is D50, and 190 nm ≤ D50 ≤ 210 nm; in another alternative embodiment, 195 nm ≤ D50 ≤ 205 nm. For example, D50 is 190 nm, 195 nm, 200 nm, 205 nm or 210 nm. When D50 is too large (e.g., greater than 210 nm), the coverage area of the negative electrode binder on the surface of the negative electrode material particles decreases, and the physical adsorption sites are insufficient, resulting in a decrease in the bonding performance of the negative electrode binder. Furthermore, the negative electrode material in the negative electrode material layer is prone to peeling during charge and discharge, causing an increase in the internal resistance of the lithium-ion battery and an accelerated capacity decay; when D50 is too small (e.g., less than 190 nm), although the coverage area of the negative electrode binder on the surface of the negative electrode material particles increases, too small a particle size more easily leads to poor dispersibility of the negative electrode binder in the negative electrode slurry and is more likely to form agglomerates, resulting in uneven distribution of the negative electrode binder in the negative electrode material layer and prone to problems such as insufficient local bonding force of the negative electrode plate, causing instability in the performance of the lithium-ion battery.

[0027] The negative electrode plate of the present application contains the above-mentioned negative electrode binder, which can reduce the occurrence of the problem of negative electrode material peeling during the charge and discharge process of the lithium-ion battery, improve the rate performance of the lithium-ion battery and reduce the DC impedance of the lithium-ion battery, thereby improving the stability and service life of the lithium-ion battery, and is beneficial to improving the operation stability and service life of the energy storage device. This may be because the modified styrene-butadiene rubber particles with the above particle size range can increase the coverage area of the negative electrode binder per unit mass on the surface of the negative electrode material particles, that is, increase the contact area between the negative electrode binder and the negative electrode material, providing more physical adsorption sites for the negative electrode binder; when the carbon chain length is too short, the flexibility of the unsaturated fatty acid decreases; when the carbon chain length is too long, the intermolecular force of the unsaturated fatty acid increases, which may lead to entanglement and aggregation of the molecular chains, reducing the dispersibility of the unsaturated fatty acid on the surface of the negative electrode material, thereby reducing the effective adsorption sites; and, too long a carbon chain may increase the viscosity of the negative electrode binder, affecting the coating uniformity of the negative electrode slurry, and further having an adverse impact on the rate performance and cycle stability of the lithium-ion battery. The carbon chain length selected in the present application is C 14 ~C 24The long-chain unsaturated fatty acids have good flexibility and can deeply wind between the layers of the negative electrode material (such as graphite layers), adapting to the volume change of the negative electrode material during charge and discharge, making the negative electrode material less likely to expand and deform; moreover, the unsaturated double bonds in the long-chain unsaturated fatty acids can chemically react with the edge active sites of the particles of the negative electrode material (such as graphite) to form a stable connection; furthermore, the strong polar functional groups of the acid anhydride compounds can form hydrogen bonds with the oxygen-containing functional groups on the surface of the particles of the negative electrode material (such as graphite) and generate dipole-dipole interactions, further enhancing the anchoring effect of the negative electrode binder at the chemical level; in addition, the modified styrene-butadiene rubber particles with the above particle size range can also make the long-chain unsaturated fatty acids and acid anhydride compounds more evenly distributed on the surface of the negative electrode material, forming a dense bonding network structure; and the moderate particle size of the modified styrene-butadiene rubber particles can provide more physical adsorption sites, further enhancing the interaction between the long-chain unsaturated fatty acids and acid anhydride compounds and the negative electrode material, thereby jointly enhancing the anchoring effect of the negative electrode binder at the physical and chemical levels. Under the combined action of the above physical and chemical factors, a bonding network with high bonding strength is constructed in the negative electrode material layer, thereby reducing the occurrence of the problem of negative electrode material peeling during the charge and discharge process of the lithium-ion battery, improving the rate performance of the lithium-ion battery and reducing the DC impedance of the lithium-ion battery, and further improving the stability and service life of the lithium-ion battery, which is beneficial to improving the operation stability and service life of the energy storage device.

[0028] In this application, D50 represents the particle size at which, in the particle size distribution based on volume, starting from the small particle size side, the cumulative volume reaches 50%.

[0029] In some embodiments of this application, the modified styrene-butadiene rubber particles have unsaturated double bonds and styrene units, and the molar ratio of the unsaturated double bonds to the styrene units is 1∶(1.2~1.8). In this way, a good synergistic effect can be achieved between the unsaturated double bonds and the styrene units, enabling the modified styrene-butadiene rubber particles to have sufficient flexibility to adapt to the volume change of the negative electrode material during charge and discharge cycles and having appropriate rigidity to maintain the structural stability of the electrode; moreover, the presence of the unsaturated double bonds can chemically react with the edge active sites of the graphite particles to form a stable connection, while the styrene units enhance the mechanical strength of the negative electrode binder through their rigid structure, thereby improving the bonding performance and cycle stability of the negative electrode sheet as a whole. The above unsaturated double bonds are derived from long-chain unsaturated fatty acids.

[0030] In some embodiments of this application, the long-chain unsaturated fatty acids include at least one of linoleic acid, oleic acid, and linolenic acid.

[0031] In some embodiments of this application, the acid anhydride compounds include at least one of maleic anhydride, phthalic anhydride, and trimellitic anhydride.

[0032] In a second aspect, the present application provides a method for preparing a negative electrode sheet as described in any of the above embodiments, comprising the following steps: Step A, preparation of seed emulsion: Styrene monomer, butadiene monomer, a first dispersant and a first initiator are added to water to react to form a seed emulsion containing a styrene-butadiene rubber backbone; Step B, modification of styrene-butadiene rubber: A long-chain unsaturated fatty acid with a carbon chain length of C 14 ~C 24 , an acid anhydride compound, a second dispersant and a second initiator are mixed with the seed emulsion, and after modification, modified styrene-butadiene rubber particles are obtained. The stirring speed during the modification process is 400 rpm to 600 rpm, and the reaction temperature is 45°C to 75°C; Step C, preparation of negative electrode sheet: A negative electrode material, a conductive agent, modified styrene-butadiene rubber particles and a solvent are mixed to form a negative electrode slurry, and the negative electrode slurry is coated on at least one surface of a negative electrode current collector to form a negative electrode material layer.

[0033] Exemplarily, step A specifically includes the following steps: Add deionized water accounting for 50% to 70% of the total mass of the reaction system to the reaction kettle, and then weigh the first dispersant according to 2% to 4% of the total mass of the styrene monomer and the butadiene monomer; start stirring, adjust the rotation speed to 350 rpm to 450 rpm, slowly heat the reaction kettle to 48°C to 52°C, and after the temperature is stable, add the weighed first dispersant and stir until the solution is clear and transparent; slowly add the styrene-butadiene mixed monomer solution containing the first initiator to the reaction kettle through a constant pressure dropping funnel at a speed of 1.0 mL / min to 2.0 mL / min. During the dropping process, fine-tune the temperature to 50°C to 55°C in real time; after the monomer dropping is completed, increase the stirring speed to 550 rpm to 650 rpm and quickly heat to 63°C to 67°C to cause the styrene monomer and the butadiene monomer to undergo a polymerization reaction to form a styrene-butadiene rubber backbone, obtaining a seed emulsion.

[0034] In step A, an on-line laser particle size analyzer can be used to monitor the change in the chain length of the generated styrene-butadiene rubber backbone, record the chain length data every 15 minutes, and determine the content of the styrene-butadiene rubber backbone in the seed emulsion by an infrared spectrometer.

[0035] In the above styrene-butadiene mixed monomer solution, the molar ratio of the styrene monomer to the butadiene monomer is 1:1, and the concentration of the first initiator is 0.1% to 0.3% of the total mass of the styrene monomer and the butadiene monomer.

[0036] Exemplarily, step B specifically includes the following steps: Slowly cool the seed emulsion prepared in step A to 43°C - 47°C, then weigh a certain amount of the seed emulsion and add it to a flask; weigh the second dispersant according to 1% - 2% of the total mass of the reaction system, and weigh the second initiator according to 0.3% - 0.5% of the total mass of the reaction system in the flask; add the weighed second dispersant to the flask and stir at a speed of 350 rpm - 450 rpm for 10 min - 15 min to uniformly disperse the emulsion in the flask; then weigh C 14 ~C 24 of long-chain unsaturated fatty acids and acid anhydride compounds; dissolve the weighed long-chain unsaturated fatty acids and acid anhydride compounds in anhydrous ethanol to obtain a mixed solution, then add the weighed second initiator to the mixed solution, fully stir and dissolve it, pour it into a constant pressure dropping funnel, and slowly drop it into the above-mentioned flask. The dropping time is 1.3 h - 1.8 h, and continuous stirring is carried out during the dropping process at a stirring speed of 450 rpm - 550 rpm, and the flask is covered with a light-shielding cloth throughout the process; after the dropping is completed, remove the light-shielding cloth, raise the reaction temperature to 73°C - 77°C, adjust the stirring speed to 580 rpm - 620 rpm, and carry out the graft modification reaction for 4 h - 7 h to obtain modified styrene-butadiene rubber particles.

[0037] In step B, during the reaction, a small amount of emulsion can be sampled every 30 min with a sampling needle, and the change of characteristic absorption peaks can be detected by an infrared spectrometer to judge the progress of the graft modification reaction; in addition, after the synthesis reaction of the modified styrene-butadiene rubber particles is completed, the polymerization reaction can be terminated by adding a terminator, and then the purified modified styrene-butadiene rubber particles can be obtained through a purification process. The above-mentioned terminator includes but is not limited to alcohol, phenol or amine compounds, for example, isopropyl alcohol or hydroquinone, etc. Exemplarily, the purification process includes: separating the unreacted monomers from the reaction mixture through vacuum distillation or flash distillation process to obtain the purified modified styrene-butadiene rubber particles.

[0038] When preparing the negative electrode plate, it may also include processes such as cold pressing, slitting, cutting, and welding the tab, which are not particularly limited in this application as long as the negative electrode plate can be obtained.

[0039] In some embodiments of the present application, based on the content of the styrene-butadiene rubber main chain, the addition amount of the long-chain unsaturated fatty acid is a, where 2% ≤ a ≤ 5%, and the addition amount of the acid anhydride compound is b, where 0.5% ≤ b ≤ 1.5%; in another alternative embodiment, 3% ≤ a ≤ 4%, and 1% ≤ b ≤ 1.5%. For example, a is 2%, 3%, 3.5%, 4% or 5%; b is 0.5%, 1%, 1.2% or 1.5%. By regulating a and b within the above ranges, it is beneficial for the long-chain unsaturated fatty acid and the acid anhydride compound to fully react with the styrene-butadiene rubber main chain. On the one hand, the carboxyl groups (-COOH) of the long-chain unsaturated fatty acid and the acid anhydride compound can form hydrogen bonds or van der Waals forces with the graphite surface, enhancing the adhesion between the modified styrene-butadiene rubber particles and the anode material (such as graphite), thereby improving the mechanical strength of the electrode and playing a role in enhancing the adhesion; on the other hand, the hydrophobic chains of the long-chain unsaturated fatty acid and the acid anhydride compound can adsorb on the graphite surface, reducing the surface energy of the graphite particles, thereby inhibiting the floating phenomenon of the binder in the anode slurry and further enhancing the adhesion performance.

[0040] In some embodiments of the present application, the first dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and fatty alcohol polyoxyethylene ether, preferably fatty alcohol polyoxyethylene ether; the first initiator includes ammonium persulfate.

[0041] In some embodiments of the present application, the second dispersant includes nonylphenol polyoxyethylene ether, and the second initiator includes azobisisobutyronitrile.

[0042] The present application has no particular limitation on the method for regulating the average particle size of the modified styrene-butadiene rubber particles, as long as the purpose of the present application can be achieved. During the preparation of the seed emulsion, the chain length of the styrene-butadiene rubber main chain usually decreases with the increase in the stirring speed during the polymerization reaction, or the chain length of the styrene-butadiene rubber main chain usually decreases with the increase in the reaction temperature of the polymerization reaction, and the average particle size of the modified styrene-butadiene rubber particles is usually positively correlated with the chain length of the styrene-butadiene rubber main chain. Based on this, the present application can regulate the average particle size of the modified styrene-butadiene rubber particles by regulating the stirring speed and / or reaction temperature during the polymerization reaction.

[0043] The preparation method of the anode electrode sheet of the present application can increase the coverage area of the anode binder per unit mass on the surface of the anode material by regulating the average particle size of the modified styrene-butadiene rubber particles within the above range, providing more physical adsorption sites for the anode binder; by a carbon chain length of C 14 ~C 24Modifying the main chain of styrene-butadiene rubber with long-chain unsaturated fatty acids and acid anhydride compounds can improve the bonding effect of modified styrene-butadiene rubber particles at the chemical level. Through the combined action of physical and chemical factors, the negative electrode binder therein has a bonding network with high bonding strength. When this negative electrode sheet is applied to a lithium-ion battery, it can reduce the occurrence of the problem of negative electrode material peeling during the charge and discharge process of the lithium-ion battery, improve the rate performance of the lithium-ion battery and reduce the DC impedance of the lithium-ion battery, thereby improving the stability and service life of the lithium-ion battery.

[0044] In this application, the negative electrode material layer can be disposed on one surface or two surfaces in the thickness direction of the negative electrode current collector. In this application, the negative electrode material layer is disposed on the surface of the negative electrode current collector, that is, the negative electrode material layer can be disposed in a partial area of one surface of the negative electrode current collector or in the entire area of one surface of the negative electrode current collector. There is no particular limitation on the negative electrode current collector in this application, as long as the purpose of this application can be achieved. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collector, etc. In this application, there is no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness is 4 μm to 12 μm.

[0045] In this application, the negative electrode material layer includes a negative electrode material. Among them, there is no particular limitation on the negative electrode material, as long as the purpose of this application can be achieved. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, and silicon-carbon.

[0046] This application also provides a battery including the negative electrode sheet described in any of the above embodiments.

[0047] The battery of this application may further include a positive electrode sheet, a separator, and an electrolyte. Among them, the separator is located between the positive electrode sheet and the negative electrode sheet and plays an isolating role.

[0048] There is no particular limitation on the positive electrode sheet in this application, as long as the purpose of this application can be achieved. For example, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode material layer. The positive electrode material layer can be disposed on one surface in the thickness direction of the positive electrode current collector or on two surfaces in the thickness direction of the positive electrode current collector. In this application, the positive electrode material layer is disposed on the surface of the positive electrode current collector, that is, the positive electrode material layer can be disposed in a partial area of one surface of the positive electrode current collector or in the entire area of one surface of the positive electrode current collector. There is no particular limitation on the positive electrode current collector in this application, as long as the purpose of this application can be achieved. For example, it can include, but is not limited to, aluminum foil, aluminum alloy foil, or composite current collector, etc. In this application, there is no particular limitation on the thickness of the positive electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness is 8 μm to 13 μm. The single-sided thickness of the positive electrode material layer of this application can be 100 μm to 200 μm.

[0049] In the present application, the positive electrode material layer includes a positive electrode material. There is no particular limitation on the positive electrode material in the present application, as long as the object of the present application can be achieved. For example, it may include at least one of lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, and lithium manganese iron phosphate.

[0050] In the present application, the positive electrode material layer may further include a positive electrode binder. There is no particular limitation on the positive electrode binder in the present application, as long as the object of the present application can be achieved. For example, it may include at least one of, but not limited to, fluororesin, polypropylene resin, fiber-type binder, rubber-type binder, or polyimide-type binder.

[0051] There is no particular limitation on the separator in the present application, and those skilled in the art can select it according to actual needs, as long as the object of the present application can be achieved. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, film, or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0052] The battery of the present application further includes an electrolyte. There is no particular limitation on the electrolyte in the present application, and those skilled in the art can select it according to actual needs, as long as the object of the present application can be achieved. For example, after mixing at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC), etc. in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, a lithium salt is added and dissolved and mixed evenly. There is no limitation on the type of lithium salt in the present application, as long as the object of the present application can be achieved. For example, the lithium salt may include LiPF 6 、LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiSiF 6, at least one of lithium bis(oxalato)borate (LiBOB) or lithium difluoroborate.

[0053] The present application has no particular limitation on the concentration of the lithium salt in the electrolyte, as long as the object of the present application can be achieved. Taking LiPF 6 as an example, the concentration of LiPF 6 in the electrolyte is 1 mol / L to 2 mol / L. For example, the concentration of LiPF 6 is 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L.

[0054] The battery of the present application further includes a housing, and the present application has no particular limitation on the housing. Those skilled in the art can select according to actual needs as long as the object of the present application can be achieved. For example, the housing may include an aluminum-plastic film.

[0055] The present application has no particular limitation on the preparation method of the battery, and a preparation method well-known in the art can be selected as long as the object of the present application can be achieved. For example, the preparation method of the battery includes but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence, and performing operations such as winding and folding according to needs to obtain a wound bare battery cell, putting the bare battery cell into a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain the battery.

[0056] The present application also provides an energy storage device, including a box body and at least one battery in any of the above embodiments, and the battery is housed in the box body. The energy storage device with this battery has excellent performance, which is beneficial to the use of the energy storage device. By housing the battery in the box body, the fixing and protection of the battery can be increased, and the service life of the energy storage device can be improved. It can be understood that the energy storage device may have one or more batteries. When the energy storage device contains multiple batteries, the multiple batteries can be connected by at least one of parallel connection and series connection.

[0057] The present application also provides an electrical equipment, including the energy storage device in the above embodiment, which is beneficial to improving the product competitiveness and use performance of the electrical equipment. In an optional embodiment, the electrical equipment includes an electrical equipment body, and the energy storage device is used to supply power to the electrical equipment body. In an optional embodiment, the electrical equipment body includes an equipment positive electrode and an equipment negative electrode, and the positive electrode sheet of the battery in the energy storage device is used to electrically connect to the equipment positive electrode of the electrical equipment body, and the negative electrode sheet of the battery in the energy storage device is used to electrically connect to the equipment negative electrode of the electrical equipment body to supply power to the electrical equipment.

[0058] The electrical equipment of the present application may include, but is not limited to: containers, battery cars, electric vehicles, ships, spacecraft, electric toys, electric tools, etc. Among them, spacecraft such as airplanes, rockets, space shuttles, and spaceships, etc., electric toys include, for example, stationary or mobile electric toys, specifically, for example, electric vehicle toys, electric ship toys, and electric airplane toys, etc., and electric tools include, for example, metal cutting electric tools, grinding electric tools, assembly electric tools, and electric tools for railways, specifically, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers.

[0059] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a household energy storage system according to an embodiment of the present application, and the present application Figure 1 takes the household energy storage scenario in user-side energy storage as an example for illustration, and the energy storage device of the present application is not limited to the household energy storage scenario.

[0060] The present application provides a household energy storage system, which includes an electric energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as household appliances like air conditioners), etc., and an energy storage device 1. The energy storage device 1 is a small energy storage box and can be installed on an outdoor wall in a wall-mounted manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during the low electricity price period, and the energy storage device 1 is used to store the electric energy and supply it to the street lamp and household appliances for use during the high electricity price period, or supply power when the power grid is powered off / out of power.

[0061] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of a commercial energy storage system 400 according to an embodiment of the present application, and the present application Figure 2 takes the shared energy storage scenario on the power generation / distribution side as an example for illustration, and the energy storage device 1 of the present application is not limited to its energy storage scenario on the power generation / distribution side.

[0062] The present application provides a commercial energy storage system 400, which includes: a high-voltage cable 410, a first power conversion device 420, a second power conversion device 430, and the energy storage device 1 provided by the present application. In the case of power generation, the first power conversion device 420 and the second power conversion device 430 are used to convert other forms of energy into electric energy, connect to the high-voltage cable 410 and supply it for use on the power consumption side of the distribution network. When the power consumption load is low and the first power conversion device 420 and the second power conversion device 430 generate excessive power, the excess power is stored in the energy storage device 1 to reduce the wind curtailment and light curtailment rates and improve the problem of new energy power generation accommodation. When the power consumption load is high, the power grid issues an instruction to transmit the electric energy stored in the energy storage device 1 in a grid-connected mode in cooperation with the high-voltage cable 410 for use by the power consumption side, providing various services such as peak shaving, frequency modulation, and standby for the operation of the power grid, giving full play to the role of the power grid in peak shaving, promoting the peak shaving and valley filling of the power grid, and alleviating the power supply pressure of the power grid.

[0063] Optionally, the first power conversion device 420 and the second power conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, mechanical energy, etc. into electric energy.

[0064] The number of the energy storage devices 1 can be multiple. The multiple energy storage devices 1 are connected in series or in parallel with each other, and the multiple energy storage devices 1 are supported and electrically connected by a separator (not shown in the figure). In this embodiment, "multiple" means two or more. An energy storage box can also be provided outside the energy storage device 1 for accommodating the energy storage device 1.

[0065] Optionally, the energy storage device 1 can include, but is not limited to, battery modules, battery packs, battery systems, etc. Among them, the battery module can be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack can include multiple batteries of the present application, and the battery system can be a charge and discharge system including the batteries or battery packs of the present application.

[0066] The actual application form of the energy storage device 1 provided by the embodiments of the present application can be, but is not limited to, the listed products, and can also be other application forms. The embodiments of the present application do not strictly limit the application form of the energy storage device 1. The embodiments of the present application are only described by taking the energy storage device 1 as a multi-core battery as an example. When the energy storage device 1 includes single cells, the single cells can be at least one of cylindrical batteries, square batteries, etc.

[0067] Example Hereinafter, preparation examples, examples, and comparative examples are given to more specifically illustrate the implementation manners of the present application. Various tests and evaluations are carried out according to the following methods.

[0068] Example 1 <Preparation of the negative electrode binder> <Preparation of Seed Emulsion> Add deionized water accounting for 60% of the total mass of the reaction system into the reaction kettle. Then weigh the first dispersant sodium dodecylbenzenesulfonate at 3% of the total mass of styrene monomer and butadiene monomer. Start stirring and adjust the rotation speed to 400 rpm. Slowly heat the reaction kettle to 50 °C. After the temperature stabilizes, add the weighed sodium dodecylbenzenesulfonate and stir until the solution is clear and transparent. Slowly add the styrene-butadiene mixed monomer solution containing the first initiator ammonium persulfate into the reaction kettle through a constant pressure dropping funnel at a speed of 1.5 mL / min. During the dropping process, finely adjust the temperature to 50 °C in real time. After the monomer dropping is completed, increase the stirring speed to 600 rpm and quickly heat up to 65 °C to cause the polymerization reaction of styrene monomer and butadiene monomer to generate the main chain of styrene-butadiene rubber, and measure the content of the main chain of styrene-butadiene rubber in the seed emulsion to obtain the seed emulsion.

[0069] <Modification of Styrene-Butadiene Rubber> Slowly cool the prepared seed emulsion to 45 °C, then weigh a certain amount of the seed emulsion and add it to the flask. Then weigh the second dispersant nonylphenol polyoxyethylene ether at 1.5% of the total mass of the reaction system, and weigh the second initiator azobisisobutyronitrile at 0.4% of the total mass of the reaction system in the flask. Add the weighed second dispersant into the flask and stir at a speed of 400 rpm for 15 min to uniformly disperse the emulsion in the flask. Then weigh the long-chain unsaturated fatty acid at 3% of the mass of the main chain of styrene-butadiene rubber in the flask, and weigh the acid anhydride compound at 1% of the mass of the main chain of styrene-butadiene rubber in the flask. Among them, the long-chain unsaturated fatty acid is linoleic acid, and the acid anhydride compound is maleic anhydride. Dissolve the weighed long-chain unsaturated fatty acid and acid anhydride compound in anhydrous ethanol to obtain a mixed solution. Then add the weighed nonylphenol polyoxyethylene ether to the mixed solution, fully stir and dissolve it, pour it into a constant pressure dropping funnel, and slowly add it dropwise to the above flask. The dropping time is 1.5 h. During the dropping process, continuously stir, the stirring speed is 500 rpm, and the flask is covered with a light-shielding cloth throughout the process. After the dropping is completed, remove the light-shielding cloth, raise the reaction temperature to 75 °C, adjust the stirring speed to 600 rpm, and carry out the graft modification reaction. After reacting for 5 h, obtain the modified styrene-butadiene rubber particles.

[0070] <Preparation of Negative Electrode Plate> Mix the negative electrode material artificial graphite, the conductive agent conductive carbon black, and the prepared modified styrene-butadiene rubber particles according to a mass ratio of 80∶10∶10, add deionized water, and formulate it into a negative electrode slurry with a solid content of 60 wt%, and stir evenly. Uniformly coat the negative electrode slurry on one surface of the negative electrode current collector copper foil with a thickness of 10 μm, and the coating thickness is 190 μm. First, vacuum dry it at 80 °C for 12 h, then vacuum dry it at 120 °C for 8 h, and roll it to make the negative electrode plate.

[0071] <Preparation of electrolyte> In an argon atmosphere glove box with a water content ≤ 1 ppm, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:1, and then lithium salt LiPF 6 was added and dissolved in the above solvent. After mixing evenly, an electrolyte was obtained. Among them, LiPF 6 had a molar concentration of 1 mol / L in the electrolyte.

[0072] <Assembly of lithium-ion battery> The prepared negative electrode sheet and lithium sheet were put into a press for pressing. Then, a circular negative electrode sheet with a diameter of 15 mm and a circular lithium sheet with a diameter of 15 mm were cut using a punch. Then, the circular negative electrode sheet, separator, and circular lithium sheet were stacked in sequence, with the separator placed between the circular negative electrode sheet and the circular lithium sheet to play an isolating role. Then, the prepared electrolyte was injected to assemble a lithium-ion battery.

[0073] Examples 2 to 5 Except that in <Preparation of seed emulsion>, by adjusting the stirring speed to control the average particle size of the modified styrene-butadiene rubber particles according to Table 1, the rest was the same as in Example 1.

[0074] Examples 6 to 8 Except that in <Modification of styrene-butadiene rubber>, the addition amount of long-chain unsaturated fatty acids was controlled according to Table 1, the rest was the same as in Example 1.

[0075] Examples 9 to 11 Except that in <Modification of styrene-butadiene rubber>, the addition amount of acid anhydride compounds was controlled according to Table 1, the rest was the same as in Example 1.

[0076] Examples 12 to 15 Except that in <Modification of styrene-butadiene rubber>, the types of long-chain unsaturated fatty acids and acid anhydride compounds were controlled according to Table 2, the rest was the same as in Example 1.

[0077] Comparative Example 1 Except that in <Preparation of negative electrode sheet>, the seed emulsion was directly used as the negative electrode binder, that is, unmodified styrene-butadiene rubber was directly used, the rest was the same as in Example 1.

[0078] Comparative Examples 2 to 3 Except that in <Preparation of negative electrode binder>, by adjusting the stirring speed to control the average particle size of the modified styrene-butadiene rubber particles according to Table 1, the rest was the same as in Example 1.

[0079] Table 1: Preparation parameters of Examples 1 to 11 and Comparative Examples 1 to 3

[0080] In Table 1, " / " indicates that there are no relevant preparation parameters.

[0081] Table 2: Preparation parameters of Example 1, Examples 12 - 15

[0082] Testing methods and equipment: Testing the average particle size of modified styrene - butadiene rubber particles: Prepare a dilute solution sample of modified styrene - butadiene rubber particles (the solvent is deionized water and the concentration is 0.1 wt%). After ultrasonic dispersion, use a laser particle size analyzer to measure the average particle size of the modified styrene - butadiene rubber particles in the sample according to the instrument operation procedure. Each sample is tested 3 times, and then the average value of the 3 test results is taken.

[0083] Testing the molar ratio of unsaturated double bonds to styrene units in the negative electrode binder: Use a spatula of appropriate size to scrape powders from the upper, middle, and lower layers of the cleaned negative electrode plate respectively, and ensure that the scraping force is uniform to avoid damaging the negative electrode plate. Then mix the scraped powders evenly and dry them to remove moisture interference. Subsequently, perform infrared spectroscopy testing to accurately identify the characteristic absorption peaks of the unsaturated double bonds of linoleic acid and the styrene units of SBR. Calculate the peak intensity by the integral area method, subtract the background signal, and finally calculate the molar ratio of unsaturated double bonds to styrene units according to the peak intensity ratio.

[0084] Testing the peel strength of the negative electrode plate: Stick one side of the negative electrode plate of the specimen on the steel plate with double - sided tape, and install the steel plate on the fixed fixture at the lower part of the high - speed rail tensile testing machine. Confirm that the bottom layer of the specimen on the steel plate is firmly bonded to the steel plate. Tear about 1 cm along the interface between the negative electrode plate and the double - sided tape at one end in the length direction of the specimen, and clamp one corner of the torn negative electrode plate on the movable fixture at the upper part of the high - speed rail tensile testing machine. The specimen is ready. Test: Tensile angle 90°, tensile speed 20 mm / min, until the interface between the negative electrode plate and the double - sided tape - bonded specimen is completely opened. After opening, the negative electrode material layer is bonded to the surface of the double - sided tape, and the other side of the opened interface is the negative electrode plate with at least part of the negative electrode current collector exposed. Record the average value of the load force (N) during the stretching process, divide it by the specimen width to obtain the peel strength between the negative electrode material layer and the negative electrode current collector, and then take the average value.

[0085] Testing the rate performance: Step (1): At 45 °C, the prepared lithium-ion battery is left standing for 1 h, and then the following operations are carried out: ① Charge at a rate of 1C to 3.65 V, ② Stand for 10 min, ③ Discharge at a rate of 1C to 2.5 V, ④ Stand for 10 min. Repeat the charge-discharge process of step (1) ①→②→③→④ twice; Step (2): At 25 °C, the lithium-ion battery treated in step (1) is left standing for 1 h, and then the following operations are carried out: ① Charge at a rate of 0.5C to 3.65 V, ② Stand for 10 min, ③ Discharge at a rate of 0.5C to 2.5 V, ④ Stand for 10 min. Repeat the charge-discharge process of step (2) ①→②→③→④ three times, and record the discharge capacity of the third discharge process as the initial discharge capacity, denoted as C 0 , with the unit of Ah; Step (3): At 25 °C, the lithium-ion battery treated in step (2) is left standing for 30 min, and then the following operations are carried out: ① Charge at a rate of 2C to 3.65 V, ② Stand for 10 min, ③ Discharge at a rate of 2C to 2.5 V, ④ Stand for 10 min, and complete the charge-discharge process at a rate of 2C. Record the discharge capacity of the 2C discharge process as the 2C discharge capacity, denoted as C 1 , with the unit of Ah.

[0086] The 2C rate energy efficiency of the lithium-ion battery = (C 1 / C 0 ) × 100%.

[0087] DC resistance (DCR) test: The test temperature is 25 °C. The lithium-ion battery is charged at a constant current of 0.5 rate (C) to 3.65 V, then charged at a constant voltage of 3.65 V until the current is 0.05C, left standing for 30 min, and then cycled 9 times according to the following process: discharge at a constant current of 0.1C for 60 min, stand for 60 min, and record the voltage V 1 after standing for 60 min, and then discharge at a constant current of 1.07C for 30 s, and record the voltage V 2 at the end of the discharge; then stand for 40 s, and then charge at a constant current of 1.07C for 30 s, and stand for 10 min. Take the state of charge (SOC) after the 5th cycle discharge end as the 50% SOC of the lithium-ion battery. Then, according to the V 1 and V 2 recorded in the 5th cycle, calculate the discharge DCR according to the following formula: DCR = (V 1 -V 2 ) / I, where I = 1.07C.

[0088] Table 3: Performance data of each example and comparative example

[0089] It can be seen from Examples 1 to 15 and Comparative Examples 1 to 3 that when only the particle size is regulated without graft modification (such as Comparative Example 1), the peel strength of the negative electrode sheet is low, the rate energy efficiency of the lithium-ion battery is low and the DCR is high; when only graft modification is carried out without regulating the particle size of the modified styrene-butadiene rubber particles (such as Comparative Examples 1 and 2), the peel strength of the negative electrode sheet is also low, the rate energy efficiency of the lithium-ion battery is low and the DCR is high; while the negative electrode sheet of the present application has a higher peel strength, and at the same time the lithium-ion battery shows a higher rate energy efficiency and a lower DCR, indicating that the negative electrode sheet of the present application improves the rate performance of the lithium-ion battery and reduces its DC impedance, thereby improving the stability and service life of the lithium-ion battery.

[0090] The addition amounts of the long-chain unsaturated fatty acid and the acid anhydride compound usually also affect the performance of the negative electrode sheet. It can be seen from Examples 1, 6 to 11 that on the basis of the modified styrene-butadiene rubber particles of the present application, by regulating the above preparation parameters within the scope of the present application, it is beneficial to obtain a negative electrode sheet with high peel strength, and thus it is more beneficial to obtain a lithium-ion battery with good rate performance and low DC impedance.

[0091] The types of the long-chain unsaturated fatty acid and the acid anhydride compound usually also affect the performance of the negative electrode sheet. It can be seen from Examples 1, 12 to 15 that on the basis of the modified styrene-butadiene rubber particles of the present application, by regulating the above preparation parameters within the scope of the present application, it is beneficial to obtain a negative electrode sheet with high peel strength, and thus it is more beneficial to obtain a lithium-ion battery with good rate performance and low DC impedance.

[0092] The above has introduced in detail a negative electrode sheet, a battery, an energy storage device and an electrical equipment disclosed in the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the technical solution and the core inventive point of the embodiments of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A negative electrode plate, characterized in that: The invention comprises a negative electrode current collector, at least one side of which has a negative electrode material layer, and the negative electrode material layer comprises a negative electrode material and a negative electrode binder, wherein: The negative electrode binder comprises a styrene-butadiene rubber main chain, a carbon chain length of C 14 ~C 24 Modified styrene-butadiene rubber particles formed by long-chain unsaturated fatty acids and acid anhydride compounds; The average particle size of the modified styrene-butadiene rubber particles is D50, 190nm≤D50≤210nm.

2. The negative electrode sheet according to claim 1, characterized in that: 195nm≤D50≤205nm.

3. The negative electrode sheet according to claim 1, characterized in that: The modified styrene-butadiene rubber particles have unsaturated double bonds and styrene units, and the molar ratio of the unsaturated double bonds to the styrene units is 1:(1.2-1.8).

4. The negative electrode sheet according to claim 1, characterized in that: Includes at least one of the following features: a), the long-chain unsaturated fatty acid comprises at least one of linoleic acid, oleic acid and linolenic acid; b) The acid anhydride compound includes at least one of maleic anhydride, phthalic anhydride and trimellitic anhydride.

5. A method for preparing a negative electrode sheet according to any one of claims 1 to 4, characterized in that: The following steps are involved: Adding styrene monomer, butadiene monomer, a first dispersant and a first initiator into water to react and generate a seed emulsion containing a styrene-butadiene rubber main chain; The carbon chain length is C 14 ~C 24 The long-chain unsaturated fatty acid, anhydride compound, a second dispersant and a second initiator are mixed with the seed emulsion to obtain modified styrene-butadiene rubber particles after modification, wherein the stirring speed during the modification process is 400 rpm to 600 rpm and the reaction temperature is 45° C. to 75° C.; A negative electrode material, a conductive agent, the modified styrene-butadiene rubber particles and a solvent are mixed to form a negative electrode slurry, and the negative electrode slurry is coated on at least one surface of a negative electrode current collector to form a negative electrode material layer.

6. The preparation method according to claim 5, characterized in that: Based on the content of the styrene-butadiene rubber main chain, the addition amount of the long-chain unsaturated fatty acid is a, 2%≤a≤5%, and the addition amount of the acid anhydride compound is b, 0.5%≤b≤1.5%.

7. The preparation method according to claim 6, characterized in that: 3%≤a≤4%, and 1%≤b≤1.5%.

8. The preparation method according to claim 5, characterized in that: Includes at least one of the following features: a), the first dispersant includes at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether, and the first initiator includes ammonium persulfate; b) The second dispersant includes nonylphenol polyoxyethylene ether, and the second initiator includes azobisisobutyronitrile.

9. A battery, characterized in that: A negative electrode sheet comprising the negative electrode sheet as described in any one of claims 1 to 4, or a negative electrode sheet made by the method for making a negative electrode sheet as described in any one of claims 5 to 8.

10. An energy storage device, characterized in that: The invention comprises a casing and at least one battery according to claim 9, wherein the battery is accommodated in the casing.

11. An electrical device, characterized in that: It includes the energy storage device as described in claim 10, and the energy storage device supplies power to the electrical equipment.

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