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, the negative electrode material layer comprises a negative electrode additive, the negative electrode additive comprises a compound shown in a formula (I), and based on the mass of the negative electrode material layer, the formula (I) is shown in the description. The mass percentage of the compound shown in the formula (I) is a, and a is more than or equal to 0.1% and less than or equal to 0.4%.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a negative electrode plate, a battery, an energy storage device and an electrical equipment. Background Art

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

[0003] As one of the main structures of secondary batteries, the negative electrode sheet plays an important role in the performance of secondary batteries. As the hardness of the negative electrode sheet increases, the risk of cracking of the negative electrode sheet increases, which affects the performance and life of the secondary battery, and thus affects the life of the energy storage device. Therefore, how to reduce the hardness and brittleness of the negative electrode sheet to reduce the risk of cracking of the negative electrode sheet has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses a negative electrode plate, a battery, an energy storage device and an electrical equipment to reduce the hardness and brittleness of the negative electrode plate and improve the performance of the secondary battery.

[0005] In a first aspect, the present application provides a negative electrode sheet, comprising a negative electrode current collector, wherein at least one side of the negative electrode current collector has a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode additive, and wherein the negative electrode additive comprises a compound represented by formula (I): , In formula (I), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently selected from a hydrogen atom, a substituted or unsubstituted C 1 ~C 5 Alkyl, -OCH 3 or Ra, and R 1 ~R 6 At least one of them is Ra, Ra is selected from -(OCH 2 CH 2 CH 2 ) m OH, -(OCH 2 CH 2 ) n OH, -CO(OCH 2 CH 2 ) n OH or -CO(OCH 2 CH 2 CH 2 )m OH, n≥3, 2≤m≤8; Based on the mass of the negative electrode material layer, the mass percentage of the compound represented by formula (I) is a, 0.1%≤a≤0.4%.

[0006] In some embodiments of the present application, the relative molecular mass of the compound represented by formula (I) is M 1 , 190≤M 1 ≤600.

[0007] In some embodiments of the present application, the compound represented by formula (I) is selected from at least one of the following compounds: , , , , , , , , , , .

[0008] In some embodiments of the present application, the negative electrode material layer also includes a negative electrode material, a negative electrode conductor, a negative electrode binder and a negative electrode thickener. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode material is b, 95%≤b≤97.8%, the mass percentage of the negative electrode conductor is c, 1%≤c≤2%, the mass percentage of the negative electrode binder is d, 1%≤d≤2%, and the mass percentage of the negative electrode thickener is e, 0.1%≤e≤1.5%.

[0009] In some embodiments of the present application, the surface tension of the negative electrode slurry used to form the negative electrode material layer is F 1 , F 1 ≤68 mN / m.

[0010] In some embodiments of the present application, the hardness and brittleness value of the negative electrode plate is T 1 , 110 mN≤T 1 ≤140mN.

[0011] In some embodiments of the present application, the negative electrode material includes at least one of natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon and soft carbon.

[0012] In a second aspect, the present application provides a battery, comprising the negative electrode plate described in the first aspect.

[0013] In a third aspect, the present application provides an energy storage device, comprising a housing and at least one battery as described in the second aspect, wherein the battery is accommodated in the housing.

[0014] In a fourth aspect, the present application provides an electrical device, comprising the energy storage device described in the third aspect, wherein the energy storage device supplies power to the electrical device.

[0015] Compared with the prior art, this application has at least the following beneficial effects: The present application provides a negative electrode plate, a battery, an energy storage device and an electrical device, wherein the negative electrode plate includes a negative electrode current collector, at least one side of the negative electrode current collector has a negative electrode material layer, the negative electrode material layer includes a negative electrode additive, the negative electrode additive includes a compound represented by formula (I), based on the mass of the negative electrode material layer, the mass percentage of the compound represented by formula (I) is a, 0.1%≤a≤0.4%. The negative electrode plate of the present application contains the compound represented by formula (I), and by regulating the content of the compound represented by formula (I) within the above range, the hardness and brittleness of the negative electrode plate can be reduced, thereby reducing the risk of cracking of the negative electrode plate and improving the initial energy efficiency of the secondary battery. When a secondary battery having the negative electrode plate of the present application is used in an energy storage device, the service life of the energy storage device is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application; Figure 2 A schematic diagram of the structure of a commercial energy storage system according to an implementation scheme of the present application; Figure 3 This is a photo of the negative electrode sheet prepared in Example 1; Figure 4 This is a photo of the negative electrode sheet prepared in Comparative Example 1.

[0018] Explanation of the accompanying drawings: 1-energy storage device, 2-electric energy conversion device, 3-first user load, 4-second user load, 400-commercial energy storage system, 410-high voltage cable, 420-first electric energy conversion device, 430-second electric energy conversion device. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0021] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency 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.

[0022] In addition, the terms "installed", "set", "provided with", "connected", and "connected" 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 a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. 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.

[0023] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (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, elements or components. Unless otherwise specified, "plurality" means two or more.

[0024] It should be noted that, in the present application, a lithium-ion battery is used as an example of a secondary battery to explain the present application, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0025] The present application provides a negative electrode plate, which includes a negative electrode current collector, at least one side of the negative electrode current collector has a negative electrode material layer, the negative electrode material layer includes a negative electrode additive, and the negative electrode additive includes a compound represented by formula (I): , In formula (I), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently selected from a hydrogen atom, a substituted or unsubstituted C 1 ~C 5 Alkyl, -OCH 3 or Ra, and R 1 ~R 6 At least one of them is Ra, Ra is selected from -(OCH 2 CH 2 CH 2 ) m OH, -(OCH 2 CH 2 ) n OH, -CO(OCH 2 CH 2 ) n OH or -CO(OCH 2 CH 2 CH 2 ) m OH, n≥3, 2≤m≤8; preferably, 3≤n≤10; based on the mass of the negative electrode material layer, the mass percentage of the compound represented by formula (I) is a, 0.1%≤a≤0.4%. For example, a is 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35% or 0.4%. When the content of the compound represented by formula (I) is too low (for example, less than 0.1%), the effect of reducing the hardness and brittleness of the negative electrode sheet is not obvious, and the negative electrode sheet still has a high risk of cracking; when the content of the compound represented by formula (I) is too high (for example, higher than 0.4%), the relative content of the negative electrode material in the negative electrode material layer decreases, which is not conducive to improving the initial energy efficiency of the lithium ion battery. By regulating the content of the compound represented by formula (I) within the above range, the hardness and brittleness of the negative electrode sheet can be reduced, thereby reducing the risk of cracking of the negative electrode sheet, and can also improve the initial energy efficiency of the lithium ion battery. When the lithium-ion battery with the negative electrode plate of the present application is used in an energy storage device, the service life of the energy storage device is increased.

[0026] In the present application, the initial energy efficiency refers to the energy efficiency corresponding to the third cycle during the charge and discharge cycle test of the lithium-ion battery.

[0027] In some embodiments of the present application, the relative molecular mass of the compound represented by formula (I) is M 1 , 190≤M 1 ≤600. For example, M 1 190, 200, 300, 400, 500 or 600. 1The compound represented by formula (I) within the above range has a relatively high boiling point (for example, a boiling point higher than 150° C.), is not easy to volatilize during the coating process of the negative electrode slurry to cause environmental pollution, and has a significant effect on reducing the flexibility, hardness and brittleness of the negative electrode sheet, and has a good anti-cracking effect.

[0028] In some embodiments of the present application, the compound represented by formula (I) is selected from at least one of the following compounds: , , , , , , , , , , .

[0029] By selecting at least one of the compounds represented by formula (I-1) to (I-11) above, it is helpful to reduce the hardness and brittleness of the negative electrode sheet, thereby reducing the risk of cracking of the negative electrode sheet.

[0030] In some embodiments of the present application, the negative electrode material layer further includes a negative electrode material, a negative electrode conductive agent, a negative electrode binder and a negative electrode thickener. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode material is b, 95%≤b≤97.8%, the mass percentage of the negative electrode conductive agent is c, 1%≤c≤2%, the mass percentage of the negative electrode binder is d, 1%≤d≤2%, and the mass percentage of the negative electrode thickener is e, 0.1%≤e≤1.5%. For example, b is 95%, 96%, 97% or 97.8%; c is 1%, 1.5%, 1.8% or 2%; d is 1%, 1.5%, 1.8% or 2%; e is 0.1%, 0.5%, 1.0% or 1.5%. By regulating the contents of the negative electrode material, the negative electrode conductive agent and the negative electrode binder within the above range, it is beneficial to obtain a lithium-ion battery with low hardness and brittleness, high capacity and high initial energy efficiency.

[0031] In some embodiments of the present application, the surface tension of the negative electrode slurry used to form the negative electrode material layer is F 1 , F 1 ≤68 mN / m. For example, F 1 The compound represented by formula (I) of the present application can reduce the surface tension of the negative electrode slurry, thereby improving the wettability of the negative electrode material (such as graphite), improving the dispersion uniformity of the negative electrode material, and improving the wettability of the electrolyte to the negative electrode plate, thereby reducing the hardness and brittleness of the negative electrode plate and improving the initial energy efficiency of the lithium ion battery.

[0032] In some embodiments of the present application, the hardness and brittleness value of the negative electrode plate is T 1 , 110 mN≤T 1 ≤140 mN. For example, T 1 is 110 mN, 120 mN, 130 mN or 140 mN. By adjusting the hardness and brittleness value T of the negative electrode 1 Within the above range, the negative electrode plate can have lower hardness and brittleness, thereby reducing the risk of cracking of the negative electrode plate.

[0033] In some embodiments of the present application, the negative electrode material includes at least one of natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon and soft carbon.

[0034] The present application also provides a battery, comprising the negative electrode plate described in any embodiment of the present application.

[0035] The lithium-ion battery of the present application also includes a positive electrode plate, a separator and an electrolyte, wherein the separator is located between the positive electrode plate and the negative electrode plate to play an isolating role.

[0036] The present application has no special restrictions on the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the positive electrode sheet usually includes a positive current collector and a positive electrode material layer. The positive electrode material layer can be arranged on one surface in the thickness direction of the positive current collector, or on two surfaces in the thickness direction of the positive current collector. In the present application, the positive electrode material layer is arranged on the surface of the positive current collector, that is, the positive electrode material layer can be arranged in a partial area of ​​one surface of the positive current collector, or in the entire area of ​​one surface of the positive current collector. The present application has no special restrictions on the positive current collector, as long as the purpose of the present application can be achieved, for example, it can include but is not limited to aluminum foil, aluminum alloy foil or composite current collector. In the present application, there is no special restriction on the thickness of the positive current collector, as long as the purpose of the present application can be achieved, for example, the thickness is 8μm~13μm. The single-sided thickness of the positive electrode material layer of the present application can be 100μm~200μm.

[0037] In the present application, the positive electrode material layer includes a positive electrode material, and the present application has no particular restrictions on the positive electrode material, as long as the purpose of the present application can be achieved. The positive electrode material can be selected from lithium transition metal oxides and modified materials thereof, and the modified material can be a doping modification or coating modification of the lithium transition metal oxide. For example, the lithium transition metal oxide can be selected from at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0038] In the present application, the positive electrode material layer may also include a positive electrode conductive agent. The present application has no particular restrictions on the positive electrode conductive agent, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes or multi-walled carbon nanotubes. In the present application, the positive electrode material layer may also include a positive electrode binder. The present application has no particular restrictions on the positive electrode binder, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0039] In the present application, the negative electrode material layer can be arranged on one surface or two surfaces in the thickness direction of the negative electrode current collector. In the present application, the negative electrode material layer is arranged on the surface of the negative electrode current collector, that is, the negative electrode material layer can be arranged in a partial area of ​​one surface of the negative electrode current collector, or it can be arranged in the entire area of ​​one surface of the negative electrode current collector. The present application has no special restrictions on the negative electrode current collector, as long as the purpose of the present 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 the present application, there is no special restriction on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness is 4μm~12μm. The single-sided thickness of the negative electrode material layer of the present application can be 70μm~200μm.

[0040] The present application has no particular limitation on the negative electrode conductive agent, as long as the purpose of the present application can be achieved. For example, it may include at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0041] The present application has no particular limitation on the negative electrode binder, as long as the purpose of the present application can be achieved, for example, it may include at least one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0042] The present application has no particular limitation on the negative electrode thickener, as long as the purpose of the present application can be achieved, for example, it may include at least one of sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li) and sodium alginate (SA).

[0043] The present application has no particular restrictions on the diaphragm, and any known porous structure diaphragm with good chemical stability and mechanical stability can be selected, such as at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and PVDF. The diaphragm can be a single-layer film or a multi-layer composite film. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different.

[0044] The battery of the present application also includes an electrolyte. The present application has no particular restrictions on the electrolyte, and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE) is mixed in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, and then a lithium salt is added to dissolve and mix evenly. The present application has no particular limitation on the content of the organic solvent. For example, the mass percentage of the organic solvent in the electrolyte is 65% to 85%.

[0045] The present application has no restrictions on the type of lithium salt, as long as it can achieve the purpose of the present application. For example, lithium salts include but are not limited to lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) and lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), at least one of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0046] The present application has no particular limitation on the concentration of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. 6 For example, LiPF 6 The concentration in the electrolyte is 10wt%~15wt%, for example, LiPF 6 The concentration is 10wt%, 11wt%, 12wt%, 13wt% or 15wt%.

[0047] The electrolyte may also optionally include additives, wherein the types of additives are not specifically limited and may be selected according to needs. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature performance, etc.

[0048] The battery of the present application also includes a shell, and the present application has no particular limitation on the shell, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, the shell may include an aluminum-plastic film.

[0049] The present application does not particularly limit the preparation method of the battery, and a preparation method known in the art can be selected as long as the purpose 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 order, and winding (or laminating) them as needed to obtain a bare cell, placing the bare cell in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a battery.

[0050] The present application also provides an energy storage device, including a housing and at least one battery in any of the above embodiments, wherein the battery is contained in the housing. The energy storage device having the battery has excellent performance, which is beneficial to the use of the energy storage device. By containing the battery in the housing, the fixation and protection of the battery can be increased, thereby improving the service life of the energy storage device. It is understandable that the energy storage device may have one or more batteries, and when the energy storage device contains multiple batteries, the multiple batteries may be connected in at least one of parallel and series connection.

[0051] The present application also provides an electrical device, including the energy storage device in the above-mentioned implementation scheme, which is conducive to improving the product competitiveness and performance of the electrical device. In an optional implementation scheme, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional implementation scheme, the electrical device body includes a positive electrode of the device and a negative electrode of the device, the positive electrode plate of the battery in the energy storage device is used to electrically connect to the positive electrode of the device body of the electrical device, and the negative electrode plate of the battery in the energy storage device is used to electrically connect to the negative electrode of the device body of the electrical device, so as to supply power to the electrical device.

[0052] The electrical equipment of the present application may include but is not limited to: containers, battery vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecrafts include airplanes, rockets, space shuttles and spacecrafts, etc., electric toys include fixed or mobile electric toys, such as electric car toys, electric ship toys and electric airplane toys, etc., and electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0053] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application, and the present application Figure 1 The implementation plan is described using a household energy storage scenario in user-side energy storage as an example, but the energy storage device of the present application is not limited to the household energy storage scenario.

[0054] The present application provides a household energy storage system, which includes an energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as air conditioner and other household appliances), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be mounted on an outdoor wall by wall hanging. Specifically, the photovoltaic panel can convert solar energy into electrical energy during the period of low electricity prices. The energy storage device 1 is used to store the electrical energy and supply it to street lamps and household appliances for use during peak electricity prices, or to supply power when the power grid is out of power / power outage.

[0055] See also Figure 2 , Figure 2 A schematic diagram of a commercial energy storage system 400 according to an embodiment of the present application. Figure 2 The implementation plan is described using the shared energy storage scenario on the generation / distribution side as an example, and the energy storage device 1 of the present application is not limited to the energy storage scenario on the generation / distribution side.

[0056] The present application provides a commercial energy storage system 400, which includes: a high-voltage cable 410, a first electric energy conversion device 420, a second electric energy conversion device 430 and an energy storage device 1 provided in the present application. In the case of power generation, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used to convert other forms of energy into electric energy, which are connected to the high-voltage cable 410 and supplied to the power distribution network for use. When the power load is low and the first electric energy conversion device 420 and the second electric energy conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, thereby reducing the wind and solar power abandonment rates and improving the problem of new energy power generation and consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1 in conjunction with the high-voltage cable 410 in a grid-connected mode to the power consumption side, thereby providing peak load regulation, frequency regulation, standby and other services for the power grid operation, giving full play to the peak load regulation of the power grid, promoting peak load shaving and valley filling of the power grid, and alleviating the power supply pressure of the power grid.

[0057] Optionally, the first electric energy conversion device 420 and the second electric energy conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electric energy.

[0058] The number of energy storage devices 1 can be multiple, and multiple energy storage devices 1 are connected in series or in parallel. Multiple energy storage devices 1 are supported and electrically connected by isolation plates (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to accommodate the energy storage device 1.

[0059] Optionally, the energy storage device 1 may include but is not limited to a battery module, a battery pack, a battery system, etc. Among them, the battery module may be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack may include multiple batteries of the present application, and the battery system may be a charging and discharging system including the battery or battery pack of the present application.

[0060] The actual application form of the energy storage device 1 provided in the embodiment of the present application may be, but is not limited to, the listed products, and may also be other application forms. The embodiment of the present application does not strictly limit the application form of the energy storage device 1. The embodiment of the present application only takes the energy storage device 1 as a multi-core battery as an example for explanation. When the energy storage device 1 includes a single cell, the single cell may be at least one of a cylindrical battery, a square battery, and the like.

[0061] Example Hereinafter, the embodiments of the present application will be described in more detail with reference to preparation examples, examples and comparative examples. Various tests and evaluations were performed according to the following methods.

[0062] Example 1 <Preparation of positive electrode sheet> The positive electrode material is lithium iron phosphate (LiFePO 4 ), conductive carbon black (Super-P), and binder PVDF are mixed in a mass ratio of 97:0.7:2.3; then N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 60wt%, and stirred evenly, and then the positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85℃; then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. After cold pressing, striping, and cutting, a positive electrode sheet is obtained. The single-sided thickness of the positive electrode material layer is 100μm.

[0063] <Preparation of negative electrode sheet> The negative electrode material artificial graphite, negative electrode additive, negative electrode conductive agent conductive carbon black (Super-P), negative electrode thickener CMC, and negative electrode binder SBR are mixed in a mass ratio of 95.8:0.2:1:1:2, deionized water is added, and a negative electrode slurry with a solid content of 52wt% is prepared and stirred evenly. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 85°C; then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode material layer coated on both sides. After cold pressing, striping, and cutting, a negative electrode sheet is obtained. The single-sided thickness of the negative electrode material layer is 70μm. The types of negative electrode additives are shown in Table 1.

[0064] <Preparation of Electrolyte> In an argon atmosphere glove box with a moisture content of ≤1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 1:1:1, and then lithium salt LiPF 6 And dissolved in the above solvent, mixed evenly to obtain the electrolyte, LiPF 6 The content in the electrolyte is 12.5wt%.

[0065] <Preparation of Separator> A polypropylene (PP) porous polymer film with a thickness of 16 μm was used as the separator.

[0066] <Preparation of lithium-ion batteries> The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive electrode and the negative electrode to play an isolating role, and wound to obtain a bare cell. The bare cell is placed in an aluminum-plastic film packaging bag, vacuum dried, and then injected with electrolyte, and a lithium-ion battery is obtained through vacuum packaging, standing, and formation processes.

[0067] Embodiment 2 to Embodiment 6 Except that the type of negative electrode additive is adjusted according to Table 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0068] Embodiment 7~embodiment 9 Except that the content of the negative electrode additive is adjusted according to Table 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0069] Embodiment 10~embodiment 14 Except that the type of negative electrode additive is adjusted according to Table 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0070] Comparative Example 1~Comparative Example 2 Except that the type of negative electrode additive is adjusted according to Table 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0071] Wherein, the structural formula of the compound represented by formula (II) is: .

[0072] Comparative Example 3~Comparative Example 4 Except that the content of the negative electrode additive is adjusted according to Table 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0073] Table 1: Preparation parameters of each embodiment and each comparative example

[0074] Test methods and equipment: Negative electrode slurry surface tension test: The test was carried out using a surface tension meter (model: dataphysics DCAT 15) and the platinum plate method. The test principle is: when the sensor is immersed in the negative electrode slurry to be tested, the surrounding area of ​​the platinum plate will be affected by the surface tension. The surface tension of the negative electrode slurry will pull the platinum plate down as much as possible. When the surface tension of the negative electrode slurry and other related forces reach equilibrium, the sensing platinum plate will stop immersing into the negative electrode slurry. At this time, the balance sensor of the surface tension meter will measure the immersion depth and convert the immersion depth into the surface tension value of the negative electrode slurry.

[0075] Hardness and brittleness test of negative electrode: Cut the negative electrode sheet into samples of 60 cm in length and 40 cm in width with a cutting knife, and then put the samples into the fixture of the hardness and brittleness tester (model PY-H613), so that the negative electrode sheet and the test head are at 90 degrees, and the test head is vertically pressed into the negative electrode sheet to a depth of 8±0.5mm. Record the maximum pressure value displayed by the test head sensor, which is the hardness and brittleness value in mN. The larger the hardness and brittleness value, the higher the hardness of the negative electrode sheet.

[0076] Energy efficiency test: The lithium-ion batteries prepared in the embodiments and comparative examples were subjected to charge and discharge cycle tests on a charge and discharge instrument (model: BAT-NEEFLCT-05300-V010), the test temperature was 25°C, the cycle rate was 0.5P (i.e., both the charge rate and the discharge rate were 0.5P), the charging voltage was 2.5V to 3.65V, and the energy efficiency and capacity retention rate after the cycle were calculated.

[0077] The energy efficiency calculation formula is: (discharge energy after the nth cycle / charge energy after the nth cycle) × 100%.

[0078] Table 2: Performance data of each embodiment and each comparative example

[0079] It can be seen from Examples 1 to 6 and Comparative Examples 1 to 2 that the surface tension of the negative electrode slurry of Comparative Example 1 is still too large, the hardness of the negative electrode sheet is too high, and the initial energy efficiency of the lithium ion battery is too low. This may be due to the limited effect of 1,3-butanediol on reducing the surface tension of the negative electrode slurry, and therefore the limited degree of reduction in the hardness and brittleness of the negative electrode sheet, and the volatility of such additives is relatively good, requiring additional investment in a recovery system, otherwise it will cause pollution to the environment; the surface tension of the negative electrode slurry of Comparative Example 2 is too large, the hardness of the negative electrode sheet is too high, and the initial energy efficiency of the lithium ion battery is too low, which may be due to the low degree of polymerization of the compound represented by formula (II), which is not conducive to reducing the hardness and brittleness of the negative electrode sheet; it can be seen from Examples 1, 7 to 9, and Comparative Examples 3 to 4 that when the content of the compound represented by formula (I) is too low (for example, Comparative Example 5), the surface tension of the negative electrode slurry of Comparative Example 2 is too large, the hardness of the negative electrode sheet is too high, and the initial energy efficiency of the lithium ion battery is too low. In Example 3, the surface tension of the negative electrode slurry is still high, the hardness of the negative electrode sheet is still high, the effect of reducing the hardness and brittleness of the negative electrode sheet is not obvious, the negative electrode sheet still has a high risk of cracking, and the initial energy efficiency of the lithium ion battery is low; when the content of the compound represented by formula (I) is too high (for example, comparative example 4), although the surface tension of the negative electrode slurry is reduced and the hardness of the negative electrode sheet is reduced, the relative content of the negative electrode material decreases, and the initial energy efficiency of the lithium ion battery is still low; the negative electrode sheet of the present application contains the compound represented by formula (I), and by regulating the content of the compound represented by formula (I) within the scope of the present application, the surface tension of the negative electrode slurry is reduced, the hardness of the negative electrode sheet is reduced, and the initial energy efficiency of the lithium ion battery is improved, thereby reducing the hardness and brittleness of the negative electrode sheet, reducing the risk of cracking of the negative electrode sheet, and improving the initial energy efficiency of the lithium ion battery.

[0080] The type of compound represented by formula (I) and the content of compound represented by formula (I) will usually also affect the performance of the negative electrode. It can also be seen from Examples 1 to 14 that by regulating the type and content of the compound represented by formula (I) within the scope of this application, it is beneficial to reduce the hardness and brittleness of the negative electrode, reduce the risk of cracking of the negative electrode, and improve the initial energy efficiency of the lithium-ion battery.

[0081] Figure 3 This is a photo of the negative electrode obtained in Example 1. Figure 3 It can be seen that the surface of the negative electrode is relatively flat and there is no cracking; Figure 4 This is a photo of the negative electrode obtained in Comparative Example 1. Figure 4 It can be seen that cracks appear on the surface of the negative electrode.

[0082] The above is a detailed introduction to a negative electrode plate, a battery, an energy storage device and an electrical equipment disclosed in the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on 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, the negative electrode material layer comprises a negative electrode additive, and the negative electrode additive comprises a compound represented by formula (I): ， In formula (I), R1, R2, R3, R4, R5 and R6 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, -OCH3 or Ra, and at least one of R1-R6 is Ra, and Ra is selected from -(OCH2CH2CH2) m OH, -(OCH2CH2) n OH, -CO(OCH2CH2) n OH or -CO(OCH2CH2CH2) m OH, n≥3, 2≤m≤8; Based on the mass of the negative electrode material layer, the mass percentage of the compound represented by formula (I) is a, 0.1%≤a≤0.4%.

2. The negative electrode sheet according to claim 1, characterized in that: The relative molecular mass of the compound represented by formula (I) is M1, 190≤M1≤600.

3. The negative electrode sheet according to claim 1, characterized in that: The compound represented by formula (I) is selected from at least one of the following compounds: 、 、 、 、 、 、 、 、 、 、 。 4. The negative electrode sheet according to claim 1, characterized in that: The negative electrode material layer also includes a negative electrode material, a negative electrode conductor, a negative electrode binder and a negative electrode thickener. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode material is b, 95%≤b≤97.8%, the mass percentage of the negative electrode conductor is c, 1%≤c≤2%, the mass percentage of the negative electrode binder is d, 1%≤d≤2%, and the mass percentage of the negative electrode thickener is e, 0.1%≤e≤1.5%.

5. The negative electrode sheet according to claim 1, characterized in that: The surface tension of the negative electrode slurry used to form the negative electrode material layer is F1, and F1≤68 mN / m.

6. The negative electrode sheet according to claim 1, characterized in that: The hardness and brittleness value of the negative electrode plate is T1, 110 mN≤T1≤140 mN.

7. The negative electrode sheet according to claim 1, characterized in that: The negative electrode material includes at least one of natural graphite, artificial graphite, mesophase micro carbon beads, hard carbon and soft carbon.

8. A battery, characterized in that: A negative electrode sheet comprising the negative electrode sheet according to any one of claims 1 to 7.

9. An energy storage device, characterized in that: The invention comprises a casing and at least one battery according to claim 8, wherein the battery is accommodated in the casing.

10. An electrical device, characterized in that: It includes the energy storage device as described in claim 9, and the energy storage device supplies power to the electrical equipment.

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