Negative electrode sheet, battery, energy storage device and electrical equipment

Abstract

The present application provides a negative electrode sheet, a battery, an energy storage device and an electrical equipment. The negative electrode sheet includes a negative electrode current collector, at least one surface 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), and based on the mass of the negative electrode material layer, the mass percentage content of the compound represented by formula (I) is a, and 0.1% ≤ a ≤ 0.4%.

Description

Technical Field

[0001] The present 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 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 thus widely used in fields such as energy storage devices.

[0003] As one of the main structures of secondary batteries, the negative electrode plate plays an important role in the performance of secondary batteries. With the increase in the hardness of the negative electrode plate, the risk of cracking of the negative electrode plate increases, resulting in the performance and life of the secondary battery being affected, and thus the life of the energy storage device being affected. Therefore, how to reduce the brittleness of the negative electrode plate to reduce the risk of cracking of the negative electrode plate has become a technical problem 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 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 plate, including a negative electrode current collector, at least one surface of the negative electrode current collector having a negative electrode material layer, the negative electrode material layer including a negative electrode additive, and the negative electrode additive including a compound represented by formula (I):

[0006] ,

[0007] In formula (I), R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 each independently selected from a hydrogen atom, a substituted or unsubstituted C 1 ~C 5 alkyl group, -OCH 3 or Ra, and at least one of R 1 ~R 6 is Ra, and 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 2CH 2 ) m OH, n ≥ 3, 2 ≤ m ≤ 8;

[0008] Based on the mass of the negative electrode material layer, the mass percentage of the compound shown in formula (I) is a, 0.1% ≤ a ≤ 0.4%.

[0009] In some embodiments of the present application, the relative molecular mass of the compound shown in formula (I) is M 1 , 190 ≤ M 1 ≤ 600.

[0010] In some embodiments of the present application, the compound shown in formula (I) is selected from at least one of the following compounds:

[0011] , , , , , , , , , , .

[0012] 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%.

[0013] 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.

[0014] In some embodiments of the present application, the brittleness value of the negative electrode plate is T 1 , 110 mN ≤ T 1 ≤ 140 mN.

[0015] In some embodiments of the present application, the negative electrode material includes at least one of natural graphite, artificial graphite, mesophase microbeads, hard carbon, and soft carbon.

[0016] In a second aspect, the present application provides a battery including the negative electrode plate described in the first aspect.

[0017] In a third aspect, the present application provides an energy storage device, including a box body and at least one battery described in the second aspect, and the battery is received in the box body.

[0018] In a fourth aspect, the present application provides an electrical equipment, including the energy storage device described in the third aspect, and the energy storage device supplies power to the electrical equipment.

[0019] Compared with the prior art, the present application has at least the following beneficial effects:

[0020] The present application provides a negative electrode tab, a battery, an energy storage device and an electrical equipment. The negative electrode tab includes a negative electrode current collector, at least one surface 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 shown in formula (I), and based on the mass of the negative electrode material layer, the mass percentage content of the compound shown in formula (I) is a, and 0.1% ≤ a ≤ 0.4%. The negative electrode tab of the present application contains the compound shown in formula (I), and by controlling the content of the compound shown in formula (I) within the above range, the hard brittleness of the negative electrode tab can be reduced, thereby reducing the cracking risk of the negative electrode tab and improving the initial energy efficiency of the secondary battery. When the secondary battery with the negative electrode tab of the present application is applied to the energy storage device, the service life of the energy storage device is improved. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used 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.

[0022] Figure 1 It is a schematic structural diagram of a household energy storage system according to an implementation scheme of the present application;

[0023] Figure 2 It is a schematic structural diagram of a commercial energy storage system according to an implementation scheme of the present application;

[0024] Figure 3 It is a photo of the negative electrode tab prepared in Example 1;

[0025] Figure 4 It is a photo of the negative electrode tab prepared in Comparative Example 1.

[0026] Description of the 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 Embodiments

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part rather than all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0028] In the present application, the orientation or positional relationship indicated by terms such as "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 accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation or be constructed and operated in a specific orientation.

[0029] Moreover, in addition to being able to represent the 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 the present application can be understood according to specific circumstances.

[0030] In addition, the terms "mount", "set", "provided with", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral structure; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, or there may be internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0031] In addition, terms such as "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 stated, the meaning of "a plurality" is two or more.

[0032] It should be noted that in the content of the present application, lithium-ion batteries are used as examples of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0033] 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):

[0034] ,

[0035] 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 at least one of R 1 ~R 6 is Ra, and 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 shown in 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 shown in 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 there is still a high risk of cracking in the negative electrode sheet; when the content of the compound shown in 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 adjusting the content of the compound shown in formula (I) within the above range, the hardness and brittleness of the negative electrode sheet can be reduced, thereby reducing the cracking risk of the negative electrode sheet, and the initial energy efficiency of the lithium-ion battery can also be improved. When the lithium-ion battery with the negative electrode sheet of the present application is applied to an energy storage device, the service life of the energy storage device is improved.

[0036] In the present application, the initial energy efficiency refers to the energy efficiency corresponding to the third cycle during the charge-discharge cycle test of the lithium-ion battery.

[0037] In some embodiments of the present application, the relative molecular mass of the compound shown in formula (I) is M 1 , 190≤M 1 ≤600. For example, M 1is 190, 200, 300, 400, 500 or 600. M 1 The compounds represented by formula (I) within the above range have a relatively high boiling point (for example, the boiling point is higher than 150 °C), are not easily volatilized during the coating process of the negative electrode slurry, which may cause environmental pollution, and have an obvious effect on reducing the flexibility and brittleness of the negative electrode sheet, and have a good anti-cracking effect.

[0038] In some embodiments of the present application, the compound represented by formula (I) is selected from at least one of the following compounds:

[0039] , , , , , , , , , , .

[0040] By selecting at least one of the compounds represented by formula (I-1) to formula (I-11) above, it is beneficial to reduce the brittleness of the negative electrode sheet, thereby reducing the cracking risk of the negative electrode sheet.

[0041] 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 content of the negative electrode material is b, 95% ≤ b ≤ 97.8%, the mass percentage content of the negative electrode conductive agent is c, 1% ≤ c ≤ 2%, the mass percentage content of the negative electrode binder is d, 1% ≤ d ≤ 2%, and the mass percentage content 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 adjusting 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 brittleness, high capacity, and high initial energy efficiency.

[0042] 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 1It is 60 mN / m, 62 mN / m, 65 mN / m or 68 mN / m. The compound shown in 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 can improve the wettability of the electrolyte to the negative electrode sheet, while reducing the brittleness of the negative electrode sheet and improving the initial energy efficiency of the lithium-ion battery.

[0043] In some embodiments of the present application, the brittleness value of the negative electrode sheet is T 1 , 110 mN ≤ T 1 ≤ 140 mN. For example, T 1 is 110 mN, 120 mN, 130 mN or 140 mN. By regulating the brittleness value T of the negative electrode sheet 1 within the above range, the negative electrode sheet can have lower brittleness, thereby reducing the cracking risk of the negative electrode sheet.

[0044] In some embodiments of the present application, the negative electrode material includes at least one of natural graphite, artificial graphite, mesophase microbeads, hard carbon and soft carbon.

[0045] The present application also provides a battery, including the negative electrode sheet described in any embodiment of the present application.

[0046] The lithium-ion battery of the present application further includes 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 isolation role.

[0047] The present application has no special limitation on the positive electrode sheet, as long as the purpose of the present 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 can be disposed on two surfaces in the thickness direction of the positive electrode current collector. In the present 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 on a partial area of one surface of the positive electrode current collector, or can be disposed on the entire area of one surface of the positive electrode current collector. The present application has no special limitation on the positive 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 aluminum foil, aluminum alloy foil or composite current collector, etc. In the present application, there is no special limitation on the thickness of the positive electrode current collector, as long as the purpose of the present 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 the present application can be 100 μm to 200 μm.

[0048] 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 purpose of the present application can be achieved. The positive electrode material may be selected from lithium transition metal oxides and their modified materials, and the modified materials may be doping modification or coating modification of the lithium transition metal oxides. For example, the lithium transition metal oxide may 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.

[0049] In the present application, the positive electrode material layer may further include a positive electrode conductive agent. There is no particular limitation on the positive electrode conductive agent in the present application, 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 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 further include a positive electrode binder. There is no particular limitation on the positive electrode binder in the present application, 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).

[0050] In the present application, the negative electrode material layer may be disposed 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 disposed on the surface of the negative electrode current collector, that is, the negative electrode material layer may 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 the present application, as long as the purpose of the present application can be achieved. For example, it may 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 particular limitation 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 4 μm to 12 μm. The single-sided thickness of the negative electrode material layer in the present application may be 70 μm to 200 μm.

[0051] There is no particular limitation on the negative electrode conductive agent in the present application, 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.

[0052] There is no particular limitation on the negative electrode binder in the present application, 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).

[0053] The present application has no particular limitation on the negative thickener, as long as the object 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).

[0054] The present application has no particular limitation on the separator, and any well-known porous structure separator 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 separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0055] The battery of the present application further includes an electrolyte. The present application has no particular limitation on the electrolyte, and 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, after mixing 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), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE) 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. 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% - 85%.

[0056] The present application has no limitation on the type of lithium salt, as long as the object of the present application can be achieved. For example, the lithium salt includes but is not limited to lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro bis(oxalato)phosphate (LiTFOP).

[0057] 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 10 wt% to 15 wt%. For example, the concentration of LiPF 6 is 10 wt%, 11 wt%, 12 wt%, 13 wt% or 15 wt%.

[0058] The electrolyte may also optionally include additives, and there is no specific limitation on the type of additives, which can be selected according to requirements. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature performance of the battery, etc.

[0059] The battery of the present application further includes a housing, and the present application has no particular limitation on the housing, 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 housing may include an aluminum-plastic film.

[0060] The present application has no particular limitation on the preparation method of the battery, and the well-known preparation methods 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 winding (or laminating) them as needed to obtain a 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.

[0061] 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 one or more batteries may be included in the energy storage device. When the energy storage device contains multiple batteries, the multiple batteries can be connected by at least one of parallel connection and series connection.

[0062] The present application also provides an electrical equipment, including the energy storage device in the above embodiments, which is beneficial to improving the product competitiveness and service 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.

[0063] The electrical equipment of the present application may include, but is not limited to: containers, battery cars, electric vehicles, ships, spacecrafts, electric toys, electric tools, etc. Among them, spacecrafts such as airplanes, rockets, space shuttles, and spaceships, etc., electric toys include, for example, stationary or mobile electric toys, specifically, such as 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, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers.

[0064] 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 embodiment of the present application Figure 1 is described by taking the household energy storage scenario in user-side energy storage as an example. The energy storage device of the present application is not limited to the household energy storage scenario.

[0065] The present application provides a household energy storage system, which includes an electric energy conversion device 2 (solar 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 solar 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 / blacked out.

[0066] 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 embodiment of the present application Figure 2 is described by taking the shared energy storage scenario on the power generation / distribution side as an example. The energy storage device 1 of the present application is not limited to its energy storage scenario on the power generation / distribution side.

[0067] 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 with 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 excess power, the excess power generated is stored in the energy storage device 1 to reduce the rate of wind and light abandonment 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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 only take the energy storage device 1 as a multi-core battery as an example for illustration. When the energy storage device 1 includes single cells, the single cells can be at least one of cylindrical batteries, square batteries, etc.

[0072] Embodiment

[0073] 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.

[0074] Example 1

[0075] <Preparation of the positive electrode sheet>

[0076] Mix lithium iron phosphate (LiFePO 4 ), conductive carbon black (Super-P), and binder PVDF in a mass ratio of 97:0.7:2.3; then add N-methylpyrrolidone (NMP) as a solvent to prepare a positive electrode slurry with a solid content of 60 wt%, and stir evenly. Then, evenly coat the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and dry it at 85 °C; afterwards, repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. After cold pressing, slitting, and die cutting, a positive electrode sheet is obtained. The single-sided thickness of the positive electrode material layer is 100 μm.

[0077] <Preparation of the negative electrode sheet>

[0078] Mix artificial graphite as the negative electrode material, negative electrode additive, negative electrode conductive agent conductive carbon black (Super-P), negative electrode thickener CMC, and negative electrode binder SBR in a mass ratio of 95.8:0.2:1:1:2, add deionized water, and prepare a negative electrode slurry with a solid content of 52 wt%, and stir evenly. Evenly coat the negative electrode slurry on one surface of a negative electrode current collector copper foil with a thickness of 6 μm, and dry it at 85 °C; afterwards, repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode material layer. After cold pressing, slitting, and die cutting, a negative electrode sheet is obtained. The single-sided thickness of the negative electrode material layer is 70 μm. The types of negative electrode additives are shown in Table 1.

[0079] <Preparation of the electrolyte>

[0080] In an argon atmosphere glove box with a water content ≤ 1 ppm, mix ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 1:1:1, and then add lithium salt LiPF 6 and dissolve it in the above solvent. After mixing evenly, an electrolyte is obtained, and the content of LiPF 6 in the electrolyte is 12.5 wt%.

[0081] <Preparation of the separator>

[0082] Use a polypropylene (PP) porous polymer film with a thickness of 16 μm as the separator.

[0083] <Preparation of the lithium-ion battery>

[0084] Stack the prepared positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive and negative electrodes to play an isolation role, and wind them to obtain a bare battery cell. Place the bare battery cell in an aluminum-plastic film packaging bag, inject electrolyte after vacuum drying, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, and formation.

[0085] Examples 2 to 6

[0086] Except that in the <Preparation of Negative Electrode Sheet>, the types of negative electrode additives are adjusted according to Table 1, the rest are the same as in Example 1.

[0087] Examples 7 to 9

[0088] Except that in the <Preparation of Negative Electrode Sheet>, the content of negative electrode additives is adjusted according to Table 1, the rest are the same as in Example 1.

[0089] Examples 10 to 14

[0090] Except that in the <Preparation of Negative Electrode Sheet>, the types of negative electrode additives are adjusted according to Table 1, the rest are the same as in Example 1.

[0091] Comparative Examples 1 to 2

[0092] Except that in the <Preparation of Negative Electrode Sheet>, the types of negative electrode additives are adjusted according to Table 1, the rest are the same as in Example 1.

[0093] Among them, the structural formula of the compound shown in formula (II) is: .

[0094] Comparative Examples 3 to 4

[0095] Except that in the <Preparation of Negative Electrode Sheet>, the content of negative electrode additives is adjusted according to Table 1, the rest are the same as in Example 1.

[0096] Table 1: Preparation Parameters of Each Example and Each Comparative Example

[0097]

[0098] Testing Methods and Equipment:

[0099] Testing of the Surface Tension of the Negative Electrode Slurry:

[0100] The test was carried out by a surface tensiometer (model: dataphysics DCAT 15) using the platinum plate method. The test principle is as follows: When the sensor is immersed in the negative electrode paste to be tested, the platinum plate will be affected by the surface tension. The surface tension of the negative electrode paste will pull the platinum plate down as much as possible. When the surface tension of the negative electrode paste and other related forces reach equilibrium, the sensing platinum plate will stop immersing into the negative electrode paste. At this time, the balance sensor of the surface tensiometer will measure the immersion depth and convert the immersion depth into the surface tension value of the negative electrode paste.

[0101] Hard brittleness value test of the negative electrode plate:

[0102] The negative electrode plate was cut into samples with a length of 60 cm and a width of 40 cm by a cutting knife, and then the samples were placed in the fixture of a hard brittleness tester (model: PY-H613) so that the negative electrode plate was at a 90° angle to the test head. The depth at which the test head was vertically pressed into the negative electrode plate was 8 ± 0.5 mm. The maximum pressure value displayed by the test head sensor was recorded, which is the hard brittleness value, with the unit of mN. The larger the hard brittleness value, the higher the hardness of the negative electrode plate.

[0103] Energy efficiency test:

[0104] The lithium-ion batteries prepared in each example and comparative example 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 0.5C (i.e., both the charge rate and the discharge rate were 0.5C), and the charge voltage was from 2.5 V to 3.65 V. The energy efficiency and capacity retention rate after cycling were calculated.

[0105] The energy efficiency calculation formula is: (discharge energy after the nth cycle / charge energy after the nth cycle) × 100%.

[0106] Table 2: Performance data of each example and each comparative example

[0107]

[0108] It can be seen from Examples 1 to 6 and Comparative Examples 1 to 2 that the surface tension of the negative electrode paste in Comparative Example 1 is still relatively large, the hardness of the negative electrode sheet is relatively high, and the initial energy efficiency of the lithium-ion battery is relatively low. This may be because the effect of 1,3-butanediol on reducing the surface tension of the negative electrode paste is limited. Therefore, the reduction degree of the brittleness of the negative electrode sheet is limited. Moreover, the volatility of this type of additive is relatively good, and an additional investment in a recovery system is required. Otherwise, it will cause environmental pollution. The surface tension of the negative electrode paste in Comparative Example 2 is relatively large, the hardness of the negative electrode sheet is relatively high, and the initial energy efficiency of the lithium-ion battery is relatively low. This may be because the degree of polymerization of the compound shown in formula (II) is too low, which is not conducive to reducing the brittleness of the negative electrode sheet. It can be seen from Example 1, Examples 7 to 9, and Comparative Examples 3 to 4 that when the content of the compound shown in formula (I) is too low (such as Comparative Example 3), the surface tension of the negative electrode paste is still relatively high, the hardness of the negative electrode sheet is still relatively high, the reduction effect on the brittleness of the negative electrode sheet is not obvious, and there is still a high risk of cracking of the negative electrode sheet. The initial energy efficiency of the lithium-ion battery is relatively low. When the content of the compound shown in formula (I) is too high (such as Comparative Example 4), although the surface tension of the negative electrode paste 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 relatively low. The negative electrode sheet of the present application contains the compound shown in formula (I). By adjusting the content of the compound shown in formula (I) within the scope of the present application, the surface tension of the negative electrode paste is reduced, the hardness of the negative electrode sheet is reduced, and the initial energy efficiency of the lithium-ion battery is improved. Thereby, the brittleness of the negative electrode sheet is reduced, the cracking risk of the negative electrode sheet is reduced, and the initial energy efficiency of the lithium-ion battery is improved.

[0109] The type of the compound shown in formula (I) and the content of the compound shown in formula (I) usually also affect the performance of the negative electrode sheet. It can also be seen from Examples 1 to 14 that by adjusting the type and content of the compound shown in formula (I) within the scope of the present application, it is beneficial to reduce the brittleness of the negative electrode sheet, reduce the cracking risk of the negative electrode sheet, and improve the initial energy efficiency of the lithium-ion battery.

[0110] Figure 3 is a photograph of the negative electrode sheet prepared in Example 1. From Figure 3 it can be seen that the surface of its negative electrode sheet is relatively flat and there is no cracking phenomenon; Figure 4 is a photograph of the negative electrode sheet prepared in Comparative Example 1. From Figure 4 it can be seen that cracks appear on the surface of its negative electrode sheet.

[0111] 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 herein 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, 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, 3≤n≤10, 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%; The relative molecular mass of the compound represented by formula (I) is M1, 190≤M1≤600.

2. 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: 、 、 、 、 、 、 、 、 、 、 。 3. 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%.

4. 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.

5. 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.

6. 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.

7. A battery, characterized in that: The negative electrode sheet comprises the negative electrode sheet as described in any one of claims 1 to 6.

8. An energy storage device, characterized in that: The invention comprises a casing and at least one battery according to claim 7, wherein the battery is accommodated in the casing.

9. An electrical device, characterized in that: It includes the energy storage device as described in claim 8, and the energy storage device supplies power to the electrical equipment.

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