Secondary battery and preparation method therefor, and electric device

Abstract

A secondary battery and a preparation method therefor, and an electric device. The secondary battery comprises a positive electrode sheet and a negative electrode sheet; the positive electrode sheet and / or the negative electrode sheet comprise a current collector (10) and an active material layer (11); the active material layer (11) is provided on at least one side of the current collector (10); the active material layer (11) comprises an additive, and the additive is provided with through holes; and the tortuosity of the active material layer (11) is 1.9-5.68. In this way, the transmission path of an electrolyte can be shortened, and the transmission rate of the electrolyte on the positive electrode sheet and / or the negative electrode sheet can be increased, thereby improving the infiltration effect of the electrolyte on the electrode sheet, improving the exertion of a capacity per gram of the electrode sheet, and improving the rate performance and the energy density of batteries.

Description

Secondary battery and preparation method thereof, and electrical equipment Technical Field

[0001] The present application relates to the field of batteries, and in particular, to secondary batteries and methods for preparing the same, as well as electrical equipment. Background Art

[0002] Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. In order to increase the transmission rate of the electrolyte on the electrode, it is necessary to form pores in the active material layer. Currently, the transmission rate of the electrolyte on the electrode in the battery is slow, especially for thick electrodes. The electrolyte infiltration effect on the part of the active material layer close to the current collector is poor, which reduces the battery's rate performance and energy density.

[0003] Summary of the Invention

[0004] In view of the technical problems existing in the background technology, the present application provides a secondary battery that can increase the transmission rate of the electrolyte and improve the rate performance and energy density of the battery.

[0005] The first aspect of the present application provides a secondary battery comprising: a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet comprises: a current collector; and an active material layer, wherein the active material layer is disposed on at least one side of the current collector, the active material layer comprises an additive, the additive has a through hole, and the tortuosity of the active material layer is 1.9-5.68. This shortens the electrolyte transmission path and increases the electrolyte transmission rate, thereby improving the electrolyte's infiltration effect on the electrode sheet, increasing the electrode sheet's specific capacity, and thereby improving the battery's rate performance and energy density.

[0006] According to some embodiments of the present application, the tortuosity of the active material layer on the positive electrode plate is 1.9-5.6. Thus, by forming through holes in the active material layer to reduce the tortuosity of the active material layer, the transmission rate of the electrolyte on the positive electrode plate is increased, thereby improving the electrolyte infiltration effect on the positive electrode plate, improving the specific capacity of the positive electrode plate, and thus improving the rate performance and energy density of the battery.

[0007] According to some embodiments of the present application, the tortuosity of the active material layer on the negative electrode plate is 1.62-5.68. Thus, by forming through holes in the active material layer to reduce the tortuosity of the active material layer, the transmission rate of the electrolyte on the negative electrode plate is increased, thereby improving the electrolyte infiltration effect on the negative electrode plate, improving the specific capacity of the negative electrode plate, and thus improving the rate performance and energy density of the battery.

[0008] According to some embodiments of the present application, the additive accounts for 0.5% to 10% of the total mass of the active material layer. By ensuring the additive content is within the above range, the number of through-holes in the active material layer can be further increased, thereby increasing the electrolyte transmission rate, thereby improving the electrolyte's wetting effect on the electrode, increasing the electrode's specific capacity, and thus improving the battery's rate performance and energy density.

[0009] According to some embodiments of the present application, the additive satisfies one or more of the following conditions: the diameter of the through-hole is 100 nm to 500 nm; the length of the through-hole is 1 μm to 20 μm. This improves the liquid-phase mass transfer capacity of the through-hole and increases the electrolyte transfer rate.

[0010] According to some embodiments of the present application, the additive includes whisker carbon nanotubes. Thus, the additive has a through-hole structure, which can increase the transmission rate of the electrolyte, thereby improving the electrolyte's infiltration effect on the electrode, increasing the specific capacity of the electrode, and thus improving the battery's rate performance and energy density.

[0011] According to some embodiments of the present application, the thickness of the active material layer on the positive electrode sheet is greater than or equal to 300 μm; or the thickness of the active material layer on the negative electrode sheet is between 120 μm and 210 μm. Therefore, when the active material layer is thicker, the through-hole structure of the active material layer can increase the electrolyte transmission rate, improve the electrolyte infiltration effect on the active material layer near the current collector, and improve the specific capacity of the electrode, thereby improving the rate performance and energy density of the battery.

[0012] According to some embodiments of the present application, the porosity of the positive electrode sheet and / or the negative electrode sheet is 20%-47%, thereby improving the transmission rate of the electrolyte.

[0013] According to some embodiments of the present application, the active material layer includes a first active material layer and a second active material layer, wherein the first active material layer is disposed on at least one side of the current collector, and the second active material layer is disposed on a side of the first active material layer away from the current collector, and the second active material layer contains the additive. Thus, by disposing the additive in the second active material layer, a concentration difference exists between the ions in the second active material layer and the first active material layer, which can further increase the rate of the electrolyte and improve the electrolyte's wetting effect on the electrode.

[0014] According to some embodiments of the present application, the thickness of the second active material layer is greater than or equal to the thickness of the first active material layer.

[0015] According to some embodiments of the present application, a ratio of the thickness of the second active material layer to the thickness of the first active material layer is 1.2-1.4.

[0016] Therefore, by making the thickness of the second active material layer and the thickness of the first active material layer satisfy the above relationship, the wetting effect of the electrolyte on the first active material layer can be improved, thereby increasing the specific capacity of the electrode and improving the energy density of the battery.

[0017] According to some embodiments of the present application, the active material layer of the negative electrode plate includes the additive, thereby increasing the electrolyte transfer rate on the negative electrode plate and improving the rate performance of the battery.

[0018] The second aspect of the present application provides a method for preparing a secondary battery, comprising: preparing a positive electrode sheet and / or a negative electrode sheet, and the method for preparing the positive electrode sheet and / or the negative electrode sheet comprises: forming an active material layer on at least one side of a current collector, the active material layer comprising an additive, the additive having a through hole, and the tortuosity of the active material layer being 1.9-5.68. Thus, the secondary battery prepared by this method has all the features and advantages of the secondary battery provided in the first aspect of the present application, which will not be repeated here. In general, it has at least excellent rate performance and high energy density.

[0019] According to some embodiments of the present application, the method for forming the active material layer includes: forming a first active material layer on at least one side of the current collector; and forming a second active material layer on a side of the first active material layer away from the current collector, wherein the second active material layer includes the additive. This further increases the electrolyte transmission rate and improves the electrolyte's wetting effect on the electrode sheet.

[0020] A third aspect of the present application provides an electrical device, comprising the secondary battery provided in the first aspect of the present application.

[0021] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0023] FIG1 is a schematic structural diagram of a positive electrode sheet or a negative electrode sheet according to an embodiment of the present application;

[0024] FIG2 is a schematic structural diagram of a pole piece according to another embodiment of the present application.

[0025] FIG3 is a SEM image of whisker carbon nanotubes.

[0026] FIG4 is a schematic diagram of a battery according to an embodiment of the present application.

[0027] FIG. 5 is an exploded view of the battery shown in FIG. 4 according to an embodiment of the present application.

[0028] FIG6 is a schematic diagram of a battery module according to an embodiment of the present application.

[0029] FIG7 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0030] FIG8 is an exploded view of the battery pack shown in FIG7 according to an embodiment of the present application.

[0031] FIG9 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0032] Explanation of the reference numerals: 1: positive electrode sheet; 1': negative electrode sheet; 10: current collector; 11: active material layer; 111: first active material layer; 112: second active material layer; 6: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery; 51: casing; 52: electrode assembly; 53: cover plate. DETAILED DESCRIPTION

[0033] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0034] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0038] Currently, market developments indicate that batteries are increasingly being used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing.

[0039] In order to increase the transmission rate of the electrolyte on the electrode, it is necessary to form pores in the active material layer. In the related art, pores are mainly formed by adding ammonium bicarbonate pore formers and azo pore formers to the active material layer. The air channels generated after the decomposition of the pore former can be used as pores for electrolyte transmission. However, the pores formed in this way are tortuous, which increases the length of the electrolyte transmission path, reduces the ion transmission rate, and reduces the wetting effect on the active material layer. In particular, when the thickness of the active material layer on the electrode is relatively thick, the electrolyte infiltration effect of the part of the active material layer close to the current collector is poor, which reduces the utilization of the electrode capacity, thereby reducing the rate performance and energy density of the battery.

[0040] The secondary battery provided by the present application includes an additive with a through hole in the active material layer on the positive electrode sheet and / or the negative electrode sheet. The through hole can be directly used for electrolyte transmission. Compared with the tortuous channel formed by the pore-forming agent, the through hole has a small degree of curvature, which shortens the path of electrolyte transmission on the positive electrode sheet and / or the negative electrode sheet, increases the transmission rate of the electrolyte, and is more conducive to the backflow of the electrolyte. The acceleration of the transmission rate can improve the wetting effect of the electrolyte on the active material layer, reduce liquid phase polarization, thereby improving the utilization rate of the active material, improving the gram capacity of the positive electrode sheet and / or the negative electrode sheet, and thus improving the energy density and rate performance of the battery. Due to the accelerated transmission rate of the electrolyte, the low temperature performance of the battery can also be improved.

[0041] The secondary battery proposed in this application includes a lithium-ion battery or a sodium-ion battery, and the secondary battery disclosed in the embodiments of this application can be used in electrical equipment that uses a secondary battery as a power source or various energy storage systems that use a battery as an energy storage element. Electrical equipment may include but is not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0042] In a first aspect, the present application provides a secondary battery, comprising a positive electrode sheet 1 and a negative electrode sheet 1', wherein the positive electrode sheet 1 and / or the negative electrode sheet 1' comprises a current collector 10: an active material layer 11, wherein the active material layer 11 is arranged on at least one side of the current collector 10, the active material layer 11 comprises an additive, the additive has a straight through hole, and the tortuosity of the active material layer 11 is 1.9-5.68. Thus, by providing an additive having through-holes within the active material layer 11 of the positive electrode sheet 1 and / or the negative electrode sheet 1', the tortuosity of the active material layer 11 can be reduced, and the electrolyte is directly transmitted through the through-holes, shortening the transmission path of the electrolyte on the positive electrode sheet 1 and / or the negative electrode sheet 1' and increasing the electrolyte transmission rate. This can improve the electrolyte's wetting effect on the positive electrode sheet 1 and / or the negative electrode sheet 1', reduce liquid phase polarization, and thereby improve the utilization rate of the active material, increase the gram capacity of the positive electrode sheet 1 and / or the negative electrode sheet 1', and thereby improve the battery's rate performance and energy density. Due to the accelerated electrolyte transmission rate, the low-temperature performance of the battery can also be improved.

[0043] In the present application, a through hole refers to a hole with a diameter change rate of ≤5% and a curvature of ≤10% in the extending direction of the through hole.

[0044] In this application, tortuosity refers to the degree of curvature of the electrolyte transmission path of the porous electrode. The tortuosity of the active material layer 11 is tested by measuring the pore ion resistance Rion by a symmetrical cell, and calculating the tortuosity τ based on the porosity, electrode thickness and electrolyte conductivity, τ = (Rion × A × ε × σ) / d, where Rion is the pore ion resistance and A is the electrode area in cm 2 , ε is the porosity, the unit is %, σ is the conductivity, the unit is ms / cm, d is the electrode thickness, the unit is cm.

[0045] According to some embodiments of the present application, the tortuosity of the active material layer 11 is 1.9-5.68, for example, it can be 1.9, 2.51, 3.02, 3.53, 4.12, 4.57, 5.12 or 5.68, or it can be a range composed of any of the above values. Therefore, controlling the tortuosity of the active material 11 within the above range can shorten the transmission path of the electrolyte, increase the transmission rate of the electrolyte, improve the infiltration effect of the electrolyte on the active material layer 11, and improve the rate performance and energy density of the battery. According to some specific embodiments of the present application, the tortuosity of the active material layer 11 is 1.9-4.26.

[0046] According to some embodiments of the present application, based on the total mass of the active material layer 11, the mass proportion of the additive can be 0.5%-10%. For example, it can be 0.5%, 1%, 3%, 5%, 7%, 9% or 10%, etc., or it can be a range composed of any of the above values. Therefore, by making the content of the additive within the above range, the number of through holes on the active material layer 11 can be further increased, the transmission rate of the electrolyte can be increased, thereby improving the wetting effect of the electrolyte on the electrode 1, improving the utilization of the 1 gram capacity of the electrode, and thus improving the rate performance and energy density of the battery.

[0047] In this application, the test method for the content of additives is thermogravimetric testing. Specifically, under a nitrogen atmosphere, the air flow rate is 50 ml / min, the temperature is increased from room temperature to 2000°C, and the heating rate is 20°C / min. The content of the additive is obtained based on the mass ratio of the decomposition characteristic peak.

[0048] According to some embodiments of the present application, the diameter of the through-hole can be 100 nm to 500 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, or a range of any of the above values. This allows the through-hole to have liquid-phase mass transfer capabilities while increasing the transfer rate of the electrolyte on the electrode 1, thereby improving the electrolyte's infiltration effect on the active material layer 11, and increasing the capacity of the electrode per gram, thereby improving the rate performance and energy density of the battery.

[0049] In this application, the aperture of a through hole refers to the diameter of the hole on the cross section of the through hole. The aperture of the through hole can be tested by scanning electron microscopy.

[0050] According to some embodiments of the present application, the length of the through hole is 1 μm-20 μm, for example, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm or 20 μm, or a range of any of the above values. Thus, by making the length of the through hole within the above range, the transmission rate of the electrolyte on the active material layer 11 can be increased, thereby improving the electrolyte infiltration effect on the active material layer 11, improving the capacity of the electrode per gram, and thus improving the rate performance and energy density of the battery.

[0051] In the present application, the length of the through hole can be measured by a scanning electron microscope.

[0052] According to some embodiments of the present application, the additive includes whisker carbon nanotubes. Thus, the above-mentioned type of additive has a through-hole structure, and the through-hole can be directly used for electrolyte transmission, shortening the transmission path of the electrolyte and increasing the transmission rate of the electrolyte, thereby improving the electrolyte's wetting effect on the positive electrode plate 1 and / or the negative electrode plate 1', reducing liquid phase polarization, and thereby improving the utilization rate of active materials, improving the gram capacity of the positive electrode plate 1 and / or the negative electrode plate 1', and thereby improving the battery's rate performance and energy density. Due to the accelerated transmission rate of the electrolyte, the low-temperature performance of the battery can also be improved.

[0053] According to some embodiments of the present application, the thickness of the active material layer on the positive electrode plate 1 is greater than or equal to 300 μm; or the thickness of the active material layer on the negative electrode plate 1 'is 1200 μm-210 μm. For example, the thickness of the active material layer on the positive electrode plate 1 can be 300 μm, 330 μm, 360 μm, 390 μm, 420 μm, 450 μm, 480 μm, or 500 μm, or can be any range of the above values; the thickness of the active material layer on the negative electrode plate 1 'can be 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, or 210 μm, or can be any range of the above values. At this time, although the active material layer 11 is relatively thick, because the additives in the active material layer 11 have a through-hole structure, the through-holes can be directly used for electrolyte transmission, shortening the electrolyte transmission path and increasing the electrolyte transmission rate. This can improve the electrolyte's wetting effect on the positive electrode sheet 1 and / or the negative electrode sheet 1', and in particular, can improve the electrolyte's wetting effect on the portion of the active material layer 11 near the current collector 10, reducing liquid phase polarization, thereby improving the utilization rate of the active material, and increasing the gram capacity of the positive electrode sheet 1 and / or the negative electrode sheet 1', thereby improving the battery's rate performance and energy density. Due to the accelerated electrolyte transmission rate, the low-temperature performance of the battery can also be improved.

[0054] According to some embodiments of the present application, the porosity of the positive electrode sheet 1 and / or the negative electrode sheet 1' can be 20%-47%. For example, it can be 20%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45% or 47%, etc., or can be a range composed of any of the above values. Therefore, by making the porosity of the positive electrode sheet 1 and / or the negative electrode sheet 1' within the above range, the transmission path of the electrolyte can be increased, thereby increasing the transmission rate of the electrolyte on the positive electrode sheet 1 and / or the negative electrode sheet 1', improving the infiltration effect of the electrolyte on the active material layer 11, improving the utilization rate of the active material, and thus improving the rate performance and energy density of the battery.

[0055] In this application, the porosity test method involves pre-treatment: 30 discs with good appearance and no powdering on the edges are selected and placed in a sample cup. The number of discs is recorded and the apparent volume is calculated. Testing: The sample cup containing the sample is placed in a true density tester. The test system is sealed, and helium is introduced according to the program. The pressure of the gas in the sample chamber and expansion chamber is measured, and the true volume is calculated according to Bohr's law (PV = nRT) to obtain the porosity of the sample.

[0056] According to some embodiments of the present application, the active material layer 11 may include a first active material layer 111 and a second active material layer 112. The first active material layer 111 is disposed on at least one side of the current collector 10, and the second active material layer 112 is disposed on a side of the first active material layer 111 away from the current collector 10. The second active material layer 112 contains the additive. Thus, by having the additive in the second active material layer 112, the electrolyte transfer rate in the second active material layer 112 is greater than the transfer rate in the first active material layer 111, and the ion concentration in the second active material layer 112 is greater than the ion concentration in the first active material layer 111. That is, there is a concentration difference between the ions in the second active material layer 112 and the first active material layer 111. This concentration difference can further increase the electrolyte transfer rate and improve the electrolyte's wetting effect on the first active material layer 111, thereby improving the utilization rate of the active material in the first active material layer 111, increasing the capacity per gram of the electrode, and thereby improving the rate performance and energy density of the battery.

[0057] According to some embodiments of the present application, the thickness of the second active material layer 112 is greater than or equal to the thickness of the first active material layer 111. In other words, the ratio of the thickness of the active material layer 11 provided with the additive to the thickness of the entire active material layer 11 is greater than or equal to 0.5. This increases the mass proportion of the additive in the entire active material layer 11, increases the number of through-holes, and thus increases the number of electrolyte transmission paths, increases the electrolyte transmission rate, and thus improves the rate performance and energy density of the battery. According to some specific embodiments of the present application, the ratio of the thickness of the second active material layer 112 to the thickness of the first active material layer 111 is 1.2-1.4.

[0058] In the present application, the thickness of the active material layer 11 can be measured by scanning electron microscopy.

[0059] According to some embodiments of the present application, the active material layer of the negative electrode plate 1' includes the additive. By providing the additive with through-holes within the negative electrode active material layer 11 of the negative electrode plate 1', the electrolyte transfer rate and ion transfer rate on the negative electrode plate 1' can be increased, thereby improving the battery's rate performance and the battery's fast charging capability.

[0060] The second aspect of the present application provides a method for preparing a secondary battery, including preparing a positive electrode plate 1 and a negative electrode plate 1', and the method for preparing the positive electrode plate 1 and / or the negative electrode plate 1' includes: forming an active material layer 11 on at least one side of a current collector 10, the active material layer 11 including an additive, the additive having a straight-through hole, and the tortuosity of the active material layer 11 is 1.9-5.68. Therefore, the positive electrode plate 1 and / or the negative electrode plate 1' prepared by this method only need to provide an additive with a straight-through hole structure in the active material layer 11 to reduce the tortuosity of the active material layer 11, and the electrolyte is directly transmitted through the straight-through hole, which can shorten the path of electrolyte transmission, and does not require pore formation through other process means, which can reduce damage to the positive electrode plate 1 and / or the negative electrode plate 1'.

[0061] According to some embodiments of the present application, when the active material layer 11 includes a first active material layer 111 and a second active material layer 112, the method of forming the active material layer 11 includes: forming the first active material layer 111 on at least one side of the current collector 10; and forming the second active material layer 112 on a side of the first active material layer 111 away from the current collector 10, wherein the second active material layer 112 includes the additive. This further improves the electrolyte transmission rate and the electrolyte's wetting effect on the incoming sheet.

[0062] Specifically, slurries of the first active material layer 111 and the second active material layer 112 may be separately formed, simultaneously coated on the current collector 10 , and dried to form the first active material layer 111 and the second active material layer 112 .

[0063] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0064] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material of the first aspect of the present application.

[0065] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0066] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0067] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may adopt the positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0068] In some embodiments, such as when the battery is a sodium ion battery, the positive electrode active material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analogue, as examples.

[0069] Examples of the layered transition metal oxides include:

[0070] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 One or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0071] Na 0.67 Mn 0.7 Ni z M2 0.3-z O2, where M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, and 0 < z ≤ 0.1;

[0072] Na a Li b Ni c Mn d Fe e O2, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, and b + c + d + e = 1.

[0073] As an example of the above polyanion compound, for example, the following can be listed:

[0074] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 is one or more of H, Li, Na, K and NH4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 is one or more of F, Cl and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0075] Na n M 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu and Zn, X 2 is one or more of F, Cl and Br, 0 < n ≤ 2;

[0076] Na p M 5 q (SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0077] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2 or 3.

[0078] Examples of the above Prussian blue analogues include, for example:

[0079] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + , NH4 + , one or more of alkali metal cations and alkaline earth metal cations, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Ra 2+ one or more of, and M 6 and M 7 are each independently cations of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn and W.

[0080] The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0081] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorinated acrylate resin.

[0082] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0083] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0084] [Negative electrode]

[0085] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0086] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0087] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. When the battery is a lithium-ion battery, lithium titanate is used as the titanate; when the battery is a sodium-ion battery, sodium titanate is used as the titanate. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0090] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0093] [Electrolytes]

[0094] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0095] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0096] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0097] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0098] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0099] In some embodiments, the electrolyte may optionally include negative electrode film-forming additives, positive electrode film-forming additives, and other additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0100] [Isolation film]

[0101] In some embodiments, the battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0102] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0103] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0104] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0105] In some embodiments, the battery outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the battery outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0106] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG4 shows a square-structured battery 5 as an example.

[0107] In some embodiments, referring to Figure 5, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0108] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0109] FIG6 shows an example battery module 4. Referring to FIG6 , within the battery module 4, multiple batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, the arrangement may also be arranged in any other manner. Furthermore, the multiple batteries 5 may be secured using fasteners.

[0110] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of batteries 5 are received in the receiving space.

[0111] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0112] Figures 7 and 8 illustrate an example battery pack 6. Referring to Figures 7 and 8 , the battery pack 6 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0113] In addition, the present application also provides an electric device, which includes at least one of the batteries, battery modules, or battery packs provided in the present application. The battery, battery module, or battery pack can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0114] As the electrical device, a battery, a battery module or a battery pack can be selected according to its usage requirements.

[0115] Figure 9 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0116] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0117] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0118] Example 1

[0119] 1. Preparation of negative electrode sheet

[0120] SiC, superconducting carbon (SuperP), whisker carbon nanotubes, and polyacrylate lithium (PAALi) are added to the solvent deionized water in a mass ratio of 91.8%: 1.1%: 5%: 2.1%, and stirred evenly under the action of a vacuum mixer. The slurry has a solid content of 45%, and is coated on the negative electrode current collector copper foil. After oven drying and cold pressing, the negative electrode sheet can be obtained. The thickness of the negative electrode active material layer is 201 μm.

[0121] 2. Preparation of positive electrode sheet

[0122] NCM96 (Ni 0.94 Co 0.03 Mn 0.03 O2), SuperP, and PVDF are added to NMP in a mass ratio of 96%:2.6%:1.4%, stirred evenly under the action of a vacuum mixer, coated on both sides of the aluminum foil, dried in an oven, and cold pressed to obtain a positive electrode sheet. The thickness of the positive electrode active material layer is 436μm.

[0123] 3. Prepare electrolyte

[0124] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. The fully dried electrolyte salt LiPF6 was dissolved in the above solvent and mixed evenly to obtain an electrolyte solution with a concentration of 1 mol / L.

[0125] 4. Isolation film

[0126] A porous polyethylene film was used as the separator.

[0127] 5. Preparation of batteries

[0128] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery is obtained.

[0129] Example 2, Comparative Example 1, and the preparation methods of the batteries in Comparative Example 2 and Example 1 are the same as those in Example 1, with the differences detailed in Table 1.

[0130] Example 3

[0131] 1. Preparation of negative electrode sheet

[0132] SiC, superconducting carbon (SuperP), and lithium polyacrylate (PAALi) were added to deionized water as a solvent in a mass ratio of 96.8%: 1.1%: 2.1%, and stirred evenly under the action of a vacuum mixer. The slurry had a solid content of 45%, and was coated on the negative electrode current collector copper foil and dried in an oven to form a first active material layer. The thickness of the first active material layer was 61 μm.

[0133] SiC, superconducting carbon (SuperP), whisker carbon nanotubes, and polyacrylate lithium (PAALi) are added to deionized water as a solvent in a mass ratio of 96.5%: 1.1%: 0.3%: 2.1%, stirred evenly under the action of a vacuum mixer, and coated on the side of the first active material layer away from the copper foil to form a second active material layer. After oven drying and cold pressing, the negative electrode sheet can be obtained. The thickness of the second active material layer is 140 μm.

[0134] 2. Preparation of positive electrode sheet

[0135] NCM96 (Ni 0.94 Co 0.03 Mn 0.03O2), SuperP, and PVDF are added to NMP in a mass ratio of 96%:2.6%:1.4%, stirred evenly under the action of a vacuum mixer, coated on both sides of the aluminum foil, dried in an oven, and cold pressed to obtain a positive electrode sheet. The thickness of the positive electrode active material layer is 436μm.

[0136] 3. Prepare electrolyte

[0137] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. The fully dried electrolyte salt LiPF6 was dissolved in the above solvent and mixed evenly to obtain an electrolyte solution with a concentration of 1 mol / L.

[0138] 4. Isolation film

[0139] A porous polyethylene film was used as the separator.

[0140] 5. Preparation of batteries

[0141] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery is obtained.

[0142] The preparation methods of the batteries in Examples 4 to 12 are the same as those in Example 3, with the differences detailed in Table 2.

[0143] Example 13

[0144] 1. Preparation of negative electrode sheet

[0145] SiC, superconducting carbon (SuperP), and lithium polyacrylate (PAALi) are added to the solvent deionized water in a mass ratio of 96.8%:1.1%:2.1%, and stirred evenly under the action of a vacuum mixer. The slurry has a solid content of 45%. It is coated on the negative electrode current collector copper foil, dried in an oven, and cold pressed to obtain a negative electrode sheet. The thickness of the negative electrode active material layer is 201 μm.

[0146] 2. Preparation of positive electrode sheet

[0147] NCM96, superconducting carbon (SuperP), and PVDF were added to the solvent deionized water in a mass ratio of 96%:2.6%:1.4%, and stirred evenly under the action of a vacuum mixer. The slurry had a solid content of 72%, and was coated on the negative electrode current collector copper foil and dried in an oven to form a first active material layer. The thickness of the first active material layer was 136 μm.

[0148] NCM96, superconducting carbon (SuperP), whisker carbon nanotubes, and PVDF are added to the solvent deionized water in a mass ratio of 95.7%:2.6%:0.3%:1.4%, stirred evenly under the action of a vacuum mixer, and coated on the side of the first active material layer away from the copper foil to form a second active material layer. After oven drying and cold pressing, the negative electrode sheet can be obtained. The thickness of the second active material layer is 300 μm.

[0149] 3. Prepare electrolyte

[0150] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. The fully dried electrolyte salt LiPF6 was dissolved in the above solvent and mixed evenly to obtain an electrolyte solution with a concentration of 1 mol / L.

[0151] 4. Isolation film

[0152] A porous polyethylene film was used as the separator.

[0153] 5. Preparation of batteries

[0154] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery is obtained.

[0155] The preparation methods of the batteries in Examples 14 to 22 are the same as those in Example 13, with the differences detailed in Table 3.

[0156] Performance testing:

[0157] 1. Active material layer thickness test method

[0158] Testing with a scanning electron microscope

[0159] 2. Active material layer tortuosity test method

[0160] The Rion pore ion resistance is measured by a symmetrical battery, and the tortuosity τ is calculated based on the porosity, electrode thickness and electrolyte conductivity. τ = (Rion × A × ε × σ) / d, where Rion is the pore ion resistance and A is the electrode area in cm 2, ε is the porosity, the unit is %, σ is the conductivity, the unit is ms / cm, d is the electrode thickness, the unit is cm.

[0161] 3. Electrode porosity test method

[0162] Select 30 discs with good appearance and no powdering on the edges and place them in a sample cup. Record the number of discs and calculate the apparent volume. Testing: Place the sample cup containing the sample in a true density tester. Close the test system and introduce helium according to the program. By measuring the gas pressure in the sample chamber and expansion chamber, calculate the true volume according to Bohr's law (PV = nRT) to obtain the porosity of the sample.

[0163] 4. Rate performance test method

[0164] The stacked three-electrode test method is to remove the positive and negative electrode sheets and soak them in DMC solvent for more than 72 hours. After the electrolyte solvent, lithium salt, and additives are completely leached, the sheets are dried in a vacuum oven. The positive and negative electrode sheets are then assembled into a stacked three-electrode battery cell, in which copper wire is used as the reference electrode. At 25°C, the lithium deposition charge rate of the stacked cell is tested at each SOC. The maximum charge rate is recorded when the reference electrode potential drops to 0mV. According to this method, with 5% SOC as a point, the maximum charge rate at each 5% SOC is tested, such as 20% SOC, 25% SOC, 30% SOC to 100% SOC. The continuous charging time at 20% SOC-80% SOC is calculated according to the maximum charge rate at 20% SOC-80% SOC obtained from this test, which is the fast charging time.

[0165] 5. Energy density test method

[0166] Battery Cell Capacity Test: The prepared battery cell was allowed to stand at 25°C for 2 hours, ensuring the cell temperature was 25°C. At 25°C, the battery cell was charged at 0.1C to the charge cutoff voltage. Constant voltage charging was then continued at the same charge cutoff voltage until the current reached 0.05C, at which point the charge was cutoff (where C represents the rated capacity of the battery cell). The battery cell was allowed to stand at 25°C for 1 hour. At 25°C, the battery cell was discharged at 0.1C to the discharge cutoff voltage. The total discharge capacity (C0) released by the battery cell was recorded, and the total discharge energy (E0) was recorded.

[0167] Battery cell weight measurement: Place the battery cell on an electronic balance until the weight stabilizes, and read the battery cell weight value M0.

[0168] Energy density calculation: Battery cell discharge energy E0 / battery cell weight M0 is the energy density of the battery cell.

[0169] The test results of Comparative Example, Comparative Example 2, Example 1 and Example 2 are shown in Table 4.

[0170] The test results of Example 3 to Example 12 are shown in Table 5.

[0171] The test results of Examples 13 to 22 are shown in Table 6.

[0172] Table 4

[0173] Table 5

[0174] Table 6

[0175] Conclusion: It can be seen from Tables 1 to 6 that the electrode proposed in this application can improve the rate performance and energy density of the battery, which means that by arranging an additive with a through hole on the electrode, the transmission path of the electrolyte can be shortened and the transmission rate of the electrolyte can be increased. The accelerated transmission rate can accelerate the infiltration effect of the electrolyte on the active material layer for electrodes with a thicker active material layer, thereby improving the utilization rate of the active material.

[0176] It can be seen from the comparison of Examples 3 to 22 with Examples 1 and 2 that, whether it is the positive electrode sheet or the negative electrode sheet, the active material layer is designed in a layered manner, and the additives are set in the active material layer away from the current collector, which can further improve the rate performance of the battery compared to the active material layer not being layered (the additives are set in the entire active material layer).

[0177] It can be seen from the comparison between Examples 3 to 12 and Examples 13 to 22 that placing the additive on the negative electrode plate can further improve the rate performance of the battery.

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A secondary battery, wherein: include: A positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet comprises: Current collector: An active material layer is provided on at least one side of the current collector, the active material layer comprises an additive, the additive has straight through holes, and the tortuosity of the active material layer is 1.9-5.

68.

2. The secondary battery according to claim 1, wherein The tortuosity of the active material layer on the positive electrode sheet is 1.9-5.

6.

3. The secondary battery according to claim 1 or 2, wherein The tortuosity of the active material layer on the negative electrode plate is 1.62-5.

68.

4. The secondary battery according to any one of claims 1 to 3, wherein: Based on the total mass of the active material layer, the mass proportion of the additive is 0.5%-10%.

5. The secondary battery according to any one of claims 1 to 4, wherein: One or more of the following conditions are met: The through hole has a diameter of 100 nm to 500 nm; The through hole has a length of 1 μm-20 μm.

6. The secondary battery according to any one of claims 1 to 5, wherein: The additive includes whisker carbon nanotubes.

7. The secondary battery according to any one of claims 1 to 6, wherein: The thickness of the active material layer on the positive electrode sheet is greater than or equal to 300 μm; or The thickness of the active material layer on the negative electrode sheet is 120 μm-210 μm.

8. The secondary battery according to any one of claims 1 to 7, wherein: The porosity of the positive electrode sheet and / or the negative electrode sheet is 20%-47%.

9. The secondary battery according to any one of claims 1 to 8, wherein: The active material layer includes a first active material layer and a second active material layer. The first active material layer is disposed on at least one side of the current collector, and the second active material layer is disposed on a side of the first active material layer away from the current collector. The second active material layer contains the additive.

10. The secondary battery according to claim 9, wherein The thickness of the second active material layer is greater than or equal to the thickness of the first active material layer.

11. The secondary battery according to claim 9 or 10, wherein The ratio of the thickness of the second active material layer to the thickness of the first active material layer is 1.2-1.

4.

12. The secondary battery according to any one of claims 1 to 11, wherein: The active material layer of the negative electrode sheet includes the additive.

13. A method for preparing the secondary battery according to any one of claims 1 to 12, wherein: include: The positive electrode sheet and the negative electrode sheet are prepared. The method for preparing the positive electrode sheet and / or the negative electrode sheet includes: An active material layer is formed on at least one side of a current collector, wherein the active material layer includes an additive, the additive has straight through holes, and the tortuosity of the active material layer is 1.9-5.

68.

14. The method according to claim 13, wherein The method of forming the active material layer includes: forming a first active material layer on at least one side of the current collector; A second active material layer is formed on a side of the first active material layer away from the current collector, wherein the second active material layer includes the additive.

15. An electrical device, wherein: A secondary battery comprising the secondary battery according to any one of claims 1 to 12.

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