Secondary battery, preparation method thereof and electric equipment

Abstract

The invention discloses a secondary battery and a preparation method thereof and electric equipment, the secondary battery comprises a positive pole piece and a negative pole piece, the positive pole piece and / or the negative pole piece comprises a current collector and an active material layer, the active material layer is arranged on at least one side of the current collector, the active material layer comprises an additive, and the additive is arranged on the active material layer. The additive is provided with a straight through hole, and the tortuosity of the active material layer is 1.9-5.68. Therefore, the transmission path of the electrolyte is shortened, and the transmission rate of the electrolyte on the positive pole piece and / or the negative pole piece is improved, so that the infiltration effect of the electrolyte on the pole pieces is improved, the gram volume of the pole pieces is improved, and the rate capability and the energy density of the battery are further improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and specifically, to secondary batteries, their preparation methods, and electrical equipment. Background Art

[0002] Batteries are not only applied to energy storage power systems such as hydraulic, thermal, wind, and solar power stations, but also widely used in electric transportation such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace. In order to improve the transmission rate of the electrolyte on the electrode sheet, pores need to be formed in the active material layer. Currently, the transmission rate of the electrolyte in the battery on the electrode sheet is slow. Especially for thick electrodes, the wetting effect of the electrolyte on the part of the active material layer close to the current collector is poor, reducing the rate performance and energy density of the battery. Summary of the Invention

[0003] In view of the technical problems existing in the background art, the present application provides a secondary battery that can improve the transmission rate of the electrolyte, and improve the rate performance and energy density of the battery.

[0004] A first aspect of the present application provides a secondary battery, including: a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet includes: a current collector; an active material layer provided on at least one side of the current collector, 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. Thereby, the transmission path of the electrolyte is shortened, the transmission rate of the electrolyte is increased, so as to improve the wetting effect of the electrolyte on the electrode sheet, improve the utilization of the specific capacity of the electrode sheet, and further improve the rate performance and energy density of the battery.

[0005] According to some embodiments of the present application, the tortuosity of the active material layer on the positive electrode sheet is 1.9 - 5.6. Thereby, by forming straight through-holes in the active material layer, the tortuosity of the active material layer is reduced, the transmission rate of the electrolyte on the positive electrode sheet is increased, so as to improve the wetting effect of the electrolyte on the positive electrode sheet, improve the utilization of the specific capacity of the positive electrode sheet, and further improve the rate performance and energy density of the battery.

[0006] According to some embodiments of the present application, the tortuosity of the active material layer on the negative electrode sheet is 1.62 - 5.68. Thereby, by forming straight through-holes in the active material layer, the tortuosity of the active material layer is reduced, the transmission rate of the electrolyte on the negative electrode sheet is increased, so as to improve the wetting effect of the electrolyte on the negative electrode sheet, improve the utilization of the specific capacity of the negative electrode sheet, and further improve the rate performance and energy density of the battery.

[0007] According to some embodiments of the present application, based on the total mass of the active material layer, the mass ratio of the additive is 0.5%-10%. Thus, by making the content of the additive within the above range, the number of straight through holes on the active material layer can be further increased, the transmission rate of the electrolyte can be increased, thereby improving the wetting effect of the electrolyte on the electrode sheet, improving the utilization of the specific capacity of the electrode sheet, and further improving the rate performance and energy density of the battery.

[0008] According to some embodiments of the present application, the additive satisfies one or more of the following conditions: the pore diameter of the straight through hole is 100nm-500nm; the length of the straight through hole is 1μm-20μm. Thus, the liquid mass transfer ability of the straight through hole is improved, and the transmission rate of the electrolyte is increased.

[0009] According to some embodiments of the present application, the additive includes whisker carbon nanotubes. Thus, the above-mentioned type of additive has a straight through hole structure, which can increase the transmission rate of the electrolyte, thereby improving the wetting effect of the electrolyte on the electrode sheet, improving the utilization of the specific capacity of the electrode sheet, and further improving the rate performance and energy density of the battery.

[0010] 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 300μm; or the thickness of the active material layer on the negative electrode sheet is 120μm-210μm. Thus, when the thickness of the active material layer is relatively large, due to the straight through hole structure of the active material layer, the transmission rate of the electrolyte can be increased, the wetting effect of the electrolyte on the active material layer near the current collector can be improved, the utilization of the electrode specific capacity can be improved, and further the rate performance and energy density of the battery can be improved.

[0011] According to some embodiments of the present application, the porosity of the positive electrode sheet and / or the negative electrode sheet is 20%-47%. Thus, the transmission rate of the electrolyte is increased.

[0012] According to some embodiments of the present application, the active material layer includes a first active material layer and a second active material layer. The first active material layer is provided on at least one side of the current collector, and the second active material layer is provided on the side of the first active material layer away from the current collector. The second active material layer contains the additive. Thus, by making the additive located in the second active material layer, there is an ion concentration difference between the second active material layer and the first active material layer, which can further increase the rate of the electrolyte and improve the wetting effect of the electrolyte on the electrode sheet.

[0013] 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.

[0014] According to some embodiments of the present application, 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.

[0015] Thus, 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 improving the specific capacity of the electrode sheet and the energy density of the battery.

[0016] According to some embodiments of the present application, the active material layer of the negative electrode sheet includes the additive. Thus, the transmission rate of the electrolyte on the negative electrode sheet is increased, and the rate performance of the battery is improved.

[0017] The second aspect of the present application provides a method for manufacturing a secondary battery, including: manufacturing a positive electrode sheet and / or a negative electrode sheet, and the method for manufacturing the positive electrode sheet and / or the negative electrode sheet includes: forming an active material layer on at least one side of a current collector, the active material layer including an additive, the additive having straight through holes, and the tortuosity of the active material layer being 1.9 - 5.68. Thus, the secondary battery manufactured by this method has all the characteristics and advantages of the secondary battery provided in the first aspect of the present application, which will not be elaborated here. Generally speaking, it has at least excellent rate performance and a relatively high energy density.

[0018] 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; forming a second active material layer on the side of the first active material layer away from the current collector, the second active material layer including the additive. Thus, the transmission rate of the electrolyte is further increased, and the wetting effect of the electrolyte on the electrode sheet is improved.

[0019] The third aspect of the present application provides an electrical device, including the secondary battery provided in the first aspect of the present application.

[0020] The additional aspects and advantages of the present application will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present application. Description of the Drawings

[0021] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0022] Figure 1 is a schematic structural diagram of a positive electrode sheet or a negative electrode sheet according to an embodiment of the present application;

[0023] Figure 2 It is a schematic structural diagram of a pole piece according to another embodiment of the present application.

[0024] Figure 3 It is an SEM image of whisker carbon nanotubes.

[0025] Figure 4 It is a schematic diagram of a battery according to an embodiment of the present application.

[0026] Figure 5 is Figure 4 An exploded view of the battery according to an embodiment of the present application shown in the figure.

[0027] Figure 6 It is a schematic diagram of a battery module according to an embodiment of the present application.

[0028] Figure 7 It is a schematic diagram of a battery pack according to an embodiment of the present application.

[0029] Figure 8 is Figure 7 An exploded view of the battery pack according to an embodiment of the present application shown in the figure.

[0030] Figure 9 It is a schematic diagram of an electrical device using the battery according to an embodiment of the present application as a power source.

[0031] Explanation of reference numerals:

[0032] 1: positive pole piece; 1': negative pole piece; 10: current collector; 11: active material layer; 111: first active material layer; 112: second active material layer; 6: battery pack; 2: upper box body; 3: lower box body; 4: battery module; 5: battery; 51: housing; 52: electrode assembly; 53: top cover assembly. Specific embodiments

[0033] The embodiments of the technical solutions of the present application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, so they are only examples and cannot be used to limit the protection scope of the present application.

[0034] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0035] If there is no special description, 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 new technical solutions.

[0037] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0038] Currently, from the perspective of the development of the market situation, the application of batteries is becoming more and more extensive. Batteries are not only applied to energy storage power systems such as hydraulic, thermal, wind and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in many fields such as military equipment and aerospace. With the continuous expansion of the battery application field, the market demand is also constantly increasing.

[0039] In order to improve the transmission rate of the electrolyte on the electrode sheet, pores need to be formed in the active material layer. In the related art, pores are mainly formed by adding ammonium bicarbonate pore-forming agent and azo pore-forming agent to the active material layer. The air channels generated after the decomposition of the pore-forming agent can be used as pores for electrolyte transmission. However, the pore channels formed in this way are winding, increasing the length of the electrolyte transmission path, reducing the ion transmission rate, reducing the wetting effect on the active material layer. Especially when the thickness of the active material layer on the electrode sheet is relatively thick, the wetting effect of the electrolyte on the part of the active material layer close to the current collector is poor, reducing the utilization rate of the active material, and further reducing the rate performance and energy density of the battery.

[0040] In the secondary battery provided by this application, the active material layer on the positive electrode sheet and / or the negative electrode sheet includes an additive with straight through-holes. The straight through-holes can be directly used for electrolyte transmission. Compared with the winding pore channels formed by the pore-forming agent, the bending degree of the straight through-holes is small, shortening the path of the electrolyte transmission on the positive electrode sheet and / or the negative electrode sheet, improving the transmission rate of the electrolyte, and being more conducive to the reflux of the electrolyte. The accelerated transmission rate can improve the wetting effect of the electrolyte on the active material layer, reduce the liquid-phase polarization, thereby improving the utilization rate of the active material, improving the utilization rate of the specific capacity of the positive electrode sheet and / or the negative electrode sheet, and further 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 the secondary battery as a power source or various energy storage systems that use the battery as an energy storage element. The electrical equipment may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, and so on. Among them, the electric toys may include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. The spacecraft may include airplanes, rockets, space shuttles, and spaceships, etc.

[0042] In the first aspect of this application, a secondary battery is provided, which includes a positive electrode plate 1 and a negative electrode plate 1'. The positive electrode plate 1 and / or the negative electrode plate 1' includes a current collector 10: an active material layer 11, and the active material layer 11 is provided on at least one side of the current collector 10. The active material layer 11 includes an additive, and the additive has straight through-holes. The tortuosity of the active material layer 11 is 1.9 - 5.68. Thus, by providing an additive with straight through-holes in the active material layer 11 of the positive electrode plate 1 and / or the negative electrode plate 1', the tortuosity of the active material layer 11 can be reduced, and the electrolyte is directly transmitted through the straight through-holes, shortening the transmission path of the electrolyte on the positive electrode plate 1 and / or the negative electrode plate 1', improving the transmission rate of the electrolyte, thereby improving the wetting effect of the electrolyte on the positive electrode plate 1 and / or the negative electrode plate 1', reducing the liquid-phase polarization, further improving the utilization rate of the active material, improving the discharge capacity per gram of the positive electrode plate 1 and / or the negative electrode plate 1', and further improving the rate performance and energy density of the battery. Since the transmission rate of the electrolyte is accelerated, the low-temperature performance of the battery can also be improved.

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

[0044] In this application, the tortuosity refers to the degree of bending of the electrolyte transmission path of a porous electrode. The test method for the tortuosity of the active material layer 11 is: measure the Rion pore ion resistance through a symmetric battery, and calculate the tortuosity τ according to the porosity, electrode thickness, and electrolyte conductivity, τ = (Rion × A × ε × σ) / d, where Rion is the pore ion resistance, A is the electrode area, with the unit of cm 2 , ε is the porosity, with the unit of %, σ is the conductivity, with the unit of ms / cm, and d is the electrode thickness, with the unit of 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, 5.68, etc., or it can be a range composed of any of the above values. Thus, by controlling the tortuosity of the active material 11 within the above range, the transmission path of the electrolyte can be shortened, the transmission rate of the electrolyte can be increased, the wetting effect of the electrolyte on the active material layer 11 can be improved, and the rate performance and energy density of the battery can be improved. 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 ratio of the additive can be 0.5% - 10%. For example, it can be 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, etc., or it can be a range composed of any of the above values. Thus, by making the content of the additive within the above range, the number of straight 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 sheet 1, improving the utilization of the specific capacity of the electrode sheet 1, and further improving the rate performance and energy density of the battery.

[0047] In the present application, the test method for the content of the additive is thermogravimetric test. Specifically, in a nitrogen atmosphere, the gas flow rate is 50 ml / min, the temperature is raised from room temperature to 2000 °C, and the heating rate is 20 °C / min. The content of the additive is obtained according to the mass ratio of the decomposition characteristic peak.

[0048] According to some embodiments of the present application, the pore diameter of the straight through hole can be 100 nm - 500 nm. For example, it can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc., or it can be a range composed of any of the above values. Thus, while enabling the straight through hole to have the ability of liquid mass transfer, the transmission rate of the electrolyte on the electrode sheet 1 can be increased, thereby improving the wetting effect of the electrolyte on the active material layer 11, improving the utilization of the specific capacity of the electrode sheet 1, and further providing the rate performance and energy density of the battery.

[0049] In the present application, the pore diameter of the straight through hole refers to the diameter of the hole on the cross-section of the straight through hole. The pore diameter of the straight through hole can be tested by a scanning electron microscope.

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

[0051] In the present application, the length of the straight 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 straight through-hole structure, and the straight through-hole can be directly used for electrolyte transport, shortening the electrolyte transport path and increasing the electrolyte transport rate, thereby improving the wetting effect of the electrolyte on the positive electrode sheet 1 and / or the negative electrode sheet 1', reducing the liquid-phase polarization, further improving the utilization rate of the active material, improving the discharge capacity per gram of the positive electrode sheet 1 and / or the negative electrode sheet 1', and further improving the rate performance and energy density of the battery. Since the electrolyte transport rate is increased, 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 sheet 1 is greater than or equal to 300 μm; or the thickness of the active material layer on the negative electrode sheet 1' is 1200 μm - 210 μm. For example, the thickness of the active material layer on the positive electrode sheet 1 can be 300 μm, 330 μm, 360 μm, 390 μm, 420 μm, 450 μm, 480 μm, 500 μm, etc., or can be a range composed of any of the above values; the thickness of the active material layer on the negative electrode sheet 1' can be 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, etc., or can be a range composed of any of the above values. At this time, although the thickness of the active material layer 11 is relatively thick, due to the straight through-hole structure of the additive in the active material layer 11, the straight through-hole can be directly used for electrolyte transport, shortening the electrolyte transport path and increasing the electrolyte transport rate, thereby improving the wetting effect of the electrolyte on the positive electrode sheet 1 and / or the negative electrode sheet 1', especially improving the wetting effect of the electrolyte on the part of the active material layer 11 close to the current collector 10, reducing the liquid-phase polarization, further improving the utilization rate of the active material, improving the discharge capacity per gram of the positive electrode sheet 1 and / or the negative electrode sheet 1', and further improving the rate performance and energy density of the battery. Since the electrolyte transport rate is increased, 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. Thus, 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 improving the transmission rate of the electrolyte on the positive electrode sheet 1 and / or the negative electrode sheet 1', improving the wetting effect of the electrolyte on the active material layer 11, improving the utilization rate of the active material, and further improving the rate performance and energy density of the battery.

[0055] In the present application, the test method for porosity is pretreatment: Select 30 round pieces with good appearance and no powder falling off at the edges and place them in a sample cup. Record the number of pieces and calculate the apparent volume; Test: Place the sample cup containing the sample in a true density tester, seal the test system, introduce helium gas according to the program, calculate the true volume by detecting the pressure of the gas in the sample chamber and the expansion chamber, and then obtain the porosity of the sample to be tested according to Boyle's law (PV = nRT).

[0056] According to some embodiments of the present application, the active material layer 11 can include a first active material layer 111 and a second active material layer 112. The first active material layer 111 is provided on at least one side of the current collector 10, and the second active material layer 112 is provided on the side of the first active material layer 111 away from the current collector 10. The second active material layer 112 has the additive. Thus, by making the additive located in the second active material layer 112, the transmission rate of the electrolyte in the second active material layer 112 is greater than that in the first active material layer 111, and the ion concentration in the second active material layer 112 is greater than that in the first active material layer 111, that is, there is an ion concentration difference between the second active material layer 112 and the first active material layer 111. The concentration difference can further improve the transmission rate of the electrolyte, improve the wetting effect of the electrolyte on the first active material layer 111, thereby improving the utilization rate of the active material in the first active material layer 111, improving the discharge capacity per gram of the electrode sheet 1, and further 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. That is to say, 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. Thereby, the mass proportion of the additive on the entire active material layer 11 is increased, the number of straight through holes is increased, the number of electrolyte transmission paths is thus increased, the transmission rate of the electrolyte is increased, and further the rate performance and energy density of the battery are improved. 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 tested by a scanning electron microscope.

[0059] According to some embodiments of the present application, the active material layer of the negative electrode tab 1' includes the additive. By providing an additive with straight through holes in the negative electrode active material layer 11 of the negative electrode tab 1', the transmission rate of the electrolyte on the negative electrode tab 1' can be increased, the transmission rate of ions on the negative electrode tab 1' can be increased, and further the rate performance of the battery and the fast charging ability of the battery can be improved.

[0060] The second aspect of the present application provides a method for preparing a secondary battery, including preparing a positive electrode tab 1 and a negative electrode tab 1'. The method for preparing the positive electrode tab 1 and / or the negative electrode tab 1' includes: forming an active material layer 11 on at least one side of the current collector 10, the active material layer 11 including an additive, the additive having straight through holes, and the tortuosity of the active material layer 11 being 1.9 - 5.68. Thereby, for the positive electrode tab 1 and / or the negative electrode tab 1' prepared by this method, only by providing an additive with a straight through hole structure in the active material layer 11, the tortuosity of the active material layer 11 can be reduced, and the electrolyte can be directly transmitted through the straight through holes, which can shorten the transmission path of the electrolyte and does not require other process means to create holes, and can reduce the damage to the positive electrode tab 1 and / or the negative electrode tab 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 for forming the active material layer 11 includes: forming a first active material layer 111 on at least one side of the current collector 10; forming a second active material layer 112 on the side of the first active material layer 111 away from the current collector 10, the second active material layer 112 including the additive. Thereby, the transmission rate of the electrolyte is further increased, and the wetting effect of the electrolyte on the tab is improved.

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

[0063] Generally, a battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are inserted into and extracted from between the positive electrode plate and the negative electrode plate. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short - circuit between the positive and negative electrodes, while allowing ions to pass through.

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

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

[0066] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as substrates 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 active material can be a positive active material known in the art for lithium - ion batteries. As an example, the positive active material can include at least one of the following materials: lithium - containing phosphates with olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive active materials can also be used. These positive active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can 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 (which can also be abbreviated as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 )、lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of the olivine structure lithium-containing phosphate may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated 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 manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0068] In some embodiments, for example, when the battery is a sodium-ion battery, as an example, the positive electrode active material may include but is not limited to at least one of layered transition metal oxides, polyanion compounds, and Prussian blue analogs.

[0069] As an example of the above-mentioned layered transition metal oxides, for example, the following can be listed:

[0070] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 is one or several 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-mentioned Prussian blue analogues include, for example:

[0079] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + 、NH4 + 、an alkali metal cation or an alkaline earth metal cation, 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, 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 plate can be prepared in the following manner: the components for preparing the positive electrode plate, 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 processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0084] [Negative electrode plate]

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

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

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

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

[0089] In some embodiments, the negative electrode active material layer may further optionally 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 optionally include a conductive agent. The conductive agent 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 thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.

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

[0093] [Electrolyte]

[0094] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. There is no specific limitation on the type of the electrolyte in this application, and it can be selected according to requirements.

[0095] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes 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 bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0097] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate) borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0098] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0099] In some embodiments, the electrolyte may further optionally include a negative electrode film-forming additive, a positive electrode film-forming additive, and may also include other additives capable of improving certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0100] [Separator membrane]

[0101] In some embodiments, the battery further includes a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

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

[0103] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator membrane can be made into an electrode assembly by a winding process or a stacking process.

[0104] In some embodiments, the battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0105] In some embodiments, the outer package of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and examples of the plastic can include polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0106] The present application does not particularly limit the shape of the battery, and it can be cylindrical, square or any other arbitrary shape. For example, Figure 4 is a battery 5 with a square structure as an example.

[0107] In some embodiments, with reference to Figure 5, the outer packaging may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with 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 separator can be formed into an electrode assembly 52 by 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 included 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, the battery can be assembled into a battery module. The number of batteries included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0109] Figure 6 is a battery module 4 as an example. Refer to Figure 6 , in the battery module 4, multiple batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the multiple batteries 5 can be fixed by fasteners.

[0110] Optionally, the battery module 4 can further include a housing with a receiving space, and multiple batteries 5 are received in the receiving space.

[0111] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0112] Figure 7 and Figure 8 is a battery pack 6 as an example. Refer to Figure 7 and Figure 8 , the battery pack 6 can include a battery box and multiple battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for receiving the battery module 4. The multiple battery modules 4 can be arranged in the battery box in any way.

[0113] In addition, the present application also provides an electrical device, which includes at least one of the battery, battery module, or battery pack provided by the present application. The battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical 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, satellites, energy storage systems, etc., but is not limited thereto.

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

[0115] Figure 9 Take an electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack or battery module can be adopted.

[0116] Another example of the device can be a mobile phone, tablet computer, laptop computer, etc. This device usually requires being thin and light, and a battery can be used as the 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 in combination with 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 shall in no way be construed as a limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0118] Embodiment 1

[0119] 1. Preparation of the negative electrode sheet

[0120] SiC, SuperP, whisker carbon nanotubes, and polyacrylic acid lithium (PAALi) were added to deionized water as the solvent in a mass ratio of 91.8%: 1.1%: 5%: 2.1%, and stirred evenly under the action of a vacuum mixer. The solid content of the slurry was 45%. It was coated on the negative electrode current collector copper foil, dried in an oven, and cold-pressed to obtain the negative electrode sheet. The thickness of the negative electrode active material layer was 201 μm.

[0121] 2. Preparation of the positive electrode sheet

[0122] NCM96 (Ni 0.94 Co 0.03Mn 0.03 (MnO2), SuperP, and PVDF were 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 the positive electrode sheet. The thickness of the positive electrode active material layer was 436 μm.

[0123] 3. Preparation of electrolyte

[0124] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 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 after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0125] 4. Separator

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

[0127] 5. Preparation of battery

[0128] The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator placed between the positive and negative electrode sheets to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly was placed in an outer package, and the prepared electrolyte was injected into the dried lithium-ion battery. After vacuum packaging, standing, forming, and shaping processes, a lithium-ion battery was obtained.

[0129] The preparation methods of the batteries in Example 2, Comparative Example 1, Comparative Example 2, and Example 1 were the same as those in Example 1, and the differences are shown in Table 1 for details.

[0130] Example 3

[0131] 1. Preparation of negative electrode sheet

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

[0133] SiC, Superconducting carbon (SuperP), whisker carbon nanotubes, and polyacrylic acid lithium (PAALi) were 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, coated on the side of the first active material layer away from the copper foil to form a second active material layer, dried in an oven, and cold-pressed to obtain the negative electrode sheet. The thickness of the second active material layer was 140 μm.

[0134] 2. Preparation of the positive electrode plate

[0135] Add NCM96 (Ni 0.94 Co 0.03 Mn 0.03 O2), SuperP, and PVDF into NMP according to the mass ratio of 96%: 2.6%: 1.4%, stir evenly under the action of a vacuum mixer, coat both sides of the aluminum foil, dry in an oven, and cold press to obtain the positive electrode plate. The thickness of the positive active material layer is 436 μm.

[0136] 3. Preparation of the electrolyte

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

[0138] 4. Separator

[0139] Use a porous polyethylene film as the separator.

[0140] 5. Preparation of the battery

[0141] Stack the positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive and negative electrode plates to play a separating role, and then wind to obtain an electrode assembly; place the electrode assembly in the outer packaging, inject the prepared electrolyte into the dried lithium-ion battery, and after vacuum packaging, standing, forming, and shaping processes, obtain a lithium-ion battery.

[0142] The preparation method of the battery in Examples 4 - 12 is the same as that in Example 3, and the differences are shown in Table 2 for details.

[0143] Example 13

[0144] 1. Preparation of the negative electrode plate

[0145] Add SiC, superconducting carbon (SuperP), and polyacrylic acid lithium (PAALi) into deionized water as the solvent according to the mass ratio of 96.8%: 1.1%: 2.1%, stir evenly under the action of a vacuum mixer, with the solid content of the slurry being 45%, coat it on the negative current collector copper foil, dry in an oven, and cold press to obtain the negative electrode plate. The thickness of the negative active material layer is 201 μm.

[0146] 2. Preparation of the positive electrode plate

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

[0148] NCM96, Superconducting carbon (SuperP), whisker carbon nanotubes, and PVDF were added to deionized water as a solvent in a mass ratio of 95.7%: 2.6%: 0.3%: 1.4%, and stirred evenly under the action of a vacuum mixer. It was coated on the side of the first active material layer away from the copper foil to form the second active material layer, dried in an oven, and cold-pressed to obtain the negative electrode sheet. The thickness of the second active material layer was 300 μm.

[0149] 3. Preparation of electrolyte

[0150] In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), 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 after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0151] 4. Separator

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

[0153] 5. Preparation of battery

[0154] The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator placed between the positive and negative electrode sheets to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly was placed in an outer package, and the prepared electrolyte was injected into the dried lithium-ion battery. After vacuum packaging, standing, forming, and shaping processes, a lithium-ion battery was obtained.

[0155] The preparation method of the battery in Examples 14 - 22 was the same as that in Example 13, and the differences are shown in Table 3 for details.

[0156]

[0157]

[0158]

[0159] Performance test:

[0160] 1. Test method for the thickness of the active material layer

[0161] Test by scanning electron microscope

[0162] 2. Test method for tortuosity of active material layer

[0163] Test the Rion pore ion resistance by means of a symmetric cell, and calculate the tortuosity τ according to the porosity, electrode thickness and electrolyte conductivity, τ = (Rion × A × ε × σ) / d, where Rion is the pore ion resistance, A is the electrode area in cm 2 , ε is the porosity in %, σ is the conductivity in mS / cm, and d is the electrode thickness in cm.

[0164] 3. Test method for electrode porosity

[0165] Select 30 round wafers with good appearance and no powder falling off at the edges and put them into the sample cup. Record the number of wafers and calculate the apparent volume; Test: Place the sample cup with the sample in a true density tester, seal the test system, introduce helium gas according to the procedure, calculate the true volume by detecting the pressure of the gas in the sample chamber and the expansion chamber, and then obtain the porosity of the sample to be tested.

[0166] 4. Test method for rate performance

[0167] Stacked three-electrode test method. Take out the positive electrode and negative electrode and soak and clean them in DMC solvent for more than 72 h until the electrolyte solvent, lithium salt and additives are completely leached out. Dry the electrodes in a vacuum oven, and then assemble the positive electrode and negative electrode into a stacked three-electrode battery cell, with a copper wire as the reference electrode. At 25 °C, test the lithium deposition charging rate at each SOC of the stacked battery cell. The maximum charging rate is terminated when the potential of the reference electrode drops to 0 mV, and record the maximum charging rate at this SOC. According to this method, take 5% SOC as a point and test the maximum charging rate at every 5% SOC, such as 20% SOC, 25% SOC, 30% SOC to 100% SOC. Calculate the continuous charging time at 20% SOC - 80% SOC as the fast charging time according to the maximum charging rate at 20% SOC - 80% SOC obtained from this test.

[0168] 5. Test method for energy density

[0169] Capacity test of the battery cell: Let the prepared battery cell stand at 25°C for 2 h to ensure that the temperature of the battery cell is 25°C. At 25°C, charge the battery cell at 0.1C until the charge cut-off voltage is reached, and then continue to perform constant voltage charging at this charge cut-off voltage until the current is 0.05C, and the charging is terminated (where C represents the rated capacity of the battery cell). Let the battery cell stand at 25°C for 1 h. At 25°C, discharge the battery cell at 0.1C until the discharge cut-off voltage is reached, and record the total discharge capacity C0 released by the battery cell. The total discharge energy is E0.

[0170] Battery cell weight measurement: Place the battery cell on an electronic balance until the weight is stable, and read the weight value M0 of the battery cell.

[0171] Energy density calculation: The energy density of the battery cell is the discharge energy E0 of the battery cell divided by the weight M0 of the battery cell.

[0172] The test results of Comparative Example, Comparative Example 2, Example 1 and Example 2 are shown in Table 4.

[0173] The test results of Example 3 - Example 12 are shown in Table 5.

[0174] The test results of Example 13 - Example 22 are shown in Table 6.

[0175] Table 4

[0176]

[0177] Table 5

[0178]

[0179] Table 6

[0180]

[0181]

[0182] Conclusion: As can be seen from Tables 1 - 6, the electrode sheet proposed in this application can improve the rate performance and energy density of the battery, indicating that by setting an additive with straight through holes on the electrode sheet in this application, the transmission path of the electrolyte can be shortened, the transmission rate of the electrolyte can be increased, and for an electrode with a relatively thick active material layer, the acceleration of the transmission rate can accelerate the wetting effect of the electrolyte on the active material layer and improve the utilization rate of the active material.

[0183] As can be seen from the comparison between Examples 3 - 22 and Examples 1 and 2, whether it is the positive electrode sheet or the negative electrode sheet, with the layered design of the active material layer, setting the additive in the active material layer away from the current collector can further improve the rate performance of the battery compared to the non-layered active material layer (where the additive is set within the entire active material layer).

[0184] As can be seen from the comparison between Examples 3 - 12 and Examples 13 - 22, setting the additive on the negative electrode sheet can further improve the rate performance of the battery.

[0185] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, Comprising: a positive electrode plate and a negative electrode plate, wherein the positive electrode plate and / or the negative electrode plate comprises: a current collector: an active material layer provided on at least one side of the current collector, the active material layer comprising an additive having straight through-holes, and the tortuosity of the active material layer being 1.9 - 5.

68.

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

6.

3. The secondary battery according to claim 1 or 2, characterized in that, 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, characterized in that, Based on the total mass of the active material layer, the mass ratio of the additive is 0.5% - 10%.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, Satisfying one or more of the following conditions: The aperture of the straight through-holes is 100 nm - 500 nm; The length of the straight through-holes is 1 μm - 20 μm.

6. The secondary battery according to any one of claims 1-5, characterized in that, The additive comprises whisker carbon nanotubes.

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

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The porosity of the positive electrode plate and / or the negative electrode plate is 20% - 47%.

9. The secondary battery according to any one of claims 1-8, characterized in that, The active material layer comprises a first active material layer and a second active material layer, the first active material layer being provided on at least one side of the current collector, and the second active material layer being provided on the side of the first active material layer away from the current collector, and the second active material layer having 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, characterized in that, 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 1-11, characterized in that, The active material layer of the negative electrode plate comprises the additive.

13. A method for preparing a secondary battery according to any one of claims 1-12, characterized in that, Comprising: Preparing a positive electrode plate and a negative electrode plate, and the method for preparing the positive electrode plate and / or the negative electrode plate comprises: Forming an active material layer on at least one side of the current collector, the active material layer comprising an additive having straight through-holes, and the tortuosity of the active material layer being 1.9 - 5.

68.

14. The method according to claim 13, wherein The method for forming the active material layer comprises: Forming a first active material layer on at least one side of the current collector; Forming a second active material layer on the side of the first active material layer away from the current collector, the second active material layer comprising the additive.

15. An electrical device, characterized in that, A secondary battery according to any one of claims 1 - 12.

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