Positive plate and method of manufacturing the same, battery and electric device

Abstract

The present application discloses a positive plate, a method for manufacturing the same, a battery, and an electric device. The positive plate comprises a positive current collector and a positive active layer installed on at least one surface of the positive current collector, wherein the positive active layer comprises a first active layer and a second active layer, and the second active layer is located between the positive current collector and the first active layer; wherein the first active layer comprises a first positive active material and the second active layer comprises a second positive active material, and the operating voltage range of the first positive active material is greater than the operating voltage range of the second positive active material, and the operating voltage range of the second positive active material is 3.0V or less. The first positive active material begins to decay after passing through a relatively large voltage platform, thereby realizing the effect of the operating voltage continuing through the relatively low operating voltage range of the second positive active material, and furthermore, the high-output discharge voltage range is expanded, while the second positive active material has reaction activity even in a relatively low charge state, thus having excellent discharge capability.

Description

Technology Field

[0001] The present application claims priority to a Chinese patent application filed with the Chinese Patent Office on November 23, 2023, with application number 202311580592.4 and invention title "Polygonal plate and method of manufacturing the same, battery and electric device," the full contents of which are incorporated into the present application by reference.

[0002] This application belongs to the field of battery technology, and specifically relates to a positive electrode, a method for manufacturing the same, a battery, and an electric device. Background Technology

[0003] With the recent rapid development of new energy vehicles, battery drive systems are a key factor affecting their performance and cost. Currently, secondary batteries are emerging as the most preferred option for power batteries among new energy vehicle battery drive systems, as they possess characteristics such as high energy density, low memory effect, and high operating voltage.

[0004] A secondary battery cell generally includes a positive electrode, a separator, and a negative electrode. The positive active material within the positive electrode typically decays rapidly after passing through a certain discharge voltage platform, affecting the battery's discharge capacity.

[0005] In light of the aforementioned problem, the present application provides a positive electrode, a method for manufacturing the same, a battery, and an electric device, and aims to solve the technical problem of how to make the positive electrode have excellent discharge capability.

[0006] In a first aspect, an embodiment of the present application provides an anode piece comprising an anode current collector and an anode active layer installed on at least one surface of the anode current collector, wherein the anode active layer comprises a first active layer and a second active layer, and the second active layer is located between the anode current collector and the first active layer;

[0007] The first active layer comprises a first positive active material, and the second active layer comprises a second positive active material, wherein the operating voltage range of the first positive active material is greater than the operating voltage range of the second positive active material, and the operating voltage range of the second positive active material is 3.0V or less.

[0008] By matching a positive active material having a different operating voltage range to the positive active layer, specifically, the operating voltage range of the first positive active material in the first active layer on one side far from the positive current collector is larger than the operating voltage range of the second positive active material in the second active layer on one side close to the positive current collector, so that when the first positive active material begins to decay after passing through a relatively large voltage platform, the operating voltage is immediately connected through a relatively low operating voltage range of 3.0V or less in the presence of the second positive active material, thereby realizing the effect of the operating voltage being immediately connected. Furthermore, the high-output discharge voltage range of the positive piece of the present application is expanded, and at the same time, since the second positive active material on one side close to the positive current collector still has reaction activity even in a low charge state, such a positive piece enables the battery to have excellent discharge capability.

[0009] In some embodiments, the operating voltage range of the first positive active material is greater than 3.0 V, and optionally, the operating voltage range of the first positive active material is 3.1 V to 4.0 V; and / or,

[0010] The operating voltage range of the second positive active material is 1.5V to 3.0V.

[0011] By selectively combining the operating voltage ranges of the first and second positive active materials described above, the voltage continuity function can be better utilized, and furthermore, the discharge capability of the battery is improved.

[0012] In some embodiments, the first positive electrode active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate; and / or,

[0013] The second positive active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate, and at the same time comprises at least one of lithium iron silicate and lithium vanadate, optionally, the ratio of the total weight of lithium iron phosphate and lithium manganese iron phosphate to the total weight of lithium iron silicate and lithium vanadate in the second positive active material is 1:1 to 9:1.

[0014] By selecting and combining the types of the first positive active material and the second positive active material described above, the operating voltage range of the first positive active material and the operating voltage range of the second positive active material can be made to satisfy the range required in the present application.

[0015] In some embodiments, the particle size Dv50 of the first positive active material is larger than the particle size Dv50 of the second positive active material; optionally, the particle size Dv50 of the first positive active material is 300 nm to 2 μm, and the particle size Dv50 of the second positive active material is 10 nm to 300 nm.

[0016] Since the positive electrode active material with a relatively small particle size has a high charge / discharge output density and a relatively low voltage platform, the combination of the first positive electrode active material and the second positive electrode active material having the aforementioned particle size can not only achieve voltage continuity well but also make it difficult for excessive voltage polarization to occur, thereby further improving the output density.

[0017] In some embodiments, the weight ratio of the first positive active material and the second positive active material is 7:3 to 9:1.

[0018] At that weight ratio, the operating voltage platform of the entire anode is relatively high, which helps to improve battery energy density.

[0019] In some embodiments, the coating weight of the first active layer is 160 mg / 1540.25 mm 2 ~500mg / 1540.25mm 2 and the coating weight of the second active layer is 16 mg / 1540.25 mm 2~100mg / 1540.25mm 2 and / or,

[0020] The total compressive density of the first active layer and the second active layer is 2.3 to 3.0 g / cm³ 3 am.

[0021] Under the corresponding coating weight range and relatively high compression density, the energy density of the battery can be significantly improved, and the battery has relatively strong application potential.

[0022] In some embodiments, the porosity of the first active layer is greater than the porosity of the second active layer; and / or,

[0023] The curvature of the first active layer is smaller than the curvature of the second active layer.

[0024] By combining the porosity and curvature of the first and second active layers described above, a curvature and porosity are generated such that the anode segments are distributed in a constant gradient, thereby further reducing the concentration polarization of the liquid phase, which is advantageous for performing high-power charging and discharging.

[0025] In some embodiments, a conductive coating layer is also installed between the second active layer and the positive current collector, and based on the total weight of the conductive coating layer as 100%, the conductive coating layer contains 50 to 95% of a conductive agent.

[0026] By installing a high content of the conductive agent in the conductive coating layer, the conductive performance of the anode active layer and the anode current collector can be improved.

[0027] In a second aspect, the embodiments of the present application provide a method for manufacturing the anode section described above, which:

[0028] A step of manufacturing the second active layer on at least one surface of the anode current collector;

[0029] The method includes the step of manufacturing the first active layer on the surface of the second active layer located far from the anode current collector.

[0030] Obtaining a positive electrode by sequentially manufacturing a second active layer and a first active layer unique to the positive electrode current collector not only simplifies the process, but also expands the high-output discharge voltage range through the relationship between the second positive electrode active material in the second active layer and the first positive electrode active material in the first active layer, and maintains reaction activity even in a relatively low charge state, thereby enabling the manufactured positive electrode to have excellent discharge capability in the battery.

[0031] In some embodiments, the step of forming the second active layer on at least one surface of the anode current collector is:

[0032] First, the method comprises the step of preparing a conductive coating layer on at least one surface of the positive current collector, and then preparing the second active layer on the surface of the conductive coating layer located far from the positive current collector: wherein, based on 100% of the total weight of the conductive coating layer, the conductive coating layer contains 50 to 95% of a conductive agent.

[0033] By manufacturing a conductive coating layer with a high content of the conductive agent, the conductive performance of the positive active layer and the positive current collector can be improved.

[0034] In a third aspect, an embodiment of the present application provides a battery, which comprises a positive electrode provided in the first aspect of an embodiment of the present application and / or a positive electrode manufactured by a manufacturing method provided in the second aspect of an embodiment of the present application.

[0035] Based on the characteristics of the positive electrode of the embodiment of the present application, the battery of the embodiment of the present application has excellent discharge capability.

[0036] In a fourth aspect, an embodiment of the present application provides an electric device comprising a battery provided in the third aspect of the present application.

[0037] An electric device using a battery provided in the second aspect of the embodiment of the present application has good charging and discharging performance and can operate better.

[0038] The foregoing description is merely an overview of the technical method of the present application. To more clearly understand the technical means of the present application, and to more clearly understand the purposes, features, and advantages other than those described above, specific embodiments of the present application are specifically listed below. Brief explanation of the drawing

[0039] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become apparent to those skilled in the art. The drawings are used merely to illustrate preferred embodiments and should not be construed as a limitation to this application. Additionally, the same parts are indicated by the same drawing symbols in all drawings. In the drawings: FIG. 1 is a schematic structural diagram of one anode piece of an embodiment of the present application; FIG. 2 is a schematic structural diagram of another anode piece of an embodiment of the present application; FIG. 3 is a rate-limiting discharge voltage curve of lithium iron phosphate in the anode portion of an embodiment of the present application; FIG. 4 is a schematic diagram of the battery cell structure of one embodiment of the secondary battery of the embodiment of the present application; FIG. 5 is a schematic exploded view of a battery cell of a secondary battery shown in FIG. 4; FIG. 6 is a structural schematic diagram of one embodiment of a battery module of an embodiment of the present application; FIG. 7 is a structural schematic diagram of one embodiment of a battery pack of an embodiment of the present application; FIG. 8 is a schematic diagram of the exploded structure of the battery pack shown in FIG. 7; FIG. 9 is a schematic diagram of one embodiment of an electric device including a secondary battery as a power source according to an embodiment of the present application. Specific details for implementing the invention

[0040] Hereinafter, embodiments of the technical solution of the present application will be described in detail with reference to the attached drawings. The following embodiments are merely examples intended to more clearly explain the technical solution of the present application and do not limit the scope of protection of the present application.

[0041] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art of this application; terms used in this application are used merely for the purpose of describing specific embodiments and are not intended to limit this application; and the terms “comprising” and “having,” and any variations thereof, used in the specification, claims, and description of the drawings of this application are intended to encompass non-exclusive inclusion.

[0042] In the description of the embodiments of this application, technical terms such as "first," "second," etc., are used merely to distinguish different objects and should not be understood as indicating or implying relative importance, or as implicitly indicating the quantity of the indicated technical features, a specific order, or the relationship between the primary and secondary. In the description of the embodiments of this application, "plural" means two or more unless otherwise specified and specifically limited.

[0043] As used herein, "Examples" means that specific features, structures, or properties described by combining examples may be included in at least one of the embodiments of this application. The words appearing in various places in this specification do not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive from other embodiments. Those skilled in the art will understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

[0044] In the description of the embodiments of this application, the term "and / or" merely describes an association relationship describing associated objects and indicates that three relationships may exist; for example, A and / or B may represent the three cases where A exists alone, where A and B exist simultaneously, or where B exists alone. Additionally, the symbol " / " in this application generally indicates that the preceding and succeeding associated objects are in an "or" relationship.

[0045] In the description of the embodiments of the present application, the term “plural” refers to two or more (including two), and likewise, “plural group” refers to two or more groups (including two groups), and “plural part” refers to two or more parts (including two parts). “At least one” refers to one or more (including one, two, three, etc.).

[0046] In the description of the embodiments of the present application, the directional or positional relationships indicated by technical terms such as "center," "vertical direction," "horizontal direction," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top part," "bottom," "inside," "outside," "clockwise," "counterclockwise," "axial direction," "radial direction," "circular direction," etc., are based on the directional or positional relationships depicted in the drawings. This is merely intended to facilitate and simplify the description of the embodiments of the present application, and does not imply or suggest that the indicated device or element must necessarily have a specific direction or be configured and operated in a specific direction; therefore, it should not be understood as a limitation on the embodiments of the present application.

[0047] Unless otherwise clearly specified and limited in the description of the embodiments of this application, technical terms such as "mounting," "interconnecting," "connecting," and "fixing" should be understood in a broad sense, for example, they may be fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections via an intermediate medium; or communication within two elements or an interactive relationship between two elements. To those skilled in the art, the specific meaning of the terms described above in the embodiments of this application may be understood according to the specific circumstances.

[0048] With the gradual depletion of existing energy resources, the development of new energy storage devices is receiving increasing attention. Among these, rechargeable batteries are garnering particular interest due to their characteristics of high energy density, high theoretical capacity, excellent circulation stability, and eco-friendliness. Rechargeable batteries can be applied not only to energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, but are also widely utilized in various fields, including electric transportation such as electric bicycles, motorcycles, and vehicles. As the application areas of rechargeable batteries used as power batteries continue to expand, market demand is steadily increasing, and at the same time, requirements regarding performance, such as battery circulation capabilities, are becoming increasingly stringent.

[0049] The output performance of a secondary battery is closely related to positive polarization during the battery discharge process. A secondary battery cell generally includes a positive electrode, a separator, and a negative electrode. If the electrode thickness is too thick, the degree of polarization is prone to increasing; therefore, to reduce the polarization of the positive electrode, general battery designs usually [constantly] the weight per coating area (CW, typically 0–400g / 1540.25mm²) of the positive electrode. 2By designing the electrode plate to be thin, this design, on the one hand, thins the diffusion path of active ions such as lithium ions, thereby reducing the liquid-phase diffusion distance; on the other hand, it shortens the electron transport path along the thickness direction of the electrode plate and lowers the electron transport impedance, ultimately realizing the effect of reducing the polarization of the anode plate. However, as the weight per coating area decreases, the volumetric proportion of inactive materials (e.g., current collectors, separators) within the battery increases significantly. This lowers the space utilization rate of the anode active material and further reduces the volumetric energy density, which is disadvantageous for improving the driving range of new energy vehicles. Additionally, the decrease in volumetric energy density leads to an increase in battery costs, which in turn increases the purchase cost of new energy vehicles.

[0050] As the adoption rate of new energy vehicles continues to rise, hybrid and range-extended vehicles are gradually entering the market, leading to increasingly higher requirements for the output performance of secondary batteries. Lithium-ion batteries are a type of secondary battery characterized by high energy density, long service life, energy efficiency, and eco-friendliness. In secondary batteries, the active material within the positive electrode generally decays rapidly after passing through a certain discharge voltage range; consequently, without a continuous operating voltage process, the battery's discharge capacity is easily affected.

[0051] Taking the above considerations into account, in order to improve the discharge capability of a secondary battery, a positive active layer comprising a first active layer and a second active layer is installed on at least one surface of a positive current collector, and the discharge capability of the secondary battery can be improved based on the combination of operating voltage ranges of the positive active material within the first active layer and the second active layer. Accordingly, the following technical solution is presented.

[0052] Anode section and method of manufacturing the same

[0053] In a first aspect, an embodiment of the present application provides an anode, and some embodiments of the present application summarized as shown in FIGS. 1 and 2, the anode comprises (1) an anode current collector (11) and (2) an anode active layer (12). Here, the anode active layer (12) is installed on at least one surface of the anode current collector (11), that is, the anode active layer (12) is installed on one surface of the anode current collector (11), or the anode active layer (12) is installed on both opposing surfaces of the anode current collector (11).

[0054] The positive current collector (11) is a structure or component that collects current from a battery. The positive active layer (12) refers to a film layer containing a positive active material in a battery. When the battery is charged or discharged, the positive active material within the positive active layer (12) can perform insertion and extraction of active metal ions.

[0055] The positive active layer (12) includes a first active layer (121) and a second active layer (122), the second active layer (122) is located between the positive current collector (11) and the first active layer (121), the first active layer (121) includes a first positive active material, the second active layer (122) includes a second positive active material, and there is a constant relationship between the operating voltage range of the first positive active material and the second positive active material, that is, the operating voltage range of the first positive active material is greater than the operating voltage range of the second positive active material, and the operating voltage range of the second positive active material is 3.0V or less.

[0056] The operating voltage refers to the potential range of the reversible reaction of the electrode material within the battery. Specifically, the operating voltage range of the positive active material within the positive electrode of the embodiment of the present application may refer to the range of potential change of the positive active material during the charging and discharging process, and may also reflect the maximum voltage platform that the battery can provide. Generally, the positive electrode can be assembled into a button-type half-cell, and the discharge energy E and capacity C of the button-type half-cell during charging and discharging can be tested, and the charging and discharging voltage platform range of the positive active material can be obtained using the formula V=E / C.

[0057] In the embodiment of the present application, the second positive active material has a relatively low operating voltage range of 3.0V or less. Therefore, when the first positive active material begins to decay after passing through a relatively large voltage platform, based on the presence of the second positive active material, the effect of the operating voltage continuing directly through the relatively low operating voltage range of the second positive active material is realized, and furthermore, the high-output discharge voltage range is expanded. At the same time, since the second positive active material is located on one side close to the second active layer (122), that is, the positive current collector (11), the second positive active material still has reaction activity even in a relatively low charge state, so the positive part of the embodiment of the present application can enable the battery to have excellent discharge capability.

[0058] In some embodiments, the first positive active material in the first active layer (121) comes into contact with the electrolyte first, and generally, a discharge reaction occurs first. If the operating voltage range is greater than 3.0V, a discharge reaction having a relatively large discharge voltage may occur first. Then, when a second positive active material having a relatively low operating voltage range is added, the discharge voltage of the first positive active material is expected to rapidly attenuate after rising above the 3.0V platform, the effect of the voltage platform of the first positive active material dropping rapidly after 3.0V is mitigated, and the operating voltage continues, and furthermore, the high-output discharge voltage range of the entire positive active layer (12) is expanded to improve its discharge capability. Optionally, the operating voltage range of the first positive active material is 3.1V to 4.0V, and charging and discharging operations can be performed by controlling the operating voltage range of the first positive active material to within 3.1V to 4.0V.

[0059] In some embodiments, the operating voltage range of the second positive active material in the second active layer (122) is 1.5V to 3.0V. By installing a second positive active material having a corresponding relatively low operating voltage range on one side of the positive active layer (12) close to the positive current collector (11), the effect of continuous operating voltage can be realized.

[0060] In some embodiments, the operating voltage range of the first positive active material is 3.1V to 4.0V, and the operating voltage range of the second positive active material is 1.5V to 3.0V; by selectively combining the operating voltage ranges of the first positive active material and the second positive active material described above, the voltage continuous function can be better performed, and furthermore, the discharge capability of the battery is improved.

[0061] In some embodiments, the first positive active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate. Both lithium iron phosphate and lithium manganese iron phosphate are positive active materials with relatively high voltage, and when installed on one side of the positive active layer (12) far from the positive current collector (11), high-rate discharge can be achieved.

[0062] In some embodiments, the second positive active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate, and at least one of lithium iron silicate and lithium vanadate. By combining at least one positive active material of lithium iron phosphate and lithium manganese iron phosphate with at least one positive active material of lithium iron silicate and lithium vanadate, a second positive active material having a relatively low voltage can be installed on one side of the positive active layer (12) close to the positive current collector (11), and when the voltage platform of the first positive active material during high-rate discharge is rapidly lowered, the second positive active material can implement a voltage continuity function. At the same time, the second positive active material still has reaction activity even at a low state of charge (SOC), and at this time, the second positive active material can still react because the output is strong, which enables the battery to have excellent discharge capability.

[0063] For example, when lithium iron phosphate is the first positive electrode active material, as shown in Fig. 3, which is a high-rate discharge decay curve of lithium iron phosphate, the discharge voltage of lithium iron phosphate will rapidly decay after the 3.3V level. The reason for the decay is that as the discharge progresses, lithium ions are detached from the negative electrode and inserted into the lithium iron phosphate crystal lattice, leading to a decrease in the voltage of lithium iron phosphate. Since lithium iron phosphate is a phase change material, the voltage drops sharply when it is fully inserted. However, if the second positive electrode active material contains at least one of lithium iron silicate and lithium vanadate in addition to lithium iron phosphate, for example, if lithium iron silicate is present, continuous discharge is possible down to 2.0V or even 1.5V, and the function of voltage continuity can be realized.

[0064] In some embodiments, the ratio of the total weight of lithium iron phosphate and lithium manganese iron phosphate to the total weight of lithium iron silicate and lithium vanadate in the second positive electrode active material is 1:1 to 9:1. For example, the second positive electrode active material may comprise lithium iron phosphate and lithium iron silicate, and the weight ratio of the two materials may be 1:1, 2:1, 3:1, 4:1, 6:1, 8:1, 9:1, etc.

[0065] A slurry formulated with a second positive active material within the corresponding weight ratio range has good stability and can be coated well, thereby improving the processing performance of the positive plate while maintaining excellent compatibility with current mass production lines. At the same time, by selectively combining the types of the first positive active material and the second positive active material described above, the operating voltage range of the first positive active material and the operating voltage range of the second positive active material can be made to satisfy the range required in this application.

[0066] In some embodiments, the particle size Dv50 of the first positive active material is larger than the particle size Dv50 of the second positive active material.

[0067] The size of a particulate material is referred to as particle size, and the percentage of the total quantity occupied by particles within different particle size ranges is referred to as particle size distribution. The volumetric particle size is a particle size calculated by accumulating the particle volume as a unit. For example, Dv50 represents the particle size corresponding when the percentage of the cumulative volumetric particle size distribution within the sample reaches 50%, and in a specific embodiment, the average particle size can be measured using a particle size meter.

[0068] At the discharge end, the electrochemical reaction region gradually moves downward from the first active layer (121) to the second active layer (122), and the second active layer (122) is coated with a second positive active material having a relatively small particle size, so the total time for solid phase diffusion is reduced, which is advantageous for the rapid occurrence of solid phase reactions and further reduces the electrochemical polarization phenomenon at the high-output discharge end, which is advantageous for improving the output performance of the battery and extending the discharge time. Specifically, the second positive active material and the first positive active material, in which particle size distribution is gradient along the thickness direction of the positive plate, are affected by the polarization of the liquid phase concentration difference of the electrode plate during the discharge process in the low-charge state. In the case of the high-charge state, the reaction of the first positive active material far from the positive current collector (11) has already finished, and the second positive active material in the region close to the positive current collector (11) mainly becomes the electrochemical reaction region. At this time, the region where the lithium insertion reaction occurs mainly is the second active layer (122), and since the particle size of the second positive active material in the second active layer (122) is relatively small, the total time for solid phase diffusion is reduced, and the solid phase lithium insertion reaction occurs rapidly. Furthermore, the electrochemical polarization phenomenon at the end of the high-output discharge is reduced, which is advantageous for improving the output performance of the battery and extending the discharge time.

[0069] Therefore, since the positive electrode active material with a relatively small particle size not only has a high charge / discharge output density but also a relatively low voltage platform, the combination of the first positive electrode active material and the second positive electrode active material having the aforementioned particle size can not only achieve good voltage continuity but also make it difficult for excessive voltage polarization to occur, thereby further improving the output density.

[0070] In some embodiments, the particle size Dv50 of the first positive active material is 300 nm to 2 μm, and the particle size Dv50 of the second positive active material is 10 nm to 300 nm. For example, the particle size Dv50 of the first positive active material may be 300 nm, 500 nm, 800 nm, 900 nm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, etc., and the particle size Dv50 of the second positive active material may be 10 nm, 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, etc. The first positive active material within the particle size range described above enables the battery to have excellent charge-discharge kinetic performance, and at the same time, the processing performance of the corresponding slurry is also good, and the second positive active material within the particle size range described above can realize a relatively low voltage platform and can be combined with the first positive active material to achieve voltage continuity.

[0071] In some embodiments, the weight ratio of the first positive active material and the second positive active material is 7:3 to 9:1. For example, the weight ratio of the two may be 7:3, 8:2, 9:1, etc. The first positive active material and the second positive active material combined under the weight ratio conditions help to improve battery energy density by making the operating voltage platform of the entire positive plate relatively high.

[0072] In some embodiments, the coating weight of the first active layer is 160 mg / 1540.25 mm 2 ~500mg / 1540.25mm 2 and the coating weight of the second active layer is 16 mg / 1540.25 mm 2~100mg / 1540.25mm 2 is. For example, the coating weight of the first active layer is 160 mg / 1540.25 mm 2 , 200mg / 1540.25mm 2 , 250mg / 1540.25mm 2 , 300mg / 1540.25mm 2 , 350mg / 1540.25mm 2 , 400mg / 1540.25mm 2 , 450mg / 1540.25mm 2 , 500mg / 1540.25mm 2 It may be, etc.; the coating weight of the second active layer is 16 mg / 1540.25 mm 2 , 25mg / 1540.25mm 2 , 30mg / 1540.25mm 2 , 40mg / 1540.25mm 2 , 50mg / 1540.25mm 2 , 60mg / 1540.25mm 2 , 70mg / 1540.25mm 2 , 80mg / 1540.25mm 2 , 90mg / 1540.25mm 2 It may be, etc. However, the total compressive density of the first and second active layers is 2.3–3.0 g / cm³ 3 It could be.

[0073] Under the aforementioned coating weight range and relatively high compression density, the energy density of the battery cell can reach 400 to 470 Wh / L, thus having relatively strong application potential.

[0074] The coating weight described above is the cross-sectional coating weight, which is the weight per unit area of ​​the cross section after the active layer slurry is applied to the anode current collector (11) and dried. The anode piece of the embodiment of the present application can simultaneously obtain a relatively high coating weight and a relatively high compression density, and the output density is not easily attenuated.

[0075] Porosity refers to the percentage between the volume of pores and the total volume of the material in its natural state in a porous material. The ratio between the total volume of interconnected small pores within a porous material and the apparent volume of the porous material is called effective porosity and is denoted by φ_e; the ratio between the total volume of all interconnected or non-interconnected small pores within a porous material and the apparent volume of the porous medium is called absolute porosity or total porosity and is denoted by φ_T. The active layer porosity of the embodiments of the present application refers to the effective porosity φ_e of the active layer material.

[0076] In some embodiments, the porosity of the first active layer (121) is greater than the porosity of the second active layer (122). By combining the porosities of the first active layer (121) and the second active layer (122) described above, the anode section is formed with a porosity distribution with a constant gradient: that is, the porosity of the anode active layer (12) tends to decrease from one side far from the anode current collector (11) to one side close to the anode current collector (11). This is advantageous for reducing polarization of liquid concentration differences and for performing high-power charging and discharging.

[0077] Tortuosity is also referred to as tortuosity: in the porous structure of a lithium-ion battery electrode, polarization of the liquid phase concentration difference occurs due to the existence of a natural phenomenon where the pores themselves are bent. To quantify and define this phenomenon, tortuosity is defined as the ratio between the actual path length through which the electrolyte diffuses and passes in the lithium-ion battery electrode and the macroscopic coating layer thickness of the electrode. The overall tortuosity of the electrode can be measured by electrochemical impedance spectroscopy (EIS), and the comparative relationship between the tortuosity of the first active layer and the second active layer within the electrode can be measured by SEM tomography.

[0078] In some embodiments, the curvature of the first active layer (121) is smaller than the curvature of the second active layer (122). By combining the porosity and curvature of the first active layer (121) and the second active layer (122) described above, the anode section is formed with a curvature distribution with a constant gradient: that is, the curvature of the anode active layer (12) tends to increase from one side far from the anode current collector (11) to one side close to the anode current collector (11). This is advantageous for reducing polarization of liquid concentration differences and for performing high-power charging and discharging.

[0079] After the anode piece is manufactured, the magnitudes of the curvature and porosity of the first active layer and the second active layer can be compared by observing and comparing the cross-section of the anode piece using a high-resolution scanning electron microscope.

[0080] In some embodiments, the first active layer (121) comprises a first positive active material, a conductor, and an adhesive, wherein the mass ratio of the first positive active material may be 95% to 100%, i.e., the conductor and the adhesive may or may not be added. Specifically, the mass ratio of the first positive active material, the conductor, and the adhesive in the first active layer (121) may be (95 to 99):(0.5 to 2.5):(0.5 to 2.5). The second active layer (122) comprises a second positive active material, a conductor, and an adhesive, wherein the mass ratio of the second positive active material may be 95% to 100%, i.e., the conductor and the adhesive may or may not be added. Specifically, the mass ratio of the second positive active material, the conductor, and the adhesive in the second active layer (122) may be (97 to 99):(0.5 to 1.5):(0.5 to 1.5).

[0081] As an example, the adhesive may comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductor may comprise at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive current collector (11) may use a metal foil or a composite current collector. For example, aluminum foil or stainless steel foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. 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 polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0083] In some embodiments, a conductive coating layer (123) is also installed between the second active layer (122) and the positive current collector (11), and the conductive coating layer (123) contains 50 to 95% of a conductive agent based on 100% of the total weight of the conductive coating layer (123). By installing a high content of the conductive agent in the conductive coating layer (123), the conductivity performance of the positive active layer (12) and the positive current collector (11) can be improved.

[0084] Specifically, the conductive coating layer (123) is composed of a conductive agent and an adhesive, and the conductive agent of the conductive coating layer (123) may include at least one of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes, and the adhesive of the conductive coating layer (123) may include one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), carboxymethyl cellulose, styrene-butadiene rubber, and calcium hydroxide, wherein the weight ratio of the conductive agent is high at 50 to 95%, thereby improving the conductive performance between the positive active layer (12) and the positive current collector (11).

[0085] In a second aspect, the embodiments of the present application provide a method for manufacturing the anode section described above, which:

[0086] S01: A step of manufacturing a second active layer (122) on at least one surface of a positive current collector (11);

[0087] S02: Includes the step of manufacturing a first active layer (121) on the surface of a second active layer (122) far from the positive current collector (11).

[0088] By sequentially manufacturing a second active layer (122) and a first active layer (121) unique to the positive current collector (11) to obtain the positive active layer (12) of the positive plate, the process is not only simple, but the high-output discharge voltage range can be expanded through the relationship between the second positive active material in the second active layer (122) and the first positive active material in the first active layer (121), and the reaction activity is still maintained even in a relatively low charge state, so the manufactured positive plate can be made to have excellent discharge capability of the battery.

[0089] Specifically, the specific material types and combinations of the positive current collector (11), the second active layer (122), and the first active layer (121) are described above.

[0090] In some embodiments, a method for manufacturing a positive active layer (12) comprises the step of applying a second positive slurry containing a second positive active material, a conductor, and an adhesive in the ratios described above to a positive current collector (11) and drying it to obtain a second active layer (122) of the positive active layer (12), and then applying a first positive slurry containing a first positive active material, a conductor, and an adhesive in the ratios described above to the second active layer (122) and drying it to obtain a first active layer (121) of the positive active layer (12). Here, the first active layer (121) and the second active layer (122) described above constitute the positive active layer (12).

[0091] In some embodiments, the step of forming a second active layer (122) on at least one surface of the positive current collector (11) is:

[0092] First, a conductive coating layer (123) is prepared on at least one surface of a positive current collector (11), and then a second active layer (122) is prepared on the surface of the conductive coating layer (123) located far from the positive current collector (11). Here, based on the total weight of the conductive coating layer (123) as 100%, the conductive coating layer (123) contains 50 to 95% of a conductive agent. Refer to the above for the selection of specific material types for the conductive coating layer (123). By preparing the conductive coating layer (123) with a high content of the conductive agent, the conductive performance of the positive active layer (12) and the positive current collector (11) can be improved.

[0093] After manufacturing the positive electrode product through the general electrode manufacturing method of subsequent cold pressing and die cutting, the battery is manufactured by assembling it together with the negative electrode, separator, and electrolyte.

[0094] battery

[0095] In a third aspect, an embodiment of the present application provides a battery, which comprises a positive electrode provided in the first aspect of an embodiment of the present application and / or a positive electrode manufactured by a manufacturing method provided in the second aspect of an embodiment of the present application.

[0096] In the battery provided in the embodiment of the present application, the unique positive electrode of the embodiment of the present application is used, and based on the characteristics of the positive electrode of the embodiment of the present application, the battery of the embodiment of the present application has excellent discharge capability.

[0097] Specifically, the battery may be a secondary battery comprising a positive electrode, a negative electrode, and a separator installed between the positive electrode and the negative electrode. The positive electrode is the positive electrode provided in the first aspect of the embodiment of the present application and / or the positive electrode manufactured by the manufacturing method provided in the second aspect of the embodiment of the present application.

[0098] In some embodiments, the secondary battery includes a lithium-ion battery. During the charging and discharging process of the battery, active lithium ions are inserted and extracted back and forth between the positive electrode and the negative electrode. The electrolyte serves to conduct ions between the positive electrode and the negative electrode. A separator is installed between the positive electrode and the negative electrode and primarily serves to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through.

[0099] The electrolyte serves to conduct ions between the anode and the cathode. The embodiments of the present application have no particular limitations on the type of electrolyte and can be selected according to demand. For example, the electrolyte may be in the form of a liquid, gel, or a completely solid.

[0100] In some embodiments, the cathode plate comprises a cathode current collector and a cathode active layer installed on at least one surface of the cathode current collector. The cathode current collector may use 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate, such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0101] The cathode active layer contains a cathode active material comprising at least one of synthetic graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. It also optionally includes an adhesive. The adhesive 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). The cathode active layer also optionally includes a conductor. The conductor may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the cathode active layer also optionally includes other auxiliary agents such as a dispersant, a thickener (e.g., sodium carboxymethylcellulose), etc.

[0103] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution comprises an electrolyte salt and a solvent. If the secondary battery is a lithium-ion battery, the electrolyte salt may be selected from 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 difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro(bis-oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0104] In some embodiments, the solvent in the electrolyte 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.

[0105] In some embodiments, the electrolyte also optionally includes additives. For example, the additives may include a cathode film-forming additive and an anode film-forming additive, and may also include additives that can improve specific performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, etc.

[0106] In some embodiments, the secondary battery of the embodiments of the present application may include any one of a battery cell, a battery module, and a battery pack.

[0107] Here, the battery cell refers to a battery housing and an electrode assembly packaged in the battery housing. There are no specific restrictions on the shape of the battery cell, and it may be cylindrical, rectangular, or any other shape. It is a battery cell (20) with a rectangular structure as shown in FIG. 4.

[0108] In some embodiments, as illustrated in FIG. 5, the external packaging of the battery cell (20) may include a housing (21) and an upper cover assembly (22). The housing (21) may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving chamber. The housing (21) has an opening communicating with the receiving chamber and is installed by covering the opening using the upper cover assembly (22) to close the receiving chamber. The positive electrode, separator, and negative electrode included in the secondary battery of the embodiment of the present application may undergo a winding process and / or a lamination process to form an electrode assembly (23). The electrode assembly (23) is packaged within the receiving chamber. An electrolyte is infiltrated into the electrode assembly (23). The number of electrode assemblies (23) included in the battery cell (20) may be one or more and may be adjusted according to actual demand.

[0109] The method of manufacturing the battery cell (20) is known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte may be assembled to form the battery cell (20). As an example, the positive electrode, the separator, and the negative electrode may undergo a winding process or a lamination process to form an electrode assembly (23), and the electrode assembly (23) may be placed in an external packaging material, dried, then an electrolyte may be injected, and the battery cell (20) may be obtained through processes such as vacuum packaging, settling, formation, and molding.

[0110] The battery module refers to being assembled from the corresponding battery cells (20), that is, it may contain a plurality of the corresponding battery cells (20), and the specific number may be adjusted according to the application and capacity of the battery module.

[0111] In some embodiments, FIG. 6 is a schematic diagram of a battery module (30) as an example. In the battery module (30), a plurality of battery cells (20) may be installed by sequentially arranging them along the longitudinal direction of the battery module (30). Of course, they may also be arranged in any other arbitrary manner. The plurality of battery cells (20) may be secured with fasteners.

[0112] Optionally, the battery module (30) may also include a housing having a receiving space, and a plurality of battery cells (20) are received in the receiving space.

[0113] A battery pack refers to one assembled from the battery cells (20) mentioned above, that is, the battery pack may contain a plurality of battery cells (20), wherein the plurality of corresponding battery cells (20) may be assembled into the battery modules (30) mentioned above. The specific number of battery cells (20) or battery modules (30) included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0114] For example, in the embodiment, FIGS. 7 and 8 are schematic diagrams of a battery pack (40) as an example. The battery pack (40) may include a battery case and a plurality of battery modules (30) installed within the battery case. The battery case includes an upper case (41) and a lower case (42), and the upper case (41) is installed over the lower case (42) to form a closed space for accommodating the battery modules (30). The plurality of battery modules (30) may be arranged in any manner within the battery case.

[0115] electrical device

[0116] In a fourth aspect, an embodiment of the present application also provides an electric device comprising a battery provided in the third aspect of the present application. The battery may be used as a power source for the electric device or as an energy storage unit for the electric device. Thus, the electric device of the embodiment of the present application can operate well due to its excellent charge and discharge performance.

[0117] The electric device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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. Depending on the usage demand, the electric device may select a secondary battery, battery module, or battery pack.

[0118] FIG. 9 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack or battery module may be used to meet the demand for high power output and high energy density of the electric device.

[0119] Other exemplary electric devices may include mobile phones, tablet computers, laptop computers, etc. Such electric devices should typically be thin and light and can use a secondary battery as a power source.

[0120] Examples

[0121] The following describes embodiments of the present application. The embodiments described below are illustrative and are intended only to interpret the present application and should not be construed as a limitation thereof. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature of the art or product descriptions. Where the manufacturer of the reagents or equipment used is not specified, they are all general products available on the market.

[0122] 1. Examples of anode pieces and methods for manufacturing the same

[0123] Example A1

[0124] A positive plate comprising a positive current collector and a second active layer and a first active layer sequentially installed on the positive current collector; wherein the positive current collector is a 15 μm aluminum foil, and the material of the first active layer (based on 100% of the total weight) is 48% of lithium iron phosphate with a Dv50 of 100 nm, 48% of lithium iron silicate with a Dv50 of 200 nm, 2% of acetylene black, and 2% of PVDF, and the material of the second active layer (based on 100% of the total weight) is 96% of lithium iron phosphate with a Dv50 of 0.3 μm, 2% of acetylene black, and 2% of PVDF; and the weight ratio of the second active layer to the first active layer is 10:90.

[0125] The method for manufacturing the anode section of an embodiment of the present application comprises the following steps:

[0126] Lithium iron phosphate with a Dv50 of 100 nm, lithium iron silicate with a Dv50 of 200 nm, acetylene black as a conductor, and PVDF as an adhesive are uniformly mixed by stirring in an N-methylpyrrolidone solvent at a ratio of 48%, 48%, 2%, and 2% of the final coating layer to obtain a coating slurry of the second active layer; lithium iron phosphate with a Dv50 of 0.3 μm, acetylene black as a conductor, and PVDF as an adhesive are uniformly mixed by stirring in an N-methylpyrrolidone solvent at a ratio of 96%, 2%, and 2% of the final coating layer to obtain a coating slurry of the first active layer; The second active layer coating slurry and the first active layer coating slurry are uniformly applied to a 15μm aluminum foil anode current collector through a double-layer coating die head (weight ratio of 10:90 during compression spraying) to form sequentially stacked second active layer and first active layer, i.e., an anode active layer, and the total weight of the single-sided coating after final drying is 430mg / 1540.25mm 2 Based on the weight, followed by drying, 2.63 g / cm³ 3 Cold pressing and cutting were performed to obtain an anode piece.

[0127] Example A2

[0128] The difference from Example A1 regarding the anode piece and the method of manufacturing the same is that a conductive coating layer is first prepared on the aluminum foil anode current collector before preparing the second active layer and the first active layer on the aluminum foil anode current collector. Specifically, acetylene black, CMC, PAA, and calcium hydroxide were stirred and mixed in an N-methylpyrrolidone solvent at a ratio of 85%, 5%, 5%, and 5% of the final coating layer to obtain a conductive coating layer coating slurry. Then, the conductive coating layer coating slurry was uniformly applied to a 15 μm aluminum foil anode current collector by a compression spray method, and then dried to prepare a conductive coating layer on the aluminum foil anode current collector. Subsequently, the second active layer and the first active layer were prepared.

[0129] Example A3

[0130] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0131] Example A4

[0132] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0133] Example A5

[0134] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0135] Example A6

[0136] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0137] Example A7

[0138] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0139] Example A8

[0140] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0141] Example A9

[0142] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0143] Example A10

[0144] Refer to Table 1 for differences from Example A1 as the positive electrode.

[0145] Comparative Example A1

[0146] The difference from Example A1 regarding the anode piece and the method of manufacturing the same is:

[0147] Only the first active layer is prepared on a 15μm aluminum foil anode current collector, and the coating weight of the first active layer after drying is 430mg / 1540.25mm 2 Based on the weight, followed by drying, 2.63 g / cm³ 3 Cold pressing and cutting were performed to obtain the anode piece.

[0148] Comparative Example A2

[0149] The difference from Example A1 regarding the anode piece and the method of manufacturing the same is:

[0150] A single-layer anode active layer is formed, specifically: lithium iron phosphate with a Dv50 of 100 nm, lithium iron phosphate with a Dv50 of 0.3 μm, acetylene black, and PVDF are uniformly mixed by stirring in an N-methylpyrrolidone solvent at percentage contents of 9.6%, 86.4%, 2%, and 2% in the final anode active layer, respectively, to obtain an anode coating slurry; then, the anode coating slurry is uniformly applied to a 15 μm undercoating substrate by a pressure spray method to form a single-layer anode active layer, and the coating weight of the anode active layer after drying is 430 mg / 1540.25 mm 2 Based on the weight, followed by drying, 2.63 g / cm³ 3 Cold pressing and cutting were performed to obtain the anode piece.

[0151] 2. Example of a secondary battery cell

[0152] Examples B1 to B10 and Comparative Examples B1 to B2;

[0153] Examples B1 to B10 and Comparative Examples B1 to B2 each provide a secondary battery cell, and each secondary battery cell includes a bare cell formed of a positive electrode, a separator, and a negative electrode, and also includes an electrolyte. Here, the positive electrodes of Examples B1 to B10 and Comparative Examples B1 to B2 correspond to the positive electrodes provided in Examples A1 to A10 and Comparative Examples A1 to A2, respectively. Here, the positive electrode of Example A1 is used as the positive electrode of the battery cell of secondary battery Example B1, the positive electrode of Example A2 is used as the positive electrode of the battery cell of secondary battery Example B2, and thus, the positive electrode of Comparative Example A10 is used as the positive electrode of the battery cell of secondary battery Comparative Example B10.

[0154] A method for manufacturing a secondary battery cell includes the following:

[0155] Preparation of anode section: Refer to the anode sections provided in Examples A1 to A10 and Comparative Examples A1 to A2.

[0156] Manufacturing of the cathode:

[0157] Natural graphite, synthetic graphite, single-walled carbon nanotubes, acetylene black, CMC, and SBR were stirred and uniformly mixed in proportions of 42%, 42%, 10%, 2.0%, 1.8%, and 2.2% to obtain a cathode slurry; then, the slurry was uniformly applied to a 6 µm copper foil current collector by a pressure spray method, and then dried, cold pressed, and cut to obtain a cathode piece.

[0158] Preparation of electrolyte:

[0159] In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC), which are organic solvents, were uniformly mixed in a volume ratio of 3 / 7, 12.5% ​​of LiPF6 lithium salt was added and dissolved in the organic solvent, and the mixture was uniformly stirred to obtain an electrolyte.

[0160] Separator: A polypropylene membrane is used as a separator.

[0161] [Battery Assembly]

[0162] Secondary battery assembly: Re-formed negative electrode, positive electrode, and polypropylene porous separator are sequentially stacked, and an electrode assembly with a theoretical capacity of 30Ah is manufactured through a winding process, and then through processes such as packaging, electrolyte injection, formation, and screening, it is manufactured into a cylindrical lithium-ion secondary battery, i.e., a secondary battery cell.

[0163] Performance test

[0164] The positive electrode and secondary battery cell of the above-described examples and comparative examples were each tested.

[0165] (1) bipolar plate

[0166] [Particle Size Test]

[0167] Positive active material D v 50 test stages:

[0168] 10 mg of positive electrode active material was dispersed in an ethanol solution, ultrasonic dispersion was initiated, and the particle size was tested using the laser particle size test method with a Malvern Master3000 particle size analyzer. After computer data processing is completed, a particle size distribution curve of the positive electrode active material can be obtained, and the particle size corresponding to the cumulative volume distribution reaching 50%, i.e., Dv50, can be obtained.

[0169] [Voltage Platform Test]

[0170] Voltage Platform Calculation: A button-type half-cell was assembled with a positive electrode containing a positive active material, a separator, and a metallic lithium anode. The button-type half-cell was charged at 0.33C until it reached 3.8V (LFP) or 4.2V (LMFP), then left to stand for 10 minutes, and discharged at 0.33C until the voltage of the button-type half-cell reached 1.5V. During the 0.33C discharge process, the discharge energy E and capacity C of the battery cell were recorded, and the charge / discharge voltage platform range of the battery cell was obtained using the formula V=E / C, which is the operating voltage range of the corresponding positive active material.

[0171] [Coating Layer Flexibility Test]

[0172] Measurement of the curvature of the entire positive active layer (Electrochemical Impedance Spectroscopy): An electrode piece containing the positive active material and a separator were assembled into a soft-pack type symmetrical battery. 60 μL of 50 mM tetrabutylammonium perchlorate electrolyte (where the solvent EC:DMC=1:1 and the lithium-ion conductivity: 1.7 mS / cm) was added to each battery, and the electrochemical impedance spectrum was obtained by testing in the frequency range of 200 kHz to 50 m Hz. The curvature can be calculated using the formula τ / ε = Rion × S × kint / l. Here, τ is the curvature, ε is the porosity, l is the thickness of the electrode piece, S is the area of ​​the electrode piece, kint is the lithium-ion conductivity of the electrolyte, and Rion is the lithium-ion impedance. Rion = 3 × (Rh - Rl), where Rh is the high-frequency intercept of the impedance spectrum and Rl is the low-frequency intercept.

[0173] Comparative measurement of curvature between the first and second active layers (calculation of curvature in single-layer SEM electron microscope images): Single-layer SEM images were loaded into ImageJ software, and ion paths without active material were obtained by adjusting grayscale and contrast. Then, the ratio between the ion flow path in the direction of electrode thickness and the corresponding electrode coating layer thickness was calculated using the imaging method, and a curvature comparison was performed.

[0174] (2) Secondary battery cell

[0175] Electrochemical performance test: A discharge DCR (internal resistance) test under room temperature conditions was performed on the secondary battery cells manufactured in the above-described examples and comparative examples: the battery cell was fully charged at 1 / 3C at 25℃, discharged to 50% SOC at 1 / 3C, left to stand for 30 minutes, and the voltage at this point was recorded as V0, then discharged for 10 seconds at a discharge current I of 4C, and the voltage at this point was recorded as V1, and DCR=[(V0-V1) / I].

[0176] The test results are as shown in Table 2.

[0177] Table 1 Material ratio of the anode active layer

[0178] Parameters of each layer Second active layer First active layer Weight ratio of the first positive active material and the second positive active material Total compression density (g / cm 3 ) Second positive active material Dv50 Voltage range (V) Coating weight / 1540.25mm 2 1st positive active material Dv50 Voltage range (V) Coating weight / 1540.25mm 2 Example A1 Lithium iron phosphate 100nm Lithium iron silicate 200nm 2.0-3.0 43mg Lithium iron phosphate 0.3μm 3.1-4.0 387mg 9:1 2.63 Example A2 Difference from Example A1: There is a conductive coating layer between the second active layer and the current collector. Example A3 Difference from Example A1: The first active layer has no conductive agent, and the ratio of the first active material to the adhesive is 98:2. Example A4 Difference from Example A1: The coating weight of the second active layer is 129 mg, and the coating weight of the first active layer is 301 mg (the weight ratio of the first positive active material to the second positive active material is 7:3). Example A5 Difference from Example A1: The ratio of lithium iron phosphate:lithium iron silicate:conductor:adhesive in the second active layer is 86.4:9.6:2:2. Example A6 Difference from Example A1: The second positive electrode active material is lithium iron phosphate (100 nm) and lithium vanadate (300 nm) in equal proportions. Example A7 Difference from Example A1: The first positive electrode active material is lithium manganese iron phosphate (0.3 μm), and the voltage range is 3.1 to 4.2 V. Example A8 Difference from Example A1: The first positive active material is lithium iron phosphate (0.1 μm). Example A9 Difference from Example A1: The first positive active material is lithium iron phosphate (1 μm). Example A10 Difference from Example A1: The second positive active material is lithium iron phosphate (200 nm) and lithium iron silicate (500 nm) in equal proportions; and the first positive active material is lithium iron phosphate (0.5 μm). Comparative Example A1 Difference from Example 1: Only the first active layer is prepared on the anode current collector, and the coating weight is 430 mg. Comparative Example A2 Difference from Example 1: Lithium iron phosphate with a Dv50 of 100 nm, lithium iron silicate with a Dv50 of 0.3 μm, acetylene black, and PVDF are coated on the entire cathode active layer at percentage contents of 86.4%, 9.6%, 2%, and 2%, respectively, and the coating weight is 430 mg.

[0179] Table 2 Test Results

[0180] Test parameters Curvature of the positive plate of a secondary battery cell DCRΩ of a secondary battery cell Secondary battery cell 50% SOC, 25℃, 5KW discharge end voltage (V) Relationship between the curvature magnitudes of the second active layer and the first active layer Overall curvature Example B1 Second active layer > First active layer 3.0 0.040 2.3 Example B2 Second active layer > First active layer 3.0 0.038 2.32 Example B3 Second active layer = First active layer 3.0 0.042 2.1 Example B4 Second active layer > First active layer 3.0 0.037 2.4 Example B5 Second active layer > First active layer 3.0 0.041 2.29 Example B6 Second active layer > First active layer 3.0 0.036 2.42 Example B7 Second active layer > First active layer 3.0 0.034 2.7 Example B8 Second active layer > First active layer 3.4 0.039 2.31 Example B9 Second active layer > First active layer 3.3 0.050 2.0 Example B10 Second active layer > First active layer 3.5 0.048 2.05 Comparative Example B1 - 3.9 0.055 1.6 Comparative Example B2 3.6 0.051 2.0

[0181] As can be seen in Table 2, based on the embodiment of the present application, the positive active layer of the positive plate comprises two layers, namely a second active layer and a first active layer sequentially installed on the positive current collector, and the operating voltage range of the first positive active material is 3.1 to 4.0 V, which is greater than the operating voltage range of the second positive active material, which is 2.0 to 3.0 V, and furthermore, the overall curvature is smaller than that of the comparative example having only a single active layer. Accordingly, the DCR internal resistance of the battery of the embodiment of the present application becomes smaller, and the discharge terminal voltage tested under the same conditions (50% SOC, 25℃, 5KW discharge) becomes larger, that is, the discharge capability of the battery of the embodiment of the present application is better.

[0182] Here, compared to Example B1, the positive electrode of the battery in Example B2 has a conductive coating layer between the second active layer and the current collector, thereby further improving the discharge capacity of the battery. Compared to Example B1, the positive electrode of the battery in Example B3 omits the conductor in the second active layer, and since the curvature of the two active layers is substantially the same, the discharge capacity of the battery is slightly lower. Compared to Example B1, the specific gravity of the second positive electrode active material in the positive electrode of Example B4 increases, so the discharge capacity in the low-voltage range can be extended, thereby slightly improving the discharge capacity of the battery cell. Compared to Example B1, the proportion of lithium iron silicate in the second active layer in the positive electrode of Example B5 is lower, so the discharge capacity in the low-voltage range decreases, and thus the discharge capacity of the battery cell is slightly lower. Compared to Example B1, lithium vanadate is used in the second active layer in the positive electrode of Example B6, and since the ion transport path is extended due to the three-dimensional ion transport channel of lithium vanadate, the discharge capacity is slightly improved. Compared to Example B1, the positive electrode of the battery in Example B7 uses lithium manganese iron phosphate in the first active layer, and since the voltage of lithium manganese iron phosphate is higher, the discharge terminal voltage of the battery cell increases, thereby further improving the discharge capability. Compared to Example B1, compared to Example B1, compared to Example B8, compared to Example B1, compared to Example B8, compared to Example B8, compared to Example B1, compared to Example B8, compared to Example B9, compared to Example B1, compared to Example B9, compared to Example B1, compared to Example B9, compared to Example B1, compared to Example B1, compared to Example B1, compared to Example B1, compared to Example B1, compared to Example B10, compared to Example B1, compared to Example B1, compared to Example B1, since the lithium ion diffusion path is increased, the discharge capability is slightly weakened.

[0183] Finally, it should be noted that each of the above embodiments is used merely to illustrate the technical solution of this application and is not intended to limit it; although this application has been described in detail with reference to each of the aforementioned embodiments, those skilled in the art may still modify the technical solution described in each of the aforementioned embodiments or replace some or all of the technical features therein with equivalents, provided that such modification or replacement does not deviate the essence of the corresponding technical solution from the scope of the technical solution of each embodiment of this application, and that all such modifications or replacements are included within the scope of the claims and specification of this application. In particular, all technical features mentioned in each embodiment may be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein and includes all technical solutions that fall within the scope of the claims. Explanation of the symbols

[0184] 11-Anode current collector; 12-Anode active layer; 121-First active layer; 122-Second active layer; 123-Conductive coating layer; 20-Battery cell; 21-Housing; 22-Top cover assembly; 23-Electrode assembly; 30-Battery module; 40-Battery pack; 41-Top case; 42-Bottom case

Claims

Claim 1 A positive plate, wherein the positive plate comprises a positive current collector and a positive active layer installed on at least one surface of the positive current collector, wherein the positive active layer comprises a first active layer and a second active layer, and the second active layer is located between the positive current collector and the first active layer; wherein the first active layer comprises a first positive active material and the second active layer comprises a second positive active material, wherein the operating voltage range of the first positive active material is greater than the operating voltage range of the second positive active material, the operating voltage range of the first positive active material is greater than 3.0V, and the operating voltage range of the second positive active material is 1.5V to 3.0V, and the second positive active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate, and simultaneously comprises lithium iron silicate. Claim 2 In claim 1, the first positive active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate. Claim 3 A positive plate according to claim 1, wherein the ratio of the total weight of lithium iron phosphate and lithium manganese iron phosphate and the total weight of lithium iron silicate among the second positive active materials is 1:1 to 9:

1. Claim 4 In claim 1, the anode piece, wherein the particle size Dv50 of the first anode active material is larger than the particle size Dv50 of the second anode active material. Claim 5 In claim 4, the anode piece, wherein the particle size Dv50 of the first anode active material is 300 nm to 2 μm and the particle size Dv50 of the second anode active material is 10 nm to 300 nm. Claim 6 A positive plate according to claim 1, wherein the weight ratio of the first positive active material to the second positive active material is 7:3 to 9:

1. Claim 7 In claim 6, the coating weight of the first active layer is 160 mg / 1540.25 mm 2 ~ 500mg / 1540.25mm 2 and the coating weight of the second active layer is 16 mg / 1540.25 mm 2 ~ 100mg / 1540.25mm 2 and / or, the total compressive density of the first active layer and the second active layer is 2.3 to 3.0 g / cm³ 3 Phosphorus, bipolar side. Claim 8 In claim 1, the porosity of the first active layer is greater than the porosity of the second active layer; and / or, the curvature of the first active layer is smaller than the curvature of the second active layer, an anode piece. Claim 9 An anode piece according to claim 1, wherein a conductive coating layer is also installed between the second active layer and the anode current collector, and the conductive coating layer contains 50 to 95% of a conductive agent based on the total weight of the conductive coating layer as 100%. Claim 10 A method for manufacturing an anode according to claim 1, wherein the method comprises: a step of manufacturing the second active layer on at least one surface of the anode current collector; and a step of manufacturing the first active layer on a surface of the second active layer located far from the anode current collector. Claim 11 A method of manufacturing according to claim 10, wherein the step of manufacturing the second active layer on at least one surface of the positive current collector comprises: first manufacturing a conductive coating layer on at least one surface of the positive current collector, and then manufacturing the second active layer on a surface of the conductive coating layer located far from the positive current collector; wherein, based on 100% of the total weight of the conductive coating layer, the conductive coating layer contains 50 to 95% of a conductive agent. Claim 12 A battery comprising, wherein, a positive electrode according to claim 1 and / or a positive electrode manufactured by the manufacturing method according to claim 10. Claim 13 An electric device including a battery according to paragraph 12. Claim 14 delete

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