Battery, positive pole piece, preparation method of positive pole piece and power utilization device

Abstract

The invention provides a battery, a positive pole piece, a preparation method of the positive pole piece and a power utilization device. The battery comprises a positive pole piece, the positive pole piece comprises a positive pole film layer, and the positive pole film layer comprises a positive pole active layer and a positive pole interface layer arranged on the surface of the positive pole active layer; wherein the positive electrode interface layer comprises a polar polymer and a polar solvent, and the polar solvent comprises one or more of a sulfone solvent, a sulfoxide solvent, a nitrile solvent, fluorocarbonate, a fluoroether solvent, fluorosulfate, fluorocarboxylate and fluorosilane. Therefore, the cycle performance and the storage performance of the battery can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery, a positive electrode sheet, a preparation method thereof, and an electric device. BACKGROUND

[0002] In recent years, with the application range of batteries becoming more and more extensive, batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since the battery has developed greatly, higher requirements have been put forward for the cycle performance and storage performance of the battery. SUMMARY

[0003] To achieve the above-mentioned purpose, the present application provides a battery with better cycle performance and storage performance. In addition, a positive electrode sheet, a preparation method thereof, and an electric device are also provided.

[0004] In a first aspect of the present application, a battery is provided, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode film layer, the positive electrode film layer comprising a positive electrode active layer and a positive electrode interface layer arranged on the surface of the positive electrode active layer.

[0005] The positive electrode interface layer comprises a polar polymer and a polar solvent, and the polar solvent comprises one or more of a sulfone solvent, a sulfoxide solvent, a nitrile solvent, a fluorinated carbonate, a fluorinated ether solvent, a fluorinated sulfate, a fluorinated carboxylate, and a fluorinated silane.

[0006] Therefore, in the battery, the positive electrode interface layer is constructed on the surface of the positive electrode film layer of the positive electrode sheet, and the polar polymer in the positive electrode interface layer interacts with the specific type of polar solvent, which can improve the cycle performance and storage performance of the battery.

[0007] In some embodiments of the present application, in the positive electrode interface layer, the polar solvent is filled in the interior of the polar polymer. The polar solvent is bound in the interior of the polar polymer by the polar functional groups of the polymer, showing a state similar to a gel, and the positive electrode interface layer can also be referred to as a gel interface layer.

[0008] In some embodiments of the present application, the polar polymer comprises one or more of polyether sulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, and a modified product thereof.

[0009] In some embodiments of the present application, the oxidation voltage of the polar polymer is > 4.3V vs Li / Li + .

[0010] In some embodiments of the application, the polar solvent comprises one or more of a nitrile solvent, a sulfone solvent, a sulfoxide solvent, a fluorinated carbonate, a fluorinated ether solvent, a fluorinated sulfates, a fluorinated carboxylate, a fluorinated nitrile solvent, and a fluorinated silane.

[0011] In some embodiments of the application, the polar solvent comprises one or more of dimethyl sulfoxide, sulfolane, and tetramethyl sulfoxide.

[0012] In some embodiments of the application, the mass content of the polar solvent in the cathode film layer is > 0 and ≤ 1%.

[0013] In some embodiments of the application, the cathode interface layer further comprises an electrolyte salt.

[0014] Optionally, the electrolyte salt comprises a lithium salt; more optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium hexafluoroarsenate, and lithium bis-trifluoromethanesulfonylimide.

[0015] In some embodiments of the application, the mass content of the electrolyte salt in the cathode interface layer is 0% to 50%.

[0016] In some embodiments of the application, the upper limit of the charge cut-off voltage of the battery is > 4.3 V vs Li / Li + .

[0017] Optionally, the upper limit of the charge cut-off voltage of the battery is ≥ 4.4 V vs Li / Li + .

[0018] In some embodiments of the application, the cathode active layer comprises a cathode active material, which comprises one or more of lithium cobaltate, lithium nickel-manganese-oxide, lithium cobalt-phosphate, lithium nickel-phosphate, lithium iron-silicate, lithium manganese-iron-silicate, and coated and doped modifications thereof.

[0019] In some embodiments of the application, the cathode active layer further comprises a binder, which comprises one or more of polyether sulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, styrene butadiene rubber, butadiene-acrylonitrile rubber, hydrogenated butadiene-acrylonitrile rubber, polyvinyl butyral, polyetherimide, and modifications thereof; optionally, the binder comprises one or more of polyether sulfone, polyacrylonitrile, and aliphatic polysulfone.

[0020] In some embodiments of the application, the cathode active layer comprises a cathode active material, and the mass content of the cathode active material in the cathode active layer is 70% to 98%.

[0021] In some embodiments of the present application, the battery further comprises an electrolyte, and the electrolyte contains a carbonate;

[0022] Optionally, the carbonate comprises one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0023] In a second aspect of the present application, a positive electrode sheet is provided, which comprises a positive electrode film layer, and the positive electrode film layer comprises a positive electrode active layer and a positive electrode interface layer arranged on the surface of the positive electrode active layer.

[0024] The positive electrode interface layer comprises a polar polymer and a polar solvent, and the polar solvent comprises one or more of a nitrile-based solvent, a sulfone-based solvent, a fluoro-carbonate, a fluoro-ether-based solvent, a fluoro-sulfate, a fluoro-carboxylate, a fluoro-nitrile-based solvent, a fluoro-sulfone-based solvent, and a fluoro-silane.

[0025] In some embodiments of the present application, the positive electrode sheet is defined as in the battery of the first aspect of the present application.

[0026] In a third aspect of the present application, a preparation method of a positive electrode sheet is provided, which comprises the following steps:

[0027] The coating liquid is used to coat at least the surface of the positive electrode active layer in the positive electrode sheet raw material, and then dried.

[0028] The positive electrode active layer in the positive electrode sheet raw material comprises a polar polymer, and the coating liquid comprises a polar solvent; or the positive electrode active layer in the positive electrode sheet raw material does not contain a polar polymer, and the coating liquid comprises a polar solvent and a polar polymer.

[0029] The polar solvent comprises one or more of a nitrile-based solvent, a sulfone-based solvent, a fluoro-carbonate, a fluoro-ether-based solvent, a fluoro-sulfate, a fluoro-carboxylate, a fluoro-nitrile-based solvent, a fluoro-sulfone-based solvent, and a fluoro-silane.

[0030] In some embodiments of the present application, the polar polymer comprises one or more of polyether sulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, and modified products thereof.

[0031] In some embodiments of the present application, the positive electrode active layer in the positive electrode sheet raw material comprises a polar polymer, and the mass content of the polar polymer in the positive electrode active layer is 0.1% to 10%, and / or the mass content of the polar solvent in the coating liquid is 90% to 100%, optionally 95% to 100%; or,

[0032] The positive electrode active layer in the positive electrode tab raw material does not contain a polar polymer, the coating liquid contains a polar solvent and a polar polymer, the solid content of the coating liquid is 0.1 wt % to 10 wt %, optionally 0.1 wt % to 5 wt %, and / or the mass content of the polar solvent in the coating liquid is 90% to 99.9%, optionally 95% to 99.9%.

[0033] In some embodiments of the present application, the coating liquid further comprises an electrolyte salt;

[0034] Optionally, the electrolyte salt comprises a lithium salt; more optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium hexafluoroarsenate, and lithium bis-trifluoromethanesulfonylimide.

[0035] In some embodiments of the present application, the coating liquid further comprises a polar polymer, and the mass ratio of the polar polymer to the electrolyte salt in the coating liquid is (1-10):1.

[0036] In some embodiments of the present application, the mass content of the coating liquid coated on the positive electrode tab raw material is 1% to 50%, optionally 1% to 15%, relative to the mass of the positive electrode film layer.

[0037] In a fourth aspect of the present application, a power-using device is provided, comprising one or more of the battery provided in the first aspect of the present application, the positive electrode tab provided in the second aspect of the present application, and the positive electrode tab prepared by the preparation method provided in the third aspect of the present application.

[0038] The power-using device of the present application comprises the battery provided in the present application, and thus at least has the same advantages as the battery.

[0039] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to better describe and illustrate the embodiments or examples provided in the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments or examples, and any one of the best modes of these applications presently understood. Moreover, the same reference numbers are used to represent the same components throughout the drawings. In the drawings:

[0041] Figure 1 A schematic diagram of a secondary battery according to an embodiment of the present application.

[0042] Figure 2is Figure 1 is an exploded view of the secondary battery of one embodiment of the present application.

[0043] Figure 3 is a schematic view of the battery module of one embodiment of the present application.

[0044] Figure 4 is a schematic view of the battery pack of one embodiment of the present application.

[0045] Figure 5 is Figure 4 is an exploded view of the battery pack of one embodiment of the present application.

[0046] Figure 6 is a schematic view of an electric device using the secondary battery of one embodiment of the present application as a power supply.

[0047] Figure 7 is a graph of the capacity retention rate of the batteries of Example 1 and Comparative Example 1 in the 45 °C cycle property test.

[0048] Figure 8 is a graph of the cycle DCR of the batteries of Example 1 and Comparative Example 1 in the 45 °C cycle property test.

[0049] Figure 9 is a graph of the storage reversible capacity retention rate of the batteries of Example 1 and Comparative Example 1 in the 45 °C storage property test.

[0050] Figure 10 is a graph of the storage reversible capacity of the batteries of Example 1 and Comparative Example 1 in the 45 °C storage property test.

[0051] BRIEF DESCRIPTION OF DRAWINGS

[0052] 1, battery pack; 2, upper case; 3, lower case; 4, battery module; 5, battery cell; 51, case; 52, electrode assembly; 53, cover plate. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0054] "ranges" disclosed herein can be defined, for example, by the lower and upper values. Any lower limit can independently be combined with any upper limit to define a range of any value. For example, if a range of 60-120 and 80-110 is listed, it is understood that a range of 60-110 and 80-120 is also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, the use of "a" or "an" to describe a single item can be taken as a non-limiting term that means "one or more." Unless otherwise noted, the use of the singular includes the plural. The use of "or" means "and / or," unless otherwise noted. The use of the term "including" as well as other forms for, e.g., "include," "includes," "included," and "includes," is intended to cover a non-exclusive inclusion, such that any process or method that includes several steps can consist of those steps only, or of those steps in combination with one or more stated or implied steps. In this application, expressions of

[0055] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "A" or "an" means "one or more" in reference to an element which can exist more than one at a time. For example, "a" or "an" can mean one or more but not all of something. It is also to be noted that single reference signs can be used with different series of embodiments unless otherwise specified.

[0056] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0057] Reference herein to "an embodiment" or "one embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly understood that the embodiments described herein are merely examples from a potentially infinite variety of embodiments that can be claimed. It is explicitly understood that the phrase "implementation" is used in a similar manner.

[0058] It is understood by those skilled in the art that the order of writing each step in the method of each embodiment or example does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0059] In the present application, A (such as B) means that B is one non-limiting example of A, and it is understood that A is not limited to B.

[0060] In the present application, "optionally", "optional" and "optional" mean that it can or can not be, that is, it means to select from any one of the two parallel schemes of "have" or "have". If there are multiple "options" in a technical solution, if there is no special statement and no contradictory or mutually restrictive relationship, each "option" is independent.

[0061] Currently, higher requirements are put forward for the cycle performance and storage performance of batteries. However, in the battery of the high-voltage positive electrode material system, the carbonic acid ester organic matter in the electrolyte will be oxidized and reduced on the surface of the high-voltage positive electrode material, and the metal ions in the high-voltage positive electrode active material directly contact with the electrolyte, which will accelerate the dissolution under the action of the electrolyte, seriously restricting the play of the electrochemical performance of the high-voltage positive electrode material, and causing the safety problem of the battery.

[0062] Based on this, an embodiment of the present application provides a battery, and correspondingly provides a positive electrode sheet thereof and a preparation method thereof.

[0063] An embodiment of the present application provides a battery and a positive electrode sheet thereof. The battery comprises a positive electrode sheet. The positive electrode sheet comprises a positive electrode film layer, and the positive electrode film layer comprises a positive electrode active layer and a positive electrode interface layer arranged on the surface of the positive electrode active layer. The positive electrode interface layer comprises a polar polymer and a polar solvent, and the polar solvent comprises one or more of a sulfone solvent, a sulfoxide solvent, a nitrile solvent, a fluorinated carbonate, a fluorinated ether solvent, a fluorinated sulfate, a fluorinated carboxylate and a fluorinated silane.

[0064] It can be understood that the positive electrode interface layer in the application plays the role of an artificial chemical-electrochemical interface (CEI) film.

[0065] Therefore, in the battery, the positive electrode interface layer is constructed on the surface of the positive electrode film layer, which can slow down the speed of the electrolyte contacting the positive electrode film layer from the kinetics, thereby inhibiting or reducing the oxidative decomposition of the electrolyte on the positive electrode sheet from the kinetics, and also delaying the dissolution of the metal ions in the positive electrode active material body in the positive electrode film layer under the action of the electrolyte. Specifically, the polar polymer in the positive electrode interface layer interacts with the specific type of polar solvent, forms a good adhesion between the polar polymer and the positive electrode film layer, and at the same time, the polar solvent is bound to the positive electrode film layer side; and the polar solvent mainly plays the role of improving ion conduction, participates in the film formation reaction as a part of the sacrificial agent, and at the same time, may induce a local high concentration of solvation structure, change the oxidative decomposition path of the electrolyte. In this way, the positive electrode film layer containing the positive electrode interface layer can improve the cycle performance and storage performance of the battery.

[0066] Further, the positive electrode film layer containing the positive electrode interface layer can also delay the dissolution of the metal ions in the positive electrode active material body in the positive electrode film layer under the action of the electrolyte, and reduce the deposition of the metal ions in the positive electrode active material body on the negative electrode sheet.

[0067] An embodiment of the application provides a preparation method of a positive electrode sheet, comprising the following steps S10.

[0068] S10, coating at least the surface of the positive electrode active layer in the positive electrode sheet raw material with a coating liquid, and drying.

[0069] In the positive electrode sheet raw material, the positive electrode active layer contains a polar polymer, and the coating liquid contains a polar solvent; or the positive electrode active layer in the positive electrode sheet raw material does not contain a polar polymer, and the coating liquid contains a polar solvent and a polar polymer.

[0070] It can be understood that the positive electrode sheet raw material in S10 includes a positive electrode active layer, which can be self-made, can be purchased or pre-prepared. The positive electrode sheet raw material in S10 can also be called a positive electrode sheet intermediate product.

[0071] It is worth mentioning that the positive electrode interface layer is formed after the coating liquid is dried. The polar polymer in the positive electrode interface layer can have two sources. On the one hand, it can come from the positive electrode film layer. If the positive electrode tab raw material in S10 contains a polar polymer, the coating liquid can contain a polar solvent, and it can not need to contain a polar polymer. Of course, a polar polymer can also be appropriately added as needed. On the other hand, it can come from the coating liquid. For example, the positive electrode active layer in the positive electrode tab raw material does not contain a polar polymer, and the coating liquid contains a polar solvent and a polar polymer.

[0072] Therefore, the above-mentioned preparation method of the positive electrode tab coats or clads the surface of the positive electrode film layer at the tab level to form a positive electrode interface layer, which is different from the traditional cladding of the positive electrode active material particles or the addition of electrolyte additives, slurry additives, etc. in the positive electrode film layer. This method does not affect the normal processing of the positive electrode film layer, does not adversely affect the slurry processing production process of the positive electrode film layer, and does not affect the ion conductivity and electronic conductivity between the particles inside the positive electrode film layer. Moreover, the preparation method does not adversely affect the negative electrode tab.

[0073] More importantly, through research, it is found that, unlike dry film cladding, the present application needs to use a coating liquid containing a specific type of polar solvent to treat the positive electrode film layer, and the prepared positive electrode tab also contains the presence of a polar solvent. The polar solvent is conducive to ion conduction, and at the same time, a part of it can also act as a sacrificial agent to participate in film formation, and can induce a local high-concentration solvation structure to change the oxidation decomposition path of the electrolyte. The polar polymer plays a role in binding the polar solvent on the positive side, reducing the adverse effects of the polar solvent on the negative electrode, such as the incompatibility of dimethyl sulfoxide with graphite negative electrode materials. In this way, the use of the positive electrode film layer containing the positive electrode interface layer can improve the cycle performance and storage performance of the battery.

[0074] Therefore, in some embodiments of the present application, the negative electrode tab of the above-mentioned battery of the present application can contain graphite negative electrode active material. In some embodiments of the present application, optionally, no sulfoxide solvents such as dimethyl sulfoxide and sulfone solvents are actively added to the electrolyte of the above-mentioned battery of the present application to reduce the incompatibility of such solvents with graphite negative electrode materials.

[0075] In some embodiments of the present application, in the positive electrode interface layer, the polar solvent is filled in the interior of the polar polymer. The polar solvent is bound by the polar functional groups of the polymer in the interior of the polar polymer, showing a state similar to a gel, and the positive electrode interface layer can also be called a gel interface layer.

[0076] In some embodiments of the present application, the upper limit of the charge cut-off voltage of the battery is >4.3V vs Li / Li + ; optionally, the upper limit of the charge cut-off voltage of the battery is ≥4.4V vs Li / Li+ The battery of the present application has a high upper limit of the charge cut-off voltage, which can obtain good energy density and power performance, and meanwhile, the above-mentioned positive electrode sheet can inhibit or reduce the oxidative decomposition of the electrolyte on the positive electrode sheet, change the oxidative decomposition path of the electrolyte, delay the dissolution of the metal ions in the positive active material body in the positive electrode film layer under the action of the electrolyte, so as to obtain good energy density and power performance, and play a good cycle performance and storage performance.

[0077] Further, the positive active layer includes a positive active material with a working voltage > 4.3V vs Li / Li + under the charging state of the above-mentioned battery; optionally, the positive active material has a working voltage ≥ 4.4V vs Li / Li + The positive active material with a high working voltage has the advantages of high energy density and high power performance, and meanwhile, through the setting of the positive electrode interface layer, the cycle performance and storage performance of the battery can be improved.

[0078] In some embodiments of the present application, the positive active layer includes a positive active material, and the positive active material includes but is not limited to one or more of lithium cobaltate, lithium nickel manganese acid, lithium cobalt phosphate, lithium nickel phosphate, lithium iron metasilicate, lithium manganese iron metasilicate, and their coated and doped modifications. These positive active materials all belong to high-voltage positive active materials, which have the advantages of high energy density and high power performance, and meanwhile, through the setting of the positive electrode interface layer, the cycle performance and storage performance of the battery can be improved.

[0079] In some embodiments of the present application, in the positive active layer, the mass content of the positive active material is 70% to 98%, for example, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or a range formed by any two of the above-mentioned values as end values; optionally, 85% to 98%, and more optionally, 90% to 98%.

[0080] In some embodiments of the present application, the oxidation voltage of the polar polymer is > 4.3V vs Li / Li + , and optionally, the oxidation voltage of the polar polymer is ≥ 4.4V vs Li / Li + . Thus, these polar polymers still have good stability under a voltage > 4.3V vs Li / Li + , which can be beneficial to the stability of the positive electrode interface layer, and play a role in improving the cycle performance and storage performance of the battery.

[0081] Polar polymer oxidation voltage test method: polar polymer and SP are added into NMP with a mass ratio of 8:2 to stir to obtain a slurry with a certain viscosity, then drop on the end metal part of the platinum electrode, first heat in the air drying oven at 80°C for 24h, then vacuum dry at 100°C for 24h, assemble to obtain an electrolytic cell with platinum electrode as working electrode and lithium metal electrode as reference electrode, and the electrolyte is organic solution of EC (ethylene carbonate) / DMC (dimethyl carbonate) / DEC (diethyl carbonate) (volume ratio 1:1:1) containing 1 mol / L of LiPF6, at this time the platinum electrode as working electrode.

[0082] The linear sweep voltammetry test of the electrochemical workstation is used for testing, the voltage range is set from 3V to 6V, the scan rate is 0.1mV / s, and the dot interval is 1mV, and the potential corresponding to the initial peak position of the obtained LSV curve is the oxidation potential (note that it is necessary to exclude the oxidation potential of lithium salt or electrolyte solvent).

[0083] In some embodiments of the present application, the polar polymer includes but is not limited to one or more of polyether sulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate and modified products thereof. These polar polymers have good stability at a voltage > 4.3V vs Li / Li + The halogenated polyolefin, halogenated polyacrylate and the like still have good stability at a voltage > 4.3V vs Li / Li

[0084] Further, the polar polymer includes one or more of polyether sulfone, polyacrylonitrile and aliphatic polysulfone, which has a better binding effect on the above-mentioned polar solvents than halogenated polyolefin, halogenated polyacrylate and the like. Further, the polar polymer includes polyacrylonitrile.

[0085] In some embodiments of the present application, the mass content of the polar polymer contained in the positive electrode interface layer is 0-99.99%, not 0. As an example, the mass content of the polar polymer contained in the positive electrode interface layer can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99.99%, or a range formed by any two of the above values as end values.

[0086] Further, the sulfone solvent in the polar solvent includes but is not limited to one or more of unhalogenated sulfone solvents and fluorinated sulfone solvents. Further, the sulfone solvent includes but is not limited to cyclic sulfone solvents, which have ring-opening tension, are prone to ring-opening reaction, and the reaction products thereof can participate in the construction of the positive electrode interface layer.

[0087] Further, the sulfoxide solvent in the polar solvent includes but is not limited to one or more of unhalogenated sulfoxide solvents and fluorinated sulfoxide solvents.

[0088] Further, the nitrile solvent in the polar solvent includes but is not limited to one or more of unhalogenated nitrile solvents and fluorinated nitrile solvents.

[0089] Further, the polar solvent includes one or more of dimethyl sulfoxide (DMSO), sulfolane, and tetramethyl sulfoxide. Further, the polar solvent includes dimethyl sulfoxide (DMSO).

[0090] Further, the polar polymer includes polyacrylonitrile, and the polar solvent includes dimethyl sulfoxide (DMSO).

[0091] In some embodiments of the present application, the mass content of the polar solvent in the positive electrode film layer is >0 and ≤1%, as an example, it can be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range formed by any two of the above values as end values. By binding a small amount of polar solvent in the positive electrode interface layer through the polar polymer, the polar solvent is relatively fixed in position, which can inhibit the polar solvent from entering the electrolyte or reduce the adverse effects of the polar solvent on the negative electrode compared to the scheme of directly adding such polar solvent in the electrolyte, for example, the problem of incompatibility of dimethyl sulfoxide with the negative electrode graphite.

[0092] The polar solvent in the positive electrode film layer can be characterized by XPS to qualitatively and quantitatively detect the characteristic elements of the components in the positive electrode interface layer of the positive electrode sheet, the corresponding valence and the environment of the atoms.

[0093] In some embodiments of the present application, the positive electrode interface layer further comprises an electrolyte salt. The electrolyte salt mainly functions to improve the ionic conductivity of the positive electrode interface layer.

[0094] Optionally, the electrolyte salt comprises a lithium salt; more optionally, the lithium salt comprises one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bisfluorosulfonylimide (LiFSI), lithium hexafluoroarsenate (LiAsF6), and lithium bis-trifluoromethanesulfonylimide (LiTFSI). The lithium salt mainly functions to improve the lithium ion conductivity.

[0095] In some embodiments of the present application, the mass content of the electrolyte salt in the positive electrode interface layer is 0% to 50%. For example, the mass content of the electrolyte salt in the positive electrode interface layer can be 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or within a range defined by any two of the above values as end values.

[0096] In some embodiments of the present application, in the preparation method of the positive electrode sheet, the positive electrode active layer in the positive electrode sheet raw material contains a polar polymer, and the coating liquid contains a polar solvent, and can not contain a polar polymer, and thus the mass content of the polar solvent in the coating liquid is 90% to 100%, and can be 95% to 100%, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%, or within a range defined by any two of the above values as end values.

[0097] Further, the positive electrode active layer in the positive electrode sheet raw material contains a polar polymer, and the mass content of the polar polymer in the positive electrode active layer is 0.1% to 10%, for example, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, or within a range defined by any two of the above values as end values, and can be 0.5% to 5%.

[0098] Further, the coating liquid also contains a polar polymer. The polar polymer itself functions to physically separate the positive electrode and the electrolyte, and the addition of the polar polymer in the coating liquid is more conducive to the formation of the positive electrode interface layer by the polar polymer, and the polar polymer itself also functions as an artificial CEI film to inhibit the side reaction of the electrolyte at high voltage.

[0099] Further, the positive electrode active layer in the positive electrode sheet raw material contains a polar polymer, but does not contain one or more of polyether sulfone, polyacrylonitrile, and aliphatic polysulfone, and one or more of polyether sulfone, polyacrylonitrile, and aliphatic polysulfone can be further added in the coating liquid as a polar polymer.

[0100] As an example, when the positive active layer in the positive electrode sheet raw material contains a halogenated polyolefin such as PVDF as a binder, but does not contain one or more of polyether sulfone, polyacrylonitrile and aliphatic polysulfone, the PVDF is insufficient in the solvent binding ability to DMSO and the like, and therefore a polar polymer with stronger polarity can be further added to the coating liquid to bind the solvent molecules to oxidize and decompose to participate in the construction of the positive electrode interfacial layer. In other words, in some embodiments, the positive active layer and the positive electrode interfacial layer contain different kinds of polar polymers, and the polar polymer contained in the positive active layer has a polarity smaller than that of the polar polymer in the positive electrode interfacial layer.

[0101] In some embodiments of the present application, in the preparation method of the positive electrode sheet, the positive active layer in the positive electrode sheet raw material does not contain a polar polymer, and the coating liquid contains a polar solvent and a polar polymer.

[0102] In some embodiments of the present application, the solid content in the coating liquid is 0-10 wt %. Understandably, the solid content in the coating liquid is 0, i.e. the coating liquid is pure solvent. As an example, the solid content in the coating liquid, in terms of mass content, can be 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of the above point values as end values.

[0103] Further, the solid content in the coating liquid is 0.1 wt %-10 wt %, which can be 0.1 wt %-5 wt %, and more preferably 0.1 wt %-2 wt %. Further, the mass content of the polar solvent in the coating liquid is 90%-99.9%, which can be 95%-99.9%, and as an example, can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or a range formed by any two of the above point values as end values. The content of the polar polymer and the electrolyte salt in the coating liquid determines the solid content of the coating liquid, and the solid content affects the viscosity of the solution, the wet film thickness on the surface of the electrode sheet or the coating amount of the coating liquid during coating, and further affects the thickness of the positive electrode interfacial layer.

[0104] In some embodiments of the present application, the coating liquid further comprises an electrolyte salt. Optionally, the electrolyte salt comprises a lithium salt; more optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonimide, lithium hexafluoroarsenate and lithium bis-trifluoromethanesulfonimide.

[0105] Understandably, the coating liquid contains a polar solvent and a polar polymer, at this time, the solid content in the coating liquid refers to the mass content of the polar polymer in the coating liquid. Understandably, the coating liquid contains a polar solvent, a polar polymer and an electrolyte salt, at this time, the solid content in the coating liquid refers to the mass content of the polar polymer and the electrolyte salt in the coating liquid. In other words, the solid content in the coating liquid refers to the sum of the mass content of the solute in the coating liquid except the solvent.

[0106] In some embodiments of the present application, the coating liquid further comprises an electrolyte salt and a polar polymer. At this time, the positive electrode interface layer comprises a polar solvent, an electrolyte salt and a polar polymer. In this way, the electrolyte salt and the polar polymer together build the positive electrode interface layer as an artificial CEI film. The electrolyte salt forms a higher concentration in the positive electrode interface layer, and the solvation structure is changed into a lithium salt wrapped solvent molecule, and the anion is preferentially decomposed to form a more stable CEI film than the solvent, and at the same time, the electrolyte also shows a wider electrochemical window, thereby improving the cycle and storage life at high voltage.

[0107] In some embodiments of the present application, the mass content of the polar polymer in the coating liquid is 0-10%, optionally 0-5%, optionally 0-2%, and more optionally 0-1%. Further, the mass content of the polar polymer in the coating liquid can be 0.1%-10%, optionally 0.1%-5%, optionally 0.1%-2%, and more optionally 0.1%-1%.

[0108] In some embodiments of the present application, the mass content of the electrolyte salt in the coating liquid is 0-5%, optionally 0-2%, and more optionally 0-1%. Further, the mass content of the electrolyte salt in the coating liquid can be 0.1%-5%, optionally 0.1%-2%, and more optionally 0.1%-1%.

[0109] Further, the mass ratio of the polar polymer to the electrolyte salt in the coating liquid is (1-10):1, optionally (1.5-10):1, more optionally (2-10):1, (1-9):1, (1.5-8):1, (2-9):1, (1-2):1, or (1.5-3):1, for example, it can be 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or a range formed by any two of the above as end values.

[0110] In some embodiments of the present application, the mass content of the coating liquid coated on the positive electrode sheet raw material relative to the mass of the positive electrode film layer is 1% to 50%, optionally 1% to 15%, and more optionally 1% to 5%; for example, it can be 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range formed by any two of the above values as end values.

[0111] In the present application, coating includes but is not limited to one or more of dip coating, gravure coating, spray coating, spin coating, printing, dot coating, blade coating, and slot coating. Further, gravure coating includes but is not limited to microgravure coating. Dip coating includes but is not limited to pull-up coating.

[0112] For example, using pull-up coating, the positive electrode sheet containing the positive electrode active layer is first soaked in the coating liquid, then pulled out of the coating liquid at a certain speed, and then dried. Further, the soaking time can be 1 min to 2 min. Further, the pulling speed can be 1 mm / s to 10 mm / s, for example, the pulling speed is 4.67 mm / s, and the pulling speed will affect the wet film thickness on the surface of the sheet. Using a slow pulling speed can obtain a thicker wet film thickness. Further, gradient temperature drying is used, and too fast temperature rising or too high temperature will affect the film forming integrity and continuity of the polymer on the surface of the sheet. For example, drying at room temperature, 45°C, 80°C, and 110°C for 12 h respectively.

[0113] The positive electrode sheet also includes a positive electrode current collector, and the positive electrode active layer described above is provided on the positive electrode film layer of at least one surface of the positive electrode current collector, and the positive electrode interface layer is provided on the side of the positive electrode active layer away from the positive electrode current collector.

[0114] As a non-limiting example, the positive electrode current collector has two opposite surfaces in its own thickness direction, and the positive electrode active layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector. Optionally, the positive electrode interface layer is provided on the positive electrode active layer of any one or both of the two opposite surfaces of the positive electrode current collector.

[0115] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. 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 base layer. The composite current collector can be obtained by forming a metal material on a polymer material base material. Non-limiting examples of the metal material in the positive current collector can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. Non-limiting examples of the polymer material base material in the positive current collector can include one or more of a polypropylene (PP), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polystyrene (PS), a polyethylene (PE), and the like.

[0116] It can be appreciated that if the positive active layer contains the above-mentioned polar polymer, it also functions as a binder. In some embodiments, the positive active layer can employ other binders, or further contain other binders thereon.

[0117] In some embodiments, the positive active layer can further optionally include a binder. Further, the binder includes one or more of a polyether sulfone, a polyacrylonitrile, an aliphatic polysulfone, a polysiloxane, a polyimide, a halogenated polyolefin, a halogenated polyacrylate, a styrene butadiene rubber, an acrylonitrile butadiene rubber, a hydrogenated acrylonitrile butadiene rubber, a polyvinyl butyral, a polyetherimide, and a modification thereof. Further, the halogen element in the halogenated polyolefin and the halogenated polyacrylate includes, but is not limited to, one or more of a fluorine element, a chlorine element. Further, the halogenated polyolefin includes, but is not limited to, one or more of a polyvinyl chloride, a polyvinylidene fluoride, a polytetrafluoroethylene (PTFE), a polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer. Further, the halogenated polyacrylate includes, but is not limited to, a fluorine-containing acrylate resin.

[0118] Further, the binder can include one or more of a polyether sulfone, a polyacrylonitrile, an aliphatic polysulfone, a styrene butadiene rubber, an acrylonitrile butadiene rubber, a hydrogenated acrylonitrile butadiene rubber, a polyvinyl chloride, a polyvinyl butyral, a polyetherimide, a polyvinylidene fluoride (PVDF), a polytetrafluoroethylene (PTFE), a polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0119] Further, the binder can include one or more of a polyether sulfone, a polyacrylonitrile, and an aliphatic polysulfone. Optionally, the binder can include a polyacrylonitrile.

[0120] Further, the mass content of the binder in the positive electrode active layer is 0.1% to 10%; for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values as the end value, and it can be 0.5% to 5%.

[0121] In some embodiments, the positive electrode active layer also optionally includes a conductive agent. As a non-limiting example, the conductive agent can include one or more of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the positive electrode active layer can be prepared by dispersing the components described above for preparing the positive electrode active layer, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector; and drying, cold-pressing, or the like to obtain a positive electrode sheet containing the positive electrode active layer.

[0123] Further, in the step of preparing the positive electrode active layer, the solvent can include, but is not limited to, N-methyl pyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector, or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s to 25000mPa·s. When coating the positive electrode slurry, the coating unit area density, in terms of dry weight (excluding solvent), can be 15mg / cm 2 ~35mg / cm 2 . The compaction density of the positive electrode sheet can be 3.0g / cm 3 ~3.6g / cm 3 , optionally 3.3g / cm 3 ~3.5g / cm 3 .

[0124] Generally, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly serves to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0125] Electrolyte

[0126] In some embodiments of the application, the battery further includes an electrolyte. The electrolyte has a function of conducting ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as desired.

[0127] Further, the electrolyte contains a carbonate. The above positive electrode sheet is particularly suitable for an electrolyte system containing a carbonate because carbonate organic substances in the electrolyte are oxidized and reduced on the surface of the high-voltage positive electrode material, and the above positive electrode sheet containing a positive electrode interface layer can suppress the oxidation of the electrolyte on the positive electrode sheet from the kinetic point of view, thus being advantageous in improving the cycle performance and storage performance of the high-voltage battery of the electrolyte system.

[0128] Optionally, the carbonate includes, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). These carbonates can be used as solvents in the electrolyte.

[0129] Further, the above electrolyte further includes an ether solvent, which can include one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), and 1,3-dioxolane (DOL).

[0130] In some embodiments, the electrolyte includes an electrolyte salt for conducting ions. Further, the electrolyte salt includes a lithium salt.

[0131] Further, the electrolyte salt in the electrolyte can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0132] In some embodiments, the electrolyte further optionally includes an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, and the like.

[0133] Negative electrode sheet

[0134] The negative electrode sheet includes a negative current collector. Further, the negative electrode sheet can further include a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer including a negative active material.

[0135] As a non-limiting example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active material layer is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0136] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. 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 base layer. The composite current collector can be obtained by forming a metal material on a polymer material base layer. Non-limiting examples of the metal material in the negative current collector can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the like. Non-limiting examples of the polymer material base layer in the negative current collector can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0137] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As a non-limiting example, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like. The silicon-based material can include one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include one or more of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. The negative active material can be used alone only one kind, or two or more kinds in combination. Optionally, the negative active material includes graphite such as artificial graphite and natural graphite.

[0138] In some embodiments, the negative active material layer can further optionally include a binder. The binder can include one or more 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).

[0139] In some embodiments, the negative active material layer can optionally further include a conductive agent. The conductive agent can include one or more of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the negative active material layer can optionally further include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0141] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative current collector, and after processes such as drying, cold pressing, and the like, obtaining the negative electrode sheet. The surface of the negative current collector to which the negative electrode slurry is coated can be either one surface of the negative current collector or both surfaces of the negative current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 to 10000 mPa·s. When coating the negative electrode slurry, the coating unit area density (excluding the solvent) can be 75 to 220 g / m 2 . The compaction density of the negative electrode sheet can be 1.0 g / cm 3 to 1.8 g / cm 3 .

[0142] Separator film

[0143] In some embodiments, the secondary battery further includes a separator film. The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be used.

[0144] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0145] In some embodiments, the thickness of the separator film is 6 μm to 40 μm, and can be 12 μm to 20 μm.

[0146] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be used to make an electrode assembly through a winding process or a stacking process.

[0147] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and the electrolyte.

[0148] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0149] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0150] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of realizing mutual conversion between chemical energy and electrical energy, and further, generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0151] The battery and the electric device of the present application are described below with appropriate reference to the accompanying drawings.

[0152] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 The illustrated secondary battery is a battery cell, which is an example of a square structure of a battery cell.

[0153] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above. In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0154] In some embodiments, referring to Figure 2 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by a person skilled in the art according to actual needs.

[0155] In some embodiments, the secondary battery can be a battery module or a battery pack. The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0156] Figure 3 The battery module 4 is an example. Refer to Figure 3 In the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. The plurality of battery cells 5 can be further fixed by fasteners.

[0157] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0158] In some embodiments, the battery module described above can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0159] Figure 4 And Figure 5 The battery pack 1 is an example. Refer to Figure 4 And Figure 5 In the battery pack 1, a battery box and a plurality of battery modules 4 arranged in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0160] In addition, the application also provides a power utilization device, which includes one or more of the battery, the positive electrode sheet and the positive electrode sheet prepared by the preparation method described above.

[0161] The battery can be used as a power source of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0162] As the power utilization device, the battery can be selected according to the use requirement thereof.

[0163] Figure 6The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. as an example. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module can be used.

[0164] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery monomer can be used as a power supply.

[0165] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. The description of the at least one exemplary embodiment below is actually only illustrative, but not as any limitation on the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0166] Unless otherwise specified in the embodiments, the technology or conditions are carried out according to the technology or conditions described in the literature in the art or according to the product manual. Unless otherwise specified, the reagents or instruments used are all conventional products that can be obtained from the market.

[0167] Embodiment 1

[0168] The manufacturing process of the battery is as follows:

[0169] (1) Manufacturing of the positive electrode sheet:

[0170] The lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), the conductive agent carbon black (Super P), the polyacrylonitrile and the carbon nanotube are mixed in a mass ratio of 97:1:1:1, and then added into a solvent N-methyl pyrrolidone to be coated on both sides of an aluminum foil. After cold pressing and punching, a positive electrode sheet with a positive electrode active layer formed on both sides is obtained. The obtained positive electrode sheet is immersed in a coating liquid (pure DMSO, dimethyl sulfoxide) for 1 min, and then pulled out of the coating liquid at a speed of 4.67 mm / s. At this time, the mass content of the coating liquid in the positive electrode sheet is 1%. The mass content of the coating liquid in the positive electrode sheet is the mass percentage of the coating liquid and the positive electrode film layer except the current collector in the positive electrode sheet.

[0171] Then, the positive electrode sheet with the positive electrode interface layer is obtained by drying at room temperature, 45°C, 80°C and 110°C respectively for 12 h.

[0172] (2) Manufacturing of the negative electrode sheet:

[0173] The graphite, conductive carbon black, styrene polybutadiene rubber, sodium carboxymethyl cellulose are sampled according to the weight ratio of 96.2:0.8:1.8:1.2, and then water is added and uniformly mixed (the kneaded solid content is 62%, and the total solid content is 50%), and then coated on both sides of the copper foil. After cold pressing and punching, the negative electrode sheet is obtained.

[0174] (3) Isolation film:

[0175] A polyethylene film with a thickness of 12 μm is used as the isolation film.

[0176] (4) Preparation of electrolyte:

[0177] Ethylene carbonate, diethyl carbonate, dimethyl carbonate are mixed according to the volume ratio of 1:1:1, and LiPF6 is dissolved in the above solution to obtain the electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0178] (5) Assembly of battery:

[0179] The positive electrode sheet, the isolation film and the negative electrode sheet are alternately stacked in this order to form a stacked structure; then the electrode and the isolation film are tightly attached through processes such as rolling and hot pressing; next, the electrolyte is fully infiltrated into the electrode sheet by injection and sealing; finally, formation, capacity detection, and packaging into a finished product of the stacked cell.

[0180] Example 2

[0181] Example 2 is basically the same as Example 1, except that the preparation process of the positive electrode sheet is different, specifically as follows:

[0182] In step (1), 0.1wt% of polyacrylonitrile is further added to the coating solution in the preparation of the positive electrode sheet.

[0183] Example 3

[0184] Example 3 is basically the same as Example 1, except that the preparation process of the positive electrode sheet is different, specifically as follows:

[0185] In step (1), 1wt% of polyacrylonitrile is further added to the coating solution in the preparation of the positive electrode sheet.

[0186] Example 4

[0187] Example 4 is basically the same as Example 1, except that the preparation process of the positive electrode sheet is different, specifically as follows:

[0188] In step (1), 2wt% of polyacrylonitrile is further added to the coating solution in the preparation of the positive electrode sheet.

[0189] Example 5

[0190] Example 5 is substantially the same as Example 1, except that the preparation process of the positive electrode sheet is different, specifically as follows:

[0191] Step (1) 0.1wt% polyacrylonitrile is further added in the coating liquid in the preparation of the positive electrode sheet.

[0192] Examples 6-11

[0193] Example 6 is substantially the same as Example 1, except that the parameters shown in Table 1 are different.

[0194] Specifically, 1wt% polyacrylonitrile and 0.1wt% lithium hexafluorophosphate are further added in the coating liquid in the preparation of the positive electrode sheet in Step (1) of Example 6.

[0195] Specifically, 1wt% polyacrylonitrile and 0.5wt% lithium hexafluorophosphate are further added in the coating liquid in the preparation of the positive electrode sheet in Step (1) of Example 7.

[0196] Specifically, 1wt% polyacrylonitrile and 1wt% lithium hexafluorophosphate are further added in the coating liquid in the preparation of the positive electrode sheet in Step (1) of Example 8.

[0197] Specifically, the coating liquid in the preparation of the positive electrode sheet in Step (1) of Example 9 is pure tetramethyl sulfoxide.

[0198] Specifically, 0.1wt% polyacrylonitrile is further added in the coating liquid in the preparation of the positive electrode sheet in Step (1) of Example 10, and equal mass of polyvinylidene fluoride is used to replace the polyacrylonitrile in Example 1 in the positive active layer.

[0199] Specifically, equal mass of polyvinylidene fluoride is used to replace the polyacrylonitrile in Example 1 in the positive active layer in Example 11.

[0200] Comparative Example 1

[0201] Comparative Example 1 is substantially the same as Example 1, except that the preparation of the positive electrode sheet is different, specifically as follows:

[0202] Step (1) The step of processing in the coating liquid in the preparation of the positive electrode sheet is omitted.

[0203] Comparative Example 2

[0204] Comparative Example 2 is substantially the same as Example 1, except that the preparation of the positive electrode sheet and the components of the electrolyte are different, specifically as follows:

[0205] Step (1) The step of processing in the coating liquid in the preparation of the positive electrode sheet is omitted; 1wt% DMSO (dimethyl sulfoxide) is added in the electrolyte.

[0206] Comparative Example 3

[0207] Comparative Example 3 is basically the same as Example 1, except that the preparation of the positive electrode plate in step (1) is different, specifically as follows: the components of the coating liquid are different, specifically pure N-methyl pyrrolidone (NMP) is used, and other parameters are unchanged.

[0208] The following are performance tests.

[0209] The prepared stack cells are subjected to 45℃ cycle performance test, 45℃ storage performance test, mainly focusing on cycle capacity retention rate, cycle capacity, cycle DCR, storage reversible capacity retention rate, storage reversible capacity.

[0210] (1) 45℃ cycle performance test: the following charge-discharge cycle test is carried out at 45℃. The charge-discharge voltage range is 3.5V~4.9V; the charging process in each charge-discharge cycle is: charging to 4.9V at a charge rate of 0.2C, constant voltage charging to current <0.05C; the discharging process in each charge-discharge cycle is: discharging to 3.5V at a discharge rate of 0.5C; wherein, every 50 cycles are discharged once at 0.04C.

[0211] (2) 45℃ storage performance test: the fully charged battery (100% SOC) is stored at 45℃ for 30 days, and one battery is taken out for charge-discharge test at a fixed time every day; the charge-discharge voltage range is 3.5V~4.9V.

[0212] Specifically, first discharge to 3.5V at a discharge rate of 0.33C, then charge to 4.9V at a charge rate of 0.2C, constant voltage charging to current <0.05C; then rest for 5min, and then discharge to 3.5V at a discharge rate of 0.33C, and then rest for 5min and then discharge to 3.5V at a discharge rate of 0.04C.

[0213] The charge-discharge voltage range is 3.5V~4.9V; the charging process is: charging to 4.9V at a charge rate of 0.2C, constant voltage charging to current <0.05C; the discharging process is: first discharging to 3.5V at a charge rate of 0.33C, then resting for 5min and then discharging to 3.5V at a charge rate of 0.04C.

[0214] The capacity retention rate curve of the battery of Example 1 and Comparative Example 1 in the 45℃ cycle performance test, and the cycle DCR curve of the 45℃ cycle performance test, are shown in Figure 7 and Figure 8 The storage reversible capacity retention rate curve of the 45℃ storage performance test, and the storage reversible capacity curve of the 45℃ storage performance test, are shown in Figure 9 and Figure 10 respectively. Among them, the green curve corresponds to Example 1, and the black curve corresponds to Comparative Example 1.

[0215] The preparation parameters and performance tests for each embodiment and comparative example are shown in Table 1 below. Cycling performance refers to the capacity retention rate after 150 cycles at 45°C, and storage performance refers to the reversible capacity retention rate after 30 days of storage at 45°C.

[0216] Table 1

[0217]

[0218] As can be seen from the table above, the performance of the batteries prepared by Comparative Example 1 without coating solution treatment and Comparative Example 3 with pure NMP solvent treatment is comparable. However, Comparative Example 2 without coating solution treatment and with the addition of 1 wt% DMSO to the electrolyte has an adverse effect on the cycle performance and storage performance of the battery.

[0219] Compared with the comparative examples, the battery produced in this application has improved cycle performance and storage performance.

[0220] Compared with Example 1, Examples 2-4 show that Example 1 has higher cycle performance and storage performance. Examples 2-4 also added polar polymers to the coating solution, which is beneficial for the polar polymers to form a positive electrode interface layer, which plays a role in physically isolating the positive electrode and the electrolyte. In addition, it also acts as an artificial CEI film, suppressing the side reactions of the electrolyte under high voltage.

[0221] The coating solutions in Examples 5-8 also contain electrolyte salts, which facilitates the co-construction of the positive electrode interface layer with the electrolyte salts and polar polymers as an artificial CEI film. A high concentration of electrolyte salts is formed at the positive electrode interface layer, and the solvation structure transforms into lithium salt encapsulating solvent molecules. Anions preferentially decompose before the solvent, forming a more stable CEI film. Simultaneously, the electrolyte exhibits a wider electrochemical window, thereby improving cycle life and storage life under high voltage.

[0222] A comparison of Examples 10 and 11 shows that the binder used in the positive electrode active layer is polyvinylidene fluoride. Compared with the coating solution with pure solvent in Example 11, the addition of polyacrylonitrile in the coating solution of Example 10 can improve the cycle performance and storage performance of the battery.

[0223] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0224] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A battery, characterized in that, It includes a positive electrode sheet, the positive electrode sheet includes a positive electrode film layer, the positive electrode film layer includes a positive electrode active layer and a positive electrode interface layer disposed on the surface of the positive electrode active layer; The positive electrode interface layer comprises a polar polymer and a polar solvent, wherein the polar solvent includes one or more of sulfone solvents, sulfoxide solvents, nitrile solvents, fluorocarbonates, fluoroether solvents, fluorosulfates, fluorocarboxylic acids, and fluorosilanes.

2. The battery as described in claim 1, characterized in that, In the positive electrode interface layer, the polar solvent fills the interior of the polar polymer.

3. The battery as described in claim 1 or 2, characterized in that, The polar polymer includes one or more of polyethersulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, and their modified forms.

4. The battery according to any one of claims 1 to 3, characterized in that, The oxidation voltage of the polar polymer is >4.3V vs Li / Li + .

5. The battery according to any one of claims 1 to 4, characterized in that, The polar solvent includes one or more of dimethyl sulfoxide, sulfolane cyclobutane, and tetramethyl sulfoxide.

6. The battery according to any one of claims 1 to 5, characterized in that, In the positive electrode film layer, the mass content of the polar solvent is >0 and ≤1%.

7. The battery according to any one of claims 1 to 6, characterized in that, The positive electrode interface layer also includes an electrolyte salt; Optionally, the electrolyte salt includes a lithium salt; more preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, and lithium bis(trifluoromethanesulfonyl)imide.

8. The battery as claimed in claim 7, characterized in that, In the positive electrode interface layer, the mass content of the electrolyte salt is 0% to 50%.

9. The battery according to any one of claims 1 to 8, characterized in that, The upper limit of the charging cutoff voltage of the battery is >4.3V vs Li / Li + ; Optionally, the upper limit of the charging cutoff voltage of the battery is ≥4.4V vs Li / Li. + .

10. The battery according to any one of claims 1 to 9, characterized in that, The positive electrode active layer includes a positive electrode active material, which includes one or more of lithium cobalt oxide, lithium nickel manganese oxide, lithium cobalt phosphate, lithium nickel phosphate, lithium iron phosphate, lithium manganese iron silicate, and their coatings and doping modifiers.

11. The battery according to any one of claims 1 to 10, characterized in that, The positive electrode active layer further includes a binder, which includes one or more of polyethersulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, styrene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, polyvinyl butyral, polyetherimide, and their modified forms; optionally, the binder includes one or more of polyethersulfone, polyacrylonitrile, and aliphatic polysulfone.

12. The battery according to any one of claims 1 to 11, characterized in that, The positive electrode active layer includes a positive electrode active material, and the mass content of the positive electrode active material in the positive electrode active layer is 70% to 98%.

13. The battery according to any one of claims 1 to 12, characterized in that, The battery also includes an electrolyte containing carbonate; Optionally, the carbonate includes one or more of ethylene carbonate, propylene carbonate, butene carbonate, vinylene carbonate, fluoroethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

14. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive electrode film layer, which includes a positive electrode active layer and a positive electrode interface layer disposed on the surface of the positive electrode active layer. The positive electrode interface layer comprises a polar polymer and a polar solvent, wherein the polar solvent includes one or more of nitrile solvents, sulfone solvents, fluorocarbonates, fluoroether solvents, fluorosulfates, fluorocarboxylic acids, fluoronitrile solvents, fluorosulfonates, and fluorosilanes.

15. The positive electrode sheet as described in claim 14, characterized in that, The positive electrode is as defined in any one of claims 2 to 13.

16. A method for preparing a positive electrode sheet, characterized in that, Includes the following steps: The coating solution is applied to at least the surface of the positive electrode active layer in the positive electrode material, and then dried. Wherein, the positive electrode active layer in the positive electrode raw material contains a polar polymer, and the coating liquid contains a polar solvent; or, the positive electrode active layer in the positive electrode raw material does not contain a polar polymer, and the coating liquid contains a polar solvent and a polar polymer. The polar solvent includes one or more of nitrile solvents, sulfone solvents, fluorocarbonates, fluoroether solvents, fluorosulfates, fluorocarboxylic acids, fluoronitrile solvents, fluorosulfonates, and fluorosilanes.

17. The method for preparing the positive electrode sheet as described in claim 16, characterized in that, The polar polymer includes one or more of polyethersulfone, polyacrylonitrile, aliphatic polysulfone, polysiloxane, polyimide, halogenated polyolefin, halogenated polyacrylate, and their modified forms.

18. The method for preparing the positive electrode sheet as described in claim 16 or 17, characterized in that, The positive electrode active layer in the positive electrode raw material contains a polar polymer, the mass content of the polar polymer in the positive electrode active layer is 0.1% to 10%, and / or the mass content of the polar solvent in the coating solution is 90% to 100%, optionally 95% to 100%; optionally, the coating solution also contains a polar polymer. Alternatively, the positive electrode active layer in the positive electrode raw material does not contain a polar polymer, the coating solution contains a polar solvent and a polar polymer, the solid content of the coating solution is 0.1wt%~10wt%, optionally 0.1wt%~5wt%, and / or the mass content of the polar solvent in the coating solution is 90%~99.9%, optionally 95%~99.9%.

19. The method for preparing the positive electrode sheet as described in claim 16, characterized in that, The coating solution also includes electrolyte salts; Optionally, the electrolyte salt includes a lithium salt; more preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, and lithium bis(trifluoromethanesulfonyl)imide.

20. The method for preparing the positive electrode sheet as described in claim 19, characterized in that, The coating solution also includes a polar polymer, and the mass ratio of the polar polymer to the electrolyte salt in the coating solution is (1~10):

1.

21. The method for preparing the positive electrode sheet according to any one of claims 16 to 20, characterized in that, The mass content of the coating liquid coated on the positive electrode raw material is 1% to 50% relative to the mass of the positive electrode film layer, and can be selected as 1% to 15%.

22. An electrical appliance, characterized in that, It includes one or more of the following: the battery according to any one of claims 1 to 13, the positive electrode sheet according to claim 14 or 15, and the positive electrode sheet prepared by the preparation method according to any one of claims 16 to 21.

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