Positive electrode additive, positive electrode plate, battery and electric device

Abstract

The invention relates to a positive electrode additive, a positive electrode plate, a battery and an electric device. The positive electrode additive has a structure as shown in a formula (1), each R1 independently comprises any one of H, and at least one of two R1 connected to two adjacent carbon atoms comprises n which is an integer greater than or equal to 1; and each R2 is independently selected from any one of a substituted or unsubstituted alkyl group and a substituted or unsubstituted alkoxy group. The positive electrode additive has good toughening performance, can be used as a toughening agent, can be used in a positive electrode plate of a battery as the positive electrode additive to play a role in toughening, and can improve the flexibility of the positive electrode plate, so that the processability of the positive electrode plate can be improved, and meanwhile, relatively high compaction density can be realized, thereby improving the energy density of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode additive, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, as the application scope of lithium-ion batteries and other batteries has become increasingly wide, lithium-ion batteries and other batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. Accordingly, higher requirements are placed on the energy density of batteries. One of the key factors affecting energy density is the compaction density of the positive electrode sheet. However, one of the main factors limiting the improvement of compaction density is that the increase in compaction density reduces the flexibility of the positive electrode sheet. After hot pressing in the winding process, the inner circle of the sheet will be folded in half, and eventually the positive electrode sheet will crack due to poor flexibility, resulting in a decrease in battery cell capacity or causing safety problems. Therefore, how to achieve a higher compaction density while improving the processing performance of the positive electrode sheet is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] Based on this, it is necessary to provide a positive electrode additive, a positive electrode sheet, a battery and an electrical device, aiming to improve the flexibility of the positive electrode sheet, thereby improving the processing performance of the positive electrode sheet while achieving a higher compaction density, thereby improving the energy density of the battery.

[0005] This application is achieved through the following technical solutions.

[0006] In a first aspect of the present application, a positive electrode additive is provided, wherein the positive electrode additive has a structure as shown in formula (1):

[0007]

[0008] Each R1 independently comprises or H, at least one of the two R1s connected to two adjacent carbon atoms includes n is an integer ≥ 1;

[0009] Each R2 is independently selected from any one of a substituted or unsubstituted alkyl group and a substituted or unsubstituted alkoxy group.

[0010] The above-mentioned positive electrode additive uses a castor oil structure as the mother core structure, which has multiple long flexible chain segments, so it can provide good flexibility. The castor oil structure is introduced into R1 through the maleic anhydride open ring structure. R1 is a rigid styrene or polystyrene structure, which can reduce the self-agglomeration of the positive electrode additive molecules. In addition, the end groups of the maleic anhydride open ring structure are independently selected from any one of substituted or unsubstituted alkyl and substituted or unsubstituted alkoxy groups, which can avoid the problem that the end groups are active groups such as hydroxyl groups that react in the battery and cause the battery performance to deteriorate. The above-mentioned positive electrode additive has good toughening properties and can be used as a toughening agent. It is used in the positive electrode sheet of the battery as a positive electrode additive to play a toughening role, which can improve the flexibility of the positive electrode sheet, and then achieve a larger compaction density while improving the processing performance of the positive electrode sheet, thereby improving the energy density of the battery. On the other hand, due to the improved flexibility of the positive electrode sheet, its anti-cracking performance when subjected to stress can be improved, thereby improving the service life of the positive electrode sheet.

[0011] In any embodiment of the present application, each R2 is independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms.

[0012] In any embodiment of the present application, each R2 is a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms; or, each R2 is a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms.

[0013] In any embodiment of the present application, each R2 is methyl; or, each R2 is -OCH3.

[0014] In any embodiment of the present application, one of the two R1s connected to two adjacent carbon atoms is the other is H; and / or,

[0015] n is an integer from 1 to 15.

[0016] The second aspect of the present application provides a method for preparing a positive electrode additive, comprising the following steps:

[0017] The compound of formula (2) and H-R2 are subjected to an esterification reaction to obtain a positive electrode additive of formula (1);

[0018] The structures of the positive electrode additive of formula (1) and the compound of formula (2) are as follows, wherein each R2 is a substituted or unsubstituted alkoxy group;

[0019]

[0020] The second aspect of the present application provides a method for preparing a positive electrode additive, comprising the following steps:

[0021] The compound of formula (2) is subjected to an acyl halide reaction with an acyl halide reagent to obtain a compound of formula (3);

[0022] Then, the compound of formula (3) is subjected to a nucleophilic substitution reaction with an organic lithium reagent R2-Li to obtain a positive electrode additive of formula (1);

[0023] The structures of the positive electrode additive of formula (1), the compound of formula (2) and the compound of formula (3) are as follows, wherein each R2 is a substituted or unsubstituted alkyl group;

[0024]

[0025] The third aspect of the present application provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer, wherein the positive electrode film layer is arranged on at least one surface of the positive electrode current collector, and the components of the positive electrode film layer include a positive electrode active material and the positive electrode additive provided in the first aspect of the present application.

[0026] Adding the aforementioned positive electrode additive to the positive electrode film layer of the aforementioned positive electrode sheet can improve the flexibility of the positive electrode sheet, thereby improving the processing performance of the positive electrode sheet while achieving a higher compaction density, thereby increasing the energy density of the battery. Furthermore, the increased flexibility of the positive electrode sheet can improve its crack resistance under stress, thereby extending the service life of the positive electrode sheet.

[0027] In any embodiment of the present application, in the positive electrode film layer, the mass content of the positive electrode additive is 0.05% to 5%.

[0028] In any embodiment of the present application, in the positive electrode film layer, the mass content of the positive electrode additive is 0.1% to 1%.

[0029] In any embodiment of the present application, in the positive electrode film layer, the mass content of the positive electrode active material is 80% to 98%.

[0030] In any embodiment of the present application, the positive electrode sheet satisfies at least one of the following conditions:

[0031] (1) The positive electrode film layer further includes a conductive agent, and the mass content of the conductive agent in the positive electrode film layer is 0.1% to 5%;

[0032] (2) The positive electrode film layer further includes a binder, and the binder has a mass content of 0.1% to 5% in the positive electrode film layer.

[0033] In any embodiment of the present application, the positive electrode active material is lithium iron phosphate, and the compaction density of the positive electrode sheet is 2.3 g / cm 3 ~2.8g / cm 3 .

[0034] In any embodiment of the present application, the positive electrode active material is a ternary positive electrode material, and the compaction density of the positive electrode sheet is 3.3 g / cm 3 ~3.8g / cm 3 .

[0035] In any embodiment of the present application, the compaction density of the positive electrode sheet is 3.55 g / cm 3 ~3.8g / cm 3 .

[0036] In a fourth aspect of the present application, a battery is provided, comprising the positive electrode additive provided in the first aspect of the present application and at least one of the positive electrode plates provided in the third aspect of the present application.

[0037] In a fifth aspect of the present application, an electrical device is provided, which includes at least one of the positive electrode additive provided in the first aspect of the present application, the positive electrode plate provided in the third aspect of the present application, and the battery provided in the fourth aspect of the present application.

[0038] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0040] Figure 1 Schematic diagram of a battery cell according to one embodiment of the present application.

[0041] Figure 2 yes Figure 1 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0042] Figure 3 Schematic diagram of a battery module according to one embodiment of the present application.

[0043] Figure 4 Schematic diagram of a battery pack according to one embodiment of the present application.

[0044] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0045] Figure 6 Schematic diagram of an electrical device using a battery as a power source according to one embodiment of the present application.

[0046] Figure 7 This is a morphology diagram of the innermost positive electrode sheet of the wound electrode assembly prepared in Example 1 of the present application after processing performance testing.

[0047] Figure 8 This is a morphology diagram of the innermost positive electrode sheet of the wound electrode assembly prepared in comparative example 1 of the present application after processing performance testing.

[0048] Figure 9 25° C., the discharge DCR-SOC curves of the batteries of Example 1 and Comparative Example 1 at different states of charge (SOC).

[0049] Figure 10 1 is a discharge DCR-SOC curve diagram of the batteries of Example 1 and Comparative Example 1 at different states of charge (SOC) at -25°C.

[0050] Figure 11 It is a cycle curve diagram of the battery of Example 1 and Comparative Example 1 of the present application.

[0051] Description of reference numerals:

[0052] 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover; 2. Battery pack; 21. Upper case; 22. Lower case; 3. Battery module; 4. Electrical device. DETAILED DESCRIPTION

[0053] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0055] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0056] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0058] In this application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen atom, such as methane losing a hydrogen atom to form a methyl group.

[0059] "Alkyl" includes "chain alkane". The term "chain alkane" refers to a group formed by losing one hydrogen in an alkane in which the carbon atoms are connected by single carbon-carbon bonds and do not form a ring, and the remaining bonds are bonded to hydrogen. It includes either a straight-chain alkane group or a branched-chain alkane group.

[0060] In the present application, the number of carbon atoms in the "alkyl" group may be 1 to 20, further 1 to 10 or 1 to 6. Non-limiting examples include methane, ethane, n-propane, isopropane, n-butane, isobutane, 2-ethylbutane, 3,3-dimethylbutane, n-pentane, isopentane, neopentane, 1-methylpentane, 3-methylpentane, 2-ethylpentane, 4-methyl-2-pentane, n-hexane, 1-methylhexane, 2-ethylhexane, 2-butylhexane, n-heptane, 1-methylheptane, 2,2-dimethylheptane, 2-ethylheptane, n-octane, n-nonane, n-decane, etc., which are formed by losing a hydrogen atom.

[0061] In the present application, when a linking site is not specified in a group, it means that any linking site in the group can be used as the linking site.

[0062] In the present application, "substituted or unsubstituted" means that the defined group may be substituted or unsubstituted.

[0063] When the defined group is substituted, it is understood that it is optionally substituted by the following substituent groups acceptable in the art, including but not limited to: C1-C30 alkyl, heterocyclic group containing 3-20 ring atoms, aryl containing 5-20 ring atoms, heteroaryl containing 5-20 ring atoms, and at least one of halogen.

[0064] Furthermore, the substituent groups include, but are not limited to, at least one of: a C1-C10 alkyl group, a heterocyclic group containing 3-10 ring atoms, an aryl group containing 5-10 ring atoms, a heteroaryl group containing 5-10 ring atoms, and a halogen.

[0065] Furthermore, the substituent groups include, but are not limited to, at least one of: C1-C6 alkyl, heterocyclic group containing 3-6 ring atoms, aryl group containing 5-6 ring atoms, heteroaryl group containing 5-6 ring atoms, and halogen.

[0066] One embodiment of the present application provides a positive electrode additive having a structure shown in formula (1):

[0067]

[0068] Each R1 independently comprises or H, at least one of the two R1s connected to two adjacent carbon atoms includes n is an integer ≥ 1;

[0069] Each R2 is independently selected from any one of an alkyl group or an alkoxy group.

[0070] The above-mentioned positive electrode additive uses a castor oil structure as the mother core structure, which has multiple long flexible chain segments, so it can provide good flexibility. The castor oil structure is introduced into R1 through the maleic anhydride open ring structure. R1 is a rigid styrene or polystyrene structure, which can prevent the positive electrode additive molecules from self-aggregating. In addition, the end groups of the maleic anhydride open ring structure are independently selected from any one of substituted or unsubstituted alkyl and substituted or unsubstituted alkoxy groups, which can avoid the end groups being active groups such as hydroxyl groups reacting in the battery and causing the battery performance to deteriorate. The above-mentioned positive electrode additive has good toughening properties and can be used as a toughening agent. It is used in the positive electrode sheet of the battery as a positive electrode additive to play a toughening role, which can improve the flexibility of the positive electrode sheet, and then achieve a larger compaction density while improving the processing performance of the positive electrode sheet, thereby improving the energy density of the battery. On the other hand, due to the improved flexibility of the positive electrode sheet, its anti-cracking performance when subjected to stress can be improved, thereby improving the service life of the positive electrode sheet.

[0071] In some embodiments, each R1 is independently selected from Or any one of H, at least one of the two R1 connected to two adjacent carbon atoms is selected from

[0072] It is understood that at least one of the two R1s connected to two adjacent carbon atoms is It means that one or both of the two R1s connected to two adjacent carbon atoms are In some embodiments, one of the two R1s attached to two adjacent carbon atoms is The other is H, and the connection position of R1 can be any one of the two adjacent carbon atoms.

[0073] It should be noted that when R1 is The attachment site can be on any side of the carbon-carbon chain in the styrene or polystyrene structure.

[0074] In some embodiments, n is an integer from 1 to 15, and for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and further can be 5 to 15.

[0075] In some embodiments, each R2 is independently selected from any one of an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms. Further, each R2 is independently selected from any one of an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.

[0076] In some embodiments, each R2 is an alkyl group having 1 to 10 carbon atoms; or, each R2 is an alkoxy group having 1 to 10 carbon atoms. Further, each R2 is an alkyl group having 1 to 6 carbon atoms; or, each R2 is an alkoxy group having 1 to 6 carbon atoms.

[0077] Further, each R2 is methyl; or, each R2 is -OCH3.

[0078] As an example, the structure of the positive electrode additive may be one of the following compounds:

[0079]

[0080] Among them, one of the two R1s connected to two adjacent carbon atoms is The other is H, and the attachment position of R1 can be any one of the two adjacent carbon atoms; each R2 in compound (1-3) is ethyl, and each R2 in compound (1-4) is n-pentyl. Further, n=6.

[0081] Another embodiment of the present application further provides a method for preparing the above-mentioned positive electrode additive, which uses the compound of formula (2) as a raw material to synthesize the positive electrode additive of formula (1).

[0082] When each R2 is a substituted or unsubstituted alkoxy group, and further, each R2 is a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, the preparation method of the positive electrode additive of formula (1) comprises the following steps:

[0083] The compound of formula (2) and H-R2 are subjected to an esterification reaction to obtain the positive electrode additive of the above formula (1).

[0084] It is understood that H-R2 is an alcohol compound, which undergoes an esterification reaction with the hydroxyl group in the compound of formula (2). The definition of R1 is as described above and will not be repeated here.

[0085] When each R2 is a substituted or unsubstituted alkyl group, and further, each R2 is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, the preparation method of the positive electrode additive of formula (1) includes the following steps S10 to S20:

[0086] S10, subjecting the compound of formula (2) to an acyl halide reaction with an acyl halide reagent to obtain a compound of formula (3). The definition of R1 is as described above and will not be repeated here.

[0087] Wherein, X in the positive electrode additive of the compound of formula (3) is a halogen element, selected from at least one of F, Cl, Br, and I.

[0088] Furthermore, the acyl halide reagent includes but is not limited to at least one of thionyl chloride, phosphorus pentachloride, and phosphorus trichloride.

[0089] S20. The compound of formula (3) is subjected to a nucleophilic substitution reaction with an organic lithium reagent R2-Li to obtain the positive electrode additive of the above formula (1), wherein R2 is a substituted or unsubstituted alkyl group.

[0090]

[0091] It is understood that the route of synthesizing the positive electrode additive of the above formula (1) by using the compound of formula (2) as a raw material in the present application is not limited to this, wherein R2 is a substituted or unsubstituted alkyl group.

[0092] The above-mentioned positive electrode additive has good toughening properties and can be used as a toughening agent. It is used as a positive electrode additive in the positive electrode sheet of the battery. It can improve the flexibility of the positive electrode sheet, and then achieve a larger compaction density while improving the processing performance of the positive electrode sheet, thereby improving the energy density of the battery.

[0093] Another embodiment of the present application further provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer, wherein the positive electrode film layer is disposed on at least one surface of the positive electrode current collector. Components of the positive electrode film layer include a positive electrode active material and the above-mentioned positive electrode additive.

[0094] Adding the aforementioned positive electrode additive to the positive electrode film layer of the aforementioned positive electrode sheet can improve the flexibility of the positive electrode sheet, thereby improving the processing performance of the positive electrode sheet while achieving a higher compaction density, thereby increasing the energy density of the battery. Furthermore, the increased flexibility of the positive electrode sheet can improve its crack resistance under stress, thereby extending the service life of the positive electrode sheet.

[0095] In addition, the addition of the above-mentioned positive electrode additives to the positive electrode sheet will basically not affect the DC internal resistance and capacity retention rate of the battery, which means that it can improve the processing performance of the positive electrode sheet without having a significant negative impact on the kinetic performance and cycle performance of the battery. It can also improve the compaction density of the positive electrode sheet, thereby improving the energy density of the battery.

[0096] Furthermore, the positive electrode active material and the positive electrode additive are mixed with each other in the positive electrode film layer.

[0097] In some embodiments, the positive electrode film layer may further include other additives that can act as toughening agents.

[0098] In some embodiments, the positive electrode film layer may also include additives that can improve other properties of the battery. These other additives may include film-forming additives, anti-overcharge additives, etc., and for example, also include but are not limited to additives that can improve the high or low temperature performance of the battery.

[0099] It can be understood that the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0100] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0101] In some embodiments, in the positive electrode film layer, the mass content of the positive electrode additive of the above formula (1) is 0.05% to 5%. As an example, the mass content can be 0.05%, 0.1%, 0.2%, 0.3%, 0.5%, 1%, 2%, 2.5%, 3%, 4%, or 5%. Furthermore, the mass content of the positive electrode additive of the above formula (1) in the positive electrode film layer is 0.1% to 1%, and further 0.1% to 0.5%. By controlling the mass content of the positive electrode additive of the above formula (1) in the positive electrode film layer, on the one hand, the positive electrode additive of the above formula (1) can exert excellent toughening properties, improve the compaction density of the positive electrode sheet, and thus improve the energy density of the battery. On the other hand, the DC internal resistance DCR of the battery can be controlled within a lower range, thereby providing good power performance.

[0102] In some embodiments, the mass content of the positive electrode active material in the positive electrode film layer is 80% to 98%. As an example, the mass content may be 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 96%, or 98%. Furthermore, the mass content of the positive electrode active material in the positive electrode film layer may be 90% to 98%.

[0103] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art, including but not limited to at least one of a lithium ion active material and a sodium ion active material.

[0104] As non-limiting examples of lithium-ion active materials, the positive electrode active material may include one or more of the following: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, this application is not limited to these materials; other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used singly or in combination.

[0105] Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof. Non-limiting examples of lithium phosphates containing olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0106] Among them, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc. belong to ternary positive electrode materials, and the ternary positive electrode material includes at least one of doped or undoped lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0107] It is understandable that, taking lithium-ion active materials as an example, the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode active material is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode active material is applied to the positive electrode plate in the battery system. After the charge and discharge cycle, the Li content in the positive electrode active material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode active material, and a non-limiting example is coating modification. The sodium ion active material below is similar.

[0108] In the examples of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual oxygen (O) content will fluctuate. The oxygen (O) content can be measured by molar content, but is not limited to this.

[0109] As non-limiting examples of sodium ion active materials, the sodium ion active materials may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0110] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides may be Na x MO2, wherein M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0111] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4) n- valence.

[0112] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0113] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0114] Polyanionic compounds may include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) wherein M′ in NaM′PO4F may include one or more of V, Fe, Mn and Ni.

[0115] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may include Na a Me b Me' c (CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0116] In some embodiments, the positive electrode film layer may also optionally include a conductive agent. Furthermore, the mass content of the conductive agent in the positive electrode film layer is 0.1% to 10%. As an example, the mass content may be 0.1%, 0.2%, 0.3%, 0.5%, 1%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Furthermore, the mass content of the conductive agent in the positive electrode film layer is 0.5% to 5%.

[0117] As non-limiting examples, the conductive agent may include one or more conductive carbons such as superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, and carbon nanofibers.

[0118] Furthermore, the conductive agent includes at least one of carbon black, carbon nanotubes, and artificial graphite. Furthermore, the conductive agent includes carbon black, carbon nanotubes, and artificial graphite, and the three can be mixed in any proportion. As an example, the mass ratio of carbon black, carbon nanotubes, and artificial graphite can be 1-2:0.2-1:0-1, and further can be 1:1:1. Furthermore, the carbon black can be SP, and the artificial graphite can be KS-6.

[0119] In some embodiments, the positive electrode film layer may further include a binder. Furthermore, the binder content in the positive electrode film layer is 0.1% to 10% by mass. As an example, the binder content may be 0.1%, 0.2%, 0.3%, 0.5%, 1%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Furthermore, the binder content in the positive electrode film layer is 0.5% to 5% by mass.

[0120] As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0121] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0122] The type of solvent can be selected from, but not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The positive electrode slurry can be applied to a single surface of the positive electrode current collector or to both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt % to 80 wt %. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0123] In some embodiments, the positive electrode active material is lithium iron phosphate, and the compaction density of the positive electrode sheet is 2.3 g / cm 3 ~2.8g / cm 3 As an example, the compaction density of the positive electrode sheet can be 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.7g / cm 3 , 2.8g / cm 3 By adding the above-mentioned positive electrode additives to the positive electrode film layer of the positive electrode sheet, the flexibility of the positive electrode sheet can be improved, thereby preventing the positive electrode sheet from cracking at a higher compaction density, thereby improving the processing performance of the positive electrode sheet while achieving a higher compaction density.

[0124] In some embodiments, the positive electrode active material is a ternary positive electrode material, and the compaction density of the positive electrode sheet is 3.3 g / cm3 ~3.8g / cm 3 Optionally, the compaction density of the positive electrode sheet is 3.55g / cm 3 ~3.8g / cm 3 , optional 3.6g / cm 3 ~3.8g / cm 3 , further 3.6g / cm 3 ~3.7g / cm 3 As an example, the compaction density of the positive electrode sheet can be 3.3g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.55g / cm 3 、3.6g / cm 3 、3.6g / cm 3 、3.65g / cm 3 、3.7g / cm 3 、3.8g / cm 3 By adding the above-mentioned positive electrode additives to the positive electrode film layer of the positive electrode sheet, the flexibility of the positive electrode sheet can be improved, thereby preventing the positive electrode sheet from cracking at a higher compaction density, thereby improving the processing performance of the positive electrode sheet while achieving a higher compaction density.

[0125] The compaction density can be calculated using the following formula: Compaction density = surface density of the electrode film layer / (total thickness of the electrode after rolling - current collector thickness). Compaction density test: Disassemble the battery cell, remove the electrode, and punch it into two small discs with an area of ​​S. Measure the weight M and thickness L of one of the small discs; erase the film layer on the surface of the other small disc, leaving an empty current collector foil. Measure the mass M0 and thickness L0 of the empty current collector foil. The compaction density PD = (M-M0) / (S*ΔL), where ΔL = L-L0.

[0126] In some embodiments, the positive electrode plate can be hot pressed at a pressure of 7 T for 120 seconds without cracking.

[0127] It can be understood that the above-mentioned positive electrode additives in the positive electrode film layer of the positive electrode sheet can be detected by the following method: the positive electrode film layer is peeled off from the positive electrode sheet of the battery, and dissolved in ethylene carbonate (EC) solvent, the undissolved solids are removed, and the solution is taken for detection using liquid chromatography / mass spectrometry (LC / MS) technology. The presence of the above-mentioned positive electrode additives can be determined by the characteristic peaks of the mass spectrum.

[0128] Another embodiment of the present application provides a battery comprising at least one of the above-mentioned positive electrode additive and the above-mentioned positive electrode plate.

[0129] Another embodiment of the present application provides an electrical device, which includes at least one of the above-mentioned positive electrode additive, the above-mentioned positive electrode plate, and the above-mentioned battery.

[0130] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0131] Negative electrode

[0132] The negative electrode plate includes a negative electrode current collector. Further, the negative electrode plate may also include a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0133] Furthermore, the negative electrode film layer includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material.

[0134] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0135] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0136] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0137] In some embodiments, the negative electrode active material layer may further include a binder. The binder may 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).

[0138] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0140] In some embodiments, the negative electrode sheet can be prepared by dispersing the components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, 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 of a negative electrode current collector, and performing drying, cold pressing, and other processes to obtain the negative electrode sheet. The negative electrode current collector surface coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode 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.

[0141] electrolytes

[0142] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0143] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0144] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0145] In some embodiments, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0146] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0147] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0148] Isolation film

[0149] In some embodiments, the battery further includes a separator.

[0150] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0151] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0152] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0153] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0154] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0155] A battery includes at least one battery cell. A battery may include one or more battery cells.

[0156] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0157] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0158] The battery and the electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0159] See also Figure 1 , Figure 1 The battery shown is a battery cell 1 , which is an example of a battery cell with an exemplary square structure.

[0160] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery may also be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic. Further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] In some of these embodiments, reference Figure 2The outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to actual needs.

[0162] In some embodiments, the battery may be a battery module or a battery pack. A battery module includes at least one battery cell. A battery module may contain one or more battery cells, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0163] Figure 3 3 is an example of a battery module. Figure 3 In the battery module 3, the plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 3. Of course, they may also be arranged in any other manner. The plurality of battery cells 1 may further be fixed by fasteners.

[0164] Optionally, the battery module 3 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0165] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0166] Figure 4 and Figure 5 The battery pack 2 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 3 disposed in the battery box. The battery box includes an upper box body 21 and a lower box body 22. The upper box body 21 can cover the lower box body 22 and form an enclosed space for accommodating the battery modules 3. The multiple battery modules 3 can be arranged in the battery box in any manner.

[0167] In addition, one embodiment of the present application further provides an electrical device, comprising the battery provided herein. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, and the like. Examples of mobile devices include, but are not limited to, mobile phones and laptop computers; examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0168] As an electrical device, a battery can be selected according to its usage requirements.

[0169] Figure 6 The power consumption device 4 is used as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of the battery, a battery pack or battery module can be used.

[0170] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0171] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0172] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0173] 1. Preparation of positive electrode additives

[0174] 1. Preparation of compound (1-1)

[0175] The structure of compound (1-1) is as follows:

[0176]

[0177] Among them, one of the two R1s connected to two adjacent carbon atoms is The other is H, the connection position of R1 is any one of the two adjacent carbon atoms, and n=6.

[0178] The preparation steps are as follows:

[0179]

[0180] a. Castor oil (CO), maleic anhydride (MAH), and styrene (ST) were added to a toluene solvent in a mass ratio of 1.0:0.2:1.3, and 0.5% of azobisisobutyronitrile (AIBN) was added as an initiator based on the total mass of castor oil (CO), maleic anhydride (MAH), and styrene (ST). The mixture was reacted at 90° C. for 4 h to obtain a compound of formula (2);

[0181] Where R is n=6.

[0182]

[0183] b. Mix 1 mol of the compound of formula (2) with 10 mol of methanol, stir, and react at 30°C for 12 h. Then raise the temperature to 50°C and continue the reaction for 2 h to remove excess methanol. The remaining liquid is compound (1-1).

[0184] 2. Preparation of compound (1-3)

[0185] The preparation steps are basically the same as those of compound (1-1), except that step b is different, as follows:

[0186] 1 mol of the compound of formula (2) was mixed with 5 mol of ethanol and stirred, and the mixture was reacted at 65°C for 12 h. The temperature was then raised to 85°C and the reaction was continued for 2 h to remove excess ethanol. The remaining liquid was compound (1-3).

[0187]

[0188] Wherein, each R2 is an ethyl group, and one of the two R1s connected to two adjacent carbon atoms is The other is H, the connection position of R1 is any one of the two adjacent carbon atoms, and n=6.

[0189] 3. Preparation of compound (1-4)

[0190] The preparation steps are basically the same as those of compound (1-1), except that step b is different, as follows:

[0191] 1 mol of the compound of formula (2) was mixed with 10 mol of n-pentanol, stirred, and reacted at 65° C. for 12 h. The temperature was then raised and the reaction was continued for 2 h to remove excess n-pentanol, thereby obtaining compound (1-4).

[0192]

[0193] Wherein, each R2 is n-pentyl, and one of the two R1s connected to two adjacent carbon atoms is The other is H, the connection position of R1 is any one of the two adjacent carbon atoms, and n=6.

[0194] 2. Battery Preparation

[0195] Example 1

[0196] (1) Preparation of positive electrode sheet

[0197] The positive electrode active material (NCM 811 ), a conductive agent (SP, KS-6, and CNT in a mass ratio of 1:1:1), a binder PVDF, and a positive electrode additive (details shown in Table 1) were dispersed in a solvent NMP at a weight ratio of 96.8:2:1:0.2 and mixed uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of the composite current collector, dried, and cold-pressed to obtain a positive electrode sheet. The compaction density of the positive electrode sheet is shown in Table 1.

[0198] (2) Preparation of negative electrode sheet

[0199] The negative electrode active material artificial graphite, conductive agent (Super P), dispersant sodium carboxymethyl cellulose, and adhesive styrene-butadiene rubber were mixed in a mass ratio of 96:2:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and transferred to a 120°C oven for drying for 1 hour, and then super-cold pressed and cut to obtain negative electrode sheets.

[0200] (3) Isolation film

[0201] A 12μm thick polypropylene isolation film was selected.

[0202] (4) Preparation of electrolyte

[0203] An organic solvent was prepared: a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with the volume ratio of EC, EMC, and DEC being 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte.

[0204] (5) Preparation of batteries

[0205] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrodes to provide insulation. The cells are then wound into a square bare cell. The bare cell is then enclosed in aluminum-plastic film and baked at 80°C to remove moisture. The electrolyte is then injected and sealed. After standing, hot and cold pressing, formation, clamping, and capacity grading, the finished battery is obtained.

[0206] Examples 2 to 7

[0207] The method is basically the same as Example 1, except that in the preparation step of the positive electrode sheet, at least one of the type and content of the positive electrode additive in the positive electrode slurry is different. When the content of the positive electrode additive changes, the meaning of the positive electrode active material is adjusted accordingly to maintain the total content of the positive electrode active material and the positive electrode additive at 97% (as shown in Table 1). The specific steps are as follows:

[0208] Comparative Example 1

[0209] Comparative Example 1 is substantially the same as Example 1, except that the above-mentioned positive electrode additive is not added to the positive electrode slurry in the preparation step of the positive electrode sheet. The specific steps are as follows:

[0210] The positive electrode active material (NCM 811 ), a conductive agent (the mass ratio of SP, KS-6, and CNT is 1:1:1) and a binder PVDF are dispersed in a solvent NMP according to a weight ratio of 97:2:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the double-sided surfaces of the above-mentioned composite current collector, and after drying and cold pressing, a positive electrode sheet is obtained.

[0211] (1) Processing performance test

[0212] The wound electrode assemblies (bare cells) prepared in Examples 1 to 7 and Comparative Example 1 were used as test objects. A pressure of 7T was applied to the bare cells and hot pressed for 120s. The cells were disassembled and the cracking of the innermost circle of the positive electrode sheet of the electrode assembly was observed.

[0213] The standard for judging whether there is cracking: the innermost positive electrode is facing the light source, and the observer observes the positive electrode from the backlight. If there is any light leakage position, it is judged as cracking; if there is no light leakage position, it is judged as not cracking.

[0214] It should be noted that the pressure applied during the processing performance test is much lower than the pressure during cold pressing during electrode preparation. Therefore, the pressure applied during the processing performance test will not significantly change the compaction density of the positive electrode. The electrode assembly is used as the test object to better simulate the state of the electrode in the battery state. In addition, the cracking of the innermost positive electrode in the electrode assembly, where the stress is the greatest, can represent the cracking condition and processing performance of the entire positive electrode.

[0215] The wound electrode assembly prepared in Example 1 has a compaction density of 3.6 g / cm 3 , after hot pressing for 120s under a pressure of 7T, the morphology of the innermost positive electrode piece is as follows: Figure 7 As shown in the figure, it can be seen that the innermost positive electrode plate of Example 1 is not cracked.

[0216] The compaction density of the positive electrode sheet of the wound electrode assembly prepared in Comparative Example 1 is 3.5 g / cm 3 , after hot pressing for 120s under a pressure of 7T, the morphology of the innermost positive electrode piece is as follows: Figure 8 As shown in the figure, it can be seen that the innermost positive electrode plate of comparative example 1 is cracked.

[0217] This shows that compared with Comparative Example 1, the positive electrode sheet in Example 1 has better flexibility, so the positive electrode sheet can have good flexibility while having a higher compaction density.

[0218] In all other embodiments, after hot pressing for 120 seconds at a pressure of 7 T, no cracking occurred in the innermost positive electrode plates.

[0219] (2) Battery dynamics test

[0220] At 25°C, the DC resistance of each battery at different states of charge (20%, 50%, and 90%) was tested:

[0221] Each of the batteries prepared above was placed under a constant temperature environment of 25°C for 30 minutes, discharged to 2.8V at a constant current of 0.33C, allowed to stand for 30 minutes, charged to 4.25V at a constant current of 0.33C, then charged at a constant voltage with a cut-off current of 0.05C, and then allowed to stand for 30 minutes, then discharged to 2.8V at 0.33C, and the discharge capacity C0 was recorded. The battery was allowed to stand for 30 minutes, charged to 4.25V at a constant current of 0.33C, charged at a constant voltage with a cut-off current of 0.05C, and then allowed to stand for 5 minutes, and then discharged at 0.33C with a cut-off current of 0.5C0. The battery was allowed to stand for 1 hour, and the voltage U1 at this time was recorded. The battery was discharged for 30 seconds at a current of I = 5C (5C indicates the current discharge current. For example, for a battery with a capacity of 2Ah, 5C means 10A discharge). The voltage U2 at this time was recorded, and the battery was allowed to stand for 5 minutes. DCR@25°C at 20% SOC, 50% SOC, and 90% SOC = (U1-U2) / I.

[0222] At -25°C, the DC resistance of each battery at different states of charge (20%, 50%, and 90%) was tested:

[0223] Each battery prepared above was placed in a constant temperature environment at -25°C for 30 minutes, discharged at a constant current of 0.33C to 2.8V, allowed to stand for 30 minutes, charged at a constant current of 0.33C to 4.25V, then charged at a constant voltage with a cutoff current of 0.05C, allowed to stand for 30 minutes, and discharged at 0.33C to 2.8V. The discharge capacity C0 was recorded. The battery was allowed to stand for 30 minutes, charged at a constant current of 0.33C to 4.25V, then charged at a constant voltage with a cutoff current of 0.05C, and allowed to stand for 5 minutes. The battery was discharged at 0.33C with a cutoff current of 0.5C0, allowed to stand for 1 hour, and the voltage U1 was recorded at this time. The battery was discharged at a current of I = 5C for 30 seconds, and the voltage U2 was recorded at this time. The battery was then allowed to stand for 5 minutes. DCR @ -25°C at 20% SOC, 50% SOC, and 90% SOC = (U1 - U2) / I.

[0224] Among them, at 25 ° C, the discharge DCR-SOC curves of the batteries provided in Example 1 and Comparative Example 1 at different states of charge (SOC) are as follows: Figure 9 At -25°C, the discharge DCR-SOC curves of the batteries provided in Example 1 and Comparative Example 1 at different states of charge (SOC) are shown in FIG. Figure 10 shown.

[0225] Depend on Figure 9 and Figure 10 It can be seen that there is no obvious difference in the DCR-SOC curves of the two at different temperatures, indicating that the addition of the above compounds as positive electrode additives will not have a significant negative impact on the resistance of the positive electrode sheet.

[0226] (3) Cyclic performance test

[0227] At 25 ° C, the battery prepared above was charged at a constant current rate of 1C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cut-off voltage of 2.8V, allowed to stand for 5 minutes. This is one charge and discharge cycle. According to this method, the battery was subjected to a cyclic charge and discharge test for 500 cycles, and the discharge capacity of each cycle was recorded. The capacity retention rate after 500 cycles of charge and discharge was calculated in this way, as shown in Table 1.

[0228] 500-cycle capacity retention rate = discharge capacity after 500 cycles / first-cycle discharge capacity.

[0229] Figure 11The black (Comparative Example 1) and blue (Example 1) curves are respectively shown in the figure as the cycle performance graphs of the batteries of Example 1 and Comparative Example 1. The two curves basically overlap, which means that the batteries provided by Example 1 and Comparative Example 1 have basically the same capacity retention rate after 500 cycles at 25°C. That is to say, the above-mentioned compound is added to the positive electrode sheet as a positive electrode additive, which basically does not affect the cycle performance of the battery.

[0230] Please see Table 1 for the relevant physical parameters and test results in each embodiment and comparative example.

[0231] Table 1

[0232]

[0233] As can be seen from the above table, compared with Comparative Example 1 in which the above-mentioned positive electrode additives are not added, the embodiment of the present application adopts the above-mentioned positive electrode additives as positive electrode additives, which improves the flexibility of the positive electrode sheet, thereby enabling the positive electrode sheet to achieve a higher compaction density without cracking, indicating that it can achieve a larger compaction density while improving the processing performance of the positive electrode sheet.

[0234] Furthermore, the addition of the aforementioned positive electrode additive to the positive electrode sheet had no significant negative impact on the battery's DC internal resistance and 500-cycle capacity retention, indicating no significant negative impact on the battery's kinetic and cycling performance. Among Examples 1-5, Examples 1-4 had high compaction densities and excellent cycling performance, while Example 5 exhibited slightly lower cycling performance. This is due to the increased internal resistance caused by the larger amount of positive electrode additive added, which reduced the positive electrode active material content. However, this performance was still considered good.

[0235] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0236] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. A positive electrode additive, characterized in that The positive electrode additive has a structure shown in formula (1): Each R1 independently comprises or H, at least one of the two R1s connected to two adjacent carbon atoms includes n is an integer ≥ 1; Each R2 is independently selected from any one of a substituted or unsubstituted alkyl group and a substituted or unsubstituted alkoxy group.

2. The positive electrode additive according to claim 1, wherein Each R2 is independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms.

3. The positive electrode additive according to claim 1, wherein Each R2 is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms; or each R2 is a substituted or unsubstituted alkoxy group having 1 to 6 carbon atoms.

4. The positive electrode additive according to claim 1, wherein Each R2 is methyl; or, each R2 is -OCH3.

5. The positive electrode additive according to any one of claims 1 to 4, characterized in that One of the two R1s connected to two adjacent carbon atoms is the other is H; and / or, n is an integer from 1 to 15.

6. A method for preparing a positive electrode additive, characterized in that: The steps include: The compound of formula (2) and H-R2 are subjected to an esterification reaction to obtain a positive electrode additive of formula (1); The structures of the positive electrode additive of formula (1) and the compound of formula (2) are as follows, wherein each R2 is a substituted or unsubstituted alkoxy group; 7. A method for preparing a positive electrode additive, characterized in that: The steps include: The compound of formula (2) is subjected to an acyl halide reaction with an acyl halide reagent to obtain a compound of formula (3); Then, the compound of formula (3) is subjected to a nucleophilic substitution reaction with an organic lithium reagent R2-Li to obtain a positive electrode additive of formula (1); The structures of the positive electrode additive of formula (1), the compound of formula (2) and the compound of formula (3) are as follows, wherein each R2 is a substituted or unsubstituted alkyl group; 8. A positive electrode plate, characterized in that: The positive electrode film layer comprises a positive electrode current collector and a positive electrode film layer, wherein the positive electrode film layer is arranged on at least one surface of the positive electrode current collector, and the components of the positive electrode film layer include a positive electrode active material and the positive electrode additive according to any one of claims 1 to 5.

9. The positive electrode sheet according to claim 8, characterized in that: In the positive electrode film layer, the mass content of the positive electrode additive is 0.05% to 5%.

10. The positive electrode sheet according to claim 9, wherein: In the positive electrode film layer, the mass content of the positive electrode additive is 0.1% to 1%.

11. The positive electrode sheet according to any one of claims 8 to 10, characterized in that: In the positive electrode film layer, the mass content of the positive electrode active material is 80% to 98%.

12. The positive electrode sheet according to any one of claims 8 to 11, characterized in that: The positive electrode sheet satisfies at least one of the following conditions: (1) The positive electrode film layer further includes a conductive agent, and the mass content of the conductive agent in the positive electrode film layer is 0.1% to 5%; (2) The positive electrode film layer further includes a binder, and the binder has a mass content of 0.1% to 5% in the positive electrode film layer.

13. The positive electrode sheet according to any one of claims 8 to 12, characterized in that: The positive electrode active material is lithium iron phosphate, and the compaction density of the positive electrode sheet is 2.3g / cm 3 ~2.8g / cm 3 .

14. The positive electrode sheet according to any one of claims 8 to 12, characterized in that: The positive electrode active material is a ternary positive electrode material, and the compaction density of the positive electrode sheet is 3.3 g / cm 3 ~3.8g / cm 3 .

15. The positive electrode sheet according to claim 14, wherein: The compaction density of the positive electrode sheet is 3.55 g / cm 3 ~3.8g / cm 3 .

16. A battery, characterized in that: The method comprises at least one of the positive electrode additive according to any one of claims 1 to 5 and the positive electrode sheet according to any one of claims 8 to 15.

17. An electrical device, characterized in that: The electrical device comprises at least one of the positive electrode additive according to any one of claims 1 to 5, the positive electrode sheet according to any one of claims 8 to 15, and the battery according to claim 16.

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