Negative pole piece, preparation method of negative pole piece, secondary battery and electric device

Abstract

The invention relates to a negative pole piece and a preparation method thereof, a secondary battery and a power utilization device, the negative pole piece comprises a negative active material layer, the negative active material layer comprises an additive, and the additive comprises a compound containing a carbon-carbon double bond and a lithium sulfonate group or a sodium sulfonate group. In the preparation process of the battery negative electrode slurry, an additive containing carbon-carbon double bonds and lithium silicate or sodium silicate is added, and an ultrathin polymer film protection layer can be polymerized on the surface of a graphite negative electrode by the additive by utilizing an in-situ electrochemical polymerization technology, so that the comprehensive performance of a negative electrode piece and even a battery is finally remarkably improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a negative electrode sheet and its preparation method, a secondary battery, and an electrical device. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] Secondary batteries are widely used in various consumer electronics, electric vehicles, aerospace, and large-scale energy storage due to their outstanding characteristics such as light weight, no pollution, and no memory effect. Graphite is currently the most commonly used negative electrode active material in secondary batteries, possessing advantages such as abundant raw materials, low cost, and low operating potential (0.01 V vs. Li). + Advantages include good performance (e.g., Li / Li) and good cycle performance.

[0004] During the initial charge and discharge of a battery, the electrolyte undergoes a reduction and decomposition reaction on the graphite anode surface, forming a solid electrolyte interphase (SEI) film. An ideal SEI film should passivate the graphite anode surface, effectively preventing further electrolyte reactions; simultaneously, it should possess excellent ionic conductivity and electronic insulation. However, in reality, the graphite anode undergoes a certain degree of volume expansion during lithium intercalation, causing the SEI film to rupture and expose new active sites. This leads to continuous electrolyte decomposition, resulting in a continuous increase in SEI film thickness, increased battery internal resistance, and ultimately, battery capacity decay and reduced cycle performance. Summary of the Invention

[0005] This application provides a negative electrode sheet that can effectively improve cycle performance while taking into account capacity, as well as a method for preparing the same, a secondary battery, and an electrical device.

[0006] To achieve the above objectives, a first aspect of this application provides a negative electrode sheet comprising a negative electrode active material layer, the negative electrode active material layer containing an additive, the additive comprising a compound containing a carbon-carbon double bond and a sulfonate group, the sulfonate group comprising one of a lithium sulfonate group and a sodium sulfonate group.

[0007] Therefore, this application incorporates additives into the negative electrode active material layer of the negative electrode sheet. These additives include compounds containing carbon-carbon double bonds and sulfonate groups, with the sulfonate groups including lithium sulfonate groups or sodium sulfonate groups. Due to the presence of carbon-carbon double bonds, the additives preferentially electropolymerize on the surface of the negative electrode active material at a lower potential during battery cycling, generating an ultra-thin polymer film in situ. This effectively reduces or even avoids problems such as SEI film rupture and exposure of new active sites caused by volume expansion of the negative electrode active material during battery charge-discharge cycles, leading to continuous electrolyte decomposition and consequently, an increase in SEI film thickness and increased battery internal resistance. Simultaneously, since the polymer film formed by the additive polymerization possesses excellent mechanical strength and toughness, it effectively protects the stability of the negative electrode active material. Therefore, the negative electrode sheet provided by this application exhibits excellent cycle performance while maintaining capacity. Furthermore, because the additives contain lithium sulfonate groups or sodium sulfonate groups, they can transfer lithium or sodium ions. Thus, the polymer film formed by the additive polymerization protects the negative electrode active material while improving its electrochemical performance, ultimately enhancing the overall performance of the battery.

[0008] In some embodiments of this application, the additive comprises a compound having the structure shown in formula (I):

[0009]

[0010] The element M includes either Li or Na.

[0011] In some embodiments of this application, the element M is Li, and the additive includes lithium allyl phenyl ether sulfonate;

[0012] Optionally, the additive includes one or more of lithium 2-allylphenyl ether sulfonate, lithium 3-allylphenyl ether sulfonate, and lithium 4-allylphenyl ether sulfonate.

[0013] In some embodiments of this application, the element M is Na, and the additive includes sodium allyl phenyl ether sulfonate;

[0014] Optionally, the additive includes one or more of sodium 2-allylphenyl ether sulfonate, sodium 3-allylphenyl ether sulfonate, and sodium 4-allylphenyl ether sulfonate.

[0015] In some embodiments of this application, the additive accounts for 0.5%-3% of the mass of the negative electrode active material layer.

[0016] In some embodiments of this application, the negative electrode active material layer further comprises one or more of a negative electrode active material, a conductive agent, and a binder;

[0017] Optionally, the negative electrode active material includes a carbon-based material, which may be one or more of natural graphite, artificial graphite, and mesophase carbon microspheres;

[0018] Optionally, the negative electrode active material accounts for 94%-98% of the mass of the negative electrode active material layer;

[0019] Optionally, the conductive agent accounts for 0.5%-3% of the mass of the negative electrode active material layer;

[0020] Optionally, the binder accounts for 1%-3% of the mass of the negative electrode active material layer.

[0021] A second aspect of this application provides a method for preparing a negative electrode sheet according to the first aspect of this application, the method comprising the step of preparing a negative electrode slurry for forming the negative electrode active material layer, the negative electrode slurry comprising the additive.

[0022] In some embodiments of this application, the additive includes sodium allyl phenyl ether sulfonate, and the preparation method of sodium allyl phenyl ether sulfonate includes:

[0023] Sodium hydroxybenzenesulfonate, sodium methoxide, and methanol are mixed in a protective atmosphere to prepare a mixture.

[0024] After introducing the protective gas into the mixture, allyl bromide is added to carry out the first reaction to prepare the sodium allyl phenyl ether sulfonate.

[0025] Optionally, the sodium hydroxybenzenesulfonate includes one or more of sodium 2-hydroxybenzenesulfonate, sodium 3-hydroxybenzenesulfonate, and sodium 4-hydroxybenzenesulfonate;

[0026] Optionally, the molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-6), or optionally 1:(2-3;

[0027] Optionally, the molar ratio of sodium methoxide to methanol is 1:(6-12), or optionally 1:(6-8);

[0028] Optionally, the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate is (2-6):1, or optionally (2-3):1;

[0029] Optionally, the temperature of the first reaction is 70℃-80℃;

[0030] Optionally, the reaction time is 1h-10h, or 2h-5h.

[0031] In some embodiments of this application, the additive includes lithium allyl phenyl ether sulfonate, and the preparation method of the lithium allyl phenyl ether sulfonate includes:

[0032] Sodium allyl phenyl ether sulfonate was prepared using the method described above.

[0033] The sodium allyl phenyl ether sulfonate is mixed with an aqueous solution containing lithium salt to carry out a second reaction, thereby preparing the lithium allyl phenyl ether sulfonate.

[0034] Optionally, the molar ratio of sodium allyl phenyl ether sulfonate to the lithium salt is 1:(1-5), or optionally 1:(2-3);

[0035] Optionally, the lithium salt includes one or more of LiCl, LiBr, Li2SO4, LiNO3, Li2CO3, and Li3PO4;

[0036] Optionally, the concentration of the aqueous solution containing the lithium salt is 1 mol / L-6 mol / L; optionally, it is 1 mol / L-2 mol / L.

[0037] Optionally, the temperature of the second reaction is 60℃-100℃, and optionally 70℃-90℃;

[0038] Optionally, the second reaction takes 12-24 hours.

[0039] A third aspect of this application provides a secondary battery, including a negative electrode sheet of the first aspect of this application or a negative electrode sheet prepared using the preparation method of the second aspect of this application.

[0040] The secondary battery of this application includes the negative electrode sheet of this application, which has excellent cycle performance while taking into account capacity.

[0041] In some embodiments of this application, the secondary battery is a lithium-ion battery.

[0042] In some embodiments of this application, the secondary battery is a sodium-ion battery.

[0043] A fourth aspect of this application provides an electrical device that includes the secondary battery of the third aspect of this application. The electrical device of this application includes the secondary battery provided in this application and therefore has at least the same advantages as the secondary battery.

[0044] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0045] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0046] Figure 1 The principle of electropolymerization of compounds having the structure shown in formula (I);

[0047] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0048] Figure 3 for Figure 2 An exploded view of a battery cell according to one embodiment of this application is shown.

[0049] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0050] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0051] Figure 6 for Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0052] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0053] Figure 8 The NMR spectrum of lithium 4-allylphenyl ether sulfonate prepared in Example 1;

[0054] Figure 9 The infrared spectrum of graphite and lithium 4-allylphenyl ether sulfonate after electropolymerization on graphite in Example 1 is shown.

[0055] Figure 10 The first charge-discharge curves of the electrodes prepared in Examples 1-3 and Comparative Example 1 in the battery;

[0056] Figure 11 These are TEM images of the electrodes prepared in Example 1 and Comparative Example 1 after battery cycling tests;

[0057] Figure 12 The results of cycle stability tests of the electrodes prepared in Example 1 and Comparative Example 1 in the battery;

[0058] Figure 13The change in DCR of the electrodes prepared in Example 1 and Comparative Example 1 with the number of cycles during battery cycling.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device. Detailed Implementation

[0061] The modified negative electrode material, its preparation method, negative electrode sheet, secondary battery, and power device of this application are described in detail below with appropriate reference to the accompanying drawings. However, some unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0062] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0063] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0064] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0065] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0066] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply 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. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0067] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0068] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0069] Secondary batteries using graphite anodes suffer from capacity decay and reduced cycle performance during charge-discharge cycles.

[0070] In related technologies, the improvement methods adopted to address this problem mainly include: (1) Material surface coating: Amorphous carbon, metals or non-metals and their oxides are coated on the graphite surface. Although the coating layer has good strength and stability, due to the large brittleness of the inorganic coating layer, it is not possible to well limit the volume change of the graphite material during charging and discharging, which easily leads to the cracking and peeling of the inorganic coating layer, thus making it impossible to realize the practical application of coated graphite materials. (2) Element doping: By doping heteroatoms into graphite, the electronic structure and surface properties of graphite can be changed, thereby improving the chemical reactivity of graphite materials. However, this doping preparation process is more complicated, the manufacturing cost is higher, and it also brings environmental pollution, safety hazards and other problems. (3) Electrolyte functional additives: By adding a small amount of additives, such as vinylene carbonate, to the electrolyte, it decomposes on the graphite surface during battery cycling to form an SEI film, thereby protecting the graphite anode material. While the formation of an SEI film can help passivate the graphite surface, residual additives in the battery can cause the SEI film to continue growing on the graphite surface, increasing the battery's internal resistance and thus affecting its long-term stability. Furthermore, the low or insoluble solubility of many functional additives in electrolyte solvents limits the types of additives that can be selected, leading to higher manufacturing and usage costs.

[0071] Based on the above problems, this application adds an additive containing carbon-carbon double bonds and lithium silicate or sodium silicate during the preparation of the negative electrode slurry. Using in-situ electrochemical polymerization technology, the additive can polymerize an ultra-thin polymer film protective layer on the graphite negative electrode surface, which ultimately significantly improves the overall performance of the negative electrode and even the battery.

[0072] An embodiment of this application provides a negative electrode sheet, which includes a negative electrode active material layer containing additives. The additives include compounds containing carbon-carbon double bonds and sulfonate groups, wherein the sulfonate groups include one of lithium sulfonate groups and sodium sulfonate groups.

[0073] Understandably, by setting additives in the negative electrode active material layer of the negative electrode sheet, and the additives including compounds containing carbon-carbon double bonds and sulfonate groups, the sulfonate groups include lithium sulfonate groups or sodium sulfonate groups; due to the presence of carbon-carbon double bonds, during battery cycling, the additives can preferentially undergo electropolymerization on the surface of the negative electrode active material at a lower potential, generating an ultra-thin polymer film layer in situ. This effectively reduces or even avoids problems such as SEI film rupture and exposure of new active sites caused by the volume expansion of the negative electrode active material during battery charge-discharge cycles, continuous electrolyte decomposition, and consequently, the continuous increase in SEI film thickness and battery internal resistance. Simultaneously, since the polymer film formed by the additive polymerization has excellent mechanical strength and toughness, it can effectively protect the stability of the negative electrode active material. Therefore, the negative electrode sheet provided in this application has excellent cycle performance while maintaining capacity. Furthermore, since the additives contain lithium sulfonate groups or sodium sulfonate groups, they can transfer lithium or sodium ions. Thus, the polymer film formed by the additive polymerization protects the negative electrode active material while improving its electrochemical performance, ultimately improving the overall performance of the battery.

[0074] As an example, the types of additives mentioned above and the functional groups they contain can be determined using nuclear magnetic resonance and infrared spectrophotometry.

[0075] In some embodiments, the additive comprises a compound having the structure shown in formula (I):

[0076]

[0077] The element M includes either Li or Na.

[0078] The electropolymerization principle of compounds having the structure shown in formula (I) is as follows: Figure 1 As shown. By Figure 1 It is known that this additive can generate a polymer film in situ through electropolymerization.

[0079] In some exemplary embodiments, element M is Li, and the additive includes lithium allyl phenyl ether sulfonate. Therefore, this additive can be used in lithium-ion batteries.

[0080] In some alternative embodiments, the additive includes one or more of lithium 2-allylphenyl ether sulfonate, lithium 3-allylphenyl ether sulfonate, and lithium 4-allylphenyl ether sulfonate.

[0081] In some embodiments, element M is Na, and the additive includes sodium allyl phenyl ether sulfonate. Therefore, this additive can be used in sodium-ion batteries.

[0082] In some alternative embodiments, the additive includes one or more of sodium 2-allylphenyl ether sulfonate, sodium 3-allylphenyl ether sulfonate, and sodium 4-allylphenyl ether sulfonate.

[0083] As one possible implementation, the additive's mass percentage in the negative electrode active material layer is 0.5%-3%; for example, it can be, but is not limited to, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any two of the above values. When the additive's mass percentage in the negative electrode active material layer is within the above range, it can form a sufficient polymer film to protect the negative electrode surface without increasing the battery's cycle DCR and deteriorating battery performance.

[0084] As an example, the mass percentage of the aforementioned additives in the negative electrode active material layer can be determined by inductively coupled plasma (ICP) to measure the content of sulfur (S) element, and then the content of the additives can be deduced.

[0085] In some embodiments, the negative electrode active material layer further comprises one or more of a negative electrode active material, a conductive agent, and a binder.

[0086] As one possible implementation method, the negative electrode active material includes carbon-based materials.

[0087] In some alternative implementations, the negative electrode active material includes one or more of natural graphite, artificial graphite, and mesophase carbon microspheres.

[0088] In some embodiments, the negative electrode active material may also be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0089] In some optional embodiments, the mass percentage of the negative electrode active material in the negative electrode active material layer is 94%-98%; as an example, the mass percentage of the negative electrode active material in the negative electrode active material layer can be, but is not limited to, 94%, 95%, 96%, 97%, 98% or any range between the above two values.

[0090] In some optional embodiments, the mass percentage of the conductive agent in the negative electrode active material layer is 0.5%-3%; for example, the mass percentage of the conductive agent in the negative electrode active material layer can be, but is not limited to, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.7%, 3%, or any range between any two of the above values.

[0091] In some embodiments, the conductive agent may include one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0092] In some embodiments, the binder accounts for 1%-3% of the mass of the negative electrode active material layer. For example, the mass percentage of the binder in the negative electrode active material layer can be, but is not limited to, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.7%, 3%, or any range between any two of the above values.

[0093] In some embodiments, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylic acid, polyimide, and polyacrylonitrile. The binder may also optionally include one or more of sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode active material layer comprises, by weight percentage: 94%-98% negative electrode active material, 0.5%-3% conductive agent, 1%-3% binder and 0.5%-3% additives.

[0095] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] The negative electrode sheet also includes a negative current collector, with the negative active material layer located on at least one side of the negative current collector. As a non-limiting example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative active material layer is disposed on either or both of the opposite surfaces of the negative current collector.

[0097] 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0098] An embodiment of this application provides a method for preparing a negative electrode sheet, which can be used to prepare the aforementioned negative electrode sheet. The preparation method includes the step of preparing a negative electrode slurry for forming a negative electrode active material layer, wherein the negative electrode slurry contains the additives.

[0099] Understandably, during the preparation of battery negative electrode slurry, additives containing carbon-carbon double bonds and lithium silicate or sodium silicate are added. Using in-situ electrochemical polymerization technology, these additives can polymerize an ultra-thin polymer film protective layer on the graphite negative electrode surface, ultimately significantly improving the overall performance of the negative electrode sheet and even the battery.

[0100] In some embodiments, the negative electrode sheet can be prepared by dispersing components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder, and additives, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector 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 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit areal density (dry weight, minus solvent) can be 0.05-0.18g / 1540.25mm. 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 -1.8g / cm 3 .

[0101] In some embodiments, the additive includes sodium allyl phenyl ether sulfonate. The preparation method of sodium allyl phenyl ether sulfonate includes: mixing sodium hydroxybenzenesulfonate, sodium methoxide, and methanol in a protective atmosphere to prepare a mixture; then, after introducing a protective gas into the mixture, adding allyl bromide to carry out a first reaction to prepare sodium allyl phenyl ether sulfonate. This preparation method is convenient to operate, does not add excessive components, and does not cause environmental pollution or safety hazards.

[0102] As one possible implementation method, the preparation of the mixture includes: adding sodium hydroxybenzenesulfonate and sodium methoxide to methanol under a protective atmosphere and stirring to prepare the mixture.

[0103] As a non-limiting example, allyl bromide is added dropwise.

[0104] In some embodiments, sodium hydroxybenzenesulfonate includes one or more of sodium 2-hydroxybenzenesulfonate, sodium 3-hydroxybenzenesulfonate, and sodium 4-hydroxybenzenesulfonate.

[0105] As one possible implementation, the molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-6); for example, it can be, but is not limited to, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, or any range between two of the above ratios. A molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide within the above range is beneficial for increasing yield and reducing impurity generation.

[0106] In some alternative embodiments, the molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-3).

[0107] In some embodiments, the molar ratio of sodium methoxide to methanol is 1:(6-12); for example, it can be, but is not limited to, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5, 1:11, 1:11.5, 1:12, or any range between two of the above ratios. A molar ratio of sodium methoxide to methanol within the above range is beneficial for increasing yield and reducing impurity generation.

[0108] In some alternative embodiments, the molar ratio of sodium methoxide to methanol is 1:(6-8).

[0109] In one possible implementation, the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate is (2-6):1; for example, it can be, but is not limited to, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, or any range between two of the above ratios. A molar ratio of allyl bromide to sodium hydroxybenzenesulfonate within the above range is beneficial for increasing yield and reducing impurity generation.

[0110] In some alternative embodiments, the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate is (2-3):1.

[0111] In some embodiments, the temperature of the first reaction is 70°C-80°C; for example, it can be, but is not limited to, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, or any range between two of the above temperatures. When the temperature of the first reaction is within the above range, a relatively fast reaction rate is achieved without the reaction causing weight loss of reactants or decomposition of products due to excessively high temperatures.

[0112] As one possible implementation, the time for the first reaction is 1-10 hours; for example, it can be, but is not limited to, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any range between two of the above times.

[0113] In some alternative implementations, the time for the first reaction is 2-5 hours.

[0114] It should be noted that the temperature and time of the first reaction can be combined in any suitable way, and both can be selected from any of the first reaction temperatures and times described in this article.

[0115] In some embodiments, the product of the first reaction is cooled to room temperature to precipitate a solid, which is then washed with methanol. Finally, the product is vacuum dried at 50°C-80°C for 12-36 hours to obtain sodium allyl phenyl ether sulfonate.

[0116] As one possible implementation method, the protective atmosphere includes nitrogen.

[0117] In some alternative embodiments, a protective gas is introduced into the mixture for 10-60 minutes.

[0118] In some embodiments, the additive includes lithium allyl phenyl ether sulfonate, and the preparation method of lithium allyl phenyl ether sulfonate includes: preparing sodium allyl phenyl ether sulfonate using the above-described method for preparing sodium allyl phenyl ether sulfonate; mixing sodium allyl phenyl ether sulfonate with an aqueous solution containing lithium salt to carry out a second reaction to prepare lithium allyl phenyl ether sulfonate.

[0119] It should be noted that in this application, the terms "first reaction," "second reaction," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0120] In some embodiments, the molar ratio of sodium allyl phenyl ether sulfonate to lithium salt is 1:(1-5); for example, it can be, but is not limited to, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any range between two of the above ratios. A molar ratio of sodium allyl phenyl ether sulfonate to lithium salt within the above range is beneficial for increasing yield and reducing impurity generation.

[0121] As one possible implementation, the lithium salt includes one or more of LiCl, LiBr, Li2SO4, LiNO3, Li2CO3, and Li3PO4.

[0122] In some embodiments, the concentration of the aqueous solution containing lithium salt is 1 mol / L to 6 mol / L; for example, it can be, but is not limited to, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, or any range between two of the above concentrations. Optionally, the concentration of the aqueous solution containing lithium salt is 1 mol / L to 2 mol / L.

[0123] In one possible implementation, the temperature of the second reaction is 60℃-100℃; for example, it can be, but is not limited to, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, or any range between two of the above temperatures. When the temperature of the second reaction is within the above range, it has a relatively fast reaction rate without causing weight loss of reactants or decomposition of products due to excessively high temperatures. Optionally, the temperature of the second reaction is 70℃-90℃. More preferably, the temperature of the second reaction is 80℃. In some optional implementations, the time of the second reaction is 12h-24h; for example, it can be, but is not limited to, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any range between two of the above times.

[0124] It should be noted that the temperature and time of the second reaction can be combined in any suitable way, and both can be selected from any of the temperatures and times of the second reaction described in this article.

[0125] As a non-limiting example, the product of the second reaction was cooled to room temperature to precipitate a solid, which was then washed with deionized water until neutral. Finally, the product was vacuum dried at 80°C-100°C for 12-36 hours to obtain lithium allyl phenyl ether sulfonate.

[0126] In some embodiments, the preparation method of sodium allyl phenyl ether sulfonate includes:

[0127] S1. In a protective atmosphere, sodium hydroxybenzenesulfonate, sodium methoxide, and methanol are mixed to prepare a mixture. The molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-6). The molar ratio of sodium methoxide to methanol is 1:(6-12). The protective atmosphere includes nitrogen.

[0128] S2. After introducing a protective gas into the mixture, add allyl bromide to carry out the first reaction to prepare sodium allyl phenyl ether sulfonate. The molar ratio of allyl bromide to sodium hydroxybenzene sulfonate is (2-6):1. The temperature of the first reaction is 70℃-80℃. The reaction time is 1h-10h. Introduce the protective gas into the mixture for 10min-60min.

[0129] As a non-limiting example, a method for preparing lithium allyl phenyl ether sulfonate includes:

[0130] S1. In a protective atmosphere, sodium hydroxybenzenesulfonate, sodium methoxide, and methanol are mixed to prepare a mixture. The molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-6). The molar ratio of sodium methoxide to methanol is 1:(6-12). The protective atmosphere includes nitrogen.

[0131] S2. After introducing a protective gas into the mixture, add allyl bromide to carry out the first reaction to prepare sodium allyl phenyl ether sulfonate. The molar ratio of allyl bromide to sodium hydroxybenzene sulfonate is (2-6):1. The temperature of the first reaction is 70℃-80℃. The reaction time is 1h-10h. Introduce the protective gas into the mixture for 10min-60min.

[0132] S3. Sodium allyl phenyl ether sulfonate is mixed with an aqueous solution containing lithium salt to carry out a second reaction, preparing lithium allyl phenyl ether sulfonate. The molar ratio of sodium allyl phenyl ether sulfonate to lithium salt is 1:(1-5). The lithium salt includes one or more of LiCl, LiBr, Li₂SO₄, LiNO₃, Li₂CO₃, and Li₃PO₄. The concentration of the aqueous solution containing lithium salt is 1 mol / L-6 mol / L. The temperature of the second reaction is 60℃-100℃. The reaction time is 12h-24h.

[0133] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0134] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0135] The secondary battery of this application includes the negative electrode sheet of this application or the negative electrode sheet prepared by the preparation method of the negative electrode sheet of this application, which has excellent cycle performance while taking into account capacity.

[0136] Positive electrode sheet

[0137] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0138] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0139] 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0140] In some embodiments, the secondary battery is a lithium-ion battery; the positive electrode active material of the lithium-ion battery includes lithium-ion active materials.

[0141] In some embodiments, the positive electrode active material may further include one or more of ternary materials and lithium manganese iron phosphate materials; wherein, the ternary material includes Li x (Ni a Co b Mn c )1-dM d O2-yA y (x is 0.2-1.2) and / or Li x A a (Nia Co b Mn c )1-dM d O2-yA y (x+a is 0.2-1.2); Lithium manganese iron phosphate materials include Li a Mn 1-y B y P 1-z C z O 4-n D n (a is 0-1.1) and / or Li a A x Mn 1-y B y P 1-z C z O 4-n D n (a+x is 0-1.1).

[0142] It should be noted that the above limitation on x includes the molar content of Li under different charge and discharge states of the battery (typically the battery voltage is between 2-5V).

[0143] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0144] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0145] In some embodiments, the positive electrode active material may also employ other positive electrode active materials known in the art for use in batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and 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 alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.80 Co 0.15 Al 0.05 O2.

[0146] In some embodiments, the secondary battery is a sodium-ion battery; the positive electrode material of the sodium-ion battery includes sodium-ion active materials.

[0147] As a non-limiting example, sodium-ion active materials may include one or more of the following: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0148] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of a sodium transition metal oxide is Na. x MO2, where M can include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0149] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. 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- The price state.

[0150] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds consisting of anionic units and halide 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- The valence state; halogens can be one or more of F, Cl and Br.

[0151] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (ZO). y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0152] Polyanionic compounds can 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 One or more of (0≤y≤1). Among them, M' in NaM'PO4F can include one or more of V, Fe, Mn and Ni.

[0153] Prussian blue compounds can contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds containing Prussian blue. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of Prussian blue compounds is Na. a Me b Me' c (CN)6, wherein Me and Me' can each be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0154] In some embodiments, the positive electrode active material layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0155] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt%-80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s-25000 mPa·s. When coating the positive electrode slurry, the coating areal density per unit area (dry weight, minus solvent) can be 0.2-0.45 g / 1540.25 mm. 2 The compaction density of the positive electrode sheet can be 2.4 g / cm³. 3 -2.8g / cm 3 2.4g / cm³ is an optional value. 3 -2.7g / cm 3 .

[0157] electrolytes

[0158] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0159] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0160] 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 bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0161] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butene carbonate ( One or more of the following: fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0162] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0163] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0164] Separating membrane

[0165] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0166] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven 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.

[0167] In some embodiments, the thickness of the separator is 6-40 μm, optionally 10-16 μm.

[0168] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0169] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0170] In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0171] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0172] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0173] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 The example shown is a square-structured battery cell 5.

[0174] In some of these embodiments, reference is made to Figure 3 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0175] The secondary battery can be either battery module 4 or battery pack 1.

[0176] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0177] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0178] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0179] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0180] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0181] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0182] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0183] Figure 7 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0184] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0185] Example

[0186] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0187] I. Preparation of Electrodes

[0188] Example 1

[0189] Step S1: Under a nitrogen atmosphere and with stirring, sodium 4-hydroxybenzenesulfonate and sodium methoxide are added to the solvent methanol, wherein the molar ratio of sodium 4-hydroxybenzenesulfonate to sodium methoxide is 1:2 and the molar ratio of sodium methoxide to the solvent methanol is 1:6. After purging with nitrogen for 60 min, allyl bromide is added dropwise, wherein the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate is 2:1. The first reaction is carried out by reflux at 80 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to precipitate a solid. The solid is then washed with methanol and dried under vacuum at 80 °C for 36 h to obtain sodium 4-allylphenyl ether sulfonate.

[0190] Step S2: Sodium 4-allylphenyl ether sulfonate was added to a 1 mol / L aqueous solution containing lithium salt LiCl, with a molar ratio of sodium 4-allylphenyl ether sulfonate to lithium salt of 1:2. The mixture was heated under reflux at 80°C for 12 h to carry out the second reaction. After the reaction, the mixture was cooled to room temperature to precipitate a solid. The solid was then washed with deionized water until it was neutral. Finally, the solid was vacuum dried at 80°C for 36 h to obtain lithium 4-allylphenyl ether sulfonate.

[0191] Step S3: Artificial graphite, conductive agent SP, CMC-SBR (carboxymethyl cellulose-styrene-butadiene rubber) mixed binder, and additive 4-allylphenyl ether sulfonate lithium are mixed at a mass ratio of 96:0.5:2.5:1. Deionized water is added, and a negative electrode slurry is obtained under vacuum stirring. The negative electrode slurry is uniformly coated onto both sides of a copper foil. After the copper foil is dried at room temperature, it is transferred to a 120℃ oven for 1 hour. Then, it is cold-pressed and slit to obtain the electrode sheet, wherein the coating amount per unit area on both sides is 0.15g / 1540.25mm. 2 .

[0192] The NMR spectrum of lithium 4-allylphenyl ether sulfonate prepared in Example 1 is shown below. Figure 8 As shown. By Figure 8It is known that in the NMR spectrum of lithium 4-allylphenyl ether sulfonate, the peak with a chemical shift of approximately 3.33 ppm is a water peak, and the peak with a chemical shift of approximately 2.5 ppm is a solvent peak. Significant para-substitution exists in the aromatic region; the chemical shifts of the ortho protons of the sulfonic acid group (A) and the ether bond (B) are 7.5 ppm and 6.9 ppm, respectively, both with an integral of 2H. The doublet peak with an integral of 2H at 4.6 ppm (E) is due to the proton in E being bonded to an electronegative group (-O), causing a lower field shift in the chemical shift. Methane protons are chemically inequivalent, exhibiting two triplet states at 5.3 ppm (D), with an integral of 2H. At 6.0 ppm, the complexed multiplicity with an integral of 1H corresponds to the secondary vinyl proton (C). Therefore, the lithium 4-allylphenyl ether sulfonate prepared in Example 1 contains carbon-carbon double bonds and lithium sulfonate groups.

[0193] The infrared spectra of graphite and lithium 4-allylphenyl ether sulfonate after electropolymerization on graphite in Example 1 are as follows: Figure 9 As shown. By Figure 9 It can be seen that in the infrared spectrum of 4-allylphenyl ether sulfonated olefin / graphite, at 1410 cm⁻¹... -1 1481cm -1 and 1620cm -1 The absorption peak at 860 cm⁻¹ corresponds to the stretching vibration of the benzene ring skeleton, indicating the presence of a benzene ring in the compound; -1 The absorption peak at position 930 cm⁻¹ indicates that it is a para-disubstituted benzene; -1 The absorption peak at position 1007 cm⁻¹ corresponds to the SO bond; -1 1044cm -1 and 1124cm -1 The absorption peak at 1179 cm⁻¹ corresponds to the stretching vibration of O=S=O; -1 The absorption peak at that point corresponds to the CO stretching vibration. These results indicate that lithium 4-allylphenyl ether sulfonate forms the expected polymer on the graphite electrode surface.

[0194] Examples 2-8

[0195] The preparation methods for Examples 2-8 are similar to those for Example 1, with the differences detailed in Table 1. Examples 2 and 5-7 also differ from Example 1 in the following ways:

[0196] The adhesive used in step S3 of Example 2 is a polyacrylic acid adhesive.

[0197] In Example 5, step S1 involves purging with nitrogen for 10 minutes; the product of the first reaction is cooled to room temperature to precipitate a solid, which is then washed with methanol and vacuum-dried at 80°C for 12 hours. In step S2, the concentration of lithium salt in the aqueous solution is 6 mol / L; the product of the second reaction is cooled to room temperature to precipitate a solid, which is then washed with deionized water until neutral and dried at 100°C for 12 hours. In step S3, the negative electrode active material is natural graphite, and the conductive agent is acetylene black.

[0198] In Example 6, step S1 involves purging with nitrogen for 30 minutes; the product of the first reaction is cooled to room temperature to precipitate a solid, which is then washed with methanol and vacuum-dried at 80°C for 12 hours. In step S2, the product of the second reaction is cooled to room temperature to precipitate a solid, which is then washed with deionized water until neutral and dried at 100°C for 12 hours. In step S3, the negative electrode active material used is natural graphite, and the binder is polyacrylic acid binder.

[0199] In Example 7, step S1 involves purging with nitrogen for 30 minutes; the product of the first reaction is cooled to room temperature to precipitate a solid, which is then washed with methanol and vacuum-dried at 80°C for 12 hours. In step S2, the concentration of lithium salt in the aqueous solution is 2 mol / L; the product of the second reaction is cooled to room temperature to precipitate a solid, which is then washed with deionized water until neutral and dried at 100°C for 12 hours. In step S3, the negative electrode active material used is natural graphite, and the binder is polyacrylic acid binder.

[0200] Comparative Example 1

[0201] No additives were added in Comparative Example 1; details are as follows:

[0202] Artificial graphite, conductive agent acetylene black, and CMC-SBR (carboxymethyl cellulose-styrene-butadiene rubber) binder were mixed at a mass ratio of 96:0.5:3.5. The negative slurry was uniformly coated onto both sides of a copper foil. After the copper foil was air-dried at room temperature, it was transferred to a 120℃ oven for 1 hour. Then, it was cold-pressed and slit to obtain electrode sheets, with a coating weight of 0.15 g / 1540.25 mm² on both sides. 2 .

[0203] Comparative Example 2

[0204] No additives were added in Comparative Example 2; details are as follows:

[0205] Natural graphite, conductive agent SP, and polyacrylic acid binder were mixed at a mass ratio of 96:0.5:3.5, and deionized water was added. The mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto both sides of a copper foil. After the copper foil was dried at room temperature, it was transferred to a 120℃ oven for 1 hour. The foil was then cold-pressed and slit to obtain electrode sheets. The coating amount per unit area on both sides was 0.15 g / 1540.25 mm. 2 .

[0206] Comparative Example 3

[0207] The difference between Comparative Example 3 and Example 1 is that lithium dodecyl sulfonate is used instead of lithium 4-allylphenyl ether sulfonate, while the preparation method of the negative electrode is the same.

[0208] Comparative Example 4

[0209] The difference between Comparative Example 4 and Example 1 is that vinyl phosphate is used instead of lithium 4-allylphenyl ether sulfonate, while the preparation method of the negative electrode is the same.

[0210] The preparation parameters of the above embodiments and comparative examples are shown in Table 1.

[0211] Table 1

[0212]

[0213] In Table 1, n1 represents the molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide; n2 represents the molar ratio of sodium methoxide to methanol; n3 represents the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate; n4 represents the molar ratio of sodium allyl phenyl ether sulfonate to lithium salt; and n5 represents the mass ratio of negative electrode active material, conductive agent, binder, and additives in the negative electrode slurry.

[0214] II. Performance Testing

[0215] 1. First Coulomb efficiency test

[0216] The electrodes prepared in the above embodiments and comparative examples were assembled into batteries in a 2016-type coin cell case. The prepared electrodes served as the positive electrode, a Celgard film (19 mm in diameter) as the separator, lithium metal as the negative electrode, and 1M LiPF6 / EC:DMC (EC:DMC, v:v = 1:1) as the electrolyte. Battery assembly was carried out entirely in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). After assembly, the batteries were allowed to stand for four hours. The batteries were charged at a constant current of 0.33C to 3.65V, and then charged at a constant voltage of 3.65V to 0.05C. The total charging capacity at this point was recorded as C0. Subsequently, the batteries were discharged at a constant current of 0.33C to 2.5V, and then discharged at a constant current of 0.04C to 2.0V. The total discharging capacity at this point was D0. D0 / C0 is the initial coulombic efficiency.

[0217] The first charge-discharge curves of the electrodes prepared in Examples 1-3 and Comparative Example 1 in the battery are shown below. Figure 10 As shown. By Figure 10 It can be seen that the introduction of additives improves the capacity of the electrode; this may be because sulfonated polyallylphenyl ether itself has electrochemical lithiation effects in addition to lithium ion conduction; carbon-carbon double bonds and sulfonic acid oxygen are active sites for lithium storage, which may generate additional capacity for the electrode.

[0218] 2. Cyclic performance test

[0219] Preparation of the positive electrode sheet: Lithium iron phosphate, conductive carbon black SP, and binder PVDF are dispersed in the solvent N-methylpyrrolidone at a weight ratio of 96:2:2 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained, wherein the coating amount per unit area on both sides is 0.25g / 1540.25mm. 2 .

[0220] The electrodes prepared in the above embodiments and comparative examples are used as negative electrodes.

[0221] Separating membrane: A 12μm thick polyethylene separating membrane is selected.

[0222] Electrolyte preparation: The organic solvent was a mixture containing ethylene carbonate (EC) and diethyl carbonate (DEC), with a volume ratio of EC to DEC of 3:7. In an argon-atmosphere glove box with a water content of <10 ppm, thoroughly dried lithium salt LiPF6 was dissolved in the organic solvent, and 2 wt% of fluoroethylene carbonate (FEC) was added simultaneously. The mixture was thoroughly mixed to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L.

[0223] Secondary battery assembly: The positive electrode / separator / negative electrode are stacked in sequence to form a cell, and the bare cell is placed in an outer package, injected with the above electrolyte and sealed to obtain secondary batteries;

[0224] The secondary battery was charged to 3.65V at a constant current of 0.5C, and then discharged to 2.5V at a constant current of 0.5C. This charge-discharge cycle was repeated multiple times until the battery reached 600 cycles. The discharge specific capacity D1 at this point was recorded, and the capacity retention rate after 600 cycles was further calculated.

[0225] TEM images of the electrodes prepared in Example 1 and Comparative Example 1 after battery cycling tests are shown below. Figure 11 As shown. Among them, Figure 11 In Figure (a), the electrode sheet prepared in Comparative Example 1 is shown. Figure 11(b) shows the electrode sheet prepared in Example 1. Figure 11 It can be seen that, since the electrode of Comparative Example 1 has no protective layer, the SEI film on the graphite surface is very thick and uneven after 600 battery cycles; while the electrode prepared in Example 1 has a protective layer, and even after 600 cycles, the SEI film on the graphite surface is thin and evenly distributed on the graphite surface, resulting in better battery stability.

[0226] The cycle stability test results of the electrodes prepared in Example 1 and Comparative Example 1 in the battery are as follows: Figure 12 As shown. By Figure 12 It can be seen that after 600 cycles, the capacity retention rate of the battery in Comparative Example 1 is 95.7%; after 600 cycles, the capacity retention rate of Example 1 is 96.3%, which is better than the performance of the battery in the Comparative Example. This shows that after the same number of cycles, Example 1 has a higher discharge capacity compared with Comparative Example 1; it also shows that the electrode provided in this application has superior cycle performance.

[0227] 3. DCR Test

[0228] Data from the discharge process during the cycle performance test was collected. The change in DCR during the cycle was obtained by subtracting the voltage after 30 seconds of discharge from the initial discharge voltage and dividing by the discharge current. This data reflects the cell's discharge polarization as the cycle progresses. The results are shown in Table 2. The changes in DCR with the number of cycles for Example 1 and Comparative Example 1 are shown below. Figure 13 As shown.

[0229] The test results of the above embodiments and comparative examples are shown in Table 2.

[0230] Table 2

[0231]

[0232] As can be seen from the comparison of the results of Examples 1-8 and Comparative Examples 1-4 in Table 2, the negative electrode provided by this application has better cycle performance and lower DCR while taking into account capacity.

[0233] The results of Example 1 and Comparative Examples 3-4 show that the additive has a synergistic effect when it contains both carbon-carbon double bonds and lithium sulfonate groups.

[0234] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0235] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A negative electrode sheet, characterized in that, The device includes a negative electrode active material layer, which contains additives. The additives include compounds containing carbon-carbon double bonds and sulfonate groups, wherein the sulfonate groups include one of lithium sulfonate groups and sodium sulfonate groups.

2. The negative electrode sheet as described in claim 1, characterized in that, The additive includes compounds having the structure shown in formula (I): The element M includes either Li or Na.

3. The negative electrode sheet as described in claim 2, characterized in that, The element M is Li, and the additive includes lithium allyl phenyl ether sulfonate; Optionally, the additive includes one or more of lithium 2-allylphenyl ether sulfonate, lithium 3-allylphenyl ether sulfonate, and lithium 4-allylphenyl ether sulfonate.

4. The negative electrode sheet as described in claim 2, characterized in that, The element M is Na, and the additive includes sodium allyl phenyl ether sulfonate. Optionally, the additive includes one or more of sodium 2-allylphenyl ether sulfonate, sodium 3-allylphenyl ether sulfonate, and sodium 4-allylphenyl ether sulfonate.

5. The negative electrode sheet as described in any one of claims 1 to 4, characterized in that, The additive accounts for 0.5%-3% of the mass of the negative electrode active material layer.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that, The negative electrode active material layer further comprises one or more of the following: negative electrode active material, conductive agent, and binder; Optionally, the negative electrode active material includes a carbon-based material, which may be one or more of natural graphite, artificial graphite, and mesophase carbon microspheres; Optionally, the negative electrode active material accounts for 94%-98% of the mass of the negative electrode active material layer; Optionally, the conductive agent accounts for 0.5%-3% of the mass of the negative electrode active material layer; Optionally, the binder accounts for 1%-3% of the mass of the negative electrode active material layer.

7. A method for preparing a negative electrode sheet as described in any one of claims 1 to 6, characterized in that, The preparation method includes the step of preparing a negative electrode slurry for forming the negative electrode active material layer, wherein the negative electrode slurry contains the additive.

8. The preparation method according to claim 7, characterized in that, The additive includes sodium allyl phenyl ether sulfonate, and the preparation method of sodium allyl phenyl ether sulfonate includes: Sodium hydroxybenzenesulfonate, sodium methoxide, and methanol are mixed in a protective atmosphere to prepare a mixture. After introducing the protective gas into the mixture, allyl bromide is added to carry out the first reaction to prepare the sodium allyl phenyl ether sulfonate. Optionally, the sodium hydroxybenzenesulfonate includes one or more of sodium 2-hydroxybenzenesulfonate, sodium 3-hydroxybenzenesulfonate, and sodium 4-hydroxybenzenesulfonate; Optionally, the molar ratio of sodium hydroxybenzenesulfonate to sodium methoxide is 1:(2-6), or optionally 1:(2-3; Optionally, the molar ratio of sodium methoxide to methanol is 1:(6-12), or optionally 1:(6-8); Optionally, the molar ratio of allyl bromide to sodium hydroxybenzenesulfonate is (2-6):1, or optionally (2-3):1; Optionally, the temperature of the first reaction is 70℃-80℃; Optionally, the reaction time is 1h-10h, or 2h-5h.

9. The preparation method according to claim 7, characterized in that, The additive includes lithium allyl phenyl ether sulfonate, and the preparation method of lithium allyl phenyl ether sulfonate includes: Sodium allyl phenyl ether sulfonate was prepared using the method described in claim 8. The sodium allyl phenyl ether sulfonate is mixed with an aqueous solution containing lithium salt to carry out a second reaction, thereby preparing the lithium allyl phenyl ether sulfonate. Optionally, the molar ratio of sodium allyl phenyl ether sulfonate to the lithium salt is 1:(1-5), or optionally 1:(2-3); Optionally, the lithium salt includes one or more of LiCl, LiBr, Li2SO4, LiNO3, Li2CO3, and Li3PO4; Optionally, the concentration of the aqueous solution containing the lithium salt is 1 mol / L-6 mol / L, and optionally 1 mol / L-2 mol / L; Optionally, the temperature of the second reaction is 60℃-100℃, and optionally 70℃-90℃; Optionally, the second reaction takes 12-24 hours.

10. A secondary battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1 to 6 or the negative electrode sheet prepared by the preparation method described in any one of claims 7 to 9.

11. The secondary battery as described in claim 10, characterized in that, The secondary battery is a lithium-ion battery.

12. The secondary battery as described in claim 10, characterized in that, The secondary battery is a sodium-ion battery.

13. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 10 to 12.

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