Battery cell, negative electrode sheet, battery device, energy storage device, and electric device

Abstract

The present application relates to the technical field of batteries, and in particular relates to a battery cell, a negative electrode sheet, a battery device, an energy storage device, and an electric device. The battery cell comprises a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and an interface layer disposed on at least one side of the negative electrode current collector; the interface layer comprises a negative electrode material and a binder; the negative electrode material comprises unsaturated bonds; and the binder comprises a main polymer and an aromatic group that is grafted onto the main polymer. In the present application, the interaction between the binder and the negative electrode material can be enhanced, and the cohesion of the interface layer can be improved; therefore, negative electrode material particles can remain in intimate contact after repeated charging and discharging while the adhesion between the interface layer and the current collector is not enhanced, such that the interface layer only has a weak adhesive action on the current collector, thereby achieving specific adhesion.

Description

Battery cell, negative electrode, battery device, energy storage device, electrical device

[0001] This application claims priority to Chinese Patent Application No. 202411813029.1, filed on December 10, 2024, with the Chinese Patent Office, entitled “Battery Cell, Negative Electrode, Battery Device, Energy Storage Device, and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to battery cells, negative electrode sheets, battery devices, energy storage devices, and electrical devices. Background Technology

[0003] Lithium-free all-solid-state batteries do not use lithium or other active anode materials; instead, they use a current collector (such as copper foil) as the anode. This battery system has several advantages over current all-solid-state battery systems that use metallic lithium as the anode: ① Higher volumetric and gravimetric energy densities; ② Improved battery safety because the anode does not require excessive amounts of reactive metallic lithium; ③ Simplified manufacturing processes as no free metallic lithium is needed during assembly.

[0004] In lithium-free all-solid-state batteries, the interface between the negative electrode and the solid electrolyte is typically modified. For example, a coating (interface layer) with interface modification function can be applied to the surface of the negative electrode current collector. On the one hand, to improve the electron / ion transport performance of the negative electrode after repeated charge and discharge cycles, the materials in the interface layer need to be in close contact, which requires increasing the cohesive force of the interface layer. On the other hand, to facilitate the smooth deposition of lithium ions onto the surface of the negative electrode current collector, the adhesion between the interface layer and the negative electrode current collector must not be too strong. If the cohesive force of the interface layer increases, it indicates that the adhesive force of the binder in the interface layer increases, which will make the adhesion between the interface layer and the negative electrode current collector too strong, resulting in an excessively high energy barrier for lithium deposition on the current collector surface. Summary of the Invention

[0005] This application is made in view of the above-mentioned technical problems, and its purpose is to solve the problem that the adhesion between the interface layer and the current collector increases when the cohesion of the interface layer is improved in lithium-free anodes.

[0006] To achieve the above objectives, this application provides a battery cell, a negative electrode sheet, a battery device, an energy storage device, and an electrical device.

[0007] The first aspect of this application provides a battery cell including a negative electrode sheet, the negative electrode sheet including a negative current collector and an interface layer disposed on at least one side of the negative current collector, the interface layer including a negative electrode material and a binder; the negative electrode material including unsaturated bonds; the binder including a host polymer and aromatic groups, the aromatic groups being grafted onto the host polymer.

[0008] The negative electrode sheet of this application embodiment is a lithium-free negative electrode (the corresponding battery cell includes a lithium-free negative electrode battery). Its interface layer uses a material including unsaturated bonds as the negative electrode material, and aromatic groups are grafted onto the main polymer of the binder, which can achieve a specific bonding effect.

[0009] After grafting aromatic groups onto the bulk polymer of the binder, these aromatic groups can generate π-π interactions with the unsaturated bonds of the negative electrode material. Thus, in addition to hydrogen bonding (binders typically achieve bonding through hydrogen bonding between their bulk polymer and the negative electrode material), π-π interactions are added between the binder and the negative electrode material, thereby enhancing the binder's adhesion to the negative electrode material, increasing the cohesive force of the interface layer, and ensuring that the negative electrode material particles remain in close contact even after repeated charge-discharge cycles. Since the surface of the negative electrode current collector contains almost no unsaturated bonds or aromatic groups, the aromatic groups on the binder will not generate π-π interactions with the negative electrode current collector. Therefore, they will not enhance the adhesion between the interface layer and the current collector, resulting in only a weak adhesion between the interface layer and the current collector, thus achieving specific bonding.

[0010] With the help of this binder, the negative electrode material particles in the interface layer can remain tightly connected after repeated charge and discharge, which is beneficial to improving the electron / ion transport performance of the negative electrode sheet after repeated charge and discharge. At the same time, the adhesion between the interface layer and the current collector is weak, and the deposition energy barrier of lithium ions on the surface of the negative electrode current collector is low during charging, making it easy to achieve lithium deposition. Under the combined effect, the battery can exhibit excellent cycle performance, as well as high capacity and high first-time efficiency.

[0011] In some embodiments, the aromatic group includes one or more of substituted or unsubstituted pyrrole, substituted or unsubstituted pyridyl, substituted or unsubstituted phenyl, substituted or unsubstituted piperidyl, and substituted or unsubstituted anthracene.

[0012] These groups all exhibit aromaticity and can generate π-π interactions with the unsaturated bonds of the negative electrode material, thereby enhancing the interaction between the binder and the negative electrode material, increasing the cohesion of the interface layer, and enabling the negative electrode material particles to maintain close contact even after repeated charging and discharging.

[0013] In some embodiments, the aromatic group includes one or more of the following: pyrroleyl, pyridyl, phenyl, piperidyl, and anthraceneyl.

[0014] Electron-donating groups can enhance the π-π interaction between aromatic groups and negative electrode materials, thereby strengthening the cohesion of the interface layer.

[0015] In some embodiments, the aromatic groups in the binder contain 0.001% to 0.04% by mass, optionally 0.01% to 0.02%.

[0016] In this embodiment, grafting a small amount of aromatic groups can generate π-π interactions with the unsaturated bonds of the negative electrode material, thereby enhancing the interaction between the binder and the negative electrode material and improving the cohesion of the interface layer; at the same time, it can keep the binder stable and prevent side reactions.

[0017] In some embodiments, aromatic groups are grafted onto the main chain of the host polymer. This reduces steric hindrance, enhances the interaction between the binder and the negative electrode material, and improves the cohesiveness of the interfacial layer.

[0018] In some embodiments, the main polymer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0019] These main polymers have a certain degree of viscosity and can interact with the negative electrode material through hydrogen bonds. They also work together with the grafted aromatic groups to tightly bond the negative electrode material particles together and improve the cohesion of the interface layer.

[0020] In some embodiments, the adhesive content in the interface layer is 1% to 6% by mass, optionally 3% to 5%.

[0021] With a suitable binder ratio, the bonding effect of the binder on the negative electrode material can be effectively improved, and the cohesion of the interface layer can be increased, without taking up too much of the proportion of the negative electrode material, which is conducive to the negative electrode material fully exerting its function.

[0022] In some embodiments, the negative electrode material includes one or more of the following: carbon materials, unsaturated bond-modified metal materials, unsaturated bond-modified conductive / ion-conducting polymers, and unsaturated bond-modified inorganic oxides.

[0023] Materials such as carbon materials, metallic materials, conductive / ion-conducting polymers, and inorganic oxides can promote electron / ion transport (e.g., carbon materials, PEO) or improve the deposition behavior of lithium on the surface of the negative electrode current collector (e.g., Sn, Au, alumina), and can usually be used as interface modification materials between solid electrolytes and negative electrode sheets.

[0024] Carbon materials typically possess unsaturated bonds. Specifically, carbon materials are usually obtained through heat treatment. This heat treatment process causes dehydrogenation or other chemical bond breakage on the carbon material surface, making the six-membered ring structure of the carbon material aromatic. That is, the six-membered ring develops unsaturated bonds, which can generate π-π interactions with the aromatic groups in the binder. At the same time, the carbon material can also interact with the main polymer of the binder through hydrogen bonds. Under the combined effect of these two effects, the cohesion of the interfacial layer can be greatly improved, allowing the carbon material to maintain a tight bond even after repeated charging and discharging.

[0025] Similarly, unsaturated bond-modified metallic materials, unsaturated bond-modified conductive / ion-conducting polymers, and unsaturated bond-modified inorganic oxides can interact with binders to improve the cohesion of the interface layer.

[0026] In some embodiments, the unsaturated bonds include one or more of carbon-carbon double bonds and carbon-carbon triple bonds. These unsaturated bonds can originate from olefinic groups, alkyneic groups, aromatic rings, etc., and can generate π-π interactions with aromatic groups in the binder, thereby enhancing the interaction between the binder and the negative electrode material and strengthening the cohesion of the interface layer.

[0027] A second aspect of this application provides a negative electrode sheet, including a negative electrode current collector and an interface layer disposed on at least one side of the negative electrode current collector. The interface layer includes a negative electrode material and a binder. The negative electrode material includes unsaturated bonds. The binder includes a host polymer and aromatic groups, with the aromatic groups grafted onto the host polymer.

[0028] In the negative electrode interface layer of this application embodiment, a material including unsaturated bonds is used as the negative electrode material, and aromatic groups are grafted onto the main polymer of the binder. This can improve the cohesive force of the interface layer without increasing the adhesion force between the interface layer and the negative electrode current collector, thus achieving a specific bonding effect.

[0029] A third aspect of this application provides a battery device comprising a plurality of battery cells.

[0030] The battery cell in this application has good cycle performance. Therefore, applying the battery cell to a battery device can improve the cycle performance of the battery device and extend its service life.

[0031] The fourth aspect of this application provides an energy storage device, including a plurality of battery cells or a plurality of battery devices, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0032] The aforementioned battery cells and battery devices with good cycle performance are used to store or provide electrical energy for energy storage devices, which can extend the service life of energy storage devices.

[0033] The fifth aspect of this application provides an electrical device including a plurality of battery cells or a plurality of battery devices, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0034] The aforementioned battery cells and battery devices with good cycle performance can be used as power sources for electrical devices or as energy storage units for electrical devices, thereby extending the service life of electrical devices. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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 these drawings without creative effort.

[0036] Figure 1 is a schematic diagram of the working mechanism of the adhesive in an embodiment of this application;

[0037] Figure 2 is a schematic diagram of a battery cell according to an embodiment of this application;

[0038] Figure 3 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 2.

[0039] Reference numerals: 01-Housing, 02-Cover plate, 03-Electrode assembly. Detailed Implementation

[0040] The embodiments of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, 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.

[0041] The "range" disclosed in this application is defined by 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 and can be arbitrarily combined; that is, 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 understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are 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 "a–b" 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 "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may 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.

[0045] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0046] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0047] Lithium-ion batteries, with their high energy density and good cycle stability, are among the most widely used energy storage systems. Traditional lithium-ion batteries use liquid electrolytes to conduct lithium ions, but their energy density tends towards its upper limit, and certain safety issues exist. Compared to liquid lithium-ion batteries, all-solid-state lithium batteries, using metallic lithium as the negative electrode, offer higher energy density and safety. However, unavoidable dendrite growth and interfacial side reactions limit the practical application of all-solid-state lithium batteries, while significant volume expansion during charging and discharging causes irreversible capacity decay.

[0048] To address these issues, researchers have developed a lithium-free all-solid-state battery. In a lithium-free all-solid-state battery, the negative electrode is lithium-free, meaning it contains no lithium or other active negative electrode materials. Instead, a current collector (such as copper foil) serves as the negative electrode. During the first charge, the Li₂ extracted from the positive electrode... + Lithium combines with electrons on the negative electrode surface, thus depositing on the negative electrode surface. During discharge, the lithium deposited on the negative electrode surface dissolves and returns to the positive electrode. Compared with the current all-solid-state battery system that uses metallic lithium as the negative electrode, this battery system has the following advantages: ① Higher volumetric energy density and gravimetric energy density; ② Improved battery safety performance because the negative electrode does not need to contain excessive amounts of reactive metallic lithium; ③ Simplified manufacturing process as no free metallic lithium is required during assembly.

[0049] However, lithium-free all-solid-state batteries still face many technical challenges. For example, lithium deposited on the negative electrode surface has high reducing properties, which can cause numerous side reactions, generating a large amount of inactive lithium and thus affecting the battery's cycle performance. Furthermore, during charge and discharge, the deposition and dissolution of lithium cause significant volume changes in the negative electrode, resulting in poor interfacial contact between the negative electrode and the solid electrolyte. Uneven lithium deposition can also lead to dendrite formation, causing short circuits. To address these issues, modifying the negative electrode / solid electrolyte interface is an excellent strategy. For instance, a coating (interface layer) with interface modification properties can be applied to the surface of the negative electrode current collector.

[0050] However, after repeated charge-discharge cycles, the electron / ion transport performance of the interface layer decreases, leading to a decline in battery performance. This may be due to fatigue damage occurring within the interface layer after repeated charge-discharge cycles, making it difficult for the binder to maintain tight contact between the negative electrode material (e.g., carbon materials) particles. The binder in the interface layer primarily relies on hydrogen bonds to bond the negative electrode material. However, after repeated charge-discharge cycles, the functional groups on the surface of the negative electrode material (e.g., oxygen-containing functional groups on the surface of carbon materials) undergo chemical changes, weakening the original binding effect of the binder. This reduces the cohesion of the interface layer, consequently decreasing electron / ion transport performance. Therefore, it is essential to improve the cohesion of the interface layer. Improving the cohesion of the interface layer can be achieved by enhancing the bonding effect of the binder on the negative electrode material within the interface layer.

[0051] Enhancing the adhesion of the binder in the interface layer to the negative electrode material usually also enhances the adhesion between the interface layer and the current collector. However, in lithium-free all-solid-state batteries, lithium must be deposited onto the surface of the current collector during the first charge. If the adhesion between the interface layer and the current collector is too strong, the deposition energy barrier for lithium on the current collector surface will be too high. As a result, lithium will be difficult to deposit on the current collector surface and will instead be deposited in the interface layer or at the interface between the interface layer and the electrolyte. This may exacerbate side reactions, lithium dendrite formation, and other problems, leading to a deterioration in battery performance.

[0052] Therefore, how to enhance the cohesion of the interface layer so that the negative electrode material particles can still be in close contact after repeated charging and discharging, without enhancing the adhesion between the interface layer and the current collector, and achieving a weak bond between the interface layer and the current collector, is an urgent problem to be solved.

[0053] Based on this, in the embodiment of this application, a material containing unsaturated bonds is used as the negative electrode material in the interface layer of the lithium-free negative electrode, and a binder is added. The binder has aromatic groups grafted onto the main polymer. The aromatic groups can generate π-π interactions with the unsaturated bonds of the negative electrode material, thereby enhancing the interaction between the binder and the negative electrode material and improving the cohesion of the interface layer. This allows the negative electrode material particles to maintain close contact even after repeated charging and discharging. At the same time, the aromatic groups do not generate π-π interactions with the current collector and do not enhance the adhesion between the interface layer and the current collector. This results in the interface layer having only a weak bonding effect on the current collector, thereby achieving specific bonding.

[0054] With the help of this binder, the negative electrode material particles in the interface layer can remain tightly connected after repeated charge and discharge, which is beneficial to improving the electron / ion transport performance of the negative electrode sheet after repeated charge and discharge. At the same time, the adhesion between the interface layer and the current collector is weak, and the deposition energy barrier of lithium ions on the surface of the negative electrode current collector is low during charging, making it easier to achieve lithium deposition and improving lithium deposition. Under the combined effect, the battery can exhibit excellent cycle performance, as well as high capacity and high first-time efficiency.

[0055] This application provides a battery cell including a negative electrode, a positive electrode, and a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes and is in contact with both electrodes. During battery charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The solid electrolyte acts as a conductor for ions between the positive and negative electrodes.

[0056] [Negative electrode plate]

[0057] The negative electrode sheet of this application embodiment includes a negative electrode current collector and an interface layer disposed on at least one side of the negative electrode current collector. The interface layer includes a negative electrode material and a binder. The negative electrode material includes unsaturated bonds. The binder includes a host polymer, and aromatic groups are grafted onto the host polymer.

[0058] The negative electrode sheet of this application embodiment is a lithium-free negative electrode, containing no lithium or other negative electrode active materials. The interface layer, also known as the interface modification layer, serves to modify the interface and typically also functions to improve electron / ion transport, enhance the deposition of active ions (such as lithium ions), and improve the interfacial contact between the negative electrode sheet and the solid electrolyte. The negative electrode material is the main material in the interface layer and, unlike the negative electrode active material, does not participate in the electrochemical reaction of active ions. The negative electrode material includes unsaturated bonds; exemplary unsaturated bonds include one or more of carbon-carbon double bonds and carbon-carbon triple bonds. These unsaturated bonds can originate from olefinic groups, alkyneic groups, aromatic rings, etc.

[0059] The main polymer in an adhesive refers to the major polymer molecules that constitute the adhesive, also known as the polymer molecular body of the adhesive. Aromatic groups are groups that possess aromaticity; they typically have a conjugated ring system with highly delocalized π electrons. The aromaticity of a group can be determined using Hückel's rule.

[0060] Infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) techniques can be used to test the interface layer to determine whether the negative electrode material contains unsaturated bonds, whether it contains a host polymer, and whether the host polymer is grafted with aromatic groups.

[0061] In the negative electrode interface layer of this application embodiment, a material including unsaturated bonds is used as the negative electrode material, and aromatic groups are grafted onto the main polymer of the binder, which can achieve a specific bonding effect. The working mechanism can be seen in Figure 1. Figure 1 takes polytetrafluoroethylene (PTFE) as the main polymer as an example, and R1 includes aromatic groups.

[0062] After grafting aromatic groups onto the bulk polymer of the binder, these aromatic groups can generate π-π interactions (more specifically, π-π stacking interactions) with the unsaturated bonds of the negative electrode material. Thus, in addition to hydrogen bonding (which binders typically achieve by utilizing hydrogen bonding between their bulk polymer and the negative electrode material), π-π interactions are added between the binder and the negative electrode material, thereby enhancing the binder's adhesion to the negative electrode material and increasing the cohesive force of the interfacial layer. This allows the negative electrode material particles to remain in close contact even after repeated charge-discharge cycles. Since the surface of the negative electrode current collector contains almost no unsaturated bonds or aromatic groups, the aromatic groups on the binder will not generate π-π interactions with the negative electrode current collector. Therefore, they will not enhance the adhesion between the interfacial layer and the current collector, resulting in only a weak adhesive effect between the interfacial layer and the current collector, thus achieving specific adhesion.

[0063] In some embodiments, the aromatic group comprises one or more of substituted or unsubstituted pyrrole, substituted or unsubstituted pyridyl, substituted or unsubstituted phenyl, substituted or unsubstituted piperidyl, and substituted or unsubstituted anthracene.

[0064] Pyrroleyl is a group formed by the loss of one hydrogen atom from pyrrole; pyridyl is a group formed by the loss of one hydrogen atom from pyridine; phenyl is a group formed by the loss of one hydrogen atom from benzene; piperidinyl is a group formed by the loss of one hydrogen atom from piperidine; and anthracene is a group formed by the loss of one hydrogen atom from anthracene. These groups can be identified using techniques such as infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). The term "substituted or unsubstituted" refers to the fact that a group may or may not contain substituents. Substituents can be any group that will not react with the materials in the negative electrode or the solid electrolyte.

[0065] Substituted or unsubstituted pyrrole groups exhibit aromaticity and can generate π-π interactions with the unsaturated bonds of the negative electrode material, thereby enhancing the interaction between the binder and the negative electrode material, increasing the cohesive force of the interface layer, and enabling the negative electrode material particles to maintain close contact even after repeated charging and discharging.

[0066] In some embodiments, the aromatic group includes one or more of the following: pyrroleyl, pyridyl, phenyl, piperidyl, and anthraceneyl groups substituted with electron-donating groups. Exemplary electron-donating groups include one or more of alkyl, amino (-NH2), hydroxyl (-OH), acyloxy (-OCOR3), alkoxy (-OR3), and alkylamino (-NHR3), wherein R3 represents an alkyl group. Exemplary alkyl groups include C1-C5 alkyl groups, i.e., one or more of methyl, ethyl, propyl, butyl, and pentyl groups. Electron-donating groups can enhance the π-π interaction between the aromatic group and the negative electrode material, thereby strengthening the cohesion of the interfacial layer.

[0067] Understandably, aromatic groups can also contain electron-withdrawing groups. Although electron-withdrawing groups may weaken π-π interactions, as long as aromatic groups are grafted onto the main polymer of the binder, they can still generate π-π interactions with the negative electrode material, enhance the interaction between the binder and the negative electrode material, and improve the cohesion of the interface layer.

[0068] In some embodiments, the aromatic groups in the binder are present in a mass content of 0.001% to 0.04%, optionally less than 0.04%, for example 0.01% to 0.02%, such as any one of 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, or a range between any two.

[0069] Mass spectrometry can be used to obtain mass information of different chain segments, thereby calculating the relevant mass content. In this embodiment, grafting a small amount of aromatic groups can generate π-π interactions with the unsaturated bonds of the negative electrode material, thereby enhancing the interaction between the binder and the negative electrode material and improving the cohesion of the interface layer; at the same time, it can maintain the stability of the binder and prevent side reactions.

[0070] In some embodiments, aromatic groups are grafted onto the main chain of the host polymer. Optionally, the aromatic groups can be grafted onto the main chain of the host polymer and serve as end-capping groups. This structure can be analyzed using infrared spectroscopy and nuclear magnetic resonance (NMR) techniques. Grafting aromatic groups onto the main chain of the host polymer can reduce steric hindrance, which is beneficial for enhancing the interaction between the binder and the negative electrode material, and improving the cohesion of the interface layer.

[0071] Understandably, aromatic groups can also be grafted onto the side chains of the host polymer, although the steric hindrance is usually less when aromatic groups are grafted onto the main chain of the host polymer.

[0072] In some embodiments, the main polymer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0073] These main polymers have a certain degree of viscosity and can interact with the negative electrode material through hydrogen bonds. They also work together with the grafted aromatic groups to tightly bond the negative electrode material particles together and improve the cohesion of the interface layer.

[0074] Optionally, the host polymer in this application embodiment includes fluorinated alkane segments. Such host polymers include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, and polyhexafluoropropylene. These host polymers exhibit strong hydrogen bonding with the negative electrode material, which is more conducive to enhancing the cohesive force of the interface layer.

[0075] In some embodiments, the adhesive has a structural formula including R1-R-R1, where R1 includes an aromatic group and R includes the host polymer. Exemplarily, the host polymer includes polytetrafluoroethylene (PTFE), and the adhesive has a structural formula including... R1 is grafted onto the PTFE main chain and serves as the end-capping group. n1 is 200–6000, optionally 4000–5000. For example, n1 can be any one of the values ​​from 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, and 6000, or a range between any two. The main polymer includes polyvinylidene fluoride (PVDF), and the adhesive's structural formula includes… R1 is grafted onto the main chain of PVDF and serves as the end-capping group. n2 is 3500 to 10000, optionally 4500 to 10000, and further optionally 4500 to 5000. For example, n2 can be any one of the following values ​​or any range between two: 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, and 10000.

[0076] Understandably, the above structural formulas are merely examples and do not necessarily represent that a host polymer molecule must be grafted with one or two aromatic groups. In fact, a host polymer molecule can be grafted with one or more aromatic groups R1.

[0077] In some embodiments, the adhesive content in the interface layer is 1% to 6% by mass, optionally 3% to 5%, for example, it can be any one of 1%, 2%, 3%, 4%, 5%, 6% or any range between two.

[0078] Based on the different decomposition temperatures of the various substances in the interface layer, the mass content of the binder can be determined by thermogravimetric analysis. At an appropriate binder ratio, the bonding effect of the binder to the negative electrode material can be effectively improved, increasing the cohesion of the interface layer, without excessively occupying the proportion of the negative electrode material, thus allowing the negative electrode material to fully exert its function.

[0079] In some embodiments, the negative electrode material includes one or more of the following: carbon materials, unsaturated bond-modified metallic materials, unsaturated bond-modified conductive / ion-conducting polymers, and unsaturated bond-modified inorganic oxides. Carbon materials include one or more of silicon-carbon, graphene, amorphous carbon, mesophase carbon microspheres, carbon nanotubes, carbon fibers, and metal-carbon composites. Exemplary metallic materials include one or more of Sn and Au. Exemplary conductive / ion-conducting polymers include polyethylene oxide (PEO). Exemplary inorganic oxides include alumina. Unsaturated bond modification may include surface modification with organic ligands containing unsaturated bonds. Exemplary organic ligands containing unsaturated bonds may include organic ligands containing one or more structures of olefinic groups, alkyne groups, and directional rings. Furthermore, these surface-modified organic ligands do not react with other materials in the interface layer, the negative electrode current collector, or the solid electrolyte.

[0080] Materials such as carbon materials, metallic materials, conductive / ion-conducting polymers, and inorganic oxides can promote electron / ion transport (e.g., carbon materials, PEO) or improve the deposition behavior of lithium on the surface of the negative electrode current collector (e.g., Sn, Au, alumina), and can usually be used as interface modification materials between the solid electrolyte membrane and the negative electrode.

[0081] Carbon materials typically possess unsaturated bonds. Specifically, carbon materials are usually obtained through heat treatment. This heat treatment process causes dehydrogenation or other chemical bond breakage on the carbon material surface, making the six-membered ring structure of the carbon material aromatic. That is, the six-membered ring develops unsaturated bonds, which can generate π-π interactions with the aromatic groups in the binder. At the same time, the carbon material can also interact with the main polymer of the binder through hydrogen bonds. Under the combined effect of these two effects, the cohesion of the interfacial layer can be greatly improved, allowing the carbon material to maintain a tight bond even after repeated charging and discharging.

[0082] Similarly, unsaturated bond-modified metallic materials, unsaturated bond-modified conductive / ion-conducting polymers, and unsaturated bond-modified inorganic oxides can interact with binders to improve the cohesion of the interface layer.

[0083] In some embodiments, the mass proportion of the negative electrode material in the interface layer is 94% to 99%, optionally 95% to 97%, for example, it can be any one of 94%, 95%, 96%, 97%, 98%, 99%, or any range between two. At a high proportion, the interface modification effect of these negative electrode materials can be fully utilized, improving the performance of the battery.

[0084] In some implementations, the thickness of the interface layer is 10 μm to 30 μm, for example, any one of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or a range between any two.

[0085] The interface layer thickness in this application embodiment can be designed as needed and is not limited to the thickness range listed above. With different interface layer thicknesses, the solutions in this application embodiment can improve the cohesion of the interface layer while simultaneously achieving weak adhesion between the interface layer and the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and an interface layer is disposed on either or both of the opposite surfaces of the negative electrode current collector. The negative electrode current collector includes one or more of metal foil and composite current collector. For example, one or more of copper foil, stainless steel foil, nickel foil, and titanium foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, stainless steel, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate [such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.].

[0087] In some implementations, the negative electrode sheet can be prepared in the following manner:

[0088] The components used to prepare the negative electrode sheet, such as the negative electrode material and binder, are dispersed in a solvent to form a negative electrode slurry. The negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0089] Among them, solvents with good solubility for adhesives can be selected, such as one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl carbonate (DCM), ethylene glycol methyl ether (DME), and ethanol.

[0090] The binder in the interface layer can be prepared by graft copolymerization, for example, by reacting the host polymer with a monomer or polymer containing aromatic groups under the action of an initiator (and in the presence of a crosslinking agent).

[0091] [Positive electrode plate]

[0092] The positive electrode sheet of this application embodiment includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes a positive active material, a solid electrolyte, a conductive agent, and a binder.

[0093] In some embodiments, the positive electrode active material may include one or more of lithium phosphates having an olivine structure and their modified compounds, lithium transition metal oxides and their modified compounds. Examples of lithium phosphates having an olivine structure include lithium iron phosphate (such as LiFePO4, i.e., LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides may include lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides [such as LiNi]. 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 O2), lithium niobium oxides (such as lithium niobate), lithium titanium oxides (such as Li4Ti5O) 12One or more of these positive electrode active materials and their modified compounds. These positive electrode active materials can be used alone or in combination of two or more.

[0094] The mass content of the positive electrode active material in the positive electrode active layer can be 70% to 98%, or 80% to 98%, for example, any one of 70%, 75%, 80%, 85%, 90%, 92%, 94%, 96%, 98%, or any range between two.

[0095] In some embodiments, the solid electrolyte in the positive electrode active layer includes one or more of sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, optionally including sulfide solid electrolytes. Sulfide solid electrolytes include one or more of Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, and Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.). Oxide solid electrolytes include lithium oxide garnet (Li7La3Zr2O). 12 This includes one or more of the following: LLZO, tin oxide (SnO2), and bismuth oxide (Bi2O3). Polymer solid electrolytes include one or more of the following: polyethylene oxide electrolytes, polycarbonate electrolytes, and polysiloxane electrolytes.

[0096] The mass content of the solid electrolyte in the positive electrode active layer may include 20% to 30%, optionally 25% to 27%, for example, any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any range between two.

[0097] In some embodiments, the conductive agent in the positive electrode active layer includes one or more of carbon fibers (e.g., vapor-grown carbon fiber VGCF), superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0098] The mass content of the conductive agent in the positive electrode active layer can be 1% to 5%, for example, it can be any one of 1%, 2%, 3%, 4%, 5% or any range between two.

[0099] In some embodiments, the binder in the positive electrode active layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0100] The mass content of the binder in the positive electrode active layer can be 0.5% to 5%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, 5% or any range between two.

[0101] In some embodiments, the positive electrode active layer may optionally include additives, such as additives that can improve certain properties of the positive electrode sheet, such as additives with lithium replenishment effects.

[0102] In some embodiments, the positive current collector includes two surfaces opposite each other in its own thickness direction, and the positive active layer can be disposed on either or both of the opposite surfaces of the positive current collector. The positive current collector includes one or more of a metal foil and a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate [such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.].

[0103] In some implementations, the positive electrode sheet can be prepared in the following manner:

[0104] The components used to prepare the positive electrode sheet, such as the positive electrode active material, solid electrolyte, conductive agent, binder, and any other components, are mixed, formed into a film, and pressed to obtain the positive electrode film. The positive electrode film is then combined with a positive electrode current collector to obtain the positive electrode sheet.

[0105] The thickness of the positive electrode film is 10μm to 30μm, for example, any value of 10μm, 15μm, 20μm, 25μm, 30μm or any range between two. The thickness of the positive electrode film can be designed as needed and is not limited to the thickness range listed above.

[0106] [Solid electrolyte]

[0107] The battery cell in this application embodiment includes a solid electrolyte, which is typically used in the form of a membrane, i.e., a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode plates and is in contact with both plates. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode plates, and the solid electrolyte membrane acts as a conductor of ions between them.

[0108] The solid electrolyte of the battery cell in this application embodiment includes one or more of sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, optionally including sulfide solid electrolytes. Sulfide solid electrolytes include one or more of Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, and Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.). Oxide solid electrolytes include lithium oxide garnet (Li7La3Zr2O). 12 This includes one or more of the following: LLZO, tin oxide (SnO2), and bismuth oxide (Bi2O3). Polymer solid electrolytes include one or more of the following: polyethylene oxide electrolytes, polycarbonate electrolytes, and polysiloxane electrolytes.

[0109] Solid electrolyte membranes can be prepared using the following method:

[0110] A solid electrolyte is mixed with a binder to form a membrane of suitable thickness. In the solid electrolyte membrane, the mass of the binder can be 0.5% to 5%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, or 5%, or a range between any two. The binder in the solid electrolyte membrane includes one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0111] [Outer Packaging]

[0112] A single battery cell may include an outer packaging that can be used to encapsulate the positive electrode, the negative electrode, and the solid electrolyte membrane.

[0113] The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft package, such as a pouch. The material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0114] The outer packaging can be cylindrical, square, or any other shape. For example, Figure 2 shows a battery cell with a square outer packaging structure as an example.

[0115] Referring to Figure 3, the outer packaging may include a housing 01 and a cover plate 02. The housing 01 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 01 has an opening communicating with the receiving cavity, and the cover plate 02 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a solid electrolyte membrane can be stacked to form an electrode assembly 03. One or more electrode assemblies 03 are encapsulated within the receiving cavity.

[0116] [Battery cell]

[0117] In this embodiment, the battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. Optionally, the battery cell in this embodiment is a lithium-free negative electrode battery, and more preferably, a lithium-free negative electrode all-solid-state lithium-ion battery. It is understood that the battery cell in this embodiment can also be a lithium-free negative electrode liquid lithium-ion battery or a lithium-free negative electrode semi-solid-state lithium-ion battery. In this case, the solid electrolyte can be adapted to be a liquid electrolyte, or a liquid electrolyte can be added to the solid electrolyte.

[0118] In the interface layer of the negative electrode sheet in the battery cell of this application, aromatic groups are grafted onto the main polymer of the binder. Under the action of this binder, the negative electrode material particles in the interface layer can still be tightly connected after repeated charge and discharge, which is beneficial to improving the electron / ion transport performance of the negative electrode sheet after repeated charge and discharge. At the same time, the adhesion between the interface layer and the current collector is weak, and the deposition energy barrier of lithium ions on the surface of the current collector of the negative electrode is low during charging, making it easier to achieve lithium deposition and improving lithium deposition. Under the combined effect, the battery can exhibit excellent cycle performance, as well as high capacity and high first-time efficiency.

[0119] A single battery cell can be assembled as follows: The positive electrode, solid electrolyte membrane, and negative electrode are stacked in that order, and pressure is applied to ensure close contact between the positive and negative electrodes and the solid electrolyte membrane. Specifically, the interface layer of the negative electrode is in contact with the solid electrolyte membrane.

[0120] [Battery Device]

[0121] This application provides a battery apparatus including multiple battery cells. Specifically, the battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0122] The battery cell in this application has good cycle performance. Therefore, applying the battery cell to a battery device can improve the cycle performance of the battery device and extend its service life.

[0123] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0124] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0125] In some implementations, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0126] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0127] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0128] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0129] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0130] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0131] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0132] [Energy Storage Device]

[0133] This application provides an energy storage device, including multiple battery cells or multiple battery devices, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0134] The aforementioned battery cells and battery devices with good cycle performance are used to store or provide electrical energy for energy storage devices, which can extend the service life of energy storage devices.

[0135] In some implementations, the energy storage device includes one or more battery clusters to increase the voltage and capacity of the energy storage device. A battery cluster may include multiple battery units connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, the battery clusters are connected in parallel to increase the capacity of the energy storage device.

[0136] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, an energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage system provided in this application embodiment can be any power system that requires energy storage devices.

[0137] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0138] In some implementations, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet.

[0139] In some implementations, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0140] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0141] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes a slave battery management unit (SBMU), a fusion switch, and other modules.

[0142] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0143] As an example, the fire protection module includes a control panel, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in the energy storage system.

[0144] As an example, a power distribution module can be used to distribute power to modules in an energy storage device that require electricity.

[0145] [Electrical appliances]

[0146] This application provides an electrical device, including multiple battery cells or multiple battery devices, wherein the battery cells or battery devices are used to store or provide electrical energy.

[0147] The aforementioned battery cells and battery devices with good cycle performance can be used as power sources for electrical devices or as energy storage units for electrical devices, thereby extending the service life of electrical devices.

[0148] Electrical devices may include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0149] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques 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.

[0150] Example 1

[0151] 1. Negative electrode plate

[0152] Vapor-deposited silicon carbon and binder were mixed at a mass ratio of 95:5, and NMP solvent was added. The mixture was stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0153] The binder includes PTFE, with methyl-substituted pyrrole groups grafted onto the main chain of PTFE. Its structural formula is as follows: R1 is a methyl-substituted pyrrole group, and n1 is approximately 5000.

[0154] 2. Positive electrode plate

[0155] The positive electrode active material NCM811, the sulfide solid electrolyte Li6PS5Cl, and the conductive agent VGCF were uniformly mixed for 10 min at a mass ratio of 70:27:3 to obtain a composite positive electrode powder. PTFE binder, equivalent to 1% of the mass of the first three materials, was added and rolled into a positive electrode film (approximately 20 μm thick).

[0156] 3. Solid electrolyte

[0157] The sulfide solid electrolyte Li6PS5Cl was thoroughly mixed with 1% (by mass) of binder PTFE and rolled into a solid electrolyte membrane.

[0158] 4. Battery assembly

[0159] The negative electrode, solid electrolyte membrane, and positive electrode are stacked in that order from bottom to top. After being subjected to a 600MPa isostatic pressing, the battery cell is obtained, which is then packaged in an aluminum-plastic bag and subjected to battery cell performance testing.

[0160] Example 2

[0161] The difference between this embodiment and Embodiment 1 is that the PTFE main chain is grafted with an amino-substituted pyridinyl group, that is, R1 is an amino-substituted pyridinyl group and n1 is about 4000.

[0162] Example 3

[0163] The difference between this embodiment and Embodiment 1 is that the binder for the negative electrode sheet includes PVDF, and methyl-substituted anthracene groups are grafted onto the main chain of PVDF, with the following structural formula: Where R1 is a methyl-substituted anthracene group, and n2 is approximately 5000.

[0164] Example 4

[0165] The difference between this embodiment and Embodiment 1 is that phenol groups are grafted onto the main chain of PTFE, i.e., R1 is a phenol group.

[0166] Example 5

[0167] The difference between this embodiment and Embodiment 1 is that nitrobenzene is grafted onto the main chain of PTFE, i.e., R1 is nitrobenzene.

[0168] Example 6

[0169] The difference between this embodiment and Embodiment 1 is that R1 is grafted onto the PTFE branch.

[0170] Comparative Example 1

[0171] The difference between this comparative example and Example 1 is that the binder in the negative electrode sheet is PTFE (ungrafted methyl-substituted pyrrole), while the rest is the same as in Example 1.

[0172] Performance testing was conducted as follows. During the testing process, the full battery charge / discharge test parameters were as follows: test temperature 25℃~60℃; charge / discharge voltage range: 2.5~4.3V vs. Li+ / Li; positive electrode surface capacity: 3mAh / cm². 2 ~5mAh / cm 2 External pressure applied during testing: 0MPa~5MPa, optionally 0.5MPa~3MPa.

[0173] 1. Negative electrode adhesion force

[0174] At 25℃, the negative electrode sheet is cut into test specimens of 20mm×100mm size for later use. One side of the double-sided tape is attached to the surface of the steel plate, and the other side is attached to the side of the specimen to be tested. The tape is then pressed with a pressure roller to ensure complete adhesion to the specimen. One end of the current collector is bent in the opposite direction at a bending angle of 180°. The test is conducted using a high-speed rail tensile testing machine. One end of the steel plate is fixed to the lower clamp of the tensile testing machine, and the bent end of the current collector is fixed to the upper clamp. The angle of the current collector is adjusted to ensure that the upper and lower ends are in a vertical position. The specimen is then stretched at a speed of 50mm / min until the interface layer is completely peeled off from the surface of the current collector. The displacement and force during the process are recorded. The force when the force is balanced is taken as the adhesive force of the specimen. The adhesive strength, i.e., the negative electrode adhesion force, is obtained by dividing this force by the adhesion length of the specimen.

[0175] 2. Negative electrode cohesion

[0176] At 25℃, the negative electrode sheet is cut into test specimens of 20mm×100mm size for later use. One side of the double-sided adhesive is pasted onto the surface of the steel plate, and the other side is pasted onto one side of the specimen. The specimen is then pressed with a pressure roller to ensure complete adhesion. Cohesion test tape is pasted onto the other side of the specimen and pressed with a pressure roller. One end of the cohesion test tape is bent in the opposite direction at a bending angle of 180°. A universal tensile testing machine is used. One end of the steel plate is fixed to the lower clamp of the tensile testing machine, and the bent end of the current collector of the specimen is fixed to the upper clamp. The angle of the current collector is adjusted to ensure that the upper and lower ends are in a vertical position. The specimen is then stretched at a speed of 50mm / min until the interface layer is completely peeled off from the surface of the current collector. The displacement and force during the process are recorded. The force when the force is balanced is taken as the adhesive force of the specimen. The adhesive strength, i.e., the cohesion of the negative electrode sheet, is then divided by the adhesion length of the specimen.

[0177] 3. 0.1C discharge capacity, first-efficiency

[0178] At 60℃, charge at a constant current of 0.1C to 4.3V, then switch to constant voltage charging until the current is less than 0.05C. Record the initial charge capacity C1 at 0.1C. Then discharge at 0.1C to 2.5V and record the initial discharge capacity C2 at 0.1C, which is the cell discharge capacity at 0.1C. C2 / C1×100% is the first efficiency.

[0179] 4. 0.33C capacity retention rate of 80% and number of cycles

[0180] At 60℃, charge at a constant current of 0.33C to 4.3V, then switch to constant voltage charging until the current is less than 0.05C, and then discharge at 0.33C to 2.5V. Record the initial discharge capacity C1 at 0.33C. Repeat this cycle X times, and record the discharge capacity C after X cycles. X Until C X / C1≤80%, then X is the number of cycles with a capacity retention of 80% at 0.33C.

[0181] Table 1

[0182] The test results are shown in Table 1. The results indicate that, compared to Comparative Example 1 (where the binder of the negative electrode sheet did not have the relevant groups grafted onto it), Examples 1-6 exhibit higher negative electrode cohesion, while the negative electrode adhesion is similar to or slightly lower than that of Example 1. This result reflects that Examples 1-6, by grafting aromatic groups onto the binder, can enhance the negative electrode cohesion without increasing the negative electrode adhesion, i.e., without increasing the bonding force between the interface layer and the negative electrode current collector, achieving weak adhesion between the interface layer and the current collector, thus realizing specific adhesion. This is mainly because the aromatic groups grafted onto the binder in Examples 1-6 can generate π-π interactions with silicon carbon. Therefore, in addition to the common hydrogen bonding, π-π interactions are added between the binder and silicon carbon, thereby enhancing the interaction between the binder and silicon carbon and increasing the cohesion of the interface layer. Meanwhile, since there is no π-π interaction between the aromatic groups on the adhesive and the current collector (copper foil), the adhesion between the interface layer and the copper foil will not be enhanced by the grafting of aromatic groups. This makes the adhesion between the interface layer and the copper foil comparable to that without the grafting of aromatic groups, or the adhesion between the interface layer and the copper foil weakened due to the influence of aromatic groups.

[0183] After achieving the aforementioned specific adhesion, the electron / ion transport performance of the negative electrode sheet after repeated charging and discharging can be significantly improved. At the same time, lithium ions can still be easily deposited on the copper foil surface, ultimately improving the battery's discharge capacity, first-time efficiency, and cycle performance.

[0184] 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 battery cell, characterized in that, The device includes a negative electrode sheet, which comprises a negative current collector and an interface layer disposed on at least one side of the negative current collector. The interface layer comprises a negative electrode material and a binder. The negative electrode material comprises unsaturated bonds. The binder comprises a host polymer and aromatic groups, wherein the aromatic groups are grafted onto the host polymer.

2. The battery cell according to claim 1, characterized in that, The aromatic group includes one or more of the following: substituted or unsubstituted pyrrole, substituted or unsubstituted pyridyl, substituted or unsubstituted phenyl, substituted or unsubstituted piperidyl, and substituted or unsubstituted anthracene.

3. The battery cell according to claim 1 or 2, characterized in that, The aromatic group includes one or more of the following: pyrroleyl, pyridyl, phenyl, piperidyl, and anthracene.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The aromatic groups in the adhesive contain 0.001% to 0.04% by mass.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The aromatic groups in the binder have a mass content of 0.01% to 0.02%.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The aromatic groups are grafted onto the main chain of the host polymer.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The main polymer includes one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide, polyacrylonitrile, polyacrylate, polyethylene ether, polymethyl methacrylate, polyhexafluoropropylene, and styrene-butadiene rubber.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The adhesive has a mass content of 1% to 6% in the interface layer.

9. The battery cell according to claim 8, characterized in that, The adhesive has a mass content of 3% to 5% in the interface layer.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The negative electrode material includes one or more of the following: carbon materials, unsaturated bond-modified metallic materials, unsaturated bond-modified conductive / ion-conducting polymers, and unsaturated bond-modified inorganic oxides.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The unsaturated bonds include one or more of carbon-carbon double bonds and carbon-carbon triple bonds.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The battery cell includes a lithium-free negative electrode battery.

13. A negative electrode sheet, characterized in that, The device includes a negative electrode current collector and an interface layer disposed on at least one side of the negative electrode current collector. The interface layer includes a negative electrode material and a binder. The negative electrode material includes unsaturated bonds. The binder includes a host polymer and aromatic groups, wherein the aromatic groups are grafted onto the host polymer.

14. A battery device, characterized in that, It includes the battery cell described in any one of claims 1 to 12.

15. An energy storage device, characterized in that, It includes a battery cell according to any one of claims 1 to 12 or a battery device according to claims 13, wherein the battery cell or the battery device is used to store or provide electrical energy.

16. An electrical appliance, characterized in that, It includes a battery cell according to any one of claims 1 to 12 or a battery device according to claims 13, wherein the battery cell or the battery device is used to store or provide electrical energy.

Images