Binder, electrode material and battery

Abstract

The invention relates to a binder, an electrode material and a battery. The binder comprises the following preparation raw materials: a temperature-sensitive polymer and a conductive agent, the temperature-sensitive polymer comprises at least one of polyalkyl pyrrole, polyalkyl thiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polypropylene or polyimide. The structure and properties of the temperature-sensitive polymer can be changed when the temperature rises, so that the conductivity, the adhesive property and the mechanical strength of the material are adjusted, the adhesive can automatically insulate reaction in a battery cell and prevent thermal runaway, and the adhesive is good in stability at high temperature, does not decompose or degrade to release toxic gas, and is safe and reliable. The safety performance of the product is greatly improved; by combining with the conductive agent, a network structure with strong adhesive force, good conductivity and high heat conduction efficiency can be formed, and the obtained adhesive has good adhesive force and conductivity at room temperature and excellent insulativity and safety performance at high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a binder, an electrode material and a battery. Background Art

[0002] In the fields of electrochemical energy, polymer materials and chemical engineering, the research and development of battery technology has always been the focus of research. Lithium-ion batteries have become the main power source for mobile electronic devices and electric vehicles due to their high energy density, long life and good charging performance. In lithium-ion batteries, the safety performance of the battery cell is particularly important. The safety performance of the battery cell directly affects the safety and reliability of the entire battery system.

[0003] In existing technologies, the main method to improve the safety performance of battery cells is to use binders in the battery cells. Binders are polymer materials that can help fix electrode materials and improve the mechanical strength and conductivity of electrodes. At the same time, binders can also form a network structure inside the battery cell, which helps to conduct ions and heat.

[0004] However, existing technologies still have some problems in improving the safety performance of battery cells. First, existing binders are generally not temperature-sensitive, so they cannot automatically respond to temperature changes, and thus cannot effectively prevent the occurrence of thermal runaway. Secondly, existing binders may decompose or degrade when the temperature rises, which will not only reduce the mechanical strength and conductivity of the electrode, but also release harmful gases, further threatening the safety performance of the battery cell. Finally, the network structure formed by existing binders inside the battery cell may also be affected by temperature, thereby affecting the conduction efficiency of ions and heat. Therefore, how to develop a temperature-sensitive binder that can automatically respond to temperature changes and improve the safety performance of the battery cell is an important issue facing current technology. Summary of the invention

[0005] The present invention aims to solve one of the above-mentioned technical problems existing in the prior art. To this end, one of the purposes of the present invention is to provide a binder on which a temperature-sensitive functional group is grafted, which can change its structure and properties when the temperature rises, thereby affecting the single electric capacity of the electrode, automatically insulating the reaction in the battery cell, and preventing thermal runaway from occurring.

[0006] A second object of the present invention is to provide an electrode material.

[0007] A third object of the present invention is to provide a method for preparing the above-mentioned electrode material.

[0008] A fourth object of the present invention is to provide a battery.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] The first aspect of the present invention provides a binder, comprising the following preparation materials: a temperature-sensitive polymer and a conductive agent; the temperature-sensitive polymer comprises at least one of polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polypropylene or polyimide.

[0011] The adhesive according to the first aspect of the present invention has at least the following beneficial effects:

[0012] The temperature-sensitive polymer used in the present invention has a temperature-sensitive functional group, which can change its structure and properties when the temperature rises, thereby adjusting the conductivity, bonding performance and mechanical strength of the material, so that the binder can automatically insulate the reaction in the battery core to prevent thermal runaway, and the binder has good stability at high temperatures and will not decompose or degrade to release toxic gases, thereby greatly improving the safety performance of the product; and the temperature-sensitive polymer selected in the present invention has a good bonding effect. As the main raw material for achieving the bonding effect, it can form a network structure with strong adhesion, good conductivity and efficient heat conduction in combination with a conductive agent. The obtained binder has good adhesion and conductivity at room temperature, as well as excellent insulation and safety performance at high temperatures.

[0013] In some embodiments of the present invention, the conductive agent includes at least one of carbon nanotubes, conductive carbon black, acetylene black, Ketjen black, graphene or carbon nanofibers.

[0014] In some embodiments of the present invention, the mass ratio of the temperature sensitive polymer to the conductive agent is 1:(0.1-5).

[0015] Adding an appropriate amount of conductive agent to the adhesive can form a good conductive network, improve the electrical conductivity and heat conduction efficiency of the adhesive, and enable the adhesive to maintain good bonding properties and mechanical properties.

[0016] In some embodiments of the present invention, the raw materials for preparing the binder further include a cross-linking agent.

[0017] In some embodiments of the present invention, the cross-linking agent comprises an epoxy resin.

[0018] In some embodiments of the present invention, the mass percentage of the cross-linking agent in the raw material for preparing the binder is 1 to 10 wt %.

[0019] By adding a cross-linking agent (such as epoxy resin) to the adhesive, the cross-linking agent can form chemical bonds at high temperatures, thereby enhancing the mechanical properties and thermal stability of the adhesive, preventing it from decomposing, degrading or releasing toxic gases at high temperatures, thereby improving the performance and safety of the material.

[0020] A second aspect of the present invention provides an electrode material comprising an electrode active material bound by a solidified material, wherein the solidified material is formed by the binder according to the first aspect of the present invention.

[0021] The electrode material according to the second aspect of the present invention has at least the following beneficial effects:

[0022] The binder provided in the first aspect of the present invention has good adhesion, can effectively fix the electrode active material, and improve the mechanical strength and conductivity of the electrode material; at the same time, the binder can also form a network structure inside the electrode material, which is helpful for conducting electrons, ions and heat. The network structure also has good high-temperature stability and is not easy to decompose, degrade or release toxic gases in a high-temperature environment. Therefore, the obtained electrode material has good electrical conductivity, thermal conductivity and high-temperature stability; and the temperature-sensitive polymer in the binder will automatically respond to temperature changes. When the temperature rises, the temperature-sensitive functional groups on the polymer will change their structure and properties, thereby deteriorating the conductivity of the electrode, automatically insulating the reaction on the electrode, and preventing thermal runaway from occurring.

[0023] In some embodiments of the present invention, the electrode material comprises a positive electrode material.

[0024] The binder provided by the present invention is particularly suitable for the preparation of positive electrode materials, and is used to improve the bonding stability, electrical conductivity, thermal conductivity, high temperature stability, high temperature insulation and safety of the positive electrode materials.

[0025] In some embodiments of the present invention, the cured product includes a network structure formed by the temperature sensitive polymer and the conductive agent.

[0026] The temperature-sensitive polymer and the conductive agent form a network structure to achieve bonding and fixation of the electrode active material, and the network structure and the electrode active material can effectively cooperate with each other to improve the conductive effect. The obtained electrode material has good electrical conductivity, thermal conductivity and high-temperature stability.

[0027] In some embodiments of the present invention, the mass ratio of the solidified material to the electrode active material is 1:(10-50).

[0028] Controlling the specific dosage ratio of the solidified material and the electrode active material can optimize the conductive network structure formed by the binder, adjust the conductive properties and mechanical properties of the electrode material, and make it have better comprehensive performance.

[0029] The third aspect of the present invention provides a method for preparing the electrode material described in the second aspect of the present invention, comprising the following steps: mixing a binder with an electrode active material to obtain a precursor, and curing the precursor to obtain the electrode material.

[0030] The method for preparing the electrode material according to the third aspect of the present invention has at least the following beneficial effects:

[0031] The preparation method of the electrode material provided by the present invention is simple and easy, and can obtain an electrode material with high conductivity, high stability and high safety.

[0032] In some embodiments of the present invention, the curing temperature is 100-180°C.

[0033] In some embodiments of the present invention, the curing time is 0.5 to 5 hours.

[0034] By controlling the curing conditions, the network structure formed by the binder after curing can be optimized, thereby improving the mechanical strength and conductivity of the electrode material.

[0035] The fourth aspect of the present invention provides a battery, wherein the raw materials for preparing the positive electrode material of the battery include the binder described in the first aspect of the present invention; or, the positive electrode material of the battery includes the electrode material described in the second aspect of the present invention; or, the positive electrode material of the battery is prepared by the preparation method described in the third aspect of the present invention.

[0036] The battery according to the fourth aspect of the present invention has at least the following beneficial effects:

[0037] The binder provided by the present invention can form a good conductive network structure, and in particular can cooperate with the electrode active material to promote the bonding and fixation of the material and the improvement of the conductive effect. The obtained electrode material has good conductivity at room temperature and can effectively reduce the conductivity at high temperature, achieve insulation and prevent thermal runaway effects, thereby obtaining a battery with good conductivity, stability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a SEM image of the positive electrode sheet obtained in electrode example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following is a detailed description of the embodiments of the present invention, which are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The term "comprising" and other equivalent descriptions involved in the specification and claims of this application are intended to cover non-exclusive inclusions, including both the contents clearly described in the specification and claims and the steps or units that are not described in the specification and claims but are inherent in the product, method or structure.

[0040] A first aspect of an embodiment of the present invention provides an adhesive, comprising the following preparation materials: a temperature-sensitive polymer and a conductive agent; the temperature-sensitive polymer comprises at least one of polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polypropylene or polyimide.

[0041] The temperature-sensitive polymer used in the present invention has a temperature-sensitive functional group, which can change its structure and properties when the temperature rises, thereby adjusting the conductivity, bonding performance and mechanical strength of the material, so that the binder can automatically insulate the reaction in the battery core to prevent thermal runaway, and the binder has good stability at high temperatures and will not decompose or degrade to release toxic gases, thereby greatly improving the safety performance of the product; and the temperature-sensitive polymer selected in the present invention has a good bonding effect. As the main raw material for achieving the bonding effect, it can form a network structure with strong adhesion, good conductivity and efficient heat conduction in combination with a conductive agent. The obtained binder has good adhesion and conductivity at room temperature, as well as excellent insulation and safety performance at high temperatures.

[0042] In some embodiments of the present invention, the temperature-sensitive polymer includes one of polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polypropylene or polyimide; in some specific embodiments of the present invention, the temperature-sensitive polymer includes one of polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer or polypropylene.

[0043] In some embodiments of the present invention, the conductive agent includes at least one of carbon nanotubes, conductive carbon black (SP), acetylene black, Ketjen black, graphene or carbon nanofibers; in some specific embodiments of the present invention, the conductive agent includes at least one of carbon nanotubes, conductive carbon black (SP), acetylene black or Ketjen black; in some examples of the present invention, the conductive agent includes carbon nanotubes, conductive carbon black (SP) or a combination thereof.

[0044] In some embodiments of the present invention, the mass ratio of the temperature sensitive polymer to the conductive agent is 1:(0.1~5); in some specific embodiments of the present invention, the mass ratio of the temperature sensitive polymer to the conductive agent is 1:(0.3~3); in some examples of the present invention, the mass ratio of the temperature sensitive polymer to the conductive agent is 1:(0.5~2); non-limiting specific examples are 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, and 1:2.

[0045] Adding an appropriate amount of conductive agent to the adhesive can form a good conductive network, improve the electrical conductivity and heat conduction efficiency of the adhesive, and enable the adhesive to maintain good bonding properties and mechanical properties.

[0046] In some embodiments of the present invention, the raw materials for preparing the adhesive further include a cross-linking agent; in some specific embodiments of the present invention, the cross-linking agent includes epoxy resin.

[0047] In some embodiments of the present invention, the mass percentage of the crosslinking agent in the raw material for preparing the binder is 1-10wt%; in some specific embodiments of the present invention, the mass percentage of the crosslinking agent in the raw material for preparing the binder is 2-8wt%; in some examples of the present invention, the mass percentage of the crosslinking agent in the raw material for preparing the binder is 3-7wt%. Non-limiting specific examples are 3wt%, 4wt%, 5wt%, 6wt%, and 7wt%.

[0048] By adding a cross-linking agent (such as epoxy resin) to the adhesive, the cross-linking agent can form chemical bonds at high temperatures, thereby enhancing the mechanical properties and thermal stability of the adhesive, preventing it from decomposing, degrading or releasing toxic gases at high temperatures, thereby improving the performance and safety of the material.

[0049] In some embodiments of the present invention, the raw materials for preparing the binder also include a solvent; in some specific embodiments of the present invention, the solvent in the binder is selected from an organic solvent; in some examples of the present invention, the solvent in the binder is selected from N-methylpyrrolidone (NMP). The temperature-sensitive polymer in the present invention has good solubility in N-methylpyrrolidone (NMP).

[0050] In some embodiments of the present invention, the mass ratio of the temperature sensitive polymer to the solvent is 1:(5-15); in some specific embodiments of the present invention, the mass ratio of the temperature sensitive polymer to the solvent is 1:(6-12); in some examples of the present invention, the mass ratio of the temperature sensitive polymer to the solvent is 1:(8-10). Non-limiting specific examples include 1:8, 1:8.5, 1:9, 1:9.5, and 1:10.

[0051] A second aspect of the embodiments of the present invention provides an electrode material, comprising an electrode active material bonded by the solidified material, wherein the solidified material is formed by the binder according to the first aspect of the embodiments of the present invention.

[0052] The binder provided in the first aspect of the embodiment of the present invention has good adhesion, can effectively fix the electrode active material, and improve the mechanical strength and conductivity of the electrode material; at the same time, the binder can also form a network structure inside the electrode material, which is helpful to conduct electrons, ions and heat. The network structure also has good high-temperature stability and is not easy to decompose, degrade or release toxic gases in a high-temperature environment. Therefore, the obtained electrode material has good conductivity, thermal conductivity and high-temperature stability; and the temperature-sensitive polymer in the binder will automatically respond to temperature changes. When the temperature rises, the temperature-sensitive functional groups on the polymer will change their structure and properties, thereby deteriorating the conductivity of the electrode, automatically insulating the reaction on the electrode, and preventing thermal runaway from occurring.

[0053] In some embodiments of the present invention, the electrode material includes a positive electrode material.

[0054] The binder provided by the present invention is particularly suitable for the preparation of positive electrode materials, and is used to improve the bonding stability, electrical conductivity, thermal conductivity, high temperature stability, high temperature insulation and safety of the positive electrode materials.

[0055] In some embodiments of the present invention, the electrode active material includes a positive electrode active material.

[0056] In some embodiments of the present invention, the positive electrode active material includes a lithium-containing phosphate, a lithium-containing transition metal oxide, or a combination thereof; in some specific embodiments of the present invention, the lithium-containing phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate; the lithium-containing transition metal oxide includes lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, or lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 is NCM333, LiNi 0.5 Co 0.2 Mn 0.3 O2 is NCM523, LiNi 0.5 Co 0.25 Mn 0.25 O2 is NCM211, LiNi 0.6 Co 0.2 Mn 0.2 O2 is NCM622, LiNi 0.8 Co 0.1 Mn 0.1 It should be noted that the present invention includes but is not limited to the above-mentioned positive electrode active materials, and any material that can be used as a positive electrode active material is within the protection scope of the present invention.

[0057] In some embodiments of the present invention, the cured product includes a network structure formed by a temperature-sensitive polymer and a conductive agent.

[0058] The temperature-sensitive polymer and the conductive agent form a network structure to achieve bonding and fixation of the electrode active material, and the network structure and the electrode active material can effectively cooperate with each other to improve the conductive effect. The obtained electrode material has good electrical conductivity, thermal conductivity and high-temperature stability.

[0059] In some embodiments of the present invention, the mass ratio of the solidified material to the electrode active material is 1:(10-50); in some specific embodiments of the present invention, the mass ratio of the solidified material to the electrode active material is 1:(12-40); in some examples of the present invention, the mass ratio of the solidified material to the electrode active material is 1:(15-35). Non-limiting specific examples include 1:15, 1:20, 1:25, 1:30, and 1:35.

[0060] Controlling the specific dosage ratio of the solidified material and the electrode active material can optimize the conductive network structure formed by the binder, adjust the conductive properties and mechanical properties of the electrode material, and make it have better comprehensive performance.

[0061] The third aspect of the embodiment of the present invention provides a method for preparing the electrode material of the second aspect of the embodiment of the present invention, comprising the following steps: mixing a binder with an electrode active material to obtain a precursor, and curing the precursor to obtain an electrode material.

[0062] The preparation method of the electrode material provided in the embodiment of the present invention is simple and easy, and can obtain an electrode material with high conductivity, high stability and high safety.

[0063] In some embodiments of the present invention, the curing temperature is 100-180°C; in some specific embodiments of the present invention, the curing temperature is 120-170°C; in some examples of the present invention, the curing temperature is 140-160°C. Non-limiting specific examples are 140°C, 145°C, 150°C, 155°C, and 160°C.

[0064] In some embodiments of the present invention, the curing time is 0.5 to 5 hours; in some specific embodiments of the present invention, the curing time is 0.8 to 4 hours; in some examples of the present invention, the curing time is 1 to 3 hours. Non-limiting specific examples include 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0065] By controlling the curing conditions, the network structure formed by the binder after curing can be optimized, thereby improving the mechanical strength and conductivity of the electrode material.

[0066] In some embodiments of the present invention, no curing agent is required in the curing process. By adjusting the specific curing temperature and curing time, the binder can be effectively cured to obtain an electrode material with a good conductive network structure; and the introduction of a curing agent may lead to other side reactions, affecting the conductive properties of the material.

[0067] The fourth aspect of the embodiments of the present invention provides a battery, wherein the raw materials for preparing the positive electrode material of the battery include the binder of the first aspect of the embodiments of the present invention; or, the positive electrode material of the battery includes the electrode material of the second aspect of the embodiments of the present invention; or, the positive electrode material of the battery is prepared by the preparation method including the third aspect of the embodiments of the present invention.

[0068] The binder provided in the embodiment of the present invention can form a good conductive network structure, and in particular can cooperate with the electrode active material to promote the bonding and fixation of the material and the improvement of the conductive effect. The obtained electrode material has good conductivity at room temperature and can effectively reduce the conductivity at high temperature, achieve insulation and prevent thermal runaway effects, thereby obtaining a battery with good conductivity, stability and safety.

[0069] In some embodiments of the present invention, the battery can also monitor the operating temperature of the battery to adjust the working state of the battery in real time when it is working; for example, the current, voltage, etc. can be adjusted to prevent the battery cell from overheating and thermal runaway. Specifically, when the operating temperature of the battery exceeds 130°C, the impedance is increased and the operating current of the battery cell is reduced to prevent the battery cell from overheating and thermal runaway.

[0070] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0071] Binder Example 1

[0072] A binder, the preparation steps are as follows:

[0073] Step 1: Select 1.5 parts by weight of polyalkylpyrrole as the base of the binder, and dissolve it in NMP solvent to 10% solid content to obtain a glue solution;

[0074] Step 2: Add 2 parts by mass of carbon nanotubes as a conductive agent into the glue to prepare a binder.

[0075] Binder Example 2

[0076] A binder, which differs from binder example 1 in that the mass fraction of polyalkylpyrrole used in this example is 2 parts; other raw materials and steps are the same as those in binder example 1.

[0077] Binder Example 3

[0078] A binder, which differs from binder example 1 in that the mass fraction of polyalkylpyrrole used in this example is 3 parts; other raw materials and steps are the same as those in binder example 1.

[0079] Binder Example 4

[0080] A binder, which differs from binder example 2 in that polyalkylpyrrole is replaced by polyalkylthiophene in this example; other raw materials and steps are the same as those in binder example 2.

[0081] Binder Example 5

[0082] A binder, which differs from binder example 2 in that polyalkylpyrrole is replaced by polymethyl methacrylate in this example; other raw materials and steps are the same as those in binder example 2.

[0083] Binder Example 6

[0084] A binder, which differs from binder example 2 in that polyalkylpyrrole is replaced by ethylene-vinyl acetate copolymer in this example; other raw materials and steps are the same as those in binder example 2.

[0085] Binder Example 7

[0086] A binder, which differs from binder example 2 in that polyalkylpyrrole is replaced by polypropylene in this example; other raw materials and steps are the same as those in binder example 2.

[0087] Binder Comparative Example 1

[0088] A binder, which is different from binder example 1 in that polyalkylpyrrole is replaced by polyvinylidene fluoride (PVDF) in this example; other raw materials and steps are the same as those of binder example 1.

[0089] Electrode Example 1

[0090] A positive electrode sheet, comprising a binder 1 obtained in binder embodiment 1, and the preparation steps are as follows:

[0091] 96.5 parts by mass of positive electrode active material (NCM622) was added to the binder 1, mixed and coated, and cured at a curing temperature of 150° C. and a curing time of 2 hours, followed by die-cutting to prepare a positive electrode sheet.

[0092] The SEM image of the positive electrode obtained in Electrode Example 1 is as follows Figure 1 As shown, from Figure 1 It can be seen that the temperature-sensitive polymer and the conductive agent can form a network structure, thereby achieving effective bonding and fixation of the electrode active materials.

[0093] Electrode Examples 2 to 7 and Electrode Comparative Example 1

[0094] Electrode Examples 2 to 7 and Electrode Comparison Example 1 each provide a positive electrode sheet, which differs from Electrode Example 1 in that the binder in Electrode Examples 2 to 7 and Electrode Comparison Example 1 is replaced by the binder in Binder Examples 1 to 7 and Binder Comparison Example 1, respectively; other raw materials and preparation methods are the same as those in Electrode Example 1.

[0095] The raw material compositions of the positive electrode sheets of electrode embodiments 1 to 7 and electrode comparison example 1 are shown in Table 1.

[0096] Table 1 Composition of the positive electrode sheets of electrode embodiments 1 to 7 and electrode comparative example 1

[0097]

[0098]

[0099] Battery Example 1

[0100] A lithium ion battery, comprising the positive electrode sheet obtained in Electrode Example 1, is prepared in the following steps:

[0101] The negative electrode formula is Gr (graphite): CMC: SP = 96%: 2%: 2%. The slurry is prepared according to the above mass ratio, and coated and die-cut to obtain the negative electrode plate; then it is stacked with the positive electrode plate obtained in Electrode Example 1 to obtain a battery cell, and then liquid injection, infiltration, formation, aging, and capacity division are performed to obtain a lithium-ion battery.

[0102] Battery Examples 2 to 7 and Battery Comparative Example 1

[0103] Battery Examples 2 to 7 and Battery Comparison Example 1 each provide a lithium-ion battery, which differs from Battery Example 1 in that the positive electrode plates in Battery Examples 2 to 7 and Battery Comparison Example 1 are replaced with the positive electrode plates of Electrode Examples 1 to 7 and Electrode Comparison Example 1, respectively; other raw materials and preparation methods are the same as those of Battery Example 1.

[0104] Performance Testing

[0105] The industry standard test method was used to test the conductivity of the binders of binder embodiments 1 to 7 and binder comparative example 1 at 25°C and 130°C; the adhesion and surface resistance of the positive electrode sheets of electrode embodiments 2 to 7 and electrode comparative example 1 were tested; the number of cycles when the lithium-ion batteries of battery embodiments 2 to 7 and battery comparative example 1 reached 90% health status (90% SOH) at 1C / 1C was tested, as well as the cell needle puncture pass rate. The cell needle puncture pass rate was measured by the following method: a 5mm high temperature resistant steel needle (the cone angle of the needle tip was 45°, and the surface of the needle was smooth, free of rust, oxide layer and oil) was used to penetrate the test cell at a speed of 25mm / s from the direction perpendicular to the battery plate. The steel needle stayed in the battery and observed for 1h. If no smoke, explosion, fire or the like occurred, it means that the needle puncture test was passed. The ratio of the number of samples that passed the needle puncture test to the total number of test samples was calculated, which was the cell needle puncture pass rate.

[0106] The test results are shown in Table 2.

[0107] Table 2 Performance test results of embodiments and comparative examples

[0108]

[0109]

[0110] As can be seen from Table 2, among the binders of the embodiments of the present invention, polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer and polypropylene are polymer materials with good temperature sensitivity, which will undergo structural changes at high temperatures, thereby affecting the electrical conductivity of the material, and the prepared lithium-ion battery has good thermal stability, high safety performance, and a high cell needle puncture pass rate; while the polyvinylidene fluoride (PVDF) used in Comparative Example 1 has poor safety performance and a significantly lower cell needle puncture pass rate. As for conductive agents such as carbon nanotubes, they can form a good conductive network inside the cell, thereby improving the electrical conductivity and heat conduction efficiency of the cell, so that it has good electrical conductivity when used at room temperature. During the cell testing process of the lithium-ion battery prepared in the embodiment of the present invention, the cell mixed with the temperature-sensitive binder can sense the working temperature of the cell, thereby adjusting the working state of the cell in real time; specifically, when the working temperature exceeds 130°C, the cell can avoid overheating of the cell by increasing impedance and reducing working current, thereby preventing the occurrence of thermal runaway. The binder with temperature-sensitive functional groups provided in the embodiment of the present invention effectively improves the safety performance of the battery.

[0111] In summary, the temperature-sensitive polymer provided in the embodiment of the present invention can change its structure and properties when the temperature rises, thereby adjusting the conductivity, adhesion and mechanical strength of the material, so that the adhesive can automatically insulate the reaction inside the battery cell to prevent thermal runaway, and the adhesive has good stability at high temperatures and will not decompose or degrade to release toxic gases, thereby greatly improving the safety performance of the product; combined with the conductive agent, a network structure with strong adhesion, good conductivity and efficient heat conduction can be formed, and the obtained adhesive has good adhesion and conductivity at room temperature, as well as excellent insulation and safety performance at high temperatures.

Claims

1. A binder, characterized in that: The preparation method comprises the following raw materials: a temperature-sensitive polymer and a conductive agent; the temperature-sensitive polymer comprises at least one of polyalkylpyrrole, polyalkylthiophene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polypropylene or polyimide.

2. The adhesive according to claim 1, characterized in that The conductive agent includes at least one of carbon nanotubes, conductive carbon black, acetylene black, Ketjen black, graphene or carbon nanofibers; And / or, the mass ratio of the temperature sensitive polymer to the conductive agent is 1:(0.1-5).

3. The adhesive according to claim 1, characterized in that The raw materials for preparing the binder also include a cross-linking agent.

4. The adhesive according to claim 3, characterized in that The cross-linking agent includes epoxy resin; And / or, the mass percentage of the cross-linking agent in the raw materials for preparing the binder is 1 to 10 wt %.

5. An electrode material, characterized in that: The invention comprises an electrode active material bound by a solidified material, wherein the solidified material is formed by the binder according to any one of claims 1 to 4.

6. The electrode material according to claim 5, characterized in that The electrode material includes a positive electrode material.

7. The electrode material according to claim 5, characterized in that The solidified material includes a network structure formed by the temperature-sensitive polymer and the conductive agent; And / or, the mass ratio of the solidified material to the electrode active material is 1:(10-50).

8. A method for preparing an electrode material according to any one of claims 5 to 7, characterized in that: The following steps are involved: The binder is mixed with the electrode active material to obtain a precursor, and the precursor is cured to obtain the electrode material.

9. The preparation method according to claim 8, characterized in that: The curing temperature is 100-180°C; And / or, the curing time is 0.5 to 5 hours.

10. A battery, characterized in that: The raw material for preparing the positive electrode material of the battery includes the binder described in any one of claims 1 to 4; or, the positive electrode material of the battery includes the electrode material described in any one of claims 5 to 7; or, the positive electrode material of the battery is prepared by the preparation method described in claim 8 or 9.

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