CN110739458B

CN110739458B - Conductive polymer alkali metal salt with heat-sensitive characteristic and preparation method and application thereof

Info

Publication number: CN110739458B
Application number: CN201810790006.1A
Authority: CN
Inventors: 马强; 李阳兴; 秦德君
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-07-18
Filing date: 2018-07-18
Publication date: 2021-08-31
Anticipated expiration: 2038-07-18
Also published as: CN110739458A

Abstract

The embodiment of the invention provides a conductive polymer alkali metal salt with heat-sensitive property, which comprises a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, wherein the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, the substituted imine alkali metal salt comprises one or more of a substituted imide alkali metal salt and a substituted sulfimide alkali metal salt, and the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom. The conductive polymer alkali metal salt has excellent heat-sensitive property, conductive ion capacity and ion conduction capacity, and can be applied to a secondary battery, so that the safety and the electrochemical performance of the battery can be effectively improved, and the thermal runaway of the battery can be avoided. The embodiment of the invention also provides a preparation method and application of the conducting polymer alkali metal salt.

Description

Conductive polymer alkali metal salt with heat-sensitive characteristic and preparation method and application thereof

Technical Field

The invention relates to the technical field of secondary batteries, in particular to a conductive polymer alkali metal salt with heat-sensitive property and a preparation method and application thereof.

Background

With the development of science and technology, electronic consumer products (mobile phones and digital cameras) and some professional electronic devices are gradually developing towards miniaturization and portability, and the use functions are continuously expanded, so that higher requirements on the energy density of energy storage devices (such as batteries) are provided, and the safety problem of high-energy density devices is urgently needed to be solved. At present, the electrolyte of a secondary battery is mainly a nonaqueous organic electrolyte (generally a carbonate electrolyte), and when the battery is in an abuse state (such as thermal shock, overcharge, acupuncture, external short circuit and the like), the electrolyte has hidden dangers of easy volatilization, easy combustion and the like, so that the safety problem caused by thermal runaway of the battery is easily caused.

For the safety problem caused by thermal runaway of the battery, the currently mainstream adopted strategies include the following three aspects: 1) the flame-retardant electrolyte is developed, but although the use of the flame-retardant electrolyte can reduce the combustion failure rate of the battery to a certain extent, the existing flame-retardant electrolyte has a certain negative effect on the electrochemical performance of the battery; 2) the coating diaphragm is developed, the heat resistance of the diaphragm can be improved by adopting the coating diaphragm, the safety performance of the battery is improved to a certain extent, but the use of the coating diaphragm can bring the contact problem and can not meet the requirement of the safety of the battery; 3) thermosensitive materials have been developed, which means materials that cause chemical or physical changes by thermal energy, and the resistance of which is greatly affected by temperature.

At present, the thermosensitive material mainly includes three major types, i.e., inorganic oxide material (such as strontium-doped barium titanate, lead-doped barium titanate, etc.), conductive agent and polymer mixed material (such as carbon black mixed with polyoxyethylene), and conductive polymer material (such as polythiophene compound). The conductive polymer material is generally composed of a macromolecular chain structure and monovalent anions or cations which are not bonded with the chain, so that the conductive polymer not only has the metal characteristics (such as high conductivity) and semiconductor characteristics caused by doping, but also has the characteristics of diversified molecular design structures, processability, light specific gravity and the like. However, although the conventional conductive polymer thermosensitive material has excellent thermosensitive property and conductive property, and can effectively avoid thermal runaway behavior of the battery when being applied to the battery, so as to improve the safety of the battery, the conventional conductive polymer thermosensitive material does not have conductive property, and reduces the performances of the battery, such as cycle, rate, low temperature and the like. Therefore, it is necessary to develop a material having multifunctional properties such as heat-sensitive properties, electron-conductive properties, and ion-conductive properties.

Disclosure of Invention

In view of this, a first aspect of the embodiments of the present invention provides a conductive polymer alkali metal salt with thermal sensitivity, which has excellent thermal sensitivity, conductivity and ion conductivity, and can be applied to a secondary battery to effectively improve the safety and electrochemical performance of the battery, so as to solve the problem that the existing conductive polymer thermal sensitive material can improve the safety of the battery to a certain extent, but does not have ion conductivity, which results in the reduction of the cycle, rate and low temperature performance of the battery.

Specifically, according to the first aspect of the embodiments of the present invention, there is provided a conductive polymer alkali metal salt with a heat-sensitive property, including a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, where the conductive polymer repeating unit includes a five-membered unsaturated heterocyclic structure, the substituted imine alkali metal salt includes one or more of a substituted imide alkali metal salt and a substituted sulfonyl imide alkali metal salt, and the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom.

Wherein the chemical expression of the substituted imide alkali metal salt is-N^-(M⁺)-C(＝O)-Z₁Wherein M is Li, Na, K, Rb or Cs, Z₁Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

Wherein the chemical expression of the substituted sulfimide alkali metal salt is-N^-(M⁺)-S(＝O)₂-Z₂Wherein M is Li, Na, K, Rb or Cs, Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

The conducting polymer alkali metal salt comprises one or more of the conducting polymer repeating units.

The conductive polymer repeating unit includes one or more five-membered unsaturated heterocyclic structures. Specifically, the five-membered unsaturated heterocyclic structure comprises at least one of thiophene, pyrrole and furan.

The conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, and the groups at the 3-position and the 4-position of the five-membered unsaturated heterocyclic structure are respectively R₁And R₂SaidR₁And R₂Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₁And R₂At least one of them is the substituted imine alkali metal salt.

The conductive polymer repeating unit comprises a plurality of five-membered unsaturated heterocyclic structures, at least one group in all groups at the 3-position and the 4-position of the five-membered unsaturated heterocyclic structures is the substituted imine alkali metal salt, and the rest groups are respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.

Z is₁Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

Z is₂Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

The R is₁And R₂Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

According to the conductive polymer alkali metal salt with the thermal sensitivity provided by the embodiment of the invention, the substituted imine alkali metal salt is grafted to the repeating unit containing the five-membered unsaturated heterocyclic structure to form the substituted imine alkali metal salt grafted conductive polymer material, and the conductive polymer material has excellent thermal sensitivity, excellent conductive ion capacity and excellent ion conduction capacity, and can be applied to a secondary battery, so that the safety of the battery can be effectively improved, the electrochemical performance of the battery can be improved, and the problem that the cycle, the multiplying power, the low temperature and other performances of the battery are reduced due to the fact that the existing conductive polymer thermal sensitive material can improve the safety of the battery to a certain extent but does not have the ion conduction performance is solved.

Accordingly, a second aspect of embodiments of the present invention provides a method for preparing an alkali metal salt of a conductive polymer having heat-sensitive characteristics, comprising the steps of:

the polymer monomer reacts for 6 to 48 hours at a temperature of between 40 ℃ below zero and 100 ℃ in the presence of an initiator and a solvent, polymerizing the polymer monomer to obtain the conductive polymer alkali metal salt with heat-sensitive property, the polymer monomer comprises a five-membered unsaturated heterocyclic structure and a substituted imine alkali metal salt positioned on the five-membered unsaturated heterocyclic structure, the conductive polymer alkali metal salt comprises a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, the substituted imide alkali metal salt comprises one or more of substituted imide alkali metal salt and substituted sulfonyl imide alkali metal salt, the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom.

Wherein the polymer monomer is prepared by adopting the following steps:

reacting a five-membered unsaturated heterocyclic compound substituted by halogen with a substituted amine compound at 0-60 ℃ for 6-48 hours in the presence of an acid-binding agent and a solvent to obtain amine salt; the substituted amine compound comprises one or more of a substituted amide compound and a substituted sulfonamide compound;

under the protection of inert gas, reacting the amine salt with anhydrous alkali carbonate at 0-30 ℃ for 2-24 hours to obtain alkali metal salt, and obtaining the polymer monomer.

Specifically, theThe chemical expression of the substituted amide compound is Z₁-C(＝O)-NH₂The chemical expression of the substituted sulfonamide compound is Z₂-S(＝O)₂-NH₂Z is the same as₁And Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

The groups at the 3-position and the 4-position in the halogen substituted five-membered unsaturated heterocyclic compound are respectively R₃And R₄Said R is₃And R₄Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₃And R₄At least one of which is fluorine, chlorine, bromine or iodine.

The initiator comprises one or more of Azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), potassium persulfate, hydrogen peroxide-ferrous chloride and anhydrous ferric chloride.

The molar ratio of the polymer monomer to the initiator is 1: 0.1-8.

The molar ratio of the halogen substituted five-membered unsaturated heterocyclic compound to the acid-binding agent is 1: 1-10; the molar ratio of the halogen substituted five-membered unsaturated heterocyclic compound to the substituted amine compound is 1: 1-8; the molar ratio of the amine salt to the anhydrous alkali carbonate is 1: 1-10.

The preparation method provided by the second aspect of the embodiment of the invention has simple process and is easy to operate.

According to a third aspect of the embodiments of the present invention, there is provided a composite current collector, including a current collector body and a heat-sensitive material layer disposed on one side surface or both side surfaces of the current collector body, where the heat-sensitive material layer includes the conductive polymer alkali metal salt having heat-sensitive characteristics according to the first aspect of the present invention.

Wherein the heat-sensitive material layer further comprises a binder, and the conductive polymer alkali metal salt with heat-sensitive property is fixed in the heat-sensitive material layer through the binder.

In the thermosensitive material layer, the mass ratio of the conductive polymer alkali metal salt with thermosensitive property to the binder is 1-100: 1.

The thickness of the thermosensitive material layer is 0.01-10 μm.

Embodiments of the present invention further provide an electrode material, including an electrode active material and a coating layer disposed on a surface of the electrode active material, where the coating layer includes a conductive polymer alkali metal salt having a heat-sensitive property according to the first aspect of the embodiments of the present invention, and the electrode active material is a positive electrode active material or a negative electrode active material.

Wherein the thickness of the coating layer is 1nm-10 μm.

The embodiment of the invention also provides an electrode plate, which comprises a current collector and an electrode active material layer arranged on the current collector, wherein the electrode active material layer comprises the conducting polymer alkali metal salt with the heat-sensitive property, and the electrode plate is a positive plate or a negative plate.

The embodiment of the invention also provides a composite diaphragm, which comprises a diaphragm body and heat-sensitive material layers arranged on one side surface or two side surfaces of the diaphragm body, wherein the heat-sensitive material layers comprise the conducting polymer alkali metal salt with the heat-sensitive property of the first aspect of the invention.

Accordingly, embodiments of the present invention further provide a secondary battery, including a positive electrode, a negative electrode, and a separator and an electrolyte disposed between the positive electrode and the negative electrode, where the positive electrode, the negative electrode, and/or the separator includes the conductive polymer alkali metal salt with heat-sensitive characteristics described above in embodiments of the present invention.

By implementing the embodiment of the invention, the safety performance and the electrochemical performance of the secondary battery are greatly improved, the safety problem of the secondary battery caused by thermal runaway in the prior art is solved, and the problem of the electrochemical performance reduction of the battery caused by the introduction of the conventional conductive polymer heat-sensitive material is solved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present invention, the drawings required to be used in the embodiments or the background art of the present invention will be described below.

Fig. 1 is a schematic structural diagram of a composite current collector according to an embodiment of the present invention;

fig. 2 is a schematic structural view of a composite current collector in another embodiment of the present invention;

FIG. 3 is a schematic structural diagram of an electrode material according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of an electrode sheet according to an embodiment of the present invention;

fig. 5 is a schematic structural view of an electrode sheet according to another embodiment of the present invention;

FIG. 6 is a schematic structural view of a composite diaphragm according to an embodiment of the present invention;

fig. 7 is a schematic structural view of a composite separator according to another embodiment of the present invention.

Detailed Description

The embodiments of the present invention will be described below with reference to the drawings.

With the continuous development of scientific technology, the market demand for high energy density secondary batteries is increasing, and the safety problem of the secondary batteries caused by thermal runaway is also aggravated by high heat generated by the high energy density, and in order to prevent the thermal runaway, a heat-sensitive material (such as a conductive polymer) with heat-sensitive characteristics is added into the batteries. Therefore, it is necessary to provide a heat-sensitive material that can improve the safety of a battery and ensure good electrochemical performance of the battery.

Based on the above, the embodiment of the invention provides a conductive polymer alkali metal salt with a heat-sensitive property, which comprises a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, wherein the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, the substituted imine alkali metal salt comprises one or more of a substituted imide alkali metal salt and a substituted sulfonyl imide alkali metal salt, and the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom.

The conducting polymer alkali metal salt with the heat-sensitive property provided by the embodiment of the invention has excellent heat-sensitive property, electron conductivity and ion conductivity, and can effectively improve the safety performance and electrochemical performance of a battery when applied to a secondary battery, because the conducting polymer alkali metal salt with the heat-sensitive property is a conducting polymer grafted by substituted imine alkali metal salt, and simultaneously contains a repeating unit of a five-membered unsaturated heterocyclic structure and a substituted imine alkali metal salt structure, wherein the repeating unit of the five-membered unsaturated heterocyclic structure has excellent heat-sensitive property and good electron conductivity, can be subjected to electrochemical oxidation doping during charging to improve the conductivity, and when the temperature of the battery exceeds a certain temperature (Curie temperature), the resistance of the battery rapidly rises, so that the current is interrupted, and the safety of the battery is improved; and the substituted imine alkali metal salt structure can effectively improve the transference number of alkali metal ions and is beneficial to the transmission of ions, thereby improving the performances of the battery such as circulation, multiplying power, low temperature and the like. The secondary battery may be a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, or the like.

In the embodiment of the invention, the chemical expression of the substituted imide alkali metal salt is-N^-(M⁺)-C(＝O)-Z₁Wherein M is Li, Na, K, Rb or Cs, Z₁Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy. In an embodiment of the present invention, Z is₁Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20. In particular, Z is₁May be but is not limited to-CF₃，-CF₂CF₃，-CF₂CF₂CF₂CF₃，-CF₂CF₂CF₂H，-CH₂CF₃And the like.

In the embodiment of the invention, the chemical expression of the substituted sulfimide alkali metal salt is-N^-(M⁺)-S(＝O)₂-Z₂Wherein M is Li, Na, K, Rb or Cs, Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy. In an embodiment of the present invention, Z is₂Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20. In particular, Z is₂May be but is not limited to-CF₃，-CF₂CF₃，-CF₂CF₂CF₂CF₃，-CF₂CF₂CF₂H，-CH₂CF₃And the like.

In an embodiment of the present invention, the conductive polymer alkali metal salt comprises one or more of the conductive polymer repeating units. The plurality includes two or more species.

In an embodiment of the present invention, the five-membered unsaturated heterocyclic structure includes at least one of thiophene, pyrrole, and furan.

In an embodiment of the invention, the conductive polymer repeat unit comprises one or more five-membered unsaturated heterocyclic structures. The plurality includes two or more. When the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, at least one of the groups at the 3-position and the 4-position of the five-membered unsaturated heterocyclic structure is the substituted imine alkali metal salt, and the other group is any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy. When the conductive polymer repeating unit comprises a plurality of five-membered unsaturated heterocyclic structures, at least one group in all groups at the 3-position and the 4-position of the five-membered unsaturated heterocyclic structures is the substituted imine alkali metal salt, and the rest groups are respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.

In one embodiment of the present invention, the conductive polymer alkali metal salt comprises a conductive polymer repeating unit, and the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, and the chemical structural formula of the conductive polymer repeating unit can be represented by formula (1):

wherein X is NH, O or S, n is an integer greater than 1, R₁And R₂Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₁And R₂At least one of them is the substituted imine alkali metal salt.

In another embodiment of the present invention, the conductive polymer alkali metal salt comprises a conductive polymer repeating unit comprising two five-membered unsaturated heterocyclic structures, and the chemical structural formula of the conductive polymer repeating unit can be represented by formula (2):

in the structure represented by formula (2), in one embodiment of the present invention, X is₁、X₂Are respectively selected from NHO or S, and X₁、X₂Different, n is an integer greater than 1, R₅、R₆、R₇And R₈Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₅、R₆、R₇And R₈At least one of them is the substituted imine alkali metal salt.

In another embodiment of the present invention, the structure represented by formula (2) is such that X is₁、X₂Are independently selected from NH, O or S, and X₁、X₂N is an integer greater than 1, and X is₁In the five-membered heterocycle₅、R₆And said X₂In the five-membered heterocycle₇、R₈At least one is different, said R₅、R₆、R₇And R₈Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₅、R₆、R₇And R₈At least one of them is the substituted imine alkali metal salt.

By analogy, in other embodiments of the present invention, the conductive polymer repeating unit may also include three or more five-membered unsaturated heterocyclic structures with different structures.

In another embodiment of the present invention, the conductive polymer alkali metal salt comprises two conductive polymer repeating units, and the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, and the chemical structural formula of the conductive polymer repeating unit can be represented by formula (3):

in the structure represented by formula (3), in one embodiment of the present invention, X is₁、X₂Are independently selected from NH, O or S, and X₁、X₂Different from each other, n₁、n₂Is an integer greater than 1, R₁And R₂Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₁And R₂At least one of them is the substituted imine alkali metal salt.

In another embodiment of the present invention, the structure represented by formula (3) is such that X represents a hydrogen atom₁、X₂Are independently selected from NH, O or S, and X₁、X₂Same, n₁、n₂Is an integer greater than 1, R₁And R₂Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₁And R₂At least one of them is the substituted imine alkali metal salt, and X is₁In the five-membered heterocycle₁、R₂And said X₂R in the repeating unit₁、R₂At least one is different.

In this way, in other embodiments of the present invention, the conductive polymer alkali metal salt may also include three or more conductive polymer repeating units with different structures.

In an embodiment of the present invention, the above-mentioned alkyl group, haloalkyl group, alkoxy group, and haloalkoxy group have 1 to 20 carbon atoms, the alkenyl group, haloalkenyl group, alkenyloxy group, and haloalkenyloxy group have 2 to 20 carbon atoms, and the aryl group, haloaryl group, aryloxy group, and haloaryloxy group have 6 to 20 carbon atoms. The alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy may be linear or branched. The halogen in the halogenated alkyl, the halogenated alkoxy, the halogenated alkenyl, the halogenated alkenyloxy, the halogenated aryl and the halogenated aryloxy comprises fluorine, chlorine, bromine and iodine, and the halogen is perhalogenated or partially halogenated.

Specifically, in the embodiment of the present invention, the structural formula of the conductive polymer material may be as shown in (a) to (P):

the conductive polymer alkali metal salt with the thermal sensitivity provided by the embodiment of the invention has excellent thermal sensitivity, excellent conductive ion capacity and excellent ion conductivity, and can be applied to a secondary battery, so that the safety and electrochemical performance of the battery can be effectively improved, the battery is prevented from burning and explosion due to thermal runaway, and the battery has good rate capability.

Correspondingly, the embodiment of the invention also provides a preparation method of the conducting polymer alkali metal salt with the heat-sensitive characteristic, which comprises the following steps:

reacting a polymer monomer at-40-100 ℃ for 6-48 hours in the presence of an anhydrous initiator and a solvent, polymerizing the polymer monomer to obtain the conductive polymer alkali metal salt with heat-sensitive property, the polymer monomer comprises a five-membered unsaturated heterocyclic structure and a substituted imine alkali metal salt positioned on the five-membered unsaturated heterocyclic structure, the conductive polymer alkali metal salt comprises a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, the substituted imide alkali metal salt comprises one or more of substituted imide alkali metal salt and substituted sulfonyl imide alkali metal salt, the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom.

The alkali metal salt of the conductive polymer prepared by the above preparation method in the embodiment of the present invention is as described in the previous part of the embodiment of the present invention, and is not described herein again.

In the embodiment of the invention, the structural formula of the polymer monomer is shown as a formula (4),

wherein X is NH, O or S, R₁And R₂Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₁And R₂At least one of them is a substituted imine alkali metal salt. In an embodiment of the invention, R is₁And R₂Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

In the embodiment of the invention, the chemical expression of the substituted imide alkali metal salt is-N^-(M⁺)-C(＝O)-Z₁Wherein M is Li, Na, K, Rb or Cs, Z₁Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy. In an embodiment of the present invention, Z is₁Wherein the alkyl, haloalkyl, alkoxy and haloalkoxy have 1 to 20 carbon atoms, and the alkenyl, haloalkenyl, alkenyloxy and haloalkenyloxy have 1 to 20 carbon atomsThe atomic number is 2-20, and the carbon atomic number of the aryl, the halogenated aryl, the aryloxy and the halogenated aryloxy is 6-20. In particular, Z is₁May be but is not limited to-CF₃，-CF₂CF₃，-CF₂CF₂CF₂CF₃，-CF₂CF₂CF₂H，-CH₂CF₃And the like.

In the embodiment of the present invention, the polymer monomer added may be one or more. The selection can be specifically carried out according to the molecular structure of the alkali metal salt of the pre-designed conducting polymer. For example, when preparing the conductive polymer alkali metal salt represented by formula (2) in the embodiment of the present invention, in one embodiment, the polymer monomer includes both the compound represented by formula (4) and the five-membered unsaturated heterocyclic compound in which neither the 3-position nor the 4-position is substituted by the substituted imine alkali metal salt.

In an embodiment of the present invention, the initiator includes, but is not limited to, Azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), potassium persulfate, hydrogen peroxide-ferrous chloride, anhydrous ferric chloride, and the like.

In an embodiment of the present invention, the molar ratio of the polymer monomer to the initiator is 1:0.1 to 8, and further, the molar ratio may be 1:0.2 to 1, 1:2 to 6.

In an embodiment of the present invention, the solvent includes one or more of ethane, cyclohexane, dichloromethane, chloroform, diethyl ether, petroleum ether, benzene, toluene, chlorobenzene, fluorobenzene, acetone, acetonitrile, methanol, ethanol, tetrahydrofuran, nitromethane, dimethyl sulfoxide, N-dimethylformamide, ethyl acetate, and butyl acetate.

In the embodiment of the invention, stirring is carried out in the polymerization reaction process, after the reaction is finished, filtering, drying under reduced pressure, recrystallizing by ethanol/toluene, filtering, washing, and drying in vacuum at 40-80 ℃ for 12-48 hours to obtain the conductive polymer alkali metal salt with heat-sensitive property.

In an embodiment of the present invention, the polymer monomer may be prepared as follows:

a) reacting a five-membered unsaturated heterocyclic compound substituted by halogen with a substituted amine compound at 0-60 ℃ for 6-48 hours in the presence of an acid-binding agent and a solvent to obtain amine salt; the substituted amine compound comprises one or more of a substituted amide compound and a substituted sulfonamide compound;

b) and under the protection of inert gas, reacting the amine salt with anhydrous alkali carbonate at 0-30 ℃ for 2-24 hours to obtain alkali metal salt, thus obtaining the polymer monomer.

In an embodiment of the present invention, the chemical formula of the substituted amide compound is Z₁-C(＝O)-NH₂The chemical expression of the substituted sulfonamide compound is Z₂-S(＝O)₂-NH₂Z is the same as₁And Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

In the embodiment of the invention, the structural formula of the halogen-substituted five-membered unsaturated heterocyclic compound is shown as a formula (5), wherein the groups at the 3-position and the 4-position are respectively R₃And R₄Said R is₃And R₄Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₃And R₄At least one of which is fluorine, chlorine, bromine or iodine.

In an embodiment of the present invention, the halogen-substituted five-membered unsaturated heterocyclic compound includes at least one of halogen-substituted thiophene, halogen-substituted furan, and halogen-substituted pyrrole. Specifically, the halogen-substituted five-membered unsaturated heterocyclic compound includes, but is not limited to, 3-bromo-substituted thiophene, 3, 4-dichloro-substituted thiophene, 3-chloro-4-bromo-substituted thiophene, 3, 4-dibromo-substituted thiophene, 3-bromo-4-n-butyl-substituted thiophene, 3-bromo-4-n-hexyl-substituted thiophene, 3-bromo-4-n-heptyl-substituted thiophene, 3-bromo-4-n-octyl-substituted thiophene, 3-bromo-substituted furan, 3, 4-dichloro-substituted furan, 3-chloro-4-bromo-substituted furan, 3, 4-dibromo-substituted furan, 3-bromo-4-n-butyl-substituted furan, 3-bromo-4-n-hexyl-substituted furan, 3-bromo-4-n-butyl-substituted thiophene, 3-bromo-4-n-butyl-substituted thiophene, 3-bromo-4-bromo-n-butyl-substituted thiophene, 3-bromo-4-substituted furan, and 3-bromo-4-n-butyl-substituted thiophene, 3-bromo-4-n-heptenyl-substituted furan, 3-bromo-4-n-octylenyl-substituted furan, 3-bromo-substituted pyrrole, 3, 4-dichloro-substituted pyrrole, 3-chloro-4-bromo-substituted pyrrole, 3, 4-dibromo-substituted pyrrole, 3-bromo-4-n-butylalkyl-substituted pyrrole, 3-bromo-4-n-hexylenyl-substituted pyrrole, 3-bromo-4-n-heptenyl-substituted pyrrole, 3-bromo-4-n-octylenyl-substituted pyrrole, and the like.

In an embodiment of the present invention, the acid-binding agent includes at least one of triethylamine, N-dimethylcyclohexylamine, pyridine, pyrimidine, and quinoline.

In an embodiment of the present invention, the anhydrous alkali metal carbonate includes one or more of anhydrous lithium carbonate, anhydrous sodium carbonate, anhydrous potassium carbonate, anhydrous rubidium carbonate, and anhydrous cesium carbonate.

In an embodiment of the invention, the molar ratio of the halogen substituted five-membered unsaturated heterocyclic compound to the acid-binding agent is 1:1-1:10, further 1:2-1:7, and further 1:3-1: 5; the molar ratio of the halogen substituted five-membered unsaturated heterocyclic compound to the substituted amine compound is 1:1-1:8, further 1:2-1:6, and further 1:3-1: 5; the molar ratio of the amine salt to the anhydrous alkali carbonate is 1:1 to 1:10, further 1:2 to 1:7, further 1:3 to 1: 5.

The alkali metal salt of a conductive polymer having a heat-sensitive characteristic provided in the embodiments of the present invention may be applied to a secondary battery in various ways to improve the safety and electrochemical performance of the battery.

Specifically, the embodiment of the invention provides a composite current collector, which comprises a current collector body and a heat-sensitive material layer arranged on one side surface or two side surfaces of the current collector body, wherein the heat-sensitive material layer comprises the conductive polymer alkali metal salt with heat-sensitive property. Fig. 1 and fig. 2 are schematic structural views of a composite current collector according to two embodiments of the present invention. In an embodiment of the present invention, as shown in fig. 1, the composite current collector includes a current collector body 10 and a thermosensitive material layer 20 disposed on a surface of one side of the current collector body 10. In another embodiment of the present invention, as shown in fig. 2, the composite current collector includes a current collector body 10 and heat sensitive material layers 20 disposed on two side surfaces of the current collector body 10.

In the embodiment of the present invention, the thermosensitive material layer 20 further includes a binder, and the conductive polymer alkali metal salt having thermosensitive property is fixed in the thermosensitive material layer 20 by the binder. The conductive polymer alkali metal salt having heat-sensitive characteristics is uniformly dispersed in the heat-sensitive material layer 20.

In the present embodiment, in the thermosensitive material layer 20, the mass ratio of the conductive polymer alkali metal salt having thermosensitive property to the binder is 1-100:1, and further may be 50-95: 1. The binder may be one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), Polyimide (PI), polyethylene glycol (PEG), polyethylene oxide (PEO), Polydopamine (PDA), sodium carboxymethylcellulose/styrene butadiene rubber (CMC/SBR), polyvinyl alcohol (PVA), polyacrylic acid (PAA), lithium polyacrylate (lipa), polyvinylpyrrolidone (PVP), polylactic acid (PLA), Sodium Alginate (SA), polyethylene p-benzenesulfonic acid (PSS), polyethylene p-benzenesulfonic acid (LiPSS), and gelatin.

In the embodiment of the present invention, the thickness of the thermosensitive material layer 20 may be 0.01 μm to 10 μm, and further may be 1 μm to 8 μm, 3 μm to 6 μm, and 5 μm to 7 μm.

In embodiments of the present invention, the current collector body may be an existing conventional commercial current collector, including but not limited to aluminum foil, copper foil, carbon-coated aluminum foil, and the like.

Accordingly, an embodiment of the present invention provides a secondary battery, including a positive electrode, a negative electrode, and a separator and an electrolyte disposed between the positive electrode and the negative electrode, where the positive electrode includes a positive electrode current collector, the negative electrode includes a negative electrode current collector, and the positive electrode current collector and/or the negative electrode current collector are/is the composite current collector described above in the embodiment of the present invention. The secondary battery has excellent safety and electrochemical properties due to the introduction of the above-described conductive polymer alkali metal salt having heat-sensitive characteristics in the current collector according to the embodiment of the present invention. The secondary battery includes a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, and the like.

As shown in fig. 3, an embodiment of the present invention further provides an electrode material 30, including an electrode active material 110 and a coating layer 120 disposed on a surface of the electrode active material 110, where the coating layer 120 includes the above-mentioned conductive polymer alkali metal salt having a heat-sensitive property according to an embodiment of the present invention, and the electrode active material is a positive electrode active material or a negative electrode active material.

In the embodiment of the present invention, the thickness of the coating layer 120 may be 1nm to 10 μm, and further 2nm to 1 μm, 10nm to 3 μm, or 100nm to 5 μm.

In the embodiment of the present invention, the positive electrode active material and the negative electrode active material are conventional materials, and the present invention is not particularly limited. The positive electrode active material may be, for example, lithium cobaltate or the like, and the negative electrode active material may be, for example, graphite or the like. The coating layer may be prepared to the surface of the electrode active material by an existing conventional slurry pulping method.

The embodiment of the invention also provides an electrode plate, which comprises a current collector and an electrode active material layer arranged on the current collector, wherein the electrode active material layer comprises the conductive polymer alkali metal salt with the heat-sensitive characteristic, and the electrode plate is a positive plate or a negative plate.

In one embodiment of the present invention, as shown in fig. 4, the electrode sheet includes a current collector 210 and an electrode active material layer 220 disposed on the current collector 210, the electrode active material layer 220 includes a conductive polymer alkali metal salt 23 having a heat-sensitive property and an electrode active material 110, and the conductive polymer alkali metal salt 23 having a heat-sensitive property is uniformly dispersed in the electrode active material layer 220. The electrode active material layer 220 further includes a conductive agent, a binder, and the like. The electrode active material 110 may be a positive electrode active material or a negative electrode active material.

In the embodiment of the present invention, the alkali metal salt 23 of the conductive polymer having a heat-sensitive property accounts for 0.1% to 20%, further 1% to 10%, and 2% to 6% of the total mass of the electrode active material layer 220.

In another embodiment of the present invention, as shown in fig. 5, the electrode sheet includes a current collector 210 and an electrode active material layer 220 disposed on the current collector 210, and the electrode active material layer 220 includes the electrode material 30 and the conductive agent 40 according to the embodiment of the present invention. Specifically, in an implementable manner, if the conductive polymer alkali metal salt having heat-sensitive characteristics is dissolved in the slurry solvent during electrode pulping, the final alkali metal salt may be present on the surface of the electrode active material layer in the form of a coating layer.

Correspondingly, the embodiment of the invention also provides a secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the diaphragm and the electrolyte are arranged between the positive electrode and the negative electrode, and the positive electrode and/or the negative electrode comprise the electrode slice in the embodiment of the invention. The secondary battery includes a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, and the like.

The embodiment of the invention also provides a composite diaphragm, which comprises a diaphragm body and heat-sensitive material layers arranged on one side surface or two side surfaces of the diaphragm body, wherein the heat-sensitive material layers comprise the conducting polymer alkali metal salt with the heat-sensitive property. Fig. 6 and 7 are schematic structural views of a composite diaphragm according to two embodiments of the present invention. In one embodiment of the present invention, as shown in fig. 6, the composite diaphragm includes a diaphragm body 50 and a heat sensitive material layer 60 disposed on one side surface of the diaphragm body 50. In another embodiment of the present invention, as shown in fig. 7, the composite diaphragm includes a diaphragm body 50 and heat sensitive material layers 60 disposed on both side surfaces of the diaphragm body 50.

In the embodiment of the present invention, the heat-sensitive material layer 60 further includes a binder, and the conductive polymer alkali metal salt having heat-sensitive property is fixed in the heat-sensitive material layer 60 by the binder. The conductive polymer alkali metal salt having heat-sensitive characteristics is uniformly dispersed in the heat-sensitive material layer 60.

In the heat-sensitive material layer 60 according to an embodiment of the present invention, the mass ratio of the alkali metal salt of the conductive polymer having heat-sensitive characteristics to the binder may be 1 to 100:1, and may be 50 to 95: 1. The binder may be one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), Polyimide (PI), polyethylene glycol (PEG), polyethylene oxide (PEO), Polydopamine (PDA), sodium carboxymethylcellulose/styrene butadiene rubber (CMC/SBR), polyvinyl alcohol (PVA), polyacrylic acid (PAA), lithium polyacrylate (lipa), polyvinylpyrrolidone (PVP), polylactic acid (PLA), Sodium Alginate (SA), polyethylene p-benzenesulfonic acid (PSS), polyethylene p-benzenesulfonic acid (LiPSS), and gelatin.

In the embodiment of the present invention, the thickness of the thermosensitive material layer 60 is 0.01 μm to 10 μm, and further may be 1 μm to 8 μm, 3 μm to 6 μm, 5 μm to 7 μm.

In embodiments of the present invention, the separator body may be an existing conventional commercial separator, including but not limited to, a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP separator.

Correspondingly, the embodiment of the invention provides a secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the diaphragm and the electrolyte are arranged between the positive electrode and the negative electrode, and the diaphragm adopts the composite diaphragm. The secondary battery includes a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, and the like.

The following examples are intended to illustrate the invention in more detail.

Example 1

Modifying a current collector by adopting poly (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) lithium imide (shown as a formula (D)) and applying the modified current collector to a lithium secondary battery, wherein the method comprises the following steps:

(1) the preparation of poly (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) lithium imide (D) has the synthetic route shown in formula (6):

a) respectively adding 0.5mol of 3-bromo-4-n-octyl substituted thiophene, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of trifluoromethyl sulfonamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) imine triethylamine salt;

b) respectively adding 0.25mol of (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) imine triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at the temperature of 25 ℃, stirring for reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) imine lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric trichloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) lithium imide is slowly added into the three-neck flask at the temperature of 0 ℃, stirred and reacted for 12 hours, after the reaction is finished, filtered, decompressed and dried, then recrystallized by ethanol/toluene, filtered, washed, and vacuum-dried for 24 hours at the temperature of 60 ℃, and the poly (4-n-octyl substituted thiophene) (trifluoromethyl sulfonyl) lithium imide (D) is obtained, wherein the yield is 86%.

(2) Preparing a composite current collector:

weighing 90 mass percent of lithium poly (4-N-octyl substituted thiophene) (trifluoromethyl sulfonyl) imide (D) and 10 mass percent of polyvinylidene fluoride (PVDF), dissolving the lithium poly (4-N-octyl substituted thiophene) (trifluoromethyl sulfonyl) imide (D) and the PVDF in N-methylpyrrolidone (NMP), stirring and mixing the solution to form a uniform solution, and uniformly coating the solution on two surfaces of an aluminum foil current collector by using a 1-micrometer scraper to prepare the composite current collector disclosed in the embodiment 1 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the mixture into NMP, fully stirring and uniformly mixing to obtain slurry, coating the slurry on the composite current collector prepared in the embodiment 1, and drying, cold pressing and slitting to prepare the positive pole piece. Weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

Example 2

Modifying a current collector by adopting poly (4-n-heptane-substituted furan) (hexafluoropropyl sulfonyl) lithium imide (shown as a formula (G)) and applying the modified current collector to a lithium secondary battery, wherein the method comprises the following steps:

(1) the preparation of poly (4-n-heptane substituted furan) (hexafluoropropyl sulfonyl) lithium (G) imide has the synthetic route shown in the formula (7):

a) respectively adding 0.5mol of 3-bromo-4-n-heptane substituted furan, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of hexafluoropropyl sulfonamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (4-n-heptane substituted furan) (hexafluoropropyl sulfonyl) imide triethylamine salt;

b) respectively adding 0.25mol of (4-n-heptane-substituted furan) (hexafluoropropyl sulfonyl) imide triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at the temperature of 25 ℃, stirring and reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (4-n-heptane-substituted furan) (hexafluoropropyl sulfonyl) imide lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric chloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of (4-n-heptane-substituted furan) (hexafluoropropyl sulfonyl) lithium imide is slowly added into the three-neck flask at the temperature of 0 ℃, stirred and reacted for 12 hours, after the reaction is finished, filtered, decompressed and dried, and then recrystallized by ethanol/toluene, filtered, washed and dried in vacuum at the temperature of 60 ℃ for 24 hours to obtain the poly (4-n-heptane-substituted furan) (hexafluoropropyl sulfonyl) lithium imide (G), and the yield is 83%.

(2) Preparing a composite current collector:

weighing 90 mass percent of lithium (G) poly (4-N-heptane-substituted furan) (hexafluoropropyl sulfonyl) imide and 10 mass percent of PVDF, dissolving the lithium (G) poly (4-N-heptane-substituted furan) (hexafluoropropyl sulfonyl) imide and the PVDF in N-methylpyrrolidone (NMP), stirring and mixing the solution to form a uniform solution, and uniformly coating the uniform solution on two sides of a copper foil current collector by using a scraper with the diameter of 1 mu m to prepare the composite current collector in the embodiment 2 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the materials into NMP, fully stirring and uniformly mixing to obtain slurry, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain the positive pole piece. Weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on the composite current collector of the embodiment 2 of the invention, and drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

Comparative example 1

The current collector is modified by poly (3-n-octyl substituted) thiophene (P3OT) and is applied to a lithium secondary battery, and the method comprises the following steps:

(1) preparing a composite current collector:

weighing 90 mass percent of poly (3-N-octyl substituted) thiophene (P3OT) and 10 mass percent of PVDF, dissolving the poly (3-N-octyl substituted) thiophene and the PVDF in N-methylpyrrolidone (NMP), stirring the mixture to form a uniform solution, and uniformly coating the uniform solution on two sides of an aluminum foil current collector by using a scraper with the diameter of 1 mu m to prepare the composite current collector of the comparative example 1.

(2) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the materials into NMP, fully stirring and uniformly mixing to obtain slurry, coating the slurry on the composite current collector of the comparative example 1, and drying, cold pressing and slitting to obtain the positive pole piece. Weighing 2 mass percent of CMC, 3 mass percent of SBR, 1 mass percent of acetylene black and 94 mass percent of graphite, sequentially adding the materials into deionized water, and fully stirring and mixingUniformly mixing to obtain slurry, coating the slurry on a copper current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

The lithium secondary batteries manufactured in examples 1 to 2 of the present invention and comparative example 1 were subjected to the following tests:

(1) and (4) safety performance testing: a high-temperature-resistant steel needle with the diameter of 3-8mm is adopted to carry out a needle punching experiment on the lithium secondary battery at the speed of 10-40mm/s, and whether the battery core is on fire or not is recorded, and the result is shown in table 1.

(2) And (3) rate performance test: rate capability test was performed on lithium secondary batteries at charge and discharge rates of 0.2/0.2C, 0.2/0.5C, 0.2/1.0C, 0.2/1.5C and 0.2/2.0C, graphite/LiCoO₂The voltage range of the battery was 3.0-4.4V, and the test results are shown in Table 1.

Table 1 results of testing safety and rate capability of batteries corresponding to different conductive polymer modified composite current collectors

As can be seen from the test results in table 1, the batteries of examples 1 and 2 according to the present invention did not cause ignition when subjected to the needle punching test, whereas the batteries of comparative example 1 did not cause ignition when subjected to the needle punching test, indicating that the batteries containing the conductive polymer-modified composite current collector grafted with a substituted lithium imide salt according to examples of the present invention had higher flame resistance, and when the temperature of the batteries increased above a certain temperature (curie temperature), the resistance thereof sharply increased, the current was interrupted, and the safety of the lithium secondary batteries was improved.

In addition, as can be seen from the test results in table 1, compared with comparative example 1, the batteries in examples 1 and 2 of the present invention have better rate performance, which is mainly because the conductive polymer grafted with the substituted imine lithium salt in the examples of the present invention has not only excellent thermal sensitivity and electronic conductivity, but also good ion conductivity, and can effectively increase the mobility of lithium ions, which is beneficial to the transmission of lithium ions, thereby increasing the rate performance of the lithium secondary battery.

Example 3

The method is characterized in that poly (4-n-octyl substituted thiophene) (pentafluoroethyl sulfonyl) imide lithium (shown as a formula (E)) is adopted to modify an electrode plate and is applied to a lithium secondary battery, and the method comprises the following steps:

(1) the preparation of poly (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) lithium imide (E) has a synthetic route shown in a formula (8):

a) respectively adding 0.5mol of 3-bromo-4-n-octyl substituted thiophene, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of pentafluoroethyl sulfonamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (pentafluoroethyl sulfonyl) imine triethylamine salt;

b) respectively adding 0.25mol of (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) imine triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at the temperature of 25 ℃, stirring and reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) imine lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric chloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) lithium imide is slowly added into the three-neck flask at the temperature of 0 ℃, the mixture is stirred and reacted for 12 hours, after the reaction is finished, the mixture is filtered, decompressed and dried, then ethanol/toluene is used for recrystallization, suction filtration and washing are carried out, vacuum drying is carried out for 24 hours at the temperature of 60 ℃, and the poly (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) lithium imide (E) is obtained, wherein the yield is 85%.

(2) Preparing a positive pole piece:

weighing 2 mass percent of lithium poly (4-n-octyl substituted thiophene) (pentafluoroethylsulfonyl) imide (E), 1 mass percent of polyvinylidene fluoride (PVDF) and 95 mass percent of lithium cobaltate (LiCoO)₂) Dissolving the mixture in N-methylpyrrolidone (NMP), stirring and mixing the mixture to form a uniform solution, then weighing polyvinylidene fluoride (PVDF) with the mass percentage of 1% and a conductive agent super P with the mass percentage of 1% and sequentially adding the polyvinylidene fluoride (PVDF) and the conductive agent super P into the solution, fully stirring and uniformly mixing the mixture to obtain slurry, coating the slurry on an aluminum foil current collector, and drying, cold pressing and cutting the aluminum foil current collector to obtain the positive pole piece (the structural schematic diagram is shown in figure 5) in the embodiment 3 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

Example 4

Poly (4-n-hexane substituted pyrrole) (trifluoroethylsulfonyl) imide lithium (shown as a formula (H)) is adopted to modify an electrode plate and is applied to a lithium secondary battery, and the method comprises the following steps:

(1) the preparation of poly (4-n-hexane substituted pyrrole) (trifluoroethylsulfonyl) lithium imide (H) has a synthetic route shown as a formula (9):

a) respectively adding 0.5mol of 3-bromo-4-n-hexane substituted pyrrole, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of trifluoroethyl sulfonamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (4-n-hexane substituted pyrrole) (trifluoroethylsulfonyl) imide triethylamine salt;

b) respectively adding 0.25mol of (4-n-hexane-group substituted pyrrole) (trifluoroethylsulfonyl) imine triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at the temperature of 25 ℃, stirring and reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (4-n-hexane-group substituted pyrrole) (trifluoroethylsulfonyl) imine lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric chloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of (4-n-hexane group substituted pyrrole) (trifluoroethylsulfonyl) lithium imide is slowly added into the three-neck flask at the temperature of 0 ℃, the mixture is stirred and reacted for 12 hours, after the reaction is finished, the mixture is filtered, decompressed and dried, and then recrystallized by ethanol/toluene, filtered, washed and dried in vacuum at the temperature of 60 ℃ for 24 hours, so that poly (4-n-hexane group substituted pyrrole) (trifluoroethylsulfonyl) lithium imide (H) is obtained, and the yield is 81%.

(2) Preparing a negative pole piece:

weighing poly (4-n-hexane-based substituted pyrrole) (trifluoroethylsulfonyl) lithium imide (H) with the mass percentage of 2%, 93% of graphite, 1.5% of CMC, 2.5% of SBR and 1% of acetylene black, dissolving the materials in deionized water, fully stirring and uniformly mixing the materials to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting the copper foil current collector to obtain the negative pole piece (the structural schematic diagram is shown in figure 4) of the embodiment 4 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the aluminum foil into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing to obtain slurry, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆The electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) is prepared into a soft package of about 3.9Ah through chemical synthesis and other processesA lithium secondary battery.

Comparative example 2

The preparation of the lithium secondary battery is carried out by adopting the electrode plate of the conventional commercial lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the aluminum foil into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing to obtain slurry, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece; weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a battery cell, packaging by adopting a polymer, and pouring 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

The lithium secondary batteries manufactured in examples 3 to 4 of the present invention and comparative example 2 were subjected to the following tests:

(1) and (4) safety performance testing: a high-temperature-resistant steel needle with the diameter of 3-8mm is adopted to carry out a needle punching experiment on the lithium secondary battery at the speed of 10-40mm/s, and whether the battery core is on fire or not is recorded, and the result is shown in Table 2.

(2) And (3) rate performance test: rate capability test was performed on lithium secondary batteries at charge and discharge rates of 0.2/0.2C, 0.2/0.5C, 0.2/1.0C, 0.2/1.5C and 0.2/2.0C, graphite/LiCoO₂The voltage range of the battery was 3.0-4.4V, and the test results are shown in Table 2.

TABLE 2 safety and rate capability test results of different conductive polymer modified electrode sheets corresponding to batteries

As can be seen from the test results in table 2, the batteries of examples 3 and 4 according to the present invention did not suffer from ignition when subjected to the needle punching test, whereas the batteries of comparative example 2 suffered from ignition when subjected to the needle punching test, which indicates that the batteries of examples according to the present invention comprising the conductive polymer-modified electrode sheet grafted with a substituted lithium imide salt had higher flame resistance, and when the temperature of the batteries increased above a certain temperature (curie temperature), the resistance thereof sharply increased, the current was interrupted, and the safety of the lithium secondary batteries was improved.

In addition, as can be seen from the test results in table 2, compared with comparative example 2, the batteries in examples 3 and 4 of the present invention have better rate performance, which is mainly because the conductive polymer grafted with the substituted imine lithium salt in the examples of the present invention has not only excellent thermal sensitivity and electronic conductivity, but also good ion conductivity, and can effectively improve the mobility of lithium ions, which is beneficial to the transmission of lithium ions, thereby improving the rate performance of the lithium secondary battery.

Example 5

The method for modifying the diaphragm by adopting the lithium poly (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) imide (shown as the formula (F)) and applying the diaphragm to the lithium secondary battery comprises the following steps:

(1) the preparation of poly (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) lithium imide (F) has a synthetic route shown in formula (10):

a) respectively adding 0.5mol of 3-bromo-4-n-octyl substituted thiophene, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of perfluorobutanesulfonamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (perfluorobutanesulfonyl) imide triethylamine salt;

b) respectively adding 0.25mol of (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) imide triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at the temperature of 25 ℃, stirring for reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) imide lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric trichloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) lithium imide is slowly added into the three-neck flask at the temperature of 0 ℃, stirred and reacted for 12 hours, after the reaction is finished, filtered, decompressed and dried, and then recrystallized by ethanol/toluene, filtered, washed and dried in vacuum at the temperature of 60 ℃ for 24 hours to obtain the poly (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) lithium imide (F), and the yield is 87%.

(2) Preparing a composite diaphragm:

weighing 90 mass percent of lithium (F) poly (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) imide and 10 mass percent of PVDF, dissolving the lithium (F) poly (4-n-octyl substituted thiophene) (perfluorobutylsulfonyl) imide and the 10 mass percent of PVDF in NMP, stirring and mixing to form a uniform solution, and uniformly coating the solution on one surface of a PP diaphragm by using a 1 mu m scraper to obtain the composite diaphragm of the embodiment 5 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding the aluminum foil into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing to obtain slurry, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece; weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and composite diaphragm into a battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

Example 6

The diaphragm is modified by adopting poly (thiophene) (trifluoroacetyl) imide lithium (shown as a formula (A)) and is applied to a lithium secondary battery, and the method comprises the following steps:

(1) the preparation of poly (thiophene) (trifluoroacetyl) imine lithium (A) has a synthetic route shown as a formula (11):

a) respectively adding 0.5mol of 3-bromine substituted thiophene, 1.1mol of triethylamine and 500mL of dichloromethane solvent into a 1000mL three-neck flask, slowly adding 0.5mol of trifluoroacetamide into the three-neck flask at the temperature of 30 ℃, stirring for reacting for 18 hours, filtering, and drying under reduced pressure to obtain (thiophene) (trifluoroacetyl) imine triethylamine salt;

b) respectively adding 0.25mol of (thiophene) (trifluoroacetyl) imine triethylamine salt and 250mL of acetonitrile solvent into a 500mL three-neck flask under the protection of argon, adding 0.5mol of anhydrous lithium carbonate solid into the three-neck flask in three batches at 25 ℃, stirring and reacting for 6 hours, filtering after the reaction is finished, and drying under reduced pressure to obtain (thiophene) (trifluoroacetyl) imine lithium;

c) under the protection of argon, 1.0mol of anhydrous ferric trichloride and 250mL of acetonitrile solvent are respectively added into a 500mL three-neck flask, 0.2mol of lithium (thiophene) (trifluoroacetyl) imide is slowly added into the three-neck flask at the temperature of 0 ℃, the mixture is stirred and reacted for 12 hours, after the reaction is finished, the mixture is filtered, decompressed and dried, and then recrystallized by ethanol/toluene, filtered, washed and dried in vacuum at the temperature of 60 ℃ for 24 hours to obtain the lithium (A) poly (thiophene) (trifluoroacetyl) imide, wherein the yield is 82%.

(2) Preparing a composite diaphragm:

weighing 90 mass percent of lithium poly (thiophene) (trifluoroacetyl) imide (A) and 10 mass percent of PVDF, dissolving the mixture in NMP, stirring the mixture to form a uniform solution, and uniformly coating the solution on one surface of a PP diaphragm by using a 1-micrometer scraper to obtain the composite diaphragm of the embodiment 6 of the invention.

(3) Preparation of lithium secondary battery:

weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass₂) Sequentially adding into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing to obtain slurry, coating the slurry on an aluminum foil current collector, drying and coolingPressing and slitting to obtain a positive pole piece; weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing to obtain slurry, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain a negative pole piece; preparing the prepared positive pole piece, negative pole piece and composite diaphragm into a battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF₆And (3) preparing the electrolyte (EC, EMC, DEC, PC and FEC in a weight ratio of 30:25:30:10:5) into the soft package lithium secondary battery of about 3.9Ah through chemical synthesis and other processes.

Comparative example 3

The method for modifying the diaphragm by adopting poly (3-n-octyl substituted) thiophene (P3OT) and applying the diaphragm to the lithium secondary battery comprises the following steps:

(1) preparing a composite diaphragm:

weighing 90 mass percent of poly (3-n-octyl substituted) thiophene (P3OT) and 10 mass percent of PVDF (polyvinylidene fluoride) in NMP (N-methyl pyrrolidone), stirring and mixing to obtain a uniform solution, and uniformly coating the solution on one surface of a PP diaphragm by using a 1 mu m scraper to obtain the diaphragm of the comparative example 3;

(2) preparation of lithium secondary battery:

The lithium secondary batteries manufactured in examples 5 to 6 of the present invention and comparative example 3 were subjected to the following tests:

(1) and (4) safety performance testing: a high-temperature resistant steel needle with the diameter of 3-8mm is adopted to carry out a needle punching experiment on the lithium secondary battery at the speed of 10-40mm/s, and whether the battery core is on fire is recorded, and the result is shown in table 3.

(2) And (3) rate performance test: rate capability test was performed on lithium secondary batteries at charge and discharge rates of 0.2/0.2C, 0.2/0.5C, 0.2/1.0C, 0.2/1.5C and 0.2/2.0C, graphite/LiCoO₂The voltage range of the cell was 3.0-4.4V and the test results are shown in Table 3.

TABLE 3 test results of safety and rate capability of different conductive polymer modified composite diaphragms corresponding to batteries

As can be seen from the test results in table 3, the batteries of examples 5 and 6 according to the present invention did not cause ignition when subjected to the needle punching test, whereas the batteries of comparative example 3 did not cause ignition when subjected to the needle punching test, indicating that the batteries comprising the conductive polymer-modified composite separator grafted with a substituted lithium imide salt according to examples of the present invention had higher flame resistance, and when the temperature of the batteries increased above a certain temperature (curie temperature), the resistance thereof sharply increased, the current was interrupted, and the safety of the lithium secondary batteries was improved.

In addition, as can be seen from the test results in table 3, compared with comparative example 3, the batteries in examples 5 and 6 of the present invention have better rate performance, which is mainly because the conductive polymer grafted with the substituted imine lithium salt in the examples of the present invention has not only excellent thermal sensitivity and electron conductivity, but also good ion conductivity, and can effectively increase the mobility of lithium ions, which is beneficial to the transmission of lithium ions, thereby increasing the rate performance of the lithium secondary battery.

Claims

1. A conductive polymer alkali metal salt with heat-sensitive characteristics is characterized by comprising a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, wherein the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structureThe five-membered unsaturated heterocyclic structure comprises at least one of thiophene, pyrrole and furan, the substituted imine alkali metal salt comprises one or more of substituted imide alkali metal salt and substituted sulfonyl imine alkali metal salt, and the substituted imine alkali metal salt forms an N-C bond with a C atom in the five-membered unsaturated heterocyclic structure through an N atom; the chemical expression of the substituted imide alkali metal salt is-N^-(M⁺)-C(＝O)-Z₁Wherein M is Li, Na, K, Rb or Cs, Z₁Any one selected from the group consisting of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy; the chemical expression of the substituted sulfimide alkali metal salt is-N^-(M⁺)-S(＝O)₂-Z₂Wherein M is Li, Na, K, Rb or Cs, Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

2. A conducting polymer alkali metal salt having heat-sensitive properties according to claim 1 wherein said conducting polymer alkali metal salt comprises one or more of said conducting polymer repeating units.

3. A conductive polymer alkali metal salt having thermosensitive properties according to claim 1, wherein the conductive polymer repeating unit comprises one or more five-membered unsaturated heterocyclic structures.

4. The alkali metal salt of a conductive polymer having thermosensitive characteristics according to claim 3, wherein the repeating unit of the conductive polymer comprises a five-membered unsaturated heterocyclic structure in which groups at positions 3 and 4 are R, respectively₁And R₂Said R is₁And R₂Are respectively selected from hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, alkyl, halogenated alkyl, alkoxy and halogenated imine alkali metal saltAny one of alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R₁And R₂At least one of them is the substituted imine alkali metal salt.

5. The alkali metal salt of a conductive polymer having a heat-sensitive property according to claim 3, wherein the repeating unit of the conductive polymer comprises a plurality of five-membered unsaturated heterocyclic structures, at least one of all groups at positions 3 and 4 of the plurality of five-membered unsaturated heterocyclic structures is the substituted imine alkali metal salt, and the remaining groups are independently selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, the substituted imine alkali metal salt, an alkyl group, a haloalkyl group, an alkoxy group, a haloalkoxy group, an alkenyl group, a haloalkenyl group, an alkenyloxy group, a haloalkenyloxy group, an aryl group, a haloaryl group, an aryloxy group, and a haloaryloxy group.

6. The alkali metal salt of a conductive polymer having heat-sensitive properties of claim 1, wherein Z is₁Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

7. The alkali metal salt of a conductive polymer having heat-sensitive properties of claim 1, wherein Z is₂Wherein the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group and the halogenated alkoxy group is 1 to 20, the number of carbon atoms of the alkenyl group, the halogenated alkenyl group, the alkenyloxy group and the halogenated alkenyloxy group is 2 to 20, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group and the halogenated aryloxy group is 6 to 20.

8. The alkali metal salt of a conductive polymer having heat-sensitive properties of claim 4, wherein R is₁And R₂In (1), the alkyl, haloalkyl, alkoxyThe carbon atoms of the aryl, the halogenated aryl, the aryloxy and the halogenated aryloxy are 1-20, the carbon atoms of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy are 2-20, and the carbon atoms of the aryl, the halogenated aryl, the aryloxy and the halogenated aryloxy are 6-20.

9. A method for preparing an alkali metal salt of a conductive polymer having heat-sensitive characteristics, comprising the steps of:

reacting a polymer monomer at-40-100 ℃ for 6-48 hours in the presence of an initiator and a solvent, and polymerizing the polymer monomer to obtain a conductive polymer alkali metal salt with heat-sensitive property, wherein the polymer monomer comprises a five-membered unsaturated heterocyclic structure and a substituted imine alkali metal salt positioned on the five-membered unsaturated heterocyclic structure, the conductive polymer alkali metal salt comprises a conductive polymer repeating unit and a substituted imine alkali metal salt grafted on the conductive polymer repeating unit, the conductive polymer repeating unit comprises a five-membered unsaturated heterocyclic structure, the five-membered unsaturated heterocyclic structure comprises at least one of thiophene, pyrrole and furan, the substituted imine alkali metal salt comprises one or more of a substituted imide alkali metal salt and a substituted sulfimide alkali metal salt, and the substituted imine alkali metal salt forms N through N atoms and C atoms in the five-membered unsaturated heterocyclic structure -a C bond; the chemical expression of the substituted imide alkali metal salt is-N^-(M⁺)-C(＝O)-Z₁Wherein M is Li, Na, K, Rb or Cs, Z₁Any one selected from the group consisting of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy; the chemical expression of the substituted sulfimide alkali metal salt is-N^-(M⁺)-S(＝O)₂-Z₂Wherein M is Li, Na, K, Rb or Cs, Z₂Selected from any one of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy.

10. The method of claim 9, wherein the polymer monomer is prepared by:

reacting a five-membered unsaturated heterocyclic compound substituted by halogen with a substituted amine compound at 0-60 ℃ for 6-48 hours in the presence of an acid-binding agent and a solvent to obtain amine salt; the substituted amine compound comprises one or more of a substituted amide compound and a substituted sulfonamide compound; the chemical expression of the substituted amide compound is Z₁-C(＝O)-NH₂The chemical expression of the substituted sulfonamide compound is Z₂-S(＝O)₂-NH₂Z is the same as₁And Z₂Any one selected from the group consisting of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy and haloaryloxy;

11. The method according to claim 10, wherein the halogen-substituted five-membered unsaturated heterocyclic compound comprises at least one of halogen-substituted thiophene, halogen-substituted furan and halogen-substituted pyrrole, and groups at positions 3 and 4 in the halogen-substituted five-membered unsaturated heterocyclic compound are R₃And R₄Said R is₃And R₄Respectively selected from any one of hydrogen, fluorine, chlorine, bromine, iodine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy, and the R is₃And R₄At least one of which is fluorine, chlorine, bromine or iodine.

12. The method of claim 9, wherein the initiator comprises one or more of azobisisobutyronitrile, dibenzoyl peroxide, potassium persulfate, hydrogen peroxide-ferrous chloride, and anhydrous ferric chloride; the molar ratio of the polymer monomer to the initiator is 1: 0.1-8.

13. The preparation method of claim 10, wherein the molar ratio of the halogen-substituted five-membered unsaturated heterocyclic compound to the acid-binding agent is 1: 1-10; the molar ratio of the halogen substituted five-membered unsaturated heterocyclic compound to the substituted amine compound is 1: 1-8; the molar ratio of the amine salt to the anhydrous alkali carbonate is 1: 1-10.

14. A composite current collector comprising a current collector body and a heat sensitive material layer disposed on one or both side surfaces of the current collector body, wherein the heat sensitive material layer comprises the conductive polymer alkali metal salt having heat sensitive property according to any one of claims 1 to 8.

15. The composite current collector of claim 14, wherein the heat sensitive material layer further comprises a binder, and wherein the alkali metal salt of a conductive polymer having heat sensitive properties is fixed in the heat sensitive material layer by the binder.

16. The composite current collector of claim 15, wherein the mass ratio of the alkali metal salt of the conductive polymer having heat-sensitive properties to the binder in the heat-sensitive material layer is 1-100: 1.

17. The composite current collector of claim 14, wherein the thickness of the thermal sensitive material layer is 0.01 μ ι η to 10 μ ι η.

18. An electrode material comprising an electrode active material and a coating layer disposed on a surface of the electrode active material, the coating layer comprising the conductive polymer alkali metal salt having a thermosensitive property according to any one of claims 1 to 8, the electrode active material being a positive electrode active material or a negative electrode active material.

19. The electrode material of claim 18, wherein the coating has a thickness of 1nm to 10 μ ι η.

20. An electrode sheet comprising a current collector and an electrode active material layer disposed on the current collector, the electrode active material layer comprising the conductive polymer alkali metal salt having heat-sensitive characteristics according to any one of claims 1 to 8, the electrode sheet being a positive electrode sheet or a negative electrode sheet.

21. A composite separator comprising a separator body and a heat-sensitive material layer provided on one side surface or both side surfaces of the separator body, the heat-sensitive material layer comprising the alkali metal salt of a conductive polymer having heat-sensitive properties as set forth in any one of claims 1 to 8.

22. A secondary battery comprising a positive electrode, a negative electrode, and a separator and an electrolytic solution provided between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode, and/or the separator comprises the conductive polymer alkali metal salt having a heat-sensitive property according to any one of claims 1 to 8.