CN113422060A - High-temperature-resistant integrated electrode for lithium ion battery and preparation method thereof - Google Patents

Abstract

Disclosed herein are a high temperature resistant integrated electrode for a lithium ion battery and a method for preparing the same. Firstly, a PI adhesive is used for preparing a battery active material into a battery pole piece, and a nanofiber membrane or a polymer/inorganic material nanofiber composite membrane is covered on the surface of the battery pole piece by an electrostatic spinning method, so that the high-temperature-resistant integrated electrode is obtained. In this high temperature resistant integrated electrode, the PI adhesive has better structural stability under the high temperature condition, guarantees that battery sheet keeps stable in structure under the high temperature condition, plays the supporting role to nanofiber membrane heat shrink, and the nanofiber layer provides insulating nature, high temperature dimensional stability, and high liquid retention prevents the inside short circuit of battery, prevents that the battery of assembling from causing the thermal runaway because the high temperature diaphragm shrink causes the internal short circuit to improve the battery thermal safety characteristic. The invention has simple and easy technical process, obviously improves the safety of the battery assembled by the pole piece, and has good application prospect.

Description

High-temperature-resistant integrated electrode for lithium ion battery and preparation method thereof

Technical Field

The invention relates to the technical field of electrode plates of lithium ion batteries and preparation methods thereof, in particular to a high-temperature-resistant integrated electrode for a lithium ion battery and a preparation method thereof.

Background

Lithium ion batteries have been widely used in small electronic devices such as PCs, mobile phones, AV equipment and the like by virtue of their advantages of environmental friendliness, long cycle life and the like. With the application of the lithium ion battery in electric vehicles, the lithium ion battery begins to develop towards large capacity and high specific energy, and the safety problem is increasingly highlighted, so that the design of the lithium ion battery with high energy density and high safety becomes an important part.

The lithium ion battery consists of positive and negative electrodes, diaphragm, electrolyte and other parts, and the positive and negative electrodes consist of powdered active matter, conducting agent, electrode current collector and adhesive. As the binder, a fluorine-based resin such as a homopolymer or a copolymer of vinylidene fluoride, an acrylic copolymer, a CMC/styrene-butadiene rubber, or the like is used.

However, the conventional adhesive has poor temperature resistance, so that the connectivity among the positive and negative electrode active materials, the conductive agent and the electrode current collector under a high-temperature condition is weakened, and the electrode prepared by the conventional adhesive has poor structural stability under the high-temperature condition, thereby causing the attenuation of the battery capacity. In addition, the existing adhesive is easy to degrade at high temperature, and the safety problems of battery failure, runaway and the like are easily caused.

In order to solve the problems, a nanofiber membrane is directly spun on the surface of a ceramic diaphragm in patent CN 104681764A, a composite lithium ion battery diaphragm is prepared, wherein the nanofiber layer can reinforce and constrain ceramic particles to prevent falling off, and can also be used as a soft buffer layer to improve the contact between the diaphragm and an electrode surface. In the process of high-power charging and discharging of the power lithium ion battery, the local temperature of the battery reaches 80-100 ℃, and occasionally 150 ℃ thermal shock exists, which has higher requirements on a battery system. Therefore, the work of designing and developing high-safety and high-temperature-resistant integrated electrodes to improve the safety of the battery is urgent and important.

Therefore, the invention provides that the polyimide adhesive is used as the lithium ion battery electrode adhesive, the polyimide adhesive is sequentially subjected to the excellent high and low temperature resistance and chemical stability of polyimide, the excellent heat resistance can keep the structural stability of the positive electrode plate at high temperature, and meanwhile, the high-temperature resistant polymer nanofiber membrane or the high-temperature resistant polymer/inorganic material nanofiber membrane is compounded on the surface of the electrode plate by applying the electrostatic spinning technology to prepare the high-safety high-temperature resistant integrated electrode.

Disclosure of Invention

The invention provides a high-temperature-resistant integrated electrode for a lithium ion battery and a preparation method thereof. According to the invention, the lithium ion battery pole piece and the nanofiber membrane are compounded together through an electrostatic spinning process, so that the preparation of the high-temperature-resistant and high-safety integrated electrode can be realized: the battery pole piece with the PI as the adhesive provides support for the dimensional stability of the nanofiber membrane under the high-temperature condition, the nanofiber layer provides insulativity to prevent the internal short circuit of the battery, and the specific process of the preparation is that the PI is used as the adhesive to prepare the battery pole piece, and then the electrostatic spinning process is applied to compound the high-temperature resistant polymer nanofiber membrane or the high-temperature resistant polymer/inorganic material composite nanofiber membrane on the surface of the battery pole piece to finally form the high-temperature resistant integrated electrode.

The Polyimide (PI) is characterized in that one or more diamines and/or polyamines containing functional groups, one or more diamines and/or polyamines containing non-functional groups and one or more dibasic acids and/or polybasic acid anhydrides are selected as raw materials in a certain proportion, solution condensation polymerization is carried out to obtain polyamic acid solution, and the polyamic acid solution is subjected to high-temperature cyclization to obtain the Polyimide (PI).

Further, the functional group-containing diamine and/or polyamine is an aromatic ring or an aromatic ring derivative, preferably one or more of 2,2 '-bis (3-amino-4-hydroxyphenyl) propane (BAHPP), 3' -diamino-4, 4 '-dihydroxybiphenyl (DADHBP), 4' -diamino-4 ″ -hydroxytriphenylmethane (DHTM), and hydroxydiamine (OHDA);

the non-functional group diamine and/or polyamine is aromatic ring or aromatic ring derivative, preferably one or more of Phenylenediamine (PDA), 4 '-diaminodiphenyl ether (ODA) and 3,3' -diaminodiphenyl ether (BAPB);

the dibasic acid and/or polybasic acid anhydride is aromatic ring or aromatic ring derivative, preferably one or more of pyromellitic dianhydride (PMDA), 1,4,5, 8-Naphthalene Tetracarboxylic Dianhydride (NTDA), biphenyl dianhydride (BPDA), and 4, 4-diphenyl ether dianhydride (ODPA);

the proportion of diamine and/or polyamine containing functional groups, diamine and/or polyamine containing non-functional groups, and diacid and/or polybasic acid anhydride is that the molar ratio of the functional group diamine to all diamines is 3-90%, preferably 5-80%;

the solid content of the polyamic acid solution is 5-40%, preferably 6-30%

The high-temperature cyclization process comprises the following steps: the heating rate is 0.5-25 ℃ per minute^-1Preferably 1 to 20 ℃ per minute^-1The final heat treatment temperature is 180-460 ℃, preferably 200-450 ℃.

The high-temperature-resistant integrated electrode is characterized by being formed by compounding a nanofiber membrane, a lithium ion battery pole piece and a nanofiber membrane which are sequentially arranged, wherein the battery pole piece is prepared by taking Polyimide (PI) as an adhesive and the nanofiber membrane is a high-temperature-resistant polymer or a high-temperature-resistant polymer/electrodeless material mixture through electrostatic spinning.

Further, the polymer nanofiber membrane is compounded on the surface of the battery pole piece by taking the battery pole piece as a receiving base to form a high-temperature-resistant integrated electrode

Further, the lithium ion battery pole piece contains an active substance, a conductive agent and a PI adhesive;

the lithium ion battery pole piece is one of a positive pole piece and a negative pole piece, and the active substance of the positive pole piece is any one or a combination of multiple of NCM ternary material, lithium iron phosphate pole piece, lithium manganate, lithium manganese iron phosphate and lithium cobaltate; the negative pole piece active substance is one or a combination of a plurality of carbon materials, silicon oxide materials and tin materials; further, the conductive agent is one or a combination of more of graphite, conductive carbon black, carbon nano tubes and graphene

Further, the mass percentage of the PI adhesive in the active substance is 1-15%, preferably 1.0-10.0%; the conductive agent accounts for 0.5-20% of the mass of the active substance, and preferably 0.5-8%.

Further, the high-temperature resistant polymer is any one or combination of aramid fiber, P84, Polyetherimide (PEI), polyvinylidene fluoride (PVDF), Polyacrylonitrile (PAN) and Polyimide (PI);

further, the thickness of the polymer nanofiber membrane is 0.2 to 20 μm, and preferably the thickness is 0.5 to 20 μm.

Furthermore, the thickness of the lithium ion battery pole piece is 30-500 mu m, and the preferable thickness is 40-300 mu m

The inorganic material is selected from the group consisting of ceramic, boehmite, oxide electrolyte, sulfide electrolyte, and chloride electrolyte, the oxide electrolyte is selected from the group consisting of perovskite type, NASICON type, LISICON type, and garnet type, the glassy oxide electrolyte is selected from the group consisting of LiPON type, and the sulfide electrolyte is selected from the group consisting of Li, and Li_4-xGe_1-xP_xS₄(a ═ Ge, Si, etc., B ═ P, A1, Zn), chloride dielectric predominantly Li_aMX_bM is a metal element of a third group and a thirteenth group and one or a combination of more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Mg, Pb and the like, a is between 1 and 3, b is between 3 and 6, the inorganic material is particles, and the particle size is 30 to 3000nm, preferably 50 to 2000 nm.

A preparation method of a high-temperature-resistant integrated electrode is characterized by comprising the following steps:

A. selecting one or more diamines and/or polyamines containing functional groups, one or more non-functional diamines and/or polyamines and one or more dibasic acids and/or polybasic acids as raw materials in a certain proportion, and preparing a polyamic acid solution with a specific concentration after solution condensation polymerization;

B. uniformly mixing an active substance, a conductive agent and a polyamic acid solution to prepare slurry, coating the slurry on the surface of a current collector, and performing high-temperature thermal imidization treatment after rolling to prepare a lithium ion battery pole piece with polyimide as an adhesive;

C. adding the high-temperature resistant polymer into an organic solvent for full dissolution to obtain an electrostatic spinning solution with the solid content of 4-30%, preferably 5-25%; or adding the high-temperature resistant polymer into an organic solvent to be fully dissolved to obtain a solution with the solid content of 4-30%, preferably 5-25%, and adding an inorganic material into the solution, wherein the inorganic material accounts for 1-60% of the mass of the high-temperature resistant polymer to obtain an electrostatic spinning solution;

d: and D, performing electrostatic spinning on the electrostatic spinning solution obtained in the step C by using an electrostatic spinning machine, and rolling by taking a battery pole piece as a receiving base to obtain the high-temperature-resistant integrated electrode.

Further, the organic solvent is one or more of DMF, DMAC, NMP and DMSO;

further, the high-temperature resistant polymer is any one or combination of aramid fiber, P84, Polyetherimide (PEI), polyvinylidene fluoride (PVDF), Polyacrylonitrile (PAN) and Polyimide (PI);

wherein, the spinning solution of the PI nanofiber is a polyamic acid solution, and PAA electrostatic spinning solution with solid content of 4-30%, preferably 5-25% is prepared by polycondensation reaction of one or more diamine and one or more dibasic acid and/or dibasic anhydride; the nanofiber membrane prepared by electrostatic spinning with PAA as spinning solution is rolled and then subjected to high-temperature cyclization treatment at 300-400 ℃;

further, in the step C, the inorganic material accounts for 2-50% of the mass of the high-temperature resistant polymer;

further, the adopted thermal imidization process comprises the following steps: the heating rate is 0.5-25 ℃ per minute^-1Preferably 1 to 20 ℃ per minute^-1The final heat treatment temperature is 180-460 ℃, preferably 200-450 ℃.

A battery containing a high temperature resistant integrated electrode.

Compared with the prior art, the method has the following technical characteristics and effects:

1. the high-temperature-resistant integrated electrode prepared by the invention is applied to a battery pole piece prepared from polyimide, has good cohesiveness, high-temperature resistance and electrochemical stability, can maintain structural stability, dimensional stability and cohesive force at high temperature, can provide a supporting effect for a nanofiber membrane compounded on the surface of the battery pole piece, prevents the nanofiber membrane from generating thermal shrinkage at high temperature, and has good high-temperature resistance.

2. The integrated pole piece is simple in preparation process and excellent in safety performance, and is beneficial to improving the high-temperature cycle performance and the safety performance of the lithium ion battery.

Drawings

FIG. 1 is a schematic view of a high temperature resistant integrated electrode structure;

FIG. 2 SEM photograph of high temperature resistant integrated electrode of example 1

FIG. 3 SEM photograph of high temperature resistant integrated electrode of comparative example 1

Detailed Description

It should be noted that:

the invention provides a high-temperature-resistant integrated electrode for a lithium ion battery and a preparation method thereof, wherein the preparation method of the electrode plate taking high-temperature-resistant PI as an adhesive comprises the following steps:

a: selecting one or more monomers in diamine (such as BAPBA, PDA, ODA, BAPB and the like) and one or more monomers in dibasic acid anhydride (PMDA, NTDA, BPDA, ODPA) as raw materials, and carrying out solution polycondensation at low temperature to obtain polyimide precursor-polyamide acid solution with different structures, wherein the solid content of the solution is between 8 and 25 percent, and the solvent is DMF, DMAc, DMSO and NMP;

b, preparing a lithium ion battery pole piece, uniformly mixing the active substance, the conductive agent and the polyamic acid solution to prepare slurry, coating, drying, rolling, and carrying out high-temperature thermal imidization treatment to prepare the battery pole piece with polyimide as an adhesive; the thermal imidization treatment is to slowly raise the temperature at a constant speed, and the final heat treatment temperature is between 250 and 450 ℃.

The electrochemical performance and the application of the high-temperature-resistant integrated electrode for the lithium ion battery are that the electrode is assembled into a buckle battery for charge and discharge test by a conventional method in the field, a 2Ah soft package battery is assembled for safety performance evaluation, and the processes of preparing the electrode piece and assembling the buckle battery are as follows:

preparing a positive pole piece, mixing an active material, an adhesive solution and a conductive agent according to the proportion of the embodiment, stirring at the speed of 10000r/min for 20min to obtain slurry, coating the slurry on the surface of a current collector, drying after coating the slurry containing polyimide, carrying out heat treatment, heating from room temperature to 300 ℃, and keeping the temperature for 60 min. Cutting into 12mm round pieces, rolling, weighing, and drying in a vacuum oven at 200 deg.C for 12 h.

Drying the pole piece, putting the dried pole piece into a glove box, and assembling the button cell by applying a 2032 type button cell case: the negative electrode shell, the lithium plate, the diaphragm, the positive electrode plate, the gasket and the elastic sheet are sequentially placed, 7 drops of electrolyte are dripped, the positive electrode shell is covered, the button cell is sealed on a sealing machine, the current of 0.1C is used for testing, and the voltage range is 2.5-4.3V.

The pole pieces and the corresponding pole pieces are used for preparing the 2Ah soft package battery, and the 2Ah soft package battery is used in heating tests.

The present pole piece preparation and battery assembly is applicable to all of the following examples and comparative examples.

The following is further illustrated with reference to specific examples, which should be construed as follows: the following examples are given for the purpose of illustration only and are not intended to limit the scope of the present invention, and all equivalent substitutions made on the basis of the claims of the present application are intended to fall within the scope of the present invention.

Example 1

A high-temperature-resistant integrated electrode A is formed by preparing an 8-series NCM ternary material into a positive electrode plate by using a PI adhesive with the mass ratio of 3%, and then covering a polymer nanofiber membrane layer on the surface of the positive electrode plate by using an electrostatic spinning technology. Wherein, the total thickness of the high-temperature resistant integrated electrode is 155 μm, the thickness of the 8-series NCM ternary material positive pole piece is 147 μm, and the thickness of the high-temperature resistant polymer nanofiber membrane layer is 8 μm. The preparation method of the high-temperature-resistant integrated electrode A comprises the following steps:

the method comprises the following steps: preparing a positive pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. Mixing 90%, 5% and 5% of a positive electrode active material NCM811, conductive carbon black and a polyamide acid solution in parts by mass, adding an NMP solvent to dissolve the mixture, and stirring for 20min to obtain positive electrode slurry. Coating the polyimide slurry on an aluminum foil and drying at room temperature for 12h, wherein the heat treatment process comprises the steps of uniformly heating from room temperature to 135 ℃ within 60min, preserving heat for 60min, uniformly heating from 135 ℃ to 300 ℃ within 60min, and preserving heat for 60 min.

Step two: weighing 10g of PAN powder, adding the PAN powder into 90g N N Dimethylformamide (DMF), and stirring at 60 ℃ until PAN is completely dissolved to obtain PAN electrostatic spinning solution with solid content of 10%; electrospinning the spinning solution by an electrostatic spinning machine, wherein the pole piece is used as a receiving base, and the spinning parameters of the spinning machine are as follows: the spinning distance is 15cm, the spinning voltage is 20kV until the thickness of the nanofiber layer reaches 8 mu m; and rolling, and placing in an oven at 80 ℃ for 5h to obtain the high-temperature-resistant integrated electrode A.

Assembling the pole piece, the matched negative pole piece and the 7-micrometer PE diaphragm into a VDA-sized 20Ah battery, and carrying out heating test according to GB/T31485-2015 standard; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell, testing the electrical property, wherein the specific capacity is 200mAh/g, the first effect is 89%, the cycle is 100 weeks, and the capacity retention rate is 91%.

Comparative example 1, a positive electrode plate (without a nanofiber membrane), a matched negative electrode plate and a 15 μm PE separator (i.e., the total thickness of the nanofiber membrane and the PE membrane in the example) having the same thickness as the above example were assembled into a VDA-sized 20Ah battery, and a heating test was performed according to GB/T31485-2015 standard; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell, testing the electrical property, wherein the specific capacity is 195mAh/g, the first effect is 87%, the cycle is 100 weeks, and the capacity retention rate is 88%. .

Comparative example 1-1, the binder of the positive electrode plate in the example is changed into PVDF, the two sides are compounded with the nanofiber membrane, the 20Ah battery with VDA size is assembled by the negative electrode plate matched with the positive electrode plate in the example 1 and the 15 mu mPE membrane (namely the total thickness of the nanofiber membrane and the PE membrane in the example) with the same thickness as the example, and the heating test is carried out according to the GB/T31485-2015 standard; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell to test the electrical performance, wherein the specific capacity is 193mAh/g, the first effect is 86.5%, the cycle is 100 weeks, and the capacity retention rate is 89%.

In examples 1-2, the content of the PI binder of the electrode sheet in example 1 was adjusted to 8%, the conductive carbon black was adjusted in a corresponding proportion to the positive electrode, and the other conditions were unchanged, and the sheet was cut into 12mm round pieces, rolled, weighed, and dried in a vacuum oven at 200 ℃ for 12 hours, and the assembled button half cell was tested for electrical performance, 0.1C, specific capacity of 190mAh/g, first effect of 87.5%, cycle of 100 weeks, and capacity retention of 85%.

Examples 1-3, the thickness of the nanofiber film in example 1 was adjusted to 3 μm, other conditions were unchanged, cut into 12mm round pieces, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12h, assembled button half cells tested for electrical performance, 0.1C, specific capacity of 203mAh/g, initial efficiency of 89.5%, cycle of 100 weeks, capacity retention of 93%.

Example 2

A high-temperature-resistant integrated electrode B is formed by compounding a negative electrode plate made of a silicon-carbon 650 composite material by using a PI adhesive and then covering a polymer nanofiber membrane layer on the surface of the negative electrode plate by using an electrostatic spinning technology. The total thickness of the high-temperature-resistant integrated electrode B is 97 mu m, the thickness of a negative pole piece made of a silicon-carbon composite material is 90 mu m, and the thickness of a high-temperature-resistant polymer nanofiber membrane layer is 7 mu m. The preparation method of the high-temperature-resistant integrated electrode B comprises the following steps:

the method comprises the following steps: preparing a battery pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. Mixing the silicon-carbon 650 composite material, the conductive carbon black and the polyamic acid solution according to the mass parts of 88%, 7% and 5%, adding an NMP solvent to dissolve the mixture, and stirring for 20min to obtain the negative electrode slurry. Coating the polyimide slurry on a copper foil and drying at room temperature for 12h, wherein the heat treatment process comprises uniformly heating from room temperature to 135 ℃ within 60min, preserving heat for 60min, uniformly heating from 135 ℃ to 300 ℃ within 60min, preserving heat for 60min, and heating to more than 100 ℃ under vacuum.

Step two: weighing 15g of P84 resin powder, adding the resin powder into 85g N N Dimethylformamide (DMF), and stirring at 60 ℃ until P84 is completely dissolved to obtain P84 electrostatic spinning solution with solid content of 15%; electrospinning the spinning solution by an electrostatic spinning machine, taking the prepared cathode plate as a receiving base, wherein the spinning parameters of the spinning machine are as follows: spinning distance is 15cm, spinning voltage is 30kV until the thickness of the nanofiber layer reaches 7 mu m, and a negative electrode integrated electrode with a double-sided covered P84 high-temperature-resistant nanofiber membrane layer is obtained; and placing the electrode in an oven at 80 ℃ for 5 hours to obtain the high-temperature-resistant integrated electrode B.

Assembling the pole piece, a matched NCM523 positive pole piece and a 7-micron PE diaphragm into a VDA-sized 20Ah battery, and carrying out national standard heating test; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell to test the electrical property, testing the electrical property at 0.1C, wherein the specific capacity is 647mAh/g, the first effect is 88%, circulating for 100 weeks, and the capacity retention rate is 80%.

Comparative example 2, a 20Ah cell of VDA size was assembled from the negative electrode tab (without nanofiber membrane) of the example, the matching NCM523 positive electrode tab, and the PE separator of 14 μm thickness equal to the thickness of the above example (i.e., the total thickness of nanofiber membrane and PE membrane of the example), and a national standard heating test was performed; meanwhile, the negative pole piece (without the nanofiber membrane) in the embodiment is cut into a 12mm wafer, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12 hours, and assembled to be a button type half cell to test the electrical performance, wherein the specific capacity is 647mAh/g, the first effect is 88%, the cycle is 100 weeks, and the capacity retention rate is 75%.

Example 3

A high-temperature-resistant integrated electrode C is formed by preparing a lithium iron phosphate material into a positive electrode plate by using a PI (polyimide) adhesive, and then covering a polymer nanofiber membrane layer on the surface of the positive electrode plate by using an electrostatic spinning technology. The total thickness of the high-temperature-resistant integrated electrode C is 163 micrometers, the total thickness of the lithium iron phosphate positive electrode piece is 158 micrometers, and the thickness of the high-temperature-resistant polymer nanofiber membrane layer is 5 micrometers. The preparation method of the high-safety integrated composite electrode C comprises the following steps:

the method comprises the following steps: preparing a battery pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. And mixing the lithium iron phosphate composite material, the conductive carbon black and the polyamic acid solution according to the mass parts of 93%, 4% and 3%, adding an NMP solvent to dissolve the mixture, and stirring for 20min to obtain the negative electrode slurry. Coating the polyimide slurry on a copper foil and drying at room temperature for 12h, wherein the heat treatment process comprises uniformly heating from room temperature to 135 ℃ within 60min, preserving heat for 60min, uniformly heating from 135 ℃ to 300 ℃ within 60min, preserving heat for 60min, and heating to more than 100 ℃ under vacuum.

Step two: regulating the solid content of the PAA solution to 10 percent to be used as electrostatic spinning solution; carrying out electrospinning on the spinning solution by an electrostatic spinning machine, taking a lithium iron phosphate pole piece as a receiving base, wherein the spinning parameters of the spinning machine are as follows: spinning at a distance of 15cm and a spinning voltage of 25kV until the nanofiber membrane reaches 7 microns to obtain a composite electrode with the surface covered with the PAA high-temperature-resistant nanofiber membrane, heating the composite electrode to 300 ℃, and preserving the temperature for 30min to obtain a high-temperature-resistant integrated electrode, wherein the thickness of the PI nanofiber layer is 5 microns;

assembling the pole piece, the matched negative pole piece and the 7-micrometer PE diaphragm into a 20Ah battery with the VDA size, and carrying out national standard heating test; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell, testing the electrical property, wherein the specific capacity is 156mAh/g, the first effect is 96.5%, the cycle is 100 weeks, and the capacity retention rate is 95%. .

Comparative example 3, the positive electrode plate (without nanofiber membrane), the matched negative electrode plate and the 13 μmPE separator (i.e., the total thickness of the nanofiber membrane and the PE membrane in the example) having the same thickness as the above example were assembled into a VDA-sized 20Ah battery, and a national standard heating test was performed; meanwhile, the pole piece (without the nanofiber membrane) in example 3 is cut into a 12mm round piece, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12 hours, and the assembled button type half cell is tested for electrical performance, 0.1C, specific capacity of 155mAh/g, first effect of 96%, circulation of 100 weeks, and capacity retention rate of 93%.

Example 4

A high-temperature-resistant integrated electrode D is formed by preparing a positive electrode plate from a lithium cobaltate material by using a PI (polyimide) adhesive, and covering a polymer/oxide solid electrolyte nanofiber membrane layer on the surface of the positive electrode plate by using an electrostatic spinning technology. The total thickness of the high-temperature-resistant integrated electrode D is 129 micrometers, the thickness of the lithium cobaltate positive pole piece is 124 micrometers, and the thickness of the high-temperature-resistant polymer/oxide solid electrolyte nanofiber membrane layer is 5 micrometers. The preparation method of the high-temperature-resistant integrated electrode D comprises the following steps:

the method comprises the following steps: preparing a battery pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. Mixing a lithium cobaltate material, conductive carbon black and a polyamic acid solution according to the mass parts of 94%, 3% and 3%, adding an NMP solvent to dissolve the mixture, and stirring for 20min to obtain negative electrode slurry. Coating the polyimide slurry on a copper foil and drying at room temperature for 12h, wherein the heat treatment process comprises the steps of uniformly heating from room temperature to 135 ℃ within 60min, preserving heat for 60min, uniformly heating from 135 ℃ to 300 ℃ within 60min, preserving heat for 60min, and heating to more than 100 ℃ under vacuum.

Step two: weighing 15g of diamine and dianhydride in a total mass according to a molar ratio of 1:1, adding the diamine and the dianhydride into 85g N-methylpyrrolidone (NMP), and synthesizing a PAA solution to obtain a PAA electrostatic spinning solution with a solid content of 15%; diluting the spinning solution to solid content of 10%, adding 1.5g of D50 bit 500nm oxide electrolyte, fully and uniformly stirring, carrying out electrospinning on the spinning solution by using an electrostatic spinning machine, taking a lithium cobaltate pole piece as a receiving base, wherein the spinning parameters of the spinning machine are as follows: the spinning distance is 15cm, the spinning voltage is 30kV until the thickness of the polymer/oxide solid electrolyte nano-fiber film is 7 mu m, the integrated electrode needs to be subjected to high-temperature cyclization treatment at 300 ℃ for 30min, and the thickness of the PI/oxide solid electrolyte nano-fiber film is 5 mu m;

assembling the pole piece, the matched negative pole piece and the 7-micrometer PE diaphragm into a 20Ah battery with the VDA size, and carrying out national standard heating test; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell, testing the electrical property, wherein the specific capacity is 158mAh/g, the first effect is 90%, the cycle is 100 weeks, and the capacity retention rate is 87%.

Comparative example 4, the positive electrode plate (without nanofiber membrane), the matched negative electrode plate and the 12 μm PE separator (i.e., the total thickness of nanofiber membrane and PE membrane in example) having the same thickness as in example above were assembled into a VDA-sized 20Ah battery, and a national standard heating test was performed; meanwhile, the pole piece (without the nanofiber membrane) in example 4 is cut into a 12mm wafer, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12h, and assembled to be a button half cell to test the electrical performance, the specific capacity is 156mAh/g, the first effect is 89%, the cycle is 100 weeks, and the capacity retention rate is 85%.

Example 5

A high-temperature resistant integrated composite electrode E is prepared by preparing 8-series NCA into a positive electrode plate by using a PI adhesive, and then covering a polymer nanofiber membrane layer on the surface of the positive electrode plate by using an electrostatic spinning technology. The total thickness of the high-temperature-resistant integrated electrode E is 153 micrometers, the thickness of the NCA positive pole piece is 146 micrometers, and the thickness of the high-temperature-resistant polymer nanofiber membrane layer is 7 micrometers. The preparation method of the high-temperature-resistant integrated composite electrode E comprises the following steps:

the method comprises the following steps: preparing a battery pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. Mixing 8-series NCA material, conductive carbon black and polyamic acid solution according to the mass parts of 92%, 4% and 4%, adding NMP solvent to dissolve the mixture, and stirring for 20min to obtain negative electrode slurry. Coating the polyimide slurry on a copper foil and drying at room temperature for 12h, wherein the heat treatment process comprises uniformly heating from room temperature to 135 ℃ within 60min, preserving heat for 60min, uniformly heating from 135 ℃ to 300 ℃ within 60min, preserving heat for 60min, and heating to more than 100 ℃ under vacuum.

Step two: weighing 15g P84 resin particles, adding the resin particles into 85g N N Dimethylformamide (DMF), and stirring at 60 ℃ until P84 is completely dissolved to obtain P84 electrostatic spinning solution with solid content of 15%; electrospinning the spinning solution by an electrostatic spinning machine, taking an NCA pole piece as a receiving base, wherein the spinning parameters of the spinning machine are as follows: the spinning distance is 15cm, the spinning voltage is 25kV until the thickness of the nanofiber membrane reaches 9 mu m; obtaining the high-temperature-resistant integrated electrode with the surface covered with the P84 high-temperature-resistant nanofiber membrane layer,

assembling the pole piece, the matched negative pole piece and the 7-micrometer PE diaphragm into a 20Ah battery with the VDA size, and carrying out national standard heating test; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell, testing the electrical property of the button half cell to be 0.1C, testing the specific capacity to be 195mAh/g, testing the first effect to be 91%, circulating for 100 weeks, and maintaining the capacity to be 91%. .

Comparative example 5, the positive electrode plate (without nanofiber membrane), the matched negative electrode plate and the 16 μm PE separator (i.e., the total thickness of nanofiber membrane and PE membrane in example) having the same thickness as in the above example were assembled into a VDA-sized 20Ah battery, and a national standard heating test was performed; meanwhile, the pole piece (without the nanofiber membrane) in example 5 is cut into a 12mm wafer, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12h, and assembled to be a button half cell to test the electrical performance, the electrical performance is 0.1C, the specific capacity is 192mAh/g, the first effect is 89.5%, the cycle is 100 weeks, and the capacity retention rate is 89%.

Example 6

A high-temperature-resistant integrated composite electrode F is formed by preparing a carbon negative electrode material into a negative electrode plate by using a PI (polyimide) adhesive, and then covering a polymer nanofiber membrane layer on the surface of the negative electrode plate by using an electrostatic spinning technology. The total thickness of the high-safety integrated composite electrode F is 115 micrometers, the thickness of the carbon negative electrode piece is 110 micrometers, and the thickness of the high-temperature-resistant polymer nanofiber membrane layer is 5 micrometers. The preparation method of the high-temperature-resistant integrated electrode F comprises the following steps:

the method comprises the following steps: preparing a battery pole piece, synthesizing a PAA solution to obtain a polyamic acid solution with the solid content of 20%, and preparing the polyamic acid solution into a glue solution with the solid content of 12%. Mixing 93%, 4% and 3% of carbon negative electrode material (natural graphite), conductive carbon black and a polyamide acid solution in parts by mass, adding NMP solvent to dissolve the mixture, and stirring for 20min to obtain negative electrode slurry. Coating the polyimide slurry on a copper foil and drying at room temperature for 12h, wherein the heat treatment process comprises uniformly heating from room temperature for 60min to 135 ℃, keeping the temperature for 60min, uniformly heating from 135 ℃ to 300 ℃ for 60min, keeping the temperature for 60min, and heating at the temperature of more than 100 ℃ under vacuum.

Step two: weighing 10g of PAN powder, adding the PAN powder into 90g N N Dimethylformamide (DMF), and stirring at 60 ℃ until PAN is completely dissolved to obtain PAN electrostatic spinning solution with solid content of 10%; electrospinning the spinning solution by an electrostatic spinning machine, taking a carbon cathode pole piece as a receiving base, wherein the spinning parameters of the spinning machine are as follows: spinning distance is 15cm, spinning voltage is 20kV until the thickness of the nanofiber membrane is 5 mu m, and an integrated electrode with a PAN high-temperature resistant nanofiber membrane layer covered on the surface is obtained; and rolling and forming to obtain the high-temperature-resistant integrated electrode F.

Assembling the pole piece, a matched lithium iron phosphate positive pole piece and a 7-micrometer PE diaphragm into a 20Ah battery with the VDA size, and carrying out national standard heating test; and simultaneously cutting into 12mm wafers, rolling, weighing, drying in a vacuum oven at 200 ℃ for 12h, assembling the button half cell to test the electrical property, testing the electrical property at 0.1C, wherein the specific capacity is 335mAh/g, the first effect is 92%, circulating for 100 weeks, and the capacity retention rate is 91%. .

Comparative example 6, a 20Ah cell with VDA size was assembled from the negative electrode plate (without nanofiber membrane), the lithium iron phosphate positive electrode plate and the PE separator (i.e. the total thickness of nanofiber membrane and PE membrane in example) with 12 μm thickness equal to the above example, and a national standard heating test was performed; meanwhile, the pole piece (without the nanofiber membrane) in example 6 is cut into a 12mm wafer, rolled, weighed, dried in a vacuum oven at 200 ℃ for 12h, and assembled to be a button half cell to test the electrical performance, the electrical performance is 0.1C, the specific capacity is 331mAh/g, the first effect is 91.5%, the cycle is 100 weeks, and the capacity retention rate is 87%.

And (3) testing results:

TABLE 1 Performance of batteries prepared in examples and comparative examples

Heating the fully charged battery to 150 ℃ at a speed of 2 ℃/min, preserving heat for 30min, continuing to heat to 160 ℃ if the battery is not ignited and smokes, preserving heat for 30min if the battery is not ignited and smokes, continuing to heat for 30min until the battery is ignited and smokes, and determining that the battery fails the test if the battery is ignited and smokes

Compared with the battery assembled by the high-temperature-resistant integrated electrode and the field, the battery assembled by the high-temperature-resistant integrated electrode provided by the invention has the advantages that the safety performance is obviously improved, the thermal safety performance of the battery is obviously improved, and the cycle performance of the battery is obviously improved compared with the battery assembled by a PE diaphragm and a common battery pole piece which are commonly sold in the market at present.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (8)

1. The high-temperature-resistant integrated electrode is characterized in that the high-temperature-resistant integrated composite electrode is formed by compounding a nanofiber membrane (2), a lithium ion battery pole piece (1) and the nanofiber membrane (2) which are sequentially arranged, the battery pole piece (1) is prepared by taking Polyimide (PI) which is formed by condensation polymerization of dibasic acid or polybasic acid anhydride and diamine or polyamine as an adhesive, and the nanofiber membrane (2) is a high-temperature-resistant polymer or a high-temperature-resistant polymer/non-polar material mixture through electrostatic spinning.

2. The high-temperature-resistant integrated electrode according to claim 1, wherein the lithium ion battery pole piece (1) contains an active material, a conductive agent and a PI adhesive; the lithium ion battery pole piece (1) is one of a positive pole piece and a negative pole piece, and the active material of the positive pole piece is a positive pole piece prepared by any one or a combination of multiple of NCM ternary material, lithium iron phosphate pole piece, lithium manganate, lithium manganese iron phosphate and lithium cobaltate; the negative pole piece active material is a pole piece prepared by one or a combination of a plurality of carbon materials, silicon oxide materials and tin materials; the conductive agent is one or a combination of more of graphite, conductive carbon black, carbon nano tubes and graphene.

3. The high-temperature-resistant integrated electrode and the battery pole piece (1) comprising the same as claimed in claim 1 and claim 2, wherein the adhesive of the battery pole piece (1) is a PI adhesive, and the PI adhesive is prepared by mixing and polycondensing any diamine and any dicarboxylic anhydride; or any diamine and several kinds of dibasic acid anhydrides are subjected to copolycondensation reaction to obtain the diamine; or prepared by copolycondensation reaction of a plurality of diamines and a dicarboxylic anhydride; or a PAA solution is prepared from several diamines and several dicarboxylic anhydrides through copolycondensation reaction, the PAA solution is finally converted into a PI adhesive through high-temperature cyclization, the mass percentage of the adhesive in the negative electrode membrane active material is 1.0-15.0%, and the mass percentage of the adhesive in the positive electrode membrane active material is 1.0-15.0%.

4. The high temperature resistant integrated electrode according to claim 1, wherein the high temperature resistant polymer nanofiber membrane (2) is any one or more combination of aramid, P84, Polyetherimide (PEI), polyvinylidene fluoride (PVDF), Polyacrylonitrile (PAN) and Polyimide (PI), or a mixture of the above polymers and inorganic particle materials, and has a thickness of 0.5-20 μm.

5. The high-temperature-resistant integrated electrode according to claim 1, wherein the inorganic material is ceramic, boehmite, an oxide electrolyte, a sulfide dielectric or a chloride dielectric, and the particle size of the inorganic material is 50-2000 nm.

6. The preparation method of the high-temperature-resistant adhesive for the lithium ion battery and the battery pole piece (1) applying the adhesive according to any one of claims 1 to 5 is characterized by comprising the following steps:

method 1

A. Selecting any one or more monomers in diamine containing functional groups in a certain proportion, any one or more monomers in diamine containing non-functional groups in a certain proportion and any one or more monomers in dicarboxylic anhydride in a certain proportion as raw materials, carrying out solution condensation polymerization to obtain a polyimide precursor-polyamic acid solution, and preparing the polyamic acid solution into a solution with a specific concentration;

B. the preparation method comprises the steps of preparing a battery pole piece using the adhesive, uniformly mixing an active substance, a conductive agent and a polyamic acid solution to prepare slurry, coating the slurry on the surface of a current collector, and performing high-temperature thermal imidization treatment after rolling to prepare the lithium ion battery pole piece using polyimide as the adhesive.

C. Adding the polymer into an organic solvent for full dissolution to obtain an electrostatic spinning solution with the solid content of 5-25%, wherein the organic solvent is one or more of DMF, DMAC, NMP and DMSO; the spinning solution of the PI nano fiber is a polyamic acid solution and is prepared by carrying out mixed polycondensation reaction on any diamine and any dicarboxylic anhydride; or any diamine and several kinds of dibasic acid anhydrides are subjected to copolycondensation reaction to obtain the diamine; or prepared by copolycondensation reaction of a plurality of diamines and a dicarboxylic anhydride; or the PAA electrostatic spinning solution with solid content of 5-25% is prepared by copolycondensation reaction of a plurality of diamines and a plurality of dicarboxylic anhydrides;

d: c, performing electrostatic spinning on the electrostatic spinning solution obtained in the step C by using an electrostatic spinning machine, taking the battery pole piece (1) as a receiving base, wherein the thickness of the nanofiber membrane (2) is 0.5-20 mu m, rolling to obtain a high-temperature-resistant integrated electrode with the surface covered with a high-temperature-resistant polymer nanofiber membrane, and performing high-temperature cyclization treatment on the nanofiber membrane prepared by taking PAA as the spinning solution at 300-400 ℃;

the second method comprises the following steps:

A. selecting any one or more monomers in diamine containing functional groups in a certain proportion, any one or more monomers in diamine containing non-functional groups in a certain proportion and any one or more monomers in dicarboxylic anhydride in a certain proportion as raw materials, carrying out solution condensation polymerization to obtain a polyimide precursor-polyamic acid solution, and preparing the polyamic acid solution into a solution with a specific concentration;

B. the preparation method comprises the steps of preparing a battery pole piece using the adhesive, uniformly mixing an active substance, a conductive agent and a polyamic acid solution to prepare slurry, coating the slurry on the surface of a current collector, and performing high-temperature thermal imidization treatment after rolling to prepare the lithium ion battery pole piece using polyimide as the adhesive.

C. Adding the polymer into an organic solvent for full dissolution to obtain an electrostatic spinning solution with the solid content of 5-25%, wherein the organic solvent is one or more of DMF, DMAC, NMP and DMSO; the spinning solution of the PI nano fiber is a polyamic acid solution and is prepared by carrying out mixed polycondensation reaction on any diamine and any dicarboxylic anhydride; or any diamine and several kinds of dibasic acid anhydrides are subjected to copolycondensation reaction to obtain the diamine; or prepared by copolycondensation reaction of a plurality of diamines and a dicarboxylic anhydride; or the PAA electrostatic spinning solution with solid content of 5-25% is prepared by copolycondensation reaction of a plurality of diamines and a plurality of dicarboxylic anhydrides; adding an inorganic material which accounts for 2-50% of the mass of the polymer before spinning the spinning solution, and fully stirring and uniformly dispersing to obtain a final spinning solution;

d: and D, performing electrostatic spinning on the electrostatic spinning solution containing the inorganic material obtained in the step C by using an electrostatic spinning machine, taking the battery pole piece (1) as a receiving base, wherein the thickness of the nanofiber membrane (2) is 0.5-20 mu m, rolling to obtain a high-temperature-resistant integrated electrode with the surface covered with the high-temperature-resistant polymer nanofiber membrane, and performing high-temperature cyclization treatment at 300-400 ℃ on the nanofiber membrane prepared by taking PAA as the spinning solution.

7. The method according to claim 1, claim 2 and claim 6, wherein the thermal imidization process is a high-temperature thermal imidization process, the temperature is slowly increased at a constant speed, and the temperature increase rate is 0.5-25 ℃ per minute^-1The final heat treatment temperature is between 180 and 460 ℃.

8. A high temperature resistant integrated electrode according to any one of claims 1 to 7 and a battery assembled therewith.

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