Quick charge-discharge lithium ion battery and preparation method thereof

文档序号：737801 发布日期：2021-04-20 浏览：13次中文

阅读说明：本技术 一种快速充放锂离子电池及其制备方法 (Quick charge-discharge lithium ion battery and preparation method thereof ) 是由魏冠杰徐子福于 2020-12-28 设计创作，主要内容包括：本发明提供了一种快速充放锂离子电池及其制备方法,该电池包含：正极片、负极片、隔膜、电解液及外包装结构；其中正极片包含：正极集流体、涂覆在正极集流体上的第一导热功能涂层及涂覆在第一导热功能涂层上的正极活性材料层；负极片包含：负极集流体及涂覆在负极集流体上的负极活性材料层；隔膜包含：高分子基膜及涂覆在高分子基膜上的第二导热功能涂层；隔膜设置在正极片和负极片之间,且隔膜上的第二导热功能涂层与正极片相对。本发明通过在正极集流体和隔膜上引入导热功能涂层,将快充过程中局部产热迅速传导到电池全身,一方面起自加热作用,降低充电极化,提高充电速度,另一方面减小局部产热引起的老化,提高电池循环寿命及安全性能。(The invention provides a rapid charge-discharge lithium ion battery and a preparation method thereof, wherein the battery comprises: the positive plate, the negative plate, the diaphragm, the electrolyte and the outer package structure; wherein positive plate contains: the heat-conducting coating comprises a positive current collector, a first heat-conducting functional coating coated on the positive current collector and a positive active material layer coated on the first heat-conducting functional coating; the negative electrode sheet includes: a negative current collector and a negative active material layer coated on the negative current collector; the separator includes: the high polymer base film and a second heat conduction functional coating coated on the high polymer base film; the diaphragm is arranged between the positive plate and the negative plate, and the second heat-conducting functional coating on the diaphragm is opposite to the positive plate. According to the invention, the heat-conducting functional coating is introduced on the positive current collector and the diaphragm, so that local heat generated in the quick charging process is quickly transferred to the whole battery, and therefore, on one hand, the self-heating effect is achieved, the charging polarization is reduced, the charging speed is improved, on the other hand, the aging caused by the local heat generation is reduced, and the cycle life and the safety performance of the battery are improved.)

1. A fast charge-discharge lithium ion battery is characterized in that the battery comprises: the positive plate, the negative plate, the diaphragm, the electrolyte and the outer package structure;

the positive plate comprises a positive current collector, a first heat-conducting functional coating coated on the positive current collector and a positive active material layer coated on the first heat-conducting functional coating;

the negative plate comprises a negative current collector and a negative active material layer coated on the negative current collector;

the diaphragm comprises a polymer base film and a second heat-conducting functional coating coated on the polymer base film;

the diaphragm is arranged between the positive plate and the negative plate, and the second heat-conducting functional coating on the diaphragm is opposite to the positive plate;

the first heat conduction functional coating and the second heat conduction functional coating comprise heat conduction materials and binders, and the heat conduction materials are at least one of high-heat-conduction flexible graphite, high-heat-conduction carbon fibers, vapor deposition nano carbon fibers, high-heat-conduction foam carbon, carbon nano tubes and graphene.

2. The rapid charge-discharge lithium ion battery according to claim 1, wherein the positive electrode active material layer comprises a positive electrode active material, a binder and a conductive agent; the positive active material is at least one of lithium cobaltate, lithium iron phosphate and a ternary material, and the ternary material is LiNi_1-x-y-zCo_xMn_yAl_zO₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is more than or equal to 0 and less than or equal to 1.

3. The rapid charge-discharge lithium ion battery according to claim 1, wherein the negative electrode active material layer comprises a negative electrode active material, a binder and a conductive agent; the negative active material is at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon and compounds thereof, and tin and compounds thereof.

4. The rapid charge-discharge lithium ion battery according to claim 1, wherein the polymer-based film of the separator is at least one of a polyethylene film, a polypropylene film, an aramid film, and a polyimide film; the thickness of the base film is 5-10 um, and the porosity is 40-50%.

5. The rapid charge-discharge lithium ion battery according to claim 1, wherein the binder is at least one of polyvinylidene fluoride and polymethyl methacrylate.

6. The rapid charge-discharge lithium ion battery according to claim 1, wherein the mass percentage of the heat conductive material in the first heat conductive functional coating and the second heat conductive functional coating is 50-70%.

7. The rapid charge-discharge lithium ion battery according to claim 1, wherein the thickness of the first heat-conducting functional coating is 0.2-5 um.

8. The rapid charge-discharge lithium ion battery according to claim 1, wherein the thickness of the second heat-conducting functional coating is 0.1-3 um.

9. The rapid charge-discharge lithium ion battery according to claim 1, wherein the electrolyte comprises a lithium salt, a solvent and an additive; the outer packaging structure is an aluminum-plastic packaging shell.

10. The preparation method of the rapid charge-discharge lithium ion battery according to claim 1, characterized by comprising the following steps:

mixing a heat conduction material and a binder in proportion, adding an N-methyl pyrrolidone solvent, stirring to prepare heat conduction functional coating slurry, and coating the heat conduction functional coating slurry on a positive current collector and a base film to obtain a first heat conduction functional coating and a second heat conduction functional coating; wherein the heat conduction material accounts for 50-70% of the mass of the heat conduction functional coating, and the binder accounts for 30-50% of the mass of the heat conduction functional coating;

step two, mixing the positive active material, polyvinylidene fluoride and a conductive agent according to a certain proportion, adding N-methyl pyrrolidone, uniformly stirring to prepare positive slurry, coating the positive slurry on the surface of the first heat-conducting functional coating and drying; rolling the obtained positive plate, cutting into strips, and welding lugs for later use;

mixing a negative electrode active material, sodium carboxymethylcellulose, styrene butadiene rubber and a conductive agent according to a certain proportion, adding water as a solvent, uniformly stirring to prepare a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector and drying; rolling the obtained negative plate, cutting into strips, and welding tabs for later use;

placing the diaphragm between the positive plate and the negative plate, and winding the second heat-conducting functional coating on the diaphragm opposite to the positive plate to prepare a winding core; and placing the obtained roll core in an outer packaging structure, sealing the top side, injecting electrolyte, standing, forming, degassing, sealing, aging and grading to prepare the polymer lithium ion battery.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a quick charge-discharge lithium ion battery and a preparation method thereof.

Technical Field

At present, the quick charging technology is developed vigorously, and electronic products such as smart phones, notebook computers and mobile power supplies are carried with the quick charging technology in sequence to improve user experience. Among them, the high-end customers of OPPO and vivo mobile phones are more characterized by fast charging. This requires high power charging capability for the battery system. However, when the battery is charged and discharged at a high rate, various polarizations (ohms, concentration and electrochemistry) in the battery are sharply increased, so that local heat generation near the tab is too large, the electrolyte is consumed too fast, side reactions at an electrode/electrolyte interface are aggravated, lithium precipitation is induced, the cycle life is greatly shortened, and even a safety problem is caused. Therefore, the existing quick charging technology faces the problem of poor cycle life and safety caused by local temperature rise, and a technical scheme is urgently needed to solve the problem.

Disclosure of Invention

The invention aims to provide a quick charge-discharge lithium ion battery and a preparation method thereof, which are used for solving the problems of poor cycle life and safety caused by local temperature rise of the conventional quick charge battery and greatly improving the cycle performance of the battery.

In order to achieve the above object, the present invention provides a fast charge and discharge lithium ion battery, comprising: the positive plate, the negative plate, the diaphragm, the electrolyte and the outer package structure;

the negative plate comprises a negative current collector and a negative active material layer coated on the negative current collector;

the diaphragm comprises a polymer base film and a second heat-conducting functional coating coated on the polymer base film;

the diaphragm is arranged between the positive plate and the negative plate, and the second heat-conducting functional coating on the diaphragm is opposite to the positive plate;

The positive active material layer comprises a positive active material, a binder and a conductive agent; the positive active material is at least one of lithium cobaltate, lithium iron phosphate and a ternary material, and the ternary material is LiNi_1-x-y-zCo_xMn_yAl_zO₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is more than or equal to 0 and less than or equal to 1.

The negative electrode active material layer comprises a negative electrode active material, a binder and a conductive agent; the negative active material is at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon and compounds thereof, and tin and compounds thereof.

The high-molecular base film of the diaphragm is at least one of a polyethylene film, a polypropylene film, an aramid film and a polyimide film; the thickness of the base film is 5-10 um, and the porosity is 40-50%.

The binder is at least one of polyvinylidene fluoride and polymethyl methacrylate.

The mass percentage of the heat conduction material in the first heat conduction functional coating and the second heat conduction functional coating is 50-70%.

The thickness of first heat conduction function coating be 0.2 ~ 5 um.

The thickness of the second heat conduction functional coating is 0.1-3 um.

The electrolyte comprises lithium salt, a solvent and an additive; the outer packaging structure is an aluminum-plastic packaging shell.

The preparation method of the rapid charge-discharge lithium ion battery comprises the following steps:

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, the heat-conducting functional coating is introduced on the positive current collector and the diaphragm, so that the local heat generated at the position close to the tab in the high-rate charge-discharge process is quickly transferred to the whole battery body, and therefore, on one hand, the self-heating effect is achieved, the charge polarization is reduced, the charge speed is improved, and the charge time is greatly shortened; on the other hand, battery aging caused by local heat generation is reduced, so that the cycle life and the safety performance of the battery are remarkably improved.

Drawings

Fig. 1 is a charging curve of the lithium ion batteries of example 1 and comparative example 1 of the present invention.

Fig. 2 is a plot of the cycling capacity of the lithium ion batteries of example 1 of the present invention versus comparative example 1.

Detailed Description

The foregoing aspects of the present invention are described in further detail below by way of examples, but it should not be construed that the scope of the subject matter of the present invention is limited to the following examples, and that all the technologies realized based on the above aspects of the present invention are within the scope of the present invention. The experimental procedures used in the examples below are conventional procedures unless otherwise specified, and the reagents, methods and equipment used therein are conventional in the art unless otherwise specified.

In the description of the present invention, it is also to be noted that: terms such as "first, second or third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

A fast charge and discharge lithium ion battery, the battery comprising: positive plate, negative plate, diaphragm, electrolyte and outer package structure.

The positive plate comprises a positive current collector, a first heat conduction functional coating coated on the positive current collector and a positive active material layer coated on the functional coating.

The negative plate comprises a negative current collector and a negative active material layer coated on the negative current collector.

The diaphragm comprises a polymer base film and a second heat-conducting functional coating coated on the polymer base film.

The diaphragm is arranged between the positive plate and the negative plate, and the heat conduction functional coating on the diaphragm is opposite to the positive plate.

The positive current collector is generally an aluminum foil, which has a high resistivity and poor thermal conductivity relative to the copper foil of the negative current collector. The positive electrode active material is generally a metal oxide, while the negative electrode active material is generally a carbon material, the former having a much higher resistivity than the latter. By combining the factors, the resistivity of the positive plate is generally 1 to 2 orders of magnitude higher than that of the negative plate. Therefore, in the process of high-rate charge and discharge, the heat generation of the positive plate is higher than that of the negative plate, and the heat distribution is more uneven than that of the negative plate. According to the invention, the heat-conducting coating is coated on the positive current collector, so that the generated heat can be uniformly distributed on the pole piece, the local overheating near the pole lug is effectively reduced, the battery aging is reduced, and the cycle life is prolonged.

Pores in the lithium ion battery diaphragm have certain tortuosity, so that resistance exists in the transmission of lithium ions between the positive electrode and the negative electrode, and the diaphragm can also generate certain heat in the process of high-rate charge and discharge. For some cell structures with non-uniform electric field distribution, such as the monopolar ear biased winding structure, the heat distribution is quite non-uniform. The heat-conducting coating is coated on the base film and is opposite to the positive plate, so that heat distribution on the positive plate can be further uniform, heat generation of the diaphragm can be uniformly distributed, battery aging is reduced, and cycle life and safety are improved.

The positive active material layer comprises a positive active material, a binder and a conductive agent. The positive electrode active material is at least one of lithium cobaltate, lithium iron phosphate and a ternary material, and the ternary material is LiNi_1-x-y-zCo_xMn_yAl_zO₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is more than or equal to 0 and less than or equal to 1.

The negative electrode active material layer contains a negative electrode active material, a binder and a conductive agent. The negative active material is at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon and compounds thereof, and tin and compounds thereof.

The polymer base film of diaphragm is at least one of polyethylene film, polypropylene film, aramid fiber membrane and polyimide film, base film thickness is 5 ~ 10um, and the porosity is 40 ~ 50%.

The first heat-conducting functional coating and the second heat-conducting functional coating comprise heat-conducting materials and binders. The heat conduction material comprises at least one of high-heat-conduction flexible graphite, high-heat-conduction carbon fiber, vapor deposition carbon nanofiber, high-heat-conduction foam carbon, carbon nano tubes and graphene. The binder is at least one of polyvinylidene fluoride and polymethyl methacrylate.

The mass percentage of the heat conduction material in the heat conduction coating is 50-70%. Wherein, the thickness of first heat conduction function coating is 0.2 ~ 5um, and the thickness of second heat conduction function coating is 0.1 ~ 3 um.

Too large a thickness of the thermally conductive coating on the separator may hinder lithium ion conduction, reduce the high-rate charge-discharge capacity of the battery, and deteriorate cycle performance. Therefore, the thickness of the second heat-conducting functional coating is set to be 0.1-3 um.

The electrolyte comprises lithium salt, solvent and additive.

The invention also provides a preparation method of the rapid charge-discharge lithium ion battery, which comprises the following steps:

And step two, mixing the positive active material, polyvinylidene fluoride and the conductive agent according to a certain proportion, adding N-methyl pyrrolidone, uniformly stirring to prepare positive slurry, coating the positive slurry on the surface of the first heat-conducting functional coating, and drying. And rolling the obtained positive plate, cutting the positive plate into strips, and welding the lugs for later use.

And step three, mixing the negative electrode active material, sodium carboxymethylcellulose, styrene butadiene rubber and a conductive agent according to a certain proportion, adding water as a solvent, uniformly stirring to prepare negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and drying. And rolling the obtained negative plate, cutting into strips, and welding the lugs for later use.

And fourthly, placing the diaphragm between the positive plate and the negative plate, enabling the second heat-conducting functional coating on the diaphragm to be opposite to the positive plate, and winding to obtain the winding core. And placing the obtained roll core in an aluminum-plastic packaging shell, sealing the top side, injecting electrolyte, standing, forming, degassing, sealing, aging and grading to prepare the polymer lithium ion battery.

The following examples are given to further illustrate the present invention but should not be construed as limiting the scope of the invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.

Example 1

Step one, mixing graphene and polyvinylidene fluoride according to a mass ratio of 60%: mixing 40%, adding N-methyl pyrrolidone solvent, stirring to prepare slurry, and coating the slurry on the positive current collector and the base film to obtain a first heat-conducting functional coating and a second heat-conducting functional coating. The thickness of the first heat-conducting functional coating is 1um, and the thickness of the second heat-conducting functional coating is 0.5 um.

And step two, manufacturing the positive plate. Mixing the lithium cobaltate positive electrode material, polyvinylidene fluoride and the conductive agent according to a certain proportion, adding N-methyl pyrrolidone, uniformly stirring to prepare positive electrode slurry, coating the positive electrode slurry on the surface of the first heat-conducting functional coating, and drying. And rolling the obtained positive plate, cutting the positive plate into strips, and welding the lugs for later use.

Mixing the artificial graphite negative electrode material, sodium carboxymethylcellulose, styrene butadiene rubber and a conductive agent according to a certain proportion, adding water as a solvent, uniformly stirring to prepare a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and drying. And rolling the obtained negative plate, cutting into strips, and welding the lugs for later use.

Example 2

Step one, mixing a single-wall carbon nanotube and polyvinylidene fluoride according to a mass ratio of 60%: mixing 40%, adding N-methyl pyrrolidone solvent, stirring to prepare slurry, and coating the slurry on the positive current collector and the base film to obtain a first heat-conducting functional coating and a second heat-conducting functional coating. The thickness of the first heat-conducting functional coating is 0.5um, and the thickness of the second heat-conducting functional coating is 0.2 um.