阅读说明：本技术 一种锂离子电池隔膜及其锂离子电池 (Lithium ion battery diaphragm and lithium ion battery thereof ) 是由 崔日俊 李国敏 于 2020-05-26 设计创作，主要内容包括：本发明公开了一种锂离子电池隔膜及其锂离子电池,所述的隔膜包括基膜和涂覆在基膜表面的第一涂层及第二涂层,所述的第一涂层为陶瓷固态电解质层,所述的第二涂层为粘合剂聚合物涂层,所述的第一涂层涂覆在基膜表面,所述第二涂层涂覆在第二涂层表面。本发明可提高隔膜的热稳定性及机械强度,增大锂离子转移能力,提高离子电导率,防止锂离子电池在负极表面不均匀的沉积而导致析锂,同时也可显著地提高隔膜电解液浸润性及隔膜与电极之间界面作用力,防止界面上形成难以除去的气泡使电极和隔膜逐渐分层,与现有商业化隔膜相比,使用本发明所制备的锂离子电池具有更好的循环稳定性及安全性能,在能量密度方面具有更高的优势。(The invention discloses a lithium ion battery diaphragm and a lithium ion battery thereof, wherein the diaphragm comprises a base film, a first coating and a second coating, the first coating and the second coating are coated on the surface of the base film, the first coating is a ceramic solid electrolyte layer, the second coating is an adhesive polymer coating, the first coating is coated on the surface of the base film, and the second coating is coated on the surface of the second coating. The invention can improve the thermal stability and mechanical strength of the diaphragm, increase the lithium ion transfer capacity, improve the ionic conductivity, prevent lithium ion battery from precipitating because of uneven deposition on the surface of the negative electrode, can also obviously improve the wettability of the diaphragm electrolyte and the interfacial force between the diaphragm and the electrode, prevent bubbles which are difficult to remove from forming on the interface and enable the electrode and the diaphragm to be gradually layered, compared with the existing commercialized diaphragm, the lithium ion battery prepared by the invention has better cycle stability and safety performance, and has higher advantage in the aspect of energy density.)

1. The lithium ion battery diaphragm is characterized by comprising a base film, a first coating and a second coating, wherein the first coating and the second coating are coated on the surface of the base film, the first coating is a ceramic solid electrolyte coating, the second coating is an adhesive polymer coating, the first coating is coated on the surface of the base film, and the second coating is coated on the surface of the second coating.

2. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the base film is one or more of polyethylene, polypropylene/polyethylene/polypropylene, polyvinylidene fluoride-hexafluoropropylene copolymer.

3. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the thickness of the base film is 9-16 μm.

4. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the ceramic solid electrolyte coating comprises a ceramic solid electrolyte and a small amount of polymer binder, and the weight ratio of the dry powder is 70-90%: 10-30%; the ceramic solid electrolyte is one or more of lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide and tantalum-doped lithium lanthanum zirconium oxide.

5. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the thickness of the ceramic solid electrolyte coating is 1-3 μm.

6. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the binder in the binder polymer coating is one or more of acrylic acid, polyurethane, polyimide, polyvinylidene fluoride and polyacrylonitrile.

7. The lithium ion battery separator and the lithium ion battery thereof according to claim 1, wherein the thickness of the adhesive polymer coating is 0.5-2 μm.

8. A lithium ion battery comprising a positive electrode, a negative electrode and a separator, wherein the separator according to claims 1 to 7 is disposed between the positive electrode and the negative electrode.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery diaphragm and a lithium ion battery thereof.

Background

Lithium ion batteries have high energy density, high operating voltage, no memory characteristics, and long service life, and have become important energy forms in the field of new energy, and have also been widely used in hybrid vehicles, mobile portable devices, and other applications. The safety of lithium ion batteries is also a focus of attention.

The diaphragm is one of important components of the internal structure of the lithium ion battery and plays a critical role in safety performance. Currently, commercially available lithium battery separators in the market are mainly microporous polyolefin separators mainly made of Polyethylene (PE) and polypropylene (PP), and such separators are widely used in lithium battery separators due to their advantages of low cost, good mechanical properties, excellent chemical stability and electrochemical stability. The practical application of the diaphragm also comprises a single-layer PP or PE diaphragm, a double-layer PE/PP composite diaphragm, a double-layer PP/PP composite diaphragm and a three-layer PP/PE/PP composite diaphragm. The polyolefin composite diaphragm is developed by Celgard company, and mainly comprises a PP/PE composite diaphragm and a PP/PE/PP composite diaphragm, because the PE diaphragm has good flexibility, but the melting point is 135 ℃, the pore-closing temperature is low, the PP diaphragm has good mechanical property and the melting point is 165 ℃, the combination of the two makes the composite diaphragm have the advantages of low pore-closing temperature and high fusing temperature, the diaphragm automatically closes pores at higher temperature without melting, but the polyolefin diaphragm has poor wetting property and insufficient liquid retention, and the ionic conductivity and the cycle performance of a lithium ion battery are influenced. At present, the energy density of the battery is higher and higher, and the diaphragm needs to be thinner, and the mechanical strength and the heat resistance are better so as to meet the safety performance of the battery. Therefore, it is urgently required to develop a separator having the above-mentioned excellent overall properties to meet the demand.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a lithium ion battery diaphragm and a lithium ion battery thereof, and aims to improve the thermal/mechanical stability and the liquid absorption rate of the diaphragm, improve the wettability between the diaphragm and an electrode, reduce the interface impedance of the battery, improve the rate capability of the battery, and simultaneously improve the cycle performance and the safety performance of the battery and the energy density of the battery.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the diaphragm comprises a base film, a first coating and a second coating, wherein the first coating and the second coating are coated on the surface of the base film, the first coating is a ceramic solid electrolyte coating, the second coating is an adhesive polymer coating, the first coating is coated on the surface of the base film, and the second coating is coated on the surface of the second coating.

The base film is one or more of polyethylene, polypropylene/polyethylene/polypropylene, polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene copolymer. Further, the base film is one or more of polyethylene, polypropylene and polypropylene/polyethylene/polypropylene.

The thickness of the base film is 9-16 mu m. Further, the thickness of the base film is 12-16 mu m.

The ceramic solid electrolyte coating comprises a ceramic solid electrolyte and a small amount of polymer adhesive, and the weight ratio of dry powder is 70-90%: 10 to 30 percent. The ceramic solid electrolyte is one or more of lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide and tantalum-doped lithium lanthanum zirconium oxide. Further, the ceramic solid electrolyte coating comprises a ceramic solid electrolyte and a small amount of polymer adhesive, and the weight ratio of dry powder is 80-90%: 10 to 20 percent.

The thickness of the ceramic solid electrolyte coating is 1-3 mu m. Further, the thickness of the ceramic solid electrolyte coating is 1-2 μm.

The adhesive in the adhesive polymer coating is one or more of acrylic acid, polyurethane, polyimide, polyvinylidene fluoride and polyacrylonitrile, and is preferably one or more of acrylic acid and polyurethane.

The thickness of the adhesive polymer coating is 0.5-2 μm. Furthermore, the thickness of the adhesive polymer coating is 0.5-1 μm.

A lithium ion battery comprising a positive electrode, a negative electrode and a separator, the separator according to claims 1 to 7 being provided between the positive electrode and the negative electrode.

The invention has the beneficial effects that: the lithium ion battery diaphragm contains the ceramic solid electrolyte coating, the adopted solid electrolyte can improve the thermal stability and the mechanical strength of the diaphragm, increase the lithium ion transfer capacity, improve the ionic conductivity, prevent lithium precipitation caused by uneven deposition of the lithium ion battery on the surface of a negative electrode, and simultaneously coat a layer of adhesive polymer on the surface of the ceramic solid electrolyte coating, so that the wettability of the diaphragm electrolyte can be obviously improved.

Compared with the existing commercial diaphragm, the lithium ion battery prepared by the invention has better cycle stability and safety performance and has higher advantage in the aspect of energy density.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.

Example 1:

selecting polyethylene with the thickness of 12 mu m as a diaphragm base material, uniformly mixing the lithium lanthanum titanium oxide and the polyvinylidene fluoride as ceramic solid electrolytes, uniformly coating the mixture on two sides of a base film, coating polyurethane adhesives on two sides of the ceramic solid electrolytes, and drying to obtain the lithium ion battery diaphragm, wherein the single-layer thickness of the ceramic solid electrolyte coating is 2 mu m, and the single-layer thickness of the adhesive polymer coating is 1 mu m.

Uniformly dispersing the ternary positive electrode active material, the conductive agent and the adhesive, coating the mixture on the surface of an aluminum foil, drying, rolling, slitting and punching to obtain a positive electrode plate; and uniformly dispersing the artificial graphite negative electrode active material, the conductive agent, the thickening agent and the adhesive, coating the mixture on the surface of copper foil, drying, rolling, slitting and punching to obtain the negative electrode plate.

And separating the prepared positive pole piece and the negative pole piece by using the prepared diaphragm, stacking the positive pole piece and the negative pole piece into a bare cell, and packaging the bare cell by using an aluminum plastic film, injecting liquid and packaging to obtain the lithium ion battery.

Example 2:

selecting polyethylene with the thickness of 12 mu m as a diaphragm base material, uniformly mixing the ceramic solid electrolyte lithium lanthanum zirconium oxide and polyvinylidene fluoride, uniformly coating the mixture on two surfaces of a base film, and drying to obtain the lithium ion battery diaphragm, wherein the single-layer thickness of the ceramic solid electrolyte coating is 2 mu m.

Uniformly dispersing the ternary positive electrode active material, the conductive agent and the adhesive, coating the mixture on the surface of an aluminum foil, drying, rolling, slitting and punching to obtain a positive electrode plate; and uniformly dispersing the artificial graphite negative electrode active material, the conductive agent, the thickening agent and the adhesive, coating the mixture on the surface of copper foil, drying, rolling, slitting and punching to obtain the negative electrode plate.

And separating the prepared positive pole piece and the negative pole piece by using the prepared diaphragm, stacking the positive pole piece and the negative pole piece into a bare cell, and packaging the bare cell by using an aluminum plastic film, injecting liquid and packaging to obtain the lithium ion battery.

Example 3:

selecting polyethylene with the thickness of 12 mu m as a diaphragm base material, coating a polyurethane adhesive on two sides of tantalum-doped lithium lanthanum zirconium oxide of a ceramic solid electrolyte, and drying to obtain the lithium ion battery diaphragm, wherein the single-layer thickness of the adhesive polymer coating is 1 mu m.

Uniformly dispersing the ternary positive electrode active material, the conductive agent and the adhesive, coating the mixture on the surface of an aluminum foil, drying, rolling, slitting and punching to obtain a positive electrode plate; and uniformly dispersing the artificial graphite negative electrode active material, the conductive agent, the thickening agent and the adhesive, coating the mixture on the surface of copper foil, drying, rolling, slitting and punching to obtain the negative electrode plate.

And separating the prepared positive pole piece and the negative pole piece by using the prepared diaphragm, stacking the positive pole piece and the negative pole piece into a bare cell, and packaging the bare cell by using an aluminum plastic film, injecting liquid and packaging to obtain the lithium ion battery.

Comparative example 1:

the same procedure as in example 1 was repeated except that the separator was changed to a commercially available polyethylene separator.

Comparative example 2:

the same procedure as in example 1 was repeated except that the separator was changed to a commercially available ceramic separator.

The lithium ion battery diaphragm provided by the invention obviously improves the thermal stability and the mechanical stability of the diaphragm, and also helps the absorption rate of electrolyte to a certain extent, so that the wettability between the diaphragm and an electrode is effectively improved, the interface impedance of the battery is reduced, the multiplying power performance of the battery is improved, and meanwhile, the recycling performance, the safety performance and the energy density of the battery are improved to a certain extent.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.