阅读说明：本技术 一种用于锂硫二次电池的涂覆隔膜材料及其应用 (Coating diaphragm material for lithium-sulfur secondary battery and application thereof ) 是由 段晓波 赵致远 王昆 蔡欣 张蕾 于 2019-09-05 设计创作，主要内容包括：本发明涉及一种用于锂硫二次电池的隔膜涂覆材料及其应用,属于锂硫二次电池领域。所述隔膜涂覆材料包括一种或多种金属氢化物,所述金属氢化物中金属元素包括稀土元素、Mg、Ca、Ti、V、Cr、Ni、Fe、Co、Zr中的一种或多种。所述隔膜涂覆的辅助材料还包括高分子粘结剂和添加剂,按重量份数所述隔膜涂覆材料包括金属氢化物20-98份,高分子粘结剂1-50份,炭黑0-30份。本发明隔膜涂覆材料中的金属氢化物对锂硫二次电池中多硫化物具有较强的化学吸附能力,可有效阻碍多硫化物的扩散,改善锂硫二次电池的综合电化学性能。(The invention relates to a diaphragm coating material for a lithium-sulfur secondary battery and application thereof, belonging to the field of lithium-sulfur secondary batteries. The diaphragm coating material comprises one or more metal hydrides, wherein the metal elements in the metal hydrides comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co and Zr. The auxiliary material for coating the diaphragm also comprises a high molecular binder and an additive, and the material for coating the diaphragm comprises 20-98 parts of metal hydride, 1-50 parts of the high molecular binder and 0-30 parts of carbon black according to parts by weight. The metal hydride in the diaphragm coating material has stronger chemical adsorption capacity to polysulfide in the lithium-sulfur secondary battery, can effectively obstruct the diffusion of the polysulfide, and improves the comprehensive electrochemical performance of the lithium-sulfur secondary battery.)

1. A separator coating material for a lithium-sulfur secondary battery, comprising one or more metal hydrides, wherein the metal elements of the metal hydrides comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co, Zr.

2. The separator coating material according to claim 1, wherein the metal hydride comprises a metal hydride containing one metal element or a metal hydride containing a plurality of metal elements.

3. The membrane coating material as claimed in claim 1, further comprising a polymer binder and an additive, wherein the membrane coating material comprises 20-98 parts by weight of metal hydride, 1-50 parts by weight of polymer binder and 0-30 parts by weight of carbon black.

4. Separator coating material according to claim 3, wherein the particle size of the metal hydride is below 100 μm.

5. The separator coating material according to claim 4, wherein the purity of the metal hydride is 90% or more.

6. A method for preparing the separator coating material according to any one of claims 1 to 5, comprising the steps of: under the protection of inert gas, ball-milling the metal hydride until the granularity is lower than 100 mu m, dissolving 1-50 parts of the high-molecular binder in a solvent with the weight of 15-20 times, uniformly mixing 20-98 parts of refined metal hydride and 0-30 parts of carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.

7. A separator coated with the separator coating material according to claim 6.

8. The preparation method of the separator according to claim 7, wherein the separator coating slurry is coated on a polymer porous separator with a thickness of 30-150 μm, dried and cut to shape as required.

9. A lithium sulfur secondary battery comprising the separator of claim 7.

Technical Field

The invention relates to a diaphragm coating material for a lithium-sulfur secondary battery and application thereof, belonging to the field of lithium-sulfur secondary batteries.

Background

The lithium-sulfur secondary battery takes a sulfur-containing substance as a positive electrode and metal lithium as a negative electrode, has the advantages of high theoretical energy density, low cost, environmental friendliness and the like, is considered to be the first choice of a next-generation high-specific-energy chemical power source following a lithium ion battery, and is widely valued by countries in the world.

Although lithium-sulfur secondary batteries have a series of advantages such as high energy density, the indexes such as self-discharge performance, coulombic efficiency and cycle performance of lithium-sulfur secondary batteries still cannot be compared with those of lithium-ion batteries. The main reason is that lithium polysulfide, a discharge intermediate product of a sulfur positive electrode, can be dissolved in a large amount in an electrolyte and shuttles back and forth between the positive electrode and the negative electrode, resulting in poor self-discharge, cycle performance and coulombic efficiency. Therefore, the key to improving the performance of the lithium sulfur secondary battery is to suppress the shuttling effect of the lithium sulfur secondary battery. An effective method adopted by the academia at present is to coat a polar compound on the surface of the diaphragm, and utilize the adsorption effect of the compound on polysulfide to block the diffusion of polysulfide from a positive electrode to a negative electrode. Among them, many coating compounds are oxides, sulfides, and the like, but these materials generally have a high specific gravity and a low conductivity, and affect the electron transfer ability of the sulfur positive electrode.

Disclosure of Invention

In view of the above problems, the present invention provides a separator coating material and a separator having high conductivity and good sulfur blocking effect, which aims to block shuttling of lithium polysulfide and improve the dynamic properties of a lithium sulfur secondary battery.

A separator coating material for a lithium-sulfur secondary battery, comprising one or more metal hydrides, wherein the metal elements comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co, Zr.

Further, the metal hydride includes a metal hydride containing one metal element or a metal hydride containing a plurality of metal elements.

Furthermore, the diaphragm coating material also comprises a polymer binder and an additive, and the diaphragm coating material comprises 20-98 parts of metal hydride, 1-50 parts of the polymer binder and 0-30 parts of carbon black according to parts by weight.

Further, the particle size of the metal hydride is less than 100 μm.

Further, the purity of the metal hydride is more than 90%.

Further, the metal hydride is preferably a metal hydride in which the metal element is one or more of Mg, Ti, V, Cr, Ni, and Fe, in view of hydride stability and cost.

Preferably, TiH is an index which comprehensively considers the improvement effect on the battery performance, the cost, the operation simplicity, whether the current industrial-grade supply capacity is available or not, and the like₂With MgH₂Mixtures are a relatively good choice.

Preferably, the separator coating material comprises TiH in parts by weight₂45 portions of MgH₂45 parts of high molecular adhesive and 5 parts of carbon black.

A preparation method of a separator coating material for a lithium-sulfur secondary battery comprises the following steps: under the protection of inert gas, ball-milling the metal hydride until the granularity is lower than 100 mu m, dissolving 1-50 parts of the polymer binder in a solvent with the weight of 15-20 times that of the polymer binder, uniformly mixing 20-98 parts of the refined metal hydride and 0-30 parts of carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.

Further, the inert gas includes argon or nitrogen.

A separator comprising the separator coating material described above.

The preparation method of the diaphragm comprises the following steps: coating the diaphragm coating slurry on a high-molecular porous diaphragm, wherein the thickness of a coating layer is 30-150 mu m, and cutting and forming as required after drying.

A lithium sulfur secondary battery comprising the separator described above.

The effective component of the diaphragm coating material is metal hydride which contains metal bonds, has free electrons and has high conductivity at the metal level. In the prior art, metal hydrides are mainly used as power source negative electrode materials in alkaline electrolyte, such as metal hydride graphene batteries of CN109037666A public cloth, and are used as battery negative electrode materials. In lithium ion batteries, researchers also propose that a few hydrides have certain lithium intercalation capacity at 0-0.5V (metallic lithium is the standard potential) and have potential to be used as a lithium ion battery cathode material, but lithium is difficult to remove under the current technical conditions, the cycle performance is poor, and no practicability exists.

In the earlier research process, the invention discovers that metal hydride is easy to chemically adsorb polysulfide ions and is suitable for being used as a coating material of a lithium-sulfur secondary battery diaphragm. Although the mechanism of the hydride to adsorb polysulfide ions is not clear at present, and presumably may be related to the surface polarity or reducibility of the hydride, the technical effect is significant.

The beneficial effects of the invention include:

(1) the metal hydride has stronger chemical adsorption capacity to polysulfide in an oxidation state, can effectively hinder the diffusion of the polysulfide and improve the comprehensive electrochemical performance of the battery.

(2) The metal hydride has higher conductivity and can not reduce the electron transfer capability of the sulfur anode.

(3) The metal hydride is relatively easy to synthesize, has brittleness similar to inorganic ceramic, and can easily realize the regulation and control of the particle size by mechanical means such as ball milling and the like.

Drawings

For a clearer explanation of the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a first charge and discharge curve of the battery in example 1.

Fig. 2 is a first charge and discharge curve of the battery in example 2.

Fig. 3 is a first charge and discharge curve of the battery in example 3.

Fig. 4 is a first charge and discharge curve of the battery in example 4.

Fig. 5 is a first charge and discharge curve of the battery in example 5.

Fig. 6 is a first charge and discharge curve of the battery of example 6.

Fig. 7 is a first charge and discharge curve of the battery in example 7.

Fig. 8 is a first charge and discharge curve of the battery of example 8.

Fig. 9 is a first charge and discharge curve of the battery in example 9.

Fig. 10 is a first charge-discharge curve of the battery in example 10.

Fig. 11 is a first charge and discharge curve of the battery in example 11.

Fig. 12 is a first charge and discharge curve of the battery of example 12.

Fig. 13 is a first charge and discharge curve of the battery in example 13.

Fig. 14 is a first charge and discharge curve of the battery of example 14.

Fig. 15 is a first charge and discharge curve of the battery in example 15.

Fig. 16 is a first charge and discharge curve of the battery of example 16.

Fig. 17 is a first charge-discharge curve of the battery in example 17.

Fig. 18 is a first charge-discharge curve of the battery in the comparative example.

Fig. 19 is an electron Scanning Electron Microscope (SEM) photograph of the hydride powder of example 17.

FIG. 20 is a graph showing the charge and discharge curves of the hydride powder of example 17 in the range of 1-3V operating voltage.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, belong to the scope of protection of the present invention.