阅读说明：本技术 一种隔膜的锂化处理方法及其处理后的隔膜材料 (Lithiation treatment method for diaphragm and its treated diaphragm material ) 是由 吴如森 于 2021-02-20 设计创作，主要内容包括：本发明属于锂离子电池隔膜制备技术领域,尤其涉及一种隔膜的锂化处理方法及其处理后的隔膜材料,所述隔膜的锂化处理方法包括以下步骤：步骤一：将隔膜通过适当的酸处理,然后用蒸馏水将隔膜清洗到中性,烘干；步骤二：将经过步骤一处理的隔膜,浸泡在中性可溶解锂盐溶液中,经过一定时间的高温浸煮；步骤三：将固化剂喷涂在隔膜上；步骤四：进行烘干。本发明提供一种利用隔膜的高比表面积,高孔隙率的特点,在隔膜中添加少量的锂盐,为锂电池的化成反应提供额外的锂离子的隔膜的锂化处理方法及其处理后的隔膜材料。(The invention belongs to the technical field of lithium ion battery diaphragm preparation, and particularly relates to a lithiation treatment method of a diaphragm and a diaphragm material treated by the lithiation treatment method, wherein the lithiation treatment method of the diaphragm comprises the following steps: the method comprises the following steps: treating the diaphragm with proper acid, then cleaning the diaphragm to be neutral by using distilled water, and drying; step two: soaking the diaphragm treated in the first step in a neutral soluble lithium salt solution, and soaking and boiling at a high temperature for a certain time; step three: spraying a curing agent on the diaphragm; step four: and (5) drying. The invention provides a lithiation treatment method of a diaphragm and a diaphragm material treated by the method, wherein a small amount of lithium salt is added into the diaphragm by utilizing the characteristics of high specific surface area and high porosity of the diaphragm to provide additional lithium ions for a formation reaction of a lithium battery.)

1. A method for lithiation treatment of a separator, characterized by: the lithiation treatment method for the separator includes the steps of:

the method comprises the following steps: treating the diaphragm with proper acid, then cleaning the diaphragm to be neutral by using distilled water, and drying;

step two: soaking the diaphragm treated in the first step in a neutral soluble lithium salt solution, and soaking and boiling at a high temperature for a certain time;

step three: spraying a curing agent on the diaphragm, and fixing soluble lithium salt on the surface and inside of the diaphragm by using the curing agent;

step four: and (5) drying.

2. The lithiation treatment method for a separator according to claim 1, characterized in that: in the first step, the acid is hydrochloric acid, nitric acid or sulfuric acid, or a mixture of two or three of the hydrochloric acid, the nitric acid and the sulfuric acid, and the concentration of the acid is 0.1-20 wt%.

3. The lithiation treatment method for a separator according to claim 1, characterized in that: the standard for cleaning to neutrality in the step one is that 1 part of the membrane after cleaning is soaked in 9 parts of distilled water, and the pH value is tested by using pH test paper or a pH meter and is shown to be 6-8.

4. The lithiation treatment method for a separator according to claim 1, characterized in that: and in the second step, the neutral soluble lithium salt is lithium sulfate, lithium nitrate or lithium dihydrogen phosphate, and the concentration of the neutral soluble lithium salt solution is 0.1-15 wt%.

5. The lithiation treatment method for a separator according to claim 1, characterized in that: the temperature of the high-temperature soaking and boiling in the second step is between 60 and 150 ℃, and the duration is 1 to 100 hours.

6. The lithiation treatment method for a separator according to claim 1, characterized in that: the curing agent in the third step is a silane coupling agent, and the concentration of the aqueous solution is 1-20 wt%; the coating is sprayed on a diaphragm by adopting a spraying or atomizing method, and the load capacity of the silane coupling agent on the diaphragm is 1-100 g/m²。

7. The lithiation treatment method for a separator according to claim 1, characterized in that: in the fourth step, the drying temperature is 50-100 ℃, the time is 12-48 h, and the drying environment is a vacuum environment of 0.001-0.05 MPa.

8. A separator material, characterized by: the separator material is obtained by processing the separator material according to any one of claims 1 to 7 by a lithiation treatment method.

Technical Field

The invention belongs to the technical field of preparation of lithium ion battery diaphragms, and particularly relates to a lithiation treatment method of a diaphragm and a diaphragm material treated by the lithiation treatment method.

Background

The prior art and the defects are as follows:

the lithium ion battery mainly comprises the following components: a positive electrode, a negative electrode, an electrolyte and a separator. The performance of the separator may affect the electrical and safety performance of the battery. The main function is to separate the anode and the cathode to prevent short circuit, and the unique microporous structure can allow lithium ions to pass through, thereby influencing the electrochemical performance of the battery to a certain extent. There are three common separator materials currently on the market: single layer polypropylene, single layer polyethylene, three layers polypropylene or polyethylene composite membrane. These battery separators can be classified into dry and wet types according to the manufacturing process, and the biggest difference between the dry and wet types is that the principle of internal pore forming is different.

The lithium ion battery is a secondary battery system which takes a lithium intercalation compound capable of reversibly intercalating and deintercalating lithium ions as the positive and negative electrodes of the battery from the working principle. Lithium ion batteries, like other batteries, store and release energy through redox reactions of electrode materials, but utilize the directional movement of lithium ions under the action of an electric field to complete charge transfer inside the lithium ion battery. Generally, the anode material is a layered transition metal oxide, the cathode is graphite, and the electrochemical reaction generated in the charge and discharge process is as follows:

and (3) cathode reaction: li_xC→xLi⁺+xe^-+C

And (3) positive pole reaction: MO (metal oxide semiconductor)₂+xLi⁺+xe^-→Li_xMO₂

And (3) total reaction: li_xC+MO₂＝C+Li_xMO₂

During charging, lithium ions and electrons are extracted from the layered transition metal oxide lattice, generating an electron hole and a lithium hole. The generated lithium ions reach the negative electrode through the separator via the electrolyte solution, and are inserted into the graphite layer. At the same time, the electrons reach the negative electrode through an external circuit to combine with lithium ions. During charge and discharge, lithium ions are repeatedly inserted and extracted between the positive electrode and the negative electrode.

The battery system uses graphite as a negative electrode, and a Solid Electrolyte Interface (SEI) film formed on the surface of the graphite negative electrode is unstable, so that the movable Li + of the battery is continuously lost in the circulation process, and the battery capacity is attenuated. Therefore, how to improve the stability of the SEI film and increase the mobile lithium ions in the battery is an urgent problem to be solved for improving the cycle life of the battery. CN112072186A discloses a method for improving the wettability and the stability of an SEI film of a soft package battery, which is characterized in that before vacuum liquid injection of a battery core, at least two pre-sealing treatments are performed at the junction of a winding core and an air bag to obtain a first pre-sealing area, then the vacuum liquid injection is performed, the air bag is sealed at the opening of the air bag, and the battery core is obtained through formation, air extraction, heat sealing and cutting. CN110034336A discloses a battery formation method for forming a stable SEI film. Characterized in that the method comprises the following steps: (1) applying voltage on an electrode of a battery to be formed to perform linear scanning to obtain a battery with a pre-constructed SEI film; (2) carrying out SEI film reforming on the battery with the pre-constructed SEI film in the step (1) to obtain a battery with a reformed SEI film; (3) and (3) applying voltage to the electrode of the battery with the reformed SEI film in the step (2) for linear scanning to obtain the battery after formation.

In recent years, more and more researchers have looked at separator materials. Since 2007, the related separator patent applications have also grown rapidly, with the rapid development of lithium batteries in electric drive applications. For example, CN105246692B discloses a polyolefin multilayer microporous membrane material. It has oxidation resistance, excellent electrolyte injectability and shutdown properties, and further excellent permeability and strength balance. CN101511588B discloses a multilayer microporous membrane. It has well-balanced closure properties, melt properties, permeability and pin puncture strength.

The reference is merely illustrative of the structural changes of the battery separator and does not mention the technique of making a lithiated separator, i.e., functionalization.

The difficulty and significance for solving the technical problems are as follows:

therefore, based on the problem of low first charge-discharge efficiency of the lithium ion battery, the lithiation treatment method of the diaphragm and the diaphragm material after treatment have important practical significance by adding a small amount of lithium salt in the diaphragm and providing additional lithium ions for the formation reaction of the lithium battery by utilizing the characteristics of high specific surface area and high porosity of the diaphragm.

Disclosure of Invention

The invention aims to provide a lithiation treatment method of a diaphragm and a diaphragm material treated by the method, which utilizes the characteristics of high specific surface area and high porosity of the diaphragm and adds a small amount of lithium salt into the diaphragm to provide additional lithium ions for the formation reaction of a lithium battery.

The technical scheme adopted by the invention for solving the technical problems in the prior art is as follows:

a lithiation treatment method for a separator, comprising the steps of:

the method comprises the following steps: treating the diaphragm with proper acid, then cleaning the diaphragm to be neutral by using distilled water, and drying;

soluble impurities attached to the diaphragm are removed, and meanwhile, activation points are formed on the surface of the diaphragm material, so that the subsequent electrochemical application of the diaphragm is facilitated.

Step two: soaking the diaphragm treated in the first step in a neutral soluble lithium salt solution, and soaking and boiling at a high temperature for a certain time;

the advantage of the digestion is that the micropores of the separator can sufficiently absorb lithium ions. And (4) steaming at high temperature to enable lithium ions to be fully immersed into the surface pores and the space structure of the diaphragm and to be attached to the inside of the diaphragm. In the subsequent charge-discharge reaction process of the lithium ion battery, an additional lithium source can be provided under the electrolyte and the hydrofluoric acid environment generated in the electrolyte in a trace amount.

Step three: spraying a curing agent on the diaphragm, and fixing soluble lithium salt on the surface and inside of the diaphragm by using the curing agent;

step four: and (5) drying.

The invention can also adopt the following technical scheme:

in the lithiation treatment method of the separator, further, in the step one, the acid is hydrochloric acid, nitric acid or sulfuric acid, or a mixture of two or three of the hydrochloric acid, the nitric acid and the sulfuric acid, and the concentration of the acid is 0.1-20 wt%.

In the lithiation treatment method of the separator, further, the standard for washing to neutrality in the step one is that 1 part of the washed separator is soaked in 9 parts of distilled water and tested by using a pH test paper or a pH meter, and the pH value is 6-8.

In the lithiation treatment method of the separator, the neutral soluble lithium salt in the second step is lithium sulfate, lithium nitrate or lithium dihydrogen phosphate, and the concentration of the neutral soluble lithium salt solution is 0.1-15 wt%.

In the lithiation treatment method of the separator, further, the temperature of the high-temperature digestion in the second step is between 60 and 150 ℃ and the duration is 1 to 100 hours.

In the lithiation treatment method of the diaphragm, further, the curing agent in the third step is a silane coupling agent, and the concentration of the aqueous solution of the silane coupling agent is 1-20 wt%; the coating is sprayed on a diaphragm by adopting a spraying or atomizing method, and the load capacity of the silane coupling agent on the diaphragm is 1-100 g/m²。

In the lithiation treatment method of the diaphragm, further, in the fourth step, the drying temperature is 50-100 ℃, the time is 12-48 hours, and the drying environment is a vacuum environment of 0.001-0.05 MPa.

A separator material obtained by subjecting the separator material to lithiation treatment in any one of the above-described separator processes.

In conclusion, the invention has the following advantages and positive effects:

1. the invention utilizes the characteristics of high specific surface area and high porosity of the diaphragm, adds a small amount of lithium salt into the diaphragm to realize lithium pre-storage, provides lithium salt for formation reaction of the lithium battery, solves the problem of low first charge-discharge efficiency of the lithium battery, realizes that the diaphragm is used as a lithium supplement carrier, and realizes that structural components of the diaphragm are converted into functional components.

Drawings

Fig. 1 is an electron microscope photograph of a separator having a microporous lithium storage structure on the surface thereof treated in the first example.

Detailed Description

Example 1

A lithiation treatment method of a separator comprises the following steps:

the separator was first soaked with 0.1% by weight of dilute hydrochloric acid and then washed with distilled water until the pH test paper showed 6 (measurement standard: 1 part of separator and 9 parts of distilled water were soaked for 10 minutes and then measured). Taking out and drying, soaking in 0.1 wt% lithium sulfate solution, heating to 60 deg.C, and maintaining for 100 hr. Taking out and drying. Using 1 percent by weight of silane coupling agent, spraying the silane coupling agent on the diaphragm, and controlling the loading amount of the silane coupling agent on the diaphragmIs 1g/m². Taking out the diaphragm, and drying at 50 deg.C under 0.05MPa for 48 hr.

The diaphragm material treated by the method can greatly improve the first charge-discharge efficiency of the lithium ion battery. For example, the 18650 lithium iron phosphate battery made into 1800mAh specification can improve the first charge-discharge efficiency of the battery from 89% to 91%.

As can be seen from the attached figure 1 in the specification, the fibers of the diaphragm are about 100nm in diameter, the surface of the diaphragm is provided with a large number of tiny holes formed by the process, and the holes have large actual surface area. The micro holes can form lithium storage sites, and a continuous lithium source is provided for subsequent lithium battery reactions.

Example 2

A lithiation treatment method of a separator comprises the following steps:

the separator was first soaked with 20% by weight of nitric acid and then washed with distilled water until the pH paper showed 8 (measurement standard: 1 part separator and 9 parts distilled water were soaked for 10 minutes and then measured). Taking out, drying, soaking in 15 wt% lithium dihydrogen phosphate solution, sealing, heating to 150 deg.C (water boiling above 100 deg.C, and sealing at treatment temperature above 100 deg.C), and maintaining for 1 hr. Taking out and drying. Using 20 percent of silane coupling agent by weight, spraying the silane coupling agent on the membrane, and controlling the loading capacity of the silane coupling agent on the membrane to be 100g/m². Taking out the diaphragm, and drying at about 100 deg.C under 0.001MPa for 12 hr.

The diaphragm material treated by the method can greatly improve the first charge-discharge efficiency of the lithium ion battery. For example, the lithium ion battery is made into a ternary soft package battery with the specification of 5Ah, and the first charge-discharge efficiency of the lithium ion battery can be improved from 87% to 93%.

Example 3

A lithiation treatment method of a separator comprises the following steps:

the separator was first soaked with 10% by weight of sulfuric acid and then washed with distilled water until the pH paper showed 7 (measurement standard: 1 part separator and 9 parts distilled water were soaked for 10 minutes and then measured). Taking out and drying the mixture, and then soaking the mixture in 5 weight percent% of the solution of lithium nitrate is heated to 100 ℃ and kept for 2 h. Taking out and drying. Using 8 percent of silane coupling agent by weight, evenly spraying the silane coupling agent on the diaphragm, and controlling the load capacity of the silane coupling agent on the diaphragm to be 20g/m². Taking out the diaphragm, vacuum-drying at about 80 deg.C under 0.01MPa for 48 hr.

The diaphragm material treated by the method greatly improves the first charge-discharge efficiency of the lithium ion battery. For example, the 811-system ternary aluminum shell battery with the 10Ah specification can improve the first charge-discharge efficiency of the lithium ion battery from 84% to 89%.

Example 4

The comparative effect of the lithiation treatment method of the separator comprises the following steps:

the membrane was first soaked with a solution of 8% by weight of hydrochloric acid + sulfuric acid (sulfuric acid to hydrochloric acid weight ratio of 1:1), and then washed with distilled water until a pH indicator paper showed 6.5 (measurement standard: 1 part membrane was soaked with 9 parts distilled water for 10 minutes). Taking out and drying, and taking two samples, wherein A is: soaking the material in 7 wt% lithium nitrate solution, heating to 100 deg.c and maintaining for 2 hr. Wherein B is: only soaking in distilled water, heating to 100 deg.C, and holding for 2 hr. Then taking out and drying. Using 10 percent by weight of silane coupling agent, uniformly spraying the silane coupling agent on the diaphragm, and controlling the load of the silane coupling agent on the diaphragm to be 50g/m². Taking out the diaphragm, and drying at about 100 deg.C under 0.001MPa for 24 hr.

The two diaphragm materials processed by the method are respectively manufactured into a soft package 811 ternary system battery with the capacity of 63 Ah. The first charge-discharge efficiency of the lithium ion battery is 88.5% by using the product of the A diaphragm, and lithium ions with the same specification are manufactured by using the B diaphragm. The first charge-discharge efficiency was only 83.7%. The process provided by the invention is proved to have superiority.

In summary, the present invention provides a lithiation treatment method for a separator, which utilizes the characteristics of the separator such as high specific surface area and high porosity to add a small amount of lithium salt in the separator to provide additional lithium ions for the formation reaction of a lithium battery, and a treated separator material.

The present invention has been described in detail with reference to the above examples, but the description is only for the preferred examples of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.