Capsule, method for its preparation and use

Abstract

The application discloses a capsule, a preparation method and application thereof, and comprises silica and foamed microspheres, wherein the silica is coated on the surface of the foamed microspheres. The capsule provided by the application is added into an electrolyte, in the case of high temperature, the capsule is broken, the foamed microspheres absorb the electrolyte, and the silica blocks the internal circuit, so that the battery combustion and explosion are prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to a capsule and a preparation method and application, and belongs to the field of lithium battery thermal safety protection. BACKGROUND

[0002] Lithium batteries are widely used in the fields of automobile power, communication base station and industry due to their moderate price, high specific capacity and long cycle life. Lithium battery fire is an endogenous fire. When the lithium battery is out of control, the temperature rises continuously, the electrolyte decomposes to generate a large amount of flammable gas, and then a chain explosion is triggered. The existing technology generally uses external addition of PTC elements to limit current or internal addition of electrolyte to add flame retardants. These methods all belong to passive protection strategies, and cannot interrupt the thermal runaway reaction when the chain thermal runaway reaction occurs, so as to prevent the occurrence of combustion and explosion. SUMMARY

[0003] In order to solve the above problems, the present application provides a silica-coated foamed microsphere capsule which is added to the electrolyte. In the case of high temperature, the capsule breaks and the foamed microspheres absorb the electrolyte, and the silica blocks the internal circuit to prevent the battery from burning and exploding.

[0004] According to one aspect of the present application, a capsule is provided, comprising silica and foamed microspheres, wherein the silica is coated on the surface of the foamed microspheres.

[0005] Optionally, the mass ratio of the silica to the foamed microspheres is 1:(0.2-1).

[0006] Optionally, the mass ratio of the silica to the foamed microspheres is selected from any value or a range value between two values in 1:0.2, 1:0.4, 1:0.6, 1:0.8 and 1:1.

[0007] Optionally, the diameter of the foamed microspheres is 2-10 μm.

[0008] According to another aspect of the present application, a preparation method of a capsule is provided, comprising the following steps:

[0009] a dissolving foamed microspheres, cetyltrimethylammonium bromide and tetraethyl orthosilicate in an alcohol solvent, stirring to obtain a mixed solution;

[0010] b passing ammonia water into the mixed solution prepared in step a, reacting, filtering and drying to obtain foamed microsphere capsules coated with silica.

[0011] Optionally, the mass ratio of the foamed microspheres to cetyltrimethylammonium bromide is 1:(0.375-2.7).

[0012] Optionally, the mass ratio of the foamed microspheres to cetyltrimethylammonium bromide is selected from any value or a range value between two values in the group consisting of 1:0.375, 1:1, 1:1.5, 1:2, 1:2.7.

[0013] Optionally, the mass of the foamed microspheres to the volume of tetraethyl orthosilicate is (3-8)g:(5-15)mL.

[0014] Optionally, the mass of the foamed microspheres to the volume of tetraethyl orthosilicate is selected from any ratio or a range value between two ratios in the group consisting of 3g:5mL, 4g:6mL, 5g:8mL, 6g:10mL, 8g:15mL.

[0015] Optionally, the volume ratio of the ammonia water to the tetraethyl orthosilicate is (2-5):(5-15).

[0016] Optionally, the volume ratio of the ammonia water to the tetraethyl orthosilicate is selected from any ratio or a range value between two ratios in the group consisting of 2:5, 3.5:8, 4:9, 5:15.

[0017] Optionally, the concentration of the ammonia water is 14-28%.

[0018] Optionally, the concentration of the ammonia water is selected from any value or a range value between two values in the group consisting of 14%, 18%, 22%, 27%, 28%.

[0019] Optionally, the alcohol solvent comprises water and ethanol, and the volume ratio of the water to the ethanol is 1:0.3-3.

[0020] Optionally, the reaction condition is that the temperature is 25-40℃ and the time is 2-5h.

[0021] Optionally, the temperature of the reaction is selected from any value or a range value between two values in the group consisting of 25℃, 30℃, 35℃, 40℃.

[0022] Optionally, the time of the reaction is selected from any value or a range value between two values in the group consisting of 2h, 3h, 4h, 5h.

[0023] Optionally, the temperature of the drying is 50-60℃.

[0024] Optionally, the temperature of the drying is selected from any value or a range value between two values in the group consisting of 50℃, 52℃, 54℃, 56℃, 60℃.

[0025] Optionally, the flow rate of the ammonia water is 0.2-0.5mL / min.

[0026] Optionally, the specific steps of step a are:

[0027] a-1 water and ethanol are mixed into solution A;

[0028] a-2 Dissolve the foamed microspheres and cetyltrimethylammonium bromide in solution A, and mark it as solution B;

[0029] a-3 Dissolve the tetraethyl orthosilicate in solution B, and mark it as solution C.

[0030] According to still another aspect of the present application, there is provided an electrolyte solution comprising LiPF6, vinyl carbonate, dimethyl carbonate and capsules, wherein the capsules are selected from the capsules described above or prepared according to the method described above.

[0031] Optionally, the volume ratio of the vinyl carbonate to the dimethyl carbonate is 1:(1-2).

[0032] Optionally, the volume ratio of the vinyl carbonate to the dimethyl carbonate is selected from any value or a range value between two values in 1:1, 1:1.25, 1:1.5, 1:1.75, 1:2.

[0033] Optionally, the concentration of LiPF6 in the electrolyte solution is 1-2 mol / L.

[0034] Optionally, the concentration of LiPF6 in the electrolyte solution is selected from any value or a range value between two values in 1 mol / L, 1.25 mol / L, 1.5 mol / L, 1.75 mol / L, 2.0 mol / L.

[0035] Optionally, the capsules account for 10-30% of the mass of the electrolyte solution.

[0036] As a specific application, the electrolyte solution described above is applied in battery assembly, to assemble an aluminum-plastic film soft-pack battery with NCM622 as the positive electrode, graphite as the negative electrode, a PP-PE composite separator and the electrolyte solution described above as the electrolyte solution.

[0037] The beneficial effects that can be produced by the present application include:

[0038] The capsules provided by the present application are applied to block the battery circuit under overheating conditions, and under high temperature, the capsules rupture to release the foamed microspheres to absorb the electrolyte, and the silicon dioxide blocks the internal circuit, to achieve the effect of active protection. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a scanning electron microscope image of the silicon dioxide coated foamed microspheres in Example 1 of the present application;

[0040] Figure 2 It is a micrograph of the silicon dioxide coated foamed microspheres in Example 1 of the present application;

[0041] Figure 3 It is the thermal failure test data of Example 1 and the comparative example of the present application;

[0042] Figure 4 To compare the state of the foamed microspheres of the present application at room temperature and at 120°C. DETAILED DESCRIPTION

[0043] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

[0044] The raw materials in the examples of the present application are all purchased through commercial channels unless otherwise specified.

[0045] The analysis method in the examples of the present application is as follows:

[0046] The scanning electron microscope graph of the capsule of the silica-coated foamed microspheres is obtained by using a field emission scanning electron microscope (device);

[0047] The assembled aluminum-plastic film soft-pack battery is placed in a high-temperature explosion-proof box for thermal failure experiment.

[0048] Since the separator will melt at about 120°C, causing the positive and negative electrodes to come into contact and short circuit, thereby generating a large amount of heat, the temperature of the high-temperature explosion-proof box is increased to 120°C at a temperature increasing rate of 30°C / min, and the battery temperature change is recorded by a temperature sensor.

[0049] Example 1

[0050] (1) Coating of foamed microspheres: 500 ml of a mixture of deionized water and ethanol in a volume ratio of 2:1 is prepared and is referred to as solution A; 5 g of foamed microspheres with a diameter of 2-10 μm and 5 g of cetyltrimethylammonium bromide are weighed and added to solution A, and are thoroughly stirred to obtain solution B; 8 ml of tetraethyl orthosilicate is added to solution B, and is thoroughly stirred to obtain solution C; 3.5 ml of 27% ammonia water is slowly introduced into solution C through a peristaltic pump over a period of 1 h, and is thoroughly stirred and reacted, and is filtered, washed, and dried at 50°C to constant weight to obtain silica-coated foamed microsphere capsules. The foamed microspheres and the silica-coated foamed microsphere capsules are shown in Figure 1 and Figure 2 , wherein Figure 2 the A graph of Figure 2 the B graph of Figure 1 and Figure 2 , it can be seen that the foamed microspheres are coated with a layer of silica protective layer.

[0051] (2) Preparation of electrolyte and assembly of battery: 15 wt% of the silica-coated foamed microsphere capsules are added to LiPF6 / EC+DMC to prepare electrolyte 1; NCM622 is used as the positive electrode, graphite is used as the negative electrode, a PP-PE composite separator is used, and electrolyte 1 is used as the electrolyte to assemble an aluminum-plastic film soft-pack battery 1.

[0052] (3) Battery thermal runaway test: The soft pack battery 1 was placed in a high temperature explosion-proof box and heated to 120°C at a rate of 30°C / min. The temperature change of the battery was recorded by a temperature sensor.

[0053] Comparative Example 1

[0054] (1) Battery assembly: Using NCM622 as the positive electrode, graphite as the negative electrode, PP-PE composite separator, and LiPF6 / EC+DMC as the electrolyte, an aluminum-plastic film soft pack battery is assembled.

[0055] (2) Battery thermal runaway test: The soft pack battery was placed in a high temperature explosion-proof box and heated to 120°C at a rate of 30°C / min. The temperature change of the battery was recorded by a temperature sensor.

[0056] pass Figure 3 It can be seen that when the temperature rises to 120℃, the temperature of both Example 1 and the control group increases accordingly due to the side reactions inside the battery. The difference is that, because the control group cannot effectively suppress the chain of exothermic reactions inside the battery under high temperature conditions, the internal temperature of the battery rises sharply at around 180℃, leading to thermal runaway. Conversely, in Example 1, due to the addition of silica-coated foamed microsphere capsules, the foamed microspheres expand and rupture at 120℃, causing them to absorb electrolyte and thus blocking the internal circuitry of the battery.

[0057] pass Figure 4 It is known that at 120℃, the foamed microspheres will expand to a certain extent. This is beneficial when the battery overheats, as the foamed microspheres expand and break through the silicon dioxide coating layer, thereby achieving circuit blocking inside the battery.

[0058] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An electrolyte, characterized by, The electrolyte comprises LiPF6, vinyl carbonate, dimethyl carbonate and capsules, wherein the capsules comprise silica and foamed microspheres, and the silica is coated on the surface of the foamed microspheres. The mass ratio of the silica to the foamed microspheres is 1:(0.2-1). The diameter of the foamed microspheres is 2-10 μm.

2. The electrolyte according to claim 1, characterized in that, The preparation method of the capsules comprises the following steps: a dissolving foamed microspheres, cetyltrimethylammonium bromide and tetraethyl orthosilicate in an alcohol solvent, stirring to obtain a mixed solution; b introducing ammonia water into the mixed solution prepared in step a, reacting, filtering and drying to obtain the foamed microsphere capsules coated with silica.

3. The electrolyte according to claim 2, characterized in that, The mass ratio of the foamed microspheres to cetyltrimethylammonium bromide is 1:(0.375-2.7).

4. The electrolyte of claim 2, wherein, The mass of the foamed microspheres to the volume of tetraethyl orthosilicate is (3-8) g:(5-15) mL.

5. The electrolyte of claim 2, wherein The volume ratio of the ammonia water to the tetraethyl orthosilicate is (2-5):(5-15).

6. The electrolyte of claim 2, wherein, The concentration of the ammonia water is 14-28%.

7. The electrolyte of claim 2, wherein The alcohol solvent comprises water and ethanol, and the volume ratio of the water to the ethanol is 1:0.3-3.

8. The electrolyte of claim 2, wherein, The reaction conditions are as follows: temperature 25-40℃, time 2-5 h.

9. The electrolyte of claim 2, wherein, The drying temperature is 50-60℃.

10. The electrolyte of claim 2, wherein, The introduction rate of the ammonia water is 0.2-0.5 mL / min.

11. The electrolyte of claim 2, wherein, The specific steps of step a are as follows: a-1 preparing solution A by mixing water and ethanol; a-2 dissolving foamed microspheres and cetyltrimethylammonium bromide in solution A, denoted as solution B; a-3 dissolving tetraethyl orthosilicate in solution B, denoted as solution C.

12. The electrolyte of claim 1, wherein, The volume ratio of the vinyl carbonate to the dimethyl carbonate is 1:(1-2).

13. The electrolyte of claim 1, wherein, The concentration of LiPF6 in the electrolyte is 1-2 mol / L.

14. The electrolyte of claim 1, wherein, The capsules account for 10-30% of the mass of the electrolyte.

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