Microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a microcapsule, which is suitable for an ion battery and comprises an outer-layer wall material and a supplementary core material wrapped in the outer-layer wall material, in terms of 100% of the mass of the microcapsule, the content of the outer layer wall material is 10%-30%, and the content of the supplementary core material is 70%-90%; the outer-layer wall material is a polystyrene wall material; the supplement core material comprises the following components in percentage by mass: 1-3% of a positive electrode supplement and 97-99% of a metal salt electrolyte. The invention also provides a preparation method and application of the microcapsule. The outer layer wall material is made of the polystyrene material, the supplementary core material is used as the inner layer to prepare the microcapsule, and the prepared microcapsule has an extremely thin film, so that the energy density of the battery is not influenced while the loss of a solvent and active metal ions in the cycle process of the ion battery is effectively supplemented, and the service life of the battery is prolonged. And the cycle performance and the capacity of the ion battery can be effectively improved. The preparation method disclosed by the invention is simple and has higher adaptability to large-batch production.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a microcapsule and a preparation method and application thereof. Background Art

[0002] With the rapid development of lithium-ion energy storage batteries, market competition is becoming increasingly fierce, and the requirements for the battery life of lithium-ion batteries are becoming higher and higher. The cycle performance of lithium-ion batteries is a key indicator to measure their lifespan. It refers to the number of charge and discharge cycles that the battery can withstand before its capacity drops significantly. At present, energy storage lithium batteries are usually required to withstand tens of thousands of weeks of charge and discharge cycles.

[0003] The cycle performance of lithium-ion batteries is mainly determined by the positive and negative active materials and the electrolyte, among which the electrolyte plays an important role in conducting lithium ions. When the battery is charged for the first time, the electrolyte will react with the surface of the negative electrode, consuming part of the solvent and active lithium ions in the electrolyte to form a solid electrolyte interface film (SEI), which maintains electronic insulation while allowing lithium ions to pass quickly. However, during the charge and discharge process, the expansion change of the negative electrode volume will expose the new negative electrode surface, and the SEI film will continue to form and thicken, resulting in the loss of active lithium ions and the continuous loss or even drying of the electrolyte, causing the battery polarization to increase and the cycle performance to continue to decline.

[0004] By improving the mechanical properties, chemical and thermal stability, electronic resistance, ionic conductivity and thickness of the SEI film, the loss of electrolyte and active lithium ions caused by the continuous repair of the negative electrode SEI film during the cycle can be reduced. At present, the existing technology generally improves the relevant properties of the SEI film by adding film-forming additives (such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (DTD), tris(trimethylsilyl) phosphite (TMSP), etc.) to conventional electrolytes. However, the use of film-forming additives also has some disadvantages, such as the need to limit the amount of initial additives added. Too much addition will cause a series of problems such as increased electrolyte viscosity, increased acidity, and reduced conductivity.

[0005] Patent application CN113097424A discloses a battery cell housing and a self-puncturing side lithium replenishing battery cell. This lithium replenishing device is relatively complex, takes a long time to make, is costly, and is difficult to popularize. Patent application CN114695883A discloses a lithium-ion battery electrolyte replenishing capsule, which can replenish the lithium-ion battery under non-destructive conditions. However, its use method is complicated and requires heating the battery capsule to work, which can easily damage the battery. Summary of the invention

[0006] The purpose of the present invention is to provide a microcapsule and a preparation method and application thereof, so as to solve the technical problems that the existing lithium (sodium) ion batteries are prone to loss of active lithium (sodium) ions and continuous loss or even drying of electrolyte during the charge and discharge process, which causes increased battery polarization and continuous decline in cycle performance.

[0007] To achieve the above-mentioned purpose, on the one hand, an embodiment of the present invention provides a microcapsule suitable for an ion battery, comprising an outer wall material and a supplementary core material wrapped in the outer wall material; based on the mass of the microcapsule being 100%, the outer wall material is 10% to 30%, and the supplementary core material is 70% to 90%; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components in mass percentage: 1% to 3% positive electrode supplement and 97% to 99% metal salt electrolyte.

[0008] As a preferred embodiment, the outer wall material is prepared by the following method: 95% to 98% polystyrene, 1% to 3% initiator and 1% to 2% dispersant are uniformly mixed to obtain the outer wall material; the percentages are all mass percentages.

[0009] The polystyrene is prepared from styrene monomers through polymerization reaction; the molecular weight of the polystyrene is preferably 100,000 to 250,000.

[0010] The initiator is preferably benzoyl peroxide (BPO).

[0011] The dispersant is preferably gelatin or polyvinyl alcohol.

[0012] As a preferred embodiment, when the ion battery is a lithium ion battery, the positive electrode supplement is one of lithium-rich nickel oxide (LNO), lithium-rich lithium iron oxide (LFO) or lithium-rich nickel oxide (LNO) or a mixture of at least two thereof.

[0013] As a preferred embodiment, when the ion battery is a lithium ion battery, the metal salt electrolyte is a mixed solution of an ester solvent and a lithium salt Li PF6.

[0014] As a preferred embodiment, when the ion battery is a sodium ion battery, the positive electrode supplement is one or a mixture of at least two of the positive electrode sodium supplements sodium sulfate (Na2S), sodium oxide (Na2O), sodium citrate (Na3C6H5O7), sodium oxalate (Na2C6O6) and sodium carbonate (Na2CO3).

[0015] As a preferred embodiment, when the ion battery is a sodium ion battery, the metal salt electrolyte is a mixed solution of an ester solvent and a sodium salt NaPF6.

[0016] As a preferred embodiment, the supplementary core material is prepared by the following method: 1% to 3% of the positive electrode supplement and 97% to 99% of the metal salt electrolyte are stirred evenly to obtain the supplementary core material; the percentages are mass percentages.

[0017] On the other hand, an embodiment of the present invention also provides a method for preparing the microcapsules, comprising the following steps: stirring 10% to 30% of the outer wall material in a constant temperature water bath at 65°C to 75°C for 4h to 5h to obtain a wall material mixed liquid, adding 70% to 90% of the core material (mixed evenly at room temperature) to the wall material mixed liquid, cooling the temperature to 30°C to 50°C and continuing the suspension polymerization reaction for 1h to 2h to obtain a reaction mixture; cooling the reaction mixture to room temperature and then filtering, taking the filter residue, washing it and vacuum drying it at 30°C to 50°C for 3h to 4h to obtain microcapsules.

[0018] The cleaning is performed by washing with anhydrous ethanol 2 to 5 times.

[0019] By controlling the conditions of the suspension polymerization reaction, the brittleness of the outer wall material can be effectively adjusted and the sensitivity of the outer wall material to pressure can be increased. In the later stage of the battery cycle, when the battery swells and the internal pressure increases, the microcapsules gradually rupture, releasing the lithium supplement and electrolyte, thereby solving the problem of decreased battery cycle performance. If the reaction temperature is too low, the polymerization reaction will be slow and the wall material will be incomplete; if the reaction temperature is too high, the electrolyte will fail.

[0020] On the other hand, the embodiments of the present invention also provide applications of the microcapsules, and the microcapsules can be applied to lithium-ion batteries or sodium-ion batteries.

[0021] As a preferred embodiment, the lithium-ion battery is an energy storage lithium battery or a ternary power lithium battery.

[0022] The technical solution proposed in the present invention has the following beneficial effects: the present application uses polystyrene material as the outer wall material and a supplementary core material as the inner layer to prepare microcapsules. The prepared microcapsules have extremely thin films. While effectively supplementing the loss of solvents and active metal ions in the ion battery during the cycle, it does not affect the energy density of the battery, and can effectively improve the cyclic performance and capacity of the ion battery. The prepared microcapsules are sensitive to pressure. In the later stage of the battery cycle, when the battery swells and causes the internal pressure to increase, the microcapsules gradually rupture, releasing the lithium supplement and electrolyte, solving the problem of decreased battery cycle performance, and making the battery have a longer service life, which can meet the demand for long-life batteries in the energy storage market. The microcapsules of the present application are small in size, have little effect on the energy density of the battery cell, and have a simple preparation method, a long shelf life, stronger adaptability to mass production, and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a graph showing the cycle performance test results of a lithium ion battery prepared using the microcapsules of Example 1 of the present invention and a lithium ion battery of Comparative Example 1. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, top, bottom...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0026] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0028] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] Example 1

[0030] A microcapsule, suitable for an ion battery, comprises an outer wall material and a supplementary core material wrapped in the outer wall material; based on the mass of the microcapsule being 100%, the outer wall material is 10%, and the supplementary core material is 90%; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components in mass percentage: 1% positive electrode supplement and 99% metal salt electrolyte.

[0031] The outer wall material is prepared by the following method: 95% polystyrene, 3% initiator and 2% dispersant are uniformly mixed to obtain the outer wall material; the percentages are all mass percentages.

[0032] The polystyrene is prepared from styrene monomers through polymerization reaction; the molecular weight of the polystyrene is 100,000.

[0033] The initiator is benzoyl peroxide. The dispersant is gelatin.

[0034] The ion battery is a lithium ion battery, the positive electrode supplement is lithium-rich nickel acid. The metal salt electrolyte is a mixed solution of an ester solvent and a lithium salt LiPF6. In the embodiment of the present application, the metal salt electrolyte can be a general lithium ion battery electrolyte.

[0035] The supplementary core material is prepared by the following method: 1% positive electrode supplement and 99% metal salt electrolyte are stirred evenly to obtain the supplementary core material; the percentage is mass percentage.

[0036] The preparation method of the microcapsule comprises the following steps: stirring 10% of the outer wall material in a constant temperature water bath at 70°C for 4 hours to obtain a wall material mixed liquid, adding 90% of the core material (mixed uniformly at room temperature) to the wall material mixed liquid, cooling to 30°C and continuing suspension polymerization reaction for 1 hour to obtain a reaction mixture; cooling the reaction mixture to room temperature and filtering it, taking the filter residue, washing it and vacuum drying it at 30°C for 3 hours to obtain microcapsules.

[0037] The cleaning was performed by washing with anhydrous ethanol twice.

[0038] The microcapsules of the present application are applied to lithium-ion batteries (energy storage lithium batteries), and the performance test of the lithium-ion batteries is carried out on the number of cycles. The test results are as follows: Figure 1 As shown (i.e. Figure 1 Scheme A in Figure 1 It can be seen that the lithium-ion battery using the microcapsule of the present application has better cycle performance.

[0039] Example 2

[0040] A microcapsule, suitable for an ion battery, comprises an outer wall material and a supplementary core material wrapped in the outer wall material; based on the mass of the microcapsule being 100%, the outer wall material accounts for 20% and the supplementary core material accounts for 80%; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components in mass percentage: 2% positive electrode supplement and 98% metal salt electrolyte.

[0041] The outer wall material is prepared by the following method: 97% polystyrene, 2% initiator and 1% dispersant are uniformly mixed to obtain the outer wall material; the percentages are all mass percentages.

[0042] The polystyrene is prepared from styrene monomers through polymerization reaction; the molecular weight of the polystyrene is 150,000.

[0043] The initiator is benzoyl peroxide. The dispersant is polyvinyl alcohol.

[0044] The ion battery is a lithium ion battery, the positive electrode supplement is lithium-rich lithium ferrate; and the metal salt electrolyte is a mixed solution of an ester solvent and a lithium salt Li PF6.

[0045] The supplementary core material is prepared by the following method: 2% positive electrode supplement and 98% metal salt electrolyte are stirred evenly to obtain the supplementary core material; the percentage is mass percentage.

[0046] The preparation method of the microcapsule comprises the following steps: stirring 20% ​​of the outer wall material in a constant temperature water bath at 65°C for 5 hours to obtain a wall material mixed liquid, adding 80% of the core material (mixed uniformly at room temperature) to the wall material mixed liquid, cooling to 40°C and continuing suspension polymerization for 1.5 hours to obtain a reaction mixture; cooling the reaction mixture to room temperature and filtering it, taking the filter residue, washing it and vacuum drying it at 40°C for 4 hours to obtain microcapsules.

[0047] The cleaning was performed by washing with anhydrous ethanol three times.

[0048] Example 3

[0049] A microcapsule, suitable for an ion battery, comprises an outer wall material and a supplementary core material wrapped in the outer wall material; based on the mass of the microcapsule being 100%, the outer wall material accounts for 30% and the supplementary core material accounts for 70%; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components in mass percentage: 3% positive electrode supplement and 97% metal salt electrolyte.

[0050] The outer wall material is prepared by the following method: 98% polystyrene, 1% initiator and 1% dispersant are uniformly mixed to obtain the outer wall material; the percentages are all mass percentages.

[0051] The polystyrene is prepared from styrene monomers through polymerization reaction; the molecular weight of the polystyrene is 250,000.

[0052] The initiator is benzoyl peroxide. The dispersant is polyvinyl alcohol.

[0053] The ion battery is a sodium ion battery, the positive electrode supplement is a positive electrode sodium supplement sodium sulfate; the metal salt electrolyte is a mixed solution of an ester solvent and a sodium salt NaPF6. In the embodiment of the present application, the metal salt electrolyte can be a general sodium ion battery electrolyte.

[0054] The supplementary core material is prepared by the following method: 3% positive electrode supplement and 97% metal salt electrolyte are stirred evenly to obtain the supplementary core material; the percentage is mass percentage.

[0055] The preparation method of the microcapsule comprises the following steps: stirring 30% of the outer wall material in a constant temperature water bath at 75°C for 4.5 hours to obtain a wall material mixed liquid, adding 70% of the core material (mixed uniformly at room temperature) to the wall material mixed liquid, cooling to 50°C and continuing suspension polymerization for 2 hours to obtain a reaction mixture; cooling the reaction mixture to room temperature and filtering it, taking the filter residue, washing it and vacuum drying it at 50°C for 3.5 hours to obtain microcapsules.

[0056] The cleaning was performed by washing with anhydrous ethanol 5 times.

[0057] Comparative Example 1

[0058] The performance test of the number of cycles was carried out on a lithium ion battery (the same type of battery as the lithium ion battery in Example 1, but without the addition of the microcapsules in Example 1). The test results are as follows: Figure 1 As shown (i.e. Figure 1 Solution B) from Figure 1 It can be seen that the cycle performance of the lithium-ion battery without the microcapsule of the present application is worse than that of solution A.

[0059] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A microcapsule, characterized in that: Suitable for ion batteries, including an outer wall material and a supplementary core material wrapped in the outer wall material; based on the mass of the microcapsule being 100%, the outer wall material is 10% to 30%, and the supplementary core material is 70% to 90%; the outer wall material is a polystyrene wall material; the supplementary core material includes the following components in mass percentage: 1% to 3% positive electrode supplement and 97% to 99% metal salt electrolyte.

2. The microcapsule according to claim 1, characterized in that The outer wall material is prepared by the following method: 95% to 98% polystyrene, 1% to 3% initiator and 1% to 2% dispersant are uniformly mixed to obtain the outer wall material; the percentages are all mass percentages.

3. The microcapsule according to claim 2, characterized in that The polystyrene is prepared from styrene monomers through polymerization reaction; the molecular weight of the polystyrene is 100,000 to 250,000; The initiator is benzoyl peroxide; the dispersant is gelatin or polyvinyl alcohol.

4. The microcapsule according to claim 1, characterized in that When the ion battery is a lithium ion battery, the positive electrode supplement is one or a mixture of at least two of lithium-rich nickel acid, lithium-rich lithium iron oxide, or lithium-rich nickel acid; The metal salt electrolyte is a mixed solution of an ester solvent and a lithium salt LiPF6.

5. The microcapsule according to claim 1, characterized in that When the ion battery is a sodium ion battery, the positive electrode supplement is one or a mixture of at least two of the positive electrode sodium supplements sodium sulfate, sodium oxide, sodium citrate, sodium oxalate and sodium carbonate; The metal salt electrolyte is a mixed solution of an ester solvent and sodium salt NaPF6.

6. The microcapsule according to claim 1, characterized in that The supplementary core material is prepared by the following method: 1% to 3% of the positive electrode supplement and 97% to 99% of the metal salt electrolyte are uniformly stirred to obtain the supplementary core material; the percentages are mass percentages.

7. The method for preparing microcapsules according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: stirring 10% to 30% of the outer wall material in a constant temperature water bath at 65°C to 75°C for 4h to 5h to obtain a wall material mixed liquid; adding 70% to 90% of the core material into the wall material mixed liquid, cooling the temperature to 30°C to 50°C and continuing the suspension polymerization reaction for 1h to 2h to obtain a reaction mixture; cooling the reaction mixture to stand at room temperature and filtering it, taking the filter residue, washing it and vacuum drying it at 30°C to 50°C for 3h to 4h to obtain microcapsules.

8. The method for preparing microcapsules according to claim 7, characterized in that: The cleaning is performed by washing with anhydrous ethanol 2 to 5 times.

9. Use of the microcapsule according to any one of claims 1 to 6, characterized in that: The microcapsule can be applied to lithium ion batteries or sodium ion batteries.

10. The use of the microcapsules according to claim 9, characterized in that: The lithium-ion battery is an energy storage lithium battery or a ternary power lithium battery.

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