Microcapsules, methods for their preparation and use

Abstract

The application discloses a microcapsule suitable for an ion battery, which comprises an outer wall material and a supplementary core material wrapped in the outer wall material; the outer wall material accounts for 10-30% and the supplementary core material accounts for 70-90% according to 100% of the mass of the microcapsule; the outer wall material is a polystyrene wall material; the supplementary 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 application further provides a preparation method of the microcapsule and application thereof. The microcapsule is prepared by taking a polystyrene material as the outer wall material and taking the supplementary core material as the inner layer, the prepared microcapsule has an extremely thin film, the loss of a solvent and active metal ions of the ion battery in a cycle process is effectively supplemented, meanwhile, the energy density of the battery is not affected, the cycle performance and capacity of the ion battery can be effectively improved. The preparation method is simple and has stronger adaptability to mass production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a microcapsule and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of lithium ion energy storage batteries, market competition is becoming increasingly fierce, and the endurance requirement of lithium ion batteries is also becoming higher and higher. The cycle performance of a lithium ion battery is a key indicator for measuring the service life of the battery, which refers to the number of charge and discharge cycles that the battery can withstand before the capacity significantly decreases. At present, energy storage lithium batteries are generally required to withstand tens of thousands of charge and discharge cycles.

[0003] The cycle performance of a lithium ion battery is mainly determined by the positive and negative active materials and the electrolyte. Among them, 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 negative electrode surface, consume part of the solvent and active lithium ions in the electrolyte to generate a solid electrolyte interface film (SEI), which maintains electronic insulation while allowing lithium ions to pass quickly. However, during the charging and discharging process, the expansion and change of the negative electrode volume will expose new negative electrode surfaces and continuously generate and thicken the SEI film, resulting in the loss of active lithium ions and the continuous loss of electrolyte, even drying out, causing the polarization of the battery to increase and the cycle performance to continuously decrease.

[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 process can be reduced. At present, the existing technology generally adds film-forming additives (such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (DTD), tris(trimethylsilyl) phosphite (TMSP), etc.) to the conventional electrolyte to improve the related performance of the SEI film. However, the use of film-forming additives also has some disadvantages, such as the need to limit the addition amount of the initial additive, and too high an addition amount will cause a series of problems such as increased viscosity, increased acidity, and reduced conductivity of the electrolyte.

[0005] Patent application CN113097424A discloses a battery cell shell and a self-piercing side lithium supplementing battery. This lithium supplementing device is relatively complex, has a long manufacturing time and high cost, and is difficult to popularize. Patent application CN114695883A discloses a lithium ion battery electrolyte supplementing capsule, which can supplement the electrolyte of a lithium ion battery under non-destructive conditions. However, its use method is complex, and the battery needs to be heated with the capsule to work, which is easy to cause damage to the battery. SUMMARY

[0006] The purpose of this invention is to provide a microcapsule and its preparation method and application, in order to solve the technical problems of existing lithium (sodium) ion batteries, such as the loss of active lithium (sodium) ions and continuous loss or even drying of electrolyte during charging and discharging, which leads to increased battery polarization and continuous decline in cycle performance.

[0007] To achieve the above objectives, in one aspect, embodiments of the present invention provide a microcapsule suitable for ion batteries, comprising an outer wall material and a supplementary core material encapsulated within the outer wall material; based on the mass of the microcapsule as 100%, the outer wall material comprises 10% to 30%, and the supplementary core material comprises 70% to 90%; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components by mass percentage: 1% to 3% positive electrode supplement and 97% to 99% metal salt electrolyte.

[0008] In a preferred embodiment, the outer wall material is prepared by mixing 95%–98% polystyrene, 1%–3% initiator and 1%–2% dispersant evenly to obtain the outer wall material; all percentages are by mass.

[0009] The polystyrene is prepared by polymerization of styrene monomers; 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] In a preferred embodiment, 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 (LNO), lithium-rich lithium iron ore (LFO), or lithium-rich nickel acid (LNO).

[0013] In 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 lithium salt LiPF6.

[0014] In 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 following: sodium sulfate (Na2S), sodium oxide (Na2O), sodium citrate (Na3C6H5O7), sodium oxalate (Na2C6O6), and sodium carbonate (Na2CO3).

[0015] In 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 sodium salt NaPF6.

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

[0017] In another aspect, the present application also provides a preparation method of the microcapsule, comprising the following steps: stirring 10-30% outer wall material in a constant temperature water bath at 65-75 DEG C for 4-5h to obtain a wall material mixture, adding 70-90% core material (uniformly mixed at room temperature) into the wall material mixture, and continuing to carry out suspension polymerization reaction at 30-50 DEG C for 1-2h to obtain a reaction mixture; filtering the reaction mixture after cooling and standing to room temperature, washing the filter residue, and vacuum drying at 30-50 DEG C for 3-4h to obtain the microcapsule.

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

[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 improved. In the later stage of battery cycle, when the battery is swollen to cause the internal pressure to rise, the microcapsule gradually breaks, releasing the lithium supplement and electrolyte, thereby solving the problem of the decline in the cycle performance of the battery. 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 be ineffective.

[0020] In another aspect, the present application also provides the application of the microcapsule, which can be applied in 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] In the technical solution of the present application, the microcapsule is prepared by using polystyrene material as the outer wall material and supplement core material as the inner layer, and the prepared microcapsule has an extremely thin film. The prepared microcapsule can effectively supplement the loss of solvent and active metal ions in the cycle process of the ion battery, does not affect the energy density of the battery, can effectively improve the cycle performance and capacity of the ion battery, is sensitive to pressure, and gradually breaks when the internal pressure rises due to the swelling of the battery in the later stage of the battery cycle, thereby releasing the lithium supplement and electrolyte, solving the problem of the decline in the cycle performance of the battery, and prolonging the service life of the battery to meet the demand of the energy storage market for long-life batteries. The microcapsule has a small volume, has little effect on the energy density of the battery, has a simple preparation method, has a long storage time, has better adaptability to mass production, and has a low cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The cycle performance test results of the lithium ion battery prepared by using the microcapsule of the embodiment 1 of the present application and the lithium ion battery of the comparative example 1 are shown in the following figure. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present application.

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

[0026] In the present application, unless otherwise explicitly specified and limited, the terms “mounting”, “connection”, “connecting”, “fixing” and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or can be integrated; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] It should be noted that when an element is referred to as “fixed to” or “disposed on” another element, it can be directly on the other element or there can be a middle element. When an element is referred to as “connected to” another element, it can be directly connected to the other element or there can be a middle element.

[0028] In addition, if the embodiments of the present application involve “first”, “second” and the like, the “first”, “second” and the like are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first”, “second” can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope of the present application.

[0029] Embodiment 1

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

[0031] The outer wall material is prepared by mixing 95% polystyrene, 3% initiator and 2% dispersing agent uniformly to obtain the outer wall material; the percentages are all mass percentages.

[0032] The polystyrene is prepared by polymerization reaction of styrene monomer; the molecular weight of the polystyrene is 100,000.

[0033] The initiator is benzoyl peroxide. The dispersing agent is gelatin.

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

[0035] The supplementary core material is prepared by stirring 1% positive electrode supplement and 99% metal salt electrolyte uniformly to obtain the supplementary core material; the percentages are mass percentages.

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

[0037] The washing is carried out by washing twice with anhydrous ethanol.

[0038] The microcapsule of the present application is applied to a lithium ion battery (energy storage lithium battery), and the performance of the lithium ion battery is tested for the number of cycles, and the test results are shown in Figure 1 (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 ion battery, comprising an outer wall material and a supplementary core material wrapped in the outer wall material; the outer wall material is 20% and the supplementary core material is 80% according to 100% of the mass of the microcapsule; the outer wall material is a polystyrene wall material; the supplementary core material comprises the following components in percentage by mass: 2% positive electrode supplement and 98% metal salt electrolyte.

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

[0042] The polystyrene is prepared by polymerization reaction of styrene monomer; 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 iron phosphate; the metal salt electrolyte is a mixed solution of ester solvent and lithium salt LiPF6.

[0045] The supplementary core material is prepared by stirring 2% positive electrode supplement and 98% metal salt electrolyte uniformly to obtain the supplementary core material; the percentages are mass percentages.

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

[0047] The washing is carried out by washing with anhydrous ethanol for 3 times.

[0048] Example 3

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

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

[0051] The polystyrene is prepared by polymerization of styrene monomers; 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, and the positive electrode supplement is sodium sulfate, a sodium-containing agent for the positive electrode; the metal salt electrolyte is a mixed solution of an ester solvent and sodium salt NaPF6. In this embodiment, a general sodium-ion battery electrolyte can be used as the metal salt 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 a mass percentage.

[0055] The preparation method of the microcapsules includes 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 mixture; adding 70% of the core material (mixed evenly at room temperature) to the wall material mixture; cooling to 50°C and continuing the suspension polymerization reaction for 2 hours to obtain a reaction mixture; cooling the reaction mixture to room temperature and filtering; taking the filter residue, washing it, and vacuum drying it at 50°C for 3.5 hours to obtain microcapsules.

[0056] The cleaning process involved washing five times with anhydrous ethanol.

[0057] Comparative Example 1

[0058] The lithium-ion battery (the same model as the lithium-ion battery in Example 1, but without the microcapsules of Example 1) was subjected to cycle life performance testing, and the test results are as follows: Figure 1 As shown (i.e.) Figure 1 Option B in the plan). Figure 1 As can be seen, the cycle performance of lithium-ion batteries that do not use the microcapsules of this application is worse than that of scheme A.

[0059] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A microcapsule, characterized in that, The application relates to a microcapsule suitable for an ion battery, which comprises an outer wall material and a supplementary core material wrapped in the outer wall material; the outer wall material accounts for 10-30% of the mass of the microcapsule, and the supplementary core material accounts for 70-90% of the mass of the microcapsule; the outer wall material is a polystyrene wall material; and the supplementary 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.

2. The microcapsule according to claim 1, wherein The outer wall material is prepared by uniformly mixing 95-98% of polystyrene, 1-3% of an initiator and 1-2% of a dispersing agent to obtain the outer wall material; the percentages are all percentages by mass.

3. The microcapsule according to claim 2, wherein The polystyrene is prepared by polymerization of styrene monomers, and the molecular weight of the polystyrene is 100-250 thousand; The initiator is benzoyl peroxide, and the dispersing agent is gelatin or polyvinyl alcohol.

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

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

6. The microcapsule of claim 1, wherein The supplementary core material is prepared by uniformly stirring 1-3% of a positive electrode supplement and 97-99% of a metal salt electrolyte to obtain the supplementary core material; the percentages are percentages by mass.

7. Process for the preparation of microcapsules according to any one of claims 1 to 6, characterized in that, The application further relates to a preparation method of the microcapsule, which comprises the following steps: stirring 10-30% of an outer wall material in a constant-temperature water bath at 65-75 DEG C for 4-5 h to obtain a wall material mixture, adding 70-90% of a core material into the wall material mixture, continuing to perform suspension polymerization at a temperature of 30-50 DEG C for 1-2 h to obtain a reaction mixture, cooling and standing the reaction mixture to room temperature, filtering the reaction mixture, washing the filter residue and vacuum drying the filter residue at a temperature of 30-50 DEG C for 3-4 h to obtain the microcapsule.

8. The method of claim 7, wherein the microcapsules are prepared by The washing is performed by washing 2-5 times with anhydrous ethanol.

9. Use of microcapsules according to any one of claims 1 to 6, characterized in that The microcapsule is applied to a lithium ion battery or a sodium ion battery.

10. Use of 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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