Energy storage lithium battery modified diaphragm as well as preparation method and application thereof

Abstract

The invention discloses an energy storage lithium battery modified diaphragm as well as a preparation method and application thereof. The energy storage lithium battery modified diaphragm comprises a diaphragm and a functional layer arranged on one side of the diaphragm, wherein the functional layer is a fullerene derivative modified layer. The lithium battery diaphragm disclosed by the invention has relatively high mechanical property, and can effectively inhibit the growth of lithium dendrites and prevent the lithium dendrites from penetrating through the diaphragm to cause short circuit of the battery. In the electrochemical process, the fullerene derivative reacts with the lithium negative electrode to generate a Li2O electrolyte interface in situ, so that uniform deposition of lithium ions on the surface of the negative electrode is facilitated, and generation of lithium dendrites is inhibited. When the lithium battery is applied, the safety and the long-period stability of the lithium battery can be improved.

Description

Technical Field

[0001] The invention relates to a modified diaphragm for an energy storage lithium battery and a preparation method and application thereof, belonging to the technical field of batteries. Background Art

[0002] In recent years, with the booming development of the new energy market, its application has become more and more extensive. In addition to consumer electronics, new energy vehicles, power tools, etc., large-scale energy storage and distributed energy storage power stations are becoming more and more common. Lithium batteries are small, light, and have strong power storage capacity, and are widely used in various fields of energy storage. However, during the energy storage process, lithium batteries will cause serious losses if a safety accident occurs, and the lithium dendrites generated at the negative electrode are the main cause of battery safety accidents. In addition, the generation of lithium dendrites will also cause a decrease in battery capacity, which directly and seriously affects the cycle life of energy storage lithium batteries. Summary of the invention

[0003] In view of this, the present invention provides a modified diaphragm for energy storage lithium battery and its preparation method and application, and the technical problem to be solved is that Li is generated in situ by reacting fullerene derivatives with lithium negative electrode. 2 O electrolyte interface is conducive to the uniform deposition of lithium ions on the negative electrode surface and inhibits the generation of lithium dendrites.

[0004] To achieve the above object, the present invention provides a modified diaphragm for an energy storage lithium battery, the modified diaphragm for an energy storage lithium battery comprising a diaphragm and a functional layer arranged on one side of the diaphragm, wherein the functional layer is a fullerene derivative modified layer.

[0005] The purpose of the present invention and the technical problems to be solved can be further achieved by adopting the following technical measures.

[0006] Preferably, in the aforementioned modified separator for energy storage lithium battery, the fullerene derivative is C 60 -(OLi) n , n is selected from an integer from 3 to 6.

[0007] Preferably, in the aforementioned modified diaphragm for energy storage lithium battery, the functional layer is coated on one side of the diaphragm.

[0008] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. The present invention proposes a method for preparing a modified diaphragm for an energy storage lithium battery, comprising the following steps:

[0009] The fullerene derivative is mixed with a binder evenly, and then N-methylpyrrolidone is added and ground and mixed evenly; the obtained mixture is coated on one side of the diaphragm and dried to obtain a modified diaphragm for energy storage lithium battery with a fullerene derivative modified layer.

[0010] The purpose of the present invention and the technical problems to be solved can be further achieved by adopting the following technical measures.

[0011] Preferably, in the aforementioned method for preparing the modified diaphragm for energy storage lithium battery, the mass ratio of the fullerene derivative to the binder is 6:4 to 9:1.

[0012] Preferably, in the aforementioned method for preparing the modified diaphragm for energy storage lithium battery, the grinding time is 1 h to 24 h.

[0013] Preferably, in the aforementioned method for preparing a modified separator for an energy storage lithium battery, the thickness of the fullerene derivative modified layer is 5 μm to 20 μm.

[0014] Preferably, in the aforementioned method for preparing the modified diaphragm for energy storage lithium battery, the drying time is 6h to 48h.

[0015] Preferably, in the aforementioned method for preparing the modified diaphragm for energy storage lithium battery, the drying temperature is 25°C to 80°C.

[0016] The purpose of the present invention and the solution of its technical problems can also be achieved by the following technical measures. The present invention proposes an energy storage lithium battery, including a diaphragm, wherein the positive electrode adopts an energy storage lithium battery modified diaphragm; the energy storage lithium battery modified diaphragm includes a diaphragm and a functional layer arranged on one side of the diaphragm, wherein the functional layer is a fullerene derivative modified layer.

[0017] Compared with the prior art, the modified diaphragm for energy storage lithium battery and its preparation method and application described in the present invention have the following beneficial effects:

[0018] The lithium battery separator of the present invention has high mechanical properties and can effectively inhibit the growth of lithium dendrites, preventing lithium dendrites from passing through the separator and causing battery short circuit. In the electrochemical process, the fullerene derivative reacts with the lithium negative electrode to generate Li 2 O electrolyte interface is conducive to the uniform deposition of lithium ions on the negative electrode surface and inhibits the generation of lithium dendrites. When applied to lithium batteries, it can improve the safety and long-term stability of lithium batteries.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the modified diaphragm of the energy storage lithium battery of the present invention;

[0021] Figure 2 The present invention is a flow chart of the preparation method of the modified diaphragm for energy storage lithium battery. DETAILED DESCRIPTION

[0022] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a modified diaphragm for energy storage lithium battery and its preparation method and application thereof, and its specific implementation, structure, characteristics and effects thereof, in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0023] Unless otherwise specified, the materials and reagents mentioned below are all commercial products known to those skilled in the art; unless otherwise specified, the methods described are all methods known in the art. Unless otherwise defined, the technical terms or scientific terms used should have the common meanings understood by ordinary technicians in the field to which the present invention belongs. If no specific experimental steps or conditions are specified below, the conventional experimental steps or conditions described in the literature in the field can be used.

[0024] See also Figure 1 Some embodiments of the present invention provide a modified diaphragm for an energy storage lithium battery, the modified diaphragm comprising a diaphragm 1 and a functional layer coated on one side of the diaphragm 1, wherein the functional layer is a fullerene derivative modified layer 2. The functional layer is adhered to the diaphragm by a binder.

[0025] In some embodiments, the fullerene derivative may be C 60 -(OLi) n , n is selected from one of the integers of 3-6, such as 3, 4, 5, 6, for example, n=4.

[0026] See also Figure 2 Some embodiments of the present invention also provide a method for preparing the modified diaphragm of the energy storage lithium battery, comprising the following steps:

[0027] S1: Weigh a certain amount of fullerene derivatives and place them in a grinding jar, then add a binder;

[0028] S2: Add N-methylpyrrolidone (NMP) to the mixture obtained in step S1, grind and mix evenly; the NMP solvent has two functions: 1. dissolve polyvinylidene fluoride (PVDF) to play its role as a binder and have viscosity; 2. turn the fullerene derivative and binder powder into slurry for subsequent membrane coating. After coating, dry and evaporate the NMP solvent;

[0029] S3: coating the mixture on one side of the separator 1, placing it in a vacuum oven for drying, and obtaining the energy storage lithium battery modified separator having the fullerene derivative modified layer 2.

[0030] In some embodiments, optionally, the mass ratio of the fullerene derivative to the binder in step S1 is 6:4 to 9:1, for example, 6:4, 7:3, 8:2 or 9:1; the binder only plays a bonding role, bonding the fullerene derivative to the diaphragm, as long as a good bonding effect is achieved; if the mass ratio of the fullerene derivative to the binder is less than 6:4, too much binder content will increase the volume and weight, and reduce the volume energy density and weight energy density of the battery. If the mass ratio of the fullerene derivative to the binder is greater than 9:1, the effect of bonding the fullerene derivative to the diaphragm will be poor. Considering the better bonding effect and dosage, the mass ratio of the two is preferably 8:2; and the binder is preferably PVDF (polyvinylidene fluoride).

[0031] In some embodiments, optionally, the grinding time in step S2 is 1 h to 24 h, for example, 1 h, 4 h, 7 h, 10 h, 12 h, 14 h, 17 h, 20 h or 24 h, preferably 12 h; the purpose of grinding is to dissolve the binder in the NMP solvent and fully mix it with the fullerene derivative powder to form a muddy slurry for subsequent coating.

[0032] In some embodiments, optionally, the thickness of the diaphragm is generally between 10 μm and 30 μm, and the thickness of the fullerene derivative modified layer should not exceed the thickness of the diaphragm, and should be less than the thickness of the diaphragm; therefore, the thickness of the fullerene derivative modified layer 2 described in step S3 is set to 5 μm to 20 μm, for example, it can be 5 μm, 10 μm, 15 μm, 20 μm; when the thickness of the diaphragm is 25 μm, the preferred thickness of the fullerene derivative modified layer is 10 μm, so that the fullerene derivative modified layer has a certain hardness, which can inhibit the growth of lithium dendrites, and will not hinder the conduction of lithium ions due to being too thick.

[0033] In some embodiments, optionally, the drying time in step S3 is set to 12h to 48h, and the main purpose of drying is to volatilize the NMP solvent; if the drying time is less than 12h, the drying effect is relatively poor; if the drying time is greater than 48h, it will cause over-drying, increasing time and energy costs; for this reason, considering complete drying, the drying time is preferably 24h.

[0034] In some embodiments, optionally, taking into account the heat resistance temperature of the diaphragm, the drying temperature in step S3 is set to 25°C to 80°C. If the drying temperature is less than 25°C, the drying effect is relatively poor; if the drying temperature is greater than 80°C, it will cause over-drying, increasing time and energy costs; for this reason, considering complete drying, the drying temperature is preferably 50°C.

[0035] In the above technical solution, the present invention can realize the negative electrode surface Li 2 In-situ generation of the O electrolyte interface layer enables Li 2 The O electrolyte interface layer guides the uniform deposition of lithium ions on the surface of the negative electrode and inhibits the generation of lithium dendrites. Inhibiting the generation and growth of lithium dendrites can improve the safety and long-term stability of lithium batteries.

[0036] Some embodiments of the present invention further provide an energy storage lithium battery, comprising a diaphragm, wherein the diaphragm adopts the above-mentioned energy storage lithium battery modified diaphragm.

[0037] The present invention is further described below in conjunction with specific embodiments.

[0038] Example 1

[0039] See also Figure 1 This embodiment provides a modified diaphragm for a lithium energy storage battery, wherein the modified diaphragm for a lithium energy storage battery comprises a diaphragm 1 and a fullerene derivative modified layer 2 coated on one side of the diaphragm 1; the thickness of the fullerene derivative modified layer 2 is 10 μm; the thickness of the diaphragm 1 is 25 μm.

[0040] The method for preparing the modified diaphragm of the energy storage lithium battery comprises the following steps:

[0041] S1: Weigh 80 mg of fullerene derivative (C 60 -(OLi) 4 ) was placed in a grinding jar and ground for 12 hours, and 20 mg of a binder was added; the mass ratio of the fullerene derivative to the binder was 8:2;

[0042] S2: Add 3 mL of NMP solvent to the mixture obtained in step S1, grind for 12 h, and mix well;

[0043] S3: The mixture is coated on one side of a 25 μm thick diaphragm 1, and is placed in a vacuum oven at 50°C for drying (24 h) to obtain the energy storage lithium battery modified diaphragm (35 μm thick) having a fullerene derivative modified layer 2, wherein the thickness of the fullerene derivative modified layer 2 is 10 μm.

[0044] Example 2

[0045] The difference between this embodiment and embodiment 1 is that the mass ratio of the fullerene derivative to the binder in step S1 of this embodiment is 6:4, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified separator for the energy storage lithium battery is 35 μm.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that the mass ratio of the fullerene derivative to the binder in step S1 of this embodiment is 7:3, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified separator for the energy storage lithium battery is 35 μm.

[0048] Example 4

[0049] The difference between this embodiment and embodiment 1 is that the mass ratio of the fullerene derivative to the binder in step S1 of this embodiment is 9:1, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified diaphragm for the energy storage lithium battery is 35 μm.

[0050] Example 5

[0051] The difference between this embodiment and embodiment 1 is that the thickness of the fullerene derivative modified layer 2 in this embodiment is 5 μm, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified separator of the energy storage lithium battery is 30 μm.

[0052] Example 6

[0053] The difference between this embodiment and embodiment 1 is that the thickness of the fullerene derivative modified layer 2 in this embodiment is 15 μm, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified separator of the energy storage lithium battery is 40 μm.

[0054] Example 7

[0055] The difference between this embodiment and embodiment 1 is that the thickness of the fullerene derivative modified layer 2 in this embodiment is 20 μm, and the other parameters and steps are the same as those in embodiment 1; wherein the thickness of the modified separator of the energy storage lithium battery is 45 μm.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that no binder is added in step S1 of this comparative example, and the remaining parameters and steps are the same as those of Example 1; wherein the thickness of the modified diaphragm is 35 μm.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that the mass ratio of the fullerene derivative to the binder in step S1 of this comparative example is 6:5, and the other parameters and steps are the same as those in Example 1; wherein the thickness of the modified diaphragm is 35 μm.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 1 is that the mass ratio of the fullerene derivative to the binder in step S1 of this comparative example is 10:1, and the other parameters and steps are the same as those in Example 1; wherein the thickness of the modified diaphragm is 35 μm.

[0062] Comparative Example 4

[0063] The difference between this comparative example and Example 1 is that the thickness of the fullerene derivative modified layer 2 in this comparative example is 4 μm, and the other parameters and steps are the same as those in Example 1; wherein the thickness of the modified diaphragm is 29 μm.

[0064] Comparative Example 5

[0065] The difference between this comparative example and Example 1 is that the thickness of the fullerene derivative modified layer 2 in this comparative example is 25 μm, and the other parameters and steps are the same as those in Example 1; wherein the thickness of the modified diaphragm is 50 μm.

[0066] The modified separators, electrolytes and lithium negative electrodes prepared in the above Examples 1-7 and Comparative Examples 1-5 were assembled into symmetrical batteries, and the electrochemical performance, including rate performance and cycle performance, was tested. The test results are shown in Table 1. The charge and discharge voltage for testing the electrochemical performance was set to -0.2V to 0.2V. In the rate performance test, the current density was set to 0.2mA / cm 2 , 0.4mA / cm 2 , 0.8mA / cm 2 , 1mA / cm 2 , 2mA / cm 2 .

[0067] Table 1

[0068]

[0069] It can be seen from the data in Table 1 that the energy storage batteries of Examples 1-7 of the present invention have an average current of 0.2 mA / cm 2 The voltage of 1000 cycles is 25-56mV, 0.2mA / cm 2 The first cycle voltage is 40-77mV, 0.4mA / cm 2 The first cycle voltage is 48-98mV, 0.8mA / cm 2 The first cycle voltage is 59-106mV, 1mA / cm 2 The first cycle voltage is 67-119mV, 2mA / cm 2 The first cycle voltage is 86-140mV. Among them, 0.2mA / cm 2 After 1000 cycles at the same current density, the device showed good voltage stability.

[0070] Compared with Example 1, as the mass ratio of fullerene derivative to binder decreases, Examples 2 and 3 have a higher 2The voltage of the cycle 1000 increases significantly; as the mass ratio of the fullerene derivative to the binder increases, Example 4 at 0.2 mA / cm 2 The voltage of the battery increases after 1000 cycles. The binder needs to better bond the fullerene derivative to one side of the diaphragm and cannot affect the function of the fullerene derivative. If the binder is too little, the bonding effect is poor, and the diaphragm modification layer will fall off during use, affecting the electrochemical performance of the battery. On the contrary, if the binder is too much, the excess binder occupies the volume and weight of the fullerene derivative, affecting the function of the fullerene derivative.

[0071] Compared with Example 1, as the thickness of the fullerene derivative modified layer decreases, Example 5 is 2 The voltage of the cycle 1000 increases; as the thickness of the fullerene derivative modified layer increases, the voltage of Examples 6 and 7 increases at 0.2 mA / cm 2 The voltage of the 1000th cycle increases significantly; the fullerene derivative modified layer needs to have a certain hardness to inhibit the growth of lithium dendrites, and will not hinder the conduction of lithium ions due to being too thick. If the thickness is not enough, the mechanical strength is not enough, and the lithium dendrites will pierce the diaphragm and cause a short circuit; on the contrary, if the thickness is too thick, the transmission path of lithium ions is increased, and the volume is increased, affecting the electrochemical performance of the battery.

[0072] Compared with Example 1, Comparative Example 1 did not add a binder, and its 2 The voltage increases significantly after 1000 cycles; the absence of a binder makes the bonding effect between the fullerene derivative and the diaphragm too poor, and the modified layer of the diaphragm will fall off during use, seriously affecting the electrochemical performance of the battery.

[0073] Compared with Example 1, as the mass ratio of the fullerene derivative to the binder decreases and the mass ratio of the two is not within the protection scope of the present invention, the comparative example 2 is 0.2 mA / cm 2 The voltage of the cycle 1000 increases significantly; as the mass ratio of the fullerene derivative to the binder increases and the mass ratio of the two is not within the scope of protection of the present invention, the comparative example 3 is 0.2mA / cm 2 The voltage increases significantly after 1000 cycles;

[0074] Compared with Example 1, as the thickness of the fullerene derivative modified layer decreases and it is not within the scope of protection of the present invention, Comparative Example 4 is at 0.2 mA / cm 2 The voltage of the cycle 1000 increases significantly; as the thickness of the fullerene derivative modified layer increases and it is not within the scope of protection of the present invention, the comparative example 5 is at 0.2 mA / cm 2 The voltage increases significantly after 1000 cycles.

[0075] The above embodiments are only used to explain the content of the present invention, and are not intended to limit the present invention. Simple technical variations within the technical concept of the present invention should be considered to be covered by the content disclosed by the present invention and belong to the protection scope of the present invention.

[0076] In the specification of the present invention, a lot of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some embodiments, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this specification.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0078] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0079] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A modified diaphragm for energy storage lithium battery, characterized in that: The modified diaphragm for energy storage lithium battery comprises a diaphragm and a functional layer arranged on one side of the diaphragm, wherein the functional layer is a fullerene derivative modified layer.

2. The modified diaphragm for energy storage lithium battery according to claim 1, characterized in that: The fullerene derivative is C 60 -(OLi) n , n is selected from an integer from 3 to 6.

3. The modified diaphragm for energy storage lithium battery according to claim 1, characterized in that: The functional layer is coated on one side of the diaphragm.

4. A method for preparing a modified diaphragm for an energy storage lithium battery, characterized in that: The following steps are involved: The fullerene derivative is mixed with a binder evenly, and then N-methylpyrrolidone is added and ground and mixed evenly; the obtained mixture is coated on one side of the diaphragm and dried to obtain a modified diaphragm for energy storage lithium battery with a fullerene derivative modified layer.

5. The method for preparing the modified diaphragm for energy storage lithium battery according to claim 4, characterized in that: The mass ratio of the fullerene derivative to the binder is 6:4 to 9:

1.

6. The method for preparing the modified diaphragm for energy storage lithium battery according to claim 4, characterized in that: The grinding time is 1h to 24h.

7. The method for preparing the modified diaphragm for energy storage lithium battery according to claim 4, characterized in that: The thickness of the fullerene derivative modified layer is 5 μm to 20 μm.

8. The method for preparing the modified diaphragm for energy storage lithium battery according to claim 4, characterized in that: The drying time is 6h to 48h.

9. The method for preparing the modified diaphragm for energy storage lithium battery according to claim 4, characterized in that: The drying temperature is 25°C to 80°C.

10. A lithium energy storage battery, characterized in that: It comprises a diaphragm, wherein the positive electrode adopts a modified diaphragm of an energy storage lithium battery; the modified diaphragm of an energy storage lithium battery comprises a diaphragm and a functional layer arranged on one side of the diaphragm, wherein the functional layer is a modified layer of a fullerene derivative.

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