Lithium ion power battery composite electrolyte and preparation method thereof

Abstract

The present invention provides a composite electrolyte for an ion power battery and its preparation. The preparation method comprises: providing a pretreated organic solvent, wherein the organic solvent comprises: 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, and 30 to 35 parts by weight of ethylene carbonate; uniformly mixing the organic solvent to form a mixed solvent; adding a refined lithium salt to the mixed solvent and uniformly mixing, wherein the lithium salt comprises 15 to 20 parts by weight of lithium hexafluorophosphate and 4 to 7 parts by weight of lithium bis(oxalatoborate); adding an additive to the above solution and uniformly mixing, wherein the additive comprises 2 to 3 parts by weight of tris(trimethylsilyl)borate, 0.1 to 0.5 parts by weight of MFE‑5 vinyl ester resin, and 0.01 to 0.05 parts by weight of polyvinyl acetate.

Description

Technical Field

[0001] The invention relates to a lithium ion power battery composite electrolyte and a preparation method thereof. Background Art

[0002] At present, lithium titanate batteries generally have the problem of high-temperature gassing, which causes their cycle performance to decay faster, thus restricting their large-scale application in the fields of power and energy storage. One of the important reasons for the high-temperature gassing of lithium titanate is that the catalytic effect of the material itself induces the organic solvent in the electrolyte to undergo chemical decomposition reactions to produce a large amount of gas, that is, LiPF6 is easily decomposed to produce hydrofluoric acid, and carbonate solvents are more likely to undergo chemical decomposition to produce various gases in the presence of a large amount of hydrofluoric acid. Therefore, improving the gassing problem of lithium titanate batteries under long-term use and high-temperature environments from the perspective of electrolyte has become the focus of many researchers. Summary of the invention

[0003] The present invention provides a lithium ion power battery composite electrolyte and a preparation method thereof, which can effectively solve the above problems.

[0004] The present invention is achieved in that:

[0005] A method for preparing a composite electrolyte for a lithium-ion power battery, comprising:

[0006] Providing a pretreated organic solvent, wherein the organic solvent comprises: 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, and 30 to 35 parts by weight of ethylene carbonate;

[0007] uniformly mixing the organic solvents to form a mixed solvent;

[0008] Adding the refined lithium salt into the mixed solvent and mixing uniformly, wherein the lithium salt comprises 15 to 20 parts by weight of lithium hexafluorophosphate and 4 to 7 parts by weight of lithium bis(oxalatoborate);

[0009] Add additives to the solution and mix evenly, wherein the additives include 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin, and 0.01-0.05 parts by weight of polyvinyl acetate.

[0010] The present invention further provides a lithium ion power battery composite electrolyte, comprising: 25-30 parts by weight of dimethyl carbonate, 10-13 parts by weight of propylene carbonate, 30-35 parts by weight of ethylene carbonate, 15-20 parts by weight of lithium hexafluorophosphate, 4-7 parts by weight of lithium bis(oxalatoborate), 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin and 0.01-0.05 parts by weight of polyvinyl acetate.

[0011] The present invention further provides a lithium ion power battery composite electrolyte, which is composed of 25-30 parts by weight of dimethyl carbonate, 10-13 parts by weight of propylene carbonate, 30-35 parts by weight of ethylene carbonate, 15-20 parts by weight of lithium hexafluorophosphate, 4-7 parts by weight of lithium bis(oxalatoborate), 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin and 0.01-0.05 parts by weight of polyvinyl acetate.

[0012] The beneficial effects of the present invention are as follows: the present invention can significantly improve the stability of the electrolyte and reduce the possibility of flatulence and deformation by optimizing the type and ratio of the organic solvent. The present invention can further effectively reduce the effect of lithium hexafluorophosphate on the reduction and decomposition of the organic solvent on the lithium titanate negative electrode by adjusting the ratio of the lithium hexafluorophosphate and the lithium bis(oxalatoborate), and further reduce the decomposition and gas generation of the organic solvent. A stable protective layer can also be formed on the surface of the lithium titanate negative electrode by adding additives. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 The present invention provides a flow chart of a method for preparing a composite electrolyte for a lithium-ion power battery. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0017] See also Figure 1 As shown, the present invention provides a method for preparing a composite electrolyte for a lithium-ion power battery, comprising:

[0018] Providing a pretreated organic solvent, wherein the organic solvent comprises: 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, and 30 to 35 parts by weight of ethylene carbonate;

[0019] uniformly mixing the organic solvents to form a mixed solvent;

[0020] Adding the refined lithium salt into the mixed solvent and mixing uniformly, wherein the lithium salt comprises 15 to 20 parts by weight of lithium hexafluorophosphate and 4 to 7 parts by weight of lithium bis(oxalatoborate);

[0021] Add additives to the solution and mix evenly, wherein the additives include 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin, and 0.01-0.05 parts by weight of polyvinyl acetate.

[0022] As a further improvement, the organic solvent includes: 28-30 parts by weight of dimethyl carbonate, 11-12 parts by weight of propylene carbonate, and 30-32 parts by weight of ethylene carbonate. By optimizing the type and proportion of the organic solvent, the stability of the electrolyte can be significantly improved, and the possibility of flatulence and deformation can be reduced.

[0023] As a further improvement, the lithium salt includes 16 to 18 parts by weight of lithium hexafluorophosphate and 5 to 6 parts by weight of lithium bis(oxalatoborate). Experiments show that when the ratio of lithium hexafluorophosphate to lithium bis(oxalatoborate) is controlled at about 3:1, the effect of lithium hexafluorophosphate on the reduction and decomposition of organic solvents on the lithium titanate negative electrode can be minimized. In one embodiment, the lithium salt includes 16.5 parts by weight of lithium hexafluorophosphate and 5.5 parts by weight of lithium bis(oxalatoborate), so that the battery expansion rate is controlled within 5%.

[0024] As a further improvement, the additive includes 2.5 parts by weight of tris(trimethylsilyl) borate, 0.2-0.3 parts by weight of MFE-5 vinyl ester resin and 0.02-0.03 parts by weight of polyvinyl acetate. The tris(trimethylsilyl) borate and MFE-5 vinyl ester resin are used to form a stable protective layer for the negative electrode during the initial charge and discharge. The polyvinyl acetate is used to improve the MFE-5 vinyl ester resin so that the curing linear shrinkage of the MFE-5 vinyl ester resin is close to zero.

[0025] The embodiment of the present invention further provides a lithium-ion power battery composite electrolyte, comprising: 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, 30 to 35 parts by weight of ethylene carbonate, 15 to 20 parts by weight of lithium hexafluorophosphate, 4 to 7 parts by weight of lithium bis(oxalatoborate), 2 to 3 parts by weight of tris(trimethylsilyl)borate, 0.1 to 0.5 parts by weight of MFE-5 vinyl ester resin, and 0.01 to 0.05 parts by weight of polyvinyl acetate.

[0026] The embodiment of the present invention further provides a lithium-ion power battery composite electrolyte, which is composed of 25-30 parts by weight of dimethyl carbonate, 10-13 parts by weight of propylene carbonate, 30-35 parts by weight of ethylene carbonate, 15-20 parts by weight of lithium hexafluorophosphate, 4-7 parts by weight of lithium bis(oxalatoborate), 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin and 0.01-0.05 parts by weight of polyvinyl acetate.

[0027] Embodiment 1:

[0028] A pretreated organic solvent is provided, wherein the organic solvent includes: 28 parts by weight of dimethyl carbonate, 11 parts by weight of propylene carbonate, and 32 parts by weight of ethylene carbonate; the organic solvent is injected into a mixer and mixed evenly to form a mixed solvent; a refined lithium salt is added into the mixed solvent and mixed evenly, wherein the lithium salt includes 16.5 parts by weight of lithium hexafluorophosphate and 5.5 parts by weight of lithium bis(oxalatoborate) injected into the mixer; an additive is added into the mixer and mixed evenly, wherein the additive includes 2.5 parts by weight of tris(trimethylsilyl)borate, 0.2 parts by weight of MFE-5 vinyl ester resin, and 0.02 parts by weight of polyvinyl acetate, and the materials are fully dissolved, mixed, and configured into a composite electrolyte in the mixer, and after passing the inspection, the product is controlled and put into storage.

[0029] Embodiment 2:

[0030] The method is basically the same as Example 1, except that the lithium salt includes 15 parts by weight of lithium hexafluorophosphate and 4 parts by weight of lithium bis(oxalatoborate) injected into the mixer.

[0031] Embodiment 3:

[0032] The method is basically the same as Example 1, except that the lithium salt includes 20 parts by weight of lithium hexafluorophosphate and 7 parts by weight of lithium bis(oxalatoborate) injected into the mixer.

[0033] Comparative Example 1: It is basically the same as Example 1, except that: the lithium salt includes 12 parts by weight of lithium hexafluorophosphate and 3 parts by weight of lithium bis(oxalatoborate) injected into the mixer.

[0034] Comparative Example 2 is basically the same as Example 1, except that the lithium salt includes 22 parts by weight of lithium hexafluorophosphate and 8 parts by weight of lithium bis(oxalatoborate) injected into the mixer.

[0035] Test Example: Take 3 batteries corresponding to the electrolytes of each embodiment and comparative example, record their initial thickness, perform 100 5C charge and discharge tests, record the initial capacity, final capacity and final thickness, and calculate the battery expansion rate and capacity retention rate (average value), as shown in Table 1.

[0036]

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite electrolyte for a lithium-ion power battery, characterized in that: include: Providing a pretreated organic solvent, wherein the organic solvent comprises: 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, and 30 to 35 parts by weight of ethylene carbonate; uniformly mixing the organic solvents to form a mixed solvent; Adding the refined lithium salt to the mixed solvent and mixing uniformly to obtain a solution, wherein the lithium salt comprises 15 to 20 parts by weight of lithium hexafluorophosphate and 4 to 7 parts by weight of lithium bis(oxalatoborate); Adding additives into the solution and mixing uniformly, wherein the additives include 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin, and 0.01-0.05 parts by weight of polyvinyl acetate.

2. The method for preparing a composite electrolyte for a lithium-ion power battery according to claim 1, characterized in that: The organic solvent comprises: 28-30 parts by weight of dimethyl carbonate, 11-12 parts by weight of propylene carbonate, and 30-32 parts by weight of ethylene carbonate.

3. The method for preparing a composite electrolyte for a lithium-ion power battery according to claim 1, characterized in that: The lithium salt includes 16 to 18 parts by weight of lithium hexafluorophosphate and 5 to 6 parts by weight of lithium bis(oxalatoborate).

4. The method for preparing a composite electrolyte for a lithium-ion power battery according to claim 1, characterized in that: The additive comprises 2.5 parts by weight of tris(trimethylsilyl)borate, 0.2-0.3 parts by weight of MFE-5 vinyl ester resin and 0.02-0.03 parts by weight of polyvinyl acetate.

5. A composite electrolyte for a lithium-ion power battery, characterized in that: include: 25-30 parts by weight of dimethyl carbonate, 10-13 parts by weight of propylene carbonate, 30-35 parts by weight of ethylene carbonate, 15-20 parts by weight of lithium hexafluorophosphate, 4-7 parts by weight of lithium bis(oxalatoborate), 2-3 parts by weight of tris(trimethylsilyl)borate, 0.1-0.5 parts by weight of MFE-5 vinyl ester resin and 0.01-0.05 parts by weight of polyvinyl acetate.

6. A lithium-ion power battery composite electrolyte, characterized in that: The invention comprises 25 to 30 parts by weight of dimethyl carbonate, 10 to 13 parts by weight of propylene carbonate, 30 to 35 parts by weight of ethylene carbonate, 15 to 20 parts by weight of lithium hexafluorophosphate, 4 to 7 parts by weight of lithium bis(oxalatoborate), 2 to 3 parts by weight of tris(trimethylsilyl)borate, 0.1 to 0.5 parts by weight of MFE-5 vinyl ester resin and 0.01 to 0.05 parts by weight of polyvinyl acetate.

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