Metal lithium negative electrode interface protection layer, preparation method and application of metal lithium negative electrode interface protection layer in lithium battery

Abstract

The invention relates to the technical field of lithium batteries, in particular to a metal lithium negative electrode interface protection layer, a preparation method and application of the metal lithium negative electrode interface protection layer in a lithium battery, the interface protection layer comprises orthophosphate AxPO4, an organic polymer and a conductive carbon material, the mass of orthophosphate AxPO4 accounts for 40-70% of the total mass, the mass of the organic polymer accounts for 5-30% of the total mass, and the mass of the conductive carbon material accounts for 5-30% of the total mass. And the mass of the conductive carbon material accounts for 10-50% of the total mass. When the protective layer is applied to the lithium battery, orthophosphate AxPO4 can be decomposed in the first charging process to generate lithium phosphate and A, and alloying / dealloying reaction, namely generation and decomposition of Li3 / xA alloy, is carried out in subsequent circulation, so that the high activity of a lithium metal negative electrode is ensured, the dendritic crystal growth problem is inhibited, the service life of the battery is prolonged, and the safety of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a metal lithium negative electrode interface protection layer, a preparation method and application thereof in lithium batteries. Background Art

[0002] In recent years, with the support of national policies, the new energy industry has developed rapidly and has become an important economic pillar of my country. As an efficient energy storage device for the mutual conversion of electrical energy and chemical energy, lithium-ion batteries have been successfully applied to 3C electronic devices due to their high energy density, long life, stable performance, and environmental friendliness. With the continuous expansion of the market, the demand for batteries with higher energy density and longer cycle life is growing continuously, especially in the field of electric vehicles, which means longer driving range. In lithium-ion batteries, the positive electrode material determines the upper limit of the battery's energy and is basically close to the energy barrier, but there are unlimited possibilities on the negative electrode side. The current battery system with graphite (372mAh / g) as the negative electrode cannot meet the development requirements of the industry due to its low energy density. Lithium metal makes the application of higher energy batteries possible due to its ultra-high theoretical specific capacity (3860mAh / g), ultra-low potential (-3.04V) and ultra-low density (0.534g / cm3). However, lithium metal is much more active than other negative electrode materials. It is very easy to react with electrolytes in both liquid and solid batteries. In addition, the uneven deposition of lithium during the charging process will lead to the growth of lithium dendrites, which will pierce the diaphragm or solid electrolyte, causing short circuits and even battery explosions. These problems have become the research focus of the entire industry, and there is still a long way to go before the true commercialization of lithium metal negative electrodes.

[0003] Therefore, it is necessary to develop a metal lithium negative electrode interface protection layer to solve the above problems. Summary of the invention

[0004] The present application provides a metal lithium negative electrode interface protection layer, a preparation method and its application in a lithium battery to solve the technical problems that the existing lithium electrode is prone to produce lithium dendrites and the lithium electrode and electrolyte are irreversibly consumed due to the reaction.

[0005] In a first aspect, the present application provides a metal lithium negative electrode interface protection layer, which comprises, by weight:

[0006] Orthophosphate 40~70%

[0007] Organic polymer 5~30%

[0008] Conductive carbon material 10~50%

[0009] Among them, the general formula of orthophosphate is A x PO4 , A is one or more of Sb, Zn, Mg, Al, Sn, Zr, Bi, Ag, In, Se, B, and Si, and x is 1-3.

[0010] Optionally, the interface protection layer is located between the metallic lithium negative electrode and the separator or electrolyte.

[0011] Optionally, the thickness of the interface protection layer is 0.1-50 μm.

[0012] Optionally, the organic polymer is one or more of polyethylene oxide PEO, polyacrylonitrile PAN, polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyethylene glycol PEG, polyacrylic acid PPA, polyether sulfone PES, and polypropylene carbonate PPC;

[0013] The conductive carbon material includes one or more of Super P, acetylene black, conductive carbon black, Super C45, Super C65, CNT, VGCF, Ketjen black, and graphene.

[0014] In a second aspect, the present invention further provides a method for preparing an interface protective layer of a metal lithium negative electrode, comprising the following steps:

[0015] S1, dispersing 5 to 30 parts of an organic polymer in an organic solvent, heating and stirring until the polymer is completely dissolved to form a uniform glue solution;

[0016] S2, adding 10 to 50 parts of conductive carbon material to the glue solution, dispersing and stirring evenly, and then adding 40 to 70 parts of orthophosphate, and after it is completely dissolved, obtaining a mixed slurry;

[0017] S3, evenly scrape or spray the mixed slurry on the surface of the lithium metal, and obtain the modified metal lithium negative electrode after drying, and form an interface protection layer after power is applied.

[0018] Optionally, the reaction environment is a glove box filled with argon with a water content of <0.1 ppm and an oxygen content of <0.1 ppm.

[0019] Optionally, the organic solvent is one or more of xylene, p-xylene, o-xylene, n-hexane, cyclopentane, cyclopentane, tetrahydrofuran, ethyl acetate, butyl acetate, acetonitrile, and acetone.

[0020] Optionally, the drying process in step S3 is carried out under an inert atmosphere, the drying temperature is 50 to 100° C., and the drying time is 0.5 to 10 hours.

[0021] In a third aspect, the present invention provides a metal lithium battery, comprising a metal lithium negative electrode, a positive electrode, a separator and an electrolyte, wherein a metal lithium negative electrode interface protection layer described in the first aspect is arranged between the metal lithium negative electrode and the electrolyte.

[0022] Optionally, the metal lithium battery includes but is not limited to a liquid lithium battery, a semi-solid lithium battery, a solid lithium battery, a lithium-sulfur battery, and a lithium-air battery.

[0023] The above technical solution provided by the present invention has the following advantages compared with the prior art:

[0024] The present invention provides a metal lithium negative electrode interface protection layer, a preparation method and its application in a lithium battery. The negative electrode interface protection layer provided by the present invention uses orthophosphate as a modified material. The lithium phosphate generated by decomposition during the charging process is a fast ion conductor and can effectively conduct lithium ions. The ions that can be reversibly alloyed with lithium can induce the uniform deposition of lithium ions and avoid the growth of lithium dendrites. The addition of organic polymers can improve the toughness and elasticity of the protective layer and provide a better protection effect. The conductive carbon material can quickly transmit electrons and reduce the interface resistance, which is helpful to improve the electrochemical performance and safety performance of the battery. It can be seen that the interface protection layer in the present invention can not only conduct lithium ions, but also conduct electrons. In addition, the preparation process of the interface protection layer in the present invention is simple, the controllability is high, the cost is low, and stable product materials can be obtained, which has broad application prospects in the field of lithium battery preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic flow chart of a method for preparing a metal lithium negative electrode interface protection layer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0030] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] In a first aspect, the present application provides a metal lithium negative electrode interface protection layer, calculated by weight, comprising:

[0033] Orthophosphate 40~70%

[0034] Organic polymer 5~30%

[0035] Conductive carbon material 10~50%

[0036] Among them, the general formula of orthophosphate is A x PO 4 , A is an ion that can be alloyed with lithium, including one or more of Sb, Zn, Mg, Al, Sn, Zr, Bi, Ag, In, Se, B, and Si, and x is 1-3.

[0037] In some embodiments, the interface protection layer is located between the metallic lithium negative electrode and the separator or the electrolyte.

[0038] In some embodiments, the interface protection layer has a thickness of 0.1 to 50 μm.

[0039] In some embodiments, the organic polymer is one or more of polyethylene oxide PEO, polyacrylonitrile PAN, polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyethylene glycol PEG, polyacrylic acid PPA, polyether sulfone PES, and polypropylene carbonate PPC;

[0040] The conductive carbon material includes one or more of Super P, acetylene black, conductive carbon black, Super C45, Super C65, CNT, VGCF, Ketjen black, and graphene.

[0041] In a second aspect, the present invention also provides a method for preparing an interface protective layer of a metal lithium negative electrode, referring to Figure 1 , including the following steps:

[0042] S1, dispersing 5 to 30 parts of an organic polymer in an organic solvent, heating and stirring until the polymer is completely dissolved to form a uniform glue solution;

[0043] S2, adding 10 to 50 parts of conductive carbon material to the glue solution, dispersing and stirring evenly, and then adding 40 to 70 parts of orthophosphate, and after it is completely dissolved, obtaining a mixed slurry;

[0044] S3, evenly scrape or spray the mixed slurry on the surface of lithium metal, and obtain the modified metal lithium negative electrode after drying. After the metal lithium negative electrode is energized, the A in the mixed slurry x PO 4During the first charge, decomposition occurs to generate lithium phosphate and A, and then alloying / de-alloying reactions occur in subsequent cycles, i.e., Li 3 / xA alloy is generated and decomposed to form an interface protective layer.

[0045] In order to ensure that the reaction is carried out in an oxygen-free and dry environment, in some embodiments, the reaction environment for preparing the interface protective layer is a space with a water content of less than 0.1 ppm, an oxygen content of less than 0.1 ppm and filled with inert gas. For those skilled in the art, a glove box filled with argon is a better reaction environment.

[0046] In some embodiments, the organic solvent may be one or more of xylene, p-xylene, o-xylene, n-hexane, cyclopentane, cyclopentane, tetrahydrofuran, ethyl acetate, butyl acetate, acetonitrile, and acetone, and the grade of the solvent is anhydrous.

[0047] In some embodiments, in order to isolate oxygen, the drying process in step S3 is performed under an inert atmosphere, the drying temperature is generally 50 to 100° C., and the drying time is 0.5 to 10 h.

[0048] In a third aspect, the present invention provides a metal lithium battery, comprising a metal lithium negative electrode, a positive electrode, a separator and an electrolyte, wherein a metal lithium negative electrode interface protection layer described in the first aspect is arranged between the metal lithium negative electrode and the electrolyte or the separator.

[0049] In some embodiments, the metal lithium battery includes but is not limited to a liquid lithium battery, a semi-solid lithium battery, a solid lithium battery, a lithium sulfur battery, and a lithium air battery.

[0050] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An interface protective layer for a metallic lithium negative electrode, characterized in that: In parts by weight, the interface protection layer comprises: Orthophosphate 40~70% Organic polymer 5~30% Conductive carbon material 10~50% Among them, the general formula of orthophosphate is A x PO4, A is one or more of Sb, Zn, Mg, Al, Sn, Zr, Bi, Ag, In, Se, B, Si, and x is 1-3.

2. The interface protection layer of the metal lithium negative electrode according to claim 1, characterized in that: The interface protection layer is located between the metal lithium negative electrode and the separator or electrolyte.

3. The interface protection layer of the metal lithium negative electrode according to claim 1, characterized in that: The thickness of the interface protection layer is 0.1-50 μm.

4. The interface protection layer of the metal lithium negative electrode according to claim 1, characterized in that: The organic polymer is one or more of polyethylene oxide PEO, polyacrylonitrile PAN, polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyethylene glycol PEG, polyacrylic acid PPA, polyether sulfone PES, and polypropylene carbonate PPC; the conductive carbon material includes one or more of Super P, acetylene black, conductive carbon black, Super C45, Super C65, CNT, VGCF, Ketjen black, and graphene.

5. A method for preparing an interface protective layer of a metal lithium negative electrode, characterized in that: The following steps are involved: S1, dispersing 5 to 30 parts of an organic polymer in an organic solvent, heating and stirring until the polymer is completely dissolved to form a uniform glue solution; S2, adding 10 to 50 parts of conductive carbon material to the glue solution, dispersing and stirring evenly, and then adding 40 to 70 parts of orthophosphate, and after it is completely dissolved, obtaining a mixed slurry; S3, evenly scrape or spray the mixed slurry on the surface of the lithium metal, and obtain the modified metal lithium negative electrode after drying, and form an interface protection layer after power is applied.

6. The method for preparing the metal lithium negative electrode interface protection layer according to claim 5, characterized in that: The reaction environment was a glove box filled with argon with a water content of <0.1 ppm and an oxygen content of <0.1 ppm.

7. The method for preparing the metal lithium negative electrode interface protection layer according to claim 5, characterized in that: The organic solvent is one or more of xylene, p-xylene, o-xylene, n-hexane, cyclopentane, cyclopentane, tetrahydrofuran, ethyl acetate, butyl acetate, acetonitrile and acetone.

8. The method for preparing the metal lithium negative electrode interface protection layer according to claim 5, characterized in that: The drying process in step S3 is carried out under an inert atmosphere, the drying temperature is 50-100° C., and the drying time is 0.5-10 h.

9. A metal lithium battery, characterized in that: The invention comprises a metal lithium negative electrode, a positive electrode, a separator and an electrolyte, wherein a metal lithium negative electrode interface protection layer according to any one of claims 1 to 4 is arranged between the metal lithium negative electrode and the electrolyte.

10. The metal lithium battery according to claim 9, characterized in that: The metal lithium battery includes but is not limited to a liquid lithium battery, a semi-solid lithium battery, a solid lithium battery, a lithium-sulfur battery, and a lithium-air battery.

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