阅读说明：本技术 一种电解液及高容量锂离子电池 (Electrolyte and high-capacity lithium ion battery ) 是由 许杰 唐毅 杨璐 袁霞 王济先 于 2021-07-12 设计创作，主要内容包括：本发明提供一种电解液及高容量锂离子电池,该电解液包括有机溶剂、锂盐和添加剂,有机溶剂包括碳酸酯类和羧酸酯类,锂盐包括六氟磷酸锂,添加剂包括润湿添加剂和成膜添加剂。本发明当中的电解液与普通电解液相比,通过在电解液当中加入润湿添加剂,使电解液的润湿性能好,提高了电解液在极片正负极颗粒材料表面的附着性和沉积量,提高了电解液在颗粒材料空隙间的扩散性能,实现了锂离子在正负极间的快速有效传输,从而提高了锂电池的容量发挥性能；同时,电解液中复合添加剂的加入,可以在正负极材料表面形成一层致密均匀且稳定的界面膜,减少了正负极材料表面的电化学活性位点,抑制了副反应发生,提高了锂电池的循环寿命。(The invention provides an electrolyte and a high-capacity lithium ion battery, wherein the electrolyte comprises an organic solvent, lithium salt and an additive, the organic solvent comprises carbonates and carboxylates, the lithium salt comprises lithium hexafluorophosphate, and the additive comprises a wetting additive and a film forming additive. Compared with the common electrolyte, the electrolyte has good wetting performance by adding the wetting additive into the electrolyte, improves the adhesion and deposition of the electrolyte on the surfaces of positive and negative electrode particle materials of a pole piece, improves the diffusion performance of the electrolyte among gaps of the particle materials, and realizes the quick and effective transmission of lithium ions between the positive and negative electrodes, thereby improving the capacity exertion performance of the lithium battery; meanwhile, due to the addition of the composite additive in the electrolyte, a layer of compact, uniform and stable interfacial film can be formed on the surfaces of the positive and negative electrode materials, so that the electrochemical active sites on the surfaces of the positive and negative electrode materials are reduced, the occurrence of side reactions is inhibited, and the cycle life of the lithium battery is prolonged.)

1. An electrolyte comprising an organic solvent, a lithium salt, and an additive, wherein the organic solvent comprises carbonates and carboxylates, the lithium salt comprises lithium hexafluorophosphate, and the additive comprises a wetting additive and a film forming additive.

2. The electrolyte of claim 1, wherein the wetting additive comprises one or more of acetyl hydrazide, benzene sulfonyl hydrazide, and p-methyl benzene sulfonyl hydrazide.

3. The electrolyte of claim 1 or 2, wherein the wetting additive is present in an amount of 0.1 to 1% by weight.

4. The electrolyte of claim 1, wherein the film forming additive comprises one or more of ethylene sulfite, ethylene carbonate, fluoroethylene carbonate, lithium bis-fluorosulfonylimide, and lithium difluoro-oxalato-borate.

5. The electrolyte of claim 1 or 4, wherein the film forming additive is present in an amount of 2-6% by weight.

6. The electrolyte of claim 1, wherein the carbonates comprise one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and wherein the carbonates comprise one or more of ethyl acetate, propyl acetate, and propylene carbonate.

7. The electrolyte of claim 1 or 6, wherein the organic solvent is present in an amount of 75-88% by weight.

8. The electrolyte of claim 1, wherein the lithium hexafluorophosphate is present in an amount of 5-20% by weight.

9. A high capacity lithium ion battery comprising a positive plate, a negative plate, a separator and an electrolyte, wherein the electrolyte is the electrolyte according to any one of claims 1 to 8.

10. The high-capacity lithium ion battery according to claim 9, wherein the material of the positive electrode sheet is lithium cobaltate, a ternary material or lithium iron phosphate, and the material of the negative electrode sheet is artificial graphite, natural graphite or composite graphite.

Technical Field

The invention relates to the technical field of batteries, in particular to an electrolyte and a high-capacity lithium ion battery.

Background

Compared with a lead-acid battery, a nickel-cadmium battery and a nickel-hydrogen battery, the lithium ion battery has the advantages of high energy density, high voltage, long service life, low self-discharge rate, no memory effect, environmental friendliness and the like, and at present, the lithium ion battery is applied more and more widely as a mobile portable power source in the market, for example, 3C products, unmanned planes, electric tools, UPS, electric bicycles, electric automobiles and the like, and the range covers the land, sea and air field. As a mobile power source, consumers expect a battery to provide energy for a long time, and therefore, development of a high-capacity, long-cycle-life lithium battery is one of important issues facing the related art.

The battery capacity is generally improved in the following ways: firstly, improving the performance of the positive and negative electrode active materials, such as nano-crystallization, doping modification, cladding and the like of material particles; secondly, the compaction density of the battery pole piece is mentioned; and thirdly, improvement of the structural design of the battery so as to provide more space for active materials, such as reduction of the thickness of a current collector and a separator.

The comprehensive result is that the increase of the battery capacity brings about the increase of the density of the materials in the battery to a certain extent, which leads to the reduction of the storage space of the electrolyte in the lithium battery, especially for the nano anode and cathode materials or a high compaction system, the pores among the pole pieces are reduced, the electrolyte is difficult to reach, the lithium ion transmission is difficult, the capacity exertion of the lithium battery is limited, and new pressure and challenge are brought to the electrolyte.

Disclosure of Invention

Based on the above, the invention aims to provide an electrolyte and a high-capacity lithium ion battery containing the electrolyte, so as to solve the technical problem that the existing high-capacity battery is difficult in lithium ion transmission.

An electrolyte according to an embodiment of the present invention includes an organic solvent including carbonates and carboxylates, a lithium salt including lithium hexafluorophosphate, and an additive including a wetting additive and a film forming additive.

Preferably, the wetting additive comprises one or more of acetyl hydrazide, benzene sulfonyl hydrazide and p-methyl benzene sulfonyl hydrazide.

Preferably, the wetting additive is present in an amount of 0.1 to 1% by weight.

Preferably, the film forming additive comprises one or more of ethylene sulfite, ethylene carbonate, fluoroethylene carbonate, lithium bis-fluoro-sulfonimide and lithium difluoro-oxalato-borate.

Preferably, the weight percentage of the film forming additive is 2-6%.

Preferably, the carbonate includes one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, and the carboxylic acid ester includes one or more of ethyl acetate, propyl acetate and propylene carbonate.

Preferably, the weight percentage of the organic solvent is 75-88%.

Preferably, the weight percentage of the lithium hexafluorophosphate is 5-20%.

A high-capacity lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the electrolyte is the electrolyte.

Preferably, the material of the positive plate is lithium cobaltate, a ternary material or lithium iron phosphate, and the material of the negative plate is artificial graphite, natural graphite or composite graphite.

Compared with the prior art: the wetting additive is added into the electrolyte, so that the wetting property of the electrolyte is good, the adhesiveness and the deposition amount of the electrolyte on the surfaces of the anode and cathode particle materials of the pole piece are improved, the diffusion property of the electrolyte among the gaps of the particle materials is improved, the quick and effective transmission of lithium ions between the anode and the cathode is realized, and the capacity exertion performance of the lithium battery is improved; meanwhile, due to the addition of the composite additive in the electrolyte, a layer of compact, uniform and stable interfacial film can be formed on the surfaces of the positive and negative electrode materials, so that the electrochemical active sites on the surfaces of the positive and negative electrode materials are reduced, the side reactions of decomposition, metal dissolution and the like of the electrolyte are inhibited, and the cycle life of the lithium battery is prolonged.

Detailed Description

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Further, as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. In the detailed description and claims, a list of items connected by the term "one of" may mean any of the listed items. For example, if items a and B are listed, the phrase "one of a and B" means a alone or B alone. In another example, if items A, B and C are listed, the phrase "one of A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements. In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" or "at least one of a or B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" or "at least one of A, B or C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

On one hand, aiming at the problems that the increase of the capacity of the existing battery brings about the increase of the density of the internal material of the battery to a certain extent, so that the storage space of the electrolyte in the lithium battery is reduced, and particularly for a nano positive and negative electrode material or a high-compaction system, the pores among pole piece particles are reduced, the electrolyte is difficult to reach, so that the lithium ion transmission is difficult, and the capacity exertion of the lithium battery is limited, the invention provides the electrolyte and the high-capacity lithium ion battery containing the electrolyte, wherein the electrolyte comprises an organic solvent, a lithium salt and an additive, the organic solvent comprises carbonates and carboxylates, the lithium salt comprises lithium hexafluorophosphate, and the additive comprises a wetting additive and a film-forming additive.

Compared with the existing common electrolyte, the electrolyte in the embodiment of the invention has the advantages that the wetting additive is added into the electrolyte, so that the wettability of the electrolyte is good, the adhesiveness and the deposition amount of the electrolyte on the surfaces of anode and cathode particle materials of a pole piece are improved, the diffusion performance of the electrolyte among gaps of the particle materials is improved, the rapid and effective transmission of lithium ions between the anode and the cathode is realized, and the capacity exertion performance of a lithium battery is improved; meanwhile, due to the addition of the composite additive in the electrolyte, a layer of compact, uniform and stable interfacial film can be formed on the surfaces of the positive and negative electrode materials, so that the electrochemical active sites on the surfaces of the positive and negative electrode materials are reduced, the side reactions of decomposition, metal dissolution and the like of the electrolyte are inhibited, and the cycle life of the lithium battery is prolonged.

In some embodiments of the present invention, the wetting additive may specifically include one or more selected from the group consisting of acetyl hydrazide, benzenesulfonyl hydrazide and p-methylbenzenesulfonyl hydrazide, and the wetting additive is added to the electrolyte. When specifically selected, the wetting additive is preferably present in an amount of 0.1 to 1% by weight, for example 0.1%, 0.2%, 0.4%, 0.5%, 0.8%, 1%, etc.

In some embodiments of the invention, the film-forming additive comprises one or more of ethylene sulfite, ethylene carbonate, fluoroethylene carbonate, lithium bis-fluorosulfonylimide, and lithium difluoro-oxalato-borate. One or more selected from ethylene sulfite, ethylene carbonate, fluoroethylene carbonate, lithium bis-fluoro-sulfonimide and lithium difluoro-oxalato-borate are added into the electrolyte. When specifically selected, the weight percent of the film-forming additive is preferably 2-6%, e.g., 2%, 3.3%, 4%, etc.

In some embodiments of the invention, the carbonate includes one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and the carboxylic acid includes one or more of ethyl acetate, propyl acetate, and propylene carbonate. When specifically selected, the weight percentage of the organic solvent is preferably 75 to 88%, for example, 75%, 83.5%, 88%, etc.

In some embodiments of the invention, the weight percentage of lithium hexafluorophosphate (LiPF6) is 5-20%, such as 10%, 12%, 13%, 15%, etc. In other examples, lithium hexafluorophosphate may also be replaced by lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorophosphate or combinations thereof.

The preparation process of the electrolyte comprises the following steps: in a glove box, mixing organic solvents used by the electrolyte according to a corresponding proportion, then adding lithium salt LiPF6 in solid powder according to a proportion, adding additives according to a corresponding proportion after the solid lithium salt is completely dissolved, and uniformly mixing to obtain the electrolyte.

The invention further provides a high-capacity lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the electrolyte is the electrolyte in any embodiment of the invention. In specific implementation, the material of the positive plate is lithium cobaltate, a ternary material or lithium iron phosphate, and the material of the negative plate is an active material, specifically artificial graphite, natural graphite or composite graphite.

The preparation process of the high-capacity lithium ion battery comprises the following steps: the method comprises the steps of firstly, obtaining a battery cell to be injected by pulping, coating, rolling, slitting, winding, welding, vacuum baking and packaging, wherein the battery cell to be injected comprises a positive plate, a negative plate and a diaphragm, injecting the prepared electrolyte into the battery cell to be injected, and obtaining the high-capacity lithium ion battery by laying aside and forming.

In order to facilitate an understanding of the invention, several embodiments of the invention are set forth below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Examples 1 to 15

The electrolyte in examples 1 to 15 of the present invention is prepared by mixing the components and the proportions thereof shown in table 1 below, wherein the units of the numerical values shown in table 1 represent the weight percentages of the corresponding components in the electrolyte, for example, in the electrolyte in example 1, the organic solvent includes ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate, and the weight percentages of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate are 25%, 35%, 13.5% and 10%, respectively; the lithium salt comprises 13% by weight of lithium hexafluorophosphate; the wetting additive comprises acethydrazide with the weight percentage of 0.2 percent; the film forming additive comprises lithium difluoro (oxalato) borate, ethylene sulfite, fluoroethylene carbonate and ethylene carbonate, wherein the weight percentages of the lithium difluoro (oxalato) borate, the ethylene sulfite, the fluoroethylene carbonate and the ethylene carbonate are respectively 0.2%, 0.5%, 1% and 1.6%.

In addition, for the convenience of understanding the superiority of the scheme of the present invention, 5 comparative examples (preparation of common electrolyte) were also provided, namely comparative examples 1 to 5, and the common electrolyte in the comparative examples 1 to 5 was prepared by mixing the components and the proportions thereof as shown in table 1 below.

Table 1:

in practical application, the electrolytes correspondingly prepared in the above examples 1 to 15 and comparative examples 1 to 5 of the present invention are used to prepare a high-capacity lithium ion battery, and room temperature 1C rate discharge and cycle life tests are performed on the prepared high-capacity lithium ion battery to obtain gram capacity exertion of the active material and capacity residual rate after cycle, wherein the test data are shown in table 2 below. It should be noted that, in order to objectively verify the superiority of the electrolyte, the high-capacity lithium ion batteries prepared in the above examples 1 to 15 and comparative examples 1 to 5 of the present invention should be the same except for different electrolytes, for example, the materials of the positive electrode sheet are uniformly selected to be smallThe particle size of the coated lithium cobaltate material is compacted to 4.2g/cm³The negative plate material is uniformly made of natural graphite and compacted to 1.65g/cm³The process steps for making high capacity lithium ion batteries are also preferably kept the same.

Table 2:

as is apparent from the data in tables 1 and 2, the electrolyte prepared in the embodiment of the present invention can significantly improve the capacity performance of the lithium battery and the cycle life of the lithium ion battery, and can better meet the current and future market demands of the lithium ion battery, and has better market competitiveness.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.