CN116093431A

CN116093431A - Electrolyte additive, electrolyte, lithium battery and electric equipment

Info

Publication number: CN116093431A
Application number: CN202211681413.1A
Authority: CN
Inventors: 张伟峰; 冯旭宁; 王莉; 王贺武; 欧阳明高
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-12-27
Filing date: 2022-12-27
Publication date: 2023-05-09

Abstract

The application relates to an electrolyte additive, electrolyte, a lithium battery and electric equipment. The electrolyte additive comprises at least one of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and diphenyl phosphate. When the electrolyte additive is applied to the lithium battery, the electrolyte additive can be combined with free lithium ions in the lithium battery at the temperature when the temperature in the lithium battery is increased to be close to or reach the initiation temperature of thermal failure in the use process of the lithium battery, and a barrier film with good thermal stability is formed on the contact interface of the electrolyte additive and an energy-containing component such as an electrode plate and the like through the self-splicing reaction and/or the mutual splicing reaction. The barrier film can timely block the contact between the electrolyte and the energy-containing components such as the electrode pole pieces, avoid continuously generating heat, inhibit the increase of the internal temperature of the lithium battery, and effectively reduce the risk of combustion and explosion of the lithium battery caused by the overhigh internal temperature.

Description

Electrolyte additive, electrolyte, lithium battery and electric equipment

Technical Field

The application relates to the technical field of lithium batteries, in particular to an electrolyte additive, electrolyte, a lithium battery and electric equipment.

Background

With the rapid development of new energy technology, lithium batteries have been widely used because of their high energy density and environmental friendliness. For example, lithium batteries have large usage in portable electric devices such as mobile phones, watches, notebook computers, and the like, and in transportation-type electric devices such as electric bicycles, electric automobiles, and the like. However, although lithium batteries have many advantages, lithium batteries themselves have certain limitations. As a manifestation of the limitations of lithium batteries themselves, thermal failure has limited the further development of lithium batteries to a large extent.

In general, thermal failure of a lithium battery is represented by a situation that during charging and using of the battery, due to the existence of abusive conditions, the temperature inside the battery is continuously increased, so that the battery loses normal service performance and fails, and at this time, due to the fact that the temperature inside the battery is higher, combustion of the battery and even explosion of the battery are easily caused. Therefore, how to reduce the risk of combustion and explosion occurring when the lithium battery is thermally failed is of great importance for the further development of the lithium battery.

Disclosure of Invention

Based on this, it is necessary to provide an electrolyte additive, an electrolyte, a lithium battery, and an electric device. The electrolyte additive can effectively reduce the combustion and explosion risks when the lithium battery is in thermal failure, improve the use safety of the lithium battery and further promote the development of the lithium battery.

In order to solve the technical problems, the technical scheme of the application is as follows:

it is an object of the present application to provide an electrolyte additive. The electrolyte additive comprises at least one of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and diphenyl phosphate.

In one embodiment, the electrolyte additive includes the 2, 3-pentafluoropropyl acrylate, the polyethylene glycol methyl ether methacrylate, and the cresyl diphenyl phosphate.

In one embodiment, the molar ratio of the 2, 3-pentafluoropropyl acrylate, the polyethylene glycol methyl ether methacrylate and the diphenyl cresyl phosphate is 1 (0.5-1.5): 0.5-1.5.

In one embodiment, the electrolyte additive undergoes a self-splicing reaction and/or a mutual-splicing reaction at a temperature of 150 ℃ to 200 ℃.

It is another object of the present application to provide an electrolyte. The electrolyte includes an electrolyte salt and the electrolyte additive described in any of the embodiments above.

In one embodiment, the electrolyte additive is 3-15% by mass of the electrolyte.

In one embodiment, the electrolyte salt comprises a lithium salt.

In one embodiment, the electrolyte further comprises a solvent.

It is yet another object of the present application to provide a lithium battery. The lithium battery comprises a positive electrode plate, a negative electrode plate and the electrolyte in any embodiment; the positive electrode piece and the negative electrode piece are both in contact with the electrolyte.

It is yet another object of the present application to provide a powered device. The electric equipment comprises the lithium battery.

The electrolyte additive comprises at least one of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and diphenyl phosphate. The inventors of the present application have conducted intensive studies on the mechanism of thermal failure of lithium batteries, and found that in lithium batteries, thermal instability of an electrolyte and thermal instability of a coexisting system of the electrolyte and other components in the battery have important effects on initiating thermal failure of lithium batteries. For example, thermal instability of the electrolyte and thermal instability of a coexisting system of the electrolyte and other components in the battery easily cause thermo-chemical reaction at contact interfaces of the electrolyte and the energy-containing components such as electrode plates, etc., so that heat generation amount of the battery system is increased, and thermal failure of the battery is further caused. When the lithium battery is in thermal failure, the temperature inside the lithium battery is rapidly increased, and the risk of battery combustion and explosion occurs. The molecular structure terminal of the electrolyte additive contains fluorine element and/or phosphorus element with strong electronegativity, and the fluorine element and/or the phosphorus element can be combined with free lithium ions in the lithium battery. The electrolyte additives are then capable of undergoing self-assembly reactions and/or inter-assembly reactions under the catalysis of lithium ions. When the electrolyte additive is applied to a lithium battery, in the use process of the lithium battery, when the temperature inside the lithium battery is increased to be close to or reach the initiation temperature of thermal failure, the electrolyte additive can be combined with free lithium ions inside the lithium battery at the temperature, and a barrier film with good thermal stability is formed on the contact interface of the electrolyte additive and an energy-containing component such as an electrode plate through the self-splicing reaction and/or the mutual splicing reaction. At this time, the barrier film can timely block the contact between the electrolyte and the energy-containing components such as the electrode pole pieces, so that the lithium battery no longer has normal use function, the continuous heat generation caused by the contact between the electrolyte and the energy-containing components such as the electrode pole pieces is avoided, and the increase of the internal temperature of the lithium battery is inhibited. Therefore, the risk of combustion and explosion of the lithium battery due to overhigh internal temperature can be effectively reduced, the function of triggering safety protection by self-destruction of the lithium battery is realized, and the use safety of the lithium battery is greatly improved. Meanwhile, the barrier film can also block crosstalk between oxidizing gas and reducing gas generated by the electrode pole piece, block chain exothermic reaction in the lithium battery, inhibit further increase of the internal temperature of the lithium battery, and further reduce risks of combustion and explosion of the lithium battery.

In addition, the electrolyte additive has higher ionic conductivity, and can not cause adverse effect on the capacity and the cycle performance of the lithium battery when being applied to the lithium battery, and even can improve the capacity and the cycle performance of the lithium battery to a certain extent, thereby improving the comprehensive performance of the lithium battery.

Drawings

Fig. 1 is a graph showing the capacity and cycle performance of lithium ion batteries in example 1 and comparative example 1 of the present application.

Fig. 2 is a surface topography of the positive electrode after thermal failure of the lithium ion battery in example 1 of the present application.

Fig. 3 is a graph showing the thermal runaway results of the lithium ion battery in example 1 of the present application.

Fig. 4 is a graph showing the thermal runaway results of the lithium ion battery of comparative example 1 of the present application.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is, however, susceptible of embodiment in many other forms than those described herein and similar modifications can be made by those skilled in the art without departing from the spirit of the application, and therefore the application is not to be limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc. indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be configured and operated in a particular orientation, and therefore should not be construed as limiting the present application.

In this application, unless specifically stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.

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 application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

An embodiment of the present application provides an electrolyte additive. The electrolyte additive comprises at least one of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and diphenyl phosphate.

In lithium batteries, thermal instability of the electrolyte and of the system in which the electrolyte coexists with other components in the battery have a significant impact on the initiation of thermal failure of the lithium battery. For example, thermal instability of the electrolyte and thermal instability of a coexisting system of the electrolyte and other components in the lithium battery easily cause thermo-chemical reaction at contact interfaces of the electrolyte and the electrode plate and other energetic components, so that heat generation amount of the battery system is increased, and thermal failure of the battery is further caused. When the lithium battery is in thermal failure, the temperature in the lithium battery is rapidly increased, so that the risk of combustion and explosion of the battery occurs. The molecular structure terminal of the electrolyte additive in this embodiment contains fluorine element and/or phosphorus element with strong electronegativity, and the fluorine element and/or phosphorus element can be combined with free lithium ions. The electrolyte additives are then capable of undergoing self-assembly reactions and/or inter-assembly reactions under the catalysis of lithium ions. When the electrolyte additive in this embodiment is applied to a lithium battery, during the use of the lithium battery, when the temperature inside the lithium battery increases to a temperature close to or reaching the initiation temperature of thermal failure, the electrolyte additive can bond with free lithium ions inside the lithium battery at the temperature and form a barrier film with good thermal stability on the contact interface with an energy-containing component such as an electrode through the self-assembly reaction and/or the mutual assembly reaction of catalysis. At this time, the barrier film can timely block the contact between the electrolyte and the energy-containing components such as the electrode, so that the lithium battery no longer has normal use function, the continuous heat generation caused by the contact between the electrolyte and the energy-containing components such as the electrode pole piece is avoided, and the increase of the internal temperature of the lithium battery is inhibited. Therefore, the risk of combustion and explosion of the lithium battery due to overhigh internal temperature can be effectively reduced, the function of triggering safety protection by self-destruction of the lithium battery is realized, and the use safety of the lithium battery is greatly improved. Meanwhile, the barrier film can also block crosstalk between oxidizing gas and reducing gas generated by the electrode pole piece, block chain exothermic reaction in the lithium battery, inhibit further increase of the internal temperature of the lithium battery, and further reduce risks of combustion and explosion of the lithium battery.

In addition, the electrolyte additive in the embodiment has higher ion conductivity, and can not cause adverse effect on the capacity and the cycle performance of the lithium battery when being applied to the lithium battery, and even can improve the capacity and the cycle performance of the lithium battery to a certain extent, thereby improving the comprehensive performance of the lithium battery.

Meanwhile, when the electrolyte additive in the embodiment is applied to a lithium battery, the electrolyte additive can participate in the construction of an SEI film (solid electrolyte interface film), so that the cycle performance and the service life of the lithium battery can be improved.

In a specific example, when the electrolyte additive is applied to a lithium battery, the electrolyte additive exists in a liquid state under normal working conditions of the battery, such as the temperature of the lithium battery is within 120 ℃, and the electrolyte additive has an ethylene oxide-propylene oxide block in a structure to dissolve lithium salt, so that the electrolyte additive can promote quick conduction of lithium ions, thus having higher ionic conductivity and being beneficial to improving the comprehensive performance of the lithium battery. When the internal environment of the lithium battery is unstable due to the abuse working condition, and the internal temperature of the battery is increased to more than 130 ℃, the electrolyte is easy to perform thermochemical reaction with the contact interface of the electrode plate and other energy-containing components, and meanwhile, when the internal temperature of the lithium battery is higher, the isolating film of the lithium battery is contracted, so that the positive electrode plate and the negative electrode plate are contacted, and the internal temperature of the lithium battery is further increased. When the temperature in the lithium battery is increased to about 180 ℃, the electrolyte additive is catalyzed by lithium ions on the contact interface of the energy-containing components such as the electrode pole pieces and the like, and self-splicing reaction and/or mutual splicing reaction are carried out to form a barrier film with good thermal stability on the contact interface, at the moment, the barrier film can timely block the contact between the electrolyte and the energy-containing components such as the electrode pole pieces and the like, so that the lithium battery does not have normal use function, heat is continuously generated due to the contact between the electrolyte and the energy-containing components such as the electrode pole pieces and the like, and the increase of the temperature in the lithium battery is restrained. Therefore, the risk of combustion and explosion of the battery due to overhigh internal temperature can be effectively reduced, the function of triggering safety protection by self-destruction of the battery is realized, and the use safety of the lithium battery is greatly improved. Meanwhile, the barrier film can also block crosstalk between oxidizing gas and reducing gas generated by the electrode pole piece, block chain exothermic reaction in the lithium battery, inhibit further increase of the temperature in the lithium battery, and further reduce risks of combustion and explosion of the battery.

It is understood that in some embodiments, the electrolyte additive includes 2, 3-pentafluoropropyl acrylate. In some embodiments, the electrolyte additive includes polyethylene glycol methyl ether methacrylate. In some embodiments, the electrolyte additive includes cresyl diphenyl phosphate. Alternatively, the electrolyte additive is 2, 3-pentafluoropropyl acrylate. Alternatively, the electrolyte additive is polyethylene glycol methyl ether methacrylate. Alternatively, the electrolyte additive is cresyl diphenyl phosphate.

It is also understood that in some embodiments, the electrolyte additive includes any two of 2, 3-pentafluoropropylacrylate, polyethylene glycol methyl ether methacrylate, and cresyl diphenyl phosphate. For example, electrolyte additives include 2, 3-pentafluoropropyl acrylate and polyethylene glycol methyl ether methacrylate. Alternatively, the electrolyte additive includes 2, 3-pentafluoropropyl acrylate and cresyl diphenyl phosphate. Alternatively, the electrolyte additive includes polyethylene glycol methyl ether methacrylate and cresyl diphenyl phosphate. Alternatively, the electrolyte additive is formed by mixing 2, 3-pentafluoropropyl acrylate and polyethylene glycol methyl ether methacrylate. Alternatively, the electrolyte additive is formed by mixing 2, 3-pentafluoropropyl acrylate and diphenyl cresyl phosphate. Or the electrolyte additive is formed by mixing polyethylene glycol methyl ether methacrylate and diphenyl cresyl phosphate.

In a specific example, the electrolyte additive includes 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate, and cresyl diphenyl phosphate. Optionally, the electrolyte additive is formed by mixing 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and diphenyl cresyl phosphate.

When the electrolyte additive includes 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and cresyl diphenyl phosphate, as a specific example of the three proportions, the molar ratio of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and cresyl diphenyl phosphate is 1: (0.5-1.5), and (0.5-1.5). Alternatively, the molar ratio of 2, 3-pentafluoropropylacrylate, polyethylene glycol methyl ether methacrylate and cresyl diphenyl phosphate may be, but is not limited to, 1 (0.5-1.5): 0.5, 1 (0.5-1.5): 0.8, 1 (0.5-1.5): 0.9, 1 (0.5-1.5): 1, 1 (0.5-1.5): 1.2, 1 (0.5-1.5): 1.5, 1:0.5 (0.5-1.5), 1:0.8 (0.5-1.5), 1:0.9 (0.5-1.5), 1:1.1 (0.5-1.5), 1:1.2 (0.5-1.5), 1:1.5-1.5, etc. Further alternatively, the method may comprise, in a further alternative, the molar ratio of 2, 3-pentafluoropropylacrylate, anisole methacrylate and cresyl diphenyl phosphate may be, but is not limited to, 1:0.5:0.5, 1:0.8:0.5, 1:0.8:0.8, 1:0.8:1, 1:0.8:0.9, 1:0.8:1, 1:0.8:1.1, 1:0.8:1.2, 1:0.9:0.8, 1:0.9:1, 1:0.9:0.9, 1:0.9:1: 1:0.9:1.1, 1:0.9:1.2, 1:0.9:1.5, 1:1:0.8, 1:1:0.9, 1:1:1, 1:1.1, 1:1:1.2, 1:1:1.5, 1:1.1:0.8, 1:1.1:1, 1:1.1:0.9, 1:1.1:1, 1:1.1:1.1, 1:1.1:1.2, 1:1.1:1.5, 1:1.2:0.8, 1:1.2:1, 1:1.2:0.9, 1:1.2:1, 1:1.2:1.2, 1:1.2:1.5, 1:1.5, etc. It will be appreciated that the molar ratio of 2, 3-pentafluoropropyl acrylate, polyethylene glycol methyl ether methacrylate and cresyl diphenyl phosphate may be chosen in other suitable ranges from 1 (0.5 to 1.5) to 0.5 to 1.5.

It is understood that the temperature at which the electrolyte additives undergo self-and/or mutual-splicing reactions is 150-200 ℃. For example, the temperature at which the electrolyte additives undergo self-assembly reactions and/or mutual assembly reactions is 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, etc. It is understood that the electrolyte additives may form a polymer barrier film with good thermal stability at their contact interface with the energized components, such as electrode sheets, by self-and/or mutual-stitching reactions.

Yet another embodiment of the present application provides an electrolyte. The electrolyte comprises an electrolyte salt and the electrolyte additive.

It is understood that when the electrolyte additive in the present application is applied to a lithium battery, the electrolyte additive is added to the electrolyte of the lithium battery, and the effect of the electrolyte additive is exerted by the electrolyte and other components in the lithium battery.

Alternatively, the electrolyte may be of a liquid electrolyte, i.e. an electrolyte solution. The electrolyte may be a solid electrolyte, a quasi-solid electrolyte, a gel electrolyte, or the like.

In a specific example, the electrolyte additive is 3-15% by mass of the electrolyte. Alternatively, the mass percent of the electrolyte additive may be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., based on the mass percent of the electrolyte. It will be appreciated that the mass percent of electrolyte additives may be selected to be in the range of 3% to 15% by mass of the electrolyte.

In one specific example, the electrolyte salt includes a lithium salt. Alternatively, the lithium salt may be lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) One or more of them. It is understood that the lithium salt may also be selected from other conventional lithium salts in lithium batteries.

In a specific example, the electrolyte further includes a solvent. Alternatively, the solvent is an organic solvent. Further, the solvent may be one or more of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC). It will be appreciated that the solvent may also be selected from other conventional solvents in lithium batteries.

In a specific example, the solvent is formed by mixing ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1.

In one specific example, the electrolyte is an electrolyte solution. The electrolyte comprises electrolyte salt, solvent and electrolyte additive.

Wherein, the mass percent of the electrolyte additive is 3-15 percent of the electrolyte solution. Alternatively, the mass percent of the electrolyte additive may be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., based on the mass percent of the electrolyte. It will be appreciated that the mass percent of electrolyte additives may be selected to be in the range of 3% to 15% by mass of the electrolyte.

Wherein the molar concentration of the electrolyte salt is 0.5mol/L to 2mol/L. For example, the molar concentration of the electrolyte salt may be, but is not limited to, 0.5mol/L, 0.8mol/L, 1mol/L, 1.2mol/L, 1.5mol/L, 1.8mol/L, 2mol/L, etc. It will be appreciated that the molar concentration of the electrolyte salt may be selected in the range of 0.5mol/L to 2mol/L.

Yet another embodiment of the present application provides a lithium battery. The lithium battery comprises a positive pole piece, a negative pole piece and the electrolyte; the positive pole piece and the negative pole piece are both in contact with the electrolyte. In the lithium battery in the embodiment, when the lithium battery has thermal failure under the abuse working condition, the function of triggering safety protection by self-destruction of the lithium battery can be realized through the action of the electrolyte, the lithium battery is disabled before the problems of combustion, explosion and the like of the lithium battery occur, and the safety performance of the lithium battery is effectively improved. Meanwhile, due to the effect of electrolyte, the capacity and the cycle performance of the lithium battery are improved to a certain extent, and the comprehensive performance of the lithium battery is improved to a certain extent.

It is understood that lithium batteries include lithium ion batteries. It is understood that the lithium battery further includes a separator located between the positive electrode tab and the negative electrode tab.

Still another embodiment of the present application provides an electrical device. The electric equipment comprises the lithium battery. Optionally, the electric equipment can be portable electric equipment such as a mobile phone, a watch, a notebook computer and the like, and can also be transportation type electric equipment such as an electric bicycle, an electric automobile and the like.

The following are specific examples.

Example 1

The electrolyte in this embodiment is an electrolyte. The electrolyte includes an additive, an electrolyte salt, and a solvent. Wherein the additive is formed by mixing 2, 3-pentafluoropropyl acrylate (CAS number: 356-86-5), polyethylene glycol methyl ether methacrylate (CAS number: 26915-72-0) and diphenyl phosphate (CAS number: 26444-49-5). The molar ratio of the 2, 3-pentafluoropropyl acrylate, the polyethylene glycol methyl ether methacrylate and the diphenyl cresyl phosphate is 1:1:1, and the additive accounts for 10 percent of the mass of the electrolyte. The solvent is prepared by mixing ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate according to the mass ratio of 1:1:1. The electrolyte salt is lithium hexafluorophosphate, and the molar concentration of the lithium hexafluorophosphate is 1mol/L.

The preparation of the lithium ion battery in this embodiment is:

and assembling the positive electrode plate, the negative electrode plate, the isolating film and the electrolyte into the lithium ion battery.

Wherein the positive electrode active material is a nickel-cobalt-manganese ternary material: liNi _x Co _y Mn _z O ₂ Wherein x: y: z=1:1:1. The negative electrode active material is graphite. The isolating film is PP isolating film.

Comparative example 1

Comparative example 1 differs from example 1 in that the electrolyte contains no additive.

Test case

(1) Capacity and cycle performance tests were performed on the lithium ion batteries in example 1 and comparative example 1. The test results are shown in FIG. 1. As can be seen from fig. 1, the capacity and cycle performance of the lithium ion battery after the additive was added to the electrolyte in example 1 were not reduced, even slightly higher than that in comparative example 1. The electrolyte additive in example 1 is shown to be added, so that the capacity and the cycle performance of the battery are not adversely affected, and even the capacity and the cycle performance of the battery can be improved to a certain extent, and the comprehensive performance of the battery is improved.

(2) The lithium ion battery in example 1 was subjected to a thermal failure test, and when the temperature of the lithium ion battery reached the failure temperature, the battery was failed, and at this time, the battery was disassembled, and the surface of the positive electrode sheet of the battery was analyzed, and the result is shown in fig. 2. In fig. 2, (b) is a partial enlarged view of (a). As can be seen from fig. 2, a barrier film is formed at the contact interface of the electrolyte and the electrode tab. The existence of the barrier film can inhibit the continuous rise of the internal temperature of the battery in time when the battery is in thermal failure, so that the battery is prevented from burning and exploding.

(3) The temperatures of the lithium ion batteries in example 1 and comparative example 1 were tested, and the results are shown in fig. 3 and 4, respectively. As can be seen from fig. 4, the battery in comparative example 1 has a thermal runaway maximum temperature of 736 ℃. As can be seen from fig. 3, the safety performance of the battery in example 1 was greatly improved, and the maximum temperature of thermal runaway of the battery was reduced by 300 ℃ or more than that of the battery of comparative example 1.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the claims. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. The scope of the patent is therefore intended to be covered by the appended claims, and the description and drawings may be interpreted as illustrative of the contents of the claims.

Claims

1. An electrolyte additive comprising at least one of 2, 3-pentafluoropropylacrylate, polyethylene glycol methyl ether methacrylate, and diphenyl cresyl phosphate.

2. The electrolyte additive of claim 1, comprising the 2, 3-pentafluoropropyl acrylate, the polyethylene glycol methyl ether methacrylate, and the diphenyl phosphate.

3. The electrolyte additive according to claim 2, wherein the molar ratio of the 2, 3-pentafluoropropyl acrylate, the polyethylene glycol methyl ether methacrylate, and the diphenyl cresyl phosphate is 1 (0.5 to 1.5): 0.5 to 1.5.

4. The electrolyte additive according to any one of claims 1 to 3, wherein the temperature at which the self-assembly reaction and/or the mutual assembly reaction occurs is 150 ℃ to 200 ℃.

5. An electrolyte comprising an electrolyte salt and the electrolyte additive of any one of claims 1 to 4.

6. The electrolyte of claim 5, wherein the electrolyte additive is present in an amount of 3 to 15 mass percent based on the mass percent of the electrolyte.

7. The electrolyte of claim 5 wherein the electrolyte salt comprises a lithium salt.

8. The electrolyte according to any one of claims 5 to 7, wherein the electrolyte further comprises a solvent.

9. A lithium battery comprising a positive electrode sheet, a negative electrode sheet, and the electrolyte of any one of claims 5 to 8; the positive electrode piece and the negative electrode piece are both in contact with the electrolyte.

10. A powered device comprising the lithium battery of claim 9.