CN116454391B

CN116454391B - Electrolyte, secondary battery, and electricity-using device

Info

Publication number: CN116454391B
Application number: CN202310687627.8A
Authority: CN
Inventors: 吴凯; 石鹏; 赵延杰; 张帆; 孟阵; 魏冠杰; 林江辉; 张宇
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-06-12
Filing date: 2023-06-12
Publication date: 2023-09-12
Anticipated expiration: 2043-06-12
Also published as: CN116454391A

Abstract

The present application relates to an electrolyte, a secondary battery, and an electric device. The electrolyte includes an additive including composite particles having an outer shell and an inner core, the inner core including a first lithium salt, the outer shell including inorganic particles; wherein the inorganic particles contain at least one element of N, P, S, F, br and O, and the solubility of the inorganic particles in a linear ester solvent at 25 ℃ is 0.01 mmol/L to 110 mmol/L. The cycle performance of the battery can be improved by including a lithium salt in the electrolyte, and an additive in which specific inorganic particles are included in the outer shell.

Description

Electrolyte, secondary battery, and electricity-using device

Technical Field

The application relates to the field of secondary batteries, in particular to electrolyte, a secondary battery and an electric device.

Background

In recent years, the application range of secondary batteries typified by lithium ion batteries has been expanding, and the secondary batteries are widely used in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like. As secondary batteries have been greatly developed, there are also demands for higher energy density, cycle performance, safety performance, and the like.

At present, in the electrolyte system of the traditional lithium ion battery, the cycle performance of the lithium ion battery is poor.

Content of the application

Based on this, it is necessary to provide an electrolyte and a secondary battery, a battery module, a battery pack, and an electric device to improve the cycle performance of a lithium ion battery.

In order to achieve the above object, a first aspect of the present application provides an electrolyte comprising an additive, the additive being a composite particle having an outer shell and an inner core, the inner core comprising a first lithium salt, the outer shell comprising inorganic particles; wherein the inorganic particles contain at least one element of N, P, S, F, br and O, and the solubility of the inorganic particles in a linear ester solvent at 25 ℃ is 0.01mmol/L to 110 mmol/L.

The electrolyte additive provided by the application adopts a shell-core structure, the inner shell comprises first lithium salt, the outer shell comprises inorganic particles, the inorganic particles contain the specific elements, the inorganic particles have specific solubility in the linear ester solvent, the dissolution process of the additive in the electrolyte containing the linear ester solvent is slowly carried out in the process of battery charge-discharge circulation, namely, when the battery starts to work, the inorganic particles in the outer shell of the additive can not be immediately dissolved, the outer shell of the additive has a slow-release effect, the inorganic particles in the outer shell are continuously dissolved in the electrolyte along with the circulation, the formation of an SEI film is participated, the ion conductivity of the SEI is improved, and along with the circulation, the lithium salt in the inner shell part is released into the electrolyte, the lithium consumption is relieved, the ion conductivity of the electrolyte is further improved, and the battery can still keep higher ion conductivity after long-term circulation is ensured, so that the circulation performance of the battery is improved.

In some of these embodiments, the inorganic particles have a solubility in the linear ester solvent of from 10 mmol/L to 100 mmol/L at 25 ℃. The solubility of the inorganic particles is within this range, and the charge-discharge cycle performance of the battery can be further improved.

In some of these embodiments, the inorganic particles include one or more of nitrate, phosphate, sulfate, fluoride, bromide, nitrite, and oxide.

In some of these embodiments, the inorganic particles comprise one or more of a metal nitrate, a metal phosphate, a metal sulfate, a metal fluoride, a metal nitrite, and a metal oxide.

Optionally, the metal element in the inorganic particles includes at least one of an alkali metal element and an alkaline earth metal element.

In some of these embodiments, the inorganic particles include one or more of lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, calcium nitrate, magnesium nitrate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, calcium phosphate, magnesium phosphate, lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, calcium sulfate, magnesium sulfate, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, calcium fluoride, magnesium fluoride, lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, magnesium bromide, lithium nitrite, sodium nitrite, potassium nitrite, magnesium nitrite, lithium oxide, sodium oxide, calcium oxide, and magnesium oxide.

Optionally, the inorganic particles include one or more of lithium nitrate, potassium nitrate, lithium fluoride, potassium fluoride, lithium sulfate, and lithium bromide.

In some of these embodiments, the first lithium salt comprises one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis (fluoro-sulfonimide), and lithium bis (fluoro-methylsulfonimide).

In some of these embodiments, the ratio of the average particle diameter Dv50 of the inorganic particles to the volume average particle diameter Dv50 of the first lithium salt is recorded as P,0.0009 +.p +.0.1, alternatively 0.01 +.p +.0.025.

In some of these embodiments, the inorganic particles have a volume average particle size Dv50 of 1nm to 100nm, optionally 5nm to 20nm; and/or the number of the groups of groups,

the first lithium salt has a volume average particle diameter Dv50 of 100nm to 2000nm, optionally 500nm to 2000nm.

In some embodiments, the mass ratio of the additive in the electrolyte is 0.5-10wt%.

Optionally, the mass ratio of the additive in the electrolyte is 1-5 wt%.

In some of these embodiments, the electrolyte further comprises a stabilizer. The stabilizer can increase the dispersity of the additive in the organic solvent, reduce agglomeration and sedimentation, and improve the compactness of the SEI film.

Optionally, the stabilizer comprises one or more of sodium oleate, octadecylamine, sodium laurate, cocoamine, sodium stearate, AES, sodium dodecyl sulfate, dodecyl diamine and sodium dodecyl benzene sulfonate.

In some embodiments, the mass ratio of the stabilizer in the electrolyte is 1-10%.

In some of these embodiments, the electrolyte further comprises a second lithium salt.

Optionally, the second lithium salt comprises one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium bisfluorosulfonyl imide, and lithium bistrifluoromethylsulfonyl imide.

In some embodiments, the molar concentration of the second lithium salt in the electrolyte is 0.5-5 mol/L.

Optionally, the molar concentration of the second lithium salt in the electrolyte is 1-2 mol/L.

In some of these embodiments, the electrolyte further comprises an organic solvent.

Optionally, the organic solvent comprises one or more of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene propyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone and diethyl sulfone.

The second aspect of the application provides a secondary battery comprising the electrolyte according to the first aspect of the application.

A third aspect of the application provides an electric device comprising the secondary battery according to the second aspect of the application.

Drawings

Fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 1.

Fig. 3 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1. a secondary battery; 11. a housing; 12. an electrode assembly; 13. a cover plate; 2. and (5) an electric device.

Detailed Description

Hereinafter, embodiments of the electrolyte, the secondary battery, and the electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

In the present application, "optional" and "optional" refer to the presence or absence of the two parallel schemes, i.e., either "with" or "without". If multiple "alternatives" occur in a technical solution, if no particular description exists and there is no contradiction or mutual constraint, then each "alternative" is independent.

In the present application, "further", "still further", "particularly" and the like are used for descriptive purposes to indicate differences in content but should not be construed as limiting the scope of the application.

In the present application, the terms "first," "second," "third," "fourth," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor as implying an importance or quantity of a technical feature being indicated. Moreover, the terms "first," "second," "third," "fourth," and the like are used for non-exhaustive list description purposes only, and are not to be construed as limiting the number of closed forms.

Lithium ion batteries are increasingly receiving attention from researchers because of their advantages of high energy density, long life, no memory effect, etc. With the continuous development of lithium ion batteries, in particular, higher requirements are put on the safety performance and cycle life of the batteries. In the existing lithium ion electrolyte system, the electrochemical performance of the battery is reduced and the cycle performance is deteriorated after a plurality of charge and discharge cycles. In the related art, a film forming additive is mostly added to an electrolyte to improve the function of an SEI film so as to improve the cycle performance of a battery, but the improvement of the charge-discharge cycle performance of the battery is still limited.

In order to solve the above problems, the present application provides an electrolyte comprising an additive. The additive includes composite particles having an outer shell and an inner core, the inner core including a first lithium salt, the outer shell including inorganic particles. Wherein the inorganic particles contain at least one element of N, P, S, F, br and O, and the solubility of the inorganic particles in a linear ester solvent at 25 ℃ is 0.01 mmol/L to 110 mmol/L.

The additive in the electrolyte provided by the application adopts a shell-core structure, the inner shell comprises a first lithium salt, the outer shell comprises inorganic particles, the inorganic particles contain the specific elements, the inorganic particles have specific solubility in the linear ester solvent, the dissolution process of the additive in the electrolyte containing the linear ester solvent is slowly carried out in the process of battery charge-discharge circulation, namely, when the battery starts to work, the inorganic particles in the outer shell of the additive can not be immediately dissolved, the outer shell of the additive has a slow-release effect, the inorganic particles in the outer shell are continuously dissolved in the electrolyte along with the circulation, the SEI film is formed, the ion conductivity of SEI is improved, the lithium salt in the inner shell part is released into the electrolyte along with the circulation, the lithium consumption is relieved, the ion conductivity of the electrolyte is further improved, and the battery can still keep higher ion conductivity after long-term circulation, thereby improving the circulation performance of the battery.

In order to increase the stability of the core-shell structure, i.e., the bonding between the shell and the core, the shell of the additive further includes a binder, and the binder may be at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin. The weight ratio of the binder in the shell may be 0 to 20% by weight based on the total weight of the shell.

The structure and composition of the additive may be determined by methods known in the art, by electron scanning microscopy, test parameters: acceleration voltage is 10kV, and magnification is 5000 times.

The above-mentioned "0.01 mmol/L-110 mmol/L" values include the minimum and maximum values of this range, and each value between such minimum and maximum values, specific examples include, but are not limited to, the point values in the examples and the point values below: 0.05 mmol/L, 0.1 mmol/L, 0.5 mmol/L, 1 mmol/L, 2 mmol/L, 3 mmol/L, 4 mmol/L, 5 mmol/L, 6 mmol/L, 7 mmol/L, 8 mmol/L, 9 mmol/L, 10 mmol/L, 11 mmol/L, 12 mmol/L, 15 mmol/L, 20 mmol/L, 25 mmol/L, 30 mmol/L, 35 mmol/L, 40 mmol/L, 45 mmol/L, 50 mmol/L, 55 mmol/L, 60 mmol/L, 65 mmol/L, 70 mmol/L, 75 mmol/L, 80 mmol/L, 85 mmol/L, 90 mmol/L, 95 mmol/L, 100 mmol/L; or a range of any two values.

In some embodiments, the inorganic particles have a solubility in the linear ester solvent of from 10mmol/L to 100 mmol/L.

The solubility of the inorganic particles in the linear ester solvent is in the meaning known in the art and can be measured by means of instruments and methods known in the art, for example by means of the test method for apparent solubility specified in the chinese pharmacopoeia, 2000 edition, wherein the solvent is a linear ester.

In some embodiments, the inorganic particles include one or more of nitrate, phosphate, sulfate, fluoride, bromide, nitrite, and oxide.

In some embodiments, optionally, the inorganic particles include one or more of a metal nitrate, a metal phosphate, a metal sulfate, a metal fluoride, a metal bromide, a metal nitrite, and a metal oxide. Further alternatively, the metal element in the inorganic particles includes at least one of an alkali metal element and an alkaline earth metal element.

In some embodiments of the present invention, in some embodiments, the inorganic particles comprise lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, calcium nitrate, magnesium nitrate, lithium phosphate sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, calcium phosphate, magnesium phosphate, lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate cesium sulfate, calcium sulfate, magnesium sulfate, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, calcium fluoride, magnesium fluoride, lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, magnesium bromide, lithium nitrite, sodium nitrite, potassium nitrite,

One or more of calcium nitrite, magnesium nitrite, lithium oxide, sodium oxide, calcium oxide and magnesium oxide.

In some alternative embodiments, the inorganic particles comprise one or more of lithium nitrate, potassium nitrate, lithium fluoride, potassium fluoride, lithium sulfate, and lithium bromide. When the inorganic particles include one or more of lithium nitrate, potassium nitrate, lithium fluoride, potassium fluoride, lithium sulfate and lithium bromide, the SEI film formed by the inorganic particles has better performance, and can further improve the cycle performance of the battery.

The type of inorganic particles may be determined using instruments and methods well known in the art, such as inductively coupled plasma spectroscopy (ICP) testing. The basic principle is as follows: and carrying out qualitative analysis according to characteristic spectral lines emitted by atoms or ions of different elements under thermal excitation. Because the energy level structures of the atoms of the elements to be detected are different, the characteristics of the emission lines are different, and therefore, the qualitative analysis can be performed. The testing method comprises the following steps: and taking 6 parallel samples of the pole pieces to be tested, respectively weighing, resolving and diluting, and then testing element types by using an inductively coupled plasma emission spectrometer of the Thermo ICAP6300 model, thereby determining the types of inorganic particles.

In some embodiments, the first lithium salt comprises lithium perchlorate (LiClO) ₄ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium hexafluorophosphate (LiPF) ₆ ) One or more of lithium bis (oxalato) borate (LiBOB), lithium difluoro (lidadiob) oxalato borate (LiFSI), lithium bis (fluorosulfonyl) imide (LiTFSI).

In some embodiments, the ratio of the volume average particle diameter Dv50 of the inorganic particles to the volume average particle diameter Dv50 of the first lithium salt is recorded as P,0.0009 +.p +.0.1, alternatively 0.01 +.p +.0.025.

In some embodiments, the inorganic particles have a volume average particle size Dv50 of 1nm to 100nm, alternatively 5nm to 20nm.

The larger the volume average particle diameter Dv50 of the inorganic particles, the smaller the specific surface area, the smaller the contact area with the organic solvent, and the slower the dissolution rate of the additive shell. The smaller the volume average particle diameter Dv50 of the inorganic particles, the larger the specific surface area, the larger the contact area with the organic solvent, and the faster the dissolution rate of the additive shell. Therefore, the volume average particle diameter Dv50 of the inorganic particles is in a proper range, and the additive can obtain better slow-release dissolution effect, so that the first lithium salt is released at a more proper time, and the effect of effectively supplementing lithium is achieved. Meanwhile, the volume average particle diameter Dv50 of the inorganic particles is too large or too small, and the formed SEI film has poor compactness, stability and other performances. The volume average particle diameter Dv50 of the inorganic particles is within the above range, which is more advantageous for improving the cycle life of the battery, in combination with various synergistic effects.

The above values of "1nm to 100nm" include the minimum and maximum values of the range, and each value between such minimum and maximum values, and specific examples include, but are not limited to, the point values in the examples and the point values below: 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm; or a range of any two values.

In some embodiments, the first lithium salt has a volume average particle size Dv50 of 100nm to 2000nm, alternatively 500nm to 2000nm.

The above-mentioned values of "100nm to 2000nm" include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, the point values in the embodiments and the following point values: 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm; or a range of any two values.

The volume average particle diameter Dv50 of the first lithium salt is in the above range, which is more advantageous for improving the cycle life of the battery. The volume average particle diameter Dv50 of the first lithium salt is too large, which affects the stability of the additive and is easy to settle. The volume average particle diameter Dv50 of the first lithium salt is too small, and the coating effect of the outer shell is poor.

The volume average particle size Dv50 of the inorganic particles and the volume average particle size Dv50 of the first lithium salt are the meanings known in the art, which means the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be tested by the instruments and methods known in the art. For example, reference may be made to GB/T19077-2016 particle size distribution laser diffraction, which is conveniently carried out using a laser particle size analyzer, such as the Mastersizer 2000E type laser particle size analyzer available from Markov instruments, UK.

In some embodiments, the mass ratio of the additive in the electrolyte is 0.5-10 wt%, it being understood that the mass ratio of the additive in the electrolyte may also include, but is not limited to, 1wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%. When the mass ratio of the additive in the electrolyte is below the above range, it is difficult to ensure the formation of a stable SEI film; when the mass ratio of the additive in the electrolyte is higher than the above range, the additive is easy to settle, the mass of the electrolyte is increased, and the energy density of the system is reduced; meanwhile, when the mass ratio of the additive in the electrolyte is too high, the cost of the electrolyte will be increased. Optionally, the mass ratio of the additive in the electrolyte is 1-5 wt%.

The additives may be obtained commercially or by methods well known in the art. In some embodiments, the method of preparing the additive comprises:

mixing the first lithium salt and the binder according to the mass ratio of (0.05-0.5) to enable the surface of the first lithium salt to be fully wetted by the binder;

and mixing the inorganic particles with the first lithium salt fully wetted by the binder, wherein the mass ratio of the inorganic particles to the first lithium salt is 1:10-10:1.

In some embodiments, the electrolyte further comprises a stabilizer. Optionally, the stabilizer comprises one or more of sodium oleate, octadecylamine, sodium laurate, cocoamine, sodium stearate, AES, sodium dodecyl sulfate, dodecyl diamine and sodium dodecyl benzene sulfonate. The dispersion degree of the additive in the organic solvent can be enhanced by adding the stabilizer, and the compactness of the SEI film is improved.

In some embodiments, the electrolyte further comprises a second lithium salt; optionally, the second lithium salt comprises lithium perchlorate (LiClO) ₄ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium hexafluorophosphate (LiPF) ₆ ) One or more of lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiDFOB), lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethylsulfonyl imide (LiTFSI).

In some embodiments, the molar concentration of the second lithium salt in the electrolyte is 0.5-5 mol/L; optionally, the concentration is 1-2 mol/L.

The first lithium salt and the second lithium salt may be the same or different.

In some embodiments, the electrolyte further comprises an organic solvent; optionally, the organic solvent comprises one or more of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene propyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone and diethyl sulfone.

All of the above raw materials, not specifically described, are commercially available.

Secondary battery

The application also provides a secondary battery, which comprises the electrolyte, wherein the electrolyte is provided by the application.

In general, the secondary battery further includes a positive electrode tab, a negative electrode tab, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

Positive electrode plate

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, wherein the positive film layer comprises a positive active material.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material on a polymeric material substrate. Wherein the metal material comprises at least one of aluminum, aluminum alloy, nickel alloy, titanium alloy, silver and silver alloy. The polymer material substrate comprises at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and Polyethylene (PE).

In some embodiments, the positive electrode active material may comprise a positive electrode active material for a battery as known in the art.

As an example, the positive electrode active material of the lithium ion secondary battery may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

The weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the second binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin. The weight ratio of the second binder in the positive electrode film layer is 0-20% by weight based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black or ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components in solvent (such as N-methyl pyrrolidone) to form positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80wt%, the viscosity at room temperature is adjusted to 5000-25000 mPa.s, and coating the positive electrode slurryCoating the surface of the positive electrode current collector, drying, and cold-pressing by a cold rolling mill to form a positive electrode plate; the compacted density of the positive pole piece is 2.3-3.7 g/cm ³ Optionally 2.8-3.5 g/cm ³ . The thickness of the positive electrode diaphragm is 0.1000-0.1750mm.

The thickness T of the positive electrode film layer can be measured by a ten-thousandth ruler, for example, the thickness T can be measured by a model Mitutoyo293-100 and a precision of 0.1 mu m. The thickness of the positive electrode film layer in the application refers to the thickness of the positive electrode film layer in the positive electrode sheet used for assembling the battery after cold pressing and compaction.

Negative pole piece

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

The negative current collector is the current collector of the first aspect of the present application, and a metal foil or a composite current collector may be used. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material on a polymeric material substrate. The metal material includes, but is not limited to, copper alloy, nickel alloy, titanium alloy, silver alloy, etc., and the polymer material substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art.

As an example, the anode active material of the lithium ion secondary battery may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

The weight ratio of the anode active material in the anode film layer is 70-100% by weight based on the total weight of the anode film layer.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0 to 30% by weight based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent may be at least one selected from superconducting carbon, carbon black (e.g., acetylene black or ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like. The weight ratio of the other auxiliary agents in the negative electrode film layer is 0-15% by weight based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity of the negative electrode slurry at room temperature is adjusted to 2000-10000 mPa.s; the obtained product is then processedThe obtained negative electrode slurry is coated on a negative electrode current collector, and is subjected to a drying procedure and cold pressing, such as roller pairing, to obtain a negative electrode plate. The compacted density of the negative pole piece is 1.2-2.0 g/m ³ The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the negative electrode membrane is 0.1000-0.1900mm.

The thickness T of the negative electrode film layer can be measured by a ten-thousandth ruler, for example, the thickness T can be measured by a ten-thousandth ruler with the model of Mitutoyo293-100 and the precision of 0.1 mu m. The thickness of the negative electrode film layer refers to the thickness of the negative electrode film layer in the negative electrode plate used for assembling the battery after cold pressing and compaction.

Isolation film

In some embodiments, a separator is further included in the secondary battery.

In some embodiments, the separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multilayer composite film, the materials of the base films may be the same or different, and are not particularly limited.

In some embodiments, the thickness of the separator is 5-30 μm, optionally 7-18 μm.

In some embodiments, the barrier film may have a permeability of 100s/100mL to 300s/100mL; alternatively, the barrier film may have a permeability of 150s/100 mL-250 s/100mL, tested according to national standard GB/T36363-2018.

The thickness of the isolation can be measured by a ten-thousandth ruler, for example, the thickness can be measured by a ten-thousandth ruler with the model of Mitutoyo293-100 and the precision of 0.1 mu m.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a secondary battery 1 of a square structure as one example.

In some embodiments, referring to fig. 2, the outer package may include a housing 11 and a cover 13. The housing 11 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 11 has an opening communicating with the accommodation chamber, and the cover plate 13 can be provided to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 included in the secondary battery 1 may be one or more, and those skilled in the art may select according to specific practical requirements.

In some embodiments, the secondary batteries 1 may be assembled into a battery module, and the number of the secondary batteries 1 included in the battery module may be one or more, and a specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

In the battery module, the plurality of secondary batteries 1 may be sequentially arranged in the longitudinal direction of the battery module. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 1 may be further fixed by fasteners.

Alternatively, the battery module may further include a case having an accommodating space in which the plurality of secondary batteries 1 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

A battery case and a plurality of battery modules disposed in the battery case may be included in the battery pack. The battery box comprises an upper box body and a lower box body, wherein the upper box body can be covered on the lower box body, and a closed space for accommodating the battery module is formed. The plurality of battery modules may be arranged in the battery case in any manner.

Power utilization device

The application also provides an electric device comprising at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 3 is an electrical device 2 as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

In order to make the technical problems, technical schemes and beneficial effects solved by the application more clear, the application will be further described in detail below with reference to the embodiments and the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by a person skilled in the art based on the embodiments of the application without any inventive effort, are intended to fall within the scope of the application.

The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

1. Preparation of secondary battery

Example 1

1. Preparation of positive electrode plate

Dissolving an anode active material lithium iron phosphate, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2 into a solvent N-methylpyrrolidone (NMP), and fully stirring and uniformly mixing to obtain anode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and cutting to obtain the positive electrode plate.

2. Preparation of negative electrode plate

Weighing graphite, a conductive agent Super P, a thickener sodium carboxymethylcellulose (CMC) and a binder styrene-butadiene rubber (SBR) according to the weight ratio of 96:1.5:1.5:1, and uniformly mixing in deionized water to prepare the negative electrode slurry, wherein the solid content of the negative electrode slurry is 45wt%. And coating the negative electrode slurry on a copper foil, drying, and then carrying out cold pressing and cutting to obtain a negative electrode plate.

3. Preparation of electrolyte

(1) Preparation of additives

The first lithium salt LiPF ₆ And the adhesive polyvinylidene fluoride PTFE are placed in a stirrer for mixing and stirring according to the mass ratio of 10:0.5, the rotating speed of the stirrer is 300 r/min, the stirring time is 0.25h, and the LiPF is used for stirring ₆ The surface is sufficiently wetted by the adhesive.

Adding inorganic particles of potassium fluoride, potassium fluoride and a first lithium salt LiPF to the above-mentioned stirrer ₆ The mass ratio of the mixture is 1:10, the stirring speed is 300 r/min, and the stirring time is 0.25h, so that the composite particles are the additive.

(2) Mixing Ethylene Carbonate (EC) and diethyl carbonate (DEC) according to a volume ratio of 3:7 to obtain an organic compoundA solvent; second lithium salt LiPF ₆ Dissolving in the organic solvent, adding fluoroethylene carbonate (FEC), and uniformly mixing to obtain a mixed solution;

and (3) adding the additive and the stabilizer prepared in the step (1) into the mixed solution, and stirring uniformly to obtain the electrolyte. Wherein, liPF ₆ The concentration of (2) is 1mol/L, and the mass percentage of fluoroethylene carbonate (FEC) is 2% based on the total mass of the electrolyte.

4. Isolation film

A polypropylene film was used as a separator.

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate, playing a role of isolation, and adding the electrolyte to assemble the laminated secondary battery.

Inorganic particle type and mass ratio of additive in electrolyte

Examples 2 to 23

The preparation method of the secondary battery in examples 2 to 23 is substantially the same as that of the secondary battery in example 1, and the difference is mainly that: at the time of preparing the electrolyte, at least one of inorganic particles and DV50 thereof, first lithium salt and DV50 thereof, additive content, second lithium salt, stabilizer and content thereof are different, specifically, table 1 below.

It is specifically noted that the electrolyte of example 23 does not contain a stabilizer.

Comparative example 1

Substantially the same as the preparation method of example 1 was conducted, except that: when the electrolyte is prepared, the inorganic particles are replaced by potassium fluoride and potassium acetate.

Comparative example 2

Substantially the same as in example 1 was conducted except that: in preparing the electrolyte, the additive is only inorganic particles and the inorganic particles are lithium nitrate.

2. Performance testing

1. Lithium ion battery formation process

The formation temperature was 25 ℃, and the battery was charged to 30% soc at 0.04C.

2. Lithium ion battery charge-discharge cycle life test

The cycling test temperature is 25 ℃, the battery is charged to 4V at a constant current of 0.33C, then is discharged to 2V at 0.33C, the capacity obtained in the step is taken as the initial capacity, the charging and discharging are repeatedly carried out to the nth turn, the cycling test of 0.33C charging/0.33C discharging is carried out, the cycling is carried out until the capacity is attenuated to 90% SOH, the corresponding cycle number is recorded, and the corresponding service life data is obtained.

TABLE 1

Note that: p in Table 1 represents the ratio of the inorganic particles Dv50 to the first lithium salt Dv 50;

the contents of all the substances in table 1 are mass percentages based on the total mass of the electrolyte.

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 illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. The scope of the application is therefore intended to be covered by the appended claims, and the description and drawings may be interpreted in accordance with the contents of the claims.

Claims

1. An electrolyte comprising an additive, the additive comprising composite particles having an outer shell and an inner core, the inner core comprising a first lithium salt, the outer shell comprising inorganic particles;

Wherein the inorganic particles comprise at least one element of N, P, S, F, br and O, and the solubility of the inorganic particles in a linear ester solvent at 25 ℃ is 0.01 mmol/L to 110 mmol/L, and the inorganic particles comprise one or more of nitrate, phosphate, sulfate, fluoride, bromide, nitrite and oxide.

2. The electrolyte according to claim 1, wherein the solubility of the inorganic particles in the linear ester solvent at 25 ℃ is 10 mmol/L to 100 mmol/L.

3. The electrolyte of claim 1, wherein the inorganic particles comprise one or more of a metal nitrate, a metal phosphate, a metal sulfate, a metal fluoride, a metal bromide, a metal nitrite, and a metal oxide.

4. The electrolyte according to claim 3, wherein the metal element in the inorganic particles includes at least one of an alkali metal element and an alkaline earth metal element.

5. The electrolyte of claim 4 wherein the inorganic particles comprise one or more of lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, calcium nitrate, magnesium nitrate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, calcium phosphate, magnesium phosphate, lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, calcium sulfate, magnesium sulfate, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, calcium fluoride, magnesium fluoride, lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, magnesium bromide, lithium nitrite, sodium nitrite, potassium nitrite, calcium nitrite, lithium oxide, sodium oxide, calcium oxide, and magnesium oxide.

6. The electrolyte of claim 1 wherein the first lithium salt comprises one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis (fluoro) sulfonimide, and lithium bis (fluoro) methylsulfonimide.

7. The electrolyte according to claim 1, wherein a ratio of an average particle diameter Dv50 of the inorganic particles to a volume average particle diameter Dv50 of the first lithium salt is P, 0.0009.ltoreq.p.ltoreq.0.1.

8. The electrolyte according to claim 1, wherein the volume average particle diameter Dv50 of the inorganic particles is 1nm to 100nm; and/or the number of the groups of groups,

the first lithium salt has a volume average particle diameter Dv50 of 100nm to 2000nm.

9. The electrolyte according to any one of claims 1 to 8, wherein the mass ratio of the additive in the electrolyte is 0.5 to 10 wt%.

10. The electrolyte of claim 1, wherein the electrolyte further comprises a stabilizer.

11. The electrolyte according to claim 10, wherein the mass ratio of the stabilizer in the electrolyte is 1-10%.

12. The electrolyte of claim 1, wherein the electrolyte further comprises a second lithium salt.

13. The electrolyte of claim 12, wherein the molar concentration of the second lithium salt in the electrolyte is 0.5 to 5mol/L.

14. The electrolyte of claim 1, wherein the electrolyte further comprises an organic solvent.

15. A secondary battery comprising the electrolyte according to any one of claims 1 to 14.

16. An electric device comprising the secondary battery according to claim 15.