CN116845370A

CN116845370A - Lithium ion battery

Info

Publication number: CN116845370A
Application number: CN202310931366.XA
Authority: CN
Inventors: 段凯嘉; 李枫; 张昌明; 谢海芳; 胡大林
Original assignee: Guangdong Highpower New Energy Technology Co Ltd
Current assignee: Guangdong Highpower New Energy Technology Co Ltd
Priority date: 2023-07-27
Filing date: 2023-07-27
Publication date: 2023-10-03

Abstract

The present application relates to a lithium ion battery. The lithium ion battery includes: the lithium ion battery comprises a positive pole piece and electrolyte, wherein the positive pole piece comprises a positive pole material, and the positive pole material comprises a lithium supplementing additive; the electrolyte comprises an additive A and an additive B; in the structural general formula of the additive A, X ₁ 、X ₂ 、X ₃ 、X ₄ 、X ₅ Each independently selected from one of fluorine atom, cyano group, isocyanate group, sulfonic group, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; at least one of the additives AThe side group contains a sulfonic acid group; in the structural general formula of the additive B, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ 、Y ₅ Each independently selected from one of fluorine atom, cyano group, isocyanate group, sulfonic group, phenyl group, silane group, siloxane group, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms. The scheme provided by the application can improve the first coulomb efficiency, high-temperature storage and high-temperature cycle performance of the battery.

Description

Lithium ion battery

Technical Field

The application relates to the technical field of lithium ion batteries, in particular to a lithium ion battery.

Background

The lithium ion battery has the advantages of high specific energy, good quick charge and discharge capability, small self discharge and the like, and is widely applied to consumer electronic products and power batteries.

In the first charging process of the lithium ion battery, a solid electrolyte interface film (SolidElectrolyte Interface, SEI for short) is formed on the surface of the negative electrode, and the SEI film can prevent the co-intercalation of solvent molecules from damaging the negative electrode material, so that the battery has good cycle performance and service life; at the same time, active lithium ions are consumed in the SEI film forming process, so that the amount of reversible lithium ions in the battery is reduced, and the initial coulombic efficiency of the battery is reduced, and the cycle performance and the storage performance are deteriorated.

Disclosure of Invention

In order to solve or partially solve the problems existing in the related art, the application provides a lithium ion battery, which can compensate lithium ions consumed by an SEI film and improve the first coulomb efficiency, high-temperature storage and high-temperature cycle performance of the battery.

The application provides a lithium ion battery, which comprises a positive electrode plate and electrolyte, wherein the positive electrode plate comprises a positive electrode material, and the positive electrode material comprises a lithium supplementing additive; the electrolyte comprises an additive A, an additive B and a solvent, wherein the solvent comprises a fluorinated organic solvent;

the structural general formula of the additive A is shown as follows:

wherein X is ₁ 、X ₂ 、X ₃ 、X ₄ 、X ₅ Each independently selected from fluorine atom, cyano group, isocyanate group, sulfonic group, and having 1 to 5 carbonsOne of saturated or unsaturated hydrocarbon groups of atoms; at least one side group of the additive a contains a sulfonic acid group;

the structural general formula of the additive B is shown as follows:

wherein Y is ₁ 、Y ₂ 、Y ₃ 、Y ₄ 、Y ₅ Each independently selected from one of fluorine atom, cyano group, isocyanate group, sulfonic group, phenyl group, silane group, siloxane group, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms;

the structural general formula of the fluoro-organic solvent is shown as follows:

wherein Z is ₁ 、Z ₂ Each independently selected from the group consisting of alkyl groups having 1 to 5 carbon atoms substituted with 1 to 6 fluorine atoms, olefinic groups.

In some embodiments of the application, the lithium supplementing additive is Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein x is more than or equal to 1 and less than or equal to 6, y is more than or equal to 1 and less than or equal to 6, and z is more than or equal to 2 and less than or equal to 12; m comprises one or more than one of Ni, co, fe, cu, al, mn, ti, P, si, C; preferably, the species of the lithium supplementing additive includes one or more.

In some embodiments of the present application, the sulfonic acid group in the additive a has a structural formula of:

wherein R is selected from one of fluorine atom, cyano group, isocyanate group, phenyl group, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms.

In some embodiments of the application, the additive a is selected from at least one of the following compounds:

and/or the additive B is selected from at least one of the following compounds:

in some embodiments of the application, the solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, and tetrahydrofuran.

In some embodiments of the application, the fluorinated organic solvent is selected from at least one of the following compounds:

in some embodiments of the application, the fluorinated organic solvent is present in the electrolyte at a mass ratio of 3% to 30%.

In some embodiments of the application, the lithium supplementing additive accounts for 0.01-10% of the positive electrode material by mass;

and/or the mass ratio of the additive A in the electrolyte is 0.01-5%;

and/or the mass ratio of the additive B in the electrolyte is 0.01-5%.

In some embodiments of the application, the electrolyte further comprises a lithium salt; the concentration of lithium salt in the electrolyte is 0.5 mol/L-2 mol/L; preferably 0.8mol/L to 2mol/L; more preferably 0.9mol/L to 1.3mol/L.

In some embodiments of the present application, the lithium ion battery further comprises a negative electrode sheet, the positive electrode sheet and the negative electrode sheet have sulfur-containing additives therein, and the ratio of the total content of the S element in the positive electrode sheet and the negative electrode sheet is not less than 100ppm.

The technical scheme provided by the application can comprise the following beneficial effects: the additive A, the additive B and the positive electrode lithium supplement additive are used in combination, so that the defect that the lithium supplement additive is unstable under high voltage is effectively overcome, and the first coulombic efficiency, the high-temperature storage and the high-temperature cycle performance of the battery are obviously improved; furthermore, the application can further improve the stability of the lithium supplementing additive under high voltage by adding the fluoro-organic solvent and matching with the additive A and the additive B in the electrolyte, thereby stabilizing the electrode material structure and improving the high-temperature storage performance and the high-temperature cycle performance of the battery.

Detailed Description

In order that the application may be readily understood, the application will be described in detail. Before the present application is described in detail, it is to be understood that this application is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

Where a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the application. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the application, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the application.

Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Although any methods and materials equivalent to those described herein can also be used in the practice or testing of the present application, the preferred methods and materials are now described.

Currently, in order to solve the problem of irreversible lithium ion loss caused by the SEI film formation process, a "prelithiation technique" has been developed. The pre-lithiation technology refers to adding lithium into the battery in advance before the lithium ion battery works to realize the supplement of lithium ions, so that lithium loss caused by the formation process of an SEI film is counteracted, and the reduction of the battery performance is avoided. At present, most of pre-lithiation means are to add a lithium supplementing additive into a silicon negative electrode material to achieve the purpose of supplementing lithium, but the lithium supplementing additive can cause unstable electrode structure after lithium removal, and side reaction with electrolyte is easy to occur under high potential to cause the increase of electrode interface impedance, thereby further deteriorating the multiplying power performance of the battery and influencing the cycle performance and the service life of the battery.

According to the application, the additive A, the additive B, the fluorinated organic solvent and the positive electrode lithium supplement additive are used in combination, so that the defect that the lithium supplement additive is unstable under high voltage is effectively overcome, and the first coulombic efficiency, high-temperature storage and high-temperature cycle performance of the battery are obviously improved.

the structural general formula of the additive A is shown as follows:

wherein X is ₁ 、X ₂ 、X ₃ 、X ₄ 、X ₅ At least one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, an alkenyl group, an alkynyl group, a fluorine atom, a cyano group, an isocyanate group, and a sulfonic acid group; at least one side group of additive a contains a sulfonic acid group;

the structural general formula of the additive B is shown as follows:

wherein Y is ₁ 、Y ₂ 、Y ₃ 、Y ₄ 、Y ₅ Selected from 1-5At least one of an alkyl group, an alkenyl group, an alkynyl group, a fluorine atom, a cyano group, an isocyanate group, a sulfonic acid group, a phenyl group, a silane group, and a siloxane group;

wherein Z is ₁ 、Z ₂ Selected from the group consisting of alkyl groups of 1 to 5 carbon atoms substituted with 1 to 6 fluorine atoms, and olefinic groups.

According to the application, the lithium supplementing additive in the positive electrode plate can provide a lithium source when the battery is charged for the first time, compensate lithium consumed by an SEI film, improve the first coulomb efficiency, and is particularly suitable for batteries containing negative electrode materials with low first coulomb efficiency such as silicon carbon, silicon oxygen and the like. With the increase of the addition amount of the positive electrode lithium supplement additive, the initial coulombic efficiency of the battery is increased, and meanwhile, the electrode interface impedance is increased and the rate performance of the battery is deteriorated due to the fact that the structure of the positive electrode lithium supplement additive is unstable after lithium removal and side reaction is easy to occur with electrolyte under high potential. When the additive A, the additive B, the fluoro-organic solvent and the positive electrode lithium supplement additive are used in combination in the electrolyte, the defect that the lithium supplement additive is unstable under high voltage can be effectively overcome, so that the first coulombic efficiency, the high-temperature storage and the high-temperature cycle performance of the battery are obviously improved.

The pyridine group in the additive A provided by the application has the function of Lewis base, can react with trace water in electrolyte and active hydrogen on the surfaces of the anode and the cathode of the battery, and reduces electrolyte components such as LiPF caused by the active hydrogen ₆ Decomposition to avoid electrolyte components such as LiPF ₆ The decomposed hydrogen fluoride causes the SEI film to decompose and break; the additive B silane thiazole derivative provided by the application can improve the stability of electrolyte, form a stable interface film, inhibit the phenomenon of air expansion of a lithium ion battery under a high-temperature condition, avoid the cyclic attenuation and thickness increase of the lithium ion battery, improve the structural stability of an electrode material and improve the cycle performance of the lithium ion battery. The application uses additive A,The synergistic effect between the additive B and the positive electrode lithium supplementing additive effectively inhibits the oxidative decomposition reaction of electrolyte components under high voltage, so that the stability of the electrolyte at high temperature is improved, the first coulombic efficiency of the lithium ion battery is improved, and the lithium ion battery has excellent high-temperature cycle performance and high-temperature storage performance. The fluorine atoms in the fluorinated organic solvent provided by the application have strong electronegativity and weak polarity, so that the fluorinated organic solvent has higher oxidation resistance, and therefore, when the fluorinated organic solvent is combined with the lithium supplement additive, the additive A and the additive B, the strong electron-withdrawing capability of the fluorinated organic solvent forms active sites on the surfaces of positive and negative electrode materials, which is beneficial to better film formation of the additive A and the additive B, and simultaneously inhibits oxidative decomposition reaction of each component in the lithium supplement additive and electrolyte under high voltage, reduces internal resistance of the battery, reduces gas production effect of the battery during high-temperature circulation and high-temperature storage, and further ensures that the lithium ion battery has excellent high-temperature circulation performance and high-temperature storage performance under high voltage.

In some embodiments, the lithium-compensating additive is Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein x is more than or equal to 1 and less than or equal to 6, y is more than or equal to 1 and less than or equal to 6, and z is more than or equal to 2 and less than or equal to 12; m comprises at least one of Ni, co, fe, cu, al, mn, ti, P, si, C; the species of the lithium supplementing additive comprise one or more. For example, li ₂ NiO ₂ 、Li ₆ CoO ₄ 、Li ₅ FeO ₄ 、Li ₂ MnO ₃ 、Li ₆ MnO ₄ Etc. The lithium supplementing additive can provide a lithium source when the battery is charged for the first time, compensate lithium consumed by the SEI film and improve the first coulombic efficiency of the battery.

In some embodiments, at least one pendant group of additive a contains a sulfonic acid group. The sulfonic acid group in the additive A provided by the application can form a stable and compact interface protection film on the surface of the electrode, thereby effectively improving the structural stability of the electrode. When the additive A with the pyridine group and the sulfonic group side group is used together with the positive electrode lithium supplement additive, the defect that the positive electrode lithium supplement additive is unstable under high voltage can be effectively overcome, so that the decomposition of electrolyte is inhibited, and the cycle performance and the high-temperature storage life of the battery are improved.

In some embodiments, the sulfonic acid group has the general structural formula:

wherein R is selected from alkyl groups with 1-5 carbon atoms, alkylene groups, alkyne groups, fluorine atoms, cyano groups, isocyanate groups and phenyl groups. When the side group of the additive contains sulfonic group and cyano group, the strong electron withdrawing capability of the cyano group can complex unstable high-valence transition metal ions at the positive electrode interface, so that the unstable high-valence transition metal ions are inhibited from damaging the negative electrode interface film, the phenomenon of air expansion of lithium ions under the high-temperature condition is reduced, the electrode material structure is stabilized, and the cycle performance of the lithium ion battery is improved.

In some embodiments, additive a is selected from at least one of the following compounds:

in some embodiments, additive B is selected from at least one of the following compounds:

in some embodiments, the solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran.

In some embodiments, the fluorinated organic solvent is selected from at least one of the following compounds:

in some embodiments, the fluorinated organic solvent is present in the electrolyte at a mass ratio of 3% to 30%. For example, the content may be 3%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%. When the addition amount of the fluoro-organic solvent is too low, the fluorine atoms which play a role are limited, and a good oxidation resistance effect is difficult to play; too much fluorinated organic solvent can increase the viscosity of the electrolyte, prevent lithium ions from shuttling, and deteriorate the high-temperature cycle performance.

In some embodiments, the lithium-compensating additive is present in the positive electrode material at a mass ratio of 0.01% to 10%. For example, the content may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%. When the amount of the lithium supplement additive is increased within the above range, the battery first coulombic efficiency increases; however, the excessive lithium-supplementing additive causes unstable electrode structure after lithium removal, and side reaction with electrolyte is easy to occur under high potential to aggravate the impedance of electrode interface, thereby deteriorating the rate performance of the battery.

In some embodiments, the mass fraction of additive a in the electrolyte is 0.01% to 5%. For example, it may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%. When the additive amount of the additive a is within the above range, the cycle performance and the high-temperature storage performance of the battery can be improved; however, as the amount of additive increases, when the amount of additive a is too large, the interfacial resistance increases, deteriorating the battery cycle performance.

In some embodiments, the mass fraction of additive B in the electrolyte is 0.01% to 5%. For example, it may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%. When the additive amount of the additive B is within the above range, the cycle performance and the high-temperature storage performance of the battery can be improved; however, as the amount of additive increases, when the amount of additive B is too large, the interfacial resistance increases, deteriorating the battery cycle performance.

In some embodiments, the mass ratio of additive a to additive B is (0.1-3): (0.1-3); preferably (1 to 3): (1-3). For example, it may be 0.1:3, 1:1, 1:2, 1:3, 3:1, 2:1, 3:0.1. The total addition amount of the additive A and the additive B in the electrolyte and the mass ratio of the additive A to the additive B are controlled within a proper range, so that the synergistic effect between the additive A and the additive B and the lithium supplementing additive can be effectively exerted, and the high-temperature cycle performance and the high-temperature storage performance of the battery are improved.

In some embodiments, the electrolyte further comprises a lithium salt; the concentration of lithium salt in the electrolyte is 0.5 mol/L-2 mol/L; further 0.8mol/L to 2mol/L; still more preferably 0.9mol/L to 1.3mol/L. When the concentration of lithium salt in the electrolyte is too low, the conductivity of the electrolyte is low, and the multiplying power and the cycle performance of the whole battery system are affected; when the lithium salt concentration is too high, the electrolyte concentration is too high, which also affects the rate of the whole battery system.

In some embodiments, the lithium salt is selected from at least one of an organic electrolyte salt, an inorganic electrolyte salt. For example: lithium perchlorate (LiClO) ₄ ) Lithium hexafluorophosphate (LiPF) ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium hexafluoroantimonate (LiSbF) ₆ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium hexafluorotantalate (LiTaF) ₆ ) Lithium tetrachloroaluminate (LiAlCl) ₄ )、Li ₂ B ₁₀ Cl ₁₀ 、Li ₂ B ₁₀ F ₁₀ The method comprises the steps of carrying out a first treatment on the surface of the Lithium trifluorosulfonyl LiCF ₃ SO ₃ Lithium difluoro (trifluoromethylsulfonyl) imide C ₂ F ₆ LiNO ₄ S ₂ Lithium bis (fluorosulfonyl) imide F ₂ LiNO ₄ S ₂ Tris (trifluoromethylsulfonyl) methyllithium LiC (SO) ₂ CF ₃ ) ₃ Etc., the application is not limited thereto. The lithium salt may also be selected from lithium salts of chelate orthoborates and chelate orthophosphates, for example: lithium dioxalate borate (LiB (C) ₂ O ₄ ) ₂ ) Lithium bis malonate borate (LiB (O) ₂ CCH ₂ CO ₂ ) ₂ ) Lithium bis (difluoromalonic acid) borate (LiB (O) ₂ CCF ₂ CO ₂ ) ₂ ) Lithium (malonate) borate (LiB (C) ₂ O ₄ )(O ₂ CCH ₂ CO ₂ ) Lithium (difluoro malonate) borate (LiB (C) ₂ O ₄ )(O ₂ CCF ₂ CO ₂ ) Lithium phosphate tribasic (LiP (C) ₂ O ₄ ) ₃ ) Lithium tris (difluoromalonic acid) phosphate (LiP (O) ₂ CCF ₂ CO ₂ ) ₃ ) Etc.

The lithium salt in the electrolyte of the present application may be selected from any one, any two or a combination of more than any of the above. The lithium salt can be decomposed to generate small molecules in a battery system, so that the small molecules are deposited on an electrode interface to form a compact interface film, and the cycle performance and the high-temperature storage performance of the battery are improved.

In some embodiments, the positive electrode material comprises a positive electrode active material, the positive electrode active material comprising 80% to 99% of the positive electrode material by mass. For example, 80%, 85%, 90%, 95%, 97% may be used.

The specific kind of the positive electrode active material in the present application is not limited, and for example, active materials known in the art to be usable for a positive electrode of a battery may be used. In some embodiments of the application, the positive electrode active material comprises lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, ternary LiNi _x Co _y Mn _z O ₂ At least one of materials (wherein x+y+z=1, x+.y).

In some embodiments, the positive electrode material may further include a binder, a conductive agent, or other optional auxiliary agents, and the specific types of the binder, the conductive agent, and the other optional auxiliary agents in the present application are not limited, and binders, conductive agents, or other optional auxiliary agents that can be used for the positive electrode material as known in the art may be used. In some embodiments, as an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), aqueous acrylic resin (water-basedacrylic resin), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, super P (SP), graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet further comprises a positive electrode current collector, wherein the positive electrode material is coated on a surface of the positive electrode current collector to form a positive electrode material layer. The positive electrode current collector may be a conventional metal foil or a composite current collector, and the specific type of the positive electrode current collector in the present application is not limited, and for example, aluminum foil known in the art may be used.

In some embodiments, the lithium ion battery further comprises a negative electrode tab. Wherein the negative electrode tab may include a negative electrode current collector and a negative electrode material on the negative electrode current collector. The negative electrode material includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

The specific types of the negative electrode current collector, the negative electrode active material, the negative electrode binder and the negative electrode conductive agent of the present application are not limited, and any materials known in the art for negative electrode materials may be used without limitation. In some embodiments, the current collector may be selected from a metal foil or a composite current collector, for example, may be selected from copper foil, as examples; the negative electrode active material may be selected from graphite and/or silicon, such as natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, li-Sn alloy, li-Sn-O alloy, sn, snO, snO ₂ Lithiated TiO of spinel structure ₂ -Li ₄ Ti ₅ O ₁₂ At least one of Li-Al alloy; the negative electrode binder may be at least one selected from styrene-butadiene rubber (SBR), aqueous acrylic resin (water-basedacrylic resin), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the negative electrode conductive agent may be at least one selected from conductive carbon black, acetylene black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and superconducting carbon.

In some embodiments, the positive electrode plate and the negative electrode plate are provided with sulfur-containing additives, and the mass ratio of the total content of S element in the positive electrode plate and the negative electrode plate is not lower than 100ppm. For example, the sulfur-containing additive may be selected from the group consisting of a sulfur-containing additive having HSO ₃ -、RSO ₂ At least one of inorganic or organic compounds containing sulfur element such as S-, etc. The sulfur-containing additive has the function of high-efficiency film formation, and the-S-S-S-bond in the sulfur-containing additive is easily reduced on the surface of the anode to form Li ₂ S negative electrode protective layer, li ₂ S has excellent lithium ion conductivity, thereby promoting rapid formation of lithium ions in SEI filmA speed channel.

In some embodiments, the electrolyte further comprises other additives. For example, negative electrode film-forming additives may be included, positive electrode film-forming additives may be included, and additives capable of improving certain properties of the battery, such as additives that improve high temperature performance, additives that improve low temperature performance of the battery, additives that improve overcharge performance of the battery.

In some embodiments, the other additives may include at least one of vinylene carbonate, vinylene carbonate derivatives, cyclic carbonates, chelate orthoborates, and chelate orthophosphate salts. For example, the other additive may be at least one of ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, and bis-fluoroethylene carbonate. When the additive is used in combination with the additive A, the additive B and the fluorinated organic solvent in the electrolyte, the SEI film can be promoted to be formed, meanwhile, organic components in the SEI film can be increased, and the toughness of the SEI film is increased by forming an organic and inorganic composite SEI film, so that the SEI film is prevented from being decomposed and broken, the damage to electrode materials caused by co-embedding of solvent molecules is avoided, the ionic conductivity can be enhanced, and the cycle performance and the service life of the whole battery system are further improved.

In some embodiments, the lithium ion battery may further include a separator. In the process of charging and discharging the battery, active ions are inserted and separated back and forth between the positive pole piece and the negative pole piece, and the isolating film is arranged between the positive pole piece and the negative pole piece to play a role in isolation; the electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate.

In some embodiments, the separator of the present application may be arbitrarily selected from known porous structure separators having good chemical and mechanical stability. The material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

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.

The battery disclosed by the embodiment of the application can be used for an electric device using the battery as a power supply or various energy storage systems using the battery as an energy storage element. The electric device includes, but is not limited to, a mobile phone, a tablet, a computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc., and is not limited herein.

In order that the application may be more readily understood, the application will be further described in detail with reference to the following examples, which are given by way of illustration only and are not limiting in scope of application. The starting materials or components used in the present application may be prepared by commercial or conventional methods unless specifically indicated.

Example 1

(1) Preparation of electrolyte

Mixing ethylene carbonate EC, propylene carbonate PC, diethyl carbonate DEC and propyl propionate PP in a mass ratio of 1:1:1:1 as an organic solvent; adding additive A, additive B and fluoro-organic solvent with the mass percentage content shown in example 1 in table 1 into organic solvent, mixing uniformly, adding LiPF ₆ Obtaining LiPF ₆ An electrolyte with a concentration of 1.1 mol/L.

(2) Preparation of positive electrode plate

Lithium cobalt oxide (LiCoO) as a positive electrode active material ₂ ) A conductive agent CNT (Carbon nano tube), a binder PVDF (polyvinylidene fluoride), a lithium supplementing additive (Li) ₂ NiO ₂ ) The mass ratio is 96:1.5:1.5:1, wherein the sum of the lithium supplementing additive and the positive electrode active material is 97%; the mixture is fully stirred and mixed in N-methyl pyrrolidone solvent to form uniform positive electrode slurry. And (3) coating the slurry on an aluminum foil of a positive current collector, drying, and cold pressing to obtain the positive plate.

(3) Preparation of negative electrode plate

And fully stirring and mixing the anode active material graphite, the conductive agent acetylene black, the adhesive styrene-butadiene rubber and the thickener sodium carboxymethyl cellulose in a proper amount of deionized water solvent according to the mass ratio of 96:1.2:1.5:1.3, so that uniform anode slurry is formed. And (3) coating the slurry on a copper foil of a negative current collector, drying, and cold pressing to obtain a negative plate.

(4) Preparation of lithium ion batteries

The PE porous polymer film is used as a diaphragm.

And sequentially stacking the positive pole piece, the diaphragm and the negative pole piece, enabling the diaphragm to be positioned between the positive pole piece and the negative pole piece, playing an isolating role, and winding the stacked pole piece and the diaphragm to obtain the winding core. And (3) placing the coiled core in an aluminum-plastic film bag formed by punching, respectively injecting the prepared electrolyte into the baked and dried electric core, and performing the procedures of vacuum packaging, standing, formation and the like to prepare the lithium ion battery.

Examples 2 to 22 and comparative examples 1 to 10 were conducted in the same manner as in example 1 except that the parameters of additive A, additive B, electrolyte solvent and lithium-compensating additive in the positive electrode material were different, and the specific differences are shown in Table 1.

TABLE 1

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Note that: "/" indicates that no additives were used.

Battery testing and analysis

(1) First coulombic efficiency test of battery

After the battery is filled with electrolyte and kept stand for a period of time, charging is carried out in an environment of 25+/-2 ℃, and charging current is used for 0.02 ℃ at first, and charging time is 2H; and charging with 0.1C current for 5H, and charging with 0.5C constant current and constant voltage to 4.45V, wherein the cut-off current is 0.02C. Discharge was performed with 0.2C until the discharge cut-off voltage was 3.0V. The final first coulombic efficiency ef=dc/(cc+cv), where DC is the discharge capacity and cc+cv is the charged constant current capacity plus the constant voltage segment capacity. The calculation results are recorded in tables 2 and 3.

(2) 45 ℃ cycle test

The testing method comprises the following steps: charging the lithium ion battery to 4.45V at a constant current and constant voltage of 1C in a constant temperature box at 45+/-2 ℃, stopping the current at 0.05C, then discharging the lithium ion battery to 3V at 1C, and carrying out charge and discharge cycles for a plurality of times according to the conditions. The capacity retention after 300 and 500 battery cycles, respectively, was calculated for each group of 5 batteries.

The calculation formula is as follows: capacity retention (%) = corresponding cycle number discharge capacity (mAh)/discharge capacity for the third cycle (mAh) 100%

The capacity retention after each group of 5 cells cycled through different cycles is averaged and reported in tables 2 and 3.

(3) High temperature storage test at 60 DEG C

And (3) carrying out 1C/0.5C charge and discharge after the lithium ion battery is kept stand for 2 hours at 25+/-2 ℃, wherein the charge and discharge voltage is 3.0V-4.45V, and the discharge capacity is the first discharge capacity, and then fully charging the battery. Placing the battery at 60 ℃ for storage, and calculating the remaining capacity retention rate of the battery after storage, wherein the calculation formula is as follows: remaining capacity retention (%) = (remaining discharge capacity on the nth day)/(first cycle discharge capacity) ×100%; and calculating the thickness expansion rate of the stored battery, wherein the calculation formula is as follows: the thickness swelling ratio (%) = (the thickness of the battery after the storage on the nth day)/(the initial thickness of the battery) ×100%. The calculation results are recorded in tables 2 and 3.

TABLE 2

As can be seen from a combination of the data in tables 1 and 2, comparative example 2 incorporates 1% of the lithium supplement additive Li as compared to comparative example 1 ₂ NiO ₂ The first coulomb efficiency of the battery is improved.

Compared with comparative example 2, comparative examples 3, 4 and 5 respectively added with additive A (2- (methylsulfonyl) nicotinonitrile), additive B (2- (trimethylsilyl) thiazole) and fluoroorganic solvent methyl trifluoroethyl carbonate, the initial coulombic efficiency of the battery is not changed obviously, and the cycle performance and the high-temperature storage performance are improved.

According to comparison of comparative examples 3, 4 and 6, the first coulombic efficiency, the cycle performance and the high-temperature storage performance of the battery are not obviously changed by simultaneously adding the additive A (2- (methylsulfonyl) nicotinonitrile) and the additive B (2- (trimethylsilyl) thiazole) into the electrolyte; as can be seen from the comparison of comparative examples 3, 5 and 7, the electrolyte is added with the additive a (2- (methylsulfonyl) nicotinonitrile) and the fluoroorganic solvent methyl trifluoroethyl carbonate at the same time, and the initial coulombic efficiency, the cycle performance and the high-temperature storage performance of the battery are not obviously changed; from the comparison of comparative examples 4, 5 and 8, it is understood that the first coulombic efficiency, the cycle performance and the high-temperature storage performance of the battery are not significantly changed by adding the additive B (2- (trimethylsilyl) thiazole) and the fluoroorganic solvent methyl trifluoroethyl carbonate to the electrolyte.

TABLE 3 Table 3

According to the embodiment and the comparative example, after the lithium supplement additive, the additives A and B and the fluoro-organic solvent are added, the first coulombic efficiency of the battery is kept above 91%, the capacity retention rate of the battery after the battery is cycled at 45 ℃ for 500 weeks is above 74%, the thermal state thickness expansion rate of the battery after the battery is stored at 60 ℃ for 30 days is below 10.5%, and the first coulombic efficiency, the high-temperature cycle performance and the high-temperature storage performance of the battery cell are obviously improved.

From the comparison of examples 1, 14 to 22, comparative examples 9 and 10, it is understood that even though the lithium supplement additive, additives a and B, and the organic solvent were added to comparative examples 9 and 10, the initial coulombic efficiency of the battery was maintained at about 91%, but the capacity retention rate was about 65% after 500 weeks of 45 ℃ cycle, and the thermal state thickness expansion rate was about 11.5% after 30 days of 60 ℃ storage; therefore, when the additive A, the additive B and the fluoro-organic solvent are matched with the lithium-supplementing additive, the first coulombic efficiency of the battery can be effectively improved, and the high-temperature cycle and the high-temperature storage performance of the battery can be greatly improved.

As is clear from the comparison of examples 1 to 13, when the amounts of the additives and the ratios of the amounts of the additives in the electrolyte were adjusted, the high-temperature cycle and the high-temperature storage properties of the battery slightly changed, but the initial coulombic efficiency of the battery could be maintained at 91% or more, the capacity retention rate at 45℃cycle 500 weeks reached 74% or more, and the thermal state thickness expansion rate at 60℃for 30 days was 10.5% or less. Therefore, the first coulombic efficiency, the high-temperature cycle and the high-temperature storage performance of the battery can be effectively improved by combining the additive A, the additive B and the fluorinated organic solvent with the lithium supplementing additive and limiting the addition amount of the additive A, the additive B and the fluorinated organic solvent within a reasonable range.

It should be noted that the above-described embodiments are only for explaining the present application and do not constitute any limitation of the present application. The application has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the application as defined in the appended claims, and the application may be modified without departing from the scope and spirit of the application. Although the application is described herein with reference to particular means, materials and embodiments, the application is not intended to be limited to the particulars disclosed herein, as the application extends to all other means and applications having the same function.

Claims

1. The utility model provides a lithium ion battery, includes positive pole piece and electrolyte, positive pole piece includes positive pole material, its characterized in that: the positive electrode material comprises a lithium supplementing additive; the electrolyte comprises an additive A, an additive B and a solvent, wherein the solvent comprises a fluorinated organic solvent;

the structural general formula of the additive A is shown as follows:

wherein X is ₁ 、X ₂ 、X ₃ 、X ₄ 、X ₅ Each independently selected from one of fluorine atom, cyano group, isocyanate group, sulfonic group, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; at least one side group of the additive a contains a sulfonic acid group;

the structural general formula of the additive B is shown as follows:

wherein Z is ₁ 、Z ₂ Each independently of the otherIs selected from the group consisting of alkyl groups, alkenyl groups having 1 to 5 carbon atoms substituted with 1 to 6 fluorine atoms.

2. The lithium ion battery of claim 1, wherein: the lithium supplementing additive is Li _x M _y O _z The method comprises the steps of carrying out a first treatment on the surface of the Wherein x is more than or equal to 1 and less than or equal to 6, y is more than or equal to 1 and less than or equal to 6, and z is more than or equal to 2 and less than or equal to 12; m comprises one or more than one of Ni, co, fe, cu, al, mn, ti, P, si, C; preferably, the species of the lithium supplementing additive includes one or more.

3. The lithium ion battery according to claim 1, wherein the sulfonic acid group in the additive a has a general structural formula:

4. A lithium ion battery according to any of claims 1-3, wherein the additive a is selected from at least one of the following compounds:

and/or the additive B is selected from at least one of the following compounds:

5. a lithium ion battery according to any one of claims 1-3, wherein: the solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran.

6. The lithium ion battery of any of claims 1-5, wherein the fluorinated organic solvent is selected from at least one of the following compounds:

7. the lithium-ion battery of any of claims 1-5, wherein: the mass ratio of the fluoro-organic solvent in the electrolyte is 3-30%.

8. The lithium-ion battery of any of claims 1-7, wherein: the mass ratio of the lithium supplementing additive in the positive electrode material is 0.01-10%;

and/or the mass ratio of the additive A in the electrolyte is 0.01-5%;

and/or the mass ratio of the additive B in the electrolyte is 0.01-5%.

9. The lithium ion battery of claim 1, wherein: the electrolyte further comprises a lithium salt; the concentration of lithium salt in the electrolyte is 0.5 mol/L-2 mol/L; preferably 0.8mol/L to 2mol/L; more preferably 0.9mol/L to 1.3mol/L.

10. The lithium ion battery of claim 1, wherein: the lithium ion battery also comprises a negative electrode plate, wherein sulfur-containing additives are arranged in the positive electrode plate and the negative electrode plate, and the ratio of the total content of S element in the positive electrode plate and the negative electrode plate is not lower than 100ppm.