CN118589019A - A battery - Google Patents
A battery Download PDFInfo
- Publication number
- CN118589019A CN118589019A CN202410862611.0A CN202410862611A CN118589019A CN 118589019 A CN118589019 A CN 118589019A CN 202410862611 A CN202410862611 A CN 202410862611A CN 118589019 A CN118589019 A CN 118589019A
- Authority
- CN
- China
- Prior art keywords
- electrolyte
- formula
- positive electrode
- battery
- lithium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
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- 239000000463 material Substances 0.000 claims abstract description 24
- 239000010941 cobalt Substances 0.000 claims abstract description 14
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 14
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- 230000000996 additive effect Effects 0.000 claims description 13
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- 159000000002 lithium salts Chemical class 0.000 claims description 8
- 238000003860 storage Methods 0.000 abstract description 21
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- YKYONYBAUNKHLG-UHFFFAOYSA-N n-Propyl acetate Natural products CCCOC(C)=O YKYONYBAUNKHLG-UHFFFAOYSA-N 0.000 description 1
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- QXOYPGTWWXJFDI-UHFFFAOYSA-N nonanedinitrile Chemical compound N#CCCCCCCCC#N QXOYPGTWWXJFDI-UHFFFAOYSA-N 0.000 description 1
- IEJCIJGHMBBDMU-UHFFFAOYSA-N oct-4-enedinitrile Chemical compound N#CCCC=CCCC#N IEJCIJGHMBBDMU-UHFFFAOYSA-N 0.000 description 1
- BTNXBLUGMAMSSH-UHFFFAOYSA-N octanedinitrile Chemical compound N#CCCCCCCC#N BTNXBLUGMAMSSH-UHFFFAOYSA-N 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- RXIMZKYZCDNHPG-UHFFFAOYSA-N pentane-1,3,5-tricarbonitrile Chemical compound N#CCCC(C#N)CCC#N RXIMZKYZCDNHPG-UHFFFAOYSA-N 0.000 description 1
- XQZYPMVTSDWCCE-UHFFFAOYSA-N phthalonitrile Chemical compound N#CC1=CC=CC=C1C#N XQZYPMVTSDWCCE-UHFFFAOYSA-N 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- MNAMONWYCZEPTE-UHFFFAOYSA-N propane-1,2,3-tricarbonitrile Chemical compound N#CCC(C#N)CC#N MNAMONWYCZEPTE-UHFFFAOYSA-N 0.000 description 1
- 229940090181 propyl acetate Drugs 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910021384 soft carbon Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 125000000542 sulfonic acid group Chemical group 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- JTOFSXGLSGTDCB-UHFFFAOYSA-N tetradecanedinitrile Chemical compound N#CCCCCCCCCCCCCC#N JTOFSXGLSGTDCB-UHFFFAOYSA-N 0.000 description 1
- ZVQXQPNJHRNGID-UHFFFAOYSA-N tetramethylsuccinonitrile Chemical compound N#CC(C)(C)C(C)(C)C#N ZVQXQPNJHRNGID-UHFFFAOYSA-N 0.000 description 1
- FYSNRJHAOHDILO-UHFFFAOYSA-N thionyl chloride Chemical group ClS(Cl)=O FYSNRJHAOHDILO-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- UOIVFVKLHGODDX-UHFFFAOYSA-N tris(2-cyanoethyl) phosphate Chemical compound N#CCCOP(=O)(OCCC#N)OCCC#N UOIVFVKLHGODDX-UHFFFAOYSA-N 0.000 description 1
- ISIQQQYKUPBYSL-UHFFFAOYSA-N undecanedinitrile Chemical compound N#CCCCCCCCCCC#N ISIQQQYKUPBYSL-UHFFFAOYSA-N 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical class CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
Abstract
Description
技术领域Technical Field
本发明属于电池技术领域,涉及一种电池。The invention belongs to the technical field of batteries and relates to a battery.
背景技术Background Art
随着电动汽车,储能系统和其他高能耗应用的发展,对锂离子电池的能量密度和充电速度要求越来越高。With the development of electric vehicles, energy storage systems and other high-energy consumption applications, the energy density and charging speed requirements of lithium-ion batteries are getting higher and higher.
锂离子电池的能量密度与其正负极材料的能量密度和电池的工作电压都息息相关。因此,提高电池正负极材料的压实密度和克容量,以及提升锂离子电池的工作电压,都是增大电池能量密度的有效途径。相比于其他正极材料,钴酸锂材料具有高比容量、高电压和大倍率放电的优势,有利于增大电池的能量密度。然而,钴酸锂材料的自身结构稳定性较差,随着电压的升高,钴酸锂材料会发生相变,使材料颗粒的体积发生膨胀和收缩,这种体积形变不仅影响材料的结构稳定性,还会导致电极材料的破坏和电芯性能的衰减,使电池在高电压下的循环性能变差。The energy density of lithium-ion batteries is closely related to the energy density of their positive and negative electrode materials and the operating voltage of the battery. Therefore, improving the compaction density and gram capacity of the positive and negative electrode materials of the battery, as well as increasing the operating voltage of the lithium-ion battery, are effective ways to increase the energy density of the battery. Compared with other positive electrode materials, lithium cobalt oxide materials have the advantages of high specific capacity, high voltage and high rate discharge, which is conducive to increasing the energy density of the battery. However, the structural stability of lithium cobalt oxide materials themselves is poor. As the voltage increases, the lithium cobalt oxide materials will undergo phase changes, causing the volume of the material particles to expand and contract. This volume deformation not only affects the structural stability of the material, but also causes the destruction of the electrode material and the attenuation of the battery cell performance, making the battery's cycle performance at high voltage worse.
锂离子电池的充电速度与电解液的电导率息息相关。本领域中常规使用的适用于高电压快充体系的电解液中通常包括多腈类化合物,该类化合物具有较宽的电化学窗口和离子电导率,且能在正极配位形成良好的保护膜避免正极材料与电解液的副反应,但该类化合物与负极材料的相容性差,导致界面阻抗电池的界面阻抗大,内阻高,不利于电池的循环性能和存储性能。The charging speed of lithium-ion batteries is closely related to the conductivity of the electrolyte. The electrolytes commonly used in the field for high-voltage fast-charging systems usually include polynitrile compounds, which have a wide electrochemical window and ionic conductivity, and can form a good protective film at the positive electrode to avoid side reactions between the positive electrode material and the electrolyte. However, these compounds have poor compatibility with the negative electrode material, resulting in large interfacial impedance and high internal resistance of the interfacial impedance battery, which is not conducive to the battery's cycle performance and storage performance.
因此,如何使电池在高电压下兼具良好的循环性能和存储性能是本领域亟待解决的技术问题。Therefore, how to make the battery have both good cycle performance and storage performance at high voltage is a technical problem that needs to be solved urgently in this field.
发明内容Summary of the invention
本发明提供一种电池,该电池通过在电解液将氟乙腈和多腈类化合物搭配使用,并控制两者含量与正极活性层中的钴元素含量满足上述关系式,进而使电池在高电压下兼具优异的循环性能、快充性能和存储性能。The present invention provides a battery, which uses fluoroacetonitrile and a polynitrile compound in an electrolyte and controls the contents of the two and the cobalt content in a positive electrode active layer to satisfy the above relationship, thereby enabling the battery to have excellent cycle performance, fast charging performance and storage performance at high voltage.
本发明提供一种电池,包括正极片、负极片、隔膜和电解液,所述正极片包括正极集流体和设置于所述正极集流体至少一侧表面的正极活性层,所述正极活性层包括钴酸锂材料;所述正极活性层中钴元素的质量百分含量为WCo;The present invention provides a battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active layer comprises a lithium cobalt oxide material; the mass percentage of the cobalt element in the positive electrode active layer is W Co ;
所述电解液包括氟乙腈和多腈类化合物;基于所述电解液的质量,所述氟乙腈的质量百分含量为Wa,所述多腈类化合物的质量百分含量为Wb;The electrolyte comprises fluoroacetonitrile and a polynitrile compound; based on the mass of the electrolyte, the mass percentage of the fluoroacetonitrile is W a , and the mass percentage of the polynitrile compound is W b ;
其中,0.12≤(Wa+Wb)/WCo≤1.12。Among them, 0.12≤(W a +W b )/W Co ≤1.12.
本发明中,多腈类化合物指的是至少含有两个氰基基团的腈类化合物。In the present invention, the polynitrile compound refers to a nitrile compound containing at least two cyano groups.
氰基是一种高活性的官能团,其能够与正极活性层中的钴元素进行配位,从而在正极与电解液之间的界面形成良好的保护膜,避免钴酸锂材料与电解液的副反应。然而负极通常使用碳材料或硅材料作为负极活性材料,碳材料或硅材料的惰性较强,不易与氰基官能团之间具有较强的相互作用力,因此电解液中传统的多腈类化合物与负极的相容性不好,导致负极与电解液之间的界面阻抗大,增大电池的内阻,对电池的循环性能和存储性能不利。The cyano group is a highly active functional group that can coordinate with the cobalt element in the positive electrode active layer, thereby forming a good protective film at the interface between the positive electrode and the electrolyte, avoiding the side reaction between the lithium cobalt oxide material and the electrolyte. However, the negative electrode usually uses carbon materials or silicon materials as the negative electrode active material. The carbon materials or silicon materials are highly inert and are not easy to have a strong interaction force with the cyano functional group. Therefore, the traditional polynitrile compounds in the electrolyte have poor compatibility with the negative electrode, resulting in a large interface impedance between the negative electrode and the electrolyte, increasing the internal resistance of the battery, and being detrimental to the battery's cycle performance and storage performance.
基于此,本发明在电解液中加入氟乙腈,相比于电解液中传统的腈类化合物,氟乙腈中含有的F原子电负性极强,可以和负极中惰性较强的碳材料或硅材料反应形成稳定的C-F或Si-F键,从而增强电解液与负极的相容性,降低电池内阻,有利于电池循环性能和存储性能的改善。Based on this, the present invention adds fluoroacetonitrile to the electrolyte. Compared with traditional nitrile compounds in the electrolyte, the F atom contained in fluoroacetonitrile is extremely electronegative and can react with the relatively inert carbon material or silicon material in the negative electrode to form a stable C-F or Si-F bond, thereby enhancing the compatibility of the electrolyte with the negative electrode, reducing the internal resistance of the battery, and being beneficial to improving the battery cycle performance and storage performance.
此外,采用氟乙腈和多腈类化合物复配,氟乙腈粘度较小,在电解液中易于传输,能够优于多腈化合物在正极表面成膜,且形成的膜含有C-F键,有利于锂离子的传输,而多腈化合物则在氟乙腈成膜的基础上,和正极材料中的钴离子配位成膜,堵塞金属溶出通道,增强钴酸锂材料的结构稳定性,因此氟乙腈形成的内层保护膜与多腈化合物形成的外层保护膜协同作用,在不影响锂离子传输的同时,还有效避免了钴元素的溶出,减少正极材料与电解液的副反应。In addition, fluoroacetonitrile and polynitrile compounds are compounded. Fluoroacetonitrile has a lower viscosity and is easy to transport in the electrolyte. It can form a film on the positive electrode surface better than polynitrile compounds, and the formed film contains C-F bonds, which is beneficial to the transmission of lithium ions. On the basis of the film formation of fluoroacetonitrile, the polynitrile compounds coordinate with the cobalt ions in the positive electrode material to form a film, block the metal dissolution channel, and enhance the structural stability of the lithium cobalt oxide material. Therefore, the inner protective film formed by fluoroacetonitrile and the outer protective film formed by the polynitrile compounds work synergistically, without affecting the transmission of lithium ions, but also effectively avoiding the dissolution of the cobalt element and reducing the side reaction between the positive electrode material and the electrolyte.
综上,发明人对氟乙腈含量Wa、多腈类化合物含量Wb和钴元素含量Wc的协同作用进行了研究,发现当三者满足0.12≤(Wa+Wb)/WCo≤1.12时,既能使电解液与负极有较低的界面阻抗,还能够增强正极材料的结构稳定性,避免钴元素的溶出,进而使电池兼具优异的循环性能和存储性能。In summary, the inventors have studied the synergistic effect of the fluoroacetonitrile content Wa , the polynitrile compound content Wb and the cobalt element content Wc , and found that when the three satisfy 0.12≤( Wa + Wb ) /WCo≤1.12 , the electrolyte and the negative electrode can have a lower interface impedance, and the structural stability of the positive electrode material can be enhanced to avoid the dissolution of the cobalt element, thereby making the battery have excellent cycle performance and storage performance.
本发明的多腈类化合物包括但不限于丁二腈(SN)、戊二腈、己二腈(AND)、1,5-二氰基戊烷、1,6-二氰基己烷、1,7-二氰基庚烷、1,8-二氰基辛烷、1,9-二氰基壬烷、1,10-二氰基癸烷、1,12-二氰基十二烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、2,6-二氰基庚烷、2,7-二氰基辛烷、2,8-二氰基壬烷、1,6-二氰基癸烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、乙二醇二(2-氰基乙基)醚、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、3,6,9,12,15,18-六氧杂二十烷酸二腈、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯和1,6-二氰基-2-甲基-5-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己烷三腈(HTCN)、1,2,6-己烷三腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷、磷酸三(氰基乙基)酯和1,2,5-三(氰基乙氧基)戊烷中的一种或多种。The polynitrile compounds of the present invention include, but are not limited to, succinonitrile (SN), glutaronitrile, adiponitrile (AND), 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,9 ... ,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanenitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol di(2-cyanoethyl) ether, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxaicosanoic acid dinitrile, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethyl) 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene and 1,6-dicyano-2-methyl-5-methyl-3-hexene, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6 - one or more of hexanetrinitrile (HTCN), 1,2,6-hexanetrinitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, tris(cyanoethyl)phosphate and 1,2,5-tris(cyanoethoxy)pentane.
在一种优选的实施方式中,(Wa 2-Wb 2)/Wa≤0.80。氟乙腈和多腈化合物满足该关系式,氟乙腈可以优先于多腈化合物在正极表面形成一层稳定的表面膜,增强了正极材料的结构稳定性,同时优化了锂离子在正极材料表面的传输路径,降低传输阻力,在此基础上,多腈化合物再与正极材料中的钴离子进行配位,堵塞金属溶出通道,同时基于内层形成的传质界面膜,在对正极界面有效保护的同时还不影响锂离子的传输性能,保证了快充条件下的锂离子的快速传输。In a preferred embodiment, (W a 2 -W b 2 )/W a ≤0.80. Fluoroacetonitrile and polynitrile compounds satisfy this relationship. Fluoroacetonitrile can form a stable surface film on the positive electrode surface in preference to polynitrile compounds, thereby enhancing the structural stability of the positive electrode material and optimizing the transmission path of lithium ions on the surface of the positive electrode material, thereby reducing the transmission resistance. On this basis, the polynitrile compound coordinates with the cobalt ions in the positive electrode material to block the metal dissolution channel. At the same time, the mass transfer interface film formed on the inner layer effectively protects the positive electrode interface without affecting the transmission performance of lithium ions, thereby ensuring the rapid transmission of lithium ions under fast charging conditions.
当电解液中氟乙腈的含量较低时,电解液的粘度较大,与负极之间的相容性也较差;当氟乙腈的含量较高时,电解液中的氰基含量较低,不利于与正极材料配位,对正极的保护作用有限。为了兼具较低的电解液粘度和使电解液中保持适宜的氟原子和氰基浓度,控制5%≤Wa≤85%,优选地,10%≤Wa≤60%。示例性的,Wa可以是5%、10%、15%、20%、25%、30%、35%、40%、45%、50%、55%、60%、65%、70%、75%、80%、85%或其中任意两个数值所组成的范围。When the content of fluoroacetonitrile in the electrolyte is low, the viscosity of the electrolyte is high and the compatibility with the negative electrode is poor; when the content of fluoroacetonitrile is high, the cyanide content in the electrolyte is low, which is not conducive to coordination with the positive electrode material and has limited protective effect on the positive electrode. In order to have both low electrolyte viscosity and maintain a suitable concentration of fluorine atoms and cyanide in the electrolyte, 5%≤W a ≤85%, preferably, 10%≤W a ≤60%. Exemplarily, Wa can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or a range consisting of any two of these values.
同样出于使电解液兼具较低粘度和适宜氰基浓度的目的,控制2%≤Wb≤10%,优选地,4%≤Wb≤6%。示例性的,Wb可以是2%、4%、4.5%、5%、5.5%、6%、8%、10%或者其中任意两个数值所组成的范围。For the purpose of making the electrolyte have both low viscosity and suitable cyanide concentration, 2%≤W b ≤10%, preferably, 4%≤W b ≤6%. Exemplarily, W b can be 2%, 4%, 4.5%, 5%, 5.5%, 6%, 8%, 10% or a range consisting of any two of them.
正极活性层中的钴元素含量越高,越有利于电池能量密度的提升;然而钴元素含量越高,正极片的结构稳定性越差。为了兼具良好的正极稳定性和电池的能量密度,控制35%≤WCo≤65%,优选地,54.8%≤WCo≤63.1%。The higher the cobalt content in the positive electrode active layer, the more conducive it is to improving the battery energy density; however, the higher the cobalt content, the worse the structural stability of the positive electrode sheet. In order to achieve both good positive electrode stability and battery energy density, 35% ≤ W Co ≤ 65%, preferably, 54.8% ≤ W Co ≤ 63.1%.
在一种优选的实施方式中,电解液中还包括式I所示的添加剂:In a preferred embodiment, the electrolyte further includes an additive shown in Formula I:
A-B-C式I;A-B-C formula I;
式I中,A选自式Ia或式Ib所示的结构,B选自单键、H或式Ic所示的结构,C选自H、式Id所示的结构或Ie所示的结构;In Formula I, A is selected from the structure shown in Formula Ia or Formula Ib, B is selected from a single bond, H or the structure shown in Formula Ic, and C is selected from H, the structure shown in Formula Id or the structure shown in Formula Ie;
式Ia中,X1选自-O-或-CH2-,n1为0~4之间的整数;In formula Ia, X 1 is selected from -O- or -CH 2 -, and n 1 is an integer between 0 and 4;
式Ib中,X2选自-O-或-CH2-,n2为0~3之间的整数;In Formula Ib, X 2 is selected from -O- or -CH 2 -, and n 2 is an integer between 0 and 3;
式Ic中,X3和X4各自独立地选自-O-或-CH2-,Y1选自-C(O)-或-S(O)2-;In Formula Ic, X 3 and X 4 are each independently selected from -O- or -CH 2 -, and Y 1 is selected from -C(O)- or -S(O) 2 -;
式Id中,X5和X6各自独立地选自-O-或-CH2-,Y2选自-C(O)-或-S(O)2-,n3为0~4之间的整数;In Formula Id, X 5 and X 6 are each independently selected from -O- or -CH 2 -, Y 2 is selected from -C(O)- or -S(O) 2 -, and n 3 is an integer between 0 and 4;
式Ie中,X7选自-O-或-CH2-,n4为0~3之间的整数。In Formula Ie, X 7 is selected from -O- or -CH 2 -, and n 4 is an integer between 0 and 3.
上述结构式中,表示在该位置与其他基团键结。In the above structural formula, Indicates that it is bonded to other groups at this position.
锂离子在氟乙腈溶剂中具有较高的溶剂化程度,导致其在嵌入正负极时去溶剂化受到的阻力较大,而式I所示的添加剂中的硫原子可提供孤对电子,与锂离子形成较强的配位键,进而改善锂离子与氟乙腈之间的配位环境,这种配位调节能够削弱锂离子在氟乙腈中的溶剂化能力,并降低锂离子与氟乙腈之间的相互作用力,提高了锂离子在氟乙腈溶剂中的脱嵌速度,更好地提升了电解液中离子的动力学性能,进而提升了电池的快充性能。Lithium ions have a high degree of solvation in fluoroacetonitrile solvents, resulting in greater resistance to desolvation when embedded in the positive and negative electrodes, and the sulfur atoms in the additive shown in Formula I can provide lone pairs of electrons to form strong coordination bonds with lithium ions, thereby improving the coordination environment between lithium ions and fluoroacetonitrile. This coordination adjustment can weaken the solvation ability of lithium ions in fluoroacetonitrile and reduce the interaction force between lithium ions and fluoroacetonitrile, thereby increasing the deintercalation rate of lithium ions in fluoroacetonitrile solvents, better improving the kinetic properties of ions in the electrolyte, and thereby improving the fast charging performance of the battery.
此外,式I所示的添加剂还能够在负极表面形成以Li2SO3为主的SEI膜,该膜具有较高的致密度和强度,氟乙腈则能在负极表面形成LiF,LiF与以Li2SO3为主的SEI膜协同,使SEI膜具有更好的机械强度,使SEI膜在循环过程中不易损坏,对负极界面形成更好保护。In addition, the additive shown in Formula I can also form a SEI film mainly composed of Li2SO3 on the surface of the negative electrode, and the film has high density and strength. Fluoroacetonitrile can form LiF on the surface of the negative electrode. LiF and the SEI film mainly composed of Li2SO3 work together to make the SEI film have better mechanical strength, making the SEI film not easily damaged during the cycle process, and forming better protection for the negative electrode interface.
另外,式I所示的添加剂中的磺酸基可在正极表面形成CEI膜,对正极界面形成保护,避免电解液与正极材料的副反应,进一步抑制电池的循环膨胀,延长其循环寿命。In addition, the sulfonic acid group in the additive shown in Formula I can form a CEI film on the surface of the positive electrode, protect the positive electrode interface, avoid side reactions between the electrolyte and the positive electrode material, further inhibit the cycle expansion of the battery, and extend its cycle life.
在一种优选的实施方式中,式I所示的添加剂选自以下化合物中的一种:In a preferred embodiment, the additive represented by formula I is selected from one of the following compounds:
以式I-2所述化合物为例,式I所示的添加剂可参照以下方法制备得到:Taking the compound of formula I-2 as an example, the additive shown in formula I can be prepared by referring to the following method:
将2,4:3,5-二-O-亚苄基-L-艾杜糖醇和2,2-二甲氧基丙烷同时置于反应容器中,并向其加入催化剂p-TsOH,反应后得到中间产物化合物1,将所得到的中间产物化合物1与碳酸二甲酯和TBD混合后发生反应,得到中间产物化合物2,再向反应容器中加入p-TsOH后得到化合物3,在其基础上加入二氯亚砜,得到化合物4,再以RuCl3为催化剂,NaIO4作为氧化剂,对化合物4进行氧化,即得到式I-2所示化合物。2,4:3,5-di-O-benzylidene-L-iditol and 2,2-dimethoxypropane are placed in a reaction container at the same time, and a catalyst p-TsOH is added thereto. After the reaction, an intermediate product compound 1 is obtained. The intermediate product compound 1 is mixed with dimethyl carbonate and TBD and reacted to obtain an intermediate product compound 2. p-TsOH is then added to the reaction container to obtain compound 3. Dichlorothionyl is added thereto to obtain compound 4. Compound 4 is then oxidized using RuCl 3 as a catalyst and NaIO 4 as an oxidant to obtain the compound shown in formula I-2.
在一种优选的实施方式中,电解液中还包括锂盐,且基于电解液的质量,锂盐的质量百分含量为Wd,所述式I所示的添加剂的质量百分含量为Wc,其中,Wd/Wc≥3。In a preferred embodiment, the electrolyte further includes a lithium salt, and based on the mass of the electrolyte, the mass percentage of the lithium salt is W d , and the mass percentage of the additive represented by formula I is W c , wherein W d /W c ≥3.
如前所述,电解液中的锂盐和式I所示的添加剂的含量满足以上关系时,进一步有利于负极界面稳定性的改善,提升电池的循环性能。As mentioned above, when the contents of the lithium salt and the additive shown in Formula I in the electrolyte satisfy the above relationship, it is further beneficial to improve the negative electrode interface stability and enhance the cycle performance of the battery.
本发明的锂盐包括但不限于六氟磷酸锂(LiPF6)、二氟磷酸锂(LiPO2F2)、二氟草酸硼酸锂(LiDFOB)、双三氟甲基磺酰亚胺锂、二氟双草酸磷酸锂、四氟硼酸锂、双草酸硼酸锂、六氟锑酸锂、六氟砷酸锂、二(三氟甲基磺酰)亚胺锂、二(五氟乙基磺酰)亚胺锂、三(三氟甲基磺酰)甲基锂或二(三氟甲基磺酰)亚胺锂中的一种或多种。The lithium salt of the present invention includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF 6 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethylsulfonylimide), lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium or lithium bis(trifluoromethylsulfonyl)imide.
在一种优选的实施方式中,0.5%≤Wc≤10%。示例性的,式I所示的添加剂的质量百分含量为0.5%、1%、2%、3%、4%、5%、6%、7%、8%、9%、10%或其中任意两个数值所组成的范围。In a preferred embodiment, 0.5%≤W c ≤10%. Exemplarily, the mass percentage of the additive represented by Formula I is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of these values.
在一种优选的实施方式中,5%≤Wd≤30%,优选地,10%≤Wd≤20%,更优选地,12%≤Wd≤17%。In a preferred embodiment, 5%≤W d ≤30%, preferably, 10%≤W d ≤20%, more preferably, 12%≤W d ≤17%.
在一种优选的实施方式中,钴酸锂材料包括第一颗粒和第二颗粒,第一颗粒和第二颗粒的粒径之比为N,其中,3≤N≤6.5。In a preferred embodiment, the lithium cobalt oxide material includes first particles and second particles, and the ratio of the particle sizes of the first particles and the second particles is N, wherein 3≤N≤6.5.
颗粒较大的钴酸锂材料有利于提供更好的电子传导性能和较高的充放电倍率,有利于电池整体功率的输出,而较小的粒径能够提供更大的比表面积,有利于增加电极与电解液之间的接触面积,提高离子传输效率和材料容量。因此,采用粒径较大的第一颗粒和粒径较小的第二颗粒在上述粒径范围比内搭配,可以平衡电子和传导性能和离子传输效率。Lithium cobalt oxide materials with larger particles are conducive to providing better electronic conductivity and higher charge and discharge rates, which are beneficial to the overall power output of the battery, while smaller particles can provide a larger specific surface area, which is conducive to increasing the contact area between the electrode and the electrolyte, and improving the ion transmission efficiency and material capacity. Therefore, the use of first particles with larger particle sizes and second particles with smaller particle sizes within the above particle size range can balance the electronic and conductive performance and ion transmission efficiency.
进一步的,第一颗粒的D50粒径为15~35μm;和/或,第二颗粒的D50粒径为5~20μm。示例性的,第一颗粒的D50粒径为15μm、20μm、25μm、30μm、35μm或其中任意两个数值所组成的范围值,第二颗粒的D50粒径为5μm、10μm、15μm、20μm或其中任意两个数值所组成的范围值。Further, the D50 particle size of the first particles is 15 to 35 μm; and/or, the D50 particle size of the second particles is 5 to 20 μm. Exemplarily, the D50 particle size of the first particles is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or a range value consisting of any two values therein, and the D50 particle size of the second particles is 5 μm, 10 μm, 15 μm, 20 μm, or a range value consisting of any two values therein.
在一种优选的实施方式中,Wa/N≥0.012。当电解液中氟乙腈的含量和钴酸锂材料中第一颗粒和第二颗粒的D50粒径之比满足上述比例时,钴酸锂材料界面与电解液界面之间具有良好的接触,缩短了离子传输距离进而降低了电池的内阻,使电池在大倍率放电时候仍具有良好的循环容量保持率。In a preferred embodiment, W a /N ≥ 0.012. When the content of fluoroacetonitrile in the electrolyte and the ratio of the D50 particle size of the first particle and the second particle in the lithium cobalt oxide material meet the above ratio, there is good contact between the interface of the lithium cobalt oxide material and the interface of the electrolyte, which shortens the ion transmission distance and thus reduces the internal resistance of the battery, so that the battery still has a good cycle capacity retention rate when discharged at a high rate.
在一种具体的实施方式中,本发明的电解液中还包括碳酸酯类溶剂和/或羧酸酯类溶剂。其中,碳酸酯类溶剂选自氟代或未取代的碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二甲酯、碳酸二乙酯(DEC)、碳酸甲乙酯中的一种或多种;羧酸酯类溶剂选自氟代或未取代的乙酸丙酯、乙酸正丁酯、乙酸异丁酯、乙酸正戊酯、乙酸异戊酯、丙酸丙酯(PP)、丙酸乙酯(EP)、丁酸甲酯、正丁酸乙酯的一种或多种。In a specific embodiment, the electrolyte of the present invention further includes carbonate solvents and/or carboxylate solvents. The carbonate solvents are selected from one or more of fluorinated or unsubstituted ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and ethyl methyl carbonate; the carboxylate solvents are selected from one or more of fluorinated or unsubstituted propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, and ethyl butyrate.
本发明的正极集流体可选自铝箔。The positive electrode current collector of the present invention can be selected from aluminum foil.
在一种具体的实施方式中,正极活性层按照质量百分含量包括80%~99.8%的正极活性材料、0.1%~10%的导电剂、0.1%~10%的粘结剂。优选的,正极活性层按照质量百分含量包括90%~99.6%的正极活性材料、0.2%~5%的导电剂、0.2%~5%的粘结剂。In a specific embodiment, the positive electrode active layer includes 80% to 99.8% of positive electrode active material, 0.1% to 10% of conductive agent, and 0.1% to 10% of binder by mass percentage. Preferably, the positive electrode active layer includes 90% to 99.6% of positive electrode active material, 0.2% to 5% of conductive agent, and 0.2% to 5% of binder by mass percentage.
在一种具体的实施方式中,本发明的正极活性层中除钴酸锂外,还可包括镍酸锂、锰酸锂、镍钴锰酸锂、镍钴铝酸锂、镍锰酸锂、磷酸铁锂、三元材料等正极活性材料。In a specific embodiment, the positive electrode active layer of the present invention may include, in addition to lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, lithium iron phosphate, ternary materials and other positive electrode active materials.
进一步的,还可以在钴酸锂材料中进行元素掺杂以增强钴酸锂材料的内部结构稳定性,其中,掺杂元素选自Ti、Mg、Al、Ni中的一种或多种。Furthermore, elements may be doped into the lithium cobalt oxide material to enhance the internal structural stability of the lithium cobalt oxide material, wherein the doping elements are selected from one or more of Ti, Mg, Al, and Ni.
上述导电剂包括但不限于导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉、碳纤维中的至少一种。The conductive agent includes but is not limited to at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.
上述粘结剂包括但不限于羧甲基纤维素钠、丁苯胶乳、聚四氟乙烯、聚氧化乙烯中的至少一种。The above-mentioned binder includes but is not limited to at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
本发明的正极片可采用如下方法制备得到:将正极活性材料、导电剂和粘结剂分散于溶剂中,得到正极活性材料层浆料,然后将浆料涂覆于正极集流体上,干燥后即可得到正极片。The positive electrode sheet of the present invention can be prepared by the following method: dispersing the positive electrode active material, the conductive agent and the binder in a solvent to obtain a positive electrode active material layer slurry, then coating the slurry on the positive electrode collector, and drying to obtain the positive electrode sheet.
本发明的负极片包括负极集流体和设置于负极集流体至少一侧表面的负极活性物质层,其中,负极集流体可选自铜箔。The negative electrode sheet of the present invention comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector, wherein the negative electrode current collector can be selected from copper foil.
在一中具体的实施方式中,负极活性层按照质量百分含量包括80%~99.8%的负极活性材料、0.1%~10%的导电剂、0.1%~10%的粘结剂。优选的,负极活性层按照质量百分含量包括90%~99.6%的负极活性材料、0.2%~5%的导电剂、0.2%~5%的粘结剂。In a specific embodiment, the negative electrode active layer includes 80% to 99.8% of negative electrode active material, 0.1% to 10% of conductive agent, and 0.1% to 10% of binder by mass percentage. Preferably, the negative electrode active layer includes 90% to 99.6% of negative electrode active material, 0.2% to 5% of conductive agent, and 0.2% to 5% of binder by mass percentage.
本发明的负极活性材料包括但不限于人造石墨、天然石墨、中间相碳微球、硬碳、软碳、硅碳材料、硅氧材料中的至少一种。The negative electrode active material of the present invention includes but is not limited to at least one of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, soft carbon, silicon-carbon material, and silicon-oxygen material.
负极活性层中的导电剂包括但不限于导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉、碳纤维中的至少一种。The conductive agent in the negative electrode active layer includes, but is not limited to, at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.
负极活性层中的粘结剂包括但不限于羧甲基纤维素钠、丁苯胶乳、聚四氟乙烯、聚氧化乙烯中的至少一种。The binder in the negative electrode active layer includes but is not limited to at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
本发明的负极片可以采用以下方法制备得到:将负极活性材料、导电剂和粘结剂分散于溶剂中,形成负极活性浆料;再将负极活性浆料涂布于负极集流体上,干燥辊压后即可得到负极片。The negative electrode sheet of the present invention can be prepared by the following method: dispersing the negative electrode active material, conductive agent and binder in a solvent to form a negative electrode active slurry; then coating the negative electrode active slurry on the negative electrode collector, and drying and rolling to obtain the negative electrode sheet.
隔膜的作用是将正极极片和负极极片隔开并提供锂离子迁移的通道。本发明的隔膜可选自聚丙烯隔膜、聚乙烯隔膜等。The function of the separator is to separate the positive electrode plate from the negative electrode plate and provide a channel for lithium ion migration. The separator of the present invention can be selected from polypropylene separators, polyethylene separators, and the like.
在一种具体实施方式中,电池采用以下方法制备得到:将正极片、隔膜和负极片依序层叠放置,使隔膜位于正极片和负极片之间,通过叠片或者卷绕工艺得到电芯,再经过烘烤、注液、化成、封装等工序即可得到本发明的电池。In a specific embodiment, the battery is prepared by the following method: the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, so that the separator is located between the positive electrode sheet and the negative electrode sheet, and the battery cell is obtained by a stacking or winding process, and then the battery of the present invention is obtained through baking, liquid injection, formation, packaging and other processes.
本发明的实施,至少具有以下有益效果:The implementation of the present invention has at least the following beneficial effects:
1)本发明的电解液中包括氟乙腈,其中氟原子极强的电负性使其与惰性的负极活性材料反应形成稳定的共价键,增强了电解液与负极之间的相容性,改善了界面阻抗,降低电池内阻,且氟乙腈还具有较低的粘度和高介电常数,提高了电解液的电导率,进而使电池具有良好的循环性能、快充性能和存储性能。1) The electrolyte of the present invention includes fluoroacetonitrile, in which the extremely strong electronegativity of fluorine atoms allows it to react with the inert negative electrode active material to form a stable covalent bond, thereby enhancing the compatibility between the electrolyte and the negative electrode, improving the interface impedance, and reducing the internal resistance of the battery. Fluoroacetonitrile also has a low viscosity and a high dielectric constant, which improves the conductivity of the electrolyte, thereby enabling the battery to have good cycle performance, fast charging performance and storage performance.
2)本发明的电解液中采用氟乙腈与多腈类化合物搭配使用,使电解液中具有足量的氰基基团与正极材料中的钴元素配位在正极表面形成保护膜,增强了钴酸锂材料的结构稳定性,抑制其在高电压下结构发生相变引起的电池厚度膨胀,并避免了正极材料与电解液的副反应,抑制电池产气。2) Fluoroacetonitrile and polynitrile compounds are used in the electrolyte of the present invention, so that there are sufficient cyano groups in the electrolyte to coordinate with the cobalt element in the positive electrode material to form a protective film on the positive electrode surface, thereby enhancing the structural stability of the lithium cobalt oxide material, inhibiting the battery thickness expansion caused by the phase change of its structure under high voltage, avoiding the side reaction between the positive electrode material and the electrolyte, and inhibiting the gas production of the battery.
3)本发明对电解液中氟乙腈含量Wa、多腈类化合物含量Wb和钴元素含量Wc的协同作用进行研究使其满足特定的关系式,使电池兼具优异的耐高压性能、循环性能、存储性能和快充性能。3) The present invention studies the synergistic effect of the fluoroacetonitrile content Wa , the polynitrile compound content Wb and the cobalt element content Wc in the electrolyte to satisfy a specific relationship, so that the battery has excellent high-voltage resistance, cycle performance, storage performance and fast charging performance.
具体实施方式DETAILED DESCRIPTION
为使本发明的目的、技术方案和优点更加清楚,下面将结合本发明的实施例,对本发明实施例中的技术方案进行清楚、完整地描述,显然,所描述的实施例是本发明一部分实施例,而不是全部的实施例。基于本发明中的实施例,本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例,都属于本发明保护的范围。In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
以下将通过具体的实施例对本发明提供的电池进一步进行详细地说明。The battery provided by the present invention will be further described in detail below through specific embodiments.
如无特殊说明,以下实施例中用到的试剂、材料以及仪器均为本领域的常规试剂、常规材料以及常规仪器,均可通过商购获得,所涉及的试剂也可通过本领域常规方法合成获得。Unless otherwise specified, the reagents, materials and instruments used in the following examples are conventional reagents, conventional materials and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.
实施例1~25以及对比例1~6Examples 1 to 25 and Comparative Examples 1 to 6
实施例1~25和对比例1~6提供一种电池,制备方法如下:Examples 1 to 25 and Comparative Examples 1 to 6 provide a battery, and the preparation method is as follows:
1、正极片的制备1. Preparation of positive electrode
将正极活性材料钴酸锂(LiCoO2)、聚偏氟乙烯(PVDF)、SP(superP)和碳纳米管(CNT)按照96:2:1.5:0.5的质量比进行混合,加入N-甲基吡咯烷酮(NMP),在真空搅拌机作用下搅拌,直至混合体系成均一流动性的正极活性浆料;将正极活性浆料均匀涂覆于铝箔的两个表面;将涂覆好的铝箔烘干,然后经过辊压、分切得到所需的正极片。The positive electrode active materials lithium cobalt oxide (LiCoO 2 ), polyvinylidene fluoride (PVDF), SP (superP) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of an aluminum foil; the coated aluminum foil is dried, and then rolled and cut to obtain the desired positive electrode sheet.
其中,钴酸锂由粒径D50为30.7μm的第一颗粒和粒径D50为8.3μm第二颗粒按照质量比为4:1混合得到,正极活性层中钴元素的质量百分含量WCo为57.8%。The lithium cobalt oxide is obtained by mixing first particles with a particle size D50 of 30.7 μm and second particles with a particle size D50 of 8.3 μm in a mass ratio of 4:1, and the mass percentage content of the cobalt element W Co in the positive electrode active layer is 57.8%.
2、负极片的制备2. Preparation of negative electrode sheet
以质量比为4:1的人造石墨和硅碳的混合物为负极活性物质,其中,硅碳的外表面具有包覆层,包覆层包括碳元素;A mixture of artificial graphite and silicon carbon in a mass ratio of 4:1 is used as the negative electrode active material, wherein the outer surface of the silicon carbon has a coating layer, and the coating layer includes carbon elements;
将负极活性物质、羧甲基纤维素钠、丁苯橡胶、导电炭黑和碳纳米管按照质量比为98.2:0.5:0.5:0.2:0.6混合均匀,加入去离子水,在真空搅拌机作用下获得负极活性浆料;将负极活性浆料均匀涂覆在铜箔的两个表面;将涂覆好的铜箔在室温下晾干,随后转移至80℃烘箱干燥10h,然后经过冷压、分切得到负极片,其中,负极活性物质层中元素钠的重量含量为0.048%。The negative electrode active material, sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black and carbon nanotubes are uniformly mixed in a mass ratio of 98.2:0.5:0.5:0.2:0.6, deionized water is added, and the negative electrode active slurry is obtained under the action of a vacuum mixer; the negative electrode active slurry is uniformly coated on both surfaces of the copper foil; the coated copper foil is dried at room temperature, and then transferred to an oven at 80° C. for drying for 10 hours, and then cold pressed and cut to obtain a negative electrode sheet, wherein the weight content of elemental sodium in the negative electrode active material layer is 0.048%.
3、电解液的制备3. Preparation of electrolyte
在充满氩气的手套箱中(H2O<0.1ppm,O2<0.1ppm),将充分干燥的锂盐加入溶剂和添加剂的混合物中,溶解后得到电解液。In a glove box filled with argon (H 2 O <0.1 ppm, O 2 <0.1 ppm), fully dried lithium salt is added to a mixture of a solvent and an additive, and the electrolyte is obtained after dissolution.
其中,溶剂通过质量比为1:1:2:6的EC、PC、EP、PP混合后得到,电解液中锂盐种类为六氟磷酸锂,质量含量Wd为15%。The solvent is obtained by mixing EC, PC, EP and PP in a mass ratio of 1:1:2:6, and the type of lithium salt in the electrolyte is lithium hexafluorophosphate, and the mass content Wd is 15%.
添加剂包括8%的FEC和其他添加剂,其他添加剂的种类和质量含量在表1中列出。The additives include 8% FEC and other additives. The types and mass contents of the other additives are listed in Table 1.
4、锂离子电池的制备4. Preparation of lithium-ion batteries
将步骤2的正极片、步骤3的负极片和隔膜(9μm的PP隔膜)按照正极片、隔膜和负极片的顺序层叠设置后,再进行卷绕得到电芯;将电芯置于外包装铝箔中,将步骤1的电解液注入外包装铝箔中,经过真空封装、静置、化成、整形、分选等工序,获得锂离子电池。The positive electrode sheet of step 2, the negative electrode sheet of step 3 and the separator (9 μm PP separator) are stacked in the order of positive electrode sheet, separator and negative electrode sheet, and then wound to obtain a battery cell; the battery cell is placed in an outer packaging aluminum foil, and the electrolyte of step 1 is injected into the outer packaging aluminum foil. After vacuum packaging, standing, formation, shaping, sorting and other processes, a lithium-ion battery is obtained.
表1Table 1
实施例26~32Embodiments 26 to 32
实施例26~32提供一种电池,其制备方法与实施例1基本一致,不同之处在于,在电解液的制备中,加入的氟乙腈的质量含量为7%,在正极片的制备中,实施例26的钴酸锂由粒径D50为30.7μm的第一颗粒和粒径D50为8.3μm第二颗粒按照质量比为4:1混合得到,实施例27的钴酸锂仅包括粒径D50为30.7μm的第一颗粒,实施例28的钴酸锂仅包括粒径D50为8.3μm第二颗粒,实施例29的钴酸锂由粒径D50为30μm的第一颗粒和粒径D50为6μm第二颗粒按照质量比为4:1混合得到,实施例30的钴酸锂由粒径D50为35μm的第一颗粒和粒径D50为5μm第二颗粒按照质量比为4:1混合得到,实施例31的钴酸锂由粒径D50为30.7μm的第一颗粒和粒径D50为3μm第二颗粒按照质量比为4:1混合得到,实施例32的钴酸锂由粒径D50为40μm的第一颗粒和粒径D50为8.3μm第二颗粒按照质量比为4:1混合得到,具体变化因素在表2中列出。Embodiments 26 to 32 provide a battery, and the preparation method thereof is basically the same as that of Embodiment 1, except that, in the preparation of the electrolyte, the mass content of the added fluoroacetonitrile is 7%, and in the preparation of the positive electrode sheet, the lithium cobalt oxide of Embodiment 26 is obtained by mixing the first particles with a particle size D50 of 30.7 μm and the second particles with a particle size D50 of 8.3 μm in a mass ratio of 4:1, the lithium cobalt oxide of Embodiment 27 includes only the first particles with a particle size D50 of 30.7 μm, the lithium cobalt oxide of Embodiment 28 includes only the second particles with a particle size D50 of 8.3 μm, and the lithium cobalt oxide of Embodiment 29 includes the second particles with a particle size D50 of 30 μm. The first particle and the second particle with a particle size D50 of 6 μm are mixed in a mass ratio of 4:1. The lithium cobalt oxide of Example 30 is obtained by mixing the first particle with a particle size D50 of 35 μm and the second particle with a particle size D50 of 5 μm in a mass ratio of 4:1. The lithium cobalt oxide of Example 31 is obtained by mixing the first particle with a particle size D50 of 30.7 μm and the second particle with a particle size D50 of 3 μm in a mass ratio of 4:1. The lithium cobalt oxide of Example 32 is obtained by mixing the first particle with a particle size D50 of 40 μm and the second particle with a particle size D50 of 8.3 μm in a mass ratio of 4:1. The specific change factors are listed in Table 2.
表2Table 2
测试例Test Case
1、循环性能1. Cycle performance
A、25℃循环800周容量保持率A. Capacity retention rate after 800 cycles at 25℃
将电池在25℃下按照5C的倍率在3.0~4.55V充放电截止电压范围内进行充放电循环800周,测试第1周的放电容量计为x1mAh,第800圈的放电容量计为y1mAh;通过y1/x1×100%计算得到25℃循环800周的容量保持率。The battery was charged and discharged for 800 cycles at 25°C at a rate of 5C within the charge and discharge cut-off voltage range of 3.0 to 4.55V. The discharge capacity in the first week of the test was calculated as x1mAh, and the discharge capacity in the 800th cycle was calculated as y1mAh. The capacity retention rate after 800 cycles at 25°C was calculated by y1/x1×100%.
B、45℃循环800周容量保持率B. Capacity retention rate after 800 cycles at 45℃
将电池在45℃下按照5C的倍率在3.0~4.55V充放电截止电压范围内进行充放电循环800周,测试第1周的放电容量计为m1 mAh,800圈的放电容量计为n1mAh;通过n1/m1×100%计算得到45℃循环800周的循环容量保持率。The battery was charged and discharged for 800 cycles at 45°C at a rate of 5C in the charge and discharge cut-off voltage range of 3.0 to 4.55V. The discharge capacity in the first week of the test was calculated as m1 mAh, and the discharge capacity after 800 cycles was calculated as n1 mAh. The cycle capacity retention rate after 800 cycles at 45°C was calculated by n1/m1×100%.
2、倍率性能2. Rate performance
测试方法:首先将化成分容后的电池静置10min,然后以0.2C放电至下限电压3V,所放出的放量标记为初始放电容量C0,静置10min,接着0.7C充电至上限电压4.55V,再在该上限电压下充电至0.025C截止,最后以5C电流放电到下限电压3.0V,记录电池的放电容量C1,通过C1/C0计算得到5C的放电倍率容量保持率。Test method: First, let the battery stand for 10 minutes after being divided into capacities, then discharge it at 0.2C to the lower limit voltage of 3V, the discharged capacity is marked as the initial discharge capacity C0, let it stand for 10 minutes, then charge it at 0.7C to the upper limit voltage of 4.55V, and then charge it at the upper limit voltage to 0.025C cutoff, finally discharge it at 5C current to the lower limit voltage of 3.0V, record the battery's discharge capacity C1, and calculate the 5C discharge rate capacity retention rate by C1/C0.
3、高温存储性能3. High temperature storage performance
测试方法:室温下,记录电池分容后的初始厚度T1,然后将满电电池放置在85℃的恒温箱中存储15天,结束存储后取出并冷却恢复至室温,记录电池的厚度T2,通过T2/T1×100%计算得到电池在85℃存储15天的厚度膨胀率。Test method: At room temperature, record the initial thickness T1 of the battery after capacity division, then place the fully charged battery in a constant temperature box at 85°C for 15 days, take it out after storage and cool it back to room temperature, record the thickness T2 of the battery, and calculate the thickness expansion rate of the battery stored at 85°C for 15 days by T2/T1×100%.
以上测试结果在表3中列出。The above test results are listed in Table 3.
表3Table 3
1)从实施例1、2、4、7、22、26的对比看出,当电解液中氟乙腈的含量过少,小于10%时,电池的25℃和45℃循环性能、快充性能和高温存储性能均会恶化。1) From the comparison of Examples 1, 2, 4, 7, 22, and 26, it can be seen that when the content of fluoroacetonitrile in the electrolyte is too low, less than 10%, the battery's 25°C and 45°C cycle performance, fast charging performance, and high-temperature storage performance will deteriorate.
2)从实施例1、3、5、6的对比可看出,当多腈类化合物的含量在4%~6%的最优选范围内能够使电池具有更为优异的综合性能,但其<4%或者>7%时,会使电池循环、倍率和高温存储性能略有下降。2) From the comparison of Examples 1, 3, 5, and 6, it can be seen that when the content of the polynitrile compound is within the optimal range of 4% to 6%, the battery can have more excellent comprehensive performance, but when it is less than 4% or greater than 7%, the battery cycle, rate and high-temperature storage performance will be slightly reduced.
3)从实施例1、8、9、23、24、25的对比可看出,采用不同种类的多腈类化合物均能使电池兼具优异的高低温循环性能、快充性能和高温存储性能。3) From the comparison of Examples 1, 8, 9, 23, 24, and 25, it can be seen that the use of different types of polynitrile compounds can enable the battery to have excellent high and low temperature cycle performance, fast charging performance, and high temperature storage performance.
4)从实施例1、10~18的对比可看出,通过加入不同取代类型的式I所示环状磺酸酯类化合物均能改善电池的高低温循环性能、快充性能和高温存储性能,尤其是快充性能的提升更为显著。4) From the comparison of Examples 1 and 10 to 18, it can be seen that the addition of cyclic sulfonate compounds of Formula I of different substitution types can improve the high and low temperature cycle performance, fast charging performance and high temperature storage performance of the battery, especially the improvement of the fast charging performance is more significant.
5)从实施例1、19~21的对比可看出,式I所示的环状磺酸酯类化合物含量少于0.5%或高于10%时,电池的高低温循环性能、快充性能和高温存储性能都会出现恶化。5) From the comparison of Examples 1 and 19 to 21, it can be seen that when the content of the cyclic sulfonate compound represented by Formula I is less than 0.5% or greater than 10%, the high and low temperature cycle performance, fast charging performance and high temperature storage performance of the battery will deteriorate.
6)从实施例1、对比例1~3的对比可看出,当电解液中不加入氟乙腈或多腈类化合物时,电池的高低温循环性能高低温循环性能、快充性能和高温存储性能明显较差。6) From the comparison of Example 1 and Comparative Examples 1 to 3, it can be seen that when no fluoroacetonitrile or polynitrile compound is added to the electrolyte, the high and low temperature cycle performance, high and low temperature cycle performance, fast charging performance and high temperature storage performance of the battery are significantly poor.
7)从对比例4~6可看出,当氟乙腈的含量Wa、多腈类化合物的含量Wb与正极活性层中Co元素的含量不满足0.12~1.12时,电池的高低温循环性能高低温循环性能、快充性能和高温存储性能也会出现明显恶化,尤其是对比例6不加入式I所示的环状磺酸酯类化合物时,其快充性能恶化地更为明显。7) It can be seen from Comparative Examples 4 to 6 that when the content Wa of fluoroacetonitrile, the content Wb of the polynitrile compound and the content of the Co element in the positive electrode active layer do not meet the range of 0.12 to 1.12, the high and low temperature cycle performance, high and low temperature cycle performance, fast charging performance and high temperature storage performance of the battery will also be significantly deteriorated, especially when the cyclic sulfonate compound shown in Formula I is not added to Comparative Example 6, the fast charging performance deteriorates more significantly.
8)从实施例26~28的对比可看出,采用大小粒径匹配第一颗粒和第二颗粒的钴酸锂材料有利于使电池具有更为优异的25℃循环性能、45℃存储性能、5C放电性能和高温存储性能;从实施例26、29~32的对比可看出,当使用的第一颗粒的D50粒径过大,或者第二颗粒D50粒径过小,或者两者的粒径D50之比N不在3~65的范围内,或者Wa/N≤0.012时候,电池的高低温循环性能、5C倍率性能、85℃高温存储性能相比于满足以上条件的均较差。8) From the comparison of Examples 26 to 28, it can be seen that the use of lithium cobalt oxide materials with first particles and second particles of matching particle size is beneficial to making the battery have better 25°C cycle performance, 45°C storage performance, 5C discharge performance and high temperature storage performance; from the comparison of Examples 26, 29 to 32, it can be seen that when the D50 particle size of the first particles used is too large, or the D50 particle size of the second particles is too small, or the ratio N of the particle sizes D50 of the two is not in the range of 3 to 65, or Wa /N≤0.012, the high and low temperature cycle performance, 5C rate performance, and 85°C high temperature storage performance of the battery are all poor compared to those that meet the above conditions.
以上各实施例仅用以说明本发明的技术方案,而非对其限制;尽管参照前述各实施例对本发明进行了详细的说明,本领域的普通技术人员应当理解:其依然可以对前述各实施例所记载的技术方案进行修改,或者对其中部分或者全部技术特征进行等同替换;而这些修改或者替换,并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.
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