WO2023159799A1 - 一种电解液添加剂、非水电解液及锂离子电池 - Google Patents

一种电解液添加剂、非水电解液及锂离子电池 Download PDF

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WO2023159799A1
WO2023159799A1 PCT/CN2022/097321 CN2022097321W WO2023159799A1 WO 2023159799 A1 WO2023159799 A1 WO 2023159799A1 CN 2022097321 W CN2022097321 W CN 2022097321W WO 2023159799 A1 WO2023159799 A1 WO 2023159799A1
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lithium
carbonate
ion battery
electrolyte
ethyl
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French (fr)
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白晶
梁洪耀
毛冲
王霹霹
周远卫
李华丽
戴晓兵
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珠海市赛纬电子材料股份有限公司
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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
    • 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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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

Definitions

  • the application relates to the field of secondary batteries, in particular to an electrolyte additive, a non-aqueous electrolyte and a lithium ion battery.
  • Lithium-ion batteries are widely used in 3C digital, electric tools, aerospace, energy storage, power vehicles and other fields due to their advantages such as high specific energy, no memory effect, and long cycle life.
  • the rapid development of electronic information technology and consumer products has a great impact on lithium-ion batteries.
  • High battery voltage and high energy density put forward higher requirements.
  • manufacturers of batteries for digital electronic products at home and abroad are all developing in the direction of high-voltage lithium-ion batteries.
  • Lithium cobalt oxide has the advantages of high discharge platform, high specific capacity, good cycle performance, and simple synthesis process.
  • Lithium cobalt oxide (LCO) is currently the mainstream cathode material for 3C lithium batteries, and the market demand is steadily increasing, so the output of LCO is steadily increasing year by year.
  • the industrialization of high-voltage ( ⁇ 4.5V) LCO has pushed LCO to a new development platform. From the conventional LCO 140mAh/g (4.2V) gram capacity to 220mAh/g (4.6V) gram capacity, the gram capacity density of LCO can be increased by 21%, which corresponds to the longer battery life and better support Communication technology has been upgraded from 4G to 5G or even 6G. At present, the modified 4.35V, 4.4V and 4.45V LCO batteries and matching electrolytes have been industrialized. However, there are still a series of challenges in the high-voltage LCO battery technology of 4.5V and above.
  • the theoretical specific capacity of Li 1-x CoO 2 can be as high as 274mAh/g.
  • x>0.7 or more the theoretical cut-off voltage of LCO is greater than 4.5V.
  • LCO when LCO is charged above 4.5 V, it undergoes a deleterious phase transition from the O3 hexagonal phase to the hybrid O1–O3 phase, which is accompanied by sliding between lattice layers and partial collapse of the O3 lattice structure. Accompanied by the increase of the internal stress of LCO, it further leads to the formation of LCO cracks and particle breakage.
  • One of the purposes of the present application is to provide an electrolyte additive, which can improve the high-temperature storage performance and cycle performance of lithium-ion batteries under high-voltage systems.
  • the second purpose of the present application is to provide a non-aqueous electrolyte containing the above electrolyte additive.
  • the third object of the present application is to provide a lithium-ion battery containing the above-mentioned non-aqueous electrolyte.
  • the first aspect of the present application provides an electrolyte additive, comprising a compound having structural formula 1,
  • R 1 , R 2 , R 3 , and R 4 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group or a selenol group.
  • the electrolyte additive of the present application contains a compound with structural formula 1, which contains a selenol phenol structure, and the electrolyte additive can be polymerized in situ at the positive electrode of lithium cobaltate to form a high-conductivity, network-like Polyselenol CEI layer.
  • the CEI layer of polyselenol has extremely high toughness, which can effectively avoid the rupture of the CEI film caused by the volume change caused by the phase transition of lithium cobalt oxide; and during the cycle, selenium can be embedded in the positive electrode material to enter the site of oxygen element Instead of partially analyzed O 2- , the oxygen lattice on the surface of lithium cobaltate stabilizes during cycling, captures oxygen free radicals, prevents the dissolution of cobalt in positive lithium cobaltate, and plays a role in stabilizing the positive electrode of lithium cobaltate. Therefore, it can effectively improve the cycle performance and high-temperature storage performance of lithium-ion batteries.
  • the number of carbon atoms in the cyano group is ⁇ 3, such as a C1-C3 cyano group.
  • the C1-C3 cyano group refers to a cyano group with 1-3 carbon atoms.
  • the carbon number of the hydrocarbon group is ⁇ 3, such as a C1-C3 hydrocarbon group, specifically, a C1-C3 hydrocarbon group refers to a hydrocarbon group with 1-3 carbon atoms.
  • the hydrocarbon group can be selected from saturated hydrocarbon groups, and can also be selected from unsaturated hydrocarbon groups.
  • the compound shown in structural formula 1 is selected from at least one of compound 1 to compound 6:
  • the second aspect of the present application provides a non-aqueous electrolyte, including a lithium salt, a non-aqueous organic solvent and the aforementioned electrolyte additive.
  • the weight percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1-1%, specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, but not limited to the listed values, other unlisted values within this range are also applicable.
  • the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium bisoxalate borate (LiBOB), lithium difluorooxalate borate (LiODFB), lithium difluorooxalate phosphate (LiPF 2 (C 2 O 4 ) 2 ), lithium tetrafluoroborate (LiBF 4 ), lithium tetrafluorooxalate phosphate (LiPF 4 (C 2 O 4 )), lithium bistrifluoromethanesulfonyl imide (LiN(SO 2 At least one of CF 3 ) 2 ), lithium bisfluorosulfonyl imide (Li[N(SO 2 F) 2 ) and lithium tetrafluoromalonate phosphate (see Chinese patent CN108822151B for its synthesis method).
  • LiPF 6 lithium hexafluorophosphate
  • the content of lithium salt accounts for 8% to 25% of the weight of the non-aqueous electrolyte, specifically 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, but not limited to the listed values, other unlisted values within this range are also applicable.
  • the concentration of the lithium salt in the non-aqueous electrolyte is 0.8-2.5 mol/L.
  • the non-aqueous organic solvent is selected from ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), ethyl acetate (EA), acetic acid Butyl ester (BA), ⁇ -butyrolactone ( ⁇ -GBL), propyl propionate (PP), ethyl propionate (EP), ethyl butyrate (EB), fluoroethylene carbonate (FEC), At least one of difluoroethyl acetate (2,2-DFEA) and ethyl 2,2,2-trifluoroacetate (2,2,2-TFEA).
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • PC propylene carbonate
  • EA ethyl acetate
  • BA acetic acid Butyl ester
  • ⁇ -GBL ⁇ -butyrolactone
  • the non-aqueous organic solvent is selected from ethylene carbonate (EC), diethyl carbonate (DEC), propyl propionate (PP), fluoroethylene carbonate (FEC), difluoroethyl acetate (2 , 2-DFEA), 2,2,2-ethyl trifluoroacetate (2,2,2-TFEA).
  • the nonaqueous organic solvent accounts for 60% to 85% of the weight of the nonaqueous electrolyte, specifically 60%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, but not limited to the listed values, other unlisted values within the range of values are also applicable.
  • the non-aqueous electrolyte also includes additives, which account for 0.1-10.5% of the weight of the non-aqueous electrolyte, specifically 0.1%, 0.3%, 0.5%, 0.7%, 1%, 2%, 3%. , 4%, 5%, 6.5%, 7%, 8%, 9%, 10%, 10.5%, but not limited to the listed values, other unlisted values within the range of values are also applicable.
  • the auxiliary agent is selected from 2,2,2-methylethyl trifluorocarbonate, 2,2,2-diethyl trifluorocarbonate, 2,2,2-ethylene-propylene trifluorocarbonate ester, vinylene carbonate (VC), difluoroethylene carbonate (DFEC), diethyl pyrocarbonate (DEPC), 1,3-propane sultone (PS), vinyl sulfate (DTD), 1 , 2-difluoroethylene carbonate (DFEC), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), 4,4'-linked-1,3 -Dioxolane-2,2'-dione (BDC), 3,3-disulfuric acid vinyl ester (BDTD), 4,4-bidisulfuric acid vinyl ester, triallyl phosphate (TAP), phosphoric acid Tripropargyl (TPP), succinonitrile (SN), adip
  • the addition of the above-mentioned additives can form a stable passivation film on the surface of the positive electrode, prevent the oxidative decomposition of the electrolyte on the surface of the positive electrode, inhibit the dissolution of transition metal ions from the positive electrode, improve the stability of the structure and interface of the positive electrode material, and then significantly increase the lithium ion concentration.
  • the high temperature storage performance and cycle performance of the battery can form a stable passivation film on the surface of the positive electrode, prevent the oxidative decomposition of the electrolyte on the surface of the positive electrode, inhibit the dissolution of transition metal ions from the positive electrode, improve the stability of the structure and interface of the positive electrode material, and then significantly increase the lithium ion concentration.
  • the third aspect of the present application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and the above-mentioned non-aqueous electrolyte.
  • the active material of the positive electrode is selected from lithium cobaltate.
  • the additive of the non-aqueous electrolyte contains selenium phenol structure, it can be polymerized with lithium cobaltate positive electrode in situ to form a high-conductivity, reticular polyselenophene CEI layer during the formation stage, and participate in the formation of nitrogen-containing CEI film at the same time, instead of Part of the separated O 2- stabilizes the oxygen lattice on the surface of lithium cobaltate during the cycle, captures oxygen free radicals, prevents the dissolution of cobalt in the positive lithium cobaltate, and plays a good role in stabilizing the positive electrode of lithium cobaltate. It can effectively improve the cycle performance and high-temperature storage performance of lithium-ion batteries under high-voltage systems, and achieve a maximum charging voltage of 4.53V.
  • lithium cobaltate can be pure LCO, doped and/or coated LCO.
  • the active material of the negative electrode is selected from any one of artificial graphite, natural graphite, lithium titanate, silicon-carbon composite material and silicon oxide.
  • the present application enumerates the following examples. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present application, and should not be regarded as a specific limitation on the present application. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.
  • Lithium cobalt oxide material, binder PVDF and conductive agent SuperP are uniformly mixed at a mass ratio of 95:1:4 to make a certain viscosity lithium ion battery positive electrode slurry, and the mixed slurry is coated with After being clothed on both sides of the aluminum foil, the positive electrode sheet is obtained after drying and rolling.
  • lithium-ion battery the positive electrode, diaphragm and negative electrode are stacked into square batteries, packed in polymer, filled with the non-aqueous electrolyte of lithium-ion battery prepared above, and processed by chemical formation, volume separation, etc. After the process, a lithium-ion battery with a capacity of 4600mAh is made.
  • the lithium-ion batteries produced in Examples 1-18 and Comparative Examples 1-2 were tested for cycle performance at room temperature, cycle performance at high temperature, and storage performance at high temperature.
  • the test conditions are as follows, and the test results are shown in Table 2.
  • Capacity retention rate discharge capacity of the last cycle / discharge capacity of the first cycle ⁇ 100%
  • Capacity retention rate discharge capacity of the last cycle / discharge capacity of the first cycle ⁇ 100%
  • the CEI layer of polyselenol has extremely high toughness, which can effectively avoid the rupture of the CEI film caused by the volume change caused by the phase transition of lithium cobaltate; and in the process of circulation, selenium can replace part of the analyzed O 2- in cobalt
  • the surface of lithium cobaltate stabilizes the oxygen lattice during the cycle, captures oxygen free radicals, prevents the dissolution of cobalt in the positive lithium cobaltate, and plays a good role in stabilizing the positive electrode of lithium cobaltate, so it can effectively improve the lithium-ion battery.
  • Cycle performance and high temperature storage performance are further improved due to the fact that its branched chain also contains the selenophenol structure.
  • Example 8 Comparing Example 8 with Examples 9-15, it can be seen that on the basis of Example 8, VC, PS, DTD, TMSP, TMSPi, BDC, DFEC and other additives are added, and the cycle performance and high temperature performance of the prepared battery are better. .
  • Example 8 Comparing Example 8 with Examples 16-18, it can be known that adding other lithium salt-type additives on the basis of lithium hexafluorophosphate has better cycle performance and high temperature performance of the battery.

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Abstract

一种电解液添加剂、非水电解液及锂离子电池，该电解液添加剂包含具有结构式1的化合物，其中，R 1、R 2、R 3、R 4各自独立地选自氢原子、卤素原子、氰基、烃基或硒酚基团。该电解液添加剂含有硒酚结构，该电解液添加剂在化成阶段能与钴酸锂正极原位聚合形成电导率高、网状的聚硒酚CEI层。该聚硒酚CEI层韧性极高，能有效的避免因钴酸锂相变产生的体积变化而造成的CEI膜破裂；且在循环的过程中，硒可代替部分析出的O 2-，在钴酸锂的表面稳定氧的晶格，捕获氧自由基，阻止正极钴酸锂中钴的溶出，起到了很好地稳定钴酸锂正极的作用，因此可有效地提高锂离子电池的循环性能和高温存储性能。

Description

一种电解液添加剂、非水电解液及锂离子电池 技术领域
本申请涉及二次电池领域，具体涉及一种电解液添加剂、非水电解液及锂离子电池。
背景技术
锂离子电池由于具有高比能量、无记忆效应、循环寿命长等优点被广泛应用于3C数码、电动工具、航天、储能、动力汽车等领域，电子信息技术及消费产品的快速发展对锂离子电池高电压以及高能量密度提出了更高的要求。目前，国内外数码类电子产品电池的生产厂家，都在朝高电压锂离子电池这个方向发展。
钴酸锂具有放电平台高、比容量较高、循环性能好、合成工艺简单等优点。钴酸锂(LCO)是目前3C锂电池正极材料的主流，市场需求稳步上升，故LCO的产量逐年稳步增加。高电压(≥4.5V)LCO的产业化，更是将LCO的推升到一个全新的发展平台。从常规LCO 140mAh/g(4.2V)的克容量到220mAh/g(4.6V)的克容量，LCO的克容量密度可增加21％，对应着电池具有更长的续航能力，能够更好的支撑通信技术由4G向5G甚至6G升级。目前改性的4.35V、4.4V及4.45V LCO电池及匹配的电解液已经产业化，然而4.5V及以上的高电压LCO电池技术仍存在一系列的挑战。
具体表现在：Li 1-xCoO 2的理论比容量可高达274mAh/g。通常当x＞0.7以上时，理论上LCO的截止电压大于4.5V。但是，当LCO充电至4.5V以上电压时，它会经历从O3六方相到杂化O1-O3相的有害相变，此过程伴随着晶格层间的滑动和O3晶格结构的部分塌陷。伴随着LCO的内部应力增加，进一步导 致LCO裂纹形成和颗粒破碎。另外，由于O 2-:2p共振带的顶部与低自旋Co 3+/4+:t 2g共振带重叠，所以氧在高电压下开始发生氧化还原反应。由于过氧根离子O 1-的离子迁移率高于O 2-，在LCO表面的O -容易转化为O 2并脱离LCO颗粒，这会破坏正极-电解质界面，从而导致界面不稳定。因此，为了获得稳定的循环性能，LCO的截止电压通常低于4.5V。所以设法稳定钴酸锂材料的正极结构，捕获氧自由基，减少钴离子溶出能有效的提升钴酸锂锂离子电池的高温性能和循环性能。
申请内容
本申请的目的之一在于提供一种电解液添加剂，此电解液添加剂能提高锂离子电池于高电压体系下的高温存储性能和循环性能。
本申请的目的之二在于提供一种含上述电解液添加剂的非水电解液。
本申请的目的之三在于提供一种含上述非水电解液的锂离子电池。
为实现上述目的，本申请第一方面提供一种电解液添加剂，包含具有结构式1的化合物，
Figure PCTCN2022097321-appb-000001
其中，R 1、R 2、R 3、R 4各自独立地选自氢原子、卤素原子、氰基、烃基或硒酚基团。
与现有技术相比，本申请的电解液添加剂包含具有结构式1的化合物，含有硒酚结构，使用该电解液添加剂在化成阶段能于钴酸锂正极原位聚合形成电导率高、网状的聚硒酚CEI层。该聚硒酚CEI层韧性极高，能有效的避免因钴酸锂相变产生的体积变化而造成的CEI膜破裂；且在循环的过程中，硒可嵌入 正极材料中进入氧元素的位点代替部分析出的O 2-，在钴酸锂的表面稳定循环过程中氧的晶格，捕获氧自由基，阻止正极钴酸锂中钴的溶出，起到了很好地稳定钴酸锂正极的作用，故而可有效地提高锂离子电池的循环性能和高温存储性能。
优选地，氰基的碳原子数≤3，如C1-C3的氰基，具体地，C1-C3的氰基是指碳原子数目为1-3的氰基。
优选地，烃基的碳原子数≤3，如C1-C3的烃基，具体地，C1-C3的烃基是指碳原子数目为1-3的烃基。其中，烃基可以选自饱和烃基，也可以选自不饱和烃基。
较佳的，所述结构式1所示化合物选自化合物1至化合物6中的至少一种：
Figure PCTCN2022097321-appb-000002
其中，化合物1、化合物2、化合物3、化合物4、化合物5的合成路线如下所示，但不局限本申请提供的合成方法。
Figure PCTCN2022097321-appb-000003
本申请第二方面提供了一种非水电解液，包括锂盐、非水有机溶剂和前述电解液添加剂。
较佳的，所述电解液添加剂于所述非水电解液中的重量百分比为0.1～1％，具体可为0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1.0％，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
较佳的，锂盐选自六氟磷酸锂(LiPF 6)、二氟磷酸锂(LiPO 2F 2)、双草酸硼酸锂(LiBOB)、二氟草酸硼酸锂(LiODFB)、二氟二草酸磷酸锂(LiPF 2(C 2O 4) 2)、四氟硼酸锂(LiBF 4)、四氟草酸磷酸锂(LiPF 4(C 2O 4))、双三氟甲基磺酰亚胺锂(LiN(SO 2CF 3) 2)、双氟代磺酰亚胺锂(Li[N(SO 2F) 2)和四氟丙二酸磷酸锂(其合成方法见中国专利CN108822151B)中的至少一种。
较佳的，锂盐的含量占非水电解液重量的8～25％，具体可为8％、9％、10％、11％、12％、13％、14％、15％、16％、17％、18％、19％、20％、21％、22％、 23％、24％、25％，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
较佳的，锂盐在非水电解液中的浓度为0.8～2.5mol/L。
较佳的，所述非水有机溶剂选自碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸丙烯酯(PC)、乙酸乙酯(EA)、乙酸丁酯(BA)、γ-丁内酯(γ-GBL)、丙酸丙酯(PP)、丙酸乙酯(EP)、丁酸乙酯(EB)、氟代碳酸乙烯酯(FEC)、乙酸二氟乙酯(2,2-DFEA)、2,2,2-三氟乙酸乙酯(2,2,2-TFEA)中的至少一种。更为优选地，非水有机溶剂选自碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、丙酸丙酯(PP)、氟代碳酸乙烯酯(FEC)、乙酸二氟乙酯(2,2-DFEA)、2,2,2-三氟乙酸乙酯(2,2,2-TFEA)中的至少一种。
较佳的，非水有机溶剂占非水电解液重量的60～85％，具体可为60％、65％、66％、67％、68％、69％、70％、71％、72％、73％、74％、75％、80％、81％、82％、83％、84％、85％，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
较佳的，非水电解液还包括助剂，助剂占非水电解液重量的0.1～10.5％，具体可为0.1％、0.3％、0.5％、0.7％、1％、2％、3％、4％、5％、6.5％、7％、8％、9％、10％、10.5％，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
较佳的，所述助剂选自2,2,2-三氟代碳酸甲乙酯、2,2,2-三氟代碳酸二乙酯、2,2,2-三氟代碳酸乙丙酯、碳酸亚乙烯酯(VC)、双氟代碳酸乙烯酯(DFEC)、焦碳酸二乙酯(DEPC)、1,3-丙烷磺酸内酯(PS)、硫酸乙烯酯(DTD)、1,2-二氟代碳酸乙烯酯(DFEC)、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)亚磷酸酯(TMSPi)、4,4'-联-1,3-二氧戊环-2,2'-二酮(BDC)、3,3-联二硫酸乙烯酯(BDTD)、4,4-联二硫酸乙烯酯、磷酸三烯丙酯(TAP)、磷酸三炔丙酯(TPP)、丁二腈(SN)、己二腈(ADN)、1,3,6-己烷三腈(HTCN)和1,2-双(氰乙 氧基)乙烷(DENE)中的至少一种。
上述助剂的添加能够在正极表面形成稳定的钝化膜，阻止电解液在正极表面的氧化分解，抑制过渡金属离子从正极中溶出，提高正极材料结构和界面的稳定性，进而显著提高锂离子电池的高温存储性能和循环性能。
本申请第三方面还提供了一种锂离子电池，包括正极、负极、隔膜及上述非水电解液。
较佳的，所述正极的活性材料选自钴酸锂。由于非水电解液的添加剂含硒酚结构，其在化成阶段能与钴酸锂正极原位聚合形成电导率高、网状的聚硒酚CEI层，同时参与形成含氮CEI膜的同时，代替部分析出的O 2-在钴酸锂的表面稳定循环过程中氧的晶格，捕获氧自由基，阻止正极钴酸锂中钴的溶出，起到了很好地稳定钴酸锂正极的作用，可有效地提高锂离子电池在高压体系下的循环性能和高温存储性能，实现最高充电电压为4.53V。
其中，钴酸锂可为纯LCO、掺杂和/或包覆的LCO。
较佳的，所述负极的活性材料选自人造石墨、天然石墨、钛酸锂、硅碳复合材料和氧化亚硅中的任意一种。
具体实施方式
为便于理解本申请，本申请列举实施例如下。本领域技术人员应该明了，所述实施例仅仅是帮助理解本申请，不应视为对本申请的具体限制。实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市售购买获得的常规产品。
实施例1
(1)非水电解液的制备：在充满氮气的手套箱(O 2＜1ppm，H 2O＜1ppm)中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、丙酸丙酯(PP)，按照质量比1:1:2混合均匀，制得非水有机溶剂79.7g，加入0.3g化合物1得到混合溶液。将混合 溶液密封打包放置急冻间(-4℃)冷冻2小时之后取出，在充满氮气的手套箱(O 2＜1ppm，H 2O＜1ppm)中，向混合溶液中缓慢加入20g六氟磷酸锂，混合均匀后即制成非水电解液。
(2)正极的制备：将钴酸锂材料、粘接剂PVDF和导电剂SuperP按质量比95:1:4混合均匀制成一定粘度的锂离子电池正极浆料，将混制的浆料涂布在铝箔的两面后，烘干、辊压后得到正极片。
(3)负极的制备：将人造石墨与导电剂SuperP、增稠剂CMC、粘接剂SBR(丁苯橡胶乳液)按质量比95:1.5:1.0:2.5的比例制成浆料，混合均匀，用混制的浆料涂布在铜箔的两面后，烘干、辊压后得到负极片。
(4)锂离子电池的制备：将正极、隔膜以及负极以叠片的方式制成方形电芯，采用聚合物包装，灌装上述制备的锂离子电池非水电解液，经化成、分容等工序后制成容量为4600mAh的锂离子电池。
实施例2～18和对比例1～2的非水电解液配方如表1所示，配制非水电解液及锂离子电池的步骤同实施例1。
表1锂离子电池非水电解液配方
Figure PCTCN2022097321-appb-000004
Figure PCTCN2022097321-appb-000005
对实施例1～18和对比例1～2制成的锂离子电池分别进行常温循环性能测试、高温循环性能测试和高温存储性能，其测试条件如下，测试结果如表2所示。
常温循环性能测试：
将锂离子电池置于25℃的环境中，以1C的电流恒流充电至4.53V，然后恒压充电至电流下至0.05C，然后以1C的电流恒流放电至3.0V，如此循环，记录第一圈的放电容量和最后一圈的放电容量。按下式计算高温循环的容量保持率。
容量保持率＝最后一圈的放电容量/第一圈的放电容量×100％
高温循环性能测试：
将锂离子电池置于45℃的环境中，以1C的电流恒流充电至4.53V，然后恒压充电至电流下至0.05C，然后以1C的电流恒流放电至3.0V，如此循环，记录第一圈的放电容量和最后一圈的放电容量。按下式计算高温循环的容量保持率。
容量保持率＝最后一圈的放电容量/第一圈的放电容量×100％
高温存储测试：
将锂离子电池置于25℃的环境中，以0.5C的电流恒流充电至4.53V然后恒压充电至电流下至0.05C，然后以0.5C的电流恒流放电至3.0V，记录此时放电容量记为C0。再将电池以0.5C的电流恒流充电至4.53V然后恒压充电至电流下至0.05C，记录此时电压为V0。再将电池放置在60℃恒温烘箱中搁置30天后取出电池，记录此时电压为V1。然后将电池在25℃的环境中搁置2小时后，在25℃的环境中以0.5C的电流恒流放电至3.0V，记录此时放电容量记为C1，然后再以0.5C的电流恒流充电至4.53V然后恒压充电至电流下至0.05C，以0.5C的电流恒流放电至3.0V。记录此时放电容量记为C2。
容量保持率＝C1/C0*100％
容量恢复率＝C2/C0*100％
压降＝V1-V0
表2锂离子电池性能测试结果
Figure PCTCN2022097321-appb-000006
Figure PCTCN2022097321-appb-000007
从表2的结果可知，相对于对比例1～2，实施例1～18的常温循环、高温循环、高温存储性能皆处于较佳的水平。这是由于本申请的电解液添加剂包含具有结构式1的化合物，含有硒酚结构，使用该电解液添加剂在化成阶段能于钴酸锂正极原位聚合形成电导率高、网状的聚硒酚CEI层。该聚硒酚CEI层韧性极高，能有效的避免因钴酸锂相变产生的体积变化而造成的CEI膜破裂；且在循环的过程中，硒可代替部分析出的O 2-在钴酸锂的表面稳定循环过程中氧的晶格，捕获氧自由基，阻止正极钴酸锂中钴的溶出，起到了很好地稳定钴酸锂正极的作用，故而可有效地提高锂离子电池的循环性能和高温存储性能。其中，实施例7由于其支链同样含硒酚结构，故而，循环性能和高温存储性能得到进 一步提高。
对比实施例8和实施例9～15可知，于实施例8的基础上加入VC、PS、DTD、TMSP、TMSPi、BDC、DFEC等助剂，所制得的电池的循环性能和高温性能更佳。
对比实施例8和实施例16～18可知，于六氟磷酸锂的基础上加入其他锂盐型添加剂，所制得的电池的循环性能和高温性能更佳。
最后应当说明的是，以上实施例仅用以说明本申请的技术方案而非对本申请保护范围的限制，尽管参照较佳实施例对本申请作了详细说明，本领域的普通技术人员应当理解，可以对本申请的技术方案进行修改或者等同替换，而不脱离本申请技术方案的实质和范围。

Claims (10)

  1. 一种电解液添加剂，其特征在于，包含具有结构式1的化合物，
    Figure PCTCN2022097321-appb-100001
    其中，R 1、R 2、R 3、R 4各自独立地选自氢原子、卤素原子、氰基、烃基或硒酚基团。
  2. 如权利要求1所述的电解液添加剂，其特征在于，所述结构式1所示化合物选自化合物1至化合物6中的至少一种：
    Figure PCTCN2022097321-appb-100002
  3. 一种非水电解液，其特征在于，包括：
    锂盐；
    非水有机溶剂；以及
    如权利要求1～2任一所述的电解液添加剂。
  4. 如权利要求3所述的非水电解液，其特征在于，所述电解液添加剂于所述非水电解液中的重量百分比为0.1～1％。
  5. 如权利要求3所述的非水电解液，其特征在于，所述锂盐选自六氟磷酸锂、二氟磷酸锂、双草酸硼酸锂、二氟草酸硼酸锂、二氟二草酸磷酸锂、四氟硼酸锂、四氟草酸磷酸锂、双三氟甲基磺酰亚胺锂、双氟代磺酰亚胺锂和四氟丙二酸磷酸锂中的至少一种。
  6. 如权利要求3所述的非水电解液，其特征在于，所述非水有机溶剂选自碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙酸乙酯、乙酸丁酯、γ-丁内酯、丙酸丙酯、丙酸乙酯、丁酸乙酯、氟代碳酸乙烯酯、乙酸二氟乙酯、2,2,2-三氟乙酸乙酯中的至少一种。
  7. 如权利要求3所述的非水电解液，其特征在于，还包括助剂，所述助剂选自2,2,2-三氟代碳酸甲乙酯、2,2,2-三氟代碳酸二乙酯、2,2,2-三氟代碳酸乙丙酯、碳酸亚乙烯酯、双氟代碳酸乙烯酯、焦碳酸二乙酯、1,3-丙烷磺酸内酯、硫酸乙烯酯、1,2-二氟代碳酸乙烯酯、三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯、4,4'-联-1,3-二氧戊环-2,2'-二酮、3,3-联二硫酸乙烯酯、4,4-联二硫酸乙烯酯、磷酸三烯丙酯、磷酸三炔丙酯、丁二腈、己二腈、1,3,6-己烷三腈和1,2-双(氰乙氧基)乙烷中的至少一种。
  8. 一种锂离子电池，包括正极、负极和隔膜，其特征在于，还包括如权利要求3-7任一项所述的非水电解液。
  9. 如权利要求8所述的锂离子电池，其特征在于，所述正极的活性材料选自钴酸锂。
  10. 如权利要求8所述的锂离子电池，其特征在于，所述负极的活性材料选自人造石墨、天然石墨、钛酸锂、硅碳复合材料和氧化亚硅中的任意一种。
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