WO2021135921A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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WO2021135921A1
WO2021135921A1 PCT/CN2020/136344 CN2020136344W WO2021135921A1 WO 2021135921 A1 WO2021135921 A1 WO 2021135921A1 CN 2020136344 W CN2020136344 W CN 2020136344W WO 2021135921 A1 WO2021135921 A1 WO 2021135921A1
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carbonate
aqueous electrolyte
cyclic carbonate
ion battery
lithium ion
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PCT/CN2020/136344
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English (en)
French (fr)
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邓永红
艾关杰
林木崇
钱韫娴
胡时光
王勇
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深圳新宙邦科技股份有限公司
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of 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 invention belongs to the technical field of new energy, and particularly relates to a lithium ion battery.
  • lithium-ion batteries can start from the following aspects: 1) increase the gram capacity of the cathode material; 2) increase the battery discharge platform; 3) increase the proportion of active materials in the battery; increase the charging cut-off voltage of the lithium-ion battery It is one of the important ways to increase the energy density of the battery, because with the increase of the charge cut-off voltage, the positive electrode material can achieve a higher gram capacity, and the discharge platform is significantly improved. The two effects have an immediate effect on the increase of the energy density. Effect.
  • the positive electrode material With the gradual increase of the battery voltage, the positive electrode material enters a higher delithiation state, the stability of the material structure will become worse, and the oxidation of the surface will also be significantly improved.
  • the instability of the material structure and its high oxidation is particularly obvious at the pole piece/electrolyte interface.
  • the specific manifestation is: the battery produces gas, the internal resistance increases rapidly, and the capacity drops sharply. The gas production of the battery will cause the internal pressure to increase, which may further develop into dangerous situations such as explosion and combustion of the battery. Therefore, the high-voltage battery and the electrolyte need to be matched.
  • cyclic ethylene carbonate can provide high conductivity for the electrolyte due to its high dielectric constant, and its negative electrode film-forming solvent can ensure good cycle performance of the battery, and is widely used in non-aqueous lithium In the secondary battery.
  • EC has poor stability against high voltage and is easily oxidized and decomposed to produce gas on the high-voltage positive electrode, resulting in degradation of battery performance.
  • Propylene carbonate (PC) has better high-voltage resistance, a dielectric constant equivalent to EC, and a wider low-temperature liquidus temperature. It is also widely used in lithium-ion batteries, but PC cannot undergo film-forming reactions on the negative electrode. , Excessive PC replacement will cause deterioration of cycle performance.
  • Fluorinated ethylene carbonate has high decomposition voltage and oxidation resistance, as well as good film-forming properties.
  • FEC Fluorinated ethylene carbonate
  • the electrolyte is more likely to generate gas, which causes the internal pressure of the battery to increase during high-temperature storage and high-temperature cycling, and the battery bulges, bloats, and even explodes.
  • the technical problem to be solved by the present invention is to provide a lithium ion battery in view of the existing high-voltage lithium-ion battery high-temperature storage and high-temperature cycle gas production problems.
  • an embodiment of the present invention provides a lithium ion battery, including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte.
  • the positive electrode includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide;
  • the non-aqueous electrolyte includes a first cyclic carbonate and a second cyclic carbonate different from the first cyclic carbonate;
  • the first cyclic carbonate is a fluorinated cyclic carbonate
  • the weight percentage of the first cyclic carbonate is 12%-22%, and the weight percentage of the second cyclic carbonate is less than or equal to 2 %.
  • the first cyclic carbonate includes fluoroethylene carbonate; the second cyclic carbonate is a cyclic carbonate substituted or unsubstituted with a non-fluorine element.
  • the unsubstituted cyclic carbonate is a cyclic carbonate with 1-10 carbon atoms.
  • the non-fluorine element-substituted cyclic carbonate is a cyano group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, an alkyl group, an ether group, and a sulfur-containing hydrocarbon group substituted cyclic carbonate.
  • the surface of the positive electrode active material is coated with a metal oxide or internally doped with other elements;
  • the metal oxide is magnesium oxide and/or aluminum oxide;
  • the doped element is selected from Li, K, One or more of Mg, Ca, Al, Cr, Cu, Ni, Ti, Nd, B, and P.
  • the charge cut-off voltage of the lithium ion battery is 4.35V and above.
  • the weight percentage of the first cyclic carbonate in the non-aqueous electrolyte is 14%-20%, and the second ring
  • the weight percentage of the crystalline carbonate in the non-aqueous electrolyte is less than or equal to 0.5%.
  • the first cyclic carbonate includes fluoroethylene carbonate; the second cyclic carbonate is a cyclic carbonate substituted or unsubstituted with a non-fluorine element.
  • the second cyclic carbonate includes ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, and 1,2-pentylene carbonate. , One or more of 2,3-pentylene carbonate.
  • the non-aqueous electrolyte further includes linear carbonate and/or carboxylate, and based on the total weight of the non-aqueous electrolyte of the lithium ion battery as 100%, the carboxylate and/or the carboxylate
  • the linear carbonate accounts for 50%-65% of the total weight percentage of the non-aqueous electrolyte.
  • the linear carbonate includes one or more of diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethylene propyl carbonate;
  • the carboxylic acid esters include ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -caprolactone, ⁇ -pentane One or more of lactone and ⁇ -caprolactone.
  • the non-aqueous electrolyte further includes an additive, and based on the total weight of the non-aqueous electrolyte of the lithium ion battery as 100%, the weight percentage of the additive is 1-20%;
  • the additives include one or more of vinylene carbonate, 1,3-propane sultone, dinitrile compounds, and trinitrile compounds;
  • the dinitrile compounds include one or more of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, and sebaconitrile, and the lithium ion battery is not
  • the total weight of the aqueous electrolyte is 100%, the weight percentage of the dinitrile compound is 0.1%-10%; the weight percentage of the 1,3-propane sultone is 1-10%.
  • the non-aqueous electrolyte solution further includes a lithium salt
  • the lithium salt includes lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate, lithium bis(trifluoromethylsulfonyl)imide And one or more of the bisfluorosulfonimide lithium salt, and the concentration of the lithium salt is 0.1M-2M.
  • the positive electrode material contains lithium cobalt oxide, the surface of which can catalyze the in-situ film-forming reaction of fluoroethylene carbonate to play a protective role.
  • the first The content of cyclic carbonate fluorinated cyclic carbonate enables it to be used as a high dielectric constant solvent in the electrolyte, and the content of the second cyclic carbonate is reduced to a lower level, which makes the electrolyte oxidized to produce gas The degree of side reactions is greatly reduced, reducing battery gas production and improving high-temperature storage performance.
  • the fluorinated cyclic carbonate has a better negative electrode film-forming effect than the second cyclic carbonate, and can ensure better cycle performance.
  • a lithium ion battery provided by an embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte.
  • the positive electrode includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide;
  • the negative electrode includes a negative active material, and the negative active material includes one or more of hard carbon, soft carbon, graphite, and silicon-containing materials.
  • the separator is provided between the positive electrode of the battery and the negative electrode of the battery, and the separator is a conventional separator in the field of lithium ion batteries, which will not be repeated here.
  • the non-aqueous electrolyte includes a first cyclic carbonate and a second cyclic carbonate different from the first cyclic carbonate; the first cyclic carbonate is a fluorinated cyclic carbonate;
  • the total weight of the non-aqueous electrolyte of the lithium ion battery is 100%, the weight percentage of the first cyclic carbonate is 12%-22%, and the weight percentage of the second cyclic carbonate is less than or equal to 2%.
  • the second cyclic carbonate such as EC, PC
  • the first cyclic carbonate Ester fluorinated cyclic carbonate such as FEC
  • FEC fluorinated cyclic carbonate
  • the first cyclic carbonate can improve cycle performance, it will cause significant gas production and affect battery performance. High temperature storage performance.
  • the inventor found through a large number of experiments and analysis that the lithium battery system using lithium cobalt oxide as the positive electrode active material has the problem of high-temperature storage and gas production.
  • the positive electrode active material contains lithium cobalt oxide and non-aqueous electrolyte.
  • the first cyclic carbonate fluorinated cyclic carbonate such as FEC
  • the content of the second cyclic carbonate, which is different from the first cyclic carbonate is reduced to a lower level
  • the lithium-ion battery using the non-aqueous electrolyte exhibits excellent high-temperature storage performance, does not produce gas, has good capacity retention and recovery performance, and the battery has good cycle performance.
  • the surface of the positive electrode active material is coated with a metal oxide or is doped with other elements; the metal oxide is magnesium oxide and/or aluminum oxide; the doped element is selected from Li, One or more of K, Mg, Ca, Al, Cr, Cu, Ni, Ti, Nd, B, and P.
  • the charge cut-off voltage of the lithium ion battery is 4.35V and above. In a preferred embodiment of the present invention, the charge cut-off voltage is 4.45V.
  • the weight percentage of the first cyclic carbonate in the non-aqueous electrolyte is 14%-20%. Specifically, The weight percentage of the first cyclic carbonate may be 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%. %. The weight percentage of the second cyclic carbonate in the non-aqueous electrolyte is less than or equal to 0.5%.
  • the content of the second cyclic carbonate is reduced to a certain level, and the first cyclic carbonate fluorinated cyclic carbonate is used as the high dielectric constant solvent in the electrolyte, and the non-aqueous electrolyte is oxidized to produce gas as a side reaction
  • the degree is greatly reduced, reducing gas production. More preferably, when the weight ratio of the second cyclic carbonate is 0, the electrolyte generates very little gas and exhibits excellent high-temperature storage performance.
  • the first cyclic carbonate includes fluoroethylene carbonate; the second cyclic carbonate is a cyclic carbonate substituted or unsubstituted with a non-fluorine element.
  • the unsubstituted cyclic carbonate is a cyclic carbonate with 1-10 carbon atoms
  • the non-fluorine-substituted cyclic carbonate is a cyano group, an oxygen-containing hydrocarbon group, and a silicon-containing cyclic carbonate.
  • Cyclic carbonates substituted with hydrocarbon groups, alkyl groups, ether groups, and sulfur-containing hydrocarbon groups.
  • the second cyclic carbonate includes ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, and 1,2-butylene carbonate.
  • the non-aqueous electrolyte further includes linear carbonate and/or carboxylate, and a mixture of low-viscosity carboxylate organic solvent and chain carbonate organic solvent is used as the lithium ion battery
  • the solvent of the non-aqueous electrolyte can reduce the viscosity of the non-aqueous electrolyte.
  • the total weight percentage of the carboxylic acid ester and/or the linear carbonate in the non-aqueous electrolyte is 50% to 65%, specifically
  • the total weight ratio of the carboxylic acid ester and the linear carbonate may be 50%, 52%, 54%, 55%, 56%, 58%, 60%, 62%, 64%, 65%.
  • the linear carbonate includes one or more of diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethylene propyl carbonate.
  • the carboxylic acid ester includes ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -hexyl
  • lactone ⁇ -valerolactone and ⁇ -caprolactone
  • the non-aqueous electrolyte further includes an additive. Based on the total weight of the non-aqueous electrolyte of the lithium ion battery as 100%, the weight percentage of the additive is 1-20%; the additive includes One or more of vinylene carbonate, 1,3-propane sultone, dinitrile compounds, and trinitrile compounds.
  • the dinitrile compounds include one or more of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, and sebaconitrile, and the lithium ion battery is not
  • the total weight of the aqueous electrolyte is 100%, the weight percentage of the dinitrile compound is 0.1%-10%; the weight percentage of the 1,3-propane sultone is 1-10%.
  • lithium salt there is no special restriction on the lithium salt in the scheme of the present invention, and various existing substances can be used.
  • the lithium salt includes lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bisfluorosulfonimide
  • concentration of the lithium salt is 0.1M-2M, preferably 0.8M-1.5M.
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 33% of propyl propionate (PP) is added to the non-aqueous electrolyte, and 12% of fluoro is added. Ethylene carbonate (FEC). In addition, on the basis of Example 1, 3% by weight of 1,3-propane sultone (1,3-PS) and 2% of succinonitrile (SN) were added as additives.
  • PP propyl propionate
  • FEC Ethylene carbonate
  • SN succinonitrile
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 29% of propyl propionate (PP) is added to the non-aqueous electrolyte, and 15% of fluoro is added.
  • Ethylene carbonate (FEC) in addition to that of Example 1, 1% by weight of ethylene carbonate (EC) and 3% by weight of 1,3-propane sultone ( 1,3-PS) and 2% succinonitrile (SN).
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 29% of propyl propionate (PP) is added to the non-aqueous electrolyte, and 15% of fluoro is added.
  • Ethylene carbonate (FEC) in addition to that in Example 1, 0.5% by weight of ethylene carbonate (EC), 0.5% propylene carbonate (PC), 3% 1,3- Propane sultone (1,3-PS) and 2% succinonitrile (SN).
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 28% propyl propionate (PP) is added to the non-aqueous electrolyte, and 5% fluoro is added.
  • PP propyl propionate
  • fluoro ethylene carbonate
  • FEC ethylene carbonate
  • EC ethylene carbonate
  • PC propylene carbonate
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 20% of propyl propionate (PP) is added to the non-aqueous electrolyte, and 25% of fluoro is added. Ethylene carbonate (FEC). In addition, on the basis of Example 1, 3% by weight of 1,3-propane sultone (1,3-PS) and 2% of succinonitrile are added (SN) as an additive.
  • PP propyl propionate
  • FEC Ethylene carbonate
  • SN succinonitrile
  • non-aqueous electrolyte based on the total weight of the non-aqueous electrolyte as 100%, 28% of propyl propionate (PP) is added to the non-aqueous electrolyte, and 22% of fluoro is added. Ethylene carbonate (FEC).
  • PP propyl propionate
  • FEC Ethylene carbonate
  • NCM111 is used as the positive electrode active material.
  • Table 1 shows the dosage of each component of the electrolyte solvent in the above examples and comparative examples.
  • the discharge capacity of the first circle and the discharge capacity of the 300th circle were calculated by calculating the capacity retention rate of the high temperature cycle to evaluate the high temperature cycle performance.
  • Capacity retention rate (%) discharge capacity of the 300th circle/discharge capacity of the first circle ⁇ 100%
  • the formed battery is charged to 4.45V with 0.5C constant current and constant voltage at room temperature, and the initial discharge capacity and thickness of the battery are measured, and then stored at 60°C for 21 days. Wait for the battery to cool to room temperature and then measure the final thickness of the battery. The thickness expansion rate of the battery; afterwards, the battery's retention capacity and recovery capacity are measured by discharging at 0.3C to 3V. Calculated as follows:
  • Battery capacity retention rate (%) retention capacity/initial capacity ⁇ 100%
  • Battery capacity recovery rate (%) recovery capacity/initial capacity ⁇ 100%
  • Battery thickness expansion rate (%) (final thickness-initial thickness)/initial thickness ⁇ 100%.
  • the formed battery is charged to 4.45V with 0.5C constant current and constant voltage at room temperature, and the initial discharge capacity and thickness of the battery are measured, and then stored at 85°C for 6 hours. After the battery is cooled to room temperature, the final thickness of the battery is measured. Calculate the thickness expansion rate of the battery; then discharge at 0.3C to 3V to measure the battery's retention capacity and recovery capacity. Calculated as follows:
  • Battery capacity retention rate (%) retention capacity/initial capacity ⁇ 100%
  • Battery capacity recovery rate (%) recovery capacity/initial capacity ⁇ 100%
  • Battery thickness expansion rate (%) (final thickness-initial thickness)/initial thickness ⁇ 100%.
  • Example 1 shows that the electrolyte with the FEC content in the range of 12%-22% and the total content of EC and PC is less than 2% by weight of the electrolyte has better high-temperature storage performance and high-temperature cycle performance. In particular, it can significantly improve the problem of gas production, and the volume expansion rate is significantly reduced.
  • Example 1 shows that the FEC content is in the range of 12%-22% and the total content of EC and PC is less than 2% by weight of the electrolyte.
  • the high-voltage lithium cobalt oxide cathode material ratio matches the NMC111 cathode.
  • the material has better storage performance, which may be that FEC can be catalyzed to form a film on the surface of the lithium cobalt oxide positive electrode and prevent further reactions, but the film-forming reaction cannot occur on the NMC111.
  • the reason may be: high dielectric in the electrolyte Too little solvent content of the electrical constant leads to too low electrical conductivity of the electrolyte, and the continuous consumption of FEC during the cycle will further reduce the electrical conductivity, which causes the polarization of the positive and negative electrodes during battery charging and discharging to become greater and greater. It quickly reaches the charge-discharge cut-off voltage and cannot perform its capacity normally, and what is more serious is that after the negative electrode is polarized so much that its potential is lower than the lithium-evolution potential, the negative electrode is lithium-depleted and cycle diving.
  • Example 7 shows that in the electrolyte with FEC between 12%-22% and the total content of EC and PC less than 2%, 1,3-PS and dinitrile compound SN are added, and the battery is High-temperature storage and high-temperature cycle performance have been more significantly improved.

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Abstract

本发明属于新能源技术领域，特别是涉及一种锂离子电池。所述锂离子电池包括正极、负极、隔膜以及非水电解液，所述正极包括正极活性材料，所述正极活性材料中包含锂钴氧化物；所述非水电解液包括第一环状碳酸酯和不同于所述第一环状碳酸酯的第二环状碳酸酯；所述第一环状碳酸酯为氟代环状碳酸酯；所述第一环状碳酸酯的重量百分数为12％～22％，所述第二环状碳酸酯的重量百分数小于等于2％。其中，第二环状碳酸酯的含量降到了较低的水平，使得电解液被氧化产气的副反应程度大幅降低，减少电池产气，第一环状碳酸酯作为电解液中的高介电常数溶剂使用，具有比第二环状碳酸酯更好的负极成膜作用，能保证较好的循环性能。

Description

一种锂离子电池 技术领域
本发明属于新能源技术领域，特别是涉及一种锂离子电池。
背景技术
随着新能源汽车对续航里程的不断提高和3C数码产品轻薄化的不断发展，电池行业越来越要求锂离子电池高能量密度化。设计高能量密度的锂离子电池可以从以下几个方面着手：1)提高正极材料克容量；2)提高电池放电平台；3)提电池中活性材料的比例；提升锂离子电池的充电的截止电压是增大电池能量密度的重要途径之一，因为随着充电截止电压的提高，正极材料可以实现更高的克容量发挥，且放电平台有明显提高，两方面的作用对能量密度的提升具有立竿见影的效果。
随着电池电压的逐渐提高，正极材料进入更高的脱锂态，材料结构稳定性会变差，且表面的氧化性也明显提高。材料结构的不稳定性及其高氧化性在极片/电解液界面表现地尤其明显，具体表现为：电池发生产气，内阻快速增长，容量急剧下降。电池产气会导致内压增大，更进一步可能会发展为电池的爆炸、燃烧等危险情况，因此高电压电池和电解液需要匹配。
公知的，环状的碳酸乙烯酯(EC)由于具有高介电常数能够为电解液提供高电导率，其负极成膜作用的溶剂又能保证电池良好的循环性能，被广泛应用于非水锂二次电池中。然而，EC的耐高电压稳定性较差，容易在高电压正极上被氧化分解产气，导致电池性能衰减。碳酸丙烯酯(PC)具有更好的耐高电压性能及与EC相当的介电常数和更宽的低温液相温度，在锂离子电池中也有广泛的应用，然而PC不能在负极发生成膜反应，过多的PC替代会导致循环性能劣化。 氟代碳酸乙烯酯(FEC)由于其具有较高的分解电压和抗氧化性，同时具有较好的成膜特性，目前作为添加剂普遍用于高电压锂离子以保证高电压电池的循环性能。但FEC作为高电压电池的电解液的添加剂时，电解液更容易产气，导致电池在高温存储和高温循环过程中内压增大，电池发生鼓包、胀气、甚至爆炸。
发明内容
本发明所要解决的技术问题是：针对现有的高电压锂离子电池高温存储和高温循环过程中产气的问题，提供一种锂离子电池。
为解决上述技术问题，本发明实施例提供一种锂离子电池，包括正极、负极、隔膜以及非水电解液，所述正极包括正极活性材料，所述正极活性材料中包含锂钴氧化物；
所述非水电解液包括第一环状碳酸酯和不同于所述第一环状碳酸酯的第二环状碳酸酯；
所述第一环状碳酸酯为氟代环状碳酸酯；
以所述锂离子电池非水电解液的总重量为100％计，所述第一环状碳酸酯的重量百分数为12％～22％，所述第二环状碳酸酯的重量百分数小于等于2％。
可选地，所述第一环状碳酸酯包括氟代碳酸乙烯酯；所述第二环状碳酸酯为非氟元素取代或未取代的环状碳酸酯。
可选的，所述未取代的环状碳酸酯为碳原子数为1-10的环状碳酸酯。
可选的，所述非氟元素取代的环状碳酸酯为氰基、含氧烃基、含硅烃基、烷基、醚基、含硫烃基取代的环状碳酸酯。
可选地，所述正极活性材料表面包覆有金属氧化物或内部掺杂有其他元素；所述金属氧化物为氧化镁和/或氧化铝；所述掺杂的元素选自Li、K、Mg、Ca、Al、Cr、Cu、Ni、Ti、Nd、B和P中的一种或多种。
可选地，所述锂离子电池充电截止电压为4.35V及以上。
可选地，以所述锂离子电池非水电解液的总重量为100％计，所述第一环状 碳酸酯占非水电解液的重量百分数为14％～20％，所述第二环状碳酸酯占非水电解液的重量百分数为小于等于0.5％。
可选地，所述第一环状碳酸酯包括氟代碳酸乙烯酯；所述第二环状碳酸酯为非氟元素取代或未取代的环状碳酸酯。
可选地，所述第二环状碳酸酯包括碳酸亚乙酯、碳酸亚丙酯、碳酸-1,2-亚丁酯、碳酸-2,3-亚丁酯、碳酸-1,2-亚戊酯、碳酸-2,3-亚戊酯中的一种或多种。
可选地，所述非水电解液还包括线性碳酸酯和/或羧酸酯，以所述锂离子电池非水电解液的总重量为100％计，所述羧酸酯和/或所述线性碳酸酯占所述非水电解液重量百分数总和为50％～65％。
可选地，所述线性碳酸酯包括碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯和碳酸乙丙酯中的一种或多种；
所述羧酸酯包括乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、γ-戊内酯、γ-己内酯、σ-戊内酯和ε-己内酯中的一种或多种。
可选地，所述非水电解液还包括添加剂，以所述锂离子电池非水电解液的总重量为100％计，所述添加剂的重量百分数为1-20％；
所述添加剂包括碳酸亚乙烯酯、1,3-丙烷磺酸内酯、二腈类化合物、三腈类化合物中的一种或多种；
所述二腈类化合物包括丁二腈、戊二腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种，并且以所述锂离子电池非水电解液的总重量为100％计，所述二腈类化合物的重量百分数为0.1％～10％；所述1,3-丙烷磺酸内酯的重量百分数为1～10％。
可选地，所述非水电解液还包括锂盐，所述锂盐包括六氟磷酸锂、高氯酸锂、四氟硼酸锂、双氟草酸硼酸锂、二(三氟甲基磺酰)亚胺锂和双氟磺酰亚胺锂盐中的一种或多种，且所述锂盐浓度为0.1M～2M。
本发明实施例提供的锂离子电池中，正极材料包含锂钴氧化物，其表面可以催化氟代碳酸乙烯酯发生原位成膜反应而起到保护作用，在非水电解液中， 增加第一环状碳酸酯氟代环状碳酸酯的含量，使其作为电解液中的高介电常数溶剂使用，且第二环状碳酸酯的含量降到了较低的水平，使得电解液被氧化产气的副反应程度大幅降低，减少电池产气，改善高温存储性能。且氟代环状碳酸酯具有比第二环状碳酸酯更好的负极成膜作用，能保证较好的循环性能。
具体实施方式
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合附图及实施例，对本发明进行进一步的详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明实施例提供的一种锂离子电池，包括正极、负极、隔膜以及非水电解液，所述正极包括正极活性材料，所述正极活性材料中包含锂钴氧化物；
所述负极包括负极活性材料，所述负极活性材料包括硬碳、软碳、石墨、含硅材料中的一种或多种。
在一些实施例中，所述电池正极和所述电池负极之间隔有所述隔膜，所述隔膜为锂离子电池领域的常规隔膜，这里不再赘述。
所述非水电解液包括第一环状碳酸酯和不同于所述第一环状碳酸酯的第二环状碳酸酯；所述第一环状碳酸酯为氟代环状碳酸酯；以所述锂离子电池非水电解液的总重量为100％计，所述第一环状碳酸酯的重量百分数为12％～22％，所述第二环状碳酸酯的重量百分数小于等于2％。
传统的，在以第二环状碳酸酯(如EC、PC)作为高介电常数溶剂的电解液中，第二环状碳酸酯一般占电解液重量10％～30％，第一环状碳酸酯氟代环状碳酸酯(如FEC)通常作为可选的负极成膜添加剂少量加入(10％以下)，而第一环状碳酸酯虽然能够改善循环性能但会导致明显产气，影响电池的高温存储性能。
发明人通过大量实验分析发现，以钴酸锂为正极活性材料的锂电池体系存在高温储存产气的问题，本发明提供的实施例中，正极活性材料中包含锂钴氧 化物，非水电解液中使用第一环状碳酸酯氟代环状碳酸酯(如FEC)作为高介电常数溶剂使用，且不同于第一环状碳酸酯的第二环状碳酸酯含量降低到了较低的水平时，使用该非水电解液的锂离子电池表现出优秀的高温存储性能，不产气并有良好的容量保持和恢复性能，同时电池具有良好的循环性能。
在一实施例中，所述正极活性材料表面包覆有金属氧化物或内部掺杂有其他元素；所述金属氧化物为氧化镁和/或氧化铝；所述掺杂的元素选自Li、K、Mg、Ca、Al、Cr、Cu、Ni、Ti、Nd、B和P中的一种或多种。
在一实施例中，所述锂离子电池充电截止电压为4.35V及以上，在本发明的一个优选实施例中，充电截止电压为4.45V。
在一实施例中，以所述锂离子电池非水电解液的总重量为100％计，所述第一环状碳酸酯占非水电解液的重量百分数为14％～20％，具体的，所述第一环状碳酸酯的重量百分比可以为14％、14.5％、15％、15.5％、16％、16.5％、17％、17.5％、18％、18.5％、19％、19.5％、20％。所述第二环状碳酸酯占非水电解液的重量百分数为小于等于0.5％。
所述第二环状碳酸酯的含量降低到一定水平，使用第一环状碳酸酯氟代环状碳酸酯作为电解液中的高介电常数溶剂，非水电解液被氧化产气的副反应程度大幅降低，减少了产气。更优选的，当所述第二环状碳酸酯重量比为0时，电解液产气非常少，表现出优良的高温存储性能。
在一实施例中，所述第一环状碳酸酯包括氟代碳酸乙烯酯；所述第二环状碳酸酯为非氟元素取代或未取代的环状碳酸酯。
在一实施例中，所述未取代的环状碳酸酯为碳原子数为1-10的环状碳酸酯，所述非氟元素取代的环状碳酸酯为氰基、含氧烃基、含硅烃基、烷基、醚基、含硫烃基取代的环状碳酸酯。
在一实施例中，所述第二环状碳酸酯包括碳酸亚乙酯、碳酸亚丙酯、碳酸-1,2-亚丁酯、碳酸-2,3-亚丁酯、碳酸-1,2-亚戊酯、碳酸-2,3-亚戊酯中的一种或多种。
需要说明的是，以上化合物是本发明所要求保护的部分化合物，但不仅限 于此，不应理解为对本发明的限制。
在一实施例中，所述非水电解液还包括线性碳酸酯和/或羧酸酯，采用低粘度的羧酸酯有机溶剂与链状碳酸酯有机溶剂的混合液作为所述锂离子电池的非水电解液的溶剂，能够降低非水电解液的粘度。
以所述锂离子电池非水电解液的总重量为100％计，所述羧酸酯和/或所述线性碳酸酯占所述非水电解液重量百分数总和为50％～65％，具体的，所述羧酸酯和所述线性碳酸酯的重量比总和可以为50％、52％、54％、55％、56％、58％、60％、62％、64％、65％。
在一实施例中，所述线性碳酸酯包括碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯和碳酸乙丙酯中的一种或多种。
在一实施例中，所述羧酸酯包括乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、γ-戊内酯、γ-己内酯、σ-戊内酯和ε-己内酯中的一种或多种。
在一实施例中，所述非水电解液还包括添加剂，以所述锂离子电池非水电解液的总重量为100％计，所述添加剂的重量百分数为1-20％；所述添加剂包括碳酸亚乙烯酯、1,3-丙烷磺酸内酯、二腈类化合物、三腈类化合物中的一种或多种。
所述二腈类化合物包括丁二腈、戊二腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种，并且以所述锂离子电池非水电解液的总重量为100％计，所述二腈类化合物的重量百分数为0.1％～10％；所述1,3-丙烷磺酸内酯的重量百分数为1～10％。
需要说明的是，以上化合物是本发明所要求保护的部分化合物，但不仅限于此，不应理解为对本发明的限制。
本发明方案中对于锂盐没有特殊限制，可采用现有的各种物质。
在一实施例中，所述锂盐包括六氟磷酸锂、高氯酸锂、四氟硼酸锂、双氟草酸硼酸锂、二(三氟甲基磺酰)亚胺锂和双氟磺酰亚胺锂盐中的一种或多种， 且所述锂盐浓度为0.1M～2M，优选的为0.8M～1.5M。
以下通过实施例对本发明进行进一步的说明。
实施例1
1)非水电解液的制备
将35％碳酸二乙酯(DEC)和28％丙酸丙酯(PP)进行混合，加入22％的氟代碳酸乙烯酯(FEC)，再加入按电解液的总重量计15％的六氟磷酸锂(LiPF 6)。
2)正极板的制备
按93:4:3的质量比混合正极活性材料钴酸锂(LiCoO 2)，导电碳黑Super-P和粘结剂聚偏二氟乙烯(PVDF)，然后将它们分散在N-甲基-2-吡咯烷酮(NMP)中，得到正极浆料。将浆料均匀涂布在铝箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上铝制引出线后得到正极板。
3)负极板的制备
按94:1:2.5:2.5的质量比混合负极活性材料人造石墨，导电碳黑Super-P，粘结剂丁苯橡胶(SBR)和羧甲基纤维素(CMC)，然后将它们分散在去离子水中，得到负极浆料。将浆料涂布在铜箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上镍制引出线后得到负极板。
4)电芯的制备
在正极板和负极板之间放置厚度为20μm的聚乙烯微孔膜作为隔膜，然后将正极板、负极板和隔膜组成的三明治结构进行卷绕，再将卷绕体压扁后放入铝塑膜包装袋，然后于85℃下烘烤24hr，得到待注液的电芯。
5)电芯的注液和化成
在露点控制在-40℃以下的手套箱中，将上述制备的非水电解液注入电芯中，电解液的量要保证充满电芯中的空隙。然后按以下步骤进行化成：0.05C恒流充电180min，0.1C恒流充电240min，搁置1hr后真空整形封口，然后进一步以0.2C的电流恒流充电至4.45V，常温搁置24hr后，以0.2C的电流恒流放电至3.0V。
实施例2
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入33％丙酸丙酯(PP)，加入12％的氟代碳酸乙烯酯(FEC)。除此之外，在实施例1的基础上再加入重量计为3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)作为添加剂。
实施例3
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入30％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)。除此之外，在实施例1的基础上再加入重量计为3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)作为添加剂。
实施例4
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入29％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为1％的碳酸乙烯酯(EC)、重量计为3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
实施例5
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入29％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为1％碳酸丙烯酯(PC)、3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
实施例6
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所 述非水电解液中加入29％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为0.5％的碳酸乙烯酯(EC)、0.5％碳酸丙烯酯(PC)、3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
实施例7
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入23％丙酸丙酯(PP)，加入22％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)作为添加剂。
对比例1
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入28％丙酸丙酯(PP)，加入5％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为12％的碳酸乙烯酯(EC)和5％碳酸丙烯酯(PC)。
对比例2
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入23％丙酸丙酯(PP)，加入5％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为12％的碳酸乙烯酯(EC)和5％碳酸丙烯酯(PC)，以及3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
对比例3
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入37％丙酸丙酯(PP)，加入8％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为3％的1,3-丙烷磺酸内酯(1,3-PS) 和2％的丁二腈(SN)作为添加剂。
对比例4
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入20％丙酸丙酯(PP)，加入25％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)作为添加剂。
对比例5
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入25％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入5％的碳酸乙烯酯(EC)、3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
对比例6
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入25％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为5％碳酸丙烯酯(PC)，以及3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
对比例7
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入25％丙酸丙酯(PP)，加入15％的氟代碳酸乙烯酯(FEC)，除此之外，在实施例1的基础上再加入重量计为2％的碳酸乙烯酯(EC)、3％碳酸丙烯酯(PC)，以及3％的1,3-丙烷磺酸内酯(1,3-PS)和2％的丁二腈(SN)。
对比例8
与实施例1的工艺相同，如表1中所示，不同之处在于：
所述非水电解液的制备步骤中，以所述非水电解液的总重量为100％计，所述非水电解液中加入28％丙酸丙酯(PP)，加入22％的氟代碳酸乙烯酯(FEC)。
所述正极板的制备步骤中，使用NCM111作为正极活性材料。
表1示出了以上实施例和对比例中的电解液溶剂各组分用量加入情况。
表1电解液溶剂的各组分用量(重量百分比)
  EC PC FEC DEC PP LiPF6 1,3-PS SN 正极活性材料
对比例1 12 5 5 35 28 15     LiCoO 2
对比例2 12 5 5 35 23 15 3 2 LiCoO 2
对比例3     8 35 37 15 3 2 LiCoO 2
对比例4     25 35 20 15 3 2 LiCoO 2
对比例5 5   15 35 25 15 3 2 LiCoO 2
对比例6   5 15 35 25 15 3 2 LiCoO 2
对比例7 2 3 15 35 25 15 3 2 LiCoO 2
对比例8     22 35 28 15     NCM111
实施例1     22 35 28 15     LiCoO 2
实施例2     12 35 33 15 3 2 LiCoO 2
实施例3     15 35 30 15 3 2 LiCoO 2
实施例4 1   15 35 29 15 3 2 LiCoO 2
实施例5   1 15 35 29 15 3 2 LiCoO 2
实施例6 0.5 0.5 15 35 29 15 3 2 LiCoO 2
实施例7     22 35 23 15 3 2 LiCoO 2
性能测试
对上述实施例1～7和对比例1～8制备得到的锂离子电池进行如下性能测试
1)高温循环性能测试
将电池置于恒温45℃的烘箱中，以1C的电流恒流充电至4.45V然后恒压充电至电流下降至0.03C，然后以1C的电流恒流放电至3.0V，如此循环300圈，记录第1圈的放电容量和第300圈的放电容量，计算高温循环的容量保持率，以评估其高温循环性能。
容量保持率的计算公式如下：
容量保持率(％)＝第300圈的放电容量/第1圈的放电容量×100％
2)高温储存性能测试
将化成后的电池在常温下用0.5C恒流恒压充至4.45V，测量电池初始放电容量及初始电池厚度，然后再60℃储存21天后，等电池冷却至常温再测电池最终厚度，计算电池厚度膨胀率；之后以0.3C放电至3V测量电池的保持容量和恢复容量。计算公式如下：
电池容量保持率(％)＝保持容量/初始容量×100％；
电池容量恢复率(％)＝恢复容量/初始容量×100％；
电池厚度膨胀率(％)＝(最终厚度-初始厚度)/初始厚度×100％。
3)高温储存性能测试
将化成后的电池在常温下用0.5C恒流恒压充至4.45V，测量电池初始放电容量及初始电池厚度，然后再85℃储存6小时后，等电池冷却至常温再测电池最终厚度，计算电池厚度膨胀率；之后以0.3C放电至3V测量电池的保持容量和恢复容量。计算公式如下：
电池容量保持率(％)＝保持容量/初始容量×100％；
电池容量恢复率(％)＝恢复容量/初始容量×100％；
电池厚度膨胀率(％)＝(最终厚度-初始厚度)/初始厚度×100％。
将计算得到的测试结果填入表2中。
表2
Figure PCTCN2020136344-appb-000001
Figure PCTCN2020136344-appb-000002
实施例1和对比例1比较，说明FEC含量在12％-22％范围之间且EC与PC总含量低于电解液重量2％以下的电解液有更好的高温存储性能和高温循环性能，尤其能明显改善产气问题，体积膨胀率明显降低。
实施例1和对比例8比较，说明FEC含量在12％-22％范围之间且EC与PC总含量低于电解液重量2％以下的电解液匹配高电压钴酸锂正极材料比匹配NMC111正极材料有更好的存储性能，这可能是FEC能在钴酸锂正极表面被催化成膜并阻止进一步的反应，而不能在NMC111上发生成膜反应。
实施例2-7与对比例2比较，说明电解液中FEC含量在12％-22％范围之间且EC与PC总含量低于电解液重量2％以下后，电池的高温存储性能特别是气胀改善尤为明显，高温循环性能也有明显的改善。
实施例2，3，7与对比例3-4比较，说明FEC在12％-22％之间且EC与PC总含量低于1％时，电池能有较好的高温存储和循环性能，且FEC含量优选的为14％～20％。FEC含量低于12％时且EC与PC总含量低于2％时，电池虽然具有较好的高温存储性能，但是高温循环性能差，并出现循环跳水的现象，原因可能是：电解液中高介电常数的溶剂含量过少导致电解液的电导率太低，循环过程中随着FEC的持续消耗会进一步降低电导率，这导致电池充放电时正负极的电位的极化越来越大，很快达到充放电截至电压而不能正常发挥容量，而更严重的是负极极化大到其电位低于析锂电位后，负极析锂而循环跳水。FEC含量 不能大于22％的原因：当FEC含量大于22％且EC与PC总含量低于2％时，电池的高温循环性能无明显影响，说明电导率和负极成膜保护是足够的，但是高温存储性能却也开始变差，原因目前还不清楚，推测是过多的FEC与LiPF6形成的溶剂化结构稳定性变差，引起电解液的分解。
实施例7与实施例1比较，说明在FEC在12％-22％之间且EC与PC总含量低于2％的电解液中，加入1,3-PS和二腈类化合物SN，电池的高温存储和高温循环性能有更加显著的提高。
实施例3-6与对比例5-7比较，说明电解液中FEC在12％-22％之间时，EC与PC总含量须低于2％的后，电池才能有良好的存储不产气性能，并保存较好的循环性能，原因还不清楚。
对比例1-2比较，在常规EC+PC溶剂的电解液中，增加1,3-PS和腈类添加剂SN更有利于改善电池的存储和循环性能。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种锂离子电池，包括正极、负极、隔膜以及非水电解液，其特征在于，
    所述正极包括正极活性材料，所述正极活性材料中包含锂钴氧化物；
    所述非水电解液包括第一环状碳酸酯和不同于所述第一环状碳酸酯的第二环状碳酸酯；
    所述第一环状碳酸酯为氟代环状碳酸酯；
    以所述锂离子电池非水电解液的总重量为100％计，所述第一环状碳酸酯的重量百分数为12％～22％，所述第二环状碳酸酯的重量百分数小于等于2％。
  2. 如权利要求1所述的锂离子电池，其特征在于，所述正极活性材料表面包覆有金属氧化物或内部掺杂有其他元素；所述金属氧化物为氧化镁和/或氧化铝；所述掺杂的元素选自Li、K、Mg、Ca、Al、Cr、Cu、Ni、Ti、Nd、B和P中的一种或多种。
  3. 如权利要求1或2所述的锂离子电池，其特征在于，所述锂离子电池充电截止电压为4.35V及以上。
  4. 如权利要求1或2所述的锂离子电池，其特征在于，以所述锂离子电池非水电解液的总重量为100％计，所述第一环状碳酸酯占非水电解液的重量百分数为14％～20％，所述第二环状碳酸酯占非水电解液的重量百分数为小于等于0.5％。
  5. 如权利要求1或2所述的锂离子电池，其特征在于，所述第一环状碳酸酯包括氟代碳酸乙烯酯；
    所述第二环状碳酸酯为非氟元素取代或未取代的环状碳酸酯。
  6. 如权利要求5所述的锂离子电池，其特征在于，所述第二环状碳酸酯包括碳酸亚乙酯、碳酸亚丙酯、碳酸-1,2-亚丁酯、碳酸-2,3-亚丁酯、碳酸-1,2-亚戊酯、碳酸-2,3-亚戊酯中的一种或多种。
  7. 如权利要求1所述的锂离子电池，其特征在于，所述非水电解液还包括 线性碳酸酯和/或羧酸酯，以所述锂离子电池非水电解液的总重量为100％计，所述羧酸酯和/或所述线性碳酸酯占所述非水电解液重量百分数总和为50％～65％。
  8. 如权利要求6所述的锂离子电池，其特征在于，所述线性碳酸酯包括碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯和碳酸乙丙酯中的一种或多种；
    所述羧酸酯包括乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、γ-戊内酯、γ-己内酯、σ-戊内酯和ε-己内酯中的一种或多种。
  9. 如权利要求1或6所述的锂离子电池，其特征在于，所述非水电解液还包括添加剂，以所述锂离子电池非水电解液的总重量为100％计，所述添加剂的重量百分数为1-20％；
    所述添加剂包括碳酸亚乙烯酯、1,3-丙烷磺酸内酯、二腈类化合物、三腈类化合物中的一种或多种；
    所述二腈类化合物包括丁二腈、戊二腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种，并且以所述锂离子电池非水电解液的总重量为100％计，所述二腈类化合物的重量百分数为0.1％～10％；所述1,3-丙烷磺酸内酯的重量百分数为1～10％。
  10. 如权利要求1所述的锂离子电池，其特征在于，所述非水电解液还包括锂盐，所述锂盐包括六氟磷酸锂、高氯酸锂、四氟硼酸锂、双氟草酸硼酸锂、二(三氟甲基磺酰)亚胺锂和双氟磺酰亚胺锂盐中的一种或多种，且所述锂盐浓度为0.1M～2M。
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