WO2024060827A1 - 锂离子电芯及锂离子电池 - Google Patents

锂离子电芯及锂离子电池 Download PDF

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WO2024060827A1
WO2024060827A1 PCT/CN2023/109632 CN2023109632W WO2024060827A1 WO 2024060827 A1 WO2024060827 A1 WO 2024060827A1 CN 2023109632 W CN2023109632 W CN 2023109632W WO 2024060827 A1 WO2024060827 A1 WO 2024060827A1
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Prior art keywords
negative electrode
electrode sheet
lithium ion
ion battery
lithium
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PCT/CN2023/109632
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English (en)
French (fr)
Inventor
陈萌
刘中奎
周保福
徐立洋
李凯
宫璐
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合肥国轩高科动力能源有限公司
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Publication of WO2024060827A1 publication Critical patent/WO2024060827A1/zh

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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
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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 present application relates to the technical field of lithium-ion batteries, specifically, to a lithium-ion battery cell and a lithium-ion battery.
  • the main purpose of this application is to provide a lithium-ion battery cell and a lithium-ion battery.
  • the above-mentioned lithium-ion battery cell has better battery thermal safety performance and overcharge performance.
  • the present application provides a lithium ion battery core, which includes a battery core unit.
  • the battery core unit includes: a positive electrode sheet; a negative electrode sheet; and a separator located between the negative electrode sheet and the positive electrode sheet to separate the positive electrode sheet and the negative electrode. film; the overcharge protection layer can conduct electrons and ions.
  • the overcharge protection layer is located between the negative electrode sheet and the separator. There is an overcharge protection layer on at least one side of the separator or the negative electrode sheet. The overcharge protection layer is more oxidizing than Oxidizing properties of lithium ions.
  • the material of the overcharge protection layer is a compound containing tetravalent titanium.
  • the tetravalent titanium-containing compound is a granular material, and the D50 particle size of the tetravalent titanium-containing compound is between 0.2 ⁇ m and 1 ⁇ m.
  • the tetravalent titanium-containing compound is any compound selected from the group consisting of lithium aluminum titanium phosphate, lithium lanthanum titanium oxide, lithium titanate, and titanium dioxide.
  • the negative electrode sheet includes a negative electrode current collector and negative electrode active material layers located on opposite sides of the negative electrode current collector.
  • An overcharge protection layer is provided on a side of the negative electrode active material layer facing away from the negative electrode current collector.
  • the ratio between the thickness of the overcharge protection layer and the thickness of the separator is greater than or equal to 0.1 and less than or equal to 0.6.
  • the ratio between the thickness of the overcharge protection layer and the thickness of the negative electrode sheet is greater than or equal to 0.005 and less than or equal to 0.05.
  • the thickness of the overcharge protection layer is greater than or equal to 1 ⁇ m and less than or equal to 4 ⁇ m.
  • the lithium-ion battery cell is formed by winding one or more battery cell units; or, the lithium-ion battery cell includes one or more battery cell units stacked in sequence.
  • the present application provides a lithium-ion battery, which includes a shell, the above-mentioned lithium-ion battery cell located in the shell, and an electrolyte filled in the shell.
  • the overcharge protective layer when the battery is overcharged, since the oxidation property of the overcharge protective layer is stronger than the oxidation property of lithium ions, the overcharge protective layer will undergo a reduction reaction before the lithium ions at the negative electrode sheet, that is, overcharge occurs.
  • the charging protection layer will obtain electrons before the lithium ions at the negative electrode piece. In this way, the lithium ions at the negative electrode piece can be prevented from being reduced to a certain extent, and the negative electrode piece can be protected to a certain extent during overcharging to avoid the negative electrode piece being damaged due to overcharging.
  • the precipitation of lithium on the surface causes safety issues such as short circuit or thermal runaway.
  • the lithium-ion battery cell of this embodiment has better battery thermal safety performance and overcharge performance, which can effectively alleviate the thermal runaway hazard of the battery that may be caused by overcharge, and reduce the battery life to a large extent.
  • the risk of overcharge failure improves the safety performance of lithium-ion batteries.
  • Figure 1 shows a schematic structural diagram of the overcharge protective layer of the lithium-ion battery cell coated on the separator according to the embodiment of the present application
  • Figure 2 shows a schematic structural diagram of the overcharge protective layer of the lithium-ion battery cell coated on the negative electrode sheet according to the embodiment of the present application
  • Figure 3 shows a schematic structural diagram of an embodiment of the lithium-ion battery cell of the present application
  • FIG4 shows a schematic structural diagram of another embodiment of a lithium-ion battery cell of the present application.
  • Figure 5 shows the continuous overcharge test voltage curve of the battery in Example 1 and Comparative Example 1 of the present application.
  • the lithium-ion battery cell includes a battery cell unit, and the battery cell unit includes a positive electrode sheet 100, a negative electrode sheet 300, a separator 10, and an overcharge protection layer 40 capable of conducting electrons and ions.
  • the separator 10 is located between the negative electrode sheet 300 and the positive electrode sheet 100 to separate the positive electrode sheet 100 and the negative electrode sheet 300;
  • the overcharge protection layer 40 is located between the negative electrode sheet 300 and the separator 10, and the overcharge protection layer 40 is provided on at least one side of the separator 10 or the negative electrode sheet 300.
  • the oxidizing property of the overcharge protection layer 40 is stronger than the oxidizing property of lithium ions.
  • the overcharge protection layer 40 when the battery is overcharged, since the oxidation property of the overcharge protection layer 40 is stronger than the oxidation property of lithium ions, the overcharge protection layer 40 will undergo a reduction reaction before the lithium ions at the negative electrode sheet 300, that is, The overcharge protection layer 40 will obtain electrons before the lithium ions at the negative electrode piece 300. In this way, the lithium ions at the negative electrode piece 300 can be prevented from being reduced to a certain extent, thereby protecting the negative electrode piece 300 to a certain extent during overcharge. This is to avoid safety problems such as short circuit or thermal runaway caused by lithium precipitation on the surface of the negative electrode sheet 300.
  • the lithium-ion battery cell of this embodiment has better battery thermal safety performance and overcharge performance, which can effectively alleviate the thermal runaway hazard of the battery that may be caused by overcharge. It reduces the risk of battery overcharge failure to a great extent and improves the safety performance of lithium-ion batteries.
  • the overcharge protection layer 40 can conduct electrons and ions. In this way, the overcharge protection layer 40 does not affect the normal charging and discharging of the battery, but can protect the negative electrode sheet 300 .
  • the overcharge protection layer 40 will obtain electrons before the lithium ions at the negative electrode sheet 300, the probability of forming lithium dendrites in the battery can be reduced.
  • the overcharge protection layer 40 is coated on the surface of the negative electrode sheet 300 or on the side of the separator 10 facing the negative electrode sheet 300 .
  • the material of the overcharge protection layer 40 is a compound containing tetravalent titanium.
  • the oxidizing property of the overcharge protection layer 40 can be made stronger than that of lithium ions, so that the overcharge protection layer 40 can be reduced prior to the lithium ions.
  • the tetravalent titanium-containing compound is any compound selected from the group consisting of lithium aluminum titanium phosphate, lithium lanthanum titanium oxide, lithium titanate, and titanium dioxide.
  • the above-mentioned materials are not only more oxidizing than lithium ions, but also have good thermal stability. This can effectively alleviate the thermal runaway of the battery that may be caused by overcharging.
  • the above-mentioned tetravalent compound is a common and easily available compound, which can reduce the production cost of lithium-ion batteries.
  • the material of the overcharge protection layer 40 is generally a material with good thermal stability that can undergo a valence change reaction with lithium ions at a low potential ( ⁇ 2V).
  • the negative electrode sheet 300 includes a negative electrode current collector 60 and negative electrode active material layers 50 located on opposite sides of the negative electrode current collector 60 .
  • An overcharge protection layer 40 is provided on one side. Through the above arrangement, the overcharge protection layer 40 can effectively protect the negative active material layer 50 .
  • the ratio between the thickness of the overcharge protection layer 40 and the thickness of the separator 10 is greater than or equal to 0.1 and less than or equal to 0.6. Since the thicker the overcharge protection layer 40 is, the better its thermal stability is. Through the above arrangement, the overcharge protection layer 40 can have better thermal stability without affecting the normal charging and discharging of the battery, thereby effectively Improve battery thermal safety performance.
  • the ratio between the thickness of the overcharge protection layer 40 and the thickness of the negative electrode sheet 300 is greater than or equal to 0.005 and less than or equal to 0.05. Since the thicker the overcharge protection layer 40 is, the better its thermal stability is. Through the above arrangement, the overcharge protection layer 40 can have better thermal stability without affecting the normal charging and discharging of the battery, thereby effectively Improve battery thermal safety performance.
  • the thickness of the overcharge protection layer 40 is greater than or equal to 1 ⁇ m and less than or equal to 4 ⁇ m.
  • the above thickness can make the overcharge protection layer 40 have better thermal stability, thereby effectively improving the thermal safety performance of the battery.
  • the tetravalent titanium-containing compound is a granular material, and the D50 particle size of the tetravalent titanium-containing compound is between 0.2 ⁇ m and 1 ⁇ m. This can increase the thermal stability of the overcharge protection layer 40, thereby effectively improving the thermal safety performance of the battery.
  • the lithium ion battery core is wound by one or more battery cell units; or, as shown in Figure 4, in the embodiment of the present application, the lithium ion battery core includes One or more stacked battery cells. In this way, lithium-ion batteries can be used in both cylindrical batteries and prismatic batteries.
  • the battery cell unit also includes a positive electrode tab 400 connected to the positive electrode sheet 100 , and a negative electrode tab 500 connected to the negative electrode sheet 300 .
  • the separator 10 is made of a PE base film (polyethylene film) with a thickness of 12 ⁇ m, and a lithium titanium aluminum phosphate coating with a thickness of 3 ⁇ m is coated on the side of the separator 10 facing the negative electrode sheet 300.
  • the particle size of the lithium titanium aluminum phosphate coating is D50. is 0.7 ⁇ m and the purity is 99.95%.
  • the positive electrode sheet is made of 622 type ternary cathode material, and the negative electrode sheet is made of graphite material.
  • a 10Ah soft-pack battery is made on a trial basis. The battery after being reduced to its component capacity is charged with a constant current of 20A to 3.6V and then switched to constant voltage charging. Stop charging until the charging current drops to 1A and leave it aside for 1 hour. Then continue charging at a constant current of 20A until charging stops at 20V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the separator 10 is made of a 12 ⁇ m thick PE base film (polyethylene film), and a 3 ⁇ m thick alumina ceramic coating is coated on the side of the separator 10 facing the negative electrode sheet 300.
  • the particle size D50 of the alumina ceramic coating is 0.7. ⁇ m, purity is 99.95%.
  • the positive electrode sheet is made of 622 type ternary cathode material, and the negative electrode sheet is made of graphite material.
  • the electrolyte is matched to trial-produce a 10Ah soft-pack battery. After the battery is divided into components, the battery is charged with a constant current of 20A to 3.6V and then switched to constant voltage charging. Stop charging when the charging current drops to 1A and leave it aside for 1 hour. Then continue charging at a constant current of 20A until charging stops at 20V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the separator 10 is made of a 9 ⁇ m thick PE base film (polyethylene film), and a 4 ⁇ m thick lithium lanthanum titanium coating is coated on the side of the separator 10 facing the negative electrode sheet 300 , where the particle size of the lithium lanthanum titanium coating is D50 is 0.4 ⁇ m and the purity is 99.92%.
  • the positive electrode sheet 100 is made of lithium iron phosphate material, and the negative electrode sheet is made of graphite material.
  • a 10Ah cylindrical battery is made by matching the electrolyte. After the battery is reduced to its component capacity, the battery is charged with a constant current of 5A to 3.2V and then switched to constant voltage charging until the charging current drops. Stop charging when it reaches 0.1A and leave it aside for 1 hour. Then continue charging at a constant current of 2A until charging stops at 5V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the separator 10 is made of a 9 ⁇ m thick PE base film (polyethylene film), and a boehmite ceramic coating with a thickness of 4 ⁇ m is coated on the side of the separator 10 facing the negative electrode sheet 300.
  • the particle size D50 of the boehmite ceramic coating is 0.4. ⁇ m, purity is 99.92%.
  • the positive electrode sheet is made of lithium iron phosphate material
  • the negative electrode sheet is made of graphite material
  • the electrolyte is matched to trial-produce a 10Ah cylindrical battery. After the battery is reduced to its component capacity, the battery is charged with a constant current of 5A to 3.2V and then switched to constant voltage charging until the charging current drops to Stop charging at 0.1A and leave it aside for 1h. Then continue charging at a constant current of 2A until charging stops at 5V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the negative electrode sheet is made of graphite material and coated with a titanium dioxide coating with a thickness of 2 ⁇ m.
  • the particle size D50 of the titanium dioxide coating is 0.8 ⁇ m and the purity is 99.90%.
  • the positive electrode sheet is made of 622 ternary positive electrode material, and the separator 10 is selected and matched with the electrolyte to make a 20Ah soft-pack battery. After the battery is divided into components, the battery is charged with a constant current of 10A to 3.6V and then switched to a constant voltage charge until the charging current drops to Stop charging at 0.05A and leave it aside for 1 hour. Then continue charging at a constant current of 10A until charging stops at 10V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the negative electrode sheet is made of graphite material and coated with an alumina ceramic coating with a thickness of 2 ⁇ m.
  • the particle size D50 of the alumina ceramic coating is 0.8 ⁇ m and the purity is 99.90%.
  • the positive electrode sheet is made of 622 ternary positive electrode material, and the separator 10 is selected and matched with the electrolyte to make a 20Ah soft-pack battery. After the battery is divided into components, the battery is charged with a constant current of 10A to 3.6V and then switched to a constant voltage charge until the charging current drops to Stop charging at 0.05A and leave it aside for 1 hour. Then continue charging at a constant current of 10A until charging stops at 10V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the negative electrode sheet is made of graphite material and coated with a lithium titanate coating with a thickness of 5 ⁇ m.
  • the particle size D50 of the lithium titanate coating is 0.5 ⁇ m and the purity is 99.94%.
  • the positive electrode sheet is made of lithium iron phosphate material, and the separator 10 is selected and matched with the electrolyte to make a 50Ah square aluminum shell battery. After the battery is divided into components, the battery is charged with a constant current of 50A to 3.2V and then switched to a constant voltage charge until the charging current drops to Stop charging at 2A and leave it aside for 1 hour. Then continue charging at a constant current of 50A until charging stops at 5V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the negative electrode sheet is made of graphite material and coated with a silica ceramic coating with a thickness of 5 ⁇ m.
  • the particle size D50 of the silica ceramic coating is 0.5 ⁇ m and the purity is 99.94%.
  • the positive electrode sheet is made of lithium iron phosphate material, and the separator 10 is selected and matched with the electrolyte to make a 50Ah square aluminum shell battery. After the battery is divided into components, the battery is charged with a constant current of 50A to 3.2V and then switched to a constant voltage charge until the charging current drops to Stop charging at 2A and leave it aside for 1 hour. Then continue charging at a constant current of 50A until charging stops at 5V, observe the battery for 1 hour, and monitor the voltage changes of the battery during the test.
  • the battery of this implementation was tested according to the continuous overcharge test conditions, and the test voltage did not reach the set voltage parameters. Therefore, during the battery overcharge process, the surface of the negative electrode sheet or the orientation of the separator was The overcharge protective layer on the side of the negative electrode sheet can be reduced before the electrons from the lithium ions (that is, the overcharge protective layer and the lithium ions undergo a reduction reaction). In this way, the voltage difference inside the battery can be reduced to avoid precipitation on the surface of the negative electrode sheet. Safety issues such as short circuit or thermal runaway caused by lithium can also be avoided to aggravate the oxidation reaction on the surface of the positive electrode, avoid superposition and accumulation of heat inside the battery, and make the internal temperature of the battery ⁇ 120°C. Therefore, the battery of this embodiment has better thermal safety performance and overcharge performance, which can effectively alleviate the hazards of thermal runaway of batteries caused by overcharge, reduce the risk of battery overcharge failure to a large extent, and improve the safety performance of lithium-ion batteries.
  • Embodiments of the present application provide a lithium ion battery.
  • the lithium-ion battery includes a casing, the above-mentioned lithium-ion battery core located in the casing, and an electrolyte filled in the casing.
  • the above-mentioned lithium-ion battery has all the advantages of the above-mentioned lithium-ion battery cell, which will not be described again here.
  • the overcharge protection layer when the battery is overcharged, since the oxidizing property of the overcharge protection layer is stronger than the oxidizing property of lithium ions, the overcharge protection layer will undergo a reduction reaction before the lithium ions at the negative electrode sheet, that is, the overcharge protection layer will obtain electrons before the lithium ions at the negative electrode sheet.
  • the lithium ions at the negative electrode sheet can be prevented from being reduced to a certain extent, so as to protect the negative electrode sheet to a certain extent during overcharging, so as to avoid safety problems such as short circuit or thermal runaway caused by lithium precipitation on the surface of the negative electrode sheet.
  • the lithium ion battery cell of this embodiment has good battery thermal safety performance and overcharge performance, thereby effectively alleviating the thermal runaway hazard that may be caused by overcharging of the battery, greatly reducing the risk of battery overcharge failure, and improving the safety performance of lithium ion batteries.

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Abstract

一种锂离子电芯及锂离子电池。锂离子电芯包括电芯单元，电芯单元包括：正极片；负极片；隔膜，位于负极片和正极片之间，以隔开正极片和负极片；过充保护层，能够传导电子和离子，过充保护层位于负极片和隔膜之间，隔膜或负极片的至少一侧上设有过充保护层，过充保护层的氧化性强于锂离子的氧化性。该锂离子电芯具有较好的电池热安全性能和过充性能。

Description

锂离子电芯及锂离子电池
本申请要求于2022年9月23日提交至中国国家知识产权局、申请号为202222529625.X、发明名称为“锂离子电芯及锂离子电池”的专利申请的优先权。
技术领域
本申请涉及锂离子电池技术领域，具体而言，涉及一种锂离子电芯及锂离子电池。
背景技术
近些年随着锂离子动力电池的广泛应用，一些电动汽车爆燃和锂电工厂的起火事件也时有发生，每次都将锂离子电池的安全性问题推到了风口浪尖。除了使用状况方面的外部因素，锂离子动力电池的安全性主要取决于电化学体系以及电极/电芯的结构、设计和生产工艺等内在因素，电池所采用的电化学体系则是决定电池安全性的最根本因素。锂离子电池的不安全行为(过充过放、快速充放电、短路、机械滥用条件和高温热箱、重物冲击)容易触发电池内部的危险性副反应而产生热量，直接破坏负极和正极表面的钝化膜，有可能导致电池温度升高进而引发电池热失控。
其中，因电池组中各单体电池在使用中电流、电压、温度等运行工况可能存在不一致现象，较易发生单一电池过充行为，锂离子电池过充将会导致多方面的严重后果，比如正极材料的晶体结构受到破坏而恶化循环寿命、加剧电解液在正极表面的氧化而引发电池热失控、以及负极析锂而引发短路或热失控等安全性问题，这样，不带夹板或安全阀不能正常开启的电池增加了爆炸风险。
发明内容
本申请的主要目的在于提供一种锂离子电芯及锂离子电池，上述锂离子电芯具有较好电池热安全性能和过充性能。
为了实现上述目的，本申请提供了一种锂离子电芯，包括电芯单元，电芯单元包括：正极片；负极片；隔膜，位于负极片和正极片之间，以隔开正极片和负极片；过充保护层，能够传导电子和离子，过充保护层位于负极片和隔膜之间，隔膜或负极片的至少一侧上设有过充保护层，过充保护层的氧化性强于锂离子的氧化性。
进一步地，过充保护层的材料为含四价钛化合物。
进一步地，含四价钛化合物为颗粒状材料，含四价钛化合物的D50粒径在0.2μm至1μm之间。
进一步地，含四价钛化合物为磷酸钛铝锂、锂镧钛氧、钛酸锂、二氧化钛中的任一种化合物。
进一步地，负极片包括负极集流体、位于负极集流体的相对两侧的负极活性物质层，负极活性物质层的背离负极集流体的一侧设有过充保护层。
进一步地，过充保护层的厚度与隔膜的厚度之间的比值大于或等于0.1，且小于或等于0.6。
进一步地，过充保护层的厚度与负极片的厚度之间的比值大于或等于0.005，且小于或等于0.05。
进一步地，过充保护层的厚度大于或等于1μm，且小于或等于4μm。
进一步地，锂离子电芯由一个或多个电芯单元卷绕而成；或者，锂离子电芯包括一个或多个依次叠置的电芯单元。
根据本申请的另一方面，本申请提供了一种锂离子电池，锂离子电池包括壳体、位于壳体内的上述的锂离子电芯和填充于壳体内的电解液。
应用本申请的技术方案，电池在有过充行为时，由于过充保护层的氧化性强于锂离子的氧化性，过充保护层会先于负极片处的锂离子发生还原反应，即过充保护层会先于负极片处的锂离子得电子，这样，可以在一定程度避免负极片处的锂离子被还原，以在过充时对负极片进行一定程度的保护，以避免因负极片表面析锂而引发短路或者热失控等安全性问题，这样，电池的电压状态不会持续上升，可以避免进一步引发正极片材料的晶体结构受到破坏的问题，从而避免加剧电解液在正极片表面的氧化的问题，因此，本实施例的锂离子电芯具有较好的电池热安全性能和过充性能，从而可以有效缓解电池可能因过充导致的热失控危害，在较大程度上降低了电池过充失效风险，提高了锂离子电池的安全性能。
附图说明
构成本申请的一部分的说明书附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1示出了本申请的实施例的锂离子电芯的过充保护层涂覆在隔膜上的结构示意图；
图2示出了本申请的实施例的锂离子电芯的过充保护层涂覆在负极片上的结构示意图；
图3示出了本申请的锂离子电芯的一个实施例的结构示意图；
图4示出了本申请的锂离子电芯的另一个实施例的结构示意图；以及
图5示出了本申请的实施例1和对比例1的电池持续过充测试电压曲线图。
其中，上述附图包括以下附图标记：
10、隔膜；40、过充保护层；50、负极活性物质层；60、负极集流体；100、正极片；300、负极片；400、正极耳；500、负极耳。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本申请。
需要说明的是，本申请的实施例中，电池充电时，锂离子从正极脱出，经电解质后，在负极处得电子发生还原并嵌入负极。
需要说明的是，本申请的实施例中，防止过充对锂离子电池的安全使用极其重要，控制充电电压是锂离子电池常用的防过充保护措施，锂离子电池充电电压变化主要来自正极材料在接近完全脱锂态时引起，但是，此时一般很难检测负极充电过程的完成程度(因为其嵌锂电位非常接近金属锂)，因此，如图1和图2所示，本申请的实施例提供了一种锂离子电芯。锂离子电芯包括电芯单元，电芯单元包括正极片100、负极片300、隔膜10和能够传导电子和离子的过充保护层40。隔膜10位于负极片300和正极片100之间，以隔开正极片100和负极片300；过充保护层40，位于负极片300和隔膜10之间，隔膜10或负极片300的至少一侧上设有过充保护层40，过充保护层40的氧化性强于锂离子的氧化性。
上述技术方案中，电池在有过充行为时，由于过充保护层40的氧化性强于锂离子的氧化性，过充保护层40会先于负极片300处的锂离子发生还原反应，即过充保护层40会先于负极片300处的锂离子得电子，这样，可以在一定程度避免负极片300处的锂离子被还原，以在过充时对负极片300进行一定程度的保护，以避免因负极片300表面析锂而引发短路或者热失控等安全性问题，这样，电池的电压状态不会持续上升，可以避免进一步引发正极片100材料的晶体结构受到破坏的问题，从而避免加剧电解液在正极片100表面的氧化，因此，本实施例的锂离子电芯具有较好的电池热安全性能和过充性能，从而可以有效缓解电池可能因过充导致的热失控危害，在较大程度上降低了电池过充失效风险，提高了锂离子电池的安全性能。
需要说明的是，本申请的实施例中，过充保护层40能够传导电子和离子，这样，过充保护层40不影响电池的正常充放电，但可以对负极片300进行保护。
具体地，本申请的实施例中，由于过充保护层40会先于负极片300处的锂离子得电子，从而可以降低在电池中形成锂枝晶的概率。
优选地，本申请的实施例中，过充保护层40涂覆于负极片300的表面或者隔膜10的朝向负极片300的一侧。
具体地，本申请的实施例中，过充保护层40的材料为含四价钛化合物。这样，可以使过充保护层40的氧化性强于锂离子的氧化性，从而使过充保护层40优先于锂离子被还原。
优选地，本申请的实施例中，含四价钛化合物为磷酸钛铝锂、锂镧钛氧、钛酸锂、二氧化钛中的任一种化合物。上述材料不仅氧化性强于锂离子的氧化性，且上述材料的热稳定性较好，这样，可以有效缓解电池可能因过充导致的热失控。
上述四价态化合物为常见且易得到的化合物，这样可以降低锂离子电芯的生产成本。
需要说明的，本申请的实施例中，过充保护层40的材料一般为在低电位下(＜2V)能够和锂离子发生变价反应的热稳定性比较好的材料。
如图2所示，本申请的实施例中，负极片300包括负极集流体60、位于负极集流体60的相对两侧的负极活性物质层50，负极活性物质层50的背离负极集流体60的一侧设有过充保护层40。通过上述设置，过充保护层40可以有效地对负极活性物质层50进行保护。
具体地，本申请的实施例中，过充保护层40的厚度与隔膜10的厚度之间的比值大于或等于0.1，且小于或等于0.6。由于过充保护层40的厚度越大，其热稳定越好，通过上述设置，在不影响电池正常充放电的情况下，可以使过充保护层40具有较好的热稳定性，从而有效地提高电池热安全性能。
具体地，本申请的实施例中，过充保护层40的厚度与负极片300的厚度之间的比值大于或等于0.005，且小于或等于0.05。由于过充保护层40的厚度越大，其热稳定越好，通过上述设置，在不影响电池正常充放电的情况下，可以使过充保护层40具有较好的热稳定性，从而有效地提高电池热安全性能。
优选地，本申请的实施例中，过充保护层40的厚度大于或等于1μm，且小于或等于4μm。上述厚度，可以使过充保护层40具有较好的热稳定性，从而有效地提高电池热安全性能。
优选地，本申请的实施例中，含四价钛化合物为颗粒状材料，含四价钛化合物的D50粒径在0.2μm至1μm之间。这样可以增加过充保护层40的热稳定性，从而有效地提高电池热安全性能。
如图3所示，本申请的实施例中，锂离子电芯由一个或多个电芯单元卷绕而成；或者，如图4所示，本申请的实施例中，锂离子电芯包括一个或多个依次叠置的电芯单元。这样，可以使锂离子电芯既适用于圆柱电池，又适用于方形电池。
如图4所示，本申请的实施例中，电芯单元还包括与正极片100连接的正极耳400，以及与负极片300连接的负极耳500。
实施例1
隔膜10选用12μm厚的PE基膜(聚乙烯膜)，在隔膜10的朝向负极片300的所在侧涂覆3μm厚度的磷酸钛铝锂涂层，其中，磷酸钛铝锂涂层的粒径D50为0.7μm，纯度为99.95％。正极片选用622型三元正极材料，负极片选用石墨材料，匹配电解液后试制成10Ah的软包电池，化成分容后的电池使用20A电流恒流充电至3.6V后转恒压充电，直至充电电流降至1A时停止充电并搁置1h。然后继续以20A电流恒流充电直至20V停止充电，观察电池1h，测试过程中监控电池的电压变化。
对比例1
隔膜10选用12μm厚的PE基膜(聚乙烯膜)，在隔膜10的朝向负极片300的所在侧涂覆3μm厚度的氧化铝陶瓷涂层，其中，氧化铝陶瓷涂层的粒径D50为0.7μm，纯度为99.95％。正极片选用622型三元正极材料，负极片选用石墨材料，匹配电解液试制成10Ah的软包电池，化成分容后的电池使用20A电流恒流充电至3.6V后转恒压充电，至充电电流降至1A时停止充电并搁置1h。然后继续以20A电流恒流充电直至20V停止充电，观察电池1h，测试过程中监控电池的电压变化。
实施例2
隔膜10选用9μm厚的PE基膜(聚乙烯膜)，在隔膜10的朝向负极片300的所在侧涂覆4μm厚度的锂镧钛氧涂层，其中，锂镧钛氧涂层的粒径D50为0.4μm，纯度为99.92％。正极片100选用磷酸铁锂材料，负极片选用石墨材料，匹配电解液试制成10Ah圆柱电池，化成分容后的电池使用5A电流恒流充电至3.2V后转恒压充电，至充电电流降至0.1A时停止充电并搁置1h。然后继续以2A电流恒流充电直至5V停止充电，观察电池1h，测试过程中监控电池的电压变化。
对比例2
隔膜10选用9μm厚的PE基膜(聚乙烯膜)，在隔膜10的朝向负极片300的所在侧涂覆4μm厚度的勃姆石陶瓷涂层，勃姆石陶瓷涂层的粒径D50为0.4μm，纯度为99.92％。正极片选用磷酸铁锂材料，负极片选用石墨材料，匹配电解液试制成10Ah圆柱电池，化成分容后的电池使用5A电流恒流充电至3.2V后转恒压充电，至充电电流降至0.1A时停止充电并搁置1h。然后继续以2A电流恒流充电直至5V停止充电，观察电池1h，测试过程中监控电池的电压变化。
实施例3
负极片选用石墨材料并涂覆2μm厚度的二氧化钛涂层，其中二氧化钛涂层的粒径D50为0.8μm，纯度为99.90％。正极片选用622三元正极材料，选用隔膜10并匹配电解液试制成20Ah软包电池，化成分容后的电池使用10A电流恒流充电至3.6V后转恒压充电，至充电电流降至0.05A时停止充电并搁置1h。然后继续以10A电流恒流充电直至10V停止充电，观察电池1h，测试过程中监控电池的电压变化。
对比例3
负极片选用石墨材料并涂覆2μm厚度的氧化铝陶瓷涂层，氧化铝陶瓷涂层的粒径D50为0.8μm，纯度为99.90％。正极片选用622三元正极材料，选用隔膜10并匹配电解液试制成20Ah软包电池，化成分容后的电池使用10A电流恒流充电至3.6V后转恒压充电，至充电电流降至0.05A时停止充电并搁置1h。然后继续以10A电流恒流充电直至10V停止充电，观察电池1h，测试过程中监控电池的电压变化。
实施例4
负极片选用石墨材料并涂覆5μm厚度的钛酸锂涂层，钛酸锂涂层的粒径D50为0.5μm，纯度为99.94％。正极片选用磷酸铁锂材料，选用隔膜10并匹配电解液试制成50Ah方形铝壳电池，化成分容后的电池使用50A电流恒流充电至3.2V后转恒压充电，至充电电流降至2A时停止充电后搁置1h。然后继续以50A电流恒流充电直至5V停止充电，观察电池1h，测试过程中监控电池的电压变化。
对比例4
负极片选用石墨材料并涂覆5μm厚度的二氧化硅陶瓷涂层，二氧化硅陶瓷涂层的粒径D50为0.5μm，纯度为99.94％。正极片选用磷酸铁锂材料，选用隔膜10并匹配电解液试制成50Ah方形铝壳电池，化成分容后的电池使用50A电流恒流充电至3.2V后转恒压充电，至充电电流降至2A时停止充电后搁置1h。然后继续以50A电流恒流充电直至5V停止充电，观察电池1h，测试过程中监控电池的电压变化。
实施例1至4和对比例1至4的电池持续过充测试数据见表1。
表1电池持续过充测试结果
由表1和图5可知，对比例的电池按照测试条件持续过充，电池内部正极材料的晶体结构可能会受到破坏，且电解液在正极表面的氧化反应会加剧，在负极面也可能会产生析锂形成锂枝晶，负极表面形成的固态电解质膜也会发生持续反应，而上述反应导致电池内部热量叠加积聚，使电池温度＞350℃，从而进一步引发电池发生热失控。
相对于对比例而言，本实施的电池按照持续过充测试条件进行测试，测试电压均未达到设置的电压参数，因此，在电池过充过程中，涂覆在负极片的表面或者隔膜的朝向负极片的所在侧的过充保护层可以先于锂离子得电子被还原(即过充保护层和锂离子发生还原反应)，这样，可以减少电池内部的电压差，以避免因负极片表面析锂而引发短路或者热失控等安全性问题，也可以避免加剧正极表面的氧化反应，避免电池内部热量叠加积聚，使电池内部温度均＜120℃，因此，本实施例的电池具有较好热安全性能和过充性能，可有效缓解电池因过充导致的热失控危害，在较大程度上降低了电池过充失效风险，提高了锂离子电池的安全性能。
本申请的实施例提供了一种锂离子电池。锂离子电池包括壳体、位于壳体内的上述的锂离子电芯和填充于壳体内的电解液。上述锂离子电池具有上述锂离子电芯的全部优点，此处不再赘述。
从以上的描述中，可以看出，本申请上述的实施例实现了如下技术效果：电池在有过充行为时，由于过充保护层的氧化性强于锂离子的氧化性，过充保护层会先于负极片处的锂离子发生还原反应，即过充保护层会先于负极片处的锂离子得电子，这样，可以在一定程度避免负极片处的锂离子被还原，以在过充时对负极片进行一定程度的保护，以避免因负极片表面析锂而引发短路或者热失控等安全性问题，这样，电池的电压状态不会持续上升，可以避免进一步引发正极片材料的晶体结构受到破坏的问题，从而避免加剧电解液在正极片表面的氧化，因此，本实施例的锂离子电芯具有较好的电池热安全性能和过充性能，从而可以有效缓解电池可能因过充导致的热失控危害，在较大程度上降低了电池过充失效风险，提高了锂离子电池的安全性能。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种锂离子电芯，其特征在于，包括电芯单元，所述电芯单元包括：
    正极片(100)；
    负极片(300)；
    隔膜(10)，位于所述负极片(300)和所述正极片(100)之间，以隔开所述正极片(100)和所述负极片(300)；
    过充保护层(40)，能够传导电子和离子，所述过充保护层(40)位于所述负极片(300)和所述隔膜(10)之间，所述隔膜(10)或所述负极片(300)的至少一侧上设有所述过充保护层(40)，所述过充保护层(40)的氧化性强于锂离子的氧化性。
  2. 根据权利要求1所述的锂离子电芯，其特征在于，所述过充保护层(40)的材料为含四价钛化合物。
  3. 根据权利要求2所述的锂离子电芯，其特征在于，所述含四价钛化合物为颗粒状材料，所述含四价钛化合物的D50粒径在0.2μm至1μm之间。
  4. 根据权利要求2所述的锂离子电芯，其特征在于，所述含四价钛化合物为磷酸钛铝锂、锂镧钛氧、钛酸锂、二氧化钛中的任一种化合物。
  5. 根据权利要求1至4中任一项所述的锂离子电芯，其特征在于，所述负极片(300)包括负极集流体(60)、位于所述负极集流体(60)的相对两侧的负极活性物质层(50)，所述负极活性物质层(50)的背离所述负极集流体(60)的一侧设有所述过充保护层(40)。
  6. 根据权利要求1至4中任一项所述的锂离子电芯，其特征在于，所述过充保护层(40)的厚度与所述隔膜(10)的厚度之间的比值大于或等于0.1，且小于或等于0.6。
  7. 根据权利要求1至4中任一项所述的锂离子电芯，其特征在于，所述过充保护层(40)的厚度与所述负极片(300)的厚度之间的比值大于或等于0.005，且小于或等于0.05。
  8. 根据权利要求1至4中任一项所述的锂离子电芯，其特征在于，所述过充保护层(40)的厚度大于或等于1μm，且小于或等于4μm。
  9. 根据权利要求1至4中任一项所述的锂离子电芯，其特征在于，所述锂离子电芯由一个或多个所述电芯单元卷绕而成；或者，所述锂离子电芯包括一个或多个依次叠置的所述电芯单元。
  10. 一种锂离子电池，其特征在于，锂离子电池包括壳体、位于所述壳体内的权利要求1至9中任一项所述的锂离子电芯和填充于所述壳体内的电解液。
PCT/CN2023/109632 2022-09-23 2023-07-27 锂离子电芯及锂离子电池 WO2024060827A1 (zh)

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