WO2023050770A1 - 一种预锂电池预锂量和预锂容量的测定方法 - Google Patents

一种预锂电池预锂量和预锂容量的测定方法 Download PDF

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WO2023050770A1
WO2023050770A1 PCT/CN2022/086567 CN2022086567W WO2023050770A1 WO 2023050770 A1 WO2023050770 A1 WO 2023050770A1 CN 2022086567 W CN2022086567 W CN 2022086567W WO 2023050770 A1 WO2023050770 A1 WO 2023050770A1
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lithium
battery
lithium battery
lithiation
negative electrode
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French (fr)
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刘浩
朱朋辉
娄帅宾
刘静
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蜂巢能源科技股份有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • the present application relates to the technical field of lithium-ion batteries, in particular to a method for measuring the pre-lithium content and pre-lithium capacity of pre-lithium batteries.
  • lithium-ion batteries have the advantages of high specific energy, long cycle life, energy saving, environmental protection, and economical applicability.
  • secondary lithium-ion batteries have high open-circuit voltage, Due to the advantages of high energy density, long life, no pollution and small self-discharge, it is considered to be the most ideal energy storage and conversion device.
  • lithium supplementation is usually carried out by pre-lithiation treatment on the negative electrode or the positive electrode to compensate for the decline in the first graphite effect and the loss of active lithium in the early stage of the battery cycle, and effectively improve the cycle life of the battery.
  • the processed batteries are called pre-lithium batteries.
  • the methods of pre-lithiation treatment mainly include lithium foil supplementation, lithium powder supplementation or positive lithium enrichment method.
  • the amount of pre-lithium is an important indicator for evaluating the service life of pre-lithium batteries.
  • the pre-lithium amount is generally calculated based on the mass of added lithium (or lithium compound) and the theoretical gram capacity of lithium (or lithium compound).
  • the gram capacity of the positive electrode gradually increases. If it increases further, the actual pre-lithium amount cannot be judged by the increase in battery capacity.
  • the technical problem to be solved in this application is to overcome the defect in the prior art that lithium batteries cannot be accurately measured, especially the actual high lithium content of lithium batteries with high lithium storage capacity, thereby providing a method for measuring the actual lithium storage capacity of lithium batteries. test methods.
  • the application provides a method for testing the amount of pre-lithium in a pre-lithium battery, comprising the steps of:
  • Sample preparation steps prepare the pre-lithium battery and the non-pre-lithium battery to be tested;
  • Test steps Disassemble the fully charged pre-lithium battery and non-pre-lithium battery under the protection of inert gas to obtain their respective negative electrodes, and perform XRD diffraction test on the negative electrodes of the pre-test lithium battery and non-pre-lithium battery , obtain the peak area of both LiC 12 peak and LiC 6 peak respectively;
  • Calculate the pre-lithium amount step calculate the pre-lithium amount according to the following formula
  • Pre-lithium amount ⁇ [a/(a+b)+1/2 ⁇ b(a+b)]/[c/(c+d)+1/2 ⁇ d(c+d)]-1 ⁇ 100%, wherein, a is the peak area of the LiC peak of the lithium battery to be measured, b is the peak area of the LiC peak of the lithium battery to be measured, c is the peak area of the LiC peak of the unpredicted lithium battery, and b is the peak area of the LiC peak of the unpredicted lithium battery. Peak area of LiC 12 peak for lithium battery.
  • the charging rate is controlled to 0.005-0.3C, and the charge-discharge cycle is 1-10 times.
  • the charge rate is 0.05C, and the charge-discharge cycle is 3-5 times. Charge to 3.8V.
  • the application provides a method for testing the absolute lithium content of a pre-lithium battery, including the method for measuring the relative lithium content of a pre-lithium battery, and also includes a nominal capacity test step: testing the nominal capacity C of the unprepared lithium battery b .
  • the design of the positive and negative electrodes of the pre-lithium battery to be tested is the same as that of the non-pre-lithium battery, the difference is only that the positive and/or negative electrodes of the pre-lithium battery to be tested have been pre-lithiated, while the positive and negative electrodes of the non-pre-lithium battery are Neither were prelithiated.
  • the pre-lithium battery to be tested can be preconditioned using existing conventional processes, including but not limited to at least one of the following (1)-(3):
  • Lithium powder is bonded to the surface of the negative electrode to supplement the negative electrode with lithium.
  • the lithium powder is bonded to the surface of the negative electrode by spray coating or gravure coating;
  • Lithium foil is bonded to the surface of the negative electrode to supplement lithium to the negative electrode.
  • the lithium foil is bonded to the surface of the negative electrode by rolling;
  • the positive electrode lithium supplement agent is selected from one or more of Li 2 NiO 2 , Li 3 N, and Li 5 FeO 4 .
  • the lithium foil can be pressed onto the surface of the negative electrode by conventional rolling, and the pressure should not exceed 50kg/cm 2 , such as the method disclosed in the patent document CN106128791A; Apply to the surface of the negative electrode, for example, using the method disclosed in patent document CN104993098; you can also use a positive electrode lithium replenishing agent to supplement lithium on the positive electrode, for example, using the method disclosed in patent document CN111834622A.
  • pre-lithium content also known as relative pre-lithium content and actual pre-lithium content
  • pre-lithium capacity refers to the battery capacity of the lithium-ion battery after the pre-treatment compared to the value of the battery capacity of the lithium-ion battery before the pre-treatment (in Ah).
  • 1-5 charge and discharge cycles are performed at a temperature of 15-45° C. and a charge rate of 0.05-0.5 C to measure the nominal capacity.
  • the measuring temperature is 20-30° C.
  • the charging rate is 0.1-0.33 C
  • 1-2 charge-discharge cycles are performed to measure the nominal capacity.
  • a step of washing the negative electrode sheet with a solvent is also included.
  • the solvent is at least one selected from dimethyl carbonate, diethyl carbonate, and dipropyl carbonate.
  • the theoretical pre-lithium content of the pre-lithium battery is not more than 80%, and may be 5%-20%.
  • the positive electrode of the lithium battery to be tested includes a current collector and a positive active material combined on the current collector, and the positive active material is selected from lithium iron phosphate, lithium manganese iron phosphate, nickel At least one of lithium manganese oxide material, lithium nickel oxide material, lithium cobalt oxide material, lithium nickel cobalt oxide material, and lithium nickel manganese cobalt oxide material.
  • the combined process can adopt the existing coating and cold pressing process.
  • the positive electrode active material, conductive agent, and binder are mixed uniformly according to the conventional ratio and added to the solvent to make a positive electrode slurry; the positive electrode slurry is evenly coated on the aluminum foil of the positive electrode current collector, and cold pressed after drying , and then carry out die-cutting and slitting to make positive electrode sheets.
  • the solid content of the positive electrode slurry can be 70-75%
  • the conductive agent can be a conventional conductive agent, such as acetylene black
  • the binder can be a conventional binder, such as styrene-butadiene rubber or vinylidene fluoride PVDF
  • the solvent can be Conventional organic solvents such as N-methylpyrrolidone NMP.
  • the negative electrode of the lithium battery to be tested includes a current collector and a negative electrode active material combined on the current collector, and the negative electrode active material is selected from graphite, hard carbon, soft carbon, mesophase At least one of carbon microspheres.
  • the combined process can adopt the existing coating and cold pressing process. Specifically, the negative electrode active material, conductive agent, thickener, and binder are mixed according to the conventional ratio, added to solvent water and mixed evenly to make a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, After drying, it is cold-pressed to make a negative electrode sheet.
  • the conductive agent can be a conventional conductive agent, such as acetylene black
  • the binder can be a conventional binder, such as styrene-butadiene rubber or vinylidene fluoride PVDF
  • a thickener Conventional thickeners, such as sodium hydroxymethylcellulose, may be used.
  • the electrode solution of the present application can adopt conventional commercially available lithium ion electrolyte, also can adopt existing conventional material self-made, for example can adopt the electrolyte solution that comprises solvent, lithium salt and additive, and described solvent is selected from ethylene carbonate, biscarbonate At least one of methyl ester and ethyl methyl carbonate.
  • the lithium salt is selected from lithium hexafluorophosphate and/or lithium tetrafluoroborate; the additive is selected from at least one of vinylene carbonate, propylene carbonate, vinyl sulfate and lithium difluorophosphate.
  • the molar concentration of lithium salt is 0.8-1.2mol/L, and ethylene carbonate (EC), dimethyl carbonate (DEC), ethyl methyl carbonate ( EMC) mixed solution is solvent.
  • the volume percentage of additives can be 0.5-5%.
  • This application can use the existing traditional diaphragm, such as PE diaphragm, PP diaphragm, PP/PE composite film, or other commercially available diaphragms.
  • the method for measuring the pre-lithium content of the pre-lithium battery includes sample preparation steps, charging steps, testing steps and steps for calculating the pre-lithium content. First, the pre-lithium battery and the non-pre-lithium battery are fully charged, and then the The negative electrode sheet in the fully charged state is tested by X-powder diffraction method, and the test results are processed to obtain the peak areas of LiC 12 peak and LiC 6 peak. After calculation, the pre-lithium amount is obtained.
  • the lithium intercalation mode of the graphite material is intercalation lithium intercalation mode, the transformation of C ⁇ LiC 24 ⁇ LiC 12 ⁇ LiC 6 occurs during charging; since N/P is generally greater than 1, LiC 12 and LiC 6 coexist in a fully charged state; in the case of other identical designs, Compared with the non-pre-lithium battery, the lithium intercalation depth of graphite in the fully charged state after pre-lithium increases, that is, the amount of LiC 12 transformed into LiC 6 increases, and the LiC 12 peak and LiC 6 peak of the pre-lithium battery and the non-pre-lithium battery are compared.
  • the actual pre-lithium amount can be calculated by substituting the peak area into the following formula: ⁇ [a/(a+b)+1/2 ⁇ b(a+b)]/[c/(c+d)+1/ 2 ⁇ d(c+d)]-1 ⁇ 100%, the method is simple and fast, and the accuracy is obviously improved compared with the conventional volumetric evaporation method.
  • the method for measuring the pre-lithium content of the pre-lithium battery provided by this application is to control the charging rate to 0.005-0.3C during the full charge process of the pre-lithium battery to be tested and the non-pre-lithium battery, and charge and discharge cycles 1-10 times.
  • the charging rate is 0.05C
  • the charging and discharging cycle is 3-5 times, which can not only fully charge the pre-battery and unpre-battery to be tested, but also reduce the consumption of lithium during the charging process, and further improve the accuracy of the test results Spend.
  • the method for measuring the pre-lithium capacity of the pre-lithium battery provided by this application is simple, quick and accurate.
  • the test temperature is controlled at 15-45°C, and the cycle rate is 0.05-0.5C.
  • the number of charging cycles is 1-5 times, and the number of discharging cycles is 1-5 times, especially when the measurement temperature is 20-30°C and the cycle rate is 0.1-0.33C, the number of charging cycles is 1-2 times, and the number of discharging cycles is 1 -2 times, the battery can be fully activated to further improve the accuracy of the test results.
  • Figure 1 is a schematic diagram of the structural changes in the graphite deintercalation lithium process
  • Fig. 2 is the XRD diagram of the pre-lithium battery (pre-lithium group) and the non-pre-lithium battery (control group) with a theoretical pre-lithium content of 15%.
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, comprising the steps of:
  • S1 sample preparation steps prepare the pre-lithium battery to be tested and the non-pre-lithium battery; the preparation of the pre-lithium battery includes the following steps: (1) preparation of the positive electrode sheet: take the positive electrode active material (lithium iron phosphate), conductive agent acetylene black, viscose The binder polyvinylidene fluoride PVDF was mixed uniformly according to the mass ratio of 96.5:2.5:1 to obtain the mixture, which was added to the solvent N-methyl-2-pyrrolidone (NMP) to prepare the positive electrode slurry (solid content: 70%). The positive electrode slurry is evenly coated on the aluminum foil of the positive electrode current collector according to the surface density of 36mg/ cm2 . The thickness of the aluminum foil is 10 ⁇ m. After drying at 85°C, it is cold-pressed, and then die-cut and slit to make a lithium-ion battery. Positive sheet.
  • NMP solvent N-methyl-2-pyrrolidone
  • Negative electrode pre-lithiation treatment 3 ⁇ m lithium foil was rolled on the surface of the negative electrode sheet, and the theoretical pre-lithium amount was 15%.
  • the preparation method of the non-pre-lithium battery is basically the same as that of the pre-lithium battery, the only difference is that the negative electrode is not pre-lithiated.
  • S2 Charging step Charge the pre-battery and the non-pre-battery to 3.8V at a temperature of 25°C and a cycle rate of 0.1C to fully charge the battery. Disassemble under protection to obtain their respective negative electrodes, and carry out XRD diffraction test on the negative electrodes of the pre-lithium battery and the non-pre-lithium battery, and obtain the peak areas of the LiC 12 peak and LiC 6 peak of the two respectively.
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, comprising the steps of:
  • Sample preparation steps prepare the pre-lithium battery to be tested and the non-pre-lithium battery; the preparation of the pre-lithium battery is basically the same as in Example 1, the difference is only that a lithium foil with a thickness of 1.4 ⁇ m is used in the negative electrode pre-lithiation treatment step, Theoretical pre-lithium content is 7%.
  • (2) Charging step Charge the pre-battery and the non-pre-battery to 3.8V at a temperature of 25°C and a cycle rate of 0.1C to fully charge the battery. Disassembled under the protection of argon to obtain the respective negative electrode sheets, the negative electrode sheets of the pre-lithium battery and the non-pre-lithium battery to be tested were tested by XRD diffraction method, and the peak areas of the LiC 12 peak and LiC 6 peak were obtained respectively.
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is basically the same as in Example 1, except that the pre-treatment method is different.
  • the pre-lithium battery of this embodiment is pre-treated by the following method: lithium powder Disperse in DMC solvent to form a slurry with a solid content of 5wt% and spray it on the surface of the negative electrode sheet, based on the mass of lithium powder, the coating amount is 0.14mg/cm 2 , and the theoretical pre-lithium amount is controlled to be 15%.
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is basically the same as in Example 1, except that the positive active material and the negative active material are different.
  • the positive active material of this application uses NCM811 (ME8E) from Rongbai Technology.
  • the negative electrode active material adopts Shanghai Shanshan's mesophase carbon microspheres (ES2A).
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is basically the same as that in embodiment 1, except that the charging rate of full charge is 0.005C.
  • This embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is basically the same as in embodiment 1, except that the charging rate for full charge is 0.3C.

Abstract

一种预锂电池预锂量和预锂容量的测定方法，包括如下步骤：样品准备步骤：准备待测预锂电池和未预锂电池；充电步骤：将待测预锂电池和未预锂电池充满电；测试步骤：将充满电后的待测预锂电池和未预锂电池在惰性气体保护下拆解，得到各自的负极片，对待测预锂电池和未预锂电池的负极片进行XRD衍射法测试，分别得到两者的LiC 12峰与LiC 6峰的峰面积；计算预锂量步骤：照如下公式计算预锂量；预锂量＝{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，方法简单快捷，准确度较常规容量挥发法明显提高。

Description

一种预锂电池预锂量和预锂容量的测定方法
本申请要求在2021年09月30日提交中国专利局、申请号为202111165606.7、发明名称为“一种预锂电池预锂量和预锂容量的测定方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池技术领域，具体涉及一种预锂电池预锂量和预锂容量的测定方法。
背景技术
21世纪以来，全球经济飞速发展，汽车产业蒸蒸日上，随之而来的是交通堵塞、环境污染、化石能源匮乏等现实问题。电动汽车的出现，既可以降低人们对化石能源的依赖，又可以减小尾气对环境的污染。锂离子电池作为电动汽车的动力输出，具有高比能量、循环寿命长、节能环保、经济适用等优点，较燃料电池、太阳能电池、全固态电池而言，二次锂离子电池具有开路电压高、能量密度高、寿命长、无污染及自放电小等优点，被认为是最理想的能量储存和转换装置。
对于负极来说，在电池的首次充电过程中由于固体电解质膜(SEI膜)的形成而消耗部分活性锂，由此而造成正极材料锂的损失，从而降低了电池的容量，造成首次效率的降低。现有技术中通常采用对负极或者正极进行预锂化处理的方式进行补锂，以弥补石墨首效的下降和电池循环前期的活性锂损失，有效地提高电池的循环寿命，这种经过预理化处理的电池称 为预锂电池。预锂化处理的方法主要有锂箔补锂、锂粉补锂或者正极富锂法等。而预锂量是评估预锂电池使用寿命的重要指标。理论上，预锂量一般是根据添加的锂(或锂的化合物)的质量、锂(或锂的化合物)的理论克容量计算得到。但是实际应用中，随着补锂量的增加，正极的克容量发挥逐渐增加，但当补锂量达到一定程度，正极克容量发挥达到理论克容量时，补锂量继续增加，正极克容量不再增加，无法通过电池容量增加量来判断实际的预锂量。
因此，急需一种方法确定预锂电池，尤其是高预锂量时的实际预锂量。
发明内容
因此，本申请要解决的技术问题在于克服现有技术中的无法准确测定锂电池，尤其是高预锂量的锂电池实际高预锂量的缺陷，从而提供一种锂电池实际预锂量的测定方法。
本申请提供了一种预锂电池预锂量的测试方法，包括如下步骤：
样品准备步骤：准备待测预锂电池和未预锂电池；
充电步骤：将待测预锂电池和未预锂电池充满电；
测试步骤：将充满电后的待测预锂电池和未预锂电池在惰性气体保护下拆解，得到各自的负极片，对待测预锂电池和未预锂电池的负极片进行XRD衍射法测试，分别得到两者的LiC 12峰与LiC 6峰的峰面积；
计算预锂量步骤：照如下公式计算预锂量；
预锂量＝{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，其中，a为待测预锂电池LiC 6峰的峰面积，b为待测预锂电池LiC 12峰的峰面积，c为未预锂电池LiC 6峰的峰面积，b为未预锂电池LiC 12峰的峰面积。
可选地，充电过程中，控制充电倍率为0.005-0.3C，充放电循环1-10次，可选地，充电倍率为0.05C，充放电循环3-5次。充电至3.8V。
本申请提供了一种预锂电池绝对预锂量的测试方法，包括所述的预锂电池相对预锂量的测定方法，还包括标称容量测试步骤：测试未预锂电池的标称容量C b。
可选地，待测预锂电池与未预锂电池的正负极设计相同，区别仅在于待测预锂电池的正极和/或负极经过预锂化处理，而未预锂电池的正极和负极均未经过预锂化处理。
可选地，待测预锂电池可采用现有常规工艺进行预理化处理，包括但不局限于如下(1)-(3)中的至少一项：
(1)将锂粉结合到负极表面对负极进行补锂，可选地，采用喷涂或凹版涂布方式将锂粉结合到负极表面；
(2)将锂箔结合到负极表面对负极进行补锂，可选地，采用辊压方式将锂箔结合到负极表面；
(3)采用正极补锂剂对正极进行补锂，可选地，正极补锂剂选自Li 2NiO 2、Li 3N、Li 5FeO 4中的一种或者多种。
具体地，本申请中可采用常规辊压的方式将锂箔压合到负极表面，压力不超过50kg/cm 2，例如采用专利文献CN106128791A公开的方法；也可采用锂粉与粘结剂混合后涂覆到负极表面，例如采用专利文献CN104993098公开的方法；也可采用正极补锂剂对正极进行补锂，例如采用专利文献CN111834622A公开的方法。
本申请中，术语预锂量，也称为相对预锂量和实际预锂量，其是指的 是经过预理化处理后锂离子电池含锂量相比于预理化处理之前锂离子电池含锂量上升的质量百分数(单位：％)。术语预锂容量是指经过预理化处理后锂离子电池的电池容量相比于预理化处理之前锂离子电池电池容量的提升值(单位Ah)。
本申请还提供了一种预锂电池含锂量的测定方法，包括上述任一所述的预电池预锂量的测试方法，还包括标称容量测试步骤：测定未预锂电池的标称容量C b，并根据如下公式计算含锂量；含锂量＝预锂量×C b。
可选地，标称容量测定步骤中，在温度为15-45℃下，充电倍率为0.05-0.5C下进行1-5次充放电循环，测得标称容量。
可选地，标称容量测定步骤中，测定温度为20-30℃，充电倍率为0.1-0.33C下进行1-2次充放电循环，测得标称容量。
可选地，负极片进行XRD测试之前还包括采用溶剂对负极片进行冲洗的步骤。
在某些可选的实施方式中，所述溶剂选自碳酸二甲酯、碳酸二乙酯、碳酸二丙酯中的至少一种。
可选地，所述预锂电池的理论预锂量不大于80％，可选为5％-20％。
在某些可选的实施方式中，所述待测预锂电池的正极包括集流体和结合在集流体上的正极活性材料，所述正极活性材料选自磷酸铁锂、磷酸锰铁锂、镍锰酸锂材料、镍酸锂材料、钴酸锂材料、镍钴酸锂材料、镍锰钴酸锂材料中的至少一种。结合的工艺可以采用现有的涂布和冷压工艺。具体地，将正极活性物质、导电剂、粘结剂按照常规比例混合均匀并加入到溶剂中，制成正极浆料；将正极浆料均匀涂布在正极集流体铝箔上，烘干 后冷压，再进行模切、分条，制成正极片。其中该正极浆料的固含量可以为70-75％，导电剂可以为常规导电剂，例如乙炔黑，粘结剂可以为常规粘结剂，例如丁苯橡胶或偏氟乙烯PVDF，溶剂可采用常规有机溶剂，例如N-甲基吡咯烷酮NMP。
在某些可选的实施方式中，所述待测预锂电池的负极包括集流体和结合在集流体上的负极活性材料，所述负极活性材料选自石墨、硬碳、软碳、中间相碳微球中的至少一种。结合的工艺可以采用现有的涂布和冷压工艺。具体地，将负极活性物质、导电剂、增稠剂、粘结剂按照常规比例混合，加入溶剂水中混合均匀并制成负极浆料；将负极浆料均匀涂布在负极集流体铜箔上，烘干后进行冷压，制成负极片。其中该负极浆料的固含量可以为50-55％，导电剂可以为常规导电剂，例如乙炔黑，粘结剂可以为常规粘结剂，例如丁苯橡胶或者偏氟乙烯PVDF，增稠剂可采用常规增稠剂，例如羟甲基纤维素钠。
本申请的电极液可采用常规市售的锂离子电解液，也可采用现有常规材料自制，例如可采用包括溶剂、锂盐和添加剂的电解液，所述溶剂选自碳酸乙烯酯、碳酸二甲酯和碳酸甲乙酯中的至少一种。所述锂盐选自六氟磷酸锂和/或四氟硼酸锂；所述添加剂选自碳酸亚乙烯酯、碳酸丙烯酯、硫酸乙烯酯和二氟磷酸锂中的至少一种。锂盐的摩尔浓度为0.8-1.2mol/L，可采用体积比为1:1:1-1:2:2的碳酸乙烯酯(EC)、碳酸二甲酯(DEC)、碳酸甲乙酯(EMC)的混合液为溶剂。添加剂的体积百分数可以为0.5-5％。本申请的可采用现有的传统隔膜，例如PE隔膜、PP隔膜、PP/PE复合薄膜，或者其他市售隔膜。
本申请技术方案，具有如下优点：
1.本申请提供的预锂电池预锂量的测定方法，包括样品准备步骤、充电步骤、测试步骤和计算预锂量步骤，先将待测预锂电池和未预锂电池充满电，然后对满电状态的负极片进行X-粉末衍射法测定测试，对测试结果进行处理得到LiC 12峰和LiC 6峰的峰面积，经过计算得到预锂量，石墨材料的嵌锂模式为插层嵌锂模式，充电时发生C→LiC 24→LiC 12→LiC 6的转变；由于一般情况下N/P大于1，满电状态下为LiC 12和LiC 6共存状态；在其他设计完全相同的情况下，与未预锂电池相比，预锂后满电状态下石墨的嵌锂深度增加，即LiC 12转变为LiC 6的量增多，将预锂电池和未预锂电池的LiC 12峰和LiC 6峰的峰面积代入下述公式中即可计算出实际预锂量：{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，方法简单快捷，准确度较常规容量挥发法明显提高。
2.本申请提供的预锂电池预锂量的测定方法，通过待测预锂电池和未预锂电池在充满电过程中，控制充电倍率为0.005-0.3C，充放电循环1-10次，可选地，充电倍率为0.05C，充放电循环3-5次，不仅能够将待测预锂电池和未预锂电池充满电，而且能够降低充电过程对锂的消耗，进一步提高测试结果的准确度。
3.本申请提供的预锂电池预锂容量的测定方法，方法简单快捷、准确，通过控制标称容量测定步骤中，通过控制测试温度为15-45℃下，循环倍率为0.05-0.5C，充电循环次数为1-5次，放电循环次数为1-5次，尤其是测定温度为20-30℃，循环倍率为0.1-0.33C下充电循环次数为1-2次，放电循环次数为1-2次，能够将电池充分活化进一步提高测试结果的准确 度。
附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是石墨脱嵌锂过程结构变化示意图；
图2是理论预锂量为15％的预锂电池(预锂组)和未预锂电池(对照组)的XRD图。
具体实施方式
提供下述实施例是为了更好地进一步理解本申请，并不局限于所述最佳实施方式，不对本申请的内容和保护范围构成限制，任何人在本申请的启示下或是将本申请与其他现有技术的特征进行组合而得出的任何与本申请相同或相近似的产品，均落在本申请的保护范围之内。
实施例中未注明具体实验步骤或条件者，按照本领域内的文献所描述的常规实验步骤的操作或条件即可进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规试剂产品。
实施例1
本实施例提供了一种预锂电池预锂量的测定方法，包括如下步骤：
S1样品准备步骤：准备待测预锂电池和未预锂电池；预锂电池的制备 包括如下步骤：(1)正极片的制备：取正极活性材料(磷酸铁锂)、导电剂乙炔黑、粘结剂聚偏氟乙烯PVDF按照质量比96.5：2.5：1混合均匀，得到混合物，加入溶剂N-甲基-2-吡咯烷酮(NMP)中，制得正极浆料(固含量为70％)，将正极浆料按照36mg/cm 2的面密度均匀涂布在正极集流体铝箔上，铝箔的厚度为10μm，在85℃下烘干后冷压，再进行模切、分条，制成锂离子电池正极片。
(2)负极片的制备：取负极活性物质石墨、导电剂乙炔黑、增稠剂羟甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按质量比96：2：1：1混合，得到混合物，将混合物加入溶剂水中混合均匀并制成负极浆料(固含量为50％)；将负极浆料按照20mg/cm 2的面密度均匀涂布在负极集流体铜箔上，铜箔的厚度6μm，在85℃下烘干后进行冷压，制成待制作锂离子电池负极片。
(3)负极预锂化处理：将3μm锂箔辊压在负极片表面，理论预锂量为15％。
(4)电解液的制备：将六氟磷酸锂溶解于体积比为5:3:2的碳酸乙烯酯、碳酸二甲酯和碳酸甲乙酯的混合溶剂中，得到浓度为1.15mol/L的六氟磷酸锂溶液，加入碳酸亚乙烯酯1vt％，二氟磷酸锂0.5vt％，硫酸乙烯酯DTD 0.5vt％，得到锂离子电池电极液。
(5)将正极片、PE隔膜(购自恩捷公司，型号：SV12)、预锂化处理后的负极片按照层叠的方式组装得到电池极组，将电池极组放置于带有PE材质下塑胶的铝制包装壳(购自科达利公司，型号52148102) 中组装，真空干燥箱中干燥，注入电解液，封口，即得半成品电芯。
未预锂电池的制备方法与预锂电池的制备方法基本相同，区别仅在于负极未进行预锂化处理。
S2标称容量测试步骤：分别对待测预锂电池和未预锂电池进行标称容量，测试温度为30℃，循环倍率为0.33C，充放电循环(先充电至3.8V，再放电至2.0V，循环2次)，测定待测预锂电池的标称容量Ca为5.34Ah，未预锂电池的Cb为5.02Ah。
S2充电步骤：将待测预锂电池和未预锂电池分别在温度为25℃的条件下，循环倍率为0.1C下，充电至3.8V，使得电池充满电，将充满电后电池在氩气保护下拆解，得到各自的负极片，对待测预锂电池和未预锂电池的负极片进行XRD衍射法测试，分别得到两者的LiC 12峰与LiC 6峰的峰面积。XRD衍射法的测试条件如下：常温和真空下测试，采用铜靶，λ＝0.15406nm。见图2所示，左侧峰为LiC 6峰，右侧峰为LiC 12峰。
S4计算预锂量步骤：根据待测预锂电池和未预锂电池上述两个特征峰的峰面积或者峰间距按照如下式计算预锂量；预锂量＝{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，其中a为待测预锂电池LiC 6峰的峰面积，b为待测预锂电池LiC 12峰的峰面积，c为未预锂电池LiC 6峰的峰面积，b为未预锂电池LiC 12峰的峰面积。
实施例2
本实施例提供了一种预锂电池预锂量的测定方法，包括如下步骤：
(1)样品准备步骤：准备待测预锂电池和未预锂电池；预锂电池的制备基本与实施例1相同，区别仅在于负极预锂化处理步骤中采用厚度为 1.4μm的锂箔，理论预锂量为7％。
(2)充电步骤：将待测预锂电池和未预锂电池分别在温度为25℃的条件下，循环倍率为0.1C下，充电至3.8V，使得电池充满电，将充满电后电池在氩气保护下拆解，得到各自的负极片，对待测预锂电池和未预锂电池的负极片进行XRD衍射法测试，分别得到两者的LiC 12峰与LiC 6峰的峰面积。XRD衍射法的测试条件如下：常温和真空下测试，采用铜靶，λ＝0.15406nm。
(3)计算预锂量步骤：根据待测预锂电池和未预锂电池上述两个特征峰的峰面积或者峰间距按照如下式计算预锂量；预锂量＝{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，其中a为待测预锂电池LiC 6峰的峰面积，b为待测预锂电池LiC 12峰的峰面积，c为未预锂电池LiC 6峰的峰面积，b为未预锂电池LiC 12峰的峰面积。
实施例3
本实施例提供了一种预锂电池预锂量的测定方法，与实施例1基本相同，区别仅在于预理化处理方法不同，本实施例的预锂电池采用如下方法进行预理化处理：锂粉分散到DMC溶剂中，形成固含量5wt％的浆料喷涂到负极片表面，以锂粉质量计，涂覆量为0.14mg/cm 2，控制理论预锂量为15％。
实施例4
本实施例提供了一种预锂电池预锂量的测定方法，与实施例1基本相同，区别仅在于正极活性材料和负极活性材料不同，本申请正极活性材料采用容百科技的NCM811(ME8E)，负极活性材料采用上海杉杉的中间相 碳微球(ES2A)。
实施例5
本实施例提供了一种预锂电池预锂量的测定方法，与实施例1基本相同，区别仅在于充满电的充电倍率为0.005C。
实施例6
本实施例提供了一种预锂电池预锂量的测定方法，与实施例1基本相同，区别仅在于充满电的充电倍率为0.3C。
对比例1克容量发挥
采用克容量发挥法计算实施例1的预锂电池的预锂量，具体方法预锂量＝(Ca-Cb)/Cb×100％。
对比例2克容量发挥
采用克容量发挥法测试实施例2的预锂电池的预锂量，具体方法为分别对实施例2的待测预锂电池和未预锂电池进行标称容量，测试温度为30℃，循环倍率为0.1C，充放电循环(先充电至3.8V，再放电至2.0V，循环2次)，分别测定待测预锂电池和未预锂电池的标称容量Ca和Cb；预锂量＝(Ca-Cb)/Cb×100％。
表1实施例1-6和对比例1-2预锂量的测试结果
Figure PCTCN2022086567-appb-000001
Figure PCTCN2022086567-appb-000002
由上表可以看出，利用克容量发挥方法与XRD方法对比；对7％预锂量电池，用克容量发挥和XRD方法进行实际预锂量计算基本一致，对于15％预锂量电池，XRD方法与理论预锂量更相近，更为准确。
显然，上述实施例仅仅是为清楚地说明所作的举例，而并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引伸出的显而易见的变化或变动仍处于本发明创造的保护范围之中。

Claims (13)

  1. 一种预锂电池预锂量的测定方法，其特征在于，包括如下步骤：
    样品准备步骤：准备待测预锂电池和未预锂电池；
    充电步骤：将待测预锂电池和未预锂电池充满电；
    测试步骤：将充满电后的待测预锂电池和未预锂电池在惰性气体保护下拆解，得到各自的负极片，对待测预锂电池和未预锂电池的负极片进行XRD衍射法测试，分别得到两者的LiC 12峰与LiC 6峰的峰面积；
    计算预锂量步骤：照如下公式计算预锂量；预锂量＝{[a/(a+b)+1/2×b(a+b)]/[c/(c+d)+1/2×d(c+d)]-1}×100％，其中a为待测预锂电池LiC 6峰的峰面积，b为待测预锂电池LiC 12峰的峰面积，c为未预锂电池LiC 6峰的峰面积，b为未预锂电池LiC 12峰的峰面积。
  2. 根据权利要求1所述的锂电池预锂量的测定方法，其特征在于，在充电过程中，控制充电倍率为0.005-0.3C，充放电循环1-10次。
  3. 根据权利要求2所述的锂电池预锂量的测定方法，其特征在于，充电倍率为0.05C，充放电循环3-5次
  4. 根据权利要求1或2或3所述的锂电池预锂量的测定方法，其特征在于，待测预锂电池与未预锂电池的正负极设计相同，区别仅在于待测预锂电池的正极和/或负极经过预锂化处理，而未预锂电池的正极和负极均未经过预锂化处理。
  5. 根据权利要求4所述的锂电池预锂量的测定方法，其特征在于，所述预锂化处理选自将锂粉结合到负极表面对负极进行补锂、将锂箔结合到负极表面对负极进行补锂和采用正极补锂剂对正极进行补锂中的至少一种； 采用辊压方式将锂箔结合到负极表面；正极补锂剂选自Li 2NiO 2、Li 3N、Li 5FeO 4中的一种或者多种。
  6. 根据权利要求5所述的锂电池预锂量的测定方法，其特征在于，所述预锂化处理选自将锂粉结合到负极表面对负极进行补锂、将锂箔结合到负极表面对负极进行补锂和采用正极补锂剂对正极进行补锂中的至少一种包括：
    采用喷涂或凹版涂布方式将锂粉结合到负极表面。
  7. 一种预锂电池预锂容量的测定方法，其特征在于，包括权利要求1-6中任一所述的预锂电池预锂量的测定方法，还包括标称容量测试步骤：测定未预锂电池的标称容量C b，并根据如下公式计算预锂容量；预锂容量＝预锂量×C b。
  8. 根据权利要求7的测试方法，其特征在于，标称容量测定步骤中，控制测试温度为15-45℃下，循环倍率为0.05-0.5C，充电循环次数为1-5次，放电循环次数为1-5次。
  9. 根据权利要求8的测试方法，其特征在于，标称容量测定步骤中，测定温度为20-30℃，循环倍率为0.1-0.33C，充放电循环次数为1-2次。
  10. 根据权利要求1-9中任一所述的测定方法，其特征在于，负极片进行XRD测试之前还包括采用溶剂对负极片进行冲洗的步骤。
  11. 根据权利要求10所述的测定方法，其特征在于，所述溶剂选自碳酸二甲酯、碳酸二乙酯、碳酸二丙酯中的至少一种。
  12. 根据权利要求1-10中任一所述的测定方法，其特征在于，所述待测预锂电池的正极包括集流体和结合在集流体上的正极活性材料，所述正极 活性材料选自磷酸铁锂、磷酸铁锰锂、镍锰酸锂材料、镍酸锂材料、钴酸锂材料、镍钴酸锂材料、镍锰钴酸锂材料中的至少一种。
  13. 根据权利要求1-12中任一所述的测定方法，其特征在于，所述待测预锂电池的负极包括集流体和结合在集流体上的负极活性材料，所述负极活性材料选自石墨、硬碳、软碳、中间相碳微球中的至少一种。
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