CN113835034A - Method for measuring pre-lithium amount and pre-lithium capacity of pre-lithium battery - Google Patents

Method for measuring pre-lithium amount and pre-lithium capacity of pre-lithium battery Download PDF

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CN113835034A
CN113835034A CN202111165606.7A CN202111165606A CN113835034A CN 113835034 A CN113835034 A CN 113835034A CN 202111165606 A CN202111165606 A CN 202111165606A CN 113835034 A CN113835034 A CN 113835034A
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lithium
lithium battery
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CN113835034B (en
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刘浩
朱朋辉
娄帅宾
刘静
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Svolt Energy Technology Co Ltd
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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
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    • 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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Abstract

The invention provides a method for measuring pre-lithium amount and pre-lithium capacity of a pre-lithium battery, which comprises the following steps: a sample preparation step: preparing a pre-lithium battery to be tested and a non-pre-lithium battery; a charging step: fully charging a pre-lithium battery to be tested and a non-pre-lithium battery; the testing steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the fully charged non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, and performing XRD diffraction method test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to respectively obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery12Peak and LiC6Peak area of the peak; calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula; prelithium amount { [ a/(a + b) +1/2 xb (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, the method is simple and rapid, and the accuracy is obviously improved compared with the conventional volume volatilization method.

Description

Method for measuring pre-lithium amount and pre-lithium capacity of pre-lithium battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a method for measuring pre-lithium amount and pre-lithium capacity of a pre-lithium battery.
Background
Since the 21 st century, the global economy has been rapidly developed, and the automobile industry has been steaming day by day, with the practical problems of traffic jam, environmental pollution, fossil energy shortage and the like. The electric automobile can reduce the dependence of people on fossil energy and reduce the pollution of tail gas to the environment. The lithium ion battery is used as the power output of the electric automobile, has the advantages of high specific energy, long cycle life, energy conservation, environmental protection, economy, applicability and the like, and compared with a fuel battery, a solar battery and an all-solid-state battery, the secondary lithium ion battery has the advantages of high open-circuit voltage, high energy density, long service life, no pollution, small self-discharge and the like, and is considered as an optimal energy storage and conversion device.
In the case of the negative electrode, part of active lithium is consumed due to the formation of a solid electrolyte film (SEI film) during the first charge of the battery, thereby causing the loss of lithium as a positive electrode material, thereby decreasing the capacity of the battery, resulting in a decrease in the first efficiency. In the prior art, lithium is supplemented by performing pre-lithiation treatment on a negative electrode or a positive electrode, so as to make up for the reduction of the first effect of graphite and the loss of active lithium in the early stage of battery cycle and effectively improve the cycle life of the battery, and the battery subjected to pre-physical and chemical treatment is called a pre-lithium battery. The pre-lithiation treatment method mainly comprises a lithium foil lithium supplement method, a lithium powder lithium supplement method, a positive electrode lithium enrichment method and the like. The pre-lithium amount is an important index for evaluating the service life of the pre-lithium battery. Theoretically, the pre-lithium amount is generally calculated based on the mass of lithium (or lithium compound) added and the theoretical gram-capacity of lithium (or lithium compound). However, in practical applications, the gram capacity of the positive electrode gradually increases with the increase of the amount of lithium supplement, but when the gram capacity of the positive electrode reaches a theoretical gram capacity after the amount of lithium supplement reaches a certain degree, the amount of lithium supplement continues to increase, the gram capacity of the positive electrode does not increase any more, and the actual amount of pre-lithium cannot be judged according to the increase of the capacity of the battery.
Therefore, there is a need for a method to determine the actual pre-lithium amount for pre-lithium cells, especially at high pre-lithium amounts.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the actual high pre-lithium amount of the lithium battery, especially the lithium battery with high pre-lithium amount, cannot be accurately determined, so as to provide a method for determining the actual pre-lithium amount of the lithium battery.
The invention provides a method for testing the pre-lithium amount of a pre-lithium battery, which comprises the following steps:
a sample preparation step: preparing a pre-lithium battery to be tested and a non-pre-lithium battery;
a charging step: fully charging a pre-lithium battery to be tested and a non-pre-lithium battery;
the testing steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the fully charged non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, and performing XRD diffraction method test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to respectively obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery12Peak and LiC6Peak area of the peak;
calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula;
prelithium amount { [ a/(a + b) +1/2 xb (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, wherein a is the pre-lithium battery LiC to be tested6Peak area of peak, b is pre-lithium battery LiC to be measured12Peak area of peak, c is non-lithium cell LiC6Peak area of peak, b is non-lithium cell LiC12Peak area of peak.
Further, in the charging process, the charging rate is controlled to be 0.005-0.3C, and the charging and discharging cycle is controlled to be 1-10 times, preferably, the charging rate is controlled to be 0.05C, and the charging and discharging cycle is controlled to be 3-5 times. Charging to 3.8V.
The invention provides a method for testing the absolute pre-lithium amount of a pre-lithium battery, which comprises a method for testing the relative pre-lithium amount of the pre-lithium battery and also comprises a nominal capacity testing step: testing nominal capacity C of unprepared lithium batteryb。
Furthermore, the positive and negative electrodes of the pre-lithium battery to be tested are designed the same as those of the non-pre-lithium battery, and the difference is that the positive electrode and/or the negative electrode of the pre-lithium battery to be tested are subjected to pre-lithiation treatment, and the positive electrode and the negative electrode of the non-pre-lithium battery are not subjected to pre-lithiation treatment.
Further, the pre-lithium battery to be tested can be subjected to pre-physical and chemical treatment by adopting the conventional process, including but not limited to at least one of the following (1) to (3):
(1) bonding lithium powder to the surface of the negative electrode to supplement lithium for the negative electrode, preferably, bonding the lithium powder to the surface of the negative electrode by adopting a spraying or gravure coating mode;
(2) bonding lithium foil to the surface of the negative electrode to supplement lithium for the negative electrode, preferably bonding the lithium foil to the surface of the negative electrode in a rolling manner;
(3) the positive electrode is subjected to lithium supplement by using a positive electrode lithium supplement agent, and preferably, the positive electrode lithium supplement agent is selected from Li2NiO2、Li3N、Li5FeO4One or more of.
Specifically, the lithium foil can be pressed on the surface of the negative electrode in a conventional rolling manner under the pressure of not more than 50kg/cm2For example, a method disclosed in patent document CN 106128791A; the lithium powder can also be mixed with a binder and coated on the surface of the negative electrode, for example, by the method disclosed in patent document CN 104993098; the positive electrode may be subjected to lithium supplementation by a positive electrode lithium supplementation agent, for example, by a method disclosed in patent document CN 111834622A.
In the present invention, the terms pre-lithium amount, also referred to as relative pre-lithium amount and actual pre-lithium amount, refer to the mass percentage (unit:%) of the lithium ion battery after pre-physicochemical treatment, which is increased in lithium content compared to the lithium ion battery before pre-physicochemical treatment. The term pre-lithium capacity refers to the increase (in Ah) in the battery capacity of the lithium ion battery after the pre-treatment compared to the battery capacity of the lithium ion battery before the pre-treatment.
The invention also provides a method for measuring the lithium content of the pre-lithium battery, which comprises any one of the methods for testing the pre-lithium content of the pre-lithium battery, and also comprises the following steps of: determination of the nominal capacity C of a non-prepumped lithium cellbAnd calculating the lithium content according to the following formula; lithium content (pre-lithium content) x Cb。
Further, in the nominal capacity measuring step, the nominal capacity is measured by performing 1-5 charge-discharge cycles at a temperature of 15-45 ℃ and a charge rate of 0.05-0.5 ℃.
Further, in the nominal capacity measuring step, the nominal capacity is measured by performing charge-discharge cycles 1 to 2 times at a measuring temperature of 20 to 30 ℃ and a charge rate of 0.1 to 0.33 ℃.
Further, the method also comprises a step of washing the negative plate by using a solvent before the XRD test of the negative plate.
In certain preferred embodiments, the solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate.
Further, the theoretical prelithium content of the prelithium cell is no greater than 80%, preferably 5% to 20%.
In some preferred embodiments, the positive electrode of the pre-lithium battery to be tested comprises a current collector and a positive active material bonded on the current collector, wherein the positive active material is at least one selected from lithium iron phosphate, lithium manganese iron phosphate, lithium nickel 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 may employ existing coating and cold pressing processes. Specifically, a positive electrode active substance, a conductive agent and a binder are uniformly mixed according to a conventional proportion and added into a solvent to prepare positive electrode slurry; and uniformly coating the positive slurry on a positive current collector aluminum foil, drying, cold pressing, and performing die cutting and strip division to prepare the positive plate. 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, and the solvent can be a conventional organic solvent such as N-methylpyrrolidone NMP.
In certain preferred embodiments, the negative electrode of the pre-lithium battery to be tested comprises a current collector and a negative active material bonded to the current collector, the negative active material being selected from at least one of graphite, hard carbon, soft carbon, mesocarbon microbeads. The combined process may employ existing coating and cold pressing processes. Specifically, mixing a negative electrode active material, a conductive agent, a thickening agent and a binder according to a conventional ratio, adding the mixture into solvent water, and uniformly mixing to prepare negative electrode slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying and then carrying out cold pressing to prepare a negative plate. The solid content of the cathode slurry can be 50-55%, 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, and the thickening agent can be a conventional thickening agent such as sodium carboxymethylcellulose.
The electrode solution of the present invention may be a lithium ion electrolyte solution that is conventionally commercially available, or may be self-prepared from existing conventional materials, for example, an electrolyte solution including a solvent, a lithium salt, and an additive, the solvent being at least one selected from the group consisting of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The lithium salt is selected from lithium hexafluorophosphate and/or lithium tetrafluoroborate; the additive is at least one selected from vinylene carbonate, propylene carbonate, vinyl sulfate and lithium difluorophosphate. The molar concentration of the lithium salt is 0.8-1.2mol/L, and a mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) in a volume ratio of 1:1:1-1:2:2 can be used as a solvent. The volume percent of the additive may be 0.5-5%. The separator of the present invention may be used with existing conventional separators such as PE separators, PP/PE composite films, or other commercially available separators.
The technical scheme of the invention has the following advantages:
1. the method for measuring the pre-lithium amount of the pre-lithium battery comprises a sample preparation step, a charging step, a testing step and a pre-lithium amount calculating step, wherein the pre-lithium battery to be measured and the non-pre-lithium battery are fully charged, then the negative plate in the full charge state is measured and tested by an X-powder diffraction method, and the LiC is obtained by processing the test result12Peak and LiC6The peak area of the peak is calculated to obtain the pre-lithium amount, the lithium intercalation mode of the graphite material is the intercalation lithium intercalation mode, and C → LiC occurs during charging24→LiC12→LiC6A transition of (a); since N/P is greater than 1 in general, LiC is in a full-charge state12And LiC6A coexistence state; in the case of otherwise identical designs, the lithium insertion depth of the graphite in the fully charged state after pre-lithiation is increased compared with a non-pre-lithiated battery, i.e. the LiC12Conversion to LiC6The amount of LiC increases, the LiC of the pre-lithium cell and the non-pre-lithium cell12Peak and LiC6The actual pre-lithium amount can be calculated by substituting the peak area of the peak into the following formula: { [ a/(a + b) +1/2 × b (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, the method is simple and rapid, and the accuracy is obviously improved compared with the conventional volume volatilization method.
2. According to the method for measuring the pre-lithium amount of the pre-lithium battery, the pre-lithium battery to be measured and the non-pre-lithium battery are controlled to have the charge multiplying power of 0.005-0.3C in the full charge process, and the charge and discharge cycle is 1-10 times, preferably, the charge multiplying power is 0.05C, and the charge and discharge cycle is 3-5 times, so that the pre-lithium battery to be measured and the non-pre-lithium battery can be fully charged, the lithium consumption in the charge process can be reduced, and the accuracy of the test result is further improved.
3. The method for measuring the pre-lithium capacity of the pre-lithium battery is simple, rapid and accurate, and can fully activate the battery to further improve the accuracy of a test result by controlling the test temperature to be 15-45 ℃, the cycle rate to be 0.05-0.5 ℃, the charging cycle frequency to be 1-5 times, the discharging cycle frequency to be 1-5 times, particularly the test temperature to be 20-30 ℃, the charging cycle frequency to be 1-2 times and the discharging cycle frequency to be 1-2 times under the cycle rate to be 0.1-0.33 ℃ in the step of measuring the nominal capacity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of a structural change of a lithium deintercalation process of graphite;
figure 2 is an XRD pattern of a pre-lithium cell (pre-lithium group) with a theoretical pre-lithium amount of 15% and a non-pre-lithium cell (control group).
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
The embodiment provides a method for measuring the pre-lithium amount of a pre-lithium battery, which comprises the following steps:
s1 sample preparation step: preparing a pre-lithium battery to be tested and a non-pre-lithium battery; the preparation of the pre-lithium battery comprises the following steps: (1) preparing a positive plate: taking a positive electrode active material (lithium iron phosphate), a conductive agent acetylene black and a binder polyvinylidene fluoride PVDF according to a mass ratio of 96.5: 2.5: 1, uniformly mixing to obtain a mixture, adding the mixture into a solvent N-methyl-2-pyrrolidone (NMP) to obtain anode slurry (the solid content is 70%), and mixing the anode slurry according to the ratio of 36mg/cm2The surface density of the aluminum foil is evenly coated on a positive current collector aluminum foil, the thickness of the aluminum foil is 10 mu m, the aluminum foil is dried at 85 ℃ and then is cold-pressed, and then die cutting and strip splitting are carried out to prepare the lithium ion battery positive plate.
(2) Preparing a negative plate: taking negative active material graphite, conductive agent acetylene black, thickening agent sodium carboxymethylcellulose (CMC) and binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 96: 2: 1:1, mixing to obtain a mixture, adding the mixture into solvent water, uniformly mixing and preparing negative electrode slurry (the solid content is 50%); the slurry of the negative electrode is mixed according to the proportion of 20mg/cm2The surface density of the copper foil is uniformly coated on the copper foil of the negative current collector, the thickness of the copper foil is 6 mu m, and the copper foil is dried at 85 ℃ and then is cold-pressed to prepare the negative plate of the lithium ion battery to be manufactured.
(3) And (3) pre-lithiation treatment of the negative electrode: and rolling a 3-micron lithium foil on the surface of the negative plate, wherein the theoretical pre-lithium amount is 15%.
(4) Preparing an electrolyte: dissolving lithium hexafluorophosphate in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 5:3:2 to obtain a lithium hexafluorophosphate solution with the concentration of 1.15mol/L, and adding 1 vt% of vinylene carbonate, 0.5 vt% of lithium difluorophosphate and 0.5 vt% of vinyl sulfate DTD to obtain the lithium ion battery electrode solution.
(5) Assembling the positive plate, the PE diaphragm (from Enjie corporation, model: SV12) and the pre-lithiated negative plate in a laminating manner to obtain a battery pole group, placing the battery pole group in an aluminum packaging shell (from Kedali corporation, model 52148102) with plastic under PE material for assembly, drying in a vacuum drying box, injecting electrolyte, and sealing to obtain a semi-finished product battery core.
The method of manufacturing a non-pre-lithium cell is substantially the same as the method of manufacturing a pre-lithium cell, except that the negative electrode is not pre-lithiated.
S2 nominal capacity test procedure: respectively carrying out nominal capacity on the pre-lithium battery to be tested and the non-pre-lithium battery, wherein the test temperature is 30 ℃, the cycle rate is 0.33C, the charge and discharge cycle (charging to 3.8V, then discharging to 2.0V, and circulating for 2 times) is carried out, the nominal capacity Ca of the pre-lithium battery to be tested is 5.34Ah, and the Cb of the non-pre-lithium battery is 5.02 Ah.
S2 charging step: respectively charging the pre-lithium battery to be tested and the non-pre-lithium battery to 3.8V at the temperature of 25 ℃ and the circulation rate of 0.1C to fully charge the batteries, disassembling the fully charged batteries under the protection of argon to obtain respective negative plates, and carrying out XRD diffraction method test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to respectively obtain LiC of the pre-lithium battery and the non-pre-lithium battery12Peak and LiC6Peak area of peak. The test conditions of the XRD diffractometry were as follows: the test was carried out at room temperature and under vacuum using a copper target, lambda-0.15406 nm. See FIG. 2, left peak is LiC6Peak, right peak LiC12Peak(s).
S4 calculating prelithium amount step: calculating the pre-lithium amount according to the following formula according to the peak areas or the peak intervals of the two characteristic peaks of the pre-lithium battery to be detected and the non-pre-lithium battery; prelithium amount { [ a/(a + b) +1/2 xb (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, wherein a is the pre-lithium battery LiC to be tested6Peak area of peak, b is pre-lithium battery LiC to be measured12Peak area of peak, c is non-lithium cell LiC6Peak area of peak, b is non-lithium cell LiC12Peak area of peak.
Example 2
The embodiment provides a method for measuring the pre-lithium amount of a pre-lithium battery, which comprises the following steps:
(1) a sample preparation step: preparing a pre-lithium battery to be tested and a non-pre-lithium battery; a pre-lithium cell was prepared essentially as in example 1, except that a lithium foil having a thickness of 1.4 μm was used in the negative electrode pre-lithiation treatment step, and the theoretical pre-lithium amount was 7%.
(2) A charging step: respectively charging the pre-lithium battery to be tested and the non-pre-lithium battery to 3.8V at the temperature of 25 ℃ and the circulation rate of 0.1C to fully charge the batteries, disassembling the fully charged batteries under the protection of argon to obtain respective negative plates, and carrying out XRD diffraction method test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to respectively obtain LiC of the pre-lithium battery and the non-pre-lithium battery12Peak and LiC6Peak area of peak. The test conditions of the XRD diffractometry were as follows: the test was carried out at room temperature and under vacuum using a copper target, lambda-0.15406 nm.
(3) Calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula according to the peak areas or the peak intervals of the two characteristic peaks of the pre-lithium battery to be detected and the non-pre-lithium battery; prelithium amount { [ a/(a + b) +1/2 xb (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, wherein a is the pre-lithium battery LiC to be tested6Peak area of peak, b is pre-lithium battery LiC to be measured12Peak area of peak, c is non-lithium cell LiC6Peak area of peak, b is non-lithium cell LiC12Peak area of peak.
Example 3
This example provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is substantially the same as example 1 except that the pre-treatment method is different, and the pre-lithium battery of this example is pre-treated by the following method: dispersing lithium powder into DMC solvent to form slurry with solid content of 5 wt%, and spraying the slurry onto the surface of the negative plate, wherein the coating amount is 0.14mg/cm based on the mass of the lithium powder2The theoretical prelithium content was controlled to 15%.
Example 4
This example provides a method for measuring the pre-lithium amount of a pre-lithium battery, which is substantially the same as example 1, except that the positive active material and the negative active material are different, the positive active material of the present application is NCM811(ME8E) of kojiki technology, and the negative active material is mesocarbon microbeads (ES2A) of sequoia jezoensis.
Example 5
This example provides a method for measuring the amount of prelithium in a pre-lithium battery, which is substantially the same as example 1 except that the fully charged charge rate is 0.005C.
Example 6
This example provides a method for measuring the amount of prelithium in a pre-lithium battery, which is substantially the same as example 1 except that the fully charged charge rate is 0.3C.
Comparative example 1 gram Capacity exertion
The pre-lithium amount of the pre-lithium battery of example 1 was calculated by the gram-capacity method, specifically, the pre-lithium amount was (Ca-Cb)/Cb × 100%.
Comparative example 2 gram Capacity exertion
The pre-lithium amount of the pre-lithium battery in the embodiment 2 is tested by adopting a gram capacity exertion method, and the specific method is that nominal capacity is respectively carried out on the pre-lithium battery to be tested and the non-pre-lithium battery in the embodiment 2, the testing temperature is 30 ℃, the cycle rate is 0.1C, charge and discharge cycles (firstly charging to 3.8V, then discharging to 2.0V, and cycling for 2 times) are carried out, and the nominal capacity Ca and Cb of the pre-lithium battery to be tested and the non-pre-lithium battery are respectively measured; the pre-lithium amount is (Ca-Cb)/Cb × 100%.
TABLE 1 test results for pre-lithiation amounts of examples 1-6 and comparative examples 1-2
Figure BDA0003291555700000111
Figure BDA0003291555700000121
As can be seen from the above table, the gram volume exertion method is compared with the XRD method; for the 7% pre-lithium battery, the gram capacity exertion method is basically consistent with the actual pre-lithium amount calculation by the XRD method, and for the 15% pre-lithium battery, the XRD method is more similar to the theoretical pre-lithium amount and more accurate.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (10)

1. A method for measuring the pre-lithium amount of a pre-lithium battery is characterized by comprising the following steps:
a sample preparation step: preparing a pre-lithium battery to be tested and a non-pre-lithium battery;
a charging step: fully charging a pre-lithium battery to be tested and a non-pre-lithium battery;
the testing steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the fully charged non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, and performing XRD diffraction method test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to respectively obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery12Peak and LiC6Peak area of the peak;
calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula; prelithium amount { [ a/(a + b) +1/2 xb (a + b)]/[c/(c+d)+1/2×d(c+d)]-1 }. times.100%, wherein a is the pre-lithium battery LiC to be tested6Peak area of peak, b is pre-lithium battery LiC to be measured12Peak area of peak, c is non-lithium cell LiC6Peak area of peak, b is non-lithium cell LiC12Peak area of peak.
2. The method for measuring the pre-lithium amount of a lithium battery according to claim 1, wherein the charging rate is controlled to be 0.005-0.3C during charging and the charging and discharging cycle is controlled to be 1-10 times, preferably, the charging rate is 0.05C and the charging and discharging cycle is controlled to be 3-5 times during charging.
3. The method for determining the pre-lithium amount of the lithium battery as claimed in claim 1 or 2, wherein the pre-lithium battery to be tested has the same anode and cathode design as the non-pre-lithium battery, and the difference is that the anode and/or the cathode of the pre-lithium battery to be tested are subjected to pre-lithiation treatment, and neither the anode nor the cathode of the non-pre-lithium battery is subjected to pre-lithiation treatment.
4. The method for measuring the pre-lithium amount of the lithium battery according to claim 3, wherein the pre-lithiation treatment is at least one selected from the group consisting of bonding lithium powder to the surface of the negative electrode to supplement lithium to the negative electrode, bonding lithium foil to the surface of the negative electrode to supplement lithium to the negative electrode, and supplementing lithium to the positive electrode by using a positive electrode lithium supplementing agent, and preferably, the lithium powder is bonded to the surface of the negative electrode by spraying or gravure coating; bonding the lithium foil to the surface of the negative electrode in a rolling manner; the positive electrode lithium supplementing agent is selected from Li2NiO2、Li3N、Li5FeO4One or more of.
5. A method for determining the pre-lithium capacity of a pre-lithium battery, comprising the method for determining the pre-lithium amount of a pre-lithium battery according to any one of claims 1 to 4, and further comprising the step of nominal capacity testing: determination of the nominal capacity C of a non-prepumped lithium cellbAnd calculating the pre-lithium capacity according to the following formula; pre-lithium capacity (pre-lithium amount × C)b。
6. The test method according to claim 5, wherein in the nominal capacity measuring step, the test temperature is controlled to be 15 to 45 ℃, the cycle rate is 0.05 to 0.5C, the number of charge cycles is 1 to 5, and the number of discharge cycles is 1 to 5.
7. The test method according to claim 6, characterized in that in the nominal capacity measuring step, the measuring temperature is 20 to 30 ℃, the cycle rate is 0.1 to 0.33C, and the number of charge and discharge cycles is 1 to 2.
8. The determination method according to any one of claims 1 to 7, wherein the negative electrode plate is further subjected to a step of washing with a solvent before XRD testing, and preferably the solvent is at least one selected from dimethyl carbonate, diethyl carbonate and dipropyl carbonate.
9. The method according to any one of claims 1 to 8, wherein the positive electrode of the pre-lithium battery to be tested comprises a current collector and a positive active material bonded on the current collector, and the positive active material is selected from at least one of lithium iron phosphate, lithium iron manganese phosphate, lithium nickel manganese oxide material, lithium nickel oxide material, lithium cobalt oxide material, lithium nickel cobalt oxide material and lithium nickel manganese cobalt oxide material.
10. The assay of any one of claims 1-9, wherein the negative electrode of the pre-lithium battery under test comprises a current collector and a negative active material bonded to the current collector, the negative active material being selected from at least one of graphite, hard carbon, soft carbon, mesocarbon microbeads.
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