CN113835034B - Method for measuring pre-lithium capacity and pre-lithium capacity of pre-lithium battery - Google Patents

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

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CN113835034B
CN113835034B CN202111165606.7A CN202111165606A CN113835034B CN 113835034 B CN113835034 B CN 113835034B CN 202111165606 A CN202111165606 A CN 202111165606A CN 113835034 B CN113835034 B CN 113835034B
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lithium
lithium battery
battery
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CN113835034A (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
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a method for measuring the pre-lithium content and the pre-lithium capacity of a pre-lithium battery, which comprises the following steps: sample preparation: preparing a pre-lithium battery to be tested and an unprelithium battery; and (3) charging: fully charging the pre-lithium battery to be tested and the non-pre-lithium battery; testingThe steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, performing XRD diffraction test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery respectively 12 Peak to LiC 6 Peak area of the peak; calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula; the amount of pre-lithium= { [ a/(a+b) +1/2×b (a+b)]/[c/(c+d)+1/2×d(c+d)]-1} ×100%, and the method is simple and quick, and the accuracy is obviously improved compared with the conventional capacity volatilization method.

Description

Method for measuring pre-lithium capacity 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 the pre-lithium content and the pre-lithium capacity of a pre-lithium battery.
Background
Since the 21 st century, global economy has rapidly progressed, and the automobile industry has been steaming on a daily basis, followed by realistic problems such as traffic jams, environmental pollution, and shortage of fossil energy. 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 cell, a solar cell 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 to be the most ideal energy storage and conversion device.
For 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 loss of positive electrode material lithium, thereby reducing the capacity of the battery, resulting in a reduction of the first efficiency. In the prior art, lithium is supplemented by pre-lithiation treatment of the negative electrode or the positive electrode to compensate for the first effect reduction of graphite and the loss of active lithium in the early cycle of the battery, so that the cycle life of the battery is effectively prolonged. The method for pre-lithiation treatment mainly comprises a lithium foil lithium supplementing method, a lithium powder lithium supplementing method or a positive electrode lithium enrichment method and the like. And the pre-lithium amount is an important index for evaluating the service life of the pre-lithium battery. Theoretically, the amount of pre-lithium is generally calculated from the mass of lithium (or lithium compound) added, and the theoretical gram capacity of lithium (or lithium compound). However, in practical application, as the lithium supplementing amount increases, the gram capacity of the positive electrode gradually increases, but when the lithium supplementing amount reaches a certain degree and the gram capacity of the positive electrode reaches the theoretical gram capacity, the lithium supplementing amount continues to increase, the gram capacity of the positive electrode does not increase any more, and the actual pre-lithium amount cannot be judged by the increase of the battery capacity.
Thus, there is an urgent need for a method of determining the actual amount of pre-lithium in a pre-lithium battery, especially at high pre-lithium amounts.
Disclosure of Invention
Therefore, the invention aims to overcome the defect that the lithium battery, especially the lithium battery with high pre-lithium content, cannot be accurately measured in the prior art, and further provides a method for measuring the actual pre-lithium content of the lithium battery.
The invention provides a method for testing the pre-lithium quantity of a pre-lithium battery, which comprises the following steps:
sample preparation: preparing a pre-lithium battery to be tested and an unprelithium battery;
and (3) charging: fully charging the pre-lithium battery to be tested and the non-pre-lithium battery;
the testing steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, performing XRD diffraction test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery respectively 12 Peak to LiC 6 Peak area of the peak;
calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula;
the amount of pre-lithium= { [ a/(a+b) +1/2×b (a+b)]/[c/(c+d)+1/2×d(c+d)]-1} ×100%, where a is the pre-lithium battery to be tested LiC 6 Peak area of peak, b is LiC of pre-lithium battery to be measured 12 Peak area of peak, c is LiC of unprelithium battery 6 Peak area of peak, b is LiC of unprelithium battery 12 Peak area of the peak.
Further, in the charging process, the charging rate is controlled to be 0.005-0.3C, the charging and discharging cycle is 1-10 times, preferably, the charging rate is 0.05C, and the charging and discharging cycle is 3-5 times. Charged to 3.8V.
The invention provides a method for testing absolute pre-lithium amount of a pre-lithium battery, which comprises the following steps of: testing nominal Capacity C of non-Pre-lithium Battery b 。
Furthermore, the positive and negative electrode designs of the to-be-detected pre-lithium battery are 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 to-be-detected pre-lithium battery 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 may be subjected to pre-physical and chemical treatments using existing conventional techniques, including but not limited to at least one of the following (1) - (3):
(1) Lithium powder is combined to the surface of the negative electrode to supplement lithium for the negative electrode, and preferably, the lithium powder is combined to the surface of the negative electrode in a spraying or gravure coating mode;
(2) Bonding a lithium foil to the surface of the negative electrode to supplement lithium to the negative electrode, and preferably bonding the lithium foil to the surface of the negative electrode by adopting a rolling mode;
(3) The positive electrode is subjected to lithium supplementation by a positive electrode lithium supplementing agent, preferably the positive electrode lithium supplementing agent is selected from Li 2 NiO 2 、Li 3 N、Li 5 FeO 4 One or more of the following.
Specifically, the lithium foil can be pressed onto the surface of the negative electrode by adopting a conventional rolling manner, and the pressure is not more than 50kg/cm 2 For example, a method disclosed in patent document CN106128791 a; the lithium powder may be mixed with a binder and then coated on the surface of the negative electrode, for example, by a method disclosed in patent document CN 104993098; the positive electrode may be subjected to lithium supplementation by a positive electrode lithium supplementing agent, for example, by a method disclosed in patent document CN111834622 a.
In the present invention, the term pre-lithium amount, also referred to as relative pre-lithium amount and actual pre-lithium amount, refers to the mass percentage (unit:%) of the lithium ion battery after the pre-physicochemical treatment that is increased compared to the lithium ion battery before the pre-physicochemical treatment. The term pre-lithium capacity refers to the improvement value (unit Ah) of the battery capacity of a lithium ion battery after the pre-physicochemical treatment compared to the battery capacity of the lithium ion battery before the pre-physicochemical treatment.
The invention also provides a method for measuring the lithium content of the pre-lithium battery, which comprises the testing method for the pre-lithium content of the pre-lithium battery, and further comprises the nominal capacity testing step of: determination of nominal Capacity C of non-Pre-lithium Battery b And calculating the lithium content according to the following formula; lithium content = pre-lithium content xc b 。
Further, in the nominal capacity measurement step, the nominal capacity is measured by performing 1 to 5 charge and discharge cycles at a temperature of 15 to 45 ℃ and a charge rate of 0.05 to 0.5 ℃.
Further, in the nominal capacity measurement step, the nominal capacity is measured by performing 1-2 charge-discharge cycles at a measurement temperature of 20-30 ℃ and a charge rate of 0.1-0.33 ℃.
Further, the anode sheet is subjected to XRD test, and then the anode sheet is rinsed with a solvent.
In certain preferred embodiments, the solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate.
Further, the theoretical pre-lithium amount of the pre-lithium battery is not more than 80%, preferably 5% -20%.
In certain preferred embodiments, the positive electrode of the pre-lithium battery to be tested comprises a current collector and a positive electrode active material bonded to the current collector, wherein the positive electrode active material is selected from at least one of 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 bonding process may employ existing coating and cold pressing processes. Specifically, uniformly mixing an anode active material, a conductive agent and a binder according to a conventional proportion, and adding the mixture into a solvent to prepare anode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying, cold pressing, and carrying out die cutting and slitting to prepare the positive electrode plate. Wherein the solid content of the positive electrode slurry may be 70-75%, the conductive agent may be a conventional conductive agent such as acetylene black, the binder may be a conventional binder such as styrene-butadiene rubber or vinylidene fluoride PVDF, and the solvent may 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 electrode active material bonded on the current collector, wherein the negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon and mesophase carbon microspheres. The bonding 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 proportion, adding the mixture into solvent water, uniformly mixing, and preparing negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil, drying, and then cold pressing to prepare a negative electrode plate. Wherein the solid content of the anode slurry may be 50-55%, the conductive agent may be a conventional conductive agent such as acetylene black, the binder may be a conventional binder such as styrene-butadiene rubber or vinylidene fluoride PVDF, and the thickener may be a conventional thickener such as sodium hydroxymethyl cellulose.
The electrode solution of the invention can be made of conventional commercially available lithium ion electrolyte or can be made of conventional materials, for example, electrolyte comprising solvent, lithium salt and additive, wherein the solvent is at least one of ethylene carbonate, dimethyl carbonate and ethylmethyl 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 the mixed solution of Ethylene Carbonate (EC), dimethyl carbonate (DEC) and methyl ethyl carbonate (EMC) with the volume ratio of 1:1:1-1:2:2 can be adopted as the solvent. The volume percent of the additive may be 0.5-5%. The present invention may employ existing conventional membranes such as PE membranes, PP/PE composite films, or other commercially available membranes.
The technical scheme of the invention has the following advantages:
1. the invention provides a method for measuring the pre-lithium quantity of a pre-lithium battery, which comprises a sample preparation step, a charging step, a testing step and a pre-lithium quantity calculating step, wherein the pre-lithium battery to be measured and the non-pre-lithium battery are fully charged first, and thenThen, the anode sheet in full charge state is subjected to X-powder diffraction method measurement test, and the test result is processed to obtain LiC 12 Peak and LiC 6 The peak area of the peak is calculated to obtain the pre-lithium amount, the lithium intercalation mode of the graphite material is an intercalation lithium intercalation mode, and C-LiC is generated during charging 24 →LiC 12 →LiC 6 Is a transition of (2); since N/P is generally greater than 1, liC in full-charge state 12 And LiC 6 A coexistence state; in the case of otherwise identical designs, the lithium intercalation depth of the graphite is increased in the pre-lithium and full-charge state, i.e. LiC, compared to an unprelithium battery 12 Conversion to LiC 6 The amount of LiC in the pre-lithium battery and the non-pre-lithium battery is increased 12 Peak and LiC 6 The 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} ×100%, and the method is simple and quick, and the accuracy is obviously improved compared with the conventional capacity volatilization method.
2. According to the method for measuring the pre-lithium content of the pre-lithium battery, the pre-lithium battery and the non-pre-lithium battery to be measured are fully charged, the charging multiplying power is controlled to be 0.005-0.3C, the charging and discharging cycle is 1-10 times, preferably, the charging multiplying power is 0.05C, and the charging and discharging cycle is 3-5 times, so that the pre-lithium battery and the non-pre-lithium battery to be measured can be fully charged, the consumption of lithium in the charging process can be reduced, and the accuracy of a test result is further improved.
3. The method for measuring the pre-lithium capacity of the pre-lithium battery is simple, quick and accurate, and can fully activate the battery and further improve the accuracy of a test result by controlling the test temperature to be 15-45 ℃ and the circulation rate to be 0.05-0.5 ℃ and the charge cycle number to be 1-5 times and the discharge cycle number to be 1-5 times, particularly by controlling the test temperature to be 20-30 ℃ and the circulation rate to be 0.1-0.33 ℃ and the charge cycle number to be 1-2 times and the discharge cycle number to be 1-2 times in the nominal capacity measuring step.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram showing structural changes in a graphite delithiation process;
fig. 2 is an XRD pattern of a pre-lithium battery (pre-lithium group) and an unprelithium battery (control group) having a theoretical pre-lithium amount of 15%.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The embodiment provides a method for measuring the pre-lithium content of a pre-lithium battery, which comprises the following steps:
s1, sample preparation: preparing a pre-lithium battery to be tested and an unprelithium battery; the preparation of the pre-lithium battery comprises the following steps: preparation of positive plate: taking an anode active material (lithium iron phosphate), a conductive agent acetylene black and a binder polyvinylidene fluoride PVDF according to the mass ratio of 96.5:2.5:1, adding the mixture into N-methyl-2-pyrrolidone (NMP) as a solvent to prepare positive electrode slurry (solid content is 70%), and mixing the positive electrode slurry according to 36mg/cm 2 The surface density of the lithium ion battery is uniformly coated on an aluminum foil of a positive current collector, the thickness of the aluminum foil is 10 mu m, the aluminum foil is dried at 85 ℃ and then cold-pressed, and then die-cut and strip-separated are carried out to prepare the positive plate of the lithium ion battery.
(2) Preparing a negative plate: taking graphite as a cathode active material and a conductive agentAcetylene black, a thickener sodium carboxymethylcellulose (CMC) and a binder styrene-butadiene rubber (SBR) according to the 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 percent); the cathode slurry was prepared at a concentration of 20mg/cm 2 The surface density of the lithium ion battery negative electrode plate is uniformly coated on a negative electrode current collector copper foil, the thickness of the copper foil is 6 mu m, and the lithium ion battery negative electrode plate is manufactured by cold pressing after drying at 85 ℃.
(3) Pre-lithiation treatment of the cathode: a3 μm lithium foil was rolled onto the negative electrode sheet surface with a theoretical pre-lithium amount of 15%.
(4) Preparation of electrolyte: and dissolving lithium hexafluorophosphate in a mixed solvent of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a volume ratio of 5:3:2 to obtain a lithium hexafluorophosphate solution with a concentration of 1.15mol/L, and adding 1vt% of ethylene carbonate, 0.5vt% of lithium difluorophosphate and 0.5vt% of ethylene sulfate DTD to obtain the lithium ion battery electrode liquid.
(5) And (3) assembling the positive plate, the PE diaphragm (purchased from Enje company, model: SV 12) and the pre-lithiated negative plate in a lamination mode to obtain a battery electrode group, putting the battery electrode group into an aluminum packaging shell (purchased from Kodali company, model 52148102) with PE material and plastic, assembling, drying in a vacuum drying box, injecting electrolyte, and sealing to obtain the semi-finished battery cell.
The preparation method of the non-pre-lithium battery is basically the same as that of the pre-lithium battery, and the difference is that the cathode is not pre-lithiated.
S2, nominal capacity testing: and respectively carrying out nominal capacity on the pre-lithium battery to be tested and the non-pre-lithium battery to be tested, wherein the test temperature is 30 ℃, the circulation multiplying power is 0.33 ℃, the charging and discharging circulation (firstly, charging to 3.8V, then discharging to 2.0V and circulating for 2 times) is carried out, and the nominal capacity Ca of the pre-lithium battery to be tested is measured to be 5.34Ah, and the Cb of the non-pre-lithium battery is measured to be 5.02Ah.
S2, charging: charging the pre-lithium battery to be tested and the non-pre-lithium battery to 3.8V under the condition that the temperature is 25 ℃ and the circulation multiplying power is 0.1 ℃ respectively, so that the batteries are fully charged, and disassembling the fully charged batteries under the protection of argon to obtain respective negative plates, wherein the pre-lithium battery to be tested and the non-lithium battery to be tested are respectively manufacturedXRD diffraction test is carried out on the negative plate of the pre-lithium battery to obtain LiC of the pre-lithium battery and LiC of the pre-lithium battery 12 Peak to LiC 6 Peak area of the peak. The XRD diffractometry test conditions were as follows: test at room temperature and vacuum, using copper target, λ= 0.15406nm. As shown in FIG. 2, the left peak is LiC 6 Peak, right peak is LiC 12 A peak.
S4, calculating a pre-lithium amount: calculating the pre-lithium amount according to the following formula according to the peak areas or peak intervals of the two characteristic peaks of the pre-lithium battery to be detected and the non-pre-lithium battery; the amount of pre-lithium= { [ a/(a+b) +1/2×b (a+b)]/[c/(c+d)+1/2×d(c+d)]-1} ×100%, where a is the pre-lithium cell to be tested LiC 6 Peak area of peak, b is LiC of pre-lithium battery to be measured 12 Peak area of peak, c is LiC of unprelithium battery 6 Peak area of peak, b is LiC of unprelithium battery 12 Peak area of the peak.
Example 2
The embodiment provides a method for measuring the pre-lithium content of a pre-lithium battery, which comprises the following steps:
(1) Sample preparation: preparing a pre-lithium battery to be tested and an unprelithium battery; the preparation of the pre-lithium battery was essentially the same 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) And (3) charging: charging the pre-lithium battery and the non-pre-lithium battery to be tested to 3.8V under the condition that the temperature is 25 ℃ and the circulation multiplying power is 0.1 ℃ respectively, so that the batteries are fully charged, disassembling the fully charged batteries under the protection of argon to obtain respective negative plates, and performing XRD diffraction test on the negative plates of the pre-lithium battery and the non-pre-lithium battery to be tested to obtain LiC of the pre-lithium battery and the non-pre-lithium battery respectively 12 Peak to LiC 6 Peak area of the peak. The XRD diffractometry test conditions were as follows: test at room temperature and vacuum, using copper target, λ= 0.15406nm.
(3) Calculating the pre-lithium amount: calculating the pre-lithium amount according to the following formula according to the peak areas or peak intervals of the two characteristic peaks of the pre-lithium battery to be detected and the non-pre-lithium battery; the amount of pre-lithium= { [ a/(a+b) +1/2×b (a+b)]/[c/(c+d)+1/2×d(c+d)]-1} ×100%, where a is the pre-lithium cell to be tested LiC 6 Peak area of peak, b isLiC of pre-lithium battery to be measured 12 Peak area of peak, c is LiC of unprelithium battery 6 Peak area of peak, b is LiC of unprelithium battery 12 Peak area of the peak.
Example 3
The present embodiment provides a method for measuring a pre-lithium amount of a pre-lithium battery, which is substantially the same as that of embodiment 1, and differs only in that the pre-physical treatment method is different, and the pre-lithium battery of the present embodiment performs the pre-physical treatment by adopting the following method: dispersing lithium powder into DMC solvent to form slurry with solid content of 5wt% and spraying the slurry onto the surface of negative electrode sheet, wherein the coating amount is 0.14mg/cm based on the mass of lithium powder 2 The theoretical pre-lithium content was controlled to 15%.
Example 4
The present embodiment provides a method for measuring the amount of pre-lithium in a pre-lithium battery, which is substantially the same as that of embodiment 1, except that the positive electrode active material and the negative electrode active material are different, the positive electrode active material of the present application adopts NCM811 (ME 8E) of the appearance hundred technologies, and the negative electrode active material adopts mesophase carbon microspheres (ES 2A) of huperzia serrata.
Example 5
The present 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 full charge rate is 0.005C.
Example 6
The present 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 full charge rate is 0.3C.
Comparative example 1 gram Capacity Spectroscopy
The pre-lithium amount of the pre-lithium battery of example 1 was calculated using a gram capacity exertion method, and the specific method pre-lithium amount= (Ca-Cb)/cb×100%.
Comparative example 2 gram Capacity Spectroscopy
Testing the pre-lithium amount of the pre-lithium battery of the embodiment 2 by adopting a gram capacity exertion method, wherein the specific method is to respectively perform nominal capacity on the pre-lithium battery to be tested and the non-pre-lithium battery of the embodiment 2, wherein the test temperature is 30 ℃, the circulation multiplying power is 0.1 ℃, and the charging and discharging cycles (firstly charging to 3.8V, then discharging to 2.0V and circulating for 2 times) are carried out, so as to respectively determine the nominal capacities Ca and Cb of the pre-lithium battery to be tested and the non-pre-lithium battery; the amount of pre-lithium= (Ca-Cb)/cb×100%.
TABLE 1 test results of the amount of pre-lithium of examples 1-6 and comparative examples 1-2
Figure BDA0003291555700000111
Figure BDA0003291555700000121
As can be seen from the above table, the gram capacity generating method is compared with the XRD method; for a 7% pre-lithium battery, the gram capacity is basically consistent with the actual pre-lithium amount calculated by an XRD method, and for a 15% pre-lithium battery, the XRD method is more similar to the theoretical pre-lithium amount and is more accurate.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims (13)

1. The method for measuring the pre-lithium content of the pre-lithium battery is characterized by comprising the following steps of:
sample preparation: preparing a pre-lithium battery to be tested and an unprelithium battery;
and (3) charging: fully charging the pre-lithium battery to be tested and the non-pre-lithium battery;
the testing steps are as follows: disassembling the fully charged pre-lithium battery to be tested and the non-pre-lithium battery under the protection of inert gas to obtain respective negative plates, performing XRD diffraction test on the negative plates of the pre-lithium battery to be tested and the non-pre-lithium battery to obtain LiC of the pre-lithium battery to be tested and the non-pre-lithium battery respectively 12 Peak to LiC 6 Peak area of the peak;
calculating the pre-lithium amount: according to the following formulaCalculating the pre-lithium amount; the amount of pre-lithium= { [ a/(a+b) +1/2×b (a+b)]/[c/(c+d)+1/2×d(c+d)]-1} ×100%, where a is the pre-lithium cell to be tested LiC 6 Peak area of peak, b is LiC of pre-lithium battery to be measured 12 Peak area of peak, c is LiC of unprelithium battery 6 Peak area of peak, b is LiC of unprelithium battery 12 Peak area of the 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 and the charge and discharge cycles are performed 1-10 times during the charging process.
3. The method for measuring the pre-lithium content of a lithium battery according to claim 2, wherein the charge rate is 0.05C and the charge-discharge cycle is 3 to 5 times.
4. The method for measuring the pre-lithium content of the lithium battery according to claim 1, wherein the design of the positive electrode and the negative electrode of the pre-lithium battery to be measured is the same as that of the non-pre-lithium battery, and the difference is only that the positive electrode and/or the negative electrode of the pre-lithium battery to be measured 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.
5. The method for measuring the amount of pre-lithium in a lithium battery according to claim 4, wherein the pre-lithiation treatment is at least one selected from the group consisting of binding lithium powder to the surface of the negative electrode to supplement lithium to the negative electrode, binding lithium foil to the surface of the negative electrode to supplement lithium to the negative electrode, and supplementing lithium to the positive electrode with a positive electrode lithium supplement.
6. The method for measuring the lithium battery pre-lithium amount according to claim 5, wherein the lithium powder is bonded to the surface of the negative electrode by spraying or gravure coating; adopting a rolling mode to bond the lithium foil to the surface of the negative electrode; the positive electrode lithium supplementing agent is selected from Li 2 NiO 2 、Li 3 N、Li 5 FeO 4 One or more of the following.
7. Pre-lithium battery pre-lithiumThe method for measuring the capacity is characterized by comprising the method for measuring the lithium pre-charge of the lithium pre-charge battery according to any one of claims 1 to 6, and further comprising a nominal capacity testing step of: determination of nominal Capacity C of non-Pre-lithium Battery b And calculating the pre-lithium capacity according to the following formula; pre-lithium capacity = pre-lithium amount x C b 。
8. The method for measuring the pre-lithium capacity of a pre-lithium battery according to claim 7, wherein in the nominal capacity measuring step, the test temperature is controlled to be 15-45 ℃, the cycle rate is controlled to be 0.05-0.5 ℃, the charge cycle number is controlled to be 1-5, and the discharge cycle number is controlled to be 1-5.
9. The method for measuring the pre-lithium capacity of a pre-lithium battery according to claim 8, wherein in the nominal capacity measuring step, the measuring temperature is 20-30 ℃, the cycle rate is 0.1-0.33 ℃, and the number of charge-discharge cycles is 1-2.
10. The method of any one of claims 1 to 9, further comprising the step of rinsing the negative electrode sheet with a solvent prior to performing the XRD test on the negative electrode sheet.
11. The method according to claim 10, wherein the solvent is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate and dipropyl carbonate.
12. The method according to any one of claims 1 to 9, wherein the positive electrode of the pre-lithium battery to be measured comprises a current collector and a positive electrode active material bonded to the current collector, and the positive electrode active material is at least one selected from the group consisting 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.
13. The method according to any one of claims 1 to 9, wherein the negative electrode of the pre-lithium battery to be measured comprises a current collector and a negative electrode active material bonded to the current collector, the negative electrode active material being selected from at least one of graphite, hard carbon, soft carbon, and mesophase carbon microspheres.
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