CN115808474A - Method for detecting lithium analysis content of lithium ion battery - Google Patents
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Abstract
The embodiment of the invention discloses a method for detecting the lithium analysis content of a lithium ion battery, which comprises the following steps: discharging the lithium ion battery to be tested until the SOC is 0%, wherein the discharging mode is constant current and constant voltage discharging, the constant current is 0.1-1C, and the constant voltage cutoff current is 0.01-0.1C; fully reacting a negative pole piece obtained by disassembling the lithium ion battery to be tested with a reactive solution containing hydroxyl to obtain hydrogen, and fully reacting the negative pole piece with the reactive solution containing hydroxyl in a sealed environment; and determining the lithium precipitation content of the negative pole piece according to the hydrogen content. The invention can improve the detection precision of the lithium content of the lithium ion battery.
Description
Technical Field
The invention relates to the technical field of battery detection, in particular to a method for detecting the lithium analysis content of a lithium ion battery.
Background
According to a power battery safety report issued in 2020, the spontaneous combustion phenomenon of the electric vehicle in the charging, standing and driving processes accounts for 80% of new energy automobile accidents in China among the accident reasons of the electric vehicle. In the accident analysis, in addition to the problems of the charging function safety design and the BMS (Battery Management System), the problem of lithium analysis of the Battery caused by irregular quick charging is particularly serious. The service life of the battery is reduced due to lithium separation, the thermal stability of the battery is poor, serious potential safety hazards are caused, and even spontaneous combustion accidents are caused, so that the effective detection of the lithium separation is very important in the field of lithium ion batteries.
The lithium analysis detection method can be mainly divided into on-line detection, off-line detection, selection method and qualitative and quantitative detection method. At present, most analysis methods focus on qualitative analysis, such as a relaxation voltage differential curve method, a discharge differential voltage curve method, an alternating current impedance method and the like, and perform data analysis according to a battery performance curve so as to judge the lithium analysis condition. The non-destructive method can make judgment without disassembling the battery, but has low maturity and poor accuracy. In quantitative assays, lithium metal can be detected by direct or indirect means. In patent CN108535659a, after discharging and disassembling a lithium ion battery to be tested, taking out a negative electrode plate, cleaning, exposing in air, heating and drying, converting precipitated lithium into lithium carbonate, and determining the lithium precipitation degree of the negative electrode plate by using corresponding data measured by EDS (Energy Dispersive Spectrometer) test or chemical titration. According to the method, a battery to be tested is disassembled and cleaned, then the negative pole piece is soaked in organic solution of metal salt, so that the metal salt and precipitated lithium are subjected to sufficient displacement reaction, and the reacted pole piece is subjected to qualitative or quantitative analysis on a biological product through an energy spectrum analyzer and the like, so that whether the negative pole piece is subjected to lithium precipitation or not and the relative size of the lithium precipitation quantity are determined. However, when the lithium metal is converted into lithium carbonate for measurement, because the negative electrode sheet has a thick SEI film (solid electrolyte interface film), the components of the SEI film contain lithium carbonate, and thus errors are caused in the detection result of lithium deposition. How to accurately detect the content of the analyzed lithium in the lithium ion battery is an urgent problem to be solved.
Disclosure of Invention
The invention provides a method for detecting the lithium analysis content of a lithium ion battery, which aims to improve the detection precision of the lithium analysis content of the lithium ion battery. The specific technical scheme is as follows:
the embodiment of the invention provides a method for detecting the lithium analysis content of a lithium ion battery, which comprises the following steps:
discharging the lithium ion battery to be tested until the SOC is 0%, wherein the discharging mode is constant current and constant voltage discharging, the constant current is 0.1-1C, and the constant voltage cutoff current is 0.01-0.1C;
fully reacting a negative pole piece obtained by disassembling the lithium ion battery to be tested with a reactive solution containing hydroxyl to obtain hydrogen, and fully reacting the negative pole piece with the reactive solution containing hydroxyl in a sealed environment;
and determining the lithium precipitation content of the negative pole piece according to the hydrogen content.
Optionally, the lithium ion battery to be tested is disassembled to obtain the negative pole piece of the lithium ion battery to be tested, and the negative pole piece is reacted with the reactive solution containing hydroxyl to obtain hydrogen, including:
disassembling the lithium ion battery to be tested in a glove box, taking out the negative pole piece, and cleaning the taken out negative pole piece in an ester electrolyte organic solvent;
vacuum drying the cleaned negative pole piece in a transition bin for 5-30min;
and (3) putting the dried negative pole piece into a reaction container, adding a reactive solution containing hydroxyl, and fully reacting the negative pole piece with the reactive solution containing hydroxyl for 30-90min, wherein the reaction container is a closed container.
Optionally, the organic solvent of the ester electrolyte is one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and ethanol.
Optionally, the reactive solution containing hydroxyl groups is at least one of water, methanol, ethanol, formic acid, and acetic acid.
Optionally, the detection mode of hydrogen content is to detect the hydrogen concentration in the reaction gas, the reaction gas is the gas in the sealed container after the negative pole piece reacts with the reactive solution containing hydroxyl in the sealed container, and the hydrogen concentration value is obtained by detecting through a gas chromatograph, and the gas chromatograph detection step includes:
introducing standard gas with a first concentration to obtain a first peak area, introducing standard gas with a second concentration to obtain a second peak area, and introducing standard gas with a third concentration to obtain a third peak area, wherein the standard gas is hydrogen;
establishing a relation between the peak area and the hydrogen concentration by applying a regression analysis method according to the first concentration, the first peak area, the second concentration, the second peak area, the third concentration and the third peak area;
extracting 5-20mL of reaction gas, injecting the reaction gas into a gas quantitative ring of a gas chromatograph, and detecting to obtain a fourth peak area;
and obtaining a hydrogen concentration value in the reaction gas according to the fourth peak area and the relational expression of the peak area and the hydrogen concentration.
As can be seen from the above, the method for detecting the lithium analysis content of the lithium ion battery provided in the embodiment of the present invention includes: discharging the lithium ion battery to be tested until the SOC is 0%, wherein the discharging mode is constant current and constant voltage discharging, the constant current is 0.1-1C, and the constant voltage cutoff current is 0.01-0.1C; fully reacting a negative pole piece obtained by disassembling the lithium ion battery to be tested with a reactive solution containing hydroxyl to obtain hydrogen, and fully reacting the negative pole piece with the reactive solution containing hydroxyl in a sealed environment; and determining the lithium precipitation content of the negative pole piece according to the hydrogen content.
By applying the embodiment of the invention, the lithium-intercalated graphite in the lithium ion battery is ensured to be completely delithiated, and the detection precision of the content of the precipitated lithium in the lithium ion battery is improved. Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.
The innovation points of the embodiment of the invention comprise:
1. when the SOC of the lithium ion battery is more than 0%, the lithium ion battery indicates that lithium ions which are not deintercalated still exist in a negative electrode plate of the lithium ion battery, namely graphite, and the detection result of lithium precipitation in the negative electrode plate can be influenced by the part of lithium ions which are not completely deintercalated. In the embodiment of the invention, the lithium ion battery is adjusted to 0% SOC by adopting a constant current and constant voltage mode, the lithium intercalation graphite in the lithium ion battery is completely delithiated, and the detection result is only from precipitated dead lithium. The SOC of the battery is adjusted through a constant-current constant-voltage discharge mode, the influence of the lithium-intercalated graphite on a detection result is eliminated, and the detection precision of the lithium-separated content of the lithium ion battery is improved.
2. Lithium analysis in the lithium ion battery negative pole piece has characteristics such as uneven distribution, difficult peeling off, it is difficult to directly measure its content, determine the lithium analysis content in the lithium ion battery through measuring the content of lithium carbonate among the prior art, because lithium ion battery negative pole piece has thick SEI membrane, can contain lithium carbonate in the SEI membrane component, if obtain the lithium analysis content in the negative pole piece through detecting the volume of lithium carbonate, this will certainly mix the volume of lithium carbonate in the SEI membrane into the testing result too, lead to the testing result inaccurate. In the embodiment of the invention, the electrode plate for lithium analysis is reacted with a hydroxyl solution to generate hydrogen, and the content of the lithium analysis is calculated by detecting the amount of the hydrogen and utilizing a stoichiometric relation. Because only the metallic lithium can react with the hydroxyl solution to generate hydrogen, the influence of a lithium compound on a detection result is eliminated, and the detection precision of the content of the separated lithium in the lithium ion battery is effectively improved.
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. It is to be understood that the drawings in the following description are merely exemplary of some embodiments of the invention. For a person skilled in the art, without inventive effort, further figures can be obtained from these figures.
Fig. 1 is a schematic flow chart of a method for detecting a lithium analysis content of a lithium ion battery according to an embodiment of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
It is to be noted that the terms "comprises" and "comprising" and any variations thereof in the embodiments and drawings of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
The invention provides a method for detecting the lithium analysis content of a lithium ion battery. The following provides a detailed description of embodiments of the invention.
Fig. 1 is a schematic flow chart of a method for detecting a lithium analysis content of a lithium ion battery according to an embodiment of the present invention. The method may comprise the steps of:
s101: and discharging the lithium ion battery to be tested until the SOC is 0%, wherein the discharging mode is constant-current and constant-voltage discharging, the constant-current is 0.1-1C, and the constant-voltage cutoff current is 0.01-0.1C.
The lithium ion battery to be tested refers to a commercially available lithium ion battery, such as a lithium iron phosphate battery, a ternary battery, a lithium manganate battery, a lithium cobaltate battery and other common lithium ion batteries. The lithium ion battery to be tested needs to be completely discharged, so that all lithium ions are extracted from the negative electrode of the battery and transferred to the positive electrode of the battery, that is, after the lithium ion battery to be tested is discharged, the SOC (State of Charge) is 0%. If SOC is more than 0%, it indicates that some lithium ions are not extracted from the negative electrode of the battery, and in this case, the detected lithium precipitation amount will be larger than the real lithium precipitation amount, resulting in an inaccurate detection result. The battery can be adjusted to 0% SOC by using a constant current and constant voltage method, wherein the constant current is 0.1-1C, and the constant voltage cutoff current is 0.01-0.1C, where C is the charge/discharge rate, i.e., the current value required by the battery to discharge its rated capacity within a specified time, and is equal to the battery rated capacity in data value.
S102: and fully reacting the negative pole piece obtained by disassembling the lithium ion battery to be tested with a reactive solution containing hydroxyl to obtain hydrogen, and fully reacting the negative pole piece with the reactive solution containing hydroxyl in a sealed environment.
When the lithium ion battery to be tested is disassembled, the lithium ion battery needs to be disassembled in a glove box, and the negative pole piece is taken out. The negative pole piece and the reactive solution containing the hydroxyl are fully reacted, namely the negative pole piece needs to be completely submerged by the reactive solution containing the hydroxyl, and lithium precipitation in the negative pole piece and the reactive solution containing the hydroxyl are completely reacted. Since the amount of hydrogen generated after the reaction needs to be used to determine the content of lithium deposited, the negative electrode sheet and the reactive solution containing hydroxyl groups need to be reacted in a closed container to prevent hydrogen leakage.
In an alternative embodiment, the reactive solution containing hydroxyl groups is at least one of water, methanol, ethanol, formic acid, acetic acid.
It should be noted that the water here may be deionized water.
In an optional embodiment, the disassembling the lithium ion battery to be tested to obtain a negative electrode plate of the lithium ion battery to be tested, and reacting the negative electrode plate with a reactive solution containing hydroxyl to obtain hydrogen includes:
and disassembling the lithium ion battery to be tested in a glove box, taking out the negative pole piece, and cleaning the taken-out negative pole piece in an ester electrolyte organic solvent.
And (4) drying the cleaned negative pole piece in a transition bin in vacuum for 5-30min.
And putting the dried negative pole piece into a reaction container, adding the hydroxyl-containing reactive solution, and fully reacting the negative pole piece with the hydroxyl-containing reactive solution for 30-90min, wherein the reaction container is a closed container.
It should be noted that, because lithium deposition in the negative electrode plate is easy to react with water, carbon dioxide, etc. in the air, it is necessary to vacuumize the closed container containing the negative electrode plate, and then fill inert gas, such as nitrogen, argon, etc., until the air pressure in the cavity of the closed container returns to the normal pressure state, and then add the reactive solution containing hydroxyl. After the negative pole piece and the reactive solution containing the hydroxyl are fully reacted, the mixed gas in the closed container after the reaction can be measured, the hydrogen content in the mixed gas is determined, and the lithium analysis content is deduced and calculated according to the stoichiometric relation of the hydrogen content.
In addition, before the negative electrode plate reacts with the reactive solution containing hydroxyl, the detection system needs to be verified and adjusted to ensure the accuracy of the detection system and control the detection error. The specific method can be, for example, detecting the lithium metal as a test object according to a detection rule, calculating a measurement error, and if the error is large, adjusting a detection system to improve the detection accuracy.
In an alternative embodiment, the ester electrolyte organic solvent is one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and ethanol.
S103: and determining the lithium analysis content of the negative pole piece according to the hydrogen content.
And determining the content of the lithium separated out in the negative pole piece by detecting the content of hydrogen in the reaction gas. There are various detection methods for detecting the content of hydrogen in the reaction gas, for example, detecting the volume of hydrogen generated, the concentration of hydrogen in the mixed gas after the reaction, the amount of the substance generating hydrogen by the reaction, and the like. Among them, the method of detecting the volume of generated hydrogen includes a water discharge method, an upward air discharge method, and the like, or a common gas collection method. The method for detecting the hydrogen concentration in the mixed Gas after the reaction includes a common Gas concentration detection method such as GC (Gas Chromatography). The method of detecting the amount of the hydrogen species generated by the reaction is a displacement reaction of hydrogen and a metal oxide. For example, the displacement reaction of hydrogen and metallic copper, the displacement reaction of hydrogen and metallic iron, the chemical equation is:
H 2 +CuO＝Cu+H 2 O
H 2 +FeO＝Fe+H 2 O
h can be determined by determining the contents of Cu and Fe 2 And further obtaining the content of the lithium separated out from the negative pole piece of the battery.
In an optional embodiment, the detecting manner of the hydrogen content is to detect a hydrogen concentration in a reaction gas, the reaction gas is a gas in a sealed container after the negative electrode plate reacts with the reactive solution containing the hydroxyl group in the sealed container, and the hydrogen concentration value is obtained by detecting with a gas chromatograph, and the detecting with the gas chromatograph includes:
and introducing standard gas with a first concentration to obtain a first peak area, introducing standard gas with a second concentration to obtain a second peak area, and introducing standard gas with a third concentration to obtain a third peak area, wherein the standard gas is hydrogen.
And establishing a relation between the peak area and the hydrogen concentration by applying a regression analysis method according to the first concentration, the first peak area, the second concentration, the second peak area, the third concentration and the third peak area.
And extracting 5-20mL of the reaction gas, injecting the reaction gas into a gas quantitative ring of the gas chromatograph, and detecting to obtain a fourth peak area.
And obtaining a hydrogen concentration value in the reaction gas according to the fourth peak area and the relational expression of the peak area and the hydrogen concentration.
It should be noted that the hydrogen concentration values of the first concentration, the second concentration and the third concentration are different from each other, and it is needless to say that hydrogen of two concentrations or hydrogen of multiple concentrations may be introduced, and the relationship between the peak area and the hydrogen gas concentration may be established by using a regression analysis method. 5-20mL of the reaction gas may be withdrawn, and the withdrawn reaction gas may be injected into a gas quantification loop of the GC apparatus and detected. And converting the peak area obtained by detection into a concentration value by using a conversion relation established by the standard gas, wherein the peak area detected by aiming at the reaction gas is the fourth peak area. And finally, converting the hydrogen content into the lithium analysis amount by utilizing the stoichiometric relation of chemical reaction.
For further understanding of the present invention, the following will describe the procedure of the method for detecting the lithium content of a lithium ion battery provided by the present invention in detail with reference to the following examples, and the scope of the present invention is not limited by the following examples.
Example 1
Weighing 5mg of metal lithium sheets in a glove box, putting the metal lithium sheets into a 500mL conical flask, plugging the conical flask into a bottle plug, and taking out the conical flask; injecting 10mL of deionized water into the conical flask, gradually dissolving the lithium sheet and generating hydrogen until the hydrogen completely disappears, and finishing the reaction; respectively introducing three bottles of standard gas into GC equipment, wherein the standard gas is hydrogen, the hydrogen concentrations are respectively 16%,21.6% and 31.6%, and the detection is carried out for 3 times; in the obtained map, the hydrogen concentration corresponding to each peak was noted. Dragging the maps corresponding to the three concentration gradients into a calibration straight line, establishing a calibration straight line and an equation to obtain A =31026.7C, wherein A is the peak area of hydrogen, C is the concentration of the hydrogen, and the unit of the concentration of the hydrogen is% v/v; 5mL of reacted gas is extracted, detection is carried out through a GC gas quantitative ring, the area value obtained by detection is converted into the hydrogen concentration according to the corresponding relation obtained by calibration, and finally the weight of the metal lithium is measured to be 5.05mg according to the reaction relation, and the measurement error is 1%.
It should be noted that, by using the metal lithium as the object for detection, the error caused by the detection system in the present embodiment can be evaluated, and the detection system includes the precision of the experimental device and the detection equipment. If the error is larger, the error influenced by the detection system can be reduced by debugging the detection system, so that the accuracy of the detection result is improved.
Example 2
Selecting a fresh NCM811 ternary soft package lithium ion battery with the battery capacity of 1Ah, wherein the NCM represents the main component Ni (nickel) Co (cobalt) Mn (manganese), and 811 represents the mixture ratio of the three components of 0.8; under the condition of the temperature of-5 ℃, the charging multiplying power is 1C, the cut-off Voltage is 4.25V, the discharging multiplying power is 0.5C, the cut-off Voltage is 2.0V, the capacity retention ratio is calculated after 20 cycles, the capacity retention ratio is 71.8 percent, then the battery is charged to 4.25V at the multiplying power of 1C, and then the battery is discharged to the cut-off Current of 0.1C at the Voltage of 2.0V by CCCV (Constant Current and Constant Voltage); disassembling the charged battery in a glove box, taking out the negative pole piece, cleaning the negative pole piece with propylene carbonate, putting the negative pole piece into a transition cabin after cleaning, and drying the negative pole piece for 30min in vacuum; putting the cleaned negative pole piece into a conical flask, plugging a plug and taking out; injecting 10mL of deionized water into the conical flask, gradually dissolving the lithium sheet and generating hydrogen until the hydrogen completely disappears, and finishing the reaction; 5mL of reacted gas is extracted and passes through a GC gas quantitative ring for detection; and converting the area value obtained by detection into hydrogen concentration according to the corresponding relation obtained by calibration, converting the hydrogen concentration into a lithium analysis amount according to the reaction relation, and finally obtaining the lithium analysis amount of 72.03mg by an actual measurement mode. In addition, the theoretical lithium deposition amount of 73.02mg can be calculated according to the battery capacity 1Ah and the capacity retention rate of 71.8%, so that the measurement error is 1.6%.
It should be noted that, in the application, the fresh battery is used as an experimental object, so that errors caused by other factors on the capacity retention rate are avoided, and further, the measurement errors are reduced. The fresh battery is circulated at a high rate under the condition of low temperature of minus 5 ℃, so that the lithium precipitation of the battery can be realized. The present example was carried out on the assumption that the capacity fade of the battery was completely converted into lithium deposition.
Example 3
Example 3 is a parallel sample of example 2, and a fresh NCM811 ternary soft-package lithium ion battery with a battery capacity of 1Ah is selected, wherein NCM represents a main component Ni (nickel) Co (cobalt) Mn (manganese), and 811 represents a mixture ratio of three components of 0.8; under the condition of the temperature of-5 ℃, the charging multiplying power is 1C, the cut-off Voltage is 4.25V, the discharging multiplying power is 0.5C, the cut-off Voltage is 2.0V, the capacity retention ratio is calculated after 20 cycles, the capacity retention ratio is 72.0 percent, then the battery is charged to 4.25V at the multiplying power of 1C, and then the battery is discharged to the cut-off Current of 0.1C at the Voltage of 2.0V by CCCV (Constant Current and Constant Voltage); disassembling the charged battery in a glove box, taking out the negative pole piece, cleaning the negative pole piece with propylene carbonate, putting the negative pole piece into a transition cabin after cleaning, and drying the negative pole piece for 30min in vacuum; putting the cleaned negative pole piece into a conical flask, plugging a plug and taking out; injecting 10mL of deionized water into the conical flask, gradually dissolving the lithium sheet and generating hydrogen until the hydrogen completely disappears, and finishing the reaction; 5mL of reacted gas is extracted and passes through a GC gas quantitative ring for detection; and converting the area value obtained by detection into hydrogen concentration according to the corresponding relation obtained by calibration, converting the area value into lithium analysis amount according to the reaction relation, and finally obtaining the lithium analysis amount of 70.97mg by an actual measurement mode. In addition, the theoretical lithium deposition amount can be calculated according to the battery capacity 1Ah and the capacity retention rate of 72.0 percent to be 72.50mg, so the measurement error can be 2.1 percent.
It can be seen from example 1 that, when metal lithium is used as an object for detection, the measurement error is only 1%, which indicates that the detection system of the embodiment of the invention has a small error, and from examples 2 and 3, the detection result error of the lithium ion battery lithium analysis content is within 5%, so that the method for detecting the lithium ion battery lithium analysis content has high accuracy and good stability.
The system and apparatus embodiments correspond to the system embodiment, and have the same technical effects as the method embodiment, and for the specific description, reference is made to the method embodiment. The device embodiment is obtained based on the method embodiment, and for specific description, reference may be made to the method embodiment section, which is not described herein again. Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
Those of ordinary skill in the art will understand that: modules in the devices in the embodiments may be distributed in the devices in the embodiments according to the description of the embodiments, or may be located in one or more devices different from the embodiments with corresponding changes. The modules of the above embodiments may be combined into one module, or further split into multiple sub-modules.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (5)
1. A method for detecting the lithium analysis content of a lithium ion battery is characterized by comprising the following steps:
discharging the lithium ion battery to be tested until the SOC is 0%, wherein the discharging mode is constant current and constant voltage discharging, the constant current is 0.1-1C, and the constant voltage cutoff current is 0.01-0.1C;
fully reacting a negative pole piece obtained by disassembling the lithium ion battery to be tested with a reactive solution containing hydroxyl to obtain hydrogen, and fully reacting the negative pole piece with the reactive solution containing hydroxyl in a sealed environment;
and determining the lithium analysis content of the negative pole piece according to the hydrogen content.
2. The method of claim 1, wherein the disassembling the lithium ion battery to be tested to obtain a negative electrode plate of the lithium ion battery to be tested, and the reacting the negative electrode plate with a reactive solution containing hydroxyl groups to obtain hydrogen comprises:
disassembling the lithium ion battery to be tested in a glove box, taking out the negative pole piece, and cleaning the taken out negative pole piece in an ester electrolyte organic solvent;
vacuum drying the cleaned negative pole piece in a transition bin for 5-30min;
and putting the dried negative pole piece into a reaction container, adding the hydroxyl-containing reactive solution, and fully reacting the negative pole piece with the hydroxyl-containing reactive solution for 30-90min, wherein the reaction container is a closed container.
3. The method of claim 2, wherein the ester electrolyte organic solvent is one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and ethanol.
4. The method of claim 1, wherein the reactive solution containing hydroxyl groups is at least one of water, methanol, ethanol, formic acid, acetic acid.
5. The method of claim 1, wherein the hydrogen content is detected by detecting the hydrogen concentration in a reaction gas in a sealed container after the reaction between the negative electrode plate and the reactive solution containing hydroxyl groups, and the hydrogen concentration value is detected by a gas chromatograph, and the detecting step by the gas chromatograph comprises:
introducing standard gas with a first concentration to obtain a first peak area, introducing standard gas with a second concentration to obtain a second peak area, and introducing standard gas with a third concentration to obtain a third peak area, wherein the standard gas is hydrogen;
establishing a relational expression between the peak area and the hydrogen concentration by applying a regression analysis method according to the first concentration, the first peak area, the second concentration, the second peak area, the third concentration and the third peak area;
extracting 5-20mL of the reaction gas, injecting the reaction gas into a gas quantitative ring of the gas chromatograph, and detecting to obtain a fourth peak area;
and obtaining a hydrogen concentration value in the reaction gas according to the fourth peak area and the relational expression of the peak area and the hydrogen concentration.
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