Method for measuring actual pre-lithium amount of pre-lithium ion battery
阅读说明：本技术 一种预锂锂离子电池实际预锂量的测定方法 (Method for measuring actual pre-lithium amount of pre-lithium ion battery ) 是由 刘浩 于 2020-12-03 设计创作，主要内容包括：本发明提供一种预锂锂离子电池实际预锂量的测定方法,所述测定方法利用预锂电池和未预锂电池在充放电时电压差分曲线的特征峰之间的电池容量变化值的差别,来计算实际预锂量,解决了现有高预锂量情况下无法判断实际预锂量的问题,而且该方法简单快捷、准确性高、无需昂贵的测试且不对电池造成额外的破坏,成本低,应用前景广阔。(The invention provides a method for measuring the actual pre-lithium amount of a pre-lithium ion battery, which calculates the actual pre-lithium amount by using the difference of battery capacity change values between characteristic peaks of voltage difference curves of a pre-lithium battery and a non-pre-lithium battery during charging and discharging, solves the problem that the actual pre-lithium amount cannot be judged under the existing high pre-lithium amount condition, and has the advantages of simplicity, rapidness, high accuracy, no need of expensive test, no additional damage to the battery, low cost and wide application prospect.)
1. A method for determining the actual amount of prelithium in a prelithium lithium ion battery, said method comprising the steps of:
(1) respectively performing charge and discharge circulation on a pre-lithium battery and a non-pre-lithium battery with the same design on the positive electrode and the negative electrode under the same condition, and processing a charge curve and/or a discharge curve to obtain a voltage difference curve;
(2) calculating corresponding battery capacity change values between the characteristic peaks according to the characteristic peaks of the voltage difference curve;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
2. The method according to claim 1, wherein the positive electrode in the pre-lithium battery and the non-pre-lithium battery in the step (1) comprises a unitary positive electrode material, a binary positive electrode material, a ternary positive electrode material or a quaternary positive electrode material.
3. The assay of claim 1 or 2, wherein the negative electrode in the pre-lithium and non-pre-lithium cells in step (1) comprises a graphite material;
preferably, the negative electrode comprises a graphite negative electrode, a mixed negative electrode of graphite and silicon oxygen or a mixed electrode of graphite and silicon carbon;
preferably, when the positive electrode materials of the pre-lithium battery and the non-pre-lithium battery are non-lithium iron phosphate, third electrodes are arranged in the pre-lithium battery and the non-pre-lithium battery, and a voltage difference curve is obtained by processing a charging curve and/or a discharging curve of graphite to the third electrodes.
4. The method according to any one of claims 1 to 3, wherein in the step (1), when the pre-lithium battery and the non-pre-lithium battery are lithium iron phosphate graphite batteries, a voltage difference curve is obtained by processing a charging curve and/or a discharging curve of the lithium iron phosphate graphite batteries;
preferably, when the positive electrode materials of the pre-lithium battery and the non-pre-lithium battery in the step (1) are non-lithium iron phosphate, the charging curve and/or the discharging curve of the negative electrode to the third electrode is processed to obtain a voltage difference curve.
5. The method according to any one of claims 1 to 4, wherein the processing in step (1) includes differential processing.
6. The method according to any one of claims 1 to 5, wherein the theoretical pre-lithium amount of the pre-lithium battery in the step (1) is 4 to 50%.
7. The method according to any one of claims 1 to 6, wherein the temperature of the charge-discharge cycle in step (1) is 0 to 60 ℃;
preferably, the cycle number of the charge-discharge cycle is 1-5 weeks;
preferably, the cycle rate of the charge-discharge cycle is 0.01-0.2C.
8. The method according to any one of claims 1 to 7, wherein the characteristic peak in the step (2) comprises LiC12Peak and LiC6Peak(s).
9. The method according to any one of claims 1 to 8, wherein LiC in the step (2) is determined from the voltage difference curve12Peak and LiC6Peak, calculated LiC in Voltage Difference Curve12Peak and LiC6The corresponding battery capacity variation value between peaks.
10. The assay according to any one of claims 1 to 9, wherein the method comprises the steps of:
(1) respectively performing charge and discharge circulation on a pre-lithium battery and a non-pre-lithium battery with the same design on the positive electrode and the negative electrode under the same condition, and performing differential processing on a charge curve and/or a discharge curve to obtain a voltage differential curve;
the temperature of the charge-discharge cycle is 0-60 ℃, the cycle number is 1-5 weeks, and the cycle multiplying power is 0.01-0.2 ℃;
(2) LiC according to the voltage difference curve12Peak and LiC6Peak, calculated LiC in Voltage Difference Curve12Peak and LiC6The corresponding battery capacity variation value between peaks;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery test, and particularly relates to a method for measuring the actual pre-lithium amount of a pre-lithium ion battery.
Background
At present, the electric automobile industry is rapidly developed, so that the dependence of people on fossil energy can be reduced, and the pollution of tail gas to the environment can be reduced.
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.
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 the loss of lithium as a positive electrode material, thereby reducing the capacity of the battery, resulting in a decrease in the first efficiency. By supplementing lithium to the negative electrode, the problem that the first effect of graphite is lower can be solved, and partial active lithium is stored in the negative electrode, so that the loss of active lithium in the early stage of battery cycle can be solved, and the cycle life of the battery can be effectively prolonged.
CN104201320A discloses a method for prelithiation of electrode material of lithium ion battery, the cathode cavity of the electrolytic cell is electrode material such as lithium ion negative electrode material, which is put in organic electrolyte with lithium ion conductivity; the anode cavity is aqueous solution or organic solution containing lithium salt; the anode cavity and the cathode cavity are separated by a lithium ion conductor ceramic membrane or a composite membrane of the lithium ion conductor ceramic and a high polymer material; and controlling the potential and current density by an external circuit charging and discharging device to ensure that lithium ions are transferred from the anode to the cathode through the diaphragm, so as to form an SEI film on the surface of the material or pre-lithiate the electrode material.
CN111710918A discloses a lithium ion battery with a pre-lithiated negative electrode and a manufacturing method thereof, which manufactures a pre-lithiated negative electrode current collector; coating the prepared negative electrode slurry on the pre-lithiated negative electrode current collector to prepare a negative electrode sheet; and preparing the negative electrode prelithiated lithium ion battery by using the negative electrode sheet.
CN109671999A and CN111430659A disclose methods for prelithiation of negative electrodes of lithium ion batteries, and thus show that there are a lot of methods and studies for prelithiation in the prior art, but there are few studies on how to calculate the actual amount of prelithiation.
The theoretical calculation of the amount of lithium to be added is generally based on the mass of lithium (or a lithium compound) to be added and the theoretical gram capacity of lithium (or a lithium compound). In practical application, the capacity of the battery is increased along with the increase of the lithium supplement amount, but when the lithium supplement amount reaches a certain degree, the gram capacity of the positive electrode reaches a theoretical value; the amount of lithium supplement continues to increase, and the capacity of the battery does not increase any more, at which point the actual amount of pre-lithium cannot be determined by the increase in capacity of the battery.
Therefore, there is an urgent need for a method for determining the actual pre-lithium amount of pre-lithium cells, especially at high pre-lithium amounts.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a method for measuring the actual pre-lithium amount of a pre-lithium ion battery, which solves the problem that the actual pre-lithium amount cannot be judged under the condition of high pre-lithium amount in the prior art, can detect the pre-lithium ion battery with the pre-lithium amount being more than or equal to 4 percent, and has high measurement accuracy and wide application prospect.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for measuring the actual pre-lithium amount of a pre-lithium ion battery, which comprises the following steps:
(1) respectively performing charge and discharge circulation on a pre-lithium battery and a non-pre-lithium battery with the same design on the positive electrode and the negative electrode under the same condition, and processing a charge curve and/or a discharge curve to obtain a voltage difference curve;
(2) calculating corresponding battery capacity change values between the characteristic peaks according to the characteristic peaks of the voltage difference curve;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
According to the method, the corresponding battery capacity change values between the characteristic peaks are calculated by utilizing the different state change conditions of the graphite in the pre-lithium battery and lithium in the charging and discharging processes and combining the characteristic peaks of the voltage difference curve, so that the actual pre-lithium amount of the pre-lithium battery is calculated according to the difference value of the pre-lithium battery and the non-pre-lithium battery. The lithium intercalation mode of graphite in the negative electrode of the method is an intercalation lithium intercalation mode, and the negative electrode is charged by C → LiC24→LiC12→LiC6The reverse during discharge; since N/P is greater than 1 in general, LiC is in a full-charge state12And LiC6A coexistence state; as shown in FIG. 2, LiC can be found in the DV curve of negative electrode to lithium charge and discharge12And LiC6Corresponding characteristic peak, according to charging, LiC can be obtained12→LiC6Conversion or LiC6→LiC12And converting the corresponding lithium ion battery capacity. 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 (a) increases; by calculating LiC in the negative pole-to-lithium DV curve12→LiC6The actual pre-lithium amount can be obtained by the corresponding difference value of the capacity change of the lithium ion battery.
In the present invention, the discharge curve of the first week and the charge curve or the discharge curve of at least two weeks during the charge-discharge cycle can be used as the basic curves for processing the voltage difference curve.
And (2) preparing a unitary anode material, a binary anode material, a ternary anode material or a quaternary anode material in the lithium battery and the non-lithium battery in the step (1).
The unitary positive electrode material of the present invention includes lithium nickelate, lithium cobaltate, lithium manganate, lithium iron phosphate/lithium manganese phosphate, etc., and the unitary positive electrode material known to those skilled in the art may be used without any particular limitation.
The binary positive electrode material in the present invention includes lithium manganese iron phosphate or cobalt-free, and any binary positive electrode material known to those skilled in the art can be used without any particular limitation.
The ternary positive electrode material in the present invention includes NCM or NCA, and any ternary positive electrode material known to those skilled in the art can be used without any particular limitation.
The quaternary positive electrode material in the present invention includes NCMA, etc., and any quaternary positive electrode material known to those skilled in the art may be used without particular limitation.
Preferably, the negative electrode in the pre-lithium battery and the non-pre-lithium battery in the step (1) comprises a graphite material.
Preferably, the negative electrode comprises a graphite negative electrode, a mixed negative electrode of graphite and silicon oxygen, or a mixed electrode of graphite and silicon carbon.
Preferably, when the positive electrode is made of other materials except for lithium iron phosphate, the pre-lithium battery and the non-pre-lithium battery are provided with third electrodes, and a voltage difference curve is obtained by processing a charging curve and/or a discharging curve of graphite to the third electrodes.
When the negative electrode is graphite and the positive electrode is a non-lithium iron phosphate material, a third electrode needs to be arranged in the pre-lithium battery and the non-pre-lithium battery, and the charging curve and/or the discharging curve of the graphite to the third electrode are/is measured.
Preferably, when the pre-lithium battery and the non-pre-lithium battery in the step (1) are lithium iron phosphate graphite batteries, the charging curve and/or the discharging curve of the lithium iron phosphate graphite battery are/is processed to obtain a voltage difference curve.
When the anode material is lithium iron phosphate, the charging curve and/or the discharging curve can be directly measured by the battery, and the method is simple, convenient and quick.
Preferably, when the positive electrode materials of the pre-lithium battery and the non-pre-lithium battery in the step (1) are non-lithium iron phosphate, the charging curve and/or the discharging curve of the negative electrode to the third electrode is processed to obtain a voltage difference curve.
And when the negative electrode is graphite and the positive electrode is a non-lithium iron phosphate material, processing a charging curve and/or a discharging curve of the graphite to the third electrode to obtain a voltage difference curve.
Preferably, the processing in step (1) includes differential processing.
Preferably, the theoretical amount of pre-lithium in the pre-lithium battery in step (1) is 4 to 50%, and may be, for example, 4%, 5%, 7%, 9%, 14%, 19%, 24%, 30%, 35%, 40%, 45%, or 50%, etc., but is not limited to the recited values, and other values not recited in this range are also applicable.
The determination method disclosed by the invention can be suitable for the battery with the theoretical pre-lithium content of 4-50%, and fills the blank in the prior art.
Preferably, the temperature of the charge-discharge cycle in the step (1) is 0 to 60 ℃, and for example, it may be 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 28 ℃, 30 ℃, 32 ℃, 34 ℃, 37 ℃, 39 ℃, 41 ℃, 43 ℃, 45 ℃, 50 ℃, 55 ℃ or 60 ℃, etc., but not limited to the recited values, and other values not recited in the range are also applicable.
According to the invention, the temperature of the charge-discharge cycle is preferably controlled to be 0-60 ℃, so that side reactions in the charge-discharge cycle are avoided, and the accuracy of measurement is improved.
Preferably, the number of cycles of the charge and discharge cycle is 1 to 5 weeks, and may be, for example, 1 week, 2 weeks, 3 weeks, 4 weeks, or 5 weeks.
Preferably, the cycle magnification of the charge and discharge cycle is 0.01 to 0.2C, and may be, for example, 0.01C, 0.04C, 0.06C, 0.08C, 0.1C, 0.12C, 0.14C, 0.16C, 0.18C, or 0.2C, but is not limited to the values listed, and other values not listed in this range are also applicable, and preferably 0.05C.
The invention preferably adopts small-magnification circulation and has higher determination accuracy.
Preferably, the characteristic peak in step (2) comprises LiC12Peak and LiC6Peak(s).
Preferably, the LiC according to the voltage difference curve in step (2)12Peak and LiC6Peak, calculated LiC in Voltage Difference Curve12Peak and LiC6The corresponding battery capacity variation value between peaks.
Preferably, before the step (1), a step of calibrating the capacity of the pre-lithium battery and the non-pre-lithium battery is further included.
As a preferable technical scheme of the invention, the method comprises the following steps:
(1) respectively performing charge and discharge circulation on a pre-lithium battery and a non-pre-lithium battery with the same design on the positive electrode and the negative electrode under the same condition, and performing differential processing on a charge curve and/or a discharge curve to obtain a voltage differential curve;
the temperature of the charge-discharge cycle is 0-60 ℃, the cycle number is 1-5 weeks, and the cycle multiplying power is 0.01-0.2 ℃;
(2) LiC according to the voltage difference curve12Peak and LiC6Peak, calculated LiC in Voltage Difference Curve12Peak and LiC6The corresponding battery capacity variation value between peaks;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the method for measuring the actual pre-lithium amount of the pre-lithium ion battery is simple, rapid and high in accuracy, does not need expensive test, does not cause additional damage to the battery, and saves cost;
(2) compared with the conventional capacity exertion method, the method for measuring the actual pre-lithium amount of the pre-lithium ion battery has higher accuracy;
(3) the method for measuring the actual pre-lithium amount of the pre-lithium ion battery provided by the invention can be used for measuring the pre-lithium battery with the pre-lithium amount of more than or equal to 4%, especially can be used for measuring the pre-lithium battery with the pre-lithium amount of more than or equal to 7%, and fills the gap that the actual pre-lithium amount of the pre-lithium ion battery with high pre-lithium amount is difficult to measure in the prior art.
Drawings
Fig. 1 is a schematic diagram of structural changes in a process of lithium intercalation and deintercalation of graphite in the method for measuring an actual pre-lithium amount of a pre-lithium ion battery provided by the invention.
Fig. 2 is a schematic diagram of a voltage difference curve and a characteristic peak in a discharging process in the method for measuring an actual pre-lithium amount of the pre-lithium ion battery provided by the invention.
Fig. 3 is a schematic diagram of a voltage difference curve and a characteristic peak in a discharging process of a pre-lithium battery and a non-pre-lithium battery in example 1 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The invention provides a method for measuring the actual pre-lithium amount of a pre-lithium ion battery, which comprises the following steps:
(1) respectively performing charge and discharge circulation on a pre-lithium battery and a non-pre-lithium battery with the same design on the positive electrode and the negative electrode under the same condition, and performing differential processing on a charge curve and/or a discharge curve to obtain a voltage differential curve;
the temperature of the charge-discharge cycle is 0-60 ℃, the cycle number is 1-5 weeks, and the cycle multiplying power is 0.01-0.2 ℃;
(2) LiC according to the voltage difference curve12Peak and LiC6Peak, calculated LiC in Voltage Difference Curve12Peak and LiC6Battery capacity corresponding between peaksA change value;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
In the present invention, as shown in FIG. 1, the lithium intercalation mode of graphite in the negative electrode material is intercalation lithium intercalation mode, and the graphite in the negative electrode is C → LiC during charging24→LiC12→LiC6The reverse during discharge; since N/P is greater than 1 in general, LiC is in a full-charge state12And LiC6A coexistence state; as shown in FIG. 2, LiC can be found in the DV curve of negative electrode to lithium charge and discharge12And LiC6Corresponding characteristic peak, according to charging, LiC can be obtained12→LiC6Conversion or LiC6→LiC12And converting the corresponding lithium ion battery capacity. 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 (a) increases; by calculating LiC in the negative pole-to-lithium DV curve12→LiC6The actual pre-lithium amount can be obtained by the corresponding difference value of the capacity change of the lithium ion battery.
First, an embodiment
Example 1
This example provides a method for determining an actual pre-lithium amount of a pre-lithium ion battery, the method comprising the steps of:
(1) taking unprepared lithium batteries A10, B10 and C10, and pre-lithium batteries B11 (theoretical pre-lithium amount of 7%) and C11 (theoretical pre-lithium amount of 15%); the batteries a10, B11 and C11 were normal design batteries, the batteries B10 and C10 were batteries separately manufactured for calculating the actual amount of pre-lithium, and the batteries were lithium iron phosphate/graphite batteries, and the design parameters thereof are shown in table 1.
TABLE 1
"N/P" in Table 1 means the ratio of the actual capacity of the negative-positive electrode material per unit area.
At 25 ℃, carrying out capacity calibration on the batteries A10, B11, B10, C11 and C10 to determine the nominal capacity of the batteries;
carrying out small-magnification charge-discharge cycles on unprepared lithium batteries A10, B10 and C10 and pre-lithium batteries B11 and C11 at 25 ℃, wherein the magnification is selected to be 0.05C, and the charge-discharge cycles are carried out for 2 weeks to obtain a discharge curve of the second week;
the discharge curve is subjected to differential processing to obtain a voltage differential curve, namely a dV/dQ-Q curve;
(2) LiC according to the voltage difference curves of batteries a10, B11, B10, C11 and C1012Peak and LiC6Peak position, as shown in FIG. 3, LiC in the voltage difference curve was calculated12Peak and LiC6The corresponding battery capacity variation value between peaks;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
For comparison, the actual amount of pre-lithium in B11 and C11 was calculated by the conventional capacity exertion method and compared with the results calculated in example 1, and the results are shown in table 2.
TABLE 2
As can be seen from table 2, on one hand, the actual pre-lithium amount calculated in example 1 is closer to the theoretical value and has higher accuracy compared with the original capacity exertion method, and on the other hand, the method provided in example 1 can be used for measuring the lithium ion battery with higher pre-lithium amount, thereby solving the problem that the actual pre-lithium amount of the existing high pre-lithium battery cannot be measured.
Example 2
This example provides a method for determining an actual pre-lithium amount of a pre-lithium ion battery, the method comprising the steps of:
(1) taking non-pre-lithium batteries B20 and C20, and pre-lithium batteries B21 (theoretical pre-lithium amount of 7%) and C21 (theoretical pre-lithium amount of 15%); the batteries B21 and C21 are normal design batteries, the batteries B20 and C20 are batteries which are separately manufactured for calculating the actual pre-lithium amount, the negative electrode material of the batteries is a mixed electrode of graphite and silicon oxygen, and the positive electrode material is NCM 523; implanting a third electrode in the battery preparation process, wherein the third electrode adopts a copper wire lithium plating mode;
at 60 ℃, carrying out capacity calibration on the batteries B21, B20, C21 and C20 to determine the nominal capacity;
carrying out small-rate charge-discharge cycles on the non-pre-lithium batteries B20 and C20 and the pre-lithium batteries B21 and C21 at 60 ℃, wherein the rate is selected to be 0.01C, and the charge-discharge cycles are carried out for 5 weeks to obtain a 5-week discharge curve of the negative electrode to the third electrode;
the discharge curve is subjected to differential processing to obtain a voltage differential curve, namely a dV/dQ-Q curve;
(2) LiC according to the voltage difference curves of batteries B21, B20, C21 and C2012Peak and LiC6Peak position, calculating LiC in voltage difference curve12Peak and LiC6The corresponding battery capacity variation value between peaks;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
The method for measuring the actual pre-lithium amount of the pre-lithium ion battery provided in this embodiment is used for measuring a battery with a ternary NCM523 as a positive electrode material, but is not limited to the positive electrode material, and other materials can achieve similar effects.
Example 3
This example provides a method for determining an actual pre-lithium amount of a pre-lithium ion battery, the method comprising the steps of:
(1) taking non-pre-lithium batteries B30 and C30, and pre-lithium batteries B31 (theoretical pre-lithium amount of 25%) and C31 (theoretical pre-lithium amount of 50%); the batteries B31 and C31 are normal design batteries, the batteries B30 and C30 are batteries which are independently manufactured for calculating the actual pre-lithium amount, the negative electrode material of the batteries is graphite, and the batteries are lithium iron phosphate/graphite batteries;
at 5 ℃, carrying out capacity calibration on the batteries B31, B30, C31 and C30 to determine the nominal capacity;
carrying out small-rate charge-discharge cycle on the non-pre-lithium batteries B30 and C30 and the pre-lithium batteries B31 and C31 at 5 ℃, wherein the rate is selected to be 0.2C, and the charge-discharge cycle lasts for 2 weeks to obtain a charge curve of the charge-discharge cycle at 2 weeks;
the charging curve is subjected to differential processing to obtain a voltage differential curve, namely a dV/dQ-Q curve;
(2) LiC according to the voltage difference curves of batteries B31, B30, C31 and C3012Peak and LiC6Peak position, calculating LiC in voltage difference curve12Peak and LiC6The corresponding battery capacity variation value between peaks;
(3) and obtaining the actual pre-lithium amount according to the difference value of the battery capacity change values in the pre-lithium battery and the non-pre-lithium battery.
In this embodiment, the pre-lithium battery with 25% and 50% pre-lithium amount is measured, and a charging curve is adopted, which is similar to that in embodiment 1, and can calculate to obtain a more accurate actual pre-lithium amount.
Example 4
This example provides a method for determining the actual pre-lithium amount of a pre-lithium ion battery, which is the same as in example 1 except that the temperature of the charge-discharge cycle in step (1) is 70 ℃.
In example 4, since the temperature of the charge/discharge cycle was relatively high and the number of side reactions was large in the charge/discharge cycle, the accuracy of the measurement was lower than that of comparative example 1, which indicates that the accuracy of the measurement was further improved by controlling the temperature of the charge/discharge cycle within a specific range.
In summary, the following steps: the method for measuring the actual pre-lithium amount of the pre-lithium ion battery solves the problem that the actual pre-lithium amount cannot be judged under the condition of high pre-lithium amount, is simple, quick and high in accuracy, does not need expensive test, does not cause additional damage to the battery, and is low in cost and wide in application prospect.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.