CN115128467A - Method and device for estimating negative electrode capacity of lithium battery - Google Patents
Method and device for estimating negative electrode capacity of lithium battery Download PDFInfo
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Abstract
The invention discloses a method and a device for estimating the negative electrode capacity of a lithium battery. The method for estimating the negative electrode capacity of the lithium battery comprises the following steps: carrying out constant current charging on a fully discharged battery to be tested; determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant current charging process; and calculating the negative electrode capacity of the battery to be tested according to the difference value between the electric quantities corresponding to the two phase change points. According to the estimation method, the estimation can be completed through data processing in the constant-current charging process of the battery to be detected, the button battery is manufactured without disassembling the battery, the execution is convenient, and the cost is low. In addition, the estimation method does not need to predict the mass of the cathode active material, the estimation principle has an electrochemical principle and experimental data as supports, and the accuracy is high.
Description
Technical Field
The embodiment of the invention relates to a battery design technology, in particular to a method and a device for estimating the negative electrode capacity of a lithium battery.
Background
Along with the development of society, the demand of people on electricity is increasing day by day, and the demand of modern society on electricity has wave crest and trough, causes the waste of energy, therefore the demand of modern society on energy storage is expanding gradually, and lithium cell has high energy conversion efficiency and high energy density as an electrochemical energy storage device, receives people's favor gradually.
In the design process of the lithium battery, the negative electrode capacity plays a crucial role in the performance of the lithium battery, and the current methods for estimating the negative electrode capacity of the lithium battery mainly comprise two methods: firstly, utilize lithium cell negative pole piece preparation button cell, utilize button cell actual measurement negative gram capacity, combine the dressing quality that the lithium cell negative pole used to extrapolate the negative pole capacity of lithium cell, the negative pole capacity of estimating according to this kind of method is comparatively accurate. Secondly, under the condition that the mass of the negative electrode material is known, the theoretical gram capacity of the negative electrode material is combined to calculate the negative electrode capacity, and the method is less difficult.
However, the first estimation method for manufacturing a button battery by using a negative electrode plate of a lithium battery is long in time consumption and high in cost; the second estimation method combining the theoretical gram capacity of the cathode material has poor accuracy.
Disclosure of Invention
The invention provides a method and a device for estimating the negative electrode capacity of a lithium battery, which are used for realizing more convenient execution of the negative electrode capacity estimation and lower cost and improving the accuracy of the estimation result.
In a first aspect, an embodiment of the present invention provides a method for estimating a negative electrode capacity of a lithium battery, where the method for estimating a negative electrode capacity of a lithium battery includes:
carrying out constant current charging on a fully discharged battery to be tested;
determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to charging parameters in the constant-current charging process;
and calculating the negative electrode capacity of the battery to be tested according to the difference value between the electric quantities corresponding to the two phase change points.
Optionally, determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant current charging process, including:
determining a relation curve of voltage and electric quantity in the charging process of the battery to be tested according to the charging parameters;
carrying out differential processing on the relation curve to generate a charging differential curve;
and determining the at least two phase change points and the electric quantity corresponding to the at least two phase change points according to the charging differential curve.
Optionally, differentiating the relationship curve to generate a charging differential curve, including:
deriving the voltage in the relation curve to the electric quantity to obtain a charging differential curve;
determining the at least two phase change points from the charging differential curve, including:
acquiring a peak point in the charging differential curve;
and determining the peak point as the phase change point.
Optionally, calculating the negative electrode capacity of the battery to be tested according to the difference between the electric quantities corresponding to the two phase change points, including:
determining the difference of electric quantity between the two phase change points;
and multiplying the electric quantity difference by a preset multiple to obtain the negative electrode capacity of the battery to be detected.
Optionally, the phase change points include a first order phase change point and a second order phase change point;
calculating the negative electrode capacity of the battery to be tested according to the difference value between the electric quantities corresponding to the two phase change points, and the method comprises the following steps:
acquiring a first electric quantity corresponding to the first-order phase change point and a second electric quantity corresponding to the second-order phase change point;
the first electric quantity is differentiated from the second electric quantity to obtain an electric quantity difference value;
and multiplying the electric quantity difference by a preset multiple to obtain the negative electrode capacity of the battery to be tested.
Optionally, the negative electrode material of the battery to be tested is graphite; the preset multiple is equal to 3.
Optionally, before the constant current charging of the fully discharged battery to be tested, the method further includes:
acquiring the actual capacity of the battery to be tested;
after the negative electrode capacity of the battery to be tested is calculated according to the difference value between the electric quantities corresponding to the two phase change points, the method further comprises the following steps:
and determining the balance ratio of the battery to be tested according to the actual capacity and the negative electrode capacity.
Optionally, the obtaining the actual capacity of the battery to be tested includes:
charging the battery to be tested to a full charge state by adopting a constant current and constant voltage mode;
performing constant-current discharge on the fully charged battery to be detected until the battery to be detected reaches a fully discharged state;
and taking the total electric quantity discharged by the battery to be tested in the constant current discharging process as the actual capacity of the battery to be tested.
Optionally, the charging the battery to be tested to a full charge state in a constant current and constant voltage mode includes:
and carrying out constant current charging on the battery to be tested by adopting a first preset current until the voltage of the battery to be tested reaches a full charge voltage:
standing the battery to be tested for a preset time;
and carrying out constant voltage charging on the battery to be tested by adopting a first preset voltage until the current of the battery to be tested reaches a full charging current.
In a second aspect, an embodiment of the present invention further provides an estimation apparatus for negative electrode capacity of a lithium battery, where the estimation apparatus for negative electrode capacity of a lithium battery includes: the charging module is used for carrying out constant-current charging on a fully discharged battery to be tested; the phase change point determining module is used for determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant current charging process; and the negative electrode capacity module is used for calculating the negative electrode capacity of the battery to be tested according to the difference value between the electric quantities corresponding to the two phase change points.
According to the estimation method for the negative electrode capacity of the lithium battery, provided by the embodiment of the invention, at least two phase change points and electric quantity corresponding to the at least two phase change points of the battery to be detected, which are subjected to phase change due to lithium intercalation, are determined according to the charging parameters of the battery to be detected in the constant current charging process, and the negative electrode capacity is calculated according to the relative relation between the electric quantity difference of the electric quantities corresponding to any two phase change points and the negative electrode capacity, so that the estimation of the negative electrode capacity of the battery is realized. In addition, the estimation method does not need to predict the mass of the cathode active material, the estimation principle has an electrochemical principle and experimental data as supports, and the accuracy is high.
Drawings
Fig. 1 is a flowchart of a method for estimating a negative electrode capacity of a lithium battery according to an embodiment of the present invention;
fig. 2 is a flowchart of another method for estimating the negative electrode capacity of a lithium battery according to an embodiment of the present invention;
fig. 3 is a flowchart of another method for estimating the negative electrode capacity of a lithium battery according to an embodiment of the present invention;
fig. 4 is a schematic diagram of charging parameter differential curves of negative half-cells of a plurality of cells to be tested of the same type according to an embodiment of the present invention;
fig. 5 is a flowchart of another method for estimating the negative electrode capacity of a lithium battery according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an estimation apparatus for negative electrode capacity of a lithium battery according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As mentioned in the background, the negative electrode capacity plays a crucial role in the performance of lithium batteries. In the optimization design of lithium batteries, negative electrode capacity estimation of finished lithium batteries is often required. The existing estimation method for the negative electrode capacity of the lithium battery mainly comprises two methods: firstly, utilize lithium cell negative pole piece preparation button cell, utilize button cell actual measurement negative gram capacity, combine the dressing quality that the lithium cell negative pole used to extrapolate the negative pole capacity of lithium cell, estimate negative pole capacity according to this kind of method and consume long and with high costs. Secondly, under the condition that the mass of the negative electrode material is known, the theoretical gram capacity of the negative electrode material is combined to calculate the negative electrode capacity, and the method is poor in accuracy. The inventor researches and finds that the two estimation modes have the following problems: the finished lithium battery is required to be disassembled by estimating the negative electrode capacity of the lithium battery in a first mode, the negative electrode pole piece is taken out to manufacture the button battery, the gram negative electrode capacity of the button battery is measured through experiments, and then the negative electrode energy of the lithium battery is reversely pushed in proportion. This kind of mode needs to disassemble finished product lithium cell and make button cell, and the lithium cell after disassembling can not reuse, and the cost is higher, and preparation button cell and experiment are consuming time and hard. The second method for estimating the negative electrode capacity of the lithium battery requires knowing the quality of the negative electrode material of the lithium battery, has a narrow application range, and is poor in reliability because the negative electrode capacity is calculated only according to the theoretical gram capacity of the negative electrode material without experimental basis.
In order to solve the above problem, an embodiment of the present invention provides an estimation method for a negative electrode capacity of a lithium battery, which may be implemented by using an estimation apparatus for a negative electrode capacity of a lithium battery, and the apparatus may be integrated in a monitoring system of a lithium battery. Fig. 1 is a flowchart of a method for estimating a negative electrode capacity of a lithium battery according to an embodiment of the present invention, and referring to fig. 1, the method for estimating a negative electrode capacity of a lithium battery includes:
and S101, performing constant current charging on the fully discharged battery to be tested.
The full discharge refers to a state when the battery to be tested discharges to the minimum voltage, and the electric quantity of the battery to be tested in the state is 0.
Specifically, after the battery to be tested is discharged until the electric quantity is 0, the battery to be tested is subjected to constant current charging by using the charging and discharging device, and the current of the constant current charging is a constant preset current so as to ensure that the electric quantity of the battery to be tested is stably increased, and exemplarily, the preset current may be less than 0.1C. In the process of constant-current charging, charging parameters of a battery to be tested need to be recorded, and the recording mode can be real-time monitoring and storage, or collection once every preset time. The charging parameters refer to data reflecting the charging state of the battery to be tested, and may include voltage and quantity of electricity.
S102, determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to charging parameters in the constant-current charging process.
The phase change point refers to a data point when the negative electrode of the battery to be tested generates phase change due to lithium intercalation.
Specifically, in the process of constant current charging, as lithium is inserted into the negative electrode material, the negative electrode material undergoes multiple phase changes, which include first-order phase changes, second-order phase changes, and third-order phase changes. The occurrence sequence of each phase change is fixed, the electric quantity difference between the phase change points is related to the negative electrode capacity, the ratio is fixed, the ratio of the electric quantity difference between the two phase change points to the negative electrode capacity is a preset value, and the preset value can be obtained according to experiment and experience parameters. The data processing device can determine the phase change point of the battery to be tested, which is caused by the phase change of the lithium intercalation according to the charging parameters, illustratively, the relationship curve between the electric quantity of the battery to be tested and the corresponding voltage can be generated according to the charging parameters, wherein the voltage is the voltage at two ends of the battery to be tested, and the electric quantity is the stored electric quantity of the battery to be tested, namely the electric quantity of the full battery. And then the relation curve is subjected to derivative on the electric quantity to obtain a differential curve. A plurality of phase change points can be determined from a plurality of peaks of the differential curve.
S103, calculating the negative electrode capacity of the battery to be measured according to the difference value between the electric quantities corresponding to the two phase change points.
The electric quantity corresponding to the phase change point is the stored electric quantity of the battery to be tested when the phase change occurs.
Specifically, after the phase change points and the electric quantities corresponding to the phase change points are determined, the difference between the electric quantities corresponding to any two phase change points can be calculated, and then the negative electrode capacity of the battery to be tested is calculated according to the proportional relation between the difference and the negative electrode capacity, wherein the proportional relation is related to the type of the negative electrode material, and the specific proportional relation can be obtained according to experiments. Illustratively, the difference value between the electric quantity when the first-order lithium intercalation occurs and the electric quantity when the second-order lithium intercalation occurs is a first difference value, and the ratio of the first difference value to the negative electrode capacity of the battery to be tested is 1/3, so that the first difference value can be multiplied by 3 to be used as the negative electrode capacity of the battery to be tested.
According to the estimation method for the negative electrode capacity of the lithium battery, at least two phase change points of the battery to be detected, which generate phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points are determined according to the charging parameters of the battery to be detected in the constant current charging process, and the negative electrode capacity is calculated according to the relative relation between the electric quantity difference of the electric quantities corresponding to any two phase change points and the negative electrode capacity, so that the estimation of the negative electrode capacity of the battery is realized. In addition, the estimation method does not need to predict the mass of the cathode active material, the estimation principle has an electrochemical principle and experimental data as supports, and the accuracy is high.
Optionally, fig. 2 is a flowchart of another method for estimating the negative electrode capacity of the lithium battery according to an embodiment of the present invention, and referring to fig. 2, the method for estimating the negative electrode capacity of the lithium battery includes:
and S201, performing constant current charging on the fully discharged battery to be tested.
Step S201 is identical to step S101, and is not described herein again.
S202, determining a relation curve of voltage and electric quantity in the charging process of the battery to be tested according to the charging parameters.
The charging parameters refer to state data of the battery to be tested in the constant current charging process, and may include electric quantity and voltage.
Specifically, the voltage and the electric quantity data in the charging parameters correspond to each other one by one, and a relation curve of the voltage and the electric quantity of the battery to be measured can be determined according to the charging parameters of the battery to be measured in the constant current charging process. The relation curve can be determined by a data processing chip.
And S203, carrying out differential processing on the relation curve to generate a charging differential curve.
The charging differential curve is a differential curve of a relation curve of voltage and electric quantity, and may represent a relation between electric quantity and a differential value of voltage.
Specifically, the voltage in the relation curve may be derived to the electric quantity to obtain a charging differential curve. One variable of the differential charge curve is the capacity and the other is the differential of the voltage versus the charge. The differential curve can show the influence of the phase change of the cathode material due to lithium intercalation on the voltage of the battery to be tested.
S204, determining at least two phase change points and electric quantity corresponding to the at least two phase change points according to the charging differential curve.
Specifically, a peak point in the charging differential curve may be obtained according to a trend of the charging differential curve, where the peak point is a maximum point in the differential curve, and may be obtained according to an image recognition technology, or may be obtained by analyzing and processing data included in the differential curve. The peak points in the charging differential curve can then be determined as phase change points, one for each electrical quantity value.
And S205, determining the electric quantity difference between the two phase change points.
Specifically, the electric quantity difference value corresponding to the two phase change points is determined, and illustratively, the electric quantity corresponding to the phase change point where the first-order phase change occurs is subtracted from the electric quantity corresponding to the phase change point where the second-order phase change occurs, so that the electric quantity difference value between the first-order phase change and the second-order phase change of the battery to be tested can be obtained. The electric quantity difference value is the electric quantity value charged into the battery to be tested from the first-order phase change to the second-order phase change of the negative electrode of the battery to be tested, and can be recorded by a charging and discharging device.
And S206, multiplying the electric quantity difference value by a preset multiple to obtain the negative electrode capacity of the battery to be tested.
Specifically, the preset multiple may be determined according to the order of the two phase change points selected in the previous step and the type of the negative electrode material of the battery to be tested, for example, when the negative electrode material is graphite, the two phase change points may be selected to be a phase change point where a first-order phase change occurs and a phase change point where a second-order phase change occurs, and then the corresponding preset multiple is 3. And multiplying the electric quantity difference between the two phase change points by 3 to obtain the negative electrode capacity of the battery to be tested of the graphite negative electrode.
The method for estimating the negative electrode capacity of the lithium battery provided by the embodiment comprises the steps of determining a relation curve of battery electric quantity and battery voltage according to charging parameters in the constant-current charging process, then performing differential processing on the relation curve to obtain a charging differential curve, determining a phase change point and electric quantity corresponding to the phase change point in the constant-current charging process according to a peak value of the differential curve, and finally multiplying a difference value of the two phase change points by a preset multiple to obtain the negative electrode capacity of the battery to be detected.
Optionally, fig. 3 is a flowchart of another method for estimating the negative electrode capacity of a lithium battery according to an embodiment of the present invention, and referring to fig. 3, the method for estimating the negative electrode capacity of a lithium battery includes:
and S301, performing constant current charging on the fully discharged battery to be tested.
And S302, determining a relation curve of the voltage and the electric quantity in the charging process of the battery to be tested according to the charging parameters.
And S303, carrying out differential processing on the relation curve to generate a charging differential curve.
Steps S301, S302, and S303 are the same as steps S201, S202, and S203, respectively, and are not described again here.
And S304, determining a first-order phase change point and a second-order phase change point according to the charging differential curve.
The first-order phase change point refers to a data point when the negative electrode material of the battery to be tested undergoes first-order phase change in the constant-current charging process. Similarly, the second-order phase change point refers to a data point when the negative electrode material of the battery to be tested undergoes second-order phase change in the constant-current charging process.
Specifically, in the process of constant-current charging, the order of each-order phase change of the negative electrode material of the battery to be tested due to lithium intercalation is fixed, illustratively, along with lithium intercalation into the negative electrode, the order of the phase change of the graphite negative electrode material is four-order phase change, three-order phase change, diluted second-order phase change, second-order phase change and first-order phase change, because the voltage change rate at the initial charging stage is high, the phase change point of the first-order phase change and the second-order phase change is more easily determined according to the peak point of a differential curve, and two phase change points which are closest to a full-charge data point in all phase change points on the charging differential curve are the second-order phase change point and the first-order phase change point.
And S305, determining the electric quantity difference between the first-order phase change point and the second-order phase change point.
Specifically, the electric quantities of the first-order phase change point and the second-order phase change point can be respectively determined in the charging differential curve or the charging parameters, and then the electric quantity difference between the electric quantity of the first-order phase change point and the electric quantity of the second-order phase change point is calculated, wherein the electric quantity difference is the total electric quantity charged by the battery to be tested from the second-order phase change to the first-order phase change of the negative electrode material of the battery to be tested.
And S306, multiplying the electric quantity difference value by a preset multiple to obtain the negative electrode capacity of the battery to be tested.
Specifically, the ratio of the electric quantity difference between the first-order phase change point and the second-order phase change point to the negative electrode capacity is fixed and is related to the negative electrode material, and the preset multiple can be obtained according to experimental data.
Fig. 4 is a schematic diagram of a charging parameter differential curve of negative half-cells of a plurality of cells to be tested of the same type according to an embodiment of the present invention, where an abscissa of the charging parameter differential curve is a negative electric quantity of the negative half-cell of the cell to be tested, and an abscissa is a differential of a negative plate electric potential to the negative electric quantity, and data are obtained through experiments. And the phase change point in the differential curve obtained according to the actual charging parameter of the battery to be measured is a peak point, and on the contrary, the phase change point in the differential curve of the charging parameter of the negative half battery is a valley point. Referring to fig. 4, the first valley point a is a first-order phase transition point where the first-order phase transition of the negative electrode material occurs, and the corresponding negative electrode electric quantity is the first electric quantity C1. The second valley point B is a second-order phase change point at which the negative electrode material undergoes a second-order phase change, the corresponding negative electrode electric quantity is a second electric quantity C2, and the third valley point C is a third-order phase change point at which the negative electrode material undergoes a third-order phase change. Fig. 4 shows that when the negative electrode material is subjected to phase change caused by lithium intercalation, the voltage of the negative electrode plate changes abruptly with respect to the differential of the negative electrode electric quantity, and the positions of the phase change points of the batteries of the same batch and the same type (the same batch and the same type can be regarded as the same negative electrode capacity) are the same.
With reference to fig. 4, the electric quantity difference between the first-order transformation point and the second-order transformation point of the battery to be tested is equal to C1-C2, and the measured value of the negative electrode capacity of the battery to be tested is referred to as CN (not shown in fig. 4, CN is the measured value measured by disassembling and manufacturing the button battery). Based on this, the embodiment of the present invention further provides a summary table of a plurality of types of battery charging parameters to be tested, which lists the ratio CN/(C1-C2) between the measured value CN of the negative electrode capacity and the difference between the measured value CN of the negative electrode capacity and the measured value of the second-order phase change point electric quantity of the first-order phase change point C1, the electric quantity C2 of the second-order phase change point, which are obtained by the test, of the plurality of types of lithium batteries with graphite as the negative electrode, as follows:
TABLE 1 summary of charging parameters of multiple batteries to be tested
The ratio CN/(C1-C2) of the measured value of the negative electrode capacity and the difference in the two-stage transformation point electric quantity in table 1 is close to 3, and the error is within 0.02. Therefore, the experimental data show that the preset multiple adopted by the battery to be tested, the negative electrode material of which is graphite, in the process of estimating the negative electrode capacity of the lithium battery can be 3.
Therefore, the preset multiple can be obtained by measuring according to the method of the multiple experiments, and the negative electrode capacity of the battery to be tested can be obtained by multiplying the second-order phase change point electric quantity difference by the preset multiple.
According to the estimation method for the negative electrode capacity of the lithium battery, the first-order phase change point, the second-order phase change point and the electric quantities of the two phase change points can be determined according to the peak value in the charging differential curve, then, the electric quantity difference value between the electric quantity of the first-order phase change point and the electric quantity of the second-order phase change point is calculated, the negative electrode capacity of the lithium battery can be determined by multiplying the electric quantity difference value by the preset multiple, the quick estimation of the negative electrode capacity of the lithium battery is achieved, the negative electrode capacity can be obtained only through data analysis in the process, the battery disassembly and the experiment are avoided, the error between the estimated value and the true value is small, and the accuracy of the estimation method is further improved.
Optionally, fig. 5 is a flowchart of another method for estimating the negative electrode capacity of a lithium battery according to an embodiment of the present invention, and referring to fig. 5, the method for estimating the negative electrode capacity of a lithium battery includes:
s501, acquiring the actual capacity of the battery to be tested.
The actual capacity refers to an upper limit of the storable amount of electricity of the battery to be tested, and is also referred to as a full battery capacity.
Specifically, the battery to be tested may be charged to a full charge state in a constant current and constant voltage mode, where the constant current and constant voltage mode includes performing constant current charging on the battery to be tested until a full charge voltage is reached, standing the battery to be tested, and then performing constant voltage charging on the battery to be tested until a charging current reaches a cut-off current or less. And then, performing constant current discharge on the fully charged battery to be tested by adopting constant current until the battery to be tested reaches a full discharge state, wherein the constant current can be 0.1C. The full discharge state refers to a state that the electric quantity of the battery is discharged, and the voltage is smaller than the full discharge voltage as the full discharge standard. And finally, the total electric quantity discharged by the battery to be tested in the constant-current discharging process can be used as the actual capacity of the battery to be tested.
And S502, performing constant current charging on the fully discharged battery to be tested.
S503, determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant-current charging process.
And S504, calculating the negative electrode capacity of the battery to be measured according to the difference value between the electric quantities corresponding to the two phase change points.
Steps S502, S503 and S504 are the same as steps S101, S102 and S103, respectively, and are not described again here.
And S505, determining the balance ratio of the battery to be tested according to the actual capacity and the negative electrode capacity.
The balance ratio is a ratio of the negative electrode capacity per unit area to the full battery capacity per unit area, and is an important design parameter in battery design.
Specifically, the actual capacity is compared with the negative electrode capacity to obtain a balance ratio of the battery to be measured, namely an N/P ratio. Since there is an important criterion in designing the capacity of the battery, the negative electrode must have a larger reversible capacity than the positive electrode. Although batteries may have some advantages such as large capacity and high first efficiency when the capacity of the negative electrode is smaller, lithium deposition on the surface of the negative electrode may occur during charging, resulting in capacity loss and safety problems. In order to design an appropriate positive electrode capacity and negative electrode capacity, determination of a balance ratio is indispensable.
According to the method for estimating the negative electrode capacity of the lithium battery, before the fully discharged battery to be tested is subjected to constant current charging, the actual capacity of the battery to be tested is obtained by adopting the constant current and constant voltage charging and constant current discharging modes, and after the negative electrode capacity of the lithium battery is determined, the balance ratio is determined according to the ratio of the actual capacity to the negative electrode capacity, so that the determination of the balance ratio is realized, data support is provided for the capacity design of the battery, and the reliability of the design result of the battery capacity can be improved.
The embodiment of the invention also provides a device for estimating the negative electrode capacity of the lithium battery, which is used for implementing any one of the methods for estimating the negative electrode capacity of the lithium battery. Fig. 6 is a schematic structural diagram of an estimation apparatus for negative electrode capacity of a lithium battery according to an embodiment of the present invention, and referring to fig. 6, the estimation apparatus for negative electrode capacity of a lithium battery includes: the device comprises a charging module 601, a phase change point determining module 602 and a negative electrode capacity module 603, wherein the charging module 601 is used for performing constant current charging on a fully discharged battery to be tested; the phase change point determining module 602 is configured to determine, according to the charging parameters in the constant current charging process, at least two phase change points where the battery to be tested undergoes phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points; the negative electrode capacity module 603 is configured to calculate a negative electrode capacity of the battery to be tested according to a difference between electric quantities corresponding to the two phase change points.
According to the estimation method and the device for the negative electrode capacity of the lithium battery, provided by the embodiment of the invention, at least two phase change points and electric quantity corresponding to the at least two phase change points of the battery to be detected, which are caused by the phase change of the battery due to lithium intercalation, are determined according to the charging parameters of the battery to be detected in the constant current charging process, and the negative electrode capacity is calculated according to the relative relation between the electric quantity difference of the electric quantities corresponding to any two phase change points and the negative electrode capacity, so that the estimation of the negative electrode capacity of the battery is realized. In addition, the estimation method does not need to predict the mass of the cathode active material, the estimation principle has an electrochemical principle and experimental data as supports, and the accuracy is high.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A method for estimating the negative electrode capacity of a lithium battery is characterized by comprising the following steps:
charging the fully discharged battery to be tested at constant current;
determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to charging parameters in the constant-current charging process;
and calculating the negative electrode capacity of the battery to be tested according to the difference value between the electric quantities corresponding to the two phase change points.
2. The method for estimating the negative electrode capacity of the lithium battery according to claim 1, wherein determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant-current charging process comprises:
determining a relation curve of voltage and electric quantity in the charging process of the battery to be tested according to the charging parameters;
carrying out differential processing on the relation curve to generate a charging differential curve;
and determining the at least two phase change points and the electric quantity corresponding to the at least two phase change points according to the charging differential curve.
3. The method for estimating the negative electrode capacity of a lithium battery as claimed in claim 2, wherein the differentiating the relationship curve to generate a charging differential curve comprises:
deriving the voltage in the relation curve with the electric quantity to obtain a charging differential curve;
determining the at least two phase change points from the charging differential curve, including:
acquiring a peak point in the charging differential curve;
and determining the peak point as the phase change point.
4. The method for estimating the negative electrode capacity of the lithium battery as claimed in claim 1, wherein calculating the negative electrode capacity of the battery to be tested according to the difference between the electric quantities corresponding to the two phase change points comprises:
determining the difference of electric quantity between the two phase change points;
and multiplying the electric quantity difference by a preset multiple to obtain the negative electrode capacity of the battery to be tested.
5. The estimation method of the negative electrode capacity of a lithium battery according to claim 2, wherein the phase change point includes a first-order phase change point and a second-order phase change point;
calculating the negative electrode capacity of the battery to be detected according to the difference value between the electric quantities corresponding to the two phase change points, and the method comprises the following steps:
acquiring a first electric quantity corresponding to the first-order phase change point and a second electric quantity corresponding to the second-order phase change point;
the first electric quantity is differentiated from the second electric quantity to obtain an electric quantity difference value;
and multiplying the electric quantity difference by a preset multiple to obtain the negative electrode capacity of the battery to be tested.
6. The method of estimating negative electrode capacity of a lithium battery according to claim 5,
the negative electrode material of the battery to be tested is graphite; the preset multiple is equal to 3.
7. The method for estimating the negative electrode capacity of the lithium battery as claimed in claim 1, wherein before the fully discharged battery to be tested is subjected to constant current charging, the method further comprises:
acquiring the actual capacity of the battery to be tested;
after the negative electrode capacity of the battery to be tested is calculated according to the difference value between the electric quantities corresponding to the two phase change points, the method further comprises the following steps:
and determining the balance ratio of the battery to be tested according to the actual capacity and the negative electrode capacity.
8. The method for estimating the negative electrode capacity of the lithium battery as claimed in claim 7, wherein the step of obtaining the actual capacity of the battery to be tested comprises:
charging the battery to be tested to a full charge state by adopting a constant current and constant voltage mode;
performing constant current discharge on the fully charged battery to be detected until the battery to be detected reaches a full discharge state;
and taking the total electric quantity discharged by the battery to be tested in the constant current discharging process as the actual capacity of the battery to be tested.
9. The method for estimating the negative electrode capacity of the lithium battery as claimed in claim 7, wherein the step of charging the battery to be tested to a full charge state in a constant current and constant voltage mode comprises:
and carrying out constant current charging on the battery to be tested by adopting a first preset current until the voltage of the battery to be tested reaches a full charge voltage:
standing the battery to be tested for a preset time;
and carrying out constant voltage charging on the battery to be tested by adopting a first preset voltage until the current of the battery to be tested reaches a full charging current.
10. An estimation device of a negative electrode capacity of a lithium battery, comprising:
the charging module is used for carrying out constant current charging on a fully discharged battery to be tested;
the phase change point determining module is used for determining at least two phase change points of the battery to be tested, which are subjected to phase change due to lithium intercalation, and electric quantities corresponding to the at least two phase change points according to the charging parameters in the constant current charging process;
and the negative electrode capacity module is used for calculating the negative electrode capacity of the battery to be detected according to the difference value between the electric quantities corresponding to the two phase change points.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117706386A (en) * | 2024-02-05 | 2024-03-15 | 苏州易来科得科技有限公司 | Calculation method and device for upper limit and lower limit of lithium intercalation coefficient of anode and cathode of lithium battery |
| WO2024103590A1 (en) * | 2022-11-16 | 2024-05-23 | 湖北亿纬动力有限公司 | Battery system equalization method, electronic device, and storage medium |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024103590A1 (en) * | 2022-11-16 | 2024-05-23 | 湖北亿纬动力有限公司 | Battery system equalization method, electronic device, and storage medium |
| CN117706386A (en) * | 2024-02-05 | 2024-03-15 | 苏州易来科得科技有限公司 | Calculation method and device for upper limit and lower limit of lithium intercalation coefficient of anode and cathode of lithium battery |
| CN117706386B (en) * | 2024-02-05 | 2024-05-07 | 苏州易来科得科技有限公司 | Calculation method and device for upper limit and lower limit of lithium intercalation coefficient of anode and cathode of lithium battery |
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