Disclosure of Invention
Therefore, it is necessary to provide a lithium ion battery evaluation method, a lithium ion battery detection system, a computer device, and a computer-readable storage medium, for solving the problems that the battery lithium analysis detection method in the conventional scheme has limitations and has no subsequent lithium ion battery evaluation method.
A lithium ion battery evaluation method includes:
charging a battery to be tested, and placing the battery to be tested in a standing state after the battery to be tested is fully charged;
collecting a voltage signal of the battery to be tested in the process that the battery to be tested is in the standing state;
generating a battery standing time-voltage differential value curve chart according to the voltage signal of the battery to be detected;
acquiring a minimum value in the battery standing time-voltage differential value curve chart, wherein the abscissa of the minimum value is the battery standing time corresponding to the minimum value;
selecting N batteries to be tested with the same model, executing the four steps for N times at N different charging multiplying factors to obtain N minimum values, and respectively calculating the lithium analysis amount of the batteries to be tested under the N different charging multiplying factors to obtain the lithium analysis amount of the N batteries to be tested;
drawing a minimum value appearance time-battery lithium analysis amount curve graph according to the N minimum values and the lithium analysis amounts of the N batteries to be detected, wherein the abscissa of the minimum value appearance time-battery lithium analysis amount curve graph is the battery standing time corresponding to the minimum values, and the ordinate of the minimum value appearance time-battery lithium analysis amount curve graph is the lithium analysis amount of the batteries to be detected;
setting the passing time t according to the minimum value appearance time-battery lithium analysis amount curve chartsAnd the amount of lithium analyzed MsAnd grid point (t)s,Ms) Determining that the battery standing time corresponding to the minimum value of the battery to be tested is less than the passing time tsAnd judging that the battery to be tested is qualified.
In one embodiment, after the step of charging the battery to be tested and placing the battery to be tested in a standing state after the battery to be tested is fully charged, the method for evaluating a lithium ion battery further includes:
when the battery to be tested is placed in the standing state, recording the current moment as the starting moment of standing; and when the battery to be tested is positioned at the standing starting moment, the standing time of the battery is 0.
In one embodiment, the step of acquiring the voltage signal of the battery to be tested in the process that the battery to be tested is in the standing state includes:
detecting voltage values at the two ends of the anode and the cathode of the battery to be detected for multiple times within a preset standing time period, and recording the voltage values as the voltage of the battery to be detected; and recording the current moment as the battery standing time corresponding to the voltage of the battery to be detected each time when the voltage of the battery to be detected is obtained.
In one embodiment, the step of generating a battery resting time-voltage differential value graph according to the voltage signal of the battery to be tested includes:
drawing a battery standing time-battery voltage curve graph with the battery standing time as an abscissa and the battery voltage to be measured as an ordinate;
and carrying out differential processing on the battery standing time-battery voltage curve chart to generate a battery standing time-voltage differential value curve chart, wherein the abscissa of the battery standing time-voltage differential value curve chart is the battery standing time, and the ordinate of the battery standing time-voltage differential value curve chart is the derivative of the voltage of the battery to be detected to the battery standing time.
In one embodiment, the step of obtaining a minimum value in the battery resting time-voltage differential value graph, where an abscissa of the minimum value is a battery resting time corresponding to the minimum value, includes:
judging whether a minimum value exists in the battery standing time-voltage differential value curve chart or not;
and if a minimum value exists in the battery standing time-voltage differential value curve chart, determining that the lithium separation phenomenon occurs in the battery to be detected, and acquiring the minimum value.
In one embodiment, the calculating the lithium separation amount of the battery to be tested respectively under the N different charging rates, and the obtaining the lithium separation amount of the N batteries to be tested specifically includes:
acquiring the capacity attenuation rate of the battery to be tested and the initial capacity of the battery to be tested;
calculating the lithium separation amount of the battery to be tested according to the following formula:
m is the lithium separation amount of the battery to be detected, AH is the initial capacity of the battery to be detected, Q is the capacity attenuation rate of the battery to be detected, e is the charge amount of a single electron, and NA is an Avogastron constant.
The application provides a battery evaluation method. The battery evaluation method comprises the steps of charging and standing a plurality of batteries to be tested with the same model at different charging multiplying powers, detecting the voltage of the batteries to be tested in a standing state, drawing a battery standing time-voltage differential value curve graph, drawing a minimum value appearance time-battery lithium analysis amount curve graph, and setting the passing time t by utilizing the characteristic that part of lithium metal analyzed in the charging process of the lithium ion battery can be re-embedded into graphite and the battery standing time-voltage differential value curve graph after the lithium ion battery is charged can have a minimum valuesAnd the amount of lithium deposited MsAnd determining that the battery standing time corresponding to the minimum value of the battery to be tested is less than the passing timeTime tsAnd judging that the battery to be detected is qualified, not only judging whether the lithium analysis phenomenon occurs in the battery to be detected, but also judging the amount of lithium analysis according to the minimum value occurrence time and the passing time tsAnd comparing the measured voltage with the reference voltage, so that the purpose of evaluating the lithium ion battery can be realized, the battery to be measured is not damaged, the operation is simple, and the application range is wide.
A battery lithium analysis detection system, comprising:
a battery to be tested;
the lithium ion battery detection equipment is used for electrically connecting with a battery to be detected by using the lithium ion battery evaluation method, so as to judge whether a lithium analysis phenomenon occurs in the battery to be detected and judge whether the battery to be detected is qualified;
and the charging device is electrically connected with the battery to be tested and is used for charging the battery to be tested at different charging multiplying powers before the battery to be tested is placed in the standing state.
The application provides a lithium ion battery detection system. The battery lithium analysis detection system is electrically connected with a battery to be detected through the lithium ion battery detection equipment, can accurately detect and judge whether a lithium analysis phenomenon is generated inside the battery to be detected, and further achieves the purpose of evaluating the lithium ion battery when the lithium analysis phenomenon is generated in the battery to be detected.
A computer device comprising a memory storing a computer program and a processor implementing the above mentioned lithium ion battery evaluation method when executing the computer program.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, implements the above-mentioned lithium ion battery evaluation method.
Detailed Description
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The application provides a lithium ion battery evaluation method, a lithium ion battery detection system, a computer device and a computer readable storage medium.
Optionally, in the lithium ion battery evaluation method, the lithium ion battery detection system, the computer device, and the computer-readable storage medium provided in the present application, the battery type of the battery is a lithium ion battery.
As shown in fig. 1, in an embodiment of the present application, a lithium ion battery evaluation method is provided.
The lithium ion battery evaluation method provided by the present application is not limited to a specific implementation subject. Optionally, an execution main body of the lithium ion battery evaluation method provided by the application is a lithium ion battery detection device. The lithium ion battery detection equipment is electrically connected with the battery to be detected and is used for detecting and judging whether a lithium analysis phenomenon is generated inside the battery to be detected. Specifically, an execution main body of the lithium ion battery evaluation method provided by the present application may be a processor in a lithium ion battery detection device. The processor may be one or more.
The lithium ion battery evaluation method comprises the following steps:
s100, charging a battery to be tested, and placing the battery to be tested into a standing state after the battery to be tested is fully charged.
The standing state is a state that the environment temperature is in a range from minus 30 ℃ to minus 25 ℃, and the battery to be tested has no input and output current.
When the electric automobile is put into use, the electric automobile is in a parking state or a rest state for the longest time. The electric automobile is in a parking state or a rest state during parking, maintenance, charging and idling. At this time, the electric vehicle is in a relatively stationary state. Correspondingly, the lithium ion battery in the electric automobile is in a standing state at the moment. The rest state is the most common state of lithium ion batteries. After the battery to be tested is placed in the standing state, the lithium analysis phenomenon in the battery to be tested is the most objective and universal.
In an embodiment of the application, the lithium ion battery detection device is connected to a charging device to charge the battery to be tested.
Optionally, a charging device may be built in the lithium ion battery detection device, so that the trouble of complicated wiring caused by external connection of the charging device is avoided.
As shown in fig. 2, in an embodiment of the present application, after the step S100, the method for evaluating a lithium ion battery further includes the following step S110:
and S110, when the battery to be tested is placed in the standing state, recording the current moment as the starting moment of standing. And when the battery to be tested is positioned at the standing starting moment, the standing time of the battery is 0.
Specifically, when the battery to be tested is fully charged, the charging is finished, the battery to be tested is placed in the standing state, and the current time is recorded as the starting time of standing. When the battery to be tested is in a full-charge state, the battery to be tested is placed still, and the lithium separation phenomenon generated inside the battery to be tested is obvious and easy to observe.
And S200, acquiring a voltage signal of the battery to be tested in the process that the battery to be tested is in the standing state.
Specifically, a voltmeter may be built in the lithium ion battery detection device, and is used to collect a voltage signal of the battery to be detected.
As shown in fig. 3, in an embodiment of the present application, the step S200 includes the following step S210:
and S210, detecting the voltage values of the anode and the cathode of the battery to be detected for multiple times within a preset standing time period, and recording the voltage values as the voltage of the battery to be detected. And recording the current moment as the battery standing time corresponding to the voltage of the battery to be tested when the voltage of the battery to be tested is obtained every time.
The preset standing time is preset by a detector. The longer the preset standing time is, the more the voltage of the battery to be detected is acquired, the more the number of samples is, and the more accurate the detection result can be understood. Specifically, in the preset standing time period, a plurality of voltages of the battery to be detected are obtained, and a plurality of groups of voltage detection values (t, U) are obtained. And the battery to be detected is detected according to the voltage of the battery to be detected, wherein t is the battery standing time, and U is the battery standing time corresponding to the voltage of the battery to be detected.
And S300, generating a battery standing time-voltage differential value curve chart according to the voltage signal of the battery to be detected.
As shown in fig. 4, in an embodiment of the present application, the step S300 includes the following steps S310 to S320:
and S310, drawing a battery standing time-battery voltage curve chart with the battery standing time as an abscissa and the battery voltage to be measured as an ordinate.
Referring to fig. 5, fig. 5 is a battery standing time-battery voltage curve chart in the lithium ion battery evaluation method according to an embodiment of the present application.
The battery standing time and the battery voltage to be detected are in a one-to-one correspondence relationship, in other words, each standing time has one battery voltage to be detected corresponding to the standing time.
As shown in fig. 5, in the process of standing the battery to be tested, the voltage of the battery to be tested gradually attenuates along with the increase of the standing time of the battery.
And S320, carrying out differential processing on the battery standing time-battery voltage curve graph to generate a battery standing time-voltage differential value curve graph. The abscissa of the battery standing time-voltage differential value graph is the battery standing time. And the ordinate of the battery standing time-voltage differential value curve graph is the derivative of the voltage of the battery to be detected to the battery standing time.
In the battery rest time-voltage differential value graph, the following formula is followed:
and D is the differential value of the voltage of the battery to be measured. And t is the standing time of the battery. And U is the voltage of the battery to be tested under the standing time.
Referring to fig. 6, fig. 6 is a graph of battery resting time-voltage differential value in the lithium ion battery evaluation method according to an embodiment of the present application.
As shown in fig. 6, in the battery resting time-voltage differential value graph, the battery resting time and the differential value of the battery voltage to be measured are in a one-to-one correspondence relationship, in other words, each battery resting time has one differential value of the battery voltage to be measured corresponding to it.
And S400, acquiring a minimum value in the battery standing time-voltage differential value curve chart. And the abscissa of the minimum value is the battery standing time corresponding to the minimum value.
In an embodiment of the present application, the step S400 includes:
and S410, judging whether a minimum value exists in the battery standing time-voltage differential value curve chart or not.
Specifically, the lithium ion battery detection apparatus analyzes the battery resting time-voltage differential value graph, and determines whether a minimum value exists in the battery resting time-voltage differential value graph.
During the standing process of the lithium ion battery after being fully charged, the voltage at two ends of the lithium ion battery is gradually attenuated. Therefore, the voltage of the battery to be tested decreases as the standing time of the battery increases. And the differential value of the voltage of the battery to be detected is the derivative of the voltage of the battery to be detected to the standing time of the battery. It is understood that the differential value of the battery voltage to be measured is actually a rate of decay of the battery voltage to be measured as the battery resting time increases.
As shown in fig. 6, the direction of the decay rate of the battery voltage under test is negative, and thus the direction of the differential value of the battery voltage under test is negative, and the ordinate is shown as being substantially negative in the graph.
If the lithium separation phenomenon does not occur in the battery to be tested, the voltage of the battery to be tested is rapidly reduced along with the increase of the standing time and then tends to be constant. Accordingly, the trend of the absolute value of the decay rate of the battery voltage to be measured should be always reduced.
As shown in fig. 5, a platform appears in the process of rapidly decreasing the voltage of the battery to be tested to a constant value. If the lithium separation phenomenon occurs in the battery to be tested, along with the increase of the standing time of the battery, a platform exists in the process that the voltage of the battery to be tested rapidly decreases to a constant value. This is because, if the battery under test is charged, a part of lithium metal is deposited on the negative electrode of the battery under test. When the battery to be tested is fully charged and enters a standing state, part of lithium metal precipitated in the charging process of the battery to be tested can be re-embedded into the graphite. Reflected in the cell rest time-cell voltage graph, is part of the plateau.
As shown in fig. 6, fig. 6 is a graph of the battery rest time-voltage differential value generated via the differentiation process of fig. 5. If the lithium analysis phenomenon occurs in the battery to be detected, the trend of the absolute value of the attenuation rate of the voltage of the battery to be detected is suddenly increased and then decreased due to the existence of the platform and reflected in the battery standing time-voltage differential value curve diagram. Thus, a minimum value (t) is generated0,D0). Refer to the minimum value (t) in FIG. 60,D0)。
And S420, if a minimum value exists in the battery standing time-voltage differential value curve chart, determining that a lithium analysis phenomenon occurs in the battery to be detected, and acquiring the minimum value.
As shown in fig. 6, at the minimum value (t)0,D0) In, t0Is the minimum value (t)0,D0) The corresponding battery resting time at the time of occurrence. D0Is the minimum value (t)0,D0) And when the differential value of the voltage of the battery to be detected occurs, the differential value of the voltage of the battery to be detected corresponds to the differential value of the voltage of the battery to be detected.
It can be understood that if there is a minimum value (t) in the battery rest time-voltage differential value graph0And D), further indicating that a special voltage platform appears in the battery standing time-battery voltage curve chart. Further, the phenomenon that part of lithium metal is re-inserted into graphite exists in the process that the battery to be tested is in the static state. Therefore, it can be determined that a lithium separation phenomenon occurs inside the battery to be tested.
By executing the steps S100 to S400, the battery standing time-battery voltage curve is differentiated by using the characteristic that a part of lithium metal separated during the charging process of the lithium ion battery is re-embedded into graphite and a special voltage platform appears on the battery standing time-battery voltage curve after the charging of the lithium ion battery, so as to obtain the battery standing time-voltage differential value curve, and then whether a minimum value appears in the battery standing time-voltage differential value curve is judged and observed, so as to judge whether the lithium separation phenomenon occurs in the battery to be detected.
And if the lithium analysis phenomenon is determined to occur in the battery to be tested, executing the subsequent steps. And if the minimum value does not exist in the battery standing time-voltage differential value curve chart, determining that no lithium separation phenomenon occurs in the battery to be detected, and interrupting the step.
S500, selecting N batteries to be tested with the same model, and executing the steps S100-S400 for N times at N different charging multiplying powers to obtain N minimum values. And under the N different charging multiplying powers, respectively calculating the lithium separation amount of the battery to be detected, and obtaining the lithium separation amount of the N batteries to be detected.
The charging rate is equal to a multiple of the rated capacity of the battery under test at the data value, generally indicated by the letter C. In an embodiment of the present application, the charging rate may be 1/6C, 1/3C, 2/3C, 1C, or 2C.
And executing the steps S100-S400 for N times at N different charging multiplying powers, specifically, firstly drawing a plurality of battery standing time pressure-battery voltage curve graphs which take the battery standing time as an abscissa and the battery voltage to be measured as an ordinate. Each battery standing time-battery voltage curve corresponds to one charging rate. Optionally, a plurality of battery resting time-battery voltage graphs corresponding to a plurality of charging rates may be integrated into one graph, so as to facilitate comparison and viewing. Referring to fig. 7, fig. 7 is a graph of battery resting time-battery voltage in a lithium ion battery evaluation method according to an embodiment of the present application. As shown in fig. 7, there are multiple battery rest time-battery voltage curves at different charge rates in fig. 7.
And drawing a battery standing time-voltage differential value curve graph by taking the battery standing time as an abscissa and taking the differential value of the battery voltage to be detected as an ordinate according to the battery standing time-battery voltage curve. Alternatively, a plurality of battery resting time-voltage differential value graphs corresponding to a plurality of charging rates can be integrated into one graph, so that comparison and viewing are facilitated. Referring to fig. 8, fig. 8 is a graph of battery resting time-voltage differential value in the lithium ion battery evaluation method according to an embodiment of the present application. As shown in fig. 8, there are a plurality of battery rest time-battery voltage differential value curves at different charging rates in fig. 8.
And finally, acquiring a plurality of minimum values according to the battery standing time-voltage differential value curve chart.
As shown in fig. 8, the battery rest time-battery voltage differential value curve at 1/6C charging rate has no minimum value. The battery standing time-battery voltage differential value curves under 1/3C, 2/3C, 1C and 2C all have minimum values.
In an embodiment of the present application, under the N different charging magnifications, respectively calculating the lithium analysis amount of the battery to be tested, and obtaining the lithium analysis amount of the N batteries to be tested specifically includes:
and S510, acquiring the capacity attenuation rate of the battery to be tested and the initial capacity of the battery to be tested.
In an embodiment of the present application, a battery capacity tester is used to test a capacity fading rate, an initial capacity and an actual capacity of the battery to be tested.
The battery capacity tester is professional charging and discharging equipment. The initial capacity of the battery to be detected is the capacity obtained by detection after the battery to be detected is charged for the first time. The actual capacity of the battery to be detected is the capacity obtained by detecting the battery to be detected after the battery to be detected is discharged for a period of time in a constant current state after being charged for the first time.
Q is the capacity decay rate of the battery to be tested, AH is the initial capacity of the battery to be tested, and CH is the use capacity of the battery to be tested.
Table 1-capacity fading rate of the battery to be tested after charging at different rates in the examples of the present application
As shown in table 1, the capacity fade rate is increased as the charge rate is increased.
S520, calculating the lithium separation amount of the battery to be tested according to the following formula:
and M is the lithium separation amount of the battery to be tested. AH is the initial capacity of the battery to be tested. And Q is the capacity attenuation rate of the battery to be tested. e is the charge of a single electron, e is 1.6 × 10-19c, i.e. e, is a fixed value of 1.6X 10-19Coulombs. NA is the Avogastron constant, i.e. a fixed value of 6.02X 1023。
S600, drawing a minimum value occurrence time-battery lithium analysis amount curve graph according to the N minimum values and the lithium analysis amounts of the N batteries to be detected. The abscissa of the minimum value appearance time-battery lithium deposition amount curve is the battery standing time corresponding to the minimum value, and the ordinate of the minimum value appearance time-battery lithium deposition amount curve is the lithium deposition amount of the battery to be tested.
Referring to fig. 9, fig. 9 is a graph of minimum value occurrence time-battery lithium deposition amount in the lithium ion battery evaluation method according to an embodiment of the present application.
As shown in fig. 9, the battery standing time corresponding to the minimum value is in a positive correlation with the lithium deposition amount of the battery to be tested. The longer the battery standing time corresponding to the minimum value is, the larger the lithium analysis amount of the battery to be tested is, and it can be understood that the larger the lithium analysis amount of the battery to be tested is, the worse the quality of the battery to be tested is.
S700, setting passing time t according to the minimum value appearance time-battery lithium deposition amount curve chartsAnd the amount of lithium analyzed MsAnd grid point (t)s,Ms). Determining that the battery standing time corresponding to the minimum value of the battery to be tested is less than the passing time tsAnd judging that the battery to be tested is qualified.
In one embodiment of the present application, the passing time t is set according to the minimum occurrence time-lithium deposition amount graphsAnd the amount of lithium analyzed MsAnd grid point (t)s,Ms). The embodiment can evaluate lithium ion batteries with different qualities and judge whether the lithium ion batteries are qualified or not.
For example, a household battery recycling plant primarily recycles some spent lithium ion batteries. When a batch of waste lithium ion batteries comes, a detection worker can set a grid point (t) by adopting the battery evaluation method provided by the applications,Ms). The detection worker can detect the battery standing time corresponding to the minimum value of the lithium ion battery one by one or sample and detect the battery standing time corresponding to the minimum value of the lithium ion battery, and if the battery standing time is less than the preset passing time tsJudging that the lithium analysis amount of the battery to be tested is less than and passes the lithium analysis amount MSAnd the quality is qualified. Otherwise, judging that the quality of the battery to be tested is unqualified. Qualified batteries to be tested can be used for recycling.
As shown in fig. 10, in an embodiment of the application, after the step S600, the method for evaluating a lithium ion battery further includes:
s800, setting a passing time range t according to the minimum value occurrence time-battery lithium deposition amount curve chart1~t2And with said passing time range t1~t2Corresponding passing through range of lithium1~M2. Determining that the battery standing time corresponding to the minimum value of the battery to be tested is in the passing time range t1~t2When the minimum value is smaller than t, namely the battery standing time corresponding to the minimum value is not less than t1And is not more than t2And judging that the battery to be tested is qualified.
The application provides a batteryThe evaluation method comprises the steps of charging and standing a plurality of batteries to be tested with the same model at different charging multiplying powers, detecting the voltage of the batteries to be tested in a standing state, drawing a battery standing time-voltage differential value curve graph, drawing a minimum value appearance time-battery analysis lithium amount curve graph, and setting the passing time t by utilizing the characteristic that part of lithium metal analyzed in the charging process of the lithium ion battery can be re-embedded into graphite and the battery standing time-voltage differential value curve graph after the lithium ion battery is charged can have a minimum valuesAnd the amount of lithium deposited MsDetermining that the battery standing time corresponding to the minimum value of the battery to be tested is less than the passing time tsAnd judging that the battery to be detected is qualified, not only judging whether the lithium analysis phenomenon occurs in the battery to be detected, but also judging the amount of lithium analysis according to the minimum value occurrence time and the passing time tsAnd comparing the measured voltage with the reference voltage, so that the purpose of evaluating the lithium ion battery can be realized, the battery to be measured is not damaged, the operation is simple, and the application range is wide.
The application also provides a lithium ion battery detection system, which comprises a battery to be detected, lithium ion battery detection equipment and a charging device. The lithium ion battery detection equipment is electrically connected with the battery to be detected. The battery to be tested is electrically connected with the charging device.
The lithium ion battery detection equipment uses the lithium ion battery evaluation method mentioned in the above to judge whether the lithium analysis phenomenon occurs in the battery to be detected and judge whether the battery to be detected is qualified
And the charging device is used for charging the battery to be tested at different charging multiplying powers before the battery to be tested is placed in the standing state.
The present application further provides a computer device comprising a memory and a processor. The memory stores a computer program. The processor implements the lithium ion battery evaluation method mentioned above when executing the computer program.
The present application also provides a computer-readable storage medium. The computer-readable storage medium has stored therein a computer program. The computer program, when executed by a processor, implements the lithium ion battery evaluation method mentioned above.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but it should not be understood that several variations and modifications can be made on the premise of the conception of the present application, and these all fall into the protection scope of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.