CN112130085A

CN112130085A - Screening method and device for self-discharge performance of lithium battery and computer equipment

Info

Publication number: CN112130085A
Application number: CN202010941612.6A
Authority: CN
Inventors: 翟玮; 张新卫; 陈小源; 王华文; 王明旺
Original assignee: Sunwoda Electric Vehicle Battery Co Ltd
Current assignee: Xinwangda Power Technology Co ltd
Priority date: 2020-09-09
Filing date: 2020-09-09
Publication date: 2020-12-25
Anticipated expiration: 2040-09-09
Also published as: CN112130085B

Abstract

The application provides a screening method and device for self-discharge performance of a lithium battery and computer equipment. And adjusting the battery cell to a third voltage, adjusting the temperature and the surface pressure of the battery cell to a second preset condition, and recording a fourth voltage of the battery cell after maintaining the second preset time. And the system calculates the self-discharge value of the battery cell according to the voltage value and the maintaining time. The system judges whether the self-discharge value meets the screening standard, and if so, the self-discharge value is qualified; if not, the judgment is not qualified. In the application, the system can realize the detection of chemical self-discharge and physical self-discharge of the lithium battery, and the self-discharge value obtained by detection is more comprehensive; and corresponding screening standards are established aiming at various types of self-discharge performance, so that the screening precision of the self-discharge capacity of the lithium battery can be greatly improved.

Description

Screening method and device for self-discharge performance of lithium battery and computer equipment

Technical Field

The application relates to the technical field of lithium batteries, in particular to a method and a device for screening self-discharge performance of lithium batteries and computer equipment.

Background

The self-discharge of the lithium battery can be mainly divided into chemical self-discharge and physical self-discharge, wherein the chemical self-discharge is mainly determined by a battery core chemical system, such as the chemical activity of the material, the interface side reaction of an electrode and electrolyte and the like; the physical self-discharge is mainly determined by micro short-circuit points in the electric core, such as the introduction of metal impurities in materials, the introduction of dust in the production process and the like. At present, the conventional self-discharge detection method mainly realizes the detection of the self-discharge performance of the lithium battery by adjusting the battery core to a higher voltage and laying aside for a long time and detecting the variation of the voltage before and after detection. However, the detection method mainly aims at chemical self-discharge of the lithium battery, and has poor detection effect on physical self-discharge, so that the accuracy of the finally obtained detection result is low, and the screening accuracy of the lithium battery is further influenced.

Disclosure of Invention

The application mainly aims to provide a screening method and device for lithium battery self-discharge performance and computer equipment, and aims to overcome the defect that the existing screening method for lithium battery self-discharge performance is low in precision.

In order to achieve the above object, the present application provides a method for screening self-discharge performance of a lithium battery, comprising:

adjusting the voltage of a battery core of the lithium battery to a first voltage;

adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to first preset conditions, and recording the current voltage of the battery cell after maintaining the first preset time to obtain a second voltage;

adjusting the second voltage of the cell to a third voltage;

adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to second preset conditions, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage;

calculating to obtain a self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time;

judging whether the self-discharge value meets the screening standard or not;

if the self-discharge value meets the screening standard, judging that the self-discharge performance of the lithium battery is qualified; and if the self-discharge value does not meet the screening standard, judging that the self-discharge performance of the lithium battery is unqualified.

Further, the step of adjusting the temperature and the surface pressure of the battery cell after the voltage adjustment to first preset conditions includes:

clamping the battery cell by using a clamp, heating the temperature of the battery cell to a first temperature through a heating plate of the clamp, and applying a first pressure to the surface of the battery cell through the clamp so as to meet the first preset condition.

Further, the step of adjusting the temperature and the surface pressure of the battery cell after the voltage adjustment to a second preset condition includes:

and heating the temperature of the battery cell to a second temperature through the heating plate, and applying a second pressure to the surface of the battery cell through the clamp so as to meet the second preset condition, wherein the second temperature is lower than the first temperature, and the second pressure is higher than the first pressure.

Further, the step of calculating the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time includes:

substituting the first voltage, the second voltage and the first preset time into a first formula, and calculating to obtain the chemical self-discharge value, wherein the first formula is as follows:

K₁is the chemical self-discharge value, V₁Is the first voltage, V₂Is the second voltage, X₁The first preset time is set;

substituting the third voltage, the fourth voltage and the second preset time into a second formula, and calculating to obtain the physical self-discharge value, wherein the second formula is as follows:

K₂is the chemical self-discharge value, V₃Is said third voltage, V₄Is said fourth voltage, X₂The second preset time is the first preset time;

and calculating the sum of the chemical self-discharge value and the physical self-discharge value to obtain the total self-discharge value.

Further, the screening standard includes a plurality of standard values of different types, and the step of determining whether the self-discharge value meets the screening standard includes:

respectively judging whether the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are greater than respective corresponding standard values;

if any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values, judging that the self-discharge value does not meet the screening standard;

and if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective corresponding standard values, judging that the self-discharge value meets the screening standard.

Further, after the step of determining that the self-discharge performance of the lithium battery is not qualified, the method includes:

generating prompt information, wherein the prompt information comprises the reason why the self-discharge performance of the lithium battery is not qualified;

and outputting the prompt information to a display interface.

Further, in the step of adjusting the voltage of the battery cell of the lithium battery to the first voltage, the adjusted SOC of the battery cell is greater than 80%;

in the step of adjusting the second voltage of the battery cell to a third voltage, the adjusted SOC of the battery cell is less than 10%;

the first preset time and the second preset time are not more than 36 h.

The application also provides a screening device of lithium cell self discharge performance, includes:

the first adjusting module is used for adjusting the voltage of the battery cell of the lithium battery to a first voltage;

the first maintaining module is used for adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to a first preset condition, and recording the current voltage of the battery cell after maintaining the first preset time to obtain a second voltage;

a second adjustment module, configured to adjust the second voltage of the battery cell to a third voltage;

the second maintaining module is used for adjusting the temperature and the surface pressure of the battery cell after the voltage is adjusted to a second preset condition, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage;

the calculation module is used for calculating a self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time;

the screening module is used for judging whether the self-discharge value meets the screening standard or not;

the first judgment module is used for judging that the self-discharge performance of the lithium battery is qualified if the self-discharge value meets the screening standard;

and the second judgment module is used for judging that the self-discharge performance of the lithium battery is unqualified if the self-discharge value does not meet the screening standard.

Further, the first adjusting module includes:

the first heating unit is used for clamping the battery cell by using a clamp, and heating the temperature of the battery cell to a first temperature through a heating plate of the clamp so as to meet the first preset condition;

and the first pressure applying unit is used for applying a first pressure to the surface of the battery cell through the clamp so as to meet the first preset condition.

Further, the second adjusting module includes:

the second heating unit is used for heating the temperature of the battery cell to a second temperature through the heating plate so as to meet the second preset condition, wherein the second temperature is lower than the first temperature;

and the second pressure applying unit is used for applying a second pressure to the surface of the battery cell through the clamp so as to meet the second preset condition, wherein the second pressure is greater than the first pressure.

Further, the self-discharge value includes a chemical self-discharge value, a physical self-discharge value and a total self-discharge value, and the calculation module includes:

the first calculation unit is configured to substitute the first voltage, the second voltage, and the first preset time into a first formula, and calculate the chemical self-discharge value, where the first formula is:

second calculation sheetThe element is used for substituting the third voltage, the fourth voltage and the second preset time into a second formula to calculate and obtain the physical self-discharge value, wherein the second formula is as follows:

and the third calculating unit is used for calculating the sum of the chemical self-discharge value and the physical self-discharge value to obtain the total self-discharge value.

Further, the screening criteria includes a plurality of different types of criteria values, and the screening module includes:

the judging unit is used for respectively judging whether the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values;

the first judgment unit is used for judging that the self-discharge value does not meet the screening standard if any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values;

and the second judgment unit is used for judging that the self-discharge value meets the screening standard if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective corresponding standard values.

Further, the screening device further includes:

the generating module is used for generating prompt information, and the prompt information comprises the reason why the self-discharge performance of the lithium battery is not qualified;

and the output module is used for outputting the prompt information to a display interface.

Further, in the first adjustment module, the SOC of the battery cell after being adjusted to the first voltage is greater than 80%;

in the second adjustment module, the SOC of the battery cell after being adjusted to the third voltage is less than 10%;

the first preset time and the second preset time are not more than 36 h.

The present application further provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any one of the above methods when executing the computer program.

The present application also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, carries out the steps of the method of any of the above.

According to the screening method, the screening device and the computer equipment for the self-discharge performance of the lithium battery, firstly, the voltage of the battery core of the lithium battery is adjusted to be the first voltage, then, the temperature and the surface pressure of the battery core after the voltage is adjusted to be the first preset conditions, the current voltage of the battery core is recorded after the first preset time is maintained, and the second voltage is obtained. And then, adjusting the second voltage of the battery cell to a third voltage, adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to a second preset condition, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage. And the system calculates the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time. The system judges whether the self-discharge value meets the screening standard, and if the self-discharge value meets the screening standard, the self-discharge performance of the lithium battery is judged to be qualified; and if the self-discharge value does not meet the screening standard, judging that the self-discharge performance of the lithium battery is unqualified. In the application, SOC, temperature and surface pressure of the battery cell are correspondingly set, so that detection of self-discharge performance (chemical self-discharge and physical self-discharge) of each type of lithium battery is completed, and self-discharge values obtained through detection are more comprehensive. Screening standards established for self-discharge performance of each type are stored in the system, and screening precision of self-discharge capacity of the lithium battery can be greatly improved by comparing self-discharge values with the corresponding screening standards.

Drawings

FIG. 1 is a schematic diagram illustrating steps of a method for screening self-discharge performance of a lithium battery according to an embodiment of the present disclosure;

fig. 2 is a block diagram of an overall structure of a screening apparatus for self-discharge performance of a lithium battery according to an embodiment of the present disclosure;

fig. 3 is a block diagram schematically illustrating a structure of a computer device according to an embodiment of the present application.

The implementation, functional features and advantages of the objectives of the present application will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

Referring to fig. 1, an embodiment of the present application provides a method for screening self-discharge performance of a lithium battery, including:

s1, adjusting the voltage of the battery cell of the lithium battery to a first voltage;

s2, adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to a first preset condition, and recording the current voltage of the battery cell after maintaining the first preset time to obtain a second voltage;

s3, adjusting the second voltage of the battery cell to a third voltage;

s4, adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to second preset conditions, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage;

s5, calculating to obtain a self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time;

s6, judging whether the self-discharge value meets the screening standard;

s7, if the self-discharge value meets the screening standard, judging that the self-discharge performance of the lithium battery is qualified; and if the self-discharge value does not meet the screening standard, judging that the self-discharge performance of the lithium battery is unqualified.

Preferably, in the step of adjusting the voltage of the battery cell of the lithium battery to the first voltage, the adjusted SOC of the battery cell is greater than 80%;

the first preset time and the second preset time are not more than 36 h.

In this embodiment, at room temperature, the system performs 1C capacity discharge on a battery cell of the lithium battery according to the definition of a provider, and adjusts the voltage of the battery cell to a first voltage. The battery cell can be a battery cell after formation or a battery cell utilized in a gradient manner, the adjusted current is determined according to the battery cells with different specifications, the value of the first voltage is determined according to an OCV-SOC curve of the battery cell, and preferably, the SOC value corresponding to the first voltage is greater than 80%. After the voltage of the battery core of the lithium battery is adjusted to the first voltage (namely, the SOC of the battery core is greater than 80%), the chemical self-discharge proportion of the battery core is amplified, which is beneficial to the detection of the chemical self-discharge performance of the battery core. The system adjusts the temperature and the surface pressure of the battery cell after the voltage is adjusted to a first preset condition, and records the voltage of the battery cell at the moment after maintaining the first preset time, namely the second voltage. Specifically, the battery core is clamped by a specially-made clamp, the clamp is provided with a heating plate and a temperature sensor, and the temperature sensor can detect the heating temperature of the clamp. The clamping face of anchor clamps contacts with two relative surfaces of electric core, and the clamping face of anchor clamps needs two relative surfaces of as big as possible cover electric core (the clamping face of preferred anchor clamps is the same with the shape of the contact surface of electric core, area, and the contact surface of electric core is the face of the clamping face direct contact of electric core and anchor clamps promptly), can guarantee that the heating to electric core distributes evenly to and the pressure of the anchor clamps that electric core surface received is even, avoids being heated or the pressurized is too concentrated, leads to electric core to damage. The system heats the whole temperature of the battery cell to a first temperature through the heating plate of the clamp, and applies a first pressure to the surface of the battery cell through the clamp so as to meet a first preset condition. By increasing the temperature of the battery cell, the chemical pair projection speed of the positive and negative electrode interfaces in the battery cell is increased, so that the battery cell can be used for increasing the chemical pair projection speedThe ratio of chemical self-discharge of a high cell to the total self-discharge. Meanwhile, the increase of the physical resistance under the high-temperature condition can cause the reduction of a micro short circuit in the electric core, thereby weakening the ratio of the physical self-discharge in the whole self-discharge. And a certain pressure (namely, a first pressure) is applied on the surface of the battery cell, so that the interfacial contact area in the battery cell can be partially increased, the chemical side reaction is facilitated, and the ratio of the chemical self-discharge in the whole self-discharge can be further increased. The system can consider that the self-discharge of the entire cell after adjustment is determined by chemical self-discharge (the physical self-discharge of the cell is weakened to a negligible extent) by adjusting the SOC (i.e., the first voltage) of the cell, the first temperature, and the applied first pressure. After the cell completes adjustment of the SOC (i.e., the first voltage), the first temperature and application of the first pressure, the cell maintains the first preset time, and then records the current voltage value of the cell, so as to obtain the second voltage. The first preset time is preferably not more than 36h, so that risks of fresh battery cell internal aging, gas generation and the like are avoided. After recording the second voltage of the battery cell, the system performs 1C capacity discharge on the battery cell again, and adjusts the voltage of the battery cell to a third voltage. Similarly, the adjusted current magnitude is determined according to the battery cells with different specifications, the value of the third voltage is determined according to the OCV-SOC curve of the battery cell, and preferably, the SOC value corresponding to the third voltage is less than 10%. And the system adjusts the temperature and the surface pressure of the battery cell after the voltage is adjusted again to a second preset condition through the clamp, and records the current voltage of the battery cell after maintaining the second preset time, namely the fourth voltage. Specifically, the second temperature is lower than the first temperature, and the system lowers the temperature of the heating plate and maintains the heating temperature of the heating plate at the second temperature, so that the temperature of the cell is also maintained at the second temperature. Meanwhile, the system applies a second pressure to the surface of the battery cell through the clamp so as to meet a second preset condition, wherein the second pressure is greater than the first pressure. When the SOC of the battery cell is less than 10%, the driving force of chemical self-discharge of the battery cell is reduced due to the reduction of the voltage of the battery cell; in addition, the first temperature of the battery cell is reduced to the second temperature, and the driving force of the chemical self-discharge of the battery cell can be reduced at the lower temperature, so that the chemical self-discharge of the battery cell is effectively reducedThe ratio of discharge to total self-discharge. By increasing the first pressure applied to the cell to the second pressure, the greater pressure can increase the contact of the metal pads on the cell plates to form micro-short circuits in the cell, thereby increasing the ratio of physical self-discharge to self-discharge of the entire cell. By adjusting the SOC (i.e., the second voltage), the second temperature, and the second pressure, the system can determine that the self-discharge of the entire adjusted cell is determined by the physical self-discharge (the chemical self-discharge of the cell is weakened to a negligible extent). After the cell completes the adjustment of the SOC (i.e., the second voltage), the second temperature and the application of the second pressure, the cell maintains the second preset time, and then records the current voltage value of the cell, so as to obtain a fourth voltage. Likewise, the second predetermined time is preferably not more than 36 h. And the system calculates the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time. Specifically, the self-discharge value comprises a chemical self-discharge value, a physical self-discharge value and a self-discharge total value, the system substitutes a first voltage, a second voltage and a first preset time into a first formula, and the chemical self-discharge value is obtained through calculation, wherein the first formula is as follows:

K₁is a chemical self-discharge value, V₁Is a first voltage, V₂Is a second voltage, X₁Is the first preset time. Substituting the third voltage, the fourth voltage and the second preset time into a second formula by the system, and calculating to obtain a physical self-discharge value, wherein the second formula is as follows:

K₂is a chemical self-discharge value, V₃Is a third voltage, V₄Is a fourth voltage, X₂Is the second preset time. And finally, the system calculates the sum of the chemical self-discharge value and the physical self-discharge value to obtain a total self-discharge value. The system is internally stored with a screening standard, the screening standard comprises a plurality of standard values of different types, specifically comprises a standard value corresponding to chemical self-discharge and a standard value corresponding to physical self-dischargeAnd a standard value corresponding to the total self-discharge. The system respectively judges whether the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective standard values. And if any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values, the system judges that the self-discharge value does not meet the screening standard, and further judges that the self-discharge performance of the lithium battery is unqualified. And if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective standard values, the system judges that the self-discharge value meets the screening standard, and further judges that the self-discharge performance of the lithium battery is qualified.

s201, clamping the battery cell by using a clamp, heating the temperature of the battery cell to a first temperature through a heating plate of the clamp, and applying a first pressure to the surface of the battery cell through the clamp so as to meet the first preset condition.

In this embodiment, electric core is by anchor clamps centre gripping, and anchor clamps are provided with hot plate and temperature sensor, and temperature sensor can detect the heating temperature of anchor clamps. The clamping face of anchor clamps contacts with two relative surfaces of electric core, and the clamping face of anchor clamps needs two relative surfaces of as big as possible cover electric core (the clamping face of preferred anchor clamps is the same with the shape of the contact surface of electric core, area, and the contact surface of electric core is the face of the clamping face direct contact of electric core and anchor clamps promptly), can guarantee that the heating to electric core distributes evenly to and the pressure of the anchor clamps that electric core surface received is even, avoids being heated or the pressurized is too concentrated, leads to electric core to damage. The system heats the whole temperature of the battery cell to a first temperature through the heating plate of the clamp, and applies a first pressure to the surface of the battery cell through the clamp (specifically, the pressure can be controlled through the nut torque on the clamp) so as to meet a first preset condition. The first temperature can be defined according to the highest specific use temperature of the battery system level, that is, the first temperature cannot exceed the tolerance temperature of the battery cell, so that the battery cell is prevented from being damaged. The initial pressure at the two ends of the battery cell is determined according to the design of the battery module, the first pressure cannot exceed the bearing limit of the surface of the battery cell, and the battery cell is prevented from being pressed to be excessively deformed and damaged. The system accelerates the projection speed of the chemical pair of the positive and negative electrode interfaces in the battery cell by increasing the temperature of the battery cell, thereby improving the ratio of the chemical self-discharge of the battery cell in the whole self-discharge. Meanwhile, the increase of the physical resistance under the high-temperature condition can cause the reduction of a micro short circuit in the electric core, thereby weakening the ratio of the physical self-discharge in the whole self-discharge. And a certain pressure (namely, a first pressure) is applied on the surface of the battery cell, so that the interfacial contact area in the battery cell can be partially increased, the chemical side reaction is facilitated, and the ratio of the chemical self-discharge in the whole self-discharge can be further increased. The system can consider that the self-discharge of the entire cell after adjustment is determined by chemical self-discharge (the physical self-discharge of the cell is weakened to a negligible extent) by adjusting the SOC (i.e., the first voltage) of the cell, the first temperature, and the applied first pressure. After the cell completes adjustment of the SOC (i.e., the first voltage), the first temperature and application of the first pressure, the cell maintains the first preset time, and then records the current voltage value of the cell, so as to obtain the second voltage. The first preset time is preferably not more than 36h, so that risks of fresh battery cell internal aging, gas generation and the like are avoided.

s401, heating the temperature of the battery cell to a second temperature through the heating plate, and applying a second pressure to the surface of the battery cell through the clamp so as to meet a second preset condition, wherein the second temperature is lower than the first temperature, and the second pressure is higher than the first pressure.

In this embodiment, the system reduces the temperature of the heating plate (the second temperature is lower than the first temperature), and maintains the heating temperature of the heating plate at the second temperature, so that the temperature of the battery cell is also maintained at the second temperature. The second temperature is preferably selected as low as possible, but is preferably controlled to be about 20 ℃ in consideration of energy consumption and efficiency of examination. Meanwhile, the system applies a second pressure to the surface of the battery cell through the clamp so as to meet a second preset condition, wherein the second pressure is greater than the first pressure. The second pressure may be selected based on the maximum expansion force of the cell cycling to EOL, but should not exceed the maximum pressure at which the cell aluminum casing deforms, and is typically selected to be 3000-5000N. When the SOC of the battery cell is less than 10%, the driving force of chemical self-discharge of the battery cell is reduced due to the reduction of the voltage of the battery cell; in addition, by reducing the first temperature of the battery cell to the second temperature, the driving force of the chemical self-discharge of the battery cell can be reduced at a lower temperature, so that the ratio of the chemical self-discharge of the battery cell in the whole self-discharge can be effectively reduced. By increasing the first pressure applied to the cell to the second pressure, the greater pressure can increase the contact of the metal pads on the cell plates to form micro-short circuits in the cell, thereby increasing the ratio of physical self-discharge to self-discharge of the entire cell. By adjusting the SOC (i.e., the second voltage), the second temperature, and the second pressure, the system can determine that the self-discharge of the entire adjusted cell is determined by the physical self-discharge (the chemical self-discharge of the cell is weakened to a negligible extent). After the cell completes the adjustment of the SOC (i.e., the second voltage), the second temperature and the application of the second pressure, the cell maintains the second preset time, and then records the current voltage value of the cell, so as to obtain a fourth voltage. Likewise, the second predetermined time is preferably not more than 36 h.

s501, substituting the first voltage, the second voltage and the first preset time into a first formula, and calculating to obtain the chemical self-discharge value, wherein the first formula is as follows:

K₁is the chemical self-discharge value, V₁Is the first voltage, V₂Is the firstTwo voltages, X₁The first preset time is set;

and S502, substituting the third voltage, the fourth voltage and the second preset time into a second formula, and calculating to obtain the physical self-discharge value, wherein the second formula is as follows:

and S503, calculating the sum of the chemical self-discharge value and the physical self-discharge value to obtain the total self-discharge value.

In the present embodiment, the self-discharge value includes three types of a chemical self-discharge value, a physical self-discharge value, and a total self-discharge value. In the first preset time, the chemical self-discharge of the battery cell is greatly enhanced, and the physical self-discharge is weakened as much as possible, so that the whole self-discharge of the battery cell in the first preset time is determined by the chemical self-discharge. And the system calculates a chemical self-discharge value according to the first voltage, the second voltage and the first preset time. Specifically, the system substitutes a first voltage, a second voltage and a first preset time into a first formula, and calculates to obtain a chemical self-discharge value, wherein the first formula is as follows:

K₁is a chemical self-discharge value, V₁Is a first voltage, V₂Is a second voltage, X₁Is the first preset time. In the second preset time, the system can consider that the self-discharge of the whole adjusted battery cell is determined by the physical self-discharge (the chemical self-discharge of the battery cell is weakened to be negligible) by reducing the SOC (namely, the second voltage) of the battery cell, the second temperature and increasing the second pressure. Substituting the third voltage, the fourth voltage and the second preset time into a second formula by the system, and calculating to obtain a physical self-discharge value, wherein the second formula is as follows:

K₂is a chemical self-discharge value, V₃Is a third voltage, V₄Is a fourth voltage, X₂Is the second preset time. And finally, the system calculates the sum of the chemical self-discharge value and the physical self-discharge value to obtain a total self-discharge value.

s601, respectively judging whether the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than respective corresponding standard values;

s602, if any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values, judging that the self-discharge value does not accord with the screening standard;

and S603, if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective corresponding standard values, judging that the self-discharge value meets the screening standard.

In this embodiment, the screening standard includes a plurality of standard values of different types, specifically including a standard value corresponding to chemical self-discharge, a standard value corresponding to physical self-discharge, and a standard value corresponding to total self-discharge. The system respectively judges whether the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective standard values. If any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values, for example, the chemical self-discharge value is larger than the corresponding standard value, or the chemical self-discharge value and the physical self-discharge value are both larger than the respective corresponding standard values, the system judges that the self-discharge value does not meet the screening standard, and further judges that the self-discharge performance of the lithium battery is unqualified. And if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective standard values, the system judges that the self-discharge value meets the screening standard, and further judges that the self-discharge performance of the lithium battery is qualified. In the embodiment, the standard values corresponding to the chemical self-discharge, the physical self-discharge and the total self-discharge are established, so that the self-discharge of each type is required to meet the standard when the self-discharge performance of the lithium battery is screened, and the screening precision of the self-discharge performance of the lithium battery can be effectively improved by the multi-standard screening method.

s8, generating prompt information, wherein the prompt information comprises the reason why the self-discharge performance of the lithium battery is not qualified;

and S9, outputting the prompt information to a display interface.

In this embodiment, after determining that the self-discharge performance of the lithium battery is not qualified, the system generates corresponding prompt information according to the reason why the self-discharge performance of the lithium battery is not qualified. For example, in the process that the system evaluates the self-discharge value of the lithium battery according to the screening standard, it is recognized that the chemical self-discharge of the lithium battery meets the corresponding screening standard, and the physical self-discharge does not meet the corresponding screening standard, and then the generated prompt information is: the physical self-discharge of the battery cell does not accord with the screening standard, and the generated prompt information is output to a display interface, so that a detector can timely know the reason why the self-discharge performance of the lithium battery is unqualified, and the reason is counted, and the failure analysis and production line of the subsequent battery cell are improved.

In the screening method for the self-discharge performance of the lithium battery provided in this embodiment, first, the voltage of the battery cell of the lithium battery is adjusted to a first voltage, then, the temperature and the surface pressure of the battery cell after the voltage adjustment are adjusted to a first preset condition, and the current voltage of the battery cell is recorded after a first preset time is maintained, so as to obtain a second voltage. And then, adjusting the second voltage of the battery cell to a third voltage, adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to a second preset condition, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage. And the system calculates the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time. The system judges whether the self-discharge value meets the screening standard, and if the self-discharge value meets the screening standard, the self-discharge performance of the lithium battery is judged to be qualified; and if the self-discharge value does not meet the screening standard, judging that the self-discharge performance of the lithium battery is unqualified. In the application, SOC, temperature and surface pressure of the battery cell are correspondingly set, so that detection of self-discharge performance (chemical self-discharge and physical self-discharge) of each type of lithium battery is completed, and self-discharge values obtained through detection are more comprehensive. Screening standards established for self-discharge performance of each type are stored in the system, and screening precision of self-discharge capacity of the lithium battery can be greatly improved by comparing self-discharge values with the corresponding screening standards.

Referring to fig. 2, an embodiment of the present application further provides a screening apparatus for self-discharge performance of a lithium battery, including:

the first adjusting module 1 is configured to adjust a voltage of a battery cell of the lithium battery to a first voltage;

the first maintaining module 2 is configured to adjust the temperature and the surface pressure of the battery cell after the voltage adjustment to first preset conditions, and record the current voltage of the battery cell after maintaining for a first preset time to obtain a second voltage;

a second adjusting module 3, configured to adjust the second voltage of the battery cell to a third voltage;

the second maintaining module 4 is configured to adjust the temperature and the surface pressure of the battery cell after the voltage adjustment to second preset conditions, and record the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage;

the calculation module 5 is configured to calculate a self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time;

the screening module 6 is used for judging whether the self-discharge value meets the screening standard or not;

the first judgment module 7 is used for judging that the self-discharge performance of the lithium battery is qualified if the self-discharge value meets the screening standard;

and the second judging module 8 is used for judging that the self-discharge performance of the lithium battery is unqualified if the self-discharge value does not meet the screening standard.

Preferably, in the first adjustment module 1, the SOC of the battery cell after being adjusted to the first voltage is greater than 80%;

in the second adjustment module 3, the SOC of the battery cell after being adjusted to the third voltage is less than 10%;

the first preset time and the second preset time are not more than 36 h.

In this embodiment, at room temperature, the system performs 1C capacity discharge on a battery cell of the lithium battery according to the definition of a provider, and adjusts the voltage of the battery cell to a first voltage. The battery cell can be a battery cell after formation or a battery cell utilized in a gradient manner, the adjusted current is determined according to the battery cells with different specifications, the value of the first voltage is determined according to an OCV-SOC curve of the battery cell, and preferably, the SOC value corresponding to the first voltage is greater than 80%. After the voltage of the battery core of the lithium battery is adjusted to the first voltage (namely, the SOC of the battery core is greater than 80%), the chemical self-discharge proportion of the battery core is amplified, which is beneficial to the detection of the chemical self-discharge performance of the battery core. The system adjusts the temperature and the surface pressure of the battery cell after the voltage is adjusted to a first preset condition, and records the voltage of the battery cell at the moment after maintaining the first preset time, namely the second voltage. Specifically, the battery core is clamped by a specially-made clamp, the clamp is provided with a heating plate and a temperature sensor, and the temperature sensor can detect the heating temperature of the clamp. The clamping face of anchor clamps contacts with two relative surfaces of electric core, and the clamping face of anchor clamps needs two relative surfaces of as big as possible cover electric core (the clamping face of preferred anchor clamps is the same with the shape of the contact surface of electric core, area, and the contact surface of electric core is the face of the clamping face direct contact of electric core and anchor clamps promptly), can guarantee that the heating to electric core distributes evenly to and the pressure of the anchor clamps that electric core surface received is even, avoids being heated or the pressurized is too concentrated, leads to electric core to damage. The system heats the whole temperature of the battery cell to a first temperature through the heating plate of the clamp, and applies a first pressure to the surface of the battery cell through the clamp so as to meet a first preset condition. By increasing the temperature of the battery cell, the chemical pair projection speed of the positive and negative electrode interfaces in the battery cell is increased, so that the ratio of the chemical self-discharge of the battery cell in the whole self-discharge can be increased. At the same time, high temperatureUnder the condition, the increase of the physical resistance can cause the reduction of a micro short circuit in the electric core, thereby weakening the ratio of the physical self-discharge in the whole self-discharge. And a certain pressure (namely, a first pressure) is applied on the surface of the battery cell, so that the interfacial contact area in the battery cell can be partially increased, the chemical side reaction is facilitated, and the ratio of the chemical self-discharge in the whole self-discharge can be further increased. The system can consider that the self-discharge of the entire cell after adjustment is determined by chemical self-discharge (the physical self-discharge of the cell is weakened to a negligible extent) by adjusting the SOC (i.e., the first voltage) of the cell, the first temperature, and the applied first pressure. After the cell completes adjustment of the SOC (i.e., the first voltage), the first temperature and application of the first pressure, the cell maintains the first preset time, and then records the current voltage value of the cell, so as to obtain the second voltage. The first preset time is preferably not more than 36h, so that risks of fresh battery cell internal aging, gas generation and the like are avoided. After recording the second voltage of the battery cell, the system performs 1C capacity discharge on the battery cell again, and adjusts the voltage of the battery cell to a third voltage. Similarly, the adjusted current magnitude is determined according to the battery cells with different specifications, the value of the third voltage is determined according to the OCV-SOC curve of the battery cell, and preferably, the SOC value corresponding to the third voltage is less than 10%. And the system adjusts the temperature and the surface pressure of the battery cell after the voltage is adjusted again to a second preset condition through the clamp, and records the current voltage of the battery cell after maintaining the second preset time, namely the fourth voltage. Specifically, the second temperature is lower than the first temperature, and the system lowers the temperature of the heating plate and maintains the heating temperature of the heating plate at the second temperature, so that the temperature of the cell is also maintained at the second temperature. Meanwhile, the system applies a second pressure to the surface of the battery cell through the clamp so as to meet a second preset condition, wherein the second pressure is greater than the first pressure. When the SOC of the battery cell is less than 10%, the driving force of chemical self-discharge of the battery cell is reduced due to the reduction of the voltage of the battery cell; in addition, by reducing the first temperature of the battery cell to the second temperature, the driving force of the chemical self-discharge of the battery cell can be reduced at a lower temperature, so that the ratio of the chemical self-discharge of the battery cell in the whole self-discharge can be effectively reduced. By a first step to be applied on the cellThe first pressure is increased to the second pressure, and the larger pressure can increase the contact of the metal pads on the battery cell to form a micro short circuit in the battery cell, so that the proportion of physical self-discharge in the self-discharge of the whole battery cell is increased. By adjusting the SOC (i.e., the second voltage), the second temperature, and the second pressure, the system can determine that the self-discharge of the entire adjusted cell is determined by the physical self-discharge (the chemical self-discharge of the cell is weakened to a negligible extent). After the cell completes the adjustment of the SOC (i.e., the second voltage), the second temperature and the application of the second pressure, the cell maintains the second preset time, and then records the current voltage value of the cell, so as to obtain a fourth voltage. Likewise, the second predetermined time is preferably not more than 36 h. And the system calculates the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time. Specifically, the self-discharge value comprises a chemical self-discharge value, a physical self-discharge value and a self-discharge total value, the system substitutes a first voltage, a second voltage and a first preset time into a first formula, and the chemical self-discharge value is obtained through calculation, wherein the first formula is as follows:

K₂is a chemical self-discharge value, V₃Is a third voltage, V₄Is a fourth voltage, X₂Is the second preset time. And finally, the system calculates the sum of the chemical self-discharge value and the physical self-discharge value to obtain a total self-discharge value. The system is internally stored with a screening standard, and the screening standard comprises a plurality of standard values of different types, specifically comprises a standard value corresponding to chemical self-discharge, a standard value corresponding to physical self-discharge and a standard value corresponding to total self-discharge. The system respectively judges the chemical self-discharge value and the chemical self-discharge objectWhether the self-discharge value and the total self-discharge value are larger than the corresponding standard values or not is judged. And if any one or two of the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are larger than the respective corresponding standard values, the system judges that the self-discharge value does not meet the screening standard, and further judges that the self-discharge performance of the lithium battery is unqualified. And if the chemical self-discharge value, the physical self-discharge value and the total self-discharge value are not more than the respective standard values, the system judges that the self-discharge value meets the screening standard, and further judges that the self-discharge performance of the lithium battery is qualified.

Further, the first adjusting module 1 includes:

Further, the second adjusting module 3 includes:

Further, the self-discharge value includes a chemical self-discharge value, a physical self-discharge value and a total self-discharge value, and the calculating module 5 includes:

a second calculation unit for calculating the third voltageSubstituting the fourth voltage and the second preset time into a second formula, and calculating to obtain the physical self-discharge value, wherein the second formula is as follows:

Further, the screening criteria includes a plurality of different types of criteria values, and the screening module 6 includes:

Further, the screening device further includes:

the generating module 9 is used for generating prompt information, and the prompt information contains the reason why the self-discharge performance of the lithium battery is not qualified;

and the output module 10 is used for outputting the prompt information to a display interface.

In the screening apparatus for self-discharge performance of a lithium battery provided in this embodiment, first, the voltage of the battery core of the lithium battery is adjusted to a first voltage, then, the temperature and the surface pressure of the battery core after the voltage adjustment are adjusted to a first preset condition, and the current voltage of the battery core is recorded after a first preset time is maintained, so as to obtain a second voltage. And then, adjusting the second voltage of the battery cell to a third voltage, adjusting the temperature and the surface pressure of the battery cell after voltage adjustment to a second preset condition, and recording the current voltage of the battery cell after maintaining the second preset time to obtain a fourth voltage. And the system calculates the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time. The system judges whether the self-discharge value meets the screening standard, and if the self-discharge value meets the screening standard, the self-discharge performance of the lithium battery is judged to be qualified; and if the self-discharge value does not meet the screening standard, judging that the self-discharge performance of the lithium battery is unqualified. In the application, SOC, temperature and surface pressure of the battery cell are correspondingly set, so that detection of self-discharge performance (chemical self-discharge and physical self-discharge) of each type of lithium battery is completed, and self-discharge values obtained through detection are more comprehensive. Screening standards established for self-discharge performance of each type are stored in the system, and screening precision of self-discharge capacity of the lithium battery can be greatly improved by comparing self-discharge values with the corresponding screening standards.

Referring to fig. 3, a computer device, which may be a server and whose internal structure may be as shown in fig. 3, is also provided in the embodiment of the present application. The computer device includes a processor, a memory, a network interface, and a database connected by a system bus. Wherein the computer designed processor is used to provide computational and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the computer device is used for storing data such as screening standards and the like. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a method for screening lithium battery self-discharge performance.

The processor executes the steps of the screening method for the self-discharge performance of the lithium battery:

s3, adjusting the second voltage of the battery cell to a third voltage;

s6, judging whether the self-discharge value meets the screening standard;

the first preset time and the second preset time are not more than 36 h.

and S9, outputting the prompt information to a display interface.

An embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements a method for screening self-discharge performance of a lithium battery, and the method includes:

s3, adjusting the second voltage of the battery cell to a third voltage;

s6, judging whether the self-discharge value meets the screening standard;

the first preset time and the second preset time are not more than 36 h.

s502, substituting the third voltage, the fourth voltage and the second preset time into a second formula, and calculating to obtain the physical self-discharge value, wherein,the second formula is:

and S9, outputting the prompt information to a display interface.

It will be understood by those skilled in the art that all or part of the processes of the methods of the above embodiments may be implemented by hardware associated with instructions of a computer program, which may be stored on a non-volatile computer-readable storage medium, and when executed, may include processes of the above embodiments of the methods. Any reference to memory, storage, database, or other medium provided herein and used in the examples may include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), double-rate SDRAM (SSRSDRAM), Enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, apparatus, article, or method. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, apparatus, article, or method that includes the element.

The above description is only for the preferred embodiment of the present application and not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application, or which are directly or indirectly applied to other related technical fields, are intended to be included within the scope of the present application.

Claims

1. A screening method for self-discharge performance of a lithium battery is characterized by comprising the following steps:

adjusting the second voltage of the cell to a third voltage;

judging whether the self-discharge value meets the screening standard or not;

2. The screening method for the self-discharge performance of the lithium battery according to claim 1, wherein the step of adjusting the temperature and the surface pressure of the battery cell after the voltage adjustment to first preset conditions includes:

3. The screening method for the self-discharge performance of the lithium battery as claimed in claim 2, wherein the step of adjusting the temperature and the surface pressure of the battery cell after the voltage adjustment to the second preset condition includes:

4. The screening method for the self-discharge performance of the lithium battery according to claim 1, wherein the self-discharge value includes a chemical self-discharge value, a physical self-discharge value and a total self-discharge value, and the step of calculating the self-discharge value of the battery cell according to the first voltage, the second voltage, the third voltage, the fourth voltage, the first preset time and the second preset time includes:

5. The screening method for the self-discharge performance of the lithium battery as claimed in claim 4, wherein the screening criteria comprises a plurality of standard values of different types, and the step of determining whether the self-discharge value meets the screening criteria comprises:

6. The method for screening the self-discharge performance of the lithium battery according to claim 1, wherein the step of determining that the self-discharge performance of the lithium battery is not qualified comprises the following steps:

and outputting the prompt information to a display interface.

7. The method for screening the self-discharge performance of the lithium battery according to claim 1, wherein in the step of adjusting the voltage of the battery cell of the lithium battery to the first voltage, the SOC of the adjusted battery cell is greater than 80%;

the first preset time and the second preset time are not more than 36 h.

8. The utility model provides a screening device of lithium cell self discharge performance which characterized in that includes:

9. A computer device comprising a memory and a processor, the memory having stored therein a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.