CN113075564B - Screening method for self-discharge of lithium iron phosphate battery - Google Patents
Screening method for self-discharge of lithium iron phosphate battery Download PDFInfo
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- CN113075564B CN113075564B CN202110314863.6A CN202110314863A CN113075564B CN 113075564 B CN113075564 B CN 113075564B CN 202110314863 A CN202110314863 A CN 202110314863A CN 113075564 B CN113075564 B CN 113075564B
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- preset time
- battery
- lithium battery
- iron phosphate
- voltage
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000012216 screening Methods 0.000 title claims abstract description 24
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 39
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 39
- 239000000178 monomer Substances 0.000 claims abstract description 14
- 238000007599 discharging Methods 0.000 claims abstract description 7
- 230000005611 electricity Effects 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
- G01R31/3835—Arrangements for monitoring battery or accumulator variables, e.g. SoC involving only voltage measurements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
Abstract
The invention discloses a screening method for self-discharge of a lithium iron phosphate battery. Belongs to the technical field of manufacturing of lithium iron phosphate batteries. The method mainly solves the problem of long screening period in the self-discharge screening method. It is mainly characterized by comprising the following steps: discharging the electricity of the single lithium battery, charging to 10% -30% of the SOC of the nominal capacity with small current, placing for a first preset time at room temperature, and measuring the voltage V1 of the single lithium battery; firstly placing the measured single lithium battery at a high temperature for a second preset time, then placing the single lithium battery at a room temperature for a third preset time, and measuring the voltage V2 of the single lithium battery; continuously placing the measured single lithium battery at room temperature for a fourth preset time, and measuring the voltage V3 of the single lithium battery; and calculating a K23 value, and eliminating the monomer lithium batteries which do not meet the requirements according to the K23 value standard. The method has the characteristics of simple operation, suitability for mass production and good screening consistency, and is mainly used for eliminating the lithium iron phosphate monomer batteries with poor consistency.
Description
Technical Field
The invention belongs to the technical field of manufacturing of lithium iron phosphate batteries, and particularly relates to a method for screening lithium iron phosphate single batteries with consistent performance through self-discharge.
Background
At present, the lithium iron phosphate battery is applied to more fields such as energy storage equipment, electric automobiles and the like. The fuel price is continuously increased, the electric automobile is energy-saving and environment-friendly and is deeply favored by customers, and the electric automobile is gradually raised in the market.
In the production process of the lithium iron phosphate battery, the lithium iron phosphate battery can be influenced by various factors such as equipment, raw materials, methods and the like, the performances of the single lithium batteries have certain differences, and the performances of the single lithium batteries directly influence the performances of the whole battery pack, so that a correct self-discharge screening method is very important.
At present, the existing self-discharge screening method comprises the following steps: the method for measuring the K value of the battery by standing at normal temperature has the standing and screening period of about 20 days, and the abnormal battery is difficult to be completely removed by adopting a normal-temperature standing scheme.
Disclosure of Invention
The invention aims to provide a self-discharge screening method for the lithium iron phosphate battery, which is used for eliminating the monomer lithium battery with poor consistency, wherein the monomer lithium iron phosphate battery has a relatively sensitive corresponding relation between capacity and voltage in a state of being charged to a relatively low state, and has a short screening period and high screening consistency accuracy.
In order to achieve the above purpose, the present invention provides the following technical solutions: the screening method for self-discharge of the lithium iron phosphate battery is used for rejecting the lithium iron phosphate single lithium battery with poor consistency and is characterized by comprising the following steps of:
firstly, discharging the electric quantity of a single lithium battery, charging to 10% -30% of the SOC of the nominal capacity with small current, placing for a first preset time at room temperature, and measuring the voltage V1 of the single lithium battery, wherein the value range of the voltage V1 is 3000mv-3330mv;
step two, firstly placing the measured single lithium battery at a high temperature for a second preset time, and then placing the single lithium battery at room temperature for a third preset time, and measuring the voltage V2 of the single lithium battery, wherein the voltage V2 is in a range of 3000-3330 mv, and 0mv is less than or equal to (V2-V1) and less than or equal to 20mv;
step three, continuously placing the measured single lithium battery at room temperature for a fourth preset time, and measuring the voltage V3 of the single lithium battery, wherein the value range of the voltage V3 is 3000-3330 mv;
and step four, calculating a K23 value, and eliminating the single batteries which do not meet the requirements according to the K23 value standard.
In the first step of the technical solution of the invention, the small current is 0.1-0.5C current, the room temperature is 20-26 ℃, and the first preset time is 12-24H.
In the second step of the technical solution of the invention, the high temperature is 40-50 ℃, the second preset time is 72-120H, the room temperature is 20-26 ℃, and the third preset time is 12-24H.
In the third step of the technical solution of the present invention, the fourth predetermined time is 72-120H.
In the fourth step of the technical solution of the invention, the K23 value= (V2-V3)/(T3-T2), and the K23 standard is 0-0.04mv/h.
In the second step, the high temperature is 40-50 ℃, the second preset time is 72-120H, the room temperature is 20-26 ℃, and the third preset time is 12-24H; in the third step, the fourth preset time is 72-120H; in the fourth step, the K23 value= (V2-V3)/(T3-T2), and the K23 standard is 0-0.04mv/h.
The beneficial effects of the invention are as follows: according to the invention, through charging the single lithium battery to the SOC in a lower state after the single lithium battery is emptied, at the moment, the capacity and the voltage of the single lithium battery are extremely sensitive, a small amount of capacity difference has large voltage change, then the internal reaction of the battery is aggravated through high-temperature aging, finally the self-discharge is selected by using K value calculation, the self-discharge screening period is shortened, and the efficiency is high. The invention adopts a method of high-temperature standing and normal-temperature standing to measure the K value of the battery, eliminates the battery with large pressure difference through high-temperature standing, shortens the standing and screening period to about 12 days, and shortens the period to about 8 days.
The method is mainly used for eliminating the lithium iron phosphate monomer batteries with poor consistency.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments.
A screening method for self-discharge of lithium iron phosphate batteries is used for rejecting lithium iron phosphate single batteries with poor consistency, and comprises the following steps:
firstly, discharging a lithium iron phosphate monomer battery to empty electricity at a current of 0.5-1C, then charging to 10-30% of SOC with a nominal capacity at a current of 0.1-0.5C, standing for a first preset time for 12-24H at a temperature of 20-26 ℃, and measuring a battery voltage V1, wherein the value range of V1 is 3000-3330 mv;
step two, placing the battery at a high temperature of 40-50 ℃ for a second preset time of 72-120H, and then placing the battery at a room temperature of 20-26 ℃ for a third preset time of 12-24H, wherein the value range of the measured battery voltage V2 is 3000mv-3330mv, and 0mv is less than or equal to (V2-V1) and less than or equal to 20mv;
step three, continuously placing the measured single lithium battery at the room temperature of 20-26 ℃ for a fourth preset time of 72-120H, and measuring the battery voltage V3, wherein the range of the V3 value is as follows: 3000mv-3330mv;
and step four, calculating a K23 value, wherein the K23 value= (V2-V3)/(T3-T2), the K23 standard is 0-0.04mv/h, and eliminating the monomer batteries which do not meet the requirements according to the K23 value standard.
Example 1
Firstly, discharging a lithium iron phosphate monomer battery to empty electricity at a current of 0.5C, then charging to 30% SOC of a nominal capacity at a current of 0.5C, standing for a first preset time 12H at a room temperature of 20-26 ℃, and measuring a battery voltage V1, wherein the V1 value is 3275mv and is in a range of 3000-3330 mv;
step two, placing the battery at a high temperature of 40-50 ℃ for a second preset time 72H, then placing the battery at a room temperature of 20-26 ℃ for a third preset time 18H, measuring the voltage V2 of the battery, wherein the V2 value is 3270mv, and the voltage is less than or equal to 0mv and less than or equal to (V2-V1) and less than or equal to 20mv within the range of 3000-3330 mv;
step three, continuously placing the measured single lithium battery at the room temperature of 20-26 ℃ for a fourth preset time of 100H, and measuring the battery voltage V3, wherein the V3 value is 3268mv and is in the range of 3000-3330 mv;
and step four, calculating a K23 value according to (V2-V3)/(T3-T2), wherein the K23 value is 0.04mv/h, and the K23 value is more than 0.04mv/h or less than 0mv/h in the standard range of 0-0.04mv/h, so that the lithium iron phosphate monomer battery which is not in compliance with the requirements is removed.
Example 2
Firstly, discharging a lithium iron phosphate monomer battery to an empty electricity with a current of 1C, then charging to 10% SOC of a nominal capacity with a current of 0.3C, standing for a first preset time 24H at a room temperature of 20-26 ℃, and measuring a battery voltage V1, wherein the V1 value is 3172mv and is in a range of 3000-3330 mv;
step two, placing the battery at a high temperature of 40-50 ℃ for a second preset time of 120H, and then placing the battery at a room temperature of 20-26 ℃ for a third preset time of 12H, wherein the measured battery voltage V2 has a V2 value of 3162mv and is within a range of 3000-3330 mv, and the voltage of 0mv is less than or equal to (V2-V1) and less than or equal to 20mv;
step three, continuously placing the measured single lithium battery at the room temperature of 20-26 ℃ for a fourth preset time 72H, and measuring the battery voltage V3, wherein the V3 value is 3160mv and is in the range of 3000-3330 mv;
and step four, calculating a K23 value according to (V2-V3)/(T3-T2), wherein the K23 value is 0.0278mv/h, and the K23 value is more than 0.04mv/h or less than 0mv/h in the standard range of 0-0.04mv/h, so that the lithium iron phosphate monomer battery which is not in line with the requirements is removed.
Example 3
Firstly, discharging a lithium iron phosphate monomer battery to empty electricity at a current of 0.8C, then charging to 20% SOC of a nominal capacity at a current of 0.1C, placing for a first preset time at a room temperature of 20-26 ℃ for 20H, and measuring a battery voltage V1, wherein the V1 value is 3231mv and is in a range of 3000-3330 mv;
step two, placing the battery at a high temperature of 40-50 ℃ for a second preset time of 90H, and then placing the battery at a room temperature of 20-26 ℃ for a third preset time of 24H, wherein the measured battery voltage V2 has a V2 value of 3224mv and is within a range of 3000-3330 mv, and the V is less than or equal to 0mv and less than or equal to 20mv (V2-V1);
step three, continuously placing the measured single lithium battery at the room temperature of 20-26 ℃ for a fourth preset time of 120H, and measuring the battery voltage V3, wherein the V3 value is 3223mv and is within the range of 3000-3330 mv;
and step four, calculating a K23 value according to (V2-V3)/(T3-T2), wherein the K23 value is 0.0167mv/h, and the K23 value is more than 0.04mv/h or less than 0mv/h in the standard range of 0-0.04mv/h, so that the lithium iron phosphate monomer battery which is not in compliance with the requirements is removed.
It can be seen from examples 1-3 that in the process of screening the lithium iron phosphate single lithium battery, the electric quantity of the lithium iron phosphate single lithium battery is firstly emptied, then the SOC in a lower state is charged with a small current, at this time, the capacity and the voltage of the lithium iron phosphate single lithium battery are extremely sensitive, a small quantity of capacity difference has large voltage variation, a K value is calculated according to (V2-V3)/(T3-T2), and the unsatisfactory lithium iron phosphate single lithium battery is removed through the K value, so that the screening period is shortened to about 12 days.
Claims (5)
1. The screening method for self-discharge of the lithium iron phosphate battery is used for rejecting the lithium iron phosphate single lithium battery with poor consistency and is characterized by comprising the following steps of:
firstly, discharging the electric quantity of a single lithium battery, charging to 10% -30% of the SOC of the nominal capacity with small current, placing for a first preset time at room temperature, and measuring the voltage V1 of the single lithium battery, wherein the value range of the voltage V1 is 3000mv-3330mv;
step two, firstly placing the measured single lithium battery at a high temperature for a second preset time, and then placing the single lithium battery at room temperature for a third preset time, and measuring the voltage V2 of the single lithium battery, wherein the voltage V2 is in a range of 3000-3330 mv, and 0mv is less than or equal to (V2-V1) and less than or equal to 20mv;
step three, continuously placing the measured single lithium battery at room temperature for a fourth preset time, and measuring the voltage V3 of the single lithium battery, wherein the value range of the voltage V3 is 3000-3330 mv;
and step four, calculating a K23 value, wherein the K23 value= (V2-V3)/(T3-T2), the K23 value standard is 0-0.04mv/h, and eliminating the monomer lithium batteries which do not meet the requirements according to the K23 value standard.
2. The method for screening self-discharge of lithium iron phosphate batteries according to claim 1, wherein the method comprises the following steps: in the first step, the small current is 0.1-0.5C current, the room temperature is 20-26 ℃, and the first preset time is 12-24H.
3. The method for screening self-discharge of lithium iron phosphate batteries according to claim 1, wherein the method comprises the following steps: in the second step, the high temperature is 40-50 ℃, the second preset time is 72-120H, the room temperature is 20-26 ℃, and the third preset time is 12-24H.
4. The method for screening self-discharge of lithium iron phosphate batteries according to claim 1, wherein the method comprises the following steps: in the third step, the fourth preset time is 72-120H.
5. The method for screening self-discharge of lithium iron phosphate batteries according to claim 2, wherein the method comprises the following steps: in the second step, the high temperature is 40-50 ℃, the second preset time is 72-120H, the room temperature is 20-26 ℃, and the third preset time is 12-24H; in the third step, the fourth preset time is 72-120H; in the fourth step, the K23 value standard is 0-0.04mv/h.
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