CN111190116A - Lithium ion battery safety management method and system - Google Patents
Lithium ion battery safety management method and system Download PDFInfo
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- CN111190116A CN111190116A CN201811351528.8A CN201811351528A CN111190116A CN 111190116 A CN111190116 A CN 111190116A CN 201811351528 A CN201811351528 A CN 201811351528A CN 111190116 A CN111190116 A CN 111190116A
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Abstract
The technical problems to be solved by the invention are as follows: the traditional method for evaluating the safety of the lithium ion battery is to evaluate whether the lithium ion battery passes through the abuse tests such as short circuit, overcharge and extrusion in international and domestic standards, and the lithium ion battery with different models which pass through the related abuse tests cannot be judged to be safer. With the use of lithium ion batteries, the service life of the lithium ion batteries is reduced, and the internal heating condition of the lithium ion batteries is changed. The invention provides a lithium ion battery safety management method and system, which can calculate the thermal runaway probability change of a lithium ion battery in real time, and when the thermal runaway probability reaches a certain value, the lithium ion battery can be judged to be unusable and to be recycled, so that the problem that the safety of the lithium ion battery cannot be evaluated after the lithium ion battery is used for a long time is solved, and the problem that the safety of lithium ions of different types cannot be evaluated and compared after the lithium ions pass safety test certification is also solved.
Description
Technical Field
The invention belongs to the field of safety evaluation of power batteries of electric automobiles. And more particularly to thermal runaway safety assessment of power cells.
Background
The lithium ion battery has the advantages of high voltage, large energy density, small volume, light weight, environmental protection, long service life and the like, and is widely applied to the fields of mobile equipment, electric automobiles, power station energy storage and the like. And with the technical progress and the improvement of cost performance of the lithium battery, the lead-acid battery can replace the prior lead-acid battery application field in wider fields. With wider application field and more applications of the lithium ion battery, the safety of the lithium ion battery becomes a key problem influencing the application of the lithium ion battery. Safety is an important technical problem for restricting the large-scale application of high-specific-energy and high-capacity lithium ion batteries, and thermal runaway is a root cause of unsafe behaviors such as explosion, combustion and the like of the batteries.
In order to test and evaluate the safety of the lithium ion battery, the lithium ion battery standards at home and abroad are as follows: the standards such as IEC62133, UL1642, UL2580 and GB31485-2015 specify the contents and methods of safety tests such as short-circuiting, overcharge, high-temperature storage and extrusion of lithium ion batteries. The abuse test is adopted in the tests to evaluate whether the batteries are on fire or not, and when the two batteries pass the related safety test, the safety of the batteries can not be judged according to the test result. Meanwhile, after the lithium ion battery is used for a long time, the service life of the lithium ion battery is aged, and the safety of the lithium ion battery cannot be tracked and judged in real time.
Disclosure of Invention
Aiming at the technical problems in the background art, the invention provides a method and a system for evaluating the safety of a lithium ion battery.
The invention provides a safety management method of a lithium ion battery, which is characterized by comprising the following steps:
the method comprises the following steps of firstly, obtaining the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
step two, putting N lithium ion batteries at normal temperature TambUnder the environmentFully charging from 0% SOC to 100% SOC at 1C multiplying power, simultaneously monitoring the surface temperature of each lithium ion battery, and recording the maximum value of the surface temperature in the charging process of the lithium ion battery as TsurfAnd the ambient temperature is denoted Tamb；
Step three, calculating the highest temperature T inside each lithium ion battery according to the following formulain：
Tin＝Tsurf+(Tsurf-Tamb)*(L*H/2K)；
Calculating the mean value mu and the standard deviation delta of the highest temperature in each lithium ion battery according to a statistical formula;
step five, calculating the thermal runaway probability value of the lithium ion battery according to the following formula:
F(Tr,μ,δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]}*100％；
and step six, outputting the safety evaluation value of the lithium ion battery based on the thermal runaway probability value calculated in the step five.
The invention also provides a lithium ion battery safety management system, which is characterized by comprising a parameter acquisition unit, a lithium ion battery charging unit, a temperature monitoring unit, a calculation unit and an output unit, wherein,
the parameter acquiring unit is used for acquiring the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
the lithium ion battery charging unit is used for charging N lithium ion batteries at normal temperature TambFully charging from 0% SOC to 100% SOC at 1C rate under the environment;
the temperature monitoring unit is used for monitoring the surface temperature of the lithium ion batteries in the charging process, and the maximum temperature value of each lithium ion battery in the charging process is recorded as TsurfAnd recording the ambient temperature Tamb；
The calculating unit is used for calculating the highest temperature T in each lithium ion battery according to the following formulain：
Tin＝Tsurf+(Tsurf-Tamb)*(L*H/2K)，
Meanwhile, the mean value mu and the standard deviation delta of the highest temperature in the N lithium ion batteries are calculated according to a statistical formula, and the thermal runaway probability value of the lithium ion batteries is calculated according to the following formula:
F(Tr,μ,δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]}*100％；
and the output unit outputs the safety evaluation value of the lithium ion battery based on the calculated thermal runaway probability value.
The method comprises the steps of monitoring the surface temperature of the lithium ion battery, calculating the highest temperature inside the lithium ion battery in a simulation mode, calculating the thermal runaway probability of the lithium ion battery by applying a probability algorithm according to the melting temperature of the isolating membrane of the lithium ion battery, and judging the safety of the lithium ion battery according to the thermal runaway probability. According to the method, the safety of the lithium ion battery can be tracked and judged in real time.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a flow chart of the system according to the present invention.
Fig. 3 is a schematic diagram of the center temperature and the surface temperature of the lithium ion battery.
Detailed Description
The lithium ion battery passes through related standard safety detection, and possible thermal runaway is possible after abuse conditions are eliminated, mainly because the temperature of the inside of the lithium ion battery is too high, the temperature of an isolation membrane is too high to melt, so that rapid internal short circuit occurs, and the thermal runaway of the lithium ion battery is caused.
Under the condition that the type number and the use condition of the lithium ion battery are determined, the heat conductivity coefficient of an internal material, the surface heat exchange coefficient and the external environment temperature of the lithium ion battery are known values, the maximum value of the surface temperature of the lithium ion battery is monitored by a monitoring system, and the maximum temperature inside the lithium ion battery can be calculated according to the calculation of a simulation algorithm.
The thermal stability of separators used inside lithium ion batteries varies depending on the raw materials and processes. The melting point of the isolating membrane made of polypropylene (PP) material is about 160 ℃, the melting point of the isolating membrane made of Polyethylene (PE) material is about 130 ℃, the melting points of the multi-layer isolating membrane are related to the components of the multi-layer isolating membrane, and the melting temperature of the isolating membrane of the lithium ion battery can be provided by a lithium ion battery supplier.
Under the same use condition, the highest temperature inside the lithium ion battery is Poisson distribution, and the thermal runaway probability of the lithium ion battery can be calculated by calculating the cumulative probability of the central temperature of the lithium ion battery below the melting temperature of the lithium ion battery isolating membrane according to the central temperature value and the melting temperature of the lithium ion battery isolating membrane.
As shown in fig. 1, the present invention provides a lithium ion battery safety management method, which includes the following steps:
the method comprises the following steps of firstly, obtaining the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
step two, putting N lithium ion batteries at normal temperature TambFully charging from 0% SOC to 100% SOC at 1C multiplying power in the environment, simultaneously monitoring the surface temperature of each lithium ion battery, and recording the maximum value of the surface temperature in the charging process of the lithium ion battery as TsurfAnd the ambient temperature is denoted Tamb；
Step three, calculating the highest temperature T inside each lithium ion battery according to the following formula (1)in：
Tin＝Tsurf+(Tsurf-Tamb) (L H/2K) formula (1)
Calculating the mean value mu and the standard deviation delta of the highest temperature in each lithium ion battery according to a statistical formula;
step five, calculating the thermal runaway probability value of the lithium ion battery according to the following formula (2):
F(Tr,μ,δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]100% of the formula (2)
And step six, outputting the safety evaluation value of the lithium ion battery based on the thermal runaway probability value calculated in the step five.
As shown in fig. 2, the present invention further provides a lithium ion battery safety management system, which comprises a parameter obtaining unit, a lithium ion battery charging unit, a temperature monitoring unit, a calculating unit and an output unit, wherein,
the parameter acquiring unit is used for acquiring the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
the lithium ion battery charging unit is used for charging N lithium ion batteries at normal temperature TambFully charging from 0% SOC to 100% SOC at 1C rate under the environment;
the temperature monitoring unit is used for monitoring the surface temperature of the lithium ion batteries in the charging process, and the maximum temperature value of each lithium ion battery in the charging process is recorded as TsurfAnd recording the ambient temperature Tamb；
The calculating unit is used for calculating the highest temperature T in each lithium ion battery according to the following formulain：
Tin＝Tsurf+(Tsurf-Tamb)*(L*H/2K)，
Meanwhile, the mean value mu and the standard deviation delta of the highest temperature in the N lithium ion batteries are calculated according to a statistical formula, and the thermal runaway probability value of the lithium ion batteries is calculated according to the following formula:
F(Tr,μ,δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]}*100％；
and the output unit outputs the safety evaluation value of the lithium ion battery based on the calculated thermal runaway probability value.
Application example 1-evaluation of safety of lithium ion batteries of different models. The safety evaluation method provided by the invention is used for carrying out safety evaluation on the lithium ion batteries with two different models through national standard strong detection authentication. Obtaining the melting point temperatures T of the lithium ion battery isolating membranes by lithium ion battery manufacturersr1And Tr2The internal heat conductivity coefficient of the lithium ion battery is K1And K1Surface heat transfer coefficient of H1And H2(constant), respectively randomly selecting 10 lithium ion batteries, and testing the lithium ion batteries to be evaluated at normal temperature TambFully putting the lithium ion battery from 100% SOC to 0% SOC at 1C multiplying power in the environment, and simultaneously monitoring the surface temperature of the lithium ion battery, wherein the maximum value is TsurfAnd the thickness of the lithium ion battery is L (refer to fig. 3), the maximum temperature T inside the lithium ion battery can be calculated according to the above formula (1)inAnd respectively obtaining the internal highest temperature of 10 lithium ion batteries, randomly extracting the lithium ion batteries, and calculating the mean value mu and the standard deviation delta of the lithium ion batteries according to a Poisson distribution statistical formula, wherein the mean value mu and the standard deviation delta are more representative as the number of the lithium ion batteries is more. Respectively obtaining the sampling mu of the highest temperature of the two lithium ion batteries under 1C discharge1、δ1And mu2、δ2. Respectively calculating the thermal runaway probability values F of the two lithium ion batteries according to the formula (2)1And F2Comparing the thermal runaway probability values, the lithium ion battery with smaller thermal runaway probability has higher safety.
Application example 2-evaluation of safety after long-term use of a power battery system. When the battery system is designed, the temperature detection temperature sensing line of the battery system is designed to be tightly attached to the center of the surface of a single battery, as shown in figure 3, and N batteries are measured simultaneously. Obtaining the melting point temperature T of the isolating membrane of the lithium ion battery by a lithium ion battery manufacturerrThe thickness of the lithium ion battery is L (refer to fig. 3), the internal thermal conductivity of the lithium ion battery is K, and the surface heat transfer coefficient is H (constant). In the running process of the vehicle, the battery management system BMS timely monitors the surface temperatures of the N batteries, and the maximum temperature T inside the N lithium ion batteries can be calculated through the formula (1)inThe method comprises the steps of calculating a mean value mu and a standard deviation delta of the Poisson distribution statistical formula, then calculating a real-time thermal runaway probability F according to the formula (2), wherein the thermal runaway probability F is larger and larger as the battery is used for a long time and the service life of the battery is aged, the battery is heated more and more seriously, the consistency of the battery is poorer and more, and the thermal runaway probability F is determined to be too large through company risk assessment, so that the thermal runaway probability of a battery system is required to be retired and replaced when the thermal runaway probability reaches a certain limit value.
The traditional method is to evaluate the safety of the lithium ion battery by various standard abuse test methods of international national standards, which only proves that the lithium ion battery can pass related abuse tests and cannot evaluate the safety of the lithium ion battery in the use process. According to the method and the system provided by the invention, the safety of the lithium ion batteries of different models can be compared by calculating the thermal runaway probability of the lithium ion batteries of different models, and meanwhile, the safety of the lithium ion batteries can be monitored in real time. According to the method and the system provided by the invention, the safety of the lithium ion battery can be evaluated in real time by monitoring the surface temperature of the lithium ion battery and simulating calculation, so that the safety evaluation method and the system can be used as a safety evaluation reference for the purchase and use of the lithium ion battery and the evaluation reference for whether the lithium ion battery system needs to be replaced and recycled.
It should be understood that the described embodiments of the present invention are only some of the examples of the present invention, and are only used for illustrating the present invention and not for limiting the scope of the present invention. Furthermore, it should be understood that various changes and modifications of the present invention as taught herein may be made by those skilled in the art, and that such evaluation methods also fall within the scope of the present invention as defined in the appended claims.
Claims (2)
1. A safety management method for a lithium ion battery is characterized by comprising the following steps:
the method comprises the following steps of firstly, obtaining the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
step two, putting N lithium ion batteries at normal temperature TambFully charging from 0% SOC to 100% SOC at 1C multiplying power in the environment, simultaneously monitoring the surface temperature of each lithium ion battery, and recording the maximum value of the surface temperature in the charging process of the lithium ion battery as TsurfAnd the ambient temperature is denoted Tamb；
Step three, calculating the highest temperature T inside each lithium ion battery according to the following formulain：
Tin＝Tsurf+(Tsurf-Tamb)*(L*H/2K)；
Calculating the mean value mu and the standard deviation delta of the highest temperature in each lithium ion battery according to a statistical formula;
step five, calculating the thermal runaway probability value of the lithium ion battery according to the following formula:
F(Tr，μ，δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]}*100％；
and step six, outputting the safety evaluation value of the lithium ion battery based on the thermal runaway probability value calculated in the step five.
2. A lithium ion battery safety management system is characterized by comprising a parameter acquisition unit, a lithium ion battery charging unit, a temperature monitoring unit, a calculation unit and an output unit, wherein,
the parameter acquiring unit is used for acquiring the following parameter values of the lithium ion battery: melting point temperature T of isolation filmrThe thickness L of the lithium ion battery, the internal heat conductivity coefficient K of the lithium ion battery and the surface heat exchange coefficient H of the lithium ion battery;
the lithium ion battery charging unit is used for charging N lithium ion batteries at normal temperature TambFully charging from 0% SOC to 100% SOC at 1C rate under the environment;
the temperature monitoring unit is used for monitoring the surface temperature of the lithium ion batteries in the charging process, and the maximum temperature value of each lithium ion battery in the charging process is recorded as TsurfAnd recording the ambient temperature Tamb；
The calculating unit is used for calculating the highest temperature T in each lithium ion battery according to the following formulain：
Tin＝Tsurf+(Tsurf-Tamb)*(L*H/2K)，
Meanwhile, the mean value mu and the standard deviation delta of the highest temperature in the N lithium ion batteries are calculated according to a statistical formula, and the thermal runaway probability value of the lithium ion batteries is calculated according to the following formula:
F(Tr，μ，δ)＝{1-[1/(2π*δ)]*exp[-(Tr-μ)2/(2*δ2)]}*100％；
and the output unit outputs the safety evaluation value of the lithium ion battery based on the calculated thermal runaway probability value.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113189491A (en) * | 2021-05-19 | 2021-07-30 | 中国科学技术大学 | Method for analyzing heat production rate of cylindrical lithium ion battery |
| CN116566019A (en) * | 2023-07-05 | 2023-08-08 | 广州市虎头电池集团股份有限公司 | Charging control method and system for lithium battery pack |
| CN113189491B (en) * | 2021-05-19 | 2024-06-11 | 中国科学技术大学 | Analysis method for heat generation rate of cylindrical lithium ion battery |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113189491A (en) * | 2021-05-19 | 2021-07-30 | 中国科学技术大学 | Method for analyzing heat production rate of cylindrical lithium ion battery |
| CN113189491B (en) * | 2021-05-19 | 2024-06-11 | 中国科学技术大学 | Analysis method for heat generation rate of cylindrical lithium ion battery |
| CN116566019A (en) * | 2023-07-05 | 2023-08-08 | 广州市虎头电池集团股份有限公司 | Charging control method and system for lithium battery pack |
| CN116566019B (en) * | 2023-07-05 | 2023-10-13 | 广州市虎头电池集团股份有限公司 | Charging control method and system for lithium battery pack |
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