CN110994059B - Temperature threshold value determination method for thermal runaway early warning - Google Patents

Temperature threshold value determination method for thermal runaway early warning Download PDF

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CN110994059B
CN110994059B CN201911251125.0A CN201911251125A CN110994059B CN 110994059 B CN110994059 B CN 110994059B CN 201911251125 A CN201911251125 A CN 201911251125A CN 110994059 B CN110994059 B CN 110994059B
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power battery
temperature
battery
self
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CN110994059A (en
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王书洋
孙焕丽
姜涛
任毅
孟祥宇
董谦
许立超
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FAW Group Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/486—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for measuring temperature
    • 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]
    • G01R31/385—Arrangements for measuring battery or accumulator variables
    • 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]
    • G01R31/392—Determining battery ageing or deterioration, e.g. state of health
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention relates to a temperature threshold value determining method for thermal runaway early warning, which adopts a power battery life single attenuation mechanism to design a corresponding life acceleration working condition, obtains a working condition influence factor of the life acceleration working condition corresponding to a specific life attenuation value of a power battery through circulating the life acceleration working condition, discretizes the whole vehicle working condition of a vehicle to be tested to obtain a working condition segment proportion corresponding to the life acceleration working condition, then calculates to obtain a safety influence factor of the power battery of the vehicle to be tested under the current state, combines the safety influence factor with a BOL battery monomer self-heat production initial temperature test value to calculate a threshold value of self-heat production initial temperature judgment of the power battery under the current healthy state, compares the threshold value with the highest temperature which can occur under the non-self-heat production condition of the power battery, and takes a small value as a temperature threshold value for thermal runaway early warning, the method can meet the temperature threshold determination of the thermal runaway early warning of the power battery in the whole life cycle.

Description

Temperature threshold value determination method for thermal runaway early warning
Technical Field
The invention belongs to the field of power batteries, and relates to a temperature threshold value determination method for thermal runaway early warning.
Background
Under the requirement of the pure electric passenger vehicle driving range in the consumption market, the energy density of the power battery is gradually increased. With the improvement of energy density of power batteries, the safety problem of the power batteries is gradually highlighted, and the safety of the power batteries is considered as a life line for the development of new energy automobiles. The method has the advantages that the prevention of thermal runaway and thermal diffusion of the battery is an important subject in the design process of the battery, and under certain irresistible situations and during a battery heating safety accident, a timely and effective early warning strategy can greatly reduce the personal and property loss of consumers. The early warning strategy is characterized in that a timely and effective temperature early warning threshold can greatly prolong the time of thermal runaway early warning, and meanwhile, the threshold is also guaranteed to be reasonable enough, so that false alarm is not carried out when no thermal runaway occurs, and unnecessary panic is caused. The safety of the battery changes along with the life decay of the battery, so that the thermal runaway temperature threshold of the battery is changed, and the thermal runaway temperature early warning threshold suitable for the whole life cycle cannot be obtained through a simple self-generated thermal initial temperature test.
CN110058173A discloses a method for testing a thermal runaway temperature curve of a battery by using an accelerated adiabatic calorimeter, and by analyzing the change rule of the temperature of a battery core, information such as a self-heat-release starting temperature, an explosion-proof valve opening temperature, a critical temperature, a thermal runaway temperature, a maximum temperature after thermal runaway and the like in the thermal runaway process of the battery is obtained, and meanwhile, the self-heat-release starting temperature can be used for thermal runaway early warning. The tested thermal runaway early warning temperature is only suitable for a new battery and cannot meet the thermal runaway early warning requirement of the battery in the whole life cycle. Meanwhile, the test conditions cannot cover all battery failure modes in the whole vehicle application, and the self-heat-generation initial temperature has certain deviation in the temperature acquisition of the battery management system under different failure modes, so that the thermal runaway temperature early warning threshold is determined only from the self-heat-generation temperature in a single dimension and is not perfect.
Therefore, it is of great significance to develop a method for determining a temperature threshold value suitable for the warning of thermal runaway in the full life cycle of a power battery.
Disclosure of Invention
The invention aims to provide a temperature threshold determining method for thermal runaway early warning, which adopts a power battery life single attenuation mechanism to design a corresponding life acceleration working condition, obtains a working condition influence factor of the life acceleration working condition corresponding to a power battery specific life attenuation value through circulating the life acceleration working condition, discretizes the whole vehicle working condition of a vehicle to be tested to obtain a working condition segment proportion corresponding to the life acceleration working condition, then calculates to obtain a safety influence factor of the power battery of the vehicle to be tested under the current state, combines the safety influence factor with a BOL battery monomer heat generation self-starting temperature test value to calculate a threshold for judging the self-generating heat starting temperature of the power battery under the current healthy state, compares the threshold with the highest temperature which can occur under the non-self-generating heat condition of the power battery, takes a small value as a temperature threshold for thermal runaway early warning, the method can meet the temperature threshold determination of the thermal runaway early warning of the power battery in the whole life cycle.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a method for testing a safety influence factor of a power battery in a current state of health, which comprises the following steps:
(1) life acceleration working condition A for designing single life attenuation mechanism of power battery1、A2，…An；
(2) The life acceleration working condition in the step (1) of the accelerated circulation is m% to the life attenuation value of the power battery, and the working condition influence factor a corresponding to the life acceleration working condition in the step (1) is obtained through testing1,m、a2,m… and an,m；
(3) Discretizing the whole vehicle running condition of the vehicle to be tested, and comparing the discretized whole vehicle running condition with the service life acceleration condition A in the step (1)1、A2，…AnCarrying out correspondence to obtain the working condition segment proportion x1、x2… and xn；
(4) Safety influence factors of the vehicle to be tested under the current state of the power battery are as follows:
αm＝a1,m×x1+a2,m×x2……+an,m×xn。
the method disclosed by the invention is used for carrying out an accelerated life test on the battery by identifying the characteristic working condition which has obvious influence on the thermal stability of the battery, determining the influence factor of a single attenuation dimension on the self-heat-release initial temperature of the battery, then carrying out statistics on the whole vehicle running working condition of a vehicle to be tested, extracting the proportion of the specific attenuation dimension segment, and further calculating to obtain the self-heat-generation temperature suitable for the whole life of the power battery.
The n value is based on a first principle and comprises 1. a temperature and voltage level, which comprises SEI film change, lithium separation or anode oxygen separation caused by dissolution of ternary materials, reaction of the ternary materials after the ternary materials penetrate through a diaphragm and react with the SEI film, positive cation mixed discharge and quick charge; 2. mechanical fatigue, respiratory effects; which contains factors causing the degradation of the life of the battery such as the falling off of the active material, the change of the crystal lattice, the powdering, etc.
The working condition influence factor a of the invention1,m、a2,m… and an,mRefers to the acceleration condition A with different service lives when the service life attenuation value of the power battery is m%1、A2，…AnAnd corresponding working condition influence factors.
The value range of the attenuation value m is usually 0-20, the value interval and the number of the attenuation value m have no clear requirements, the more dense the value is, the better the threshold value change curve obtained is fitted with the actual change, the test workload, the sample number and the work difficulty are considered, and the value interval is usually 5%. Meanwhile, the working condition influence factor is the change proportion of the self-heat-production initial temperature tested by an accelerated adiabatic calorimeter, a hot box and the like under different m, and the more densely m is selected, the better the safety change fitting of the working condition influence factor to the whole life cycle is.
Preferably, the single decay mechanism of the service life of the power battery in the step (1) comprises any one of negative electrode lithium separation, SEI film thickening, cation mixing, active material shedding or crystal lattice chalking, and further preferably negative electrode lithium separation or SEI film thickening.
The safety influence factor test needs to be carried out in combination with a power battery life attenuation mechanism, the mechanism of the power battery life attenuation generally comprises negative electrode lithium separation, SEI (solid electrolyte interphase) film thickening, cation mixed discharge, active material falling or crystal lattice pulverization and the like, wherein the attenuation factors of the negative electrode lithium separation and the SEI film thickening have great influence on the safety and the thermal stability of the battery, the power battery is attenuated according to a single mechanism due to specific life test working conditions, and a life acceleration working condition A of a single attenuation mechanism is designed1、A2，…AnAccelerating the cycle until the life attenuation value of the battery power battery is m%, and obtaining the working condition influence factor a of the corresponding life accelerating working condition1,m、a2,m… and an,mAnd the working condition influence factors are obtained by carrying out self-heating temperature test on different capacity attenuation states caused by different acceleration working conditions.
The discretization in the step (2) refers to discretization of key parameters such as battery temperature, current and the like in the operation working condition of the whole vehicle, extraction and acceleration working condition A1、A2……AnCorresponding operating mode segment ratio x1、x2……xn。
Preferably, m is any SOH state before the end of the battery life, typically 0 ≦ m ≦ 20, such as 1, 3, 5, 7, 9, 11, 13, 15, or 18, and the like.
Preferably, n is the number of conditions causing the attenuation of a single influence factor of the battery, and the conditions generally include low-temperature/high-current charging, high-temperature storage, high-rate circulation and the like.
In a second aspect, the present invention provides a method for testing a threshold of a self-heat-generation starting temperature determination in a current state of health of a power battery, where the method includes the following steps:
(a) testing of self-heating starting temperature value T based on BOL battery monomer0；
(b) The threshold value for judging the self-heat-generation starting temperature of the power battery in the current health state is as follows:
Tmax＝T0-αm×T0；
wherein alpha ismThe safety influence factor of the power battery in the current state of health is tested by the method in the first aspect.
Preferably, said T in step (a)0The material is obtained by adopting an accelerated adiabatic calorimeter or a hot box test.
In a third aspect, the present invention provides a temperature threshold determination method for warning of thermal runaway, including the following steps:
(1') testing threshold value T of self-heat-generation starting temperature judgment of power battery in current health statemax；
(2') testing the highest temperature T which can occur under the non-self-heat-production condition of the power batterymax＇；
(3 ') comparing T in step (1')maxAnd T in step (2')max', if Tmax＞Tmax' then the temperature threshold for warning of thermal runaway is Tmax' of a compound of formula I; if Tmax＜Tmax' then the temperature threshold for warning of thermal runaway is TmaxIf T ismax＝Tmax' then the temperature threshold for warning of thermal runaway is TmaxOr Tmax＇；
Wherein, the threshold T of the self-heat-generation starting temperature judgment of the power battery in the current health state is tested in the step (1')maxThe method of (3) employs a method as described in the second aspect.
The method of the invention obtains the threshold value of the self-heat-generation initial temperature judgment of the power battery in the current health state through the method of the second aspect, meanwhile, under the condition of partial function failure of the battery management system, the highest temperature which possibly occurs under the condition that the battery is not self-heat-generation is determined by combining the maximum temperature rise of the battery in the forced power-off time of the whole vehicle, the maximum temperature and the maximum temperature are compared, and the smaller value is taken as the temperature threshold value for the thermal runaway early warning.
The method comprehensively considers the change rule of the safety and the thermal stability of the battery in the full life cycle of the power battery and the highest temperature which can be reached under the non-self-heat-generation state, and can meet the early warning requirement of the thermal runaway temperature of the full life cycle of the power battery.
Preferably, the step (2') tests the highest temperature T that may occur under non-self-generating thermal conditions of the power cellmaxThe method comprises the following steps:
(A) determining temperature threshold T for stopping power output of power battery0＇；
(B) The highest temperature which can occur under the non-self-heat-production condition of the power battery is as follows:
T＇max＝T＇0+t×ΔT；
wherein T is forced power-off time, and DeltaT is the maximum temperature rise rate of the battery.
The power battery of the invention isMaximum temperature T that may occur under autogenous thermal conditionsmax' the test method, first, determining the temperature threshold T at which the power cell stops power output0', the temperature threshold T at which the power cell stops power output0' is the highest threshold of the multi-stage use temperature threshold set by the power battery in the application scene of the whole vehicle, and the battery assembly can take the action of turning off high voltage electricity and stopping power output; secondly, determining the forced power-off time T and the maximum temperature rise rate Delta T of the battery, wherein the forced power-off time T is the time occupied by the action processes of speed reduction, parking, power off and the like which are required to be carried out to ensure safety after the whole vehicle receives a power-off signal requested by a battery management system at a higher speed; the maximum temperature rise rate Delta T of the battery is that the temperature threshold T is exceeded under the partial failure condition of the battery management system0The lack of effective limitation measures leads to a temperature increase rate at which the battery continues to output at normal power, and the battery is discharged at the maximum heat generation condition during the forced power-down time t. Then the highest temperature T which can appear under the non-self-heat-production condition of the power battery is obtained by the calculation of the formulamax' if the temperature of the power cell exceeds Tmax' then, the cell is considered to exhibit side reaction exotherms.
T0' is the original highest fault level of the battery management system, and the corresponding treatment measure is usually to request the whole vehicle to perform high-voltage power-off operation.
t is the time occupied by the action processes of speed reduction, parking, power off and the like which are required to be carried out for ensuring the safety after the whole vehicle receives the power off signal requested by the battery management system at a higher speed.
And the delta T is the maximum temperature rise rate of the battery, which is the temperature rise rate corresponding to the extreme heating working condition under the EOL state of the battery. The working condition that the output power of the battery is the maximum is common, and the working condition comprises the conditions that the battery is discharged at the peak value in the whole vehicle hundred kilometers acceleration process, the battery is discharged continuously at the highest vehicle speed and constant speed, and the like.
The temperature threshold value determining method for the thermal runaway early warning comprises the step of comparing T in all health states of the power battery in the whole life cyclemaxAnd TmaxTaking smaller value asAnd (4) temperature threshold value of thermal runaway early warning in the current health state.
As a preferred technical solution of the present invention, the temperature threshold determining method for warning of thermal runaway includes the following steps:
(I) testing threshold T for judging self-heat-generation initial temperature of power battery in current health statemax(ii) a The test method comprises the following steps:
(I') designing life acceleration condition A of single life attenuation mechanism of power battery1、A2，…An；
(II ') accelerating the life acceleration condition in the step (I') of the cyclic acceleration to the life attenuation value of the power battery of m%, and testing to obtain a working condition influence factor a corresponding to the life acceleration condition in the step (I1,m、a2,m… and an,m；
(III') discretizing the whole vehicle running condition of the vehicle to be tested, and comparing the discretized whole vehicle running condition with the service life acceleration condition A in the step (I1、A2，…AnCarrying out correspondence to obtain the working condition segment proportion x1、x2… and xn；
(IV') safety influence factors of the vehicle to be tested in the current state of the power battery:
αm＝a1,m×x1+a2,m×x2……+an,m×xn；
(V') the threshold value for judging the self-heat-generation starting temperature of the power battery in the current health state is as follows:
Tmax＝T0-αm×T0；
wherein, T0The test value is based on the self-heat-generation starting temperature of the BOL battery monomer;
(II) testing the highest temperature T possibly occurring under the non-self-heat-production condition of the power batterymax', the TmaxThe test method of':
T＇max＝T＇0+t×ΔT；
wherein, T0' is the stopping work of the power batteryThe temperature threshold value of the rate output is T, the forced power-off time is T, and the delta T is the maximum temperature rise rate of the battery;
(III) comparison of T in step (I)maxAnd T in step (II)max', if Tmax＞Tmax' then the temperature threshold for warning of thermal runaway is Tmax' of a compound of formula I; if Tmax＜Tmax' then the temperature threshold for warning of thermal runaway is TmaxIf T ismax＝Tmax' then the temperature threshold for warning of thermal runaway is TmaxOr Tmax＇。
The method of the invention jointly determines the thermal runaway temperature early warning threshold value by the self-heat-production temperature test and the highest temperature test in the non-self-heat-production state of the power battery in the whole life cycle, the mutual check of the two is small, the condition of heat generation of side reaction in the battery use process can be effectively identified, the threshold value is taken as the thermal runaway trigger judgment condition, the thermal runaway early warning signal can be timely and effectively sent out, and the personal injury risk of drivers and passengers is reduced.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method comprises the steps of designing a service life acceleration working condition of a power battery service life single attenuation mechanism, then obtaining working condition influence factors under different service life acceleration working conditions through acceleration circulation, then discretizing the whole vehicle working condition of a vehicle to be tested to obtain a working condition fragment proportion, then calculating to obtain a safety influence factor under the current state of the power battery of the vehicle to be tested, and further calculating to obtain a threshold value for judging the self-heat-generation starting temperature of the power battery under the current health state, wherein the method is suitable for determining the threshold value for judging the self-heat-generation starting temperature of the power battery in the whole life cycle;
(2) the method of the invention judges the threshold value T of the self-heat-generation starting temperature of the power battery in the current health statemaxAnd the highest temperature T possibly occurring under the non-self-heat-production condition of the power batterymaxAnd the comparison is carried out, and a smaller value is taken as the temperature threshold value for the thermal runaway early warning, so that the method for determining the temperature threshold value for the thermal runaway early warning is further perfected.
Drawings
Fig. 1 is a flow chart of a temperature threshold determination method for warning of thermal runaway according to the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The flow chart of the temperature threshold determination method for the thermal runaway warning is shown in fig. 1, and as can be seen from fig. 1, the method comprises the following steps:
(1) threshold value T for judging self-heat-generation starting temperature of power battery in current health statemaxThe testing method comprises the following steps:
(1') designing an acceleration working condition with obvious influence on safety, namely designing a service life acceleration working condition of a single service life attenuation mechanism of the power battery by identifying a characteristic working condition with obvious influence on thermal stability of the battery;
(2 ') accelerating the life acceleration condition in the step (1 ') to a life attenuation value of the power battery of m% to obtain a working condition influence factor corresponding to the life acceleration condition in the step (1 ');
(3 ') discretizing the whole vehicle running condition of the vehicle to be tested, and extracting the characteristic fragment proportion corresponding to the service life acceleration condition in the step (1') to obtain the working condition fragment proportion;
(4 ') combining the working condition influence factor in the step (2 '), the working condition fragment proportion in the step (3 '), and the test value T based on the self-heat-generation starting temperature of the BOL battery monomer0Calculating to obtain a threshold T for judging the self-heat-generation initial temperature of the power battery in the current health statemax；
(2) The highest temperature T possibly occurring under the non-self-heat-production condition of the power batterymaxThe testing method comprises determining a power cell top-level temperature fault threshold T0' forced power-off time T and its corresponding power cell temperature rise rate Δ T; then calculating to obtain the highest temperature T which can appear under the non-self-heat-production condition of the power batterymax＇。
Example 1
The temperature threshold value determination method for the thermal runaway early warning comprises the following steps:
(I) testing threshold T for judging self-heat-generation initial temperature of power battery in current health statemax(ii) a The test method comprises the following steps:
(I') designing life acceleration condition A of single life attenuation mechanism of power battery1、A2；
Wherein A is1For rapid charge at-5 ℃ and discharge at 1C, A2Storing at 60 deg.C;
(II ') accelerating the life acceleration condition in the step (I') of the cyclic acceleration to the life attenuation value of the power battery of m%, and testing to obtain a working condition influence factor a corresponding to the life acceleration condition in the step (I1,m、a2,m；
When m is 20, the test results in a1,20＝50/85，a2，20＝96/85；
(III') discretizing the whole vehicle running condition of the vehicle to be tested, and comparing the discretized whole vehicle running condition with the service life acceleration condition A in the step (I1、A2Carrying out correspondence to obtain the working condition segment proportion x1、x2；
The operating condition extraction is to extract the operating data of the historical vehicle, the analysis method is based on the traditional operating condition characteristic segment extraction method, the method is not specific to the invention, and when the value of m is 20, the x extracted by the embodiment is19.8%, x23.1 percent;
(IV') safety influence factors of the vehicle to be tested in the current state of the power battery:
α20＝a1,20×x1+a2,20×x2＝0.022；
(V') the threshold value for judging the self-heat-generation starting temperature of the power battery in the current health state is as follows:
Tmax＝T0-αm×T0；
calculating to obtain Tmax＝83.13℃；
Wherein, T0Is a test value based on the self-heat-production initial temperature of a BOL battery monomer, which is obtained by testing with an accelerated adiabatic calorimeter (T)0＝85℃；
(II) testing the highest temperature T possibly occurring under the non-self-heat-production condition of the power batterymax', the TmaxThe test method of':
T＇max＝T＇0+t×ΔT；
calculating to obtain Tmax' is 73 ℃;
wherein, T0' is a temperature threshold value for stopping power output of the power battery, T is a forced power-off time, and DeltaT is a maximum temperature rise rate of the battery; in this example T0' 60 ℃, T5 min, DeltaT 2.6 ℃/min;
(III) comparison of T in step (I)maxAnd T in step (II)maxTaking the smaller value of 73 ℃ as the final threshold.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (7)

1. A method for testing safety influence factors of a power battery in a current state of health is characterized by comprising the following steps:
(1) life acceleration working condition A for designing single life attenuation mechanism of power battery1、A2，…An；
(2) The life acceleration working condition in the step (1) of the accelerated circulation is m% to the life attenuation value of the power battery, and the working condition influence factor a corresponding to the life acceleration working condition in the step (1) is obtained through testing1,m、a2,m… and an,m；
(3) Discretizing the whole vehicle running condition of the vehicle to be tested, and comparing the discretized whole vehicle running condition with the service life acceleration condition A in the step (1)1、A2，…AnCarrying out correspondence to obtain the working condition segment proportion x1、x2… and xn；
(4) Safety influence factors of the vehicle to be tested under the current state of the power battery are as follows:
αm＝a1,m×x1+a2,m×x2......+an,m×xn；
the single attenuation mechanism of the service life of the power battery in the step (1) comprises any one of negative pole lithium precipitation, SEI film thickening, cation mixed discharge, active material falling or crystal lattice pulverization;
n is the number of working conditions causing the attenuation of a single influence factor of the battery;
m is any SOH state before the service life of the battery is ended, and m is more than or equal to 0 and less than or equal to 20.
2. The method of claim 1, wherein the single decay mechanism of the power cell lifetime of step (1) is negative lithiation or SEI film thickening.
3. A method for testing a threshold value of self-heat-generation starting temperature judgment of a power battery in a current state of health is characterized by comprising the following steps:
(a) testing of self-heating starting temperature value T based on BOL battery monomer0；
(b) The threshold value for judging the self-heat-generation starting temperature of the power battery in the current health state is as follows:
Tmax＝T0-αm×T0；
wherein alpha ismThe safety influence factor of the current state of health of the power battery obtained by testing the method according to claim 1 or 2.
4. The method of claim 3, wherein said T in step (a)0The material is obtained by adopting an accelerated adiabatic calorimeter or a hot box test.
5. A method for determining a temperature threshold for warning of thermal runaway, the method comprising the steps of:
(1') testing threshold value T of self-heat-generation starting temperature judgment of power battery in current health statemax；
(2') testing the highest temperature T which can occur under the non-self-heat-production condition of the power batterymax＇；
(3 ') comparing T in step (1')maxAnd T in step (2')max', if Tmax＞Tmax' then the temperature threshold for warning of thermal runaway is Tmax' of a compound of formula I; if Tmax＜Tmax' then the temperature threshold for warning of thermal runaway is TmaxIf T ismax＝Tmax' then the temperature threshold for warning of thermal runaway is TmaxOr Tmax＇；
Wherein, the threshold T of the self-heat-generation starting temperature judgment of the power battery in the current health state is tested in the step (1')maxUsing the method as claimed in claim 3.
6. The method of claim 5, wherein step (2') tests the maximum temperature T of the power cell that may occur during non-self-generating thermal conditionsmaxThe method comprises the following steps:
(A) determining temperature threshold T for stopping power output of power battery0＇；
(B) The highest temperature which can occur under the non-self-heat-production condition of the power battery is as follows:
T′max＝T′0+t×ΔT；
wherein T is forced power-off time, and DeltaT is the maximum temperature rise rate of the battery.
7. The method according to claim 5 or 6, characterized in that it comprises the steps of:
(I) testing threshold T for judging self-heat-generation initial temperature of power battery in current health statemax(ii) a The test method comprises the following steps:
(I') designing life acceleration condition A of single life attenuation mechanism of power battery1、A2，…An；
(II ') accelerating the life acceleration condition in the step (I') of the cyclic acceleration to the life attenuation value of the power battery of m%, and testing to obtain a working condition influence factor a corresponding to the life acceleration condition in the step (I1,m、a2,m… and an,m；
(III') discretizing the whole vehicle running condition of the vehicle to be tested, and comparing the discretized whole vehicle running condition with the service life acceleration condition A in the step (I1、A2，…AnCarrying out correspondence to obtain the working condition segment proportion x1、x2… and xn；
(IV') safety influence factors of the vehicle to be tested in the current state of the power battery:
αm＝a1,m×x1+a2,m×x2......+an,m×xn；
(V') the threshold value for judging the self-heat-generation starting temperature of the power battery in the current health state is as follows:
Tmax＝T0-αm×T0；
wherein, T0The test value is based on the self-heat-generation starting temperature of the BOL battery monomer;
(II) testing the highest temperature T possibly occurring under the non-self-heat-production condition of the power batterymax', the TmaxThe test method of':
T′max＝T′0+t×ΔT；
wherein, T0' is a temperature threshold value for stopping power output of the power battery, T is a forced power-off time, and DeltaT is a maximum temperature rise rate of the battery;
(III) comparison of T in step (I)maxAnd T in step (II)max', if Tmax＞Tmax' then the temperature threshold for warning of thermal runaway is Tmax' of a compound of formula I; if Tmax＜Tmax' then the temperature threshold for warning of thermal runaway is TmaxIf T ismax＝Tmax' then the temperature threshold for warning of thermal runaway is TmaxOr Tmax＇。
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