CN110534825A - Lithium ion battery thermal runaway early warning method - Google Patents

Abstract

The present invention proposes an early warning method for thermal runaway of a lithium ion battery, comprising the following steps: Step 1: Simulate the lithium ion battery, and obtain the lithium ion battery at the time of normal charge and discharge of the lithium ion battery and at the moment of overcharging thermal runaway shell surface temperature data and deformation data, and establish a battery temperature distribution model; Step 2: In the battery temperature distribution model, determine the positions of the highest surface temperature point P1 and the lowest surface temperature point P2 of the lithium-ion battery during normal use; step Three: Monitor the temperature difference ΔT and deformation difference Δd between P1 and P2 of the lithium-ion battery in real time through the monitoring device; step four: judge the operating state of the lithium-ion battery according to preset conditions. The combination of the maximum temperature difference of the battery body and the deformation of the shell can effectively monitor the thermal runaway of the battery at an early stage. Through conditional logic judgment, the possibility of battery thermal runaway is judged with high accuracy.

Description

Early warning method for thermal runaway of lithium ion battery

technical field

The invention relates to the technical field of lithium battery safety monitoring, in particular to an early warning method for thermal runaway of a lithium ion battery.

Background technique

Lithium-ion batteries have the advantages of high working voltage, high energy density, and long cycle life. They are used more and more as energy storage carriers. They are not only widely used in various electronic consumer goods, but also widely used in electric vehicles, electric vehicles, etc. Chemical energy storage and other fields.

However, lithium-ion batteries not only have safety problems due to factors such as abuse (such as overcharging, overheating), manufacturing defects (such as internal short circuit, package damage), but also uneven temperature distribution of the battery itself due to heat dissipation problems during normal use. , The local temperature is too high, etc., causing a short circuit in the battery, and then thermal runaway.

In the lithium battery energy storage system in the prior art, the temperature at the positive and negative tabs is used for temperature monitoring, which cannot accurately reflect the temperature and temperature division of the battery itself. Therefore, there is an urgent need for a battery that can accurately reflect the battery itself The method of temperature distribution and the measures for early warning of lithium-ion battery thermal runaway based on this method.

Contents of the invention

In view of this, the present invention proposes an early warning method for thermal runaway of lithium-ion batteries, aiming to solve the problem of how to effectively carry out early warning of thermal runaway of lithium-ion batteries to prevent fire hazards to energy storage systems after thermal runaway of batteries.

In one aspect, the present invention provides a method for early warning of thermal runaway of a lithium-ion battery, comprising the following steps:

Step 1: Simulate the lithium-ion battery, obtain the shell surface temperature data of the lithium-ion battery and the shell deformation data of the lithium-ion battery at the time of normal charge and discharge of the lithium-ion battery and the instant of overcharging and thermal runaway, and Establishing a battery model according to the obtained case surface temperature data of the lithium-ion battery during normal charge and discharge and the moment of overcharging and thermal runaway and the deformation data of the lithium-ion battery;

Step 2: In the battery model, determine the highest surface temperature point P1 and the lowest surface temperature point P2 of the lithium-ion battery during normal use; according to the P1 and P2, obtain the temperature difference between the P1 and P2 ΔT1, obtaining the surface temperature difference ΔT2 of the lithium-ion battery at the moment of overcharging and thermal runaway between the P1 and P2, and obtaining the shell shape of the lithium-ion battery at the moment of overcharging and thermal runaway between the P1 and P2 Variable Δd1;

Step 3: Real-time monitoring of the temperature difference ΔT and deformation difference Δd between the P1 and P2 of the lithium-ion battery during use;

Step 4: Determine preset conditions according to the ΔT1, ΔT2, Δd1, ΔT and Δd, judge the operating state of the lithium-ion battery according to the preset conditions, and judge whether the lithium-ion battery is in the early stage of thermal runaway.

Further, in the step four, when it is judged that the lithium-ion battery is in the early stage of thermal runaway, the battery is stopped, and the alarm signal is transmitted to the fire protection system, and the fire protection system is turned on to protect the lithium-ion battery. The battery cools down.

Further, in the second step, after the P1 and P2 are determined, the accuracy of the P1 and P2 is verified.

Further, the preset conditions include a first preset condition, a second preset condition and a third preset condition,

Said judging the operating state of said lithium-ion battery according to preset conditions includes:

When the lithium-ion battery satisfies the first preset condition, it is judged that the lithium-ion battery is in a normal working state;

When the lithium-ion battery satisfies the second preset condition, it is judged that the lithium-ion battery has a risk of thermal runaway;

When the lithium-ion battery satisfies the third preset condition, it is determined that the lithium-ion battery is in an early stage of thermal runaway.

Further, the first preset condition is:

The lithium-ion battery satisfies a first temperature constraint:

ΔT<x1×ΔT1 and

The lithium-ion battery satisfies the first deformation constraint:

Δd<y1×Δd1;

Wherein, the value range of x1 is 0.6-1, and the value range of y1 is 0.1-0.3.

Further, the second preset condition is:

The lithium-ion battery satisfies a second temperature constraint:

x2×ΔT1≥ΔT≥x3×ΔT1 or

The lithium-ion battery satisfies the second deformation constraint:

y2×Δd1≥Δd≥y3×Δd1;

Wherein, the value range of x2 is 1.5-1.8, the value range of x3 is 1-1.5, the value range of y2 is 0.4-0.5, and the value range of y3 is 0.3-0.4.

Further, the third preset condition is:

The lithium-ion battery satisfies a third temperature constraint:

ΔT>x4×ΔT1 or

The lithium-ion battery satisfies the third deformation constraint:

Δd>y4×Δd1;

Wherein, the value range of x4 is 0.8-1, and the value range of y4 is 0.5-0.6.

Further, the preset condition also includes a fourth preset condition,

Said judging the operating state of said lithium-ion battery according to preset conditions includes:

When the lithium ion battery satisfies the fourth preset condition, it is determined that the lithium ion battery is in a state of thermal runaway.

Further, the fourth preset condition is:

The lithium-ion battery satisfies a fourth temperature constraint:

ΔT≥x5×ΔT2 or

The lithium-ion battery satisfies the fourth deformation constraint:

Δd≥y5×Δd1;

Wherein, x5>1, y5>0.7.

Further, in the step 3, the temperature difference ΔT and the deformation difference Δd between the P1 and P2 of the lithium-ion battery during use are monitored in real time by a monitoring device;

The monitoring device includes a temperature sensor and a deformation sensor, the temperature data of the lithium-ion battery is collected by the temperature sensor, and the deformation data of the lithium-ion battery is collected by the deformation sensor.

Compared with the prior art, the beneficial effect of the present invention is that the method of the present invention establishes a battery model by simulating the lithium-ion battery, and obtains the temperature data and the case temperature data and shell temperature data of the normal operation and thermal runaway instant of the lithium-ion battery in the battery model. Body deformation data to determine the preset conditions, and monitor the temperature difference and deformation difference of the lithium-ion battery in normal use in real time, compare the temperature difference and deformation difference with the preset conditions, and judge the lithium-ion battery according to the comparison results. It is in the running state during normal use, and can effectively monitor the thermal runaway of the lithium-ion battery at an early stage during the normal use of the lithium-ion battery, prevent the thermal runaway of the lithium-ion battery, and improve the safety performance of the lithium-ion battery during operation.

Accurately locate the temperature monitoring point and deformation measurement point of the battery through simulation, and comprehensively consider the normal deformation of the battery casing caused by the vaporization of the battery electrolyte. By comparing the monitored amount with the preset amount, the temperature of the lithium battery is too high and the explosion-proof valve is broken. Pre-judge the battery status in time, adjust the working status of the battery energy storage system, and transmit the early warning signal to the alarm, which can remind the user of the risk of battery thermal runaway.

Further, through the combined use of the maximum temperature difference of the battery body and the deformation of the shell, early detection of battery thermal runaway can be effectively performed. Through conditional logic judgment, the possibility of thermal runaway of the battery is judged, with high accuracy, and the hysteresis of gas detection and single temperature monitoring is avoided.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same components. In the attached picture:

FIG. 1 is a flow chart of an early warning method for thermal runaway of a lithium-ion battery provided by an embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

Referring to Figure 1, the present embodiment provides a method for early warning of thermal runaway of lithium-ion batteries, including the following steps:

Step 1 S101: Simulate the lithium-ion battery, and obtain the shell surface temperature data of the lithium-ion battery and the shell deformation data of the lithium-ion battery when the lithium-ion battery is charged and discharged normally and at the moment of overcharging and thermal runaway, And establish a battery model according to the obtained shell surface temperature data of the lithium-ion battery during normal charge and discharge and the lithium-ion battery at the moment of overcharging and thermal runaway and the deformation data of the lithium-ion battery;

Step 2 S102: In the battery model, determine the highest surface temperature point P1 and the lowest surface temperature point P2 of the lithium-ion battery during normal use; obtain the temperature between P1 and P2 according to the P1 and P2 Difference ΔT1, obtaining the surface temperature difference ΔT2 of the lithium-ion battery at the moment of overcharging and thermal runaway between the P1 and P2, and obtaining the shell of the lithium-ion battery at the moment of overcharging and thermal runaway between the P1 and P2 Body shape variable Δd1;

Step 3 S103: Real-time monitoring of the temperature difference ΔT and deformation difference Δd between the P1 and P2 of the lithium-ion battery during use;

Step 4 S104: Determine preset conditions according to the ΔT1, ΔT2, Δd1, ΔT, and Δd, judge the operating state of the lithium-ion battery according to the preset conditions, and judge whether the lithium-ion battery is in the early stage of thermal runaway .

The battery model is established by simulating the lithium-ion battery, and the temperature data and shell deformation data at the moment of normal operation and thermal runaway of the lithium-ion battery are obtained in the battery model to determine the preset conditions, and real-time monitoring of the lithium-ion battery in normal use Compare the temperature difference and deformation difference with the preset conditions, and judge the operating state of the lithium-ion battery in normal use according to the comparison results, and can effectively carry out the operation when the lithium-ion battery is in normal use. Early monitoring of thermal runaway of lithium-ion batteries prevents thermal runaway of lithium-ion batteries and improves the safety performance of lithium-ion batteries during operation.

Specifically, firstly, the simulation software is used to simulate the temperature distribution of the shell surface and the battery deformation at the moment of normal charge and discharge of the lithium-ion battery and the moment of overcharging and thermal runaway, and the battery temperature distribution model is established to determine the highest point and the lowest point of the temperature distribution. And use experimental means to verify the accuracy of the simulation results; measure and calculate the temperature difference ΔT1 between the highest surface temperature point P1 and the lowest surface temperature point P2 when the lithium-ion battery is in normal use, and the temperature difference ΔT2 between P1 and P2 at the moment of overcharging runaway And the shell thickness deformation Δd1 of the two points; use the monitoring device to monitor the temperature difference ΔT and deformation difference Δd of the preset two points P1 and P2 during the use of the lithium-ion battery, and judge the operating state of the lithium-ion battery according to the preset conditions , and judge whether the lithium-ion battery is in the early stage of thermal runaway.

Specifically, the above-mentioned simulation software is preferably Comsol and/or Fluent software. The above-mentioned experimental means is preferably an overcharge experimental means.

Specifically, the method of simulation plus experimental verification is used to determine the two points P1 and P2 at which the battery temperature difference is the largest, so as to ensure the accuracy of P1 and P2.

It can be seen that the temperature monitoring point and deformation measurement point of the battery are accurately positioned through the simulation, and the normal deformation of the battery shell caused by the vaporization of the battery electrolyte is comprehensively considered. Before the explosion-proof valve breaks, it can predict the battery status in time, adjust the working status of the battery energy storage system, and transmit the early warning signal to the alarm, which can remind the user of the risk of battery thermal runaway.

Further, through the combined use of the maximum temperature difference of the battery body and the deformation of the shell, early detection of battery thermal runaway can be effectively performed. Through conditional logic judgment, the possibility of thermal runaway of the battery is judged, with high accuracy, and the hysteresis of gas detection and single temperature monitoring is avoided.

Specifically, in step two S102, after P1 and P2 are determined, experiments are performed to verify the accuracy of P1 and P2.

Specifically, in step 4 S104, when it is judged that the lithium ion battery is in the early stage of thermal runaway, the battery operation is stopped, an alarm signal is transmitted to the fire protection system, and the fire protection system is turned on to cool down the temperature of the lithium ion battery.

Specifically, the temperature differences ΔT1, ΔT2 and the shell thickness deformation Δd are related to the charging and discharging conditions of the battery and the specifications of the battery, and can be determined according to the actual situation.

Specifically, the preset conditions include a first preset condition, a second preset condition and a third preset condition, wherein judging the operating state of the lithium-ion battery according to the preset conditions includes:

When the lithium-ion battery satisfies the first preset condition, it is determined that the lithium-ion battery is in a normal working state;

When the lithium-ion battery satisfies the second preset condition, it is judged that the temperature of the lithium-ion battery is too high and there is a risk of thermal runaway, so that the lithium-ion battery stops working, and an early warning signal is output;

When the lithium-ion battery satisfies the third preset condition, it is determined that the lithium-ion battery is in an early stage of thermal runaway.

It can be seen that the possibility of battery thermal runaway is judged through conditional logic judgment, which greatly improves the accuracy and avoids the hysteresis of gas detection and single temperature monitoring.

Specifically, the first preset condition is:

The lithium-ion battery satisfies a first temperature constraint:

ΔT<x1×ΔT1 and

The lithium-ion battery satisfies the first deformation constraint:

Δd<y1×Δd1;

Wherein, the value range of x1 is 0.6-1, and the value range of y1 is 0.1-0.3.

When the lithium-ion battery satisfies both ΔT<x1×ΔT1 and Δd<y1×Δd1, it is determined that the lithium-ion battery is in a normal operating state.

Preferably, when the lithium-ion battery satisfies ΔT<0.8ΔT1 and Δd<0.2Δd1 at the same time, it is determined that the lithium-ion battery is in a normal working state, and no warning is given for thermal runaway of the battery.

Specifically, the second preset condition is:

The lithium-ion battery satisfies a second temperature constraint:

x2×ΔT1≥ΔT≥x3×ΔT1 or

The lithium-ion battery satisfies the second deformation constraint:

y2×Δd1≥Δd≥y3×Δd1;

Wherein, the value range of x2 is 1.5-1.8, the value range of x3 is 1-1.5, the value range of y2 is 0.4-0.5, and the value range of y3 is 0.3-0.4.

When the lithium-ion battery satisfies one of x2×ΔT1≥ΔT≥x3×ΔT1 or y2×Δd1≥Δd≥y3×Δd1, the determined lithium-ion battery has a risk of thermal runaway.

Preferably, when the lithium-ion battery satisfies one of 1.65ΔT1≥ΔT≥1.25ΔT1 or 0.45Δd1≥Δd≥0.35Δd1, it is determined that the lithium-ion battery has a risk of thermal runaway, and the battery is immediately stopped, and an alarm is given. The signal is transmitted to the alarm, which can alert the user to the risk of battery thermal runaway.

Specifically, the third preset condition is:

The lithium-ion battery satisfies a third temperature constraint:

ΔT>x4×ΔT1 or

The lithium-ion battery satisfies the third deformation constraint:

Δd>y4×Δd1;

Wherein, the value range of x4 is 0.8-1, and the value range of y4 is 0.5-0.6.

When the lithium-ion battery satisfies one of ΔT>x4×ΔT1 or Δd>y4×Δd1, it can be determined that the lithium-ion battery is in the early stage of thermal runaway.

Preferably, when the lithium-ion battery satisfies one of ΔT>0.9ΔT1 and Δd>0.8Δd1, it can be determined that the lithium-ion battery is in the early stage of thermal runaway, and thermal runaway may occur at any time, stop the battery, and transmit the early warning signal to the fire department system, the fire protection system is turned on, and the lithium-ion battery is cooled.

Specifically, the preset condition also includes a fourth preset condition, and judging the operating state of the lithium-ion battery according to the preset condition includes: when the lithium-ion battery satisfies the fourth preset condition, judging the The lithium-ion battery is in a state of thermal runaway.

Specifically, the fourth preset condition is:

The lithium-ion battery satisfies a fourth temperature constraint:

ΔT≥x5×ΔT2 or

The lithium-ion battery satisfies the fourth deformation constraint:

Δd≥y5×Δd1;

Wherein, x5>1, y5>0.7, that is, the value range of x5 is greater than 1, and the value range of y5 is greater than 0.7.

When the lithium-ion battery satisfies one of ΔT≥x5×ΔT2 or Δd≥y5×Δd1, it can be determined that the lithium-ion battery is in a state of thermal runaway.

Preferably, when the lithium-ion battery meets one of ΔT≥1.5ΔT2 or Δd≥1.1Δd1, it can be determined that the lithium-ion battery is in a state of thermal runaway;

Specifically, the monitoring device includes a temperature sensor and a deformation sensor, the temperature sensor is used to collect temperature data of the lithium-ion battery, and the deformation sensor is used to collect deformation data of the lithium-ion battery.

Specifically, the temperature and battery case deformation sensor can be either a two-in-one device or a separate monitoring device

Specifically, the judgment of the operating state of the above-mentioned lithium-ion battery is performed by the processing unit in the battery management system. Specifically, the processing unit has built-in the above-mentioned first preset condition-fourth preset condition, and the lithium-ion battery in operation is collected in real time by the monitoring device. The temperature and deformation data of the lithium-ion battery, and transmit the temperature and deformation data of the lithium-ion battery collected in real time to the processing unit, and the processing unit real-time compares the temperature and deformation data of the lithium-ion battery it receives with its built-in first preset Condition-Compare with the fourth preset condition, and implement the output judgment result.

Specifically, the processing unit communicates with the alarm and the fire-fighting system to control the alarm and the fire-fighting system.

It can be seen that the above-mentioned early warning method for lithium battery thermal runaway has the following advantages: through the strategy of combining the maximum temperature difference judgment and the shell deformation judgment, the accuracy of the judgment result is greatly improved, and the judgment efficiency is improved; the maximum temperature difference and the maximum The shell deformation is set with thresholds ΔT1 and Δd1. When the monitoring value is close to the threshold to a certain extent, the battery will stop working, an alarm will be issued, or the fire protection device will be activated, and corresponding processing can be made in time according to the judgment results, effectively preventing the lithium-ion battery from Thermal runaway occurs, that is, the battery status can be predicted in time before the temperature of the lithium battery is too high, the electrolyte vaporizes, the shell is deformed, and the explosion-proof valve is broken, so as to ensure the efficient, stable and safe operation of the lithium-ion battery; The combination of simulation and experimental verification determines the temperature and deformation monitoring points, which improves the accuracy of the judgment results.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (10)

1. a kind of lithium ion battery thermal runaway early warning method, which comprises the following steps:

Step 1: carrying out analog simulation to lithium ion battery, when obtaining the normal charge and discharge of the lithium ion battery and overcharges hot mistake The casing surface temperature data of the lithium ion battery of moment and the shell deformation data of the lithium ion battery are controlled, and according to acquisition The lithium ion battery normal charge and discharge when and the lithium ion battery that overcharges thermal runaway moment casing surface temperature data and The deformation data of the lithium ion battery establishes battery model；

Step 2: in the battery model, surface temperature highest point P1 when determining the lithium ion battery normal use and Surface temperature minimum point P2；According to the P1 and P2, obtains the temperature difference Δ T1 between the P1 and P2, obtains the P1 and P2 Between overcharge thermal runaway moment the lithium ion battery surface temperature difference Δ T2 and obtain institute between the P1 and P2 State the shell deformation amount Δ d1 that lithium ion battery overcharges thermal runaway moment；

Step 3: temperature difference Δ T and shape between the P1 and P2 of lithium ion battery described in real-time monitoring in use Variation Δ d；

Step 4: preset condition is determined according to the Δ T1, Δ T2, Δ d1, Δ T and Δ d, institute is judged according to the preset condition The operating status of lithium ion battery is stated, and judges whether the lithium ion battery is in the early period of thermal runaway.

2. lithium ion battery thermal runaway early warning method according to claim 1, which is characterized in that in the step 4 In, when judging the lithium ion battery into the early period for being in thermal runaway, stops battery work, and alarm signal is transferred to and is disappeared Anti- system opens the fire-fighting system, to cool down to the lithium ion battery.

3. lithium ion battery thermal runaway early warning method according to claim 1, which is characterized in that in the step 2 In, after determining P1 and P2, verify the accuracy of the P1 and P2.

4. lithium ion battery thermal runaway early warning method according to claim 2, which is characterized in that the preset condition Including the first preset condition, the second preset condition and third preset condition,

The operating status that the lithium ion battery is judged according to preset condition includes:

When the lithium ion battery meets first preset condition, judges that the lithium ion battery is in and work normally shape State；

When the lithium ion battery meets second preset condition, judge that the lithium ion battery has the risk of thermal runaway；

When the lithium ion battery meets the third preset condition, judge that the lithium ion battery is in thermal runaway early period.

5. lithium ion battery thermal runaway early warning method according to claim 4, which is characterized in that described first is default Condition are as follows:

The lithium ion battery meets the first temperature restraint:

Δ T < x1 × Δ T1 and

The lithium ion battery meets the first deformation constraint:

Δ d < y1 × Δ d1；

Wherein, the value range that the value range of x1 is 0.6~1, y1 is 0.1~0.3.

6. lithium ion battery thermal runaway early warning method according to claim 4, which is characterized in that described second is default Condition are as follows:

The lithium ion battery meets second temperature constraint:

X2 × Δ T1 >=Δ T >=x3 × Δ T1 or

The lithium ion battery meets the second deformation constraint:

y2×Δd1≥Δd≥y3×Δd1；

Wherein, the value range that the value range that the value range of x2 is 1.5~1.8, x3 is 1~1.5, y2 is 0.4~0.5, The value range of y3 is 0.3~0.4.

7. lithium ion battery thermal runaway early warning method according to claim 4, which is characterized in that the third is default Condition are as follows:

The lithium ion battery meets third temperature restraint:

Δ T > x4 × Δ T1 or

The lithium ion battery meets third deformation constraint:

Δ d > y4 × Δ d1；

Wherein, the value range that the value range of x4 is 0.8~1, y4 is 0.5~0.6.

8. lithium ion battery thermal runaway early warning method according to claim 4, which is characterized in that the preset condition It further include the 4th preset condition,

The operating status that the lithium ion battery is judged according to preset condition includes:

When the lithium ion battery meets four preset condition, judge that the lithium ion battery is in thermal runaway state.

9. lithium ion battery thermal runaway early warning method according to claim 8, which is characterized in that the described 4th is default Condition are as follows:

The lithium ion battery meets the 4th temperature restraint:

Δ T >=x5 × Δ T2 or

The lithium ion battery meets the 4th deformation constraint:

Δd≥y5×Δd1；

Wherein, x5 > 1, y5 > 0.7.

10. lithium ion battery thermal runaway early warning method according to claim 1, which is characterized in that in the step In three, pass through the temperature difference Δ between the P1 and P2 of lithium ion battery described in monitoring device real-time monitoring in use T and deformation difference Δ d；

The monitoring device includes temperature sensor and changing sensor, acquires the lithium-ion electric by the temperature sensor The temperature data in pond acquires the deformation data of the lithium ion battery by the changing sensor.