An early warning method and system for thermal runaway of lithium batteries caused by overcharging

Abstract

The present invention discloses an early warning method and system for thermal runaway of a lithium battery caused by overcharging, including: 1) calculating the temperature rise rate and voltage rise rate of the lithium battery in an overcharged state in real time; 2) obtaining the temperature rise rate processing value and the voltage rise rate processing value by noise data processing; 3) establishing an early characteristic value equation for thermal runaway of the lithium battery, and calculating the early characteristic value of thermal runaway of the lithium battery; 4) obtaining the early characteristic value processing value of thermal runaway of the lithium battery by data smoothing processing; 5) calculating the change rate value of the early characteristic value of thermal runaway of the lithium battery; 6) determining the early warning conditions for thermal runaway of the lithium battery caused by overcharging, and issuing a warning when the warning conditions are met. The present invention can analyze the voltage signal and temperature signal of the lithium battery in real time, and issue an early warning based on the amplified early characteristics of thermal runaway of the lithium battery, and can add a layer of protection mechanism to avoid thermal runaway of the lithium battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery safety, and in particular to an early warning method and system for thermal runaway of a lithium battery caused by overcharging. Background Art

[0002] Lithium batteries are widely used in various portable devices, consumer electronics and battery energy storage systems, but the endless battery thermal runaway problem has always been a concern. Battery thermal runaway refers to the behavior of rapid heat generation inside the battery, causing the temperature to rise sharply to more than 200 degrees, and causing fire and explosion. Thermal abuse, electrical abuse and mechanical abuse can all induce the occurrence of battery thermal runaway. According to statistics, most battery thermal runaways in real life are caused by electrical failures, that is, electrical abuse. Among them, battery thermal runaway induced by overcharging is the main factor.

[0003] In the early stage of overcharge-induced thermal runaway of the battery, a large amount of lithium is precipitated on the surface of the graphite negative electrode inside the battery and reacts with the electrolyte, which increases the internal resistance of the battery and generates a large amount of heat. Through externally connected monitoring equipment, it can be observed that the voltage signal and temperature signal of the battery suddenly increase at this stage. Three relatively obvious raised voltage and temperature peaks can be observed in the voltage and temperature curve of the lithium battery in the thermal runaway process. The first peak indicates that the negative electrode inside the battery has a lithium precipitation reaction, the second peak indicates that the lithium precipitated from the negative electrode reacts with the electrolyte, and the third peak indicates that multiple side reactions occur inside the battery. According to experimental statistics, the battery will experience thermal runaway after three peaks, and there is a certain probability of thermal runaway after the first two peaks, and only one peak will not cause thermal runaway.

[0004] By using these small peaks that appear during battery overcharging, early warning of thermal runaway can be achieved. However, it is extremely difficult to select appropriate small peak features. The differences between these small peaks are extremely small. It is critical to accurately judge, extract the features between the small peaks, and use the features for early warning. Most of the existing early warning systems use data from a single source, or use the first small peak as an early warning of thermal runaway. The main problems are as follows:

[0005] 1. The acquired voltage signal and temperature signal data cannot be analyzed in real time, resulting in insufficient thermal runaway warning;

[0006] 2. The extracted early features of thermal runaway are not obvious enough, which may lead to false alarms of thermal runaway, resulting in premature intervention of control actions and unnecessary economic losses;

[0007] 3. The data obtained in real time is highly volatile, which affects the battery algorithm's judgment on the battery's thermal runaway behavior.

[0008] This patent couples the lithium battery voltage signal and temperature signal, amplifies the difference between small peaks, and obtains a new indicator as the early characteristic value of lithium battery thermal runaway. The second small peak that appears in the curve of the early characteristic value of lithium battery thermal runaway over time is used as an early warning indicator to maximize the accuracy of the early warning before thermal runaway and ensure sufficient time to control thermal runaway in advance. Summary of the invention

[0009] The first purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide an early warning method for thermal runaway of a lithium battery caused by overcharging. The method can analyze the acquired lithium battery voltage signal and temperature signal in real time, amplify the early characteristics of thermal runaway of the lithium battery, and provide early warning based on the amplified early characteristics of thermal runaway of the lithium battery. This can add a layer of protection mechanism to prevent thermal runaway of the lithium battery, and can be further applied to various scenarios that require real-time monitoring of the status of the lithium battery.

[0010] A second object of the present invention is to provide an early warning system for thermal runaway of lithium batteries caused by overcharging.

[0011] The first objective of the present invention is achieved by the following technical solution: an early warning method for thermal runaway of a lithium battery caused by overcharging, comprising the following steps:

[0012] 1) Using the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time, the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state are calculated in real time;

[0013] 2) performing noise data processing on the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state calculated in real time to obtain a temperature rise rate processing value and a voltage rise rate processing value;

[0014] 3) Using the temperature rise rate processing value and the voltage rise rate processing value, establish the early characteristic value equation of thermal runaway of lithium battery, and calculate the early characteristic value of thermal runaway of lithium battery;

[0015] 4) Performing data smoothing processing on the early characteristic value of thermal runaway of the lithium battery to obtain the processed value of the early characteristic value of thermal runaway of the lithium battery;

[0016] 5) Calculate the change rate value of the early characteristic value of thermal runaway of the lithium battery according to the processing value of the early characteristic value of thermal runaway of the lithium battery;

[0017] 6) Using the lithium battery thermal runaway early characteristic value and the lithium battery thermal runaway early characteristic value change rate value, determine the lithium battery thermal runaway early warning condition. When the lithium battery thermal runaway early warning condition is met, issue a lithium battery thermal runaway early warning, otherwise return to step 1) to continue calculation.

[0018] Further, in step 1), the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time are represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, U i Represents the lithium battery voltage at the i-th moment;

[0019] Real-time calculation of the temperature rise rate C of the lithium battery in the overcharge state i It is expressed as:

[0020]

[0021] C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment;

[0022] The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as:

[0023]

[0024] V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment.

[0025] Further, in step 2), the noise data processing is performed according to the following rules:

[0026] When C i <0, let C i =0;

[0027] When V i <0, let V i =0;

[0028] C i represents the temperature rise rate of the lithium battery at the i-th moment, V i Indicates the voltage increase rate of the lithium battery at the i-th moment.

[0029] Further, in step 3), the established early characteristic value equation of thermal runaway of lithium battery is as follows:

[0030]

[0031] W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; C i represents the temperature rise rate of the lithium battery at the i-th moment, V irepresents the voltage increase rate of the lithium battery at the i-th moment; α, β, and γ represent correlation coefficients, which are assigned according to the type of lithium battery.

[0032] Further, in step 4), data smoothing processing is performed on the early characteristic value of thermal runaway of the lithium battery, which means averaging a data group containing n consecutive early characteristic values ​​of thermal runaway of the lithium battery, and the average value is defined as the processed value of the early characteristic value of thermal runaway of the battery cell; the data smoothing equation is established as follows:

[0033]

[0034] X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, W i-1 They represent the early characteristic values ​​of thermal runaway of lithium batteries at moments in, i-n+1, ​​…, i-1 respectively.

[0035] Further, in step 5), the calculation equation of the rate of change of the characteristic value of the early stage of thermal runaway of the lithium battery is as follows:

[0036]

[0037] B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, X i-1 represents the early characteristic value processing value of lithium battery thermal runaway at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment.

[0038] Further, in step 6), determining the early warning conditions for thermal runaway of a lithium battery includes the following steps:

[0039] 6.1) A large number of specific lithium battery samples were tested for thermal runaway of lithium batteries caused by overcharging, and the result data were statistically analyzed to obtain a curve of the change of the characteristic value processing value of the early thermal runaway of the lithium battery over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before thermal runaway of the battery cell is determined, and the calculation formula is as follows:

[0040]

[0041] 6.2) According to the lithium battery thermal runaway early characteristic value processing value obtained in step 4) and the lithium battery thermal runaway early characteristic value change rate value obtained in step 5), the lithium battery thermal runaway early warning condition is determined as follows:

[0042] Condition 1, X i>A,X i Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment;

[0043] Condition 2, B i =0, B i Indicates the rate of change of the early characteristic value of thermal runaway of the lithium battery at the i-th moment;

[0044] When both the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when both the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the calculation is continued back to step 1).

[0045] The second objective of the present invention is achieved by the following technical solution: an early warning system for thermal runaway of a lithium battery caused by overcharging, comprising:

[0046] The temperature and voltage rise rate calculation module uses the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time to calculate the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state in real time;

[0047] The noise data processing module performs noise data processing on the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state calculated in real time to obtain a temperature rise rate processing value and a voltage rise rate processing value;

[0048] The thermal runaway early characteristic value calculation module uses the temperature rise rate processing value and the voltage rise rate processing value to establish the lithium battery thermal runaway early characteristic value equation and calculate the lithium battery thermal runaway early characteristic value;

[0049] The data smoothing processing module performs data smoothing processing on the early characteristic value of thermal runaway of the lithium battery to obtain the processed value of the early characteristic value of thermal runaway of the lithium battery;

[0050] The thermal runaway early characteristic value change rate calculation module calculates the lithium battery thermal runaway early characteristic value change rate value according to the lithium battery thermal runaway early characteristic value processing value;

[0051] The thermal runaway early warning condition determination module uses the lithium battery thermal runaway early characteristic value and the lithium battery thermal runaway early characteristic value change rate value to determine the lithium battery thermal runaway early warning condition. When the lithium battery thermal runaway early warning condition is met, the lithium battery thermal runaway early warning is issued, otherwise it returns to the temperature and voltage rise rate calculation module to continue the calculation.

[0052] Furthermore, in the temperature and voltage rise rate calculation module, the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time are respectively represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, Ui Represents the lithium battery voltage at the i-th moment;

[0053] Real-time calculation of the temperature rise rate C of the lithium battery in the overcharge state i It is expressed as:

[0054]

[0055] C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment;

[0056] The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as:

[0057]

[0058] V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment;

[0059] In the noise data processing module, noise data processing is performed according to the following rules:

[0060] When C i <0, let C i =0;

[0061] When V i <0, let V i =0;

[0062] In the thermal runaway early characteristic value calculation module, the established lithium battery thermal runaway early characteristic value equation is as follows:

[0063]

[0064] W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; α, β, and γ represent correlation coefficients, which are assigned according to the type of lithium battery;

[0065] In the data smoothing processing module, data smoothing processing is performed on the early characteristic value of thermal runaway of the lithium battery, which means finding the average value of a data group containing n consecutive early characteristic values ​​of thermal runaway of the lithium battery, and the average value is defined as the processing value of the early characteristic value of thermal runaway of the battery cell; the data smoothing equation is established as follows:

[0066]

[0067] X irepresents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, W i-1 They represent the early characteristic values ​​of thermal runaway of lithium battery at time in, i-n+1, ​​…, i-1 respectively;

[0068] In the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early characteristic value change rate value calculation equation is as follows:

[0069]

[0070] B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i-1 Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-1th moment.

[0071] Further, in the thermal runaway early warning condition determination module, the determination of the lithium battery thermal runaway early warning condition includes the following steps:

[0072] By testing the thermal runaway of lithium batteries caused by overcharging on a large number of specific lithium battery samples shipped out of the factory, the result data is statistically analyzed to obtain a curve of the change of the early characteristic value processing value of the lithium battery thermal runaway over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before the thermal runaway of the battery cell is determined, and the calculation formula is as follows:

[0073]

[0074] According to the lithium battery thermal runaway early characteristic value processing value obtained in the data smoothing processing module and the lithium battery thermal runaway early characteristic value change rate value obtained in the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early warning conditions are determined as follows:

[0075] Condition 1, X i >A,X i Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment;

[0076] Condition 2, B i =0, B i Indicates the rate of change of the early characteristic value of thermal runaway of the lithium battery at the i-th moment;

[0077] When the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the temperature and voltage rise rate calculation module is returned to continue the calculation.

[0078] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0079] 1. The present invention uses the real-time acquired lithium battery temperature signal and voltage signal to perform early warning analysis of lithium battery thermal runaway caused by overcharging, which can achieve real-time monitoring, rapid discovery, and accurate warning, and can be applied to various scenarios that require real-time monitoring of lithium battery status.

[0080] 2. Compared with other early warning methods for thermal runaway of lithium batteries caused by overcharging, the present invention couples and amplifies the two early signal features of thermal runaway of lithium batteries caused by overcharging, making the identification and extraction of features more convenient and accurate, and reducing the probability of misjudgment of thermal runaway.

[0081] 3. The present invention performs noise data processing on the temperature rise rate and voltage rise rate of the lithium battery under charging state calculated in real time, and performs data smoothing processing on the early characteristic values ​​of thermal runaway of the lithium battery, which greatly reduces the interference of abnormal data and makes the feature extraction process more accurate.

[0082] 4. The present invention selects appropriate early warning conditions for thermal runaway of lithium batteries caused by overcharging, and reserves sufficient time for the intervention of subsequent thermal runaway control measures and the transfer of personnel and property.

[0083] 5. The present invention can add a layer of protection mechanism to avoid thermal runaway of lithium batteries caused by overcharging, which can effectively reduce the probability of thermal runaway of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 The present invention is a flowchart for implementing the method.

[0085] Figure 2 The temperature signal and voltage signal diagram of thermal runaway of lithium battery caused by overcharging obtained in real time.

[0086] Figure 3 This is a graph of the temperature rise rate processed value and the voltage rise rate processed value after noise data processing.

[0087] Figure 4 This is a real-time calculated early characteristic value diagram of thermal runaway of lithium batteries.

[0088] Figure 5 This is a real-time calculated graph of the early characteristic value processing of thermal runaway of lithium batteries.

[0089] Figure 6 Schematic diagram of the characteristic critical value A before thermal runaway of lithium batteries.

[0090] Figure 7 This is a system architecture diagram of the present invention. DETAILED DESCRIPTION

[0091] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0092] Example 1

[0093] like Figure 1 As shown, this embodiment discloses an early warning method for thermal runaway of a lithium battery caused by overcharging, which acquires and analyzes lithium battery data in real time, fully considers and extracts early features of thermal runaway of a lithium battery caused by overcharging, maximizes the accuracy of early warning before thermal runaway of a lithium battery caused by overcharging, and ensures sufficient time to control thermal runaway in advance, which includes the following steps:

[0094] 1) Using the real-time collected voltage signal and temperature signal of the lithium battery in the overcharge state, they are represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, U i Represents the lithium battery voltage at the i-th moment. Figure 2 The figure shows the temperature and voltage signal curve of the whole process of thermal runaway of a lithium battery caused by overcharging in a specific embodiment. The lithium battery has thermal runaway phenomenon in the stage of rapid temperature rise. Therefore, the thermal runaway warning signal of the lithium battery should be issued in the early stage of thermal runaway.

[0095] Based on the acquired lithium battery temperature signal and voltage signal, the signal characteristics are initially extracted, and the temperature rise rate C of the lithium battery in the overcharge state is calculated in real time. i It is expressed as:

[0096]

[0097] C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment.

[0098] The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as:

[0099]

[0100] V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment.

[0101] 2) In order to eliminate the influence of outliers on the early feature extraction of lithium battery thermal runaway, it is necessary to calculate the C i and Vi The noise data processing is performed according to the following rules:

[0102] When C i <0, let C i =0;

[0103] When V i <0, let V i =0.

[0104] like Figure 3 Shown are two eigenvalues ​​C after noise data processing i and V i ,From the figure, we can find that the two eigenvalue data jitter is large, there is no small peak in the temperature rise rate value curve, while there are multiple small peaks in the voltage rise rate value, and the difference between the first few small peaks is very small. Next, the two eigenvalues ​​that have been preliminarily processed need to be further processed.

[0105] 3) The two characteristic values ​​of the temperature rise rate processing value and the voltage rise rate processing value of the lithium battery are coupled, and the early characteristic value of thermal runaway of the lithium battery is calculated using the following equation:

[0106]

[0107] W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; α, β, γ represent correlation coefficients, which are assigned according to the type of lithium battery. In this embodiment, the correlation coefficients α, β, and γ are assigned 1, 1, and 36000 respectively. By adjusting the correlation coefficients, the early characteristics of thermal runaway of lithium battery can be further amplified, making the later feature extraction simpler.

[0108] 4) Perform data smoothing on the early characteristic value of thermal runaway of lithium battery to obtain the processed value of the early characteristic value of thermal runaway of lithium battery. Figure 4 The figure shows the change curve of the early characteristic value of thermal runaway of lithium battery calculated in real time in this embodiment. It can be found from the figure that there are two very obvious small peaks in the curve of the early characteristic value of thermal runaway. However, due to the large volatility of the curve at this time, feature extraction is still difficult, so the data needs to be smoothed. Data smoothing refers to averaging a group of data containing n consecutive early characteristic values ​​of thermal runaway of lithium battery. The average value is defined as the processing value of the early characteristic value of thermal runaway of lithium battery. The data smoothing equation is established as follows:

[0109]

[0110] X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, Wi-1 They represent the early characteristic values ​​of thermal runaway of lithium battery at time in, i-n+1, ​​..., i-1 respectively. In this embodiment, n is 20, and the smoothed curve is as follows: Figure 5 As shown. Figure 5 It can be found that the small peak on the early characteristic value curve of lithium battery thermal runaway can be extracted more easily.

[0111] 5) The change rate of the early characteristic value of thermal runaway of the lithium battery is calculated based on the processing value of the early characteristic value of thermal runaway of the lithium battery. The calculation equation is as follows:

[0112]

[0113] B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i-1 Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-1th moment.

[0114] 6) Since the early thermal runaway characteristics extracted from different types of lithium batteries are different, in this embodiment, a large number of specific lithium batteries are tested for thermal runaway of the lithium batteries by overcharging in advance, and the result data are statistically analyzed to obtain a curve of the change of the early characteristic value processing value of the lithium battery thermal runaway over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before thermal runaway of the lithium battery is determined, and the calculation formula is as follows:

[0115]

[0116] like Figure 6 As shown, it is a schematic diagram of the characteristic critical value A before the thermal runaway of the lithium battery. The critical value can be adjusted up and down according to the actual lithium battery test conditions. In this embodiment, the critical value is 500.

[0117] According to the lithium battery thermal runaway early characteristic value processing value obtained in step 4) and the lithium battery thermal runaway early characteristic value change rate value obtained in step 5), the lithium battery thermal runaway early warning condition is determined as follows:

[0118] Condition 1, X i >500;

[0119] Condition 2, B i =0;

[0120] When both the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when both the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the calculation is continued back to step 1).

[0121] In this embodiment, condition 1 is satisfied during the rising section of the second small peak, and condition 2 is satisfied during the peak value of the second small peak. When both conditions are satisfied, an early warning signal for thermal runaway is issued to warn that thermal runaway is about to occur, and control measures can be intervened at this time to reduce the losses caused by thermal runaway.

[0122] Example 2

[0123] like Figure 7 As shown, this embodiment discloses an early warning system for thermal runaway of a lithium battery caused by overcharging, including the following functional modules:

[0124] The temperature and voltage rise rate calculation module uses the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time to calculate the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state in real time;

[0125] The noise data processing module performs noise data processing on the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state calculated in real time to obtain a temperature rise rate processing value and a voltage rise rate processing value;

[0126] The thermal runaway early characteristic value calculation module uses the temperature rise rate processing value and the voltage rise rate processing value to establish the lithium battery thermal runaway early characteristic value equation and calculate the lithium battery thermal runaway early characteristic value;

[0127] The data smoothing processing module performs data smoothing processing on the early characteristic value of thermal runaway of the lithium battery to obtain the processed value of the early characteristic value of thermal runaway of the lithium battery;

[0128] The thermal runaway early characteristic value change rate calculation module calculates the lithium battery thermal runaway early characteristic value change rate value according to the lithium battery thermal runaway early characteristic value processing value;

[0129] The thermal runaway early warning condition determination module uses the lithium battery thermal runaway early characteristic value and the lithium battery thermal runaway early characteristic value change rate value to determine the lithium battery thermal runaway early warning condition. When the lithium battery thermal runaway early warning condition is met, the lithium battery thermal runaway early warning is issued, otherwise it returns to the temperature and voltage rise rate calculation module to continue the calculation.

[0130] In the temperature and voltage rise rate calculation module, the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time are respectively represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, U i Represents the lithium battery voltage at the i-th moment;

[0131] Real-time calculation of the temperature rise rate C of the lithium battery in the overcharge state iIt is expressed as:

[0132]

[0133] C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment;

[0134] The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as:

[0135]

[0136] V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment.

[0137] In the noise data processing module, noise data processing is performed according to the following rules:

[0138] When C i <0, let C i =0;

[0139] When V i <0, let V i =0.

[0140] In the thermal runaway early characteristic value calculation module, the established lithium battery thermal runaway early characteristic value equation is as follows:

[0141]

[0142] W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; α, β, and γ represent correlation coefficients, which are assigned according to the type of lithium battery.

[0143] In the data smoothing processing module, data smoothing processing is performed on the early characteristic value of thermal runaway of the lithium battery, which means finding the average value of a data group containing n consecutive early characteristic values ​​of thermal runaway of the lithium battery, and the average value is defined as the processing value of the early characteristic value of thermal runaway of the battery cell; the data smoothing equation is established as follows:

[0144]

[0145] X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, W i-1They represent the early characteristic values ​​of thermal runaway of lithium batteries at moments in, i-n+1, ​​…, i-1 respectively.

[0146] In the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early characteristic value change rate value calculation equation is as follows:

[0147]

[0148] B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i-1 Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-1th moment.

[0149] In the thermal runaway early warning condition determination module, the determination of the lithium battery thermal runaway early warning condition includes the following steps:

[0150] By testing the thermal runaway of lithium batteries caused by overcharging on a large number of specific lithium battery samples shipped out of the factory, the result data is statistically analyzed to obtain a curve of the change of the early characteristic value processing value of the lithium battery thermal runaway over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before the thermal runaway of the battery cell is determined, and the calculation formula is as follows:

[0151]

[0152] According to the lithium battery thermal runaway early characteristic value processing value obtained in the data smoothing processing module and the lithium battery thermal runaway early characteristic value change rate value obtained in the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early warning conditions are determined as follows:

[0153] Condition 1, X i >A,X i Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment;

[0154] Condition 2, B i =0, B i Indicates the rate of change of the early characteristic value of thermal runaway of the lithium battery at the i-th moment;

[0155] When the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the temperature and voltage rise rate calculation module is returned to continue the calculation.

[0156] In summary, the present invention fully considers the early signal characteristics of thermal runaway of lithium batteries caused by overcharging, couples the two sets of characteristics of temperature signals and voltage signals, and amplifies the early signal characteristics of thermal runaway of lithium batteries caused by overcharging, so that the identification and extraction of early characteristics of thermal runaway are more convenient and accurate, the probability of misjudgment of thermal runaway is reduced, and sufficient time is reserved for thermal runaway control.

[0157] The present invention uses real-time acquired signal data for analysis, and can provide early warning of thermal runaway of lithium batteries in a relatively timely and effective manner. It can be applied to a variety of scenarios that require real-time monitoring of whether the battery has thermal runaway caused by overcharging, including but not limited to electric vehicles, electric vehicles, consumer electronic products, energy storage power stations, etc.

[0158] The early warning method and system for thermal runaway of lithium batteries caused by overcharging used in the present invention can be applied to various types of lithium batteries, including but not limited to lithium manganese oxide batteries, lithium iron phosphate batteries, ternary lithium batteries, lithium titanate batteries, etc. It is applicable to lithium batteries of various packaging types, including but not limited to cylindrical lithium batteries, soft-pack lithium batteries, square hard-shell lithium batteries, etc.

[0159] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An early warning method for thermal runaway of a lithium battery caused by overcharging, characterized in that: The following steps are involved: 1) Using the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time, the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state are calculated in real time; 2) performing noise data processing on the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state calculated in real time to obtain a temperature rise rate processing value and a voltage rise rate processing value; 3) Using the temperature rise rate processing value and the voltage rise rate processing value, establish the early characteristic value equation of lithium battery thermal runaway, and calculate the early characteristic value of lithium battery thermal runaway; wherein, the established early characteristic value equation of lithium battery thermal runaway is as follows: W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; C i represents the temperature rise rate of the lithium battery at the i-th moment, V i represents the voltage increase rate of the lithium battery at the i-th moment; α, β, and γ represent correlation coefficients, which are assigned according to the type of lithium battery; 4) Performing data smoothing processing on the early characteristic value of thermal runaway of the lithium battery to obtain the processed value of the early characteristic value of thermal runaway of the lithium battery; 5) Calculate the change rate value of the early characteristic value of thermal runaway of the lithium battery according to the processing value of the early characteristic value of thermal runaway of the lithium battery; 6) Determining the early warning conditions for lithium battery thermal runaway by using the early characteristic value of lithium battery thermal runaway and the rate of change of the early characteristic value of lithium battery thermal runaway, including the following steps: 6.1) A large number of specific lithium battery samples were tested for thermal runaway of lithium batteries caused by overcharging, and the result data were statistically analyzed to obtain a curve of the change of the characteristic value processing value of the early thermal runaway of the lithium battery over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before thermal runaway of the battery cell is determined, and the calculation formula is as follows: 6.2) According to the lithium battery thermal runaway early characteristic value processing value obtained in step 4) and the lithium battery thermal runaway early characteristic value change rate value obtained in step 5), the lithium battery thermal runaway early warning condition is determined as follows: Condition 1, X i >A,X i Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment; Condition 2, B i =0, B i Indicates the rate of change of the early characteristic value of thermal runaway of the lithium battery at the i-th moment; When both the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when both the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the calculation is continued back to step 1).

2. The early warning method for thermal runaway of a lithium battery caused by overcharging according to claim 1, characterized in that: In step 1), the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time are represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, U i Represents the lithium battery voltage at the i-th moment; Real-time calculation of the temperature rise rate C of the lithium battery in the overcharge state i It is expressed as: C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment; The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as: V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment.

3. The early warning method for thermal runaway of a lithium battery caused by overcharging according to claim 2, characterized in that: In step 2), the noise data processing is performed according to the following rules: When C i <0, let C i =0; When V i <0, let V i =0; C i represents the temperature rise rate of the lithium battery at the i-th moment, V i Indicates the voltage increase rate of the lithium battery at the i-th moment.

4. The early warning method for thermal runaway of a lithium battery caused by overcharging according to claim 3, characterized in that: In step 4), data smoothing processing is performed on the early characteristic value of thermal runaway of the lithium battery, which means averaging a group of data containing n consecutive early characteristic values ​​of thermal runaway of the lithium battery, and the average value is defined as the processed value of the early characteristic value of thermal runaway of the battery cell; the data smoothing equation is established as follows: X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, W i-1 They represent the early characteristic values ​​of thermal runaway of lithium batteries at moments in, i-n+1, ​​…, i-1 respectively.

5. The early warning method for thermal runaway of a lithium battery caused by overcharging according to claim 4, characterized in that: In step 5), the calculation equation for the rate of change of the characteristic value of the early stage of thermal runaway of the lithium battery is as follows: B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i represents the early characteristic value processing value of lithium battery thermal runaway at the i-th moment, X i-1 represents the early characteristic value processing value of thermal runaway of lithium battery at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment.

6. An early warning system for thermal runaway of lithium batteries caused by overcharging, characterized in that: The early warning method for thermal runaway of a lithium battery caused by overcharging as described in any one of claims 1 to 5 comprises: The temperature and voltage rise rate calculation module uses the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time to calculate the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state in real time; The noise data processing module performs noise data processing on the temperature rise rate and voltage rise rate of the lithium battery in the overcharge state calculated in real time to obtain a temperature rise rate processing value and a voltage rise rate processing value; The thermal runaway early characteristic value calculation module uses the temperature rise rate processing value and the voltage rise rate processing value to establish the lithium battery thermal runaway early characteristic value equation and calculate the lithium battery thermal runaway early characteristic value; The data smoothing processing module performs data smoothing processing on the early characteristic value of thermal runaway of the lithium battery to obtain the processed value of the early characteristic value of thermal runaway of the lithium battery; The thermal runaway early characteristic value change rate calculation module calculates the lithium battery thermal runaway early characteristic value change rate value according to the lithium battery thermal runaway early characteristic value processing value; The thermal runaway early warning condition determination module uses the lithium battery thermal runaway early characteristic value and the lithium battery thermal runaway early characteristic value change rate value to determine the lithium battery thermal runaway early warning condition. When the lithium battery thermal runaway early warning condition is met, the lithium battery thermal runaway early warning is issued, otherwise it returns to the temperature and voltage rise rate calculation module to continue the calculation.

7. An early warning system for thermal runaway of lithium batteries caused by overcharging according to claim 6, characterized in that: In the temperature and voltage rise rate calculation module, the voltage signal and temperature signal of the lithium battery in the overcharge state collected in real time are respectively represented as T i and U i , T i Indicates the lithium battery temperature at the i-th moment, U i Represents the lithium battery voltage at the i-th moment; Real-time calculation of the temperature rise rate C of the lithium battery in the overcharge state i It is expressed as: C i represents the temperature rise rate of the lithium battery at the i-th moment, T i-1 Indicates the lithium battery temperature at the i-1th moment, t i represents the i-th moment, t i-1 represents the i-1th moment; The voltage increase rate of the lithium battery in the overcharge state calculated in real time is expressed as: V i Indicates the voltage increase rate of the lithium battery at the i-th moment, U i-1 Represents the lithium battery voltage at the i-1th moment; In the noise data processing module, noise data processing is performed according to the following rules: When C i <0, let C i =0; When V i <0, let V i =0; In the thermal runaway early characteristic value calculation module, the established lithium battery thermal runaway early characteristic value equation is as follows: W i represents the early characteristic value of thermal runaway of lithium battery at the i-th moment; α, β, and γ represent correlation coefficients, which are assigned according to the type of lithium battery; In the data smoothing processing module, data smoothing processing is performed on the early characteristic value of thermal runaway of the lithium battery, which means finding the average value of a data group containing n consecutive early characteristic values ​​of thermal runaway of the lithium battery, and the average value is defined as the processing value of the early characteristic value of thermal runaway of the battery cell; the data smoothing equation is established as follows: X i represents the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment, W i-n , W i-n+1 , …, W i-1 They represent the early characteristic values ​​of thermal runaway of lithium battery at time in, i-n+1, ​​…, i-1 respectively; In the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early characteristic value change rate value calculation equation is as follows: B i represents the rate of change of the early characteristic value of thermal runaway of lithium battery at the i-th moment, X i-1 Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-1th moment.

8. An early warning system for thermal runaway of lithium batteries caused by overcharging according to claim 6, characterized in that: In the thermal runaway early warning condition determination module, the determination of the lithium battery thermal runaway early warning condition includes the following steps: By testing the thermal runaway of lithium batteries caused by overcharging on a large number of specific lithium battery samples shipped out of the factory, the result data is statistically analyzed to obtain a curve of the change of the early characteristic value processing value of the lithium battery thermal runaway over time. The average peak value of the first small peak in the curve is a, and the average peak value of the second small peak is b. The characteristic critical value A before the thermal runaway of the battery cell is determined, and the calculation formula is as follows: According to the lithium battery thermal runaway early characteristic value processing value obtained in the data smoothing processing module and the lithium battery thermal runaway early characteristic value change rate value obtained in the thermal runaway early characteristic value change rate value calculation module, the lithium battery thermal runaway early warning conditions are determined as follows: Condition 1, X i >A,X i Indicates the early characteristic value processing value of thermal runaway of lithium battery at the i-th moment; Condition 2, B i =0, B i Indicates the rate of change of the early characteristic value of thermal runaway of the lithium battery at the i-th moment; When the lithium battery thermal runaway early warning conditions 1 and 2 are met at the same time, a thermal runaway warning is issued; when the lithium battery thermal runaway early warning conditions 1 and 2 are not met at the same time, no warning is issued and the temperature and voltage rise rate calculation module is returned to continue the calculation.

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