A lithium battery aging early warning method based on energy efficiency and temperature rise rate

Abstract

The present application belongs to the field of battery health state monitoring, and relates to a lithium battery aging early warning method based on energy efficiency and temperature rise rate, comprising the following steps: S1: in the initial stage of the battery life cycle, based on the benchmark charge-discharge cycle data under the benchmark working condition, calculating the benchmark energy efficiency and the benchmark temperature rise rate in the charging process; S2: establishing a joint grading threshold interval based on the benchmark energy efficiency and the benchmark temperature rise rate in the charging process; S3: in use, real-time monitoring the voltage, current and temperature data of each charge-discharge cycle, calculating the measured energy efficiency and the measured temperature rise rate in the charging process of the current cycle; S4: correcting the measured energy efficiency; S5: comparing the measured temperature rise rate in the charging process, the corrected energy efficiency and the joint grading threshold interval, and determining the battery aging grade; S6: generating early warning information according to the battery aging grade, and alarming according to the early warning information. The problems of high online early warning cost and insufficient reliability of the lithium battery are solved.

Description

Technical Field

[0001] This invention belongs to the field of battery health status monitoring, and in particular relates to a method for early warning of lithium battery aging based on energy efficiency and temperature rise rate. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have become the core power source for new energy vehicles, energy storage systems, and other fields. However, batteries inevitably age during long-term use, manifesting as capacity decay, increased internal resistance, reduced energy efficiency, and deterioration of temperature rise characteristics. When aging accumulates to a certain extent, the battery not only fails to meet normal operating requirements but may also trigger safety accidents such as thermal runaway. Therefore, accurate and timely assessment and early warning of battery aging status are of great significance for ensuring system safety and extending battery life.

[0003] Currently, the main methods for assessing the health status of lithium-ion batteries are: 1) Assessing the degree of aging by measuring the battery's AC impedance or DC pulse internal resistance. However, this method usually requires additional excitation and detection equipment, making the system complex and costly, and it is not convenient to integrate it into the vehicle battery management system for online real-time monitoring; 2) Inferring the aging status by analyzing the changes in characteristic points (such as inflection points and plateau voltages) in the charge and discharge voltage curves. This type of method has extremely high requirements for voltage sampling accuracy and consistency, and is easily affected by changes in operating conditions such as charging rate and ambient temperature, resulting in poor robustness; 3) Obtaining the actual capacity of the battery directly through full charge and discharge tests. However, a complete capacity test takes a long time, which will interrupt the normal use of the battery, and the test results are also significantly affected by the test conditions, making it difficult to use for real-time early warning. Summary of the Invention

[0004] This invention provides a lithium battery aging early warning method based on energy efficiency and temperature rise rate, which solves the problems of high cost and insufficient reliability of existing battery aging early warning systems due to reliance on external data and sensitivity to changes in operating conditions.

[0005] The basic solution provided by this invention is a lithium battery aging early warning method based on energy efficiency and temperature rise rate, specifically including the following steps: S1: At the initial stage of the battery life cycle, acquire a complete reference charge-discharge cycle data under reference operating conditions, calculate the battery charge-discharge energy efficiency based on the data as the reference energy efficiency, and calculate the temperature rise rate during the charging process as the reference temperature rise rate during the charging process. S2: Based on battery type and application requirements, establish a joint grading threshold range based on benchmark energy efficiency and benchmark charging process temperature rise rate, with each threshold range corresponding to a different battery aging level. S3: During subsequent battery use, the voltage, current and temperature data of each charge and discharge cycle are monitored in real time to calculate the measured energy efficiency and the measured temperature rise rate during the charging process of the current cycle. S4: The measured energy efficiency is corrected using a preset temperature-rate dual-factor correction model to obtain the corrected energy efficiency; S5: Compare the measured temperature rise rate during charging, the corrected energy efficiency, and the joint grading threshold range, and determine the battery aging level according to the preset judgment rules; S6: Generates warning information based on battery aging level and issues an alarm based on the warning information.

[0006] Preferably, in step S1, when acquiring the reference charge-discharge cycle data, the charging process is performed with a current of not less than 1 / 3C to the charging cutoff condition and then left to stand for a specified time; the discharging process is performed with a current of not less than 1 / 3C to the discharging cutoff condition and then left to stand for a specified time.

[0007] Preferably, in step S4, the temperature-rate dual-factor correction model is as follows:

[0008] In the formula, This is a temperature correction factor. This is the ratio correction factor. This represents the measured energy efficiency.

[0009] More preferably, the temperature correction factor is calculated based on the Arrhenius formula, specifically,

[0010] In the formula, The apparent activation energy is related to the battery energy efficiency, and k is the Boltzmann constant. The ambient temperature is the reference operating condition cycle temperature. This represents the ambient temperature of the current cycle.

[0011] More preferably, the calculation formula for the rate correction factor is:

[0012] In the formula, This is the rate loss coefficient. The charging rate for the current cycle. It is related to the charging rate of the baseline operating cycle.

[0013] Preferably, in step S5, the preset judgment rule is: The measured temperature rise rate and corrected energy efficiency during the charging process are compared with the joint grading threshold range. First, the corrected energy efficiency is used as the main criterion and compared with the energy efficiency threshold of the joint grading threshold range to determine the preliminary aging level. The measured temperature rise rate during the charging process is used as an auxiliary criterion and compared with the temperature rise rate threshold of the joint grading threshold range. If the temperature rise rate falls into a grade range higher than the initial aging grade, the initial aging grade is increased by one level and used as the aging grade of the cycle. If the initial aging level is already the highest level, then the highest level will be directly determined as the aging level. If the rate of temperature rise falls within a range equal to or lower than the initial aging level, then the initial aging level will be used as the aging level for that cycle. The final battery aging level is determined using a rolling judgment method. Specifically, a sliding window of length N is set, and the window scrolls forward in increments of one cycle. For each position of the sliding window, the aging level determined independently for each of the N cycles within the window is obtained. The frequency of each aging level within the window is counted, and the final battery aging level is determined according to the following rules: The level that appears most frequently is taken as the final battery aging level; If multiple levels occur with the same frequency, the principle of safety priority shall be followed, and the level with the highest risk level shall be taken as the final battery aging level.

[0014] Preferably, the joint grading threshold interval is divided into multiple non-overlapping regions on a two-dimensional plane, corresponding to Level 1 normal, Level 2 mild aging, Level 3 moderate aging, and Level 4 severe aging, respectively.

[0015] Preferably, in step S6, different warning levels correspond to different warning information content, including guidance information for instructing users to take corresponding maintenance measures.

[0016] Preferably, in step S1, the reference energy efficiency is calculated as follows: The total input energy during the charging phase is determined by integrating the product of voltage and current over time. The total output energy of the discharge phase is determined by integrating the product of voltage and current over time during the discharge process. The baseline energy efficiency is calculated based on the total input energy during the charging phase and the total output energy during the discharging phase. Specifically,

[0017] In the formula, This represents the total output energy during the discharge phase. This refers to the total input energy during the charging phase.

[0018] Preferably, in step S1, the formula for calculating the temperature rise rate of the reference charging process is as follows:

[0019] In the formula, The charging end temperature. This is the starting temperature for charging. This refers to the charging time.

[0020] The principles and advantages of this invention are as follows: 1. Based on the complete charge-discharge cycle data collected in a conventional manner, the energy efficiency and the temperature rise rate during the charging process are calculated to determine the battery health status. The collected data can be directly obtained from the battery management system. It can achieve non-intrusive online monitoring of battery aging status without interrupting normal battery use or relying on complex external excitation equipment. The method is simple, easy to integrate, and does not rely on a large external historical database, which significantly reduces system complexity and implementation costs.

[0021] 2. When judging the degree of aging, the energy efficiency and the temperature rise rate during the charging process are combined for joint judgment, avoiding the defects of single voltage characteristics and single internal resistance parameters being easily affected by the fluctuation of operating conditions; at the same time, through the temperature-rate dual-factor correction model, the interference of external operating conditions such as ambient temperature and charging rate on the measured energy efficiency is eliminated, realizing the comparability of measured values ​​under different operating conditions and significantly improving the accuracy of aging assessment.

[0022] 3. Based on the benchmark energy efficiency and the benchmark charging process temperature rise rate, a joint grading threshold range is established. The measured charging process temperature rise rate and corrected energy efficiency are compared with the joint grading threshold range. The energy efficiency (reflecting internal resistance and polarization loss) and the temperature rise rate (reflecting heat generation power and thermal characteristics), two physical quantities directly related to the aging mechanism, are presented side by side. This provides a clear physical explanation for any state judgment, clearly distinguishing between uniform performance degradation and safety hazards caused by abnormal heat generation. It intuitively and clearly reflects the degree of battery aging, which is conducive to achieving graded early warning and refined maintenance, improving the safety and economy of the battery system. Moreover, different regions directly correspond to different maintenance levels and early warnings, realizing a closed loop from monitoring to management.

[0023] 4. The initial classification is based on the modified energy efficiency as the main criterion, ensuring that the core of the judgment is based on the fundamental degradation of the battery's energy conversion capability. At the same time, the measured temperature rise rate is introduced as an auxiliary criterion for one-way calibration. When the temperature rise is abnormally significant, the aging level can be upgraded, effectively capturing the additional thermal risks caused by accelerated aging. This makes up for the deficiency that a single efficiency criterion may not be able to respond adequately to the precursors of thermal runaway, reflecting the design principle of prioritizing safety.

[0024] Compared with the method of determining aging level by weighted fusion of multiple indicators, the present invention divides the state range clearly, which can more intuitively determine the level and correspond to the main influencing factors. It avoids the fundamental problem of subjective weight setting and inability to adaptively adjust with the aging stage in traditional methods, and makes engineering deployment simpler and more reliable. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the charging curve of the present invention; Figure 3 This is a schematic diagram of the discharge curve of the present invention; Figure 4 This is a schematic diagram illustrating the changes in charge / discharge energy efficiency and charging temperature rise rate of the present invention with the number of cycles. Detailed Implementation

[0026] The following detailed description illustrates the specific implementation method: The specific implementation process is as follows: (See details) Figures 1 to 4 A method for early warning of lithium battery aging based on energy efficiency and temperature rise rate, specifically including the following steps: S1: At the initial stage of the battery life cycle, acquire a complete reference charge-discharge cycle data under reference operating conditions, and calculate key reference indicators for aging warning based on the data. The key reference indicators for aging warning include reference energy efficiency and reference charging process temperature rise rate. The battery charge-discharge energy efficiency calculated based on the data collected under reference operating conditions is used as the reference energy efficiency, and the charging process temperature rise rate is calculated as the reference charging process temperature rise rate.

[0027] Specifically, the reference operating conditions include a preset reference ambient temperature and a reference charging rate; the reference charge-discharge cycle data include battery voltage, battery current, charging rate, and ambient temperature; the reference ambient temperature is 25 degrees Celsius. Step S1 further includes, when acquiring reference charge-discharge cycle data, charging at a current of not less than 1 / 3C (charge rate) to the charging cutoff condition during the charging process, and then allowing it to stand for a specified time; discharging at a current of not less than 1 / 3C (charge rate) to the discharging cutoff condition during the discharging process, and then allowing it to stand for a specified time. The cutoff condition is determined based on the standard voltage range and rated specifications of the individual battery, and the standing time is determined based on the internal electrochemical stability and thermal balance requirements of the individual battery, preferably 30~60 minutes.

[0028] In step S1, the baseline energy efficiency is calculated as follows: The total input energy during the charging phase is determined by integrating the product of voltage and current over time. Specifically,

[0029] In the formula, t C0 Let t be the charging start time (s). C1 V is the time when charging ends (s). c (t) represents the charging voltage (V) at time t, I c (t) represents the charging current (A) at time t; The total output energy of the discharge phase is determined by integrating the product of voltage and current over time during the discharge process. Specifically,

[0030] In the formula, t d0 t is the discharge start time (s). d1 V is the discharge end time (s). d (t) represents the discharge voltage (V) at time t, I d (t) represents the discharge current (A) at time t; The baseline energy efficiency is calculated based on the total input energy during the charging phase and the total output energy during the discharging phase. Specifically,

[0031] In the formula, This represents the total output energy during the discharge phase. This refers to the total input energy during the charging phase.

[0032] In step S1, the formula for calculating the temperature rise rate of the reference charging process is as follows:

[0033] In the formula, The charging end temperature. This is the starting temperature for charging. This refers to the charging time.

[0034] In this embodiment, taking a lithium iron phosphate battery as an example, in the initial stage of the battery's life cycle, a complete charge-discharge cycle is performed at a rate of 0.5C under an environment of 25°C. During charging, the charging cutoff condition is that the single cell voltage reaches 3.65V and is left to stand for 30 minutes. During discharging, the discharging cutoff condition is that the single cell voltage drops to 2.5V and is left to stand for 30 minutes. During this cycle, the battery management system (BMS) synchronously collects and records the baseline charge-discharge cycle data. Based on the collected data, the baseline energy efficiency is calculated to be 95.04%, and the baseline charging process temperature rise rate is 0.006°C / min. This calculation result is used as a key baseline indicator for aging warning.

[0035] S2: Based on battery type and application requirements, establish a joint grading threshold range based on benchmark energy efficiency and benchmark charging process temperature rise rate, with each threshold range corresponding to a different battery aging level. In step S2, the establishment of the joint hierarchical threshold interval is as follows: Determine the grading strategy and aging levels: Based on the type of target battery (such as ternary lithium, lithium iron phosphate) and its specific application scenarios (such as electric vehicles, energy storage systems) and the requirements for safety and lifespan, determine the number of aging state grades and the definition of each grade; Set the level threshold of the main criterion (energy efficiency): Using the baseline energy efficiency obtained in step S1 as the initial reference point, based on the research on the aging mechanism of this type of battery and the accelerated life test data, determine the relative decay of energy efficiency characterizing different aging levels, set the energy efficiency threshold corresponding to each level, thereby dividing the continuous variation range of energy efficiency into several intervals, each interval corresponding to a preset aging level. Set the threshold for the auxiliary criterion (temperature rise rate): Using the temperature rise rate of the baseline charging process obtained in step S1 as the initial reference point, and combining the battery thermal characteristic analysis and aging test data, determine the relative increase or increase factor of the temperature rise rate that characterizes different aging levels, set the temperature rise rate threshold corresponding to each level, and divide the continuous change range of the temperature rise rate into several intervals. Constructing a two-dimensional joint threshold interval: The energy efficiency threshold and temperature rise rate threshold corresponding to each level are combined and correlated. In a two-dimensional parameter space consisting of the corrected energy efficiency as the first dimension and the measured temperature rise rate during charging as the second dimension, multiple non-overlapping judgment regions are divided. Each region is jointly defined by a pair of energy efficiency threshold intervals and temperature rise rate threshold intervals, and uniquely corresponds to a specific battery aging level, thereby forming the joint grading threshold interval.

[0036] Preferably, multiple non-overlapping regions are divided on a two-dimensional plane by using a joint grading threshold interval, resulting in four aging levels (Level 1 Normal, Level 2 Mild Aging, Level 3 Moderate Aging, and Level 4 Severe Aging). The corresponding joint grading threshold intervals are shown in Table 1 below. Table 1. Examples of joint grading threshold ranges corresponding to the four aging levels.

[0037] In this embodiment, the joint classification threshold interval is determined based on the baseline energy efficiency of 95.04% and the baseline charging process temperature rise rate of 0.006℃ / min calculated in step S1.

[0038] Specifically, based on the application requirements of lithium iron phosphate batteries in the power battery scenario in this embodiment, the aging level is set into four levels. In order to ensure the timeliness of the warning, the warning threshold is set before the inflection point of battery performance degradation, and a safety margin is reserved. Determine the primary criterion threshold: based on the aforementioned baseline energy efficiency. Starting with 95.04%, based on accelerated aging test data and industry experience for this battery model, the following definition is made: When the energy efficiency decreases by approximately 0.8% to 1.0% relative to the initial value, corresponding to a critical point where the battery health degrades to approximately 90%, it is considered to have entered the stage of mild aging (Level 2). Based on this, the following settings are established. = 94.63%; When the cumulative decrease is approximately 1.5% to 1.8%, corresponding to a critical point where battery health has deteriorated to approximately 85%, it is considered to have entered moderate aging (Level 3). = 94.31%; When the cumulative decrease is approximately 2.0%~2.2%, corresponding to a battery health degradation to approximately 80% or below, it is considered to have entered a state of severe aging (Level 4), and is set as follows: = 94.12%; Determine the auxiliary criterion threshold: based on the reference charging temperature rise rate. = 0.006°C / min as the starting point.

[0039] Combining battery thermal model and aging test data, the growth factor of the temperature rise rate relative to the initial value is defined as an auxiliary criterion: When the rate of temperature rise increases to about 4-5 times the baseline value, set = 0.027°C / min, used to identify the critical point where thermal characteristics deviate from normal; When it grows to about 5-6 times, set = 0.032°C / min, which serves as the boundary for a significant increase in heat production associated with moderate aging; When it grows to more than 6 times, set = 0.037°C / min, which serves as the critical point for determining whether a battery has potential thermal runaway risks or severe internal resistance degradation leading to excessive heat generation.

[0040] Constructing a two-dimensional joint threshold interval: combining the thresholds of the above primary and secondary criteria, i.e., within the range of... For the horizontal axis, On a two-dimensional plane with the vertical axis, four distinct rectangular judgment regions are divided, forming the joint hierarchical threshold intervals as shown in Table 2. Table 2 Examples of Joint Hierarchical Threshold Ranges

[0041] The threshold determination system of this invention combines the unique energy efficiency decay characteristics and temperature rise mechanism of lithium-ion batteries to intuitively determine the aging degree of lithium-ion batteries and correspond to the main influencing factors.

[0042] S3: During subsequent battery use, the voltage, current and temperature data of each charge and discharge cycle are monitored in real time to calculate the measured energy efficiency and the measured temperature rise rate during the charging process of the current cycle. In this embodiment, the data measured by the BMS during a certain charge-discharge cycle shows that the current cycle charge-discharge energy efficiency is 95.14% and the charging temperature rise rate is 0.035℃ / min. S4: The measured energy efficiency is corrected using a preset temperature-rate dual-factor correction model to obtain the corrected energy efficiency; In step S4, the temperature-rate two-factor correction model is as follows:

[0043] In the formula, This is a temperature correction factor. This is the ratio correction factor. This represents the measured energy efficiency.

[0044] The temperature correction factor is calculated based on the Arrhenius formula, specifically,

[0045] In the formula, The apparent activation energy is related to the battery energy efficiency, and k is the Boltzmann constant. The ambient temperature is the reference operating condition cycle temperature. The ambient temperature for the current cycle; in, Apparent activation energy (in eV) related to battery energy efficiency, ternary lithium-ion battery Typically 0.15-0.25 eV, lithium iron phosphate batteries Typically, it is 0.10-0.20 eV. For the optimal parameters of a specific model, it should be precisely calibrated using test data under reference conditions; k is the Boltzmann constant, approximately 8.617 × 10⁻⁶. -5 eV / K; The reference cycling ambient temperature; The ambient temperature is the current circulating temperature. In this embodiment, the ambient temperature is 30°C.

[0046] The formula for calculating the ratio correction factor is as follows:

[0047] In the formula, This is the rate loss coefficient. The charging rate for the current cycle. Related to the charging rate of the baseline operating cycle; in, The rate loss coefficient is obtained through experimental calibration. For high-power batteries, α is typically 0.01~0.03, and for high-energy batteries... The value is typically 0.03 to 0.16. For the optimal parameters of a specific model, precise calibration should be performed using test data under reference conditions. The base cycle charge rate, The current cycle charging rate is 1C in this embodiment.

[0048] In this embodiment, the calculation was performed using a temperature-rate dual-factor correction model. ; The final corrected charge / discharge energy efficiency was obtained. .

[0049] The correction model of this invention is specifically constructed based on the unique electrochemical loss mechanism of lithium-ion batteries to improve energy efficiency. It can effectively correct the measured energy efficiency of lithium-ion batteries, thereby improving the accuracy of battery aging level assessment.

[0050] S5: Compare the measured temperature rise rate during charging, the corrected energy efficiency, and the joint grading threshold range, and determine the battery aging level according to the preset judgment rules; In step S5, the preset judgment rule is as follows: the measured temperature rise rate during charging and the corrected energy efficiency are compared with the joint grading threshold range. First, the corrected energy efficiency is used as the primary criterion and compared with the energy efficiency threshold of the joint grading threshold range to determine the preliminary aging level. The measured temperature rise rate during charging is used as an auxiliary criterion and compared with the temperature rise rate threshold of the joint grading threshold range. If the temperature rise rate falls into a level range higher than the preliminary aging level, the preliminary aging level is increased by one level and used as the aging level for this cycle. If the preliminary aging level is already the highest level, the highest level is directly determined as the aging level without using the auxiliary criterion for evaluation. If the temperature rise rate falls into a level range equal to or lower than the preliminary aging level, the preliminary aging level is used as the aging level for this cycle. To eliminate fluctuation interference, a rolling determination of the final battery aging level is performed: Define a sliding window of length N, which scrolls forward in increments of a single cycle. For each position of the sliding window, obtain the aging level determined independently by each of the N cycles within the window. Count the frequency of each aging level within the window and determine the final battery aging level according to the following rules: The most frequently occurring level is taken as the output level (final battery aging level). If multiple levels have the same frequency, the safety priority principle is followed, and the level with the highest risk (i.e. the most severe aging) is taken as the output level, where N is an integer greater than or equal to 3.

[0051] In this embodiment, the corrected efficiency falls within the range of 94.12 < ηcor ≤ 94.31, and the temperature rise rate is within the range of greater than 0.032 and less than 0.037. It is initially judged as level three (moderate aging). The judgment results are consistent for three consecutive cycles, and the warning level is finally confirmed as level three, and the aging state is moderate aging.

[0052] S6: Generates warning information based on battery aging level and issues an alarm based on the warning information.

[0053] In step S6, different warning levels correspond to different warning information content, including guidance information for instructing users to take corresponding maintenance measures; Specifically, there are pre-set guidance messages for each level of early warning information, including: Level 2 warning message "Please pay attention", Level 3 warning message "Please pay attention to monitoring and arrange inspection in time", and Level 4 warning message "Please reduce the load and contact maintenance as soon as possible". In this implementation, a three-level early warning signal is generated based on the aging level to remind users to pay attention to monitoring, arrange inspections in a timely manner, and send the signal to the user terminal.

[0054] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A lithium battery aging early warning method based on energy efficiency and temperature rise rate, characterized by, Specifically, the following steps are included: S1: At the initial stage of the battery life cycle, acquire a complete reference charge-discharge cycle data under reference operating conditions, calculate the battery charge-discharge energy efficiency based on the data as the reference energy efficiency, and calculate the temperature rise rate during the charging process as the reference temperature rise rate during the charging process. S2: Based on battery type and application requirements, establish a joint grading threshold range based on benchmark energy efficiency and benchmark charging process temperature rise rate, with each threshold range corresponding to a different battery aging level. S3: During subsequent battery use, the voltage, current and temperature data of each charge and discharge cycle are monitored in real time to calculate the measured energy efficiency and the measured temperature rise rate during the charging process of the current cycle. S4: The measured energy efficiency is corrected using a preset temperature-rate dual-factor correction model to obtain the corrected energy efficiency; S5: Compare the measured temperature rise rate during charging, the corrected energy efficiency, and the joint grading threshold range, and determine the battery aging level according to the preset judgment rules; S6: Generates warning information based on battery aging level and issues an alarm based on the warning information. 2.The energy efficiency and temperature rise rate based lithium battery aging early warning method according to claim 1, characterized in that: In step S1, when acquiring the reference charge-discharge cycle data, the charging process involves charging with a current of not less than 1 / 3C to the charging cutoff condition and then letting it stand for a specified time; the discharging process involves discharging with a current of not less than 1 / 3C to the discharging cutoff condition and then letting it stand for a specified time. 3.The energy efficiency and temperature rise rate based lithium battery aging early warning method of claim 1, wherein: In step S4, the temperature-rate two-factor correction model is as follows: In the formula, is a temperature correction factor, is a capacity correction factor, is the measured energy efficiency.

4. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 3, characterized in that: The temperature correction factor is calculated based on the Arrhenius formula, specifically, In the formula, The apparent activation energy is related to the battery energy efficiency, and k is the Boltzmann constant. The ambient temperature is the reference operating condition cycle temperature. This represents the ambient temperature of the current cycle.

5. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 3, characterized in that: The formula for calculating the ratio correction factor is as follows: In the formula, This is the rate loss coefficient. The charging rate for the current cycle. It is related to the charging rate of the baseline operating cycle.

6. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 1, characterized in that: In step S5, the preset judgment rule is: The measured temperature rise rate and corrected energy efficiency during the charging process are compared with the joint grading threshold range. First, the corrected energy efficiency is used as the main criterion and compared with the energy efficiency threshold of the joint grading threshold range to determine the preliminary aging level. The measured temperature rise rate during the charging process is used as an auxiliary criterion and compared with the temperature rise rate threshold of the joint grading threshold range. If the temperature rise rate falls into a grade range higher than the initial aging grade, the initial aging grade is increased by one level and used as the aging grade of the cycle. If the initial aging level is already the highest level, then the highest level will be directly determined as the aging level. If the rate of temperature rise falls within a range equal to or lower than the initial aging level, then the initial aging level will be used as the aging level for that cycle. The final battery aging level is determined using a rolling judgment method. Specifically, a sliding window of length N is set, and the window scrolls forward in increments of one cycle. For each position of the sliding window, the aging level determined independently for each of the N cycles within the window is obtained. The frequency of each aging level within the window is counted, and the final battery aging level is determined according to the following rules: The level that appears most frequently is taken as the final battery aging level; If multiple levels occur with the same frequency, the principle of safety priority shall be followed, and the level with the highest risk level shall be taken as the final battery aging level.

7. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 1, characterized in that: The joint grading threshold interval divides multiple non-overlapping regions on a two-dimensional plane, corresponding to Level 1 normal, Level 2 mild aging, Level 3 moderate aging, and Level 4 severe aging, respectively.

8. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 1, characterized in that: In step S6, different warning levels correspond to different warning information content, which includes guidance information to instruct users to take corresponding maintenance measures.

9. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 1, characterized in that: In step S1, the baseline energy efficiency is calculated as follows: The total input energy during the charging phase is determined by integrating the product of voltage and current over time. The total output energy of the discharge phase is determined by integrating the product of voltage and current over time during the discharge process. The baseline energy efficiency is calculated based on the total input energy during the charging phase and the total output energy during the discharging phase. Specifically, In the formula, This represents the total output energy during the discharge phase. This refers to the total input energy during the charging phase.

10. The lithium battery aging early warning method based on energy efficiency and temperature rise rate according to claim 1, characterized in that: In step S1, the formula for calculating the temperature rise rate of the reference charging process is as follows: In the formula, The charging end temperature. This is the starting temperature for charging. This refers to the charging time.

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