Three-loop control lithium ion battery flexible fast charging method and system

Abstract

The invention provides a three-loop control lithium ion battery flexible fast charging method and system, and the method comprises the steps: obtaining the current charging current and voltage of a lithium ion battery, calculating the overpotential through an electrochemical-thermal-aging coupling model, carrying out the constant overpotential lossless charging, and obtaining a preliminary control current; performing constant strain charging according to the initial control current in combination with the obtained internal strain of the lithium ion battery, and limiting the charging current in the stage by taking the expansion strain when the residual electric quantity is set as a strain boundary in the charging process; performing constant-temperature charging according to the charging current in combination with the obtained temperature of the lithium ion battery, and adjusting the charging current rate within a set temperature range; constant overpotential lossless charging control is used as an outer ring, constant strain charging is used as a middle ring, constant temperature charging is used as an inner ring, a final control current is determined through three-ring control, and flexible fast charging is achieved. According to the invention, a plurality of parameters of the battery can be monitored and controlled, and the contradiction between charging safety and rapidity is solved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery charging, and particularly relates to a flexible fast charging method and system for lithium-ion batteries with triple-loop control. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] In the existing lithium-ion battery charging technology, the traditional constant current-constant voltage (CC-CV) charging method only uses voltage / current as the control reference, and does not integrate multi-dimensional parameters such as the state of health (SOH) of the battery, the real-time polarization voltage, and the electrolyte concentration gradient, resulting in an increased risk of lithium plating on the electrode (especially in low-temperature or high-SOC working conditions), and then leading to a rapid decline in battery capacity.

[0004] In addition, in the existing improved fast charging methods, although a closed-loop control of parameters such as temperature is introduced, the internal characteristics of lithium-ion batteries change greatly in different charging stages, and relying solely on controlling a single variable cannot provide strong theoretical support for the entire fast charging process. This makes it impossible to fully utilize the maximum charging potential of lithium-ion batteries in practical applications. Therefore, in view of the changes in multi-dimensional parameters during the fast charging process of the battery, a new type of safe fast charging method is urgently needed to overcome the limitations of the existing technology. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a flexible fast charging method and system for lithium-ion batteries with triple-loop control. The present invention can monitor and control multiple parameters of the battery, and solve the contradiction between charging safety and rapidity.

[0006] According to some embodiments, the present invention adopts the following technical solutions:

[0007] A flexible fast charging method for lithium-ion batteries with triple-loop control includes the following steps:

[0008] Obtain the current charging current and voltage of the lithium-ion battery, calculate the overpotential through an electrochemical-thermal-aging coupling model, and perform constant overpotential non-destructive charging to obtain a preliminary control current;

[0009] According to the preliminary control current, combined with the internal strain of the lithium-ion battery obtained, perform constant strain charging, and use the expansion strain at a set proportion of the remaining battery power as the strain boundary to limit the charging current in this stage during the charging process;

[0010] According to the charging current, combined with the temperature of the lithium-ion battery obtained, perform constant temperature charging, and adjust the charging current rate within a set temperature range;

[0011] Taking the constant over-potential non-destructive charging control as the outer loop, the constant strain charging as the middle loop, and the constant temperature charging as the inner loop, the final control current is determined by using the three-loop control to achieve flexible fast charging.

[0012] As an alternative implementation, during the process of constant over-potential non-destructive charging, considering the formation of the solid electrolyte film and the lithium plating process during charging, the over-potential of the lithium plating side reaction is calculated, and the over-potential is controlled above the set value.

[0013] As an alternative implementation, during constant strain charging, the battery expansion strain is composed of diffusion-induced strain and thermal strain. The quantitative relationships between the diffusion-induced strain, thermal strain, battery charging rate, and temperature are determined, and then the battery expansion strain is obtained. The charging current is limited according to the set battery expansion strain as the strain boundary.

[0014] As an alternative implementation, an optical fiber strain sensor is used to obtain the internal strain of the lithium-ion battery.

[0015] As an alternative implementation, an optical fiber temperature sensor is used to obtain the temperature of the lithium-ion battery.

[0016] As an alternative implementation, the process of constant temperature charging includes: constructing an electro-thermal coupling model, using the electro-thermal coupling model to express the heat generation and heat transfer mechanisms of the battery during charging, determining the quantitative relationships between the battery charging speed, battery temperature rise, and charging method, and adjusting the charging current rate according to the quantitative relationships.

[0017] As an alternative implementation, the lower limit of the over-potential should be higher than the lithium plating potential to prevent internal short circuit caused by the growth of lithium dendrites. Combining the constraints of each loop in each control stage, the lower limit value of the over-potential of the lithium plating side reaction is dynamically corrected.

[0018] A flexible fast charging system for a lithium-ion battery with three-loop control includes:

[0019] An outer loop control module configured to obtain the current charging current and voltage of the lithium-ion battery, calculate the over-potential through an electrochemical-thermal-aging coupling model, perform constant over-potential non-destructive charging, and obtain a preliminary control current;

[0020] A middle loop control module configured to perform constant strain charging according to the preliminary control current in combination with the obtained internal strain of the lithium-ion battery, and use the expansion strain at a set remaining charge ratio during the charging process as the strain boundary to limit the charging current in this stage;

[0021] An inner loop control module configured to perform constant temperature charging according to the charging current in combination with the obtained temperature of the lithium-ion battery, adjust the charging current rate within a set temperature range, determine the final control current, and achieve flexible fast charging.

[0022] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, complete the steps in the above method.

[0023] An electronic device includes a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the steps in the above method are completed.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] In the present invention, the battery strain and temperature are monitored through an embedded optical fiber, the overpotential is calculated through an electrochemical-thermal-aging coupling model, the side reaction overpotential, strain, and temperature data during the fast charging process of the battery are obtained, the safety boundaries of the three parameters are set and closed-loop control is performed, a three-loop control charging method system of temperature-strain-potential is established, and the optimal balance between safety and efficiency is achieved through hierarchical input-output transfer and dynamic constraints.

[0026] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given in conjunction with the accompanying drawings and are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0028] Figure 1 It is a schematic diagram of the "electric-thermal" coupling model of the battery in an embodiment;

[0029] Figure 2 It is a schematic diagram of the middle-ring constant strain safety charging method in an embodiment;

[0030] Figure 3 It is a schematic diagram of the outer-ring constant overpotential non-destructive charging method in an embodiment;

[0031] Figure 4 It is a schematic diagram of the three-loop control charging method in an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] In the case of no conflict, the embodiments in this application and the features in the embodiments can be combined with each other.

[0036] Embodiment 1

[0037] A flexible fast charging method for a lithium-ion battery with a three-loop control, as Figure 4 shown, includes the following steps:

[0038] Obtain the current charging current and voltage of the lithium-ion battery, calculate the overpotential through an electrochemical-thermal-aging coupling model, and perform constant overpotential non-destructive charging to obtain a preliminary control current;

[0039] According to the preliminary control current and in combination with the internal strain of the lithium-ion battery obtained, perform constant strain charging, and use the expansion strain at a set proportion of the remaining battery charge as the strain boundary to limit the charging current in this stage during the charging process;

[0040] According to the charging current and in combination with the temperature of the lithium-ion battery obtained, perform constant temperature charging, and adjust the charging current rate within a set temperature range;

[0041] Take the constant overpotential non-destructive charging control as the outer loop, the constant strain charging as the middle loop, and the constant temperature charging as the inner loop, and use the three-loop control to determine the final control current to achieve flexible fast charging.

[0042] The following introduces the specific technical details of each link.

[0043] First, introduce the inner loop constant temperature fast charging control.

[0044] Temperature plays a decisive role in the electrochemical reaction and degradation mechanism of the battery. Its degradation is manifested as the deterioration of the battery's electrical performance, safety, and health status. Therefore, the proposed charging strategy aims to maintain the same temperature rise as the traditional charging strategy and maximize the battery charging speed. In order to clarify the quantitative relationship between the charging method, speed, and battery temperature rise, based on the "electro-thermal" coupling model, the heat generation and heat transfer mechanisms during battery charging are revealed, and thus the constant temperature fast charging control process is proposed.

[0045] The battery "electro-thermal" coupling model is as Figure 1As shown in the figure. When quantifying the heat exchange between the battery and the environment, the battery is regarded as a whole, that is, the temperature inside and outside the battery is the same. The heat generated during the battery charging process can be divided into two parts: one is dissipated to the environment in the form of heat, and the other is to continuously increase the battery temperature. Therefore, the heat generation and heat transfer mechanism during the charging process can be expressed as:

[0046]

[0047] In the formula, T c , T f are the battery temperature and the ambient temperature respectively, R u is the convective heat resistance on the battery surface, C c , C s are the equivalent thermal resistances.

[0048] According to formula (1), assuming that the total battery charging time is t1, the time for the battery to reach the upper temperature limit is t2, and the ambient temperature remains unchanged during the charging process, the upper temperature limit of the battery is denoted as T max . Integrating the battery charging power P Q (t), the total energy consumed can be obtained:

[0049]

[0050] The battery heat generation power P Q (t) can also be calculated by formula (3):

[0051]

[0052] Among them, V T is the battery terminal voltage, V OCV is the battery open-circuit voltage, R S is the battery ohmic internal resistance, R P1 is the electrochemical polarization resistance, R P2 is the concentration difference polarization resistance, and I1(t) and I2(t) are the currents flowing through the polarization resistances respectively. In the circuit, R S can reflect the sudden change characteristics of the battery terminal voltage, while the second-order RC parallel network can reflect the gradual change characteristics of the battery terminal voltage.

[0053] Both formula (2) and formula (3) are the energies consumed during the charging process, and they are equal. After simplifying and integrating formula (3), the quantitative relationship between the battery charging speed, the battery temperature rise, and the charging method can be obtained as:

[0054]

[0055] According to formula (5), the earlier the battery temperature T c reaches the upper cut-off temperature T max, the higher the average charging rate during the charging process, the faster the charging speed.

[0056] In this embodiment, the core temperature of the battery is monitored through an embedded optical fiber sensor, and then the charging temperature of the battery is tracked in real time. A relatively large charging current is allowed before reaching the set upper cut-off temperature T max to accelerate the charging rate. After reaching T max , the charging current is adjusted for constant-temperature charging to achieve "speed increase" in the inner loop.

[0057] Next, the constant-strain rapid charging process of the middle loop is introduced.

[0058] As Figure 2 shown, a constant-strain flexible charging process is established in the middle loop of this embodiment. Charging with the battery strain as the constraint can prevent problems such as overcharging, overheating, fragmentation of active particles, and gas generation from side reactions. For this reason, optical fibers are implanted into the battery to accurately monitor the internal strain of the battery, revealing the coupling relationship between the battery strain, temperature, and charging rate, and determining the strain boundary for safe battery charging. The temperature loop is used as the inner loop, and the control current output by the strain loop is converted as its input.

[0059] The test results show that compared with the mainstream constant current and constant voltage charging method, at the same charging speed, the maximum strain of the battery is reduced by 8.9%, achieving "safety guarantee".

[0060] During the fast charging process, the expansion strain ε of the battery is mainly composed of the diffusion-induced strain ε ei_c and the thermal strain ε ei_T :

[0061] ε = ε ei_c + ε ei_T (6)

[0062] The quantitative relationships between the diffusion-induced strain ε ei_c , the thermal strain ε ei_T and the battery charging rate and temperature are given by formulas (7) and (8):

[0063] ε ei_c = ΔcΩδ ij / 3 (7)

[0064] ε ei_T = αΔTδ ij (8)

[0065] In the formula, Δc is the change in the concentration of the diffusing substance, Ω is the partial molar volume of the solute in the matrix material, δ ij is the Dirichlet function, α is the coefficient of thermal expansion, and ΔT is the change in the battery temperature.

[0066] During the charging process, the increase in temperature directly leads to an increase in the heat generation of the battery's electrochemical reaction, with ΔT becoming larger, so the thermal strain ε ei_T increases as the battery temperature rises.

[0067] Secondly, analyze the diffusion-induced strain ε caused by the diffusion-induced stress in the dimension of the battery active particles ei_c . Since:

[0068]

[0069] In the formula, ΔV / V is the volume change rate of the active particles, and c s (r) represents the solid-phase lithium-ion concentration in the electrode. It can be seen that during the charging process, as the lithium-ion concentration increases, the diffusion-induced strain increases.

[0070] From the above equations, it can be known that for the charging process, the expansion strain of the battery is positively correlated with the charging current. When the ambient temperature rises, the strain change of the battery during charging at the same rate decreases. And when the SOC is low, the strain rises slowly, and when the SOC increases, the strain increase rate also increases. Applying a large-rate current at low SOC and reducing the current at high SOC can effectively reduce the strain of the battery.

[0071] Research shows that when charging at a high rate of 4C to 8C, the risks of lithium plating and thermal runaway of the battery will increase significantly after 50% SOC. Excluding the relatively large internal resistance at the initial stage of charging, when the SOC is less than 60%, the internal resistance remains relatively stable. When the SOC is above 70%, the internal resistance of the battery increases significantly with the increase of the state of charge. Therefore, in this embodiment, the expansion strain at 50% SOC is used as the strain boundary to limit the charging current, so as to reduce battery expansion and lithium plating and improve charging safety.

[0072] The outer loop establishes a constant overpotential non-destructive charging method, as Figure 3 shown. Traditional charging methods are constrained by the macroscopic characteristics of the battery (such as voltage, temperature, etc.), ignoring internal characteristics such as lithium plating in the battery, and cannot fully utilize the maximum charging potential of the battery. For this reason, this embodiment clarifies the quantitative relationship between the lithium plating overpotential and the charging rate based on the "electrochemistry-thermal-aging" coupling model, and explores the lithium-free charging boundary of the battery.

[0073] By establishing a pseudo-two-dimensional (P2D) model of the lithium-ion battery, coupling the battery thermal model, considering the formation of the solid electrolyte interphase (SEI) and the lithium plating process during the charging process, the calculation and output of the overpotential of the lithium plating side reaction are realized. Controlling the overpotential above 0V vs Li+ / Li can significantly inhibit the lithium plating reaction.

[0074] The current density of the lithium plating side reaction of the battery is given by Equation (10). Where F is the Faraday constant, R is the ideal gas constant, T is the temperature, and ηLi is the overpotential of the reaction, and α a,Li and α c,Li are the transfer coefficients of the reaction, respectively.

[0075]

[0076] Similarly, the current density of the side reaction generated by the solid electrolyte membrane of the battery is given by Equation (11). Among them are the solid-phase and liquid-phase potentials respectively, and α c,SEI is the transfer coefficient of the reaction, and E Eq,SEI is the equilibrium potential.

[0077]

[0078] The surface film thickness of the battery side reaction product is given by Equation (12). Among them, ρ SEI , M SEI , ρ Li , M Li are the density and molar mass of SEI and lithium plating respectively, c SEI,form , c Li,form are the concentrations of their reaction-generated by-products respectively, and S a is the specific surface area. σ film is the conductivity of the thin film.

[0079]

[0080]

[0081] According to the heat differential equation, the energy conservation equation of the battery can be expressed by Equation (14). When coupling the battery thermal model, three heat sources are considered, as shown in Equation (15), ohmic heat Q JH , polarization heat Q P and electrochemical heat Q R . Among them, ρ is the density, C p is the constant-pressure heat capacity, k is the thermal conductivity, and Q is the total heat generation rate.

[0082]

[0083] Q = Q JH + Q P + Q R (15)

[0084] Among them, the irreversible ohmic heat generation Q JH can be given by Equation (16). The first term represents the electrothermal generated in the solid phase, while the second term represents the ionic heat generated in the electrolyte.

[0085]

[0086] Irreversible polarization heat generation Q P is given by Equation (17). Where S a is the specific surface area of the active particles, i loc is the local current density, and η is the overpotential.

[0087] Q P = S a i loc η (17)

[0088] The reversible electrochemical heat Q R of the reaction is calculated by Equation (18). E eq is the equilibrium potential of the porous electrode reaction.

[0089]

[0090] Since the "electrochemical-thermal-aging" coupling model of the battery needs to simulate the kinetics of the internal electrochemical reactions and ion transport processes, providing more accurate information about the battery state at the microscale to calculate the overpotential of side reactions, the calculation and control process is slightly slower than the strain and temperature control, and the potential loop is placed in the outer loop.

[0091] The constant potential is the voltage at the solid-liquid interface during the battery model's simulation of the charging process, which is the electrochemical overpotential of the lithium plating side reaction. The constant potential control is to close-loop control this potential by controlling the charging current to make it as close as possible to the lower limit value η min .

[0092] The test results show that the charging method for closed-loop control of the overpotential of the lithium plating side reaction can significantly reduce lithium deposition and extend the battery cycle life by 26.5% at the same charging speed, achieving "extended life".

[0093] In summary, this embodiment establishes a three-loop control system. The inner loop constructs a constant temperature fast charging method to achieve "increased speed"; the middle loop constructs a constant strain flexible charging method to achieve "ensured safety"; the outer loop constructs a constant overpotential non-destructive charging method to achieve "extended life". This architecture realizes fast response by placing the temperature control in the inner loop, and at the same time improves the fast charging efficiency through the global optimization of the outer loop potential loop while ensuring safety.

[0094] After operation, the three loops can be controlled simultaneously.

[0095] During the control process, after the outer loop receives the battery charging current and voltage, it calculates the overpotential using the coupling model and outputs the control current to the next loop. The middle loop and the inner loop respectively receive the feedback signal of the implanted optical fiber and the control current of the previous loop, and calculate to obtain the optimal control current.

[0096] It should be noted that the lower limit of the overpotential should be higher than the lithium plating potential to prevent internal short circuit caused by the growth of lithium dendrites. Combining the constraints of each loop in the triple-loop control, the lower limit value of the overpotential for the lithium plating side reaction is dynamically corrected. As shown in Equation (19):

[0097] η min = η Li + β·Θ(SOC - 0.5)·(P - P min ) + γ(T - T max ) (19)

[0098]

[0099] Among them, the basic value η Li is taken as 0.05V, leaving a certain safety margin. The strain coefficient is β, the temperature coefficient is γ, P is the current battery expansion strain, and P min is the strain boundary corresponding to 50% SOC of the battery. The upper limit cut-off temperature T max is taken as 45°C. Specifically, after the battery is safely fast-charged to 50% SOC, the strain boundary starts to limit the charging current. According to Equation (19), in the early stage of charging, the potential loop allows a larger current, and vice versa in the later stage, further reducing the risk of lithium plating at high SOC of the battery.

[0100] Example Two

[0101] A flexible fast charging system for a lithium-ion battery with triple-loop control, comprising:

[0102] An outer-loop control module configured to obtain the current charging current and voltage of the lithium-ion battery, calculate the overpotential through an electrochemical-thermal-aging coupling model, perform constant overpotential lossless charging, and obtain a preliminary control current;

[0103] A middle-loop control module configured to perform constant strain charging according to the preliminary control current in combination with the internal strain of the lithium-ion battery obtained, and use the expansion strain at a set remaining battery charge ratio as the strain boundary to limit the charging current in this stage during the charging process;

[0104] An inner-loop control module configured to perform constant temperature charging according to the charging current in combination with the temperature of the lithium-ion battery obtained, adjust the charging current rate within a set temperature range, determine the final control current, and achieve flexible fast charging.

[0105] Example Three

[0106] A computer-readable storage medium for storing computer instructions, which when executed by a processor, complete the steps in the method provided in Example One.

[0107] Example Four

[0108] An electronic device includes a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the steps in the method provided in the first embodiment are completed.

[0109] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0110] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the specified functions in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0111] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the specified functions in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the specified functions in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art without creative efforts within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flexible fast charging method for lithium-ion batteries with three-loop control, characterized in that Including the following steps: Obtain the current charging current and voltage of the lithium-ion battery, calculate the overpotential through an electrochemical-thermal-aging coupling model, perform constant overpotential non-destructive charging, and obtain a preliminary control current; According to the preliminary control current, combine with the internal strain of the lithium-ion battery obtained, perform constant strain charging, and use the expansion strain at a set remaining charge ratio during the charging process as the strain boundary to limit the charging current in this stage; According to the charging current, combine with the temperature of the lithium-ion battery obtained, perform constant temperature charging, and adjust the charging current rate within a set temperature range; Taking constant overpotential non-destructive charging control as the outer loop, constant strain charging as the middle loop, and constant temperature charging as the inner loop, use the three-loop control to determine the final control current and achieve flexible fast charging.

2. The flexible fast charging method for a lithium-ion battery with a three-loop control according to claim 1, characterized in that, During the process of performing constant overpotential non-destructive charging, consider the formation of the solid electrolyte interphase film and the lithium plating process during charging, calculate the overpotential of the lithium plating side reaction, and control the overpotential above a set value.

3. The flexible fast charging method for a lithium-ion battery with a three-loop control according to claim 1, characterized in that, When performing constant strain charging, the battery expansion strain is composed of diffusion-induced strain and thermal strain. Determine the quantitative relationship between diffusion-induced strain, thermal strain, battery charging rate, and temperature, and then obtain the battery expansion strain. Use the set battery expansion strain as the strain boundary to limit the charging current.

4. A flexible fast charging method for a lithium-ion battery with a three-loop control as claimed in claim 1, characterized in that, Use a fiber optic strain sensor to obtain the internal strain of the lithium-ion battery.

5. The flexible fast charging method for a lithium-ion battery with a three-loop control according to claim 1, characterized in that, Use a fiber optic temperature sensor to obtain the temperature of the lithium-ion battery.

6. A flexible fast charging method for a lithium-ion battery with triple-loop control according to claim 1, characterized in that, The process of performing constant temperature charging includes: constructing an electro-thermal coupling model, using the electro-thermal coupling model to express the heat generation and heat transfer mechanisms of the battery during charging, determining the quantitative relationship between the battery charging speed, battery temperature rise, and charging method, and adjusting the charging current rate according to the quantitative relationship.

7. A flexible fast charging method for a lithium-ion battery with a three-loop control as claimed in claim 1, characterized in that, The lower limit of the overpotential should be higher than the lithium plating potential to prevent internal short circuit caused by the growth of lithium dendrites. Combine the constraints of each loop in each control stage to dynamically correct the lower limit value of the overpotential of the lithium plating side reaction.

8. A triple-loop controlled flexible fast charging system for lithium-ion batteries, characterized in that, Including: An outer loop control module configured to obtain the current charging current and voltage of the lithium-ion battery, calculate the overpotential through an electrochemical-thermal-aging coupling model, perform constant overpotential non-destructive charging, and obtain a preliminary control current; A middle loop control module configured to perform constant strain charging according to the preliminary control current in combination with the internal strain of the lithium-ion battery obtained, and use the expansion strain at a set remaining charge ratio during the charging process as the strain boundary to limit the charging current in this stage; An inner loop control module configured to perform constant temperature charging according to the charging current in combination with the temperature of the lithium-ion battery obtained, adjust the charging current rate within a set temperature range, determine the final control current, and achieve flexible fast charging.

9. A computer-readable storage medium, characterized in that, For storing computer instructions, when the computer instructions are executed by a processor, the steps in the method according to any one of claims 1-7 are completed.

10. An electronic device, characterized in that, Including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the steps in the method according to any one of claims 1-7 are completed.

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