Nickel-sodium chloride battery pack equalization charging and discharging control method based on intelligent algorithm

Abstract

The invention relates to the technical field of battery management, in particular to a sodium nickel chloride battery pack balanced charging and discharging control method based on an intelligent algorithm. The method comprises the steps of obtaining working parameters of each single battery of a battery pack and controlling the temperature to a preset range; detecting sodium and nickel ion concentration parameters of each single battery, calculating a sodium ion transmission rate, and determining a charge-discharge rate parameter; and calculating a state-of-charge value and a state-of-health value based on the working parameters and the rate parameters, and determining charging and discharging time and strategies, thereby realizing balanced charging and discharging of the battery pack. The method can improve the charge-discharge efficiency of the sodium nickel chloride battery pack, prolong the service life and ensure the safe and stable operation of the battery pack.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery management, and in particular to a sodium nickel chloride battery pack equalization charging and discharging control method based on an intelligent algorithm. BACKGROUND

[0002] With the rapid development of new energy technology, sodium nickel chloride batteries have shown broad application prospects in the fields of power storage and new energy vehicles due to their high energy density, long cycle life, environmental protection and safety advantages. As a new type of secondary battery, the working principle of sodium nickel chloride battery is to store and release electrical energy by using the redox reaction between sodium ions and nickel ions. In order to improve the overall performance and service life of sodium nickel chloride battery pack, equalization charging and discharging control technology has become a key research direction.

[0003] Currently, there are still some technical problems in the equalization charging and discharging control technology of sodium nickel chloride battery pack. The traditional battery equalization control method cannot effectively adapt to the electrochemical characteristics of sodium nickel chloride battery, and it is difficult to accurately adjust the charging and discharging strategy according to the concentration changes of sodium ions and nickel ions inside the battery, resulting in unevenness between each single battery in the battery pack, which shortens the overall life of the battery pack. The existing technology lacks a precise control mechanism for the temperature of sodium nickel chloride battery, and the electrochemical performance of sodium nickel chloride battery is closely related to temperature. Improper temperature control will lead to a decrease in ion transport efficiency inside the battery, reducing the charging and discharging performance of the battery. The existing technology cannot accurately evaluate the state of charge and health of each single battery in the sodium nickel chloride battery pack, and cannot dynamically adjust the charging and discharging strategy according to the actual state of the battery, so that the overall performance of the battery pack cannot reach the optimal state, affecting the use efficiency and life of the battery pack. SUMMARY

[0004] The embodiments of the present application provide a sodium nickel chloride battery pack equalization charging and discharging control method based on an intelligent algorithm, which can at least solve some problems existing in the prior art.

[0005] In a first aspect, the embodiments of the present application provide a sodium nickel chloride battery pack equalization charging and discharging control method based on an intelligent algorithm, comprising: obtaining the working parameters of each single battery in the sodium nickel chloride battery pack, and controlling the temperature of the single battery to reach a preset working temperature range according to the working parameters; detecting the sodium ion concentration parameters and nickel ion concentration parameters inside each single battery, calculating the sodium ion transport rate of each single battery according to the sodium ion concentration parameters and the nickel ion concentration parameters, and determining the charging and discharging rate parameters of each single battery based on the sodium ion transport rate; based on the working parameters and the charging and discharging rate parameters, calculating the state of charge value and the health value of each single battery, and determining the charging and discharging time of the sodium nickel chloride battery pack according to the state of charge value; determining a charge-discharge strategy of the sodium-chloride nickel battery pack according to the state of charge value and the state of health value, and controlling the sodium-chloride nickel battery pack to perform balanced charge-discharge based on the charge-discharge strategy.

[0006] obtaining working parameters of each single battery in the sodium-chloride nickel battery pack, and controlling the temperature of the single battery to reach a preset working temperature range according to the working parameters, including: obtaining working parameters of each single battery in the sodium-chloride nickel battery pack, and calculating the temperature change rate, voltage change rate and electrochemical impedance of each single battery based on the working parameters; judging whether each single battery is located in a preset temperature interval according to the temperature parameter in the working parameters, and calculating a temperature deviation value and a temperature gradient value of each single battery; grading the single battery based on the temperature deviation value, the temperature gradient value and the electrochemical impedance, calculating a heating priority of each single battery, and determining an initial heating power of a heating plate corresponding to each single battery and a heating plate power adjustment coefficient according to the heating priority; when the temperature change rate is less than a preset temperature response threshold value and the voltage change rate is less than a preset voltage fluctuation threshold value, increasing the heating power of the heating plate adjacent to the single battery according to the heating plate power adjustment coefficient; when the internal resistance parameter in the working parameters rises, reducing the heating power of the heating plate until the temperature parameter of the single battery reaches the preset temperature interval and the internal resistance parameter remains stable.

[0007] detecting a sodium ion concentration parameter and a nickel ion concentration parameter inside each single battery, calculating a sodium ion transmission rate of each single battery according to the sodium ion concentration parameter and the nickel ion concentration parameter, and determining a charge-discharge rate parameter of each single battery based on the sodium ion transmission rate, including: obtaining a sodium ion concentration parameter and a nickel ion concentration parameter inside a single battery reaching a preset temperature interval, and calculating a lateral concentration gradient value and a longitudinal concentration gradient value inside the single battery; calculating an ion diffusion coefficient inside the single battery based on the lateral concentration gradient value and the longitudinal concentration gradient value, and determining a sodium ion transmission rate of the single battery on the inner surface of the solid electrolyte ceramic tube according to the ion diffusion coefficient; monitoring a solid electrolyte ceramic tube inner surface potential difference and ion conductivity of the single battery, calculating an ion migration resistance coefficient of the single battery according to the crystalline orientation and grain boundary density of the solid electrolyte ceramic tube inner surface; calculating an ion migration rate of the single battery based on the potential difference, the ion conductivity and the ion migration resistance coefficient, taking a ratio of the sodium ion transport rate to the ion migration rate as an ion transport efficiency of the single battery; determining an effective ion transport rate of the single battery according to the ion transport efficiency and the concentration gradient value, and calculating a charge-discharge rate parameter of the single battery based on the effective ion transport rate.

[0008] determining an effective ion transport rate of the single battery according to the ion transport efficiency and the concentration gradient value, and calculating a charge-discharge rate parameter of the single battery based on the effective ion transport rate, comprising: calculating an ion migration path length of the single battery according to a cross-sectional area and a wall thickness of the solid electrolyte ceramic tube of the single battery, and determining a structure factor of the single battery based on the ion migration path length; obtaining a grain orientation angle and a grain boundary density of a surface of the solid electrolyte ceramic tube of the single battery, calculating an interface polarization impedance of the single battery, and determining an ion flux loss coefficient of the single battery according to the interface polarization impedance; monitoring a solid-liquid interface capacitance value and an electrolyte conductivity of the single battery, calculating an ion diffusion channel coefficient of the single battery, and determining a mass transfer loss coefficient of the single battery based on the ion diffusion channel coefficient; taking a product of the ion transport efficiency and the concentration gradient value as an initial transport rate, correcting the initial transport rate according to the structure factor, the ion flux loss coefficient and the mass transfer loss coefficient to obtain an effective ion transport rate of the single battery, and calculating a charge-discharge rate parameter of the single battery according to the effective ion transport rate.

[0009] based on the working parameter and the charge-discharge rate parameter, calculating a state of charge value and a state of health value of each single battery, and determining a charge-discharge time of the sodium nickel chloride battery pack according to the state of charge value, comprising: monitoring a polarization resistance and an ohmic resistance of a surface of the solid electrolyte ceramic tube of the single battery, calculating a internal resistance change rate of the single battery, calculating a coulomb efficiency of the single battery according to the working parameter, correcting the coulomb efficiency based on the internal resistance change rate to obtain a corrected coulomb efficiency of the single battery; obtaining a cycle number and a running time length of the single battery, calculating a capacity attenuation rate of the single battery, and determining a state of health value of the single battery according to the corrected coulomb efficiency and the capacity attenuation rate; determine the state of charge value of the single battery based on the residual capacity and the total capacity, and determine the effective capacity coefficient of the single battery based on the state of charge value and the health state value; determine the difference between the maximum value and the minimum value of the effective capacity coefficient in the sodium nickel chloride battery pack, and determine the charging and discharging time of the sodium nickel chloride battery pack based on the difference.

[0010] determine the charging and discharging strategy of the sodium nickel chloride battery pack based on the state of charge value and the health state value, and control the sodium nickel chloride battery pack to perform balanced charging and discharging based on the charging and discharging strategy, including: determine the charging and discharging impedance of the single battery, determine the charging and discharging polarization coefficient of the single battery based on the charging and discharging impedance, and determine the charging and discharging power of the single battery according to the sodium ion concentration parameter and the nickel ion concentration parameter of the single battery; group the single batteries according to the state of charge value, the health state value, the charging and discharging polarization coefficient, and the charging and discharging power, and determine the charging and discharging strategy of the sodium nickel chloride battery pack based on the grouping result; control the sodium nickel chloride battery pack to perform balanced charging according to the charging and discharging strategy, control the sodium ions in the second electrolyte to transfer to the inner surface of the solid electrolyte ceramic tube, control the sodium chloride in the positive electrode material to dissociate into sodium ions and chlorine ions, the sodium ions are supplemented to the second electrolyte, and the chlorine ions react with nickel ions to generate nickel chloride; When it is detected that the state of charge value of the single battery reaches a preset charging threshold, control the liquid sodium metal to lose electrons to generate sodium ions, control the sodium ions to transfer from the outside of the ceramic tube to the inner surface of the ceramic tube to combine with chlorine ions to generate sodium chloride, and control the nickel ions to gain electrons to generate metal nickel, so as to control the sodium nickel chloride battery pack to perform balanced discharging.

[0011] group the single batteries according to the state of charge value, the health state value, the charging and discharging polarization coefficient, and the charging and discharging power, and determine the charging and discharging strategy of the sodium nickel chloride battery pack based on the grouping result, including: divide the single batteries into different charge groups according to the distribution interval of the state of charge value; calculate the residual life of the single battery based on the health state value, and divide the single batteries in different charge groups into different attenuation groups based on the residual life; monitoring ion diffusion coefficients and ion conductivities of solid electrolyte ceramic tube surfaces of the single cells, calculating ion migration rates of the single cells according to the ion diffusion coefficients and the ion conductivities, correcting the charge-discharge polarization coefficients based on the ion migration rates to obtain polarization correction coefficients of the single cells; obtaining solid-liquid interface capacitance values and electrolyte conductivities of the single cells, calculating ion transport fluxes of the single cells according to the solid-liquid interface capacitance values and the electrolyte conductivities, correcting the charge-discharge powers based on the ion transport fluxes to obtain power correction coefficients of the single cells; grouping the single cells in the attenuation group according to the polarization correction coefficients and the power correction coefficients to obtain a plurality of charge-discharge groups, and determining a charge-discharge strategy of the sodium nickel chloride battery group according to distributions of the plurality of charge-discharge groups.

[0012] In a second aspect of the embodiment of the present application, a sodium nickel chloride battery group equalization charge-discharge control system based on an intelligent algorithm is provided, which comprises: A first unit is configured to obtain working parameters of each single cell in a sodium nickel chloride battery group, and control temperatures of the single cells to reach a preset working temperature range according to the working parameters. A second unit is configured to detect sodium ion concentration parameters and nickel ion concentration parameters in each single cell, calculate sodium ion transport rates of each single cell according to the sodium ion concentration parameters and the nickel ion concentration parameters, and determine charge-discharge rate parameters of each single cell based on the sodium ion transport rates. A third unit is configured to calculate state of charge values and health state values of each single cell based on the working parameters and the charge-discharge rate parameters, and determine charge-discharge times of the sodium nickel chloride battery group according to the state of charge values. A fourth unit is configured to determine a charge-discharge strategy of the sodium nickel chloride battery group according to the state of charge values and the health state values, and control the sodium nickel chloride battery group to perform equalization charge-discharge based on the charge-discharge strategy.

[0013] In a third aspect of the embodiment of the present application, an electronic device is provided, which comprises: a processor; a memory for storing processor-executable instructions; The processor is configured to invoke the instructions stored in the memory to execute the method described above.

[0014] In a fourth aspect of the embodiment of the present application, a computer readable storage medium is provided, which stores computer program instructions, and the computer program instructions are executed by a processor to implement the method described above.

[0015] The application ensures that the battery pack works under the optimal temperature condition by acquiring the working parameters of each single battery in the sodium nickel chloride battery pack and controlling the temperature to reach the preset range, and effectively improves the charge-discharge efficiency and service life of the battery.

[0016] The transmission rate is calculated by detecting the sodium ion and nickel ion concentration parameters, and the charge-discharge rate parameter is determined based on this, which realizes accurate grasp of the internal electrochemical reaction of the battery, solves the problem that the traditional control method cannot adapt to the characteristics of the sodium nickel chloride battery, and improves the charge-discharge performance of the battery pack.

[0017] The application determines the charge-discharge strategy and performs balancing control based on the state of charge value and the state of health value, effectively avoids the inconsistency problem between each single battery in the battery pack, prolongs the cycle life of the battery pack, and improves the overall energy utilization rate and operation safety of the battery pack. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a flowchart of the sodium nickel chloride battery pack balancing charge-discharge control method based on the intelligent algorithm of the embodiment of the application.

[0019] Figure 2 It is a flowchart of the calculation of the charge-discharge rate parameter of the single battery. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiment of the application clearer, the technical scheme in the embodiment of the application will be described clearly and completely below in combination with the drawings in the embodiment of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0021] The technical scheme of the application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in some embodiments.

[0022] Figure 1 It is a flowchart of the sodium nickel chloride battery pack balancing charge-discharge control method based on the intelligent algorithm of the embodiment of the application. As shown in Figure 1 The method comprises: acquiring the working parameters of each single battery in the sodium nickel chloride battery pack, and controlling the temperature of the single battery to reach the preset working temperature range according to the working parameters; detecting sodium ion concentration parameters and nickel ion concentration parameters inside each of the single batteries, calculating sodium ion transmission rates of each of the single batteries according to the sodium ion concentration parameters and the nickel ion concentration parameters, determining charge-discharge rate parameters of each of the single batteries based on the sodium ion transmission rates; based on the working parameters and the charge-discharge rate parameters, calculating state of charge values and health state values of each of the single batteries, determining charge-discharge times of the sodium nickel chloride battery pack according to the state of charge values; determining charge-discharge strategies of the sodium nickel chloride battery pack according to the state of charge values and the health state values, and controlling the sodium nickel chloride battery pack to perform balanced charge-discharge based on the charge-discharge strategies.

[0023] The present application realizes balanced charge-discharge and performance optimization of the battery pack by precisely controlling the temperature of the single battery, monitoring the ion concentration, calculating the transmission rate and determining the charge-discharge strategy.

[0024] The working parameters of each single battery in the sodium nickel chloride battery pack include battery voltage, current, internal resistance, temperature, etc., which can be collected by a distributed sensor network. The sampling frequency is set to 100 Hz to ensure the real-time and accuracy of data collection. The collected data is processed by low-pass filtering to filter out high-frequency noise and improve signal quality. For example, for a 32-string 10-parallel battery pack, the single battery voltage range is 2.8V-3.6V, the working current is -20A to +20A (negative value represents discharge, positive value represents charge), the internal resistance is 5mΩ to 15mΩ, and the initial temperature is 15℃ to 35℃.

[0025] According to the obtained working parameters, the temperature of the single battery needs to be controlled to reach the preset working temperature range. The optimal working temperature range of the sodium nickel chloride battery is 25℃ to 40℃. Within this temperature range, the chemical reaction rate of the battery is moderate, and the ion conduction performance is best. Temperature control is realized by using a liquid cooling system combined with an active heating device. The liquid cooling system is composed of high-efficiency cooling liquid, micro-channel cooling plate and variable speed circulating pump, and the cooling capacity can reach 1500W. When the temperature of the single battery is detected to be higher than 40℃, the flow of the cooling liquid is increased to accelerate heat dissipation; when the temperature is lower than 25℃, the thin film heater integrated at the bottom of the battery is started, the heating power is adjustable from 200W to 500W, the temperature rising rate is controlled within 5℃ / min, and the internal stress of the battery caused by too large temperature gradient is avoided. The temperature control accuracy is ±1℃, which ensures that the battery works in the best temperature range.

[0026] After the battery reaches a suitable working temperature, the sodium ion concentration parameter and the nickel ion concentration parameter inside each single battery cell are detected. The detection uses an electrochemical impedance spectroscopy technique combined with a characteristic frequency analysis method. By applying a small amplitude alternating current signal to both ends of the battery, the impedance response of the battery at different frequencies is analyzed, and the internal ion concentration state of the battery is indirectly obtained. The sodium ion concentration parameter is usually between 0.5 mol / L and 2.5 mol / L, and the nickel ion concentration parameter is between 0.1 mol / L and 0.8 mol / L. In actual measurement, the scanning frequency range is 0.01 Hz to 10 kHz, the impedance values at different frequency points are obtained, and the ion concentration distribution is calculated by the impedance change trend of the characteristic frequency point.

[0027] The sodium ion transport rate can be calculated according to the measured sodium ion concentration parameter and nickel ion concentration parameter. The sodium ion transport rate can be calculated by analyzing the polarization characteristics of the battery at different current densities and combining the ion concentration gradient.

[0028] The charge and discharge rate parameters of each single battery cell can be determined based on the sodium ion transport rate. The charge and discharge rate is directly related to the charge and discharge efficiency and life of the battery. The safe and efficient charge and discharge rate can be determined according to the calculated sodium ion transport rate, combined with the battery capacity and electrode material characteristics. For single battery cells with high transport rate, the charge and discharge rate can be appropriately increased; for single battery cells with low transport rate, the charge and discharge rate can be reduced to avoid excessive polarization. In one example, when the battery capacity is 100 Ah and the sodium ion transport rate is 3x10^-6 mol / (cm²·s), the determined optimal charge rate is 0.5C (i.e. 50A) and the discharge rate is 1C (i.e. 100A); when the transport rate increases to 4x10^-6 mol / (cm²·s), the charge rate can be increased to 0.8C (80A) and the discharge rate can be increased to 1.5C (150A).

[0029] The state of charge value and the state of health value of each single battery can be calculated based on the working parameters and the charge-discharge rate parameters. The state of charge value is calculated using an improved coulomb counting method combined with an open-circuit voltage correction method, which combines current integration with an open-circuit voltage characteristic curve to improve estimation accuracy. The state of health value is evaluated comprehensively through three dimensions of capacity retention rate, internal resistance growth rate and charge-discharge efficiency. First, record the open-circuit voltage characteristic points of the battery at different states of charge, such as 2.8V at 0% SOC, 3.0V at 25% SOC, 3.2V at 50% SOC, 3.4V at 75% SOC and 3.6V at 100% SOC. In actual operation, the current can be integrated in real time, and the cumulative error can be corrected by open-circuit voltage at appropriate time. In the calculation of the state of health value, the capacity retention rate of a new battery is 100%, the internal resistance growth rate is 0%, the charge-discharge efficiency is more than 95%, and the comprehensive score is 100 points; as the number of cycles increases, when the capacity retention rate decreases to 80%, the internal resistance growth rate reaches 50%, and the charge-discharge efficiency decreases to 85%, the state of health value decreases to 70 points, indicating that the battery performance has obviously degraded.

[0030] The charge-discharge time of the sodium nickel chloride battery pack can be determined according to the state of charge value. The charge time calculation considers the current state of charge of the battery, the charge rate, the charge efficiency and the capacity. The constant current-constant voltage two-stage charging strategy can be used for charging the battery pack. Taking a 100 Ah battery pack as an example, when the state of charge is 20%, 80% of the capacity needs to be charged. At a rate of 0.5C, considering a charge efficiency of 90%, the constant current charging time is about 96 minutes; after entering the constant voltage stage, the current gradually decreases, and it takes about 30 minutes to complete the remaining 10% capacity charging, with a total charging time of 126 minutes. The discharge time calculation is based on the discharge rate and the available capacity. When the state of charge is 100% and the discharge rate is 1C, the theoretical discharge time is 60 minutes, considering the polarization effect and temperature influence of the battery, the actual available time is about 55 minutes.

[0031] The charge-discharge strategy of the sodium nickel chloride battery pack can be determined according to the state of charge value and the state of health value. Based on the differences between single batteries, an adaptive charge-discharge strategy can be used. For single batteries with a high state of health value, a wider state of charge working range is allowed, such as 10%-90%; for single batteries with a low state of health value, the state of charge working range is reduced, such as 20%-80%, to slow down the degradation rate. The charging strategy uses a multi-stage charging method, using a larger rate in the initial stage (0%-50% SOC), reducing the rate in the middle stage (50%-80% SOC), and further reducing the rate in the final stage (80%-100% SOC). In a certain battery pack, a single battery with a state of health value of 95 points is allowed to be charged at a rate of 0.8C to 90% SOC; while a single battery with a state of health value of 75 points is limited to a rate of 0.5C and a maximum of 85% SOC.

[0032] The sodium nickel chloride battery pack can be controlled to perform balanced charging and discharging based on the charging and discharging strategy, so as to optimize the overall performance of the battery pack. The balanced charging and discharging adopts an active balancing technology, and the directional transmission of energy between single batteries is realized through a distributed power electronic converter. The balanced triggering threshold is set as a voltage difference between single batteries exceeding 50 mV or a state of charge difference exceeding 5%. The balanced current can be adjusted in a range of 0.5 A to 5 A and is adaptively adjusted according to the unbalanced degree. In actual application, when it is detected that the voltage of a single battery is 3.45 V and the voltage of an adjacent battery is 3.38 V, the balancing module is started, a balanced current of 2 A is set to transmit energy from the high-voltage battery to the low-voltage battery, and the balanced duration is about 10 minutes until the voltage difference is reduced to within 20 mV. For a single battery that has shown a low capacity for a long time, more charging time is allocated to it in the next charging cycle to improve its state of charge, so as to maximize the utilization of the overall capacity of the battery pack.

[0033] Through the above embodiments, comprehensive monitoring and accurate control of the parameters of single batteries are realized, the performance and life of the batteries are effectively balanced, the energy utilization efficiency and cycle life of the battery pack are significantly improved, and technical support is provided for the wide application of sodium nickel chloride batteries in energy storage systems.

[0034] In an alternative embodiment, the working parameters of each single battery in the sodium nickel chloride battery pack are obtained, and the temperature of the single battery is controlled to reach a preset working temperature range according to the working parameters, including: The working parameters of each single battery in the sodium nickel chloride battery pack are obtained, and the temperature change rate, voltage change rate and electrochemical impedance of each single battery are calculated based on the working parameters; It is determined whether each single battery is located in a preset temperature interval according to the temperature parameter in the working parameters, and the temperature deviation value and temperature gradient value of each single battery are calculated; Each single battery is classified based on the temperature deviation value, the temperature gradient value and the electrochemical impedance, the heating priority of each single battery is calculated, and the initial heating power of the heating plate corresponding to each single battery and the heating plate power adjustment coefficient are determined according to the heating priority; When the temperature change rate is less than a preset temperature response threshold and the voltage change rate is less than a preset voltage fluctuation threshold, the heating power of the heating plate adjacent to the single battery is increased according to the heating plate power adjustment coefficient; When the internal resistance parameter in the working parameters rises, the heating power of the heating plate is reduced until the temperature parameter of the single battery reaches the preset temperature interval and the internal resistance parameter remains stable.

[0035] In the present embodiment, firstly, the working parameters of each single battery in the sodium-chloride nickel battery pack are acquired, which include but are not limited to battery temperature, voltage, internal resistance, charging and discharging current and other data. The acquisition of working parameters can be realized by the sensor network arranged in the battery pack, which is composed of temperature sensors, voltage collectors, current collectors and the like, and the sampling frequency is set to 2 times per second to ensure that the battery state changes can be captured in time. For example, for a sodium-chloride nickel battery pack composed of 12 single batteries, each single battery is equipped with an independent parameter acquisition device to record the real-time temperature (such as 270℃~350℃), terminal voltage (such as 2.0V~2.6V), charging and discharging current (such as -20A~+20A) and other parameters of the single battery.

[0036] Based on the acquired working parameters, the temperature change rate, voltage change rate and electrochemical impedance of each single battery can be calculated. The temperature change rate is obtained by dividing the difference between two consecutive temperature sampling values by the sampling time interval, with the unit of ℃ / s; the voltage change rate is calculated by dividing the difference between two consecutive voltage sampling values by the sampling time interval, with the unit of V / s; and the electrochemical impedance is obtained by electrochemical impedance spectroscopy technology, which applies a small alternating current signal to the battery and analyzes the response characteristics of the battery to represent the electrochemical reaction state inside the battery, with the unit of Ω. For example, under standard working conditions, the temperature change rate of the single battery should generally be maintained within 0.05℃ / s, the voltage change rate should be maintained within 0.002V / s, and the electrochemical impedance should be maintained within the range of 0.5~0.8Ω at a working temperature of 300℃.

[0037] Subsequently, it is judged whether each single battery is located within the preset temperature interval according to the temperature parameter in the working parameters. The preset temperature interval is set to 270℃~350℃ according to the characteristics of the sodium-chloride nickel battery, when the temperature of the single battery is lower than 270℃, the battery activity is insufficient and the internal resistance increases; and when the temperature is higher than 350℃, the battery will have the risk of thermal runaway. The temperature deviation value and temperature gradient value of each single battery are calculated, the temperature deviation value is the difference between the actual temperature of the single battery and the center temperature (310℃) of the preset temperature interval; and the temperature gradient value is the temperature difference between the single battery and the adjacent battery. For example, when the temperature of a single battery is 260℃, the temperature deviation value is -50℃, indicating that the temperature of the battery is too low; and if the temperature of the adjacent battery is 280℃, the temperature gradient value is 20℃, indicating that there is a significant temperature unevenness in the battery pack.

[0038] The monomer battery can be graded based on the temperature deviation value, temperature gradient value and electrochemical impedance, the heating priority of each monomer battery is calculated, and the grading standard is set as: the high-risk level when the absolute value of the temperature deviation value exceeds 30 DEG C; the medium-risk level when the temperature gradient value exceeds 15 DEG C; the medium-risk level when the electrochemical impedance exceeds 1.5 times of the standard value. The heating priority is determined according to the risk level and the deviation degree, the heating priority of the high-risk level battery is 1, the heating priority of the medium-risk level battery is 2, and the heating priority of the low-risk level battery is 3. The initial heating power of the corresponding heating plate and the heating plate power adjustment coefficient of each monomer battery are determined according to the heating priority. For example, the initial heating power of the corresponding heating plate of the monomer battery with the heating priority of 1 is set to 80% of the maximum power (if the maximum power is 500 W, the initial heating power is 400 W), and the power adjustment coefficient is 0.2, which means that 20% of the power can be increased or decreased each time in the subsequent adjustment process.

[0039] In the temperature control process, when the temperature change rate is less than the preset temperature response threshold (such as 0.03 DEG C / s) and the voltage change rate is less than the preset voltage fluctuation threshold (such as 0.001 V / s), it indicates that the current heating power is insufficient to make the battery reach the ideal working state, and the heating power needs to be increased. According to the heating plate power adjustment coefficient, the heating power of the heating plate adjacent to the monomer battery is increased, for example, for the heating plate with a power adjustment coefficient of 0.2, the current power is 400 W, and then the adjusted power is 480 W. After adjustment, the battery temperature change rate and the voltage change rate are continuously monitored until they reach the expected range.

[0040] When the internal resistance parameter in the working parameter rises, it indicates that the battery temperature has been too high or there is other abnormal condition, and the heating power of the heating plate needs to be reduced to prevent the battery from overheating. For example, when the internal resistance rises from 0.6 ohm to 0.8 ohm, the heating power is reduced according to the power adjustment coefficient, for example, from 480 W to 384 W. The heating power is continuously monitored and adjusted until the temperature parameter of the monomer battery reaches the preset temperature interval and the internal resistance parameter remains stable.

[0041] In practical application, for a sodium nickel chloride battery pack composed of 12 monomer batteries, the initial state of each monomer battery temperature distribution is 250 DEG C~330 DEG C, through the above control process, all monomer battery temperatures can reach the range of 300 DEG C±10 DEG C within 30 minutes, and the internal resistance parameter is stable in the range of 0.6 ohm±0.1 ohm, realizing the temperature control of the battery pack and improving the charging and discharging efficiency and cycle life of the battery pack.

[0042] The present application can accurately control the temperature of each monomer battery in the sodium nickel chloride battery pack, so that it can be kept in the best working temperature range, effectively solving the performance degradation problem of the traditional sodium nickel chloride battery pack caused by uneven temperature, and improving the overall performance and service life of the battery pack.

[0043] In an alternative embodiment, the sodium ion concentration parameter and the nickel ion concentration parameter inside each of the single cells are detected, the sodium ion transmission rate of each of the single cells is calculated according to the sodium ion concentration parameter and the nickel ion concentration parameter, and the charge-discharge rate parameter of each of the single cells is determined based on the sodium ion transmission rate, including: The sodium ion concentration parameter and the nickel ion concentration parameter inside the single cell reaching a preset temperature interval are obtained, and the transverse concentration gradient value and the longitudinal concentration gradient value inside the single cell are calculated; Based on the transverse concentration gradient value and the longitudinal concentration gradient value, the ion diffusion coefficient inside the single cell is calculated, and the sodium ion transmission rate of the single cell on the inner surface of the solid electrolyte ceramic tube is determined according to the ion diffusion coefficient; The potential difference and the ion conductivity of the inner surface of the solid electrolyte ceramic tube of the single cell are monitored, the ion migration resistance coefficient of the single cell is calculated according to the crystalline orientation and the grain boundary density of the inner surface of the solid electrolyte ceramic tube; Based on the potential difference, the ion conductivity and the ion migration resistance coefficient, the ion migration rate of the single cell is calculated, and the ratio of the sodium ion transmission rate to the ion migration rate is taken as the ion transmission efficiency of the single cell; The effective ion transmission rate of the single cell is determined according to the ion transmission efficiency and the concentration gradient value, and the charge-discharge rate parameter of the single cell is calculated based on the effective ion transmission rate.

[0044] Figure 2 The flowchart for calculating the charge-discharge rate parameter of the single cell according to the embodiment of the present application is shown. As shown in FIG. 1, the sodium ion concentration parameter and the nickel ion concentration parameter inside the single cell are detected, the sodium ion transmission rate of the single cell is calculated according to the sodium ion concentration parameter and the nickel ion concentration parameter, and the charge-discharge rate parameter of the single cell is determined based on the sodium ion transmission rate. Figure 2As shown, the monomer battery can be preheated to reach a preset temperature interval, for example, the monomer battery can be placed in a constant temperature environment of 25-35°C for 30 minutes. The ion concentration detector is used to detect the sodium ion concentration and nickel ion concentration inside the monomer battery reaching the preset temperature interval. In an example, the detection obtained the sodium ion concentration of the positive electrode region of the monomer battery is 0.85 mol / L, the sodium ion concentration of the negative electrode region is 0.25 mol / L; the nickel ion concentration of the positive electrode region is 0.55 mol / L, and the nickel ion concentration of the negative electrode region is 0.15 mol / L. Based on these concentration data, the lateral concentration gradient value and the longitudinal concentration gradient value inside the monomer battery are calculated. The lateral concentration gradient value calculation method is the ion concentration difference between the positive and negative electrodes divided by the distance between the two electrodes. For example, when the distance between the electrodes is 5 mm, the lateral concentration gradient value of sodium ion is (0.85-0.25) / 0.005=120 mol / (L•m), and the lateral concentration gradient value of nickel ion is (0.55-0.15) / 0.005=80 mol / (L•m). The longitudinal concentration gradient value calculation method is the ion concentration difference between the upper and lower parts of the battery divided by the longitudinal distance. For example, when the distance between the upper and lower measurement points is 10 mm, the upper sodium ion concentration is 0.6 mol / L, and the lower sodium ion concentration is 0.5 mol / L, the longitudinal concentration gradient value is (0.6-0.5) / 0.01=10 mol / (L•m).

[0045] According to the measured lateral concentration gradient value and longitudinal concentration gradient value, combined with the temperature parameter inside the battery (such as 28°C) and the medium viscosity coefficient (such as 3.5 mPa•s), the ion diffusion coefficient inside the monomer battery is calculated. In this example, the diffusion coefficient of sodium ion inside the monomer battery can be calculated by applying the ion diffusion model to be 4.2×10^-10 m² / s, and the diffusion coefficient of nickel ion is 2.8×10^-10 m² / s. Based on these ion diffusion coefficients, combined with the lateral concentration gradient value, the sodium ion transmission rate of the monomer battery on the inner surface of the solid electrolyte ceramic tube is determined. In this example, the calculated sodium ion transmission rate is 5.04×10^-8 mol / (m²•s).

[0046] The potential difference of the monomer battery on the inner surface of the solid electrolyte ceramic tube is monitored using a potential measuring device, and the ion conductivity is measured by electrochemical impedance spectroscopy. In this example, the potential difference is 0.25 V, and the ion conductivity is 15 mS / cm. The X-ray diffraction technology and electron microscope are used to analyze the crystal orientation and grain boundary density of the inner surface of the solid electrolyte ceramic tube, and the main crystal face is (110) face, and the grain boundary density is 3.2×10^6 / cm². According to these parameters, the ion migration resistance coefficient of the monomer battery is calculated. In this example, the calculated value of the ion migration resistance coefficient is 1.8, which represents the additional resistance of ion migration caused by the imperfect crystal orientation and grain boundary.

[0047] Based on the potential difference, ion conductivity and ion migration resistance coefficient, the ion migration rate of the single battery is calculated, and the ion migration rate calculation value is 4.17*10^-8 mol / (m²•s). The ratio of the sodium ion transport rate (5.04*10^-8 mol / (m²•s)) to the ion migration rate (4.17*10^-8 mol / (m²•s)) is taken as the ion transport efficiency of the single battery, and the ion transport efficiency is calculated to be 1.21, indicating that the diffusion mechanism contributes more to the sodium ion transport than the migration mechanism.

[0048] According to the ion transport efficiency and the concentration gradient value, the effective ion transport rate of the single battery is determined, and the effective ion transport rate calculation method is to multiply the ion transport efficiency by the sodium ion transport rate and divide by a normalization factor (the value is 1.5), and the effective ion transport rate is 4.06*10^-8 mol / (m²•s). Based on the effective ion transport rate, combined with the active material mass and the theoretical capacity of the battery, the charge and discharge rate parameter of the single battery is calculated, and when the battery active material mass is 25g and the theoretical capacity is 120mAh / g, the optimal charge and discharge rate of the single battery is calculated to be 2.5C.

[0049] This method can also be applied to the evaluation of the performance of the single battery under temperature change. Taking the test results at three different temperatures as an example: at 20℃, the effective transport rate of sodium ions is 3.25*10^-8 mol / (m²•s), and the corresponding charge and discharge rate is 2.0C; at 30℃, the effective transport rate of sodium ions is 4.06*10^-8 mol / (m²•s), and the corresponding charge and discharge rate is 2.5C; at 40℃, the effective transport rate of sodium ions is 4.88*10^-8 mol / (m²•s), and the corresponding charge and discharge rate is 3.0C. This shows that the increase of temperature can enhance the transport ability of sodium ions and improve the charge and discharge rate that the battery can withstand.

[0050] This method can also be used to evaluate the influence of different types of electrolytes on the performance of the single battery. When using fluorine-containing electrolyte, the ion transport efficiency is increased to 1.35, the effective ion transport rate is 4.54*10^-8 mol / (m²•s), and the corresponding charge and discharge rate is 2.8C; when using additive modified electrolyte, the ion transport efficiency is increased to 1.42, the effective ion transport rate is 4.77*10^-8 mol / (m²•s), and the corresponding charge and discharge rate is 3.0C. This shows that the selection and modification of electrolyte has a significant influence on improving the rate performance of the single battery.

[0051] In an alternative embodiment, the effective ion transport rate of the single battery is determined according to the ion transport efficiency and the concentration gradient value, the charge-discharge rate parameter of the single battery is calculated based on the effective ion transport rate, comprising: The ion migration path length of the single battery is calculated according to the cross-sectional area and the wall thickness of the solid electrolyte ceramic tube of the single battery, and the structure factor of the single battery is determined based on the ion migration path length; The grain orientation angle and the grain boundary density of the surface of the solid electrolyte ceramic tube of the single battery are obtained, the interfacial polarization impedance of the single battery is calculated, and the ion flux loss coefficient of the single battery is determined according to the interfacial polarization impedance; The solid-liquid interface capacitance value and the electrolyte conductivity of the single battery are monitored, the ion diffusion channel coefficient of the single battery is calculated, and the mass transfer loss coefficient of the single battery is determined based on the ion diffusion channel coefficient; The product of the ion transport efficiency and the concentration gradient value is taken as the initial transport rate, the initial transport rate is corrected according to the structure factor, the ion flux loss coefficient and the mass transfer loss coefficient to obtain the effective ion transport rate of the single battery, and the charge-discharge rate parameter of the single battery is calculated according to the effective ion transport rate.

[0052] In the embodiment of the application, the effective ion transport rate of the single battery needs to be determined according to the ion transport efficiency and the concentration gradient value, and the charge-discharge rate parameter is calculated based on the rate.

[0053] In the implementation process, first, the cross-sectional area data and the wall thickness data of the solid electrolyte ceramic tube of the single battery are obtained, for example, the cross-sectional area of the electrolyte ceramic tube is 78.5 square millimeters (circular cross-section with a diameter of 10 millimeters) and the wall thickness is 0.5 millimeters, which can be measured by high-precision measuring equipment. Based on these data, the ion migration path length of the single battery is calculated. Since the ion needs to migrate through the wall thickness, the ion migration path length is basically equal to the wall thickness, i.e. 0.5 millimeters. However, considering the complexity of the internal structure of the ceramic tube, the actual migration path is usually greater than the ideal value. By measuring the porosity of the ceramic tube inside as 15% and the tortuosity of the migration path as 1.3, it is calculated that the actual ion migration path length is 0.65 millimeters. Based on the path length, the structure factor of the single battery is determined as 1.3, which reflects the ratio of the actual migration path to the ideal straight path.

[0054] The grain orientation angle and grain boundary density of the surface of the solid electrolyte ceramic tube are then obtained. Through electron backscatter diffraction analysis, the average grain orientation angle is measured to be 23 degrees, and the grain boundary density is 4.2 per square micron. Using these data, the interfacial polarization resistance of the single cell is calculated. In actual measurement, the interfacial polarization resistance of the cell at room temperature is 85 ohm*cm2. This resistance value is mainly affected by the grain boundary density and the grain orientation. The higher the grain boundary density, the greater the resistance value; the closer the grain orientation angle to the ideal orientation (0 degrees), the smaller the resistance value. According to the interfacial polarization resistance value, the ion flux loss coefficient is determined to be 0.82, indicating that 18% of the ion flux is lost at the interface.

[0055] The solid-liquid interface capacitance value and electrolyte conductivity of the single cell are further monitored. Through electrochemical impedance spectroscopy measurement, the solid-liquid interface capacitance value is obtained to be 22 microfarads / cm2, and the electrolyte conductivity is 1.2*10^-3 Siemens / cm (under room temperature conditions). Based on these data, the ion diffusion channel coefficient of the single cell is calculated. In actual calculation, this coefficient is inversely proportional to the solid-liquid interface capacitance and proportional to the electrolyte conductivity. By processing these data, the ion diffusion channel coefficient is obtained to be 0.75. Based on this coefficient, the mass transfer loss coefficient is determined to be 0.88, indicating that 12% of the theoretical mass transfer efficiency is lost in the actual transmission process.

[0056] After all the necessary parameters have been obtained, the product of the ion transport efficiency and the concentration gradient value can be taken as the initial transmission rate. For example, the measured ion transport efficiency is 0.92, and the concentration gradient value is 2.5 mol / L / mm. The product of the two is 2.3 mol / L / mm, which is taken as the initial transmission rate. Then, the initial transmission rate is corrected according to the structure factor (1.3), ion flux loss coefficient (0.82), and mass transfer loss coefficient (0.88) calculated earlier. The specific correction method is: divide the initial transmission rate by the structure factor, and then multiply it by the ion flux loss coefficient and the mass transfer loss coefficient respectively, i.e. 2.3 ÷ 1.3 × 0.82 × 0.88 ≈ 1.28 mol / L / mm, to obtain the effective ion transmission rate of the single cell.

[0057] Based on the calculated effective ion transmission rate, the charge-discharge rate parameter of the single cell can be further calculated. This parameter is positively correlated with the effective ion transmission rate, and is also related to factors such as the theoretical specific capacity of the battery active material and the electrode thickness. In actual application, assuming that the theoretical specific capacity of the battery active material is 150 mAh / g, the electrode thickness is 50 microns, and the active material loading is 12 mg / cm2, the charge-discharge rate parameter of the single cell is calculated to be 3.2C, which means that the battery can theoretically complete the charging and discharging process within 1 / 3.2 hours (about 19 minutes).

[0058] In the actual verification test, the researchers used the parameters calculated by the above method to conduct charge-discharge tests on 10 sample batteries. The results showed that the average capacity retention rate of these batteries reached 87% at 3C rate, with an error of less than 7% compared to the theoretical calculation result (3.2C), verifying the accuracy and practicality of the calculation method. Through this method, battery designers can accurately estimate the charge-discharge performance of the battery at the initial stage of battery design, improve design efficiency, and reduce trial and error costs. In addition, this method can also be applied to battery performance optimization, by adjusting battery structure parameters such as tube wall thickness, grain orientation, etc., to improve the charge-discharge rate performance of the battery.

[0059] In an alternative embodiment, based on the working parameters and the charge-discharge rate parameters, the state of charge value and the state of health value of each single battery are calculated, and the charge-discharge time of the sodium nickel chloride battery pack is determined according to the state of charge value, comprising: The polarization resistance and ohmic resistance of the solid electrolyte ceramic tube surface of the single battery are monitored, the internal resistance change rate of the single battery is calculated, the coulomb efficiency of the single battery is calculated according to the working parameters, and the coulomb efficiency is corrected based on the internal resistance change rate to obtain the corrected coulomb efficiency of the single battery; The cycle number and running time of the single battery are obtained, the capacity attenuation rate of the single battery is calculated, and the state of health value of the single battery is determined according to the corrected coulomb efficiency and the capacity attenuation rate; Based on the working parameters and the charge-discharge rate parameters, the remaining capacity and the total capacity of the single battery are determined, and the state of charge value of the single battery is determined based on the remaining capacity and the total capacity; The effective capacity coefficient of the single battery is determined according to the state of charge value and the state of health value, the difference between the maximum value and the minimum value of the effective capacity coefficient in the sodium nickel chloride battery pack is counted, and the charge-discharge time of the sodium nickel chloride battery pack is determined based on the difference.

[0060] In this embodiment, the real-time working parameters of each single battery can be collected first, including voltage, current, temperature and other data. For example, when the working temperature of a single battery is 280℃, the voltage is 2.58V, and the current is 30A, these parameters can be recorded and stored in the database. At the same time, the charge-discharge rate parameters are also obtained, such as 0.5C charge rate and 1C discharge rate.

[0061] The polarization resistance and ohmic resistance of the surface of the solid electrolyte ceramic tube of the single battery are monitored by electrochemical impedance spectroscopy measurement technology. When measuring, a small signal alternating current excitation is applied to the battery, the frequency range is from 0.01 Hz to 10 kHz, and the impedance response at different frequencies is recorded. For example, the ohmic resistance is 0.15Ω and the polarization resistance is 0.22Ω in the new battery state; after 1000 cycles, the ohmic resistance can increase to 0.18Ω and the polarization resistance increases to 0.30Ω. According to the comparison of the initial internal resistance value and the current internal resistance value, the internal resistance change rate is calculated. If the initial internal resistance is 0.37Ω and the current internal resistance is 0.48Ω, the internal resistance change rate is 29.7%.

[0062] The coulomb efficiency, i.e. the ratio of discharge capacity to charge capacity, is calculated according to real-time charge and discharge data. For a new sodium nickel chloride battery, the coulomb efficiency is usually about 0.98. The increase of internal resistance will cause the increase of energy loss, and the coulomb efficiency is corrected using the internal resistance change rate. The correction method is to multiply the original coulomb efficiency by the compensation factor of the internal resistance change rate, which is obtained by looking up the table. For example, when the internal resistance change rate is 29.7%, the compensation factor is 0.96, and if the original coulomb efficiency is 0.98, the corrected coulomb efficiency is 0.94.

[0063] The cycle number and running time information of the single battery are obtained from the battery management system database, for example, a certain battery has been running for 1200 cycles and the total running time is 8760 hours. The capacity attenuation rate is calculated according to the ratio of the actual capacity of the battery to the rated capacity. If the rated capacity of the battery is 200Ah and the actual capacity is measured to be 176Ah after 1200 cycles, the capacity attenuation rate is 12%.

[0064] The state of health value (SOH) is calculated according to the corrected coulomb efficiency and the capacity attenuation rate, in which the corrected coulomb efficiency can be given a weight of 70% and the capacity attenuation rate can be given a weight of 30%. For example, if the corrected coulomb efficiency is 0.94 and the capacity attenuation rate is 12%, the state of health value is calculated to be 88%, indicating that the battery retains 88% of the initial performance.

[0065] The remaining capacity of the single battery is calculated by the ampere-hour integration method. During discharging, the current value is recorded every second, and the values are time-integrated to obtain the discharged capacity. For example, discharging at 30A for 20 minutes discharges 10Ah. If the total capacity of the battery is 200Ah, the remaining capacity is 190Ah. The state of charge value (SOC) is the ratio of the remaining capacity to the total capacity, which is 95% in this example.

[0066] An effective capacity coefficient of the single battery is calculated based on the state of charge value and the state of health value, and the effective capacity coefficient is equal to the state of charge value multiplied by the state of health value. In the above example, the effective capacity coefficient is 95% x 88% = 83.6%. Statistical analysis is performed on the effective capacity coefficients of all single batteries in the sodium nickel chloride battery pack to find the maximum value and the minimum value. Assuming that there are 100 single batteries in the battery pack, the maximum effective capacity coefficient is 83.6%, the minimum effective capacity coefficient is 68.9%, and the difference is 14.7%.

[0067] The charging and discharging time is determined according to the difference of the effective capacity coefficient. When the difference is less than 5%, the battery pack has good balance, and the standard charging and discharging time can be used; when the difference is between 5% and 15%, the charging time needs to be extended by 20% to ensure that the battery with low capacity coefficient is fully charged; when the difference is greater than 15%, the charging time needs to be extended by 30% and the discharging depth needs to be reduced by 10% to avoid excessive discharge of the low-capacity battery. For the above difference of 14.7%, the standard charging time is extended from 4 hours to 4.8 hours, and the discharging time remains unchanged.

[0068] During the charging and discharging process, the voltage, temperature and other parameters of each single battery are continuously monitored. If the temperature of a single battery exceeds 320℃ or the voltage is lower than 2.0V, the charging and discharging process is immediately terminated and an alarm is issued. The charging and discharging strategy is dynamically adjusted according to the overall state of the battery pack, for example, when the average state of health value of the battery pack is lower than 80%, the charging and discharging rate is automatically reduced from 1C to 0.8C, prolonging the service life of the battery pack.

[0069] Through the above, the charging and discharging time of the sodium nickel chloride battery pack can be accurately grasped, overcharging and overdischarging can be avoided, the service life of the battery pack can be prolonged, and the energy utilization efficiency can be improved.

[0070] In an alternative embodiment, a charging and discharging strategy of the sodium nickel chloride battery pack is determined according to the state of charge value and the state of health value, and the sodium nickel chloride battery pack is controlled to perform balanced charging and discharging based on the charging and discharging strategy, comprising: The charging impedance and discharging impedance of the single battery are determined, the charging and discharging polarization coefficient of the single battery is determined based on the charging impedance and the discharging impedance, and the charging and discharging power of the single battery is determined according to the sodium ion concentration parameter and the nickel ion concentration parameter of the single battery; The single battery is grouped according to the state of charge value, the state of health value, the charging and discharging polarization coefficient, and the charging and discharging power, and the charging and discharging strategy of the sodium nickel chloride battery pack is determined based on the grouping result; According to the charging and discharging strategy, the sodium nickel chloride battery pack is controlled to be balanced charged, the sodium ions in the second electrolyte are controlled to be transmitted to the inner surface of the solid electrolyte ceramic tube, the sodium chloride in the positive electrode material is controlled to be dissociated into sodium ions and chlorine ions, the sodium ions are supplemented to the second electrolyte, and the chlorine ions react with nickel ions to generate nickel chloride; When it is detected that the state of charge value of the single battery reaches the preset charging threshold, the liquid metal sodium loses electrons to generate sodium ions, the sodium ions are transmitted from the outside of the ceramic tube to the inner surface of the ceramic tube to combine with chlorine ions to generate sodium chloride, and the nickel ions obtain electrons to generate metal nickel, so as to control the sodium nickel chloride battery pack to be balanced discharged.

[0071] In the process of implementing the present application, first, the state of charge value and the health state value of each single battery in the sodium nickel chloride battery pack are obtained, which are the basis for determining the battery charging and discharging strategy. The sodium nickel chloride battery pack includes a plurality of single batteries, each single battery is composed of a negative electrode, a first electrolyte, a solid electrolyte ceramic tube, a second electrolyte and a positive electrode, wherein the negative electrode is liquid metal sodium, the first electrolyte is a sodium-containing electrolyte, the solid electrolyte ceramic tube has the characteristic of selectively transmitting sodium ions, the second electrolyte is a nickel-containing electrolyte, and the positive electrode material includes sodium chloride and nickel material.

[0072] After obtaining the state of charge value and the health state value of the single battery, the charging impedance and the discharging impedance of the single battery need to be determined. By applying a small current pulse to the single battery, the voltage response change curve is recorded, and the charging impedance and the discharging impedance can be calculated. In actual testing, a group of sodium nickel chloride batteries is applied with a 0.5C current pulse for 10 seconds, and the charging impedance of battery 1 is measured to be 0.12Ω, and the discharging impedance is 0.15Ω; the charging impedance of battery 2 is 0.14Ω, and the discharging impedance is 0.18Ω; the charging impedance of battery 3 is 0.11Ω, and the discharging impedance is 0.13Ω.

[0073] Based on the measured charging impedance and discharging impedance, the charging and discharging polarization coefficient of the single battery is determined. The charging and discharging polarization coefficient is a function of the charging impedance and the discharging impedance, which can be fitted according to the experimental data. For example, for the above-mentioned battery group, the charging and discharging polarization coefficient of battery 1 is 0.8, that of battery 2 is 0.78, and that of battery 3 is 0.85.

[0074] The charging and discharging power of the single battery is determined according to the sodium ion concentration parameter and the nickel ion concentration parameter of the single battery. The sodium ion and nickel ion concentration parameters can be obtained by electrochemical impedance spectroscopy (EIS) measurement. For the tested battery pack, the sodium ion concentration of battery 1 is 4.2 mol / L, the nickel ion concentration is 2.1 mol / L, and the calculated charging and discharging power is 150 W; the sodium ion concentration of battery 2 is 4.1 mol / L, the nickel ion concentration is 2.0 mol / L, and the charging and discharging power is 145 W; the sodium ion concentration of battery 3 is 4.3 mol / L, the nickel ion concentration is 2.2 mol / L, and the charging and discharging power is 155 W.

[0075] The single batteries can be grouped according to the obtained state of charge value, state of health value, charging and discharging polarization coefficient and charging and discharging power. The grouping standard is based on the similarity of these parameters, and the batteries with similar parameters are grouped into the same group. In the actual case, assuming that there are 12 single batteries, they are divided into three groups according to the above parameters: the first group contains batteries 1, 4, 7 and 10, characterized by a state of charge value between 80% and 85%, and a state of health value between 95% and 98%; the second group contains batteries 2, 5, 8 and 11, with a state of charge value between 75% and 78%, and a state of health value between 92% and 94%; the third group contains batteries 3, 6, 9 and 12, with a state of charge value between 88% and 92%, and a state of health value between 97% and 99%.

[0076] The charging and discharging strategy of the sodium nickel chloride battery pack can be determined based on the grouping results, and different charging currents and discharge depths are used for different groups of batteries to achieve balanced charging and discharging. For example, for the first group of batteries, a 0.5C charging current is used, and the discharge depth is limited to 80%; for the second group of batteries, a 0.4C charging current is used, and the discharge depth is limited to 75%; for the third group of batteries, a 0.6C charging current is used, and the discharge depth is limited to 85%.

[0077] The sodium nickel chloride battery pack can be controlled to perform balanced charging according to the formulated charging and discharging strategy. During the charging process, the current passes through the positive electrode, and the sodium ions in the second electrolyte are transported to the inner surface of the solid electrolyte ceramic tube, while the sodium chloride in the positive electrode material is dissociated into sodium ions and chloride ions. The dissociated sodium ions are supplemented to the second electrolyte, and the chloride ions react with the nickel ions to form nickel chloride. During this process, the battery management system monitors the voltage, temperature and current of each single battery in real time to ensure the safety and efficiency of the charging process.

[0078] When the state of charge value of a single battery reaches a preset charging threshold, the discharge mode is automatically converted. The preset charging threshold is set according to the battery health state and the use environment, usually between 90%-95%. During the discharge process, the liquid sodium loses electrons to generate sodium ions, which are transported from the outside of the ceramic tube to the inner surface of the ceramic tube and combine with chloride ions to form sodium chloride. At the same time, nickel ions gain electrons to form metallic nickel. In this way, the sodium nickel chloride battery pack is balanced and discharged.

[0079] In practical applications, the state parameters of each single battery can be continuously monitored by an intelligent battery management system, and the charging and discharging strategy can be dynamically adjusted. For example, when the temperature of a certain single battery is detected to rise to a threshold value (such as 55℃), the charging current of the battery will be reduced or the charging will be suspended to prevent overheating damage; when the state of charge value of a certain group of batteries is significantly lower than that of other groups, the group of batteries will be preferentially charged to improve the consistency of the overall battery pack.

[0080] Through the above-mentioned balanced charging and discharging strategy, the service life of the sodium nickel chloride battery pack is effectively prolonged, and the energy utilization efficiency is improved. In the cycle life test, the capacity retention rate of the battery pack using this strategy reaches 85% after 2000 cycles, while the control group without using this strategy is only 70%, proving the effectiveness of this method.

[0081] In an alternative embodiment, the single batteries are grouped according to the state of charge value, the health state value, the charging and discharging polarization coefficient, and the charging and discharging power, and the charging and discharging strategy of the sodium nickel chloride battery pack is determined based on the grouping results, including: The single batteries are divided into different charge groups according to the distribution interval of the state of charge value; the remaining life of the single batteries is calculated based on the health state value, and the single batteries in different charge groups are divided into different attenuation groups based on the remaining life; The ion diffusion coefficient and ion conductivity of the solid electrolyte ceramic tube surface of the single battery are monitored, the ion migration rate of the single battery is calculated according to the ion diffusion coefficient and the ion conductivity, the charging and discharging polarization coefficient is corrected based on the ion migration rate, and the polarization correction coefficient of the single battery is obtained; The solid-liquid interface capacitance value and electrolyte conductivity of the single battery are obtained, the ion transport flux of the single battery is calculated according to the solid-liquid interface capacitance value and the electrolyte conductivity, and the charging and discharging power is corrected based on the ion transport flux to obtain the power correction coefficient of the single battery; According to the polarization correction coefficient and the power correction coefficient, the single batteries in the attenuation group are secondarily grouped to obtain a plurality of charge-discharge groups, and a charge-discharge strategy of the sodium nickel chloride battery group is determined according to the distribution of the plurality of charge-discharge groups.

[0082] The state of charge value, the state of health value, the charge-discharge polarization coefficient and the charge-discharge power of the single battery can be obtained first, which are the basis for battery grouping and charge-discharge strategy making.

[0083] For the grouping of the state of charge value, the single batteries can be divided according to the distribution interval of the state of charge value. For example, the single batteries with a state of charge value of 0%-20% can be divided into a low power group, the single batteries with a state of charge value of 20%-80% can be divided into a medium power group, and the single batteries with a state of charge value of 80%-100% can be divided into a high power group. In actual application, assuming that a sodium nickel chloride battery group contains 100 single batteries, 15 of which have a state of charge value in the interval of 0%-20%, 60 of which have a state of charge value in the interval of 20%-80%, and 25 of which have a state of charge value in the interval of 80%-100%, these batteries will be classified into the corresponding low, medium and high power groups respectively.

[0084] After the grouping of the charge group is completed, the remaining life of the single battery can be calculated based on the state of health value, and the remaining life calculation can be obtained by multiplying the state of health value by the nominal cycle life of the battery. For example, for a sodium nickel chloride battery with a nominal cycle life of 5000 times, if the state of health value of a single battery is 80%, the remaining life of the battery is 4000 cycles. According to the calculated remaining life, the batteries in different charge groups are further divided into attenuation groups. For example, the batteries with a remaining life of 0-1000 cycles are classified into a high attenuation group, the batteries with a remaining life of 1000-3000 cycles are classified into a medium attenuation group, and the batteries with a remaining life of 3000-5000 cycles are classified into a low attenuation group. In this way, the batteries in each charge group are subdivided into different attenuation subgroups.

[0085] To improve the accuracy of battery management, the ion diffusion coefficient and ion conductivity on the surface of the solid electrolyte ceramic tube of the single battery are monitored, which can be obtained by a micro sensor built-in the battery or by periodic measurement through a special test equipment. Assuming that the measured ion diffusion coefficient of a certain battery is 3.5x10^-6 cm² / s and the ion conductivity is 0.15 S / cm, the ion migration rate is calculated according to these parameters. When calculating, the thickness, effective area and structure factor of the electrolyte ceramic tube and other parameters are considered. The calculated ion migration rate is used to correct the charge-discharge polarization coefficient to obtain the polarization correction coefficient. For example, if the original polarization coefficient is 1.2, after correction, it can be changed to 1.15 or 1.25, depending on the deviation direction and size of the ion migration rate from the reference value.

[0086] At the same time, the solid-liquid interface capacitance value and electrolyte conductivity of the single battery can be obtained, which can be obtained by electrochemical impedance spectroscopy test or extracted from real-time data of the battery management system. For example, the solid-liquid interface capacitance value of a certain battery is 25 µF / cm², and the electrolyte conductivity is 0.12 S / cm. According to these parameters, the ion transport flux is calculated, which reflects the number of ions passing through a unit area per unit time inside the battery. The calculated ion transport flux is used to correct the charging and discharging power to obtain a power correction coefficient. If the original charging and discharging power is 200W, according to the power correction coefficient of 0.95, the corrected actual available power is 190W.

[0087] After the above correction is completed, the single batteries in the attenuation group can be re-grouped according to the polarization correction coefficient and the power correction coefficient, for example, the batteries with a polarization correction coefficient in the range of 0.9-1.1 and a power correction coefficient in the range of 0.95-1.05 can be divided into a stable charging and discharging group; the batteries with a polarization correction coefficient greater than 1.1 or a power correction coefficient less than 0.95 are divided into a limited charging and discharging group; the batteries with a polarization correction coefficient less than 0.9 or a power correction coefficient greater than 1.05 are divided into an enhanced charging and discharging group. Through this secondary grouping, a plurality of charging and discharging groups are finally obtained.

[0088] According to the distribution characteristics of these charging and discharging groups, the charging and discharging strategy of the sodium nickel chloride battery pack can be determined, such as for the batteries in the stable charging and discharging group, a standard charging and discharging current is used; for the batteries in the limited charging and discharging group, a lower charging and discharging current is used to prolong its service life; for the batteries in the enhanced charging and discharging group, the charging and discharging current can be appropriately increased to improve the overall performance. Specifically, if 60% of the batteries in a certain battery pack belong to the stable charging and discharging group, 25% belong to the limited charging and discharging group, and 15% belong to the enhanced charging and discharging group, the overall charging and discharging current can be set to 85% of the standard current to balance the performance and life requirements.

[0089] Through the above, the fine management of the sodium nickel chloride battery pack can be realized, the overall performance and service life of the battery pack can be improved, and the performance degradation and safety risks caused by the differences between single batteries can be reduced.

[0090] The sodium nickel chloride battery pack equalization charging and discharging control system based on intelligent algorithm according to the embodiment of the application comprises: A first unit is configured to obtain the working parameters of each single battery in the sodium nickel chloride battery pack, and control the temperature of the single battery to reach a preset working temperature range according to the working parameters. The second unit is configured to detect the sodium ion concentration parameter and the nickel ion concentration parameter in each single battery, calculate the sodium ion transmission rate of each single battery according to the sodium ion concentration parameter and the nickel ion concentration parameter, and determine the charge-discharge rate parameter of each single battery based on the sodium ion transmission rate. The third unit is configured to calculate the state of charge value and the state of health value of each single battery based on the working parameter and the charge-discharge rate parameter, and determine the charge-discharge time of the sodium nickel chloride battery pack according to the state of charge value. The fourth unit is configured to determine the charge-discharge strategy of the sodium nickel chloride battery pack according to the state of charge value and the state of health value, and control the sodium nickel chloride battery pack to perform balanced charge-discharge based on the charge-discharge strategy.

[0091] In a third aspect, an electronic device is provided, comprising: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to invoke the instructions stored in the memory to perform the method described above.

[0092] In a fourth aspect, a computer-readable storage medium is provided, which stores computer program instructions, and the computer program instructions are executed by a processor to implement the method described above.

[0093] The present application can be a method, device, system and / or computer program product. The computer program product can include a computer-readable storage medium having stored thereon computer-readable program instructions that, when executed by a computer, cause the computer to carry out various aspects of the present application.

[0094] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for equalizing charge and discharge control of sodium-nickel chloride battery packs based on intelligent algorithms, characterized in that, include: The operating parameters of each individual cell in the sodium nickel chloride battery pack are obtained, and the temperature of the individual cell is controlled to reach a preset operating temperature range based on the operating parameters. The sodium ion concentration parameters and nickel ion concentration parameters inside each of the individual cells are detected. The sodium ion transport rate of each individual cell is calculated based on the sodium ion concentration parameters and the nickel ion concentration parameters. The charge / discharge rate parameters of each individual cell are determined based on the sodium ion transport rate. Based on the operating parameters and the charge / discharge rate parameters, the state of charge (SOC) and state of health (SQH) values ​​of each individual battery cell are calculated, and the charge / discharge time of the sodium-nickel chloride battery pack is determined based on the SOC values. The charging and discharging strategy of the nickel chloride battery pack is determined based on the state of charge value and the state of health value, and the nickel chloride battery pack is controlled to perform balanced charging and discharging based on the charging and discharging strategy.

2. The method according to claim 1, characterized in that, Obtaining the operating parameters of each individual cell in a nickel-sodium chloride battery pack, and controlling the temperature of each individual cell to reach a preset operating temperature range based on the operating parameters, includes: The operating parameters of each individual cell in the sodium nickel chloride battery pack are obtained, and the temperature change rate, voltage change rate and electrochemical impedance of each individual cell are calculated based on the operating parameters. Based on the temperature parameter in the working parameters, determine whether each individual cell is within the preset temperature range, and calculate the temperature deviation value and temperature gradient value of each individual cell; The individual cells are classified based on the temperature deviation value, the temperature gradient value, and the electrochemical impedance. The heating priority of each individual cell is calculated, and the initial heating power and heating plate power adjustment coefficient of each individual cell are determined according to the heating priority. When the rate of temperature change is less than a preset temperature response threshold and the rate of voltage change is less than a preset voltage fluctuation threshold, the heating power of the heating plate adjacent to the single battery cell is increased according to the heating plate power adjustment coefficient. When the internal resistance parameter in the operating parameters increases, the heating power of the heating plate is reduced until the temperature parameter of the single cell reaches the preset temperature range and the internal resistance parameter remains stable.

3. The method according to claim 1, characterized in that, The process involves detecting the sodium ion concentration and nickel ion concentration parameters inside each individual battery cell, calculating the sodium ion transport rate of each individual battery cell based on the sodium ion concentration and nickel ion concentration parameters, and determining the charge / discharge rate parameters of each individual battery cell based on the sodium ion transport rate, including: Obtain the sodium ion concentration parameters and nickel ion concentration parameters inside a single cell that has reached a preset temperature range, and calculate the lateral concentration gradient value and the longitudinal concentration gradient value inside the single cell. Based on the lateral concentration gradient value and the longitudinal concentration gradient value, the ion diffusion coefficient inside the single cell is calculated, and the sodium ion transport rate of the single cell on the inner surface of the solid electrolyte ceramic tube is determined according to the ion diffusion coefficient. Monitor the potential difference and ion conductivity of the inner surface of the solid electrolyte ceramic tube of the single cell, and calculate the ion migration resistance coefficient of the single cell based on the crystal orientation and grain boundary density of the inner surface of the solid electrolyte ceramic tube. The ion migration rate of the single cell is calculated based on the potential difference, the ion conductivity and the ion migration resistance coefficient, and the ratio of the sodium ion transport rate to the ion migration rate is taken as the ion transport efficiency of the single cell. The effective ion transport rate of the single cell is determined based on the ion transport efficiency and the concentration gradient value, and the charge / discharge rate parameter of the single cell is calculated based on the effective ion transport rate.

4. The method according to claim 3, characterized in that, The effective ion transport rate of the single cell is determined based on the ion transport efficiency and the concentration gradient value. The charge / discharge rate parameters of the single cell are then calculated based on the effective ion transport rate, including: The ion migration path length of the single cell is calculated based on the cross-sectional area and wall thickness of the solid electrolyte ceramic tube of the single cell, and the structural factor of the single cell is determined based on the ion migration path length. The grain orientation angle and grain boundary density of the solid electrolyte ceramic tube surface of the single cell are obtained, the interfacial polarization impedance of the single cell is calculated, and the ion flux loss coefficient of the single cell is determined based on the interfacial polarization impedance. Monitor the solid-liquid interface capacitance and electrolyte conductivity of the single cell, calculate the ion diffusion channel coefficient of the single cell, and determine the mass transfer loss coefficient of the single cell based on the ion diffusion channel coefficient. The product of the ion transport efficiency and the concentration gradient value is used as the initial transport rate. The initial transport rate is then corrected according to the structure factor, the ion flux loss coefficient, and the mass transfer loss coefficient to obtain the effective ion transport rate of the single cell. The charge / discharge rate parameter of the single cell is then calculated based on the effective ion transport rate.

5. The method according to claim 1, characterized in that, Based on the operating parameters and the charge / discharge rate parameters, the state of charge (SOC) and state of health (SQH) values ​​of each individual battery cell are calculated. The charge / discharge time of the sodium-nickel chloride (NiCC) battery pack is determined based on the SOC values, including: The polarization resistance and ohmic resistance of the solid electrolyte ceramic tube surface of the single cell are monitored, the internal resistance change rate of the single cell is calculated, the coulombic efficiency of the single cell is calculated based on the operating parameters, and the coulombic efficiency is corrected based on the internal resistance change rate to obtain the corrected coulombic efficiency of the single cell. The cycle number and operating time of the single cell are obtained, the capacity decay rate of the single cell is calculated, and the health status value of the single cell is determined based on the corrected coulombic efficiency and the capacity decay rate. The remaining capacity and total capacity of the individual battery are determined based on the operating parameters and the charge / discharge rate parameters, and the state of charge value of the individual battery is determined based on the remaining capacity and the total capacity. The effective capacity coefficient of the individual battery is determined based on the state of charge value and the state of health value. The difference between the maximum and minimum effective capacity coefficients in the sodium nickel chloride battery pack is calculated, and the charge and discharge time of the sodium nickel chloride battery pack is determined based on the difference.

6. The method according to claim 1, characterized in that, The charging and discharging strategy of the nickel-sodium chloride battery pack is determined based on the state of charge value and the state of health value, and the nickel-sodium chloride battery pack is controlled to perform equal charging and discharging based on the charging and discharging strategy, including: The charging impedance and discharging impedance of the single cell are determined, the charging and discharging polarization coefficient of the single cell is determined based on the charging impedance and the discharging impedance, and the charging and discharging power of the single cell is determined according to the sodium ion concentration parameter and nickel ion concentration parameter of the single cell. The individual cells are grouped according to the state of charge value, the state of health value, the charge / discharge polarization coefficient and the charge / discharge power, and the charge / discharge strategy of the sodium nickel chloride battery pack is determined based on the grouping results. According to the charging and discharging strategy, the sodium-nickel chloride battery pack is controlled to perform equal charging, the sodium ions in the second electrolyte are controlled to be transported to the inner surface of the solid electrolyte ceramic tube, the sodium chloride in the positive electrode material is controlled to dissociate into sodium ions and chloride ions, the sodium ions are added to the second electrolyte, and the chloride ions react with nickel ions to generate nickel chloride. When the state of charge of the single cell is detected to reach a preset charging threshold, liquid sodium metal is controlled to lose electrons to generate sodium ions. The sodium ions are then controlled to be transported from the outside of the ceramic tube to the inner surface of the ceramic tube and combine with chloride ions to generate sodium chloride. Meanwhile, nickel ions are controlled to gain electrons to generate metallic nickel, thereby controlling the sodium-nickel chloride battery pack to perform balanced discharge.

7. The method according to claim 6, characterized in that, The individual cells are grouped according to the state of charge value, the state of health value, the charge / discharge polarization coefficient, and the charge / discharge power. Based on the grouping results, a charge / discharge strategy for the sodium-nickel chloride battery pack is determined, including: The individual cells are divided into different charge groups according to the distribution range of the state of charge values; the remaining life of the individual cells is calculated based on the state of health values, and the individual cells in different charge groups are divided into different degradation groups based on the remaining life. The ion diffusion coefficient and ion conductivity of the solid electrolyte ceramic tube surface of the single cell are monitored. The ion migration rate of the single cell is calculated based on the ion diffusion coefficient and the ion conductivity. The polarization coefficient of the charge and discharge polarization is corrected based on the ion migration rate to obtain the polarization correction coefficient of the single cell. The solid-liquid interface capacitance and electrolyte conductivity of the single cell are obtained. The ion transport flux of the single cell is calculated based on the solid-liquid interface capacitance and electrolyte conductivity. The charge and discharge power is corrected based on the ion transport flux to obtain the power correction coefficient of the single cell. The individual cells within the attenuation group are regrouped based on the polarization correction coefficient and the power correction coefficient to obtain multiple charge-discharge groups. The charge-discharge strategy of the sodium-nickel chloride battery pack is determined based on the distribution of the multiple charge-discharge groups.

8. A sodium-nickel chloride battery pack equalization charge-discharge control system based on intelligent algorithms, used to implement the method as described in any one of claims 1-7, characterized in that, include: The first unit is used to acquire the operating parameters of each individual cell in the sodium nickel chloride battery pack, and control the temperature of the individual cell to reach a preset operating temperature range based on the operating parameters. The second unit is used to detect the sodium ion concentration parameters and nickel ion concentration parameters inside each of the individual cells, calculate the sodium ion transport rate of each individual cell based on the sodium ion concentration parameters and the nickel ion concentration parameters, and determine the charge / discharge rate parameters of each individual cell based on the sodium ion transport rate. The third unit is used to calculate the state of charge and state of health values ​​of each individual battery cell based on the operating parameters and the charge / discharge rate parameters, and to determine the charge / discharge time of the sodium-nickel chloride battery pack based on the state of charge values. The fourth unit is used to determine the charging and discharging strategy of the nickel-sodium chloride battery pack based on the state of charge value and the state of health value, and to control the nickel-sodium chloride battery pack to perform equal charging and discharging based on the charging and discharging strategy.

9. An electronic device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor is configured to invoke instructions stored in the memory to execute the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When the computer program instructions are executed by the processor, they implement the method described in any one of claims 1 to 7.

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