A method and system for determining a multi-frequency pulse segmented heating protocol for a sodium-ion battery

Abstract

The application discloses a kind of sodium ion battery multi-frequency pulse segmented heating system determination method and system, it is related to sodium ion battery low-temperature thermal management field, it is applicable to hard carbon negative electrode sodium ion battery low-temperature pulse heating.The heating process is divided into low-temperature section T≤‑10℃, medium-temperature section‑10℃<T<0℃, high-temperature section T≥0℃ in the application, determine the exclusive pulse frequency interval of each section by EIS test, independently control the three parameters of charge-discharge pulse, set 2.0V sodium extraction safety red line, realize temperature across section parameter adaptive switching.The application solves the problem of slow warming, uneven heating, easy to overshoot of traditional heating technology, improves low-temperature heating efficiency, safety and battery cycle life.

Description

Technical Field

[0001] This invention relates to the field of low-temperature thermal management technology for sodium-ion batteries, and is particularly applicable to pulse heating control of hard carbon negative electrode sodium-ion batteries for on-board energy storage and low-temperature conditions. Specifically, it is a method and system for determining the multi-frequency pulse segmented heating mode of sodium-ion batteries. Background Technology

[0002] The core reason for the low-temperature performance degradation of sodium-ion batteries is that as the temperature decreases, the electrolyte viscosity increases, the ionic conductivity decreases, and the ohmic impedance and charge transfer impedance of the battery cell increase significantly. The charge transfer impedance can increase to 3-5 times that at room temperature at -20℃. Pulse heating achieves cell temperature rise through the Joule heating of charge-discharge pulses. Its heat generation power is closely related to the current amplitude, frequency, and cell impedance: Joule heating power P=I 2 R, while the cell impedance shows obvious response characteristics as the pulse frequency changes. In the low frequency range, it mainly reflects the charge transfer impedance, and in the high frequency range, it mainly reflects the ohmic impedance.

[0003] The existing low-temperature pulse heating technology for sodium-ion batteries has the following drawbacks: traditional heating technologies mostly use a single fixed frequency or amplitude pulse, without taking into account the impedance characteristics of the cell in different low-temperature ranges. This results in slow heating in the low-temperature range, uneven heating in the medium-temperature range, and easy overshooting in the high-temperature range. Summary of the Invention

[0004] In view of the technical problems mentioned in the background art, traditional heating technologies mostly use a single fixed frequency or amplitude pulse, without taking into account the impedance characteristics of the battery cell in different low temperature ranges, resulting in slow heating in the low temperature range, uneven heating in the medium temperature range, and easy overshoot in the high temperature range. The purpose of this invention is to provide a method and system for determining the multi-frequency pulse segmented heating mode of sodium-ion batteries.

[0005] To achieve the objectives of this invention, the technical solution provided by this invention is as follows: First aspect This invention provides a method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery, comprising the following steps: Step S1: Divide the heating process of the hard carbon negative electrode sodium-ion battery into three temperature ranges: low temperature range T≤-10℃, medium temperature range -10℃<T<0℃, and high temperature range T≥0℃. Step S2: Conduct EIS electrochemical impedance spectroscopy tests on the battery cell in three temperature ranges, collect impedance-frequency response curves, and quantitatively determine the pulse frequency range specific to each temperature range.

[0006] The present invention targets the low-temperature impedance variation law of sodium-ion batteries, and divides the heating process into three exclusive temperature segments: a low-temperature segment (T≤-10°C), a medium-temperature segment (-10°C<T<0°C), and a high-temperature segment (T≥0°C). For each temperature segment, EIS electrochemical impedance testing (electrochemical impedance testing, a standard calibration means for electrical characteristics of batteries) is performed separately on the sodium-ion battery cell, a complete impedance-frequency response curve is collected, the variation law of impedance with frequency at different temperatures is quantitatively fitted, and the exclusive pulse frequency interval for each temperature segment is determined quantitatively in segments.

[0007] Further, the three exclusive pulse frequency intervals are as follows: 50–150Hz for the low-temperature segment, 200–500Hz for the medium-temperature segment, and 600–1000Hz for the high-temperature segment.

[0008] Based on massive test data of sodium-ion battery hard carbon anode cells, the present invention innovatively defines three fixed frequency intervals adapted to sodium batteries, which is different from all general battery heating solutions: low-temperature segment (T≤-10°C): 50–150Hz, where the cell charge transfer impedance is dominant, the frequency interval of ±20% corresponding to the charge transfer impedance peak in the impedance-frequency curve is selected to screen out the frequency with the highest heat generation efficiency, which is adapted to extreme low-temperature and high-impedance working conditions; medium-temperature segment (-10°C<T<0°C): 200–500Hz, where both the ohmic impedance and the charge transfer impedance of the cell account for a significant proportion, the frequency in the interval with the lowest impedance change rate is selected to simultaneously excite ohmic heat and polarization heat, so as to ensure the uniformity of heating in the whole domain; high-temperature segment (T≥0°C): 600–1000Hz, where the cell ohmic impedance is dominant, the frequency in the high-frequency interval with stable ohmic impedance is selected to achieve low-power consumption and precise heat preservation, and avoid temperature overshoot.

[0009] Further, the method also includes the step of independently controlling three parameters of the hard carbon anode asymmetric pulse: independently adjusting the frequency, current amplitude and conduction duty cycle of the charging pulse and the discharging pulse, wherein all parameters of the charging pulse are smaller than the corresponding parameters of the discharging pulse; the current amplitude in the low-temperature segment is 1.0–1.5C with a duty cycle of 50%–70%, the current amplitude in the medium-temperature segment is 0.6–1.0C with a duty cycle of 40%–60%, and the current amplitude in the high-temperature segment is 0.3–0.6C with a duty cycle of 30%–50%.

[0010] The present invention independently regulates the three parameters of the frequency, current amplitude and conduction duty cycle of the charging and discharging pulses: the amplitude, frequency and duty cycle of the charging pulse are all independently smaller than the parameters of the discharging pulse, which matches the reaction law of slow sodium intercalation and fast sodium deintercalation, and completely solves the problem that the general asymmetric solution cannot adapt to the heat generation characteristics of sodium batteries.

[0011] Further, the data of cell temperature, cell voltage and working current are collected in real time. When the cell temperature crosses the segment threshold, the synchronous switching of the three frequency intervals and the three charging and discharging parameters is automatically completed, so as to form a temperature cross-segment adaptive switching control logic.

[0012] Furthermore, it also includes a 2.0V sodium deposition potential safety red line constraint step: setting the 2.0V sodium deposition critical potential as a hard safety red line throughout the entire process, and monitoring the voltage of individual cells in real time; all segmented pulse frequencies, charging and discharging differentiated three parameters, and cross-segment switching logic are all based on the premise of not triggering the 2.0V sodium deposition potential.

[0013] This invention utilizes the above-mentioned solution to eliminate the risks of sodium dendrite precipitation and electrolyte decomposition from the underlying material properties, thereby constructing a sodium-electric-specific low-temperature heating safety system.

[0014] Furthermore, the pulse power is automatically reduced when the voltage of a single cell approaches the 2.0V threshold.

[0015] In addition, corresponding to the above method, the present invention also provides a system for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery, comprising the following units: The temperature range division unit is used to divide the heating process of the hard carbon negative electrode sodium-ion battery into three temperature ranges: low temperature range T≤-10℃, medium temperature range -10℃<T<0℃, and high temperature range T≥0℃. A dedicated pulse frequency range determination unit is used to conduct EIS electrochemical impedance spectroscopy tests on the battery cell in three temperature ranges, collect impedance-frequency response curves, and quantitatively determine the dedicated pulse frequency range for each temperature range.

[0016] Furthermore, the three dedicated pulse frequency ranges are as follows: low temperature range 50–150Hz, medium temperature range 200–500Hz, and high temperature range 600–1000Hz.

[0017] Furthermore, it also includes an independent control unit for the three parameters of the asymmetric pulse of the hard carbon negative electrode, which is used to independently regulate the frequency, current amplitude, and duty cycle of the charging pulse and the discharging pulse. All parameters of the charging pulse are less than the corresponding parameters of the discharging pulse. The current amplitude is 1.0–1.5C and the duty cycle is 50%–70% in the low temperature range, the current amplitude is 0.6–1.0C and the duty cycle is 40%–60% in the medium temperature range, and the current amplitude is 0.3–0.6C and the duty cycle is 30%–50% in the high temperature range.

[0018] Furthermore, it also includes a 2.0V sodium deposition potential safety red line constraint unit, which is used to set the 2.0V sodium deposition critical potential as a hard safety red line throughout the entire process and monitor the voltage of individual cells in real time; all segmented pulse frequencies, charging and discharging differentiated three parameters, and cross-segment switching logic are all based on the premise of not triggering the 2.0V sodium deposition potential.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention offers customized innovations targeting the material characteristics, impedance patterns, and safety shortcomings of hard carbon anode sodium-ion batteries, completely overcoming the shortcomings of existing technologies such as poor single-frequency adaptability, coarse asymmetric control, and lack of dedicated safety constraints. Through a synergistic technical solution involving EIS segmented quantitative and frequency control, three dedicated frequency ranges for sodium batteries, independent and differentiated control of the three charging and discharging parameters, and a 2.0V sodium deposition potential safety closed-loop constraint, this invention simultaneously achieves multi-dimensional improvements in low-temperature heating efficiency, cell temperature uniformity, low-temperature operating safety, and battery cycle life, demonstrating significant and quantifiable technical advantages. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, this embodiment provides a method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery, including the following steps: Step S1: Divide the heating process of the hard carbon negative electrode sodium-ion battery into three temperature ranges: low temperature range T≤-10℃, medium temperature range -10℃<T<0℃, and high temperature range T≥0℃. Step S2: Conduct EIS electrochemical impedance spectroscopy tests on the battery cell in three temperature ranges, collect impedance-frequency response curves, and quantitatively determine the pulse frequency range specific to each temperature range.

[0023] The three dedicated pulse frequency ranges are as follows: low temperature range 50–150Hz, medium temperature range 200–500Hz, and high temperature range 600–1000Hz.

[0024] The specific parameters for the pulse system specific to each temperature range are as follows: (1) Low temperature range: low frequency high current pulse (frequency 50-150Hz, current amplitude 1.0-1.5C, duty cycle 50%-70%) to achieve rapid heating in extreme low temperatures; (2) Medium temperature range: medium frequency medium current pulse (frequency 200-500Hz, current amplitude 0.6-1.0C, duty cycle 40%-60%) to achieve uniform heating across the entire range; (3) High temperature section: high frequency small current pulse (frequency 600-1000Hz, current amplitude 0.3-0.6C, duty cycle 30%-50%) to achieve precise constant temperature insulation.

[0025] The following combinations can be used: The first type: (1) Low temperature range -10℃: Low frequency high current pulse (frequency 50Hz, current amplitude 1.0C, duty cycle 50%) to achieve rapid heating at extreme low temperatures; (2) Medium temperature range -9℃: medium frequency medium current pulse (frequency 200Hz, current amplitude 0.6C, duty cycle 40%) to achieve uniform heating across the entire range; (3) High temperature section 0℃: High frequency small current pulse (frequency 600Hz, current amplitude 0.3C, duty cycle 30%) to achieve precise constant temperature insulation.

[0026] The second type: (1) Low temperature range -15℃: Low frequency high current pulse (frequency 150Hz, current amplitude 1.0-1.5C, duty cycle 50%-70%) to achieve rapid heating in extreme low temperatures; (2) Medium temperature range -5℃: medium frequency medium current pulse (frequency 350Hz, current amplitude 0.8C, duty cycle 50%) to achieve uniform heating throughout the entire range; (3) High temperature section 5℃: High frequency small current pulse (frequency 800Hz, current amplitude 0.35C, duty cycle 40%) to achieve precise constant temperature insulation.

[0027] The third type: (1) Low temperature range -20℃: Low frequency high current pulse (frequency 150Hz, current amplitude 1.5C, duty cycle 70%) to achieve rapid heating at extreme low temperatures; (2) Medium temperature range -1℃: medium frequency medium current pulse (frequency 500Hz, current amplitude 1.0C, duty cycle 60%) to achieve uniform heating across the entire range; (3) High temperature range 10℃: high frequency small current pulse (frequency 1000Hz, current amplitude 0.6C, duty cycle 50%) to achieve precise constant temperature insulation.

[0028] The following uses a 25Ah hard carbon negative electrode sodium-ion battery as a specific embodiment to describe the technical solution of the present invention in detail.

[0029] Impedance-frequency response segmented calibration EIS electrochemical impedance spectroscopy was performed on the same sodium-ion battery cell in three different temperature ranges, and a proprietary impedance-frequency response curve was plotted. (1) Low temperature range (-20℃): The peak frequency of charge transfer impedance is 100Hz and the impedance value is 180mΩ. The optimal working range of low temperature range is determined to be 80-120Hz. (2) Medium temperature range (-5℃): The range with the lowest impedance change rate is 300-400Hz, the impedance value is 90mΩ, and the optimal working frequency for the medium temperature range is determined to be 350Hz. (3) High temperature range (0℃): Ohmic impedance stability range 700-900Hz, impedance value 50mΩ, determine the optimal working frequency of 800Hz in the high temperature range.

[0030] Differentiated charge / discharge pulse parameter configuration Combining the asymmetric heat generation characteristics of hard carbon anode, three parameters are independently set: charging pulse amplitude 0.8C, duty cycle 45%, and discharging pulse amplitude 1.2C, duty cycle 60%. The corresponding frequencies are synchronously adapted to each temperature range to fully match the differences in sodium intercalation and deintercalation kinetics.

[0031] Segmented heating closed-loop control process (1) Initial temperature -20℃ (low temperature range): 100Hz low frequency pulse is used, and the operation is carried out with differentiated charge and discharge parameters. The heating rate is 1.5℃ / min. The single cell voltage is higher than the safety red line of 2.0V throughout the process, and there is no risk of sodium precipitation. (2) Heat up to -10℃ (medium temperature range): Automatically switch to 350Hz medium frequency pulse, synchronously adjust the three charging and discharging parameters, and the heating rate is 1.0℃ / min; (3) Heat up to 0℃ (high temperature range): switch to 800Hz high frequency pulse, reduce working power, stabilize the temperature at 0-5℃, and prevent overshoot and side reactions.

[0032] Finally, it should be noted that the above embodiments are merely illustrative and explanatory of the present invention, and are not intended to limit the present invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention.

Claims

1. A method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery, characterized in that, Includes the following steps: Step S1: Divide the heating process of the hard carbon negative electrode sodium-ion battery into three temperature ranges: low temperature range T≤-10℃, medium temperature range -10℃<T<0℃, and high temperature range T≥0℃. Step S2: Conduct EIS electrochemical impedance spectroscopy tests on the battery cell in three temperature ranges, collect impedance-frequency response curves, and quantitatively determine the pulse frequency range specific to each temperature range.

2. The method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 1, characterized in that, The three dedicated pulse frequency ranges are as follows: low temperature range 50–150Hz, medium temperature range 200–500Hz, and high temperature range 600–1000Hz.

3. The method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 2, characterized in that, It also includes a three-parameter independent control step for the asymmetric pulse of hard carbon negative electrode: independently adjusting the frequency, current amplitude, and duty cycle of the charging pulse and the discharging pulse, with all parameters of the charging pulse being less than the corresponding parameters of the discharging pulse; The current amplitude in the low temperature range is 1.0–1.5C and the duty cycle is 50%–70%; the current amplitude in the medium temperature range is 0.6–1.0C and the duty cycle is 40%–60%; and the current amplitude in the high temperature range is 0.3–0.6C and the duty cycle is 30%–50%.

4. The method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 3, characterized in that, The system collects real-time data on cell temperature, individual cell voltage, and operating current. When the cell temperature exceeds the segment threshold, it automatically completes the synchronous switching of the three frequency ranges and the three parameters of charging and discharging, forming an adaptive switching control logic for temperature cross-segment.

5. The method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 1, characterized in that, It also includes a 2.0V sodium deposition potential safety red line constraint step: the 2.0V sodium deposition critical potential is set as a hard safety red line throughout the process, and the voltage of individual cells is monitored in real time; all segmented pulse frequencies, charging and discharging differentiated three parameters, and cross-segment switching logic are all based on the premise of not triggering the 2.0V sodium deposition potential.

6. The method for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 1, characterized in that, When the voltage of a single cell approaches the 2.0V threshold, the pulse power is automatically reduced.

7. A system for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery, characterized in that, Includes the following units: The temperature range division unit is used to divide the heating process of the hard carbon negative electrode sodium-ion battery into three temperature ranges: low temperature range T≤-10℃, medium temperature range -10℃<T<0℃, and high temperature range T≥0℃. A dedicated pulse frequency range determination unit is used to conduct EIS electrochemical impedance spectroscopy tests on the battery cell in three temperature ranges, collect impedance-frequency response curves, and quantitatively determine the dedicated pulse frequency range for each temperature range.

8. A sodium-ion battery multi-frequency pulse segmented heating mode determination system according to claim 7, characterized in that, The three dedicated pulse frequency ranges are as follows: low temperature range 50–150Hz, medium temperature range 200–500Hz, and high temperature range 600–1000Hz.

9. A system for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 8, characterized in that, It also includes an independent control unit for the three parameters of the asymmetric pulse of the hard carbon negative electrode, which is used to independently adjust the frequency, current amplitude and duty cycle of the charging pulse and the discharging pulse. All parameters of the charging pulse are less than the corresponding parameters of the discharging pulse. The current amplitude in the low temperature range is 1.0–1.5C and the duty cycle is 50%–70%; the current amplitude in the medium temperature range is 0.6–1.0C and the duty cycle is 40%–60%; and the current amplitude in the high temperature range is 0.3–0.6C and the duty cycle is 30%–50%.

10. A system for determining the multi-frequency pulse segmented heating mode of a sodium-ion battery according to claim 7, characterized in that, It also includes a 2.0V sodium deposition potential safety red line constraint unit, which is used to set the 2.0V sodium deposition critical potential as a hard safety red line throughout the entire process and monitor the voltage of individual cells in real time; all segmented pulse frequencies, charging and discharging differentiated three parameters, and cross-segment switching logic are based on the premise of not triggering the 2.0V sodium deposition potential.

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