A composite regulation method and device for improving low-temperature performance of energy storage batteries

Abstract

This invention discloses a composite control device and method for improving the low-temperature performance of energy storage batteries, belonging to the field of energy storage battery technology. This invention solves problems such as battery performance degradation, increased internal resistance, and uneven temperature distribution under low-temperature environments through the synergistic effect of electrolyte system optimization and module-level intelligent temperature control. The antifreeze electrolyte system contains lithium or sodium salts, a basic solvent, and functional additives, including ethylene glycol dimethyl ether, fluoroethylene carbonate, and nano-silica, lowering the electrolyte freezing point to below -40℃. The layered heating-insulation-heat dissipation integrated module adopts a three-layer structure: a bottom heating zone, a middle insulation zone, and a top temperature control zone, combined with phase change materials and a graphene heating film. The intelligent temperature control system dynamically adjusts the heating power based on a PID algorithm, achieving multi-mode switching and ensuring that the temperature deviation within the module is controlled within 2℃. This invention enables the battery to maintain high capacity retention, low internal resistance growth, and good cycle stability in a -40℃ low-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of energy storage battery technology, specifically to a composite regulation method and apparatus for improving the low-temperature performance of energy storage batteries. Background Technology

[0002] The electrochemical performance of energy storage batteries is highly dependent on the operating temperature. When the ambient temperature is below -10℃, the viscosity of the electrolyte increases, the ion migration rate decreases significantly, and the activity of the electrode material decreases, resulting in a decrease in the battery's charge and discharge capacity, an increase in internal resistance, and a shortened cycle life. This seriously restricts the promotion and application of energy storage batteries in high-altitude and cold regions, grid energy storage, new energy vehicles, and outdoor portable power supplies.

[0003] To address the aforementioned issues, existing technologies primarily seek breakthroughs in two directions: firstly, electrolyte modification, which involves optimizing the solvent system and adding functional additives to lower the electrolyte's freezing point and improve its low-temperature ionic conductivity. For example, existing research has proposed low-temperature electrolyte solutions suitable for lithium / sodium-ion batteries, achieving charge-discharge cycles within a range of -40℃ to 70℃ by adjusting the lithium salt concentration and solvent ratio; there are also low-temperature electrolyte preparation methods for lithium iron phosphate power batteries, which improve the wettability of the electrode material-electrolyte interface and reduce SEI film impedance through additives. However, optimizing a single electrolyte formulation often fails to balance low-temperature performance and battery safety, and cannot solve the starting difficulties caused by the battery's "cold penetration" at extreme low temperatures, leaving the internal electrochemical reaction rate of the battery severely suppressed.

[0004] Secondly, there are external battery heating technologies, such as using heating films or heating wires to preheat the battery modules. Traditional heating devices are mostly uniformly laid out, resulting in uneven temperature distribution inside the module during heating. Battery cells near the heat source are prone to localized overheating, accelerating electrolyte decomposition and SEI film damage, while cells farther from the heat source are insufficiently preheated, leading to decreased battery pack consistency and potential safety hazards. Furthermore, simple external heating consumes a lot of energy and cannot fundamentally improve the ion transport characteristics of the electrolyte at low temperatures.

[0005] In summary, existing technologies all have significant limitations and cannot achieve efficient and safe operation of energy storage batteries in extreme low-temperature environments. Therefore, there is an urgent need for a technical solution that can synergistically optimize the intrinsic properties of the electrolyte and the temperature field distribution of the module. This solution should fundamentally address the performance degradation problem of energy storage batteries in low-temperature environments through a dual synergistic mechanism of electrolyte system optimization and module-level intelligent temperature control. Summary of the Invention

[0006] The purpose of this invention is to provide a composite regulation method and apparatus for improving the low-temperature performance of energy storage batteries, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A composite regulation method for improving the low-temperature performance of energy storage batteries includes the following steps: S1 constructs an antifreeze electrolyte system, which includes lithium or sodium salt, a base solvent and functional additives. The additives include antifreeze agents for lowering the freezing point, film-forming additives for forming a solid electrolyte interface film, and nanoparticles for adjusting viscosity. S2 constructs a layered heating-insulation-heat dissipation integrated module, which includes at least a bottom heating zone, a middle insulation zone, and a top temperature control zone. The S3 monitors the temperature of individual battery cells in real time through a temperature acquisition module, and the main control chip controls the bottom heating zone, the middle insulation zone, and the top temperature control zone to work together according to a preset temperature threshold to achieve uniform and stable temperature within the module.

[0009] Furthermore, in step S1 above, the lithium salt is lithium hexafluorophosphate with a concentration of 1.0 to 1.2 mol / L; the base solvent is a mixed solvent of ethylene carbonate and chain carbonate with a volume ratio of 3:7 to 4:6.

[0010] Furthermore, in step S1 above, the functional additives include: ethylene glycol dimethyl ether as an antifreeze agent, with a mass fraction of 3% to 8%; fluoroethylene carbonate as a film-forming additive, with a mass fraction of 1% to 2%; and nano-silica as a viscosity modifier, with a mass fraction of 0.5% to 1%.

[0011] Furthermore, the S2 step specifically includes: attaching a highly thermally conductive flexible graphene heating film to the bottom heating zone to provide heat; wrapping the sides of the battery cell with a phase change material in the middle insulation zone, wherein the phase change material is a paraffin-based or fatty acid ester with a temperature between 12°C and 15°C, for thermal buffering; integrating a temperature sensor and a microchannel heat dissipation structure in the top temperature control zone for real-time temperature acquisition and high-temperature heat dissipation; and filling the space between each functional layer and the battery cell with a highly thermally conductive silicone pad to reduce contact thermal resistance.

[0012] Furthermore, in step S3 above, the heating power of the bottom heating zone is dynamically adjusted based on the deviation between the target temperature and the average temperature using a PID control algorithm.

[0013] Furthermore, in step S3 above, the main control chip performs multi-mode switching according to preset thresholds: when the temperature of any battery cell is lower than the start-up threshold of 0°C or -5°C, the bottom heating zone is activated for preheating; when the battery temperature is within the insulation threshold range of 5°C to 10°C, the phase change material in the middle insulation zone is used for insulation; when the temperature of any battery cell exceeds the heat dissipation threshold of 25°C, the microchannel heat dissipation structure in the top temperature control zone is activated for heat dissipation.

[0014] Furthermore, in step S3 above, closed-loop control is used to keep the temperature deviation between individual cells in the module within 2°C.

[0015] An apparatus for a composite control method includes: an antifreeze electrolyte system filled inside a battery cell; a layered heating-insulation-heat dissipation integrated module covering the outside of the battery cell, wherein the module comprises, from bottom to top, a bottom heating zone, a middle insulation zone, and a top temperature control zone; and an intelligent temperature control system including a temperature acquisition module, a main control chip, and a power regulation module, wherein the temperature acquisition module is located in the top temperature control zone and connected to the main control chip, and the main control chip is connected to the bottom heating zone through the power regulation module.

[0016] Furthermore, the aforementioned bottom heating zone uses a graphene heating film with a power density of 5 to 8 W / dm²; the aforementioned middle insulation zone is filled with paraffin-based or fatty acid ester phase change material; the aforementioned top temperature control zone is provided with a microchannel heat dissipation plate, the aforementioned microchannel heat dissipation plate is provided with microchannels, the aforementioned microchannels have a diameter range of 2 to 2.5 mm, and a spacing range of 10 to 12 mm.

[0017] Furthermore, the temperature acquisition module mentioned above is an NTC thermistor, which acquires the temperature of each battery cell in real time at a frequency of 1 to 10 Hz.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves high-performance operation of energy storage batteries in extreme low-temperature environments through the dual synergistic regulation of an antifreeze electrolyte system and an intelligent temperature control module. In the antifreeze electrolyte system, ethylene glycol dimethyl ether acts as an antifreeze agent, lowering the electrolyte's freezing point to below -40°C. Nano-silica acts as a viscosity modifier, effectively improving low-temperature ionic conductivity, maintaining the electrolyte's ionic conductivity at -30°C at over 60% of that at room temperature. Combined with the active preheating of the layered heating module, the battery's discharge capacity retention rate in extreme low-temperature environments (-40°C) reaches over 78% for sodium-ion batteries and over 82% for lithium-ion batteries, significantly superior to single modification schemes.

[0019] 2. This invention employs a three-layer functional structure: bottom heating, middle insulation, and top heat dissipation. Combined with high thermal conductivity silicone pads and phase change materials, it achieves precise temperature control within the module. The bottom graphene heating film provides a uniform heat source, the middle phase change material provides thermal buffering through latent heat storage, and the top microchannel heat dissipation structure efficiently removes excess heat. With the assistance of a PID closed-loop control algorithm, the temperature deviation between individual cells within the module can be controlled within 2°C, completely solving the problems of localized overheating and uneven preheating caused by traditional heating methods.

[0020] 3. This invention effectively suppresses side reactions at low temperatures through dual regulation. Fluoroethylene carbonate, as a film-forming additive, forms a dense and stable SEI film on the negative electrode surface. This SEI film remains stable at low temperatures, effectively inhibiting the continuous decomposition of the electrolyte. Simultaneously, precise temperature control avoids SEI film damage and electrolyte decomposition caused by localized overheating. This allows the battery to maintain a high capacity retention rate after 200 deep charge-discharge cycles at -20°C, significantly extending the battery's service life at low temperatures.

[0021] 4. The composite regulation device and method described above are not only applicable to lithium-ion battery systems, but can also be perfectly adapted to sodium-ion battery systems by adjusting the lithium salt to sodium salt and optimizing the ratio. Furthermore, this technical solution can be extended to other electrochemical energy storage systems such as solid-state batteries and potassium-ion batteries, and has extremely broad market prospects in low-temperature application scenarios such as grid energy storage in high-altitude and cold regions, on-board energy storage for new energy vehicles, portable outdoor energy storage power supplies, aerospace, and polar scientific research.

[0022] 5. This invention is not a simple combination of electrolyte modification and thermal management, but rather a synergistic effect achieved through the deep integration of material and structural innovations. The antifreeze electrolyte solves the intrinsic problem of ion transport at low temperatures, providing a fundamental guarantee for the low-temperature operation of the battery; the intelligent temperature control module solves the problem of temperature field distribution within the battery body, creating suitable environmental conditions for the electrolyte to perform optimally. The synergistic effect of these two components achieves a technical effect greater than the sum of its parts, fundamentally solving the technical challenge of existing technologies that struggle to balance low-temperature performance and temperature uniformity. Attached Figure Description

[0023] Figure 1 This is a flowchart of the intelligent temperature control steps provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the overall structure of the composite control device provided in an embodiment of the present invention. Detailed Implementation

[0024] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The method in this embodiment is executed by a terminal, which can be a mobile phone, computer, PDA, laptop or desktop computer, etc. Of course, it can also be other devices with similar functions, and this embodiment does not limit them.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the following will provide a more detailed description of the composite regulation device and method for improving the low-temperature performance of energy storage batteries, in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Any modifications, substitutions, or combinations made by those skilled in the art based on the embodiments of this invention that do not depart from the spirit and essence of this invention are within the scope of protection of this invention.

[0027] This invention aims to address the problems of decreased electrolyte ionic conductivity, reduced electrode activity, drastically increased internal resistance, and uneven temperature distribution within the module in existing energy storage batteries at low temperatures, especially -10°C and below, through a dual synergistic mechanism of electrolyte system optimization and module-level intelligent temperature control. The core of this invention lies in organically combining material modification techniques for antifreeze electrolytes with physical control methods for layered thermal management modules, and achieving precise control through intelligent algorithms, thereby achieving a technical effect greater than the sum of its parts (1+1>2).

[0028] I. Overall Structure of the Composite Control Device like Figure 2 As shown, the composite control device of the present invention mainly comprises two core components: an antifreeze electrolyte system filled inside the battery cell, and an integrated module covering the outside of the battery cell. This module has a three-layer functional structure arranged closely from bottom to top, as detailed below: The top-level temperature control zone is located on the top layer of the module and integrates a temperature acquisition module and a heat dissipation execution module. The temperature acquisition module uses a surface-mount NTC thermistor, which is attached to the top surface or terminal of the battery cell to collect the battery's temperature data in real time. The heat dissipation execution module is a microchannel heat sink, with densely etched microchannels inside. The microchannel diameter is preferably 2 to 2.5 mm, and the spacing is 10 to 12 mm. The two ends of the microchannels are connected to an inlet pipe and an outlet pipe, respectively, for introducing coolant to remove heat.

[0029] The middle insulation layer surrounds the sides of the battery cell. This layer is filled with phase change material, which is in direct contact with the battery casing. The phase change temperature of the phase change material is set between 10°C and 15°C through material selection. For example, paraffin-based phase change materials or fatty acid ester phase change materials can be selected, utilizing their endothermic melting and exothermic solidification properties near the phase change point to act as a thermal buffer.

[0030] The bottom heating zone is located at the bottom of the battery cell. This layer is bonded with a highly thermally conductive flexible graphene heating film, with a heating power density designed to be 5 to 8 W / dm². To reduce contact thermal resistance, highly thermally conductive silicone pads are coated or placed between the heating film and the bottom of the battery cell, as well as at the junction of the heating film and the middle insulation zone, ensuring that heat can be efficiently and evenly conducted to the battery body.

[0031] The intelligent temperature control system is not a separate physical layer, but rather a control unit integrated outside the module, including a main control chip and a power regulation module. The temperature acquisition module is connected to the input of the main control chip via a signal line, and the output of the main control chip is connected to the pump and valve mechanism of the graphene heating film in the bottom heating zone and the microchannel heat sink in the top temperature control zone via the power regulation module, forming a closed-loop control circuit.

[0032] II. General Preparation Methods and Mechanisms of Antifreeze Electrolyte Systems Before proceeding with specific embodiments, the general preparation mechanism and method of the antifreeze electrolyte system of the present invention will be explained first. This system is applicable to subsequent lithium-ion battery and sodium-ion battery embodiments.

[0033] The low-temperature performance of an electrolyte is mainly determined by its freezing point. ionic conductivity The properties are determined by the interfacial film-forming characteristics. This invention achieves simultaneous optimization of the above-mentioned properties by introducing multiple additives with synergistic effects.

[0034] 1. Basic composition of electrolyte Lithium or sodium salts, such as lithium hexafluorophosphate (LiPF6) or sodium hexafluorophosphate (NaPF6), are used at a concentration controlled between 1.0 and 1.2 mol / L. The basic solvent system is a mixture of ethylene carbonate (EC) and chain carbonates (DMC, EMC, DEC). Because ethylene carbonate has a high dielectric constant but high viscosity, while chain carbonates have low viscosity but low dielectric constant, their mixture achieves complementary properties. In this invention, the volume ratio of ethylene carbonate to chain carbonates is controlled between 3:7 and 4:6.

[0035] 2. Functional additives and their mechanisms of action Dimethyl ethylene glycol ether (DME): As an antifreeze agent, its mass fraction is 3%–8%. Its mechanism of action can be described by the freezing point depression formula.

[0036] in This is the freezing point depression constant. This represents the molar concentration of DME. The addition of DME significantly increases the molar concentration of the solute, lowering the freezing point of the electrolyte system to below -40°C.

[0037] Fluorinated ethylene carbonate (FEC): As a film-forming additive, its mass fraction is 1%–2%. FEC has a lower reduction potential than EC and preferentially reduces on the negative electrode surface during the first charge-discharge process of the battery, forming a dense, thin, and stable LiF-rich solid electrolyte interphase (SEI) film. This SEI film effectively inhibits the continuous decomposition of the electrolyte on the negative electrode surface and also has good lithium-ion / sodium-ion conductivity. Its film-forming reaction can be simplified as follows:

[0038] Nano-silica (SiO2): Used as a viscosity modifier and structural stabilizer, with a mass fraction of 0.5%–1%. Nano-SiO2 particles have a large specific surface area and can adsorb free PF6 in the electrolyte. - The presence of anions promotes the migration of lithium / sodium ions, thereby increasing ionic conductivity. Its mechanism can be approximated by Walden's rule:

[0039] By adjusting the microstructure of the electrolyte using nano-SiO2, the local viscosity can be reduced. This indirectly improves ionic conductivity. .

[0040] With the above ratio, the ionic conductivity of this electrolyte system can still be maintained at more than 60% of that at room temperature (25℃) at -30℃, which is significantly better than that of traditional electrolytes.

[0041] III. Thermal Management Mechanism of Layered Modules The thermal management mechanism of the layered heating-insulation-heat dissipation integrated module in this invention can be described by the following thermodynamic formula: 1. Top-level heat dissipation mechanism The top-level temperature control zone employs a microchannel heat dissipation structure, where the coolant flows and carries away heat, resulting in a significant heat dissipation capacity. It can be estimated as follows:

[0042] in The convective heat transfer coefficient is... For heat dissipation area, This refers to the temperature difference between the heat dissipation surface and the coolant.

[0043] 2. Middle layer insulation mechanism The middle insulation layer uses phase change materials for latent heat energy storage. for:

[0044] in For the quality of phase change materials, This is the latent heat of phase change per unit mass. When the battery temperature is higher than the phase change temperature... When the temperature is below a certain point, the phase change material absorbs heat and melts; when the temperature is below a certain point... When the phase change material solidifies, it releases heat, thus acting as a "thermal buffer".

[0045] 3. Bottom Heating Mechanism The bottom heating zone uses a graphene heating film, which has a heating capacity of for:

[0046] in For power density, For heating area, This refers to the heating time.

[0047] IV. Control Algorithm of Intelligent Temperature Control System This invention employs a PID control algorithm to dynamically adjust the heating power, ensuring that the temperature deviation of each individual unit within the module is controlled within 2℃. The expression for the PID control algorithm is:

[0048] in , For the target operating temperature, This is the real-time average temperature. , , These are the PID control parameters.

[0049] V. Examples The following provides two detailed implementation cases based on specific application scenarios of lithium-ion batteries and sodium-ion batteries.

[0050] Example 1: Application of lithium-ion energy storage batteries Step 1: Preparation of the antifreeze electrolyte system For lithium-ion energy storage batteries, an electrolyte solution was prepared. The specific procedure was as follows: In a glove box filled with argon atmosphere (water and oxygen content both below 0.1 ppm), 1.1 mol of lithium hexafluorophosphate (LiPF6) was slowly added to a mixed solvent consisting of 350 mL of ethylene carbonate (EC) and 650 mL of dimethyl carbonate (DMC), and stirred on a magnetic stirrer until completely dissolved. Then, 50 g of dimethyl glycol ether (DME, approximately 5% by mass), 15 g of fluoroethylene carbonate (FEC, approximately 1.5% by mass), and 10 g of nano-silica (SiO2, approximately 1% by mass) were weighed and added to the above solution. Stirring continued for 4 hours until all additives were completely dissolved and the mixture was homogeneous. After standing for 12 hours to remove bubbles, the target antifreeze electrolyte was obtained.

[0051] Calculated based on the freezing point depression formula ; Adding DME can lower the freezing point of the electrolyte to below -42°C, meeting the requirements for low-temperature use.

[0052] Step 2: Construction of the layered heating-insulation-heat dissipation integrated module Selecting a square aluminum-cased lithium iron phosphate battery cell with a nominal capacity of 100Ah, constructing as follows Figure 2 The module structure shown.

[0053] During the assembly of the bottom heating zone, a highly thermally conductive flexible graphene heating film with a size approximately equal to the area of ​​the bottom of the battery is cut, and its heating power density is set to 6W / dm². According to the heating capacity formula... ; With a heating area of ​​0.01m², heating for 30 seconds can generate approximately 180J of heat, which is sufficient to raise the temperature at the bottom of the battery by more than 5°C.

[0054] During the assembly of the middle insulation layer, a paraffin-based phase change material with a phase change temperature set at 12℃ is encapsulated within a pre-formed insulating shell. The battery cells are then embedded within this shell, ensuring that all four sides of the battery are completely encased in the phase change material. The latent heat of phase change L of the selected phase change material is 180 J / g. According to the latent heat storage formula... When 100g of phase change material is used, it can store 18000J of heat, which can effectively absorb the pulse heat generated by battery charging and discharging.

[0055] During the assembly of the top-level temperature control area, an NTC thermistor is attached to the top cover of the battery cell using thermally conductive adhesive. Next to the thermistor, a microchannel heat sink is installed, with microchannels 2mm in diameter and spaced 10mm apart, ensuring a tight fit between the heat sink and the battery top cover. According to the heat dissipation formula...

[0056] When the convective heat transfer coefficient h is 1000W / (m²·K), the heat dissipation area A is 0.005m², and the temperature difference ΔT is 10℃, the heat dissipation can reach 50W, which can effectively control the battery temperature rise.

[0057] When connecting the control unit, connect the signal line of the NTC thermistor to the ADC input pin of the STM32F103 main control chip. Connect the PWM output pin of the main control chip to the power regulation module, and connect the output of the power regulation module to the power supply line of the graphene heating film and the miniature pump relay of the microchannel heat sink, respectively.

[0058] Step 3: Setting and Operating the Intelligent Temperature Control System like Figure 1As shown, the intelligent temperature control system operates according to the following process: System initialization: The main control chip reads preset thresholds: preheating start threshold set to -5℃, heat preservation threshold range set to 5℃ to 10℃, and heat dissipation start threshold set to 28℃. Target operating temperature set to 20℃. PID control parameters... , , Adjusted based on experience.

[0059] During temperature acquisition, the NTC thermistor collects the temperature of each battery cell in real time at a frequency of 10Hz. The current temperature value is obtained after filtering by the main control chip.

[0060] During mode detection and execution, after being left to stand in a -35°C low-temperature environment, the system detected the lowest battery temperature. ,satisfy Upon receiving the required conditions, the system enters preheating mode. The main control chip adjusts the temperature based on the real-time average temperature. Through PID control algorithm

[0061] Calculate the required heating power, where The power regulation module dynamically adjusts the input voltage of the graphene heating film accordingly, enabling the battery to heat up at the optimal rate.

[0062] When the battery temperature rises to 8°C and falls within the 5°C to 10°C insulation threshold range, the system switches to insulation mode. The heating film stops heating, and the phase change material in the middle insulation layer begins to function. The Joule heat generated by battery charging and discharging is absorbed and stored by the phase change material to prevent the battery from overheating; when the battery is left to cool down, the phase change material releases latent heat, delaying battery cooling.

[0063] In high-temperature environments or under high-rate charge / discharge conditions, when the battery's highest temperature... Exceeding the heat dissipation threshold When the system activates its cooling mode, the micro-pumps of the microchannel heat sink start, and coolant flows through the microchannels to carry away heat until the temperature drops back to a safe range.

[0064] Step 4: Performance Test Results The device and battery were placed in a -35°C high and low temperature test chamber for 12 hours, and then subjected to a 1C constant current discharge test. The test results showed: 1. Capacity retention: Compared to the discharge capacity at room temperature of 25℃, the battery retains 82% of its discharge capacity at -35℃.

[0065] 2. Internal resistance change: DC internal resistance (DCR) test showed that the internal resistance at -35℃ increased by about 40% compared with the normal temperature, which was significantly lower than the control group without composite control (internal resistance increased by more than 100%).

[0066] 3. Temperature Uniformity: During preheating and discharging, temperature deviations in different areas inside individual battery cells are monitored by temperature sensors placed at different locations within the module. The temperature was consistently kept below 1.8℃, demonstrating the temperature uniformity of the heating film and the thermal pad.

[0067] 4. Cycle life: After 200 deep charge-discharge cycles at -20℃, the battery retains more than 78% of its capacity, demonstrating excellent low-temperature cycle stability.

[0068] Example 2: Application of sodium-ion energy storage batteries To verify the universality of the technical solution of the present invention, this embodiment uses a sodium-ion battery system for verification.

[0069] Step 1: Preparation of the antifreeze electrolyte system For sodium-ion energy storage batteries, an electrolyte solution was prepared. The specific procedure was as follows: In a glove box filled with argon atmosphere, 1.2 mol of sodium hexafluorophosphate (NaPF6) was slowly added to a mixed solvent consisting of 400 mL of ethylene carbonate (EC) and 600 mL of ethyl methyl carbonate (EMC) (volume ratio 4:6), and stirred until completely dissolved. Then, 30 g of dimethyl ethylene glycol ether (DME, approximately 3% by mass), 20 g of fluoroethylene carbonate (FEC, approximately 2% by mass), and 5 g of nano-silica (SiO2, approximately 0.5% by mass) were weighed and added to the above solution. Stirring continued until completely homogeneous, and after standing to remove bubbles, the target antifreeze electrolyte was obtained.

[0070] According to the freezing point depression formula

[0071] After adding DME, the electrolyte's freezing point drops below -40°C. According to Walden's rule... The addition of nano-SiO2 reduces local viscosity and improves ionic conductivity.

[0072] Step 2: Construction of the layered heating-insulation-heat dissipation integrated module A pouch-type sodium-ion battery with a nominal capacity of 80Ah was selected to construct the module structure. Unlike Example 1, a more flexible silicone pad was used for the thermal pad, taking into account the characteristics of the pouch battery, to ensure good adhesion to the battery surface. The heating power density was set to 5W / dm². The phase change material in the middle insulation layer was a fatty acid ester material with a phase change temperature of 15℃.

[0073] Step 3: Setting parameters for the intelligent temperature control system The parameter settings are as follows: the preheating start threshold is set to 0℃ (considering that sodium-ion batteries are more sensitive to low temperatures, the start threshold is appropriately increased); the heat preservation threshold range is set to 10℃ to 15℃; the heat dissipation start threshold is set to 25℃. The control algorithm also adopts PID closed-loop control, and the PID parameters are retuned according to the thermal characteristics of the sodium-ion battery. , , .

[0074] Step 4: Performance Test Results The device and battery were placed in a high and low temperature test chamber at -40℃ for testing. The test results showed: 1. Capacity retention: The discharge capacity retention rate at -40℃ is 78% of that at room temperature.

[0075] 2. Ionic conductivity: Through sampling and testing of the electrolyte, the ionic conductivity of the electrolyte remains at about 65% of that at room temperature (25℃) at -30℃.

[0076] 3. Temperature control performance: During the low-temperature start-up phase, the battery preheating time from -40℃ to 0℃ is reduced by 70% compared to the unheated module. In subsequent charge and discharge cycles, the internal temperature difference of the module remains stable within 2℃.

[0077] VI. Comparative Example To highlight the inventiveness of this invention, the following comparative examples are provided.

[0078] Comparative Example 1 (Single Electrolyte Modification) Referring to existing technologies (such as prior art CN118825418A), only an improved low-temperature electrolyte was used, but a layered intelligent temperature control module was not employed. Lithium-ion batteries simply filled with the antifreeze electrolyte from Example 1 were tested at -35°C. The results showed that although the battery could barely start, due to the extremely low battery temperature, the initial discharge voltage plateau was significantly low, and the capacity dropped sharply in the early stages of discharge. The capacity retention rate throughout the discharge process was only 65%, far lower than the 82% in Example 1. This indicates that electrolyte modification alone cannot solve the problem of the battery's "cold penetration" at extreme low temperatures, and the internal electrochemical reaction rate of the battery remains severely suppressed.

[0079] Comparative Example 2 (Single External Heating) Referring to existing technologies, only a traditional bottom heating film is used to heat the battery, but conventional electrolytes are used instead of the antifreeze electrolyte system and intelligent temperature control strategy of this invention. The battery was placed in a -35°C environment, and the heating film was turned on for preheating. The results showed that, due to the lack of buffering and temperature equalization by phase change materials, the temperature near the bottom of the heating film rose rapidly, while the top of the battery and the terminal sections remained at low temperatures, resulting in a temperature difference of over 8°C within the module. Localized overheating accelerated electrolyte decomposition and SEI film damage, while the low-temperature areas exhibited huge internal resistance, ultimately leading to deterioration of battery consistency and a significant decrease in cycle performance.

[0080] in conclusion: As can be seen from Comparative Examples 1 and 2, neither simple electrolyte modification nor simple physical heating can fully solve the low-temperature problem of energy storage batteries. However, this invention achieves a "1+1>2" technical effect by synergistically optimizing the electrolyte system materials and regulating the physical control of module-level thermal management, significantly improving the overall performance of the battery in extreme low-temperature environments, and demonstrating significant progress and outstanding substantive features.

[0081] VII. Industrial Applications The composite regulation device and method described in this invention are not only applicable to lithium-ion and sodium-ion batteries, but can also be extended to other electrochemical energy storage systems such as solid-state batteries and potassium-ion batteries. It has extremely broad market prospects and application value in low-temperature application scenarios such as grid energy storage in high-altitude and cold regions, on-board energy storage for new energy vehicles, portable outdoor energy storage power supplies, aerospace, and polar scientific research.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0084] Those skilled in the art will recognize that the modules and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0085] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the described apparatus, equipment, and modules can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0086] Furthermore, it should be noted that the combination of the various technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0087] It should be noted that the above examples are merely specific embodiments of the present invention, and the present invention is obviously not limited to the above embodiments, with many similar variations. All modifications that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should fall within the protection scope of this invention.

[0088] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite control method for improving the low-temperature performance of energy storage batteries, characterized in that, Includes the following steps: S1 constructs an antifreeze electrolyte system, the electrolyte system comprising lithium salt or sodium salt, a basic solvent and functional additives, the additives including an antifreeze agent for lowering the freezing point, a film-forming additive for forming a solid electrolyte interface film and nanoparticles for adjusting viscosity. S2 constructs a layered heating-insulation-heat dissipation integrated module, the module including at least a bottom heating zone, a middle insulation zone and a top temperature control zone; S3 monitors the temperature of individual battery cells in real time through a temperature acquisition module, and the main control chip controls the bottom heating zone, the middle insulation zone, and the top temperature control zone to work together according to a preset temperature threshold to achieve uniform and stable temperature within the module.

2. The composite regulation method according to claim 1, characterized in that, In step S1, the lithium salt is lithium hexafluorophosphate with a concentration of 1.0 to 1.2 mol / L; the base solvent is a mixed solvent of ethylene carbonate and chain carbonate with a volume ratio of 3:7 to 4:

6.

3. The composite regulation method according to claim 1, characterized in that... In step S1, the functional additives include: ethylene glycol dimethyl ether as an antifreeze agent, with a mass fraction of 3% to 8%; fluoroethylene carbonate as a film-forming additive, with a mass fraction of 1% to 2%; and nano-silica as a viscosity modifier, with a mass fraction of 0.5% to 1%.

4. The composite regulation method according to claim 1, characterized in that, The S2 step specifically includes: attaching a highly thermally conductive flexible graphene heating film to the bottom heating zone to provide heat; wrapping the sides of the battery cell with a phase change material in the middle insulation zone, wherein the phase change material is a paraffin-based or fatty acid ester with a temperature between 12°C and 15°C, for thermal buffering; integrating a temperature sensor and a microchannel heat dissipation structure in the top temperature control zone for real-time temperature acquisition and high-temperature heat dissipation; and filling the space between each functional layer and the battery cell with a highly thermally conductive silicone pad to reduce contact thermal resistance.

5. The composite regulation method according to claim 1, characterized in that, In step S3, the heating power of the bottom heating zone is dynamically adjusted based on the deviation between the target temperature and the average temperature using a PID control algorithm.

6. The composite regulation method according to claim 1 or 5, characterized in that, In step S3, the main control chip performs multi-mode switching according to a preset threshold: when the temperature of any battery cell is lower than the start-up threshold, the bottom heating zone is activated for preheating, and the start-up threshold can be set to 0℃ or -5℃; when the battery temperature is in the heat preservation threshold range of 5℃ to 10℃, the phase change material of the middle heat preservation zone is used for heat preservation; when the temperature of any battery cell exceeds the heat dissipation threshold of 25℃, the microchannel heat dissipation structure of the top temperature control zone is activated for heat dissipation.

7. The composite regulation method according to claim 6, characterized in that, In step S3, closed-loop control is used to keep the temperature deviation between individual cells in the module within 2°C.

8. An apparatus for implementing the composite control method as described in any one of claims 1 to 7, characterized in that, include: An antifreeze electrolyte system is filled inside the battery cell; A layered heating-insulation-heat dissipation integrated module is wrapped around the outside of the battery cell. The module includes, from bottom to top, a bottom heating zone, a middle insulation zone, and a top temperature control zone. The intelligent temperature control system includes a temperature acquisition module, a main control chip, and a power regulation module. The temperature acquisition module is located in the top temperature control zone and connected to the main control chip. The main control chip is connected to the bottom heating zone through the power regulation module.

9. The apparatus according to claim 8, characterized in that, The bottom heating zone uses a graphene heating film with a power density of 5 to 8 W / dm²; the middle insulation zone is filled with paraffin-based or fatty acid ester phase change material; the top temperature control zone is equipped with a microchannel heat dissipation plate, which contains microchannels with a diameter of 2 to 2.5 mm and a spacing of 10 to 12 mm.

10. The apparatus according to claim 8, characterized in that, The temperature acquisition module is an NTC thermistor that acquires the temperature of each battery cell in real time at a frequency of 1 to 10 Hz.

Images