Stepwise temperature rising system and control method for heating lithium batteries in low temperature environment

Abstract

The present invention discloses a stepped temperature rising system and a control method for heating a lithium battery in a low temperature environment, belonging to the technical field of lithium ion battery processing. The system includes an exothermic reaction box, a bracket, a battery box and a control terminal; the exothermic reaction box is arranged at the bottom of the bracket, and a hot gas outlet is arranged at the top thereof; a gas guiding channel in close connection with the hot gas outlet is arranged in the middle of the bracket; the battery box is arranged at the top of the bracket, a preheating chamber located at the center and two heating chambers located at the sides are arranged inside the battery box, a heat transfer channel in close connection with the gas guiding channel is arranged in the middle of the preheating chamber, a preheating chamber battery is arranged in the preheating chamber, a heating chamber battery is arranged in the heating chamber, and first and second phase change materials are respectively filled in the preheating chamber and the heating chamber. The application adopts a stepped heating method to gradually increase the temperature of the lithium battery, ensures that the battery pack can supply power normally in a low temperature environment, does not consume the power of the battery pack itself during heat supply, significantly reduces the loss of the battery pack, and is beneficial to prolonging the service life of the lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery processing, and particularly relates to a stepwise temperature-rising system and a control method for heating a lithium battery in a low-temperature environment. Background Art

[0002] As an electrochemical energy storage element with high energy density, fast response speed, and long cycle life, lithium-ion batteries have been widely used in fields such as electric vehicles, large-scale energy storage, and mobile electronic devices in recent years. The suitable temperature range for lithium-ion batteries during operation is approximately 0 - 45°C. If the battery is charged and discharged in a low-temperature environment below 0°C, the ionic conductivity and diffusion rate of the battery will both decrease, which will slow down the electrochemical reaction rate inside the battery, increase the risk of lithium plating on the negative electrode, cause rapid attenuation of the battery capacity, and even cause short circuits between the positive and negative electrodes in extreme cases, threatening the cycle life and safety performance of the battery.

[0003] In order to avoid the negative problems caused by the low-temperature environment to the battery operation, corresponding heating devices are equipped in existing large-scale energy storage devices such as electric vehicles and energy storage containers. However, the existing lithium-ion battery heating devices generally have problems such as high energy consumption and low heating efficiency. In addition, for small battery modules such as mobile electronic devices, under the constraint of limited cost, it is still necessary to rely on the DC discharge method for heating. This heating method will cause a large energy storage loss in the overall battery module and there are problems of voltage and temperature inconsistency at the battery module scale. Therefore, how to quickly increase the temperature of lithium-ion batteries in a low-temperature environment has become one of the key problems urgently needed to be solved in the industry.

[0004] Developing low-temperature lithium-ion batteries or increasing the temperature of the surrounding environment of lithium-ion batteries are two relatively common and effective methods to help lithium batteries work properly in a low-temperature environment.

[0005] Although low-temperature lithium-ion batteries have good application prospects in a low-temperature environment, in terms of the current research and development status, it is difficult for low-temperature lithium-ion batteries to break through technical bottlenecks, and their research and development costs and application costs are relatively high, and the economy is not strong.

[0006] Methods for increasing the ambient temperature around lithium-ion batteries mainly include liquid conduction heating, electrothermal film heating, high-temperature air heating, etc. Although liquid conduction heating has good heating effects, since liquids are conductive, there is a certain risk of leakage in lithium-ion batteries that use liquid conduction heating to help the system warm up, and the reliability and safety of the system are greatly reduced. Although the electrothermal film heating method has the advantages of simple structure, high efficiency, good versatility, and convenient assembly, electrothermal film heating consumes the energy of the battery pack. When the lithium-ion battery is heated, it needs to discharge itself, which seriously affects the power consumption of the lithium-ion battery system and has high energy consumption. The high-temperature air heating method has the advantages of simple operation and high efficiency. Compared with the above two heating methods, the high-temperature air heating method can not only avoid the risk of lithium battery leakage caused by liquid overflow, but also does not consume the energy of the battery pack, greatly improving the usage time of the battery pack.

[0007] However, there are also certain problems in using the high-temperature air heating method to integrally heat the battery module. When the battery box is integrally heated, due to the large heating space, a large amount of energy is often required to generate sufficient heat. And to facilitate the smooth delivery of high-temperature air, complex transportation pipelines usually need to be equipped in the battery box and fixedly connected to external heat generation devices, which significantly limits the position of the battery pack and makes it difficult to move flexibly. Moreover, relying solely on the heat conduction of the continuously introduced high-temperature air to heat the battery, the heat uniformity of the battery is not high. When discharging under different temperatures at different parts of the battery, it will exacerbate the imbalance of the battery, which will have an adverse impact on its capacity, life, self-discharge energy, battery performance differences, etc., and is not conducive to the long-term stable operation of the battery module. For example, a lithium battery heating device for convenient replacement of lithium batteries disclosed in Chinese Patent CN216563317 U has heating sheets laid on the inner walls on both sides of the battery compartment, an air inlet compartment is provided at one end of the battery box, an electric heating wire is provided in the air cavity inside the air compartment, and a blower is provided at one end of the air cavity. The electric heating wire is used to heat the air passing through the air cavity, and the lithium battery is pre-heated by the hot air. After pre-heating, the heating sheets laid on the inner walls on both sides of the battery compartment are started to raise the temperature of the lithium battery. This device combines the electrothermal film heating method and the high-temperature air heating method to heat the lithium battery in a low-temperature environment. However, the scheme of pre-heating by passing hot air on one side will cause the temperature of the battery near the air cavity to rise quickly while the temperature of the battery on the other side rises slowly, and there are obvious differences in the temperature between single batteries, which is not conducive to the normal operation of the battery in the later stage, and the disadvantages inherent in the electrothermal film heating method cannot be avoided.

[0008] Therefore, in view of the problems existing in the high-temperature air heating method, further improvement and enhancement are still needed, with the expectation of maximizing energy conservation while uniformly and stably increasing the ambient temperature of lithium-ion batteries, and enhancing the effectiveness and economy of the working process. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of high energy consumption for heating lithium batteries and high energy storage loss rate in the prior art at low temperatures, and to provide a stepped temperature-rising system and control method for heating lithium batteries in a low-temperature environment.

[0010] The present invention is implemented as follows: A stepped temperature-rising system for heating lithium batteries in a low-temperature environment includes an exothermic reaction box, a bracket, a battery box, and a control terminal; the exothermic reaction box is provided at the bottom of the bracket, and a hot air outlet is provided at its top; a gas guide channel is provided in the middle of the shelf board of the bracket, and the bottom surface of the gas guide channel is hermetically connected to the hot air outlet; the battery box is provided at the top of the bracket, and the interior of the battery box is divided into three chambers, namely a preheating chamber in the center and heating chambers on both sides. A heat transfer channel is provided in the middle of the preheating chamber, the bottom of the heat transfer channel is hermetically connected to the top of the gas guide channel, and the top is hermetically connected to the bottom surface of the cover plate. A preheating chamber battery is provided in the preheating chamber, and a heating chamber battery is provided in the heating chamber. The batteries in a single chamber are connected in series, and after a wire connection port is led out at the end, they are connected in parallel to the control terminal; a first phase change material is poured into the preheating chamber, and a second phase change material is poured into the heating chamber.

[0011] Furthermore, the thermal melting point of the first phase change material is lower than that of the second phase change material.

[0012] Furthermore, the heat transfer channel is made of a material with high thermal conductivity, and a pressure relief valve is provided at the top of the heat transfer channel.

[0013] Furthermore, the preheating chamber batteries are evenly distributed circumferentially around the heat transfer channel, and the heating chamber batteries are arranged in an array in the heating chamber; a first temperature sensor is provided in the preheating chamber, and a second temperature sensor is provided in each of the two heating chambers. The three temperature sensors are respectively in contact with the surface of a battery in the corresponding chamber, and the first and second temperature sensors are electrically connected to the control terminal.

[0014] Furthermore, heat conducting fins are provided in both the preheating chamber and the heating chamber.

[0015] Furthermore, a feeding port is provided on the side wall of the exothermic reaction box, and a slag discharge port is provided at the bottom. The feeding port is provided at the upper part of the side wall of the exothermic reaction box, and a movable baffle is provided at the feeding port. The slag discharge port is sealed with a sealing cover, and a fuel pack that can release heat based on a chemical reaction is placed in the exothermic reaction box.

[0016] Furthermore, a collapsible support leg is provided at each of the four corner positions at the bottom of the shelf board of the bracket, and a right-angle support is provided at each of the four corner positions at the top of the shelf board. The space formed by enclosing the right-angle supports is adapted to the external shape of the box body, and the battery box is snap-connected between the right-angle supports above the bracket.

[0017] Furthermore, a connecting plate is provided below the shelf board of the bracket. Sliding grooves extending along its length direction are provided on both sides of the connecting plate. A slider extending along its length direction is provided at each of the two side positions at the top of the exothermic reaction box. The shape of the slider is adapted to that of the sliding groove. The slider is connected to the sliding groove on the corresponding side of the connecting plate and can slide along it.

[0018] The control method of the above stepwise temperature rise system is as follows:

[0019] 1) Put the fuel pack and water into the exothermic reaction box from the feeding port. A large amount of hot gas generated by the chemical reaction is transmitted out from the hot gas outlet, and the hot gas flows into the heat transfer channel.

[0020] 2) The heat of the high-temperature gas in the heat transfer channel is transferred to the first phase change material in the preheating chamber through heat conduction. The temperature of the first phase change material rises, and the ambient temperature around the battery in the preheating chamber rises accordingly. When the first temperature sensor monitors that the temperature of the battery in the preheating chamber is higher than 20°C, stop the feeding of the fuel pack, the exothermic reaction ends, and the preheating chamber battery is enabled by the control terminal, and the preheating chamber battery independently conducts the power supply work.

[0021] 3) The waste heat in the preheating chamber and the heat generated by the normal operation of the preheating chamber battery diffuse outward and are transferred to the second phase change material in the heating chamber. The temperature of the second phase change material rises, and the ambient temperature around the battery in the heating chamber rises accordingly.

[0022] 4) When the second temperature sensor monitors that the temperature of the battery in the heating chamber is higher than 20°C, the heating chamber battery is independently enabled by the control terminal, and the heating chamber battery starts to conduct the power supply work, and the entire battery box is in a full-load working state.

[0023] Furthermore, in step 1), when the pressure in the heat transfer channel exceeds the set pressure of the pressure relief valve, the pressure relief valve is triggered, and the excess hot gas is discharged from the pressure relief valve so that the pressure in the heat transfer channel is restored below the set pressure.

[0024] Beneficial effects:

[0025] 1. The stepwise temperature rise system disclosed in this application uses the heat conduction of hot air to heat the lithium battery in a low-temperature environment before startup, effectively solving the problem that the lithium-ion battery cannot work properly or has low working efficiency due to too low ambient temperature; moreover, the heat generated by the fuel pack does not need to be used to raise the temperature of the entire battery box. It only needs to ensure that the batteries in the preheating chamber reach the corresponding temperature requirements. The batteries in the heating chamber under low-temperature conditions mainly use the waste heat of the preheating chamber and the heat generated during the operation of the batteries in the preheating chamber to achieve the purpose of temperature rise in the later stage. Therefore, there is no need for an external heat source to directly participate in the energy supply of the heating chamber. This stepwise temperature rise working mode reduces the overall heating demand, significantly saves the amount of fuel required for reaction heat generation, and achieves the effect of energy conservation;

[0026] 2. This application mainly uses the phase change materials and heat conduction fins filled in different chambers to achieve the purpose of heat conduction and temperature rise. Therefore, the uniformity of the heat conduction process can be improved, ensuring that there is no large temperature difference between different single batteries in a single chamber, reducing the adverse impact of the temperature gradient on the battery life, and helping to improve the service life of the battery;

[0027] 3. The stepwise temperature rise system for heating lithium batteries in a low-temperature environment disclosed in this application divides the battery box into three independently working chambers. The single batteries in the preheating chamber or the heating chamber are respectively connected in parallel to the control terminal after being connected in series, that is, the batteries in the three chambers can independently supply power at full load in units of chambers. Furthermore, the heat generated after the preheating chamber batteries are started in advance can be used to supply heat to the heating chamber batteries, reducing energy supply and achieving the purpose of energy conservation;

[0028] 4. The temperature rise system disclosed in this application only relies on the heat generated by the chemical reaction of the fuel pack to provide heat source for the preheating chamber batteries, without the participation of an external heating power supply for heat supply. It belongs to a power-free heating method, greatly expanding the application scenarios of the battery; and the working process does not consume the energy of the battery pack itself, reducing battery loss and effectively extending the service time of the battery pack;

[0029] 5. The structure of the temperature rise system disclosed in this application is simple and not fixedly connected to external large-scale heating equipment. Therefore, it is convenient to move the position of the battery box, improving the flexibility of use;

[0030] 6. A pressure relief valve is provided in the heat transfer channel disclosed in this application. When the pressure in the channel reaches the set pressure of the pressure relief valve, the pressure relief valve will automatically open to relieve pressure, ensuring that the gas pressure in the heat transfer channel is within a safe range and improving the safety during the use of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 An isometric view of the stepwise temperature rise system for heating lithium batteries in a low-temperature environment;

[0032] Figure 2 An isometric view of one angle of the exothermic reaction box;

[0033] Figure 3 An isometric view of another angle of the exothermic reaction box;

[0034] Figure 4 An isometric view of the bracket;

[0035] Figure 5 An isometric view of the battery box after removing the top cover plate;

[0036] Figure 6 An isometric view of the battery box body;

[0037] Wherein, 1 - exothermic reaction box, 2 - bracket, 3 - battery box, 4 - control terminal;

[0038] 11 - feeding port, 12 - slag discharge port, 13 - hot gas outlet, 14 - slider;

[0039] 21 - support leg, 22 - air guiding channel, 23 - right-angle support, 24 - connecting plate, 25 - sliding groove;

[0040] 31 - box body, 32 - preheating chamber, 33 - heating chamber, 34 - heat transfer channel, 35 - preheating chamber battery, 36 - heating chamber battery, 37 - pressure relief valve, 38 - heat conducting fin. Detailed implementation manners

[0041] The preferred embodiments of the present invention are elaborated in detail below, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0042] Embodiment 1. A stepped temperature rising system for heating lithium batteries in a low-temperature environment

[0043] In order to solve the problem that lithium-ion batteries are difficult to operate efficiently in a low-temperature environment, a stepped temperature rising system for heating lithium batteries is provided in this embodiment, including an exothermic reaction box 1, a bracket 2, a battery box 3 and a control terminal 4. The control terminal 4 is mainly used to connect with the electrical components in the system for end control.

[0044] The exothermic reaction box 1 is arranged at the bottom of the bracket 2. A feeding port 11 is arranged on the side wall of the exothermic reaction box 1, a slag discharge port 12 is arranged at the bottom, and a hot gas outlet 13 is arranged at the top. An activity baffle is arranged at the feeding port 11, and the slag discharge port 12 is sealed by a sealing cover. After the operation is completed, the sealing cover can be opened to take out the fuel residue in the exothermic reaction box from the slag discharge port 12.

[0045] Inside the exothermic reaction box 1, a self-heating fuel pack is to be put in. Such fuel packs are made of existing materials, and their main components are calcium oxide, aluminum particles, and sodium bicarbonate. After putting the fuel pack into the box and injecting water, calcium oxide will first react with water to release heat and form calcium hydroxide. Then, calcium hydroxide reacts with sodium bicarbonate to form calcium carbonate and sodium hydroxide. Finally, sodium hydroxide and aluminum particles react violently to generate a large amount of hot gas, which includes two violent exothermic reactions to release enough heat.

[0046] To prevent hot gas from splashing rapidly and injuring the operator during the feeding process, in this embodiment, the feeding port 11 is selected to be located at the upper part of the side wall of the exothermic reaction box 1.

[0047] At the four corner positions of the bottom of the shelf board of the bracket 2, there is a support leg 21 respectively. In the middle of the shelf board, there is a longitudinally penetrating air guide channel 22. The bottom surface of the air guide channel 22 is closely connected to the hot gas outlet 13, so that the high-temperature gas flowing out of the exothermic reaction box 1 can be directly conducted into the air guide channel 22 without overflowing from the interface.

[0048] To facilitate the connection of the battery box 3, at the four corner positions of the top of the shelf board, there is a right-angle support 23 respectively.

[0049] The support leg 21 is a foldable structure, which is convenient to fold up the support leg 21 during the process of moving the battery box 3 to reduce the space occupied by the system and improve the convenience during transportation.

[0050] To facilitate the loading and unloading of the exothermic reaction box 1 from the bracket 2, the exothermic reaction box 1 is detachably and movably connected to the bottom of the bracket 2. Specifically, a connecting plate 24 is provided below the shelf board. On both sides of the connecting plate 24, there are sliding grooves 25 extending along its length direction. At the two side positions of the top of the exothermic reaction box 1, there is a sliding block 14 extending along its length direction respectively. The shape of the sliding block 14 is adapted to that of the sliding groove 25. The sliding block 14 is connected to the sliding groove 25 on the corresponding side of the connecting plate 24 and can slide along it.

[0051] The battery box 3 is snap-connected between the right-angle supports 23 at the top of the bracket 2. The space formed by the surrounding of the right-angle supports 23 is adapted to the external shape of the box body 31, so that the battery box 3 can be stably snap-connected above the bracket 2.

[0052] The battery box 3 includes a box body 31 and a top cover plate. Inside the box body 31, three chambers are evenly separated by partition plates, namely a preheating chamber 32 located in the center and heating chambers 33 located on both sides. In the middle of the preheating chamber 32, there is a cylindrical heat transfer channel 34. The bottom of the heat transfer channel 34 penetrates the bottom surface of the box body 31 and is closely connected to the bottom surface of the cover plate at the top. The hot air flowing into the heat transfer channel 34 will not directly pour into the preheating chamber 32. The shape of the heat transfer channel 34 is adapted to the shape of the air guide channel 22. The bottom of the heat transfer channel 34 is closely connected to the top of the air guide channel 22. Thus, the hot air can smoothly flow out from the hot air outlet 13 on the exothermic reaction box 1, then flow into the heat transfer channel 34 through the air guide channel 22, and can preheat the preheating chamber 32 through heat conduction. In the preheating chamber 32 and around the heat transfer channel 34, several preheating chamber batteries 35 are evenly distributed. In the heating chambers 33, several heating chamber batteries 36 are arranged in an array. The batteries in a single chamber are connected in series, and after leading out a wire connection port at the end, they are then connected in parallel to the control terminal. This connection method enables the lithium batteries in the preheating chamber 32 and the heating chambers 33 to work independently without affecting each other. The preheating chamber batteries 35 can be started alone first, and then the heating chamber batteries 36 can be started. In the preheating chamber 32, a first phase change material is filled, and in the heating chambers 33, a second phase change material is filled. The thermal melting point of the first phase change material is lower than that of the second phase change material. Preferably, the thermal melting point of the first phase change material is 25°C, and the thermal melting point of the second phase change material is 35°C.

[0053] The heat transfer channel 34 is made of a material with good thermal conductivity. Preferably, a copper sheet can be selected to make the heat transfer channel 34.

[0054] To prevent the gas pressure in the heat transfer channel 34 from being too high and causing a safety accident, a pressure relief valve 37 is provided at the top of the heat transfer channel 34. When the pressure in the heat transfer channel 34 exceeds the set pressure of the pressure relief valve 37 (preferably 0.25 MPa), the pressure relief valve 37 will be triggered, and the hot air will be discharged from the pressure relief valve 37, ensuring that the medium pressure in the heat transfer channel 34 is below the set pressure, protecting the equipment and pipelines, and preventing accidents.

[0055] To facilitate monitoring the temperature of the batteries in different chambers, a first temperature sensor is provided in the preheating chamber 32, and a second temperature sensor is provided in each of the two heating chambers 33. The three temperature sensors are respectively in contact with the surface of a battery in the corresponding chamber to accurately monitor the battery temperature in that chamber. The first and second temperature sensors are both electrically connected to the control terminal. The temperature sensors can be used to monitor the ambient temperature around the lithium battery in real time, ensuring that the lithium battery is always in the optimal working temperature range, improving the thermal management technology of the lithium battery, and being beneficial to extending the service life of the lithium battery.

[0056] To accelerate the heat conduction effect, heat conducting fins 38 are provided in both the preheating chamber 32 and the heating chambers 33.

[0057] The control method of the above-mentioned stepwise temperature rise system is as follows:

[0058] 1. Put the fuel pack and water into the exothermic reaction tank 1 from the feeding port 11. A large amount of hot gas generated by the chemical reaction is transmitted from the hot gas outlet 13. The hot gas flows into the heat transfer channel 34. When the pressure in the heat transfer channel 34 exceeds the set pressure of the pressure relief valve 37, the pressure relief valve 37 is triggered, and the excessive hot gas is discharged from the pressure relief valve 37 to make the pressure in the heat transfer channel 34 return to below the set pressure;

[0059] 2. The heat of the high-temperature gas in the heat transfer channel 34 is transferred to the first phase change material in the preheating chamber 32 through heat conduction. The temperature of the first phase change material in the preheating chamber 32 rises, and the ambient temperature around the preheating chamber battery 35 also rises accordingly. When the first temperature sensor monitors that the temperature of the preheating chamber battery 35 is higher than 20 °C, stop the feeding of the fuel pack, and the exothermic reaction ends. Enable the preheating chamber battery 35 through the control terminal 4, and the preheating chamber battery 35 independently conducts the power supply work;

[0060] 3. The waste heat in the preheating chamber 32 and the heat generated by the normal operation of the preheating chamber battery 35 diffuse outward and are transferred to the second phase change material in the heating chamber 33. The temperature of the second phase change material in the heating chamber 33 rises, and the ambient temperature around the heating chamber battery 36 rises accordingly;

[0061] 4. When the second temperature sensor monitors that the temperature of the heating chamber battery 36 is higher than 20 °C, independently enable the heating chamber battery 36 through the control terminal 4, and the heating chamber battery 36 starts to conduct the power supply work. At this time, the entire battery box 3 is in a full-load working state.

[0062] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. A stepped temperature rising system for heating a lithium battery in a low-temperature environment, characterized in that It includes an exothermic reaction box, a bracket, a battery box and a control terminal; The exothermic reaction box is arranged at the bottom of the bracket, and a hot gas outlet is arranged at its top; A gas guiding channel is arranged in the middle of the shelf board of the bracket, and the bottom surface of the gas guiding channel is hermetically connected to the hot gas outlet; The battery box is arranged on the top of the bracket. The inside of the battery box body is evenly divided into three chambers, namely a preheating chamber in the center and heating chambers on both sides. A heat transfer channel is arranged in the middle of the preheating chamber. The bottom of the heat transfer channel is hermetically connected to the top of the gas guiding channel, and the top is hermetically connected to the bottom surface of the cover plate. A preheating chamber battery is arranged in the preheating chamber, and a heating chamber battery is arranged in the heating chamber. The batteries in a single chamber are connected in series, and after a wire connection port is led out at the end, they are connected in parallel to the control terminal; A first phase change material is poured into the preheating chamber, and a second phase change material is poured into the heating chamber; The thermal melting point of the first phase change material is lower than that of the second phase change material.

2. The stepwise temperature increase system for heating a lithium battery in a low-temperature environment according to claim 1, wherein The heat transfer channel is made of a material with high thermal conductivity, and a pressure relief valve is arranged at the top of the heat transfer channel.

3. The stepped temperature rise system for heating a lithium battery in a low-temperature environment according to claim 1, wherein The preheating chamber batteries are evenly distributed in a circumferential manner around the periphery of the heat transfer channel, and the heating chamber battery arrays are distributed in the heating chambers; a first temperature sensor is arranged in the preheating chamber, and a second temperature sensor is arranged in each of the two heating chambers. The three temperature sensors are respectively in contact with the surface of a battery in the corresponding chamber. The first and second temperature sensors are electrically connected to the control terminal.

4. The stepwise temperature rise system for heating a lithium battery in a low-temperature environment according to claim 1, characterized in that, Heat conducting fins are arranged in both the preheating chamber and the heating chamber.

5. The stepwise temperature increase system for heating a lithium battery in a low-temperature environment according to claim 1, wherein A feeding port is arranged on the side wall of the exothermic reaction box, and a slag discharge port is arranged at the bottom. The feeding port is arranged at the upper part of the side wall of the exothermic reaction box. A movable baffle is arranged at the feeding port. The slag discharge port is sealed by a sealing cover. A fuel pack that can release heat based on a chemical reaction is placed in the exothermic reaction box.

6. The stepwise temperature increase system for heating a lithium battery in a low-temperature environment according to claim 1, wherein A foldable support leg is arranged at each of the four corner positions at the bottom of the shelf board of the bracket, and a right-angle support is arranged at each of the four corner positions at the top of the shelf board. The space formed by enclosing the right-angle supports is adapted to the external shape of the box body, and the battery box is snap-connected between the right-angle supports above the bracket.

7. The stepped temperature rising system for heating a lithium battery in a low-temperature environment according to claim 1, wherein A connecting plate is arranged below the shelf board of the bracket. Sliding grooves extending along its length direction are arranged on both sides of the connecting plate. A slider extending along its length direction is arranged at each of the two side positions at the top of the exothermic reaction box. The shape of the slider is adapted to that of the sliding groove. The slider is connected to the sliding groove on the corresponding side of the connecting plate and can slide along it.

8. The control method of the stepped temperature rise system for heating a lithium battery in a low temperature environment according to any one of claims 1-7, characterized in that, Specifically, it includes the following steps: 1) Put the fuel pack and water into the exothermic reaction box from the feeding port. A large amount of hot gas generated by the chemical reaction is transmitted out from the hot gas outlet, and the hot gas flows into the heat transfer channel; 2) The heat of the high-temperature gas in the heat transfer channel is transferred to the first phase change material in the preheating chamber through heat conduction. The temperature of the first phase change material rises, and the ambient temperature around the preheating chamber battery rises accordingly; when the first temperature sensor monitors that the temperature of the preheating chamber battery is higher than 20 °C, stop the feeding of the fuel pack, the exothermic reaction ends, and the preheating chamber battery is enabled through the control terminal to independently perform the power supply work; 3) The waste heat in the preheating chamber and the heat generated by the normal operation of the preheating chamber battery diffuse outward and are transferred to the second phase change material in the heating chamber. The temperature of the second phase change material rises, and the ambient temperature around the heating chamber battery rises accordingly; 4) When the second temperature sensor monitors that the temperature of the battery in the heated bin is higher than 20°C, the battery in the heated bin is independently enabled through the control terminal, and the battery in the heated bin starts to supply power, and the entire battery box is in a full-load working state.

9. The control method of the stepwise temperature increase system for heating a lithium battery in a low-temperature environment according to claim 8, characterized in that, In step 1), when the pressure in the heat transfer channel exceeds the set pressure of the pressure relief valve, the pressure relief valve is triggered, and the excess hot air is discharged from the pressure relief valve to restore the pressure in the heat transfer channel below the set pressure.

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