Ultralow-temperature lithium iron phosphate battery pack and preparation process thereof

Abstract

The invention discloses an ultralow-temperature lithium iron phosphate battery pack which comprises a shell, a plurality of battery modules are arranged in the shell, a plurality of battery monomers are arranged in each battery module, and a heating module is further arranged in each battery module; the heating module comprises heating units and phase change units, and the heating units are uniformly distributed among single batteries of the battery module; the phase change unit is arranged at the central position of the battery module, and a pressure sensor and a safety valve are arranged at the top of the phase change unit. Through the synergistic effect of the double-layer shell heat insulation structure and the heating module, the heat loss of the battery in an ultralow-temperature environment can be effectively reduced. Compared with the traditional lithium iron phosphate battery pack, the battery pack provided by the invention has the advantage that the capacity retention ratio can be improved by 30-50% in an environment with the temperature of-30 DEG C or even lower. Therefore, the battery can continuously and stably provide more electric quantity in a cold region or under a low-temperature working condition, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of lithium iron phosphate batteries, and specifically to an ultra-low temperature lithium iron phosphate battery pack and a preparation process thereof. Background Art

[0002] Lithium iron phosphate batteries have great application potential in electric vehicles, energy storage systems and other fields due to their high safety, long cycle life, low cost and environmental friendliness.

[0003] The existing technology discloses a battery pack suitable for low temperature environment, which includes a heater, a battery pack temperature sensor, an ambient temperature sensor and a controller. The controller controls the heater to heat the battery pack to a target temperature. The invention is simple to operate, highly versatile, low cost, and simple in logic. It can better balance the power output capacity and heating energy consumption of electric vehicles in low temperature environments, and alleviate the mileage anxiety of electric vehicle users in low temperature driving environments.

[0004] However, the above technology uses a resistance heating wire to directly heat the battery. Due to factors such as the different distances between the battery cells at different positions in the battery pack and the heating wire, it is difficult to ensure that the battery cells in the battery pack are heated evenly, which may cause temperature differences and thus affect the consistency of the overall battery performance. Uneven heating may also cause local battery cells to overheat and age faster, reducing the overall life of the battery pack and affecting the stability of the vehicle's power output. Summary of the invention

[0005] The present invention mainly provides an ultra-low temperature lithium iron phosphate battery pack and a preparation process thereof, in order to solve the technical problems raised in the above-mentioned background technology.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: An ultra-low temperature lithium iron phosphate battery pack comprises a shell, a plurality of battery modules are arranged inside the shell, a plurality of battery cells are arranged inside each of the battery modules, and a heating module is also arranged inside the battery module; The heating module comprises a heating unit and a phase change unit, and the heating units are evenly distributed between the battery cells of the battery module; The phase change unit is arranged at the center of the battery module, and a pressure sensor and a safety valve are arranged on the top of the phase change unit.

[0007] Furthermore, the heating unit is made of a PTC thermistor, and the heating unit is electrically connected to the control module; The phase change unit is a sealed metal aluminum container, whose shell is made of aluminum alloy, and the interior of the phase change unit is filled with low-temperature phase change material that adapts to ultra-low temperature environment. The pressure sensor and the safety valve are electrically connected to the control module.

[0008] Furthermore, a plurality of battery holders are provided in the battery module, the number of the battery holders is consistent with the number of the battery cells, and the contact surfaces between the battery holders and the battery cells are provided with evenly distributed raised heat conducting fins.

[0009] Furthermore, the battery holder is made of a silicone material with high elasticity and high thermal conductivity, and its shape is a groove structure adapted to the battery cell, and reinforcing ribs are provided at the four corners of the battery holder.

[0010] Furthermore, the shell includes an outer shell and an inner shell, the outer shell is a multi-layer composite structure with a thickness of 5-10 mm, and the outer shell comprises a weather-resistant layer, a heat-insulating layer and a supporting layer from the outside to the inside; The inner shell is made of aluminum alloy with a thickness of 2-3 mm, and the inner surface of the inner shell is provided with a heat-conducting structure, which is composed of uniformly distributed tiny protrusions and grooves.

[0011] Furthermore, the outer shell and the inner shell are sealed and connected by a sealing strip, and the shell is also provided with a sealing cover, which is detachably sealed and connected to the shell, and the inner surface of the sealing cover is filled with the same insulation material as the insulation layer.

[0012] Furthermore, the control module includes a temperature monitoring module, a voltage monitoring module, a current monitoring module and a controller, and the temperature monitoring module adopts a high-precision thermistor sensor, which is distributed in the battery module; The voltage monitoring module uses a differential amplifier circuit to sample the voltage across both ends of each battery cell; The current monitoring module adopts a Hall effect current sensor, which is distributed on the charging and discharging branches of the battery pack and the battery cells.

[0013] Furthermore, the temperature monitoring module, the voltage monitoring module, and the current monitoring module are all electrically connected to the controller, and the controller is powered by an external power supply.

[0014] A preparation process of an ultra-low temperature lithium iron phosphate battery pack, used to prepare an ultra-low temperature lithium iron phosphate battery pack in the above technical solution, comprises the following steps: SP1. Install the shell, seal and connect the outer shell and the inner shell with a sealing strip, and then use a vacuum equipment to evacuate the cavity between the two shells; SP2. Install the battery, install several battery cells into the battery module inside the shell, and then connect the battery cells in series or in parallel as required; SP3, connecting components to electrically connect the control module with various components inside the housing; SP4: Battery pack molding: sealingly connecting the sealing cover to the outer shell to form the battery pack.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can effectively reduce the heat loss of the battery in an ultra-low temperature environment through the synergistic effect of the double-layer shell insulation structure and the heating module. In a temperature environment of -30°C or even lower, the capacity retention rate of the battery pack of the present invention can be increased by 30%-50% compared with the traditional lithium iron phosphate battery pack. This means that in cold areas or low temperature conditions, the battery can continuously and stably provide more power and extend the use time of the equipment.

[0016] 2. The heating unit and phase change unit in the heating module of the present invention can accurately heat or cool according to the battery temperature. During low-temperature charging, the heating unit can enable the chemical reaction inside the battery to proceed normally, reduce the internal resistance of the battery, and thus improve the charging efficiency; when the battery works in a high-temperature environment or generates heat during the charging process, the phase change unit can absorb the heat in time to prevent the battery temperature from being too high.

[0017] 3. The modular partition structure in the battery pack of the present invention enables the temperature of each battery module to be independently controlled, which is conducive to maintaining the temperature consistency between battery cells. During the charging and discharging process, the improvement of temperature consistency can reduce the performance difference of battery cells caused by temperature differences, thereby improving the overall charging and discharging efficiency of the battery pack.

[0018] 4. The combination of the inner layer high thermal conductivity metal shell and the outer layer thermal insulation composite shell in the multi-layer shell structure provided by the present invention can not only effectively insulate, but also provide a reasonable path for the conduction and dissipation of heat when the battery generates abnormal heat, thereby avoiding heat accumulation inside the battery pack.

[0019] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is an axonometric view of the internal structure of the housing of the present invention; Figure 3 A top view of the internal structure of the housing of the present invention; Figure 4 It is a cross-sectional view of the internal structure of the shell of the present invention; Figure 5 It is a schematic diagram of the battery bracket structure of the present invention; Figure 6 for Figure 4 Enlarged view of point A in the middle; Figure 7 for Figure 4 Enlarged view of point B in the middle; Figure 8 It is a preparation process step diagram of the present invention.

[0021] Description of the drawings: 1. Shell; 101. Outer shell; 1011. Weather-resistant layer; 1012. Heat-insulating layer; 1013. Support layer; 102. Inner shell; 1021. Thermal conductive structure; 103. Sealing cover; 2. Battery module; 201. Battery cell; 202. Battery holder; 203. Thermal conductive fins; 3. Heating module; 301. Heating unit; 302. Phase change unit; 303. Pressure sensor; 304. Safety valve; 4. Control module; 401. Temperature monitoring module; 402. Voltage monitoring module; 403. Current monitoring module; 404. Controller. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings, but the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the content disclosed in the present invention more thorough and comprehensive. Example

[0023] Please refer to the attached Figure 1 , 2 As shown in Figures 3 and 4, an ultra-low temperature lithium iron phosphate battery pack comprises a shell 1, wherein a plurality of battery modules 2 are arranged inside the shell 1, wherein each battery module 2 is provided with a plurality of battery cells 201, and a heating module 3 is also provided inside the battery module 2; the heating module 3 comprises a heating unit 301 and a phase change unit 302, wherein the heating unit 301 is evenly distributed between the battery cells 201 of the battery module 2, and is electrically connected to the control module 4, the phase change unit 302 is arranged at the center of the battery module 2, and a pressure sensor 303 and a safety valve 304 are arranged on the top of the phase change unit 302, and the pressure sensor 303 and the safety valve 304 are electrically connected to the control module 4.

[0024] It should be noted that the heating unit 301 is made of a PTC thermistor, and the positive temperature coefficient characteristic of the PTC thermistor enables it to achieve a self-regulating temperature function. When the battery pack starts to heat up in a low-temperature environment, the PTC thermistor has a low resistance and a large current, which can quickly generate heat and cause the battery temperature to rise rapidly. As the temperature rises and approaches its Curie temperature, the resistance value increases sharply, the current decreases accordingly, and the power decreases, thereby automatically limiting the further increase in the heating temperature, effectively preventing the risk of overheating of the battery due to excessive heating, avoiding thermal damage to the battery, and greatly improving the safety and reliability of the heating process.

[0025] It should be noted that the phase change unit 302 is a sealed aluminum alloy container, which is filled with low-temperature phase change materials adapted to ultra-low temperature environments, such as organic compounds such as n-pentane. During the operation of the battery, when the temperature rises to the melting point of the phase change material, the phase change material will change from solid to liquid, and a large amount of heat will be absorbed in this process, thereby effectively reducing the temperature of the battery module 2, avoiding battery performance degradation or safety hazards caused by overheating. In a low-temperature environment, when the battery temperature is too low, the phase change material is in a liquid state, and its higher specific heat capacity can temporarily store heat, slow down the rate of temperature drop of the battery, play a certain role in heat preservation, and buy time for the start-up of the heating unit 301 to maintain the normal working performance of the battery. In addition, when the data of the pressure sensor 303 caused by the phase change exceeds the set value, the control module 4 opens the safety valve 304 to relieve pressure to ensure the safety of the container.

[0026] It should be noted that the coordinated work of the heating unit 301 and the phase change unit 302 can respond to the battery temperature changes in a timely manner and accurately maintain the battery in a suitable operating temperature range. Whether it is in low-temperature startup or in a temperature-fluctuating environment, it can efficiently provide stable and appropriate heating protection for the battery, significantly enhancing the performance and adaptability of the battery pack in ultra-low temperature environments, extending the battery life and expanding its application range. It provides strong support and guarantee for its application in cold areas or low-temperature conditions.

[0027] Please refer to the attached Figure 3 , 5 As shown in FIG. 7 , a plurality of battery holders 202 are further provided in the battery module 2 . The number of the battery holders 202 is the same as the number of the battery cells 201 . The contact surfaces between the battery holders 202 and the battery cells 201 are provided with evenly distributed raised heat conducting fins 203 .

[0028] It should be noted that the battery holder 202 is made of a silicone material with high elasticity and high thermal conductivity. The highly elastic silicone material enables the battery holder 202 to effectively buffer the vibration, impact and other external forces that the battery cell 201 may be subjected to during use, and during the battery charging and discharging process, the heat can be efficiently conducted away through the holder, which helps to maintain the uniformity of the temperature of the battery cell 201 and the stability of the temperature of the entire battery module 2, avoiding the occurrence of local overheating or overcooling, thereby improving the working efficiency and service life of the battery; the shape of the battery holder 202 is designed to be a groove structure that matches the battery cell 201, which can allow the battery cell 201 to be firmly placed in the holder to prevent electric The battery cell 201 is displaced or shaken in the battery module 2, ensuring the tightness of the internal structure of the battery module 2 and the reliability of the connection. In addition, reinforcing ribs are provided at the four corners of the battery bracket 202 to further enhance the overall structural strength of the bracket. When facing a complex and changeable use environment and possible external forces, the reinforcing ribs can provide additional support for the battery bracket 202, so that it can better protect the battery cell 201. Even if it is used for a long time or under relatively harsh working conditions, it can maintain its own stability and continue to play its important functions such as support, heat conduction and buffering, and cooperate with other structures in the battery pack to improve the performance and safety of the entire battery pack.

[0029] Please refer to the attached Figure 3 , 4 As shown in Figures 6, the shell 1 includes an outer shell 101 and an inner shell 102. The shell 1 is also provided with a sealing cover 103. The outer shell 101 is a multi-layer composite structure with a thickness of 5-10 mm, and the outer shell 101 is composed of a weather-resistant layer 1011, a heat-insulating layer 1012 and a supporting layer 1013 from the outside to the inside; the inner shell 102 is made of aluminum alloy with a thickness of 2-3 mm, and the inner surface of the inner shell 102 is provided with a thermal conductive structure 1021, which is composed of uniformly distributed tiny protrusions and grooves. In addition, the sealing cover 103 is detachably sealed and connected to the shell 1 by bolts, and the inner surface of the sealing cover 103 is filled with the same thermal insulating material as the heat-insulating layer 1012.

[0030] It should be noted that the weather-resistant layer 1011 is a polycarbonate (PC) layer with a thickness of 1-2 mm. It has high strength, high toughness and good UV resistance, and can effectively resist physical impact and light aging in the external environment; the thermal insulation layer 1012 is an aerogel felt layer with a thickness of 5-10 mm. It has extremely low thermal conductivity, and its thermal insulation performance is more prominent in ultra-low temperature environments, which can greatly reduce the heat exchange between the battery pack and the external environment; the supporting layer 1013 is a glass fiber reinforced epoxy resin layer with a thickness of 0.5-1 mm, which provides additional mechanical strength support for the outer shell 101, enhances the compression and bending resistance of the entire outer shell 101, and ensures the stability of the shell 1 structure in complex use environments. In addition, the outer surface of the weather-resistant layer 1011 is treated with a special hydrophobic coating with a coating thickness of 50-100 microns. The hydrophobic coating can form a super-hydrophobic surface on the surface of the shell 1 similar to the lotus leaf effect. When the battery pack is used in a humid or rainy or snowy environment, moisture will form water droplets on the surface of the shell 1 and quickly slide off, preventing moisture from adhering to the shell 1 for a long time and causing erosion or affecting the performance of the shell 1 due to freezing. At the same time, it also reduces the problem of increased heat loss caused by the presence of water.

[0031] It should be noted that the outer shell 101 and the inner shell 102 are sealed with sealing strips to prevent impurities such as air and moisture from entering the cavity between the two shells. Professional vacuum exhaust equipment is used to evacuate the space between the two shells to achieve a high vacuum degree in the range of 0.01-0.1 Pascal to form a vacuum insulation cavity. Barium lithium getter and other getter materials can be installed in the vacuum insulation cavity. The getter can absorb trace gas molecules that may penetrate into the vacuum insulation cavity during the use of the battery pack, such as hydrogen, nitrogen, oxygen, etc., to ensure that the vacuum insulation cavity always maintains a high vacuum degree during long-term use and stabilizes its insulation performance.

[0032] Please refer to the attached Figure 1 , 2 As shown in Figure 3, the control module 4 includes a temperature monitoring module 401, a voltage monitoring module 402, a current monitoring module 403 and a controller 404. The controller 404 is powered by an external power supply and is electrically connected to the temperature monitoring module 401, the voltage monitoring module 402 and the current monitoring module 403. The temperature monitoring module 401 adopts a high-precision thermistor sensor, which is distributed in the battery module 2; the voltage monitoring module 402 uses a differential amplifier circuit to sample the voltage at both ends of each battery cell 201; the current monitoring module 403 adopts a Hall effect current sensor, which is distributed in the charging and discharging branches of the battery pack and the battery cell 201.

[0033] It should be noted that the sensor of the temperature monitoring module 401 transmits the collected temperature data in the form of an electrical signal to the controller 404. When the battery temperature is lower than the set low temperature threshold, the controller 404 starts the low temperature protection program after receiving the signal and turns on the heating unit 301; when the temperature is higher than the set high temperature threshold, the high temperature protection mechanism is triggered and the heating unit 301 is turned off.

[0034] It should be noted that the controller 404 receives the voltage monitoring data and determines whether the voltage of the battery cells 201 is balanced. If it is found that the voltage of a battery cell 201 is too high or too low and exceeds the preset voltage threshold range, the balancing control program is started. Through the balancing resistor connected between the battery cells 201, the energy of the battery cell 201 with too high voltage is transferred to the battery cell 201 with too low voltage, so as to achieve the balance of the battery cell voltage 201 and extend the overall service life of the battery pack.

[0035] It should be noted that the sensor of the current monitoring module 403 converts the current signal into a voltage signal and transmits it to the controller 404. The controller 404 can calculate the remaining capacity and health status of the battery based on the current monitoring data. Moreover, during the charging and discharging process, when the current exceeds the set safety threshold, the controller 404 will promptly adjust the working state of the charging and discharging circuit to limit the current size and prevent the battery from being damaged due to overcurrent.

[0036] Please refer to the attached Figure 8 As shown, a preparation process of an ultra-low temperature lithium iron phosphate battery pack, including the above-mentioned ultra-low temperature lithium iron phosphate battery pack, includes the following steps: SP1. Install the shell, seal and connect the outer shell 101 and the inner shell 102 with a sealing strip, and then use a vacuum equipment to evacuate the cavity between the two shells; SP2. Install the battery, install several battery cells 201 into the battery module 2 inside the housing 1, and then connect the battery cells 201 in series or in parallel as required; SP3, connecting components, electrically connecting the control module 4 with various components inside the housing 1; SP4. Battery pack forming: the sealing cover 103 is sealed and connected to the outer shell 101 to form the battery pack.

[0037] The specific operation process of the present invention is as follows: After the battery module 2 is fixed to the inner shell 102, the outer shell 101 is sealed and connected with the inner shell 102 through a sealing strip, and then the space between the two shells is evacuated using a professional vacuum exhaust device to achieve a high vacuum degree of 0.01-0.1 Pascal to form a vacuum insulation cavity; Then, several battery cells 201 are installed one by one into the corresponding battery holder 202, and are in full contact with the heat conducting fins 203 on the battery holder 202. The series and parallel connection modes between the battery cells 201 are determined according to the voltage and capacity requirements of the battery pack; Then, the control module 4 is electrically connected to each component inside the housing 1, and then the output end of the external power supply is connected to the input end of the controller 404 using a connecting cable, and the entire connection line is checked to confirm that there are no problems such as short circuit, open circuit or poor contact; Finally, apply a proper amount of sealant on the contact surface between the sealing cover 103 and the outer shell 101, slowly press the sealing cover 103 onto the outer shell 101, also apply sealant on the fixing bolts and screw holes, and gradually tighten the fixing screws on the sealing cover 103 to form the battery pack.

[0038] The above is an exemplary description of the present invention in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. An ultra-low temperature lithium iron phosphate battery pack, comprising a housing (1), characterized in that: A plurality of battery modules (2) are arranged inside the housing (1), each of the battery modules (2) is provided with a plurality of battery cells (201), and a heating module (3) is also provided inside the battery module (2); The heating module (3) comprises a heating unit (301) and a phase change unit (302), and the heating unit (301) is evenly distributed between the battery cells (201) of the battery module (2); The phase change unit (302) is arranged at the center of the battery module (2), and a pressure sensor (303) and a safety valve (304) are arranged on the top of the phase change unit (302).

2. The ultra-low temperature lithium iron phosphate battery pack according to claim 1, characterized in that: The heating unit (301) is made of a PTC thermistor, and the heating unit (301) is electrically connected to the control module (4); The phase change unit (302) is a sealed metal container, the outer shell of which is made of aluminum alloy, and the interior of the phase change unit (302) is filled with a low-temperature phase change material adapted to ultra-low temperature environments. The pressure sensor (304) and the safety valve (305) are electrically connected to the control module (4).

3. The ultra-low temperature lithium iron phosphate battery pack according to claim 1, characterized in that: A plurality of battery supports (202) are also provided in the battery module (2), the number of the battery supports (202) being the same as the number of the battery cells (201), and evenly distributed raised heat-conducting fins (203) are provided on the contact surfaces between the battery supports (202) and the battery cells (201).

4. The ultra-low temperature lithium iron phosphate battery pack according to claim 3, characterized in that: The battery support (202) is made of a silicone material with high elasticity and high thermal conductivity, and is in the shape of a groove structure adapted to the battery cell (201), and reinforcing ribs are provided at the four corners of the battery support (202).

5. The ultra-low temperature lithium iron phosphate battery pack according to claim 1, characterized in that: The shell (1) comprises an outer shell (101) and an inner shell (102); the outer shell (101) is a multi-layer composite structure with a thickness of 5-10 mm, and the outer shell (101) comprises, from the outside to the inside, a weather-resistant layer (1011), a heat-insulating layer (1012), and a supporting layer (1013); The inner shell (102) is made of an aluminum alloy material and has a thickness of 2-3 millimeters. The inner surface of the inner shell (102) is provided with a heat-conducting structure (1021), and the heat-conducting structure (1021) is composed of evenly distributed tiny protrusions and grooves.

6. The ultra-low temperature lithium iron phosphate battery pack according to claim 5, characterized in that: The outer shell (101) and the inner shell (102) are sealed and connected by a sealing strip, and the shell (1) is further provided with a sealing cover (103), the sealing cover (103) is detachably sealed and connected to the shell (1), and the inner surface of the sealing cover (103) is filled with the same thermal insulation material as the thermal insulation layer (1012).

7. The ultra-low temperature lithium iron phosphate battery pack according to claim 2, characterized in that: The control module (4) comprises a temperature monitoring module (401), a voltage monitoring module (402), a current monitoring module (403) and a controller (404); the temperature monitoring module (401) uses a high-precision thermistor sensor, which is distributed in the battery module (2); The voltage monitoring module (402) uses a differential amplifier circuit to sample the voltage at both ends of each battery cell (201); The current monitoring module (403) uses a Hall effect current sensor, which is distributed on the charging and discharging branches of the battery pack and the battery cell (201).

8. The ultra-low temperature lithium iron phosphate battery pack according to claim 7, characterized in that: The temperature monitoring module (401), the voltage monitoring module (402), and the current monitoring module (403) are all electrically connected to the controller (404), and the controller (404) is powered by an external power supply.

9. A process for preparing an ultra-low temperature lithium iron phosphate battery pack, comprising an ultra-low temperature lithium iron phosphate battery pack as claimed in claims 1-8, characterized in that: The following steps are involved: SP1. Install the shell, seal and connect the outer shell (101) and the inner shell (102) by means of a sealing strip, and then use a vacuuming device to evacuate the cavity between the two shells; SP2, installing the battery, installing a plurality of battery cells (201) into the battery module (2) inside the housing (1), and then connecting the battery cells (201) in series or in parallel as required; SP3, connecting components to electrically connect the control module (4) to various components inside the housing (1); SP4. The battery pack is formed by sealing the sealing cover (103) and the outer shell (101) to form the battery pack.

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