Lithium battery pack

Abstract

This invention belongs to the field of batteries, specifically a lithium battery pack. It includes a housing containing multiple battery compartments, each containing a battery cell. Between the battery cell and the sidewall of the battery compartment, a phase change composite layer, a microchannel injection layer, and a filter layer are sequentially arranged. The phase change composite layer comprises a porous substrate with a porosity of 70%-85%, and the pores of the porous substrate are filled with fire extinguishing agent particles and a flame-retardant phase change material with a melting point of 70-90°C. The microchannel injection layer comprises a metal substrate with multiple through-holes. The two sides of the metal substrate are provided with a thermistoric encapsulation film with a bursting temperature of 120-140°C, covering the openings of each through-hole. The through-holes are filled with a coolant with a boiling point of 35-60°C. A guide cavity is provided between the filter layer and the sidewall of the battery compartment. A pressure relief chamber is provided on the lower surface of the housing, and each guide cavity communicates with the pressure relief chamber. This invention can reduce the emission volume and temperature of high-temperature particles and high-temperature combustible gases, thus mitigating the harm to the surrounding environment.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and in particular to a lithium battery pack. Background Technology

[0002] Lithium-ion batteries have high energy density and are widely used in various vehicles and electronic devices. However, lithium-ion batteries are prone to thermal runaway, which can lead to fires, explosions, and the release of large amounts of flammable gases, seriously endangering the safety of nearby personnel and facilities. Currently, to address the thermal runaway problem of lithium-ion batteries, heat insulation layers, such as aerogel pads or mica sheets, are typically placed between the individual cells to slow down heat conduction. For example, utility model patent application CN201721591237.7 discloses a membrane structure for cell heat insulation and its battery pack. Simultaneously, explosion-proof pressure relief mechanisms can be incorporated to directionally release pressure and discharge high-temperature gases, as illustrated in utility model patent application CN202221498678.3, which describes a directional pressure-relieving cell and battery module. Various cooling systems can also be implemented to dissipate heat from the lithium-ion battery during operation. To reduce the risk of thermal runaway, patent application CN202511017495.3 discloses an immersion liquid-cooled battery pack. In addition, some lithium battery packs have built-in protection circuits that cut off the circuit through MOSFETs or relays when the temperature is too high. However, these rely on auxiliary power supplies and sensors, and the electronic components themselves are also at risk of damage or failure. Moreover, the electronic components cannot work reliably in the high temperature and high pressure environment caused by thermal runaway. For example, patent application CN202510479846.6 discloses a lithium battery overheat protection device.

[0003] In addition, invention patent application number CN202410324219.0 discloses an explosion-proof lithium battery pack. A compressed gas pack is installed at the bottom of the battery compartment. When the compressed gas pack is exposed to high temperatures, it ruptures, and the flame-retardant gas inside is ejected from the rupture, quickly isolating the lithium battery from the surrounding air and cooling and extinguishing the fire. A fire-extinguishing powder pack is also included; when the temperature is too high, it can spray fire-extinguishing material to assist in cooling, prevent the fire from spreading, and achieve a better explosion-proof effect.

[0004] While the aforementioned existing technologies have certain functions in reducing the risk of thermal runaway or mitigating the harm caused by thermal runaway, it is difficult to avoid the ejection of high-temperature particles and high-temperature flammable gases when thermal runaway occurs in the battery cell, which can cause harm to the surrounding environment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a lithium battery pack that reduces the amount and temperature of high-temperature particles and high-temperature combustible gases emitted, thereby reducing the harm to the surrounding environment.

[0006] To solve the above problems, the technical solution adopted by the present invention is: a lithium battery pack, including a casing and a cover, wherein multiple battery compartments are arranged inside the casing, and each battery compartment contains battery cells.

[0007] A phase change composite layer, a microchannel injection layer, and a filter layer are sequentially disposed between the battery cell and the side wall of the battery compartment. The phase change composite layer includes a porous substrate with a porosity of 70%-85%, and the pores of the porous substrate are filled with fire extinguishing agent particles and flame-retardant phase change material with a melting point of 70-90℃. The microchannel injection layer includes a metal substrate with multiple through holes, and the two sides of the metal substrate are provided with a thermistor encapsulation film with a cracking temperature of 120-140℃, which covers the opening of each through hole. The through holes are filled with a coolant with a boiling point of 35-60℃. A guide cavity is provided between the filter layer and the side wall of the battery compartment.

[0008] The lower surface of the housing is provided with a pressure relief chamber, and each guide cavity is connected to the pressure relief chamber.

[0009] Furthermore, the porous substrate is a foamed copper plate or a foamed aluminum plate with a pore size of 0.5-2 mm, and the pore size gradually decreases from the center to the edge of the porous substrate, and the inner wall of the pores is coated with an oleophilic coating.

[0010] Furthermore, the flame-retardant phase change material is a paraffin-based material with added flame retardants, and the flame retardants are one or more of ammonium polyphosphate, expanded graphite, and red phosphorus. The flame retardant rating of the flame-retardant phase change material is UL94V-0.

[0011] Furthermore, the extinguishing agent particles are sodium bicarbonate or ammonium dihydrogen phosphate particles, and the filling amount of the extinguishing agent particles is 5%-15% of the pore volume of the porous matrix.

[0012] Furthermore, the metal substrate is a copper plate or an aluminum plate, the diameter of the through holes is 0.1-0.5 mm, and the hole spacing is 0.5-1.5 mm; the coolant is a fluorinated coolant Novec 7000 or HFE-7100, and the thickness of the thermal encapsulation film 8 decreases from the center to the edge of the metal substrate.

[0013] Furthermore, the phase change composite layer has a thickness of 2-5 mm, the microchannel spray layer has a thickness of 2-3 mm, and the filter layer has a thickness of 1-3 mm.

[0014] Furthermore, the filter layer includes an alumina ceramic fiber layer and a ZSM-5 zeolite molecular sieve and alumina composite layer arranged sequentially. The alumina ceramic fiber layer has a fiber diameter of 10-20 μm and a pore size of 100-200 μm; the ZSM-5 zeolite molecular sieve and alumina composite layer has a pore size of 10-50 μm.

[0015] Furthermore, the pressure relief chamber is equipped with multiple vortex tubes, the inlet of each vortex tube is connected to the guide cavity, the cold end outlet of the vortex tube is connected to the inner cavity of the pressure relief chamber, and the hot end outlet of the vortex tube is connected to the gap between the battery cell and the phase change composite layer through a return pipe. A one-way valve is provided on the return pipe, and a dust collection box connected to the inner cavity of the vortex tube is provided on the outer wall of the hot end of the vortex tube.

[0016] Furthermore, the partition between two adjacent battery compartments includes a first plate and a second plate, with a heat dissipation gap between the first plate and the second plate. Multiple heat-conducting blocks are disposed within the heat dissipation gap. One side wall of each heat-conducting block is slidably engaged with the first plate, and the other side wall is slidably engaged with the second plate. A groove is formed at the top of each heat-conducting block, the length of which is aligned with the thickness of the heat dissipation gap. A slider is disposed within the groove, and a heat pipe is connected to the slider via a first universal ball joint. A heat-conducting strip is disposed at the top of the heat dissipation gap, and the upper end of the heat pipe is connected to the heat-conducting strip via a second universal ball joint.

[0017] Furthermore, the lid is provided with multiple strip-shaped holes, and the top of the heat-conducting strip extends out of the strip-shaped holes.

[0018] The beneficial effects of this invention are as follows: When a battery cell experiences thermal runaway, a large amount of high-temperature flue gas is emitted. This high-temperature flue gas first reaches the phase change composite layer, where the flame-retardant phase change material absorbs the heat from the flue gas and melts, lowering the flue gas temperature. Simultaneously, the fire extinguishing agent particles in the phase change composite layer decompose at high temperatures, generating inert gas, which further absorbs the heat from the flue gas. After the phase change material melts, it is ejected from the pores of the porous substrate under the high-pressure impact of the high-temperature flue gas. The high-temperature flue gas then reaches the microchannel injection layer. Under the high temperature and high-speed impact of the high-temperature flue gas, the thermistor encapsulation film ruptures, and the coolant absorbs the heat from the high-temperature flue gas and vaporizes, further lowering the temperature of the high-temperature flue gas. After entering the through-holes in the metal substrate, the high-temperature flue gas can carry the coolant and move synchronously, allowing it to penetrate the through-holes and reach the filter layer. The filter layer filters the high-temperature flue gas, removing some particulate matter and reducing its particulate content. After penetrating the filter layer, the high-temperature flue gas enters the guide cavity, then the pressure relief chamber, and finally exits through the flue gas exhaust port of the pressure relief chamber.

[0019] As can be seen, this invention can cool high-temperature flue gas multiple times, preventing the combustion of high-temperature combustible gas into the air and the resulting flame from igniting equipment and facilities around the lithium battery pack, thus reducing the hazards caused by thermal runaway. Furthermore, it can reduce the particulate matter content in the high-temperature flue gas, preventing large amounts of particulate matter from covering other surrounding equipment and causing damage, thereby reducing adverse impacts on the surrounding environment.

[0020] In addition, this invention utilizes the inherent properties of flame-retardant phase change materials and thermally sensitive encapsulation films to automatically trigger when thermal runaway occurs, eliminating the need for electronic components such as sensors and controllers, thus avoiding protection failure issues caused by damage to electronic components or failure at high temperatures. Attached Figure Description

[0021] Figure 1 This is a front sectional view of the present invention;

[0022] Figure 2 This is a magnified schematic diagram of a portion of the microchannel jetting layer;

[0023] Figure 3 This is a schematic diagram of the filter layer;

[0024] Figure 4 This is a schematic diagram of the partition;

[0025] Reference numerals: 1—Box body; 2—Box cover; 3—Baffle; 31—First plate; 32—Second plate; 33—Heat dissipation gap; 34—Heat-conducting block; 35—Slide groove; 36—Slider; 37—First universal ball joint; 38—Heat pipe; 39—Heat-conducting strip; 310—Second universal ball joint; 4—Battery cell; 5—Phase change composite layer; 6—Microchannel spray layer; 7—Filter layer; 71—Alumina ceramic fiber layer; 72—ZSM-5 zeolite molecular sieve and alumina composite layer; 8—Thermosensitive encapsulation film; 9—Coolant; 10—Guide cavity; 11—Pressure relief chamber; 12—Vortex tube; 13—Cold end outlet; 14—Hot end outlet; 15—Return pipe; 16—Dust collection box; 17—One-way valve. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] The lithium battery pack of the present invention, such as Figures 1 to 4 As shown, the device includes a housing 1 and a cover 2. Multiple battery compartments are arranged inside the housing 1, and each battery compartment contains a battery cell 4. The housing 1 is rectangular and can be a metal housing. The cover 2 is detachably installed on the top of the housing 1 to protect the battery cells 4 inside. The battery compartments can be cylindrical cavities or rectangular cavities, depending on the shape of the battery cells 4. In this invention, the battery compartments are preferably rectangular, and the interior of the housing 1 is divided into multiple battery compartments by multiple partitions 3. Existing technology can be used for the battery cells 4.

[0028] A phase change composite layer 5, a microchannel spraying layer 6, and a filter layer 7 are sequentially disposed between the battery cell 4 and the side wall of the battery compartment. The phase change composite layer 5 is closer to the battery cell 4, and the filter layer 7 is closer to the inner side wall of the battery compartment. The thickness of the phase change composite layer 5 is 2-5mm, the thickness of the microchannel spraying layer 6 is 2-3mm, and the thickness of the filter layer 7 is 1-3mm.

[0029] The phase change composite layer 5 can absorb and store heat through the phase change material. Specifically, it includes a porous matrix, which is a porous metal matrix resistant to high temperatures. This matrix can be a foamed copper or aluminum plate, or a copper or aluminum plate with numerous micropores. The porosity of the porous matrix is ​​70%-85%, and the pores are filled with fire extinguishing agent particles and a flame-retardant phase change material with a melting point of 70-90℃. The flame-retardant phase change material combines flame retardancy and phase change heat absorption functions, preventing combustion or decomposition at high temperatures. Specifically, the flame-retardant phase change material is a paraffin-based material with added flame retardants, such as ammonium polyphosphate, expanded graphite, or red phosphorus, and has a flame retardant rating of UL94V-0. The fire extinguishing agent particles can be existing fire extinguishing materials suitable for lithium battery fires, such as sodium bicarbonate or ammonium dihydrogen phosphate particles. The filling amount of the fire extinguishing agent particles is 5%-15% of the pore volume of the porous matrix.

[0030] The pore size within the metal matrix can be set according to requirements, preferably 0.5-2 mm, and the pore size gradually decreases from the center to the edge of the porous matrix. In pores with smaller pore sizes, the volume of the flame-retardant phase change material is smaller, and it can be completely melted in a shorter time; in pores with larger pore sizes, the volume of the flame-retardant phase change material is larger, and it takes a longer time to be completely melted.

[0031] The inner wall of the pores is coated with an oleophilic coating, which can be silane materials such as octadecyltrichlorosilane (OTS), perfluorodecyltrichlorosilane (FDTS), and aminosilane. The oleophilic coating can make the inner wall of the metal pores oleophilic, thereby improving the bonding force between the flame-retardant phase change material and the inner wall of the pores.

[0032] When filling the phase change composite layer 5 with flame-retardant phase change material, first heat the paraffin-based material to 100-110℃ to completely melt it. Then, add flame retardant and fire extinguishing agent particles to the melted paraffin-based material and stir thoroughly to ensure a uniform mixture of the three materials. Next, immerse the foamed copper plate or foamed aluminum plate in the paraffin-based material using a vacuum impregnation process, allowing the paraffin-based material to penetrate the pores of the foamed copper plate or foamed aluminum plate. After impregnation, cool the foamed copper plate or foamed aluminum plate to solidify the paraffin-based material, and then clean off any excess paraffin-based material from the surface of the foamed copper plate or foamed aluminum plate.

[0033] The microchannel spray layer 6 includes a metal substrate, which can be a copper or aluminum plate. Multiple through-holes are formed on the metal substrate, with a hole diameter of 0.1-0.5 mm and a hole spacing of 0.5-1.5 mm. A thermistoric encapsulation film 8 with a rupture temperature of 120-140℃ is formed on both sides of the metal substrate, covering the openings of each through-hole to seal them. The thermistoric encapsulation film 8 can be a tin-bismuth alloy film with a bismuth mass ratio of approximately 35%, capable of softening and rupturing at 130-140℃, meeting the requirements. The through-holes are filled with a coolant 9 with a boiling point of 35-60℃, which can be a fluorinated coolant such as Novec 7000 or HFE-7100. The thermistoric encapsulation film 8 melts, decomposes, or softens at high temperatures (120-140℃) and is simultaneously impacted by high-temperature flue gas, causing it to rupture and release the coolant 9 from the through-holes. The greater the thickness of the thermal encapsulation film 8, the longer it takes to rupture. In this invention, the thickness of the thermal encapsulation film 8 decreases from the center to the edge of the metal substrate, so that the thermal encapsulation film 8 at the edge of the metal substrate ruptures first, while the thermal encapsulation film 8 at the center of the metal substrate ruptures later, thus realizing the sequential release of the coolant 9.

[0034] When preparing the microchannel spray layer 6, firstly, through holes are opened on the metal substrate, then a thermal encapsulation film 8 is prepared, and the thermal encapsulation film 8 is hot-pressed onto one side of the metal substrate. Then, coolant 9 is injected into the through holes of the metal substrate, and finally, the thermal encapsulation film 8 is hot-pressed onto the other side of the metal substrate.

[0035] The filter layer 7 is used for preliminary filtration of particles in high-temperature flue gas. Specifically, the filter layer 7 includes an alumina ceramic fiber layer 71 and a ZSM-5 zeolite molecular sieve and alumina composite layer 72 arranged sequentially. The alumina ceramic fiber layer 71 has a fiber diameter of 10-20 μm and a pore size of 100-200 μm; the ZSM-5 zeolite molecular sieve and alumina composite layer 72 has a pore size of 10-50 μm. Among them, the alumina ceramic fiber layer 71 mainly filters solid particles in high-temperature flue gas. In the ZSM-5 zeolite molecular sieve and alumina composite layer 72, the ZSM-5 zeolite molecular sieve has a large number of microporous structures, which can absorb volatile organic compounds (such as acetone, methyl ethyl ketone, benzene, toluene, etc.), reduce the concentration of combustible gases, and has high thermal stability.

[0036] A guide cavity 10 is provided between the filter layer 7 and the side wall of the battery compartment. A pressure relief chamber 11 is provided on the lower surface of the housing 1. Each guide cavity 10 is connected to the pressure relief chamber 11. The pressure relief chamber 11 is provided with a flue gas exhaust port. The position of the flue gas exhaust port can be flexibly set according to the application scenario. For example, it can be set at one end of the pressure relief chamber 11 or at the bottom of the pressure relief chamber 11 for exhausting flue gas.

[0037] As is generally known, the normal charging temperature of lithium batteries is approximately 0-45℃ (optimal approximately 20-30℃); the normal discharging temperature is approximately -20-60℃ (optimal approximately 15-40℃). When the temperature of a lithium battery exceeds 60℃, the electrolyte begins to decompose, produce gas, and bulge, entering a dangerous warning zone. When the temperature reaches 80-120℃, it is a precursor to thermal runaway, with the lithium battery SEI film decomposing, the electrolyte slowly decomposing, and a small amount of gas being produced. When the temperature reaches 130-160℃, the lithium battery separator melts, an internal short circuit occurs, the temperature rises sharply, and finally, high-temperature fumes at 400-800℃ are emitted.

[0038] In this invention, when a battery cell 4 experiences thermal runaway and emits high-temperature flue gas, the flue gas first impacts the phase change composite layer 5. The paraffin-based flame-retardant phase change material (melting point 70-90℃) in the phase change composite layer 5 melts rapidly at high temperatures, absorbing the heat from the flue gas. Flame retardants (ammonium polyphosphate APP, expanded graphite, red phosphorus) act as flame retardants, achieving a UL94 V-0 flame retardancy rating, ensuring that the phase change material itself will not burn or decompose at high temperatures. Simultaneously, the extinguishing agent particles in the flame-retardant phase change material decompose at high temperatures, further absorbing heat and reducing the temperature of the flue gas. Sodium bicarbonate or ammonium dihydrogen phosphate decomposes to produce inert carbon dioxide, diluting the concentration of flammable gases. Due to the high fluidity of the liquid, the molten flame-retardant phase change material is propelled out of the pores by the high-temperature flue gas, allowing the flue gas to pass through the pores and gradually penetrate the phase change composite layer 5. After being cooled by the phase change composite layer 5, the temperature of the flue gas can be reduced to 200-300℃.

[0039] After the high-temperature flue gas penetrates the phase change composite layer 5, it reaches the microchannel injection layer 6. At this time, the temperature of the high-temperature flue gas is higher than 120-140℃, which can cause the thermally sensitive encapsulation film 8 on the side of the microchannel injection layer 6 to melt or soften rapidly and rupture rapidly under the high-speed impact of the high-temperature flue gas, thereby releasing the internal coolant 9. The boiling point of the coolant 9 is 35-60℃. The high-temperature flue gas of 200-300℃ can cause the coolant 9 to evaporate rapidly, absorbing the heat of the high-temperature flue gas, so that the temperature of the high-temperature flue gas is further reduced to 150-250℃. Coolant 9 uses fluorinated coolant Novec 7000 or HFE-7100, which is a colorless, odorless, low-toxicity, non-flammable, and non-corrosive gas after evaporation. A small amount of coolant 9 may decompose (decomposition temperature is 250-400℃) to produce trace amounts of hydrogen fluoride gas. However, the thermal runaway of lithium batteries itself will produce a certain amount of hydrogen fluoride gas. Coolant 9 will not introduce new pollutants, and hydrogen fluoride gas can be absorbed by the ZSM-5 zeolite molecular sieve and alumina composite layer 72.

[0040] As the thermally sensitive encapsulation film 8 on both sides of the microchannel injection layer 6 ruptures, the high-temperature flue gas can pass through the through holes in the microchannel injection layer 6 and reach the filter layer 7. After the high-temperature flue gas is initially filtered by the alumina ceramic fiber layer 71 to remove large solid particles, it then passes through the ZSM-5 zeolite molecular sieve and alumina composite layer 72 to absorb various combustible gases, reducing the concentration of particles and combustible gases.

[0041] After passing through the filter layer 7, the high-temperature flue gas enters the guide cavity 10, then enters the pressure relief chamber 11, and finally exits from the pressure relief chamber 11.

[0042] Because the pore size of the phase change composite layer 5 gradually decreases from the center to the edge of the porous matrix, the flame-retardant phase change material monomers in the pores at the center of the porous matrix have a larger volume and need to absorb more heat to completely liquefy and thus detach from the pores. The flame-retardant phase change material monomers in the pores at the edge of the porous matrix have a smaller volume and can completely liquefy and detach from the pores by absorbing less heat. Therefore, when the cell 4 experiences thermal runaway, the pores at the edge of the porous matrix will be opened first, and the pores at the center will be opened later. Through the sequential gradient opening, the high-temperature flue gas can be cooled more persistently.

[0043] Meanwhile, the thickness of the thermal encapsulation film 8 decreases from the center to the edge of the metal substrate. The thermal encapsulation film 8 at the edge of the metal substrate breaks first, and the thermal encapsulation film 8 at the center of the metal substrate breaks later, releasing the coolant 9 in sequence, which can continuously cool the flue gas for a certain period of time.

[0044] In this invention, the four side walls of the battery compartment are provided with a phase change composite layer 5, a microchannel injection layer 6 and a filter layer 7. The high-temperature flue gas emitted by the battery cell 4 can be discharged from the phase change composite layer 5, the microchannel injection layer 6 and the filter layer 7 on the four sides at the same time, so as to achieve the dispersed discharge of flue gas and ensure the cooling effect.

[0045] The filter layer 7 has a certain filtration effect, but in order to prevent the filter layer 7 from becoming clogged and causing the flue gas to be unable to be discharged quickly, the filter pore diameter of the filter layer 7 is relatively large, which can only filter out larger solid particles. The high-temperature flue gas also contains a large number of small solid particles and droplets. In order to further remove these droplets, reduce the particulate matter content, and further reduce the temperature of the final emitted flue gas and the temperature of the flue gas immediately after the emission, the present invention provides multiple vortex tubes 12 in the pressure relief chamber 11. Each battery compartment corresponds to one vortex tube 12. The inlet of each vortex tube 12 is connected to the guide cavity 10 through a transmission pipe. The cold end outlet 13 of the vortex tube 12 is connected to the inner cavity of the pressure relief chamber 11. The hot end outlet 14 of the vortex tube 12 is connected to the gap between the battery cell 4 and the phase change composite layer 5 through a return pipe 15. A one-way valve 17 is provided on the return pipe 15, and a dust collection box 16 connected to the inner cavity of the vortex tube 12 is provided on the outer wall of the hot end of the vortex tube 12.

[0046] The vortex tube 12 is a commonly used refrigeration device, consisting of a tube body with an inlet tangential to the tube body's side wall. The tube body has a hot-end outlet 14 and a cold-end outlet 13 at its two ends. A regulating valve is installed at the hot-end outlet 14 to adjust the ratio of cold to hot air flow. The process is as follows: high-speed flowing gas enters the vortex tube 12 through the inlet. Because the inlet is tangential to the tube body, the gas rotates at high speed inside the tube body, forming a vortex, and moves towards the hot-end outlet 14. Upon reaching the hot-end outlet 14, some gas is discharged through the regulating valve, while some gas is obstructed and flows to the center of the tube body, where it expands in volume and cools down, changing its direction of motion and flowing towards the cold-end outlet 13, ultimately exiting from the cold-end outlet 13.

[0047] In a conventional vortex tube 12, the pressure range of the gas introduced is typically 0.1-1 MPa, while the pressure of the flue gas emitted during thermal runaway of a lithium battery is typically 0.2-0.8 MPa, fully meeting the operational requirements of the vortex tube 12. In this invention, the flue gas temperature in the guide cavity 10 is approximately 150-250°C. After being processed by the vortex tube 12, the flue gas temperature discharged from the hot end outlet 14 is approximately 180-320°C, and the flue gas temperature discharged from the cold end outlet 13 is approximately 110-210°C, further reducing the temperature. The cold end outlet 13 can be connected to the pressure relief chamber 11, and ultimately discharged through the flue gas emission port of the pressure relief chamber 11. The cold end outlet 13 can also be directly connected to the external space. Although the temperature of the flue gas discharged from the hot-end outlet 14 increases, it is still far below 400-800℃. Therefore, the flue gas discharged from the hot-end outlet 14 is transported through the return pipe 15 to the space between the battery cell 4 and the phase change composite layer 5. The returned flue gas mixes with the high-temperature flue gas emitted by the battery cell 4, which can reduce the temperature of the high-temperature flue gas. After the temperature is reduced, the flue gas pressure is also reduced, thus reducing the risk of explosion. The one-way valve 17 ensures that the flue gas in the hot-end outlet 14 flows to the battery compartment, and the flue gas in the battery compartment cannot flow to the hot-end outlet 14.

[0048] Furthermore, by providing a dust collection box 16 connected to the inner cavity of the vortex tube 12 on the outer wall of the hot end of the vortex tube 12, the flue gas, rotating at high speed, possesses a strong centrifugal force. When the flue gas reaches the dust collection box 16, the particles in the flue gas enter the dust collection box 16 under the action of centrifugal force, achieving the separation of solid and liquid particles in the flue gas. This further reduces the particle content in the flue gas, preventing a large number of particles from adhering to equipment near the lithium battery pack after the flue gas is discharged, thus preventing equipment damage, and also reducing harm to the surrounding environment. Therefore, this invention can utilize the power of the high-temperature flue gas itself to remove particulate matter, without requiring an additional power source.

[0049] When each of the battery cells 4 is working normally, in order to dissipate heat in a timely manner to ensure charging and discharging performance, a heat dissipation mechanism can be set up, such as using heat pipes for active heat dissipation, referring to the invention patent application number CN201710349633.7, a thermal management system for power lithium batteries. Although heat pipes can conduct heat quickly, the heat dissipation speed is limited by the return flow rate of the working fluid.

[0050] In this invention, the partition 3 between two adjacent battery compartments includes a first plate 31 and a second plate 32. A heat dissipation gap 33 is provided between the first plate 31 and the second plate 32. Multiple heat-conducting blocks 34 are provided within the heat dissipation gap 33. One side wall of the heat-conducting block 34 is slidably engaged with the first plate 31, and the other side wall is slidably engaged with the second plate 32. A groove 35 is provided on the top of the heat-conducting block 34. The length direction of the groove 35 is consistent with the thickness direction of the heat dissipation gap 33, and a slider 36 is provided within the groove 35. The groove 35 can be a dovetail groove. The shape of the slider 36 is adapted to the shape of the slider 36, so that the slider 36 can slide along the groove 35, but cannot detach from the groove 35. The slider 36 is connected to a heat pipe 38 through a first universal ball joint 37. The heat pipe 38 is a thin-walled copper tube sealed at both ends. Its interior is evacuated and filled with pure water as the working fluid. A capillary layer is provided on the inner wall. A heat-conducting strip 39 is provided at the top of the heat dissipation gap 33, and the upper end of the heat pipe 38 is connected to the heat-conducting strip 39 through the second universal ball joint 310.

[0051] The heat generated by the battery cell 4 is transferred to the first plate 31 and the second plate 32. The first plate 31 and the second plate 32 then transfer the heat to the heat-conducting block 34, which in turn transfers the heat to the heat pipe 38. The lower end of the heat pipe 38 is the evaporation end, and the upper end is the condensation end. The liquid working fluid at the lower end of the heat pipe 38 absorbs heat and vaporizes, then moves to the upper end, where it liquefies and releases heat, thus transferring heat from inside the partition 3 to the surface heat-conducting strip 39. The heat-conducting strip 39 then transfers the heat to the outside air. The liquefied working fluid at the upper end of the heat pipe 38 flows back to the lower end under the action of gravity and the capillary layer on the inner wall of the heat pipe 38, realizing the circulation of the working fluid. The circulation speed of the working fluid determines the heat dissipation efficiency.

[0052] The partition 3 between two adjacent battery compartments is located far from the housing 1 and the cover 2, making it difficult for heat to dissipate. Therefore, placing the heat pipe 38 inside the partition 3 between the two adjacent battery compartments can promptly transfer the heat inside the partition 3 to the outside. In addition, when a battery cell 4 experiences thermal runaway, the high temperature is transferred to the partition 3. Using the heat pipe 38 to dissipate heat from the partition 3 in a timely manner can prevent the heat from spreading to the adjacent battery cell 4 through the partition 3, thereby preventing thermal runaway.

[0053] Because the heat-conducting block 34 is slidably engaged with the first plate 31 and the second plate 32, the heat-conducting block 34 can slide up, down, left, and right. When sliding, it drives the slider 36 to move, and the slider 36 can slide within the heat-conducting block 34. The sliding direction of the slider 36 is perpendicular to the sliding direction of the heat-conducting block 34, allowing the slider 36 to move in any direction. In many applications of lithium battery packs, such as vehicles and drones, they are subjected to continuous vibration. In this invention, when the lithium battery pack is vibrated, the heat-conducting block 34 slides within a certain range, and the slider 36 can also slide. When the slider 36 moves, it drives the first universal ball joint 37 to move. The first universal ball joint 37 and the second universal ball joint 310 can rotate in various directions within a certain range. When the second universal ball joint 310 cannot slide but can only rotate, the movement of the first universal ball joint 37 can cause the lower end of the heat pipe 38 to continuously oscillate. During this oscillation, the liquid working fluid condensed at the upper end of the heat pipe 38 can return to the lower end more quickly, thereby accelerating the return of the liquid working fluid and improving heat dissipation efficiency.

[0054] The cover 2 has multiple strip-shaped holes, and the heat-conducting strip 39 is located in the strip-shaped holes. The top of the heat-conducting strip 39 extends out of the strip-shaped holes, so that the top of the heat-conducting strip 39 is in direct contact with the outside air, which is conducive to faster heat dissipation.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 lithium battery pack, comprising a housing (1) and a cover (2), wherein the housing (1) contains a plurality of battery compartments, each battery compartment containing a battery cell (4), characterized in that: A phase change composite layer (5), a microchannel injection layer (6), and a filter layer (7) are sequentially disposed between the battery cell (4) and the side wall of the battery compartment. The phase change composite layer (5) includes a porous substrate with a porosity of 70%-85%. The pores of the porous substrate are filled with fire extinguishing agent particles and flame-retardant phase change material with a melting point of 70-90℃. The microchannel injection layer (6) includes a metal substrate with multiple through holes. The metal substrate has a thermal encapsulation film (8) with a rupture temperature of 120-140℃ on both sides. The thermal encapsulation film (8) covers the opening of each through hole. The through holes are filled with a coolant (9) with a boiling point of 35-60℃. A guide cavity (10) is disposed between the filter layer (7) and the side wall of the battery compartment. The lower surface of the housing (1) is provided with a pressure relief chamber (11), and each guide cavity (10) is connected to the pressure relief chamber (11); The filter layer (7) includes an alumina ceramic fiber layer (71) and a ZSM-5 zeolite molecular sieve and alumina composite layer (72) arranged sequentially. The alumina ceramic fiber layer (71) has a fiber diameter of 10-20 μm and a pore size of 100-200 μm. The ZSM-5 zeolite molecular sieve and alumina composite layer (72) has a pore size of 10-50 μm. The pressure relief chamber (11) is provided with multiple vortex tubes (12). The inlet of each vortex tube (12) is connected to the guide cavity (10). The cold end outlet (13) of the vortex tube (12) is connected to the inner cavity of the pressure relief chamber (11). The hot end outlet (14) of the vortex tube (12) is connected to the gap between the battery cell (4) and the phase change composite layer (5) through the return pipe (15). A one-way valve (17) is provided on the return pipe (15). A dust collection box (16) connected to the inner cavity of the vortex tube (12) is provided on the outer wall of the hot end of the vortex tube (12). The partition (3) between two adjacent battery compartments includes a first plate (31) and a second plate (32). A heat dissipation gap (33) is provided between the first plate (31) and the second plate (32). Multiple heat-conducting blocks (34) are provided in the heat dissipation gap (33). One side wall of the heat-conducting block (34) is slidably engaged with the first plate (31), and the other side wall is slidably engaged with the second plate (32). A sliding groove (35) is provided on the top of the heat-conducting block (34). The length direction of the sliding groove (35) is consistent with the thickness direction of the heat dissipation gap (33). A slider (36) is provided in the sliding groove (35). The slider (36) is connected to a heat pipe (38) through a first universal ball joint (37). A heat-conducting strip (39) is provided on the top of the heat dissipation gap (33). The upper end of the heat pipe (38) is connected to the heat-conducting strip (39) through a second universal ball joint (310).

2. The lithium battery pack as described in claim 1, characterized in that: The porous substrate is a foamed copper plate or a foamed aluminum plate with a pore size of 0.5-2 mm. The pore size gradually decreases from the center to the edge of the porous substrate, and the inner wall of the pores is coated with an oleophilic coating.

3. The lithium battery pack as described in claim 2, characterized in that: Flame-retardant phase change materials are paraffin-based materials with added flame retardants. The flame retardants are one or more of ammonium polyphosphate, expanded graphite, and red phosphorus. The flame retardant rating of the flame-retardant phase change materials is UL94V-0.

4. The lithium battery pack as described in claim 1, characterized in that: The extinguishing agent particles are sodium bicarbonate or ammonium dihydrogen phosphate particles, and the filling amount of the extinguishing agent particles is 5%-15% of the pore volume of the porous matrix.

5. The lithium battery pack as described in claim 1, characterized in that: The metal substrate is a copper plate or an aluminum plate, the diameter of the through hole is 0.1-0.5 mm, and the hole spacing is 0.5-1.5 mm; the coolant (9) is a fluorinated coolant Novec7000 or HFE-7100; the thickness of the thermal encapsulation film (8) decreases from the center to the edge of the metal substrate.

6. The lithium battery pack as described in claim 1, characterized in that: The phase change composite layer (5) has a thickness of 2-5 mm, the microchannel spray layer (6) has a thickness of 2-3 mm, and the filter layer (7) has a thickness of 1-3 mm.

7. The lithium battery pack as described in claim 1, characterized in that: The box cover (2) is provided with multiple strip holes, and the top of the heat-conducting strip (39) extends out of the strip holes.

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