Electrolyte suitable for low temperature, preparation method and lithium battery

Abstract

The invention belongs to the technical field of electrolytes, and particularly relates to an electrolyte suitable for low temperature, a preparation method and a lithium battery, the electrolyte comprises a solvent, a lithium source, a film-forming additive and surface modified magnetic particles; according to the invention, the magnetic particles are added in the electrolyte, then the permanent magnet on the turntable rotates to form a variable magnetic field, due to the change of the magnetic field, the magnetic domains in the magnetic particles in the electrolyte in the battery pack can change along with the magnetic field, and due to the continuous change of the external magnetic field, the magnetic domains in the magnetic particles in the electrolyte in the battery pack can change along with the magnetic field. The magnetic particles are uniformly distributed in the battery pack, so that the electrolyte can be continuously and uniformly heated, and even if the temperature of the external environment is relatively low, the magnetic domains in the magnetic particles continuously move, the magnetic hysteresis loss phenomenon occurs in the movement process, and the temperature of the magnetic particles is further increased; and therefore, the low-temperature applicability of the electrolyte is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytes, and in particular relates to an electrolyte suitable for low temperatures, a preparation method and a lithium battery. Background Art

[0002] Electrolyte is an indispensable component of energy storage devices such as batteries or supercapacitors. Its main function is to provide ionic conductivity and support the battery's charging and discharging process. The components of the electrolyte usually include the following types of solvents: Organic solvents: such as ethylene carbonate, dimethyl carbonate, acetonitrile, etc. These solvents have good electrical conductivity and chemical stability. Water: In some types of batteries (such as nickel-hydrogen batteries), water is used as a solvent; Electrolytes: Salts: Commonly used electrolytes include lithium salts and sodium salts. These salts provide ions that can move freely after dissolving in solvents; Additives: Thickeners: Such as polyvinyl alcohol, which can increase the viscosity of the electrolyte and improve its performance. Stabilizer: Used to improve the thermal stability and chemical stability of the electrolyte and avoid the occurrence of side reactions.

[0003] In the battery, the electrolyte provides ion channels for the positive and negative electrodes in the battery, supports the migration of ions during the charging and discharging process, and thus realizes the storage and release of electrical energy. At the same time, a good electrolyte should be able to remain stable within the operating voltage range of the battery to prevent decomposition or other adverse reactions. The electrolyte and its components can help dissipate heat and maintain the battery at an appropriate operating temperature. The use of additives can effectively inhibit side reactions between the electrolyte and the electrode materials, and improve the cycle life and safety of the battery.

[0004] Under low temperature conditions, conventional electrolytes will encounter the following technical defects: reduced ion conductivity: low temperature will cause the ion migration speed of the electrolyte to drop significantly, thereby reducing its ion conductivity; this will lead to reduced charging and discharging efficiency of the battery, and even affect the normal operation of the battery; at the same time, some electrolytes will undergo phase changes at low temperatures, such as solidification or thickening, resulting in poor electrolyte fluidity and inability to effectively provide ion channels; precipitation: at low temperatures, some electrolytes will precipitate solids, resulting in a decrease in the concentration of ions in the electrolyte and causing short circuits or damage to the electrodes; reduced electrochemical reaction rate: in low temperature environments, the electrochemical reaction rate is usually slow, causing the battery charging and discharging process to become slow, which seriously affects the response time and operating efficiency of the equipment; therefore, there is an urgent need for an electrolyte that can be used in low temperature environments. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, the present invention proposes an electrolyte suitable for low temperature, a preparation method and a lithium battery. The present invention is mainly used to solve the problem that the solvent of the existing electrolyte freezes in a low temperature environment and thus cannot be used.

[0006] The technical solution adopted by the present invention to solve the technical problem is: an electrolyte suitable for low temperature, comprising a solvent, a lithium source and a film-forming additive; the solvent comprises a mixed solvent consisting of linear carbonate accounting for 15%-30% of the total mass of the solvent, cyclic carbonate accounting for 50%-70% of the total mass of the solvent and polyacrylonitrile accounting for 10%-25% of the total mass of the solvent; The lithium source includes a mixture of lithium hexafluorophosphate accounting for 40-50% of the total mass of the lithium source and lithium bis(trifluoromethylsulfonyl)imide accounting for 50-60% of the total mass of the lithium source, and the film-forming additive includes polytetrafluoroethylene; Also included are surface-modified magnetic particles accounting for 3-5% of the total mass of the electrolyte.

[0007] A lithium-ion battery, comprising a battery pack prepared from the above electrolyte, and also comprising a bracket installed outside the battery pack, with thermal energy components for heating the electrolyte in the battery pack arranged on both sides of the battery pack; a terminal block is arranged on one side of the bracket, and the pins on the terminal block are electrically connected to the tabs of the battery pack through wires; The thermal energy component includes a shell and a turntable; a rotating shaft is rotatably connected inside the shell, and the rotating shaft is fixedly connected to the turntable; grooves are evenly spaced in the circumferential direction on one side of the turntable close to the battery pack, and permanent magnets are fixedly installed in the grooves; the magnetic poles of adjacent permanent magnets are arranged in opposite directions; the rotating shaft is connected to a pendulum rod through a one-way bearing; a suspension rope is fixedly connected to one end of the pendulum rod away from the rotating shaft, and a counterweight is fixedly connected to one end of the suspension rope away from the pendulum rod; a tension spring is arranged on one side of the pendulum rod away from the suspension rope; one end of the tension spring is fixedly connected to the pendulum rod, and the other end is fixedly connected to the shell.

[0008] Preferably, the cyclic carbonates include ethylene carbonate and propylene carbonate; and the linear carbonates include ethyl methyl carbonate.

[0009] Preferably, the surface-modified magnetic particles are any one of surface-coated manganese-zinc ferrite particles or surface-coated nickel-zinc ferrite particles, and the particle size of the surface-modified magnetic particles is 10-30 microns.

[0010] Preferably, the solvent comprises a mixed solvent consisting of 15%-20% linear carbonate, 50%-70% cyclic carbonate and 10%-15% polyacrylonitrile; and the particle size of the surface-modified magnetic particles is 10-20 microns.

[0011] Preferably, the surface coating material of the surface-modified magnetic particles is polystyrene.

[0012] A method for preparing an electrolyte, applicable to the above electrolyte, comprises the following steps: S1: Use a balance to weigh a certain amount of ethylene carbonate, propylene carbonate and ethyl methyl carbonate according to the designed ratio; then pour the weighed solvents into a dry mixing kettle one by one, take nitrogen protection measures to prevent moisture from the air from entering; use a magnetic stirrer to set the speed to 300-500 rpm, stir for 15-30 minutes, and ensure that the solvents are fully mixed and reach a uniform state; S2: Weigh lithium hexafluorophosphate and lithium bis(trifluoromethylsulfonyl)imide according to the designed ratio; then slowly add lithium hexafluorophosphate to the stirring solvent mixture, keep stirring during the addition, and then slowly add lithium bis(trifluoromethylsulfonyl)imide to the above mixture to ensure that the lithium salt dissolves quickly; continue stirring for 30 minutes until the lithium salt is completely dissolved to form a transparent and uniform electrolyte; S3: Weigh the polytetrafluoroethylene powder and grind it before adding it to increase its surface area; then slowly sprinkle the polytetrafluoroethylene powder into the electrolyte while stirring continuously to ensure that the film former is evenly dispersed; stir the mixture for about 10-15 minutes to ensure that the film former is completely dissolved and combined with the electrolyte; S4: weighing a number of surface-modified magnetic particles according to the designed ratio, and then adding the magnetic particles to the mixture in step S3, and maintaining continuous stirring until the magnetic particles are uniformly mixed in the mixture; S5: Then, add the designed dosage of polyacrylonitrile to the mixture in step S4 and continue stirring until all the substances are evenly mixed, thereby completing the preparation of the electrolyte.

[0013] Preferably, an expansion cylinder is fixedly connected to the inside of the shell; a sliding frame is slidably connected to the inside of the expansion cylinder, one end of the sliding frame extends to the outside of the expansion cylinder and is fixedly connected to a limiting block; one side of the limiting block is inclined; The rotating disk is provided with card slots at even intervals; a cavity on one side of the expansion cylinder away from the rotating disk is filled with a thermal expansion medium.

[0014] Preferably, an air cylinder is provided inside the shell at the lower part of the counterweight block; an air cylinder is slidably connected to the inside of the air cylinder; a pressure storage tank is provided inside the shell; the pressure storage tank is fixedly connected to the shell; a pressure switch is provided on one side of the pressure storage tank, a one-way valve is provided on one side of the pressure storage tank, and the air inlet end of the one-way valve is connected to the air cylinder, and the other side is connected to the air inlet end of the pressure switch; a nozzle is provided at the outlet end of the pressure switch; a fan blade is fixedly connected to the side of the turntable close to the nozzle.

[0015] The beneficial effects of the present invention are as follows: 1. In the present invention, external vibration is used to move the counterweight downward, which can drive the pendulum to rotate. The rotation of the pendulum can drive the turntable to rotate. Due to the rotation of the turntable, the permanent magnet thereon rotates with it. Since the magnetic poles of adjacent permanent magnets are opposite, the rotation of the permanent magnet will generate a changing magnetic field inside the battery pack as the turntable rotates. Due to the change in the magnetic field, the magnetic domains in the magnetic particles in the electrolyte inside the battery pack will follow the change of the magnetic field. Due to the continuous change of the external magnetic field, the magnetic domains inside the magnetic particles will continue to move. During the movement, hysteresis loss will occur, which will increase the temperature of the magnetic particles. Since the magnetic particles are evenly distributed inside the battery pack, the electrolyte can be heated continuously and evenly, thereby increasing the working temperature of the electrolyte in the battery, and the temperature of the electrolyte can be maintained at a higher temperature more quickly. Even when the temperature of the external environment is low, the electrolyte can be used appropriately, thereby improving the low-temperature applicability of the electrolyte.

[0016] 2. In the present invention, since surface-modified magnetic particles are added to the electrolyte, the magnetic particles in the electrolyte will settle during actual use, resulting in uneven distribution of the magnetic particles, further resulting in uneven heating, causing local heating of the battery during use. When the solvent is too thick, it will be difficult to evenly mix the magnetic particles into the solvent, resulting in uneven texture of the electrolyte, thereby affecting its quality. Therefore, in this solution, when selecting a solvent, a relatively sparse linear carbonate is mixed with a relatively viscous cyclic carbonate, and then polyacrylonitrile (which has a certain lubricating effect and can form a stable gel structure) is added thereto, so that a solvent with a more suitable viscosity can be obtained, which can not only meet the uniform distribution of the magnetic particles, but also slow down the sedimentation problem of the magnetic particles during the later use of the battery.

[0017] 3. In the present invention, an expansion cylinder is arranged inside the shell. When the external ambient temperature increases, the heat expansion medium inside the expansion cylinder will expand, which will cause the sliding frame in the expansion cylinder to move downward, so that the limit block can be inserted into the slot, thereby limiting the rotation of the turntable, thereby avoiding the situation where the heat of the battery continues to increase, thereby increasing the applicable temperature range of the battery and improving the practicality of the battery.

[0018] 4. In the present invention, when the battery is subjected to external vibration during use, the counterweight block will be driven to move downward, and then hit the inflation slide, causing the inflation slide to move downward, so that the gas inside the inflation cylinder enters the pressure storage tank. Since a one-way valve is provided, as the vibration continues, the inflation cylinder will continuously fill the pressure storage tank with gas, causing the pressure inside the pressure storage tank to continuously increase. The inflatable slide comprises a skeleton plate with through holes, the skeleton plate is slidably connected to the inner wall of the inflatable cylinder, the lower part of the skeleton plate is connected to a flexible sheet, the center position of the flexible sheet is fixedly connected to the skeleton plate, and a reset spring is arranged at the lower part of the flexible sheet for resetting. When the flexible sheet is squeezed downward by the action of the counterweight block, the skeleton plate will squeeze the flexible sheet, so that the flexible sheet will fit on the skeleton plate to close the through holes on the skeleton plate, thereby realizing the action of inflating like a pressure storage tank; when the pressure of the counterweight block is removed, the skeleton plate will move upward under the action of the reset spring. At this time, the edge of the flexible sheet lacks support, which will cause the through holes to be in a conducting state, allowing gas to enter, facilitating the subsequent continuous inflation action.

[0019] When the pressure in the pressure storage tank continues to increase, the pressure switch will open, causing the gas in the pressure storage tank to quickly eject from the nozzle, thereby driving the fan blades to rotate, and then the turntable can rotate quickly, increasing the frequency of magnetic field changes; because the surface-modified magnetic particles contain nickel-zinc ferrite particles, they will have obvious hysteresis losses in the high-frequency changing magnetic field, and thus can generate more heat, which can achieve a faster increase in the temperature of the electrolyte, and thus can improve the low-temperature adaptability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 It is a flowchart of the preparation process of the electrolyte in the present invention; Figure 2 It is a first overall structural schematic diagram of the lithium battery in the present invention; Figure 3 is a second overall structural schematic diagram of the lithium battery of the present invention; Figure 4 It is a schematic diagram of the overall structure of the thermal energy component in the present invention; Figure 5 is a schematic diagram of the first internal structure of the thermal energy component of the present invention; Figure 6 is a second internal structure schematic diagram of the thermal energy component in the present invention; Figure 7 It is a schematic diagram of the installation structure of the inflatable slide in the present invention; Figure 8 It is a schematic diagram of the internal structure of the pressure switch in the present invention; In the figure: battery pack 1, bracket 2, terminal block 3, shell 4, rotating shaft 5, turntable 6, permanent magnet 7, pendulum 8, hanging rope 9, counterweight 10, tension spring 11, expansion cylinder 12, sliding frame 13, limit block 14, slot 15, inflation cylinder 16, inflation slide 17, pressure storage tank 18, pressure switch 19, one-way valve 20, nozzle 21, fan blade 22, skeleton plate 23, through hole 24, flexible sheet 25, reset spring 26, movable frame 27, opening chamber 28, air inlet 29, air outlet 30, support plate 31, through hole 32, flexible plate 33, buffer chamber 34, support spring 35. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0023] Embodiment 1: An electrolyte suitable for low temperature, comprising a solvent, a lithium source and a film-forming additive; the solvent comprises a mixed solvent consisting of a linear carbonate (methyl ethyl carbonate) accounting for 15%-30% of the total mass of the solvent, a cyclic carbonate (ethylene carbonate and propylene carbonate) accounting for 50%-70% of the total mass of the solvent, and polyacrylonitrile accounting for 10%-25% of the total mass of the solvent; The lithium source includes a mixture of lithium hexafluorophosphate accounting for 40-50% of the total mass of the lithium source and lithium bis(trifluoromethylsulfonyl)imide accounting for 50-60% of the total mass of the lithium source, and the film-forming additive includes polytetrafluoroethylene; Also included are surface-modified magnetic particles accounting for 3-5% of the total mass of the electrolyte; The surface-modified magnetic particles are any one of surface-coated manganese-zinc ferrite particles or surface-coated nickel-zinc ferrite particles, and the particle size of the surface-modified magnetic particles is 10-30 microns; the surface coating material of the surface-modified magnetic particles is polystyrene.

[0024] Since surface-modified magnetic particles are added to the electrolyte, the magnetic particles in the electrolyte will settle during actual use, resulting in uneven distribution of the magnetic particles, further resulting in uneven heating, causing local heating of the battery during use. When the solvent is too thick, it will be difficult to evenly mix the magnetic particles into the solvent, resulting in uneven texture of the electrolyte, thus affecting its quality. Therefore, in this solution, when selecting the solvent, a relatively sparse linear carbonate is mixed with a relatively viscous cyclic carbonate, and then polyacrylonitrile is added thereto to have a certain lubricating effect, so as to form a stable gel structure and obtain a solvent with a more suitable viscosity, which can not only meet the uniform distribution of the magnetic particles, but also slow down the sedimentation problem of the magnetic particles during the later use of the battery.

[0025] The manganese-zinc ferrite has large hysteresis losses at low frequencies and releases more heat in alternating magnetic fields. In particular, materials with high magnetic permeability and large hysteresis loops will show strong hysteresis effects when the magnetic field changes. Nickel-zinc ferrite performs better at high frequencies, but also has strong hysteresis losses in low-frequency alternating magnetic fields, especially when the material has high magnetic permeability. By selecting the above two types of magnetic particles, the electrolyte can be designed and matched according to the actual use scenario of the battery. When the battery is subjected to more and more severe vibrations during use, nickel-zinc ferrite can be selected as the magnetic particle. When the vibration is less and slower, manganese-zinc ferrite can be selected as the magnetic particle, thereby increasing the applicability of the electrolyte battery.

[0026] By providing a surface layer covered with polystyrene on the surface of the magnetic particles, the magnetic particles can be prevented from directly contacting the substances in the electrolyte. The chemical relationship between polystyrene and the substances in the electrolyte is relatively stable, so that the basic functions of the electrolyte will not be destroyed after the magnetic particles are introduced, and the low-temperature adaptability of the electrolyte can be improved by the external changing magnetic field.

[0027] When choosing covering materials, you can also choose ceramic coatings such as aluminum oxide and zirconium oxide, which usually have excellent chemical inertness and can effectively isolate metal nanoparticles from direct contact with the electrolyte, preventing metal nanoparticles from inducing side reactions in the electrolyte. Ceramic coatings can also improve the antioxidant properties of the electrolyte and slow down the internal interface decomposition problem of lithium batteries; appropriate amounts of nanoparticles can promote the migration rate of lithium ions in the electrolyte by microscopic modification of the electrolyte, such as increasing the conductivity of the electrolyte or adjusting the viscosity of the electrolyte; ceramic coatings have high surface energy, which to a certain extent promotes the interaction between lithium ions and the surface of nanoparticles, thereby optimizing the ionic conductivity of the electrolyte.

[0028] Embodiment 2: Compared with embodiment 1, embodiment 2 is improved only in the following components, wherein the solvent comprises a mixed solvent consisting of linear carbonate accounting for 15%-20% of the total mass of the solvent, cyclic carbonate accounting for 50%-70% of the total mass of the solvent, and polyacrylonitrile accounting for 10%-15% of the total mass of the solvent; and the particle size of the surface-modified magnetic particles is 10-20 microns.

[0029] Embodiment 3: Figure 1 As shown, a method for preparing an electrolyte, which is applicable to the above-mentioned electrolyte, comprises the following steps: S1: Use a balance to weigh a certain amount of ethylene carbonate, propylene carbonate and ethyl methyl carbonate according to the designed ratio; then pour the weighed solvents into a dry mixing kettle one by one, take nitrogen protection measures to prevent moisture from the air from entering; use a magnetic stirrer to set the speed to 300-500 rpm, stir for 15-30 minutes, and ensure that the solvents are fully mixed and reach a uniform state; S2: Weigh lithium hexafluorophosphate and lithium bis(trifluoromethylsulfonylimide) according to the designed ratio; then slowly add lithium hexafluorophosphate to the stirring solvent mixture, keep stirring during the addition, and then slowly add lithium bis(trifluoromethylsulfonylimide) to the above mixture to ensure that the lithium salt dissolves quickly; continue stirring for 30 minutes until the lithium salt is completely dissolved to form a transparent and uniform electrolyte; S3: Weigh the polytetrafluoroethylene powder and grind it before adding it to increase its surface area; then slowly sprinkle the polytetrafluoroethylene powder into the electrolyte while stirring continuously to ensure that the film former is evenly dispersed; stir the mixture for about 10-15 minutes to ensure that the film former is completely dissolved and combined with the electrolyte; S4: weighing a number of surface-modified magnetic particles according to the designed ratio, and then adding the magnetic particles to the mixture in step S3, and maintaining continuous stirring until the magnetic particles are uniformly mixed in the mixture; S5: Then, add the designed dosage of polyacrylonitrile to the mixture in step S4 and continue stirring until all the substances are evenly mixed, thereby completing the preparation of the electrolyte.

[0030] Since polyacrylonitrile has a high viscosity, it will cause the electrolyte to form a gel-like structure after being added. Therefore, in this solution, the other two solvents are first mixed with the magnetic particles to form a stable suspended structure with a uniform texture, and then polyacrylonitrile is added again to form a gel-like structure. This can enable the magnetic particles in the electrolyte to form a more stable and uniform distribution form in the electrolyte, thereby improving the uniformity of subsequent heating, and further improving the storage stability of the electrolyte and the stability during subsequent use.

[0031] Embodiment 4: Figures 1 to 3 As shown, a lithium-ion battery comprises a battery pack 1 prepared from the above electrolyte, and also comprises a bracket 2 installed on the outside of the battery pack 1, and thermal energy components for heating the electrolyte in the battery pack 1 are arranged on both sides of the battery pack 1; a terminal block 3 is arranged on one side of the bracket 2, and the pins on the terminal block 3 are electrically connected to the tabs of the battery pack 1 through wires; The thermal energy component includes a shell 4 and a turntable 6; a rotating shaft 5 is rotatably connected inside the shell 4, and the rotating shaft 5 is fixedly connected to the turntable 6; grooves are evenly spaced along the circumferential direction on the side of the turntable 6 close to the battery pack 1, and permanent magnets 7 are fixedly installed in the grooves; the magnetic poles of adjacent permanent magnets 7 are arranged in opposite directions; the rotating shaft 5 is connected to a pendulum rod 8 through a one-way bearing; the end of the pendulum rod 8 away from the rotating shaft 5 is fixedly connected to a hanging rope 9, and the end of the hanging rope 9 away from the pendulum rod 8 is fixedly connected to a counterweight 10; a tension spring 11 is arranged on the side of the pendulum rod 8 away from the hanging rope 9; one end of the tension spring 11 is fixedly connected to the pendulum rod 8, and the other end is fixedly connected to the shell 4.

[0032] During operation, the counterweight 10 is moved downward by external vibration, which in turn drives the pendulum 8 to rotate. The rotation of the pendulum 8 drives the turntable 6 to rotate. Due to the rotation of the turntable 6, the permanent magnet 7 thereon rotates with it. Since the magnetic poles of the adjacent permanent magnets 7 are opposite, the rotation of the turntable 6 will generate a changing magnetic field inside the battery pack 1. Due to the change of the magnetic field (the permanent magnet 7 can be a neodymium iron boron magnet or an aluminum nickel cobalt magnet, etc.), the magnetic domains in the magnetic particles in the electrolyte inside the battery pack 1 will have the same magnetic field as the rotation of the turntable 6. As the magnetic field changes, due to the continuous change of the external magnetic field, the magnetic domains inside the magnetic particles will continue to move, and hysteresis loss will occur during the movement, which will increase the temperature of the magnetic particles. Since the magnetic particles are evenly distributed inside the battery pack 1, the electrolyte can be heated continuously and evenly, thereby increasing the operating temperature of the electrolyte in the battery. The temperature of the electrolyte can be maintained at a higher temperature more quickly, and the electrolyte can be used appropriately even when the temperature of the external environment is low, thereby improving the low-temperature applicability of the electrolyte.

[0033] like Figures 4 to 5 As shown, the expansion cylinder 12 is fixedly connected to the inside of the housing 4; the expansion cylinder 12 is slidably connected to the sliding frame 13, one end of the sliding frame 13 extends to the outside of the expansion cylinder 12 and is fixedly connected to the limit block 14; one side of the limit block 14 is inclined; The rotating disk 6 is provided with evenly spaced slots 15 ; the cavity on one side of the expansion cylinder 12 away from the rotating disk 6 is filled with a thermal expansion medium.

[0034] During operation, since the battery is not in a low-temperature environment for a long time during use, when the external environment or the internal temperature of the battery is high, it is not suitable to continue to increase the temperature of the electrolyte through hysteresis loss. Therefore, in this solution, an expansion cylinder 12 is arranged inside the shell 4. When the external ambient temperature increases, the thermal expansion medium inside the expansion cylinder 12 will expand into one or more mixtures of ether, Freon, ammonia or helium. This will cause the sliding frame 13 in the expansion cylinder to move downward, so that the limit block 14 can be inserted into the slot 15, thereby limiting the rotation of the turntable 6, thereby avoiding the situation where the heat of the battery continues to increase, thereby improving the applicable temperature range of the battery and improving the practicality of the battery.

[0035] like Figure 5 and Figure 6As shown, an air cylinder 16 is provided inside the shell 4 at the lower part of the counterweight 10; an air charging slide 17 is slidably connected inside the air cylinder 16; a pressure storage tank 18 is provided inside the shell 4; the pressure storage tank 18 is fixedly connected to the shell 4; a pressure switch 19 is provided on one side of the pressure storage tank 18, a one-way valve 20 is provided on one side of the pressure storage tank 18, and the air inlet end of the one-way valve 20 is connected to the air cylinder 16, and the other side is connected to the air inlet end of the pressure switch 19; a nozzle 21 is provided at the outlet end of the pressure switch 19; a fan blade 22 is fixedly connected to the side of the turntable 6 close to the nozzle 21.

[0036] During operation, when the battery is subjected to external vibrations during use, the counterweight 10 will be driven to move downward, and then hit the inflatable slide 17, causing the inflatable slide 17 to move downward, so that the gas inside the inflatable cylinder 16 enters the pressure storage tank 18. Since the one-way valve 20 is provided, as the vibration continues, the inflatable cylinder 16 will continuously fill the pressure storage tank 18 with gas, causing the pressure inside the pressure storage tank 18 to continuously increase. like Figure 7 As shown, the inflatable slide 17 includes a skeleton plate 23 with a through hole 24, the skeleton plate 23 is slidably connected to the inner wall of the inflation cylinder 16, and the lower part of the skeleton plate 23 is connected to a flexible sheet 25, the center position of the flexible sheet 25 is fixedly connected to the skeleton plate 23, and at the same time, a reset spring 26 for resetting is arranged at the lower part of the flexible sheet 25. When squeezed downward by the counterweight 10, the skeleton plate 23 will squeeze the flexible sheet 25, so that the flexible sheet 25 fits on the skeleton plate 23 to achieve the closure of the through hole on the skeleton plate 23, and realize the action of inflating like the pressure storage tank 18; when the pressure of the counterweight 10 is removed, the skeleton plate 23 moves upward under the action of the reset spring 26, and at this time, the edge of the flexible sheet 25 lacks support, which will make the through hole 24 in a conductive state, and gas enters, facilitating the subsequent continuous inflation action.

[0037] When the pressure in the pressure storage tank 18 continues to increase, the pressure switch 19 will be turned on, and the gas in the pressure storage tank 18 will be quickly ejected from the nozzle 21, thereby driving the fan blades 22 to rotate, so that the turntable 6 can rotate quickly, thereby increasing the frequency of magnetic field changes; because the surface-modified magnetic particles contain nickel-zinc ferrite particles, they will have obvious hysteresis losses in the high-frequency changing magnetic field, thereby generating more heat, which can achieve a faster increase in the temperature of the electrolyte, and thereby improve the low-temperature adaptability of the battery.

[0038] like Figure 8As shown, the pressure switch 19 component includes a switch compartment and a movable frame 27, one end of the movable frame 27 is slidably connected to the inner wall of the switch compartment; an air inlet 29 is provided at the upper end of the switch compartment, and the air inlet 29 is connected to the pressure storage tank 18; an air outlet 30 is provided on the side of the switch compartment near the lower end, and the air outlet 30 is connected to the nozzle 21; the other end of the movable frame 27 is fixedly connected to a support plate 31, and holes 32 are evenly spaced at the upper edge of the support plate 31; a flexible plate 33 is provided on the upper part of the support plate 31, and the middle part of the flexible plate 33 is fixedly connected to the support plate 31; wherein a support spring 35 is provided at the lower part of the support plate 31; and the support plate 31 and the flexible plate 33 are both slidably connected in the buffer compartment 34, and the buffer compartment 34 is filled with liquid medium; During operation, as the pressure on the upper part of the switch compartment gradually increases, the movable frame 27 will be pushed downward until the movable frame 27 is located below the air outlet 30. At this time, the air inlet 29 is connected to the air outlet 30, and the gas inside the pressure compartment will be quickly ejected through the nozzle 21 to drive the turntable 6 to rotate rapidly; after the pressure loss inside the pressure storage tank 18 is completed, under the action of the support spring 35, the support plate 31 moves upward. Since the flexible plate 33 will block the through hole 32 at this time, the liquid medium therein can only slowly pass through the connecting gap between the support plate 31 and the flexible plate 33. During the design process, the contact surface of the flexible plate 33 and the support plate 31 is provided with a convex point to achieve flow, so as to ensure that the pressure in the pressure tank can be completely consumed and the rotation time of the turntable 6 is guaranteed, so as to achieve more efficient heating and further improve the low temperature adaptability of the battery.

[0039] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. An electrolyte suitable for low temperature, comprising a solvent, a lithium source and a film-forming additive; characterized in that: The solvent includes a mixed solvent consisting of linear carbonate accounting for 15%-30% of the total mass of the solvent, cyclic carbonate accounting for 50%-70% of the total mass of the solvent, and polyacrylonitrile accounting for 10%-25% of the total mass of the solvent; The lithium source includes a mixture of lithium hexafluorophosphate accounting for 40-50% of the total mass of the lithium source and lithium bis(trifluoromethylsulfonyl)imide accounting for 50-60% of the total mass of the lithium source, and the film-forming additive includes polytetrafluoroethylene; Also included are surface-modified magnetic particles accounting for 3-5% of the total mass of the electrolyte.

2. The low temperature electrolyte according to claim 1, characterized in that: The cyclic carbonates include ethylene carbonate and propylene carbonate; the linear carbonates include ethyl methyl carbonate.

3. The low temperature electrolyte according to claim 2, characterized in that: The surface-modified magnetic particles are any one of surface-coated manganese-zinc ferrite particles or surface-coated nickel-zinc ferrite particles, and the particle size of the surface-modified magnetic particles is 10-30 microns.

4. The low temperature electrolyte according to claim 3, characterized in that: The solvent includes a mixed solvent consisting of linear carbonate accounting for 15%-20% of the total mass of the solvent, cyclic carbonate accounting for 50%-70% of the total mass of the solvent, and polyacrylonitrile accounting for 10%-15% of the total mass of the solvent; and the particle size of the surface-modified magnetic particles is 10-20 microns.

5. The low temperature electrolyte according to claim 4, characterized in that: The surface coating material of the surface-modified magnetic particles is polystyrene.

6. A method for preparing an electrolyte, applicable to the electrolyte according to any one of claims 4 to 5, characterized in that: The following steps are involved: S1: Use a balance to weigh a certain amount of ethylene carbonate, propylene carbonate and ethyl methyl carbonate according to the designed ratio; then pour the weighed solvents into a dry mixing kettle one by one, take nitrogen protection measures to prevent moisture from the air from entering; use a magnetic stirrer to set the speed to 300-500 rpm, stir for 15-30 minutes, and ensure that the solvents are fully mixed and reach a uniform state; S2: Weigh lithium hexafluorophosphate and lithium bis(trifluoromethylsulfonyl)imide according to the designed ratio; then slowly add lithium hexafluorophosphate to the stirring solvent mixture, keep stirring during the addition, and then slowly add lithium bis(trifluoromethylsulfonyl)imide to the above mixture to ensure that the lithium salt dissolves quickly; continue stirring for 30 minutes until the lithium salt is completely dissolved to form a transparent and uniform electrolyte; S3: Weigh the polytetrafluoroethylene powder and grind it before adding it to increase its surface area; then slowly sprinkle the polytetrafluoroethylene powder into the electrolyte while stirring continuously to ensure that the film former is evenly dispersed; stir the mixture for about 10-15 minutes to ensure that the film former is completely dissolved and combined with the electrolyte; S4: weighing a number of surface-modified magnetic particles according to the designed ratio, and then adding the magnetic particles to the mixture in step S3, and maintaining continuous stirring until the magnetic particles are uniformly mixed in the mixture; S5: Then, add the designed proportion of polyacrylonitrile to the mixture in step S4 and continue stirring until all the substances are evenly mixed, thereby completing the preparation of the electrolyte.

7. A lithium-ion battery, comprising a battery pack (1) prepared from the electrolyte according to claim 5, characterized in that: It also comprises a bracket (2) mounted on the outside of the battery pack (1), and thermal energy components for heating the electrolyte in the battery pack (1) are arranged on both sides of the battery pack (1); a terminal block (3) is arranged on one side of the bracket (2), and the pins on the terminal block (3) are electrically connected to the tabs of the battery pack (1) through wires; The thermal energy component comprises a shell (4) and a rotating disk (6); a rotating shaft (5) is rotatably connected inside the shell (4), and the rotating shaft (5) is fixedly connected to the rotating disk (6); a side of the rotating disk (6) close to the battery pack (1) is provided with grooves evenly spaced in a circumferential direction, and permanent magnets (7) are fixedly installed in the grooves; the magnetic poles of adjacent permanent magnets (7) are arranged in opposite directions; the rotating shaft (5) is connected to a swing rod (8) via a one-way bearing; an end of the swing rod (8) away from the rotating shaft (5) is fixedly connected to a suspension rope (9), and an end of the suspension rope (9) away from the swing rod (8) is fixedly connected to a counterweight (10); a tension spring (11) is provided on a side of the swing rod (8) away from the suspension rope (9); one end of the tension spring (11) is fixedly connected to the swing rod (8), and the other end is fixedly connected to the shell (4).

8. The lithium-ion battery according to claim 7, characterized in that: An expansion cylinder (12) is fixedly connected to the interior of the housing (4); a sliding frame (13) is slidably connected to the interior of the expansion cylinder (12); one end of the sliding frame (13) extends to the exterior of the expansion cylinder (12) and is fixedly connected to a limit block (14); one side of the limit block (14) is inclined; The rotating disk (6) is provided with slots (15) at even intervals; a cavity on a side of the expansion cylinder (12) away from the rotating disk (6) is filled with a thermal expansion medium.

9. The lithium-ion battery according to claim 8, characterized in that: An air cylinder (16) is provided inside the shell (4) at the lower part of the counterweight (10); an air slide (17) is slidably connected inside the air cylinder (16); a pressure storage tank (18) is provided inside the shell (4); the pressure storage tank (18) is fixedly connected to the shell (4); a pressure switch (19) is provided on one side of the pressure storage tank (18); a one-way valve (20) is provided on one side of the pressure storage tank (18), and an air inlet end of the one-way valve (20) is connected to the air cylinder (16), and the other side is connected to the air inlet end of the pressure switch (19); a nozzle (21) is provided at the outlet end of the pressure switch (19); and a fan blade (22) is fixedly connected to the side of the turntable (6) close to the nozzle (21).

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