Method for improving safety of thermal battery pack

Abstract

The invention relates to the technical field of thermal batteries, and discloses a method for improving the safety of a thermal battery pack, which is characterized in that a heat conduction layer and a rapid heat dissipation system are sequentially arranged outside a unit thermal battery or a battery pack, and the heat conduction layer conducts out and uniformly disperses heat generated by the battery; the phase-change material layer in the rapid heat dissipation system absorbs heat to control the temperature range, and the cold circulation device maintains the functionality of the phase-change material and carries out redundant heat. On the premise that the weight and the size of the battery are not obviously increased and the performance of the battery is not influenced, the safety performance of the thermal battery pack is greatly improved, and the thermal battery pack adapts to extreme mechanical and temperature environments and is suitable for high-power and long-time discharge type thermal batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal batteries, in particular to a method for improving the safety of a thermal battery pack. BACKGROUND

[0002] Thermal batteries are a kind of heat-activated reserve batteries, which use molten salt as electrolyte and activate discharge by using heat source to melt the electrolyte. The internal temperature of the battery is generally 450-550℃ during operation. Since thermal batteries have excellent specific energy, specific power, wide environmental temperature, long storage time, rapid and reliable activation, compact structure, no directionality during use, no influence of installation direction, good mechanical properties, no maintenance, etc., they have been favored by all circles since their inception. At present, they have become an ideal power source for emergency systems.

[0003] With the rapid development of society, there is a demand for long-time discharge, high specific energy and high specific power of thermal batteries. For example, in some application scenarios, the output power of the thermal battery needs to meet 50KW or more, and the working voltage is 400V or more. In order to meet the requirements of light weight and small size, this type of battery is generally composed of multiple large-diameter unit cells, which realize power output through series and parallel connection. In order to ensure the performance of the battery under high-power output, the heat of the battery needs to be reserved with sufficient margin. However, in a limited space volume, if the activation heat of the heating sheet in the thermal battery cannot be quickly released, thermal runaway may occur, and then safety problems may occur, which is particularly prominent under light load or no load conditions.

[0004] In order to prevent thermal runaway of the battery, the general method is to use gradient heat design inside the unit cell, that is, to fully consider the factors of heat transfer when designing the battery, and to adopt the principle of "heat complementation" design. However, this design will affect the performance of the battery to varying degrees. In addition, CN108808031B discloses an "internal temperature control structure of thermal battery", which uses progressive heat absorption to disperse heat, that is, by comprehensively applying insulation and heat absorption layers to balance the internal temperature of the unit cell, the safety of the battery is improved under the premise of ensuring the performance of the battery. However, the above measures only balance the internal temperature of the unit cell, and do not quickly guide the heat generated during the operation of the thermal battery out, the internal temperature of the thermal battery is usually kept at 60-80℃, and the temperature usually rises to above 150℃ after heat accumulation, which ultimately still leads to heat accumulation and causes safety problems. In the actual application of power batteries, due to the large thermal capacity of the thermal battery composed of multiple unit cells in series and parallel, the heat of the unit cells affects each other, the heat dissipation rate of the battery pack is limited, and thermal runaway is still easy to occur, which leads to safety problems during use.

[0005] In view of the above problems, it is necessary to explore a method that can quickly reduce the surface temperature of the battery while maintaining the internal temperature of the battery to increase the safety of the thermal battery. SUMMARY

[0006] The present application aims to provide a method for improving the safety of a thermal battery pack, solving the problem that the prior art cannot effectively export heat from the thermal battery and adapt to high-temperature scenarios.

[0007] To achieve the above purpose, the present application adopts the following technical solution: a method for improving the safety of a thermal battery pack, realized by adding a heat-conducting layer and a rapid heat dissipation system outside the unit thermal battery or battery pack, the rapid heat dissipation system comprising a phase change material layer and a cold circulation device; the heat-conducting layer uses at least one of a metal material or a carbon material with high thermal conductivity, and is attached to the outer surface of the unit thermal battery or battery pack, the heat-conducting layer exports and uniformly disperses the heat on the surface of the battery, the phase change material layer is attached to the outer side of the heat-conducting layer and is used to absorb heat to control temperature; the cold circulation device is in contact with the outer surface of the phase change material layer and is used to carry away excess heat and maintain the functionality of the phase change material.

[0008] Preferably, as an improvement, the heat-conducting layer uses at least one of a metal material or a carbon material with high thermal conductivity, and is wrapped and fixed on the outer surface of the thermal battery by glass silk tape or high-temperature insulating tape, with 1 layer or multiple layers of wrapping.

[0009] Preferably, as an improvement, the metal material is at least one of silver foil, copper foil or aluminum foil; the carbon material is at least one of graphite, carbon fiber or graphene.

[0010] Preferably, as an improvement, the phase change material layer uses at least one of a metal phase change material or a molten salt phase change material, and is fixed on the outer surface of the heat-conducting layer by glass silk tape or high-temperature insulating tape, with 1 layer or multiple layers of wrapping.

[0011] Preferably, as an improvement, the metal phase change material is at least one of Si-Mg alloy, Al-Si alloy or Mg-Cu-Zn alloy; the molten salt phase change material is at least one of LiNO3, Ca(NO3)2, MgCl2 or MgF2.

[0012] Preferably, as an improvement, the cold circulation device comprises a temperature controller, a small motor, a cold pipe and a cooling tank, the cold pipe is attached and wound around the outer surface of the phase change material layer, the two ends of the cold pipe are connected to the cooling tank, the cooling tank is arranged in the side area of the unit thermal battery or battery pack, and the cooling tank contains a cooling liquid; the temperature controller is connected to the small motor and the cold pipe, and is used to regulate the circulation state of the cooling liquid.

[0013] Preferably, as an improvement, the small motor is powered by a thermal battery with a power of less than 50W; when the surface temperature of the battery exceeds the set value of 300-400℃, the temperature controller starts the small motor to realize the circulation of the cooling liquid.

[0014] Preferably, as an improvement, the cooling liquid is water or alcohol, and the flow rate is controlled to be more than 100ml / min.

[0015] The advantages of the present scheme are: 1. The design of "external heat dissipation + layered temperature control" is adopted, which is different from the existing internal heat balance or single heat dissipation structure. The heat is dissipated through the heat conduction layer, the temperature is controlled through the phase change material layer, and the cold circulation device is used to maintain stability. The problem of heat accumulation is solved by three synergies. 2. Adapt to the high-temperature working environment of 450-550℃ of the thermal battery. The parameter design of the phase change material layer and the cold circulation device is targeted to match the high-temperature scene. 3. Compact structure, less material consumption, no need to greatly increase the weight and volume of the battery, and ensure the energy density and power density. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The structure of the heat conduction layer and the phase change material layer is shown in the figure; Figure 2 The structure of the comprehensive heat preservation layer of two unit thermal batteries is shown in the figure; Figure 3 The structure of the comprehensive heat preservation layer of three unit thermal batteries is shown in the figure.

[0017] The reference signs in the drawings of the specification include: unit thermal battery 1, heat conduction layer 2, phase change material layer 3, temperature sensor 4, temperature controller 5, cold pipe 6, motor 7, cooling liquid 8, cooling tank 9, heat dissipation layer 10. DETAILED DESCRIPTION

[0018] The following will be further described in detail through specific embodiments: Example 1: A unit thermal battery 1 with a size of Φ100x200mm is used. During use, a short circuit occurs in the unit battery after about 2000s of work. The treatment for this situation and the connection relationship of each part are as follows: Heat conduction layer 2 assembly: graphite paper is used to tightly wrap the outer surface of the unit thermal battery 1 for 1 layer, and high-temperature insulating tape is used to wrap and fix along the axial direction of the battery, with a tape lap width of 5mm, to ensure that the heat conduction layer 2 is tightly attached to the surface of the battery without gaps; Installation of cooling pipe 6: The cooling pipe is spirally wound around the outer surface of the heat-conducting layer 2 at a spacing of 20mm, and fixed to the heat-conducting layer 2 with high-temperature resistant pipe clamps to prevent displacement; both ends of the cooling pipe are sealed and connected to the small cooling tank 9 on the side through sealing joints. The cooling tank 9 is filled with alcohol solution (coolant 8) and the flow rate is set to 100ml / min. Phase change material layer 3 fixation: On the outside of the winding cooling pipe, a layer of MgCl2 molten salt phase change material layer 3 is wrapped and fixed by spiral winding with glass ribbon with a winding tension of 3-5N to ensure full contact between the phase change material layer 3 and the cooling pipe.

[0019] like Figure 1 As shown, the thermally conductive layer 2, the cooling pipe, and the phase change material layer 3 are sequentially bonded and assembled to form a synergistic heat dissipation structure. The assembled battery was discharged, and no short circuit occurred after complete discharge, and the discharge time was not shortened.

[0020] Example 2: A thermal battery pack consisting of two Φ110×300mm unit thermal cells (1), fixed by a frame with a spacing of 6mm, experienced a short circuit and meltdown after approximately 1500 seconds of operation. The handling and connection arrangements for this situation are as follows: Thermal conductive layer 2 linkage fixation: Copper foil is used to wrap two cells in two layers. Each layer of copper foil is tightly attached to the surface of the cell. The layers are fixed by spot bonding with glass ribbon. The thermal conductive layers 2 of the two cells are then linked and fixed by the pressure plate on the frame to ensure coordinated heat conduction. The cooling pipe 6 is connected to the cooling tank 9: The cooling pipes are spirally wound around the outer surface of the heat-conducting layer 2 of each battery at a spacing of 15mm. The cooling pipes of the two batteries are connected by a three-way connector and sealed to the side cooling tank 9. The cooling tank 9 is filled with an aqueous solution (coolant 8) with a flow rate set to 100ml / min. Phase change material layer 3 is linked with the cold cycle: In the cold cycle device, phase change material layer 3 is a 2-layer Si-Mg alloy, which is fixed to the outside of the cooling pipe by high-temperature insulating tape, and thermal grease is applied between the alloy layers to fill the gaps; the small motor 7 is powered by the thermal battery (power ≤50W), and the temperature controller 5 is connected to the battery surface temperature sensor 4 and the small motor 7 through wires. The battery surface temperature threshold is set to 350℃. When the temperature exceeds the threshold, the motor 7 is started to realize the circulation of coolant 8.

[0021] Structural diagram as follows Figure 2 As shown, after the above assembly, the battery discharges safely and stably, and the discharge time is extended to 2500s.

[0022] Example 3: A thermal battery pack consisting of three Φ130×400mm unit thermal cells (1), fixed by a frame with a spacing of 10mm, was used. A short circuit occurred after approximately 1000 seconds of operation. The handling and connection arrangements for this situation are as follows: The thermal conductive layer 2 is fixed as a whole: silver foil is used to wrap the three unit cells in two layers. The silver foil interface is sealed and fixed with high-temperature insulating tape. Then, the thermal conductive layer 2 of the three cells is fixed as a whole with high-temperature resistant bolts on the frame to ensure the stability of the structure. Cooling pipe 6-section connection: The cooling pipe adopts a multi-segment layout, and is wound around the outer surface of the heat-conducting layer 2 of each battery at a spacing of 18mm. The cooling pipe segments are connected to the cooling tank 9 through a four-way connector. The cooling tank 9 is filled with ethanol solution (coolant 8) and the flow rate is set to 150ml / min. Phase change material layer 3 works in conjunction with the cold cycle: In the cold cycle device, phase change material layer 3 is a 3-layer Mg-Cu-Zn alloy, which is fixed to the outside of the cooling pipe by cross-wrapping with glass ribbons, and the edge of the alloy layer is fitted and limited with the frame; the small motor 7 is powered by a thermal battery (power ≤50W), and the temperature controller 5 is connected to the temperature sensors 4 of each of the 3 batteries and the small motor 7, and the temperature threshold is set to 400℃ to achieve synchronous temperature control of multiple units.

[0023] Structural diagram as follows Figure 3 As shown, after the above assembly, the battery discharges safely and stably, and the discharge time is extended to 1500s.

[0024] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for improving the safety of a thermal battery pack, characterized in that: This is achieved by adding a thermally conductive layer and a rapid heat dissipation system to the outside of a unit thermal battery or battery pack. The rapid heat dissipation system includes a phase change material layer and a cold circulation device. The thermally conductive layer is made of at least one of a metal material or a carbon material with a high thermal conductivity and is attached to the outer surface of the unit thermal battery or battery pack. The thermally conductive layer conducts and evenly distributes the heat on the battery surface. The phase change material layer is disposed outside the thermally conductive layer and attached to the surface of the thermally conductive layer to absorb heat and control the temperature. The cold circulation device is in contact with the outer surface of the phase change material layer to remove excess heat and maintain the functionality of the phase change material.

2. The method for improving the safety of a thermal battery pack according to claim 1, characterized in that: The thermally conductive layer is wrapped and fixed to the outer surface of the thermal battery by glass ribbon or high-temperature insulating tape, and the number of wrapping layers is one or more.

3. The method for improving the safety of a thermal battery pack according to claim 2, characterized in that: The metallic material is at least one of silver foil, copper foil, or aluminum foil; the carbon material is at least one of graphite, carbon fiber, or graphene.

4. The method for improving the safety of a thermal battery pack according to claim 3, characterized in that: The phase change material layer is made of at least one of metal phase change material or molten salt phase change material, and is fixed to the outer surface of the heat-conducting layer by glass ribbon or high-temperature insulating tape, with one or more layers.

5. A method for improving the safety of a thermal battery pack according to claim 4, characterized in that: The metal phase change material is at least one of Si-Mg alloy, Al-Si alloy or Mg-Cu-Zn alloy; the molten salt phase change material is at least one of LiNO3, Ca(NO3)2, MgCl2 or MgF2.

6. The method for improving the safety of a thermal battery pack according to claim 5, characterized in that: The cold circulation device includes a temperature controller, a small motor, a cold pipe, and a cooling tank. The cold pipe is wrapped around the outer surface of the phase change material layer, and both ends of the cold pipe are connected to the cooling tank. The cooling tank is located in the side area of ​​the unit thermal battery or battery pack and is filled with coolant. The temperature controller is connected to the small motor and the cold pipe to regulate the circulation state of the coolant.

7. A method for improving the safety of a thermal battery pack according to claim 6, characterized in that: The small motor is powered by a thermal battery with a power of less than 50W. When the surface temperature of the battery exceeds the set value of 300℃-400℃, the temperature controller starts the small motor to realize the circulation of coolant.

8. A method for improving the safety of a thermal battery pack according to claim 7, characterized in that: The coolant is water or alcohol, and the flow rate is controlled at 100 ml / min or higher.

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