CN106921002A - A kind of cylinder type lithium battery with heat of transformation pooling feature - Google Patents

Abstract

The invention provides a cylindrical lithium battery with a phase change thermal buffer function, comprising: a battery winding core, a battery casing for accommodating the battery winding core, a lithium battery cap respectively located on the top of the battery winding core, and a battery bottom assembly at the bottom , there are insulating gaskets between the battery core and the lithium battery cap, and the battery bottom assembly, a first insulating layer is provided between the battery core and the battery case, a heat pipe is provided in the central hollow area of the battery core, and the battery core There is also a thermal buffer zone between the battery and the bottom of the battery. The upper and lower sides of the thermal buffer zone are provided with insulating gaskets. The thermal buffer zone is filled with composite phase change materials, and the bottom of the heat pipe extends to the thermal buffer zone. At the bottom of the zone, at least one layer of circular heat dissipation fins is provided around the heat pipe located in the heat buffer zone, and a second insulating layer is provided between the battery winding core and the heat pipe. Compared with traditional lithium batteries, the invention has better thermal stability, temperature uniformity and safety.

Description

A cylindrical lithium battery with phase change thermal buffer function

technical field

The invention belongs to the technical field of lithium batteries, and in particular relates to a cylindrical lithium battery with a phase change heat buffer function.

Background technique

Due to the shortage of energy, people are devoting themselves to the development and use of new energy sources. Lithium-ion batteries are favored by people because of their high specific energy, high voltage, long service life, no harm to the environment, no memory, and can be manufactured into arbitrary shapes.

The structure of a traditional lithium battery is shown in Figure 1, which includes: a battery core wound by a winding needle, a battery casing for accommodating the battery core, and a lithium battery cap (including the positive terminal, safety Valve, contact sheet, insulating gasket, and top cover) and the battery bottom assembly at the bottom (including negative terminal, insulating gasket, bottom cover, etc.), battery core and lithium battery cap, battery bottom assembly respectively An insulating gasket is provided, and an insulating layer is provided between the battery winding core and the battery casing. In the middle of the battery core is the central hollow area left after the winding needle is removed. When the battery core is filled with electrolyte, the central hollow area is filled with electrolyte.

Lithium batteries with traditional structure will generate a lot of heat during the working process, and the thermal conductivity of lithium battery materials is poor, so the heat inside lithium batteries with this structure will quickly accumulate, making the temperature of lithium batteries too high, which may further cause lithium batteries Hazardous consequences such as fire or explosion caused by performance degradation or thermal runaway limit its application range. The traditional air-cooled and liquid-cooled methods, on the one hand, have low temperature regulation efficiency and unsatisfactory cooling effect; However, the temperature in the central area of a single lithium battery is still maintained at a high value, so it is very easy to increase the inhomogeneity of the internal temperature distribution of the lithium battery, thereby affecting the performance of the lithium battery. Therefore, the traditional temperature regulation system will bring hidden dangers to the life and safety of the battery. Therefore, a new heat dissipation method is urgently needed to effectively solve the problems of high temperature and uneven temperature distribution of lithium batteries, which is also the prerequisite for the rapid development of lithium batteries.

Contents of the invention

Technical problem to be solved: In order to solve the problems of lithium battery performance degradation and adverse safety consequences caused by high working temperature caused by poor heat dissipation performance, the invention provides a cylindrical lithium battery with phase change thermal buffer function, The high thermal conductivity of the heat pipe in the center of the cylindrical lithium battery and the cooling fins at the bottom can quickly transfer the heat in the center of the lithium battery to the composite phase change material around the bottom, and its phase change process can quickly absorb a large amount of heat, making The battery temperature is maintained within a safe range.

Technical scheme of the present invention:

A cylindrical lithium battery with a phase change heat buffer function, comprising: a battery winding core, a battery casing for accommodating the battery winding core, a lithium battery cap on the top of the battery winding core and a battery bottom assembly at the bottom, the battery winding Insulating gaskets are provided between the core and the lithium battery cap and the battery bottom assembly, the first insulating layer is provided between the battery core and the battery case, a heat pipe is provided in the central hollow area of the battery core, and the battery core and the bottom of the battery There is also a thermal buffer zone between the components, the upper and lower sides of the thermal buffer zone are provided with insulating gaskets, the thermal buffer zone is filled with composite phase change materials, and the bottom of the heat pipe extends to the bottom of the thermal buffer zone. At least one layer of circular cooling fins is arranged around the heat pipe located in the heat buffer zone, and a second insulating layer is also arranged between the battery winding core and the heat pipe.

The battery winding core is formed by winding the positive electrode sheet, the first diaphragm, the negative electrode sheet and the second diaphragm sequentially stacked from inside to outside along the heat pipe. The side of the positive electrode sheet close to the heat pipe is provided with a positive electrode lug, which is connected to the positive terminal located in the lithium battery cap, and the negative electrode sheet is provided with a negative electrode ear, which is connected to the negative electrode terminal located in the battery bottom assembly.

The heat pipe is a copper pipe, which has many advantages such as high thermal conductivity, long durability, simple structure, and light weight.

The first insulating layer is provided with wire holes for connecting the negative electrode sheet to the bottom assembly of the battery.

The composite phase change material is a copper foam/paraffin wax composite phase change material, and the paraffin wax composite material added with foam copper has a significant improvement on the thermal conductivity of the material, so compared with the traditional paraffin wax material, it has thermal conductivity during the phase change process. High specific heat, stable chemical properties, long life, small volume change and many other advantages.

Since the heat pipe has a good heat conduction effect, it is located in the hollow area of the center of the battery core. When the temperature of the lithium battery center rises, the working fluid inside the heat pipe begins to evaporate, and the heat flows to the bottom of the heat pipe (ie, the condensation end) under the action of the pressure difference. The cooling fins at the condensing end transfer heat to the thermal buffer zone. After the heat pipe releases heat, the internal working medium recondenses into a liquid, and flows back to the evaporation section under the action of the capillary force of the internal porous material, thus circulating. When the composite phase change material in the thermal buffer absorbs heat and causes the temperature to gradually rise to the corresponding phase transition point, the phase change process begins, which can absorb a large amount of heat, so that the temperature of the lithium battery can be kept within a reasonable range. Although the temperature at the center of the lithium battery is the highest, the temperature of the lithium battery can be controlled within a suitable range after being led out through the heat pipe, and the uniformity of the temperature distribution has also been improved, thus making the performance, service life and safety of the lithium battery all possible. Guaranteed.

Beneficial effect:

The lithium battery provided by the invention can effectively reduce the maximum temperature difference between the inside and outside of the battery by 20% to 40% under the working conditions of low heat transfer coefficient and high rate charge and discharge, so it has better thermal stability than traditional lithium batteries , temperature uniformity and safety, and the invention is simple to assemble, and can be applied to lithium battery packs to improve the overall heat dissipation effect of lithium battery packs.

Description of drawings

Figure 1 is a schematic diagram of the structure of a traditional lithium battery;

Fig. 2 is a schematic structural diagram of the lithium battery of the present invention;

Fig. 3 is a structural schematic diagram of a battery core;

Among them, 1. heat pipe; 2. cooling fins; 3. thermal buffer zone; 4. battery winding core; 5. first insulating layer; 6. lithium battery cap; 7. battery bottom components; Shell; 10, central hollow area; 11, positive plate; 12, first diaphragm; 13, negative plate; 14, second diaphragm; 15, second insulating layer; 16, insulating gasket.

detailed description

The innovation of the present invention is that the heat in the center of the lithium battery is transferred to the thermal buffer zone through the heat pipe, and the heat is absorbed through the phase change of the phase change material, thereby reducing the temperature of the center of the lithium battery. The lithium battery structure proposed by the invention improves the thermal stability and safety of the lithium battery.

In order to facilitate the understanding of those skilled in the art, the structural principle of the lithium battery of the present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings.

Example 1

As shown in Figure 2, a cylindrical lithium battery with a phase change heat buffer function, comprising: a battery winding core 4, a battery casing 9 accommodating the battery winding core 4, and lithium batteries respectively located on the top of the battery winding core 4 The cap 6 and the battery bottom assembly 7 at the bottom, insulating gaskets 16 are respectively provided between the battery core 4 and the lithium battery cap 6, and the battery bottom assembly 7, and a first insulating layer is provided between the battery core 4 and the battery case 9 5. The central hollow area 10 of the battery core 4 is provided with a heat pipe 1, and a thermal buffer zone 3 is provided between the battery core 4 and the battery bottom assembly 7, and insulating pads are provided on the upper and lower sides of the thermal buffer zone 3 sheet 16, the thermal buffer zone 3 is filled with a composite phase change material, the bottom of the heat pipe 1 extends to the bottom of the thermal buffer zone 3, and at least one layer of circular fins are arranged around the heat pipe 1 in the thermal buffer zone 3 2. A second insulating layer 15 is also provided between the battery core 4 and the heat pipe 1 .

As shown in FIG. 3 , the battery winding core 4 is formed by winding the positive electrode sheet 11 , the first separator 12 , the negative electrode sheet 13 and the second separator 14 sequentially stacked from inside to outside along the heat pipe 1 . Positive tab 11 is provided with a positive tab near the heat pipe 1, which is connected to the positive terminal located in the lithium battery cap, and negative tab 13 is provided on the outside of the negative tab, which is connected to the negative terminal located in the battery bottom assembly 7.

The heat pipe 1 is a copper pipe, which can quickly transfer the heat of the battery core to the heat buffer zone.

The first insulating layer 5 is provided with wire holes 8 for connecting the negative electrode sheet 13 to the battery bottom assembly 7 .

The composite phase change material is copper foam/paraffin wax composite phase change material.

During manufacturing, the heat pipe 1 is used instead of the traditional rolling needle, covered with the second insulating layer 15, and then the multi-layer structure formed by the positive electrode sheet 11, the first separator 12, the negative electrode sheet 13 and the second separator 14 is rolled around the heat pipe 1. Winding to form a battery core 4 . After successful winding, an insulating layer 5 is added to the outer side, and an insulating gasket 16 is added to the bottom. The bottom of the heat pipe 1 and the cooling fins 2 constitute the condensation end of the heat pipe 1 , and the surrounding area is filled with a composite phase change material to form a thermal buffer zone 3 , which is located at the outer bottom of the battery core 4 . The good thermal conductivity of the heat pipe 1 is conducive to the heat conduction in the center of the lithium battery, and the composite phase change material in the bottom thermal buffer zone can absorb a large amount of heat through the phase change process, and the temperature change is small, so it can effectively solve the problem of lithium battery. If the temperature is too high, make it work in a safe temperature range.

After assembling the heat dissipation structure of the lithium battery, put it into the lithium battery casing as a whole. Since the heat dissipation structure is installed at the bottom of the battery, the negative electrode tab on the negative electrode sheet is connected to the negative electrode in the battery bottom assembly through the channel on the second insulating layer. Terminals and other structures for connection. After the electrolyte is injected, the lithium battery current collector is connected to the corresponding terminal at the top of the battery core, and structures such as an explosion-proof cap are added. The explosion-proof cap can effectively buffer the internal pressure of the battery and further improve the safety of the battery. Finally, the lithium battery is evacuated and sealed with a sealing ring.

Thermal Performance Evaluation:

Using the COMSOL Multiphysics multiphysics field coupling software, the temperature fields of the traditional lithium battery and the lithium battery of the present invention under different working conditions were simulated and calculated, and the heat dissipation performance of the lithium battery of the present invention was evaluated by comparing the simulated calculation results. It mainly establishes a three-dimensional electrochemical-thermal coupling model, sets the discharge rate as 2C, 4C, 6C, and 1OC, the ambient temperature is 298.15K, and the convective heat transfer coefficient is 1OW/fm^2·K). The results of the difference between the maximum temperature and the initial temperature of the lithium battery center are shown in Table 1.

Table 1

It can be seen from Table 1 that, compared with the traditional lithium battery, the lithium battery provided by the present invention can effectively reduce the maximum internal temperature of the lithium battery under the working conditions of low heat transfer coefficient and high rate charge and discharge, and has an effect on the overall temperature uniformity of the lithium battery. A very good improvement.

The above-mentioned implementations are only preferred embodiments of this patent, and this patent is not limited to the above-mentioned embodiments. For a person skilled in the art, without departing from the design principle of this patent, any obvious Changes all belong to the design of this patent and the scope of protection of the appended claims.

Claims (5)

1. A cylindrical lithium battery with a phase change thermal buffer function, comprising: a battery core (4), a battery casing (9) for accommodating the battery core (4), and a battery core (4) There are insulating gaskets (16) between the lithium battery cap (6) on the top and the battery bottom assembly (7) on the bottom, and the battery core (4) and the lithium battery cap (6) and the battery bottom assembly (7). A first insulating layer (5) is provided between the battery core (4) and the battery casing (9), and it is characterized in that the central hollow area (10) of the battery core (4) is provided with a heat pipe (1), and the battery coil There is also a thermal buffer zone (3) between the core (4) and the battery bottom assembly (7). The upper and lower sides of the thermal buffer zone (3) are provided with insulating gaskets (16). The thermal buffer zone (3) is filled with a composite phase change material, the bottom of the heat pipe (1) extends to the bottom of the heat buffer zone (3), and the heat pipe (1) in the heat buffer zone (3) is surrounded by at least one layer of circular heat dissipation A second insulating layer (15) is also provided between the fins (2), the battery core (4) and the heat pipe (1). 2. A cylindrical lithium battery with a phase change thermal buffer function according to claim 1, characterized in that, the battery core (4) is sequentially stacked from the inside to the outside of the positive electrode sheet (11), the second A diaphragm (12), a negative electrode sheet (13) and a second diaphragm (14) are formed by winding along the heat pipe (1). 3. A cylindrical lithium battery with a phase change heat buffer function according to claim 1 or 2, characterized in that the heat pipe (1) is a copper pipe. 4. A cylindrical lithium battery with a phase change heat buffer function according to claim 2, characterized in that the first insulating layer (5) is provided with wire holes (8) for the negative electrode sheet (13) and the battery The bottom assembly (7) is connected. 5. A kind of cylindrical lithium battery with phase change heat buffering function according to claim 1, is characterized in that, described composite phase change material is foamed copper/paraffin wax composite phase change material.