CN108417741A - A new shell material structure capable of detecting the internal pressure of the lithium battery shell - Google Patents

Abstract

The invention discloses a novel shell material structure capable of detecting the internal pressure of the lithium battery shell. According to the principle of the piezoelectric effect produced by the piezoelectric material, the piezoelectric material is coated on the surface of the aluminum shell material; After forming, during the normal use of the battery, the inside of the cell will generate a squeeze force on the shell due to gas production, which will cause positive charges to accumulate on the outer surface of the shell material. The BMS system can collect and test the outer wall of the shell and the The voltage data between the inner walls calculates and reflects the pressure received inside the battery.

Description

A new shell material structure capable of detecting the internal pressure of the lithium battery shell

technical field

The invention relates to the technical field of new materials for making lithium battery casings, in particular to a novel casing material structure capable of detecting the internal pressure of the lithium battery casing.

Background technique

At present, the lithium battery shell material is basically made of metal aluminum. On the one hand, the aluminum alloy material has high strength, which meets the safety performance of the battery. On the other hand, due to the low density of aluminum metal, it is a light metal. Compared with other metals Materials, as the battery case can effectively improve the energy density of the battery.

With the continuous development of battery manufacturing technology, the current market has increasingly stringent requirements for battery design, and batteries need to be improved in many aspects such as safety performance and energy density. When the battery is cycled, overcharged, overdischarged, or thermally out of control, gas will be generated inside the battery, resulting in an increase in the pressure of the battery case. The internal pressure of the battery is a means to characterize the state of the battery. Real-time monitoring of the pressure change inside the battery during the charging and discharging process of the battery helps to understand the state of the battery and helps the BMS system to monitor the safety performance of the battery.

At present, it is relatively difficult to test the internal pressure of the battery. Some inventions detect the pressure inside the battery by placing sensors inside the battery. This method requires adding sensors inside the battery and leading out test lines from the inside of the battery. , this method adds sensors and test lines inside the battery, which can easily lead to a short circuit of the battery, and at the same time cause difficulties in the later sealing of the battery. It can only be used as a test object for testing the internal pressure of a single battery cell, and cannot be mass-produced. It is even more unable to meet the requirements for testing and monitoring the internal pressure of the battery to support the BMS system.

Contents of the invention

Based on the technical problems existing in the background technology, the present invention proposes a new casing material structure capable of detecting the internal pressure of the lithium battery casing.

The present invention proposes a novel housing material structure capable of detecting the internal pressure of the lithium battery housing. The inner surface of the aluminum alloy housing is coated with an insulating material layer, and its outer surface is coated with a piezoelectric material layer. The side away from the aluminum alloy casing is covered with an aluminum alloy protective layer.

Preferably, the insulating material layer is made of polymer plastic or ceramics.

Preferably, the piezoelectric material layer adopts piezoelectric ceramics.

The present invention starts with the shell material of the battery case and proposes a new type of shell material. This new material has the properties of single-side conduction and single-side insulation. There is a linear relationship with the charged amount, and the internal pressure of the battery is detected by detecting the external charged amount of the shell, which provides a test method for the BMS system to monitor the internal pressure of the battery.

By adopting this type of shell material, on the one hand, there is an insulating layer inside the shell, and the risk of internal short circuit is reduced during the assembly of the battery cells into the shell. The weight improves the energy density; on the other hand, there is a piezoelectric material layer in the material, which can convert the pressure inside the cell into the charge on the surface of the cell shell, so as to intuitively show the force inside the cell; It provides support for the BMS management system of the battery post-module module to monitor the battery status, and improves the safety performance of the battery.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a new casing material capable of detecting the internal pressure of a lithium battery casing proposed by the present invention;

Fig. 2 is a working schematic diagram of the piezoelectric material;

Fig. 3 is a schematic diagram of the working of the shell material shown in Fig. 1 .

Detailed ways

Referring to Fig. 1, the present invention proposes a novel housing material structure capable of detecting the internal pressure of the lithium battery housing. The inner surface of the aluminum alloy housing 1 is coated with an insulating material layer 2, and the outer surface is coated with a piezoelectric material. Layer 3 , the side of the piezoelectric material layer 3 away from the aluminum alloy casing 1 is covered with an aluminum alloy protective layer 4 .

In the shell material structure, when the piezoelectric material layer is under pressure, charges of opposite polarity will appear on the two opposite surfaces of the piezoelectric material layer, and as the pressure increases, the surface of the piezoelectric material layer will The amount of charge increases linearly. Utilizing this feature, it can provide support for the BMS of the battery to monitor the pressure inside the battery, and convert the pressure detection inside the battery into the charge detection on the battery case.

In this embodiment, the inner surface of the aluminum alloy casing 1, that is, the inner surface of the battery casing, is coated with an insulating material layer 2, which can replace the bagging of the battery cell, prevent internal short circuit problems when the battery cell is put into the casing, and reduce the weight of the battery. Increase the energy density of the battery. Specifically, the insulating material layer 2 is made of polymer plastic or ceramics or other insulating materials.

In this embodiment, the battery case adopts the aluminum alloy case 1 as the main support. The aluminum alloy case 1 is the main material of the existing lithium battery hard shell battery. The light weight of the aluminum alloy is used to ensure the strength of the battery case. , and can ensure the lightweight of the battery. In this embodiment, an aluminum alloy protective layer 4 is added on the outer layer of the piezoelectric material layer 3 to provide protection for the piezoelectric material layer on the basis of ensuring the strength of the battery.

In this embodiment, taking piezoelectric ceramics among the piezoelectric materials as an example, the working principle of this type of new housing material for testing the internal pressure of the housing is described.

Piezoelectric ceramics is a new type of functional material. Due to its high coupling coefficient, stable performance, wide working range, and easy mass production, it is currently used in almost all fields involving functional conversion of sound, light, electricity, and heat. .

The piezoelectric ceramic material after the polarization process has a piezoelectric effect, that is, the pressure on the piezoelectric ceramic is proportional to the applied voltage, as shown in Figure 2.

In Figure 2, a downward pressure F is applied on the surface of the piezoelectric ceramic material, causing the lattice of the material to deform; negative charges Qx will be generated on the upper surface of the pressed material, and an equal amount of positive charges Qx will be generated on the lower surface; Under a certain pressure, the charge on the surface of the material is proportional to the pressure.

That is, Qx=kF, where k is the piezoelectric constant, which is the attribute value of the material.

Through the above formula, the force on the surface of the material can be inversely deduced according to the amount of charge on the surface of the material; that is

F＝ _Qx /k

Further: the voltage between materials can be expressed as:

That is, the force on the surface of the material can be calculated by measuring the voltage across the material.

Referring to Figure 3, in the case material structure provided by this embodiment, the piezoelectric material is coated on the surface of the aluminum case material according to the principle of the piezoelectric effect generated by the piezoelectric material; at the same time, after the battery module is formed, the battery is normal During use, the inside of the cell will generate a squeeze force on the shell due to gas production, which will cause positive charges to accumulate on the outer surface of the shell material. The BMS system can collect and test the voltage between the outer wall and the inner wall of the shell. Data, calculates and reflects the pressure received inside the battery.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (3)

1. A novel housing material structure capable of detecting the internal pressure of a lithium battery housing, characterized in that the inner surface of the aluminum alloy housing (1) is coated with an insulating material layer (2), and its outer surface is coated with a pressure The electric material layer (3), the side of the piezoelectric material layer (3) away from the aluminum alloy casing (1) is covered with an aluminum alloy protective layer (4). 2. The novel casing material structure capable of detecting the internal pressure of the lithium battery casing according to claim 1, characterized in that the insulating material layer (2) is made of polymer plastic or ceramics. 3. The novel housing material structure capable of detecting the internal pressure of the lithium battery housing as claimed in claim 1, wherein the piezoelectric material layer (3) adopts piezoelectric ceramics.