CN116053684A - A battery aluminum shell and a high-nickel ternary power battery - Google Patents

Abstract

The invention discloses a battery aluminum shell and a high-nickel ternary power battery. The aluminum shell bottom is concavely formed and softened, an automatic pressure relief device is arranged in the middle area of the bottom, and four vertical faces are of a composite structure. The concave bottom can be used as a first barrier of the internal pressure boundary, and when the internal pressure is increased, the concave bottom preferentially bulges downwards; the automatic pressure relief device may act as a secondary barrier to the internal pressure boundary. The four vertical faces have good heat preservation performance and flexibility, have good buffering and pressure maintaining effects, aim at instant mass gas production and high pressure caused by sudden short-circuit failure of the battery cell, can be used for buffering and releasing high internal pressure in cooperation with the pressure release device, avoid explosion, further reduce the weight of the aluminum shell, improve the energy density of the battery cell, maintain the internal temperature of the battery cell in an ultralow temperature environment, and improve the endurance mileage of the new energy electric vehicle in winter. The problem that the battery cell protrudes in the module to prop open the top baffle plate to cause the module to be damaged is solved, and the high internal pressure requirement of the high-nickel ternary anode material can be met.

Description

A battery aluminum case and a high-nickel ternary power battery

technical field

The invention belongs to the technical field of lithium-ion batteries, and relates to a composite aluminum shell of a concave type power battery capable of automatic pressure relief and an ultra-low temperature high-nickel ternary power aluminum shell battery.

Background technique

With BYD taking the lead in discontinuing the production of fuel vehicles, the era of electric vehicles replacing fuel vehicles is coming. As the core component of electric vehicles, the capacity density of batteries is also getting higher and higher. Therefore, the positive electrode material in the battery is developing towards high nickel. Although high-nickel materials can bring higher energy density, high-nickel ternary cells produce more gas, which is easy to cause deformation of the shell. Therefore, the requirements for the deformation resistance and pressure resistance of the shell are higher. The shells used in the market include square aluminum shells, soft-wrapped aluminum-plastic films, cylindrical steel shells, etc. Because square aluminum shells have the advantages of light weight, high flexibility, high group efficiency, strong sealing, and low cost, they are widely used in power batteries. It has the largest application volume in the field and is more suitable for high-nickel ternary batteries. In the power battery, the square aluminum shell mainly plays the role of packaging the core package, carrying the electrolyte and protecting the explosion-proof; the aluminum shell of the existing square battery generally has a rectangular parallelepiped structure, and the top surface of the aluminum shell is an open surface, which is welded through the top cover. Sealed, assembled into modules and battery packs after sealing, and start charging and discharging cycles.

The positive electrode material of the ternary battery has been used from the 3 series, 5 series, 6 series, 8 series and 9 series, the nickel content has been continuously increased, the gas production during the battery cell cycle has increased rapidly, and the internal pressure inside the battery cell has increased. , causing the bottom and sides of the battery to bulge, the bulging at the bottom will cause the top baffle of the module to be stretched, and the module will be damaged; while the side bulging accelerates the deformation of the inner winding core of the battery, resulting in a cycle life of the battery fast decay. When the internal pressure continues to increase, the gas will push open the explosion-proof valve on the top cover, and open circuit, short circuit, spontaneous combustion, etc. may occur.

At present, another major problem that plagues the development of new energy vehicles is the low-temperature endurance discount. The performance of the power battery of new energy vehicles will be greatly compromised in low-temperature environments. The charging and discharging power is limited, while the low-temperature internal resistance increases and the consistency becomes poor, which affects the charging and discharging performance of the power battery, and ultimately leads to a decrease in the overall battery life of the battery pack. In order to improve the performance of the power battery in low temperature environment, the most important problem is to improve the thermal insulation performance of the power battery, avoid the rapid decline of the battery cells in the battery pack, and keep the battery cells at a relatively high temperature within a certain period of time.

CN208939057U and CN212085175U all disclose a heat dissipation shell with a pressure relief device. Although the above two inventions can improve the gas production of the electric core, they have the following problems: (1) the aluminum shell is thick and heavy, and the inside can be used for the core pack. The space is reduced, and the weight of the heat dissipation plate is large, which seriously reduces the energy density of the battery cell as a whole; (2) the invention only provides an invention point for the heat dissipation performance, and is not suitable for the use of electricity in a low temperature environment; (3) the leakage The pressure relief device is directly connected with the outside world. When the internal air pressure reaches a critical value, the pressure relief device will open and close continuously, and the spring is prone to elastic fatigue and failure. In the disclosed method of CN212209632U, the start and close of the cylinder control pressure relief device are set on the top cover, and the control of the internal air pressure is more effectively realized. This invention increases the cost of the top cover on the one hand, and only solves the problem of gas production on the other hand. It is difficult to simultaneously solve the problem of battery life attenuation in low temperature environments. CN111463369A discloses an aluminum shell that can prevent battery bulging, and increases the pressure resistance of the aluminum shell by setting the large side wall of the shell in a corrugated or concave shape. When the gas production is low in the early stage of use, the aluminum shell can be used to improve the bulging; but as the cycle continues for a long time, the internal air pressure will increase, which will eventually lead to problems such as bulging deformation of the aluminum shell and abnormal attenuation of the cycle. It can reduce the bulging of the inner wall to a certain extent, but cannot fundamentally solve the problem of gas production.

In order to meet the high internal pressure and explosion-proof requirements of traditional power battery aluminum shells and top covers, CID and explosion-proof valves are usually installed on the top cover. The cost of the two structures not only accounts for more than 50% of the cost of the entire power battery structure, but also Once turned on, the battery will be useless.

Another related patent achieves heat preservation by adding insulation materials inside/outside the battery pack box or by heating the module before starting. If thermal insulation material is added to the battery pack box, it will occupy the installation space of the internal battery cells and reduce the energy density of the battery pack. At the same time, factors such as wiring harness insertion cannot completely cover the internal thermal insulation material, and the thermal insulation performance is not good; Insulation materials, due to the exposed external environment, the selection of insulation materials requires hydrophobicity and impact resistance, which requires high material selection, and at the same time increases the external volume of the battery pack, requiring a large installation space; The module is heated to heat the internal cells to a specified temperature, which not only prolongs the charging time, but also increases energy loss, and the long-term accumulated loss cost is relatively high.

Contents of the invention

Aiming at the deficiency in the prior art that automatic pressure relief and exhaust can not be achieved at the same time and is suitable for ultra-low temperature environments, the present invention provides a high-nickel ternary battery suitable for ultra-low temperature environments, with a reasonable structure and automatic pressure relief High security concave battery aluminum case.

In order to achieve the above object, the present invention adopts the following technical solutions:

A concave high-nickel ternary power battery composite aluminum case suitable for ultra-low temperature and capable of automatically releasing pressure, including the aluminum case body, wherein the bottom of the aluminum case is concave, including an upper end plate and four inclined surfaces, and the concave line forms a horizontal plane The angle is 25-30°.

Preferably, the aluminum shell is a cuboid.

As a further improvement of the aluminum case of the power battery in the present invention, softening treatment is performed on the four slopes at the bottom of the aluminum case, including the following steps: heating; hot rolling; cold rolling; annealing.

As a preferred solution, the annealing includes the following steps: heating and raising the temperature of the four slopes at the bottom of the aluminum shell at a rate of 50-80°C/h, and stopping when the temperature of the aluminum shell is 300-400°C Heating and heat preservation, the heat preservation time is 30-100min, and after the heat preservation is completed, the temperature is rapidly cooled to room temperature, and the cooling rate is 10-50°C/h. The speed of cooling determines the flexibility of the bottom slope, which in turn determines the size of the internal pressure that can be withstood. The slope at the bottom of the softened aluminum shell is formed flexibly, and the bottom expands downward as the gas generated by the internal circulation increases.

As a further improvement of the aluminum case of the power battery of the present invention, the softened bottom of the aluminum case can provide space after being concave, and an automatic pressure relief device is provided in the middle area of the upper end plate.

The upper end plate is provided with a through hole, and the opening area of the through hole is 3-8mm ² , preferably 5mm ² .

The automatic pressure relief device includes a tetrafluoro ball, a spring seat, a spring, a circular pad, and a lower end plate.

A sealing rubber ring is arranged between the tetrafluoro ball and the contact surface of the through hole. The PTFE ball is bonded to the sealing rubber ring, the bottom of the PTFE ball is fixedly connected to the spring seat, the bottom of the spring seat is connected to the spring body, the bottom of the spring body is fixedly connected to the lower end plate, and the bottom of the pad is connected to the lower end The plates are sealed and connected, and the spring body is set inside the ring pad, and the inside of the ring pad is provided with a vent hole; the lower end plate is provided with a pressure relief hole.

In the aluminum shell of the present invention, the concave inclined surface and the automatic pressure relief device play a synergistic role to jointly determine the upper limit of the internal pressure and the opening pressure of the pressure relief device. The pressure range and downward expansion degree of the concave slope are controlled by the height of the pad at the bottom of the pressure relief device. When the internal pressure does not exceed the pressure range of the inclined plane, the concave inclined plane bears pressure and bulges downward; when the internal pressure exceeds the pressure range of the inclined plane, it is pressured by the pressure relief device. After exceeding the pressure range of the pressure relief device, the device opens and starts Pressure relief; when the internal pressure drops to the pressure range of the slope, the device closes. The cooperation of the concave slope and the pressure relief device can realize the switch of the pressure relief device within a certain pressure range, which can not only ensure that the internal air pressure of the battery is always below the critical value, but also meet the high internal pressure requirements of the high-nickel ternary positive electrode material. The cycle and safety performance are greatly improved, and it also avoids the pressure relief device being continuously opened and closed at a certain pressure, causing the internal spring body to fail due to excessive fatigue.

As a further improvement of the aluminum casing of the power battery of the present invention, the four facades of the aluminum casing adopt an aluminum composite structure, and the aluminum composite structure includes aluminum, polyurethane thermal insulation film, base film, polyurethane thermal insulation film, and aluminum from the inside to the outside.

The base film of the present invention is selected from one or more of PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), aramid fibers, and plant fibers. The thickness is 10-100um.

The preparation method of the polyurethane thermal insulation film of the present invention includes raw material preparation, cooling, crushing, homogenizing, film coating and rolling.

As a preferred scheme, the preparation method of the polyurethane thermal insulation film may further comprise the steps:

(1) Prepare a thermoplastic polyurethane elastomer material with reference to the method of CN114957603A, cool to -30～0°C, and cool down for 1-3 hours;

(2) Pulverize to particle size 0.1-2um, then mix with binder to prepare slurry;

(3) Polyurethane film is obtained by coating film by dry coating technology, and rolled.

The binder according to the invention comprises PVDF and/or PTFE.

In step (2) of the present invention, the binder is used in an amount of 1-3 wt%, based on the weight of the slurry.

The polyurethane thermal insulation film of the present invention has a thickness of 50-200um.

The preparation method of the aluminum composite structure of the present invention comprises the following steps:

(a) heating the base film with a preheating roller, the heating temperature is 80-150° C., and the heating time is 30-90 minutes;

(b) coating binder PVDF on base film both sides by rubber roller;

(c) The polyurethane insulation film with a folded thickness of 500-1000um is pasted on both sides of the base film by a pasting roller, and the preheating roller and the pasting roller rotate counterclockwise to obtain a composite film;

(d) passing the preliminarily bonded composite film through a hot roller for heating and rolling, the heating temperature is 50-80°C, the heating time is 10-30 minutes, and the thickness of the composite film after rolling is 60-300um;

(e) Coating a 10-30um aluminum layer on the surface of the polyurethane insulation film by water electroplating;

(f) Aluminum metal spraying is carried out on the upper surface of the aluminum layer, and the spraying thickness is 300-600um.

As a preferred solution, the solution of the water electroplating process includes an aluminum sulfate solution with a pH value of 2-6, a concentration of the aluminum sulfate solution of 0.5-2 mol/L, and a current density of 5-20ASD.

The four facades of the aluminum shell of the present invention adopt a composite structure, and the polymer base film is used as a matrix, which is beneficial to the close bonding of the polyurethane thermal insulation film, and also increases the flexibility of the composite structure, and the deformation is larger; The metal layer can be evenly attached to the surface of the composite film, ensuring that no aluminum dendrites are produced during subsequent spraying, and the surface of the produced composite aluminum shell is smooth and tidy; the thickness of the polyurethane insulation film can determine the thermal insulation performance of the composite aluminum shell, and the spraying thickness can be adjusted. Determine the hardness of the composite aluminum shell. The actual use flexibility is high, not only can reduce the weight of the aluminum shell, increase the energy density of the battery core, maintain the internal temperature of the battery core in a low temperature environment, so as to operate normally, reduce the charge and discharge loss, and improve the cruising range of new energy electric vehicles in winter.

Compared with ordinary aluminum shells, the flexibility of composite aluminum shells has been greatly improved, and it has better buffering and pressure-holding functions. It can withstand the instantaneous large-scale gas production and high pressure caused by sudden short-circuit failure of the battery cell, effectively avoiding the instantaneous The increased internal pressure instantly acts on the concave bottom shell and the pressure relief device, causing damage to the elastic part of the pressure relief device.

Preferably, the nickel content of the ternary positive electrode material is 80% to 95%, and the higher the nickel content, the greater the gas production.

Preferably, the low temperature environment used for the composite aluminum shell is -60°C to 0°C.

The aluminum case of the present invention is suitable for high-nickel ternary positive electrode materials with high energy density and large gas production, and its molecular formula is Li( _Nia Co _b X _c )O ₂ , where a+b+c=1, a=0.8 ~0.95, X is metal manganese or metal aluminum.

The beneficial effects of the present invention are:

(1) Reduce the pressure of the gas produced inside the cell on the side and top of the cell, thereby reducing the swelling and concave of the side, and avoiding damage to the end plate of the module due to excessive expansion of the cell.

(2) After the aluminum shell of the present invention is equipped with an automatic pressure relief device, it can not only replace the CID and explosion-proof valve, reduce the cost of structural parts, but also does not affect the continued use of the battery after opening, which is economical and safe.

(3) The aluminum shell of the present invention can be applied to high-nickel ternary positive electrode materials with high energy density and large gas production, which can fundamentally improve energy density and cycle performance, and solve problems such as low battery life and spontaneous combustion.

Description of drawings

Figure 1 is a front view of the initial state of the square aluminum shell.

Figure 2 is a top view of the initial state of the square aluminum shell.

Fig. 3 is a structural schematic diagram of the automatic pressure relief device at the bottom of the square aluminum shell.

Figure 4 is a schematic diagram of the connection between the bottom slope of the square aluminum shell and the upper end plate for ultimate pressure bearing.

Fig. 5 is a schematic diagram of pressure relief when the square aluminum shell pressure relief device is opened.

In the figure: 11- aluminum shell body; 20- concave bottom of aluminum shell; 21- bottom slope; 22- upper end plate; 23- pressure relief device; 31- through hole; 32- sealing rubber ring; 33- PTFE ball; 34-spring seat; 35-spring body; 36-ring block; 37-pad air hole; 38-pressure relief hole; 39-lower end plate.

Figure 6 is the result of the internal pressure change of the closed aluminum shell.

Figure 7 shows the results of the cycle life test at 25°C and the battery capacity retention rate.

Figure 8 shows the results of the battery capacity retention rate of the -50°C cycle life test.

Detailed ways

In order to make the purpose, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the following The described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. The present invention is further explained and illustrated by more specific examples below, but does not constitute any limitation.

The main raw material that following embodiment and comparative example adopt are as follows:

High-nickel ternary cathode material: model Ni90, Yantai Zhuoneng Lithium Battery Co., Ltd.;

Anode material: artificial graphite FSN-1, Shanghai Shanshan Technology Co., Ltd.;

Electrolyte: ZH20016, Sinochem Lantian Group Co., Ltd.;

Diaphragm: 12umPE double-sided ceramic diaphragm, Enjie shares;

PET base film: 20um thick S10 base film, Japan Toray;

Conductive agent: SP, Imerythium; carbon nanotubes, Jiangsu Tiannai Technology Co., Ltd.;

Binder: PVDF, Solvay;

The related performance test adopts the following methods:

Battery cycle life: According to the test method of cycle life in GB/T 31486-2015, it is considered as a cycle when it is fully charged once. The capacity obtained by each discharge is divided by the discharge capacity of the first cycle as the capacity retention rate. When the explosion-proof valve is opened, it is regarded as the end of cycle life.

Example 1

The bottom of the aluminum shell includes an upper end plate and four slopes. The upper end plate is 60mm long, 30mm wide, and 2mm thick. The concave angle of the bottom of the aluminum shell is 30°. After stamping, the bottom slope is softened and formed, and the temperature is firstly heated. , the heating rate is 60°C/h, stop heating when the temperature of the plate is 350°C, and keep the heat preservation time for 60 minutes, and quickly cool down to room temperature after the heat preservation is completed, the cooling rate is 30°C/h, and the concave aluminum alloy is obtained shell.

An automatic pressure relief device is installed on the upper end plate. A through hole 31 is provided in the central area of the upper end plate 22, and a sealing rubber ring 32 is pasted under the through hole 31, and a tetrafluoro ball 33 is connected under the sealing ring 32, and a spring seat 34 is fixedly connected under the tetrafluoro ball 33, The spring seat 34, the spring body 35 is connected below the spring seat 34, the bottom of the spring body is fixedly connected to the lower end plate 39, the bottom of the ring pad 36 is sealed and connected to the lower end plate 39, and the spring body 35 is set on the ring pad Inside the block 36 , a vent hole 37 is arranged inside the ring spacer block 36 , and a pressure relief hole 38 is respectively opened on both sides of the lower end plate 39 .

The radius of the PTFE ball is 0.5mm, the opening area of the upper end plate is 5mm ² , the specification and model of the spring body is φ2*8*30*10N, 2 represents the wire diameter, 12 represents the outer diameter, 30 represents the free length, and 10 represents the total Number of turns.

The top cover is welded to the aluminum shell by the full welding process to form a closed aluminum shell; the liquid injection hole of the top cover is used as a pressure charging channel.

The closed aluminum shell is pressurized, and the internal pressure change of the closed aluminum shell is tested. The results are shown in Figure 6.

Among them, in this embodiment, the bottom of the aluminum shell is subjected to concave softening and molding treatment, and an automatic pressure relief device is installed. The facade is an aluminum shell with a non-composite structure. The large surface of the facade is 173mm long, 128mm high, and 0.6mm thick. The internal pressure of the closed aluminum shell changes.

Comparative example 1

At the bottom of the concave aluminum shell prepared in Example 1, an explosion-proof valve is set with reference to CN215869506 U, including an explosion-proof valve and an explosion-proof valve patch.

The top cover is welded to the aluminum shell by the full welding process to form a closed aluminum shell; the liquid injection hole of the top cover is used as a pressure charging channel.

The closed aluminum shell is pressurized, and the internal pressure change of the closed aluminum shell is tested. The results are shown in Figure 6.

It can be seen from Figure 6 that when the internal pressure gradually increases, firstly the concave inclined surface cooperates with the pressure relief device to bear the pressure, and the pressure bearing range is enhanced; when the concave inclined surface expands downward to 20°, due to the pressure relief Due to the limit function of the ring cushion block of the device, the concave slope cannot continue to bear pressure. At this time, the pressure relief device continues to bear pressure alone, but at this time the spring does not deform, and the PTFE ball is still tightly connected with the upper end plate; when the internal pressure continues Increase, exceeding the opening pressure of the pressure relief device, at this time the pressure relief device opens and begins to release the pressure. During the pressure relief process, the internal pressure continues to decrease, and at the same time the spring stretches back. When the closing pressure of the pressure relief device is reached, the PTFE ball and The upper end plate is reconnected. During this process, the internal pressure of the aluminum shell is always maintained within a certain range, and there is a certain time difference between the opening and closing of the pressure relief device, so as to avoid the continuous opening and closing of the pressure relief device at a certain pressure, resulting in excessive fatigue of the internal spring body. invalidated.

In Comparative Example 1, the aluminum shell with explosion-proof valve is used, and the interior is continuously increased until the explosion-proof valve is opened. After the explosion-proof valve is opened, the cell is in an open state and cannot be used anymore. Therefore, compared with Comparative Example 1, the concave aluminum case and pressure relief device of Example 1 can effectively solve the problem of internal pressure suppression.

Example 2

An automatic pressure relief device is installed at the bottom of the aluminum shell. Among them, the radius of the PTFE ball is 0.5mm, the contact area with the upper end plate is 5mm ² , the specification and model of the spring body is φ2*8*30*10N, 2 represents the wire diameter, 12 represents the outer diameter, 30 represents the free length, and 10 represents the total Number of turns.

With reference to the preparation method of the lithium battery in Example 2 of CN110783528 A, the cell assembly is carried out to complete the cell preparation. Among them, Ni90 (90% nickel content) was selected as the positive electrode material.

The battery cells are tested for cycle life in a 25°C incubator, and the capacity retention rate of the batteries is recorded. The results are shown in Figure 7.

Comparative example 2

Using Ni90 (nickel content 90%) as the positive electrode material, using the explosion-proof valve aluminum shell in Comparative Example 1, and referring to Example 2 to complete the cell preparation. The battery cells are tested for cycle life in a 25°C incubator, and the capacity retention rate of the batteries is recorded. The results are shown in Figure 7.

It can be seen from FIG. 7 that, compared with Comparative Example 2, the cycle life of Example 2 is increased by about 15%. It can fundamentally solve the problem of large gas production of high-nickel ternary materials, which leads to the deformation of the inner winding core of the battery core and the cyclic diving problem, and improves the cruising range of electric vehicles.

Example 3

Prepare polyurethane material with reference to the embodiment 1 of CN114957603 A, cooling temperature is to-15 ℃, cooling time is 2 hours, pulverizes to particle size 1um, pulverized material is mixed with PVDF (content 2wt%), obtains polyurethane slurry, is coated by dry method The technical coating film obtains a polyurethane film, and obtains a polyurethane film with a thickness of 50um by rolling.

The thickness of the folded polyurethane compression film is 50, 100, 150, 200um respectively.

Heat the 20um thick S10 base film PET through the preheating roller, the heating temperature is 120°C, and the heating time is 60 minutes, and then evenly coat the adhesive PVDF on both sides of the base film through the rubber roller; next, it will be ready The folded thermal insulation film is pasted on both sides of the base film PET by the pasting roller, and the preheating roller and the pasting roller rotate counterclockwise to obtain a preliminary pasted composite film; then the composite film is passed through the hot roller for heating and rolling , the heating temperature is 65°C, and the heating time is 20 minutes to obtain the composite thermal insulation film after rolling; then through the water electroplating process, an aluminum metal layer with a thickness of 30um is formed on both sides of the film, wherein: the water electroplating uses sulfuric acid with a pH value of 5 Aluminum solution, the concentration of the aluminum sulfate solution is 1mol/L, and the current density is 12ASD. The thickness of the sprayed aluminum metal layer is 450um.

Four types of composite aluminum shells with facade insulation film thicknesses of 50um, 100um, 150um and 200um were prepared.

Referring to Example 1, prepare the bottom of the aluminum shell, and refer to Example 2 to complete the preparation of the cell. Among them, Ni90 (90% nickel content) was selected as the positive electrode material.

The battery cells are tested for cycle life in a -50°C incubator, and the capacity retention rate of the batteries is recorded. The results are shown in Figure 8.

Comparative example 3

The aluminum case of Comparative Example 1 was assembled with battery cells with reference to Example 3. The cycle life test was carried out in a -50°C incubator, and the battery capacity retention rate was recorded. The results are shown in Figure 8.

It can be seen from Figure 8 that under the low temperature condition of -50°C, the cell cycle of Comparative Example 3 decays rapidly, and it dives to 80% in less than 200 cycles; while the composite of thermal insulation films with different thicknesses in Example 3 is used After the aluminum shell is assembled into a battery cell, the cycle performance is significantly improved; and the thicker the film thickness, the stronger the heat preservation ability and the higher the capacity retention rate of the cycle, which shows that the composite aluminum shell of the present invention has an obvious effect in low temperature environment .

Claims (10)

1. An aluminum battery case, comprising an aluminum case body, wherein the bottom of the aluminum case is concave, including an upper end plate and four slopes, and the angle formed by the concave line and the horizontal plane is 25-30°. 2 . The battery aluminum case according to claim 1 , wherein the four slopes at the bottom of the aluminum case are softened, comprising the following steps: heating, hot rolling, cold rolling, and annealing. 3. The battery aluminum case according to claim 1 or 2, wherein the annealing comprises the following steps: heating the four slopes at the bottom of the aluminum case at a rate of 50-80°C/h, When the temperature of the aluminum shell is 300-400°C, stop heating and keep warm for 30-100 minutes. After the heat preservation is completed, quickly cool down to room temperature at a cooling rate of 10-50°C/h. 4. The battery aluminum case according to any one of claims 1-3, wherein an automatic pressure relief device is provided in the middle area of the upper end plate at the bottom of the aluminum case. 5. The battery aluminum case according to any one of claims 1-4, characterized in that the upper end plate at the bottom of the aluminum case is provided with a through hole, and the opening area of the through hole is 3-8mm ² , preferably 5mm ² . 6. The battery aluminum case according to any one of claims 1-5, wherein the automatic pressure relief device comprises a PTFE ball, a spring seat, a spring, a spacer, and a lower end plate; the PTFE ball and A sealing rubber ring is arranged between the contact surfaces of the through holes, the PTFE ball is bonded to the sealing rubber ring, the bottom of the PTFE ball is fixedly connected to the spring seat, the bottom of the spring seat is connected to the spring body, the bottom and the lower end of the spring body The plates are fixedly connected, the bottom of the pad is sealed and connected with the lower end plate, the spring body is set inside the ring pad, and the inside of the ring pad is provided with a vent hole; the lower end plate is provided with a pressure relief hole. 7. The battery aluminum case according to any one of claims 1-6, wherein the four facades of the aluminum case adopt an aluminum composite structure, and the aluminum composite structure includes aluminum from the inside to the outside, polyurethane insulation Membrane, Base Membrane, Polyurethane Insulation Membrane, Aluminum. 8. The battery aluminum case according to any one of claims 1-7, wherein the method for preparing the aluminum composite structure comprises the following steps: (a) heating the base film with a preheating roller, the heating temperature is 80-150° C., and the heating time is 30-90 minutes; (b) coating binder PVDF on base film both sides by rubber roller; (c) The polyurethane insulation film with a folded thickness of 500-1000um is pasted on both sides of the base film by a pasting roller, and the preheating roller and the pasting roller rotate counterclockwise to obtain a composite film; (d) passing the preliminarily bonded composite film through a hot roller for heating and rolling, the heating temperature is 50-80°C, the heating time is 10-30 minutes, and the thickness of the composite film after rolling is 60-300um; (e) Coating a 10-30um aluminum layer on the surface of the polyurethane insulation film by water electroplating; (f) Aluminum metal spraying is carried out on the upper surface of the aluminum layer, and the spraying thickness is 300-600um. 9. The battery aluminum case according to claim 7 or 8, wherein the preparation method of the polyurethane thermal insulation film comprises the following steps: (1) Prepare a thermoplastic polyurethane elastomer material with reference to the method of CN114957603A, cool to -30～0°C, and cool down for 1-3 hours; (2) Pulverize to particle size 0.1-2um, then mix with binder to prepare slurry; (3) Polyurethane film is obtained by coating film by dry coating technology, and rolled. 10. A high-nickel ternary power battery, comprising _the battery aluminum shell according to any one of claims 1-9, the positive _electrode material molecular formula of the high-nickel ternary power battery is Li( _NiaCobXc )O ₂ , wherein a+b+c=1, a=0.8-0.95, and X is manganese or aluminum.

Images