Experimental method for researching aluminum shell corrosion mechanism by equivalently simulating battery negative short circuit

Abstract

The invention discloses an experimental method for researching the corrosion mechanism of an aluminum shell by equivalently simulating the negative short circuit of a battery. The experimental method comprises the following steps: firstly, in a dew point management and control environment, taking out a charged negative pole piece from the interior of a full-charge battery for later use, then combining with an aluminum foil serving as a positive pole to assemble a soft package battery, injecting an electrolyte, then performing plastic packaging to obtain a negative short condition of the negative pole in contact with the aluminum foil in an equivalent simulation battery, taking out the aluminum foil after standing reaction, and finally obtaining the negative short condition of the battery. The corrosion phenomenon is observed; and performing SEM test and ICP test on the aluminum foil after the reaction, verifying components on the aluminum foil after the reaction, and analyzing the corrosion mechanism of the aluminum shell according to the corrosion phenomenon of the aluminum foil and the components on the aluminum foil after the reaction. According to the equivalent simulation battery negative short experiment method, the electrochemical corrosion mechanism is verified by performing SEM test and ICP test on the aluminum foil, and the method is simple and convenient.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to an experimental method for studying the corrosion mechanism of aluminum shells by equivalently simulating battery negative short circuit. Background Art

[0002] In recent years, the use and popularity of electric vehicles have become increasingly widespread, and research on safety issues has also become increasingly popular. Aluminum-shell lithium-ion batteries often experience shell corrosion and leakage during use. This failure mode seriously affects the safety and life of the battery. Therefore, fully understanding the mechanism of aluminum shell corrosion in lithium-ion batteries and applying this concept to structural design and manufacturing design can effectively prevent the occurrence of this failure mode. During the use or storage of the battery, the corrosion reaction first occurs on the inner wall of the aluminum shell. As time goes by, the corrosion reaction deepens, causing the corrosion reaction of the inner wall of the aluminum shell to gradually develop to the outside of the aluminum shell. At this time, the battery will gradually fail. The main cause of aluminum shell corrosion may be that the negative electrode of the battery cell contacts the shell, causing a short circuit, or the electrode powder flows with the electrolyte to the side and bottom of the battery, forming an electron channel, forcing the aluminum shell potential to be forced to drop to the aluminum metal lithium insertion potential, triggering the electrochemical corrosion reaction; it may also be the presence of F in the electrolyte - During the cycling process, HF is formed, and the HF in the electrolyte reacts chemically with the Al2O3 on the surface of the aluminum shell to form AlF3. Therefore, it is necessary to develop an experimental method to explore the corrosion mechanism of aluminum shells in lithium-ion batteries. Summary of the Invention

[0003] In order to explore the corrosion mechanism of aluminum shell of lithium-ion battery, the purpose of this invention is to provide an experimental method for studying the corrosion mechanism of aluminum shell by simulating the negative short of battery; the corrosion mechanism of negative short aluminum shell is verified by SEM (scanning electron microscope) and ICP (inductively coupled plasma) methods.

[0004] The present invention provides an experimental method for studying the corrosion mechanism of an aluminum shell by using an equivalent simulated battery with negative short circuit, comprising the following steps: first, under a dew point controlled environment, removing a charged negative electrode from a fully charged battery for standby use, then combining the charged negative electrode with an aluminum foil serving as a positive electrode to form a soft-pack battery, injecting an electrolyte and then plastic-sealing the battery to obtain a negative short circuit situation in which the negative electrode contacts the aluminum foil in the equivalent simulated battery, allowing the aluminum foil to react, removing the aluminum foil, and observing its corrosion phenomenon; performing SEM testing and ICP testing on the aluminum foil after the reaction to verify components on the aluminum foil after the reaction, and analyzing the corrosion mechanism of the aluminum shell based on the aluminum foil corrosion phenomenon and the components on the aluminum foil after the reaction.

[0005] In the above experimental method, the static reaction time can be 1 to 3 days, depending on the corrosion situation; The corrosion phenomenon of the aluminum foil is blackening due to corrosion, which indicates that a chemical corrosion reaction occurs.

[0006] In the above experimental method, when the aluminum foil corrodes and turns black, the battery voltage, the positive electrode-shell voltage, and the shell-negative electrode voltage all appear normal. The corrosion mechanism of the aluminum shell is as follows: HF in the electrolyte inside the battery reacts with Al2O3 on the surface of the aluminum shell to produce AlF3; And / or, aluminum metal atoms on the inner surface of the aluminum shell react with HF.

[0007] In the above experimental method, when the aluminum foil corrodes and turns black, the battery voltage, the positive electrode-shell voltage, and the shell-negative electrode voltage all appear normal. The chemical reaction formula of the aluminum shell corrosion mechanism is as follows: .

[0008] In the above experimental method, when the surface of the aluminum foil is corroded and melted but there is no obvious blackening phenomenon, electrochemical corrosion occurs.

[0009] In the above experimental method, the chemical reaction formula of the electrochemical corrosion mechanism is as follows: .

[0010] In the above experimental method, when the surface of the aluminum foil is corroded and melted, and there is an obvious blackening phenomenon, the chemical corrosion reaction and the electrochemical corrosion occur.

[0011] In the present invention, the mechanism of electrochemical corrosion is as follows: metal particles or electrode powder generated in various steps during the battery manufacturing process remain inside the battery. After the electrolyte is injected, the metal particles or electrode powder flow with the electrolyte to the sides and bottom of the battery. After the battery is charged, electron channels are formed under the action of these metal particles or electrode powder, forcing the potential of the aluminum shell to be forced to drop to the lithium insertion potential of the aluminum metal, triggering the electrochemical corrosion reaction.

[0012] The present invention has the following beneficial effects: 1. The present invention verifies the electrochemical corrosion mechanism by performing SEM and ICP tests on aluminum foil; 2. The equivalent simulated battery negative short test method of the present invention is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the experimental soft-pack battery preparation process.

[0014] Figure 2 This is the corrosion condition of aluminum foil after the experimental soft-pack battery test.

[0015] Figure 3 The surface morphology of the corrosion products at the edge of the aluminum foil corrosion penetration hole was captured by SEM. DETAILED DESCRIPTION

[0016] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0017] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] Example 1. Cut the positive electrode aluminum foil of the lithium-ion battery into 8×12 cm size, wipe it with alcohol and set aside; 2. After fully charging the finished square lithium iron battery cell, disassemble it to obtain the negative electrode fully embedded with lithium; 3. Under dew point control environment (<-40℃), attach two negative electrodes to a piece of foil to form a sandwich structure, put them into soft pack, fill them with liquid, and seal them with plastic. Let them stand and wait for the reaction (such as Figure 1 shown); The reaction equation of chemical corrosion mechanism is as follows: .

[0020] 4. After standing for 3 days, dismantle the soft pack test cell to obtain the corroded aluminum foil (such as Figure 2 As shown in the figure, the surface of the aluminum foil is corroded and melted, but there is no obvious blackening phenomenon, so electrochemical corrosion may have occurred, forming AlLi alloy.

[0021] 5. Take the aluminum foil material for SEM test. The test results show that the corrosion product morphology of the aluminum shell corrosion penetrating the battery's corrosion hole edge is in the form of tiny particles and there is a powdering phenomenon (such as Figure 3 shown).

[0022] 6. An aluminum foil material was subjected to an ICP test. The test results are shown in Table 1. Table 1 shows that Li element appears in the corroded aluminum foil, indicating that electrochemical corrosion has occurred and AlLi alloy has been formed.

[0023] Table 1 Corrosion element composition of aluminum foil before and after ICP test

[0024] Therefore, the reaction equation of the electrochemical corrosion mechanism is as follows: .

Claims

1. An experimental method for studying the corrosion mechanism of aluminum shells by simulating negative short circuits in an equivalent battery, comprising the following steps: first, under a dew point controlled environment, removing a charged negative electrode from a fully charged battery for standby use, then combining it with aluminum foil as a positive electrode to form a soft-pack battery, injecting an electrolyte and then plastic-sealing the battery to obtain a negative short circuit situation in which the negative electrode contacts the aluminum foil in an equivalent simulated battery, and after standing for reaction, removing the aluminum foil and observing its corrosion phenomenon; performing SEM and ICP tests on the aluminum foil after the reaction to verify the components on the aluminum foil after the reaction, and analyzing the corrosion mechanism of the aluminum shell based on the aluminum foil corrosion phenomenon and the components on the aluminum foil after the reaction.

2. The experimental method according to claim 1, characterized in that The time of the static reaction is 1 to 3 days; The corrosion phenomenon of the aluminum foil is blackening due to corrosion, which indicates that a chemical corrosion reaction occurs.

3. The experimental method according to claim 2, characterized in that When the aluminum foil corrodes and turns black, the battery voltage, positive electrode-shell voltage, and shell-negative electrode voltage all appear normal. The aluminum shell corrosion mechanism is as follows: HF in the electrolyte inside the battery reacts with Al2O3 on the surface of the aluminum shell to produce AlF3; And / or, aluminum metal atoms on the inner surface of the aluminum shell react with HF.

4. The experimental method according to claim 2 or 3, characterized in that When the aluminum foil corrodes and turns black, the battery voltage, the positive electrode-shell voltage, and the shell-negative electrode voltage all appear normal. The chemical reaction formula of the aluminum shell corrosion mechanism is as follows: 。 5. The experimental method according to claim 1 or 2, characterized in that When the surface of the aluminum foil is corroded and melted but there is no obvious blackening phenomenon, electrochemical corrosion occurs.

6. The experimental method according to claim 5, characterized in that The chemical reaction formula of the electrochemical corrosion mechanism is as follows: 。 7. The experimental method according to claim 5, characterized in that When the surface of the aluminum foil is corroded and melted, and there is an obvious blackening phenomenon, the chemical corrosion reaction and the electrochemical corrosion occur.

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