Repeated charging-standing formation method for cylindrical battery in specific voltage interval

Abstract

The invention belongs to the technical field of cylindrical batteries, and particularly relates to a repeated charging-standing formation method for a cylindrical battery in a specific voltage interval, and the formation method comprises the following steps: S1, determining a decomposition potential interval of a solvent / lithium salt through a constant current charging technology; s2, carrying out constant-current charging on the battery to a voltage when the solvent / lithium salt begins to decompose; s3, charging the battery at constant current until the voltage is reached when the decomposition of the solvent / lithium salt is finished, and standing for 1 hour; s4, judging whether the S2-S4 are circulated for five times or not, and if the number of the S2-S4 is less than five, continuing to circulate the S2-S4; s5, after circulation of S2-S4 is carried out for five times, the battery is subjected to constant-current charging until the cut-off voltage is reached; and S6, finishing formation. The method disclosed by the invention can focus on a formation process of the battery, and the microstructure of the SEI film is finely regulated and controlled skillfully on the basis of not increasing any manufacturing cost, so that the cycle life of the battery is remarkably prolonged, and the stability of the battery is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cylindrical batteries, and in particular relates to a repeated charging-stationary formation method for cylindrical batteries in a specific voltage range. Background Art

[0002] During the constant current charging formation process, lithium-ion batteries will form a solid electrolyte interface (SEI) film at the electrode / electrolyte interface. This interface film can effectively inhibit the side reactions at the interface, thereby improving the battery's cycle life. However, the constant current charging method currently has the following problems: first, the SEI film components formed on the surface of the active material are unevenly distributed, which exacerbates the uneven transmission of lithium ions during the lithium insertion process; second, due to the rapidity of constant current charging, lithium salt anions fail to fully participate in the formation of the SEI film, resulting in a low content of inorganic components, which in turn affects the transmission efficiency of lithium ions at the interface.

[0003] At present, the solutions focus on two major directions: one is to introduce efficient film-forming additives, which, despite the high cost, can significantly increase the content of inorganic components in the SEI film; the other is to finely control the ratio of solvents to optimize the internal structure of the SEI film, thereby effectively enhancing the transmission rate of lithium ions at the interface.

[0004] The current solution focuses on adjusting the electrolyte formula. Although it has optimized the interface transmission efficiency to a certain extent, it has inevitably pushed up the manufacturing cost of the battery and posed an obstacle to the market penetration of the product. In addition, during the formation stage of constant current charging, the persistent polarization phenomenon significantly affects the construction process of the SEI film (especially the decomposition process of lithium salt anions is inhibited), causing the interface to show non-uniform distribution characteristics in chemical composition and micromorphology, constituting potential defects. These defects may be exacerbated in subsequent charge and discharge cycles, causing uncontrollable precipitation of a large amount of active lithium, directly threatening the stability of the internal structure of the battery, and easily causing battery short circuits, thereby causing serious safety hazards. Summary of the invention

[0005] The purpose of the present invention is to provide a method for repeated charging-stationary formation in a specific voltage range for cylindrical batteries, which can focus on the formation process of the battery and cleverly fine-tune the microstructure of the SEI film without increasing any manufacturing cost, thereby achieving a significant improvement in the battery cycle life and stability.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for repeatedly charging and standing for formation of cylindrical batteries in a specific voltage range, the method comprising the following steps:

[0008] S1: Determine the decomposition potential range of solvent / lithium salt by constant current charging technology;

[0009] S2: charging the battery at a constant current to the voltage at which the solvent / lithium salt begins to decompose;

[0010] S3: Charge the battery at a constant current to the voltage at which the solvent / lithium salt decomposition ends, and let it stand for 1 hour;

[0011] S4: Determine whether S2-S4 has been cycled 5 times. If it is less than 5 times, continue to cycle S2-S4;

[0012] S5: After S2-S4 cycles for 5 times, the battery is charged with constant current to the cut-off voltage;

[0013] S6: The formation is completed.

[0014] The decomposition potentials of ethylene carbonate and lithium salt were determined by constant current charge and discharge. Ethylene carbonate began to decompose at 1.0V, lithium salt decomposed at 1.65V, and ended at 1.75V. The repeated charge-rest voltage range was determined to be 0.9V-2.0V.

[0015] The constant current charging current is 0.05C.

[0016] It is charged to 1.0V with a constant current of 0.05C, then charged to 2.0V with a constant current of 0.05C, left to stand for 1h, and cycled five times. Finally, it is charged to 3.65V with a constant current of 0.05C to end the formation.

[0017] The technical effects achieved by the present invention are:

[0018] The present invention introduces an efficient formation strategy for a repeated charging-stationary formation method for a specific voltage range of a cylindrical battery, aiming to fundamentally weaken the negative impact of polarization on battery performance. This strategy focuses on the key link of lithium salt / solvent decomposition. Through repeated charging-stationary operations, the stationary process is cleverly utilized to curb the polarization effect generated during the charging process, thereby achieving active suppression of polarization. The significant highlight of this method is that, without increasing any battery manufacturing costs, the stability of the SEI film is successfully improved, and the comprehensive performance and safety performance of the battery in long-term cyclic use are greatly improved. This breakthrough not only highlights the efficiency and benefits of technological innovation, but also lays a solid foundation for promoting battery technology to a higher level of development and further broadening its application boundaries. Its importance and value are immeasurable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flowchart of steps of an embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of repeated charging-stationary formation in a specific voltage range in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0022] like Figure 1-Figure 2 As shown, a method for repeatedly charging and standing for formation of cylindrical batteries in a specific voltage range includes the following steps:

[0023] S1: Determine the decomposition potential range of the solvent / lithium salt by constant current charging technology, and the constant current charging current is 0.05C;

[0024] S2: charging the battery at a constant current to the voltage at which the solvent / lithium salt begins to decompose;

[0025] The decomposition potentials of ethylene carbonate and lithium salt were determined by constant current charge and discharge. Ethylene carbonate began to decompose at 1.0V, lithium salt decomposed at 1.65V, and ended at 1.75V. The repeated charge-rest voltage range was determined to be 0.9V-2.0V.

[0026] S3: Charge the battery at a constant current to the voltage at which the solvent / lithium salt decomposition ends, and let it stand for 1 hour;

[0027] S4: Determine whether S2-S4 has been cycled 5 times. If it is less than 5 times, continue to cycle S2-S4;

[0028] S5: After S2-S4 cycles for 5 times, the battery is charged with constant current to the cut-off voltage;

[0029] S6: The formation is completed.

[0030] It is charged to 1.0V with a constant current of 0.05C, then charged to 2.0V with a constant current of 0.05C, left to stand for 1h, and cycled five times. Finally, it is charged to 3.65V with a constant current of 0.05C to end the formation.

[0031] Among them, the test system is a lithium iron phosphate-graphite full battery, and the electrolyte is 1 mol·L-1LiPF6+0.1 mol·L-1LiBOB-EC / DEC (volume ratio 1:1).

[0032] The present invention innovatively introduces an efficient formation strategy, aiming to fundamentally weaken the negative impact of polarization on battery performance. This strategy focuses on the key link of lithium salt / solvent decomposition. Through repeated charging-resting operations, it cleverly utilizes the resting process to curb the polarization effect generated during the charging process, thereby achieving active suppression of the polarization phenomenon. The significant highlight of this change is that it successfully improves the stability of the SEI film without increasing any battery manufacturing costs, and greatly improves the comprehensive performance and safety performance of the battery in long-term cyclic use. This breakthrough not only demonstrates the efficiency and benefits of technological innovation, but also lays a solid foundation for promoting battery technology to a higher level of development and further broadening its application boundaries. Its importance and value are immeasurable.

[0033] Furthermore, this improvement greatly enhances the overall performance of the battery in long-term, high-frequency cycle use, including energy density, charge and discharge efficiency, and crucially, safety performance, injecting new vitality and possibilities into the sustainable development of battery technology.

[0034] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for repeated charging-stationary formation in a specific voltage range for cylindrical batteries, characterized in that: The formation method comprises the following steps: S1: Determine the decomposition potential range of solvent / lithium salt by constant current charging technology; S2: charging the battery at a constant current to the voltage at which the solvent / lithium salt begins to decompose; S3: Charge the battery at a constant current to the voltage at which the solvent / lithium salt decomposition ends, and let it stand for 1 hour; S4: Determine whether S2-S4 has been cycled 5 times. If it is less than 5 times, continue to cycle S2-S4; S5: After S2-S4 cycles for 5 times, the battery is charged with constant current to the cut-off voltage; S6: The formation is completed.

2. A method for repeated charging-stationary formation in a specific voltage range for cylindrical batteries according to claim 1, characterized in that: The decomposition potentials of ethylene carbonate and lithium salt were determined by constant current charge and discharge. Ethylene carbonate began to decompose at 1.0V, lithium salt decomposed at 1.65V, and ended at 1.75V. The repeated charge-rest voltage range was determined to be 0.9V-2.0V.

3. A method for repeated charging-stationary formation in a specific voltage range for cylindrical batteries according to claim 1, characterized in that: The constant current charging current is 0.05C.

4. A method for repeated charging-stationary formation in a specific voltage range for cylindrical batteries according to claim 3, characterized in that: It is charged to 1.0V with a constant current of 0.05C, then charged to 2.0V with a constant current of 0.05C, left to stand for 1h, and cycled five times. Finally, it is charged to 3.65V with a constant current of 0.05C to end the formation.

Images