Formation method of niobium titanium oxide lithium ion battery

Abstract

The invention discloses a formation method of a niobium titanium oxide lithium ion battery, which is used for carrying out gradient formation on the lithium ion battery at the formation temperature of 50-70 DEG C and under the formation pressure of 0.4-0.8 Mpa, and specifically comprises the following steps: S1, at the first stage, carrying out constant-current charging, aging and discharging on the lithium ion battery according to a first parameter; s2, at a second stage, carrying out constant-current charging, aging and discharging on the lithium ion battery according to a second parameter; and S3, in the third stage, constant current is 0.2-0.5 C, constant voltage charging is carried out to 3.2 V, and cut-off current is 0.05 C. Through the gradient low-current full-full discharge and high-temperature pressurization aging combined method, the compactness of a niobium-titanium-oxygen lithium ion battery negative electrode film can be improved, gas production of a niobium-titanium-oxygen negative electrode is inhibited, gas expansion in the battery circulation / storage process is reduced, and the battery cycle performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery processes, and particularly to a formation method for niobium titanium oxide lithium ion batteries. Background Art

[0002] As a new type of negative electrode material, niobium titanium oxide has attracted increasing attention due to its long life, high safety, and high-rate charge and discharge performance. However, in early use, it was found that the batteries prepared with it would continuously generate gas during cycling / storage, resulting in battery swelling. The main reason is that the niobium titanium oxide material cannot form a dense SEI film on its surface, and the electrolyte is always in direct contact with the surface of niobium titanium oxide during the charge and discharge process, causing continuous reduction and decomposition of the electrolyte on the negative electrode surface, leading to gas swelling. In response to this, carbon coating technology has been adopted to improve the quality of the SEI film formed on the niobium titanium oxide negative electrode during the first charge. However, limited by the small-current constant-current charging to half charge mode adopted in the conventional formation process, the formed SEI film is too loose, resulting in the niobium titanium oxide battery still swelling during cycling and a decrease in the battery retention rate.

[0003] In view of this situation, the present invention aims to develop a gradient formation process for niobium titanium oxide lithium ion batteries. Combining with the method of high-temperature and high-pressure aging, it can improve the densification of the film formation on the negative electrode of niobium titanium oxide lithium ion batteries, inhibit gas generation at the niobium titanium oxide negative electrode, reduce gas swelling during battery cycling / storage, and improve the battery cycling performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a formation method for niobium titanium oxide lithium ion batteries to solve the technical problems of how to improve the densification of the film formation on the negative electrode of niobium titanium oxide lithium ion batteries, inhibit gas generation at the niobium titanium oxide negative electrode, reduce gas swelling during battery cycling / storage, and improve the battery cycling performance.

[0005] The present invention is realized by adopting the following technical solutions: A formation method for niobium titanium oxide lithium ion batteries, which performs gradient formation on the lithium ion battery, with the formation temperature being 50°C to 70°C and the formation pressure being 0.4 Mpa to 0.8 Mpa. Specifically, it includes the following steps: S1: In the first stage, according to the first parameter, the lithium ion battery is subjected to constant current charging, aging, and discharging. S2: In the second stage, according to the second parameter, the lithium ion battery is subjected to constant current charging, aging, and discharging. S3: In the third stage, the constant current is 0.2C to 0.5C, and constant voltage charging is carried out until 3.2V, with the cut-off current being 0.05C.

[0006] Further, step S1 includes the following sub-steps: S11: Constant current at 0.05C - 0.10C and charge for 200 min - 240 min, then charge at a constant current of 0.1C - 0.15C until the voltage reaches 3.2V; S12: Age the lithium - ion battery in a high - temperature environment of 50°C - 70°C for 24 h; S13: Discharge at a constant current of 0.1C - 0.15C until the voltage reaches 1.5V.

[0007] Furthermore, step S2 includes the following sub - steps: S21: Charge at a constant current of 0.1C - 0.15C until the voltage reaches 3.2V; S22: Age the lithium - ion battery in a high - temperature environment of 50°C - 70°C for 6 h; S23: Discharge at a constant current of 0.10C - 0.15C until the voltage reaches 1.5V.

[0008] Furthermore, the lithium - ion battery includes an aluminum - plastic film casing, an electrode core, and an electrolyte; the electrode core and the electrolyte are accommodated in the aluminum - plastic film casing; the electrode core includes a positive electrode, a negative electrode, and a separator.

[0009] Furthermore, the positive electrode includes a positive - electrode substrate and a positive - electrode material layer coated on the surface of the positive - electrode substrate, and the positive - electrode material layer includes a positive - electrode active material, a positive - electrode conductive agent, and a positive - electrode binder; the negative electrode includes a negative - electrode substrate and a negative - electrode material layer coated on the surface of the negative - electrode substrate, and the negative - electrode material layer includes a negative - electrode active material, a negative - electrode conductive agent, a negative - electrode adhesive, and a dispersant.

[0010] Furthermore, the positive - electrode active material is at least one of a lithium transition - metal composite oxide and a lithium transition - metal phosphate compound, and the negative - electrode active material is niobium titanium oxide.

[0011] The beneficial effects of the present invention are as follows: By the method of combining gradient small - current full charge and full discharge with high - temperature and high - pressure aging, the present invention can improve the compactness of the film - forming on the negative electrode of the niobium titanium oxide lithium - ion battery, inhibit gas generation on the niobium titanium oxide negative electrode, reduce gas swelling during battery cycling / storage, and improve the battery cycling performance. Description of the Drawings

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0013] Figure 1 It is a flowchart of the present invention. Detailed Embodiments

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0015] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0016] The following will describe in detail some embodiments of the present invention with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0017] See Figure 1 , a formation method for a niobium titanium oxide lithium-ion battery, which performs gradient formation on the lithium-ion battery. The formation temperature is 50°C to 70°C, and the formation pressure is 0.4 Mpa to 0.8 Mpa. The specific steps are as follows: Under the conditions of a formation temperature of 50°C to 70°C and a formation pressure of 0.4 to 0.8 Mpa, first charge the niobium titanium oxide lithium-ion battery to be formed at a constant current of 0.05C to 0.15C for 200 min to 240 min, and then charge at a constant current of 0.1C to 0.15C until the voltage reaches 3.2V; then stand still in a high-temperature environment of 50°C to 70°C for 24 h; then discharge at a constant current of 0.1C to 0.15C until the voltage reaches 1.5V; then charge at a constant current of 0.1C to 0.15C until the voltage reaches 3.2V; and stand still in a high-temperature environment of 50°C to 70°C for 6 h; continue to discharge at a constant current of 0.1C to 0.15C until the voltage reaches 1.5V; finally, charge at a constant current and constant voltage of 0.2C to 0.5C to 3.2V, with a cut-off current of 0.05C.

[0018] In this embodiment, the lithium-ion battery includes an aluminum-plastic film shell, an electrode core, and an electrolyte; the electrode core and the electrolyte are accommodated in the aluminum-plastic film shell; the electrode core includes a positive electrode, a negative electrode, and a separator.

[0019] In this embodiment, the positive electrode includes a positive electrode substrate and a positive electrode material layer coated on the surface of the substrate. The positive electrode material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the negative electrode includes a negative electrode substrate and a negative electrode material layer coated on the surface of the substrate. The negative electrode material layer includes a negative electrode active material, a negative electrode conductive agent, a negative electrode adhesive, and a dispersant.

[0020] In this embodiment, the positive electrode active material is selected from at least one of lithium transition metal composite oxides and lithium transition metal phosphate compounds, and the negative electrode active material is selected from niobium titanium oxide.

[0021] It should be noted that the gradient small current formation process is beneficial to the formation of a dense SEI film between the carbon layer coated on the surface of the niobium titanium oxide material and the electrolyte during the first charge and discharge, isolating the contact between the niobium titanium oxide material and the electrolyte, preventing gas generation during subsequent cycling and storage, and improving the Coulombic efficiency of the battery in the first cycle.

[0022] One of the reasons for gas generation in the niobium titanium oxide battery during cycling is that the lithium-rich niobium titanium oxide reacts with the carbonate organic solvent in the electrolyte under the catalysis of LiPF6 during charging, causing decarboxylation, decarbonylation, and dehydrogenation reactions. Therefore, the full charge and discharge process in the formation stage can cause the niobium titanium oxide material to undergo a disproportionation reaction with the electrolyte in advance, generating a decomposition product of the electrolyte on the material surface, thereby increasing the thickness of the SEI film. At the same time, the gas generated by the decomposition is discharged into the reserved airbag through the high-temperature and high-pressure process.

[0023] The high-temperature and high-pressure aging process is used to ensure that the electrolyte and the electrode are fully infiltrated at high temperature, and the high temperature promotes the restructuring of the SEI film structure to form a loose and thick film layer, enhancing the stability of film formation. On the other hand, it promotes the electrolysis of trace water in the battery at high potential to eliminate the influence of trace water on the battery.

[0024] Through the above process improvements, the present invention can effectively inhibit gas generation during battery cycling, improve the cycling performance of the battery. There is basically no attenuation after 200 cycles of 1.0C charge and discharge, and there is no bloating phenomenon in the battery.

[0025] For the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present application is not limited by the described action sequence, because according to the present application, some steps can be carried out in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the present application.

[0026] In the above embodiments, the basic principles, main features, and advantages of the present invention are described. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications and changes made by those skilled in the art should fall within the protection scope of the appended claims of the present invention.

Claims

1. A formation method for a niobium-titanium-oxygen lithium-ion battery, characterized in that: The lithium-ion battery is subjected to gradient formation, with a formation temperature of 50°C to 70°C and a formation pressure of 0.4Mpa to 0.8Mpa, specifically including the following steps: S1: In the first stage, the lithium-ion battery is charged, aged, and discharged at a constant current according to the first parameter; S2: In the second stage, the lithium-ion battery is charged, aged, and discharged at a constant current according to the second parameter; S3: The third stage, constant current 0.2C ~ 0.5C, and constant voltage charging to 3.2V, cut-off current 0.05C.

2. A formation method for a niobium-titanium-oxygen lithium-ion battery as claimed in claim 1, characterized in that: Step S1 includes the following sub-steps: S11: Constant current 0.05C ~ 0.10C, and charge for 200min ~ 240min, then constant current 0.1C ~ 0.15C to charge to a voltage of 3.2V; S12: aging the lithium-ion battery in a high temperature environment of 50° C. to 70° C. for 24 hours; S13: Discharge at a constant current of 0.1C to 0.15C until the voltage reaches 1.5V.

3. A formation method for a niobium-titanium-oxygen lithium-ion battery as claimed in claim 2, characterized in that: Step S2 includes the following sub-steps: S21: Constant current 0.1C~0.15C charging to voltage 3.2V; S22: aging the lithium-ion battery in a high temperature environment of 50° C. to 70° C. for 6 hours; S23: Discharge at a constant current of 0.10C to 0.15C to a voltage of 1.5V.

4. A formation method for a niobium-titanium-oxygen lithium-ion battery as claimed in claim 1, characterized in that: The lithium-ion battery comprises an aluminum-plastic film shell, a battery core and an electrolyte; the battery core and the electrolyte are contained in the aluminum-plastic film shell; the battery core comprises a positive electrode, a negative electrode and a separator.

5. A formation method for a niobium-titanium-oxygen lithium-ion battery as claimed in claim 4, characterized in that: The positive electrode comprises a positive electrode substrate and a positive electrode material layer coated on the surface of the positive electrode substrate, wherein the positive electrode material layer comprises a positive electrode active material, a positive electrode conductor and a positive electrode binder; the negative electrode comprises a negative electrode substrate and a negative electrode material layer coated on the surface of the negative electrode substrate, wherein the negative electrode material layer comprises a negative electrode active material, a negative electrode conductor, a negative electrode binder and a dispersant.

6. A formation method for a niobium-titanium-oxygen lithium-ion battery as claimed in claim 5, characterized in that: The positive electrode active material is at least one of a lithium transition metal composite oxide and a lithium transition metal phosphate compound, and the negative electrode active material is niobium titanium oxide.

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