Niobium titanium oxide battery and formation method

Abstract

This invention relates to the field of battery technology, and in particular to a niobium-titanium oxide battery and its formation method. The negative electrode active material of the niobium-titanium oxide battery is TNO; the formation method includes the following steps: S1: low-temperature potential locking, controlling interface nucleation within the critical potential range of TNO surface reconstruction; S2: medium-temperature interface growth, completing interface layer expansion; S3: high-temperature interface annealing, bringing the interface layer to a thermodynamically stable state; S4: venting and sealing. The purpose of this invention is to provide a formation method targeting the intrinsic characteristics of TNO negative electrode materials. By precisely controlling the surface reconstruction kinetics of TNO during the initial electrochemical activation process, a high-quality, high-stability interface layer is constructed, thereby significantly improving the high-temperature storage performance and high-temperature cycle life of the TNO battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a niobium-titanium-oxygen battery and its formation method. Background Technology

[0002] Niobium-titanium oxide (TiNb2O7, TNO) based lithium-ion batteries are favored due to their high operating potential (approximately 1.6V vs Li / Li). + With its high theoretical capacity (387-388 mAh / g, based on a 5-electron transfer reaction) and stable crystal structure, it is considered an ideal anode material for next-generation fast-charging, wide-temperature-range lithium-ion batteries. It is comparable to lithium titanate (Li4Ti5O4). 12 Compared to graphite (175 mAh / g), TNO has a higher theoretical capacity; compared to graphite, TNO has higher safety and better low-temperature performance. However, when TNO batteries are cycled in high-temperature (≥45℃) environments, they generally suffer from severe gas generation, excessively rapid increase in DC internal resistance (DCIR), and accelerated capacity decay, which seriously restricts their application in high-end energy storage, special vehicles, and other scenarios. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and defects of the prior art and to provide a niobium-titanium-oxygen battery and its formation method.

[0004] To achieve the above objectives, this application adopts the following solution: A method for forming a niobium-titanium-oxygen battery, wherein the negative electrode active material of the niobium-titanium-oxygen battery is TNO; comprising the following steps: S1: low-temperature potential locking, controlling interface nucleation within the critical potential range reconstructed on the TNO surface; S2: medium-temperature interface growth, completing interface layer expansion; S3: high-temperature interface annealing, bringing the interface layer to a thermodynamically stable state; S4: venting and sealing.

[0005] The specific steps of step S1 are as follows: the TNO battery after liquid injection is charged at low temperature and low current so that the TNO negative electrode potential enters the critical reconstruction potential range of 1.2-1.8V; and the constant voltage is maintained within this potential range for 30-120 minutes.

[0006] The low-temperature, low-current charging method is as follows: the TNO battery is placed in a low-temperature environment of 5-15℃ and left to stand for 4-12 hours to allow the cell temperature to become uniform; then it is charged with a constant current of 0.02C-0.05C. Preferably, the particle size of TNO is D50≤3μm, and the constant pressure time is 30-60 minutes; for D50≥10μm, the constant pressure time is 90-120 minutes.

[0007] During the initial electrochemical activation process, TNO undergoes intrinsic surface reconstruction, forming an interface layer. This reconstruction process exhibits a significant potential dependence: the dissolution / diffusion of Ti from the particle surface mainly occurs in the potential range below 1.4V, while the nucleation of the interface layer begins around 1.8V. Therefore, the 1.2-1.8V range is the critical potential window for TNO surface reconstruction; within this window, the reconstruction process initiates, but excessive Ti dissolution has not yet occurred drastically. Under low temperature and low current conditions, the kinetics of the TNO surface reconstruction reaction are suppressed, and the interface layer nucleates in a slow and orderly manner, resulting in a dense, uniform interface layer with few defects.

[0008] The specific steps of step S2 are as follows: heat the battery to a room temperature environment of 25-35℃; charge it to 100% SOC with a medium current of 0.1C-0.2C; after the temperature rises, the interface layer enters the growth stage, and the efficiency can be improved by appropriately increasing the current, while avoiding the loose structure caused by excessively fast growth rate.

[0009] Step S3 involves placing a fully charged battery in a high-temperature environment of 45-55℃ for 24-72 hours. High-temperature annealing causes structural relaxation in the interface layer, eliminating lattice stress and bringing the interface layer to a thermodynamically stable state. This pre-treatment of the interface with high temperatures prevents further evolution during subsequent cycles.

[0010] The specific steps of step S4 are as follows: after high-temperature annealing, the battery is cooled to room temperature, and secondary venting is performed in a dry environment to remove trace amounts of gas generated during the high-temperature standing process; finally, the battery is sealed to complete the formation.

[0011] Before step S1, there is also step S0: a pre-formation settling and wetting treatment stage; preferably, it includes the following steps: placing the battery after electrolyte injection in an environment of 25-60°C for 12-48 hours; preferably, the settling temperature is 45°C and the settling time is 24 hours. This step ensures that the electrolyte fully penetrates into the micropores of the electrode, providing a good ion conduction basis for subsequent formation.

[0012] The present invention also includes a niobium-titanium-oxygen battery obtained by the formation method described above, comprising a positive electrode, a negative electrode, and an electrolyte.

[0013] The active material of the negative electrode is secondary TNO particles or primary TNO particles; preferably, the primary TNO particles have a D50 of 1-2 μm; the secondary TNO particles have a D50 of 10 μm and a specific gravity of 4.18 μm. 2 / g; Preferably, the active material of the positive electrode is a high-nickel ternary material; more preferably, it is LiNi. 0.8 Co 0.1 Mn 0.1 O2.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The purpose of this invention is to provide a formation method targeting the intrinsic properties of TNO anode materials. By precisely controlling the surface reconstruction kinetics of TNO during the initial electrochemical activation process, a high-quality and highly stable interface layer is constructed, thereby significantly improving the high-temperature storage performance and high-temperature cycle life of TNO batteries. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the formation process principle of the embodiments and comparative examples of the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0017] A method for the formation of a niobium-titanium-oxygen battery ( Figure 1 (See flowchart).

[0018] General pretreatment step S0 (common to all examples and comparative examples): Place the TNO battery after electrolyte injection in a 45°C environment for 24 hours to allow the electrolyte to fully wet the electrode and ensure that the state before formation is consistent.

[0019] Example 1 (48Ah pouch cell): Cell specifications: 48Ah pouch cell, negative electrode uses TNO secondary particles (D50=10μm, specific gravity 4.18m). 2 / g), the positive electrode uses a high-nickel ternary material (LiNi0.8Co0.1Mn0.1O2).

[0020] Chemical formation process: S1: Low-temperature potential lockout, controlling interface nucleation within the critical potential range reconstructed on the TNO surface; after impregnation, the cell is placed in a 10℃ low-temperature environment and left to stand for 2 hours to allow the temperature to become uniform; constant current charging at 0.03C, monitoring the negative electrode potential through the reference electrode, when the potential enters the 1.2-1.8V range (corresponding to approximately 40% SOC), maintaining constant voltage at this potential for 90 minutes; S2: Medium-temperature interface growth to complete interface layer expansion; the cell temperature is raised to 30℃ and charged to full capacity with a constant current of 0.15C; S3: High-temperature interface annealing to bring the interface layer to a thermodynamically stable state; place the fully charged cell in a 45°C environment and let it stand for 48 hours. S4: Exhausting and sealing; cooling to room temperature, secondary exhaust in a dry environment with a dew point of -40°C, and final sealing. Example 2 (3Ah soft-pack battery cell): Battery cell specifications: 3Ah soft-pack battery cell, negative electrode uses TNO primary particles (D50=1-2μm), positive electrode uses high nickel ternary material.

[0021] Chemical formation process: S1: Low-temperature potential locking controls interface nucleation within the critical potential range reconstructed on the TNO surface; After impregnation, the cell is placed in an 8°C low-temperature environment and left to stand for 2 hours; it is then charged with a constant current of 0.02C, and the negative electrode potential is monitored. When the potential enters the 1.2-1.8V range (corresponding to approximately 35% SOC), it is maintained at this potential for 50 minutes under constant voltage (small particle size materials have a larger specific surface area, more reactive sites, and faster interface nucleation, thus shortening the constant voltage time). S2: Medium-temperature interface growth, completing the interface layer expansion; heating to 28℃, charging at a constant current of 0.12C to full charge; S3: High-temperature interface annealing to bring the interface layer to a thermodynamically stable state; place the fully charged cell in a 55°C environment and let it stand for 60 hours. S4: Exhausting and sealing; cooling to room temperature, exhausting again in a dry environment with a dew point of -40°C, and finally sealing.

[0022] Example 3 (48Ah pouch cell, parameter window boundary verification): Cell specifications: same as the 48Ah pouch cell in Example 1.

[0023] Chemical formation process: S1: Low-temperature potential lockout, controlling interface nucleation within the critical potential range reconstructed on the TNO surface; after impregnation, place the cell in a 5℃ low-temperature environment and let it stand for 2 hours; charge with a constant current of 0.05C, and when the potential enters the 1.2-1.8V range, maintain constant voltage for 90 minutes; S2: Medium-temperature interface growth, completing the interface layer expansion; heating to 25℃, charging at a constant current of 0.2C to full charge; S3: High-temperature interface annealing, place the fully charged battery cell in a 55℃ environment and let it stand for 24 hours; S4: Exhaust and seal; cool to room temperature, exhaust again, and then seal.

[0024] Example 4 (48Ah pouch cell, parameter window boundary verification): Cell specifications: same as the 48Ah pouch cell in Example 1.

[0025] Chemical formation process: S1: Low-temperature potential lockout, controlling interface nucleation within the critical potential range reconstructed on the TNO surface; after impregnation, place the cell in a low-temperature environment of 15℃ and let it stand for 2 hours; charge with a constant current of 0.02C, and when the potential enters the 1.2-1.8V range, maintain constant voltage for 30 minutes; S2: Medium-temperature interface growth, completing the interface layer expansion; heating to 35℃, charging at a constant current of 0.1C to full charge; S3: High-temperature interface annealing to bring the interface layer to a thermodynamically stable state; place the fully charged cell in a 50°C environment and let it stand for 72 hours. S4: Exhaust and seal; cool to room temperature, exhaust again, and then seal.

[0026] Comparative Example 1 (48Ah pouch cell, room temperature formation): Cell specifications: same as the 48Ah pouch cell in Example 1.

[0027] Formation process: After impregnation, the battery cell is placed in a 30°C environment and charged at a constant current of 0.15C until fully charged; no high-temperature annealing is performed; the battery is directly vented and sealed.

[0028] Comparative Example 2 (48Ah pouch cell, high temperature formation) Cell specifications: same as the 48Ah pouch cell in Example 1.

[0029] Formation process: After impregnation, the battery cell is placed in a 45°C environment; it is charged at a constant current of 0.15C until fully charged without additional high-temperature annealing (the 45°C charging process already includes high temperature); it is cooled to room temperature and then vented and sealed. Comparative Example 3 (48Ah pouch cell, single-step low-temperature formation): Cell specifications: same as the 48Ah pouch cell in Example 1.

[0030] Formation process: After impregnation, place the battery cell in a 10℃ environment and charge it at 0.03C to a constant voltage of 1.2-1.8V for 60 minutes; charge it at 30℃ at 0.15C to 100% SOC; skip step C (high temperature annealing); directly vent and seal.

[0031] Comparative Example 4 (3Ah pouch cell, room temperature formation): Cell specifications: same as the 3Ah pouch cell of Example 2. Formation process is the same as Comparative Example 1.

[0032] Performance test results Test 1: Electrochemical Impedance Spectroscopy (EIS) Analysis (48Ah Cell) After formation, the cells of each embodiment and comparative example were adjusted to 50% SOC and subjected to EIS testing at 25°C. Test conditions: frequency range 10. 5 Hz to 10 -2 Hz, AC amplitude 5mV. The test results are shown in Table 1.

[0033] Table 1

[0034] As can be seen from the data in Table 1, the charge transfer impedance Rct of Examples 1, 3, and 4, formed using the three-step method of this invention, is significantly lower than that of the comparative example, indicating the formation of an interface layer with higher lithium-ion conductivity. Among them, Comparative Example 1 (formed at room temperature) has the highest Rct, reaching 28.4 mΩ, indicating that its interface layer quality is the worst.

[0035] Test 2: High-Temperature Storage Performance Test (48Ah Cell) The battery cells of each embodiment and comparative example were fully charged and stored in a 60°C constant temperature chamber for 7 days. The changes in thickness and AC internal resistance before and after storage were tested. The test results are shown in Table 2.

[0036] Table 2

[0037] As can be seen from the data in Table 2, the thickness expansion rates of Examples 1, 3, and 4, which were formed using the three-step method of this invention, were all ≤3% after storage at 60°C for 7 days, while the comparative example had a rate as high as 13%. This indicates that the interface layer formed by the method of this invention effectively suppresses side reactions and gas production at high temperatures.

[0038] Test 3: High-Temperature Cycling Performance Test (48Ah Cell) The battery cells of each embodiment and comparative example were placed in a 45°C constant temperature chamber and subjected to cyclic testing at a 1C charge-discharge rate. The change in capacity retention with the number of cycles was recorded. The test results are shown in Table 3.

[0039] Table 3

[0040] As can be seen from the data in Table 3, Examples 1, 3, and 4, which were formed using the three-step method of the present invention, all exhibited a capacity retention rate of ≥90% after 500 cycles at 45°C, while the comparative examples only showed a retention rate of 75-85%. Furthermore, the DCIR growth rate after 500 cycles was only 28.3% for Example 1, while reaching as high as 95.4% for Comparative Example 1, indicating that the interface layer formed by the method of the present invention remains stable during long-term high-temperature cycling.

[0041] Test 4: Negative electrode peel strength test (48Ah cell) The formed battery cell was disassembled in an argon-filled glove box. The TNO negative electrode sheet was removed and cut into 25mm × 100mm strips. A universal testing machine was used to perform a 180° peel strength test at a peel speed of 50mm / min. The test results are shown in Table 4.

[0042] Table 4

[0043] As can be seen from the data in Table 4, the electrode peel strength of Example 1 reached 12.2 N / m, which is significantly higher than that of Comparative Example 1 (7.8 N / m). This indicates that the interface layer formed by the method of the present invention has better compatibility with the binder and higher mechanical stability of the electrode.

[0044] Test 5: Performance data of Example 2 (3Ah pouch cell) To verify the applicability of the method of the present invention to cells of different specifications, the same test was performed on Example 2 (3Ah pouch cell, TNO primary particles) and compared with Comparative Example 4 (3Ah room temperature formation). The test conditions were the same as for the 48Ah cell.

[0045] Table 5

[0046] As can be seen from the data in Table 5, the three-step formation process of this invention also shows a significant performance improvement effect on 3Ah small cells, verifying the universality of this method for TNO materials of different specifications and particle sizes.

[0047] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for forming a niobium titanium oxide battery, characterized by, The negative electrode active material of the niobium-titanium-oxygen battery is TNO; the process includes the following steps: S1: low-temperature potential locking, controlling interface nucleation within the critical potential range reconstructed on the TNO surface; S2: medium-temperature interface growth, completing interface layer expansion; S3: high-temperature interface annealing, bringing the interface layer to a thermodynamically stable state; S4: venting and sealing.

2. The niobium-titanium oxyelectric battery formation method according to claim 1, characterized by, The specific steps of step S1 are as follows: the TNO battery after liquid injection is charged at low temperature and low current so that the TNO negative electrode potential enters the critical reconstruction potential range of 1.2-1.8V; and the constant voltage is maintained within this potential range for 30-120 minutes.

3. The method for forming a niobium-titanium-oxygen battery according to claim 2, characterized in that, The low-temperature, low-current charging method is as follows: the TNO battery is placed in a low-temperature environment of 5-15℃ and left to stand for 4-12 hours to allow the cell temperature to become uniform; then it is charged with a constant current of 0.02C-0.05C.

4. The niobium-titanium oxyelectric battery formation method according to claim 2, characterized by, For TNO with a particle size D50 ≤ 3 μm, the constant pressure time is 30-60 minutes; for D50 ≥ 10 μm, the constant pressure time is 90-120 minutes.

5. The niobium-titanium oxyelectric battery formation method according to claim 1, characterized by, The specific steps of step S2 are as follows: heat the battery to a room temperature environment of 25-35℃; charge it to 100% SOC with a medium current of 0.1C-0.2C.

6. The niobium-titanium oxyelectric battery formation method of claim 1, wherein, The specific steps of step S3 are as follows: Place the fully charged battery in a high-temperature environment of 45-55℃ and let it stand for 24-72 hours.

7. The method for forming a niobium-titanium-oxygen battery according to claim 1, characterized in that, The specific steps of step S4 are as follows: after high-temperature annealing, the battery is cooled to room temperature, and secondary venting is performed in a dry environment to remove trace amounts of gas generated during the high-temperature standing process; finally, the battery is sealed to complete the formation.

8. The method for forming a niobium-titanium-oxygen battery according to claim 1, characterized in that, Before step S1, there is also step S0: pre-formation standing and wetting treatment stage; preferably, it includes the following steps: placing the battery after liquid injection in an environment of 25-60°C for 12-48 hours; preferably, the standing temperature is 45°C and the standing time is 24 hours.

9. A niobium-titanium-oxygen battery obtained by the formation method according to any one of claims 1-8, characterized in that, It includes the positive electrode, the negative electrode, and the electrolyte.

10. The niobium-titanium-oxygen battery according to claim 8, characterized in that, The active material of the negative electrode is TNO secondary particles or TNO primary particles; preferably, the TNO primary particles have a D50 = 1-2 μm; the TNO secondary particles have a D50 = 10 μm, a specific surface of 4.18 m 2 / g. Preferably, the active material of the positive electrode is a high-nickel ternary material; preferably LiNi 0.8 Co 0.1 Mn 0.1 O2.

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