Method for realizing SEI dynamic construction of niobium-titanium-oxygen material by voltage control method and application of method in low-temperature lithium ion battery

Abstract

The invention discloses a method for realizing SEI dynamic construction of a niobium-titanium-oxygen material by a voltage control method and application of the method in a low-temperature lithium ion battery, and belongs to the field of low-temperature energy storage of the lithium ion battery. According to the lithiation voltage control strategy, SEI can be formed in the activation stage, the interface stability is improved, the lithiation potential is dynamically controlled to form SEI in the long-cycle full-life cycle according to the cycle stability change condition, the SEI is made to be in a good ion transmission state, and by regulating and controlling the cycle number and the cycle time period of low-lithiation voltage, the stability of the SEI can be improved. According to the preparation method, SEIs with different components, states and thicknesses are obtained to meet different application scenes, the strategy can promote the low-temperature desolvation rate and inhibit interface side reactions, then the gas production phenomenon is inhibited, the low-temperature cycling stability is improved, and the preparation method can be applied to the field of low-temperature and high-power niobium titanium oxygen-based lithium ion batteries.

Description

Technical Field

[0001] The present invention belongs to the field of low-temperature lithium-ion batteries, and specifically relates to a method for dynamically constructing SEI of niobium-titanium oxide materials using a voltage control method and its application in low-temperature lithium-ion batteries. Background Art

[0002] Lithium-ion batteries (LIBs) have become the dominant energy storage device in portable electronic devices and electric vehicles due to their high energy density and long cycle life. Among commercial secondary lithium-ion battery anode materials, graphite has a high theoretical specific capacity (372 mA h g) and a low cost. -1 However, its low working potential (0.1 V vs. Li + / Li) can easily induce reduction and decomposition of the electrolyte, resulting in irreversible loss of active lithium; at the same time, this potential is close to the threshold of metal lithium deposition, which poses a risk of lithium dendrite growth and may cause internal short circuits and other safety hazards, especially in low temperature environments. In the intercalation type negative electrode material system, spinel lithium titanate (Li4Ti5O 12 ) effectively avoids the problem of lithium plating with its high working potential (1.55 V vs. Li⁺ / Li), significantly improves the safety of the system, and exhibits excellent long-cycle characteristics. However, its theoretical specific capacity is relatively limited (175 mA hg -1 ), which results in limited rate performance and energy density, restricting its large-scale commercial application.

[0003] In recent years, niobium titanium oxide (TiNb2O7) has attracted extensive attention as anode materials for high-power lithium-ion batteries and is considered to be a promising alternative to spinel lithium titanate (Li4Ti5O 12 ) is a potential alternative system. This material has a typical intercalation reaction mechanism, and its excellent electrochemical performance is derived from the unique ReO3 type crystal structure: Nb / Ti cations occupy the centers of NbO6 and TiO6 octahedra respectively, and NbO6 and TiO6 octahedra are connected by sharing edges / vertices to form open three-dimensional ion channels, which can achieve rapid lithium ion transmission. TiNb2O7 not only inherits the Li4Ti5O 12The TiNb2O7 anode exhibits excellent long-term cycling stability and structural zero-strain properties, while maintaining a similar lithium insertion and deintercalation potential platform (~1.6 V vs. Li⁺ / Li). This high operating potential window effectively suppresses lithium dendrite nucleation and electrolyte reductive decomposition, significantly improving system safety. Furthermore, the TiNb2O7 material exhibits excellent low-temperature performance. However, high-potential operation results in insufficient driving force for SEI film formation at the electrode interface, resulting in a metastable, depleted SEI interface. This depleted SEI interface fails to effectively block electrode / electrolyte side reactions, continuously consuming active lithium during long cycling. Furthermore, the Nb / Ti sites continuously catalyze electrolyte oxidative decomposition, triggering gassing, which is exacerbated at high temperatures. Furthermore, the thicker SEI layer increases interfacial impedance, sacrificing rate performance. Therefore, it is urgent to develop adaptive dynamic SEI control strategies to construct a dynamic interface that combines ionic conductivity and electrochemical passivation to achieve low-temperature stable and long-term cycling of the TiNb2O7 anode. Summary of the Invention

[0004] The present invention aims to address the problem of low-temperature, long-cycle instability of the depleted SEI interface in niobium-titanium oxide materials. It provides a voltage-controlled method for dynamically constructing the SEI in niobium-titanium oxide materials, and its application in low-temperature lithium-ion batteries. This method utilizes a controlled lithiation cutoff voltage strategy to dynamically and deeply lithiate TiNb2O7 (the lithiation cutoff voltage is adjusted from 1V to 0.6-0.8V). This method partially reduces and decomposes the electrolyte to form a stable SEI. This is followed by long-term cycling at a 1V lithiation cutoff voltage. After hundreds of cycles, the SEI is consumed, and further deep lithiation is then performed at a controlled lithiation cutoff voltage (the lithiation cutoff voltage is adjusted to 0.6-0.8V). This results in a dynamically stable SEI, enhanced ion transport capacity, and promoted interfacial lithium ion desolvation rates, significantly improving the long-cycle stability of the TiNb2O7 negative electrode. This method is suitable for low-temperature, high-power lithium-ion batteries.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A voltage control method is used to achieve the dynamic construction of SEI in niobium titanium oxide materials. The steps are as follows: by controlling the lithiation cut-off voltage, the degree of reduction reaction of the electrolyte on the surface of the niobium titanium oxide negative electrode is controlled to form a dynamically stable SEI.

[0007] Furthermore, the voltage-controlled SEI formation stage can be in the first cycle activation stage or in the cycling process to obtain a dynamic SEI, depending on the actual application scenario requirements.

[0008] Furthermore, according to the electrolyte composition and battery application scenario, the voltage is adjusted to control the number of SEI cycles to obtain SEI with different components, thicknesses, and ion transport properties to meet the application requirements of different scenarios.

[0009] Preferably, the number of SEI cycles controlled by voltage is 1-5.

[0010] Furthermore, the lithiation cut-off voltage is 0.6-0.8V.

[0011] Furthermore, the electrolyte solvent used in the voltage control method to construct SEI is one or more of a carbonate system and a carboxylate system, and the lithium salt is one or more of LiPF6, LiTFSI, LiFSI, LiDFOB, and LiNO3.

[0012] Furthermore, the rate range of SEI construction by the voltage control method is 0.1-1C.

[0013] Preferably, the preparation method of the niobium titanium oxide negative electrode material is a solid phase method, a solvent thermal method or a gel method.

[0014] Preferably, the ambient temperature range for constructing SEI using the voltage control method is -20°C to 30°C.

[0015] The construction method is applied to low-temperature lithium-ion batteries, which are used for cold-region energy storage, cold-region communication base stations, shuttle buses, or low-temperature starting power supplies.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] In the present invention, dynamic SEI stabilization of niobium titanium oxide materials is achieved by controlling the lithiation cutoff voltage at intervals during the cycle. This SEI can promote rapid desolvation at low temperatures, inhibit the occurrence of interfacial side reactions, significantly improve long-cycle stability, and inhibit gas production. This preparation method can be used in the field of low-temperature, high-power niobium titanium oxide lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The charge-discharge curves of TiNb2O7 negative electrode with different lithiation cut-off voltages;

[0019] Figure 2 The long cycle performance diagrams are when the first cycle lithiation voltage is controlled at 1V, 0.8V, and 0.6V respectively during activation;

[0020] Figure 3 This is the long cycle performance diagram with the lithiation voltage controlled at 0.8V after 300 cycles;

[0021] Figure 4 This is the long cycle performance diagram with the lithiation voltage controlled at 0.6V after 300 cycles;

[0022] Figure 5 This is the -30°C low-temperature long-cycle performance diagram with the first-cycle lithiation voltage controlled at 0.8V during activation;

[0023] Figure 6 This is the -30°C low-temperature long-cycle performance diagram with the first-cycle lithiation voltage controlled at 0.6V during activation;

[0024] Figure 7 This is the long cycle performance diagram of 0.8V lithiation cut-off voltage;

[0025] Figure 8 This is the long cycle performance diagram of 0.6V lithiation cutoff voltage. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example 1:

[0028] A method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method comprises the following steps:

[0029] (1) 0.799 g of titanium dioxide and 2.658 g of niobium pentoxide were dispersed in 50 ml of ethanol solution and magnetically stirred for 4 h to uniformly mix the titanium dioxide and niobium pentoxide in the ethanol solution to obtain a suspension.

[0030] (2) The suspension was transferred to a forced air drying oven at 80°C for drying. The suspension was then transferred to a tube furnace and calcined at 1300°C for 18 h in an air atmosphere at a heating rate of 5°C / min. The suspension was then naturally cooled to room temperature to obtain a niobium titanium oxide material.

[0031] (3) Dispersing niobium titanium oxide material, acetylene black, single-walled carbon nanotubes, and polyvinylidene fluoride in N-methylpyrrolidone to form a negative electrode slurry, coating the negative electrode slurry on the negative electrode collector, drying, rolling, and punching to obtain a negative electrode sheet; wherein the mass ratio of niobium titanium oxide material, acetylene black, single-walled carbon nanotubes, and polyvinylidene fluoride is 95%:2%:1%:2%.

[0032] (4) The obtained niobium titanium oxide negative electrode sheet was used to assemble a lithium metal battery. The electrolyte was a conventional carbonate electrolyte without additives. The battery was tested for charge and discharge. The activation strategy was to insert lithium from the open circuit voltage to the cut-off voltage of 0.6V, 0.8V, and 1V at a rate of 0.1C in the first cycle, pre-form SEI, and then charge to 3V. The charge and discharge curves are shown in Figure 2. Figure 1 As shown, the charge and discharge cycle is then carried out at a high rate of 2C, and the cycle performance data is shown as follows Figure 2 、 3As shown in the figure, it is clearly observed that the cycle stability of the first cycle of lithium insertion to a cutoff voltage of 0.6V and 0.8V is better than that of the conventional 1V cutoff voltage, and the performance of the 0.6V cutoff voltage is better than that of 0.8V. This is mainly due to the formation of SEI on the surface of niobium titanium oxide at 0.6V and 0.8V, which inhibits the interfacial side reactions. This provides an important reference for the construction of low-temperature and long-cycle niobium titanium oxide batteries.

[0033] Example 2

[0034] The lithiation potential control strategy of this embodiment differs from that of Example 1 in that the activation strategy is to insert lithium from the open circuit voltage to the cut-off voltage of 1V at a first cycle at a rate of 0.1C, then perform 100 charge and discharge cycles at a rate of 2C, and then control the lithium insertion potential cut-off voltage to 0.6V and 0.8V to form a stable SEI, and then perform charge and discharge cycles.

[0035] Example 3

[0036] The lithiation potential control strategy of this embodiment is different from that of embodiment 1 in that the activation strategy is to insert lithium from the open circuit voltage to the cut-off voltage of 1V at a first cycle of 0.1C rate, then perform 200 cycles of charge and discharge at a 2C rate, and then control the lithium insertion potential cut-off voltage to 0.8V for 5 cycles to form a stable SEI, and then perform 2C rate charge and discharge cycles. Figure 3 As shown in the figure, after SEI is formed at a lithiation cutoff voltage of 0.8V, the cycle stability of the battery is significantly improved.

[0037] Example 4

[0038] The lithiation potential control strategy of this embodiment is different from that of embodiment 1 in that the activation strategy is to insert lithium from the open circuit voltage to the cut-off voltage of 1V at a first cycle of 0.1C rate, then perform 200 cycles of charge and discharge at a 2C rate, and then control the lithium insertion potential cut-off voltage to 0.6V for 5 cycles to form a stable SEI, and then perform 2C rate charge and discharge cycles. Figure 4 As shown in the figure, after SEI is formed at a lithiation cutoff voltage of 0.6V, the cycle stability of the battery is significantly improved and is better than that of the 0.8V cutoff voltage.

[0039] Example 5

[0040] The lithiation potential control strategy of this embodiment is different from that of embodiment 1 in that the activation strategy is to insert lithium from the open circuit voltage to the cut-off voltage of 0.8V at the first cycle at a rate of 0.1C to form a stable SEI, and then perform charge and discharge cycles at a low temperature of -30°C at a rate of 1C. Figure 5 As shown, the battery has excellent low-temperature cycle stability.

[0041] Example 6

[0042] The lithiation potential control strategy of this embodiment is different from that of embodiment 1 in that the activation strategy is to insert lithium from the open circuit voltage to the cut-off voltage of 0.6V at the first cycle at a rate of 0.1C to form a stable SEI, and then perform charge and discharge cycles at a low temperature of -30°C at a rate of 1C. Figure 6 As shown, the battery has excellent low-temperature cycle stability.

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 1 is that the activation strategy is to insert lithium from the open circuit voltage to the cutoff voltage of 0.4V at a rate of 0.1C in the first cycle, pre-form SEI, and then charge to 3V. It is worth noting that at the cutoff voltage of 0.4V, due to the occurrence of more reduction reactions in the electrolyte, the excessive SEI hinders the rapid transmission of ions at low temperatures, sacrificing the low-temperature rate performance.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 1 is that the charge and discharge cycle is always carried out using a 0.8V lithium cut-off voltage. The cycle performance is as follows: Figure 7 As shown, it can be clearly seen that the lithiation cutoff voltage improves the capacity, but due to excessive reduction and decomposition of the electrolyte, the long-cycle stability is poor, which further illustrates the effectiveness of controlling the potential dynamic SEI.

[0047] Comparative Example 3

[0048] The difference between this comparative example and Example 1 is that the charge and discharge cycle is always carried out using a 0.6V lithium cut-off voltage. The cycle performance is as follows: Figure 8 As shown, it can be clearly seen that the 0.6V lithiation cutoff voltage further improves the capacity compared with 0.8V, and the long-cycle stability is also poor. In summary, the above examples fully illustrate the beneficial effect of the dynamic SEI construction strategy on the negative electrode with higher lithium insertion potential, and play an important role in long-cycle stability, interface stability, and low-temperature interface desolvation rate, and is expected to be used in the field of low-temperature energy storage.

[0049] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method, characterized by: By controlling the lithiation cut-off voltage, the degree of reduction reaction of the electrolyte is controlled on the surface of the niobium titanium oxide negative electrode to form a dynamically stable SEI.

2. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The voltage-controlled SEI formation stage can be in the first cycle activation stage or in the cycle process to obtain a dynamic SEI, depending on the actual application scenario requirements.

3. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: According to the electrolyte composition and battery application scenario, the voltage is adjusted to control the number of SEI cycles to obtain SEI with different components, thicknesses, and ion transport properties to meet the application requirements of different scenarios.

4. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 3, characterized in that: The voltage-controlled SEI cycle number is 1-5 cycles.

5. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The lithiation cut-off voltage is 0.6-0.8V.

6. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The electrolyte solvent used in the voltage control method to construct SEI is one or more of the carbonate system and the carboxylate system, and the lithium salt is one or more of LiPF6, LiTFSI, LiFSI, LiDFOB, and LiNO3.

7. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The rate range of SEI construction by the voltage-controlled method is 0.1-1C.

8. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The preparation method of niobium titanium oxide negative electrode material is solid phase method, solvent thermal method or gel method.

9. The method for dynamically constructing SEI in niobium-titanium oxide materials using a voltage control method according to claim 1, characterized in that: The ambient temperature range for constructing SEI using the voltage control method is -20°C to 30°C.

10. Use of the construction method according to any one of claims 1 to 9 in low-temperature lithium-ion batteries.

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