Use of an electrode material in the preparation of a low temperature lithium ion battery

Abstract

The application relates to the manufacture of low-temperature batteries, in particular to the application of an electrode material in the preparation of low-temperature lithium ion batteries. The electrode material is a nano Nb2O5 / MoO2 composite material, and the nano Nb2O5 / MoO2 composite material is used as a negative electrode material. The application has excellent rate performance, cycle stability and a higher capacity retention rate under low-temperature or even ultra-low-temperature conditions.

Description

Technical Field

[0001] This invention relates to the manufacture of low-temperature batteries, and more specifically to the application of an electrode material in the preparation of low-temperature lithium-ion batteries. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The electrochemical performance of commercial lithium-ion batteries (LIBs) deteriorates significantly when operating temperatures drop or under other special conditions. Furthermore, the high lithium deposition tendency is another challenging issue when LIBs operate at low temperatures. For traditional graphite electrodes, Li... + The voltage required for graphite embedding is similar to that required for lithium deposition (0.01–0.2 V). Once the overpotential of LIBs exceeds this potential, Li₂ will deposit due to the lower nucleation barrier. + Lithium often reduces on the graphite surface rather than embedding into the graphite layer. Electrodeposited Li initiates a series of side reactions, producing a thicker SEI and leading to the formation of "dead" lithium, which severely depletes the limited active lithium in the battery, generating lithium dendrites and posing serious safety hazards. Therefore, there is a need for a low-temperature lithium-ion battery with excellent performance in low-temperature environments. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide an electrode material for the preparation of low-temperature lithium-ion batteries, exhibiting excellent rate performance, cycle stability, and high capacity retention under low or even ultra-low temperature conditions.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] On one hand, an electrode material is used in the preparation of low-temperature lithium-ion batteries, wherein the electrode material is a nano-Nb2O5 / MoO2 composite material, and the nano-Nb2O5 / MoO2 composite material is used as a negative electrode material.

[0007] When Nb₂O₅ is used as the anode material for LIBs, it exhibits lithium storage through intercalation pseudocapacitive behavior, resulting in a high operating potential (approximately 1.0–1.9 V vs Li / Li). + This technology avoids lithium dendrite formation, allowing it to operate at low temperatures. Furthermore, Nb₂O₅ has a high theoretical capacity (200 mAh / g), resulting in higher energy density when used as the anode material for lithium-ion batteries (LIBs). However, studies have found that Nb₂O₅ exhibits high interfacial transfer resistance at low temperatures when used as the anode material for LIBs, leading to poor electrochemical performance.

[0008] This invention uses a nano-Nb2O5 / MoO2 composite material to replace Nb2O5, which can reduce the interfacial transfer impedance of Nb2O5 at low temperatures and improve its electrochemical performance.

[0009] On the other hand, a low-temperature lithium-ion battery has a negative electrode material of nano-Nb2O5 / MoO2 composite material and an electrolyte of lithium difluorosulfonylimide in ether solution (LiFSI DEE solution).

[0010] Studies have shown that the present invention uses nano-Nb2O5 / MoO2 composite material as negative electrode material, which has good compatibility with LiFSI DEE electrolyte and still has excellent rate performance, cycle stability and high capacity retention under ultra-low temperature conditions (-60℃).

[0011] Thirdly, the above-mentioned low-temperature lithium-ion battery is used in low-temperature and / or ultra-low-temperature environments.

[0012] The beneficial effects of this invention are as follows:

[0013] 1. This invention uses nano-Nb2O5 / MoO2 composite material as the negative electrode material, which not only combines the advantages of high working potential, stable crystal structure and high energy density of Nb2O5 with intercalation pseudocapacitive behavior for lithium storage, but also the advantages of good conductivity of MoO2. Furthermore, by nano-sizing the composite material, the lithium ion diffusion path is shortened, which helps to improve the electrochemical performance of the negative electrode material at low temperature.

[0014] 2. The low-temperature lithium-ion battery provided by this invention uses LiFSI DEE solution as the electrolyte, which not only has the low melting point of diethyl ether, which can significantly improve the low-temperature performance of the electrolyte, but also, in combination with LiFSI, can effectively improve the temperature resistance and conductivity characteristics of the electrolyte, thereby enhancing battery performance and thermal safety.

[0015] 3. In the low-temperature lithium-ion battery of the present invention, the nano-Nb2O5 / MoO2 composite material exhibits good electrochemical performance in LiFSI DEE electrolyte, and can demonstrate excellent rate performance, cycle stability, and high capacity retention under low temperature or even ultra-low temperature conditions. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 The X-ray diffraction pattern of the nano-Nb2O5 / MoO2 composite material prepared in the embodiments of the present invention is shown below.

[0018] Figure 2 The voltammetric test curve of 1M LiFSI DEE electrolyte in this embodiment of the invention;

[0019] Figure 3 The images shown are scanning electron microscope (SEM) images of the nano-Nb2O5 / MoO2 composite materials prepared in the embodiments of the present invention. A is a low-magnification image of the hydrothermal method with a scale bar (short) of 1 μm; B is a medium-magnification image of the hydrothermal method with a scale bar (long) of 1 μm; C is a high-magnification image of the hydrothermal method with a scale bar of 100 nm; D is a low-magnification image of the sol-gel method with a scale bar of 50 μm; E is a medium-magnification image of the sol-gel method with a scale bar of 10 μm; and F is a high-magnification image of the sol-gel method with a scale bar of 5 μm.

[0020] Figure 4 The following are the results of electrochemical performance testing in the embodiments of the present invention: a) is the lithiation / delithiation curve of the third charge-discharge cycle at 0.5C; b) is the low-temperature rate performance test graph at -20℃; c) is the low-temperature rate performance test graph at -40℃; and d) is the low-temperature rate performance test graph at -60℃. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Given the poor electrochemical performance of lithium-ion batteries at low temperatures, especially at ultra-low temperatures, this invention proposes an application of an electrode material in the preparation of low-temperature lithium-ion batteries.

[0024] In one typical embodiment of the present invention, an electrode material is provided for use in the preparation of low-temperature lithium-ion batteries. The electrode material is a nano-Nb2O5 / MoO2 composite material, which serves as the negative electrode material.

[0025] In some embodiments, the nano-Nb₂O₅ / MoO₂ composite material is prepared by a hydrothermal method or a sol-gel method. Studies have shown that the nano-Nb₂O₅ / MoO₂ composite material prepared by the hydrothermal method has a smaller size, which is beneficial for lithium-ion transport in the anode material.

[0026] In some embodiments, the process of preparing nano-Nb₂O₅ / MoO₂ composite materials by hydrothermal method is as follows: Niobium oxalate and ammonium molybdate are dissolved in water and heated to 190–220°C for a hydrothermal reaction. The product obtained from the hydrothermal reaction is then annealed at 600–700°C. Specifically, the hydrothermal reaction time is 10–12 hours. After the hydrothermal reaction, the product is centrifuged, washed, and dried. Specifically, the annealing time is 3–4 hours.

[0027] In some embodiments, the process of preparing nano-Nb₂O₅ / MoO₂ composite materials by the sol-gel method is as follows: Niobium pentachloride and molybdenum di(acetylacetone)oxide are dissolved in ethanol and vacuum dried. The vacuum-dried sample is then subjected to a first heat treatment at 400–500°C under an inert atmosphere, followed by a second heat treatment at 700–800°C. The inert atmosphere described in this invention is formed from inert gases such as helium, argon, or nitrogen. Specifically, the first heat treatment lasts for 3–4 hours. Specifically, the second heat treatment lasts for 3–4 hours.

[0028] The negative electrode is composed of a negative electrode material and a conductive agent bonded to the surface of the current collector by an adhesive. In some embodiments, the mass ratio of the negative electrode material, conductive agent, and adhesive in the negative electrode is 6–8:1.5–2.5:1. Specifically, the current collector in the negative electrode is copper foil. More specifically, the mass loading of the negative electrode material in the negative electrode is 0.9–1.1 mg / cm³. -2 Conductive agents, such as acetylene black. Adhesives, such as polyvinylidene fluoride (PVDF).

[0029] Another embodiment of the present invention provides a low-temperature lithium-ion battery, wherein the negative electrode material is a nano-Nb2O5 / MoO2 composite material and the electrolyte is a LiFSI DEE solution.

[0030] In some embodiments, the concentration of the LiFSI DEE solution is 0.9–1.1 M. The unit M represents mol / L.

[0031] The preparation of the nano-Nb2O5 / MoO2 composite material is consistent with the description in the above application.

[0032] In some embodiments, the diaphragm used is a polypropylene microporous membrane, such as Celgard 2400.

[0033] The cathode material of the low-temperature lithium-ion battery provided by the present invention can be lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), etc.

[0034] A third embodiment of the present invention provides an application of the above-mentioned low-temperature lithium-ion battery in low-temperature and / or ultra-low-temperature environments.

[0035] The low-temperature environment described in this invention refers to an environment below -10°C, specifically -20 to -10°C, -30 to -10°C, -40 to -10°C, -50 to -10°C, -60 to -10°C, -70 to -10°C, -30 to -20°C, -40 to -20°C, -50 to -20°C, -70 to -20°C, and -70 to -20°C. The ultra-low-temperature environment described in this invention refers to an environment within the lower temperature range of the above-mentioned low-temperature environments, or an environment not exceeding the lower limit temperature of the low-temperature environment, such as an environment not exceeding -40°C, not exceeding -50°C, or not exceeding -60°C. Specifically, ultra-low-temperature environments include -40 to -70°C, -40 to -60°C, -50 to -70°C, and -50 to -60°C.

[0036] For example, energy storage in extreme environments (polar regions, high altitudes, space, etc.).

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] Example 1

[0039] The hydrothermal synthesis of nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0040] (1) Dissolve 0.4339g of niobium oxalate and 0.0356g of ammonium molybdate tetrahydrate completely in 60ml of water and place them in a 100ml reaction vessel. Heat in an oven at 200℃ for 12 hours.

[0041] (2) The hydrothermal reaction product obtained in step (1) was washed by centrifugation with ethanol and deionized water and then dried under vacuum at 80°C.

[0042] (3) The sample dried in step (2) was annealed in a horizontal tube furnace at 700°C for 3 hours to obtain nano Nb2O5 / MoO2 composite material.

[0043] Example 2

[0044] The hydrothermal synthesis of nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0045] (1) Dissolve 0.4339g of niobium oxalate and 0.0356g of ammonium molybdate tetrahydrate completely in 60ml of water and place them in a 100ml reaction vessel. Heat in an oven at 190℃ for 12 hours.

[0046] (2) The hydrothermal reaction product obtained in step (1) was washed by centrifugation with ethanol and deionized water and then dried under vacuum at 80°C.

[0047] (3) The sample dried in step (2) was annealed in a horizontal tube furnace at 700°C for 3 hours to obtain nano Nb2O5 / MoO2 composite material.

[0048] Example 3

[0049] The hydrothermal synthesis of nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0050] (1) Dissolve 0.4339g of niobium oxalate and 0.0356g of ammonium molybdate tetrahydrate completely in 60ml of water and place them in a 100ml reaction vessel. Heat in an oven at 220℃ for 10 hours.

[0051] (2) The hydrothermal reaction product obtained in step (1) was washed by centrifugation with ethanol and deionized water and then dried under vacuum at 80°C.

[0052] (3) The sample dried in step (2) was annealed in a horizontal tube furnace at 600°C for 4 hours to obtain nano Nb2O5 / MoO2 composite material.

[0053] Example 4

[0054] The sol-gel method for synthesizing nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0055] (1) Dissolve 0.165g of niobium pentachloride and 0.05g of molybdenum bis(acetylacetone) oxide (molar ratio 4:1) completely in 20ml of anhydrous ethanol and stir for 60 minutes.

[0056] (2) Heat the solution obtained in step (1) to 70°C and vacuum dry for 12 hours.

[0057] (3) The sample dried in step (2) was annealed in an argon atmosphere in a horizontal tube furnace at 450°C for 3 hours and then heated at 750°C for 4 hours to obtain nano Nb2O5 / MoO2 composite material.

[0058] Example 5

[0059] The sol-gel method for synthesizing nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0060] (1) Dissolve 0.165g of niobium pentachloride and 0.05g of molybdenum di(acetylacetone) oxide completely in 20ml of anhydrous ethanol and stir for 30 minutes.

[0061] (2) Heat the solution obtained in step (1) to 50°C and vacuum dry for 24 hours.

[0062] (3) The sample dried in step (2) was annealed in an argon atmosphere in a horizontal tube furnace at 500°C for 4 hours and then heated at 800°C for 3 hours to obtain nano Nb2O5 / MoO2 composite material.

[0063] Example 6

[0064] The sol-gel method for synthesizing nano-Nb₂O₅ / MoO₂ composite materials follows these steps:

[0065] (1) Dissolve 0.165g of niobium pentachloride and 0.05g of molybdenum di(acetylacetone) oxide completely in 20ml of anhydrous ethanol and stir for 40 minutes.

[0066] (2) Heat the solution obtained in step (1) to 70°C and vacuum dry for 12 hours.

[0067] (3) The sample dried in step (2) was annealed in an argon atmosphere in a horizontal tube furnace at 400°C for 3 hours and then heated at 700°C for 4 hours to obtain nano Nb2O5 / MoO2 composite material.

[0068] Example 7

[0069] Preparation of low-temperature electrolyte:

[0070] The preparation of the electrolyte was carried out entirely in a glove box. An appropriate amount of LiFSI electrolyte salt was dissolved in an appropriate amount of diethyl ether. After it was completely dissolved, an electrolyte with a concentration of 1M was prepared. The prepared electrolyte was then transferred to a reagent bottle, labeled, and ready for use.

[0071] Example 8

[0072] The steps for preparing Nb₂O₅ / MoO₂ electrodes are as follows:

[0073] The nano-Nb₂O₅ / MoO₂ composite material prepared in Example 1, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1 and N-methyl-2-pyrrolidone (NMP) was used as a solvent to prepare a slurry. The slurry was then coated onto a copper foil as the current collector surface to form an electrode. The coated electrode was vacuum dried at 120°C for 12 hours, and the mass loading of the active material was approximately 1 mg / cm³. -2 .

[0074] Example 9

[0075] The steps for preparing Nb₂O₅ / MoO₂ electrodes are as follows:

[0076] The nano-Nb₂O₅ / MoO₂ composite material prepared in Example 4, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1 and N-methyl-2-pyrrolidone (NMP) was used as a solvent to prepare a slurry. The slurry was then coated onto a copper foil as the current collector surface to form an electrode. The coated electrode was vacuum dried at 120°C for 12 hours, resulting in an active material mass loading of approximately 1 mg / cm³. -2 .

[0077] Electrochemical performance testing:

[0078] Half-cell assembly:

[0079] The button cell (CR2025) was assembled in a glove box containing pure argon. A lithium metal sheet was used as the counter electrode and reference electrode, and Nb₂O₅ / MoO₂ electrodes prepared in Examples 9 and 10, respectively, were used as the working electrodes. A microporous polypropylene membrane (Celgard 2400) was used as the separator. The electrolyte was 1M LiFSI DEE prepared in Example 7.

[0080] The system used to test the LSV curve of the electrolyte is also the battery system described above, except that the lithium metal sheet is used as the counter electrode and reference electrode, and the platinum sheet is used as the working electrode, while other conditions remain unchanged.

[0081] Electrochemical testing of electrodes:

[0082] (1) A battery was assembled using a platinum sheet as the working electrode and subjected to linear sweep voltammetry. The battery was connected and left to stand. The open circuit potential was read, the termination voltage was set to 7V, and the sweep rate was 1mV / s.

[0083] (2) Chronopotentiometry electrode charge-discharge test. Set an appropriate voltage window and multiple charge-discharge current densities for continuous testing.

[0084] (3) Cycling stability test. The voltage window is set to 1-3V, and a fixed charge and discharge current density is set for continuous testing.

[0085] (4) AC impedance (EIS) test. Connect the battery and let it stand still. Read the open circuit potential at a frequency of 0.1 to 100,000 Hz and an amplitude of 5 mV.

[0086] Low-temperature performance test of button cells:

[0087] After the assembled half-cells were formed by cycling 3 times at a rate of 0.5C (1C = 200mA / g) at room temperature, they were placed at -20℃, -40℃ and -60℃ for 2 hours, and then subjected to chronopotentiometry electrode charge-discharge test, cyclic stability test and AC impedance (EIS) test respectively.

[0088] result:

[0089] X-ray diffraction tests were performed on Nb₂O₅ / MoO₂ synthesized by hydrothermal and sol-gel methods, such as... Figure 1 As shown, characteristic peaks of Nb₂O₅ and MoO₂ were clearly observed in the XRD patterns of both Nb₂O₅ / MoO₂, proving the successful synthesis of Nb₂O₅ / MoO₂. Linear sweep voltammetry was used to scan the 1M LiFSI DEE electrolyte, as shown... Figure 2 As shown, leakage current of 1M LiFSI DEE electrolyte on the aluminum electrode can be observed up to approximately 6V (vs Li / Li). + It only showed a significant increase when the value was within a certain range, demonstrating good stability.

[0090] Scanning electron microscopy was used to analyze Nb₂O₅ / MoO₂ synthesized by hydrothermal and sol-gel methods, such as... Figure 3 As shown, the Nb2O5 / MoO2 prepared by the hydrothermal method has a small size, which is beneficial for the transport of lithium ions in the anode material.

[0091] The lithiation / delithiation curves of the Nb₂O₅ / MoO₂ electrodes prepared in Examples 9 and 10 under 0.5C charge-discharge cycles using 1M LiFSI DEE electrolyte are shown below. Figure 4 As shown in figure a, the initial discharge specific capacity of the electrode synthesized by the hydrothermal method is 183.8 mAh / g, which is greater than that of the sol-gel method.

[0092] To test the low-temperature performance of the battery, the assembled half-cells were activated three times at a rate of 0.5C at room temperature, and then placed at -20℃, -40℃, and -60℃ for 4 hours before testing their rate performance at low temperatures. The test results show that at -20℃, as shown in Figure b, the Nb₂O₅ / MoO₂ electrode prepared by the hydrothermal method can provide specific capacities of 152.6, 113.9, and 98.7 mAh / g (corresponding to rates of 0.5, 5, and 10C). At -40℃, as shown in Figure c, the Nb₂O₅ / MoO₂ electrode prepared by the hydrothermal method can provide specific capacities of 110.6, 74.9, and 57.5 mAh / g (corresponding to rates of 0.5, 3, and 5C). In particular, when using 1M LiFSI DEE electrolyte for low-temperature testing at -60℃, as shown in Figure d, the Nb2O5 / MoO2 electrode prepared by hydrothermal method still retains a certain capacity at charge-discharge rates of 0.5 and 1C, which are 45.3 and 29.9 mAh / g, respectively.

[0093] In summary, both methods of preparing Nb2O5 / MoO2 electrodes and 1M LiFSI DEE electrolytes exhibit good compatibility and can achieve charge-discharge rates of -20℃, -40℃, and -60℃.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-temperature lithium-ion battery, characterized in that, The negative electrode material is a nanoparticle Nb2O5 / MoO2 composite material, and the electrolyte is a LiFSI DEE solution; The nano-Nb2O5 / MoO2 composite material was prepared by a hydrothermal method; The process of preparing nano-Nb2O5 / MoO2 composite material by hydrothermal method is as follows: Niobium oxalate and ammonium molybdate are dissolved in water at a molar ratio of niobium to molybdenum of 8:1 or 4:1, and heated to 190~220℃ for 10-12h for hydrothermal reaction. The product obtained by hydrothermal reaction is annealed at 600~700℃ to obtain the final product.

2. The low-temperature lithium-ion battery as described in claim 1, characterized in that, The mass ratio of negative electrode material, conductive agent, and binder in the negative electrode is 6~8:1.5~2.5:

1.

3. The low-temperature lithium-ion battery as described in claim 1, characterized in that, The mass loading of the negative electrode material in the negative electrode is 0.9~1.1 mg / cm³. -2 .

4. The low-temperature lithium-ion battery as described in claim 1, characterized in that, The concentration of the LiFSI DEE solution is 0.9~1.1M.

5. The low-temperature lithium-ion battery as described in claim 1, characterized in that, The diaphragm used is a polypropylene microporous membrane.

6. The application of a low-temperature lithium-ion battery according to any one of claims 1 to 5 in low-temperature and / or ultra-low-temperature environments.

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