Fluorine-molybdenum double-doped chromium metal oxide positive electrode material and preparation method thereof

Abstract

The invention provides a fluorine-molybdenum double-doped chromium metal oxide positive electrode material and a preparation method thereof, the chemical formula of the fluorine-molybdenum double-doped chromium metal oxide positive electrode material is Cr < 8-x > Mo < x > O < 21-y > F < y >, x is less than or equal to 5, and y is less than or equal to 12; the fluorine-molybdenum double-doped chromium metal oxide positive electrode material is prepared from the following raw materials in parts by mass: 1 part of fluorine-molybdenum compound and 6-15 parts of chromium metal oxide; the chromium metal oxide at least comprises Cr8O21; the fluorine molybdenum compound at least comprises molybdenum hexafluoride gas. The fluorine element and the molybdenum element are introduced into the chromium metal oxide, so that the interlayer spacing, the structural stability and the conductivity of the chromium metal oxide are improved, and the rate capability, the storage performance and the safety of the chromium metal oxide are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-chromium-based metal oxide batteries, and in particular to a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material and a preparation method thereof. Background Art

[0002] High-energy-density primary batteries play an irreplaceable role in military, aerospace, medical implants, and emergency backup power applications. Traditional lithium primary battery cathode materials (such as FeS2, SOCl2, or MnO2) are limited by their low theoretical capacity (<500mAh / g) or voltage plateau (<3.0V), making them difficult to meet the stringent energy density requirements of batteries in extreme environments.

[0003] Chromium-based metal oxide positive electrode materials (such as CrO3, Cr8O 21 Due to its unique intercalation-conversion hybrid reaction mechanism, it shows significant advantages in lithium primary batteries - it has the dual high characteristics of high specific energy and high power.

[0004] However, this material system has the following technical bottlenecks: (1) Thermal management problems - chromium-based metal oxide materials release heat violently during the conversion reaction stage, limiting their high-power applications after battery assembly; (2) Poor structural stability: The short-range disordered and long-range ordered structure of chromium-based metal oxides makes them less stable, making them prone to side reactions with the electrolyte, thereby reducing the storage performance of the battery. In addition, the low self-stability also makes chromium-based metal oxides prone to explosion due to self-decomposition when preparing electrodes, thus posing certain preparation safety risks. Summary of the Invention

[0005] The object of the present invention is to provide a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material and a preparation method thereof to solve the problems in the above-mentioned background technology.

[0006] The technical solution adopted by the present invention includes: a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, characterized in that the chemical formula of the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material is Cr 8-x Mo x O 21-y F y , x≤5, y≤12.

[0007] Preferably, the raw materials for preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material include: 1 part by mass of a fluorine-molybdenum compound and 6 to 15 parts by mass of a chromium metal oxide.

[0008] Preferably, the chromium metal oxide comprises at least Cr8O 21 .

[0009] Preferably, the fluorine-molybdenum compound includes at least molybdenum hexafluoride gas.

[0010] The technical solution of the present invention also includes: a method for preparing the above-mentioned fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, which comprises the steps of:

[0011] Calcinate CrO3, grind it, and sieve it to obtain chromium metal oxide;

[0012] The chromium metal oxide is placed in a reaction gas containing a fluorine-molybdenum compound, reacts at room temperature, and then is ground and sieved to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material.

[0013] Preferably, the conditions for calcining CrO3 include at least: heating to 250-300°C in a nitrogen-oxygen mixed atmosphere and keeping the temperature for 10-13 hours.

[0014] Preferably, in the nitrogen-oxygen mixed atmosphere, the volume ratio of nitrogen to oxygen is (1-3):1.

[0015] Preferably, the conditions for calcining CrO3 include: a heating rate of 4 to 6°C / min.

[0016] Preferably, the reaction gas comprises molybdenum hexafluoride gas and nitrogen in a volume ratio of 1:(4-9).

[0017] Preferably, when preparing the chromium metal oxide: the speed of the ball mill is 200-400 r / min, the ball milling time is 4-8 h, and the mesh size is 200 mesh; when preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material: the speed of the ball mill is 100-350 r / min, the ball milling time is 5-8 h, and the mesh size is 100 mesh.

[0018] The beneficial effects of the present invention include at least: by introducing fluorine and molybdenum into the chromium metal oxide, the interlayer spacing, structural stability and conductivity of the chromium metal oxide are improved, thereby improving the rate performance, storage performance and safety of the chromium metal oxide; specifically, the fluorine element with strong electronegativity and small atomic radius is doped into the chromium metal oxide lattice, and can form Cr-F with higher bond energy than Cr-O with Cr, and increase the interlayer spacing of the material through the strong repulsive effect between the fluorine atoms and the fluorine oxygen atoms, which not only improves the structural stability of the chromium metal oxide, but also reduces the embedding energy barrier of lithium ions and increases the reaction capacity of the chromium metal oxide embedding mechanism, thereby reducing the heat generation of the material and improving the rate performance of the material; the doping of the molybdenum element not only facilitates the increase of the interlayer spacing of the material, thereby facilitating the diffusion and doping of the fluorine element between the material layers, but also promotes the doping of the fluorine element through the charge induction effect. At the same time, the doping of the molybdenum element can also improve the conductivity of the material and improve the rate performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The Cr8O prepared in step (2) of Example 1 of the present invention 21 and the Cr prepared in step (4) 7.98 Mo 0.02 O 20.88 F 0.12 XPS test chart;

[0020] Figure 2 The Cr8O prepared in step (2) of Example 1 of the present invention 21 and the Cr prepared in step (4) 7.98 Mo 0.02 O 20.88 F 0.12 XRD test pattern;

[0021] Figure 3 The Cr8O prepared in step (2) of Example 1 of the present invention is used. 21 and the Cr prepared in step (4) 7.98 Mo 0.02 O 20.88 F 0.12 Discharge curves of the lithium primary batteries equipped respectively;

[0022] Figure 4 The Cr8O prepared in step (2) of Example 1 of the present invention is used. 21 and the Cr prepared in step (4) 7.98 Mo 0.02 O 20.88 F 0.12 Discharge temperature rise curves of the respectively equipped lithium primary batteries;

[0023] Figure 5 The Cr prepared in step (4) of Example 1 of the present invention is 7.98 Mo 0.02 O 20.88 F 0.12 Optical photos of the equipment's lithium primary battery after being punctured by a needle or hit by a heavy object

[0024] Figure 6 is Cr in Example 1 of the present invention 7.98 Mo 0.02 O 20.88 F 0.12 EDS test chart of the final product of Comparative Example 1. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below.

[0026] The present invention provides a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material and a preparation method. By introducing fluorine and molybdenum elements into the chromium metal oxide, the interlayer spacing, structural stability and conductivity of the chromium metal oxide are improved, thereby improving the rate performance, storage performance and safety of the chromium metal oxide.

[0027] The first aspect of the embodiment of the present invention provides: a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, the chemical formula of which is Cr 8-x Mo x O 21-y F y , x≤5, y≤12. The raw materials for preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material include: 1 part by mass of a fluorine-molybdenum compound and 6 to 15 parts by mass of a chromium metal oxide, preferably: the chromium metal oxide is Cr8O 21 , the fluorine-molybdenum compound is molybdenum hexafluoride gas.

[0028] In the above technical solution, fluorine element with strong electronegativity and small atomic radius is doped into the lattice of chromium metal oxide to form Cr-F (such as Figure 1 As shown in the figure), and through the strong repulsion between fluorine atoms and fluorine oxygen atoms, the interlayer spacing of the material is increased, which can not only improve the structural stability of the chromium metal oxide, but also reduce the embedding energy barrier of lithium ions and increase the reaction capacity of the chromium metal oxide embedding mechanism, thereby reducing the heat generation of the material and improving the rate performance of the material; the doping of molybdenum element is not only conducive to the increase of the interlayer spacing of the material, but also conducive to the diffusion and doping of fluorine element between the material layers (refer to the attached figure). Figure 6 ), and can promote the doping of fluorine through the charge induction effect. At the same time, the doping of molybdenum can also improve the conductivity of the material and enhance the rate performance of the material.

[0029] A second aspect of the embodiments of the present invention provides: a method for preparing the above-mentioned fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, comprising the following steps:

[0030] S1. Calcinate CrO3, grind it, and sieve it to obtain chromium metal oxide.

[0031] In this step, the conditions for calcining CrO3 include: placing CrO3 in a nitrogen and oxygen mixed atmosphere, heating it to 250-300°C, preferably 260°C, and keeping it warm for 10-13 hours.

[0032] Preferably, in the nitrogen-oxygen mixed atmosphere, the volume ratio of nitrogen to oxygen is (1-3):1.

[0033] Preferably, the heating rate is 4-6°C / min, preferably 5°C / min.

[0034] In this step, the conditions for grinding and screening the calcined product of CrO3 include: the rotation speed of the ball mill is 200-400 r / min, the ball milling time is 4-8 hours, and the mesh size of the sieve is 200 mesh.

[0035] S2. placing chromium metal oxide in a reaction gas containing a fluorine-molybdenum compound, reacting at room temperature, grinding, and sieving to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material.

[0036] In this step, the reaction gas includes molybdenum hexafluoride gas and nitrogen gas in a volume ratio of 1:(4-9).

[0037] In this step, the conditions for grinding and screening the product of the reaction of chromium metal oxide and reaction gas at room temperature include: the rotation speed of the ball mill is 100-350 r / min, the ball milling time is 5-8 hours, and the mesh size of the sieve is 100 mesh.

[0038] The above steps S1 and S2 are preferably performed in a dry operating room, and the dew point temperature of the operating room is ≤-40°C.

[0039] The present invention is further described below through examples and comparative examples. Unless otherwise specified, the raw materials, reagents, or devices used in the examples and comparative examples can be obtained from conventional commercial sources.

[0040] Example 1: Preparation of Fluorine-Molybdenum Dual-Doped Chromium Metal Oxide Cathode Material

[0041] (1) CrO3 crystal powder was evenly placed in a porcelain boat, which was then placed in a tube furnace. The temperature was raised to 260°C at a rate of 5°C / min in a nitrogen-oxygen mixed atmosphere, and then maintained at that temperature for 10 h to obtain a sintered CrO3 product. The volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixed atmosphere was 1:1.

[0042] (2) The sintered product of CrO3 was placed in a ball mill, which was then placed in a planetary ball mill for ball milling. The speed of the ball mill was 200 r / min, and the ball milling time was 8 h. The ball milled product was passed through a 200-mesh sieve using a vibrating screen to obtain chromium metal oxide - Cr8O 21 .

[0043] (3) Cr8O 21 Put it into the monel alloy reactor, introduce the reaction gas containing molybdenum hexafluoride gas, and react at room temperature for 3 hours to obtain the room temperature reaction product; wherein, molybdenum hexafluoride gas and Cr8O 21 The mass ratio of molybdenum hexafluoride gas to nitrogen is 1:15. The reaction gas also contains nitrogen, and the volume ratio of molybdenum hexafluoride gas to nitrogen in the reaction gas is 1:9.

[0044] (4) The reaction product at room temperature was placed in a ball mill, which was then placed in a planetary ball mill for ball milling. The rotation speed of the ball mill was 100 r / min, and the ball milling time was 8 h. The ball milled product was passed through a 100-mesh sieve using a vibrating screen to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material - Cr 7.98 Mo 0.02 O 20.88 F 0.12 .

[0045] The product of step (2) and the product of step (4) of this embodiment were tested by XPS respectively, and the results were Figure 1 ,analyze Figure 1 It is known that after dual doping with fluorine and molybdenum, the bond energy of chromium element increases.

[0046] The product of step (2) and the product of step (4) of this embodiment were subjected to XRD test respectively, and the results were Figure 2 ,analyze Figure 2 The peak position of fluorine-molybdenum dual-doped chromium metal oxide material is different from that of undoped Cr8O 21 There is a shift toward smaller angles, indicating an increase in the spacing between material layers.

[0047] The product of step (2) and the product of step (4) of this embodiment are respectively equipped with lithium primary batteries, and discharged at a rate of 1C to obtain Figure 3 The discharge curve shown in the figure and Figure 4 The discharge temperature rise curve shown in the figure is analyzed Figure 3 and Figure 4 Know: Fluorine and molybdenum dual-doped chromium metal oxide materials are better than undoped Cr8O 21 It has a higher discharge voltage and a smaller discharge temperature rise, which indicates that the fluorine-molybdenum dual-doped chromium metal oxide material has a higher rate performance, which is mainly due to three aspects: ① The increase in the material interlayer spacing reduces the diffusion energy barrier of ions; ② The improvement in the material structure stability delays the occurrence of the conversion reaction and increases the proportion of the material's embedded reaction stage capacity in the total capacity; ③ The introduction of molybdenum element improves the conductivity of the material and reduces the polarization effect of the reaction.

[0048] The product of step (4) of this embodiment was equipped with a lithium primary battery, and subjected to needle puncture and heavy object impact tests to obtain Figure 5 The optical photograph shown, Figure 5It shows that after being punctured by a needle or hit by a heavy object, the lithium primary battery prepared using the fluorine-molybdenum dual-doped chromium metal oxide material did not burn or explode, indicating that the fluorine-molybdenum dual-doped chromium metal oxide material has a high safety. This is mainly due to the improved structural stability of the material after fluorine-molybdenum dual-doping. When the temperature rises sharply after a short circuit in the battery, the self-decomposition of the fluorine-molybdenum dual-doped chromium metal oxide material and the side reactions with the electrolyte can be slowed down, thereby avoiding the ultimate thermal runaway of the battery.

[0049] Example 2: Preparation of Fluorine-Molybdenum Dual-Doped Chromium Metal Oxide Cathode Material

[0050] (1) CrO3 crystal powder was evenly placed in a porcelain boat, which was then placed in a tube furnace. The temperature was raised to 260°C at a rate of 5°C / min in a nitrogen-oxygen mixed atmosphere and then maintained at that temperature for 13 h to obtain a sintered CrO3 product. The volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixed atmosphere was 3:1.

[0051] (2) The sintered product of CrO3 was placed in a ball mill, which was then placed in a planetary ball mill for ball milling. The speed of the ball mill was 400 r / min, and the ball milling time was 4 h. The ball milled product was passed through a 200-mesh sieve using a vibrating screen to obtain chromium metal oxide - Cr8O 21 .

[0052] (3) Cr8O 21 Put it into the monel alloy reactor, introduce the reaction gas containing molybdenum hexafluoride gas, and react at room temperature for 7 hours to obtain the room temperature reaction product; wherein, molybdenum hexafluoride gas and Cr8O 21 The mass ratio of molybdenum hexafluoride gas to nitrogen is 1:6. The reaction gas also contains nitrogen, and the volume ratio of molybdenum hexafluoride gas to nitrogen in the reaction gas is 1:4.

[0053] (4) The reaction product at room temperature was placed in a ball mill, which was then placed in a planetary ball mill for ball milling. The rotation speed of the ball mill was 350 r / min, and the ball milling time was 5 h. The ball milled product was passed through a 100-mesh sieve using a vibrating screen to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material - Cr 7.95 Mo 0.05 O 20.7 F 0.3 .

[0054] Example 3: Preparation of Fluorine-Molybdenum Dual-Doped Chromium Metal Oxide Cathode Material

[0055] (1) CrO3 crystal powder was evenly placed in a porcelain boat, which was then placed in a tube furnace. The temperature was raised to 280°C at a rate of 5°C / min in a nitrogen-oxygen mixed atmosphere and then maintained at that temperature for 11 h to obtain a sintered CrO3 product. The volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixed atmosphere was 2:1.

[0056] (2) The sintered product of CrO3 was placed in a ball mill, which was then placed in a planetary ball mill for ball milling. The speed of the ball mill was 360 r / min, and the ball milling time was 4 h. The ball milled product was passed through a 200-mesh sieve using a vibrating screen to obtain chromium metal oxide - Cr8O 21 .

[0057] (3) Cr8O 21 Put it into the monel alloy reactor, introduce the reaction gas containing molybdenum hexafluoride gas, and react at room temperature for 7 hours to obtain the room temperature reaction product; wherein, molybdenum hexafluoride gas and Cr8O 21 The mass ratio of molybdenum hexafluoride gas to nitrogen is 1:10. The reaction gas also contains nitrogen, and the volume ratio of molybdenum hexafluoride gas to nitrogen in the reaction gas is 1:4.

[0058] (4) The reaction product at room temperature was placed in a ball mill, and the ball mill was placed in a planetary ball mill for ball milling. The rotation speed of the ball mill was 200 r / min, and the ball milling time was 5 h. The ball milled product was passed through a 100 mesh sieve with a vibrating screen to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material - Cr 7.97 Mo 0.03 O 20.82 F 0.18 .

[0059] Comparative Example 1: Preparation of Fluorine-doped Chromium Metal Oxide Cathode Material

[0060] The only difference compared with Example 1 is that step (3) of Comparative Example 1 is: 21 Put it into the monel alloy reactor, introduce the reaction gas containing fluorine gas, and react at room temperature for 3 hours to obtain the room temperature reaction product; wherein, the fluorine gas and Cr8O 21 The mass ratio of fluorine gas to nitrogen is 1:15. The reaction gas also contains nitrogen, and the volume ratio of fluorine gas to nitrogen in the reaction gas is 1:9.

[0061] The final product of Example 1 and the final product of Comparative Example 1 were subjected to EDS tests respectively, and the results were Figure 6 ,analyze Figure 6 It is known that compared with the fluorine-doped chromium metal oxide positive electrode material, the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material has a wider fluorine element distribution and a higher fluorine doping amount, which indicates that the introduction of molybdenum is beneficial to the subsequent doping of fluorine. The main reason is that the introduction of molybdenum increases the interlayer spacing of the material, which facilitates the diffusion and doping of fluorine between the material layers. At the same time, molybdenum can also promote the doping of fluorine through the charge induction effect.

[0062] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the claims, or equivalents thereof.

Claims

1. A fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, characterized in that: The chemical formula of the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material is Cr 8-x Mo x O 21-y F y , x≤5, y≤12.

2. The fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 1, characterized in that The raw materials for preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material include: 1 part by mass of a fluorine-molybdenum compound and 6 to 15 parts by mass of a chromium metal oxide.

3. The fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 2, characterized in that: The chromium metal oxide comprises at least Cr8O 21 .

4. The fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 2 or 3, characterized in that: The fluorine-molybdenum compound at least includes molybdenum hexafluoride gas.

5. The method for preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to any one of claims 1 to 4, characterized in that: Including steps: Calcinate CrO3, grind it, and sieve it to obtain chromium metal oxide; The chromium metal oxide is placed in a reaction gas containing a fluorine-molybdenum compound, reacts at room temperature, and then is ground and sieved to obtain a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material.

6. The method for preparing a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 5, characterized in that: The conditions for calcining CrO3 include at least: heating to 250-300°C in a nitrogen-oxygen mixed atmosphere and keeping the temperature for 10-13 hours.

7. The method for preparing a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 6, characterized in that: In the nitrogen-oxygen mixed atmosphere, the volume ratio of nitrogen to oxygen is (1-3):

1.

8. The method for preparing a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 6 or 7, characterized in that: The conditions for calcining CrO3 include: a heating rate of 4 to 6°C / min.

9. The method for preparing a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 5, characterized in that: The reaction gas includes molybdenum hexafluoride gas and nitrogen gas in a volume ratio of 1:(4-9).

10. The method for preparing a fluorine-molybdenum dual-doped chromium metal oxide positive electrode material according to claim 5, characterized in that: When preparing the chromium metal oxide, the rotation speed of the ball mill is 200-400 r / min, the ball milling time is 4-8 hours, and the mesh size is 200 mesh; when preparing the fluorine-molybdenum dual-doped chromium metal oxide positive electrode material, the rotation speed of the ball mill is 100-350 r / min, the ball milling time is 5-8 hours, and the mesh size is 100 mesh.

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