A cathode material and its application

Abstract

The present invention relates to the technical field of lithium batteries, and discloses a cathode material. The battery cathode material is a uranium-containing oxide, and its chemical composition is A<subgt;2< / subgt;BU<subgt;3< / subgt;O<subgt;11< / subgt>, where A represents an alkali metal element and B represents a transition metal element. This novel uranium-containing oxide battery cathode material has good reversibility and stability, greatly improves the charge and discharge efficiency and battery life, and has a high volume specific capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and specifically to a cathode material for batteries and its applications. Background Art

[0002] At present, cathode materials that are widely used include lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, etc. Lithium cobalt oxide is used as a cathode material. Its role as a framework makes the process of lithium ion insertion and extraction relatively stable. However, during the process of lithium ion deintercalation and intercalation, it will have an impact on the structure, resulting in reduced cycle stability, and the cost of cobalt is relatively high, which is not suitable for industrial applications. The theoretical capacity of lithium iron phosphate reaches 170 mAh / g, and the working voltage is 3.4 V, which can be used as a power-type lithium ion battery. However, it also has many deficiencies, such as low conductivity, only 10 -9 S / cm, low diffusion coefficient, and low tap density. Therefore, it is not conducive to industrial production. Lithium manganese oxide is inexpensive and rich in resources, with a theoretical specific capacity of 148 mAh / g and has broad application prospects. However, the current electrolyte contains HF, which can dissolve the lithium manganese oxide of the electrode material, resulting in poor cycle performance. The ternary material combines the advantages of various elements and is currently an ideal cathode material due to the synergistic effect. However, it still has certain limitations in special application fields, such as in fields with low quality requirements and high space volume requirements.

[0003] With the in-depth study of the composition of uranium-containing oxides and the analysis of the microstructure, it is more conducive to designing new materials and expanding new application fields. The compound synthesized by the flux growth method in this paper contains uranium-containing oxides with transition metals. The literature shows that the most common structural feature of uranium-containing oxides is the linear or approximately linear uranyl ion UO2 2+ . The uranyl ion is loosely coordinated with four, five, or six oxygen atoms in the equatorial region to form a square, pentagon, or hexagonal bipyramid. The axial uranyl oxygen atoms are usually terminal, forming mainly zero-dimensional, one-dimensional, and two-dimensional (0D, 1D, and 2D respectively). Three-dimensional (3D) structures are not common; however, they usually exhibit unique framework topologies. It is found that the structure of Rb2MnU3O 11 crystallizes in the space group and has the albite structure type. The compound has a three-dimensional albite structure, in which the α-U3O8 type sheet (P layer) is connected by MnO6 octahedra (O layer). This is a new framework topology of uranyl oxides. Rb + ions exist in the voids between the MnO6 octahedra. These layers repeat the U3O8 type layer sequence common in the albite structure type. The uranium atom is in a 7-fold oxygen coordination environment, showing a typical uranyl bond motif, that is, two short axial bonds and five long equatorial bonds. Similar to the spinel structure of LiMn2O4, the albite structure of Rb2MnU3O 11It can also be used in the energy storage field (such as Figure 1 ). Figure 1 In Figure 1 , the continuously connected structure is the U3O8 sheet structure, the spherical structure represents the Li element, and the MnO6 octahedral structure is in the middle of the Li element.

[0004] In the literature "A2MnU3O 11 (A = K, Rb) and Li 3.2 Mn 1.8 U6O 22 : Three New Alkali-Metal Manganese Uranium(VI) Oxides Related to Natrotantite", the XRD pattern of Rb2MnU3O 11 obtained is basically the same as that in this article, indicating that the prepared sample is Rb2MnU3O 11 .

[0005] In Patent CN111224089A, although molten salt is also used as the reaction medium to prepare the ternary cathode material, this patent only considers the materials synthesized from three elements of nickel, cobalt, and manganese, and mainly examines another preparation method of the ternary material.

[0006] FOUAD G. EL-METWALY proposed in the article "Synthesis, effect of γ-ray and electrical conductivity of uranium doped nano LiMn2O4 spinels for applications as positive electrodes in Li-ion rechargeable batteries" to dope uranium into LiMnO4, and the main structure is different from that in this article, and the specific charge and discharge performance effects are not described. Summary of the Invention

[0007] (1) Technical problems to be solved

[0008] In view of the deficiencies of the prior art, the present invention provides a novel uranium-containing oxide battery cathode material and its application, which has good reversibility and stability, greatly improves the charge and discharge efficiency and battery life, and has a high volume specific capacity, solving the problems raised in the above background technology.

[0009] (2) Technical solutions

[0010] To achieve the above object, the present invention provides the following technical solution: A cathode material, the cathode material is a uranium-containing oxide, and its chemical composition is A2BU3O 11, where A represents an alkali metal element, B represents a transition metal element, the alkali metal element is Rb, and the transition metal element is Mn.

[0011] Preferably, the battery cathode material is represented as Rb2MnU3O 11 .

[0012] Preferably, the battery cathode material is prepared by the high-temperature molten crystal method, and the preparation temperature is 300 - 1400 °C.

[0013] Preferably, the battery cathode material is prepared by the high-temperature molten crystal method, and the heat preservation time is 1 h - 12 h.

[0014] Application of a novel uranium-containing oxide battery cathode material in a lithium battery cathode material.

[0015] (III) Beneficial effects

[0016] Compared with the prior art, the present invention provides a novel uranium-containing oxide battery cathode material and its application, having the following beneficial effects:

[0017] The novel uranium-containing oxide battery cathode material, the battery cathode material is a uranium-containing oxide, and the chemical composition is A2BU3O 11 , A represents an alkali metal element, B represents a transition metal element, the alkali metal element is derived from RbCl, and the transition metal element is derived from MnCl2. By using the uranium-containing oxide as a precursor to prepare a new material, the prepared battery cathode has good reversibility and stability, greatly improving the charge and discharge efficiency and battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a structural diagram of albite in the prior art;

[0019] Figure 2 is an SEM image of the synthetic material proposed by the present invention;

[0020] Figure 3 is an XRD pattern of the synthetic material proposed by the present invention;

[0021] Figure 4 is a CV diagram of the half-cell prepared from the synthetic material proposed by the present invention;

[0022] Figure 5 is a charge and discharge cycle diagram of the half-cell of the synthetic material proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Example 1

[0025] Referring to Figure 2-3 , a preparation method of a metal oxide cathode material, and the preparation process of the battery material is as follows:

[0026] Mix uranyl acetate, MnCl2 and RbCl in a molar ratio of 0.1:0.6:6.1 and stir evenly. Use the molten salt growth method for sintering, with a heating rate of 5 °C / minute, a sintering temperature of 900 °C, and a holding time of 3 h. Obtain a uranium-containing crystal oxide material. Wash and filter the obtained crystals with ultrapure water, then perform ultrasonic treatment through ultrasonic waves, and then sieve with a molecular sieve to obtain the corresponding cathode material. Analyze the test results of the obtained cathode material to obtain SEM images and XRD patterns. Figure 2 is the SEM image, Figure 3 is the XRD pattern, Figure 2 indicating an obvious layered structure.

[0027] Example 2

[0028] Referring to Figure 4 , a preparation method of a metal oxide cathode material, and the preparation process of the battery cathode material is as follows:

[0029] Mix uranyl acetate, MnCl2 and RbCl in a molar ratio of 0.1:0.6:6.1 and stir evenly. Use the molten salt growth method for sintering, with a heating rate of 5 °C / minute, a sintering temperature of 900 °C, and a holding time of 3 h. Obtain a uranium-containing crystal oxide material. Wash and filter the obtained crystals with ultrapure water, then perform ultrasonic treatment through ultrasonic waves, and then sieve with a molecular sieve to obtain the corresponding cathode material. According to the mass ratio, add the cathode material, carbon powder and PVDF in a ratio of 8:1:1 to NMP and mix evenly, then coat it on the aluminum foil, dry it at 60 °C, and then perform vacuum drying at 110 °C for 24 h to obtain the prepared cathode. Assemble the obtained cathode with the electrolyte and lithium sheet into a half-cell for cyclic voltammetry testing, and the performance is as shown in Figure 4 .

[0030] In summary, the potential difference of the redox peaks is about 0.5 V, indicating the good reversibility of the cathode.

[0031] Example 3

[0032] Reference Figure 5 , a method for preparing a metal oxide cathode material. The preparation process of the battery cathode material is as follows:

[0033] Mix uranyl acetate, MnCl2 and RbCl in a molar ratio of 0.1:0.6:6.1 and stir evenly. Use the molten salt growth method for sintering, with a heating rate of 5 °C / minute, a sintering temperature of 900 °C, and a holding time of 3 h. Obtain a uranium-containing crystal oxide material. Wash and filter the obtained crystal with ultrapure water, then perform ultrasonic treatment through ultrasonic waves, and then sieve with a molecular sieve to obtain the corresponding cathode material. According to the mass ratio, add the cathode material, carbon powder and PVDF in a ratio of 8:1:1 to NMP and mix evenly, then coat it on aluminum foil, dry it at 60 °C, and then perform vacuum drying at 110 °C for 24 h to obtain the prepared cathode. Assemble the obtained cathode with an electrolyte and a lithium sheet into a half-cell for cyclic voltammetry testing, showing as Figure 5 .

[0034] In summary, during the charge and discharge cycle, the efficiency is close to 100%. This indicates the reversibility of the material during charge and discharge, and also corroborates Example 2 from the side.

[0035] We proposed to convert uranium into a new material and apply the material to the energy field, obtaining good performance effects. Calculations show that the theoretical specific mass capacity of Rb2MnU3O 11 is 48 mAh / g. According to the literature report, the density of Rb2MnU3O 11 is 7.306 g / cm 3 , so the theoretical volume specific capacity is 350 mAh / cm 3 . Rb2MnU3O 11 material has the special property of high volume specific capacity and can be used in some special fields with low mass requirements and high space volume requirements.

[0036] It should be noted that the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0037] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Application of a cathode material in the field of lithium batteries, characterized in that: The positive electrode material is Rb2MnU3O 11 ; the uranium-containing alkali metal oxide is prepared by mixing a uranium salt, a rubidium salt, and a manganese salt; the uranium-containing alkali metal oxide material is prepared by a high-temperature molten salt method, and the preparation temperature is 300-1400 °C; the uranium-containing alkali metal oxide material is prepared by a high-temperature molten salt method, and the heat preservation time is 1 h-12 h.

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