Double anti-perovskite material and preparation method thereof, positive electrode active material and battery

Abstract

The invention provides a double anti-perovskite material and a preparation method thereof, a positive electrode active material and a battery, and relates to the field of batteries. The chemical expression general formula of the double anti-perovskite material is AxTMyCh (BaC1-a) b. Wherein 1 < = x < = 2.5, 0.8 < = y < = 1.2, 0.25 < = a < = 0.75, and 0.8 < = b < = 1.2; a is Li and / or Na, TM is selected from transition metal elements, Ch is selected from chalcogens, B is selected from at least one of negative monovalent anions and negative monovalent anion clusters, and C is selected from at least one of negative trivalent anions or negative trivalent anion clusters. The double anti-perovskite material has relatively high crystal structure stability; and when the double anti-perovskite material is applied to a battery as a positive electrode active material, the safety of the battery can be effectively improved, and the battery has high power output and high specific capacity.

Description

Technical Field

[0001] The present application relates to the field of batteries, and more specifically, to a double inverse perovskite material and a preparation method thereof, a positive electrode active material and a battery. Background Art

[0002] With the rapid development of society, environmental and energy issues are becoming increasingly prominent. The use of clean and renewable energy is the key to solving environmental and energy problems. The key to clean and renewable energy is the battery energy storage system. Lithium-ion batteries have been widely used in portable electronic devices and new energy electric vehicles due to their advantages such as high energy density and long cycle life.

[0003] At present, there is an urgent demand for lithium / sodium ion batteries with high specific capacity and high safety performance.

[0004] Lithium / sodium ion batteries are mainly composed of positive and negative electrodes as well as the separator and electrolyte between them, among which the positive and negative electrode materials are the key to determining the battery performance. Currently, commercial lithium / sodium ion batteries are limited by the low actual specific capacity of the electrode materials, which makes it difficult to further improve the battery energy density. In addition, conventional electrode materials are prone to produce gas during the actual lithium deintercalation process, which increases the internal pressure of lithium ion batteries and poses a safety hazard. Lithium cobalt oxide, a common positive electrode material, is prone to structural instability and lattice oxygen precipitation when working at high voltage. Lattice oxygen precipitation is an important factor leading to performance degradation and safety issues of lithium cobalt oxide batteries at high voltage. When the lithium-rich manganese-based positive electrode material is charged to above 4.5V, it leads to unstable electron holes and O 2- The formation of oxygen gas will lead to the release of oxygen. The reaction between the oxygen generated by the decomposition of the material and the electrolyte will release huge heat, causing thermal runaway of the battery. Summary of the invention

[0005] In view of the above problems, the present application provides a double inverse perovskite material and a preparation method thereof, a positive electrode active material and a battery. The double inverse perovskite material has a stable crystal structure and can be used as a positive electrode active material in a battery to improve the specific capacity and safety performance of the battery. The double inverse perovskite material does not contain the O element, which can avoid safety problems caused by the release of oxygen in the electrode material.

[0006] In the first aspect, the present invention provides a double inverse perovskite material, the chemical expression formula of the double inverse perovskite material is A x TM y Ch(B a C 1-a ) b. Wherein, 1≤x≤2.5, 0.8≤y≤1.2, 0.25≤a≤0.75, 0.8≤b≤1.2; A is Li and / or Na, TM is selected from transition metal elements, Ch is selected from chalcogen elements, B is selected from at least one of negative monovalent anions and negative monovalent anion clusters, and C is selected from at least one of negative trivalent anions or negative trivalent anion clusters.

[0007] The present invention obtains a cubic double inverse perovskite material with an octahedral crystal structure by cooperating A (Li and / or Na), transition metal elements, chalcogens, B (one or more negative monovalent anions or anion clusters) and C (one or more negative trivalent anions or anion clusters) and regulating their element ratios. In the crystal structure of the double inverse perovskite material, metal cations occupy the octahedral vertices, B and C jointly occupy the octahedral center, the octahedra are connected at the same vertices, and the chalcogens are located in the gaps between the octahedra, so that the double inverse perovskite material has a higher crystal structure stability. Since B and C occupy the octahedral center, they The ordered, disordered, partially ordered, and partially disordered arrangements between them form different octahedral configurations; and the double inverse perovskite material utilizes the introduction of chalcogens, B, and C so that when it is used as a positive electrode active material in a battery, on the one hand, the double inverse perovskite material basically does not contain oxygen participating in the redox reaction, which can effectively prevent it from producing oxygen under high voltage and causing the internal pressure of the battery to increase, thereby effectively improving the safety of the battery; on the other hand, the structure of the double inverse perovskite material and the A ion transmission channel can be adjusted, so that the battery made of the double inverse perovskite material can present a higher average discharge voltage in the discharge cycle, so that the battery can have high power output and high specific capacity.

[0008] In some embodiments, 1.9≤x≤2.1; and / or, 0.9≤y≤1.1; and / or, 0.45≤a≤0.55; and / or, 0.9≤b≤1.1.

[0009] In some embodiments, the TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb, and Mg.

[0010] Optionally, the valence state of TM is positive divalent.

[0011] In some embodiments, Ch includes at least one of S, Se, and Te.

[0012] Optionally, B includes F - , Cl - Br - ,I - , H - OH - 、BH4 - NH2- 、NO2 - and CN - At least one of;

[0013] Optionally, C includes N 3- 、(PO4) 3- 、(SbO4) 3- and (AsO4) 3- At least one of;

[0014] Optionally, B is selected from F - , Cl - Br - and I - At least one of, C is N 3- .

[0015] In some embodiments, the double inverse perovskite material includes Li2FeTe(N 0.5 Cl 0.5 )、Li2FeTe(N 0.5 F 0.5 ) or Li2FeSe(N 0.5 Cl 0.5 ).

[0016] In some embodiments, the double inverse perovskite material is Li2FeSe(N0.5Cl0.5).

[0017] In the second aspect, the present application provides a method for preparing the double inverse perovskite material in the above-mentioned embodiment, the preparation method comprising: ball milling the raw materials constituting the double inverse perovskite material at a rotation speed of 300-1000rmp for 10-40h under an inert atmosphere or vacuum conditions to obtain a precursor; and keeping the precursor at 300-600℃ for at least 1h.

[0018] The present application ball-mills the raw materials at a rotation speed of 300-1000rmp for 10-40h, so that the raw materials can be fully contacted with each other, and it is beneficial to ensure that the raw materials fully react and form the target anti-perovskite structure phase. No further high-temperature sintering is required, and only low-temperature treatment is required. In addition, the double anti-perovskite material prepared by ball milling + low-temperature treatment has a large mixing entropy, which is beneficial for the double anti-perovskite material to have a higher crystal structure stability; using the double anti-perovskite material as a positive electrode active material can enable a battery prepared using the positive electrode active material to have a better first-cycle discharge capacity.

[0019] In a third aspect, the present application provides a method for preparing the double inverse perovskite material in the above-mentioned embodiment, the preparation method comprising: mixing the raw materials constituting the double inverse perovskite material, and then keeping it warm at 700-1000°C for 4-15h in an inert atmosphere or vacuum conditions.

[0020] The present application uses a double inverse perovskite material prepared by mixing raw materials and then sintering at high temperature as a positive electrode active material, so that a battery made using the positive electrode active material can have a better first-cycle discharge capacity.

[0021] In a fourth aspect, the present application provides a positive electrode active material, which includes the double inverse perovskite material in the above embodiment.

[0022] In a fifth aspect, the present application provides a battery comprising the double inverse perovskite material in the above-mentioned embodiment.

[0023] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0025] Figure 1 Li2FeTe(N) prepared in Example 1 0.5 Cl 0.5 )'s XRD pattern and crystal structure diagram;

[0026] Figure 2 Li2FeTe(N) prepared in Example 2 0.5 F 0.5 )'s XRD pattern and crystal structure diagram;

[0027] Figure 3 Li2FeSe(N) prepared in Example 3 0.5 Cl 0.5 )'s XRD pattern and crystal structure diagram;

[0028] Figure 4 Li2FeSeN prepared in Example 4 0.5 (BH4) 0.5 XRD pattern and crystal structure diagram;

[0029] Figure 5 XRD diagram of Li2FeO2 prepared in Comparative Example 1;

[0030] Figure 6 The XRD pattern and crystal structure diagram of Li2FeTeO prepared in Comparative Example 2;

[0031] Figure 7 It is the first charge and discharge curve diagram of the lithium ion battery corresponding to Example 1-3 and Comparative Example 1-2. DETAILED DESCRIPTION

[0032] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0034] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0035] Currently, commercial lithium-ion batteries are limited by the low actual specific capacity of electrode materials, which makes it difficult to further improve the battery energy density. In addition, conventional electrode materials are prone to produce gas during the actual lithium insertion and extraction process, which causes the internal pressure of lithium-ion batteries to increase, posing a safety hazard.

[0036] In view of this, this application is hereby filed.

[0037] In the first aspect, the present application provides a double inverse perovskite material, the chemical expression formula of the double inverse perovskite material is A x TM y Ch(B a C 1-a ) b . Wherein, 1≤x≤2.5, 0.8≤y≤1.2, 0.25≤a≤0.75, 0.8≤b≤1.2; A is Li and / or Na, TM is selected from transition metal elements, Ch is selected from chalcogen elements, B is selected from at least one of negative monovalent anions and negative monovalent anion clusters, and C is selected from at least one of negative trivalent anions or negative trivalent anion clusters.

[0038] A cluster is a relatively stable microscopic or submicroscopic aggregate composed of several or even thousands of atoms, molecules or ions through physical or chemical binding forces. Anionic clusters refer to clusters that ultimately present a negative valence state.

[0039] B is selected from at least one type of negative monovalent anions and negative monovalent anion clusters, which means that B is a negative monovalent anion and / or a negative monovalent anion cluster. It can be understood that there are many types of negative monovalent anions and there are also many types of negative monovalent anion clusters. B can be a combination of one or more of a variety of negative monovalent anions and a variety of negative monovalent anion clusters. Similarly, C can be a combination of one or more of a variety of negative trivalent anions and a variety of negative trivalent anion clusters.

[0040] The term "and / or" is only a description of the association relationship of the associated objects, indicating that there can be three relationships. A being Li and / or Na can represent: the existence of Li alone, the existence of Li and Na at the same time, and the existence of Na alone. It can be understood that the choice of A can be based on common choices in actual applications. When the double inverse perovskite material is used as a positive electrode active material in a battery, when the battery is a lithium-ion battery, A is Li, and when the battery is a sodium-ion battery, A is Na.

[0041] The present invention obtains a cubic double inverse perovskite material having an octahedral crystal structure by coordinating A (Li and / or Na), transition metal elements, chalcogens, B (one or more negative monovalent anions or anion clusters) and C (one or more negative trivalent anions or anion clusters) and regulating their element ratios. In the crystal structure of the double inverse perovskite material, metal cations occupy the octahedral vertex positions, B and C jointly occupy the octahedral center positions, the octahedra are connected with common vertices, and the chalcogens are located in the gap positions between the octahedra, so that the double inverse perovskite material has a higher crystal structure stability; because B and C mixedly occupy the octahedron, the octahedron is more stable than the double inverse perovskite material. Center, the ordered, disordered, partially ordered, and partially disordered arrangements between them form different octahedral configurations, and the double inverse perovskite material utilizes the introduction of chalcogens, B, and C, so that when it is used as a positive electrode active material in a battery, on the one hand, the double inverse perovskite material basically does not contain oxygen participating in the redox reaction, which can effectively prevent it from generating oxygen under high voltage and causing the internal pressure of the battery to increase, effectively improving the safety of the battery, and on the other hand, the structure of the double inverse perovskite material and the A ion transmission channel can be adjusted, so that the battery made of the double inverse perovskite material can present a higher average discharge voltage in the discharge cycle, so that the battery can have high power output and high specific capacity.

[0042] Illustratively, x is any value among 1, 1.2, 1.5, 1.7, 2, 2.3 or 2.5 or between any two values, y is any value among 0.8, 0.9, 1, 1.1, 1.2 or between any two values, a is any value among 0.25, 0.35, 0.45, 0.55, 0.65, 0.75 or between any two values, and b is any value among 0.8, 0.9, 1, 1.1, 1.2 or between any two values.

[0043] In some optional embodiments, 1.9≤x≤2.1; and / or, 0.9≤y≤1.1; and / or, 0.45≤a≤0.55; and / or, 0.9≤b≤1.1.

[0044] Within the above range, adjusting the structure of the double inverse perovskite material by element ratio is beneficial to further improve the structural stability of the double inverse perovskite material and optimize the first cycle discharge specific capacity and average discharge voltage of the battery made of the double inverse perovskite material.

[0045] In some optional embodiments, the TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb and Mg.

[0046] Optionally, the valence state of TM is positive divalent.

[0047] In some optional embodiments, Ch includes at least one of S, Se and Te.

[0048] Optionally, B includes F - , Cl - Br - ,I - , H - OH - 、BH4 - NH2 - 、NO2 - and CN - At least one of .

[0049] Optionally, C includes N 3- 、(PO4) 3- 、(SbO4) 3- and (AsO4) 3- At least one of .

[0050] The above-mentioned N element has a high abundance in the earth, which can reduce the material cost and the cost of the battery. The above-mentioned anion clusters have a stable structure, which is conducive to improving the stability of the double anti-perovskite material.

[0051] Optionally, B is selected from F - , Cl -Br - and I - At least one of, C is N 3- .

[0052] The above selection is beneficial to improving the first-cycle discharge specific capacity and average discharge voltage of the double inverse perovskite material.

[0053] In some optional embodiments, the double inverse perovskite material includes Li2FeTe(N 0.5 Cl 0.5 )、Li2FeTe(N 0.5 F 0.5 ) or Li2FeSe(N 0.5 Cl 0.5 ).

[0054] Each of the above-mentioned double inverse perovskite materials not only has good crystal structure stability, but also has an average voltage of at least 1.85V when cycling between 1.2V and 3V, and has a first-cycle discharge capacity of at least 213mAh / g when cycling from 3V to 1.2V at a rate of 0.01C. That is, the above-mentioned double inverse perovskite materials have a higher average discharge voltage and a high first-cycle discharge capacity when used as positive electrode active materials in batteries.

[0055] Optionally, the double inverse perovskite material is Li2FeSe(N 0.5 Cl 0.5 ).

[0056] Li2FeSe(N 0.5 Cl 0.5 ) The double inverse perovskite material has an average voltage of 1.85 V when cycled between 1.2 V and 3 V, and has a first-cycle discharge specific capacity of about 350 mAh / g when cycled from 3 V to 1.2 V at a rate of 0.01 C, which has a high first-cycle specific capacity at a higher average discharge voltage.

[0057] The present application also provides a method for preparing the above-mentioned double inverse perovskite material.

[0058] In some optional embodiments, the preparation method of the above-mentioned double inverse perovskite material adopts ball milling + low-temperature sintering. Specifically, the preparation method includes: ball milling the raw materials constituting the double inverse perovskite material at a rotation speed of 300-1000rmp for 10-40h in an inert atmosphere or vacuum conditions to obtain a precursor; keeping the precursor at 300-600℃ for at least 1h.

[0059] The present application ball-mills the raw materials at a rotation speed of 300-1000 rpm for 10-40 hours, so that the raw materials can be fully contacted with each other, and it is beneficial to ensure that the raw materials fully react and form the target anti-perovskite structure phase. No further high-temperature (for example, 700°C and above) sintering is required, and only low-temperature treatment is required. In addition, the double anti-perovskite material prepared by ball milling + low-temperature treatment has a large mixing entropy, which is beneficial for the double anti-perovskite material to have a higher crystal structure stability; using the double anti-perovskite material as a positive electrode active material can enable a battery made using the positive electrode active material to have a better first-cycle discharge capacity.

[0060] Optionally, the insulation time is 1-10 hours.

[0061] Exemplarily, the insulation time is any value among 1 h, 3 h, 5 h, 7 h, 9 h, 10 h or between any two values.

[0062] In some optional embodiments, the preparation method of the above-mentioned double inverse perovskite material adopts a high-temperature sintering method. Specifically, the preparation method of the double inverse perovskite material includes: mixing the raw materials constituting the double inverse perovskite material, and then keeping it warm at 700-1000°C for 4-15h in an inert atmosphere or vacuum conditions.

[0063] The mixing methods include grinding mixing, stirring mixing, etc. In order to improve the uniformity of mixing, the grinding mixing method can be adopted.

[0064] Exemplarily, in the high-temperature sintering method, the holding temperature is any value among 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or between any two values, and the holding time is any value among 4h, 6h, 8h, 10h, 13h, 15h or between any two values.

[0065] The present application also provides a positive electrode active material, which includes the above-mentioned double inverse perovskite material.

[0066] It should be noted that the above-mentioned positive electrode active material may consist only of the above-mentioned double inverse perovskite material, or only part of it may consist of the above-mentioned double inverse perovskite material, and the rest may consist of other positive electrode active materials.

[0067] The present application also provides a battery, which includes the above-mentioned positive electrode active material.

[0068] The battery can be a primary battery or a secondary battery; it can be a sodium ion battery or a lithium ion battery, and those skilled in the art can choose according to actual needs.

[0069] Optionally, the battery is a secondary battery.

[0070] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0071] Example 1

[0072] This embodiment provides a double inverse perovskite material, the chemical formula of which is Li2FeTe(N 0.5 Cl 0.5 ), the compound formation energy is calculated according to the first principle, based on the chemical equation as follows: 0.5Li3N+0.5LiX+Te+Fe→Li2FeTe(N 0.5 X 0.5 ), where X is Cl, calculate Li2FeTe(N 0.5 Cl 0.5 ) has a formation energy of -1.05 eV / mol, and its absolute value is relatively large, indicating that the compound can be prepared by the above chemical equation.

[0073] Li2FeTe(N 0.5 Cl 0.5 ) comprises:

[0074] Under the protection of inert gas, L3N, LiCl, Te, and Fe were weighed and mixed in a mass ratio of 1:1:2:2, and ball-milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 600 rpm and the ball milling was performed for 20 hours. The precursor was then kept at 500°C for 5 hours.

[0075] Figure 1 Li2FeTe(N) prepared in Example 1 0.5 Cl 0.5 )'s XRD pattern and crystal structure diagram, where Figure 1 (a) is the XRD pattern, Figure 1 (b) is a schematic diagram of its crystal structure. Figure 1 It can be seen that Li2FeTe(N 0.5 Cl 0.5 ) is a trigonal antiperovskite structure with a space group of R3m, in which the metal cations and N 3- Anion or Cl - Constructing an octahedron, N 3- or Cl - Located at the center of the octahedron, the metal cations are located at the vertices of the octahedron, N 3- Central octahedron and Cl -The central octahedrons are connected alternately with the common vertices, and each metal cation is connected to a N 3- and a Cl - Coordination is a typical double anti-perovskite structure.

[0076] Example 2

[0077] This embodiment provides a double inverse perovskite material, the chemical formula of which is Li2FeTe(N 0.5 F 0.5 ).

[0078] The formation energy of the compound is calculated based on the first principles, and the chemical equation is as follows:

[0079] 0.5Li3N+0.5LiX+Te+Fe→Li2FeTe(N 0.5 X 0.5 ), where X is F, calculate Li2FeTe(N 0.5 F 0.5 ) has a formation energy of -2.37 eV / mol, and its absolute value is relatively large, indicating that the compound can be prepared by the above chemical equation.

[0080] Li2FeTe(N 0.5 F 0.5 ) comprises:

[0081] Under vacuum protection, L3N, LiF, Te, and Fe were weighed and mixed in a mass ratio of 1:1:2:2, and ball-milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 800 rpm for 12 hours. The precursor was then kept at 450°C for 5 hours.

[0082] Figure 2 Li2FeTe(N) prepared in Example 2 0.5 F 0.5 )'s XRD pattern and crystal structure diagram, where Figure 2 (a) is Li2FeTe(N 0.5 F 0.5 ), Figure 2 (b) is Li2FeTe(N 0.5 F 0.5 ) is a schematic diagram of the crystal structure of Figure 2 It can be seen that Li2FeTe(N 0.5 F 0.5 ) a trigonal antiperovskite structure with space group R3m, in which the metal cations and N 3- Anion or F - Constructing an octahedron, N 3- or F -Located at the center of the octahedron, the metal cations are located at the vertices of the octahedron, N 3- Central octahedron and F - The central octahedrons are connected alternately with the common vertices, and each metal cation is connected to a N 3- and an F - Coordination is a typical double anti-perovskite structure.

[0083] Example 3

[0084] This embodiment provides a double inverse perovskite material, the chemical formula of which is Li2FeSe(N 0.5 Cl 0.5 ).

[0085] The formation energy of the compound is calculated based on the first principle, according to the chemical equation: 0.5Li3N+0.5LiCl+Se+Fe→Li2FeSe(N 0.5 Cl 0.5 ), calculate Li2FeSe(N 0.5 Cl 0.5 ) is -1.08 eV / mol, and its absolute value is relatively large, indicating that the compound can be prepared by the above chemical equation.

[0086] Li2FeSe(N 0.5 Cl 0.5 ) comprises:

[0087] Prepared by the following steps:

[0088] Under the protection of inert gas, L3N, LiCl, Se, and Fe were weighed and mixed in a mass ratio of 1:1:2:2, and ball-milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 500 rpm, and the ball milling was performed for 12 hours. The precursor was then kept at 450°C for 2 hours.

[0089] Figure 3 Li2FeSe(N) prepared in Example 3 0.5 Cl 0.5 )'s XRD pattern and crystal structure diagram, where Figure 3 (a) is Li2FeSe(N 0.5 Cl 0.5 )XRD pattern, Figure 3 (b) is Li2FeSe(N 0.5 Cl 0.5 ) Schematic diagram of the crystal structure. Figure 3 It can be seen that Li2FeSe(N 0.5 Cl 0.5 ) a trigonal antiperovskite structure with space group R3m, in which the metal cations and N3- Anion or Cl - Constructing an octahedron, N 3- or Cl - Located at the center of the octahedron, the metal cations are located at the vertices of the octahedron, N 3- Central octahedron and Cl - The central octahedrons are connected alternately with the common vertices, and each metal cation is connected to a N 3- and a Cl - Coordination is a typical double anti-perovskite structure.

[0090] Example 4

[0091] This embodiment provides a double inverse perovskite material, the chemical formula of which is Li2FeSeN 0.5 (BH4) 0.5 .

[0092] The formation energy of the compound is calculated based on the first principle, according to the chemical equation: 0.5L3N+0.5LiBH4+Se+Fe→Li2FeSeN 0.5 (BH4) 0.5 , calculate Li2FeSeN 0.5 (BH4) 0.5 The formation energy is -0.5 eV / mol, and its absolute value is large, indicating that the compound can be prepared by the above chemical equation.

[0093] Under the protection of inert gas, L3N, LiBH4, Se, and Fe were weighed and mixed in a mass ratio of 1:1:2:2, and ball-milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 500 rpm, and the ball milling was performed for 10 hours. The precursor was then kept at 350°C for 2 hours.

[0094] Figure 4 Li2FeSeN prepared in Example 4 0.5 (BH4) 0.5 XRD pattern and crystal structure diagram of Figure 4 (a) is the XRD pattern, Figure 4 (b) is a schematic diagram of its crystal structure. Figure 4 It can be seen that Li2FeSeN 0.5 (BH4) 0.5 It is a typical double anti-perovskite structure.

[0095] Example 6

[0096] The only difference between it and Example 1 is that the ball milling speed is 1000 rpm.

[0097] Example 7

[0098] The only difference from Example 1 is that the raw materials constituting the double inverse perovskite material are ground at a rotation speed of 300 rpm for 10 minutes to be uniformly mixed, and then kept at 800° C. for 10 hours under an inert atmosphere.

[0099] Comparative Example 1

[0100] Li2FeO2 is prepared by the following steps:

[0101] Under the protection of inert gas, Li2O and FeO were weighed and mixed in a mass ratio of 1:1, and ball milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 500 revolutions per minute, and the ball milling was performed for 13 hours. The precursor was then kept at 400°C for 5 hours.

[0102] Figure 5 This is the XRD pattern of Li2FeO2 prepared in Comparative Example 1.

[0103] Comparative Example 2

[0104] Li2FeTeO was prepared by the following steps:

[0105] Under the protection of inert gas, L3N, LiCl, Te, and Fe were weighed and mixed in a mass ratio of 1:1:2:2, and ball-milled using a high-energy planetary ball mill to obtain a precursor. The ball milling speed was 400 rpm, and the ball milling was performed for 15 hours. The precursor was then kept at 360°C for 5 hours.

[0106] Figure 6 The XRD pattern and crystal structure diagram of Li2FeTeO prepared in Comparative Example 2 are shown in FIG. Figure 6 (a) is the XRD pattern, Figure 6 (b) is a schematic diagram of its crystal structure. Figure 6 It can be seen that Li2FeTeO has a hexagonal antiperovskite structure with a space group of P63 / mmc, in which the metal cations and O 2- The anion forms an octahedron, with O located at the center of the octahedron and the metal cation located at the vertices of the octahedron. The octahedrons share vertices or faces, and each metal cation is connected to two O 2- Coordination.

[0107] Test Example 1

[0108]

Positive electrode

[0109] The final materials prepared in each embodiment and comparative example were used as positive electrode active materials, respectively. The positive electrode active material, the conductive agent, and the binder were weighed in a ratio of 90:5:5, and the positive electrode active material was vacuum premixed in advance to obtain a uniformly dispersed premixed material; PVDF NMP glue was gradually added to the above-mentioned uniformly dispersed premixed material; after mixing evenly, the conductive agent Super-P and CNT were gradually added, and mixed evenly to obtain a positive electrode slurry with a certain fluidity; then, it was coated on an aluminum foil, blown dry, and roller pressed to obtain a positive electrode sheet.

[0110]

Diaphragm

[0111] Double-sided ceramic diaphragm.

[0112]

Electrolyte

[0113] Weigh 0.6122 g of sodium perchlorate and add it to 10 ml of propylene carbonate solvent, stir until the sodium perchlorate is completely dissolved, then add 3% by mass of fluoroethylene carbonate as an additive, stir thoroughly and use it as an electrolyte.

[0114]

Button battery

[0115] The positive electrode sheet, the isolation membrane and the lithium metal sheet prepared above are cut into discs of appropriate sizes and stacked in order, so that the isolation membrane is placed between the positive electrode sheet and the lithium metal sheet to play an isolating role, the isolation membrane is soaked with the electrolyte prepared above, and then compacted to obtain a button battery.

[0116]

Performance test

[0117] The testing equipment is Wuhan Blue Electric Battery Testing Equipment;

[0118] Test conditions: At 25°C, charge the button cell at a constant current of 0.1C to 3V to obtain the first charge capacity of the button cell; then discharge it at a constant current of 0.1C to 1.2V to obtain the first discharge capacity of the button cell.

[0119] in, Figure 7 The first charge and discharge curves of the lithium-ion batteries corresponding to Examples 1-3 and Comparative Examples 1-2 are shown in FIG. Figure 7 (a) is the first charge and discharge curve of the lithium ion battery corresponding to Example 1; Figure 7 (b) is the first charge and discharge curve of the lithium ion battery corresponding to Example 2; Figure 7 (c) is the first charge and discharge curve of the lithium ion battery corresponding to Example 3;

[0120] Figure 7 (d) is the first charge and discharge curve of the lithium ion battery corresponding to Comparative Example 1; Figure 7(e) is the first charge and discharge curve of the lithium ion battery corresponding to Comparative Example 2.

[0121] The performance of the lithium-ion batteries corresponding to the embodiments and comparative examples is shown in Table 1.

[0122] Table 1 Test results

[0123]

[0124]

[0125] Combination Figure 7 And Table 1, the chemical expression obtained by replacing oxygen with chalcogen is A x TM y Ch(B a C 1-a ) b The double inverse perovskite material can avoid the disadvantage of the positive electrode material producing oxygen under high voltage, thereby improving the safety of the battery. Moreover, compared with the comparative example 1-2, the only difference in the anion selection is that the embodiment 1-2 can effectively improve the first discharge capacity and the average discharge voltage.

[0126] According to Examples 1-2 and Comparative Example 2, the use of N 0.5 Cl 0.5 or N 0.5 F 0.5 Further replacement of O can further effectively increase the first discharge capacity and the average discharge voltage.

[0127] According to the comparison between Example 1 and Example 3, compared with selecting Te as Ch (chalcogen), selecting Se as Ch (chalcogen) can effectively improve the first cycle discharge capacity of the lithium-ion battery.

[0128] According to Example 3 and Example 4, N 0.5 Cl 0.5 Compared to N 0.5 (BH4) 0.5 , which can effectively improve the first cycle discharge capacity and average discharge voltage of the lithium ion battery. Although the first cycle discharge capacity and average discharge voltage of Example 4 are lower than those of Comparative Example 2, it avoids the disadvantage of the positive electrode material generating oxygen under high voltage, and can improve the safety of the battery.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A double inverse perovskite material, characterized in that: The chemical expression formula of the double inverse perovskite material is A x TM y Ch(B a C 1-a ) b ; Among them, 1≤x≤2.5, 0.8≤y≤1.2, 0.25≤a≤0.75, 0.8≤b≤1.2; A is Li and / or Na, TM is selected from transition metal elements, Ch is selected from chalcogen elements, B is selected from at least one of negative monovalent anions and negative monovalent anion clusters, and C is selected from at least one of negative trivalent anions or negative trivalent anion clusters.

2. The double inverse perovskite material according to claim 1, characterized in that: 1.9≤x≤2.1; and / or, 0.9≤y≤1.1; and / or, 0.45≤a≤0.55; and / or, 0.9≤b≤1.

1.

3. The double inverse perovskite material according to claim 1, characterized in that: The TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb and Mg; Optionally, the valence state of the TM is positive divalent.

4. The double inverse perovskite material according to claim 1, characterized in that: The Ch includes at least one of S, Se and Te; Optionally, said B includes F - , Cl - Br - ,I - , H - OH - 、BH4 - NH2 - 、NO2 - and CN - At least one of; Optionally, the C includes N 3- 、(PO4) 3- 、(SbO4) 3- and (AsO4) 3- At least one of; Optionally, B is selected from F - , Cl - Br - and I - At least one of the following, wherein C is N 3- .

5. The double inverse perovskite material according to any one of claims 1 to 4, characterized in that: The double inverse perovskite material includes Li2FeTe(N 0.5 Cl 0.5 )、Li2FeTe(N 0.5 F 0.5 ) or Li2FeSe(N 0.5 Cl 0.5 ).

6. The double inverse perovskite material according to any one of claims 1 to 4, characterized in that: The double inverse perovskite material is Li2FeSe(N 0.5 Cl 0.5 ).

7. A method for preparing a double inverse perovskite material according to any one of claims 1 to 6, characterized in that: include: The raw materials constituting the double inverse perovskite material are ball-milled at a speed of 300-1000 rpm for 10-40 hours under an inert atmosphere or vacuum condition to obtain a precursor; The precursor is kept at 300-600° C. for at least 1 h.

8. A method for preparing a double inverse perovskite material according to any one of claims 1 to 6, characterized in that: include: The raw materials constituting the double inverse perovskite material are mixed, and then kept at 700-1000° C. for 4-15 hours in an inert atmosphere or vacuum conditions.

9. A positive electrode active material, characterized in that: It comprises the double inverse perovskite material as described in any one of claims 1 to 6.

10. A battery, characterized in that: The battery comprises the positive electrode active material as claimed in claim 9.

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