A method for preparing lithium selenide

Abstract

This application relates to the field of electrolyte materials technology, and in particular to a method for preparing lithium selenide. The method includes: obtaining a precursor source, the precursor source including lithium nitride and a selenium source, and subjecting the precursor source to multiple calcination treatments to obtain lithium selenide. The present invention uses lithium nitride as a lithium source and a selenium source to undergo a redox reaction to generate lithium selenide and nitrogen gas. This method has a low cost, does not produce carbon impurities in the prepared product, and the prepared lithium selenide can be used directly as a high-purity raw material for solid electrolytes. In addition, the reaction between lithium nitride and selenium has low exothermic reaction, the reaction is easy to control, and the safety is higher, avoiding the problem of low safety caused by high exothermic reaction of elemental selenium and elemental lithium in the prior art.

Description

Technical Field

[0001] This application relates to the field of composite materials technology, and in particular to a method for preparing lithium selenide. Background Technology

[0002] Lithium selenide (Li2Se) is an important inorganic lithium-based fast ion conductor. Its anti-fluoride calcium-type crystal structure provides a three-dimensional diffusion channel for lithium ion migration, and therefore has broad application prospects in solid-state batteries.

[0003] Currently, the main methods for preparing lithium selenide include the following: 1. Reacting selenium powder and triethyl borohydride in organic solvents such as tetrahydrofuran to generate insoluble lithium selenide precipitate. This method has mild reaction conditions, but the high price of triethyl borohydride leads to high preparation costs and poor economic efficiency; 2. Dissolving selenium powder and lithium powder in liquid ammonia for reaction, followed by filtration to obtain lithium selenide. Liquid ammonia can achieve uniform reaction as a solvent, but it is toxic and volatile, resulting in poor operational safety and limiting the practical application of this method; 3. Directly synthesizing lithium selenide powder by ball milling using selenium powder and lithium hydride as raw materials under an inert atmosphere. This method is simple, but the reaction process involves the release of hydrogen and easily forms a high-temperature and high-pressure environment, posing certain safety hazards; 4. It can be prepared by sintering metallic lithium with elemental selenium, or by reducing lithium selenite with carbon materials at high temperature (such as patent CN119568998A). This type of method has mature technology, but the product often contains residual carbon impurities. Therefore, it is mainly suitable for battery positive and negative electrode material systems and is difficult to use as a high-purity raw material directly for solid electrolytes.

[0004] In summary, existing methods for preparing lithium selenide suffer from high costs, low safety, and often leave carbon impurities in the reaction products, which limits its application in solid electrolytes. Therefore, it is urgent to find a new method for preparing lithium selenide to solve these technical problems. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this application provides a method for preparing lithium selenide. The specific technical solution is as follows: This application provides a method for preparing lithium selenide, the method comprising: S1: Obtain a precursor source, wherein the precursor source includes lithium nitride and selenium source; S2: The precursor source is subjected to multiple calcination treatments to cause the lithium nitride and the selenium source to undergo a redox reaction to obtain the lithium selenide.

[0006] In a possible implementation, the molar ratio between the lithium nitride and the selenium source is 2:(3~3.05).

[0007] In a possible implementation, the step of subjecting the precursor source to multiple calcination treatments to obtain lithium selenide includes: S21: The precursor source is subjected to a calcination treatment to obtain initial lithium selenide; S22: The initial lithium selenide is subjected to a secondary calcination treatment to obtain the lithium selenide.

[0008] In a possible implementation, the calcination temperature during the secondary calcination treatment is higher than the calcination temperature during the primary calcination treatment.

[0009] In a possible implementation, the method satisfies at least one of the following characteristics: The calcination temperature range in the primary calcination process of step S21 is 200~600℃; The calcination temperature range in the secondary calcination process of step S22 is 300~700℃.

[0010] In a possible implementation, the method satisfies at least one of the following characteristics: The calcination time ranges from 0.5 to 5 hours during the first calcination process in step S21. The calcination time in the secondary calcination process of step S22 ranges from 0.5 to 3 hours.

[0011] In a possible implementation, the heating rate during the first calcination process in step S21 and the heating rate during the second calcination process in step S22 are both 7~10℃ / min.

[0012] In a possible implementation, before performing a secondary calcination treatment on the initial lithium selenide, the method further includes: grinding the initial lithium selenide to obtain ground lithium selenide.

[0013] In a possible implementation, the grinding time during the grinding process is 10-20 seconds.

[0014] In a possible implementation, the method satisfies at least one of the following characteristics: The multiple calcination treatments of the precursor source are carried out under an inert atmosphere. The process of obtaining the precursor source includes mixing the lithium nitride and selenium source to obtain the precursor source.

[0015] Based on the above technical solution, this application has the following beneficial effects: The method for preparing lithium selenide in this application includes: obtaining a precursor source, which includes lithium nitride and a selenium source; and subjecting the precursor source to multiple calcination treatments to obtain lithium selenide. This invention utilizes lithium nitride as a lithium source and a selenium source to undergo a redox reaction to generate lithium selenide and nitrogen gas. This method is low-cost, and the reaction is carried out at atmospheric pressure, eliminating the need for a high-pressure reactor. The prepared product does not produce carbon impurities, and the prepared lithium selenide can be directly used as a high-purity raw material in solid-state electrolytes. Furthermore, the reaction between lithium nitride and selenium involves low exothermic reaction, making the reaction easy to control and safer, thus avoiding the safety issues caused by the high exothermic reaction of elemental selenium and lithium in existing technologies. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0017] Figure 1 Images show the initial lithium selenide and the appearance of lithium selenide prepared in Example 3.

[0018] Figure 2 The image shows the XRD pattern of lithium selenide obtained in Example 3.

[0019] Figure 3 The XRD patterns of lithium selenide obtained in Examples 1-3 and Comparative Example 2 are shown.

[0020] Figure 4 This is an image of the initial lithium selenide obtained in Example 4.

[0021] Figure 5 The image shows the appearance of lithium selenide obtained in Comparative Example 1. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0025] The following describes a method for preparing lithium selenide according to embodiments of this application. The method includes: S1: Obtain precursor sources, including lithium nitride and selenium sources; In some embodiments, obtaining the precursor source includes mixing lithium nitride and a selenium source to obtain the precursor source. The lithium nitride and selenium source are mixed uniformly before a single calcination treatment, allowing them to fully contact each other before the redox reaction, maximizing the contact area of ​​the reactants, and improving the reaction rate and completeness.

[0026] In some embodiments, the mixing time for lithium nitride and selenium source is 5-10 minutes, and the mixing method is grinding. When the amount of precursor source is small, such as less than 20g, lithium nitride and selenium source can be mixed by manual grinding.

[0027] In some embodiments, the mixing time for lithium nitride and selenium source is 15-20 seconds, and the rotation speed during the mixing process is 20,000 r / min-30,000 r / min. When the amount of precursor source used is large and mass production is required, a pulverizer can be used to mix lithium nitride and selenium source.

[0028] In some embodiments, the mixing time for lithium nitride and selenium source is 20-40 minutes, and the mixing method is grinding. Preferably, the mixing time for lithium nitride and selenium source is 30 minutes.

[0029] Specifically, the rotation speed during the mixing process of lithium nitride and selenium source is 100~300 rpm / min. Preferably, the rotation speed during the mixing process of lithium nitride and selenium source is 200 rpm / min. By limiting the above mixing time, sufficient mixing of lithium nitride and selenium source is ensured.

[0030] In some embodiments, the mixing temperature of lithium nitride and selenium source is room temperature.

[0031] In some embodiments, the lithium nitride and selenium source are mixed by grinding or ball milling.

[0032] In some embodiments, the lithium nitride and selenium source are mixed by vibration or agitation. In this invention, the lithium nitride and selenium source are mixed and then added to the reaction vessel, where they are mixed by artificial vibration.

[0033] In some embodiments, the mixing process of lithium nitride and selenium source is carried out under an inert atmosphere. Performing the mixing of lithium nitride and selenium source under an inert atmosphere avoids the hydrolysis or oxidation of elemental selenium, which could lead to low purity of the final product.

[0034] Specifically, the inert atmosphere includes at least one of nitrogen, argon, or helium. Preferably, the inert atmosphere is nitrogen. Using nitrogen as a protective gas in an inert atmosphere can reduce preparation costs.

[0035] In some embodiments, the molar ratio between lithium nitride and selenium source is 2:(3~3.05). By accurately defining the molar ratio between lithium nitride and selenium source, the formation of various polyselenides, such as Li2Se2 and Li2Se8, is suppressed to the greatest extent, while also avoiding the presence of unreacted lithium nitride or elemental selenium residues, which could affect the purity of lithium selenide.

[0036] Specifically, the selenium source is elemental selenium.

[0037] S2: The precursor source is subjected to multiple calcination treatments to induce a redox reaction between lithium nitride and selenium source, thereby obtaining lithium selenide.

[0038] In some embodiments, the precursor source is subjected to multiple calcination processes to obtain lithium selenide, including: S21: The precursor source is calcined once to obtain initial lithium selenide; S22: The initial lithium selenide is subjected to a second calcination treatment to obtain lithium selenide. Because the initial mixing of selenium source and lithium nitride may result in poor uniformity, leading to unreacted selenium source or lithium nitride remaining after the first calcination, or the presence of metastable intermediate phases or incompletely reacted regions. Therefore, a second calcination treatment is necessary to ensure that any unreacted intermediate phases or incompletely reacted regions remaining after the first calcination can continue to react, thereby generating high-purity lithium selenide. As shown in the attached figure, after the first calcination treatment, the initial lithium selenide is a dark reddish-brown color, indicating that some selenium or lithium nitride remains unreacted. After complete reaction, it will turn into white lithium selenide.

[0039] In some embodiments, the calcination process includes: calcining the precursor source, and then cooling it to a first preset temperature after calcination to obtain initial lithium selenide. Specifically, the first preset temperature is room temperature.

[0040] In some embodiments, after calcining the precursor source, the method further includes mixing the precursor source and a leveling agent to obtain initial lithium selenide. If the product exhibits a color other than white, such as black, after calcining the precursor source, it indicates excessive lithium content, requiring the addition of selenium powder. This invention can adjust the lithium content or selenium powder in the reaction product based on the color of the calcined product, thereby ensuring that the final product is lithium selenide, rather than other intermediate products or incompletely reacted products.

[0041] Specifically, the leveling agent is selenium powder or lithium powder.

[0042] In some embodiments, the calcination temperature during the secondary calcination process is higher than that during the primary calcination process. Since the initial lithium selenide after the primary calcination process contains unreacted intermediate phases or regions that have not fully reacted, further increasing the temperature during the secondary calcination allows these unreacted intermediate phases or regions to gain the energy to overcome energy barriers at higher temperatures, enabling them to further react into lithium selenide and improve its purity. Simultaneously, because the initial lithium selenide has poor crystallinity, small grains, and numerous defects, the secondary calcination at a higher temperature allows atoms to gain sufficient kinetic energy, thereby driving grain growth and repairing crystal defects to improve the crystallinity of lithium selenide.

[0043] In some embodiments, the calcination temperature range in the primary calcination process of step S21 is 200~600℃. The upper limit of the calcination temperature can be, but is not limited to, 600℃, 599℃, 598℃, etc., and the lower limit of the calcination temperature can be, but is not limited to, 200℃, 201℃, 202℃, etc.; understandably, the calcination temperature can also be any value within the above range, which will not be enumerated here. By limiting the calcination temperature in the primary calcination process, adsorbed water, organic matter, etc., that may be present in the raw material can be removed, avoiding premature sintering and densification of the surface due to excessively high temperatures, which may trap impurity gases and result in incomplete removal of impurities, leading to poor crystallinity and low purity of the prepared lithium selenide. Preferably, the calcination temperature range in the primary calcination process of step S21 is 280~500℃. More preferably, the calcination temperature range in the primary calcination process of step S21 is 280~400℃. More preferably, the calcination temperature range in the primary calcination process of step S21 is 280℃. In some embodiments, the calcination time in step S21 during the first calcination process ranges from 0.5 to 5 hours. The upper limit of the calcination time can be, but is not limited to, 5 hours, 4.9 hours, 4.8 hours, etc., and the lower limit can be, but is not limited to, 0.5 hours, 0.6 hours, 0.7 hours, etc.; understandably, the calcination time can also be any value within the above range, which will not be enumerated here. Since solid-phase chemical reactions require sufficient time to overcome the potential barrier, allowing reactant atoms to diffuse and combine, a short first calcination time will lead to incomplete reactions, leaving a large amount of unreacted raw materials or intermediate phases in the product, while also ensuring relatively thorough impurity removal. Preferably, the calcination time in step S21 during the first calcination process ranges from 1 to 4 hours. More preferably, the calcination time in step S21 during the first calcination process ranges from 1 to 2 hours. More preferably, the calcination time in step S21 during the first calcination process ranges from 2 hours.

[0044] In some embodiments, the cooling time during the first calcination process in step S21 ranges from 2 to 4 hours. Preferably, the cooling time during the first calcination process in step S21 ranges from 3 hours.

[0045] In some embodiments, the secondary calcination process includes: calcining the initial lithium selenide, and then cooling it to a second preset temperature after calcination to obtain lithium selenide. Specifically, the second preset temperature is room temperature.

[0046] In some embodiments, the calcination temperature range in the secondary calcination process of step S22 is 300~700℃. The upper limit of the calcination temperature can be, but is not limited to, 700℃, 699℃, 698℃, etc., and the lower limit of the calcination temperature can be, but is not limited to, 300℃, 301℃, 302℃, etc.; understandably, the calcination temperature can also be any value within the above range, which will not be enumerated here. By limiting the above calcination temperature range, the reaction between lithium nitride and elemental selenium can be ensured to be complete, eliminating the compositional inhomogeneity that may exist in the first calcination, and obtaining lithium selenide with complete crystal form and high crystallinity. Preferably, the calcination temperature range in the secondary calcination process of step S22 is 400~650℃. More preferably, the calcination temperature range in the secondary calcination process of step S22 is 500~650℃. More preferably, the calcination temperature in the secondary calcination process of step S22 is 650℃.

[0047] In some embodiments, the calcination time in the secondary calcination process of step S22 ranges from 0.5 to 3 hours. The upper limit of the calcination time can be, but is not limited to, 3 hours, 2.9 hours, 2.8 hours, etc., and the lower limit can be, but is not limited to, 0.5 hours, 0.6 hours, 0.7 hours, etc.; understandably, the calcination time can also be any value within the above range, which will not be enumerated here. By limiting the secondary calcination time, on the one hand, it avoids the situation where the time is too short, resulting in too small grains and insufficient crystallinity of the product; on the other hand, it avoids the situation where the time is too long, resulting in excessive grain growth and poor battery performance when subsequently applied to solid-state batteries. Furthermore, excessive time will also reduce the generation efficiency. Simultaneously, the above time limitation ensures that the metastable phase or unreacted raw materials remaining after the primary calcination process can react completely. Preferably, the calcination time in the secondary calcination process of step S22 ranges from 1 to 2 hours. More preferably, the calcination time in the secondary calcination process of step S22 is 1 hour.

[0048] In some embodiments, the cooling time during the secondary calcination process in step S22 ranges from 2 to 4 hours. Preferably, the cooling time during the secondary calcination process in step S22 ranges from 3 hours.

[0049] In some embodiments, the heating rate during the first calcination process in step S21 and the heating rate during the second calcination process in step S22 are both 7~10℃ / min. By limiting the above heating rate, excessively rapid heating can prevent the reaction from becoming too fast, which may lead to a sharp increase in local temperature and thermal runaway. At the same time, an appropriate heating rate can allow atoms to diffuse sufficiently to form a uniform and dense lithium selenide structure. Furthermore, in the second calcination stage, if the heating is too rapid, it will result in too many or too few nucleation sites, leading to an excessively wide grain size distribution and affecting the consistency of material properties. If the heating rate is slow during the two calcination processes, it will result in poor crystallinity of the material and the appearance of impurity peaks, possibly due to incomplete reaction caused by a slow heating reaction rate.

[0050] In some embodiments, before performing a secondary calcination on the initial lithium selenide, the method further includes grinding the initial lithium selenide to obtain ground lithium selenide. Since the products of the initial reaction sinter together after the first calcination, forming large agglomerates containing unreacted raw materials and intermediate phase products, grinding effectively breaks down these agglomerates, exposing the unreacted raw materials and intermediate phase products. Simultaneously, the newly broken material surface has higher surface energy and stronger reactivity. Furthermore, grinding yields fine, uniform powder, which helps to obtain lithium selenide with uniform grain size and dense structure during the secondary calcination.

[0051] In some embodiments, the grinding time during the grinding process is 10-20 seconds. By limiting the grinding time during the grinding process, the unreacted raw materials and intermediate phase products in the above-mentioned agglomerates are fully exposed, allowing for a more complete reaction during the secondary calcination process. Preferably, the grinding time during the grinding process is 13-17 seconds. More preferably, the grinding time during the grinding process is 15 seconds.

[0052] In some embodiments, the grinding temperature during the grinding process is room temperature.

[0053] In some embodiments, the grinding process includes grinding the initial lithium selenide to a preset particle size to obtain ground lithium selenide. Specifically, the preset particle size (D50) is 7~10 μm.

[0054] In some embodiments, after the initial lithium selenide undergoes a secondary calcination treatment, the method further includes: crushing the initial lithium selenide after the secondary calcination treatment to obtain lithium selenide.

[0055] Specifically, the crushing process can be achieved through grinding, ball milling, or other methods, which are not specifically limited herein.

[0056] In some embodiments, the precursor source is subjected to multiple calcination processes under an inert atmosphere. This is to prevent selenium from being oxidized or hydrolyzed, which could generate impurities and reduce the purity of the resulting lithium selenide.

[0057] Specifically, the inert atmosphere includes at least one of nitrogen, argon, or helium. Preferably, the inert atmosphere is nitrogen.

[0058] In some embodiments, the prepared lithium selenide has a D50 particle size of 2-6 μm. Preferably, the prepared lithium selenide has a D50 particle size of 2-3 μm. More preferably, the prepared lithium selenide has a D50 particle size of 2.3 μm.

[0059] Existing methods for preparing lithium selenide suffer from high costs, low safety, and often leave carbon impurities in the reaction products, limiting their application in solid-state electrolytes. This application addresses these issues by subjecting lithium nitride and elemental selenium to multiple calcinations under normal pressure. In this process, lithium nitride and elemental selenium undergo a redox reaction to generate lithium selenide and nitrogen gas. The lithium selenide prepared using this method exhibits lower exothermic reaction temperatures, higher safety, and no carbon impurities are generated in the product. This allows the prepared lithium selenide to be used directly as a high-purity raw material in solid-state electrolytes, avoiding the safety problems associated with the high exothermic reaction of elemental selenium and lithium in existing technologies.

[0060] The following describes specific embodiments of this application in conjunction with the above-described method for preparing lithium selenide. The following embodiments further illustrate the technical solutions of this application. These embodiments are for illustrative purposes only, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. The reagents used in the embodiments are commercially available or synthesized using conventional methods and can be used directly without further processing. Similarly, the instruments and apparatus used in the embodiments are commercially available.

[0061] Example 1 This embodiment provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 0.66 mol lithium nitride (23.0 g) and 0.99 mol selenium powder (78.3 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: The reaction vessel containing the precursor source is placed in a muffle furnace, heated at a rate of 7°C / min, calcined at 400°C, and held at that temperature for 1 hour before being cooled to room temperature to obtain initial lithium selenide. S300: Under a nitrogen atmosphere, the initial lithium selenide is ground at room temperature for 15 seconds to obtain the ground selenide. The weight of the ground lithium selenide is 81.1 g and the particle size (D50) of the ground lithium selenide is 7.8 μm.

[0062] S400: The ground lithium selenide is added to a reaction vessel, heated at a rate of 10℃ / min, calcined at 500℃ and held at that temperature for 1 hour, then cooled to room temperature. The reaction product is removed from the reaction vessel and ground to obtain lithium selenide. The mass of the material is 79.4g. The particle size D of the final product lithium selenide is... 50 It is 2.3 μm.

[0063] Example 2 This embodiment provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 3.3 mol lithium nitride (115 g) and 4.96 mol selenium powder (391.6 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: The reaction vessel containing the precursor source is placed in a muffle furnace, heated at a rate of 7°C / min, calcined at 380°C, and held at that temperature for 2 hours before being cooled to room temperature to obtain initial lithium selenide. S300: Under a nitrogen atmosphere, the initial lithium selenide was ground at room temperature for 15 seconds to obtain the ground selenide. The weight of the ground lithium selenide was 453.7g and the particle size (D50) of the ground lithium selenide was 8.6μm. S400: The ground lithium selenide is added to a reaction vessel, heated at a rate of 10℃ / min, calcined at 550℃ for 2 hours, then cooled to room temperature. The reaction product is removed from the reaction vessel and ground to obtain lithium selenide. The mass of the material is 447.2g. The particle size D of the final product lithium selenide is... 50 It is 2.8μm.

[0064] Example 3 This embodiment provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 5.31 mol lithium nitride (185 g) and 7.97 mol selenium powder (630.0 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: The reaction vessel containing the precursor source is placed in a muffle furnace, the heating rate is 7℃ / min, and calcination is carried out at 280℃. After holding at this temperature for 2 hours, the temperature is lowered to room temperature to obtain the initial lithium selenide. S300: Under a nitrogen atmosphere, the initial lithium selenide was ground at room temperature for 15 seconds to obtain the ground selenide. The weight of the ground lithium selenide was 731.8 g and the particle size (D50) of the ground lithium selenide was 9.0 μm. S400: The ground lithium selenide is put into the reaction vessel, heated at a rate of 10℃ / min, calcined at 650℃, and kept at that temperature for 1 hour before being cooled to room temperature. The reaction product in the reaction vessel is taken out and ground to obtain lithium selenide. The material mass is 717.1g, and the particle size (D50) of the final product lithium selenide is 2.7μm.

[0065] Example 4 This embodiment provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 0.29 mol lithium nitride (10.0 g) and 0.42 mol selenium powder (33 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: The reaction vessel containing the precursor source is placed in a muffle furnace, the heating rate is 7℃ / min, and calcination is carried out at 400℃. After holding at 400℃ for 2 hours, the temperature is lowered to room temperature. Under the atmosphere of nitrogen, the reaction product in the reaction vessel is taken out, and 0.05 mol of elemental selenium powder is added to the reaction product to obtain the initial lithium selenide. S300: Under a nitrogen atmosphere, the initial lithium selenide was ground at room temperature for 15 seconds to obtain the ground selenide. The weight of the ground lithium selenide was 40.11 g and the particle size (D50) of the ground lithium selenide was 7.7 μm. S400: The ground lithium selenide is put into the reaction vessel, heated at a rate of 10℃ / min, calcined at 500℃, and kept at that temperature for 2 hours before being cooled to room temperature. The reaction product in the reaction vessel is taken out and ground to obtain lithium selenide. The material mass is 38.9g, and the particle size (D50) of the final product lithium selenide is 2.1μm.

[0066] Comparative Example 1 This comparative example provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 0.575 mol lithium nitride (20.0 g) and 0.862 mol selenium powder (68.1 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: Place the reaction vessel containing the precursor source into a muffle furnace, heat it at a rate of 20℃ / min, calcine it at 320℃, and hold it at that temperature for 1 hour.

[0067] The experimental results of this embodiment are attached. Figure 5 As shown, when the muffle furnace is heated to 213°C, the substances inside the reaction vessel begin to react violently and explode, causing the reaction vessel to melt through and the material to completely volatilize.

[0068] Comparative Example 2 This comparative example provides a method for preparing lithium selenide, the method comprising: S100: Under a nitrogen atmosphere, 0.43 mol lithium nitride (15.0 g) and 0.646 mol selenium powder (51.1 g) were mixed and poured into a reaction vessel. After sealing the reaction vessel, the mixture was mixed at room temperature using a pulverizer at a speed of 25000 r / min for 15 s to obtain the precursor source. S200: The reaction vessel containing the precursor source is placed in a muffle furnace, heated at a rate of 5℃ / min, calcined at 280℃, and held at that temperature for 1 hour before being cooled to room temperature to obtain initial lithium selenide. S300: Under a nitrogen atmosphere, the initial lithium selenide was ground at room temperature for 15 seconds to obtain the ground selenide. The weight of the ground lithium selenide was 58.9 g and the particle size (D50) of the ground lithium selenide was 8.4 μm. S400: The ground lithium selenide is put into the reaction vessel, heated at a rate of 7℃ / min, calcined at 400℃, and kept at that temperature for 1 hour before being cooled to room temperature. The reaction product in the reaction vessel is taken out and ground to obtain lithium selenide. The material mass is 58.2g, and the particle size (D50) of the final product lithium selenide is 2.6μm.

[0069] The experimental results of this embodiment are attached. Figure 3 As shown, attached Figure 3 The XRD characterization diagram of this embodiment shows that the peak intensity of the material is low and there are impurity peaks, indicating that the synthesized lithium selenide has low purity and poor crystallinity.

[0070] The above embodiments and comparative examples adopted the following test methods: 1. XRD Testing: X-ray diffraction data of lithium selenide obtained in Examples 1-3 and Comparative Example 2 were measured using an X-ray diffractometer. The conditions were: accelerating voltage 40 kV, Cu target, incident light wavelength between 0.1 and 1.54 nm. The test results are as follows: Figure 2-3 As shown, Figure 2 The image shows the XRD pattern of lithium selenide prepared in Example 3. Figure 3 The XRD patterns of lithium selenide prepared in Examples 1-3 and Comparative Example 2 (blue for Example 1, light purple for Example 2, brown for Example 3, and dark purple for Comparative Example 2) are shown below. Figure 2 and Figure 3 As can be seen from the XRD patterns, the peak positions and intensities of the lithium selenide prepared in Examples 1-3 are completely consistent with those of lithium selenide (Li₂Se), indicating that the lithium selenide prepared in Examples 1-3 is a pure phase substance without impurities. Figure 3 As can be seen from the data, the peaks of Example 3 are sharp and have high peak values, which proves that the lithium selenide prepared in Example 3 has the best crystallinity. In contrast, the lithium selenide prepared in Comparative Example 2 has broad peaks and low peak intensities, accompanied by impurity peaks, indicating that the lithium selenide synthesized in Comparative Example 2 has low purity and poor crystallinity.

[0071] 2. Appearance Results: The experimental results were obtained by observing the appearance of the lithium selenide prepared in the examples and comparative examples. The results are as follows: As attached Figure 1 As shown, attached Figure 1 The images show the lithium selenide prepared in Example 3. The left side of the image shows the morphology of the initial lithium selenide in Example 3, which is reddish-brown, indicating that there are unreacted selenium powder, lithium nitride, or intermediate products in the initial lithium selenide. The middle and right sides of the image show the lithium selenide after secondary calcination, which is white in appearance, indicating that there are no unreacted selenium powder, lithium nitride, or intermediate products in the lithium selenide, and that the purity is high. As attached Figure 4 As shown, attached Figure 4 The initial lithium selenide prepared in Example 4 shows a dark color, indicating an excess of lithium. Therefore, an appropriate amount of selenium powder was added to the initial lithium selenide to ensure complete reaction in subsequent reactions. (See attached image.) Figure 5 As shown, attached Figure 5 As shown in Comparative Example 1, when the muffle furnace was heated to 213°C, the substances inside the reaction vessel began to react violently and explode, causing the reaction vessel to melt and break through, and the materials to completely volatilize.

[0072] 3. Analysis of Experimental Results: Refer to Appendix Figure 1-5As can be seen from Examples 1-3, the peak value of Example 3 is higher than that of Examples 1-2. This may be because the secondary calcination temperature of Example 3 is higher, and the crystallinity of lithium selenide obtained after secondary calcination is higher.

[0073] As can be seen from Example 1 and Comparative Example 1, if the heating rate during calcination is too fast, it will lead to a violent reaction and a sharp increase in local temperature, which will result in thermal runaway and make it impossible to prepare lithium selenide.

[0074] Based on Example 1 and Comparative Example 2, it can be seen that the slow heating rate during the first calcination leads to poor crystallinity of the material and the appearance of impurity peaks, which may be due to the slow heating reaction rate causing incomplete material reaction.

[0075] The foregoing description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims. Accordingly, the scope of the claims of this application is not limited to the foregoing specific embodiments.

Claims

1. A method for preparing lithium selenide, characterized in that, The method includes: S1: Obtain a precursor source, wherein the precursor source includes lithium nitride and selenium source; S2: The precursor source is subjected to multiple calcination treatments to cause the lithium nitride and the selenium source to undergo a redox reaction to obtain the lithium selenide.

2. The method according to claim 1, characterized in that, The molar ratio between the lithium nitride and the selenium source is 2:(3~3.05).

3. The method according to claim 1, characterized in that, The process of subjecting the precursor source to multiple calcination treatments to obtain lithium selenide includes: S21: The precursor source is subjected to a calcination treatment to obtain initial lithium selenide; S22: The initial lithium selenide is subjected to a secondary calcination treatment to obtain the lithium selenide.

4. The method according to claim 3, characterized in that, The calcination temperature during the secondary calcination treatment is higher than the calcination temperature during the primary calcination treatment.

5. The method according to claim 3, characterized in that, The method satisfies at least one of the following characteristics: The calcination temperature range in the primary calcination process of step S21 is 200~600℃; The calcination temperature range in the secondary calcination process of step S22 is 300~700℃.

6. The method according to claim 3, characterized in that, The method satisfies at least one of the following characteristics: The calcination time ranges from 0.5 to 5 hours during the first calcination process in step S21. The calcination time in the secondary calcination process of step S22 ranges from 0.5 to 3 hours.

7. The method according to claim 3, characterized in that, The heating rate in the primary calcination process of step S21 and the heating rate in the secondary calcination process of step S22 are both 7~10℃ / min.

8. The method according to claim 3, characterized in that, Before performing a secondary calcination treatment on the initial lithium selenide, the method further includes: grinding the initial lithium selenide to obtain ground lithium selenide.

9. The method according to claim 8, characterized in that, The grinding time during the grinding process is 10-20 seconds.

10. The method according to any one of claims 1-9, characterized in that, The method satisfies at least one of the following characteristics: The multiple calcination treatments of the precursor source are carried out under an inert atmosphere. The process of obtaining the precursor source includes mixing the lithium nitride and selenium source to obtain the precursor source.

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