Hydride solid-state electrolyte, method for preparing the same, and use thereof

Abstract

The application relates to the field of solid electrolytes, and discloses a hydride solid electrolyte as well as a preparation method and application thereof. a B b H c The hydride solid electrolyte is synthesized by using a melting method under a decomposition temperature lower than B b H c a‑ The structure is an amorphous structure; the chemical general formula is LiAlCl3X.yLi a B b H c X includes at least one element among F, Cl, Br and I; a is greater than or equal to 1, b is greater than or equal to 1.34 and less than or equal to 1, and c is greater than or equal to 4 and less than or equal to 36. a B b H c The melting point of the electrolyte is reduced by forming a solid solution of LiAlCl3X and Li b H c a‑ The hydride electrolyte is synthesized by using a melting method under a decomposition temperature lower than B The hydride solid electrolyte has high ionic conductivity, a simple synthesis method and large-scale application prospect; in addition, the electrolyte has low electronic conductivity and is an ionic conductor.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a hydride solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in many fields and are a very important energy storage technology. Despite their widespread application, lithium dendrites generated during charging and discharging can puncture the separator, causing short circuits and posing safety hazards. Furthermore, the widespread use of ether- and ester-based organic electrolytes in commercially available lithium-ion batteries presents a risk of thermal runaway. Therefore, solid-state electrolytes that can prevent lithium dendrite punctures are a crucial direction for future battery development.

[0003] Currently, there are many types of solid-state electrolytes, including oxide electrolytes, sulfide electrolytes, halide electrolytes, hydride electrolytes, and composite electrolytes. Among them, hydride electrolytes have shown significant advantages in hydrogen storage and battery applications, primarily due to their high capacity, reversibility, and safety. Boronhydride is currently one of the most widely studied hydride electrolytes, with BH4 as its core component. - Alkali metal salts, typically represented by LiBH4, are used in this field. For example, patent CN114914435A discloses a LiBH4 solid electrolyte composite sheet and its preparation method, as well as a coin cell all-solid-state battery and its preparation method. The solid electrolyte composite sheet is composed of a positive electrode active material and a LiBH4 / LiNO3 solid electrolyte.

[0004] However, the conductivity of hydride solid electrolytes at room temperature is currently concentrated at 0.1 mS / cm, due to BH4 - The hydrogen atoms in LiBH4 have strong reducing properties, making it unstable in commercially available metal oxide cathodes (NCM, LFP, etc.). Furthermore, the decomposition temperature of LiBH4 is close to its melting temperature (275 ℃ vs. 268 ℃). To avoid LiBH4 decomposition, current main hydride electrolytes are synthesized using mechanical milling, which is energy-intensive, difficult to synthesize on a large scale, and does not meet commercialization requirements. Summary of the Invention

[0005] This invention aims to overcome the aforementioned problems of existing hydride solid electrolytes, and provides a hydride solid electrolyte, its preparation method, and its applications, using LiAlCl3X and Li a B b H c The formation of a solid solution lowers the melting point of the electrolyte, and a melting method is used to achieve a melting point below B. b H c a-The hydride electrolyte of this invention is synthesized under decomposition temperature conditions. The hydride solid electrolyte has high ionic conductivity, a simple synthesis method, and is promising for large-scale application. In addition, the electrolyte has low electronic conductivity and is an ionic conductor.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a hydride solid electrolyte, comprising LiAlCl3X and Li a B b H c Using the melt method at a temperature below B b H c a- Synthesized at the decomposition temperature, the structure is amorphous;

[0008] Its general chemical formula is: LiAlCl3X·yLi a B b H c Where: X includes at least one element selected from F, Cl, Br, and I; a≥1, 36≥b≥1, 34≥c≥4.

[0009] This invention uses LiAlCl3X and Li a B b H c The formation of a solid solution lowers the melting point of the electrolyte, and a melting method is used to achieve a melting point below B. b H c a- Hydride electrolytes were synthesized under decomposition temperature conditions. The molten state promotes free ion diffusion, and due to the anisotropic nature of ionic bonds, the crystal structure tends to rearrange during condensation, yielding a large amount of amorphous material. Benefiting from its amorphous structure, the amorphous material provides numerous lithium-ion migration channels, promoting lithium-ion migration. On the other hand, B... b H c a- It has low electronegativity and weak interaction with lithium ions, which further increases the diffusion rate of lithium ions and improves the conductivity of the electrolyte.

[0010] Ionic conductivity measures the ability of an electrolyte to transport ions. High ionic conductivity is beneficial for improving battery chemical kinetics and reducing polarization potential. Traditional hydride electrolytes have ionic conductivity below 0.1 mS / cm at room temperature. The hydride electrolyte of this invention achieves an ionic conductivity of 0.34 mS / cm at room temperature and exceeds 1 mS / cm at 45°C, demonstrating excellent ionic conductivity. Simultaneously, electronic conductivity measures the ability of a substance to transport electrons. High electronic conductivity in solid electrolytes can lead to direct electron transfer from the positive to the negative electrode, causing battery self-discharge and posing safety hazards. The invented hydride electrolyte, however, has extremely low electronic conductivity, acting as an ionic conductor, effectively avoiding the safety hazards caused by battery self-discharge.

[0011] As a preferred value, y = 0.5~2.7.

[0012] Preferably, diffraction peaks are present at 2θ = 30° ± 0.5°, 35° ± 0.5°, and 50° ± 0.5°.

[0013] Preferably, the hydride solid electrolyte has an ionic conductivity greater than 0.1 mS / cm.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned hydride solid electrolyte, comprising the following steps:

[0015] (1) The raw material Li a B b H c The mixture was thoroughly mixed and ground with LiAlCl3X in a certain proportion, and then pressed to obtain a block-shaped raw material.

[0016] (2) The block raw material is subjected to step-by-step heat treatment. The step-by-step heat treatment method is as follows: first heat at 100~180℃ for 1~24h, and then heat at 150~250℃ for 1~24h.

[0017] (3) The product after stepwise heat treatment is pulverized to obtain the hydride solid electrolyte.

[0018] Traditional hydride solid electrolytes are often synthesized using high-energy ball milling due to the high-temperature decomposition of LiBH4. High-energy ball milling consumes a large amount of energy, and the yield is low because the powder tends to agglomerate, limiting its commercial potential for large-scale synthesis. This invention uses low-temperature melt synthesis, avoiding the use of high-energy ball milling. The synthesis process requires a temperature of less than 200°C, resulting in low energy consumption. Furthermore, because of the melt synthesis method, the process involves only one step of heating and cooling, thus eliminating raw material loss and achieving extremely high yield, making it economically viable. Finally, unlike oxide electrolytes with high hardness, the plasticity of hydride electrolytes means that excessive pressure is not required during the powdering process, simplifying post-processing.

[0019] Preferably, the mechanical ball milling method used in step (1) is used to mill Li a B b H c The product is mixed and ground with LiAlCl3X. In step (3), mechanical ball milling is used to pulverize the product after stepwise heat treatment.

[0020] Preferably, the ball-to-material mass ratio during ball milling is 1~130:1, the ball milling time is 0.5~48h, and the ball milling speed is 100~700rpm.

[0021] Preferably, the pressure during pressing in step (1) is 10~300MPa.

[0022] Preferably, the preparation process in steps (1) to (3) is carried out in an inert atmosphere, where the water and oxygen content are both below 0.01 ppm.

[0023] Thirdly, the present invention provides an application of the above-mentioned hydride solid electrolyte in a solid-state battery.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] (1) Thanks to its amorphous structure, the amorphous material of the present invention can provide a large number of lithium ion migration channels, promote lithium ion migration, and improve the ionic conductivity of the hydride electrolyte; at the same time, the hydride electrolyte of the present invention has extremely low electronic conductivity and is an ionic conductor, which can effectively avoid the safety hazards caused by battery self-discharge.

[0026] (2) The hydride electrolyte of the present invention requires a synthesis temperature of less than 200°C during the synthesis process, resulting in low energy consumption. On the other hand, since the melt synthesis method is used, the synthesis process only involves one step of heating and cooling, so there is no loss of raw materials, the yield is extremely high, and it is economically efficient. Finally, unlike oxide electrolytes with high hardness, due to the plasticity of the hydride electrolyte, excessive pressure is not required during the pulverization process, the post-processing is simple, and it has the potential for large-scale synthesis. Attached Figure Description

[0027] Figure 1 This is a graph showing the relationship between the conductivity of the solid electrolyte and temperature in Examples 1-3 and Comparative Example 1 of the present invention.

[0028] Figure 2 These are the XRD patterns of the hydride solid electrolytes in Examples 1-3 of this invention.

[0029] Figure 3 This is the cyclic voltammetry curve of the hydride solid electrolyte in Example 1 of this invention.

[0030] Figure 4 It is the electronic conductivity of the hydride solid electrolyte at room temperature in Example 1 of this invention. Detailed Implementation

[0031] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0032] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0033] General Implementation Examples:

[0034] A hydride solid electrolyte, composed of LiAlCl3X and Li a B b H c Using the melt method at a temperature below B b H c a- Synthesized at the decomposition temperature, the structure is amorphous;

[0035] Its general chemical formula is: LiAlCl3X·yLi a B b H c Where: X includes at least one element selected from F, Cl, Br, and I; a≥1, 36≥b≥1, 34≥c≥4.

[0036] In one specific implementation, y = 0.5~2.7.

[0037] As one specific implementation, diffraction peaks exist at 2θ = 30° ± 0.5°, 35° ± 0.5°, and 50° ± 0.5°.

[0038] In one specific embodiment, the ionic conductivity of the hydride solid electrolyte is greater than 0.1 mS / cm.

[0039] The preparation method of the above-mentioned hydride solid electrolyte includes the following steps:

[0040] (1) The raw material Li a B b H c The mixture was thoroughly mixed and ground with LiAlCl3X in a certain proportion, and then pressed to obtain a block-shaped raw material.

[0041] (2) The block raw material is subjected to step-by-step heat treatment. The step-by-step heat treatment method is as follows: first heat at 100~180℃ for 1~24h, and then heat at 150~250℃ for 1~24h.

[0042] (3) The product after stepwise heat treatment is pulverized to obtain the hydride solid electrolyte.

[0043] As one specific implementation method, the mechanical ball milling method used in step (1) is used to mill Li a B b H c The product is mixed and ground with LiAlCl3X. In step (3), mechanical ball milling is used to pulverize the product after stepwise heat treatment.

[0044] In one specific implementation, the ball-to-material mass ratio during ball milling is 1~130:1, the ball milling time is 0.5~48h, and the ball milling speed is 100~700rpm.

[0045] In one specific implementation, the pressure during pressing in step (1) is 10~300MPa.

[0046] As a specific implementation method, the preparation process of steps (1) and (2) is carried out under an inert atmosphere, in which the water and oxygen contents are both less than 0.01 ppm.

[0047] Example 1:

[0048] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0049] (1) Take 87.12 mg of LiBH4 (4 mmol) and 351.4 mg of LiAlCl4 (2 mmol), mix them, and use a ball mill to mix and grind them. The ball-to-material mass ratio is 10:1, the speed is 100 rpm, and the ball milling time is 30 min. Then press it under 400 MPa pressure for 5 min to obtain a mixed white block solid.

[0050] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0051] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0052] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0053] Example 2:

[0054] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0055] (1) Take 43.56 mg of LiBH4 (2 mmol) and 351.4 mg of LiAlCl4 (2 mmol), mix them, and use a ball mill to mix and grind them. The ball-to-material mass ratio is 10:1, the speed is 100 rpm, and the ball milling time is 30 min. Then press it under 400 MPa pressure for 5 min to obtain a mixed white block solid.

[0056] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0057] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0058] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0059] Example 3:

[0060] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0061] (1) Take 21.78 mg of LiBH4 (1 mmol) and 351.4 mg of LiAlCl4 (2 mmol), mix them, and use a ball mill to mix and grind them. The ball-to-material mass ratio is 10:1, the speed is 100 rpm, and the ball milling time is 30 min. Then press it under 400 MPa pressure for 5 min to obtain a mixed white block solid.

[0062] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0063] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0064] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0065] Example 4:

[0066] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0067] (1) Take 311.2 mg of Li2B 12 H 12(2 mmol) was mixed with 351.4 mg of LiAlCl4 (2 mmol), and the mixture was ball-milled at a ball-to-material mass ratio of 10:1 at 100 rpm for 30 min; then it was pressed at 400 MPa for 5 min to obtain a mixed white blocky solid.

[0068] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0069] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0070] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0071] Example 5:

[0072] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0073] (1) Take 155.6 mg of Li2B 12 H 12 1 mmol of LiAlCl4 was mixed with 351.4 mg of LiAlCl4 (2 mmol) and ball-milled at a mass ratio of 10:1 at 100 rpm for 30 min. The mixture was then pressed at 400 MPa for 5 min to obtain a mixed white blocky solid.

[0074] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0075] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0076] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0077] Example 6:

[0078] A method for preparing a hydride solid electrolyte, comprising the following steps:

[0079] (1) Take 450.9 mg of Li4B 36 H 341 mmol of LiAlCl4 was mixed with 351.4 mg of LiAlCl4 (2 mmol) and ball-milled at a mass ratio of 10:1 at 100 rpm for 30 min. The mixture was then pressed at 400 MPa for 5 min to obtain a mixed white blocky solid.

[0080] (2) The mixed white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0081] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain powdered hydride solid electrolyte;

[0082] All operation steps in this embodiment are completed in a glove box filled with high-purity argon gas, where the water and oxygen content is less than 0.01 ppm.

[0083] Comparative Example 1:

[0084] A method for preparing a solid electrolyte, comprising the following steps:

[0085] (1) Take 351.4 mg of LiAlCl4 (2 mmol), mix and grind it using a ball mill with a ball-to-material mass ratio of 10:1 and a rotation speed of 100 rpm for 30 min; then press it under a pressure of 400 MPa for 5 min to obtain a white blocky solid;

[0086] (2) The white blocky solid was sealed in a reaction vessel, heated to 150°C and heat-treated for 2 hours; then heated to 200°C and heat-treated for 4 hours to obtain the blocky product.

[0087] (3) The block electrolyte was ball-milled at a mass ratio of 40:1 and a rotation speed of 250 rpm for 2 hours to obtain a powdered solid electrolyte;

[0088] All procedures in this comparative example were performed in a glove box filled with high-purity argon gas, with water and oxygen content in the argon gas both below 0.01 ppm.

[0089] The room temperature ionic conductivity of the solid electrolytes obtained in the above embodiments and comparative examples was tested, and the results are shown in Table 1.

[0090] Table 1: Test Results of Ionic Conductivity of Solid Electrolytes

[0091]

[0092] As shown in Table 1, changing the ratio of LiAlCl4 to LiBH4 used in the synthesis gradually increases the ionic conductivity of the electrolyte with increasing LiBH4 content, reaching a maximum ionic conductivity of 0.34 mS / cm at a 1:2 ratio. This indicates that the mixture melts during heating, allowing internal ions to move freely, and that during the cooling of the molten material to room temperature, the ions tend to rearrange. - In the structure, because hydrogen atoms carry a negative charge, they react with Al. 3+ The binding capacity increases. During the electrolyte structural rearrangement, BH4… - With AlCl4 - Al in 3+ By combining, a variety of [Al] can be obtained. a Cl b (BH4) c ] x- Multiple anionic clusters, mainly composed of Li, exhibit low charge density and therefore interact with Li. + The Coulomb force is low, Li + The migration is accelerated, and the ionic conductivity is improved.

[0093] Figure 1 The graph shows the relationship between the conductivity of the hydride solid electrolyte and temperature under different synthesis ratios. It can be observed that the electrolyte conductivity gradually increases with the increase of the LiBH4 content; however, after the content exceeds 2, the conductivity gradually decreases. This indicates that the hydride solid electrolyte has the highest conductivity when the LiBH4 to LiAlCl4 ratio is 2:1. This suggests that in the hydride electrolyte, BH4... - It plays a dominant role. At the same time, from... Figure 1 As can be seen, lithium borohydride and lithium tetrachloroaluminate have extremely low ionic conductivity at room temperature. Compared to these two raw materials, the hydride electrolyte of this invention exhibits significantly improved conductivity.

[0094] Figure 2 The figure shows the XRD data variations of the hydride solid electrolyte under different synthesis ratios. It can be seen that the hydride solid electrolyte prepared in this invention exhibits diffraction peaks at θ = 30°±0.5°, 35°±0.5°, and 50°±0.5°. Furthermore, it can be observed that when the proportion of LiBH4 is low, the electrolyte XRD data is dominated by LiAlCl4 and LiCl peaks. As the proportion of LiBH4 increases, the LiAlCl4 peak signal gradually weakens and disappears, leaving only the amorphous signal peaks in the low-angle region and the LiCl signal peaks. This indicates that the hydride electrolyte is an amorphous electrolyte. The amorphous structure, interconnected in a high-entropy manner, provides a faster transport channel for lithium ions, accelerating lithium ion migration.

[0095] Figure 3The cyclic voltammetry data for the electrolyte, spanning a voltage range of 3.0 V to 5.5 V, reveals an oxidation window greater than 4 V. Furthermore, the peak current disappears during subsequent cycles, indicating surface passivation of the electrolyte during cycling, inhibiting further decomposition. Generally, hydride electrolytes are unstable against high-voltage metal oxide cathodes due to the reducing agent BH4. - It can undergo redox reactions with high-valence metal ions, leading to electrolyte failure. The passivation layer formed on the surface of hydride electrolytes is the reason for their stability under high oxidation potentials.

[0096] Figure 4 The electronic conductivity of the hydride solid electrolyte in Example 1 at room temperature is shown. Compared to ionic conductivity, the electrolyte's electronic conductivity is very low, indicating that the electrolyte is an ionic conductor. Ionic conductors generate current through ion migration, while electrons cannot pass through, thereby suppressing battery self-discharge. Ionic conductors require an electrolyte electronic conductivity of less than 10. -8 S / cm.

[0097] The embodiments described herein merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A hydride solid electrolyte, characterized in that it is composed of... LiAlCl3X and Li a B b H c The material was synthesized by melting, first heating at 100~180℃ for 1~24h, and then heating at 150~250℃ for 1~24h; the structure was amorphous; diffraction peaks were observed at 2θ=30°±0.5°, 35°±0.5°, and 50°±0.5°. Its general chemical formula is: LiAlCl3X·yLi a B b H c Where: X includes at least one element from F, Cl, Br, I; a≥1, 36≥b≥1, 34≥c≥4; y=0.5~2.

7.

2. The hydride solid electrolyte according to claim 1, characterized in that, The ionic conductivity of the hydride solid electrolyte is greater than 0.1 mS / cm.

3. A method for preparing a hydride solid electrolyte as described in claim 1 or 2, characterized in that, Includes the following steps: (1) The raw material Li a B b H c The mixture was thoroughly mixed and ground with LiAlCl3X in a certain proportion, and then pressed to obtain a block-shaped raw material. (2) The block raw material is subjected to step-by-step heat treatment. The step-by-step heat treatment method is as follows: first heat at 100~180℃ for 1~24h, and then heat at 150~250℃ for 1~24h. (3) The product after stepwise heat treatment is pulverized to obtain the hydride solid electrolyte.

4. The method for preparing the hydride solid electrolyte according to claim 3, characterized in that, The mechanical ball milling method used in step (1) is used to process Li a B b H c The product is mixed and ground with LiAlCl3X. In step (3), mechanical ball milling is used to pulverize the product after stepwise heat treatment.

5. The method for preparing the hydride solid electrolyte according to claim 4, characterized in that, The ball-to-material mass ratio during ball milling is 1~130:1, the ball milling time is 0.5~48h, and the ball milling speed is 100~700rpm.

6. The method for preparing the hydride solid electrolyte according to claim 3, characterized in that, The pressure during pressing in step (1) is 10~300MPa.

7. The method for preparing the hydride solid electrolyte according to claim 3, characterized in that, The preparation processes in steps (1) to (3) are carried out under an inert atmosphere, where the water and oxygen content are both below 0.01 ppm.

8. The application of a hydride solid electrolyte as described in claim 1 or 2, or a hydride solid electrolyte prepared by any of the preparation methods described in claims 3 to 7, in a solid-state battery.

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