A solid electrolyte and its preparation method and application

Abstract

The present invention provides a solid electrolyte and its preparation method and application. The solid electrolyte of the present invention comprises a compound shown in formula 1; Li6P (1‑mx / 5) M x S5Cl, Formula 1; wherein 0 < x ≤ 1; m is the valence of element M, and M is selected from at least one of Sn, Sb, and Ge. This solid electrolyte has excellent ionic conductivity, stability, and safety.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and a preparation method and application thereof, belonging to the field of new energy technology. Background Art

[0002] Solid-state electrolytes are expected to replace the flammable liquid electrolytes used in existing lithium-ion batteries due to their potential advantages in safety, energy density, and lifespan. Among various types of solid-state electrolytes, sulfide electrolytes have been extensively studied due to their high ionic conductivity, good mechanical properties, and processability. Among them, lithium thiophosphate halide Li6PS5X (X=Cl, Br, I) electrolytes have attracted widespread attention due to their high ionic conductivity, wide electrochemical window, good formability, easy processing, and low cost.

[0003] However, existing sulfide electrolytes have the defect of poor stability. For example, when exposed to air, sulfide solid electrolytes are prone to hydrolysis reactions, generating toxic H2S gas, which causes its crystal structure to change, resulting in a decrease in the ionic conductivity of the sulfide solid electrolyte and reduced electrochemical performance of the battery. In addition, during the processing of sulfide electrolytes and the use of batteries, if the generated H2S gas cannot be handled in time, it will also lead to some safety issues.

[0004] O 2- With P 5+ Stronger bonding ability, with O 2- Partially replace S in sulfide electrolytes 2- , which can inhibit the generation of H2S gas, so oxides (Li2O and P2O5) are usually used to improve the stability and safety performance of sulfide electrolytes. Oxides will introduce oxygen atoms into the sulfide electrolyte, forming more stable non-bridging O in the sulfide electrolyte system. Although it improves the spatial stability of the sulfide electrolyte, the non-bridging oxygen atoms formed hinder the Li + The migration of sulfide electrolytes leads to a decrease in the conductivity of the electrolyte.

[0005] Zeolite, with its 3D porous structure, can act as a molecular sieve to absorb H2O and H2S, thus preventing side reactions. Therefore, existing technologies also use zeolite to improve the stability and safety of sulfide electrolytes. However, zeolite adsorption only prevents the escape of hydrogen sulfide. Over time, the zeolite's adsorption capacity decreases, and sulfide electrolytes still suffer from poor stability and safety. Summary of the Invention

[0006] The present invention provides a solid electrolyte having excellent ionic conductivity, stability and safety performance.

[0007] The present invention provides a method for preparing a solid electrolyte, which can prepare a solid electrolyte with excellent ionic conductivity, stability and safety performance.

[0008] The present invention provides a battery comprising the above-mentioned solid electrolyte, thereby having excellent safety performance and initial efficiency.

[0009] The present invention provides a solid electrolyte, comprising a compound represented by Formula 1;

[0010] Li6P (1-mx / 5) M x S5Cl, Formula 1;

[0011] Wherein, 0<x≤1; m is the valence of element M, and M is selected from at least one of Sn, Sb and Ge.

[0012] The solid electrolyte as described above, wherein the solid electrolyte has a symmetrical structure; and / or,

[0013] The solid electrolyte has Space group.

[0014] The solid electrolyte as described above, wherein 0<x≤0.1.

[0015] The present invention provides a method for preparing the solid electrolyte as described above, which comprises the following steps:

[0016] ball milling the solid electrolyte raw material to obtain a solid electrolyte precursor;

[0017] heat-treating the solid electrolyte precursor to obtain the solid electrolyte;

[0018] The solid electrolyte raw materials include Li2S, P2S5, LiCl and additives; the additives are selected from at least one of SnS2, Sb2S3 and GeS2.

[0019] In the preparation method as described above, the solid electrolyte raw material further includes S.

[0020] In the preparation method as described above, the ball milling agent used in the ball milling process is zirconium dioxide ball milling beads.

[0021] In the preparation method as described above, the ratio of the mass of the ball milling agent to the mass of the solid electrolyte raw material is (10-30):1.

[0022] The preparation method as described above, wherein the rotation speed of the ball milling treatment is 350-450 rpm.

[0023] The preparation method as described above, wherein the ball milling treatment time is 2-10 hours.

[0024] The preparation method as described above, wherein the temperature of the heat treatment is 500-650°C.

[0025] The preparation method as described above, wherein the heat treatment time is 3-10 hours.

[0026] The present invention provides a battery, comprising the solid electrolyte as described above, or comprising a solid electrolyte prepared by the preparation method as described above.

[0027] The present invention provides a solid electrolyte, comprising a compound shown in Formula 1; Li6P (1-mx / 5) M x S5Cl, Formula 1; wherein 0 < x ≤ 1; m is the valence of element M, and M is selected from at least one of Sn, Sb, and Ge. The inclusion of element M in the solid electrolyte of the present invention helps increase the migration rate of lithium ions, thereby improving the ionic conductivity of the solid electrolyte. Furthermore, because the MS bond has superior environmental stability compared to the PS bond, it is more difficult for the MS bond to break to generate H2S, thus reducing the amount of H2S released, thereby improving the stability and safety of the solid electrolyte.

[0028] The present invention provides a method for preparing a solid electrolyte, which can prepare the above-mentioned solid electrolyte. The preparation method has a simple process and is suitable for wide promotion and application.

[0029] The present invention provides a battery comprising the solid electrolyte, so the battery has excellent service life and initial efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 is the XRD pattern of the solid electrolyte obtained in Example 3 of the present invention;

[0032] Figure 2 : is the AC impedance diagram of the solid electrolyte obtained in Example 3 of the present invention;

[0033] Figure 3 : is an IT curve diagram of the solid electrolyte obtained in Example 3 of the present invention;

[0034] Figure 42 is a charge and discharge curve diagram of the battery prepared in the experimental example of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] A first aspect of the present invention provides a solid electrolyte comprising a compound represented by Formula 1;

[0037] Li6P (1-mx / 5) M x S5Cl, Formula 1;

[0038] Wherein, 0<x≤1; m is the valence of element M, and M is selected from at least one of Sn, Sb and Ge.

[0039] The existing sulfide electrolyte Li6PS5Cl has tetrahedral PS4 3- Unit. Generally speaking, adjacent PS4 3- Anions have higher ionic conductivity and better stability. 3- When the unit is bridged, P2S7 is generated 4- The anion, composed of two corner-sharing tetrahedra, has high ionic conductivity but is also more susceptible to hydrolysis. When sulfide electrolytes are exposed to air, P2S6 is formed. 4- and P2S6 2- Anions are poor ion conductors and will reduce the ionic conductivity of sulfide electrolytes. The central atom P in sulfide solid electrolytes is a strong acid. 2- Alkalinity ratio S 2- Compared with the P-S bond formed with the weak base S, P is more likely to form a P-O bond with the strong base O in the air or moisture. At the same time, S tends to bond with hydrogen in the air, resulting in the generation of H2S gas. Usually, these reactions will cause severe structural degradation, resulting in significant changes in the diffusion path and microstructure, causing the attenuation of the electrolyte air stability.

[0040] The present invention introduces M element into the solid electrolyte and uses M to replace P in Li6PS5Cl to prepare Li6P (1-mx / 5) M xS5Cl. It helps to form a strong MS bond in the solid electrolyte, thereby enhancing the stability of the solid electrolyte. According to the HSAB theory, M is a softer acid than P, and it is more stable when combined with the soft base S. That is to say, the substituted M in the lattice tends to combine with S rather than O. The selected metal M and S 2- The bonding between them is stronger, so the electrolyte has a stable crystal structure, that is, it has higher stability, is not easy to generate H2S, and thus has better safety performance.

[0041] In addition, compared with P, the heterovalent element M with a large atomic radius and low valence can expand the unit cell volume and increase the Li + Solubility, thereby reducing Li + motion activation energy and increase the corresponding ionic conductivity.

[0042] Therefore, the solid electrolyte of the present invention has excellent ionic conductivity, stability and safety performance.

[0043] It is worth mentioning that the doping of M element can not only improve the room temperature stability of the solid electrolyte, but also improve the thermal stability of the solid electrolyte.

[0044] In some embodiments of the present invention, when the solid electrolyte has a symmetrical structure, it is more conducive to the migration of lithium ions and improves the ionic conductivity of the solid electrolyte. When the space group is , the solid electrolyte has better ionic conductivity.

[0045] In some embodiments of the present invention, when 0<x≤0.1, the solid electrolyte has more excellent ion conductivity, stability and safety performance.

[0046] A second aspect of the present invention provides a method for preparing the above-mentioned solid electrolyte, which comprises the following steps:

[0047] ball milling the solid electrolyte raw material to obtain a solid electrolyte precursor;

[0048] heat-treating the solid electrolyte precursor to obtain a solid electrolyte;

[0049] The solid electrolyte raw materials include Li2S, P2S5, LiCl and additives; the additives are selected from at least one of SnS2, Sb2S3 and GeS2.

[0050] The preparation method of the solid electrolyte of the present invention specifically comprises: ball milling a solid electrolyte raw material comprising Li2S, P2S5, LiCl, and an additive to uniformly disperse the solid electrolyte raw material to form a solid electrolyte precursor; then heat treating the solid electrolyte precursor to cause a solid-phase reaction and crystallization to obtain a solid electrolyte. In some embodiments, the solid electrolyte raw material further comprises S.

[0051] The present invention does not particularly limit the specific method of ball milling. Ball milling methods commonly used in the art can be used. For example, at least one of tumbling ball milling, planetary ball milling, vibration ball milling, and stirring ball milling can be used for ball milling. In a specific embodiment, planetary ball milling can be used for ball milling.

[0052] The present invention does not particularly limit the specific method of heat treatment. Variable temperature heat treatment (i.e., including at least two of heating, constant temperature, and cooling) or constant temperature treatment can be selected.

[0053] The preparation method of the present invention can prepare a solid electrolyte with excellent ion conductivity, stability and safety performance, and the preparation method is simple, the preparation cost is low, and it is suitable for wide promotion and application.

[0054] In some embodiments of the present invention, the ball milling agent used in the ball milling process is zirconium dioxide ball milling beads.

[0055] In the present invention, zirconium dioxide ball milling beads are used as ball milling agents, which can improve the effect of ball milling treatment while saving costs, and is helpful for subsequent heat treatment.

[0056] In some embodiments of the present invention, the ratio of the mass of the ball milling agent to the mass of the solid electrolyte raw material is (10-30):1.

[0057] In the present invention, when the ratio of the mass of the ball milling agent to the mass of the solid electrolyte raw material is (10-30):1, the solid electrolyte raw material can be fully dispersed while saving the ball milling agent to form a solid electrolyte precursor with high uniformity, which is helpful for subsequent heat treatment and further improves the stability, safety performance and ion conductivity of the solid electrolyte.

[0058] In some embodiments of the present invention, when the ball milling speed is 350-450 rpm; and / or,

[0059] The ball milling time is 2-10 hours, which can fully disperse the solid electrolyte raw materials while saving energy, forming a solid electrolyte precursor with high uniformity, which is helpful for the subsequent heat treatment process and can improve the stability, safety performance and ion conductivity of the solid electrolyte.

[0060] In some embodiments of the present invention, when the heat treatment temperature is 500-650° C.; and / or,

[0061] When the heat treatment time is 3-10 hours, it helps the solid electrolyte precursor to undergo a better solid-phase reaction and crystallize to obtain a solid electrolyte, which helps to improve the stability, ion conductivity and safety performance of the solid electrolyte.

[0062] It can be understood that when the heat treatment is variable temperature heat treatment, the heat treatment time is the sum of the heating time, the constant temperature time and the cooling time.

[0063] A third aspect of the present invention provides a battery, which includes the above-mentioned solid electrolyte, or includes a solid electrolyte prepared by the above-mentioned preparation method.

[0064] The battery of the present invention, because it includes the above-mentioned solid electrolyte, has excellent ion conductivity and safety performance, and the manufacturing cost of the battery is low, and is suitable for wide promotion and application.

[0065] The technical solutions of the present invention are further illustrated below with reference to specific examples. All parts, percentages, and ratios described in the following examples are based on weight. All reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment. The instruments used in the examples are also commercially available.

[0066] Example 1

[0067] The solid electrolyte of this embodiment is prepared by a method comprising the following steps:

[0068] In an argon-filled glove box, the Li6P 0.992 Sn 0.01 Solid electrolyte raw materials Li2S, P2S5, LiCl and SnS2 were weighed in a molar ratio corresponding to S5Cl, and the solid electrolyte raw materials were added to a ball milling jar. Zirconium dioxide ball milling beads were added to the ball milling jar, which was sealed and attached to a planetary ball mill for ball milling. The ball milling jar was then opened in an argon-filled glove box to obtain a solid electrolyte precursor;

[0069] The ratio of the mass of the zirconium dioxide ball milling beads to the mass of the solid electrolyte raw material is 20:1; the ball milling speed is 400 rpm and the time is 5 hours;

[0070] In a glove box, a solid electrolyte precursor is placed into a sintered crucible, and the crucible is placed in a box furnace for heat treatment to obtain a solid electrolyte;

[0071] The heat treatment temperature was 500°C, the time was 5 h, and the heating rate was 5°C / min.

[0072] The solid electrolyte was ground into powder using an agate mortar in a glove box.

[0073] Example 2

[0074] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 1, except that the amount of SnS2 is 0.025 mol, and Li6P is prepared. 0.98 Sn 0.025 S5Cl solid electrolyte.

[0075] Example 3

[0076] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 1, except that the amount of SnS2 is 0.05 mol, and Li6P is prepared. 0.96 Sn 0.05 S5Cl solid electrolyte.

[0077] The phase composition of the solid electrolyte obtained in this example was tested using XRD. Figure 1 The XRD pattern of the solid electrolyte obtained in Example 3 of the present invention is shown in FIG. Figure 1 It can be seen that the solid electrolyte obtained in the embodiment of the present invention has a highly symmetrical crystal structure.

[0078] The AC impedance of the solid electrolyte obtained in this example was tested. Electrochemical testing of the sulfide electrolyte was performed using a Princeton electrochemical workstation to determine its ionic conductivity. A certain amount of sulfide solid electrolyte was weighed and poured into a battery mold. The tablets were pressed under a certain pressure, and their thickness was measured. The cells were then assembled into a blocking electrode / sulfide electrolyte / blocking electrode configuration for electrochemical testing. Figure 2 The AC impedance diagram of the solid electrolyte obtained in Example 3 of the present invention is shown in FIG. Figure 2 It can be seen that the solid electrolyte obtained in the embodiment of the present invention has excellent ionic conductivity.

[0079] The IT curve of the solid electrolyte obtained in this example was measured. Electrochemical testing of the sulfide electrolyte was performed using a Princeton electrochemical workstation to determine its electronic conductivity. A certain amount of sulfide solid electrolyte was weighed and poured into a battery mold. The tablet was pressed under a certain pressure, and its thickness was measured. The tablet was then assembled into a cell configuration (blocking electrode / sulfide electrolyte / blocking electrode) for electrochemical testing. Figure 3 It is the IT curve of the solid electrolyte obtained in Example 3 of the present invention. Figure 3 It can be seen that the solid electrolyte obtained in the embodiment of the present invention has excellent electronic insulation properties.

[0080] Example 4

[0081] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 1, except that the amount of SnS2 is 0.075 mol, and Li6P is prepared. 0.94 Sn 0.075 S5Cl solid electrolyte.

[0082] Example 5

[0083] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 1, except that the amount of SnS2 is 0.01 mol, and Li6P is prepared. 0.92 Sn 0.1 S5Cl solid electrolyte.

[0084] Example 6

[0085] The preparation method of the solid electrolyte of this embodiment is basically the same as that of Example 1, except that:

[0086] In an argon-filled glove box, the Li6P 0.99 Sb 0.01 The solid electrolyte raw materials Li2S, P2S5, LiCl, S and Sb2S3 were weighed in the molar ratio corresponding to S5Cl.

[0087] Example 7

[0088] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 6, except that the amount of Sb2S3 is 0.025 mol, and Li6P is prepared. 0.975 Sb 0.025 S5Cl solid electrolyte.

[0089] Example 8

[0090] The preparation method of the solid electrolyte of this embodiment is basically the same as that of Example 6, except that the amount of Sb2S3 is 0.05 mol, and Li6P is prepared. 0.95 Sb 0.05 S5Cl solid electrolyte.

[0091] Example 9

[0092] The preparation method of the solid electrolyte of this embodiment is basically the same as that of Example 6, except that the amount of Sb2S3 is 0.075 mol, and Li6P is prepared. 0.925 Sb 0.075 S5Cl solid electrolyte.

[0093] Example 10

[0094] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 6, except that the amount of Sb2S3 is 0.1 mol, and Li6P is prepared. 0.9 Sb 0.1 S5Cl solid electrolyte.

[0095] Example 11

[0096] The preparation method of the solid electrolyte of this embodiment is basically the same as that of embodiment 6, except that the amount of Sb2S3 is 0.25 mol, and Li6P is prepared. 0.75 Sb 0.25 S5Cl solid electrolyte.

[0097] Example 12

[0098] The preparation method of the solid electrolyte of this embodiment is basically the same as that of Example 1, except that:

[0099] In an argon-filled glove box, the Li6P 0.95 Ge 0.05 The solid electrolyte raw materials Li2S, P2S5, LiCl and GeS2 were weighed in the molar ratio corresponding to S5Cl.

[0100] Comparative Example 1

[0101] The solid electrolyte in this comparative example is Li6PS5Cl.

[0102] Comparative Example 2

[0103] The preparation method of the solid electrolyte of this embodiment is basically the same as that of Example 1, except that:

[0104] In an argon-filled glove box, the Li6PS 4.75 O 0.25 The solid electrolyte raw materials Li2S, P2S5, LiCl and Li2O were weighed according to the molar ratio corresponding to Cl.

[0105] Test example

[0106] 1. Batteries were prepared using the solid electrolytes obtained in Example 3 and Comparative Example 1, respectively. The steps include: mixing the solid electrolyte with the ternary positive electrode material Ni83 in a mass ratio of 3:7 to obtain a positive electrode composite material; using an In alloy as a negative electrode material; weighing a certain amount of solid electrolyte, pouring it into a battery mold, and pressing it into a sheet under a certain pressure to obtain a solid electrolyte layer. The solid electrolyte layer was placed between a positive electrode sheet formed by the positive electrode composite material and a negative electrode sheet formed by the negative electrode material to obtain a battery.

[0107] The prepared battery was placed in a conventional environment at 25°C, and constant current charge and discharge measurements were performed in the range of 1.9V to 3.65V with a charge and discharge rate of 0.1C to test the charge and discharge curve of the battery. Figure 4 The charge and discharge curve of the battery prepared in the test example of the present invention is shown in FIG. Figure 4 It can be seen that compared with the solid electrolyte obtained in Comparative Example 1, the solid electrolyte obtained by using Example 3 further improves the electrochemical performance of the battery.

[0108] 2. The ionic conductivity of the solid electrolytes obtained in the examples and comparative examples before and after storage was tested using a Princeton electrochemical workstation, and the ionic conductivity retention rate (environmental stability) was calculated. The results are shown in Table 1.

[0109] Specifically, the initial ionic conductivity of the solid electrolyte was tested using an electrochemical workstation; then, in a glove box, 2 g of the solid electrolyte material was weighed and placed in an open container. The container was then placed in a 100 L reaction box equipped with a hydrogen sulfide detection device and air with a specific humidity. The container was allowed to stand at room temperature for 24 hours. After the standing period, the sample was taken out and the ionic conductivity of the solid electrolyte after storage was tested; the ionic conductivity retention rate (environmental stability) before and after storage was calculated. The results are shown in Table 1.

[0110] Table 1

[0111]

[0112] It can be seen from Table 1 that the solid electrolyte prepared in the embodiment of the present invention has excellent ionic conductivity and environmental stability, and has excellent safety performance.

[0113] Each embodiment in this specification is described in a related manner. Similar parts between the embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A solid electrolyte, characterized in that Including the compound shown in formula 1; Li6P (1-mx / 5) M x S5Cl, formula 1; Wherein, 0<x≤1; m is the valence of element M, and M is selected from at least one of Sn and Ge.

2. The solid electrolyte according to claim 1, characterized in that The solid electrolyte has a symmetrical structure; and / or, The solid electrolyte has Space group.

3. The solid electrolyte according to claim 1 or 2, characterized in that 0＜x≤0.1。 4. A method for preparing the solid electrolyte according to any one of claims 1 to 3, characterized in that: The following steps are involved: ball milling the solid electrolyte raw material to obtain a solid electrolyte precursor; heat-treating the solid electrolyte precursor to obtain the solid electrolyte; The solid electrolyte raw materials include Li2S, P2S5, LiCl and additives; the additives are selected from at least one of SnS2 and GeS2.

5. The preparation method according to claim 4, characterized in that The solid electrolyte raw material also includes S.

6. The preparation method according to claim 4 or 5, characterized in that The ball milling agent used in the ball milling process is zirconium dioxide ball milling beads.

7. The preparation method according to claim 6, characterized in that The ratio of the mass of the ball milling agent to the mass of the solid electrolyte raw material is (10-30):

1.

8. The preparation method according to any one of claims 4 to 7, characterized in that The ball milling process is performed at a rotation speed of 350-450 rpm; and / or The ball milling treatment time is 2-10 hours.

9. The preparation method according to any one of claims 4 to 8, characterized in that The heat treatment temperature is 500-650°C; and / or, The heat treatment time is 3-10h.

10. A battery, characterized in that: The solid electrolyte comprises the solid electrolyte according to any one of claims 1 to 3, or the solid electrolyte prepared by the preparation method according to any one of claims 4 to 9.

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