Sulfide solid electrolyte, its preparation method and use

Abstract

The present invention specifically relates to a sulfide solid electrolyte and its preparation method and use. The electrolyte material of the present invention is Li6P l-a (M) a S5X (wherein M is one or more of V, Nb, and Ta, and X is one or more of F, Cl, and Br). The sulfide solid electrolyte material provided by the present invention partially replaces the P element with group 5 elements, and when ensuring that the sulfide electrolyte material has a good argillite crystal phase, the controllable doping of elements such as vanadium, niobium, and tantalum improves the compatibility with lithium-based negative electrodes, has better electrochemical stability, and further improves the cycle stability of the sulfide solid-state battery.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to a Chinese patent application filed with the China Patent Office on May 13, 2022, bearing application number 202210519948.2 and entitled "Sulfide solid electrolyte and preparation method and use thereof," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of energy technology, specifically to a sulfide solid electrolyte and its preparation method and use, and more particularly to a method for preparing a Group 5 element-halogen doped sulfide solid electrolyte and its application in a full battery. [Background technology]

[0003] Lithium-ion batteries are widely used in portable electronic devices and are increasingly attracting attention for applications in energy storage systems and electric vehicles. All-solid-state batteries with solid electrolytes are candidates for next-generation batteries with high energy density and safety. In addition, solid electrolytes significantly improve safety by replacing flammable and volatile liquid electrolytes in traditional lithium-ion batteries. Among various types of solid electrolytes, sulfide solid electrolytes have been widely studied due to their high ionic conductivity. Sulfide solid electrolytes also have great advantages in terms of processing due to their good mechanical properties.

[0004] In recent years, LPSC-type sulfide solid electrolytes have been attracting attention as one of the promising sulfide electrolytes due to their high ionic conductivity and air stability. However, LPSC-type sulfide solid electrolytes have many problems, such as poor compatibility with negative electrode materials and poor cycle stability. These problems are major challenges for future practical use. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention is aimed at overcoming the shortcomings of the prior art and providing a sulfide solid electrolyte and its preparation method and use. The composition of the Group 5 element-halogen doped sulfide solid electrolyte of the present invention is Li6P l-a (M) a S5X (M is one or more of vanadium, niobium, and tantalum elements, and X is one or more of F, Cl, and Br). The sulfide solid electrolyte material provided by the present invention partially replaces the P element with group 5 elements, and when ensuring that the sulfide electrolyte material has a good argillite crystal phase, the controllable doping of elements such as vanadium, niobium, and tantalum improves the compatibility with lithium-based negative electrodes and achieves better electrochemical stability. Furthermore, it improves the cycle stability of sulfide solid-state batteries. [Means for solving the problem]

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions: The present invention is based on the composition Li6P l-a (M) a A sulfide solid electrolyte is provided, which is S5X (wherein M is one or more of the elements V, Nb, and Ta, and X is one or more of the elements F, Cl, and Br).

[0007] Compared with other metal elements, doping with M element, which is a group 5 element, can generate a layer of M2O5 on the surface of the sulfide electrolyte, improving the cycle stability of the electrolyte and also providing good compatibility with the lithium anode. The proportion of lithium element in the crystal lattice increases with increasing doping amount of M element.

[0008] Preferably, the value of a ranges from 0 <a<1である。

[0009] The present invention further provides a method for preparing the sulfide solid electrolyte, Li6P l-a (M) aStep S1: weighing and uniformly mixing the raw materials Li, P, S, M, and X sources according to the stoichiometric ratio of S5X, and then performing a ball milling process to obtain a precursor powder of the sulfide solid electrolyte; Step S2 of sieving the precursor powder and pressing the powder into a sheet-like solid; and step S3 of sintering the sheet-like solid at high temperature in vacuum to obtain the sulfide solid electrolyte.

[0010] Preferably, in step S1, the raw material of the solid electrolyte contains the following components: Lithium source: one or more of LiH, Li2S2, and Li2S S source: one or more of S, H2S, P2S5, P4S9, P4S3, Li2S2, and Li2S P source: one or more of P, P2S5, P4S9, P4S3, P4S6, P4S5 X source: one or more of LiCl, LiBr, LiI, LiF, VCl5, NbCl5, and TaCl5 M source: one or more of VF5, NbCl5, and TaCl5.

[0011] In one embodiment of the present invention, in step S1, the rotation speed of the ball milling process is 380 to 1500 rpm, and the ball milling time is 7 to 48 hours. Prior to the ball milling, the material is first polished manually, and then mechanically milled. The manual polishing time is 15 to 30 minutes, and a planetary ball mill is used for the mechanical ball milling.

[0012] Preferably, in step S2, the pressure of the press is 300-500 MPa. If the pressure is too high, the mold is easily damaged, and if the pressure is too low, the compression is easily insufficient, resulting in the inability to form an effective crystal phase during the sintering process.

[0013] Preferably, in step S2, the thickness of the sheet-like solid is 200 to 1000 μm. If the thickness is too large, it is likely to cause difficulty in demolding and insufficient sintering during the sintering process, which may lead to crushing or breaking of the electrolyte sheet.

[0014] Preferably, in step S2, the sieving uses a sieve having a size of 300 to 1200 mesh to sieve the precursor powder.

[0015] Preferably, a polishing step is also included prior to sieving, specifically using an agate mortar.

[0016] Preferably, in step S3, the sheet-like solid is specifically sealed in a vacuum quartz tube, and then placed in a muffle furnace for high-temperature sintering to obtain the sulfide solid electrolyte.

[0017] Preferably, in step S3, the high-temperature sintering is performed at a temperature of 350-700° C. for 1-8 hours. The heating rate is 0.5-5° C. / min. If the temperature is too high or too low, it will affect the formation of effective crystalline phases of the intended electrolyte, and if the heating rate is too fast or too slow, it will also affect the formation of crystalline phases.

[0018] Preferably, in step S3, after the high-temperature sintering is completed, the temperature is lowered to room temperature at a rate of 0.5 to 5° C. / min.

[0019] Preferably, in steps S1 to S3, the weighing, uniform mixing, ball milling, sieving, pressing, and high-temperature sintering are all carried out under the protection of an inert atmosphere.

[0020] The present invention further provides an application of the sulfide solid electrolyte described in the above embodiment or the sulfide solid electrolyte prepared by the preparation method described in the above embodiment in the manufacture of a full battery.

[0021] The present invention further provides a solid-state battery including a positive electrode for a battery, a negative electrode for a battery, and a battery electrolyte, wherein at least one of the positive electrode for the battery, the negative electrode for the battery, and the battery electrolyte includes the sulfide solid electrolyte described in the above aspect.

[0022] Preferably, the weight of the solid electrolyte in the positive electrode for the battery is 0 to 40% by weight based on the total weight. x Co y Mn 1-x-y O2, LiNi x Co y Al 1-x-y O2, LiNi 0.5 Mn 1.5 O4, LiFe x Mn 1-x It is one or a mixture of two or more types of PO4.

[0023] Preferably, the negative electrode portion comprises a mixture of a negative electrode active material and the above-mentioned sulfide solid electrolyte, the negative electrode active material being a lithium-based alloy negative electrode material.

[0024] The present invention obtains a sulfide electrolyte by incorporating a halogen element and a group 5 element into a sulfide solid electrolyte. The process required for preparing the electrolyte is simple. The ionic conductivity reaches the same level as or even higher than that of electrolytes in the field. The doping of the halogen element and the incorporation of the group 5 element improve the cycle stability and ductility of the electrolyte sheet during battery operation. Thus, the present invention prepares a sulfide solid electrolyte doped with a small amount of a halogen element and a group 5 element, which has good ionic conductivity, cycle stability, and good processability at room temperature. Effect of the Invention

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) By doping with a Group 5 element, the atmospheric stability and cycle stability of the target sulfide solid electrolyte are improved.

[0027] 2) The prepared sulfide solid electrolyte material can be doped with halogen to improve the cycle stability in all-solid-state batteries.

[0028] 3) The incorporation of sulfide solid electrolyte in the preparation of the positive electrode improves the overall electrochemical performance of the battery. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a graph showing the cycle efficiency of Example 1, Example 2 and Comparative Example 1. [Diagram 2] FIG. 2 is a diagram showing the impedance of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention will be described in detail below with reference to the drawings and specific examples. The following examples are carried out on the basis of the technical solution of the present invention, and provide detailed embodiments and specific operation processes to help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following examples, and any slight adjustments or improvements made based on the concept of the present invention are within the scope of protection of the present invention. EXAMPLES

[0031] In this embodiment, Li6P 0.8 V 0.2 A S5F solid electrolyte is provided, and the specific steps of its preparation method are as follows: The pure reagents Li2S, P2S5 and VF5 were weighed and mixed according to the stoichiometric ratio Li2S:P2S5:VF5=3:0.4:0.2, and then manually ground for 15 minutes. The mixture was placed in a zirconia ball mill tank, and zirconia balls were added in a mass ratio of 1:50 for ball milling. The ball milling rotation speed was set to 550 rpm. After ball milling for 17 hours, the sample attached to the tank wall was scraped off, and then manually ground for 15 minutes using a mortar. After sieving through a 400 mesh sieve, a uniformly mixed precursor was obtained. The mixture was then compressed into tablets (diameter 12 mm) at a pressure of 350 MPa. The mixture was charged into a quartz tube and sealed. The mixture was heated to 550°C at a rate of 0.5 / min, kept at 400°C for 7 hours, and cooled, and then Li6P 0.8 V 0.2 S5F solid electrolyte powder was obtained. XRD confirmed that the solid electrolyte powder prepared by this method is a cubic phase of argon germanite with good crystal shape and high purity. The solid electrolyte powder is pressed under a pressure of 580 MPa and held for 3 minutes to obtain a solid electrolyte sheet. All the above manufacturing processes were carried out under an argon protective atmosphere.

[0032] At room temperature, the lithium ion conductivity of the solid electrolyte sheet is 5×10 -3 S / cm (The AC impedance of the sulfide electrolyte was measured at temperatures of 298-375K and frequencies of 1MHz-10Hz using a multi-channel electrochemical workstation). The cycle efficiency is shown in FIG. 1, which shows that the full battery exhibits excellent stability over 50 cycles. The impedance is shown in FIG. 2, which shows that the solid electrolyte sheet prepared in Example 1 has high ionic conductivity. EXAMPLES

[0033] In this embodiment, Li6P 0.8 Ta 0.2 A S5F solid electrolyte is provided, and the specific steps of its preparation method are as follows: The pure reagents Li2S, P2S5 and VF5 were weighed and mixed according to the stoichiometric ratio Li2S:P2S5:TaF5=3:0.4:0.2, and then manually ground for 15 minutes. The mixture was placed in a zirconia ball mill tank, and zirconia balls were added in a mass ratio of 1:50 for ball milling. The ball milling rotation speed was set to 550 rpm. After ball milling for 17 hours, the sample attached to the tank wall was scraped off, and then manually ground for 15 minutes using a mortar. After sieving through a 400 mesh sieve, a uniformly mixed precursor was obtained. The mixture was then compressed into tablets (diameter 12 mm) at a pressure of 350 MPa. The mixture was charged into a quartz tube and sealed. The mixture was heated to 550°C at a rate of 0.5 / min, kept at 400°C for 7 hours, and cooled, and then Li6P 0.8 Ta 0.2 S5F solid electrolyte powder was obtained. XRD showed that the solid electrolyte powder prepared by this method was argenteuil-germanite cubic phase with good crystal morphology and high purity. The solid electrolyte powder was pressed under a pressure of 580 MPa and held for 3 min to obtain a solid electrolyte sheet. All the above fabrication processes were carried out under an argon protective atmosphere. The lithium ion conductivity of the solid electrolyte sheet at room temperature was 5.3 × 10 -3 S / cm (The AC impedance of the sulfide electrolyte was measured at temperatures of 298 to 375 K and frequencies of 1 MHz to 10 Hz using a multichannel electrochemical workstation).

[0034] The Li6PS5F solid electrolyte, the specific steps of the preparation method are as follows: The pure reagents Li2S, P2S5 and LiF were weighed according to the required stoichiometric ratio, mixed, and then manually ground for 15 minutes. The mixture was placed in a zirconia ball mill tank, and zirconia balls were added in a mass ratio of 1:50 for ball milling. The ball milling rotation speed was set to 550 rpm. After ball milling for 17 hours, the sample attached to the tank wall was scraped off, and then manually ground for 15 minutes using a mortar. After sieving through a 400 mesh sieve, a uniformly mixed precursor was obtained. The mixture was then compressed into tablets (diameter 12 mm) at a pressure of 350 MPa. The mixture was placed in a quartz tube and sealed. The temperature was raised to 550 °C at a rate of 0.5 / min, kept at 400 °C for 7 hours, and after cooling, Li6PS5F solid electrolyte powder was obtained. The solid electrolyte powder was pressed at a pressure of 580 MPa and held for 3 minutes to obtain a solid electrolyte sheet. All the above manufacturing processes were carried out under an argon protective atmosphere. At room temperature, the lithium ion conductivity of the solid electrolyte sheet provided in Comparative Example 1 is 1.5×10 -3 S / cm. Comparative Example 2

[0035] Li6P 0.8 Sb 0.2 The preparation method was the same as in Example 1, and the only difference between the raw materials was that the raw materials in Comparative Example 2 were Li2S:P2S5:SbF5=3:0.4:0.2. At room temperature, the lithium ion conductivity of the solid electrolyte sheet obtained in Comparative Example 2 was 1.1×10 -3 It was S / cm.

[0036] The specific embodiments of the present invention have been described above. The present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications and changes within the scope of the claims, which do not affect the substantial content of the present invention.

Claims

1. A sulfide solid electrolyte, wherein the composition of the sulfide solid electrolyte is Li ６ P ｌ－ａ M ａ S ５ X, where M is one or more of the elements V, Nb, Ta, and X is one or more of F, Cl, Br, where the value range of a is 0 < a < 1, a method for preparing a sulfide solid electrolyte, step S1 of weighing Li source, P source, S source, M source, and X source as raw materials according to the stoichiometric ratio of Li6P1-aMaS5X, uniformly mixing them, and then performing ball milling treatment to obtain a sulfide solid electrolyte precursor powder; step S2 of sieving the precursor powder and then pressing the powder into a sheet-like solid; step S3 of sintering the sheet-like solid at a high temperature in a vacuum to obtain the sulfide solid electrolyte, a sulfide solid electrolyte, wherein in step S2, the pressure of pressing is 300 to 500 MPa.

2. In step S1, the raw materials of the solid electrolyte include Li source: LiH, Li ２ S ２ 、 Li ２ one or more of S, and S source: S, H ２ S, P ２ S ５ , P ４ S ９ , P ４ S ３ , Li ２ S ２ and Li ２ One or more of those in S, and P source: P, P ２ S ５ , P ４ S ９ , P ４ S ３ , P ４ S ６ , P ４ S ５ one or more of the following, and X source: one or more of LiCl, LiBr, LiI, LiF, VCl ５ , NbCl ５ , TaCl ５ and one or more of them, M source: VF ５ , NbCl ５ , TaCl ５ The sulfide solid electrolyte according to claim 1, characterized in that it contains one or more of them.

3. The sulfide solid electrolyte according to claim 1, wherein in step S1, the rotation speed of the ball milling is 380 to 1500 rpm and the ball milling time is 7 to 48 hours.

4. The sulfide solid electrolyte according to claim 1, wherein in step S2, the thickness of the sheet-like solid is 200 to 1000 μm.

5. The sulfide solid electrolyte according to claim 1, wherein in step S3, the temperature of the high-temperature sintering is 350 to 700 °C and the sintering time is 1 to 8 hours.

6. Use in the preparation of an all-solid-state battery of the sulfide solid electrolyte according to claim 1.

7. An all-solid-state battery, wherein the solid battery includes a battery positive electrode part, a battery negative electrode part, and a battery electrolyte part, and at least one part of the battery positive electrode part, the battery negative electrode part, and the battery electrolyte part includes the sulfide solid electrolyte according to claim 1.

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