Sulfide solid electrolyte and 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 sulfide solid electrolyte doped with a group 5 element and halogen 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 such as energy storage systems and electric vehicles. Solid-state batteries with solid electrolytes are potential candidates for next-generation batteries with high energy density and safety. Furthermore, solid electrolytes significantly improve safety by replacing the flammable and volatile liquid electrolytes in conventional 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 offer significant advantages in terms of processing due to their excellent mechanical properties.

[0004] In recent years, LPSC-type sulfide solid electrolytes have attracted 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 anode materials and poor cycle stability. These problems pose major challenges for their future practical application. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention overcomes the shortcomings of the prior art and aims to provide a sulfide solid electrolyte, a method for preparing the same, and its use. The composition of the Group 5 element-halogen-doped sulfide solid electrolyte of the present invention is Li6P l-a (M) a S5X (where M is one or more of vanadium, niobium, and tantalum, 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 a Group 5 element. When the sulfide electrolyte material has a good silver germanite crystal phase, the controllable doping of elements such as vanadium, niobium, and tantalum improves compatibility with lithium-based negative electrodes and achieves better electrochemical stability. Furthermore, the cycle stability of sulfide all-solid-state batteries is improved. [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 of 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) is provided.

[0007] Compared to other metal elements, doping with M, a Group 5 element, can produce an M2O5 layer on the surface of the sulfide electrolyte, improving the electrolyte's cycle stability and providing good compatibility with the lithium anode. The proportion of lithium 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 raw materials, such as a Li source, a P source, a S source, an M source, and an X source, according to the stoichiometric ratio of S5X, and then performing a ball milling process to obtain a precursor powder of a 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 a high temperature in vacuum to obtain the sulfide solid electrolyte.

[0010] Preferably, in step S1, the raw material for 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 treatment is 380 to 1500 rpm, and the ball milling time is 7 to 48 hours. Before the ball milling, the material is first manually polished, and then mechanically ball 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 pressing pressure is 300-500 MPa. If the pressure is too high, the mold is likely to be damaged, and if the pressure is too low, the compression is likely to be insufficient, resulting in the inability to form an effective crystalline 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 be difficult to release from the mold and to be insufficient in the sintering process, which may result in crushing or breaking of the electrolyte sheet.

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

[0015] Preferably, a polishing step is also included before 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 to 700°C for 1 to 8 hours. The heating rate is 0.5 to 5°C / min. If the temperature is too high or too low, it will affect the formation of an effective crystalline phase of the target electrolyte, and if the heating rate is too fast or too slow, it will also affect the formation of the crystalline phase.

[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 aspect or the sulfide solid electrolyte prepared by the preparation method described in the above aspect in the manufacture of a full battery.

[0021] The present invention further provides a solid-state battery including a battery positive electrode, a battery negative electrode, and a battery electrolyte, wherein at least one of the battery positive electrode, the battery negative electrode, 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 is made of a mixture of a negative electrode active material and the sulfide solid electrolyte, and the negative electrode active material is a lithium-based alloy negative electrode material.

[0024] The present invention provides a sulfide electrolyte by incorporating a halogen element and a Group 5 element into a sulfide solid electrolyte. The process required for preparing this electrolyte is simple. The ionic conductivity reaches the same level as or even higher than that of electrolytes in the same field. The doping of a halogen element and the incorporation of a Group 5 element improves the cycle stability and ductility of the electrolyte sheet during battery operation. Thus, the present invention provides 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. [Effects of the Invention]

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

[0026] 1) By doping with Group 5 elements, 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 cathode improves the overall electrochemical performance of the battery. [Brief explanation of the drawings]

[0029]

Figure 1

Figure 2

[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 also within the scope of protection of the present invention. [Example]

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

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

[0033] In this example, Li6P 0.8 Ta 0.2 The S5F solid electrolyte is provided, and the specific steps of its manufacturing method are as follows: The pure reagents Li2S, P2S5 and TaF5 were prepared according to the stoichiometric ratio Li2S:P2S5:TaF5=3:0.4:0.2. TaF5 were weighed and mixed, then manually ground for 15 minutes. The mixture was placed in a zirconia ball mill tank, and zirconia balls were added at a mass ratio of 1:50. The ball milling speed was set to 550 rpm. After 17 hours of ball milling, the sample adhering to the tank wall was scraped off, and the mixture was 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 (12 mm in diameter) at a pressure of 350 MPa. The mixture was then placed in a quartz tube and sealed. The mixture was heated to 550°C at a rate of 0.5 / min, maintained at that temperature for 7 hours, and then cooled. Li6P 0.8 Ta 0.2 S5F solid electrolyte powder was obtained. XRD analysis showed that the solid electrolyte powder prepared by this method was a cubic argillite phase with good crystalline form and high purity. The solid electrolyte powder was 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. 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 a temperature of 298 to 375 K and a frequency of 1 MHz to 10 Hz using a multi-channel electrochemical workstation.) Comparative Example 1

[0034] The Li6PS5F solid electrolyte is prepared by the following steps: The pure reagents Li2S, P2S5, and LiF were weighed according to the required stoichiometric ratio, mixed, and then manually milled 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. The ball milling speed was set to 550 rpm. After 17 hours of ball milling, the sample adhering to the tank wall was scraped off, and the mixture was manually milled for another 15 minutes using a mortar and pestle. After sieving through a 400-mesh sieve, a uniformly mixed precursor was obtained. The mixture was then compressed into tablets (12 mm diameter) at 350 MPa. The mixture was then placed in a quartz tube and sealed. The temperature was raised to 550 °C at a rate of 0.5 / min, maintained at this temperature for 7 hours, and cooled to obtain Li6PS5F solid electrolyte powder. The solid electrolyte powder was then pressed at 580 MPa and held for 3 minutes to obtain a solid electrolyte sheet. All of 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 S5F sulfide solid electrolyte was prepared by the same method as in Example 1, with the only difference being that the raw materials used in Comparative Example 2 were Li2S:P2S5:SbF5 = 3:0.4:0.2. The lithium ion conductivity of the solid electrolyte sheet obtained in Comparative Example 2 at room temperature was 1.1 × 10 -3 It was S / cm.

[0036] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described specific embodiments, and it should be understood that those skilled in the art can make various modifications and changes within the scope of the claims without affecting the essential content of the present invention. The invention described in the original claims of the present application is appended below. [1] A sulfide solid electrolyte having a composition of 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). A sulfide solid electrolyte. [2] The sulfide solid electrolyte of [1], characterized in that the range of the value of a is 0 < a < 1. [3] The sulfide solid electrolyte of [2], characterized in that the range of the value of a is 0 < a ≤ 0.2. [4] A method for preparing any one of the sulfide solid electrolytes of [1] to [3], Li 6 P l-a (M) a S 5 Weigh the raw material Li source, P source, S source, M source, and X source according to the stoichiometric ratio of X (where 0 < a < 1), mix them uniformly, and then perform ball milling treatment to obtain a sulfide solid electrolyte precursor powder in step S1. Step S2 of sieving the precursor powder and pressing the powder into a sheet-like solid. A preparation method characterized by including step S3 of sintering the sheet-like solid at high temperature in a vacuum to obtain the sulfide solid electrolyte. [5] 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, 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 S, 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 X source: LiCl, LiBr, LiI, LiF, VCl 5 , NbCl 5 , TaCl 5 One or more of M source: VF 5 , NbCl 5 , TaCl 5 One or more of [6] In step S1, the ball milling treatment has a rotation speed of 380 to 1500 rpm and a time of 7 to 48 hours, which is the preparation method of [4]. [7] In step S1, before the ball milling, it further includes manual polishing, and the manual polishing has a time of 15 to 30 minutes and uses an agate mortar, which is the preparation method of [4]. [8] In step S1, the ball milling uses a planetary ball mill, which is the preparation method of [4] or [6]. [9] In step S2, the sieving uses a sieve with 300 to 1200 mesh, which is the preparation method of [4].

[10] In step S2, the pressure of the pressing is 300 to 500 MPa, which is the preparation method of [4].

[11] In step S2, the thickness of the sheet-like solid is 200 to 1000 μm, which is the preparation method of [4].

[12] The method of preparing [4], wherein in step S3, the vacuum high-temperature sintering is carried out at a temperature of 350 to 700°C for 1 to 8 hours.

[13] The method according to [4] or

[12] , wherein step S3 comprises sealing the sheet-like solid in a vacuum quartz tube, then placing it in a muffle furnace and sintering it at a high temperature to obtain the sulfide solid electrolyte.

[14] The method according to

[12] , wherein the temperature rise rate of the vacuum high-temperature sintering is 0.5 to 5°C / min.

[15] The preparation method of [4], characterized in that in step S3, after the high-temperature sintering, the temperature is further decreased to room temperature at a rate of 0.5 to 5°C / min.

[16] The preparation method of [4], wherein in steps S1 to S3, the weighing, uniform mixing, ball milling, sieving, pressing and vacuum high-temperature sintering are all carried out under the protection of an inert atmosphere.

[17] Application of a sulfide solid electrolyte according to any one of [1] to [3] or a sulfide solid electrolyte prepared by any one of the preparation methods [4] to

[16] in the preparation of a full battery.

[18] A solid-state battery comprising 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 a battery, the negative electrode for a battery, and the battery electrolyte comprises a sulfide solid electrolyte according to any one of [1] to [3], or a sulfide solid electrolyte prepared by a preparation method according to any one of [4] to

[16] .

[19] The solid-state battery according to

[18] , wherein the weight of the solid electrolyte in the positive electrode for the battery is 0 to 40% by weight based on the total weight.

[20] The positive electrode active material in the positive electrode for the battery is LiCoO 2 , LiFePO 4 , LiNi x Co y Mn 1-x-y O 2 , LiNi x Co y Al 1-x-y O 2 , LiNi 0.5 Mn 1.5 O 4 , LiFe x Mn 1-x PO 4

[18] A solid-state battery characterized by being one or a mixture of two or more of the above.

[21] The solid-state battery according to

[18] , wherein the negative electrode of the battery is made of a mixture of a negative electrode active material and a sulfide solid electrolyte of any one of [1] to [3], and the negative electrode active material is a lithium alloy negative electrode material.

Claims

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

2. In step S1, the raw materials for the solid electrolyte include: Li source: LiH, Li ２ S ２ , Li ２ one or more of S. 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 S. 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: X source: LiCl, LiBr, LiI, LiF, VCl ５ , NbCl ５ , TaCl ５ and one or more of the following: M source: VF ５ , NbCl ５ , TaCl ５ 2. The method according to claim 1, wherein the compound contains one or more of the following:

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

4. 2. The method according to claim 1, wherein in step S2, the thickness of the sheet solid is 200 to 1000 μm.

5. The method according to claim 1, wherein in step S3, the vacuum high-temperature sintering is carried out at a temperature of 350-700°C for a sintering time of 1-8 hours.

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