WO2017107397A1

WO2017107397A1 - Preparation of amorphous sulfide solid electrolyte

Info

Publication number: WO2017107397A1
Application number: PCT/CN2016/085324
Authority: WO
Inventors: 于文倩; 赵成龙; 李丽; 王瑛; 王龙; 张庆朋; 陈建伟; 王超武
Original assignee: 山东玉皇新能源科技有限公司
Priority date: 2015-12-23
Filing date: 2016-06-08
Publication date: 2017-06-29
Also published as: CN105552433A

Abstract

Disclosed is a method of preparing an amorphous sulfide solid electrolyte, characterized in that the method mainly comprises the following steps: (1) adding metal lithium, elemental sulfur, and phosphorus pentasulfide of particular proportions to a water-free oxygen-free sealed container, and mixing the same; and (2) performing mechanical grinding on the raw materials mixed in step (1), to prepare an amorphous sulfide solid electrolyte. The preparation method enables precise control of proportions of lithium, sulfur, and phosphorus, thereby addressing a problem of low purity of a product of a high-temperature solid phase method because of vaporization of raw materials. Moreover, the present invention uses raw materials having abundant supplies, and a simple process in which a high-purity amorphous sulfide solid electrolyte can be obtained by a single step of ball milling.

Description

Preparation of amorphous sulfide solid electrolyte

Technical field

The invention relates to the field of lithium ion batteries, and in particular to a method for preparing an amorphous sulfide solid electrolyte.

Background technique

Low-energy, environmentally friendly new energy vehicles are the future direction of automotive development, and power batteries are a key factor affecting the performance of new energy vehicles. The power batteries of existing new energy vehicles usually use organic liquid electrolytes, but they are prone to fire or explosion in the case of improper use, and there is a great safety hazard. All solid-state batteries use solid electrolytes, there is no flammable liquid electrolyte, and the safety is greatly improved. At the same time, all solid-state batteries have more electricity storage and higher output power. However, the low ionic conductivity of solid electrolytes currently hinders the practical use of all solid batteries.

In the oxide solid electrolyte, the sulfide solid electrolyte has a larger radius of sulfur ions, less binding to lithium ions, easy migration of lithium ions, and higher conductivity. The literature "A lithium superionic conductor, Nat. Mater., 2011, 10, 682-686." reports that a sulfide solid electrolyte Li ₁₀ GeP ₂ S ₁₂ prepared by using lithium sulfide, barium sulfide and phosphorus pentasulfide as a raw material has a room temperature ionic conductivity of up to 1.2×. 10-2S/cm, which is a commercial electrolyte level, is of particular concern. However, in the current common synthetic methods, lithium sulfide is generally used as a raw material, and lithium sulfide is expensive, and it is easy to absorb moisture and hydrolyze, which affects the progress of industrialization. Chinese Patent Publication No. CN1937301A discloses "a sulfide material which can be used as a solid electrolyte for a lithium ion battery and a preparation method thereof", and a sulfide solid electrolyte is prepared by using a plurality of lithium source high temperature methods, although a sulfide solid electrolyte can be prepared. However, the high temperature treatment causes the material to crystallize, the ionic conductivity is low and the energy consumption is increased, and the product ratio is difficult to accurately control the product ratio.

Summary of the invention

In order to make up for the defects of the prior art, the present invention provides a method for preparing an amorphous sulfide solid electrolyte material by a simple mechanical grinding method using a metal lithium which is inexpensive and readily available as a lithium source.

The invention is achieved by the following technical solutions:

A method for preparing an amorphous sulfide solid electrolyte, comprising: the following steps:

(1) mixing a certain proportion of metallic lithium, elemental sulfur, and phosphorus pentasulfide into a water-free, oxygen-free closed container;

(2) The raw material mixed in the step (1) is mechanically ground to prepare an amorphous sulfide solid electrolyte.

The molar ratio of metallic lithium to elemental sulfur in the step (1) is from 1.8:1 to 3:1.

Preferably, the molar ratio of metallic lithium to elemental sulfur in step (1) is determined to be 2:1, based on the ratio of the final product.

In the step (1), the molar ratio of the metal lithium to the phosphorus pentasulfide is from 3:1 to 8:1.

Preferably, the molar ratio of metallic lithium to phosphorus pentasulfide in step (1) is determined to be 6:1, based on the ratio of the Li ₃ PS ₄ compound.

Preferably, the anhydrous oxygen-free sealed container in the step (1) is a glove box filled with an inert gas, and the glove box has a water removal system. Since the metal lithium reacts with water or oxygen, the phosphorus pentasulfide is also easy to absorb moisture. Therefore, water and oxygen must be isolated, so it must be operated in an inert atmosphere. The commercially available nitrogen or argon itself has a very low water content, and there is a water removal system in the glove box to ensure that the sample preparation process does not change.

The method of mechanical grinding described in the step (2) includes a ball milling method and a grinding method.

Preferably, the mechanical grinding method described in the step (2) is a ball milling method, and the ball milling method can control the progress of the reaction by controlling the ratio of the ball to the material, and is suitable for large-scale and automatic operations.

In the step (2), the ratio of the ball to the ball is 10:1 to 20:1, and the ratio of the ball to the material is too large, which increases the useless work loss between the grinding media and the impact friction between the medium and the ball mill, not only increases the power consumption. The output is reduced, and the wear of the ball mill can be aggravated; if the ball ratio is too small, the buffering effect of the material is increased, and the impact grinding effect is weakened; the ball milling speed is 150-250 rpm, and the rotation speed is too low and the reaction is difficult to completely And the problem that the material adheres to the ball mill tank is easy to occur. When the rotation speed is too high, the wear of the ball mill tank is easily aggravated, and the temperature rise is large to cause a side reaction; the ball milling time is 10 to 48 hours, the time is too short, the reaction is insufficient, and the particle size is insufficient. The distribution is not uniform; if the time is too long, the efficiency is affected and impurities are easily introduced.

Preferably, in the step (2), the ratio of the ball to the material is 18:1, which can fully exert the impact grinding effect of the medium and improve the working ability of the ball mill; the ball milling speed is 200 rpm, and the ball milling time is 24 hours, which can ensure sufficient reaction. complete.

The invention has the beneficial effects that the invention provides a simple method for preparing an amorphous sulfide solid electrolyte, which can precisely control the ratio of lithium, sulfur and phosphorus, and solves the problem that the purity of the product is higher when the raw material is volatilized in the high temperature solid phase method. The low problem, at the same time, the source of raw materials is rich, the process is simple, and a high-purity amorphous sulfide solid electrolyte can be obtained by a ball milling method.

DRAWINGS

The invention will now be further described with reference to the accompanying drawings.

1 is an AC impedance diagram of Li ₃ PS ₄ prepared in Example 1 of the present invention;

2 is an AC impedance diagram of Li ₈ P ₂ S ₉ prepared in Example 2 of the present invention.

Detailed ways

The invention is further described in detail below by way of specific examples, but these examples are only intended to be illustrative, and not to limit the scope of the invention.

Example 1:

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 6:3:1, in a nitrogen-filled glove box, weighed 0.2333g of metallic lithium, 0.5333g of elemental sulfur and 1.2334g of phosphorus pentasulfide, the above raw materials and 36g of zirconia balls It was placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 200 rpm for 24 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li ₃ PS ₄ .

The sample was pressed into a disk having a diameter of 15 mm and a thickness of about 0.5 mm. The wafer was sandwiched between stainless steel disks, and epoxy resin was applied to the bare solid electrolyte, and allowed to stand for 10 minutes to be solidified. The stainless steel sheets at both ends were connected to the positive and negative electrodes, respectively, and the AC impedance map was tested on an electrochemical workstation. The conductivity of the sulfide solid electrolyte was calculated based on the impedance of the test.

According to the impedance test results shown in Figure 1, the formula for calculating the conductivity is:

Where σ is the conductivity (S/cm) of the electrolyte;

l is the thickness of the electrolyte tablet (cm);

S is the area (cm ² ) of the electrolyte tablet;

R is the impedance value (Ω) obtained from the AC impedance map.

Calculated, the conductivity σ ≈ 0.7 × 10 ^-4 S / cm

Example 2:

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 8:4:1, in an argon-filled glove box, weighed 0.2759g of metallic lithium, 0.6305g of elemental sulfur and 1.0936g of phosphorus pentasulfide, the above raw materials and 36g of oxidation The zirconium balls were placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 200 rpm for 24 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li ₈ P ₂ S ₉ .

According to the impedance test result shown in Fig. 2, the electric conductivity σ ≈ 0.7 × 10 ^- ⁴ S/cm was calculated from the calculation formula of the electric conductivity.

Example 3:

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 8:4:1, in a nitrogen-filled glove box, weighed 0.2759g of metallic lithium, 0.6305g of elemental sulfur and 1.0936g of phosphorus pentasulfide, the above raw materials and 36g of zirconia The ball was placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 250 rpm for 48 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li ₈ P ₂ S ₉ .

The impedance test results were obtained experimentally, and the conductivity σ ≈ 0.6 × 10 ^-4 S/cm was calculated from the calculation formula of the conductivity.

Example 4:

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 14:7:3, in an argon-filled glove box, weighed 0.1984g of metallic lithium, 0.4534g of elemental sulfur and 1.3482g of phosphorus pentasulfide, the above raw materials and 28g oxidation The zirconium balls were placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 250 rpm for 24 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li _{4 to 5} P ₂ S ₇ .

Example 5:

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 6:2:1, in an argon-filled glove box, weighed 0.2561g of metallic lithium, 0.3902g of elemental sulfur and 1.3537g of phosphorus pentasulfide, the above raw materials and 36g oxidation The zirconium balls were placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 150 rpm for 24 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li ₆ P ₂ S ₇ .

Example 6

Metal lithium and elemental sulfur, phosphorus pentasulfide in a molar ratio of 6:2:1, in an argon-filled glove box, weighed 0.2561g of metallic lithium, 0.3902g of elemental sulfur and 1.3537g of phosphorus pentasulfide, the above raw materials and 25g oxidation The zirconium balls were placed in a 100 ml zirconia ball mill jar, completely sealed and taken out of the glove box. Then, it was ball-milled at 150 rpm for 48 hours using a planetary ball mill to obtain an amorphous sulfide solid electrolyte Li ₆ P ₂ S ₇ .

Claims

A method for preparing an amorphous sulfide solid electrolyte, comprising: the following steps:

(1) mixing a certain proportion of metallic lithium, elemental sulfur, and phosphorus pentasulfide into a water-free, oxygen-free closed container;

(2) The raw material mixed in the step (1) is mechanically ground to prepare an amorphous sulfide solid electrolyte.
The method for preparing an amorphous sulfide solid electrolyte according to claim 1, wherein the molar ratio of metallic lithium to elemental sulfur in the step (1) is from 1.8:1 to 3:1.
The method for preparing an amorphous sulfide solid electrolyte according to claim 2, wherein the molar ratio of metallic lithium to elemental sulfur in the step (1) is 2:1.
The method for preparing an amorphous sulfide solid electrolyte according to claim 1, wherein in the step (1), the molar ratio of the metal lithium to the phosphorus pentasulfide is from 3:1 to 8:1.
The method for preparing an amorphous sulfide solid electrolyte according to claim 4, wherein the molar ratio of metallic lithium to phosphorus pentasulfide in the step (1) is 6:1.
The method for preparing an amorphous sulfide solid electrolyte according to claim 1, wherein the anhydrous oxygen-free sealed container in the step (1) is a glove box filled with an inert gas, and the glove box has water removal. System, the inert atmosphere is nitrogen or argon.
The method of preparing an amorphous sulfide solid electrolyte according to claim 1, wherein the method of mechanically grinding according to the step (2) comprises a ball milling method and a grinding method.
The method for producing an amorphous sulfide solid electrolyte according to claim 1 or 7, wherein the mechanical grinding method according to the step (2) is a ball milling method.
The method for preparing an amorphous sulfide solid electrolyte according to claim 1, wherein in the step (2), the ball ratio is 10:1 to 20:1, and the ball milling speed is 150 to 250 rpm. In minutes, the ball milling time is 10 to 48 hours.
The method for preparing an amorphous sulfide solid electrolyte according to claim 1 or 9, wherein the ratio of the ball to the material in the step (2) is 18:1; the rotation speed of the ball mill is 200 rpm, and the milling time is 24 hour.