CN108511795A - A kind of O2-And F-Cooperate with the LISICON type solid electrolyte materials and preparation method thereof of doping - Google Patents

Abstract

The invention discloses a LISICON type solid electrolyte material synergistically doped with O ^{2 -} and F ^- and a preparation method thereof. The solid electrolyte material is a lithium germanium phosphorus sulfuryl oxyfluoride material, and its chemical formula is Li ₁₀ GeP ₂ S _12‑x‑y O _x F _y , wherein, 1≤x≤3, 0.5≤y≤1.5; its preparation method is first Grinding, sintering, heat preservation, and slow cooling to room temperature is the material. The ionic conductivity of the solid electrolyte material at room temperature is greater than 2×10 ^‑5 S/cm ^‑1 , and its chemical properties are stable. It is an excellent solid electrolyte material and can be applied to all-solid-state lithium-ion batteries.

Description

An O2- and F-cooperatively doped LISICON solid electrolyte material and its preparation method

technical field

The invention relates to the field of all-solid lithium ion batteries, in particular to a LISICON type lithium ion solid electrolyte material and a preparation method thereof.

Background technique

At present, there are relatively serious ecological problems in the world, such as the increasing shortage of traditional fossil energy, the increasingly serious environmental pollution, and the global greenhouse effect. Therefore, it is imperative to accelerate the development of clean energy, establish an efficient, clean, economical, and safe energy system, reduce the dependence of automobiles and industries on fossil energy, and achieve sustainable development of new energy. The lithium-ion battery has the advantages of high energy density, high output voltage, long service life, and environmental friendliness, so it has become an irreplaceable excellent energy storage device. In recent years, the development of lithium-ion batteries has been concentrated in two aspects; one is as a power source and large-scale energy storage device for automobiles and aerospace equipment; device. The emergence of these high-end products will put forward new requirements for lithium-ion batteries with high safety, long cycle life, high energy density, high power density, and low price, among which safety issues are particularly critical.

Commercial lithium-ion batteries generally use organic liquid electrolytes and gel electrolytes, which inevitably introduce flammable, explosive, volatile, and leaky organic liquids into the battery system, which brings serious safety hazards to the battery system. If solid-state batteries are prepared with solid-state electrolytes instead of traditional organic electrolytes, it is expected to fundamentally solve the safety problem of lithium-ion batteries. In order to promote the industrialization process of high safety and high energy storage batteries, the research and development and preparation of key materials (solid electrolyte, positive electrode and negative electrode) are crucial in the research and development of all-solid-state lithium-ion batteries with higher energy and power density. part of the Therefore, the research and development of solid electrolyte materials with high conductivity is an effective measure to solve the unsafe problems of current commercial batteries.

The current inorganic solid electrolytes are mainly divided into oxide-based and sulfide-based solid electrolytes. For the reported solid-state electrolyte materials, there are generally disadvantages of poor performance. Mainly reflected in: (1) the ionic conductivity at room temperature is generally low; (2) the electrochemical window is low, generally not higher than 5V; (3) the preparation process requires complex and cannot be mass-produced.

Contents of the invention

The invention provides a LISICON type solid electrolyte material synergistically doped with O ^{2 -} and F ^- and a preparation method thereof. The solid electrolyte material has high ion conductivity and stable chemical properties, and at the same time solves the problem of unsafe commercial batteries.

The O ^2- and F ^- cooperatively doped LISICON solid electrolyte material has a crystalline structure, and its chemical formula is Li ₁₀ GeP ₂ S _12-xy O _x F _y , where, 1≤x≤3, 0.5≤y≤1.5 .

Preferably: x=1 or 2 or 3, y=0.5 or 1.0 or 1.5; the best solution is: x=2, y=1.0.

The preparation method of the ^O2- and F ^- cooperatively doped LISICON type solid electrolyte material comprises the following steps:

(1) Mix and grind Li ₂ S, P ₂ S ₅ , GeS ₂ , Li ₂ O and LiF according to the molar ratio of (5-xy): 1: 1: x: y, where 1≤x≤3, 0.5≤y≤1.5;

(2) Put the powder ground in step (1) into a crucible, seal and transfer to a tube-type resistance furnace with a vacuum atmosphere, calcine and keep it warm for a period of time, and then cool naturally to obtain the solid electrolyte material.

Furthermore, the grinding in step (1) is performed alternately clockwise and counterclockwise, and the grinding is continued for 1 hour.

Furthermore, the ambient oxygen partial pressure and water pressure during grinding in step (1) are both less than 1 ppm.

Furthermore, the particle size range of the powder obtained by grinding in step (1) is about 500 mesh.

Furthermore, the calcination temperature in step (2) is 600° C., and the holding time is 24 hours.

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

1. The present invention uses lithium oxide and lithium fluoride as doping materials at the same time, which not only improves the ion conductivity (up to 1×10 ^-4 S/cm or more), but also effectively reduces the interface impedance between the electrode and the electrolyte, Improve the cycle life and rate performance of solid-state batteries;

2. Lithium oxide and lithium fluoride are used as doping materials at the same time, which reduces the energy of Li ₁₀ GeP ₂ S ₁₂ in the system, which is beneficial to the formation of solid solution Li ₁₀ GeP ₂ S _12-xy O _X F _y , where 1≤x≤ 3. 0.5≤y≤1.5, so as to have a certain stabilizing effect on the structure of Li ₁₀ GeP ₂ S ₁₂ , avoid electrolyte collapse, and improve battery safety;

3. Oxygen is introduced into the sulfide-based electrolyte, combining the high ionic conductivity of sulfide and the electrochemical stability of oxides to improve the safety of the battery;

4. Both lithium oxide and lithium fluoride are cheap materials, which reduce the cost of preparing solid electrolyte materials, thereby reducing the production cost of lithium batteries.

Description of drawings

Fig. 1 is a powder SEM image of the lithium ion solid electrolyte material prepared in Example 2 of the present invention under the condition of 10KV. (×10000, 5 microns).

Fig. 2 is a powder SEM image of the lithium ion solid electrolyte material prepared in Example 2 of the present invention under the condition of 1KV. (×2000, 20 microns).

3 is an SEM image of the electrolyte sheet of the lithium-ion solid electrolyte material prepared in Example 2 of the present invention under the condition of 1KV. (×50000, 1 micron).

FIG. 4 is an XRD pattern of the lithium ion solid electrolyte material prepared in Example 2 of the present invention.

Fig. 5 is an electrochemical impedance spectrum at room temperature of the lithium ion solid electrolyte material prepared in Example 2 of the present invention.

FIG. 6 is an EDS energy spectrum diagram of the lithium ion solid electrolyte material prepared in Example 2 of the present invention.

Detailed ways

The present invention adopts the method of combining solid-state method and high-temperature sintering to prepare the sulfide solid electrolyte material containing O ^2- and ^F- ions, which specifically includes the following steps:

(1) Lithium sulfide, phosphorus pentasulfide, germanium disulfide, lithium oxide and lithium fluoride are accurately weighed according to a suitable molar ratio in a glove box, and the molar ratio is (5-xy)Li ₂ S:P ₂ S ₅ : GeS ₂ : xLi ₂ O: yLiF, its chemical formula is Li ₁₀ GeP ₂ S _12-xy O _X F _y , where, 1≤x≤3, 0.5≤y≤1.5, put it in an agate mortar after weighing, and then Grind evenly for 1h. Among them, the ambient oxygen partial pressure and water pressure of the weighed and ground raw materials are both less than 1 ppm; the particle size of the ground powder is about 500 mesh.

(2) Put the ball-milled powder in step (1) into a crucible, seal it and transfer it to a tube-type resistance furnace with a vacuum atmosphere, pass in argon as a protective gas, calcine at a temperature of 600°C, keep it warm for 24 hours, and then cool it naturally, that is A sample is obtained, the sample is a LISICON type solid electrolyte material containing O ^2- and F ^- ions, and the composition of the solid electrolyte material is Li ₁₀ GeP ₂ S _{12-x- y} O _X F _y , wherein, 1≤x ≤3, 0.5≤y≤1.5.

(3) In order to facilitate the test of the ionic conductivity of the powder, the above-mentioned solid electrolyte powder material is pressed into a tablet in a glove box, and then a layer of conductive adhesive is evenly coated on both sides of the solid electrolyte sheet, and then calcined at a temperature of 200 ° C and kept for 2 hours. .

The structure of the LISICON type solid electrolyte material containing O ^{2 -} and F ^- ions in the present invention is determined by X-ray diffractometer (XRD). The X-ray diffraction pattern shows that the solid electrolyte material obtained after sintering is in a crystal form and is in a tetragonal phase. The morphology of the solid electrolyte material is analyzed and tested by scanning electron microscopy (SEM) on the cross-section of the sintered electrolyte sheet, and the results show that the crystal grains are tightly bonded, there are no pores, and the density is good. Its composition is tested by X-ray energy spectrometer (EDS). The EDS spectrum can confirm that the composition of the solid electrolyte is Li ₁₀ GeP ₂ S _12-xy O _X F _y , as shown in Table 1 (there is a certain difference from the actual value error).

Table 1 Element types and composition of samples

The electrochemical performance of the LISICON solid electrolyte material containing O ^{2 -} and F ^- ions in the present invention is tested by an electrochemical workstation. Measure the AC impedance spectrum of the half-cell Ag/Li ₁₀ GeP ₂ S _12-xy O _X F _y /Ag sandwich structure. According to the impedance value in the spectrum and the thickness of the solid electrolyte, the ionic conductivity can be calculated and tested three times in parallel.

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1

(1) In the glove box, weigh the raw materials lithium sulfide, phosphorus pentasulfide, germanium disulfide, lithium oxide and lithium fluoride according to the molar ratio (5-xy) Li ₂ S:P ₂ S ₅ :GeS ₂ :xLi ₂ O:yLiF amount, where x=1, y=0.5. After weighing, place it in an agate mortar and grind it uniformly for 1h.

(2) Put the ball-milled powder in step (1) into a crucible, seal it and transfer it to a tube-type resistance furnace with a vacuum atmosphere, pass in argon as a protective gas, calcine at a temperature of 600°C, keep it warm for 24 hours, and then cool it naturally, that is A LISICON-type solid electrolyte material containing O ^2- and ^F- ions is obtained.

(3) The above solid electrolyte material was pressed into a tablet in a glove box, coated with conductive glue on both sides of the solid electrolyte sheet, and then calcined at a temperature of 200° C. for 2 hours. The obtained electrolyte sheets were used for testing.

According to XRD detection and analysis, the solid electrolyte obtained in this example is Li ₁₀ GeP ₂ S _10.5 OF _0.5 . The ion conductivity of the electrolyte sheet was tested three times in parallel and the results were 2.34×10 ^-4 S/cm, 2.18×10 ^-4 S/cm, 2.26×10 ^-4 S/cm, respectively.

Example 2

(1) In the glove box, weigh the raw materials lithium sulfide, phosphorus pentasulfide, germanium disulfide, lithium oxide and lithium fluoride according to the molar ratio (5-xy) Li ₂ S:P ₂ S ₅ :GeS ₂ :xLi ₂ O:yLiF Quantity, where x=2, y=1. Place it in an agate mortar after weighing, and then grind it uniformly for 1h.

(2) Put the ball-milled powder in step (1) into a crucible, seal it and transfer it to a tube-type resistance furnace with a vacuum atmosphere, pass in argon as a protective gas, calcine at a temperature of 600°C, keep it warm for 24 hours, and then cool it naturally, that is A LISICON-type solid electrolyte material containing O ^2- and ^F- ions is obtained.

(3) Press the solid electrolyte material into a tablet in a glove box, coat the two sides of the solid electrolyte sheet with conductive glue, and then calcine the solid electrolyte sheet at a temperature of 200° C. for 2 hours. The obtained electrolyte sheets were used for testing.

Figures 1 to 3 are SEM images of the solid electrolyte material obtained in this example. It can be seen that the grains are closely bonded, no pores exist, and the density is good. Fig. 4 is an X-ray diffraction spectrum of the solid electrolyte material obtained in this example, which shows that the solid electrolyte material obtained after sintering is Li ₁₀ GeP ₂ S ₉ O ₂ F, and the crystal form is tetragonal. Figure 5 is the electrochemical impedance spectrum of the solid electrolyte material of this embodiment at room temperature. According to the impedance value in the spectrum and the thickness of the solid electrolyte, the ionic conductivity can be calculated. The results of three parallel tests are 5.41×10 ^-4 S/cm, 5.24×10 ^-4 S/cm, 5.16× ^{10 -4} S/cm.

Example 3

(1) In the glove box, weigh the raw materials lithium sulfide, phosphorus pentasulfide, germanium disulfide, lithium oxide and lithium fluoride according to the molar ratio (5-xy) Li ₂ S:P ₂ S ₅ :GeS ₂ :xLi ₂ O:yLiF amount, where x=3, y=1.5. Place it in an agate mortar after weighing, and then grind it uniformly for 1h.

(2) Put the ball-milled powder in step (1) into a crucible, seal it and transfer it to a tube-type resistance furnace with a vacuum atmosphere, pass in argon as a protective gas, calcine at a temperature of 600°C, keep it warm for 24 hours, and then cool it naturally, that is A LISICON-type solid electrolyte material containing O ^2- and ^F- ions is obtained.

(3) The above solid electrolyte material was pressed into a tablet in a glove box, coated with conductive glue on both sides of the solid electrolyte sheet, and then calcined at a temperature of 200° C. for 2 hours. The obtained electrolyte sheets were used for testing.

According to XRD detection and analysis, the solid electrolyte obtained in this example is Li ₁₀ GeP ₂ S _7.5 O ₃ F _1.5 . The ionic conductivity of the electrolyte sheet was tested three times in parallel and the results were 1.89×10 ^-4 S/cm, 1.96×10 ^-4 S/cm, 2.06×10 ^-4 S/cm, respectively.

Table 2 is the test of the ion conductivity and electrochemical stability of three examples of the present invention and the existing solid electrolyte Li ₁₀ GeP ₂ S ₁₂ (other new scheme Li ₁₀ GeP ₂ S _11.6 O _0.4 is also added as a control group) result.

Ionic conductivity and electrochemical stability of table 2 samples

It can be seen from Table 2 that the solid electrolyte Li ₁₀ GeP ₂ S _12-xy O _X F _y prepared by the present invention has better ionic conductivity and electrochemical stability than the existing solid electrolyte Li ₁₀ GeP ₂ S ₁₂ Improved significantly.

Claims (8)

1. a kind of O^2-And F^-Cooperate with the LISICON type solid electrolyte materials of doping, which is characterized in that chemical formula is Li₁₀GeP₂S_12-x-yO_xF_y, wherein 1≤x≤3,0.5≤y≤1.5.

2. LISICON types solid electrolyte material according to claim 1, which is characterized in that the x=1,2 or 3, institute State y=0.5,1.0 or 1.5.

3. a kind of preparation method of LISICON types solid electrolyte material as described in claim 1, which is characterized in that including Following steps：

(1) by Li₂S、P₂S₅、GeS₂、Li₂O and LiF is according to (5-x-y)：1：1：x：The molar ratio of y is mixed and is ground, wherein 1≤ X≤3,0.5≤y≤1.5；

(2) the ground powder of step (1) being fitted into crucible, sealing is transferred in vacuum atmosphere tube type resistance furnace, through calcining, Natural cooling is to get to the solid electrolyte material after heat preservation.

4. the preparation method of LISICON types solid electrolyte material according to claim 3, which is characterized in that the x= 1,2 or 3, the y=0.5,1.0 or 1.5.

5. the preparation method of LISICON types solid electrolyte material according to claim 3, which is characterized in that the step Suddenly grinding persistently grinds 1h using along alternate run counterclockwise in (1).

6. the preparation method of LISICON types solid electrolyte material according to claim 3, which is characterized in that the step Suddenly the ambient oxygen partial pressure in (1) when grinding and water partial pressure are respectively less than 1ppm.

7. the preparation method of LISICON types solid electrolyte material according to claim 3, which is characterized in that the step Suddenly the particle size range of grinding gained powder is 500 mesh in (1).

8. the preparation method of LISICON types solid electrolyte material according to claim 3, which is characterized in that the step Suddenly the calcination temperature in (2) is 600 DEG C, and soaking time is for 24 hours.