A mixed-conductor sulfide solid electrolyte, a preparation method thereof, and an all-solid-state battery

Abstract

The application discloses a mixed conductor sulfide solid electrolyte, a preparation method thereof and a full solid-state battery 7‑a M b P 1‑b S 6‑a X a , wherein a and b satisfy 0 The application discloses a mixed conductor sulfide solid electrolyte, a preparation method thereof and a full solid-state battery

Description

Technical Field

[0001] This invention relates to solid-state battery technology, and particularly to a hybrid conductor sulfide solid electrolyte, its preparation method, and an all-solid-state battery. Background Technology

[0002] In recent years, all-solid-state secondary batteries, which replace liquid electrolytes with solid electrolytes, have attracted widespread attention in order to improve safety.

[0003] Solid electrolytes with a sulforaphite-germanium structure (hereinafter referred to as sulforaphite-germanium solid electrolytes) have relatively high ionic conductivity (10). -4 -10 -2 There are many patents related to silver-germanium sulfide ore, such as international patent publication No. WO2016 / 009768 and Chinese patent CN107112586A. However, although existing sulfide solid electrolytes have high ionic conductivity, when the oxide cathode comes into contact with the sulfide solid electrolyte, due to the large chemical potential difference between the two, lithium ions will move from the sulfide solid electrolyte side to the oxide cathode material side. The cathode and electrolyte simultaneously form a space charge layer. However, the low electronic conductivity of the sulfide solid electrolyte layer causes the charge layer on the cathode side to disappear. In order for the chemical potential of lithium ions on the electrolyte side to reach equilibrium, they will inevitably continue to move towards the cathode, and the space charge layer will continue to be generated, forming a very large resistance inside the battery.

[0004] To address the aforementioned issues and improve the performance of all-solid-state secondary batteries, enhancing the electronic conductivity of sulfide-germanium ore-type solid electrolyte materials is an urgent problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a mixed conductor sulfide solid electrolyte, a preparation method thereof, and an all-solid-state battery. The invention utilizes variable-valence transition metal elements to dope the sulfide solid electrolyte with a sulfide structure of silver-germanium sulfide, thereby improving the electronic conductivity of the sulfide electrolyte material.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A mixed conductor sulfide solid electrolyte, the solid electrolyte comprising Li 7-a M b P 1-b S 6-a X a Where a and b satisfy 0 < a ≤ 2 and 0 < b < 1; M is a transition metal; X is a halogen element.

[0008] Preferably, the transition metal is at least one selected from Sc, Ti, V, Cr, Fe, Ni, Nb, Zn, and Y.

[0009] Preferably, the solid electrolyte has an activation energy of 0.3 eV or less.

[0010] Preferably, the solid electrolyte has a peak at the position of 2θ = 29.5 ± 1.0° in X-ray diffraction measurements using CuKα radiation.

[0011] Preferably, the solid electrolyte has a strength of 1.0 × 10⁻⁶ at a temperature of 25°C. -6 Electron conductivity above S / cm.

[0012] Preferably, the halogen element is at least one of Cl, Br, and I.

[0013] A method for preparing a mixed conductor sulfide solid electrolyte, wherein, under the protection of a safe gas, a lithium source, a transition metal source, a phosphorus source, a sulfur source, and a halogen source are mixed according to the chemical formula Li 7-a M b P 1-b S 6-a X a The mixture is mixed in the corresponding mixing ratio, and then the mixture is mechanically ground to obtain a glassy composite; then the glassy composite is heat-treated at or above the glass transition temperature of the glassy composite to convert the glassy composite into a sulfide solid electrolyte with a mixed electron-ion conductor.

[0014] Preferably, in step two, the glassy composite is heated to 550°C at a heating rate of 5°C / min, sintered for 10 hours, and then cooled to obtain a sulfide solid electrolyte with a mixed electron-ion conductor.

[0015] An all-solid-state battery includes a positive electrode, a negative electrode, and a mixed conductor sulfide solid electrolyte disposed between the positive and negative electrodes.

[0016] Compared with the prior art, the advantages of the hybrid conductor sulfide solid electrolyte, its preparation method, and the all-solid-state battery of the present invention are as follows:

[0017] (1) The mixed conductor sulfide solid electrolyte of the present invention has higher electronic conductivity because it utilizes variable valence transition metal elements to dope the sulfide electrolyte with a sulfosilver germanite structure. Since the metal elements can change the energy band of the compound, they can improve the electronic conductivity.

[0018] (2) The electron-ion mixed conductor sulfide solid electrolyte is mixed with electrode material to form an electrode with an ion-electron mixed network, which reduces the interfacial resistance. The sulfide solid electrolyte prepared by this invention is applied to all-solid-state batteries, so that the batteries have better electrochemical performance. Detailed Implementation

[0019] Example

[0020] All-solid-state batteries include a positive electrode, a negative electrode, and a mixed conductor sulfide solid electrolyte disposed between the positive and negative electrodes.

[0021] Mixed conductor sulfide solid electrolytes, including Li 7-a M b P 1-b S 6-a X a Where a and b satisfy 0 < a ≤ 2 and 0 < b < 1; M is a transition metal; X is a halogen element, the transition metal is at least one of Sc, Ti, V, Cr, Fe, Ni, Nb, Zn, and Y, and the halogen element is at least one of Cl, Br, and I.

[0022] The solid electrolyte has an activation energy of 0.3 eV or less. In X-ray diffraction measurements using CuKα radiation, the solid electrolyte exhibits a peak at 2θ = 29.5 ± 1.0°. The solid electrolyte has a 1.0 × 10⁻⁶ peak at 25 °C. -6 Electron conductivity above S / cm.

[0023] A method for preparing a mixed conductor sulfide solid electrolyte, wherein, under the protection of a safe gas, a lithium source, a transition metal source, a phosphorus source, a sulfur source, and a halogen source are mixed according to the chemical formula Li 7-a M b P 1-b S 6-a X a The mixture is mixed in the corresponding mixing ratio, and then mechanically ground to obtain a glassy composite. The glassy composite is then heat-treated at its glass transition temperature or a higher temperature to convert it into a sulfide solid electrolyte with mixed electron-ion conductors. Specifically, the glassy composite is heated to 550°C at a heating rate of 5°C / min, sintered for 10 hours, and then cooled to obtain a sulfide solid electrolyte with mixed electron-ion conductors.

[0024] Example 1

[0025] This embodiment provides a sulfide solid electrolyte Li6Nb, which is an electron-ion hybrid conductor. 0.1 P 0.9 S5Cl.

[0026] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, Nb₂S₅, P₂S₅, and LiCl were weighed in a molar ratio of 25:0.5:4.5:10. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₆Nb₂S₅ was obtained. 0.1 P 0.9 S5Cl.

[0027] Example 2

[0028] This embodiment provides a sulfide solid electrolyte Li6V, which is an electron-ion hybrid conductor. 0.1 P 0.9 S5Cl.

[0029] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiCl were weighed in a molar ratio of 25:0.5:4.5:10. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₆V₂S₅ was obtained. 0.1 P 0.9 S5Cl.

[0030] Example 3

[0031] This embodiment provides a sulfide solid electrolyte Li6V, which is an electron-ion hybrid conductor. 0.1 P 0.9 S5Br.

[0032] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiBr were weighed in a molar ratio of 25:0.5:4.5:10. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₆V₂S₅ was obtained. 0.1 P 0.9 S5Br.

[0033] Example 4

[0034] This embodiment provides a sulfide solid electrolyte Li6V, which is an electron-ion hybrid conductor. 0.1 P 0.9 S5I.

[0035] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiI were weighed in a molar ratio of 25:0.5:4.5:10. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₆V₂S₅ was obtained. 0.1 P 0.9 S5I.

[0036] Example 5

[0037] This embodiment provides a sulfide solid electrolyte Li6V, which is an electron-ion hybrid conductor. 0.5 P 0.5 S5I.

[0038] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiI were weighed in a molar ratio of 25:2.5:2.5:10. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₆V₅ was obtained. 0.5 P 0.5 S5I.

[0039] Comparative Example 1

[0040] This comparative example prepared Li6PS5Cl, a sulfide solid electrolyte commonly used in the prior art, which is a sulfide-silver-germanium ore type.

[0041] Preparation of the sulfide solid electrolyte of silver-germanium sulfide: Under nitrogen protection, Li2S, P2S5 and LiCl were weighed in a molar ratio of 25:5:10 and ball-milled for 15 h at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550 °C at a heating rate of 5 °C / min and sintered for 10 h. After cooling to room temperature, Li6PS5Cl was obtained.

[0042] Example 6

[0043] This embodiment provides a sulfide solid electrolyte Li, which is an electron-ion hybrid conductor. 6.9 V 0.1 P 0.9 S 5.9 Cl 0.1 .

[0044] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiCl were weighed in a molar ratio of 34:0.5:4.5:1. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, the electron-ion mixed conductor sulfide solid electrolyte Li₂S was obtained. 6.9 V 0.1 P 0.9 S 5.9 Cl 0.1 .

[0045] Comparative Example 2

[0046] This embodiment provides Li, a commonly used solid electrolyte of silver-germanium sulfide type in the prior art. 6.9 PS 5.9 Cl 0.1 .

[0047] Preparation of this sulfide solid electrolyte of silver-germanium sulfide type: Under nitrogen protection, Li₂S, P₂S₅, and LiCl were weighed at a molar ratio of 34:5:1, and ball-milled for 15 h at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550 °C at a heating rate of 5 °C / min and sintered for 10 h. After cooling to room temperature, LiCl was obtained. 6.9 PS 5.9 Cl 0.1 .

[0048] Example 7

[0049] This embodiment provides a sulfide solid electrolyte Li5V, which is an electron-ion hybrid conductor. 0.1 P 0.9 S4C l2 .

[0050] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiCl were weighed in a molar ratio of 15:0.5:4.5:20. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, Li₅V₅ was obtained. 0.1 P 0.9 S4C l2 .

[0051] Comparative Example 3

[0052] This embodiment provides Li5PS4Cl2, a sulfide solid electrolyte commonly used in the prior art, which is a sulfide-silver-germanium ore type.

[0053] Preparation of the sulfide solid electrolyte of silver-germanium sulfide: Under nitrogen protection, Li2S, P2S5 and LiCl were weighed in a molar ratio of 15:5:20 and ball-milled for 15 h at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550 °C at a heating rate of 5 °C / min and sintered for 10 h. After cooling to room temperature, Li5PS4Cl2 was obtained.

[0054] Example 8

[0055] This embodiment provides a sulfide solid electrolyte Li, which is an electron-ion hybrid conductor. 5.4 V 0.9 P 0.1 S 4.4 Cl 1.6 .

[0056] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, and LiCl were weighed in a molar ratio of 19:4.5:0.5:16. The mixture was then ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, LiCl was obtained. 5.4 V 0.9 P 0.1 S 4.4 Cl 1.6 .

[0057] Comparative Example 4

[0058] This embodiment provides Li, a commonly used solid electrolyte of silver-germanium sulfide type in the prior art. 5.4 PS 4.4Cl 1.6 .

[0059] Preparation of this sulfide solid electrolyte of silver-germanium sulfide type: Under nitrogen protection, Li₂S, P₂S₅, and LiCl were weighed at a molar ratio of 19:5:16, and ball-milled for 15 h at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550 °C at a heating rate of 5 °C / min and sintered for 10 h. After cooling to room temperature, LiCl was obtained. 5.4 PS 4.4 Cl 1.6 .

[0060] Example 9

[0061] This embodiment provides a sulfide solid electrolyte Li, which is an electron-ion hybrid conductor. 5.4 V 0.9 P 0.1 S 4.4 Cl 0.8 Br 0.8 .

[0062] Preparation of the mixed conductor sulfide solid electrolyte: Under nitrogen protection, Li₂S, V₂S₅, P₂S₅, LiCl, and LiBr were weighed in a molar ratio of 19:4.5:0.5:8:8. The mixture was ball-milled for 15 hours at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was then heated to 550°C at a heating rate of 5°C / min and sintered for 10 hours. After cooling to room temperature, Li₂S was obtained. 5.4 V 0.9 P 0.1 S 4.4 Cl 0.8 Br 0.8 .

[0063] Comparative Example 5

[0064] This embodiment provides Li, a commonly used solid electrolyte of silver-germanium sulfide type in the prior art. 5.4 PS 4.4 Cl 0.8 Br 0.8 .

[0065] Preparation of this sulfide solid electrolyte of silver-germanium sulfide type: Under nitrogen protection, Li₂S, P₂S₅, LiCl, and LiBr were weighed in a molar ratio of 19:5:8:8, and ball-milled for 15 h at a ball-to-material ratio of 20:1 and a rotation speed of 500 rpm to obtain a glassy composite. The glassy composite was heated to 550 °C at a heating rate of 5 °C / min and sintered for 10 h. After cooling to room temperature, Li₂ was obtained. 5.4 PS 4.4 Cl 0.8 Br 0.8 .

[0066] The ionic conductivity, electronic conductivity, and battery performance after assembly of the sulfide solid electrolytes prepared in Examples 1-9 and Comparative Examples 1-5 were tested, and the results are as follows.

[0067] The assembly method of the all-solid-state battery is as follows: cathode NCM811, areal load 2mAh / cm². 2 The N / P ratio is 1.2, the electrolyte content in both the positive and negative electrodes is 30wt%, the electrolyte layer thickness is 100μm, the charge-discharge voltage is 3.0-4.25V, the first cycle is 0.05C, and from the second cycle onwards, 200 charge-discharge cycles are performed at 0.5C. The greater the discharge capacity retention rate after 200 cycles, the better the cycle performance.

[0068]

[0069]

[0070] Although preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A mixed conductor sulfide solid electrolyte, characterized in that: The solid electrolyte includes Li 7-a M b P 1-b S 6- a X a , Where a and b satisfy 0 < a ≤ 2 and 0 < b < 1; M is a transition metal selected from at least one of Sc, Ti, V, Cr, Fe, Ni, Nb, Zn, and Y; The solid electrolyte has a strength of 1.0 × 10⁻⁶ at 25°C. -6 Electronic conductivity above S / cm; It also has a sulfide-silver-germanium mineral-type structure, where X is a halogen element; The halogen element is at least one of Cl, Br, and I.

2. The mixed conductor sulfide solid electrolyte according to claim 1, characterized in that: The solid electrolyte has an activation energy of 0.3 eV or less.

3. The mixed conductor sulfide solid electrolyte according to claim 1, characterized in that: The solid electrolyte has a peak at the position of 2θ = 29.5 ± 1.0° in X-ray diffraction measurements using CuKα radiation.

4. A method for preparing a mixed conductor sulfide solid electrolyte, characterized in that: For preparing the mixed conductor sulfide solid electrolyte according to any one of claims 1-3, under the protection of a safe gas, a lithium source, a transition metal source, a phosphorus source, a sulfur source, and a halogen source are mixed according to the chemical formula Li 7-a M b P 1-b S 6-a X a The mixture is mixed in the corresponding mixing ratio, and then the mixture is mechanically ground to obtain a glassy composite; then the glassy composite is heat-treated at or above the glass transition temperature of the glassy composite to obtain a sulfide solid electrolyte with mixed electron-ion conductors.

5. The method for preparing the mixed conductor sulfide solid electrolyte according to claim 4, characterized in that: The glassy composite was heated to 550°C at a heating rate of 5°C / min, sintered for 10 h, and then cooled to obtain a sulfide solid electrolyte with a mixed electron-ion conductor.

6. An all-solid-state battery, characterized in that: It includes a positive electrode, a negative electrode, and a mixed conductor sulfide solid electrolyte as described in any one of claims 1-3, disposed between the positive and negative electrodes.

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