Solid electrolyte and preparation method thereof, all-solid-state battery and manufacturing method thereof

Abstract

The present invention discloses a solid electrolyte and a preparation method thereof, an all-solid-state battery and a manufacturing method thereof, belonging to the field of electrochemical technology. The chemical formula of the solid electrolyte is Li x Zn y Cl (4‑y) , and the range of x and y is: 0.45≤x<3, 0.15≤y<1. The present invention uses Li3N and ZrCl4 powders to prepare a halogen nitride solid electrolyte, and the room temperature ionic conductivity of the product exceeds 1×10 ‑5 S / cm, the highest can exceed 3×10 ‑3 S / cm, and the all-solid-state lithium battery built with this electrolyte material as the core has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a solid electrolyte and a preparation method thereof, an all-solid-state battery and a manufacturing method thereof. Background Art

[0002] The rapid development of modern portable electronics and electric vehicles has greatly promoted the development of lithium-ion batteries, leading to significant progress. Therefore, among secondary energy storage devices, lithium-ion battery packs, due to their high energy density and long service life, have become the most widely studied secondary energy storage device and are used in many portable devices. However, current commercial lithium-ion batteries still face the problem of low safety standards. The use of flammable non-aqueous electrolytes makes sealed liquid batteries extremely susceptible to damage in the event of a portable device or vehicle collision, which can lead to serious accidents such as fire and explosion.

[0003] Compared with traditional liquid fuel ion batteries, all-solid-state batteries have higher operational safety. In addition, the high lithium ion conductivity and operating voltage window of solid electrolytes at room temperature have also become one of the important conditions for their extensive research. Among inorganic electrolytes, sulfides, oxides, borohydrides and halides have been studied more in the past. Among them, sulfide electrolytes (1-10mS·cm -1 ) has the highest conductivity compared to liquid electrolytes, but it has problems such as poor electrochemical stability and release of toxic H2S gas in humid air. In addition, sulfide electrolytes cannot directly contact the cathode, compared to Li + / Li, the electrochemical oxidation potential of sulfide electrolyte is only about 2.3 V. Oxide solid electrolyte has high inherent electrochemical oxidation stability, Li + Conductivity is 0.1~1mS·cm -1 However, due to its higher brittleness, its application in energy storage devices is quite difficult. It should be noted that chloride electrolytes are more electronegative and their oxidation potential is usually much higher than that of oxide electrolytes. + Conductivity is 0.1~1mS·cm -1 1 mS·cm can be achieved by using expensive rare earth metals such as In, Y, Er, Yb and Sc. -1 However, in free rare earth metal chloride solid electrolytes, such as Li2ZrCl6 solid electrolyte, its ionic conductivity is 0.45mS·cm -1 However, the insufficient ionic conductivity of the solid-state halide electrolyte Li2ZrCl6 severely limits the performance of solid-state batteries. Summary of the Invention

[0004] In order to overcome the problem that the ionic conductivity of solid halide electrolytes in the prior art is insufficient and seriously limits the performance of solid-state batteries, the present invention provides a solid electrolyte that uses solid nitrogen to dope chlorite to obtain a halogenonitride solid electrolyte with high ionic conductivity. Its chemical formula is Li x Zn y Cl (4-y) , and the value ranges of x and y are: 0.45≤x<3, 0.15≤y<1.

[0005] Preferably, the value range of x and y in the solid electrolyte chemical formula is: 0.45≤x<2.50, 0.15≤y<0.75; preferably, the value range of x and y is: 1.20 <x<1.60,0.4<y<0.6。

[0006] Preferably, its X-ray diffraction pattern (Cu Kα: ) has diffraction peaks at 2θ = 30.0±1.0 degrees, 50.2±1.2 degrees, 59.6±1.2 degrees, 73.4±1.3 degrees and 83.4±1.0 degrees.

[0007] Preferably, the solid electrolyte powder particles are needle-shaped, spherical or elliptical, with a particle size of 0.1 μm to 100 μm; the solid electrolyte powder particles are preferably granular or flake-shaped, with a size of 0.2 μm to 8 μm.

[0008] The present invention also provides a method for preparing the above-mentioned solid electrolyte, comprising the following steps:

[0009] Step 1: weigh Li3N and ZrCl4 powders in a low humidity environment (dew point temperature below -60°C), and control the molar ratio of Li3N:ZrCl4 to be (0.15-0.71):1;

[0010] Step 2: Mix the powder and ball milling beads and put them into a ball milling jar, and grind them in a planetary ball mill at a speed of 400-800 rpm for 6-36 hours to obtain a halogenonitride solid electrolyte.

[0011] The present invention also provides an all-solid-state battery, which comprises a negative electrode layer, a solid electrolyte protective layer, a solid electrolyte layer and a positive electrode layer in sequence. The solid electrolyte layer adopts the above-mentioned solid electrolyte, and the thickness of the solid electrolyte layer is 0.1μm to 1000μm.

[0012] Preferably, the positive electrode layer contains 10% to 40% by weight of the solid electrolyte relative to the positive electrode active material layer; and the negative electrode layer contains 0% to 40% by weight of the solid electrolyte relative to the negative electrode layer.

[0013] Preferably, the solid electrolyte protective layer adopts a sulfide electrolyte, preferably Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li6PS5X (X=Cl, Br, or I), Li 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 .

[0014] The present invention also provides a method for manufacturing an all-solid-state battery, using the above-mentioned solid electrolyte powder, comprising the following steps:

[0015] Step 1: weighing solid electrolyte powder and positive electrode material powder and mixing them for 10-30 minutes in a dry atmosphere to obtain a positive electrode material mixture, wherein the solid electrolyte powder accounts for 10% to 40% by weight;

[0016] Step 2: Assemble the all-solid-state lithium-ion battery in a mold, which includes two upper and lower punches made of stainless steel and a cylinder with a diameter of 8 to 10 mm made of insulating polycarbonate. Fill 30 to 50 mg of solid electrolyte powder into the cylinder and cold press at 150 to 300 MPa for 1 to 3 minutes to obtain a solid electrolyte layer; spread 5 to 10 mg of the positive electrode material mixture on one side of the solid electrolyte layer and uniaxially press at 200 to 400 MPa for 2 to 4 minutes to form a positive electrode layer; evenly apply 50 to 80 mg of solid electrolyte protective material on the other side of the solid electrolyte layer and press at 150 to 300 MPa for 0.5 to 2 minutes to form a solid electrolyte protective layer;

[0017] Step 3: Place a thin In foil with a diameter of 7 to 9 mm and a Li foil with a diameter of 5 to 7 mm on the other side of the solid electrolyte layer and apply a constant uniaxial pressure to the battery.

[0018] Step 4: At the upper punch, the upper part of the cylinder is isolated from the outside atmosphere by means of an insulating cover; at the lower punch, the connection between the cylinder and the lower punch is sealed.

[0019] Beneficial effects:

[0020] The beneficial effects of the technical solution of the present invention are as follows: by mixing Li3N and ZrCl4 powders and ball milling for a certain period of time, a new Li-Zr-N-Cl phase can be formed, which has a fast ion transport channel and an ionic conductivity of more than 1×10 -5 S / cm, the highest can exceed 3×10 -3 S / cm, and the all-solid-state lithium battery built with this electrolyte material as the core has excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a schematic diagram of a preferred all-solid-state battery structure of the present invention;

[0023] Figure 2 Schematic diagram of a mold for testing the ionic conductivity of a solid electrolyte according to the present invention;

[0024] Figure 3 is an X-ray diffraction pattern of the solid electrolyte prepared in Example 1 of the present invention;

[0025] Figure 4 1. The electrochemical impedance spectra and corresponding Arrhenius plots of the solid electrolyte at different temperatures in Example 1 of the present invention;

[0026] Figure 5 This is the first charge and discharge curve of the all-solid-state battery prepared with the solid electrolyte in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] A halogen nitride solid electrolyte, which is obtained by doping chlorite with solid nitrogen, has the characteristics of high ionic conductivity. Its chemical formula is Li x Zn y Cl (4-y) , and the value ranges of x and y are: 0.45≤x<3, 0.15≤y<1.

[0029] Here, the lithium ion conductivity of the chloride solid electrolyte is high, for example, exceeding 1×10 -5 S / cm, and the nitrogen-doped chlorite-based solid electrolyte can be crystalline or amorphous, and can be used to make all-solid-state batteries with excellent charge and discharge characteristics.

[0030] It should be noted that the halogenonitride solid electrolyte is not limited to any specific particle shape, and the shape can be needle-shaped, spherical or elliptical, and the particle size can be 0.1 micron to 100 microns.

[0031] Among them, the nitrogen-doped chlorite-based solid electrolyte material can be granular or flaky. For example, the nitrogen-doped chlorite-based solid electrolyte material is granular with a size of 0.2 microns to 8 microns to ensure higher lithium ion conductivity and uniform dispersion of the solid electrolyte material.

[0032] Preferably, the value range of x and y in the solid electrolyte chemical formula is: 0.45≤x<2.50, 0.15≤y<0.75; preferably, the value range of x and y is: 1.20 <x<1.60,0.4<y<0.6。

[0033] Preferably, its X-ray diffraction pattern (Cu Kα: ) has diffraction peaks at 2θ = 30.0±1.0 degrees, 50.2±1.2 degrees, 59.6±1.2 degrees, 73.4±1.3 degrees and 83.4±1.0 degrees.

[0034] This embodiment further provides a method for preparing the above-mentioned solid electrolyte, which is prepared by ball milling, wherein all chemical raw materials and reagents are of analytical grade purity, specifically lithium nitride (Li3N, 99.4% AlfaAesar) and zirconium (IV) chloride (ZrCl4, 98% Macklin), comprising the following steps:

[0035] Step 1: weigh Li3N and ZrCl4 powders in a low humidity environment (dew point temperature below -60°C), and control the molar ratio of Li3N:ZrCl4 to be (0.15-0.71):1;

[0036] Step 2: Mix the powder and ball milling beads and put them into a ball milling jar, and grind them in a planetary ball mill at a speed of 400-800 rpm for 6-36 hours to obtain a halogenonitride solid electrolyte.

[0037] Here, the preparation methods are kept different, and the ratio of Li3N and ZrCl4 powders is designed to obtain Examples 1 to 8, and other powder formulas are used to obtain Comparative Examples 1 to 4. The powder composition, ratio and room temperature ionic conductivity of the prepared solid electrolytes in each Example and Comparative Example are shown in Table 1.

[0038] Table 1 Test results of ionic conductivity in each embodiment and comparative example

[0039]

[0040]

[0041] This embodiment also provides a all-solid-state battery, as Figure 1 shown, successively including a negative electrode layer 100, a solid electrolyte protection layer 200, a solid electrolyte layer 300 and a positive electrode layer 400. The solid electrolyte layer 300 uses the above-mentioned solid electrolyte, and the thickness of the solid electrolyte layer 300 is 0.1 μm to 1000 μm.

[0042] As a preferred embodiment, at least one of the negative electrode layer 100, the solid electrolyte protection layer 200 and the positive electrode layer 400 contains the above-mentioned solid electrolyte.

[0043] The positive electrode layer contains 10% to 40% by weight of the solid electrolyte in the positive electrode layer. In addition, a conductive agent or a binder can be added, and lithium-containing transition metal oxides - LiCoO2 and LiNi 1-d-f Co d Al f O2 (where 0 < d, 0 < f, and 0 < (d + f) < 1)), transition metal fluorides, polyanion materials and fluorinated polyanion materials are all very suitable as positive electrode active materials.

[0044] The negative electrode layer contains 0% to 40% by weight of the solid electrolyte in the negative electrode layer. In addition, a conductive agent or a binder can be added. The negative electrode material can be a metal material, a carbon material, an oxide, a nitride, a tin compound and a silicon compound; the metal material can be an independent metal or an alloy material (lithium metal and lithium alloy); the carbon material mainly includes natural graphite, coke, spherical carbon, artificial graphite and amorphous carbon. In terms of specific capacity, the negative electrode active material can be one or more of silicon, tin, tin compounds and silicon compounds.

[0045] The solid electrolyte protection layer uses a sulfide electrolyte, preferably Li2S - P2S5, Li2S - SiS2, Li2S - B2S3, Li2S - GeS2, Li6PS5X (X = Cl, Br, or I), Li 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 .

[0046] Here, the all-solid-state battery is preferably an all-solid-state lithium-ion battery. In addition, the solid-state battery can be a primary battery or a secondary battery, and the latter is preferably a secondary battery that can be repeatedly charged and discharged.

[0047] The following describes the test method for the lithium ion conductivity of the solid electrolyte in Examples 1 to 8 and Comparative Examples 1 to 4. Figure 2 The figure shows a schematic diagram of a mold for solid electrolyte ion conductivity, wherein the mold includes a tube sleeve 1 made of insulating polycarbonate with a diameter of 10 mm, and an upper punch 2 and a lower punch 3 made of stainless steel.

[0048] First, the solid electrolyte was weighed in a glove box with a dew point temperature of -80°C, 150 mg of the electrolyte 4 was placed in a mold, the voltage regulator 5 was started, and compression was performed under a pressure environment of 300 MPa.

[0049] The electrochemical impedance spectroscopy (EIS) of solid electrolyte 4 in the mold was measured at 30°C using the AC impedance method. The measurements were performed using a Biologic VSP200 analyzer with a voltage of 50 mV and a measurement frequency range of 0.01 to 10 MHz. The lithium ion conductivity was calculated as follows:

[0050]

[0051] Where σ is the ionic conductivity of the solid electrolyte, S is the contact area between the solid electrolyte and the upper punch, and R se is the resistance value of the solid dielectric material in the impedance measurement, and t is the thickness of the solid electrolyte 4 under pressure. The solid electrolyte prepared according to Example 1 has an ionic conductivity of 3.42×10 -3 S cm -1 .

[0052] The X-ray diffraction pattern of the solid electrolyte is analyzed below. The X-ray diffraction spectrum of the solid electrolyte in Example 1 was measured using a Malvern Panalytical Empyrean X-ray diffractometer at a voltage of 40 kV and a current of 45 mA. The 2θ range was 10 to 90 degrees, the scan rate was 5 degrees per minute, and a polyimide film was used to protect the sample from air.

[0053] like Figure 3 As shown, the X-ray diffraction pattern of the solid electrolyte prepared in Example 1 has diffraction peaks at 2θ = 30.0 ± 1.0 degrees, 50.2 ± 1.2 degrees, 59.6 ± 1.2 degrees, 73.4 ± 1.5 degrees and 83.4 ± 2.0 degrees (CuKα: ), the test temperature is 30℃.

[0054] The following is an evaluation of the ionic conductivity at different temperatures. The mold unit is placed in a high and low temperature box and tested in the range of 30 to 80°C. After each heating to the predetermined temperature, it is left to stand for 1 hour before impedance spectrum measurement and calculation of the ionic conductivity.

[0055] The electrochemical impedance spectroscopy measurement results of the solid electrolyte in Example 1 are as follows: Figure 4 As shown, within the temperature range of 30 to 80° C., the solid electrolyte in Example 1 maintains high conductivity of lithium ions without sudden changes.

[0056] This embodiment also provides a method for manufacturing an all-solid-state battery, using the above-mentioned solid electrolyte powder, comprising the following steps:

[0057] Step 1: In a dry argon atmosphere, weigh solid electrolyte powder and positive electrode active material powder and mix them for 10-30 minutes to obtain a positive electrode material mixture, wherein the solid electrolyte powder accounts for 10% to 40% by weight;

[0058] Step 2: Assemble the all-solid-state lithium-ion battery in a mold comprising two upper and lower stainless steel punches and a cylinder with a diameter of 8 to 10 mm made of insulating polycarbonate. Fill the cylinder with 30 to 50 mg of solid electrolyte powder and cold press at 150 to 300 MPa for 1 to 3 minutes to obtain a solid electrolyte layer. Spread 5 to 10 mg of the positive electrode material mixture on one side of the solid electrolyte layer and uniaxially press at 200 to 400 MPa for 2 to 4 minutes to form a positive electrode active material layer. Evenly apply 50 to 80 mg of solid electrolyte protective material on the other side of the solid electrolyte layer and press at 150 to 300 MPa for 0.5 to 2 minutes to form a solid electrolyte protective layer.

[0059] Step three: Place a thin In foil with a diameter of 7 to 9 mm and a Li foil with a diameter of 5 to 7 mm on the other side of the solid electrolyte layer, and apply a constant uniaxial pressure to the battery; the weight of the thin In foil is preferably 0.042 g and the thickness is preferably 100 μm; the weight of the Li foil is preferably 0.006 g and the diameter is preferably 6 mm.

[0060] Step 4: At the upper punch, the upper part of the cylinder is isolated from the outside atmosphere by means of an insulating cover; at the lower punch, the connection between the cylinder and the lower punch is sealed.

[0061] The battery obtained above is a secondary battery. Here, the obtained secondary battery is subjected to a charge and discharge test. The obtained secondary battery is placed in a constant temperature box maintained at 30°C, and the prepared all-solid-state battery is charged and discharged at a rate of 0.1C in a voltage range of 2.4 to 3.6V (relative to Li-In). The results are as follows Figure 5As shown, an all-solid-state battery using a nitrogen-doped chloride electrolyte is a test case of this embodiment. It uses the solid electrolyte of Example 1, a Li6PS5Cl solid electrolyte protective layer, a Li-In composite negative electrode and a LiCoO2 positive electrode. The battery is normally charged and discharged at room temperature and the first discharge capacity value reaches 124mAh / g.

[0062] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A solid electrolyte, characterized in that Its chemical formula is Li x Zn y Cl 4-y , and the value ranges of x and y are: 0.45≤x<3, 0.15≤y<1.

2. A solid electrolyte according to claim 1, characterized in that The value ranges of x and y in the solid electrolyte chemical formula are: 0.45≤x<2.50, 0.15≤y<0.

75.

3. A solid electrolyte according to claim 1, characterized in that: The range of x and y values ​​is: 1.20 <x<1.60,0.4<y<0.6。 4. The solid electrolyte according to claim 1 or 2, characterized in that Its X-ray diffraction pattern Cu Kα:λ=1.5405Å has diffraction peaks at 2θ=30.0±1.0 degrees, 50.2±1.2 degrees, 59.6±1.2 degrees, 73.4±1.3 degrees and 83.4±1.0 degrees.

5. The solid electrolyte according to claim 1 or 2, characterized in that The powder particles of the solid electrolyte are in the shape of needles, spheres, flakes or ellipses, and have a particle size of 0.1µm to 100µm.

6. The solid electrolyte according to claim 1 or 2, characterized in that The powder particle size of the solid electrolyte is 0.2µm~8µm.

7. A method for preparing the solid electrolyte according to claim 1 or 2, characterized in that: The steps include: Step 1: weigh Li3N and ZrCl4 powders in an environment with a dew point temperature below -60°C, and control the molar ratio of Li3N:ZrCl4 to be (0.15-0.71):1; Step 2: Mix and grind the powders to obtain a halide nitride solid electrolyte.

8. The method for preparing a solid electrolyte according to claim 7, characterized in that: In step 2, the powder and ball milling beads are mixed and placed in a ball mill jar, and mixed and ground in a planetary ball mill at a speed of 400-800 rpm for 6-36 hours.

9. An all-solid-state battery, characterized in that: It comprises a negative electrode layer, a solid electrolyte protective layer, a solid electrolyte layer and a positive electrode layer in sequence, wherein the solid electrolyte layer adopts the solid electrolyte as claimed in claim 1 or 2, and the thickness of the solid electrolyte layer is 0.1µm~1000µm.

10. The all-solid-state battery according to claim 9, characterized in that: The positive electrode layer contains the solid electrolyte in an amount of 10% to 40% by weight of the positive electrode layer; and the negative electrode layer contains the solid electrolyte in an amount of 0% to 40% by weight of the negative electrode layer.

11. The all-solid-state battery according to claim 9, characterized in that: The solid electrolyte protective layer adopts sulfide electrolyte, The sulfide electrolyte is Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li6PS5X, where X is Cl, Br or I, Li 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 .

12. A method for manufacturing an all-solid-state battery, characterized in that: Using the solid electrolyte as claimed in claim 1 or 2, comprising the following steps: Step 1: In a dry atmosphere, weighing solid electrolyte powder and positive electrode material powder and mixing them for 10-30 minutes to obtain a positive electrode material mixture, wherein the solid electrolyte powder accounts for 10% to 40% by weight; Step 2: Assemble the all-solid-state lithium-ion battery in a mold, which includes two upper and lower punches made of stainless steel and a cylinder with a diameter of 8-10 mm made of insulating polycarbonate. Fill 30-50 mg of solid electrolyte powder into the cylinder and cold press at 150-300 MPa for 1-3 minutes to obtain a solid electrolyte layer; spread 5-10 mg of the positive electrode material mixture on one side of the solid electrolyte layer and uniaxially press at 200-400 MPa for 2-4 minutes to form a positive electrode layer; evenly apply 50-80 mg of solid electrolyte protective material on the other side of the solid electrolyte layer, pressurize at 150-300 MPa for 0.5-2 minutes to form a solid electrolyte protective layer; Step 3: Place an In foil with a diameter of 7 to 9 mm and a thickness of 100 μm and a Li foil with a diameter of 5 to 7 mm on the other side of the solid electrolyte layer, and apply a constant uniaxial pressure to the battery; Step 4: At the upper punch, the upper part of the cylinder is isolated from the outside atmosphere by means of an insulating cover; at the lower punch, the connection between the cylinder and the lower punch is sealed.

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