CN115882053A - Solid electrolyte, preparation method thereof and all-solid-state battery - Google Patents

Abstract

The invention discloses a solid electrolyte, a preparation method thereof and an all-solid-state battery, belonging to the technical field of electrochemistry and aiming at solving the problems that the solid electrolyte is prepared by Li according to molar ratio ₂ S:Li ₃ N = (1.00-2.34): 1 mixing the powder and ball milling to obtain the nitrogen sulfide solid electrolyte with the chemical formula of Li _(2+x) N _x S _(1‑x) And wherein x is in the range of 0.35 to 0.55. The invention adopts Li ₂ S and Li ₃ The N powder is mixed and ball-milled for a certain time to form a novel Li-N-S phase which has good compatibility with lithium metal, can solve the problem that the traditional sulfide electrolyte is not compatible with a lithium metal cathode, and can construct a high specific energy all-solid-state lithium battery using the lithium metal cathode; can realizeStable cycling of lithium symmetrical batteries, lithium symmetrical batteries employing the solid electrolyte, can cycle more than 750 cycles.

Description

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

Technical Field

The invention relates to the technical field of electrochemistry, in particular to a solid electrolyte, a preparation method thereof and an all-solid-state battery.

Background

Lithium ion batteries are receiving increasing attention from the industry as the field of energy storage expands rapidly. However, in the face of energy storage requirements of consumer electronics and electric vehicles, lithium ion batteries still have problems of low energy density and safety. The solid electrolyte is used for replacing inflammable organic electrolyte in the traditional lithium ion battery to construct an all-solid battery, so that the safety performance of the battery is expected to be improved, and meanwhile, novel electrode materials such as a high-specific-capacity lithium metal cathode and the like can be unlocked, so that the energy density of the battery is expected to be remarkably improved.

The solid electrolyte is the core of all-solid batteries, and among the existing various types of solid electrolytes, the sulfide solid electrolyte has excellent lithium ion conductivity (1 to 10 mS/cm), and is considered to be one of the most promising solid electrolytes. However, most sulfide solid electrolytes have a narrow electrochemical stability window, and are particularly poor in compatibility with lithium metal cathodes, such as a tendency to chemically react with the lithium metal cathode or a tendency to grow lithium dendrites, which affects introduction of the lithium metal cathode. Therefore, it is important to develop a solid electrolyte material stable for a lithium negative electrode.

Disclosure of Invention

In order to solve the problems that the electrochemical stability window of a sulfide solid electrolyte in the prior art is narrow, particularly the compatibility of the sulfide solid electrolyte to a lithium metal cathode is insufficient, the sulfide solid electrolyte is easy to generate chemical reaction with the lithium metal cathode or is easy to grow lithium dendrite so as to influence the introduction of the lithium metal cathode, the invention provides the solid electrolyte, and the chemical formula of the solid electrolyte is Li _(2+x) N _x S _(1-x) And wherein x is in the range of 0.35 to 0.55. The solid electrolyte has good compatibility with lithium metal, can realize stable circulation of a lithium symmetrical battery, and can circulate for more than 750 circles in a lithium battery adopting the solid electrolyte.

Here, x is preferably in the range of 0.48 to 0.52.

Preferably, its X-ray diffraction pattern (copper target, wavelength)

) Diffraction peaks exist at positions of 2 θ =28.18 ± 0.50 °, 32.54 ± 0.50 °, 46.97 ± 0.50 °, 55.75 ± 0.50 °, 58.57 ± 0.50 °.

Preferably, the normalized full width at half maximum of a diffraction peak corresponding to 2 θ =28.18 ± 0.50 ° in the X-ray diffraction pattern thereof is F ₍₁₁₁₎ A,/λ, and satisfy F ₍₁₁₁₎ Lambda/λ > 0.3, preferably, where F ₍₁₁₁₎ /λ＞0.42。

The invention also provides a preparation method of the solid electrolyte, which comprises the following steps of mixing Li in molar ratio ₂ S:Li ₃ N = (1.00-2.34). 1, mixing the powder and ball milling to obtain the nitrogen sulfide solid electrolyte.

Preferably, the ball mass ratio of the ball materials used in the ball milling process is (1-60): 1, and the mixture is ball milled for 1-24 hours at the rotating speed of 150-900 rpm to obtain the nitrogen sulfide solid electrolyte.

The invention also provides an all-solid-state battery which sequentially comprises a negative electrode layer, an electrolyte layer and a positive electrode layer, wherein the electrolyte layer contains the solid electrolyte.

Preferably, the negative electrode layer includes a negative electrode active material selected from one or more of a metal material, a carbon material, and a silicon material;

preferably, the metallic material is selected from lithium metal or a lithium alloy;

preferably, the carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite, and amorphous carbon;

preferably, the negative electrode layer does not contain the first electrolyte material; or the negative electrode layer comprises the first electrolyte material, and the weight of the first electrolyte material in the negative electrode layer does not exceed 70% of the total weight; the first electrolyte material comprises the solid state electrolyte;

preferably, the thickness of the negative electrode layer is 10 to 500 μm.

Preferably, the electrolyte layer comprises a second electrolyte material comprising the solid state electrolyte;

preferably, the second electrolyte material further includes a sulfide solid state electrolyte material and/or a halide solid state electrolyte material;

preferably, the sulfide solid state electrolyte material is selected from li ₂ S-P ₂ S ₅ 、L i ₂ S-SiS ₂ 、Li ₂ S-B ₂ S ₃ 、L i ₂ S-GeS ₂ 、L i ₆ PS ₅ C l、L i _3.25 Ge _0.25 P _0.75 S ₄ And L i ₁₀ GeP ₂ S ₁₂ One or more of;

preferably, the halide solid state electrolyte material is selected from li ₃ I nCl ₆ 、Li ₂ ZrCl ₆ 、L i ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of (a);

preferably, the electrolyte layer has a thickness of 1 to 500 μm.

Preferably, the positive electrode layer includes a positive electrode active material and a third electrolyte material, the third electrolyte material including the solid electrolyte;

preferably, the positive active material is selected from one or more of lithium iron phosphate, lithium-containing transition metal oxides, transition metal sulfides, transition metal oxysulfides, transition metal fluorides, polyanionic materials, elemental sulfur and lithium sulfide;

preferably, the positive electrode layer contains 5 to 70% by weight of the third electrolyte material, the third electrolyte material including a solid electrolyte material different from the solid electrolyte;

preferably, the third electrolyte material includes a sulfide solid state electrolyte material and/or a halide solid state electrolyte material;

preferably, the sulfide solid state electrolyte material is selected from li ₂ S-P ₂ S ₅ 、L i ₂ S-SiS ₂ 、Li ₂ S-B ₂ S ₃ 、L i ₂ S-GeS ₂ 、L i ₆ PS ₅ C l、L i _3.25 Ge _0.25 P _0.75 S ₄ And L i ₁₀ GeP ₂ S ₁₂ One or more of;

preferably, the first and second electrodes are formed of a metal,the halide solid state electrolyte material is selected from the group consisting of li ₃ I nCl ₆ 、Li ₂ ZrCl ₆ 、L i ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of;

preferably, the thickness of the positive electrode layer is 10 to 500 μm.

Has the advantages that:

the technical scheme of the invention has the following beneficial effects:

with Li ₂ S and L i ₃ The N powder is mixed and ball-milled for a certain time to form a novel Li-N-S phase which has good compatibility with lithium metal, can solve the problem that the traditional sulfide electrolyte is not compatible with a lithium metal cathode, and can construct a high specific energy all-solid-state lithium battery using the lithium metal cathode; the stable circulation of the lithium symmetrical battery can be realized, and the lithium symmetrical battery adopting the solid electrolyte can circulate for more than 750 circles.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic view of an all-solid-state battery according to the present invention;

FIG. 2 is an X-ray diffraction pattern of the solid electrolyte obtained in examples 1 to 2 of the present invention and comparative examples 1 to 4;

FIG. 3 is an AC impedance spectrum and lithium ion conductivity of the solid electrolyte obtained in examples 1 to 2 of the present invention and comparative examples 1 to 3 measured at a temperature of 27 ℃;

FIG. 4 is a graph showing the change in lithium ion conductivity with temperature of the solid electrolyte obtained in example 1 of the present invention;

FIG. 5 is a result of constant current cycle test of the lithium symmetrical batteries obtained in example 1 of the present invention and comparative example 5;

fig. 6 is a charge/discharge curve diagram of the all solid-state lithium battery obtained in example 1 of the present invention at a temperature of 27 ℃.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or instruments used are conventional products available from normal commercial vendors, not indicated by the manufacturer.

The solid electrolyte in this embodiment has a chemical formula of li _(2+x) N _x S _(1-x) And wherein x is in the range of 0.35 to 0.55. The solid electrolyte has good compatibility with lithium metal, can realize stable circulation of a lithium symmetrical battery, and can circulate more than 750 circles in the lithium symmetrical battery adopting the solid electrolyte.

Here, the value of x is preferably in the range of 0.48 to 0.52.

The X-ray diffraction pattern of the solid electrolyte was analyzed, and the X-ray diffraction pattern (copper target, wavelength)

) Diffraction peaks exist at positions of 2 θ =28.18 ± 0.50 °, 32.54 ± 0.50 °, 46.97 ± 0.50 °, 55.75 ± 0.50 °, 58.57 ± 0.50 °.

Further, the normalized full width at half maximum of a diffraction peak corresponding to 2 θ =28.18 ± 0.50 ° in the X-ray diffraction pattern thereofIs F ₍₁₁₁₎ A,/λ, and satisfy F ₍₁₁₁₎ Lambda > 0.3, preferably, where F ₍₁₁₁₎ /λ＞0.42。

The embodiment also provides a preparation method of the solid electrolyte, which comprises the following steps:

step one, li is added ₂ S and L i ₃ Weighing N powder in low humidity environment (dew point temperature below-60 deg.C), and controlling molar ratio at L i ₂ S:L i ₃ N＝(1.00～2.34):1；

And step two, mixing the powder and the ball milling beads, putting the mixture into a ball milling tank, mixing and grinding the mixture for 1 to 24 hours in a planetary ball mill at the rotating speed of 150 to 900rpm to obtain the nitrogen sulfide solid electrolyte, wherein the ball mass ratio of the powder to the ball milling beads is (1 to 60): 1.

The present embodiment also provides an all-solid-state battery, as shown in fig. 1, which includes a negative electrode layer 100, an electrolyte layer 200, and a positive electrode layer 300 in this order, and the electrolyte layer 200 contains the solid electrolyte.

The negative electrode layer 100 includes a negative electrode active material 101, the negative electrode layer 100 may or may not include a first electrolyte material 102, and the first electrolyte material 102 includes the solid electrolyte;

wherein the negative electrode active material 101 is selected from one or more of a metal material, a carbon material, and a silicon material; the metal material is selected from lithium metal or lithium alloy; the carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite and amorphous carbon;

the content of the first electrolyte material 102 in the negative electrode layer 100 is not more than 70% from the viewpoint of the energy density and output of the battery; and the thickness of the negative electrode layer 100 is 10 to 500 μm.

It is further noted herein that the first electrolyte material 102 is a material containing a solid electrolyte; the first electrolyte material 102 may be a material containing the above-described solid electrolyte as a main component; the first electrolyte material 102 may also be a material composed of the above-described nitrogen solid electrolyte.

As a preferred embodiment, the electrolyte layer 200 includes a second electrolyte material including the solid electrolyte;

here, the second electrolyte material contained in the electrolyte layer 200 may be constituted only by the above-described solid electrolyte; the second electrolyte material contained in the electrolyte layer 200 may also be composed of the above-described solid electrolyte and a solid electrolyte material different from the above-described solid electrolyte material.

The different solid state electrolyte materials here may be a sulfide solid state electrolyte material and a halide solid state electrolyte material. Wherein the sulfide solid electrolyte material is selected from Li ₂ S-P ₂ S ₅ 、Li ₂ S-Si S ₂ 、Li ₂ S-B ₂ S ₃ 、L i ₂ S-GeS ₂ 、L i ₆ PS ₅ C l、L i _3.25 Ge _0.25 P _0.75 S ₄ And L i ₁₀ GeP ₂ S ₁₂ One or more of; the halide solid electrolyte material is selected from the group consisting of li ₃ I nC l ₆ 、Li ₂ ZrCl ₆ 、L i ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of (a); the thickness of the electrolyte layer 200 is 1 to 500 μm from the viewpoint of energy density and output of the battery.

As a preferred embodiment, the positive electrode layer 300 includes a positive electrode active material 301 and a third electrolyte material 302, the electrolyte material 302 including the solid electrolyte;

here, the positive electrode active material 301 is selected from one or more of lithium iron phosphate, lithium-containing transition metal oxide, transition metal sulfide, transition metal oxysulfide, transition metal fluoride, polyanion material, elemental sulfur, and lithium sulfide;

the third electrolyte material 302 contained in the positive electrode layer 300 may be composed of only a solid electrolyte material different from the above-described solid electrolyte material. The third electrolyte material 302 contained in the positive electrode layer 300 may also contain a solid electrolyte material different from the above-described nitrogen sulfide solid electrolyte material.

The positive electrode layer 300 contains the third electrolyte material 302 in an amount of 5 to 70% by weight thereof from the viewpoint of energy density and output of the battery; the third electrolyte material 302 includes a sulfide solid state electrolyte material and/or a halide solid state electrolyte material;

wherein the sulfide solid electrolyte material is selected from the group consisting of Li ₂ S-P ₂ S ₅ 、L i ₂ S-SiS ₂ 、L i ₂ S-B ₂ S ₃ 、Li ₂ S-GeS ₂ 、L i ₆ PS ₅ C l、L i _3.25 Ge _0.25 P _0.75 S ₄ And L i ₁₀ GeP ₂ S ₁₂ One or more of (a);

the halide solid electrolyte material is selected from the group consisting of li ₃ I nC l ₆ 、Li ₂ ZrCl ₆ 、L i ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of; the thickness of the positive electrode layer is 10 to 500 μm.

Example 1

Preparing a solid electrolyte:

in a glove box under an argon atmosphere, 12.4 mmol of Li were weighed out ₃ N (431 mg), 12.4 mmol of Li ₂ S (568 mg), corresponding to x =0.5. Grinding and mixing the raw materials in an agate mortar, and then putting the mixture into a 45ml ball milling tank; ball milling is carried out by using zirconia balls, the number ratio of small balls (with the diameter of 3 mm) to large balls (with the diameter of 8 mm) is 5; mixing and grinding in a planetary ball mill (FRITSCH PULVERISTETE 7) at the rotating speed of 500rpm for 7.5 hours, and stopping the ball mill for 5 minutes every 15 minutes; after the reaction is finished, opening the ball milling tank in a glove box under argon atmosphere, and taking out the materials. Thus, a solid electrolyte material of example 1 was obtained.

The solid electrolyte material of example 1 was subjected to X-ray diffraction, ion conductivity test, solid electrolyte activation energy test, lithium symmetric battery test, and full battery test, and the results were as follows:

(1) Ion conductivity test

The lithium ion conductivity is tested by an alternating current impedance spectrum, and the testing method comprises the following steps: the solid electrolyte was weighed in a glove box under argon atmosphere, 100mg of the electrolyte was placed in a die cell and pressed into a tablet at a pressure of 500MPa for 5 minutes, then the pressure was reduced to 250MPa, a symmetrical cell of "stainless steel | solid electrolyte | stainless steel" was assembled directly in the die cell, and the ac impedance of the cell at open circuit was measured. The measurement adopts a Biologic VSP200 analyzer, the voltage is 50mV, the measurement frequency range is 1 Hz-7 MHz, and the measurement temperature is 27 ℃. After the measurement, the solid electrolyte sheet was taken out from the die battery, and its thickness was measured using a micrometer.

The calculation formula of the lithium ion conductivity is as follows:

where σ is the ionic conductivity of the solid electrolyte under test, R _se Is the AC impedance value of the solid electrolyte material in impedance measurement, S is the contact area between the solid electrolyte and the stainless steel electrode, and d is the thickness of the solid electrolyte material. Specific results of lithium ion conductivity are shown in table 1; fig. 3 is an ac impedance spectrum and lithium ion conductivity measured at a temperature of 27 ℃.

The results showed that the lithium ion conductivity of the solid electrolyte of example 1 was 2.1 × 10 ^-4 S/cm。

(2) Diffraction by X-ray

Measuring an X-ray diffraction spectrogram of a sample by a Malvern Panalytical Empyrean X-ray diffractometer, wherein the specific parameters are as follows: the voltage is 40kV, and the current is 45mA;2 θ range: 10 to 80 degrees; scanning rate: 7 ℃ min ^-1 (ii) a Polyimide film was used to protect the sample from air. Copper Ka ray (wavelength) was used for X-ray diffraction

) And (4) measuring. The X-ray diffraction pattern of the sample is shown in figure 2.

The results showed that the X-ray diffraction pattern had diffraction peaks at the positions 2 θ =28.18 °, 32.54 °, 46.97 °, 55.75 ° and 58.57 °. And 2 θ =28.18 ° of the diffraction peak F ₍₁₁₁₎ /λ＝0.42。

(3) Solid electrolyte activation energy test

The activation energy test method of example 1 is to measureThe ionic conductivity of the solid electrolyte material at the same temperature is tested by the following method: the die battery is placed in a high-low temperature box, the temperature range is 30-110 ℃, the heating rate is 10 ℃ h ^-1 And testing the alternating current impedance of the die battery when the die battery is in an open circuit in the heating process, wherein the calculation formula of the lithium ion conductivity is shown as the formula. FIG. 4 shows Li in example 1 _2.5 N _0.5 S _0.5 Lithium ion conductivity of the solid electrolyte is plotted as a function of temperature.

The results show that the solid electrolyte of example 1 has an activation energy Ea =0.38eV at the temperature range tested.

(4) Lithium symmetrical cell testing

Using a die battery as a battery housing, the battery comprising two metal posts and an insulated liner; lithium metal sheets were used as the positive electrode and the negative electrode of the battery, and the solid electrolyte prepared in example 1 was used as the electrolyte.

100mg of the solid electrolyte powder of example 1 was taken and placed in a mold cell cylinder and held at 500MPa for 5 minutes; then, the pressure is removed, and a lithium sheet and a stainless steel column are respectively added at the two ends of the electrolyte sheet; and placing the cylinder into a battery flange of a die, giving a pressure of 25MPa, screwing screws, and sealing to obtain the lithium symmetrical battery. In the constant current cycle test of a lithium symmetrical cell, the cell was left standing at 27 ℃ for 2 hours, and then a cycle of 30 minutes of charging and 30 minutes of discharging was carried out with a constant cycle current density of 0.1 mA-cm ^-1 . Fig. 5 shows the results of constant current cycling tests for lithium symmetrical cells.

The results show that the lithium symmetric battery using the solid electrolyte of example 1 can be cycled for more than 750 cycles, corresponding to the solid electrolyte of example 1 having good compatibility with lithium metal, stable cycling of the lithium symmetric battery can be achieved.

(5) Full cell test

Step one, weighing Li in a dry atmosphere ₆ PS ₅ C l solid electrolyte powder and commercial Li CoO ₂ Mixing the anode powder for 10-30 minutes to obtain an anode material mixture, wherein the solid electrolyte accounts for 10-70% of the weight of the anode mixture;

and step two, using a die battery comprising two metal posts and an insulating lining as a battery shell. 80mg of the solid electrolyte powder of example 1 was taken, placed in a battery cylinder of a mold, held at a pressure of 200MPa for 2 minutes, and then the pressure was removed to obtain a first electrolyte layer. Subsequently, 120mg of Li were added ₆ PS ₅ Cl solid electrolyte powder, held at a pressure of 400MPa for 2 minutes, and then the pressure was removed to obtain a second electrolyte layer.

And step three, adding 10mg of the positive electrode mixture into one side of the electrolyte layer, uniformly coating, and keeping for 2 minutes under the pressure of 200MPa to obtain the positive electrode layer. Adding a lithium sheet and a stainless steel column at the other end of the electrolyte sheet; the cylinder was placed in a die battery flange, 50MPa pressure was applied, the screws were tightened and the die battery was sealed. The cell was left to stand at 27 ℃ for 12 hours after assembly, and then subjected to charge and discharge tests at a voltage range of 2.5 to 4.2V (relative to Li/Li +) at a rate of 0.1C. Fig. 6 is a charge-discharge curve diagram of an all-solid battery to which the solid electrolyte of example 1 is applied at 27 ℃.

The results show that L i is used _(2+x) N _x S _(1-x) Wherein the solid electrolyte (x = 0.5) shows a first-cycle discharge capacity of 138mAh g ^-1 。

Example 2

9.6 mmoles of L i were each weighed out ₃ N (336 mg), 114.4 mmol of Li ₂ S (664 mg), corresponding to x =0.4. Except for this, a solid electrolyte material of example 2 was obtained in the same manner as in example 1.

The lithium ion conductivity of the solid electrolyte of example 2 at 27 ℃ was measured in the same manner as in example 1, and as shown in FIG. 3, the result was 9.4X 10 ^-5 S/cm。

The X-ray diffraction pattern of example 2 was measured in the same manner as in example 1, and the results are shown in fig. 2. The results showed that there were diffraction peaks in the X-ray diffraction pattern at the positions 2 θ =28.10 °, 32.38 °, 46.67 °, 55.40 ° and 58.09 °. And 2 θ =28.10 ° of the diffraction peak F ₍₁₁₁₎ /λ＝0.43。

Comparative example 1

Separately calledTake 7 mmol of Li ₃ N (245 mg), 16.4 mmol of Li ₂ S (755 mg), corresponding to x =0.3. Except for this, a solid electrolyte material of comparative example 1 was obtained in the same manner as in example 1.

The lithium ion conductivity at 27 ℃ of the solid electrolyte of comparative example 1 was measured in the same manner as in example 1, and as shown in FIG. 3, the result was 4.4X 10 ^-5 S/cm。

The X-ray diffraction pattern of comparative example 1 was measured in the same manner as in example 1, and the results are shown in fig. 2. The results showed that there were diffraction peaks in the X-ray diffraction pattern at the positions 2 θ =27.60 °, 31.88 °, 45.96 °, 54.47 °, and 56.97 °. And 2 θ =27.60 ° of the diffraction peak F ₍₁₁₁₎ /λ＝0.42。

Comparative example 2

15.3 mmoles of L i were each weighed out ₃ N (532 mg), 10.2 mmol of Li ₂ S (468 mg), corresponding to x =0.6. Except for this, a solid electrolyte material of comparative example 2 was obtained in the same manner as in example 1.

The lithium ion conductivity at 27 ℃ of the solid electrolyte of comparative example 2 was measured in the same manner as in example 1, and as shown in FIG. 3, the result was 1.6X 10 ^-4 S/cm。

The X-ray diffraction pattern of comparative example 2 was measured in the same manner as in example 1, and the results are shown in fig. 2. The results indicate that the X-ray diffraction pattern has diffraction peaks at positions 2 θ =28.44 °, 32.85 °, 47.49 °, 56.16 °, and 59.19 °; whereas diffraction peaks for the hetero-phase were present at 2 θ =31.95 °, 50.84 °, 52.10 °, comparative example 2 was not a pure phase.

Comparative example 3

18.3 mmoles of L.i.were each weighed out ₃ N (639 mg), 7.86 mmol of Li ₂ S (361 mg), corresponding to x =0.7. Except for this, a solid electrolyte material of comparative example 3 was obtained in the same manner as in example 1.

The lithium ion conductivity at 27 ℃ of the solid electrolyte of comparative example 3 was measured in the same manner as in example 1, and as shown in FIG. 3, the result was 1.2X 10 ^-4 S/cm。

The X-ray diffraction pattern of comparative example 3 was measured in the same manner as in example 1, and the results are shown in fig. 2. The results show that the X-ray diffraction pattern has diffraction peaks at the positions of 2 θ =28.56 °, 33.28 °, 47.79 °, 56.04 ° and 59.21 °; whereas diffraction peaks for the hetero-phase were present at 2 θ =31.95 °, 50.84 °, 52.10 °, comparative example 3 was not a pure phase.

Comparative example 4

The lithium ion conductivity at 27 ℃ of comparative example 4 was measured in the same manner as in example 1, and as a result, it was less than 1X 10 ^-9 S/cm。

Using commercial L i ₂ And (4) S powder. The X-ray diffraction pattern of comparative example 4 was measured in the same manner as in example 1, and the results are shown in fig. 2. The results show that the X-ray diffraction pattern has diffraction peaks at the positions of 2 θ =27.19 °, 31.49 °, 53.34 °, 55.90 ° and 65.48 °, 72.23 °, 74.38 °.

Comparative example 5

Using commercial L i ₆ PS ₅ A lithium symmetric cell was assembled and tested in the same manner as in example 1, except for the C l solid electrolyte. The results of the constant current cycling test for the lithium symmetric cell are shown in fig. 5. The results show that the short circuit phenomenon occurs when the battery is cycled for no more than 60 circles.

Table 1 conductivity test results for each of the examples and comparative examples

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A solid electrolyte characterized by the chemical formula Li _(2+x) N _x S _(1-x) And wherein x is in the range of 0.35 to 0.55.

2. A solid state electrolyte as claimed in claim 1, wherein x is in the range of 0.48 to 0.52.

3. The solid electrolyte of claim 1, characterized by an X-ray diffraction pattern (copper target, wavelength)

) Diffraction peaks exist at positions of 2 θ =28.18 ± 0.50 °, 32.54 ± 0.50 °, 46.97 ± 0.50 °, 55.75 ± 0.50 °, 58.57 ± 0.50 °.

4. The solid electrolyte according to claim 3, wherein the normalized full width at half maximum of a diffraction peak corresponding to 2 θ =28.18 ± 0.50 ° in an X-ray diffraction pattern thereof is F ₍₁₁₁₎ A,/λ, and satisfies F ₍₁₁₁₎ Lambda > 0.3, preferably, where F ₍₁₁₁₎ /λ＞0.42。

5. A method of producing a solid electrolyte as claimed in any one of claims 1 to 4, characterized in that Li is used in a molar proportion ₂ S:Li ₃ N = (1.00-2.34). 1, mixing the powder and ball milling to obtain the nitrogen sulfide solid electrolyte.

6. The preparation method of the solid electrolyte as claimed in claim 5, wherein the mass ratio of the ball materials used in the ball milling process is (1-60): 1, and the mixture is ball milled for 1-24 hours at the rotating speed of 150-900 rpm to obtain the nitrogen sulfide solid electrolyte.

7. An all-solid battery comprising, in order, a negative electrode layer, an electrolyte layer and a positive electrode layer, wherein the electrolyte layer contains the solid electrolyte according to any one of claims 1 to 4.

8. The all-solid battery according to claim 7, wherein the negative electrode layer comprises a negative electrode active material selected from one or more of a metal material, a carbon material and a silicon material;

preferably, the metallic material is selected from lithium metal or a lithium alloy;

preferably, the carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite, and amorphous carbon;

preferably, the negative electrode layer does not contain the first electrolyte material; or the negative electrode layer comprises the first electrolyte material, and the weight of the first electrolyte material in the negative electrode layer does not exceed 70% of the total weight; the first electrolyte material comprises the solid state electrolyte;

preferably, the thickness of the negative electrode layer is 10 to 500 μm.

9. The all-solid battery according to claim 7, wherein the electrolyte layer comprises a second electrolyte material, the second electrolyte material comprising the solid electrolyte;

preferably, the second electrolyte material further includes a sulfide solid state electrolyte material and/or a halide solid state electrolyte material;

preferably, the sulfide solid state electrolyte material is selected from Li ₂ S-P ₂ S ₅ 、Li ₂ S-SiS ₂ 、Li ₂ S-B ₂ S ₃ 、Li ₂ S-GeS ₂ 、Li ₆ PS ₅ Cl、Li _3.25 Ge _0.25 P _0.75 S ₄ And Li ₁₀ GeP ₂ S ₁₂ One or more of;

preferably, the halide solid state electrolyte material is selected from Li ₃ InCl ₆ 、Li ₂ ZrCl ₆ 、Li ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of;

preferably, the electrolyte layer has a thickness of 1 to 500 μm.

10. The all-solid battery according to claim 7, wherein the positive electrode layer includes a positive electrode active material and a third electrolyte material;

preferably, the positive active material is selected from one or more of lithium iron phosphate, lithium-containing transition metal oxide, transition metal sulfide, transition metal oxysulfide, transition metal fluoride, polyanionic material, elemental sulfur and lithium sulfide;

preferably, the positive electrode layer contains 5 to 70% by weight of the third electrolyte material, and the third electrolyte material includes a solid electrolyte material different from the solid electrolyte;

preferably, the third electrolyte material includes a sulfide solid state electrolyte material and/or a halide solid state electrolyte material;

preferably, the sulfide solid state electrolyte material is selected from Li ₂ S-P ₂ S ₅ 、Li ₂ S-SiS ₂ 、Li ₂ S-B ₂ S ₃ 、Li ₂ S-GeS ₂ 、Li ₆ PS ₅ Cl、Li _3.25 Ge _0.25 P _0.75 S ₄ And Li ₁₀ GeP ₂ S ₁₂ One or more of;

preferably, the halide solid state electrolyte material is selected from Li ₃ InCl ₆ 、Li ₂ ZrCl ₆ 、Li ₃ YCl ₆ And Li ₃ ScCl ₆ One or more of (a);

preferably, the thickness of the positive electrode layer is 10 to 500 μm.

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