Lithium-containing cyanamide halide material, preparation method, application and battery

Abstract

The invention discloses a lithium-containing cyanamide halide material, a preparation method, application and a battery. The structural general formula of the lithium-containing cyanamide halide material is nLi2CN2-Mm + Xm, M comprises one or more of Zr, Ta, Sc, Y, La, Hf, Al, Ga and In, and X comprises one or more of F, Cl, Br and I; 0.2 < = n < 1.7. The lithium-containing cyanamide halide material prepared by the invention is in an amorphous state, has high ionic conductivity at the temperature of 25 DEG C, is stable to lithium metal and has a wide electrochemical window; the preparation method is simple and low in cost; when an all-solid-state lithium ion battery is prepared, high initial coulombic efficiency, excellent cycling stability and excellent electrochemical performance under high magnification are achieved.

Description

Technical Field

[0001] The present invention specifically relates to a lithium cyanamide halide material, a preparation method, an application, and a battery. Background Art

[0002] With the development of the renewable energy market, society's expectations for clean energy are increasing. Among them, the development of next-generation energy storage technologies has become a key driving force for the transition to sustainable energy. All-solid-state lithium-ion batteries (ASSLBs), as an emerging energy storage technology, are receiving increasing attention due to their higher energy density, stronger safety, and longer cycle life compared to traditional batteries.

[0003] As a key component of all-solid-state lithium batteries, the development and application of solid electrolytes directly affect the performance and safety of the batteries. These electrolytes can be mainly divided into three categories: oxides, sulfides, and halides. Among them, halide electrolytes have become a research hotspot in recent years. On the one hand, halide electrolytes exhibit excellent ionic conductivity, especially at high temperatures, where their conductivity is superior to that of oxides and sulfides. This makes halide electrolytes have great potential in improving the energy density of batteries and ensuring long-term stable performance. However, halide electrolytes still face some limitations in practical applications, especially in terms of interface instability with lithium metal and low intrinsic ionic conductivity at room temperature (such as ρLi 2 ZrCl 6 ≈0.4mS cm -1 ). Specifically, the interface instability is mainly due to the fact that halide electrolytes containing high-valent transition metals are prone to irreversible side reactions with electrode materials or lithium metal, resulting in capacity decay and battery failure.

[0004] To address these issues, current research mainly focuses on alleviating battery performance decay and failure through lithium alloying and adding buffer layers. However, the potential of lithium metal alloys is higher than that of pure lithium metal, which can lead to a decrease in battery voltage and energy density. In addition, the introduction of buffer layers will increase the interface resistance, thereby increasing the overall resistance of the battery. Therefore, there is an urgent need to develop a solid electrolyte that is inherently stable and compatible with lithium metal to fully utilize the advantages of lithium metal anodes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the technical problems of low intrinsic conductivity and poor stability in the actual application of pure halide solid electrolyte materials in the prior art, and to provide a lithium cyanamide halide material, a preparation method, an application and a battery thereof. The lithium cyanamide halide material prepared by the present invention is amorphous, has high ionic conductivity, is stable to lithium metal and has a wide electrochemical window at a temperature of 25 °C; moreover, the preparation method is simple and the cost is low; when preparing an all-solid-state lithium ion battery, it has a high initial Coulomb efficiency and excellent electrochemical cycling stability.

[0006] The present invention obtains a lithium cyanamide halide material by ball-milling a lithium metal cyanamide compound and a metal halide. In this lithium cyanamide halide material, cyanamide groups enter the lattice of the metal halide material to stabilize the structure and increase the structural void ratio; this lithium cyanamide halide material is amorphous and has excellent electrochemical properties. Mechanistically, the conjugated cyanamide groups increase the lattice of the metal halide, which is beneficial to the transfer of lithium ions in the pores, thereby increasing the ionic conductivity; at the same time, the traction effect of the cyanamide groups on lithium ions improves the structural stability of the material, effectively improving the cycling performance of the lithium cyanamide halide material during the cycling process of the all-solid-state battery.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] The present invention provides a lithium cyanamide halide material, the structural general formula of which is nLi 2 CN 2 -M m+ X m , where M includes one or more of Zr, Ta, Sc, Y, La, Hf, Al, Ga and In, and X includes one or more of F, Cl, Br and I; 0.2 ≤ n < 1.7.

[0009] In the present invention, in the structural general formula of the lithium cyanamide halide material, m+ refers to the valence of metal M. The lithium cyanamide halide material belongs to a compound rather than a mixture.

[0010] In the present invention, the lithium cyanamide halide material preferably macroscopically presents an amorphous state. The lithium cyanamide halide material preferably also has a monoclinic crystal structure. That is, the lithium cyanamide halide material belongs to a state of short-range order and long-range disorder.

[0011] In the present invention, in the structural general formula of the lithium cyanamide halide material, M is preferably Zr and / or Ta.

[0012] In the present invention, in the structural general formula of the lithium cyanamide halide material, X is preferably Cl.

[0013] In the present invention, in the general structural formula of the lithium cyanamide halide material, preferably, 0.3≤n<1, for example, 0.4, 0.5, 0.52, 0.55, 0.56, 0.6, 0.67, 0.7 or 0.8, more preferably, 0.4≤n≤0.53 or 0.6<n<0.7.

[0014] In a specific embodiment, the general structural formula of the lithium cyanamide halide material is 0.5Li 2 CN 2 -ZrCl 4 、0.5Li 2 CN 2 -TaCl 5 、0.67Li 2 CN 2 -TaCl 5 、0.56Li 2 CN 2 -ZrCl 4 or 0.56Li 2 CN 2

[0015] -TaCl 5 .

[0016] In the present invention, the ionic conductivity of the lithium cyanamide halide material at room temperature (25° C.) is preferably ρ ≥ 0.25 mS cm -1 , for example 0.30 mS cm -1 、0.42mS cm -1 、0.5mS cm -1 、0.64mS cm -1 、0.75mS cm -1 、0.8mS cm -1 、0.87mS cm -1 or 1.0mS cm -1 , preferably ρ ≥ 0.5 mS cm -1 .

[0017] In the present invention, the electrochemical stability window of the lithium cyanamide halide material is preferably ≥3.8V.

[0018] In the present invention, the lithium cyanamide halide material is heated to 0.1C (1C = 180 mAh g -1 ), the first cycle discharge capacity within the voltage range of 2.8-4.2V can be 110-150mAh g –1 , for example 114mAh g –1 , 120mAh g –1 , 125mAh g –1 , 128mAh g–1 or 135 mAh / g –1 , preferably 120 - 140 mAh / g –1 .

[0019] In the present invention, the lithium cyanamide halide material has an initial discharge specific capacity within the voltage range of 2.5 - 4.2 V at 0.1 C (1 C = 180 mAh / g -1 ) that can be 100 - 200 mAh / g –1 , preferably 150 - 180 mAh / g –1 , such as 172 mAh / g –1 .

[0020] The present invention also provides a method for preparing the lithium cyanamide halide material, which includes the following steps: preparing by ball-milling a mixture of a lithium metal cyanamide compound and a metal M-containing halide.

[0021] In the present invention, the chemical formula of the lithium metal cyanamide compound is generally Li 2 CN 2 .

[0022] In the present invention, the lithium metal cyanamide compound can be obtained by conventional commercial purchase or self-preparation. The preparation method of the lithium metal cyanamide compound preferably includes the following steps: preparing by calcining a mixture of a lithium source, a nitrogen source, and a carbon source.

[0023] Among them, the lithium source can be one or more of lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium amide, lithium hydride, lithium nitride, and lithium borate, such as lithium amide or lithium nitride.

[0024] Among them, the nitrogen source can be one or more of melamine, dicyandiamide, urea, and ammonium nitrate.

[0025] Among them, the carbon source can be one or more of ammonium carbonate, melamine, and lithium carbonate.

[0026] Among them, the molar ratio of lithium in the lithium source, nitrogen in the nitrogen source, and carbon in the carbon source is preferably 1:(1 - 4.2):(0.5 - 2.5), such as 1:1:0.5 or 1:4:2.

[0027] When the lithium source is lithium amide and the carbon source and the nitrogen source are both melamine at the same time, the molar ratio of lithium amide to melamine can be 6:(1 - 2), such as 6:1.

[0028] When the lithium source is lithium nitride and the carbon source and the nitrogen source are both melamine at the same time, the molar ratio of lithium nitride to melamine can be 1:(1.5 - 3), such as 1:2.

[0029] Among them, in the preparation method of the lithium metal cyanamide compound, preferably, a catalyst can also be added. The catalyst can be hexachlorobenzene. The molar ratio of the lithium source to the catalyst can be 1:(0.0001 - 0.005), such as 1:0.0005 or 1:0.001.

[0030] Among them, the preparation method of the mixture containing the lithium source, nitrogen source, and carbon source can be conventional in the art. Preferably, it includes the following process: grinding the lithium source, nitrogen source, and carbon source for 5 - 30 min. The grinding is generally carried out under the protection of an inert gas. The grinding is generally carried out in a mortar. The grinding time is preferably 5 - 15 min, such as 10 min or 15 min.

[0031] Among them, the calcination is generally carried out in a tube furnace. The calcination is usually carried out under the protection of an inert gas. The temperature of the calcination can be 400 - 800 °C, preferably 500 - 700 °C, such as 550 °C or 600 °C. The time of the calcination can be 2 min - 2 h, such as 5 min, 10 min, 20 min, or 30 min. The rate of heating up to the calcination temperature can be 1 - 20 °C / min, such as 5 °C / min, 10 °C / min, or 15 °C / min. The rate of cooling after the calcination can be 1 - 10 °C / min, preferably 5 °C / min.

[0032] In some preferred embodiments, the calcination includes the following process: first, heating up at a heating rate of 5 - 15 °C / min to 200 - 300 °C and holding for 5 - 15 min; then continuing to heat up at a heating rate of 1 - 5 °C / min to 310 - 350 °C, without holding, and then continuing to heat up at a heating rate of 5 - 15 °C / min to 500 - 700 °C and holding for 10 - 60 min.

[0033] In some more preferred embodiments, the calcination includes the following process: first, heating up at a heating rate of 10 °C / min to 270 °C and holding for 10 min; then continuing to heat up at a heating rate of 1 °C / min to 330 °C, without holding, and then continuing to heat up at a heating rate of 10 °C / min to 600 °C and holding for 30 min.

[0034] In some preferred embodiments, the calcination includes the following process: first, heating up at a heating rate of 1 - 10 °C / min to 250 - 350 °C and holding for 5 - 15 min; then continuing to heat up at a heating rate of 5 - 15 °C / min to 400 - 800 °C and holding for 2 - 30 min.

[0035] In some preferred embodiments, the calcination includes the following process: first, the temperature is raised to 300 °C at a heating rate of 5 °C / min and held for 10 min; then, the temperature is continuously raised to 600 °C at a heating rate of 10 °C / min and held for 5 min.

[0036] In the present invention, the halide containing metal M may be one or more of a chloride containing metal M, a bromide containing metal M, a fluoride containing metal M, and an iodide containing metal M.

[0037] Among them, the chloride containing metal M may be one or more of zirconium chloride, tantalum chloride, iron chloride, and indium chloride. The bromide containing metal M may be one or more of zirconium bromide, tantalum bromide, and iron bromide.

[0038] In the present invention, the molar ratio of the lithium metal cyanamide compound to the halide containing metal M can be weighed according to the structural general formula of the lithium cyanamide halide material in a stoichiometric ratio, generally 0.2 - 1.7, preferably 0.3 - 1, such as 0.4, 0.5, 0.52, 0.55, 0.56, 0.6, 0.67, 0.7, or 0.8, more preferably 0.4 - 0.53 or 0.6 - 0.7.

[0039] In the present invention, the preparation method of the mixture of the lithium metal cyanamide compound and the halide containing metal M can be conventional in the art, generally obtained by mixing the lithium metal cyanamide compound and the halide containing metal M. The mixing is generally carried out in a mortar. The mixing is generally carried out under the protection of an inert gas. The mixing time can be 1 - 10 min.

[0040] In the present invention, the ball milling is generally carried out in a ball mill equipped with a ball milling tank. The ball milling is generally carried out under the protection of an inert gas. The rotation speed of the ball milling can be 300 - 1200 rpm, such as 100 rpm, 400 rpm, 600 rpm, 800 rpm, or 900 rpm, preferably 400 - 800 rpm. The ball milling time can be 8 - 24 h, preferably 10 - 18 h, such as 12 h, 14 h, or 16 h.

[0041] In some preferred embodiments, the ball milling includes the following process: first, ball milling is carried out at a rotation speed of 50 - 200 rpm for 0.5 - 4 h, and then ball milling is carried out at a rotation speed of 400 - 1000 rpm for 8 - 24 h.

[0042] In a specific embodiment, the ball milling includes the following process: first, ball milling is carried out at a rotation speed of 100 rpm for 2 h, and then ball milling is carried out at a rotation speed of 600 rpm for 12 h.

[0043] In the present invention, during the ball milling process, the diameter of the grinding balls used can be 2 - 10 mm, such as 2 mm, 5 mm, 8 mm or 10 mm.

[0044] In the present invention, during the ball milling process, the ball-to-material ratio can be (20 - 50):1, such as 20:1, 30:1, 35:1, 40:1, 45:1 or 50:1. The ball-to-material ratio refers to the mass ratio of the grinding balls to the material to be ball milled.

[0045] In a specific embodiment, during the ball milling process, the diameter of the grinding balls used is 8 mm and the ball-to-material ratio is 40:1.

[0046] In the present invention, according to the routine in the art, after the ball milling, screening is generally required. The screening is generally carried out under the protection of an inert gas. The mesh number of the sieve used for screening can be 150 - 500 meshes, such as 200 meshes, 250 meshes, 300 meshes, 400 meshes or 450 meshes. The particle size of the material selected after screening is preferably below 100 μm, more preferably below 80 μm.

[0047] The present invention also provides a lithium cyanamide halide material prepared by the preparation method as described above.

[0048] The present invention also provides an application of the lithium cyanamide halide material as described above as a solid electrolyte in all-solid-state lithium-ion batteries.

[0049] The present invention also provides an all-solid-state lithium-ion battery, which includes the lithium cyanamide halide material as described above.

[0050] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0051] The reagents and raw materials used in the present invention are all commercially available.

[0052] The positive and progressive effects of the present invention are as follows:

[0053] (1) Compared with traditional oxides and sulfides, the lithium cyanamide halide material prepared in the present invention has low raw material cost, simple preparation method and short preparation cycle;

[0054] (2) The lithium cyanamide halide material prepared in the present invention has more excellent room-temperature ionic conductivity and excellent electrochemical performance compared with traditional halides;

[0055] (3) The lithium cyanamide halide material prepared in the present invention is stable to lithium metal, has a wide electrochemical window, can directly match the lithium metal negative electrode, and improves the energy density of the device. Description of the Drawings

[0056] Figure 1SEM image of the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0057] Figure 2 XRD pattern of the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0058] Figure 3 Elemental analysis and mapping distribution diagram of the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0059] Figure 4 Impedance spectrum of the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0060] Figure 5 Impedance spectrum of the Ta-based lithium-containing cyanamide halide material prepared in Example 2;

[0061] Figure 6 Impedance spectrum of the Ta-based lithium-containing cyanamide halide material prepared in Example 3;

[0062] Figure 7 Impedance spectrum of the Zr-based lithium-containing cyanamide halide material prepared in Example 4;

[0063] Figure 8 Impedance spectrum of the Ta-based lithium-containing cyanamide halide material prepared in Example 5;

[0064] Figure 9 Impedance spectrum of the Ta-based lithium-containing cyanamide halide material prepared in Comparative Example 1;

[0065] Figure 10 Impedance spectrum of the Zr-based lithium-containing cyanamide halide material prepared in Comparative Example 2;

[0066] Figure 11 Cyclic voltammogram of the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0067] Figure 12 Cycling diagram of the Li metal symmetric battery assembled with the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0068] Figure 13 Cycling diagram of the all-solid-state battery assembled with the Zr-based lithium-containing cyanamide halide material prepared in Example 1;

[0069] Figure 14 Initial cycle capacity performance diagram of the Zr-based lithium-containing cyanamide halide material prepared in Example 1 at (2.8 - 4.2 V);

[0070] Figure 15Capacity performance graph of the Zr-based lithium-containing cyanamide halide material prepared in Example 1 at (2.5 - 4.2 V) in the first cycle. Detailed implementation manners

[0071] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0072] Example 1

[0073] Zr-based lithium-containing cyanamide halide material 0.5Li 2 CN 2 -ZrCl 4 Preparation:

[0074] S1, under argon protection, weigh 60 mmol of lithium amide and 10 mmol of melamine, mix them in an agate mortar, and dry-grind for 10 min to make the powder mixture uniform. Then transfer the powder to an alumina boat and transfer it to a tube furnace under argon protection; in an argon atmosphere, rapidly heat it to 270 °C at a heating rate of 10 °C / min within 27 min, and keep the temperature for 10 min; then continue to heat it to 330 °C at a heating rate of 1 °C / min within 60 min, without insulation, and then continue to rapidly heat it to 600 °C at a heating rate of 10 °C / min within 27 min based on 330 °C, and keep the temperature for 30 min; then cool it to room temperature at a cooling rate of 5 °C / min to obtain the lithium salt precursor Li 2 CN 2 ;

[0075] S2, under argon protection, weigh 25 mmol of the lithium salt precursor Li 2 CN 2 , 50 mmol of zirconium tetrachloride, grind them in a mortar for 5 min, mix them and transfer them to a zirconia-lined ball mill tank filled with argon, and add zirconia ball mill beads with a diameter of 8 mm into the tank. The mass ratio of the feedstock to the ball mill beads is 1:40. Finally, seal the ball mill tank; under argon protection, transfer the ball mill tank to a planetary ball mill, set the rotation speed to 100 rpm, and the ball milling time to 2 h; then increase the rotation speed to 600 rpm, and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back to an argon atmosphere;

[0076] S3, under argon protection, screen the ball-milled product in S2, select a 200-mesh stainless steel sieve for screening, control the particle size of the product to be below 75 μm, and collect the screened powder to obtain the lithium-containing cyanamide halide material.

[0077] Example 2

[0078] Ta-based lithium cyanamide halide material 0.5Li 2 CN 2 -TaCl 5 Preparation:

[0079] S1, under argon protection, weigh 60 mmol of lithium amide, 10 mmol of melamine, and 0.03 mmol of hexachlorobenzene, mix them in an agate mortar, and dry-grind for 10 min to make the powder mixture uniform. Then transfer the powder to an alumina boat and transfer it to a tubular furnace under argon protection. Under argon protection, rapidly heat to 270 °C at a heating rate of 10 °C / min within 27 min, and keep the temperature for 10 min. Then continue to heat to 330 °C at a heating rate of 1 °C / min within 60 min, without holding the temperature. Then, based on 330 °C, continue to rapidly heat to 600 °C at a heating rate of 10 °C / min within 27 min, and keep the temperature for 30 min. After that, cool to room temperature at a cooling rate of 5 °C / min to obtain the lithium salt precursor Li 2 CN 2 ;

[0080] S2, under argon protection, weigh 12.5 mmol of the lithium salt precursor Li 2 CN 2 , 25 mmol of tantalum pentachloride, grind for 5 min to mix, then transfer to a zirconia-lined ball mill tank filled with argon, and add zirconia ball mill beads with a diameter of 8 mm into the tank. The mass ratio of the feedstock to the ball mill beads is 1:40. Finally, seal the ball mill tank. Under argon protection, transfer the ball mill tank to a planetary ball mill: set the rotation speed to 100 rpm and the ball milling time to 2 h. Then increase the rotation speed to 600 rpm and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back to the argon atmosphere;

[0081] S3, under argon protection, screen the ball-milled product in S2, select a 200-mesh stainless steel sieve for screening, control the particle size of the product to be below 75 μm, and collect the screened powder to obtain the lithium cyanamide halide material.

[0082] Example 3

[0083] Ta-based lithium cyanamide halide material 0.67Li 2 CN 2 -TaCl 5 Preparation:

[0084] S1. Under argon protection, weigh 60 mmol of lithium amide, 10 mmol of melamine, and 0.03 mmol of hexachlorobenzene, mix them in an agate mortar, and perform dry grinding for 10 min to make the powder mixture uniform. Then transfer the powder to an alumina boat and transfer it to a tube furnace under argon protection. Under argon protection, rapidly heat it to 270 °C at a heating rate of 10 °C / min within 27 min, and keep it at this temperature for 10 min. Then continue to heat it to 330 °C at a heating rate of 1 °C / min within 60 min. Without insulation, then continue to rapidly heat it to 600 °C at a heating rate of 10 °C / min based on 330 °C within 27 min, and keep it at this temperature for 30 min. After that, cool it to room temperature at a cooling rate of 5 °C / min to obtain the lithium salt precursor Li 2 CN 2 ;

[0085] S2. Under argon protection, weigh 20 mmol of the lithium salt precursor Li 2 CN 2 , 30 mmol of tantalum pentachloride, grind and mix them for 5 min, then transfer them into a zirconia-lined ball mill tank filled with argon. Add zirconia ball mill beads with a diameter of 8 mm into the tank, and the mass ratio of the feedstock to the ball mill beads is 1:40. Finally, seal the ball mill tank. Under argon protection, transfer the ball mill tank into a planetary ball mill: set the rotation speed to 100 rpm and the ball milling time to 2 h. Then increase the rotation speed to 600 rpm and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back into the argon atmosphere;

[0086] S3. Under argon protection, screen the ball-milled product in S2, select a 200-mesh stainless steel sieve for screening, control the particle size of the product to be below 75 μm, and collect the screened powder to obtain the lithium cyanamide halide material.

[0087] Example 4

[0088] Preparation of 0.56Li 2 CN 2 -ZrCl 4 :

[0089] S1. Under argon protection, weigh 60 mmol of lithium amide, 10 mmol of melamine, and 0.03 mmol of hexachlorobenzene. Mix them in an agate mortar and grind them dry for 10 min to make the powder mixture homogeneous. Then transfer the powder to an alumina porcelain boat and transfer it to a tube furnace under argon protection. Under argon protection, rapidly heat it to 270 °C at a heating rate of 10 °C / min within 27 min, and keep it at this temperature for 10 min. Then heat it to 330 °C at a heating rate of 1 °C / min within 60 min. Without insulation, based on 330 °C, continue to rapidly heat it to 600 °C at a heating rate of 10 °C / min within 27 min, and keep it at this temperature for 30 min. Then cool it to room temperature at a cooling rate of 5 °C / min to obtain the lithium salt precursor Li 2 CN 2 ;

[0090] S2. Under argon protection, weigh 20 mmol of the lithium salt precursor Li 2 CN 2 and 36 mmol of zirconium tetrachloride. Grind and mix them for 5 min, then transfer them to a zirconia-lined ball mill tank filled with argon. Add zirconia ball mill beads with a diameter of 8 mm to the tank. The mass ratio of the feedstock to the ball mill beads is 1:40. Finally, seal the ball mill tank. Under argon protection, transfer the ball mill tank to a planetary ball mill: set the rotation speed to 100 rpm and the ball milling time to 2 h. Then increase the rotation speed to 600 rpm and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back to the argon atmosphere;

[0091] S3. Under argon protection, screen the ball-milled product in S2. Select a 400-mesh stainless steel sieve for screening, control the particle size of the product to be below 38 μm, and collect the screened powder to obtain the final product.

[0092] Example 5

[0093] Preparation of Ta-based lithium cyanamide halide material 0.56Li 2 CN 2 -TaCl 5 :

[0094] S1. Under argon protection, weigh 30 mmol of lithium nitride, 60 mmol of melamine, and 0.03 mmol of hexachlorobenzene, mix them in an agate mortar, and perform dry grinding for 10 min to make the powder mixture uniform. Then transfer the powder to an alumina porcelain boat and transfer it to a tube furnace under argon protection. Under argon protection, heat it to 300 °C at a heating rate of 5 °C / min within 60 min, and keep it at this temperature for 10 min. Then, continue to rapidly heat it to 600 °C at a heating rate of 10 °C / min within 30 min, and keep it at this temperature for 5 min. After that, cool it to room temperature at a cooling rate of 5 °C / min to obtain the lithium salt precursor Li 2 CN 2 ;

[0095] S2. Under argon protection, weigh 20 mmol of the lithium salt precursor Li 2 CN 2 , 36 mmol of tantalum pentachloride, grind and mix them for 5 min, then transfer them to a zirconia-lined ball mill tank filled with argon. Add zirconia ball milling beads with a diameter of 8 mm into the tank, and the mass ratio of the feedstock to the ball milling beads is 1:40. Finally, seal the ball mill tank. Under argon protection, transfer the ball mill tank to a planetary ball mill: set the rotation speed to 100 rpm and the ball milling time to 2 h. Then increase the rotation speed to 600 rpm and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back to the argon atmosphere;

[0096] S3. Under argon protection, screen the ball milling product in S2, select a 400-mesh stainless steel sieve for screening, control the product particle size to be below 38 μm, and collect the screened powder to obtain the lithium cyanamide halide material.

[0097] Comparative Example 1

[0098] Preparation of Ta-based halide material LiTaCl 6 :

[0099] S1. Under argon protection, weigh 50 mmol of lithium chloride and 50 mmol of tantalum pentachloride, grind and mix them for 5 min, and then transfer them to a zirconia-lined ball mill tank.

[0100] S2. Under argon protection, transfer the ball mill tank in S1 to a planetary ball mill, add zirconia ball milling beads with a diameter of 8 mm into the tank, and the mass ratio of the feedstock to the ball milling beads is 1:40. Finally, seal the ball mill tank. Set the rotation speed to 100 rpm and the ball milling time to 2 h. Then increase the rotation speed to 600 rpm and set the ball milling time to 12 h. After the ball milling is completed and the rotation speed naturally drops, transfer the ball mill tank back to the argon atmosphere;

[0101] S3. Under argon protection, screen the ball-milled product described in S2. Select a 200-mesh stainless steel sieve for screening, control the product particle size to be below 75 μm, and collect the screened powder to obtain the final product.

[0102] Comparative Example 2

[0103] Zr-based halide material Li 2 ZrCl 6 Preparation:

[0104] S1. Under argon protection, weigh 60 mmol of lithium chloride and 30 mmol of zirconium tetrachloride, grind for 5 min and mix, then transfer to a ball-milling jar with a zirconia lining.

[0105] S2. Under argon protection, transfer the ball-milling jar described in S1 to a planetary ball mill, add 8-mm diameter zirconia ball-milling beads into the jar, with the mass ratio of the feedstock to the ball-milling beads being 1:40, and finally seal the ball-milling jar. Set the rotation speed to 100 rpm and the ball-milling time to 2 h; then increase the rotation speed to 600 rpm and set the ball-milling time to 12 h. After the ball-milling is completed and the rotation speed naturally drops, transfer the ball-milling jar back to the argon atmosphere.

[0106] S3. Under argon protection, screen the ball-milled product described in S2. Select a 200-mesh stainless steel sieve for screening, control the product particle size to be below 75 μm, and collect the screened powder to obtain the final product.

[0107] Effect Example

[0108] (1) SEM, XRD characterization and elemental analysis characterization

[0109] Figure 1 SEM image of 0.5Li 2 CN 2 -ZrCl 4 in Example 1; it can be seen from the figure that the sample particle size is small, the morphology has no obvious regular shape, and it is overall amorphous. The impedance at the grain boundaries of the amorphous particles is small, which is beneficial to the migration and diffusion of lithium ions and is beneficial to the improvement of ionic conductivity.

[0110] Figure 2 XRD pattern of 0.5Li 2 CN 2 -ZrCl 4 in Example 1; it can be seen from the figure that the sample has a monoclinic crystal structure and no extra impurity peaks.

[0111] From Figure 3 it can be seen that various elements are obvious and evenly distributed.

[0112] (2) Impedance Test

[0113] Under argon protection, 100 mg of the final product materials prepared in Examples 1-5 and Comparative Examples 1-2 were respectively taken and evenly spread on the electrode posts of a special all-solid-state battery mold. Then, it was hand-pressed flat with another electrode post. The above mold was placed in a hydraulic press, and an external pressure of about 4 tons was applied, and the pressure holding time was maintained at 3-5 min to make it a flat and dense electrolyte sheet. Finally, the electrolyte sheet was connected to an electrochemical workstation for impedance testing, and the test results are shown in Figures 4 - 10 and Table 1.

[0114] (3) Lithium Stability Test

[0115] Symmetric Battery Assembly Test:

[0116] Under argon protection, about 100 mg of the final product material prepared in Example 1 was taken and evenly spread on the electrode posts of a special all-solid-state battery mold. Then, it was hand-pressed flat with another electrode post. The above mold was placed in a hydraulic press, and an external pressure of about 1 ton was applied, and the pressure holding time was maintained at 3-5 min to make it a flat and dense electrolyte sheet; lithium sheets with a thickness of 50 μm and a diameter of 10 mm were added on both sides of the electrolyte sheet, and it was pressed with the electrode post to make it in close contact with the electrolyte sheet to complete the assembly of the lithium-ion symmetric battery.

[0117] The above assembled lithium-ion symmetric battery was placed in a stainless steel sleeve, and the sleeve was placed in a hydraulic press. After applying an external pressure of 0.5 ton, the stud was tightened to complete the assembly of the battery test device. The above battery was connected to an electrochemical workstation for charge and discharge testing, and the current was set to 0.1 mA cm -2 .

[0118] Figure 12 For the test results of the symmetric battery, at the set current density of 0.1 mA cm -2 the polarization voltage of the battery was only 50 mV, and the stable cycling duration exceeded 600 h, demonstrating the excellent lithium stability of the material in Example 1.

[0119] (4) Electrochemical Performance Test

[0120] Under argon protection, take the material prepared in Example 1 (7 mg) and conductive carbon SP (3 mg), grind and mix them evenly for later use. Then take 100 mg of commercial lithium phosphorus sulfur chloride powder and place it in a full-solid-state battery test mold, apply an external pressure of 1 ton, and maintain the pressure for 3 - 5 minutes to make it a flat and dense electrolyte sheet; add the above-mentioned evenly mixed powder of Example 1 and SP on one side of the electrolyte sheet, flatten it with an electrode column, and apply an external pressure of about 4 tons; finally, add a lithium sheet with a thickness of 50 μm and a diameter of 10 mm on the other side of the electrolyte sheet, and press it with an electrode column to make it in close contact with the electrolyte sheet to complete the assembly of the battery. Connect the above battery to the Autolab system for cyclic voltammetry testing. According to Figure 11 The test results show that the lithium oxidation potential of the material in Example 1 is about 3.8 V, having a relatively high electrochemical stability window.

[0121] Under argon protection, take 100 mg of the final product materials prepared in Examples 1 - 5 and Comparative Examples 1 - 2 respectively, evenly sprinkle them on the electrode column of a special full-solid-state battery mold, and then hand-press them flat with another electrode column. Place the above mold on a hydraulic press, apply an external pressure of about 1 ton, and maintain the pressure for 3 - 5 minutes to make it a flat and dense electrolyte sheet; take the final product materials prepared in Examples 1 - 5 and Comparative Examples 1 - 2, commercial lithium cobalt oxide and SuperP, and mix them evenly in a mass ratio of 30:70:1, and grind for 20 minutes to make the powder evenly mixed; slowly take out the electrode column on one side of the above mold, take about 10 mg of the above mixed powder, evenly sprinkle it on one side of the electrolyte sheet of the product material, and then hand-press it flat with an electrode column. Place the mold containing the mixed powder and the electrolyte sheet on the hydraulic press again, apply an external pressure of about 5 tons, and maintain the pressure for 5 - 8 minutes to make the two layers of powder in close contact; finally, remove the mold, take out the electrode column on the other side of the electrolyte sheet, add a lithium sheet with a thickness of 50 μm and a diameter of 10 mm at the other side of the electrolyte sheet, and press it with the taken-out electrode column to make it in close contact with the electrolyte sheet to complete the assembly of the all-solid-state lithium-ion battery.

[0122] Place the above complete battery mold in a stainless steel sleeve, place the sleeve on a hydraulic press, apply an external pressure of 0.5 ton and then tighten the stud to complete the assembly of the battery test device. Connect the whole above battery to an electrochemical workstation for charge-discharge testing, set 1C = 180 mAh g -1 , and the test results are shown in Figures 13 - 15 and Table 2, Table 3.

[0123] Table 1

[0124] Sample Impedance (Ω) <![CDATA[Ionic conductivity at 25 °C (mScm -1 )]]> Example 1 92 0.87 Example 2 81 1.00 Example 3 185 0.42 Example 4 125 0.64 Example 5 265 0.30 Comparative Example 1 470 0.17 Comparative Example 2 385 0.21

[0125] Note: ρ = L / RS, where ρ is the ionic conductivity, R is the impedance, S is the area, and L is the thickness. Among them, S is 0.785 cm -2, L is 0.066 cm.

[0126] According to the data of Examples 1-5, it can be seen that the lithium cyanamide halide material prepared by the present invention has a smaller impedance, and is much smaller than that of Comparative Examples 1-2.

[0127] Table 2

[0128] Sample Voltage range Initial discharge specific capacity Initial efficiency Example 1 2.8-4.2V <![CDATA[128mAhg -1 > 92％ Example 2 2.8-4.2V <![CDATA[135mAhg -1 > 98％ Example 3 2.8-4.2V <![CDATA[125mAhg -1 > 98％ Example 4 2.8-4.2V <![CDATA[120mAhg -1 > 94.7％ Example 5 2.8-4.2V <![CDATA[114mAhg -1 > 92.1％ Comparative Example 1 2.8-4.2V <![CDATA[102mAhg -1 > 93％ Comparative Example 2 2.8-4.2V <![CDATA[104mAhg -1 > 90.5％

[0129] According to the data of Examples 1-5, it can be seen that the lithium cyanamide halide material prepared by the present invention can provide a higher first-cycle discharge specific capacity.

[0130] Table 3

[0131] Example 1 cycling (0.5C) Discharge specific capacity Initial cycle <![CDATA[102mAhg -1 > 25 cycles <![CDATA[105mAhg -1 > 50 cycles <![CDATA[109mAhg -1 > 75 cycles <![CDATA[106mAhg -1 > 100 cycles <![CDATA[108mAhg -1 >

[0132] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A lithium cyanamide halide material, characterized in that: Its general structural formula is nLi2CN2-M m+ X m , wherein M includes one or more of Zr, Ta, Sc, Y, La, Hf, Al, Ga and In, and X includes one or more of F, Cl, Br and I; 0.2≤n<1.

7.

2. The lithium cyanamide halide material according to claim 1, characterized in that The lithium cyanamide halide material meets one or more of the following conditions: (1) The lithium cyanamide halide material is macroscopically amorphous, and preferably has a monoclinic crystal structure; (2) In the general structural formula of the lithium cyanamide halide material, M is Zr and / or Ta; (3) In the general structural formula of the lithium cyanamide halide material, X is Cl; (4) In the general structural formula of the lithium cyanamide halide material, 0.3≤n<1, for example, 0.4, 0.5, 0.52, 0.55, 0.56, 0.6, 0.67, 0.7 or 0.8, preferably, 0.4≤n≤0.53 or 0.6<n<0.7; (5) The general structural formula of the lithium cyanamide halide material is 0.5Li2CN2-ZrCl4, 0.5Li2CN2-TaCl5, 0.67Li2CN2-TaCl5, 0.56Li2CN2-ZrCl4 or 0.56Li2CN2-TaCl5.

3. The lithium cyanamide halide material according to claim 1 or 2, characterized in that: The lithium cyanamide halide material meets one or more of the following conditions: (1) The ionic conductivity of the lithium cyanamide halide material at room temperature is ρ≥0.25 mS cm -1 , for example 0.30mScm -1 、0.42mS cm -1 、0.5mS cm -1 、0.64mS cm -1 、0.75mS cm -1 、0.8mS cm -1 、0.87mS cm -1 or 1.0mScm -1 , preferably ρ ≥ 0.5 mS cm -1 ; (2) The electrochemical stability window of the lithium cyanamide halide material is ≥3.8V; (3) The lithium cyanamide halide material contains lithium cyanamide at 0.1C, 1C = 180 mAh g -1 The first cycle discharge capacity in the voltage range of 2.8-4.2V is 110-150mAh g –1 ; (4) The lithium cyanamide halide material contains lithium cyanamide at 0.1C, 1C = 180 mAh g -1 The first cycle discharge capacity in the voltage range of 2.5-4.2V is 100-200mAh g –1 .

4. A method for preparing a lithium cyanamide halide material according to any one of claims 1 to 3, characterized in that: It includes the following steps: The method is prepared by ball milling a mixture of a lithium metal cyanamide compound and a halide containing a metal M.

5. The method for preparing the lithium cyanamide halide material according to claim 4, characterized in that: The chemical formula of the lithium metal cyanamide compound is Li2CN2; And / or, the preparation method of the lithium metal cyanamide compound comprises the following steps: calcining a mixture of a lithium source, a nitrogen source and a carbon source to obtain the lithium metal cyanamide compound.

6. The method for preparing the lithium cyanamide halide material according to claim 5, characterized in that: The preparation method of the lithium metal cyanamide compound satisfies one or more of the following conditions: (1) The lithium source is one or more of lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium amide, lithium hydride, lithium nitride and lithium borate; (2) The nitrogen source is one or more of melamine, dicyandiamide, urea and ammonium nitrate; (3) The carbon source is one or more of ammonium carbonate, melamine and lithium carbonate; (4) the molar ratio of lithium in the lithium source, nitrogen in the nitrogen source and carbon in the carbon source is 1:(1-4.2):(0.5-2.5); (5) The calcination temperature is 400-800°C, preferably 500-700°C, for example 550°C or 600°C; (6) The calcination time is 2 min-2 h, for example, 5 min, 10 min, 20 min or 30 min.

7. The method for preparing the lithium cyanamide halide material according to claim 4, characterized in that: The preparation method meets one or more of the following conditions: (1) The ball mill has a rotation speed of 300-1200 rpm, such as 100 rpm, 400 rpm, 600 rpm, 800 rpm or 900 rpm, preferably 400-800 rpm; (2) The ball milling time is 8-24 hours, preferably 10-18 hours, such as 12 hours, 14 hours or 16 hours; (3) During the ball milling process, the diameter of the grinding balls used is 2-10 mm, for example, 2 mm, 5 mm, 8 mm or 10 mm; (4) During the ball milling process, the ball-to-material ratio is (20-50):1, for example, 20:1, 30:1, 35:1, 40:1, 45:1 or 50:1; (5) Screening is required after the ball milling. The mesh size of the screen used for the screening is preferably 150-500 mesh, such as 200 mesh, 250 mesh, 300 mesh, 400 mesh or 450 mesh.

8. The method for preparing the lithium cyanamide halide material according to claim 4, characterized in that: The halide containing metal M is one or more of chloride containing metal M, bromide containing metal M, fluoride containing metal M and iodide containing metal M; Wherein, the chloride containing metal M is preferably one or more of zirconium chloride, tantalum chloride, iron chloride and indium chloride; and / or, the molar ratio of the lithium metal cyanamide compound to the halide containing the metal M is 0.2-1.7, preferably 0.3-1, such as 0.4, 0.5, 0.52, 0.55, 0.56, 0.6, 0.67, 0.7 or 0.8, more preferably 0.4-0.53 or 0.6-0.7; And / or, the ball milling includes the following process: firstly ball milling at a rotation speed of 50-200 rpm for 0.5-4 h, and then ball milling at a rotation speed of 400-1000 rpm for 8-24 h.

9. Use of the lithium cyanamide halide material as claimed in any one of claims 1 to 3 as a solid electrolyte in an all-solid-state lithium ion battery.

10. An all-solid-state lithium-ion battery, characterized in that: It comprises the lithium cyanamide halide material as described in any one of claims 1 to 3.

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