Reduction metal-doped lithium titanium silicate material and preparation method, application and battery

Abstract

This invention discloses a reduced metal-doped lithium titanium silicate material, its preparation method, applications, and batteries. The reduced metal-doped lithium titanium silicate material has a Li composition. 2‑mx M m+ x Ti y N n+ (4‑4y) / n SiO 5‑z M is one or more of Na, K, and Mg, where 0 ≤ x ≤ 2; N is one or more of Zr, Nb, Ta, Mo, and W, where 0.8 < y ≤ 1. The reduced metal-doped lithium titanium silicate material prepared by this invention has a lower voltage plateau, higher capacity, and excellent long-cycle stability. Furthermore, the preparation method is simple, low-cost, and conducive to industrial production.

Description

Technical Field

[0001] This invention relates to a reduced metal-doped lithium titanium silicate material, its preparation method, applications, and batteries. Background Technology

[0002] Titanium-based oxides (TiO2, Li4Ti5O) 12 TiNb2O7, LiTi n O 2n+1 Lithium titanium silicate (Li₂TiSiO₅), due to its high structural stability, superior safety, and cycle reversibility, is widely used as anode material for lithium-ion batteries. However, its high operating voltage and low capacity often result in low energy density, which is detrimental to industrial applications. Among them, lithium titanium silicate, as a ternary metal oxide, undergoes an additional TiO₂-TiO₄ intercalation reaction when used as anode material in lithium-ion batteries, in addition to the intercalation reaction. 4+ / Ti 2+ A redox conversion reaction was performed to obtain 308 mAh g. -1 It boasts a high theoretical specific capacity. Furthermore, lithium titanium silicate operates at a low voltage of approximately 0.28V, which not only prevents lithium dendrite formation but also ensures high energy density. These advantages make it a very promising replacement for commercial graphite and Li4Ti5O. 12 Lithium titanium silicate is a common anode material for lithium-ion batteries. However, its low intrinsic electronic conductivity severely affects its capacity and cycle stability. Furthermore, compared to silicon anode materials and some sulfide anode materials, its theoretical specific capacity is still relatively low, greatly limiting its application prospects. Therefore, preparing high-capacity, long-cycle-stability lithium titanium silicate materials is a necessary and challenging task. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the limitations of existing technologies in obtaining lithium titanium silicate materials with high capacity and long cycle stability. This invention provides a reduced metal-doped lithium titanium silicate material, its preparation method, applications, and batteries. The reduced metal-doped lithium titanium silicate material prepared by this invention exhibits a lower voltage plateau, higher capacity, and excellent long cycle stability. Furthermore, the preparation method is simple, low-cost, and conducive to industrial production.

[0004] This invention involves exchanging sodium / potassium titanium silicate with lithium and / or magnesium salt ions to form a phase, and then... Li was prepared by gas reduction. 2-mx M m+ x Ti y N n+ (4-4y) / n SiO 5-zThe material maintains a wide interlayer spacing of sodium / potassium titanium silicate, which helps activate inactive sites in the interlayer, thus significantly improving capacity. On the other hand, reduction further lowers the valence states of elements in the lithium titanium silicate material, generating a small amount of elemental silicon to provide additional capacity while also providing abundant oxygen vacancies. This not only significantly reduces the voltage plateau and increases the energy density but also improves the electronic conductivity. Furthermore, high-valence transition metal doping further enhances the capacity at low voltages.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0006] This invention provides a reduced metal-doped lithium titanium silicate material, the composition of which is Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO 5-z M is one or more of Na, K and Mg, 0≤x≤2; N is one or more of Zr, Nb, Ta, Mo and W, 0.8<y≤1.

[0007] In this invention, in the composition of the reduced metal-doped lithium titanium silicate material, z refers to the oxygen loss caused during the reduction process. According to conventional practice in the art, the value of y is generally in the range of 0. <z<2。

[0008] In this invention, the composition of the reduced metal-doped lithium titanium silicate material preferably has 0 ≤ x ≤ 1, for example 0.01, 0.02, 0.1, 0.2, 0.5, 1 or 1.5.

[0009] In this invention, the composition of the reduced metal-doped lithium titanium silicate material is preferably 0.85≤y≤1, for example 0.9, 0.95 or 1, and more preferably 0.85≤y<1.

[0010] In some preferred embodiments, M is Na and / or K in the composition of the reduced metal-doped lithium titanium silicate material.

[0011] In some specific embodiments, the reduced metal-doped lithium titanium silicate material has the composition LiNaTiSiO2. 5-z 、Li 1.98 Na 0.02 TiSiO 5-z LiKTiSiO 5-z 、Li 1.99 Na 0.01 TiSiO 5-z 、Li 1.98 Na 0.02 Ti0.9 Zr 0.1 SiO 5-z 、Li 1.6 Mg 0.2 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z 、Li 1.98 Na 0.02 Ti 0.9 Nb 0.08 SiO 5-z Or Li 1.98 Na 0.02 Ti 0.9 Mo 0.067 SiO 5-z .

[0012] In this invention, the reduced metal-doped lithium titanium silicate material preferably belongs to the tetragonal crystal system.

[0013] In this invention, the main phase component of the reduced metal-doped lithium titanium silicate material is generally Li₂TiSiO₅; the space group of the main phase component is preferably P₄ / nmm. The reduced metal-doped lithium titanium silicate material preferably also includes elemental silicon; the space group of the elemental silicon is preferably P₄22. Original metal-doped lithium titanium silicate materials typically also contain small amounts of impurities. Na2TiSi4O 11 The Na2TiSi4O1 The space group of 1 is preferably I⁴ / m. According to conventional art, the lower the impurity content of the reduced metal-doped lithium titanium silicate material, the better its performance. The main phase generally refers to the main body and basic components constituting the material, which constitutes the largest proportion and has a decisive influence on the overall performance of the material.

[0014] In this invention, the voltage plateau of the reduced metal-doped lithium titanium silicate material can be 0.22-0.28V, for example 0.245V, 0.253V, 0.254V, 0.259V, 0.265V, 0.272V or 0.278V. The voltage plateau refers to the voltage value corresponding to the smallest voltage change and the largest capacity change.

[0015] In this invention, the reduced metal-doped lithium titanium silicate material is at 20 mAg -1 The initial charging capacity is preferably 400-600mAh g -1 For example, 430mAh g -1 438mAg -1 450mAh g -1 452mAg -1 501mAh g -1 515mAh g -1 520mAh g -1521mAg -1 533mAg -1 548mAh g -1 566mAg -1 Or 572mAg -1 .

[0016] The present invention also provides a method for preparing the reduced metal-doped lithium titanium silicate material, which includes the following steps:

[0017] An intermediate is obtained by ion-exchange treatment of a mixture containing alkali metal titanium silicate salt and "lithium salt and / or magnesium salt"; the intermediate is then calcined in the presence of a reducing gas to obtain the reduced metal-doped lithium titanium silicate material; wherein the alkali metal in the alkali metal titanium silicate salt is Na and / or K.

[0018] In this invention, the chemical formula of the alkali metal titanium silicate salt is preferably A₂Ti. y N n+ (4-4y) / n SiO5, where A is Na and / or K; N is one or more of Zr, Nb, Ta, Mo, and W, and 0.8 < y ≤ 1. The meaning of y is the same as that in the reduced metal-doped lithium titanium silicate material.

[0019] The alkali metal titanium silicate salt can be commercially available or prepared in-house. A preferred method for preparing the alkali metal titanium silicate salt includes the following steps: calcining a mixture containing an alkali metal carbonate, silicon dioxide, titanium dioxide, and an oxide containing metal N; wherein the alkali metal carbonate is sodium carbonate and / or potassium carbonate.

[0020] The molar ratio of the alkali metal carbonate, silicon dioxide, titanium dioxide, and oxide containing metal N is generally determined by weighing according to the stoichiometric ratio of the chemical formula of the alkali metal titanium silicate, preferably (0.9-1.1):(0.9-1.1):1:(0-0.2), for example 1:1:1:0, 1.1:1.1:1:0.09, 1.1:1.1:1:0.074, 1.1:1.1:1:0.11, or 1.1:1.1:1:0.15.

[0021] According to conventional practice in the art, the alkali metal carbonate, silicon dioxide, titanium dioxide, and oxide containing metal N are generally mixed and treated, for example, by ball milling, before calcination.

[0022] The calcination atmosphere is generally air, and the calcination is generally carried out in a muffle furnace. The calcination temperature can be 400-1300℃, preferably 700-1100℃, such as 800℃, 900℃, or 1000℃. The calcination time can be 1-12 hours, preferably 2-8 hours, such as 2 hours, 4 hours, or 6 hours.

[0023] In some specific embodiments, the chemical formula of the alkali metal titanium silicate is Na₂TiSiO₅, K₂TiSiO₅, or Na₂Ti 0.9 Zr 0.1 SiO5, Na2Ti 0.9 Nb 0.08 SiO5 or Na2Ti 0.9 Mo 0.067 SiO5.

[0024] In this invention, the chemical formula of the intermediate is generally Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO5, where M is one or more of Na, K, and Mg, 0 ≤ x ≤ 2; and N is one or more of Zr, Nb, Ta, Mo, and W, 0.8 < y ≤ 1.

[0025] In the chemical formula of the intermediate, preferably, 0 ≤ x ≤ 1, for example, 0.01, 0.02, 0.1, 0.2, 0.5, 1 or 1.5; preferably, 0.85 ≤ y ≤ 1, for example, 0.9, 0.95 or 1.

[0026] In this invention, the lithium salt may be one or more of lithium chloride, lithium bromide, lithium iodide, lithium nitrate, and lithium sulfate.

[0027] In this invention, the magnesium salt may be one or more of magnesium chloride, magnesium bromide, magnesium iodide, and magnesium nitrate.

[0028] In this invention, the molar ratio of the alkali metal titanium silicate salt to the "lithium salt and / or magnesium salt" is generally determined based on the molar amount of alkali metal in the alkali metal titanium silicate salt. Usually, it is sufficient to allow the alkali metal ions in the alkali metal titanium silicate salt to be partially or completely replaced by lithium ions in the lithium salt and / or magnesium ions in the magnesium salt. Preferably, it is 1:(1-10), more preferably 1:(1-5), for example 1:1.5, 1:2, 1:2.2, 1:2.3 or 1:3.

[0029] In some specific embodiments, when both the lithium salt and the magnesium salt are present, the molar ratio of the lithium salt to the magnesium salt may be (8-12):1, for example, 10:1 or 11:1.

[0030] In this invention, the ion exchange treatment is preferably performed by a hydrothermal method or a molten salt method, and more preferably by a hydrothermal method.

[0031] In the hydrothermal method, according to conventional practice in the art, a solvent is generally added. The solvent may be any solvent conventional in the art capable of dissolving the lithium salt and / or magnesium salt, such as deionized water and / or ethanol. The ratio of the sum of the mass of the alkali metal titanium silicate salt and the lithium salt and / or magnesium salt to the volume of the solvent may be (0.01-40) g / mL, preferably (0.05-10) g / mL, for example 0.1 g / mL, 0.14 g / mL, 0.3 g / mL, 0.5 g / mL, 1.0 g / mL, 2.0 g / mL, 5.0 g / mL or 8.0 g / mL.

[0032] The hydrothermal method is generally carried out in a reaction vessel. When using the hydrothermal method, the temperature of the hydrothermal reaction can be 80-250℃, preferably 120-220℃, such as 150℃, 160℃, 180℃, or 200℃; the reaction time can be 1-40 hours, preferably 4-20 hours, such as 8 hours, 10 hours, 12 hours, or 15 hours. According to conventional practice in the art, washing and drying are generally required after the hydrothermal reaction is completed when using the hydrothermal method.

[0033] In some specific embodiments, the hydrothermal method preferably includes the following process: subjecting a solution containing the mixture of the alkali metal titanium silicate salt and "lithium salt and / or magnesium salt" to a hydrothermal reaction at 120-220°C for 4-20 hours.

[0034] The molten salt method generally refers to heating a mixture containing salt to melt the salt, and then reacting the reactants within the molten salt to produce products. The molten salt method is typically carried out in a muffle furnace or a tube furnace. Alternatively, it can be performed in air.

[0035] The molten salt method preferably includes the following process: heating the mixture of alkali metal titanium silicate salt and "lithium salt and / or magnesium salt" at 200-900°C for 1-40 hours.

[0036] The heating temperature is preferably 250-750°C, for example 300°C, 350°C, 400°C, 450°C or 500°C. The heating time is preferably 5-20 hours, for example 6 hours, 10 hours or 12 hours.

[0037] In this invention, the reducing gas preferably includes hydrogen and / or ammonia. The flow rate of the reducing gas can be 50-500 sccm, for example 100 sccm, 200 sccm or 300 sccm.

[0038] In this invention, the calcination is generally carried out in a tube furnace. The calcination temperature can be 300-1000℃, preferably 400-800℃, for example 450℃, 500℃, 600℃ or 700℃; the calcination time can be 2-12h, for example 3h, 5h or 8h.

[0039] The present invention also provides an application of the reduced metal-doped lithium titanium silicate material in a battery.

[0040] In this invention, the battery is preferably a lithium-ion battery.

[0041] The present invention also provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrode solution, wherein the negative electrode comprises a reduced metal-doped lithium titanium silicate material as described above.

[0042] All raw materials and reagents used in this invention are commercially available.

[0043] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0044] The reagents and raw materials used in this invention are all commercially available.

[0045] The positive and progressive effects of this invention are as follows:

[0046] The reduced metal-doped lithium titanium silicate material prepared by this invention has a lower voltage plateau, higher capacity and excellent long-term cycle stability. Moreover, the preparation method is simple, low-cost and conducive to industrial production. Attached Figure Description

[0047] Figure 1 Here is a SEM image of the alkali metal titanium silicate Na2TiSiO5 prepared in Example 1;

[0048] Figure 2 The LiNaTiSiO2 prepared in Example 1 5-z SEM image;

[0049] Figure 3 The LiNaTiSiO2 prepared in Example 1 5-z xrd plot;

[0050] Figure 4 Photos of the material before and after restoration; Figure 4 Part (a) is a photograph of the intermediate LiNaTiSiO5 prepared in Example 1; Figure 4 Part (b) is the LiNaTiSiO prepared in Example 1. 5-z Photos of the actual product;

[0051] Figure 5The LiNaTiSiO2 prepared in Example 1 5-z Electrochemical performance curves at 0.1C (first cycle);

[0052] Figure 6 The LiNaTiSiO2 prepared in Example 1 5-z The dQ / dV curve;

[0053] Figure 7 The LiNaTiSiO2 prepared in Example 1 5-z The 1C cycle performance diagram. Detailed Implementation

[0054] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0055] Example 1: Reduction of metal-doped lithium titanium silicate material LiNaTiSiO 5-z Preparation

[0056] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide (60nm) and 6.0g nano silicon dioxide (1-100nm) were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0057] (2) Take 10.1g of alkali metal titanium silicate salt and add it to a hydrothermal reactor. Add 100mL of aqueous solution containing 4.25g LiCl, sonicate for 10 minutes, and place it at 180℃ for hydrothermal reaction for 10h. Filter, wash with deionized water 3 times, and dry to obtain intermediate LiNaTiSiO5.

[0058] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material LiNaTiSiO2. 5-z .

[0059] Example 2: Reduction of metal-doped lithium titanium silicate material Li 1.98 Na 0.02 TiSiO 5-z Preparation

[0060] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide and 6.0g nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0061] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 350℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.98 Na 0.02 TiSiO5.

[0062] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.98 Na 0.02 TiSiO 5-z .

[0063] Example 3: Reduction of metal-doped lithium titanium silicate material LiKTiSiO 5-z Preparation

[0064] (1) At room temperature, 13.8g of potassium carbonate, 8.0g of nano titanium dioxide and 6.0g of nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate K2TiSiO5.

[0065] (2) Take 10.1g of alkali metal titanium silicate salt and add it to a hydrothermal reactor. Add 100mL of aqueous solution containing 4.25g LiCl, sonicate for 10 minutes, react at 180℃ for 10h, filter, wash with deionized water 3 times, and dry to obtain intermediate LiKTiSiO5.

[0066] (3) Place the intermediate in a tube furnace and introduce an Ar / H2 mixture (mixed gas) at a flow rate of 200 sccm. The gas was reduced (with a volume fraction of 5% H2) and calcined at 500℃ for 5 hours to obtain the final product, reduced metal-doped lithium titanium silicate material LiKTiSiO2. 5-z .

[0067] Example 4: Reduction of metal-doped lithium titanium silicate material Li 1.99 Na 0.01 TiSiO 5-z Preparation

[0068] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide and 6.0g nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0069] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 500℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.99 Na 0.01 TiSiO5.

[0070] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture is 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.99 Na 0.01 TiSiO 5-z .

[0071] Example 5: Reduction of metal-doped lithium titanium silicate material Li 1.98 Na 0.02 TiSiO 5-z Preparation

[0072] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide and 6.0g nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0073] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 350℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.98 Na 0.02 TiSiO5.

[0074] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction of 5%) at a flow rate of 200 sccm. The mixture was then calcined at 700℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.98 Na 0.02 TiSiO 5-z .

[0075] Example 6: Reduction of metal-doped lithium titanium silicate material Li 1.98 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z Preparation

[0076] (1) At room temperature, 10.6 g sodium carbonate, 7.2 g nano titanium dioxide, 1.23 g zirconium dioxide and 6.0 g nano silica were mixed and ball-milled at 400 rpm for 4 h. The mixture was then calcined in a muffle furnace at 900 °C for 4 h to obtain alkali metal titanium silicate Na2Ti. 0.9 Zr 0.1 SiO5.

[0077] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, The mixture was placed in a muffle furnace and reacted at 350°C for 10 h. After washing three times with deionized water, it was filtered, dried, and the intermediate Li was obtained. 1.98 Na 0.02 Ti 0.9 Zr 0.1 SiO5.

[0078] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.98 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z .

[0079] Example 7: Reduction of metal-doped lithium titanium silicate material Li 1.6 Mg 0.2 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z Preparation

[0080] (1) At room temperature, 10.6 g sodium carbonate, 7.2 g nano titanium dioxide, 1.23 g zirconium dioxide and 6.0 g nano silica were mixed and ball-milled at 400 rpm for 4 h. The mixture was then calcined in a muffle furnace at 900 °C for 4 h to obtain alkali metal titanium silicate Na2Ti. 0.9 Zr 0.1 SiO5.

[0081] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.861g of MgCl2, 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 350℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.6 Mg 0.2 Ti 0.9 Zr 0.1 SiO5.

[0082] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.6 Mg 0.2 Ti 0.9 Zr 0.1 SiO 5-z .

[0083] Example 8: Reduction of metal-doped lithium titanium silicate material Li 1.98 Na 0.02 Ti 0.9 Nb 0.08 SiO 5-z Preparation

[0084] (1) At room temperature, 10.6 g of sodium carbonate, 7.2 g of nano-titanium dioxide, 2.13 g of niobium pentoxide and 6.0 g of nano-silica were mixed and ball-milled at 400 rpm for 4 h. The mixture was then calcined in a muffle furnace at 900 °C for 4 h to obtain alkali metal titanium silicate Na2Ti. 0.9 Nb 0.08 SiO5.

[0085] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 350℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.98 Na 0.02 Ti 0.9 Nb 0.08 SiO5.

[0086] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.98 Na 0.02 Ti 0.9 Nb 0.08 SiO 5-z .

[0087] Example 9: Reduction of metal-doped lithium titanium silicate material Li 1.98 Na 0.02 Ti 0.9 Mo 0.067 SiO 5-z Preparation

[0088] (1) At room temperature, 10.6 g sodium carbonate, 7.2 g nano titanium dioxide, 0.96 g molybdenum trioxide and 6.0 g nano silica were mixed and ball-milled at 400 rpm for 4 h. The mixture was then calcined in a muffle furnace at 900 °C for 4 h to obtain alkali metal titanium silicate Na2Ti. 0.9 Mo 0.067 SiO5.

[0089] (2) Take 10.1g of alkali metal titanium silicate, mix it with 0.77g of LiCl and 5.65g of LiNO3, place it in a muffle furnace and react at 350℃ for 10h. Wash it three times with deionized water, filter it, and dry it to obtain the intermediate Li. 1.98 Na 0.02 Ti 0.9 Mo 0.067 SiO5.

[0090] (3) The intermediate was placed in a tube furnace and reduced by introducing an Ar / H2 mixture (H2 volume fraction in the mixture was 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material Li. 1.98 Na 0.02 Ti 0.9 Mo 0.067 SiO 5-z .

[0091] Comparative Example 1: Alkali metal-doped lithium titanium silicate material Li 1.98 Na 0.02 Preparation of TiSiO5

[0092] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide and 6.0g nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0093] (2) Take 10.1 g of alkali metal titanium silicate, mix it with 0.77 g of LiCl and 5.65 g of LiNO3, place it in a muffle furnace and react it at 350 °C for 10 h. Wash it three times with deionized water, filter it, and dry it to obtain the product Li. 1.98 Na 0.02 TiSiO5.

[0094] Comparative Example 2: Reduced sodium titanium silicate material Na₂TiSiO 5-z Preparation

[0095] (1) At room temperature, 10.6g sodium carbonate, 8.0g nano titanium dioxide and 6.0g nano silicon dioxide were mixed and ball-milled at 400rpm for 4h. The mixture was then placed in a muffle furnace and calcined at 900℃ for 4h to obtain alkali metal titanium silicate Na2TiSiO5.

[0096] (2) Alkali metal titanium silicate salt was placed in a tube furnace and reduced by introducing an Ar / H2 mixed gas (H2 volume fraction in the mixed gas is 5%) at a flow rate of 200 sccm. The mixture was then calcined at 500℃ for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate anode material Na2TiSiO. 5-z .

[0097] Effect Example

[0098] (1) EDS elemental analysis

[0099] The chemical formulas of the intermediates and reduced metal-doped lithium titanium silicate materials prepared in Examples 1-9 were obtained by EDS elemental analysis.

[0100] (2) The morphology and EDS elemental analysis results of the alkali metal titanium silicate and reduced metal doped lithium titanium silicate materials prepared in Example 1 are shown in the figure below. Figure 1-Figure 2 According to Table 1, the atomic ratio of Na:Si:Ti in alkali metal titanium silicate is approximately 2:1:1; after lithium ion exchange and reduction treatment, the atomic ratio of Na:Si:Ti changes to 1:1:1. Simultaneously, visual observation reveals that the product color changes from white to gray after reducing the intermediate. Figure 4 This indicates that the valence state of the element decreases and the number of oxygen vacancies decreases, suggesting that its chemical composition is LiNaTiSiO. 5-z . Figure 3 XRD test results show that the reduced metal-doped lithium titanium silicate material prepared in Example 1 belongs to the tetragonal crystal system, with Li₂TiSiO₅ as the main phase (P₄ / nmm) and Na₂TiSi₄ as the secondary phase. 11 The reduced metal-doped lithium titanium silicate materials prepared in Examples 2-9 also exhibited the same structure as those prepared by XRD analysis, containing (I4 / m) and a small amount of silicon particles (P422). The material prepared in Comparative Example 2 without ion exchange was also tested by XRD analysis, which showed that it belonged to the Na2TiSiO5 phase, and its structure and composition were completely different from those of the reduced metal-doped lithium titanium silicate materials prepared in Examples 1-9.

[0101] Table 1

[0102]

[0103] (3) Electrochemical performance testing (half-cell)

[0104] Testing equipment: Blue Battery Testing System

[0105] The reduced metal-doped lithium titanium silicate materials obtained in Examples 1-9 and the final products prepared in Comparative Examples 1-2 were used as test samples and assembled into coin cells for electrochemical performance testing. The specific steps are as follows:

[0106] (a) Mix the sample to be tested, PVDF, and SP in a mass ratio of 70:10:20, add NMP and stir until homogeneous to make a slurry;

[0107] (b) The above slurry is coated onto copper foil and baked in a vacuum drying oven at 100°C for 24 hours. Then, it is rolled using a roller press and finally formed into electrode sheets using a die-casting machine (electrode slurry loading is 1.5 mg / cm³). 2 );

[0108] (c) Assemble the above electrode sheets into a coin cell with lithium metal as the counter electrode. The electrolyte composition is 1M LiPF6, and the solvent is a mixed solvent of DEC, EC, FEC and VC. The volume ratio of DEC:EC is 1:1, the volume ratio of FEC to the total solvent is 10%, and the volume ratio of VC to the total solvent is 1%. The assembly process is carried out in a vacuum glove box filled with high-purity argon.

[0109] (d) Electrochemical performance testing is performed after assembly:

[0110] The test conditions for discharge capacity, first-efficiency, and dQ / dV curves were: constant current charge-discharge at 0.1C (1C = 200mA g) at room temperature. -1 The voltage range is 0.01 to 2.0V;

[0111] Test results are available Figures 5-7 And Table 2:

[0112] Table 2

[0113]

[0114]

[0115] As shown in Table 2, the reduced metal-doped lithium titanium silicate material prepared in this invention exhibits excellent electrochemical performance when used as a negative electrode material for lithium batteries, especially with higher capacity, lower voltage plateau, and excellent long-cycle stability. In Comparative Example 1, the product after lithium-ion exchange was not subjected to gas reduction treatment, resulting in poorer capacity and long-cycle stability of the prepared material, as well as a higher voltage plateau. In Comparative Example 2, no lithium-ion exchange was performed, resulting in a Na2TiSiO5 phase material. Although this material had a lower voltage plateau, its capacity and long-cycle stability were both poor.

[0116] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A reduced metal-doped lithium titanium silicate material, characterized in that, Its composition is Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO 5-z M is one or more of Na, K and Mg, 0 < x < 2; N is one or more of Zr, Nb, Ta, Mo and W, 0.8 < y ≤ 1, and z refers to the oxygen loss caused during the reduction process.

2. The reduced metal-doped lithium titanium silicate material as described in claim 1, characterized in that, The reduced metal-doped lithium titanium silicate material satisfies one or more of the following conditions: (1) The reduced metal-doped lithium titanium silicate material belongs to the tetragonal crystal system; (2) In the reduced metal-doped lithium titanium silicate material, the main phase component is Li2TiSiO5; (3) The reduced metal-doped lithium titanium silicate material also includes elemental silicon; (4) In the composition of the reduced metal-doped lithium titanium silicate material, x is 0.01, 0.02, 0.1, 0.2, 0.5 or 1; (5) In the composition of the reduced metal-doped lithium titanium silicate material, 0.85≤y≤1; (6) The voltage plateau of the reduced metal-doped lithium titanium silicate material is 0.22-0.28V; (7) The reduced metal-doped lithium titanium silicate material at 20 mA g -1 The initial capacity is 400-600 mAh g -1 ; (8) The composition of the reduced metal-doped lithium titanium silicate material is LiNaTiSiO 5-z Li 1.98 Na 0.02 TiSiO 5-z LiKTiSiO 5-z Li 1.99 Na 0.01 TiSiO 5-z Li 1.98 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z Li 1.6 Mg 0.2 Na 0.02 Ti 0.9 Zr 0.1 SiO 5-z Li 1.98 Na 0.02 Ti 0.9 Nb 0.08 SiO 5-z Or Li 1.98 Na 0.02 Ti 0.9 Mo 0.067 SiO 5-z .

3. The reduced metal-doped lithium titanium silicate material as described in claim 2, characterized in that, In the reduced metal-doped lithium titanium silicate material, the space group of the main phase component is P4 / nmm.

4. The reduced metal-doped lithium titanium silicate material as described in claim 2, characterized in that, The space group of the silicon is P422.

5. The reduced metal-doped lithium titanium silicate material as described in claim 2, characterized in that, In the composition of the reduced metal-doped lithium titanium silicate material, y is 0.9, 0.95, or 1.

6. The reduced metal-doped lithium titanium silicate material as described in claim 2, characterized in that, The voltage plateau of the reduced metal-doped lithium titanium silicate material is 0.245V, 0.253V, 0.254V, 0.259V, 0.265V, 0.272V, or 0.278V.

7. A method for preparing a reduced metal-doped lithium titanium silicate material as described in any one of claims 1-6, characterized in that, It includes the following steps: An intermediate is obtained by ion-exchange treatment of a mixture containing alkali metal titanium silicate salt and "lithium salt and / or magnesium salt"; the intermediate is then calcined in the presence of a reducing gas to obtain the reduced metal-doped lithium titanium silicate material; wherein the alkali metal in the alkali metal titanium silicate salt is Na and / or K.

8. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 7, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The chemical formula of the alkali metal titanium silicate is A2Ti y N n+ (4-4y) / n SiO5, where A is Na and / or K; N is one or more of Zr, Nb, Ta, Mo and W, and 0.8 < y ≤ 1; (2) The lithium salt is one or more of lithium chloride, lithium bromide, lithium iodide, lithium nitrate and lithium sulfate; (3) The magnesium salt is one or more of magnesium chloride, magnesium bromide, magnesium iodide and magnesium nitrate; (4) The molar ratio of the alkali metal titanium silicate salt and the "lithium salt and / or magnesium salt" is 1: (1-10).

9. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 8, characterized in that, The preparation method of the alkali metal titanium silicate includes the following steps: calcining a mixture containing alkali metal carbonate, silicon dioxide, titanium dioxide and an oxide containing metal N; wherein the alkali metal carbonate is sodium carbonate and / or potassium carbonate.

10. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 9, characterized in that, The molar ratio of the alkali metal carbonate, silicon dioxide, titanium dioxide and oxide containing metal N is (0.9-1.1):(0.9-1.1):1:(0-0.2).

11. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 10, characterized in that, The molar ratio of the alkali metal carbonate, silicon dioxide, titanium dioxide, and oxide containing metal N is 1:1:1:0, 1.1:1.1:1:0.09, 1.1:1.1:1:0.074, 1.1:1.1:1:0.11, or 1.1:1.1:1:0.

15.

12. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 9, characterized in that, The calcination atmosphere is air.

13. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 9, characterized in that, The calcination temperature is 400-1300℃.

14. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 13, characterized in that, The calcination temperature is 800℃, 900℃ or 1000℃.

15. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 9, characterized in that, The calcination time is 1-12 hours.

16. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 15, characterized in that, The calcination time is 2-8 hours.

17. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 16, characterized in that, The calcination time is 2 hours, 4 hours, or 6 hours.

18. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 8, characterized in that, The molar ratio of the alkali metal titanium silicate salt to the "lithium salt and / or magnesium salt" is 1:(1-5).

19. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 18, characterized in that, The molar ratio of the alkali metal titanium silicate salt to the lithium salt and / or magnesium salt is 1:1.5, 1:2, 1:2.2, 1:2.3 or 1:

3.

20. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 7, characterized in that, The chemical formula of the intermediate is Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO5, where M is one or more of Na, K and Mg, 0 < x < 2; N is one or more of Zr, Nb, Ta, Mo and W, 0.8 < y ≤ 1; And / or, the ion exchange treatment is performed by a hydrothermal method or a molten salt method.

21. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 20, characterized in that, The hydrothermal method satisfies one or more of the following conditions: (1) When using the hydrothermal method, a solvent also needs to be added; (2) When the hydrothermal method is used, the temperature of the hydrothermal reaction is 80-250℃; (3) When the hydrothermal method is used, the hydrothermal reaction time is 1-40 h; (4) The hydrothermal method includes the following process: a solution containing the mixture of the alkali metal titanium silicate salt and "lithium salt and / or magnesium salt" is subjected to a hydrothermal reaction at 120-220°C for 4-20 hours.

22. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 21, characterized in that, The solvent is a solvent capable of dissolving the lithium salt and / or magnesium salt.

23. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 22, characterized in that, The solvent is deionized water and / or ethanol.

24. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 21, characterized in that, The ratio of the sum of the masses of the alkali metal titanium silicate salt and the lithium salt and / or magnesium salt to the volume of the solvent is (0.01-40) g / mL.

25. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 24, characterized in that, The ratio of the sum of the masses of the alkali metal titanium silicate and the lithium and / or magnesium salts to the volume of the solvent is (0.05-10) g / mL.

26. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 25, characterized in that, The ratio of the sum of the masses of the alkali metal titanium silicate salt and the lithium salt and / or magnesium salt to the volume of the solvent is 0.1 g / mL, 0.14 g / mL, 0.3 g / mL, 0.5 g / mL, 1.0 g / mL, 2.0 g / mL, 5.0 g / mL or 8.0 g / mL.

27. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 21, characterized in that, The temperature of the hydrothermal reaction is 120-220℃.

28. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 27, characterized in that, The hydrothermal reaction temperature is 150℃, 160℃, 180℃ or 200℃.

29. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 21, characterized in that, The hydrothermal reaction takes 4-20 hours.

30. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 29, characterized in that, The hydrothermal reaction time is 8h, 10h, 12h or 15h.

31. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 20, characterized in that, The molten salt method includes the following process: heating the mixture of the alkali metal titanium silicate salt and "lithium salt and / or magnesium salt" at 200-900°C for 1-40 hours.

32. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 31, characterized in that, The heating temperature is 250-750℃.

33. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 32, characterized in that, The heating temperature is 300℃, 350℃, 400℃, 450℃ or 500℃.

34. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 31, characterized in that, The heating time is 5-20 hours.

35. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 34, characterized in that, The heating time is 6 hours, 10 hours, or 12 hours.

36. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 7, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The reducing gas includes hydrogen and / or ammonia; (2) The flow rate of the reducing gas is 50-500 sccm; (3) The calcination temperature is 300-1000℃; (4) The calcination time is 2-12h.

37. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 36, characterized in that, The flow rate of the reducing gas is 100 sccm, 200 sccm, or 300 sccm.

38. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 36, characterized in that, The calcination temperature is 400-800℃.

39. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 38, characterized in that, The calcination temperature is 450℃, 500℃, 600℃ or 700℃.

40. The method for preparing reduced metal-doped lithium titanium silicate material as described in claim 36, characterized in that, The calcination time is 3h, 5h or 8h.

41. The application of a reduced metal-doped lithium titanium silicate material as described in any one of claims 1-6 in a battery.

42. A battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode comprises a reduced metal-doped lithium titanium silicate material as described in any one of claims 1-6.

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