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

Abstract

The invention discloses a reducing metal doped lithium titanium silicate material, a preparation method, application and a battery. The composition of the reducing metal doped lithium titanium silicate material is Li < 2-m < x > M < m + x > Ti < y > N < n + > (4-4y) / n > SiO < 5-z >, M is one or more of Na, K and Mg, and x is more than or equal to 0 and less than or equal to 2; n is one or more of Zr, Nb, Ta, Mo and W, and y is larger than 0.8 and smaller than or equal to 1. The reducing metal doped lithium titanium silicate material prepared by the invention has a lower voltage platform, higher capacity and excellent long cycle stability, and the preparation method is simple, low in cost and beneficial to industrial production.

Description

Technical Field

[0001] The invention relates to a reducing metal-doped lithium titanium silicate material, a preparation method, an application and a battery. Background Art

[0002] Titanium-based oxides (TiO2, Li4Ti5O 12 、TiNb2O7、LiTi n O 2n+1 Lithium titanium silicate (Li2TiSiO5) is widely used as anode material of lithium-ion batteries due to its high structural stability, superior safety and cycle reversibility. However, due to its high operating voltage and low capacity, it often leads to low energy density, which is not conducive to industrial application. Among them, lithium titanium silicate (Li2TiSiO5) is a ternary metal oxide. When used as anode material of lithium-ion batteries, on the basis of the embedding reaction, an additional TiO and Li4SiO4 reaction occurs. 4+ / Ti 2+ Redox conversion reaction, thus obtaining 308 mAh g -1 In addition, the working voltage of lithium titanium silicate is low, about 0.28V, which can not only avoid the formation of lithium dendrites, but also ensure high energy density. These advantages make it very promising to replace commercial graphite and Li4Ti5O 12 However, its low intrinsic electronic conductivity seriously affects its capacity and cycle stability. In addition, compared with silicon negative electrode materials and some sulfide negative electrode materials, its theoretical specific capacity is still low, which greatly limits the application prospects of this material. Therefore, it is very necessary and challenging to prepare high-capacity and long-cycle-stability lithium titanium silicate materials. Summary of the invention

[0003] The technical problem solved by the present invention is to overcome the problem that the prior art cannot obtain lithium titanium silicate materials with high capacity and long cycle stability, and provide a reduced metal-doped lithium titanium silicate material and a preparation method, application and battery. The reduced metal-doped lithium titanium silicate material prepared by the present invention has a lower voltage platform, higher capacity and excellent long cycle stability, and the preparation method is simple, low cost, and is conducive to industrial production.

[0004] The present invention is to exchange sodium titanium silicate / potassium with "lithium salt and / or magnesium salt ions" to form a phase, and then pass Li is prepared by gas reduction 2-mx M m+ x Ti y N n+ (4-4y) / n SiO 5-zOn the one hand, the material maintains the wide interlayer spacing of sodium titanium silicate / potassium, which helps to activate the inactive sites between the layers, thereby greatly improving the capacity; on the other hand, through reduction, the valence state of the elements in the lithium titanium silicate material is further reduced, and a small amount of silicon is generated to provide additional capacity while providing abundant oxygen vacancies, which not only greatly reduces the voltage platform of the material, improves the energy density, but also improves the electronic conductivity of the material. In addition, by doping with high-valent transition metals, the capacity at low voltage is further improved.

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

[0006] The present invention provides a reducing metal-doped lithium titanium silicate material, which is composed of 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 the present invention, in the composition of the reduced metal-doped lithium titanium silicate material, z refers to the oxygen loss caused by the reduction process. According to the conventional art, the value range of y is generally 0 <z<2。

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

[0009] In the present invention, in the composition of the reducing metal-doped lithium titanium silicate material, preferably, 0.85≤y≤1, such as 0.9, 0.95 or 1, more preferably, 0.85≤y<1.

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

[0011] In some specific embodiments, the composition of the reducing 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 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 the present invention, the reducing metal-doped lithium titanium silicate material preferably belongs to the tetragonal system.

[0013] In the present 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 silicon; the space group of the silicon is preferably P422. The original metal-doped lithium titanium silicate material usually also includes a small amount of impurities Na2TiSi4O 11 ; The Na2TiSi4O1 The space group of 1 is preferably I4 / m. According to the conventional art, the lower the impurity content of the reduced metal-doped lithium titanium silicate material, the better the performance of the reduced metal-doped lithium titanium silicate material. The main phase generally refers to the main body and basic components of the material, which has the highest proportion and has a decisive influence on the overall performance of the material.

[0014] In the present invention, the voltage platform of the reducing metal-doped lithium titanium silicate material may be 0.22-0.28V, such as 0.245V, 0.253V, 0.254V, 0.259V, 0.265V, 0.272V or 0.278V, and the voltage platform refers to the voltage value corresponding to the smallest voltage change and the largest capacity change.

[0015] In the present invention, the reducing metal doped lithium titanium silicate material is -1 The initial charge capacity is preferably 400-600 mAh g -1 , for example 430mAh g -1 、438mAg -1 , 450mAh g -1 、452mAg -1 , 501mAh g -1 , 515mAh g -1 , 520mAh g -1, 521mAg -1 、533mAg -1 , 548mAh g -1 、566mAg -1 or 572mAg -1 .

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

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

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

[0019] The alkali metal titanium silicate can be commercially available or prepared by itself. The preparation method of the alkali metal titanium silicate preferably comprises the following steps: calcining a mixture containing an alkali metal carbonate, silicon dioxide, titanium dioxide and an oxide containing metal N; 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 the oxide containing metal N is generally weighed according to the stoichiometric ratio based on 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 the common practice in the art, the alkali metal carbonate, silicon dioxide, titanium dioxide and the oxide containing metal N generally need to be mixed before calcination, for example, by ball milling.

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

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

[0024] In the present invention, the chemical formula of the intermediate is generally Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO5, 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.

[0025] Wherein, 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 the present invention, the lithium salt may be one or more of lithium chloride, lithium bromide, lithium iodide, lithium nitrate and lithium sulfate.

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

[0028] In the present invention, the molar ratio of the alkali metal titanium silicate and the "lithium salt and / or magnesium salt" is generally determined according to the molar amount of the alkali metal in the alkali metal titanium silicate, and usually the alkali metal ions in the alkali metal titanium silicate are partially or completely replaced by the lithium ions in the lithium salt and / or the magnesium ions in the magnesium salt, preferably 1: (1-10), preferably 1: (1-5), for example 1: 1.5, 1: 2, 1: 2.2, 1: 2.3 or 1: 3.

[0029] In certain specific embodiments, when the lithium salt and the magnesium salt are contained at the same time, the molar ratio of the lithium salt to the magnesium salt may be (8-12):1, such as 10:1 or 11:1.

[0030] In the present invention, the ion exchange treatment is preferably carried out by a hydrothermal method or a molten salt method, more preferably a hydrothermal method.

[0031] When the hydrothermal method is used, a solvent is generally added according to the conventional practice in the art. The type of the solvent can be a conventional solvent in the art that can dissolve 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 and the "lithium salt and / or magnesium salt" to the volume of the solvent can be (0.01-40) g / mL, preferably (0.05-10) g / mL, such as 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] Wherein, the hydrothermal method is generally carried out in a reactor. When the hydrothermal method is used, the temperature of the hydrothermal reaction can be 80-250°C, preferably 120-220°C, such as 150°C, 160°C, 180°C or 200°C; the time of the hydrothermal reaction can be 1-40h, preferably 4-20h, such as 8h, 10h, 12h or 15h. When the hydrothermal method is used, according to the conventional art, washing and drying are generally required after the hydrothermal reaction is completed.

[0033] In some specific embodiments, the hydrothermal method preferably includes the following process: subjecting a solution containing a 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 h.

[0034] The molten salt method generally refers to heating a mixture containing salt to melt the salt, and reacting the reactants in the salt melt to generate products. The molten salt method is generally carried out in a muffle furnace or a tube furnace. The molten salt method is generally carried out in air.

[0035] The molten salt method preferably 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 1-40h.

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

[0037] In the present invention, the reducing gas preferably includes hydrogen and / or ammonia. The reducing gas may be introduced at a flow rate of 50-500 sccm, such as 100 sccm, 200 sccm or 300 sccm.

[0038] In the present invention, the calcination is generally carried out in a tube furnace. The calcination temperature may be 300-1000°C, preferably 400-800°C, such as 450°C, 500°C, 600°C or 700°C; the calcination time may be 2-12h, such as 3h, 5h or 8h.

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

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

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

[0042] The raw materials and reagents used in the present invention are commercially available.

[0043] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0044] The reagents and raw materials used in the present invention are commercially available.

[0045] The positive and progressive effects of the present invention are:

[0046] The reduced metal-doped lithium titanium silicate material prepared by the present invention has a lower voltage platform, a higher capacity and excellent long-cycle stability, and the preparation method is simple, the cost is low, and it is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0048] Figure 2 LiNaTiSiO prepared in Example 1 5-z SEM images of

[0049] Figure 3 LiNaTiSiO prepared in Example 1 5-z XRD diagram of

[0050] Figure 4 Before and after photos of the restored material; Figure 4 Part (a) is a physical photo of the intermediate LiNaTiSiO5 prepared in Example 1; Figure 4 Part (b) is LiNaTiSiO prepared in Example 1 5-z Physical photos of

[0051] Figure 5LiNaTiSiO prepared in Example 1 5-z The electrochemical performance curve of the first cycle at 0.1C;

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

[0053] Figure 7 LiNaTiSiO prepared in Example 1 5-z 1C cycle performance diagram. DETAILED DESCRIPTION

[0054] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

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

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

[0057] (2) 10.1 g of alkali metal titanium silicate was added to a hydrothermal kettle, and 100 mL of an aqueous solution containing 4.25 g of LiCl was added. The mixture was ultrasonicated for 10 minutes, and the mixture was placed at 180° C. for hydrothermal reaction for 10 hours. The mixture was filtered, washed with deionized water for three times, and dried to obtain the intermediate LiNaTiSiO5.

[0058] (3) The intermediate was placed in a tube furnace, and Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500°C for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate material LiNaTiSiO 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, 10.6 g of sodium carbonate, 8.0 g of nano-titanium dioxide and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 °C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2TiSiO5.

[0061] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered, and dried to obtain the intermediate Li 1.98 Na 0.02 TiSiO5.

[0062] (3) The intermediate was placed in a tube furnace, and Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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, 13.8 g potassium carbonate, 8.0 g nano-titanium dioxide and 6.0 g nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 °C in a muffle furnace for 4 h to obtain alkali metal titanium silicate K2TiSiO5.

[0065] (2) 10.1 g of alkali metal titanium silicate was added to a hydrothermal kettle, and 100 mL of an aqueous solution containing 4.25 g of LiCl was added. The mixture was ultrasonicated for 10 minutes, and reacted at 180° C. for 10 hours. The mixture was filtered, washed with deionized water for three times, and dried to obtain the intermediate LiKTiSiO5.

[0066] (3) The intermediate was placed in a tube furnace and Ar / H2 mixed gas (mixed The volume fraction of H2 in the combined gas is 5%), and then calcined at 500℃ for 5h to obtain the final product, reduced metal-doped lithium titanium silicate material LiKTiSiO 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, 10.6 g of sodium carbonate, 8.0 g of nano-titanium dioxide and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 °C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2TiSiO5.

[0069] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace and reacted at 500°C for 10 h. The mixture was washed with deionized water three times, filtered, and dried to obtain the intermediate Li 1.99 Na 0.01 TiSiO5.

[0070] (3) The intermediate was placed in a tube furnace, and Ar / H2 (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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, 10.6 g of sodium carbonate, 8.0 g of nano-titanium dioxide and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 °C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2TiSiO5.

[0073] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered, and dried to obtain the intermediate Li 1.98 Na 0.02 TiSiO5.

[0074] (3) The intermediate was placed in a tube furnace, and Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 700°C 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 of sodium carbonate, 7.2 g of nano-titanium dioxide, 1.23 g of zirconium dioxide, and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 ° C in a muffle furnace 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 and mix it with 0.77g of LiCl and 5.65g of LiNO3. Place in a muffle furnace at 350 ° C for 10 hours, wash with deionized water three times, filter and dry to obtain the intermediate Li 1.98 Na 0.02 Ti 0.9 Zr 0.1 SiO5.

[0078] (3) The intermediate was placed in a tube furnace, and Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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 of sodium carbonate, 7.2 g of nano-titanium dioxide, 1.23 g of zirconium dioxide, and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 ° C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2Ti 0.9 Zr 0.1 SiO5.

[0081] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.861 g of MgCl2, 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered and dried 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 Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 ° C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2Ti 0.9 Nb 0.08 SiO5.

[0085] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered, and dried 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 Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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 of sodium carbonate, 7.2 g of nano-titanium dioxide, 0.96 g of molybdenum trioxide, and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 ° C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2Ti 0.9 Mo 0.067 SiO5.

[0089] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered, and dried 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 Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) was introduced at a flow rate of 200 sccm for reduction, and calcined at 500° C. 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, 10.6 g of sodium carbonate, 8.0 g of nano-titanium dioxide and 6.0 g of nano-silicon dioxide were mixed, ball-milled at 400 rpm for 4 h, and calcined at 900 °C in a muffle furnace for 4 h to obtain alkali metal titanium silicate Na2TiSiO5.

[0093] (2) 10.1 g of alkali metal titanium silicate was mixed with 0.77 g of LiCl and 5.65 g of LiNO3, and the mixture was placed in a muffle furnace at 350°C for 10 h, washed with deionized water three times, filtered, and dried to obtain the product Li 1.98 Na 0.02 TiSiO5.

[0094] Comparative Example 2 Reduction of sodium titanium silicate material Na2TiSiO 5-z Preparation

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

[0096] (2) Alkali metal titanium silicate is placed in a tube furnace, Ar / H2 mixed gas (the volume fraction of H2 in the mixed gas is 5%) is introduced at a flow rate of 200 sccm for reduction, and calcined at 500°C for 5 h to obtain the final product, reduced metal-doped lithium titanium silicate negative electrode material Na2TiSiO 5-z .

[0097] Effect Example

[0098] (1) EDS element 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 the reducing metal doped lithium titanium silicate materials prepared in Example 1 are shown in Figure 1-Figure 2 As shown in Table 1, the atomic ratio of Na:Si:Ti in the 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. At the same time, it can be found by naked eye observation that the color of the product changes from white to gray after the intermediate is reduced ( Figure 4 ), indicating that the element valence is reduced and the oxygen vacancies are reduced, indicating that its chemical composition is LiNaTiSiO 5-z . Figure 3 The XRD test results show that the reduced metal-doped lithium titanium silicate material prepared in Example 1 belongs to the tetragonal system, and its main phase is Li2TiSiO5 (P4 / nmm), and its secondary phase is Na2TiSi4O 11 (I4 / m) and a small amount of silicon particles (P422). The reduced metal-doped lithium titanium silicate materials prepared in Examples 2-9 also have the same structure after XRD testing; the material prepared in Comparative Example 2 without ion exchange is tested by XRD, and the results show that it belongs to the Na2TiSiO5 phase, which is completely different from the structure and composition of the reduced metal-doped lithium titanium silicate materials prepared in Examples 1-9.

[0101] Table 1

[0102]

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

[0104] Test equipment: Blue Power battery test system

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

[0106] (a) The sample to be tested, PVDF and SP were mixed in a mass ratio of 70:10:20, and NMP was added and stirred until uniform to prepare a slurry;

[0107] (b) The slurry was coated on copper foil and baked in a vacuum oven at 100°C for 24 h, then rolled with a roller mill, and finally formed into a pole piece with a punching machine (the pole piece slurry loading was 1.5 mg / cm 2 );

[0108] (c) assembling the above-mentioned electrode into a button cell with metallic lithium as the counter electrode, wherein the electrolyte composition is 1M LiPF6, and the solvent is a mixed solvent of DEC, EC, FEC and VC, wherein 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%, and the assembly process is carried out in a vacuum glove box filled with high-purity argon gas;

[0109] (d) After assembly, electrochemical performance test is performed:

[0110] The test conditions for discharge capacity, first effect and dQ / dV curve are: at room temperature, 0.1C constant current charge and discharge (1C = 200mA g -1 ), the voltage range is 0.01~2.0V;

[0111] Test results see Figure 5-Figure 7 and Table 2:

[0112] Table 2

[0113]

[0114]

[0115] According to Table 2, the reduced metal-doped lithium titanium silicate material prepared by the present invention exhibits excellent electrochemical properties when used as a negative electrode material for lithium batteries, especially having higher capacity, lower voltage platform and excellent long cycle stability. In Comparative Example 1, the product after lithium ion exchange was not subjected to gas reduction treatment, resulting in poor capacity and long cycle stability of the prepared material, and a higher voltage platform; in Comparative Example 2, lithium ion exchange was not performed, and a Na2TiSiO5 phase material was obtained. Although the voltage platform of this material was not high, the capacity and long cycle stability were poor.

[0116] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A reducing 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.

2. The reduced metal-doped lithium titanium silicate material according to claim 1, characterized in that: The reducing 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 system; (2) In the reducing metal-doped lithium titanium silicate material, the main phase component is Li2TiSiO5; the space group of the main phase component is preferably P4 / nmm; (3) The reducing metal-doped lithium titanium silicate material further comprises silicon; the space group of the silicon is preferably P422; (4) In the composition of the reducing metal-doped lithium titanium silicate material, 0≤x≤1, for example, 0.01, 0.02, 0.1, 0.2, 0.5, 1 or 1.5; (5) In the composition of the reducing metal-doped lithium titanium silicate material, 0.85≤y≤1, for example, 0.9, 0.95 or 1; (6) The voltage platform of the reduced metal-doped lithium titanium silicate material is 0.22-0.28 V, for example, 0.245 V, 0.253 V, 0.254 V, 0.259 V, 0.265 V, 0.272 V or 0.278 V; (7) The reducing metal doped lithium titanium silicate material is at 20 mAg -1 The initial capacity is 400-600mAh g -1 ; (8) The composition of the reducing 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. A method for preparing the reduced metal-doped lithium titanium silicate material as claimed in claim 1 or 2, characterized in that: It includes the following steps: A mixture containing an alkali metal titanium silicate and "lithium salt and / or magnesium salt" is subjected to ion exchange treatment to obtain an intermediate; the intermediate is then calcined in the presence of a reducing gas to obtain the reducing metal-doped lithium titanium silicate material; wherein the alkali metal in the alkali metal titanium silicate is Na and / or K.

4. The method for preparing the reduced metal-doped lithium titanium silicate material according to claim 3, characterized in that: The preparation method meets 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, A is Na and / or K; N is one or more of Zr, Nb, Ta, Mo and W, 0.8<y≤1; Preferably, the preparation method of the alkali metal titanium silicate comprises the following steps: calcining a mixture containing an alkali metal carbonate, silicon dioxide, titanium dioxide and an oxide containing metal N to obtain the alkali metal carbonate; the alkali metal carbonate is sodium carbonate and / or potassium carbonate; The molar ratio of the alkali metal carbonate, silicon dioxide, titanium dioxide and the oxide containing metal N is 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; The calcination atmosphere is preferably air; the calcination temperature is preferably 400-1300°C, more preferably 700-1100°C, such as 800°C, 900°C or 1000°C; the calcination time is preferably 1-12h, more preferably 2-8h, such as 2h, 4h or 6h; (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 to the "lithium salt and / or magnesium salt" is 1:(1-10), preferably 1:(1-5), for example 1:1.5, 1:2, 1:2.2, 1:2.3 or 1:

3.

5. The method for preparing the reduced metal-doped lithium titanium silicate material according to claim 3, characterized in that: The chemical formula of the intermediate is Li 2-mx M m+ x Ti y N n+ (4-4y) / n SiO5, 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 carried out by a hydrothermal method or a molten salt method.

6. The method for preparing the reduced metal-doped lithium titanium silicate material according to claim 5, characterized in that: The hydrothermal method satisfies one or more of the following conditions: (1) When the hydrothermal method is used, a solvent needs to be added; The type of the solvent is preferably a solvent that can dissolve 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 and the "lithium salt and / or magnesium salt" to the volume of the solvent is preferably (0.01-40) g / mL, more preferably (0.05-10) g / mL, such as 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; (2) When the hydrothermal method is used, the temperature of the hydrothermal reaction is 80-250°C, preferably 120-220°C, such as 150°C, 160°C, 180°C or 200°C; (3) When the hydrothermal method is used, the hydrothermal reaction time is 1-40 h, preferably 4-20 h, such as 8 h, 10 h, 12 h or 15 h; (4) The hydrothermal method comprises the following process: a solution containing a 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.

7. The method for preparing the reduced metal-doped lithium titanium silicate material according to claim 5, characterized in that: The molten salt method comprises 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 h; The heating temperature is preferably 250-750°C, such as 300°C, 350°C, 400°C, 450°C or 500°C; the heating time is preferably 5-20h, such as 6h, 10h or 12h.

8. The method for preparing the reduced metal-doped lithium titanium silicate material according to claim 3, characterized in that: The preparation method meets one or more of the following conditions: (1) The reducing gas includes hydrogen and / or ammonia; (2) The reducing gas has an inlet flow rate of 50-500 sccm, for example, 100 sccm, 200 sccm or 300 sccm; (3) The calcination temperature is 300-1000°C, preferably 400-800°C, such as 450°C, 500°C, 600°C or 700°C; (4) The calcination time is 2-12 hours, for example 3 hours, 5 hours or 8 hours.

9. Use of the reduced metal-doped lithium titanium silicate material as claimed in claim 1 or 2 in a battery.

10. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an electrode liquid, wherein the negative electrode comprises the reducing metal-doped lithium titanium silicate material as claimed in claim 1 or 2.

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