Negative electrode material and preparation method and application thereof

Abstract

The invention discloses a negative electrode material as well as a preparation method and application thereof. The negative electrode material for a lithium battery, which contains Bi < x > Ti < y > O < z > and / or Li Bi TicO < z >, can have relatively proper discharge potential (so that the whole battery has relatively low lithium precipitation risk and relatively high specific energy) and relatively high specific capacity when being applied to the lithium battery; particularly, the invention innovatively proposes that BixTiyOz and / or LiaBibTicOz are / is combined with the silicon-based material, unexpected better power / rate characteristics can be obtained, the silicon-based negative electrode material is endowed with excellent electrochemical characteristics under high current (high power), and the silicon-based negative electrode material has potential and advantages of application as a large energy storage system, a power battery and the like.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a negative electrode material, its preparation method, and its application. Background Technology

[0002] With the transformation of the global energy structure and the rapid development of electric vehicles and large-scale energy storage power stations, unprecedented high demands have been placed on electrochemical energy storage devices, especially lithium-ion batteries, in terms of energy density, power density, cycle life, and safety. As a core component of lithium-ion batteries, the performance of the anode material directly determines the overall performance indicators of the battery.

[0003] While traditional graphite-based or hard carbon anode materials are widely used, their low theoretical specific capacity, tendency to form dendrites during charge and discharge, and poor fast-charging performance have become key bottlenecks in improving battery energy density and safety. To overcome these shortcomings, researchers have developed various alternative materials, such as spinel-structured lithium titanate (Li4Ti5O4). 12 Li4Ti5O3 (Li4Ti5O3) has attracted much attention in lithium-ion batteries due to its excellent cycle stability and safety ("zero strain" characteristics, high lithium-ion diffusion coefficient, and no lithium dendrite formation). However, Li4Ti5O3... 12 The relatively high operating voltage platform (approximately 1.55V vs. Li+ / Li) brings safety advantages but also results in a lower overall battery energy density. Furthermore, its theoretical specific capacity is only 175mAh / g, which limits its application in high-energy-density scenarios. Therefore, developing a novel anode material that combines high specific capacity with low operating voltage (e.g., 0.1-1.0V) has become a research hotspot and important development direction in the field of battery anode materials. Such materials can be matched with high-voltage cathode materials to construct a new generation of batteries with a wider operating voltage window and higher energy density, meeting the needs of high-end market applications.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0005] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide a new negative electrode material or silicon-based composite material for lithium batteries.

[0006] The present invention also provides a negative electrode sheet comprising a negative electrode material or a silicon-based composite material, or a battery made therefrom.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A negative electrode material for lithium batteries, the negative electrode material comprising the components shown in general formula (I);

[0009] Bi x Ti y O z (Ⅰ), where x and y are greater than 0, and the values ​​of x, y and z make equation (Ⅰ) satisfy the equilibrium of valence states.

[0010] In some embodiments of the present invention, in formula (Ⅰ), 3x + 4y = 2z.

[0011] In this invention, the values ​​of x, y, and z are not specifically limited; they can be integers or decimals, as long as they can satisfy the equilibrium of the valence states in equation (Ⅰ).

[0012] For example, in some cases, x and y can be independently greater than 0 and less than or equal to 50, such as being independently selected from 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, etc.

[0013] According to some specific aspects of the present invention, the negative electrode material may include, but is not limited to, materials selected from Bi2Ti2O7 and Bi4Ti3O7. 12 Bi2Ti4O 11 Bi 12 TiO 20 Bi 20 TiO 32 Bi6Ti2O 13 Bi6Ti4O 17 Bi2Ti6O 15 Bi4Ti2O 10 One, two, three or more combinations of them.

[0014] In some embodiments of the present invention, the component represented by general formula (I) is prepared by the following method:

[0015] Bismuth oxide and titanium oxide are mixed uniformly in stoichiometric ratio and selectively ground to obtain a precursor; or bismuth salt and alkyl alcohol titanium are weighed in stoichiometric ratio and dispersed in alkyl alcohol to form a sol, and then the sol is converted into a gel and selectively dried to obtain a precursor.

[0016] The precursor is subjected to calcination treatment.

[0017] In some embodiments of the present invention, the bismuth oxide may include, but is not limited to, bismuth trioxide, etc.

[0018] In some embodiments of the present invention, the titanium oxide may include, but is not limited to, titanium dioxide.

[0019] In some embodiments of the present invention, the bismuth salt includes, but is not limited to, one, two, or a combination of three selected from bismuth nitrate, bismuth sulfate, and bismuth phosphate. In the present invention, the bismuth salt can be in hydrate form, or it can be anhydrous.

[0020] In some embodiments of the present invention, the alkyl alcohol titanium includes, but is not limited to, C... 2-6 Alkyl alcohol titanium, etc.

[0021] Furthermore, the C 2-6 Alkyl alcohol titanium includes, but is not limited to, one, two, three or more combinations of titanium ethoxide, titanium isopropoxide, titanium n-propoxide, and tetrabutyl titanate.

[0022] In some embodiments of the present invention, the alkyl alcohol includes, but is not limited to, one, two, three or more combinations selected from ethanol, isopropanol, n-propanol and butanol.

[0023] In some embodiments of the present invention, the gel is obtained by aging the sol and then adding water and allowing it to stand and separate into layers.

[0024] Furthermore, the aging time can be 8-16 hours.

[0025] Furthermore, the aging temperature can be 50-70℃.

[0026] In some embodiments of the present invention, the calcination process is controlled to be carried out at 1000-1200°C, for example, at 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, or 1200°C.

[0027] In some embodiments of the present invention, the heating rate of the calcination treatment is controlled to be 1-15℃ / min, further to 2-8℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, etc.

[0028] In some embodiments of the present invention, the roasting time is controlled to be 2-12 hours, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 hours, etc.

[0029] In some embodiments of the present invention, the grinding can be performed by adding a mixture of bismuth oxide and titanium oxide into a mortar or grinding jar, and using manual grinding or planetary ball milling. Further, the grinding speed can be 300–500 r / min; even further, the grinding time can be 15–60 minutes.

[0030] In some embodiments of the present invention, after the calcination process, cooling is performed, and further, the material can be naturally cooled to room temperature.

[0031] The preparation method of this invention is simple and easy to scale up industrially. The specific capacity test of the prepared material shows small deviation in each batch, and the consistency and repeatability of the materials are good across batches.

[0032] Another technical solution provided by the present invention: a negative electrode material for lithium batteries, the negative electrode material comprising the components shown in general formula (II);

[0033] Li a Bi b Ti c O z (II), where a, b, and c are all greater than 0, and the values ​​of a, b, c, and z make equation (II) satisfy the equilibrium of valence states.

[0034] In some embodiments of the present invention, a+mb+nc=2z, m is the valence of Bi and includes valences of 0, +1, +2, +3, +4 or +5, and n is the valence of Ti and includes valences of 0, +1, +2, +3 or +4.

[0035] In some embodiments of the present invention, 'a' can be selected from 0.001-10, or 0.001-9.9, or 0.001-9.8, or 0.001-9.7, or 0.001-9.6, or 0.001-9.5, or 0.002-9, or 0.003-8.5, or 0.004-8, or 0.005-7.5, or 0.006-7, or 0.007-6.5, or 0.008-6, or 0.009-5.5, or 0.01-8, or 0.02-7, or 0.03-6, or 0.04-5, or 0.05-4, or 0.06-3, etc.

[0036] Another technical solution provided by the present invention: a method for preparing the above-mentioned negative electrode material for lithium batteries, the preparation method comprising:

[0037] An electrode made of a material containing the components shown in general formula (Ⅰ) is used as the working electrode;

[0038] The working electrode participates in the charging or discharging process of the battery to generate the components shown in general formula (II);

[0039] The battery includes a lithium-containing electrode;

[0040] Bi x Ti y O z (Ⅰ), where x and y are greater than 0, and the values ​​of x, y and z make equation (Ⅰ) satisfy the equilibrium of valence states.

[0041] According to the present invention, the component represented by general formula (II) is obtained by the component represented by general formula (I) in a lithium battery by obtaining lithium from a lithium source (e.g., a material such as a counter electrode or a positive electrode) and inserting it into the lithium battery through discharge or charging.

[0042] In some embodiments of the present invention, when the battery is a half-cell, the working electrode participates in the discharge process of the battery. When a half-cell is used, the lithium in the component shown in general formula (II) can be derived from a lithium-containing counter electrode, such as metallic lithium.

[0043] In some embodiments of the present invention, when the battery is a full battery, the working electrode participates in the charging process of the battery. When a full battery is used, the lithium in the component shown in general formula (II) can be derived from lithium-containing cathode materials, such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide (such as LMO, LiMn2O4), lithium iron phosphate (LiFePO4, abbreviated as LFP), lithium-rich manganese-based cathode materials, etc.

[0044] In some embodiments of the present invention, the preparation method further includes: after charging or discharging, separating the working electrode from the battery to obtain the negative electrode material for lithium batteries.

[0045] In practical applications, since the battery is pre-assembled, the negative electrode material for lithium batteries containing the components shown in general formula (II) does not need to be disassembled and can be used directly in the battery. Of course, it can also be disassembled and reassembled into a new battery when needed.

[0046] Another technical solution provided by this invention: the application of bismuth titanate in the preparation of negative electrode materials for lithium batteries, wherein the chemical formula of bismuth titanate is: Bi x Ti y O z (Ⅰ), where x and y are greater than 0, and the values ​​of x, y and z make equation (Ⅰ) satisfy the equilibrium of valence states.

[0047] Another technical solution provided by the present invention: a silicon-based composite material, wherein the silicon-based composite material comprises a silicon-based material and a component represented by general formula (II); Li a Bi b Ti c O z (II), where a, b, and c are all greater than 0, and the values ​​of a, b, c, and z make equation (II) satisfy the equilibrium of valence states.

[0048] In some embodiments of the present invention, the silicon-based material comprises more than 50% by mass percentage in the silicon-based composite material containing the component shown in general formula (II), for example including but not limited to 50%, 52%, 55%, 58%, 60%, 62%, 63%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0049] In some embodiments of the present invention, in the silicon-based composite material containing the components shown in general formula (II), the silicon-based material comprises one, two, or a combination of three of elemental silicon, silicon-oxygen materials, and silicon-carbon materials.

[0050] Elemental silicon, silicon-oxygen materials, and silicon-carbon materials are all conventional materials in this field and will not be described in detail here.

[0051] In some embodiments of the present invention, in the silicon-based composite material containing the component shown in general formula (II), the mass ratio of the silicon-based material to the component shown in general formula (II) is 0.001-1:1, or 0.01-0.8, or 0.02-0.75, or 0.03-0.7, or 0.04-0.65, or 0.05-0.60, or 0.06-0.55, or 0.07-0.50, or 0.08-0.45, or 0.09-0.40, or 0.1-0.35, or 0.11-0.30.

[0052] In some embodiments of the present invention, the silicon-based composite material is prepared by the following method:

[0053] An electrode made of a material containing silicon-based material and the components shown in general formula (Ⅰ) is used as the working electrode;

[0054] The working electrode is involved in the charging or discharging process of the battery to generate a silicon-based composite material containing silicon-based materials and components shown in general formula (II).

[0055] The battery includes a lithium-containing electrode.

[0056] Furthermore, the preparation process of the silicon-based composite material may also include: after charging or discharging, separating the working electrode from the battery to obtain the silicon-based composite material.

[0057] Another technical solution provided by the present invention is a lithium battery negative electrode sheet, wherein the material of the lithium battery negative electrode sheet includes the negative electrode material for lithium batteries described above, or includes the negative electrode material for lithium batteries prepared by the preparation method described above, or includes the silicon-based composite material described above.

[0058] In some embodiments of the present invention, the material of the lithium battery negative electrode sheet further includes a conductive agent, a binder, and a current collector.

[0059] Furthermore, the aforementioned negative electrode material is mixed with a conductive agent and a binder and then placed on a current collector to form a negative electrode sheet. Even further, the mixture of the aforementioned negative electrode material with the conductive agent and binder can be placed on the current collector by coating or pressing, followed by drying or baking steps to obtain a preliminary electrode sheet, which can then be processed into a negative electrode sheet of a predetermined shape, such as a circle or square.

[0060] In some embodiments of the present invention, the conductive agent, binder, and current collector can be substances or materials commonly used in the art. For example, the conductive agent can be conductive carbon black, the binder can be polyacrylic acid, polytetrafluoroethylene, etc., and the current collector can be copper foil, stainless steel, etc., without further details or limitations.

[0061] Another technical solution provided by the present invention is a lithium battery, which includes the lithium battery negative electrode sheet described above.

[0062] Another technical solution provided by the present invention: a silicon-based composite material, wherein the silicon-based composite material comprises a silicon-based material and bismuth titanate; the chemical formula of bismuth titanate is: Bi x Ti y O z (Ⅰ), where x and y are greater than 0, and the values ​​of x, y and z make equation (Ⅰ) satisfy the equilibrium of valence states.

[0063] In some embodiments of the present invention, the silicon-based material in the bismuth titanate-containing silicon-based composite material accounts for more than 50% by mass percentage, for example including but not limited to 50%, 52%, 55%, 58%, 60%, 62%, 63%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0064] In some embodiments of the present invention, in the silicon-based composite material containing bismuth titanate, the silicon-based material comprises one, two, or a combination of three of elemental silicon, silicon-oxygen materials, and silicon-carbon materials.

[0065] In some embodiments of the present invention, in the silicon-based composite material containing bismuth titanate, the mass ratio of the silicon-based material to the bismuth titanate is 0.001-1:1, or 0.01-0.8, or 0.02-0.75, or 0.03-0.7, or 0.04-0.65, or 0.05-0.60, or 0.06-0.55, or 0.07-0.50, or 0.08-0.45, or 0.09-0.40, or 0.1-0.35, or 0.11-0.30.

[0066] In some embodiments of the present invention, the silicon-based composite material is prepared by mixing silicon-based materials and bismuth titanate.

[0067] Another technical solution provided by the present invention is a negative electrode material, wherein the negative electrode material comprises the silicon-based composite material described above.

[0068] Another technical solution provided by the present invention is a negative electrode sheet, wherein the negative electrode sheet comprises the negative electrode material described above.

[0069] In some embodiments of the present invention, the material of the negative electrode sheet further includes a conductive agent, a binder, and a current collector.

[0070] Furthermore, in the preparation process of the negative electrode sheet, the aforementioned negative electrode material can be mixed with a conductive agent and a binder and then placed on a current collector to form a negative electrode sheet. Even further, the mixture of the aforementioned negative electrode material with the conductive agent and binder can be placed on the current collector by coating or pressing, followed by drying or baking steps to obtain a preliminary electrode sheet, which can then be processed into a negative electrode sheet of a predetermined shape, such as a circle or square.

[0071] In some embodiments of the present invention, during the preparation of the negative electrode sheet, the conductive agent, binder, and current collector can be substances or materials commonly used in the art. For example, the conductive agent can be conductive carbon black, the binder can be polyacrylic acid, polytetrafluoroethylene, etc., and the current collector can be copper foil, stainless steel, etc., without further details or limitations.

[0072] In some embodiments of the present invention, the mass ratio of the components shown in general formula (Ⅰ), the conductive agent, and the binder is (85-95):(1-10):(1-10).

[0073] In some embodiments of the present invention, the mass ratio of the components shown in general formula (II), the conductive agent, and the binder is (85-95):(1-10):(1-10).

[0074] In some embodiments of the present invention, the mass ratio of silicon-based composite material, conductive agent, and binder is (85-95):(1-10):(1-10).

[0075] Another technical solution provided by the present invention: a battery, the battery comprising the negative electrode sheet described above.

[0076] In some embodiments of the present invention, the battery is a lithium battery or a sodium battery.

[0077] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0078] During extensive experimental research, the inventors of this invention unexpectedly discovered that when lithium battery anode materials containing components shown in general formula (I) or general formula (II) are used in lithium batteries, they can have a suitable discharge potential (so that the whole cell has a lower risk of lithium plating while having a higher specific energy) and a higher specific capacity. In particular, this invention innovatively proposes combining the components shown in general formula (I) and / or general formula (II) with silicon-based materials, which unexpectedly yields superior power / rate characteristics, endowing silicon-based anode materials with excellent electrochemical properties under high current (high power). Furthermore, through further mechanistic studies, it is believed that this is because the components shown in general formula (I) or general formula (II) are combined with silicon-based materials in the anode material, and there is a sequential relationship between them in terms of discharge. The components shown in general formula (I) or general formula (II) will discharge preferentially before silicon-based materials, and form highly conductive substances during the discharge process, promoting electron and ion transport in the electrode, providing a buffer space and buffer time for the silicon-based anode to discharge. Therefore, it has better rate characteristics in both full cells and half cells, and has the potential and advantages for applications such as large-scale energy storage systems and power batteries. Attached Figure Description

[0079] Figure 1 The image shows the XRD pattern of the bismuth titanate anode material obtained in Example 1.

[0080] Figure 2 This is a SEM image of the bismuth titanate anode material obtained in Example 1.

[0081] Figure 3 The charge-discharge curves of the bismuth titanate anode material obtained in Example 1 after being assembled into CR2025 coin cells are shown at 30mA / g, 60mA / g, 90mA / g, 150mA / g, 300mA / g, 600mA / g, 900mA / g, 1500mA / g, 3000mA / g, 4500mA / g, and 6000mA / g.

[0082] Figure 4 The image shows the XRD pattern of the bismuth titanate anode material obtained in Example 2.

[0083] Figure 5 This is a SEM image of the bismuth titanate anode material obtained in Example 2.

[0084] Figure 6 The image shows the XRD pattern of the bismuth titanate anode material obtained in Example 3.

[0085] Figure 7 This is a SEM image of the bismuth titanate anode material obtained in Example 3.

[0086] Figure 8 The image shows the XRD pattern of the bismuth titanate anode material obtained in Example 4.

[0087] Figure 9 This is a SEM image of the bismuth titanate anode material obtained in Example 4.

[0088] Figure 10 The charge-discharge curves of Examples 2-4 at a current of 30 mA / g are shown.

[0089] Figure 11 The charge-discharge curves of Examples 5 and 6 at a current of 180 mA / g are shown.

[0090] Figure 12 The charge-discharge curves of Example 6 and Comparative Example 1 were measured at a discharge current of 180 mA / g and a charging current of 1800 mA / g.

[0091] Figure 13 The charge-discharge curves of Example 6 and Comparative Example 1 were measured at a discharge current of 180 mA / g and a charging current of 3600 mA / g.

[0092] Figure 14 The charge-discharge curves of Example 6 and Comparative Example 1 at a current of 180 mA / g are shown.

[0093] Figure 15 The charge-discharge curves for Example 7 were measured at rates of 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C.

[0094] Figure 16 The above are charge-discharge curves of Comparative Example 2 measured at 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C rates. Detailed Implementation

[0095] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0096] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0097] In the following description, FEC stands for fluoroethylene carbonate, and EMC stands for methyl ethyl carbonate. The silicon carbide powder is spherical silicon carbide powder with batch number SS02 from Shanghai Shanshan Technology Co., Ltd.

[0098] Example 1:

[0099] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0100] Specifically, the component shown in general formula (I) is used as the negative electrode material for lithium batteries. The component shown in general formula (I) is prepared by the sol-gel method: 0.4851 g of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.2842 g of titanium isopropoxide Ti(OC3H7)4 are weighed and dissolved in 50 mL of isopropanol. After stirring at 600 rpm for 4 hours, a sol is obtained. The obtained sol is then aged at 60 °C for 12 hours. After aging, 100 mL of deionized water is added each time, and the aqueous phase is removed after standing. This process is repeated 3 times to obtain a gel. The obtained gel is baked at 120 °C for 12 hours and then calcined at 1100 °C (heating rate of about 5 °C / min) for 6 hours to obtain the bismuth titanate negative electrode material (i.e., the component shown in general formula (I)). The XRD pattern of the obtained bismuth titanate negative electrode material is shown below. Figure 1 (As can be seen from the figure, the obtained bismuth titanate material has strong crystallinity); SEM images are shown below. Figure 2 ,Depend on Figure 2 It can be seen that the particle size of the bismuth titanate anode material obtained in this example is approximately 500 nm-1 μm.

[0101] The obtained bismuth titanate anode material, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 90:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for baking for 12 hours. The resulting electrode was then cut into circular electrodes with a diameter of 10 mm. These electrodes were then combined with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L). LiPF6 was dissolved in a mixed solution of FEC / EMC (where FEC and EMC were configured at a volume ratio of 1:3) and assembled into CR2025 coin cells. The charge-discharge curves measured at currents of 30 mA / g, 60 mA / g, 90 mA / g, 150 mA / g, 300 mA / g, 600 mA / g, 900 mA / g, 1500 mA / g, 3000 mA / g, 4500 mA / g, and 6000 mA / g are shown below. Figure 3 The test results show that the obtained bismuth titanate anode material (i.e., the component shown in general formula (Ⅰ)) has good rate performance in lithium batteries, and still has a specific capacity of more than 120 mAh / g at a current of 6000 mA / g.

[0102] Example 2:

[0103] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0104] Specifically, the component shown in general formula (I) is used as the negative electrode material for lithium batteries. The component shown in general formula (I) is prepared by solid-state sintering: 2.3298g of Bi2O3 and 0.7987g of TiO2 are weighed, uniformly mixed, and calcined at 1100℃ (heating rate of about 5℃ / min) for 2 hours to obtain bismuth titanate negative electrode material (i.e., the component shown in general formula (I)). The XRD pattern of the obtained bismuth titanate negative electrode material is as follows. Figure 4 (The XRD peak positions and intensities are similar to those in Example 1, indicating that the obtained material structure is the same.) SEM images are shown below. Figure 5 (The resulting material particles are larger than those in Example 1, with a particle size of approximately 5-10 μm).

[0105] The obtained bismuth titanate anode material, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 90:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for 12 hours. The resulting electrode sheet was then cut into circular sheets with a diameter of 10 mm. These sheets were then assembled with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L LiPF6 dissolved in a mixed solution of FEC / EMC, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 30 mA / g as shown below. Figure 10 .

[0106] Example 3:

[0107] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0108] Specifically, the component shown in general formula (I) is used as the negative electrode material for lithium batteries. The component shown in general formula (I) is prepared by solid-state sintering: 2.3298g of Bi2O3 and 0.7987g of TiO2 are weighed, uniformly mixed, and calcined at 1100℃ (heating rate of about 5℃ / min) for 6 hours to obtain bismuth titanate negative electrode material (i.e., the component shown in general formula (I)). The XRD pattern of the obtained bismuth titanate negative electrode material is as follows. Figure 6 (The XRD peak positions and intensities are similar to those in Example 1, indicating that the obtained material structure is the same.) SEM images are shown below. Figure 7 (The resulting material particles are larger than those in Example 1, with a particle size of approximately 5-10 μm).

[0109] The obtained bismuth titanate anode material, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 90:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for 12 hours. The resulting electrode sheet was then cut into circular sheets with a diameter of 10 mm. These sheets were then assembled with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L LiPF6 dissolved in a mixed solution of FEC / EMC, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 30 mA / g as shown below. Figure 10 .

[0110] Example 4:

[0111] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0112] Specifically, the component shown in general formula (I) is used as the negative electrode material for lithium batteries. The component shown in general formula (I) is prepared by solid-state sintering: 2.3298g of Bi2O3 and 0.7987g of TiO2 are weighed, uniformly mixed, and calcined at 1100℃ (heating rate of about 5℃ / min) for 12 hours to obtain bismuth titanate negative electrode material (i.e., the component shown in general formula (I)). The XRD pattern of the obtained bismuth titanate negative electrode material is as follows. Figure 8 (The XRD peak positions and intensities are similar to those in Example 1, indicating that the obtained material structure is the same.) SEM images are shown below. Figure 9 (The resulting material particles are larger than those in Example 1, with a particle size of approximately 5-10 μm).

[0113] The obtained bismuth titanate anode material, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 90:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for 12 hours. The resulting electrode sheet was then cut into circular sheets with a diameter of 10 mm. These sheets were then assembled with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L LiPF6 dissolved in a mixed solution of FEC / EMC, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 30 mA / g as shown below. Figure 10 .

[0114] Example 5:

[0115] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0116] Specifically, the negative electrode material comprises the bismuth titanate negative electrode material obtained in Example 1, silicon carbide powder, conductive agent (Super P) and binder (polyacrylic acid, PAA), mixed in a ratio of 10:80:5:5.

[0117] The bismuth titanate anode material obtained in Example 1, silicon carbon powder, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 10:80:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60°C forced-air oven, the mixture was transferred to an 80°C vacuum oven for baking for 12 hours. The resulting electrode sheet was then cut into circular electrodes with a diameter of 10 mm. These electrodes were then assembled with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L LiPF6 dissolved in a FEC / EMC mixed solution, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 180 mA / g as shown below. Figure 11 .

[0118] Example 6:

[0119] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0120] Specifically, the negative electrode material comprises the bismuth titanate negative electrode material obtained in Example 1, silicon carbide powder, conductive agent (Super P) and binder (polyacrylic acid, PAA), mixed in a ratio of 5:85:5:5.

[0121] The bismuth titanate anode material obtained in Example 1, silicon carbon powder, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 5:85:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60°C forced-air oven, the mixture was transferred to an 80°C vacuum oven for baking for 12 hours. The resulting electrode sheet was then cut into circular electrodes with a diameter of 10 mm. These electrodes were then assembled with a 0.65 mm lithium metal sheet, a 16 μm polypropylene separator, and an electrolyte (1.0 mol / L LiPF6 dissolved in a FEC / EMC mixed solution, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 180 mA / g as shown below. Figure 11 The charge-discharge curves measured at a discharge current of 180 mA / g and a charging current of 1800 mA / g are as follows: Figure 12 The charge-discharge curves measured at a discharge current of 180 mA / g and a charging current of 3600 mA / g are as follows: Figure 13 .

[0122] Depend on Figure 11It can be seen that in Examples 5 and 6, the addition of bismuth titanate anode material has a relatively small negative impact on the specific capacity of the overall electrode. However, the more bismuth titanate is added, the more obvious the plateau at 0.8V becomes, which helps to improve rate performance and cycle performance.

[0123] Comparative Example 1:

[0124] The process is basically the same as in Example 6, except that the bismuth titanate anode material obtained in Example 1 is not added to the anode material, and it is replaced with silicon carbon powder; that is, the anode material in this example contains silicon carbon powder, conductive agent (Super P) and binder (polyacrylic acid, PAA), mixed in a ratio of 90:5:5.

[0125] Specifically, silicon carbon powder, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 90:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for baking for 12 hours. The resulting electrode was then cut into 10mm diameter circular electrodes and assembled with a 0.65mm lithium metal sheet, a 16μm polypropylene separator, and an electrolyte (1.0mol / L LiPF6 dissolved in a FEC / EMC mixed solution, wherein FEC and EMC were prepared in a 1:3 volume ratio) to form a CR2025 coin cell. The charge-discharge curves were measured at a current of 180mA / g as shown below. Figure 14 The charge-discharge curves measured at a discharge current of 180 mA / g and a charging current of 1800 mA / g are as follows: Figure 12 The charge-discharge curves measured at a discharge current of 180 mA / g and a charging current of 3600 mA / g are as follows: Figure 13 .

[0126] Depend on Figure 12 It can be seen that Example 6 has a smaller polarization potential (corresponding to a smaller voltage difference between the charge and discharge curves) compared to Comparative Example 1, which is beneficial for improving energy efficiency, extending cycle life (reducing active material loss and side reactions), improving rate performance (supporting higher current charge and discharge), and enhancing safety (reducing the risk of thermal runaway).

[0127] Depend on Figure 13 It can be seen that Example 6 has a smaller polarization potential (corresponding to a smaller voltage difference between the charge and discharge curves) compared to Comparative Example 1, and Comparative Example 1 showed voltage fluctuations under a larger current, indicating that the bismuth titanate anode in Example 6 has the effect of stabilizing silicon-carbon materials.

[0128] Depend on Figure 13 and Figure 14 It is known that the addition of an appropriate amount of bismuth titanate material will hardly have a negative impact on the specific capacity of silicon-based anode materials. In particular, it can improve the voltage stability under larger currents, which has obvious positive benefits.

[0129] Example 7:

[0130] This example provides a negative electrode material for lithium batteries, its preparation method, and its application in lithium batteries.

[0131] Specifically, the negative electrode material comprises the bismuth titanate negative electrode material obtained in Example 1, silicon carbide powder, conductive agent (Super P) and binder (polyacrylic acid, PAA), mixed in a ratio of 5:85:5:5.

[0132] The bismuth titanate anode material obtained in Example 1, silicon carbon powder, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a ratio of 5:85:5:5 and uniformly coated onto copper foil. After preliminary drying in a 60°C forced-air oven, the mixture was transferred to an 80°C vacuum oven for baking for 12 hours. The resulting electrode sheet was then cut into 36mm×56mm pieces and assembled into a soft-pack battery with a matched 36mm×56mm cathode (mainly composed of commercially available polycrystalline NCM material), a 16μm polypropylene separator, and an electrolyte (1.0mol / L LiPF6 dissolved in a FEC / EMC mixed solution, wherein FEC and EMC are configured in a 1:3 volume ratio). Charge-discharge curves were measured at 0.1C (fully charged or discharged in 10 hours), 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C rates as shown below. Figure 15 .

[0133] Depend on Figure 15 It can be seen that the charge-discharge curves measured at 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C rates showed discharge specific capacities of 213.32mAh / g, 209.73mAh / g, 206.86mAh / g, 202.78mAh / g, 195.57mAh / g, 179.00mAh / g, and 119.20mAh / g, respectively.

[0134] Comparative Example 2:

[0135] The process is basically the same as in Example 7, except that the bismuth titanate anode material obtained in Example 1 is not added to the anode material, and it is replaced with silicon carbon powder; that is, the anode material in this example contains silicon carbon powder, conductive agent (Super P) and binder (polyacrylic acid, PAA), mixed in a ratio of 90:5:5.

[0136] Specifically, silicon carbon powder, conductive agent (Super P), and binder (polyacrylic acid, PAA) were mixed in a 90:5:5 ratio and uniformly coated onto copper foil. After preliminary drying in a 60℃ forced-air oven, the mixture was transferred to an 80℃ vacuum oven for 12 hours. The resulting electrode was then cut into 36mm×56mm pieces and assembled into a soft-pack battery with a matched 36mm×56mm positive electrode (mainly composed of commercially available polycrystalline NCM material), a 16μm polypropylene separator, and an electrolyte (1.0mol / L LiPF6 dissolved in a FEC / EMC mixed solution, where FEC and EMC were configured in a 1:3 volume ratio). Charge-discharge curves were measured at 0.1C (fully charged or discharged in 10 hours), 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C rates, as shown below. Figure 16 .

[0137] Depend on Figure 16 It can be seen that the charge-discharge curves measured at 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C rates showed discharge specific capacities of 200.16mAh / g, 195.67mAh / g, 191.25mAh / g, 182.07mAh / g, 149.51mAh / g, 29.63mAh / g, and 10.05mAh / g, respectively.

[0138] contrast Figure 15 and Figure 16 This fully demonstrates that bismuth titanate, when applied to silicon-based anode materials, can improve the rate performance of full-cell batteries.

[0139] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0140] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A negative electrode material for lithium batteries, characterized in that, The negative electrode material comprises a component represented by general formula (I); Bi x Ti y O z (I), wherein x, y are greater than 0, respectively, and x, y, z have values such that formula (I) satisfies valence state balance.

2. The negative electrode material for lithium batteries according to claim 1, characterized in that, 3x+4y=2z.

3. The anode material for lithium batteries according to claim 1, characterized in that, The negative electrode material comprises one, a combination of two, three or more selected from Bi2Ti2O7, Bi4Ti3O 12 , Bi2Ti4O 11 , Bi 12 TiO 20 , Bi 20 TiO 32 , Bi6Ti2O 13 , Bi6Ti4O 17 , Bi2Ti6O 15 , Bi4Ti2O 10 .

4. The anode material for lithium batteries according to claim 1, characterized in that, The component represented by general formula (I) is prepared by the following method: The oxide of bismuth and the oxide of titanium are mixed in stoichiometric ratio and uniformly, and are optionally ground to obtain a precursor; or a bismuth salt and a titanium alkylate are weighed in stoichiometric ratio and dispersed in an alkyl alcohol to prepare a sol, and then the sol is converted into a gel, and the gel is optionally dried to obtain the precursor; The precursor is subjected to a calcination treatment.

5. The anode material for lithium batteries according to claim 4, characterized in that, The oxide of bismuth comprises bismuth trioxide; and / or, the oxide of titanium comprises titanium dioxide; and / or, the bismuth salt comprises a combination of one, two or three of bismuth nitrate, bismuth sulfate and bismuth phosphate; and / or, the titanium alkoxide comprises C 2-6 The titanium alkoxide further comprises C 2-6 The titanium alkoxide comprises a combination of one, two, three or more of titanium ethoxide, titanium isopropoxide, titanium n-propoxide, and tetrabutyl titanate; and / or, the alkyl alcohol comprises a combination of one, two, three or more of ethanol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol; and / or, the gel is obtained by aging the sol followed by adding water and standing to separate layers; and / or, the calcination process is controlled to be performed at 1000-1200°C; and / or, the calcination process is controlled to have a temperature increasing rate of 1-15°C / min, further 2-8°C / min; and / or, the calcination process is controlled to have a time of 2-12 hours.

6. A negative electrode material for lithium batteries, characterized in that, The negative electrode material comprises a component represented by general formula (II); Li a Bi b Ti c O z (II), wherein a, b, c are greater than 0, respectively, and a, b, c, z have values such that formula (II) satisfies valence state balance.

7. The anode material for lithium batteries according to claim 6, characterized in that, a+mb+nc=2z, m is the valence of Bi and comprises 0, +1, +2, +3, +4 or +5, and n is the valence of Ti and comprises 0, +1, +2, +3 or +4.

8. A method of producing the negative electrode material for lithium batteries as claimed in claim 6 or 7, characterized by, The preparation method comprises: An electrode made of a material comprising the component represented by general formula (I) is used as a working electrode; The working electrode is involved in the charging process or the discharging process of a battery to generate a component represented by general formula (II); The battery comprises a lithium-containing electrode; Bi x Ti y O z (I), wherein x, y are greater than 0, respectively, and x, y, z have values such that formula (I) satisfies valence state balance.

9. The method of claim 8, wherein the lithium battery anode material is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. When the battery is a half battery, the working electrode is involved in the discharging process of the battery; When the battery is a full battery, the working electrode is involved in the charging process of the battery; And / or, the preparation method further comprises: after charging or discharging, the working electrode is separated from the battery to obtain the negative electrode material for lithium batteries.

10. Use of bismuth titanate in the preparation of a negative electrode material for lithium batteries, the chemical formula of the bismuth titanate being: Bi x Ti y O z (I), wherein x and y are greater than 0, and the values of x, y and z make formula (I) satisfy the valence state balance.

11. A silicon-based composite material, characterized by, The silicon-based composite material comprises a silicon-based material and a component represented by general formula (II); Li a Bi b Ti c O z (II), wherein a, b, and c are each greater than 0, and the values of a, b, c, and z satisfy the valence state balance of formula (II).

12. The silicon-based composite material of claim 11, wherein, In the silicon-based composite material, the silicon-based material accounts for more than 50% in terms of mass percentage; and / or, the silicon-based material comprises one, a combination of two or three of elemental silicon, silicon-oxygen material and silicon-carbon material.

13. The silicon-based composite material of claim 11, wherein, The mass ratio of the silicon-based material to the component represented by general formula (II) is 0.001-1:1, or 0.01-0.8, or 0.02-0.75, or 0.03-0.7, or 0.04-0.65, or 0.05-0.60, or 0.06-0.55, or 0.07-0.50, or 0.08-0.45, or 0.09-0.40, or 0.1-0.35, or 0.11-0.

30.

14. The silicon-based composite material of claim 11, wherein, The silicon-based composite material is prepared by the following method: An electrode made of a material comprising a silicon-based material and a component represented by general formula (I) is used as a working electrode; The working electrode is involved in the charging process or the discharging process of a battery to generate a silicon-based composite material comprising a silicon-based material and a component represented by general formula (II); The battery comprises a lithium-containing electrode; Further, it further comprises: after charging or discharging, the working electrode is separated from the battery to obtain a silicon-based composite material.

15. A lithium battery negative electrode sheet, characterized by, The material of the lithium battery negative electrode sheet comprises the negative electrode material for lithium batteries according to any one of claims 1-7, or is prepared by the preparation method according to any one of claims 8-9, or comprises the silicon-based composite material according to any one of claims 11-15.

16. A lithium battery, characterized by The lithium battery comprises the lithium battery negative electrode sheet according to claim 15.

17. A silicon-based composite material, characterized by, The silicon-based composite material comprises a silicon-based material and bismuth titanate; the chemical formula of the bismuth titanate is: Bi x Ti y O z (I), wherein x and y are greater than 0, respectively, and the values of x, y and z make formula (I) satisfy the valence state balance.

18. The silicon-based composite material of claim 17, wherein, The silicon-based material accounts for 50% or more in the silicon-based composite in terms of mass percentage; and / or the silicon-based material comprises one, a combination of two, or a combination of three of elemental silicon, a silicon-oxygen material, and a silicon-carbon material.

19. The silicon-based composite material of claim 17, wherein, The mass ratio of the silicon-based material to the bismuth titanate is 0.001-1:1, or 0.01-0.8, or 0.02-0.75, or 0.03-0.7, or 0.04-0.65, or 0.05-0.60, or 0.06-0.55, or 0.07-0.50, or 0.08-0.45, or 0.09-0.40, or 0.1-0.35, or 0.11-0.

30.

20. The silicon-based composite material of claim 17, wherein, The silicon-based composite is prepared by mixing a silicon-based material and bismuth titanate.

21. A negative electrode material, characterized by, The negative electrode material comprises the silicon-based composite according to any one of claims 17-20.

22. A negative electrode sheet characterized by comprising: The negative electrode plate comprises the negative electrode material according to claim 21.

23. A battery, characterized by The battery comprises the negative electrode plate according to claim 22.

24. The battery of claim 23, wherein, The battery is a lithium battery or a sodium battery.

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