A polyanionic silicate compound, a positive electrode material based on the compound, and a preparation method and application thereof

Abstract

The embodiment of the present application discloses a kind of polyanionic silicate compounds, based on this compound positive electrode material and preparation method and application, it has general formula Na x Ni y (SiO4) z Structure, wherein 0≤x≤2, 0≤y≤1, 0≤z≤1, also discloses a kind of positive electrode material including above-mentioned polyanionic silicate compound and carbon-based material.The compound is obtained by mixing sintering sodium source, nickel source and silicon source, and the positive electrode material is obtained by mixing and sintering sodium source, nickel source, silicon source and carbon-based material precursor.The compound Na x Ni y (SiO4) z Provided by the present application, only contains sodium, nickel metal element, compared with general sodium manganese silicate material, has higher specific capacity play.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a polyanionic silicate compound, a cathode material based on this compound, its preparation method, and its application. Background Technology

[0002] Compared to lithium-ion batteries, sodium-ion batteries have a larger radius and atomic mass, making ion diffusion more difficult and resulting in inferior theoretical capacity and reaction kinetics. Specifically, sodium-ion batteries experience greater difficulty and slower electrode insertion / extraction, and are more prone to morphological damage to the cathode material, thus significantly impacting the specific capacity, lifespan, and safety performance of sodium-ion batteries.

[0003] Secondary ion batteries, as one of many energy storage methods, have advantages such as good cycle performance, long service life, high safety, and ease of use, and have been widely used in portable electronic devices, electric vehicles, and other fields. However, with the scarcity of resources such as lithium and cobalt and the rapid development of renewable clean energy, there is an urgent need to develop new, efficient, low-cost, and environmentally friendly secondary ion battery technologies. However, their development is limited by the lack of excellent cathode materials. Compared to other secondary ion battery cathode materials, sodium-ion-based polyanionic compounds have advantages such as a rich variety of types, diverse structures, adjustable operating voltage, and good cycle stability, making them ideal cathode materials for developing low-cost and environmentally friendly secondary ion batteries. Based on the type of polyanion, the corresponding cathode material systems are divided into phosphate, sulfate, other single polyanion, and mixed polyanion types. For example, various cathode materials represented by compounds such as NaFePO4, Na3V2(PO4)3, NaVPO4F, Na2Fe2(SO4)3, and NaFeSO4F have relatively low specific capacities (specific capacity, even with the addition of conductive agents) due to their crystal structure, electrochemical performance, and energy storage mechanism. They are generally below 130 mAh / g. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a polyanionic silicate compound, a cathode material based on this compound, its preparation method, and its application. The cathode material provided by this invention has a specific capacity of over 150 mAh / g and, while ensuring high specific capacity, also exhibits high first-pass efficiency.

[0005] To achieve the above technical objectives, the technical solution adopted by this invention is as follows:

[0006] The first aspect of the present invention aims to provide a polyanionic silicate compound having the general formula Na x Ni y (SiO4) z The structure is , where 0 < x ≤ 2, 0 < y ≤ 1, and 0 < z ≤ 1.

[0007] Furthermore, as a preferred embodiment, x / y ≥ 2:1, x + 2y = 4z; as an even more preferred embodiment, x:y = 2:1.

[0008] The second aspect of this invention aims to provide a cathode material based on a polyanionic silicate compound, which is a composite of the aforementioned polyanionic silicate compound and a carbon-based material. Based on the total weight of the cathode material, Na... x Ni y (SiO4) z The polyanionic compound comprises 90%-99.9% by weight, preferably 94%-98%. The proportion of the carbon-based material is 0.1%-10%, which can be exemplarily a value between one or any two of the following ranges: 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0009] Furthermore, the carbon-based material is obtained by carbonizing a carbon-based material precursor, which is selected from at least one of amorphous carbon, Superp, multi-arm carbon nanotubes, single-arm carbon nanotubes, VGCF, graphene, graphene oxide, reduced graphene oxide, Ketjen black, acetylene black, C65, conductive graphite, and KS6.

[0010] Furthermore, the amorphous carbon is carbonized from a carbon source selected from at least one of citric acid, glucose, cellulose, pitch, methane, ethylene, propylene, and acetylene.

[0011] Furthermore, the particle size of the carbon-based material is 1 nm-10 μm; it coats the surface of the polyanionic silicate compound and / or is doped inside the polyanionic silicate compound; when it forms a coating layer on the surface of the polyanionic silicate compound, the thickness of the coating layer is 1 nm-5 μm, which can be exemplarily a value between one or any two of the following: 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm.

[0012] The technical objective of the third aspect of this invention is to provide a method for preparing the polyanionic silicate compound, which involves sintering a mixture of sodium source, nickel source and silicon source.

[0013] Furthermore, the sodium source is selected from at least one of sodium carbonate, sodium oxide, sodium hydroxide, sodium acetate, and sodium sulfate; the nickel source is selected from at least one of nickel carbonate, nickel oxide, nickel hydroxide, nickel acetate, and nickel sulfate; the silicon source is selected from at least one of silicon dioxide, orthosilicic acid, silicic acid, and organosilicon esters; wherein the organosilicon ester is a compound having the structure shown in formula (RCOO)4Si, where R is a C1-C11 alkyl or substituted alkyl group; the silicon dioxide is preferably fumed silica.

[0014] Furthermore, the preparation method also includes the process of purifying, refining and mixing the sodium source, nickel source and silicon source under an inert atmosphere, wherein the purification, refining and mixing steps are not sequential.

[0015] Furthermore, the sintering temperature is 600-950℃, preferably 750-900℃, more preferably 800-850℃, and is carried out under an inert atmosphere.

[0016] The technical objective of the fourth aspect of this invention is to provide a method for preparing the cathode material based on the polyanionic silicate compound, comprising the steps of mixing and sintering a sodium source, a nickel source, a silicon source and a carbon-based material precursor.

[0017] Furthermore, the sodium source is selected from at least one of sodium carbonate, sodium oxide, sodium hydroxide, sodium acetate, and sodium sulfate; the nickel source is selected from at least one of nickel carbonate, nickel oxide, nickel hydroxide, nickel acetate, and nickel sulfate; the silicon source is selected from at least one of silicon dioxide, orthosilicic acid, silicic acid, and organosilicon esters; wherein the organosilicon ester is a compound having the structure shown in formula (RCOO)4Si, where R is a C1-C11 alkyl or substituted alkyl group; the silicon dioxide is preferably fumed silica.

[0018] Furthermore, the carbon-based material precursor is selected from one of the following: amorphous carbon, Superp, multi-arm sodium nanotubes, single-arm sodium nanotubes, VGCF, graphene, graphene oxide, reduced graphene oxide, Ketjen black, acetylene black, C65, conductive graphite, KS6, etc. The amorphous carbon is formed by carbonization of a carbon source, and the carbon source is selected from at least one of citric acid, glucose, cellulose, pitch, methane, ethylene, propylene, and acetylene.

[0019] Furthermore, the amount of the carbon-based material precursor added is 0.1%-10% of the total weight of the sodium source, nickel source and silicon source, preferably 2%-8%.

[0020] Furthermore, the carbon-based material precursor is preferably carbon nanotubes, Superp and a combination of carbon nanotubes, methane, ethylene, propylene and acetylene, wherein the methane, ethylene, propylene and acetylene are composited with the polyanionic silicate compound by vapor deposition.

[0021] Furthermore, the preparation method also includes purifying, refining, and mixing the sodium, nickel, and silicon sources under an inert atmosphere. The purification, refining, and mixing steps are not sequential. The refining process involves pulverizing the sodium, nickel, and silicon sources to a particle size D50 of 0.02-20 μm. The pulverizing method is selected from ball milling, sand milling, and air jet milling.

[0022] Furthermore, the sintering temperature is 600-950℃, preferably 750-900℃, more preferably 800-850℃, and is carried out under an inert atmosphere.

[0023] Furthermore, the inert atmosphere described in the above technical solutions is selected from at least one of nitrogen, argon, and helium.

[0024] The technical objective of the fifth aspect of this invention is to provide the application of the aforementioned positive electrode material based on polyanionic silicate compound as a positive electrode material for sodium-ion batteries.

[0025] The sodium-ion battery is a solid-state sodium-ion battery.

[0026] The technical solution of this invention has the following advantages:

[0027] (1) The compound Na provided by this invention x Ni y (SiO4) z It contains only sodium and nickel metal elements, and has a higher specific capacity compared with ordinary sodium manganese silicate materials.

[0028] (2) The sodium-ion cathode material of the present invention solves the problem of poor electronic conductivity of polyanions by doping or coating with conductive materials, so that it can be used in sodium-ion batteries and as a power supply for electrical devices, with good battery utilization and cycle life, etc.

[0029] (3) The method for preparing sodium ion cathode material of the present invention is simple to operate, mild under mild conditions, and easy to prepare on a large scale.

[0030] The present invention will be further described in detail below with reference to specific embodiments: Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope image of the cathode material prepared in Example 11. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0035] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0036] S2, the purified materials are refined separately under an inert atmosphere;

[0037] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 600°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0038] Example 2

[0039] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0040] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0041] S2, the purified materials are refined separately under an inert atmosphere;

[0042] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 650°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0043] Example 3

[0044] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0045] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0046] S2, the purified materials are refined separately under an inert atmosphere;

[0047] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 700°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0048] Example 4

[0049] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0050] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0051] S2, the purified materials are refined separately under an inert atmosphere;

[0052] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 750°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0053] Example 5

[0054] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0055] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0056] S2, the purified materials are refined separately under an inert atmosphere;

[0057] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 800°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0058] Example 6

[0059] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0060] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0061] S2, the purified materials are refined separately under an inert atmosphere;

[0062] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 850°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0063] Example 7

[0064] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0065] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0066] S2, the purified materials are refined separately under an inert atmosphere;

[0067] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with carbon nanotubes. The amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. The mixture is then sintered at 900°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0068] Example 8

[0069] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0070] S1, purifying sodium acetate, nickel acetate and fumed silica;

[0071] S2, the purified materials are refined separately under an inert atmosphere;

[0072] S3, the refined sodium acetate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with SP and carbon nanotubes. The amount of SP added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica, and the amount of carbon nanotubes added is 3% of the total weight of sodium acetate, nickel acetate and fumed silica. Then the above mixture is sintered at 800°C under an inert atmosphere to obtain the cathode material based on polyanionic silicate compound.

[0073] Example 9

[0074] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0075] S1, purifying sodium carbonate, nickel acetate and fumed silica;

[0076] S2, the purified materials are refined separately under an inert atmosphere;

[0077] S3, the refined sodium carbonate, nickel acetate and fumed silica are mixed in a molar ratio of 2:1:1, and then mixed with SP and carbon nanotubes. The amount of SP added is 3% of the total weight of sodium carbonate, nickel acetate and fumed silica, and the amount of carbon nanotubes added is 3% of the total weight of sodium carbonate, nickel acetate and fumed silica. Then the above mixture is sintered at 800°C under an inert atmosphere to obtain the cathode material based on polyanionic silicate compound.

[0078] Example 10

[0079] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0080] S1, purifying sodium carbonate, nickel carbonate and fumed silica;

[0081] S2, the purified materials are refined separately under an inert atmosphere;

[0082] S3, the refined sodium carbonate, nickel carbonate and fumed silica are mixed in a molar ratio of 1:1:1, and then mixed with SP and carbon nanotubes. The amount of SP added is 3% of the total weight of sodium carbonate, nickel carbonate and fumed silica, and the amount of carbon nanotubes added is 3% of the total weight of sodium carbonate, nickel carbonate and fumed silica. Then the above mixture is sintered at 800°C under an inert atmosphere to obtain the cathode material based on polyanionic silicate compound.

[0083] Example 11

[0084] This embodiment provides a method for preparing a cathode material based on a polyanionic silicate compound, comprising the following steps:

[0085] S1, purifying sodium carbonate, nickel acetate and fumed silica;

[0086] S2, the purified materials are refined separately under an inert atmosphere;

[0087] S3, refined sodium carbonate, nickel acetate and fumed silica are mixed in a molar ratio of 1:1:1, and then coated on the mixture using a vapor deposition method with methane as the carbon source, and sintered at 800°C under an inert atmosphere to obtain the cathode material based on polyanionic silicate compound.

[0088] The scanning electron microscope image of the cathode material prepared in Example 11 is shown below. Figure 1 , Figure 1It can be seen from the data that the prepared sample consists of single-crystal particles with a particle size of less than 4 μm.

[0089] Example 12

[0090] This example prepared a polyanionic silicate compound: the basic proportions and reaction conditions were the same as in Example 10, but SP and carbon nanotubes were not added.

[0091] S1, purifying sodium carbonate, nickel carbonate and fumed silica;

[0092] S2, the purified materials are refined separately under an inert atmosphere;

[0093] S3, the refined sodium carbonate, nickel carbonate and fumed silica are mixed in a molar ratio of 1:1:1, and then the mixture is sintered at 800°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0094] Comparative Example 1

[0095] Sodium manganese silicate compound was prepared under the same conditions as in Example 12, except that manganese carbonate was used instead of nickel carbonate:

[0096] S1, purifying sodium carbonate, manganese carbonate and fumed silica;

[0097] S2, the purified materials are refined separately under an inert atmosphere;

[0098] S3, the refined sodium carbonate, manganese carbonate and fumed silica are mixed in a molar ratio of 1:1:1, and then the mixture is sintered at 800°C under an inert atmosphere to obtain the cathode material based on the polyanionic silicate compound.

[0099] Comparative Example 2

[0100] For comparison, a cathode material was prepared using the sodium manganese silicate compound of Comparative Example 1 combined with the optimized conductive agent of the present invention, i.e., the cathode material was prepared under the same conditions as in Example 10, except that manganese carbonate was used instead of nickel carbonate:

[0101] S1, purifying sodium carbonate, manganese carbonate and fumed silica;

[0102] S2, the purified materials are refined separately under an inert atmosphere;

[0103] S3, refined sodium carbonate, manganese carbonate and fumed silica are mixed in a molar ratio of 1:1:1, and then mixed with SP and carbon nanotubes. The amount of SP added is 3% of the total weight of sodium carbonate, manganese carbonate and fumed silica, and the amount of carbon nanotubes added is 3% of the total weight of sodium carbonate, manganese carbonate and fumed silica. Then the above mixture is sintered at 800°C under an inert atmosphere to obtain a positive electrode material of sodium manganese silicate and carbon-based composite.

[0104] The positive electrode materials of Examples 1-12 and Comparative Examples 1-2 were assembled into sodium-ion 2016 coin cells, and the performance of the sodium-ion cells could be tested. The electrolyte was 1M NaPF6, EC / PC 5:5, 3% VC + 1% NaDFOB, and the negative electrode was a sodium negative electrode.

[0105] The specific capacity performance test method for sodium-ion batteries is as follows: At room temperature, the battery is left to stand for 5 minutes, then charged at a constant current rate of 0.1C to 3.95V, followed by constant voltage charging until the current is less than or equal to 0.05C. After that, it is left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 1.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is recorded as the discharge capacity of the sodium-ion secondary battery in the first cycle. The specific capacity performance and initial efficiency results of the battery are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] As shown in Table 1, the cathode of this invention exhibits a high specific capacity when used in batteries, reaching a maximum of 167.2 mAh / g. Examples 1-7 demonstrate that using water-soluble sodium acetate as the sodium source and employing different sintering temperatures results in varying material performance, with 800℃ being the optimal sintering temperature and exhibiting the best specific capacity. This is because sintering below 800℃, especially below 750℃, degrades the structural stability of the material, leading to poor performance. Conversely, sintering temperatures above 900℃, especially above 850℃, cause side reactions in the metal oxides, resulting in a slight decrease in performance.

[0110] As can be seen from Examples 8-10, since carbon nanotubes alone have linear contacts, using SP+carbon nanotubes can achieve a point and line conductive network, thus improving its specific capacity. The nickel sodium silicate composite SP+carbon nanotube conductive agent combination of the present invention has better specific capacity performance. The present invention optimizes the conductive agent combination and doping amount with relatively better performance in combination with Na2NiSiO4.

[0111] In Examples 9-11, sodium carbonate was used as the sodium salt. In particular, Example 11 employed a different gas-phase carbon coating method, which achieved more uniform coating and further improved the electronic conductivity of the material. This resulted in Example 11 exhibiting the highest specific capacity and the best capacity retention.

[0112] As can be seen from Example 12 and Comparative Example 1, without carbon coating, the Na2NiSiO4 of Example 12 exhibits higher specific capacity and better capacity retention than the Na2MnSiO4 of Comparative Example 1.

[0113] As can be seen from Example 10 and Comparative Example 2, under the same preparation conditions, after the composite conductive agent is used, the specific capacity of Na2NiSiO4 of the present invention is increased by 4.8 percentage points compared with Na2MnSiO4, and the initial efficiency is also higher.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material based on a polyanionic silicate compound, characterized in that, The composite comprises a polyanionic silicate compound and a carbon-based material; The poly-anionic silicate compound is obtained by mixing and sintering a sodium source, a nickel source, a silicon source and a carbon-based material precursor, and the sintering temperature is 600-950°C; the poly-anionic silicate compound has a structure of general formula Na x Ni y (SiO4) z , wherein x / y≥2:1, x+2y=4z, and 0 Na x Ni y (SiO4) z The weight percentage of the polyanionic compound is 90-99.9%, and the percentage of the carbon-based material is 0.1-10%. The carbon-based material is obtained by carbonizing a carbon-based material precursor, and the carbon-based material precursor is Super p and carbon nanotube; The sodium source in the polyanionic silicate compound is selected from sodium carbonate.

2. A method for producing the positive electrode material based on the polyanion silicate compound according to claim 1, characterized by, The nickel source is selected from at least one of nickel carbonate, nickel oxide, nickel hydroxide, nickel acetate and nickel sulfate; The silicon source is selected from at least one of silicon dioxide, orthosilicic acid, silicic acid and organosilicon ester; wherein the organosilicon ester is a compound having a structure represented by formula (RCOO)4Si, wherein R is C1-C11 alkyl or substituted alkyl; The preparation method further comprises the processes of purifying, refining under inert atmosphere and mixing the sodium source, the nickel source and the silicon source, and the purifying, refining and mixing steps are not arranged in a specific order.

3. The preparation method according to claim 2, wherein: The particle size of the carbon-based material is 1 nm-10 μm; It is coated on the surface of the polyanionic silicate compound and / or doped in the polyanionic silicate compound; When the carbon-based material forms a coating layer on the surface of the polyanionic silicate compound, the thickness of the coating layer is 1 nm-5 μm.

4. Application of the polyanionic silicate compound-based positive electrode material prepared by the preparation method of claim 3 as a positive electrode material of a sodium ion battery.

Images