A sodium superion conductor positive electrode material coated with nickel boride and carbon double layer, and its preparation method and application

Abstract

The present invention relates to the field of battery material technology, and in particular to a sodium superionic conductor positive electrode material coated with a double layer of nickel boride and carbon, as well as its preparation method and application. The sodium superionic conductor material comprises a manganese-based NASICON structure core and a nickel boride / carbon double-layer coating coated on the outside of the manganese-based NASICON structure core; the chemical formula of the manganese-based NASICON structure core is Na3MnTi(PO4)3. In terms of mass percentage, the nickel boride accounts for 1% to 10% of the sodium superionic conductor material. The present invention obtains a sodium ion battery positive electrode material by coating the manganese-based NASICON structure core with a double layer of nickel boride and carbon. The positive electrode material can effectively suppress the Jan-Taylor effect and improve the conductive properties of the material. The prepared battery has excellent cycle stability and relatively good capacity, and has important application value in the field of sodium ion battery material processing.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a sodium superion conductor positive electrode material coated with a double layer of nickel boride and carbon, and a preparation method and application thereof. Background Art

[0002] In the current energy storage field, sodium-ion batteries (SIBs) have become a research hotspot due to their significant advantages in cost, widespread resource distribution, and environmental friendliness. Given the abundant reserves of sodium in the Earth's crust and its low extraction cost, SIBs are considered a promising energy storage technology, particularly for large-scale energy storage systems. Furthermore, compared to lithium-ion batteries, SIBs exhibit superior environmental compatibility in terms of material recovery and recycling.

[0003] Among the numerous sodium-ion battery cathode materials, polyanions have attracted considerable attention due to their unique structural properties and superior electrochemical performance. These materials typically exhibit excellent cycling stability. This structural characteristic of polyanion cathode materials effectively improves the cycle life of sodium-ion batteries, providing a significant impetus for advancements in sodium-ion battery technology.

[0004] Although polyanion cathode materials have shown great potential in sodium-ion battery applications, they still need to overcome challenges such as energy density and low conductivity. Therefore, continuous scientific research and technological innovation are crucial to improving the performance of these materials. Summary of the Invention

[0005] To address the challenges of the existing technology, the present invention provides a sodium superion conductor cathode material coated with a nickel boride and carbon double layer, as well as its preparation method and application. The double layer of nickel boride and carbon reduces the Jan-Teller effect of manganese, improves conductivity, and, when fabricated into a battery, exhibits excellent cycle stability and capacity.

[0006] In a first aspect, the present invention provides a sodium superionic conductor material, comprising a manganese-based NASICON structure core and a nickel boride / carbon double-layer coating coated on the manganese-based NASICON structure core;

[0007] In terms of mass percentage, the nickel boride accounts for 1% to 10% of the sodium superionic conductor material.

[0008] Nickel boride material has excellent mechanical properties and certain electrical conductivity. The present invention adopts a double-layer coating of nickel boride and carbon. On the one hand, the ratio between the elements of the main polyanion positive electrode material is retained, and the polyanion structure is not changed after coating. On the other hand, the Mn 3+The Jiang-Taylor effect ensures the structural integrity of the material, and the prepared positive electrode material has excellent cycle stability and capacity.

[0009] Furthermore, in terms of mass percentage, the nickel boride accounts for 1% to 5% of the sodium superionic conductor material.

[0010] Furthermore, the manganese-based NASICON structure core can be one or more of Na3MnTi(PO4)3, Na4MnV(PO4)3 or Na3MnPO4CO3, preferably Na3MnTi(PO4)3.

[0011] Furthermore, the mass ratio of the nickel boride to the carbon is (1-10):(10-20).

[0012] Furthermore, the particle size of the sodium superion conductor material is 0.5-3 μm.

[0013] The sodium superionic conductor material prepared by the present invention has an optimal particle size, which can significantly shorten the diffusion path of sodium ions, improve the material's rate performance, and achieve a higher specific capacity at high rates. It also has good cycling stability. Compared with larger particle sizes, it increases the contact area between the material and the electrolyte, while reducing the volume expansion of the particles during the charge and discharge process, thereby improving the material's structural stability.

[0014] In a second aspect, the present invention provides a pole piece for a sodium ion battery, which is prepared from the aforementioned sodium superion conductor material.

[0015] Furthermore, the aforementioned pole piece for sodium ion battery comprises, in parts by weight: 5 to 9 parts of the sodium superion conductor material, 1 to 3 parts of carbon nanotubes and 0.5 to 2 parts of PVDF.

[0016] In a third aspect, the present invention provides a battery prepared from the aforementioned electrode sheet for sodium ion battery.

[0017] In a fourth aspect, the present invention provides a method for preparing the aforementioned sodium superionic conductor material, comprising:

[0018] A sodium source component, a manganese source component, a titanium source component, a phosphorus source component and water are mixed, and after mixing, spray drying and calcination are performed to obtain a carbon-coated manganese-based NASICON structure core;

[0019] The carbon-coated manganese-based NASICON structure core, the nickel source component and the boron source component are mixed, mixed in an ethanol solvent environment for 2 to 6 hours, and centrifuged to dry.

[0020] Furthermore, the sodium source component includes: at least one of sodium carbonate, sodium hydroxide, sodium chloride, sodium acetate, sodium citrate or sodium bicarbonate;

[0021] The manganese source component includes: at least one of manganese nitrate, manganese chloride, manganese acetate or manganese acetylacetonate;

[0022] The titanium source component includes at least one of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate or di(2-hydroxypropionic acid) diammonium dihydroxide titanium;

[0023] The nickel source component includes: at least one of nickel chloride, nickel nitrate, nickel sulfate or nickel acetate;

[0024] The boron source component is sodium borohydride or boric acid;

[0025] The mass ratio of the carbon-coated manganese-based NASICON structure core, the nickel source component and the boron source component is 1: (0.03-0.1): (0.001-0.01).

[0026] The inlet temperature of the spray drying is 100-200°C, the air intake is 60-90%, and the feed rate is 1-5 mL / min;

[0027] The calcination temperature is 500-800° C., and the calcination time is 3-10 hours.

[0028] Furthermore, the calcination temperature is 600-800° C. and the calcination time is 4-7 hours.

[0029] Furthermore, the calcination temperature is independently selected from any value of 600°C, 650°C, 700°C, 7500°C, 800°C or a range between any two of the above values.

[0030] Furthermore, the calcination time is independently selected from any value among 4h, 5h, 6h, 7h or a range between any two of the above.

[0031] Preferably, after calcination at 650°C for 4 hours, the performance of the coated Na3MnTi(PO4)3 positive electrode material reaches the optimal performance.

[0032] In a fifth aspect, the present invention provides the use of the aforementioned sodium superionic conductor material in the preparation of sodium ion batteries.

[0033] Furthermore, the sodium superion conductor material is ground for more than 30 minutes according to the ratio of the aforementioned sodium ion battery electrode, ground for more than 3 hours in an NMP solvent environment, and then coated on aluminum foil and vacuum dried to obtain a sodium ion battery electrode.

[0034] Furthermore, the prepared sodium ion battery electrode sheet is used as the positive electrode sheet and assembled in the order of positive electrode shell, positive electrode sheet, diaphragm, sodium sheet, gasket, spring sheet and negative electrode shell, and the sodium ion battery can be prepared by adding electrolyte.

[0035] The electrolyte includes: 0.5-2M NaClO4 EC:PC solution and 3-10% fluoroethylene carbonate (FEC).

[0036] The present invention has the following beneficial effects:

[0037] The present invention coats a double-layer coating of nickel boride and carbon on the outer surface of the manganese-based NASICON structure core. Compared with existing manganese-based NASICON materials, it exhibits better capacity and cycle stability during electrochemical cycling, promoting the application of NASICON materials in sodium ion batteries.

[0038] The preparation process of the sodium superionic conductor material provided by the present invention is simple and environmentally friendly, and can be applied to the production process of large-scale products. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 For each sample in Example 1 of this application (NMTP, NMTP / C and NMTP / C@Ni x B) XRD pattern, where NMTP is Na3MnTi(PO4)3, NMTP / C is Na3MnTi(PO4)3 / C, and NMTP / C@Ni x B is Na3MnTi(PO4)3 / C@Ni x B.

[0041] Figure 2 For each sample in Example 1 of this application (NMTP, NMTP / C and NMTP / C@Ni x B) SEM image.

[0042] Figure 3 For each sample in Example 1 of this application (NMTP, NMTP / C and NMTP / C@Ni x B) TEM image.

[0043] Figure 4 NMTP / C@Ni in Example 1 of this application x EDS diagram of B.

[0044] Figure 5For each sample in Example 1 of this application (NMTP, NMTP / C and NMTP / C@Ni x B) Discharge curve at 0.2C.

[0045] Figure 6 For each sample in Example 1 of this application (MTP, NMTP / C and NMTP / C@Ni x B) Cycling stability test at 1C.

[0046] Figure 7 For each sample in Experimental Example 1 of this application (MTP, NMTP / C and NMTP / C@Ni x B) FIB-SEM image after stability test. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0048] Unless otherwise specified, the experimental methods involved in the following examples are all conventional methods in the art. For example, reference can be made to experimental manuals in the art, or the conditions recommended by the manufacturer's instructions.

[0049] Unless otherwise specified, the experimental materials and reagents involved in the following examples can be obtained from commercial sources.

[0050] In the following examples, constant current charge and discharge tests were performed using a Xinwei battery testing system (cut-off voltage 2.0-4.2 V, current 0.2C and 1C, where 1C = 135 mAh / g); the sample morphology was observed using a JEF-2100 transmission electron microscope; and the sample XRD was performed using a German Bruker D8.

[0051] In the following examples: NMTP is Na3MnTi(PO4)3, NMTP / C is Na3MnTi(PO4)3 / C, NMTP / C@Ni x B is Na3MnTi(PO4)3 / C@Ni x B.

[0052] Example 1

[0053] The present invention provides a method for preparing Na3MnTi(PO4)3 / C@Ni x B, and applying it to a method for preparing a battery, including the following process:

[0054] 1. Preparation of Na3MnTi(PO4)3 / C@Ni x B

[0055] (1) Add 10 mmol of citric acid monohydrate to 100 mL of deionized water and dissolve completely at room temperature. Then add 5 mmol of manganese acetate tetrahydrate and sodium dihydrogen phosphate dihydrate. Then add 5 mmol of titanium diammonium di(2-hydroxypropionic acid) dihydroxide and stir evenly before spray drying. Spray drying parameters are: inlet temperature 200°C, air volume 90%, and feed rate 3 mL / min. Samples are then collected.

[0056] (2) The obtained powder was collected and placed in an argon furnace at 650 °C for 4 h. After the furnace temperature dropped to 100 °C, it was immediately taken out and stored in a glove box to obtain Na3MnTi(PO4)3 / C for later use.

[0057] (3) Disperse 2.5g of Na3MnTi(PO4)3 / C cathode material in ethanol, add 112mg of nickel acetate tetrahydrate and 5.9mg of sodium borohydride, stir for 4h and then centrifuge and dry to obtain the target sample Na3MnTi(PO4)3 / C@Ni x B.

[0058] The present invention further focuses on Na3MnTi(PO4)3 / C@Ni x B was tested, and its particle size was 2 μm, Ni x The content of B is 3wt%, and the content of C is 13wt%.

[0059] The present invention further performs X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) on the target sample obtained, and obtains the following Figures 1-4 The results shown.

[0060] like Figure 1 As shown, from Figure 1 It can be seen that the two samples prepared by this method have the typical structure of polyanionic Na3MnTi(PO4)3, and the coating will not affect the crystal structure of the material.

[0061] like Figure 2 , 3 shown, from Figure 2 , Figure 3 It can be seen that the two samples prepared by this method have similar structural morphology. Under the same preparation temperature and time, coating does not affect the morphology of the material; however, after coating, a layer of other substances is shown on the outermost layer.

[0062] like Figure 4As shown, from Figure 4 It can be seen that the elements are evenly distributed after coating, and the elements of the coating material are mainly distributed in the outermost layer, indicating that the material is successfully coated.

[0063] 2. Use Na3MnTi(PO4)3 / C to prepare and assemble pole pieces for sodium ion batteries

[0064] (1) The polyanionic cathode material prepared in step 1, i.e., the active material, was weighed according to a mass ratio of 350 mg active material: 100 mg carbon nanotubes: 50 mg PVDF = 7:2:1, and ground in a glove box. After 30 minutes, 700 μL of NMP solvent was added. After further grinding for 3 hours, the slurry was evenly coated on aluminum foil using a 300 μm scraper.

[0065] (2) The aluminum foil coated with the slurry was transferred to a vacuum drying oven and dried at 120°C for 12 hours to obtain the coated polyanionic Na3MnTi(PO4)3 positive electrode material.

[0066] 3. Assemble the coated polyanionic Na3MnTi(PO4)3 positive electrode material obtained in step 2 into a button cell for testing. The specific steps are as follows:

[0067] Assemble the positive electrode shell, positive electrode sheet, separator, sodium sheet, gasket, spring, and negative electrode shell in this order. Add 100μL of electrolyte (1.0M NaClO₄ in EC:PC solution + 5% FEC). After standing for 12 hours, perform a cyclic charge-discharge test (voltage window 2.0-4.0V).

[0068] like Figure 5 As shown, at a current density of 0.2C, Na3MnTi(PO4)3 / C@Ni x B (3wt%) has the best electrochemical performance.

[0069] like Figure 6 As shown in the figure, after 200 cycles of NMTP at 1C, its capacity drops sharply, and after 1000 cycles of NMTP / C, its capacity retention rate is only 62.5%. x After 2000 cycles, the capacity retention rate of B (3wt%) reached 73.5%. This shows that the cycling stability of the material is effectively enhanced after coating. x B vs. Mn 3+ The Jiang Taylor effect has a certain inhibitory effect.

[0070] Experimental Example 1

[0071] The present invention further subjected the battery prepared in Example 1 to a constant current charge and discharge test on a Xinwei system, and then disassembled the battery for FIB-SEM testing. The specific steps are as follows:

[0072] The battery's charge and discharge cycle was set as follows: rest for 30 seconds, charge at 0.1C, rest for 30 seconds, discharge at 0.1C, and return to step 1 after less than 500 cycles to complete the battery's cyclic charge and discharge test. After 500 cycles, the battery was disassembled, the positive electrode was obtained, and the powder was scraped off. After drying, Fiber-Band Scanning Electron Microscope (FiB-SEM) analysis was performed.

[0073] The results are as follows Figure 7 As shown in the figure, after cycling, obvious cracks appear on the surface of NMTP, and the cross-section can clearly observe the obvious cracks. Although NMTP / C also has crack distribution, the number of cracks is significantly reduced compared with NMTP. In contrast to the two materials, NMTP / C@Ni x B has no obvious cracks after cycling, indicating that the material has good structural stability. x B vs. Mn 3+ The Jiang Taylor effect has a certain inhibitory effect.

[0074] Experimental Example 2

[0075] The present invention further prepares Na3MnTi(PO4)3 / Ni x B. The method is as follows: dissolve 5mmol of manganese acetate tetrahydrate and sodium dihydrogen phosphate dihydrate in 100mL of deionized water, then add 5mmol of di(2-hydroxypropionic acid) diammonium titanium dihydride and stir evenly before spray drying. Spray drying setting parameters: inlet temperature 200℃, air intake 90%, feed rate 3mL / min. Then collect the sample. (2) Collect the obtained powder and place it in an air furnace at 650℃ for 4h. After the furnace temperature drops to 100℃, take it out and store it in a glove box to obtain Na3MnTi(PO4)3. (3) Disperse 2.5g of Na3MnTi(PO4)3 positive electrode material in ethanol, add 112mg of nickel acetate tetrahydrate and 5.9mg of sodium borohydride, stir for 4h and centrifuge to obtain the target sample Na3MnTi(PO4)3@Ni x B.

[0076] Prepared Na3MnTi(PO4)3 / Ni x B material (particle size: 2μm, Ni x A battery was prepared using the same method as in Example 1. Constant current charge and discharge tests and the same cycling stability test as in Experimental Example 1 were performed. The results showed that although the material stability was improved, the material capacity was reduced by more than half.

[0077] This shows that the Ni coating alone x B obtained Na3MnTi(PO4)3 / Ni x The capacity of B material decreases, and the cycle stability effect is limited. The double-layer coating of C and Ni x B combines significantly higher capacity and cycling stability.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A sodium superion conductor material, characterized in that The sodium superionic conductor material comprises a manganese-based NASICON structure core and a nickel boride / carbon double-layer coating layer coated on the manganese-based NASICON structure core; In terms of mass percentage, the nickel boride accounts for 1% to 10% of the sodium superionic conductor material; The chemical formula of the manganese-based NASICON structure core is Na3MnTi(PO4)3.

2. The sodium superion conductor material according to claim 1, characterized in that The mass ratio of the nickel boride to the carbon is (1-10):(10-20).

3. The sodium superion conductor material according to claim 1 or 2, characterized in that The particle size of the sodium superion conductor material is 0.5-3 μm.

4. A pole piece for a sodium ion battery, characterized in that: The method is prepared from the sodium superionic conductor material according to any one of claims 1 to 3.

5. The pole piece for sodium ion battery according to claim 4, characterized in that: Calculated in parts by weight, the composition comprises: 5 to 9 parts of the sodium superion conductor material, 1 to 3 parts of carbon nanotubes, and 0.5 to 2 parts of PVDF.

6. A battery, characterized in that: The sodium ion battery is prepared from the electrode sheet according to claim 4 or 5.

7. The method for preparing the sodium superionic conductor material according to any one of claims 1 to 3, characterized in that: include: A sodium source component, a manganese source component, a titanium source component, a phosphorus source component and water are mixed, and after mixing, spray drying and calcination are performed to obtain a carbon-coated manganese-based NASICON structure core; The carbon-coated manganese-based NASICON structure core, the nickel source component and the boron source component are mixed, mixed in an ethanol solvent environment for 2 to 6 hours, and centrifuged to dry.

8. The preparation method according to claim 7, characterized in that The sodium source component includes: at least one of sodium carbonate, sodium hydroxide, sodium chloride, sodium acetate, sodium citrate or sodium bicarbonate; and / or, The manganese source component includes: at least one of manganese nitrate, manganese chloride, manganese acetate or manganese acetylacetonate; and / or, The titanium source component includes at least one of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate or di(2-hydroxypropionic acid) diammonium dihydroxide titanium; and / or The nickel source component includes: at least one of nickel chloride, nickel nitrate, nickel sulfate or nickel acetate; and / or, The boron source component is sodium borohydride or boric acid; and / or, The inlet temperature of the spray drying is 100-200°C, the air intake is 60-90%, and the feed rate is 1-5 mL / min; and / or, The calcination temperature is 500-800° C., and the calcination time is 3-10 hours.

9. Use of the sodium superionic conductor material according to any one of claims 1 to 3 in the preparation of sodium ion batteries.

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