Electrochemical activation treatment method for improving sodium storage specific capacity of large-grain-size titanium dioxide negative electrode

Abstract

The invention provides an electrochemical activation treatment method for improving the sodium storage specific capacity of a large-grain-size titanium dioxide negative electrode, which comprises the following steps: carrying out electrochemical activation on anatase-phase and rutile-phase large-grain-size titanium dioxide negative electrodes under specific working conditions to promote the improvement of the reaction depth of titanium dioxide; therefore, the sodium storage specific capacity of the large-grain-size titanium dioxide negative electrode is obviously improved; according to the electrochemical activation method provided by the invention, the sodium storage specific capacity of the large-grain-size titanium dioxide negative electrode is effectively improved, the process is simple and effective, and the titanium dioxide negative electrode treated by the method shows high mass specific capacity, high volume specific capacity and long cycle stability when being applied to a sodium ion battery, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to an electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes. Background Technology

[0002] Establishing large-scale electrochemical energy storage systems is crucial for the efficient storage and scientific redistribution of clean and renewable energy in the power grid, and is an important foundation for accelerating the promotion of new energy and the energy revolution. Sodium-ion batteries possess abundant raw material resources, low manufacturing costs, wide operating temperature range, and high safety, making them suitable for large-scale energy storage applications. Currently, hard carbon is widely used as the anode material in commercial sodium-ion batteries. While it has high sodium storage capacity and low reaction potential, its "pore-filling" mechanism results in slow sodium-ion storage kinetics, exhibiting poor rate performance. Furthermore, its low reaction potential easily induces sodium dendrite growth, posing certain safety risks. Therefore, developing anode materials that combine low cost, high performance, and high safety is of great significance for the promotion and widespread adoption of sodium-ion batteries.

[0003] Titanium dioxide is not only abundant (titanium ranks ninth in abundance among elements in the Earth's crust), inexpensive, stable, non-flammable, and non-toxic and pollution-free, but also possesses other advantages. Anatase and rutile phase titanium dioxide have been extensively studied as anodes in lithium-ion batteries; however, their sodium-ion energy storage mechanisms differ from those of lithium-ion batteries. Recent literature [Nature Communications, 2025, 16, 2015; Advanced Materials, 2025, 37, 2419999] indicates that anatase and rutile titanium dioxide cannot reversibly store sodium ions. An irreversible amorphization reaction occurs upon the initial sodium ion insertion, and this amorphization reaction is limited to the grain surface area of ​​~5 nm. This results in the sodium storage specific capacity of anatase and rutile titanium dioxide exhibiting a grain size-dependent characteristic. Specifically, when the grain size is less than or equal to 10 nm, titanium dioxide has a high specific capacity of ~250 mAh / g, but anatase titanium dioxide with grain sizes of 20 nm and 100 nm only has specific capacities of 175 mAh / g and 33 mAh / g, respectively. The reliance on a surface area of ​​only ~5 nm leads to low material utilization, or the precise preparation of 10 nm uniformly sized titanium dioxide materials requires strict process control in synthesis. Furthermore, titanium dioxide electrodes with small grain sizes of 10 nm and below have low compaction density and low volumetric capacity, making them difficult to apply industrially. Therefore, developing a simple process to overcome the limitation of titanium dioxide's specific capacity to a depth of approximately 5.0 nm from the surface layer, enabling large-grain titanium dioxide (20–100 nm) to achieve a specific capacity exceeding 200 mAh / g, would be of great significance for advancing the application of large-grain titanium dioxide in sodium-ion batteries. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an electrochemical activation treatment method for improving the sodium storage capacity of large-grain-size titanium dioxide anodes. This method is simple to operate, quick to complete, and compatible with existing sodium-ion battery manufacturing processes, and can significantly improve the sodium storage capacity of large-grain-size titanium dioxide anodes.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes, characterized by comprising the following steps:

[0007] 1) 20-100nm titanium dioxide is uniformly dispersed in deionized water with conductive additives and binders to form a slurry, which is then uniformly coated on aluminum foil, dried, and cut into titanium dioxide electrode sheets.

[0008] 2) In an argon atmosphere, the titanium dioxide electrode, the sodium metal electrode, and the electrolyte are assembled into a sodium-ion half-cell and left to stand.

[0009] 3) The titanium dioxide electrode sheet was subjected to cyclic electrochemical activation treatment by electrochemical charging and discharging at a constant current of 0.01 to 0.1 A / g in a temperature environment of 40 to 70℃.

[0010] Furthermore, the conductive additive mentioned in step 1) is Ketjen Black; the binder is styrene-butadiene rubber and sodium carboxymethyl cellulose in a mass ratio of 1:1.

[0011] Furthermore, the mass ratio of the titanium dioxide to the conductive additive and the binder is (8.0-9.0):(0.5-1):(0.5-1).

[0012] Furthermore, in step 2), the solute of the electrolyte is sodium hexafluorophosphate, and the solvent is diethylene glycol dimethyl ether.

[0013] Furthermore, the solubility of the electrolyte in step 2) is 0.5–1.5 mol / L.

[0014] Furthermore, in step 2), the settling time is 1 to 12 hours.

[0015] Furthermore, in step 3), the charging / discharging potential range is 2.5-0.05V vs. Na. + / Na.

[0016] Furthermore, in step 3), the number of charge-discharge cycles is 1 to 5.

[0017] Furthermore, the titanium dioxide is anatase phase titanium dioxide or rutile phase titanium dioxide.

[0018] Through numerous experiments, the inventors discovered that the active amorphous layer formed on the surface of large-grained titanium dioxide during the initial sodium intercalation determines the subsequent reversible capacity. However, the formation of this amorphous layer is limited by the extremely slow diffusion of sodium ions, resulting in a limited thickness. Therefore, this invention, based on Fick's diffusion law, uses a novel high-temperature, low-current electrochemical activation treatment method to enhance the amorphization reaction depth of titanium dioxide, thereby increasing the reversible sodium ion storage capacity of large-grained titanium dioxide (anatase or rutile phase).

[0019] The beneficial effects of this invention are as follows:

[0020] The electrochemical activation method employed in this invention is simple to operate. It involves activating the titanium dioxide anode under specific electrochemical activation conditions, significantly enhancing the surface amorphization reaction depth of the titanium dioxide anode material. This allows for the complete transformation of anatase and rutile phase titanium dioxide with grain sizes of 20–100 nm into amorphous titanium dioxide, fully converting them into the active phase, thereby significantly improving the sodium storage capacity of the titanium dioxide anode. Based on this method, large-grain-size titanium dioxide anodes activated electrochemically can be used in low-cost, high-power sodium-ion batteries.

[0021] Unlike widely reported battery formation (patent CN116598622A) and pre-sodiumization processes (patent CN107240715A) that address the stability of the electrode-electrolyte interface and the first-cycle coulombic efficiency, this invention aims to activate the sodium storage specific capacity of large-grained titanium dioxide. Taking anatase titanium dioxide with a grain size of 35 nm as an example, the reversible specific capacity reached 218.7 mAh / g after electrochemical activation treatment (Example 2). The large-grained titanium dioxide anode treated by this electrochemical activation method exhibited high specific capacity, high volumetric specific capacity, high rate performance, and long cycle stability in sodium-ion batteries. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 These are the first charge-discharge curves of the titanium dioxide electrodes treated using the methods of Example 2 and Comparative Example 1 of this invention;

[0024] Figure 2These are the X-ray diffraction patterns of the titanium dioxide electrodes treated using the methods of Example 2 and Comparative Example 1 of this invention in the first fully discharged state;

[0025] Figure 3 This is a comparison chart of the reversible mass specific capacity of titanium dioxide electrodes treated using the methods of the embodiments and comparative examples of the present invention;

[0026] Figure 4 This is a comparison chart of the reversible volumetric capacity of titanium dioxide electrodes treated using the methods of the embodiments and comparative examples of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but 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.

[0028] In this invention, the titanium dioxide is a conventionally used, untreated commercial anatase or rutile phase titanium dioxide material with a grain size preferably of 20-100 nm. The nanoparticles have better wettability in contact with the electrolyte, which is beneficial for the reversible insertion and extraction of sodium ions.

[0029] Example 1

[0030] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0031] 1) Anatase phase titanium dioxide with a grain size of 20nm, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber are uniformly dispersed in deionized water at a mass ratio of 80:10:5:5 to form a slurry, which is then uniformly coated on aluminum foil, dried and cut into titanium dioxide electrode sheets.

[0032] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 0.5 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 1 hour.

[0033] 3) In a 40℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + Electrochemical activation of the titanium dioxide electrode in the / Na range for one charge-discharge cycle.

[0034] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 1 was 2.09 g / cm³. 3After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 216.8 mAh / g, and the volumetric specific capacity is 453.1 mAh / cm³. 3 .

[0035] Example 2

[0036] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0037] 1) Anatase phase titanium dioxide with a grain size of 35nm, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber are uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 to form a slurry, which is then uniformly coated on aluminum foil, dried and cut into titanium dioxide electrode sheets.

[0038] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0039] 3) Using a constant current of 0.01 A / g in a 70℃ environment at 2.5-0.05 V vs. Na + Electrochemical activation of the titanium dioxide electrode in the / Na range for one charge-discharge cycle.

[0040] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 2 was 2.12 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 218.7 mAh / g, and the volumetric specific capacity is 463.6 mAh / cm³. 3 .

[0041] Example 3

[0042] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0043] 1) Anatase phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 100nm were uniformly dispersed in deionized water at a mass ratio of 90:5:2.5:2.5 to form a slurry, which was then uniformly coated on aluminum foil, dried and cut into titanium dioxide electrode sheets.

[0044] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.5 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0045] 3) Using a constant current of 0.01 A / g in a 70℃ environment at 2.5-0.05 V vs. Na + Electrochemical activation of the titanium dioxide electrode was performed in the / Na range for 5 charge-discharge cycles.

[0046] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 3 was 2.19 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 210.5 mAh / g, and the volumetric specific capacity is 461.0 mAh / cm³. 3 .

[0047] Example 4

[0048] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0049] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 20 nm was uniformly dispersed in deionized water at a mass ratio of 80:10:5:5 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0050] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 0.5 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 1 hour.

[0051] 3) In a 40℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + Electrochemical activation of the titanium dioxide electrode in the / Na range for one charge-discharge cycle.

[0052] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 4 was 2.12 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 209.9 mAh / g, and the volumetric specific capacity is 445.0 mAh / cm³. 3 .

[0053] Example 5

[0054] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0055] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0056] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0057] 3) Using a constant current of 0.01 A / g in a 70℃ environment at 2.5-0.05 V vs. Na + Electrochemical activation of the titanium dioxide electrode in the / Na range for one charge-discharge cycle.

[0058] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 5 was 2.14 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 210.3 mAh / g, and the volumetric specific capacity is 450.0 mAh / cm³. 3 .

[0059] Example 6

[0060] The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes in this embodiment is as follows:

[0061] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 100 nm was uniformly dispersed in deionized water at a mass ratio of 90:5:2.5:2.5 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0062] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.5 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0063] 3) Using a constant current of 0.01 A / g in a 70℃ environment at 2.5-0.05 V vs. Na + Electrochemical activation of the titanium dioxide electrode was performed in the / Na range for 5 charge-discharge cycles.

[0064] The compaction density of the electrochemically activated titanium dioxide anode obtained in Example 6 was 2.21 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 208.5 mAh / g, and the volumetric specific capacity is 460.8 mAh / cm³. 3 .

[0065] Comparative Example 1

[0066] The electrochemical activation treatment method for large-grain-size titanium dioxide is as follows:

[0067] 1) Anatase phase titanium dioxide with a grain size of 35nm, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber are uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 to form a slurry, which is then uniformly coated on aluminum foil, dried and cut into titanium dioxide electrode sheets.

[0068] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0069] 3) In a 25℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0070] The compaction density of the titanium dioxide anode obtained from Comparative Example 1 was 2.12 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 94.4 mAh / g, and the volumetric specific capacity is 200.1 mAh / cm³. 3 .

[0071] Comparative Example 2

[0072] The electrochemical activation treatment method for large-grain-size titanium dioxide is as follows:

[0073] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0074] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0075] 3) Using a constant current of 0.01 A / g in a 25℃ environment at 2.5-0.05 V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0076] The compaction density of the titanium dioxide anode obtained from Comparative Example 2 was 2.12 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 142.3 mAh / g, and its volumetric specific capacity is 301.7 mAh / cm³. 3 .

[0077] Comparative Example 3

[0078] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0079] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0080] 3) In a 70℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0081] The compaction density of the titanium dioxide anode obtained from Comparative Example 3 was 2.12 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 170.8 mAh / g, and the volumetric specific capacity is 362.1 mAh / cm³. 3 .

[0082] Comparative Example 4

[0083] The electrochemical activation treatment method for large-grain-size titanium dioxide is as follows:

[0084] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0085] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0086] 3) In a 25℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0087] The compaction density of the titanium dioxide anode obtained from Comparative Example 4 was 2.14 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 68.3 mAh / g, and the volumetric specific capacity is 146.2 mAh / cm³. 3 .

[0088] Comparative Example 5

[0089] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0090] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0091] 3) Using a constant current of 0.01 A / g in a 25℃ environment at 2.5-0.05 V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0092] The compaction density of the titanium dioxide anode obtained from Comparative Example 5 was 2.14 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 87.8 mAh / g, and the volumetric specific capacity is 187.9 mAh / cm³. 3 .

[0093] Comparative Example 6

[0094] 1) A slurry of rutile phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 35 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0095] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0096] 3) In a 70℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0097] The compaction density of the titanium dioxide anode obtained from Comparative Example 6 was 2.14 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 136.4 mAh / g, and the volumetric specific capacity is 291.9 mAh / cm³. 3 .

[0098] Comparative Example 7

[0099] 1) A slurry of bronze mineral phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 20 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0100] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0101] 3) In a 25℃ environment, using a constant current of 0.1A / g at 2.5-0.05V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0102] The compaction density of the titanium dioxide anode obtained from Comparative Example 7 was 1.96 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. +The reversible specific capacity of Na within its potential range is 153.1 mAh / g, and its volumetric specific capacity is 300.1 mAh / cm³. 3 .

[0103] Comparative Example 8

[0104] 1) A slurry of bronze mineral phase titanium dioxide, Ketjen black, sodium carboxymethyl cellulose and styrene-butadiene rubber with a grain size of 20 nm was uniformly dispersed in deionized water at a mass ratio of 85:7:4:4 and uniformly coated on aluminum foil. After drying, it was cut into titanium dioxide electrode sheets.

[0105] 2) In a glove box filled with argon, the above-mentioned titanium dioxide electrode, sodium metal electrode and 1.0 mol / L sodium hexafluorophosphate dissolved in diethylene glycol dimethyl ether electrolyte were assembled into a sodium ion half cell and left to stand for 12 hours.

[0106] 3) Using a constant current of 0.01 A / g in a 70℃ environment at 2.5-0.05 V vs. Na + The titanium dioxide electrode was subjected to one charge-discharge cycle within the / Na range.

[0107] The compaction density of the titanium dioxide anode obtained from Comparative Example 7 was 1.96 g / cm³. 3 After standing at 25℃ for 12 hours, the sample was subjected to a constant current of 0.1 A / g at 25℃ under conditions of 3-0.01 V vs. Na. + The reversible specific capacity of Na within its potential range is 154.8 mAh / g, and its volumetric specific capacity is 303.4 mAh / cm³. 3 .

[0108] Performance testing

[0109] The compaction density and electrochemical sodium storage mass and volumetric specific capacity test results of the electrodes of each embodiment and comparative example are shown in Table 1 below.

[0110] Table 1

[0111]

[0112] Comparing the data from Example 2 and Comparative Example 2, and Comparative Example 5 and Comparative Example 5, it is evident that, under the same conditions, increasing the operating temperature can improve the reversible sodium storage capacity of anatase and rutile phase titanium dioxide anodes. Comparing the data from Example 2 and Comparative Example 3, and Comparative Example 5 and Comparative Example 6, it is evident that, under the same conditions, decreasing the current density can also improve the reversible sodium storage capacity of anatase and rutile phase titanium dioxide anodes. Comparison of the data from Example 2 and Comparative Example 1, and Example 5 and Comparative Example 4, shows that, compared to the treatment methods of Comparative Example 1 and Comparative Example 4, the electrochemical activation treatment method of the present invention, which combines high-temperature, low-current charge-discharge cycling, can activate the sodium storage capacity of large-grain-size anatase and rutile phase titanium dioxide anodes. Furthermore, comparing the data from Comparative Example 7 and Comparative Example 8, it is evident that the high-temperature, low-current charge-discharge cycling electrochemical activation treatment method used in the present invention is difficult to improve the sodium storage capacity of bronze phase titanium dioxide anodes.

[0113] Figure 1 The first charge-discharge curves are shown for titanium dioxide electrodes with a grain size of 35 nm treated by the methods of Example 2 and Comparative Example 1. The negative electrode treated by the method of Comparative Example 1 consistently exhibits a sloping curve and a low initial discharge mass capacity of 83.8 mAh / g, indicating the low initial sodium storage activity of titanium dioxide. In contrast, the first charge-discharge curve of the negative electrode treated by the method of Example 2 shows a voltage plateau corresponding to the irreversible phase transition from crystalline to amorphous titanium dioxide and a high initial discharge capacity of 335.4 mAh / g, indicating that the method of the present invention can promote the amorphization of titanium dioxide and significantly improve the initial discharge mass capacity.

[0114] X-ray diffraction tests were performed on the electrodes treated by the method in Example 2 and Comparative Example 1, such as... Figure 2 As shown in the figure. The results show that the negative electrode treated by the conventional method still retains good crystallinity, while the diffraction peaks corresponding to titanium dioxide in the negative electrode treated by the method of Example 2 all disappeared, that is, a high degree of amorphization transformation occurred. This proves that high temperature and low current electrochemical charge and discharge can significantly improve the amorphization reaction depth of large grain size titanium dioxide and activate sodium storage capacity.

[0115] like Figure 3 and 4 As shown, the titanium dioxide anode using the electrochemical activation treatment method of this invention achieves higher specific capacity in both mass and volume compared to titanium dioxide anodes treated using methods described in Comparative Document 1 and Comparative Document 2. Taking anatase titanium dioxide with a grain size of 35 nm as an example, the titanium dioxide anode treated using the method described in Comparative Document 1 provides a reversible specific capacity of 94.4 mAh / g and a specific volume capacity of 200.1 mAh / cm³. 3(Comparative Example 1) The reversible mass specific capacity provided by the electrochemical activation treatment of the present invention reached 218.7 mAh / g, and the volumetric specific capacity was increased to 463.6 mAh / cm³. 3 (Example 2)

[0116] The above results demonstrate that the simple and efficient electrochemical treatment method for titanium dioxide anodes provided by this invention can successfully transform crystalline titanium dioxide into an amorphous structure and be electrochemically activated, which can significantly improve the sodium storage capacity of titanium dioxide anodes and has good prospects for industrial application.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes, characterized in that, Includes the following steps: 1) 20-100nm titanium dioxide is uniformly dispersed in deionized water with conductive additives and binders to form a slurry, which is then uniformly coated on aluminum foil, dried, and cut into titanium dioxide electrode sheets. 2) In an argon atmosphere, the titanium dioxide electrode, the sodium metal electrode, and the electrolyte are assembled into a sodium-ion half-cell and left to stand. 3) The titanium dioxide electrode was subjected to cyclic electrochemical activation treatment by electrochemical charging and discharging at a constant current of 0.01 to 0.1 A / g in a temperature environment of 40 to 70℃.

2. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1, characterized in that, The conductive additive mentioned in step 1) is Ketjen Black; the binder is styrene-butadiene rubber and sodium carboxymethyl cellulose in a mass ratio of 1:

1.

3. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1 or 2, characterized in that, The mass ratio of titanium dioxide to conductive additives and binders is (8.0-9.0):(0.5-1):(0.5-1).

4. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1, characterized in that, The solute in the electrolyte described in step 2) is sodium hexafluorophosphate, and the solvent is diethylene glycol dimethyl ether.

5. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1 or 4, characterized in that, The solubility of the electrolyte in step 2) is 0.5–1.5 mol / L.

6. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1, characterized in that, The settling time in step 2) is 1 to 12 hours.

7. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1, characterized in that, In step 3), the charging / discharging potential range is 2.5-0.05V vs. Na. + / Na.

8. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1 or 7, characterized in that, In step 3), the number of charge-discharge cycles is 1 to 5.

9. The electrochemical activation treatment method for improving the sodium storage specific capacity of large-grain-size titanium dioxide anodes according to claim 1, characterized in that, The titanium dioxide is anatase phase titanium dioxide or rutile phase titanium dioxide.

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