Hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as negative electrode

Abstract

The invention discloses a hybrid capacitor taking a titanium-niobium-oxygen doped porous carbon material as a negative electrode, the hybrid capacitor comprises a positive electrode, the negative electrode, a diaphragm and a lithium salt organic electrolyte, an active material of the positive electrode is coal-based graphitized porous carbon, and an active material of the negative electrode is a titanium-niobium-oxygen in-situ doped porous carbon composite material. The GPC substrate is utilized to construct a three-dimensional conductive network and an ion rapid transmission channel, so that the electronic conductivity and the ion diffusion rate of the niobium-based oxide are remarkably improved, and the inherent dynamic bottleneck of the niobium-based oxide is effectively solved. The GPC / TNO GPC hybrid capacitor constructed by the method realizes a wide voltage window of 0-4 V, has high energy density (up to 170.2 Wh kg <-1 >) and high power density (up to 24 kW kg <-1 >), and has excellent long cycle stability, and a new scheme is provided for developing a next-generation high-performance double-high energy storage device.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage device technology, and relates to a lithium-ion hybrid capacitor with optimized electrode structure and highly matched positive and negative electrode dynamics. Specifically, it relates to a novel hybrid capacitor system with coal-based graphitized porous carbon as the positive electrode and titanium-niobium-oxygen / porous carbon composite material as the negative electrode. Background Technology

[0002] Hybrid capacitors, as energy storage devices positioned between supercapacitors and secondary batteries, have attracted considerable attention due to their potential to simultaneously achieve high energy density and high power density (“dual high”). Their typical structure typically employs a double-layer capacitive material (such as porous carbon) as the positive electrode and a battery-type material (such as lithium titanate or niobium-based oxide) as the negative electrode. However, the core challenge of this structural design lies in the inherent kinetic mismatch between the positive and negative electrodes: the ion adsorption / desorption process at the positive electrode is extremely rapid, while the Faraday reaction at the negative electrode typically involves slow ion diffusion and phase transition processes, which severely limits the device's power output at high rates.

[0003] Niobium-based oxides, especially titanium niobium oxide (TiNb₂O₇, TNO), are considered ideal anode materials for matching carbon cathodes due to their high theoretical specific capacity and safe lithiation potential. However, the inherently poor electronic conductivity and slow ion diffusion kinetics of TNO materials result in actual capacities at high rates that are far lower than theoretical values, making it difficult to meet the requirements of high-performance hybrid capacitors for fast charging and discharging of the anode.

[0004] In existing technologies, TNO is typically improved by physically mixing or surface coating it with conductive carbon materials (such as carbon black and graphene). However, these simple composite methods struggle to achieve uniform and tight bonding between TNO and carbon materials at the nanoscale, resulting in high interfacial contact resistance and the potential for conductive network failure due to volume changes during long-term cycling. Furthermore, non-in-situ carbon coating may block ion transport channels, failing to fundamentally address the problem of slow ion diffusion. Therefore, developing a negative electrode material and device structure that can simultaneously enhance electron conduction and ion diffusion rates and perfectly match high-power carbon cathodes is a pressing technical challenge in this field. Summary of the Invention

[0005] To address the issues of mismatched positive and negative electrode kinetics and poor conductivity and ion diffusion of niobium-based oxide negative electrode materials in existing hybrid capacitors, this invention provides a hybrid capacitor using titanium-niobium-oxygen-doped porous carbon material as the negative electrode. This hybrid capacitor achieves high energy and high power output over a wide voltage window through innovative design of the negative electrode material and synergistic matching of the positive and negative electrodes. This invention utilizes a GPC substrate to construct a three-dimensional conductive network and a fast ion transport channel, significantly improving the electronic conductivity and ion diffusion rate of niobium-based oxides, effectively solving their inherent kinetic bottlenecks. The GPC / / TNO@GPC hybrid capacitor constructed in this way achieves a wide voltage window of 0–4 V, while also possessing high energy density (up to 170.2 Wh / kg). -1 ) and high power density (up to 24 kW kg) -1 Its excellent long-cycle stability provides a new solution for developing next-generation high-performance "dual-high" energy storage devices.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A hybrid capacitor using titanium-niobium-oxygen-doped porous carbon material as the negative electrode includes a positive electrode, a negative electrode, a separator, and a lithium salt organic electrolyte, wherein:

[0008] The active material of the positive electrode is coal-based graphitized porous carbon (GPC), with a specific surface area of ​​1500~3000 m². 2 / g, pore volume 1.0~2.0 cm³ 3 / g;

[0009] The active material of the negative electrode is a titanium-niobium-oxygen in-situ doped porous carbon composite material (TNO@GPC).

[0010] The hybrid capacitor has an operating voltage window of 0~4 V and can be used in energy storage systems that require high energy density and high power density output.

[0011] The titanium-niobium-oxygen in-situ doped porous carbon composite material is prepared by the following steps:

[0012] Step (1) Preparation of precursor suspension: Titanium source, niobium source and coal-based graphitized porous carbon (GPC) are dispersed together in an organic solvent and stirred to form a uniform precursor suspension, wherein: the molar ratio of titanium source to niobium source is 1:2 to match the ideal stoichiometric ratio of TiNb2O7; the mass of coal-based graphitized porous carbon accounts for 5~20% of the total mass of titanium source and niobium source, preferably 8~15%; the coal-based graphitized porous carbon is prepared by pre-carbonization and potassium-based activation of Zhundong coal as precursor, and its specific surface area is 1500~3000 m². 2 / g, pore volume 1.0~2.0 cm³ 3 / g; the titanium source is tetrabutyl titanate, titanium sulfate or isopropyl titanate, preferably tetrabutyl titanate; the niobium source is niobium pentachloride, niobium oxalate or niobium ethanol, preferably niobium pentachloride; the organic solvent is ethanol, ethylene glycol or isopropanol, preferably anhydrous ethanol;

[0013] Step (2) Solvothermal reaction: The precursor suspension is subjected to a solvothermal reaction to allow the titanium niobium oxygen precursor to grow in situ on the surface and pores of coal-based graphitized porous carbon, thereby obtaining a composite material precursor. The temperature of the solvothermal reaction is 150~200℃, preferably 170~190℃, and the time is 12~36 hours, preferably 18~30 hours.

[0014] Step (3) High-temperature crystallization treatment: The composite material precursor is subjected to high-temperature crystallization treatment under the protection of an inert atmosphere to obtain a crystalline titanium niobium oxygen in-situ doped porous carbon composite material (TNO@GPC), wherein: the inert atmosphere is argon or nitrogen, the gas flow rate is 100~300 mL / min; the heating rate of the high-temperature crystallization treatment is 2~10℃ / min, the temperature is 700~900℃, preferably 750~850℃, and the holding time is 2~6 hours.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. Superior Anode Performance: This invention utilizes an in-situ solvothermal method to uniformly grow and chemically bond titanium niobium oxide (TNO) nanocrystals on a highly conductive and porous GPC substrate. The GPC constructs a three-dimensional continuous conductive network, significantly improving the electronic conductivity of the composite material. Its hierarchical porous structure provides rapid channels for electrolyte wetting and lithium-ion transport, synergistically solving the dual bottlenecks of poor conductivity and slow ion diffusion in TNO materials. The prepared TNO@GPC anode exhibits specific capacities of 278.9 mAh / g and 133.5 mAh / g at 0.1 C and 50 C rates, respectively, demonstrating excellent rate performance and structural stability.

[0017] 2. Highly Matched Positive and Negative Electrode Kinetics: This invention innovatively employs homologous coal-based graphitized porous carbon (GPC) as both the positive electrode active material and the negative electrode composite substrate. This "homogeneous" design ensures that the positive and negative electrodes have similar interfacial properties and ion transport environments, effectively bridging the kinetic gap between the electric double-layer mechanism and the Faraday reaction, and ensuring efficient capacity release of the device during rapid charge and discharge.

[0018] 3. Excellent overall device performance: The TNO@GPC / / GPC lithium-ion hybrid capacitor constructed based on the above positive and negative electrodes achieves a wide operating voltage window of 0~4 V. This device achieves a maximum energy density of 170.2 Wh / kg and a maximum power density of 24 kW / kg, while also exhibiting excellent long-term cycle stability (74% capacity retention after 8000 cycles at 2 A / g), achieving a synergistic improvement in both energy and power density. Its performance far surpasses that of hybrid capacitors based on pure-phase TNO negative electrodes. Attached Figure Description

[0019] Figure 1 Cyclic voltammetry (CV) curves of the TNO@GPC / / GPC hybrid capacitor assembled in Example 3 at different scan rates;

[0020] Figure 2 Constant current charge-discharge (GCD) curves of the TNO@GPC / / GPC hybrid capacitor assembled in Example 3 at different current densities;

[0021] Figure 3 Ragone plot (energy density-power density relationship) of the TNO@GPC / / GPC hybrid capacitor assembled in Example 3.

[0022] Figure 4 The cycling performance diagram is for the TNO@GPC / / GPC hybrid capacitor assembled in Example 3. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0024] Example 1: Preparation of coal-based graphitized porous carbon (GPC)

[0025] Using Xinjiang Zhundong coal as a precursor, pre-carbonization was carried out at 700℃ for 1 hour under a nitrogen atmosphere with a heating rate of 5℃ / min. The pre-carbonized product was mixed with KOH at a mass ratio of 1:3 and activated at 900℃ for 1 hour. After natural cooling, the product was washed with 5 mol / L HCl and 10 wt% HF, then washed with deionized water until neutral, and dried at 80℃ to obtain graphitized porous carbon (GPC). Its specific surface area was approximately 2731 m². 2 / g, pore volume approximately 1.4 cm³ 3 / g.

[0026] Example 2: Preparation of titanium-niobium-oxygen in-situ doped porous carbon composite material (TNO@GPC)

[0027] (1) Weigh 2.5 mmol tetrabutyl titanate and 5 mmol niobium pentachloride, and add them together with 60 mg (accounting for 10% of the total mass of the titanium niobium source) of GPC prepared in Example 1 into 60 mL of anhydrous ethanol. Stir magnetically for 60 minutes to form a uniform suspension.

[0028] (2) Transfer the suspension to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and react it in an oven at 180°C for 24 hours.

[0029] (3) After the reaction is complete, the precipitate is collected by centrifugation and washed with ethanol to obtain the precursor.

[0030] (4) Place the precursor in a tube furnace and heat it to 800°C at a rate of 5°C / min under an argon atmosphere (flow rate 200 mL / min) and hold for 5 hours.

[0031] (5) Cool the sample to room temperature in the furnace, take it out and dry it overnight at 80°C to obtain blue TNO@GPC composite material.

[0032] Example 3: Preparation of titanium-niobium-oxygen in-situ doped porous carbon composite material (TNO@GPC)

[0033] (1) Weigh 2.5 mmol tetrabutyl titanate and 5 mmol niobium oxalate, and add them together with 45 mg (accounting for 7.5% of the total mass of the titanium niobium source) of GPC prepared in Example 1 into 60 mL of ethylene glycol. Stir magnetically for 90 minutes to form a uniform suspension.

[0034] (2) Transfer the suspension to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and react it in an oven at 190°C for 20 hours.

[0035] (3) After the reaction is complete, the precipitate is collected by centrifugation and washed with ethanol to obtain the precursor.

[0036] (4) Place the precursor in a tube furnace and heat it to 750°C at a rate of 3°C / min under a nitrogen atmosphere (flow rate 150 mL / min) and hold for 6 hours.

[0037] (5) Cool the sample to room temperature in the furnace, take it out and dry it overnight at 80°C to obtain blue TNO@GPC composite material.

[0038] Example 4: Assembly and Performance Testing of Hybrid Capacitors

[0039] Cathode preparation: GPC, acetylene black and polytetrafluoroethylene (PTFE) prepared in Example 1 were mixed in ethanol at a mass ratio of 8:1:1, rolled into a thin sheet and pressed onto carbon-coated aluminum foil, and vacuum dried at 110°C for 12 hours.

[0040] Negative electrode preparation: TNO@GPC, acetylene black, and polyvinylidene fluoride (PVDF) prepared in Example 2 were mixed evenly in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, coated onto copper foil, and vacuum dried at 70°C for 12 hours.

[0041] Negative electrode pre-lithiation: The negative electrode sheet and lithium sheet are assembled into a half cell, cycled 3 times at a current density of 30 mA / g, and discharged to 1.1 V to complete the pre-lithiation.

[0042] Full device assembly: In an argon glove box, a CR2032 type button hybrid capacitor was assembled using pre-lithiated TNO@GPC as the negative electrode, GPC as the positive electrode, Whatman GF / F glass fiber as the separator, and 1M LiPF6 (EC:DEC:DMC=1:1:1) as the electrolyte.

[0043] Comparative Example 1:

[0044] Pure-phase TNO material was prepared according to the method of Example 2, but without the addition of GPC. A GPC / / TNO hybrid capacitor was assembled according to the method of Example 4, using pure-phase TNO as the negative electrode and GPC as the positive electrode.

[0045] Performance comparison: Electrochemical tests were performed on the TNO@GPC prepared in Example 2. Its discharge specific capacity at 0.1 C and 50 C rates was 278.9 mAh / g and 133.5 mAh / g, respectively, which is much higher than the 72.5 mAh / g of pure phase TNO in Comparative Example 1 at 50 C.

[0046] The TNO@GPC / / GPC hybrid capacitor assembled in Example 3 achieved a maximum energy density of 170.2 Wh / kg and a power density of 24 kW / kg, with a capacity retention of 74% after 8000 cycles. In contrast, the GPC / / TNO hybrid capacitor assembled in Comparative Example 1 had a maximum energy density of only 111 Wh / kg and a power density of only 8.75 kW / kg, with a capacity retention decreasing to 61% after 1000 cycles.

[0047] Through ingenious material design and device construction, this invention has successfully developed a novel hybrid capacitor with a wide voltage window, high energy density, and high power density, providing an effective technical solution to the current "double high" problem of energy storage devices.

Claims

1. A hybrid capacitor using titanium-niobium-oxygen-doped porous carbon material as the negative electrode, comprising a positive electrode, a negative electrode, a separator, and a lithium salt organic electrolyte, characterized in that... The active material of the positive electrode is coal-based graphitized porous carbon, and the active material of the negative electrode is a titanium-niobium-oxygen in-situ doped porous carbon composite material.

2. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 1, characterized in that... The operating voltage window of the hybrid capacitor is 0~4 V.

3. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 1, characterized in that... The titanium-niobium-oxygen in-situ doped porous carbon composite material is prepared by the following steps: Step (1) Preparation of precursor suspension: Titanium source, niobium source and coal-based graphitized porous carbon are dispersed together in an organic solvent and stirred to form a uniform precursor suspension, wherein: the molar ratio of titanium source to niobium source is 1:2; the mass of coal-based graphitized porous carbon accounts for 5~20% of the total mass of titanium source and niobium source; Step (2) Solvothermal reaction: The precursor suspension is subjected to a solvothermal reaction to allow the titanium niobium oxygen precursor to grow in situ on the surface and pores of coal-based graphitized porous carbon to obtain a composite material precursor. The temperature of the solvothermal reaction is 150~200℃ and the time is 12~36 hours. Step (3) High-temperature crystallization treatment: The precursor of the composite material is subjected to high-temperature crystallization treatment under the protection of an inert atmosphere to obtain a crystalline titanium niobium oxygen in-situ doped porous carbon composite material, wherein: the temperature of the high-temperature crystallization treatment is 700~900℃ and the holding time is 2~6 hours.

4. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 3, characterized in that... The mass of the coal-based graphitized porous carbon accounts for 8-15% of the total mass of the titanium and niobium sources.

5. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 1, 3, or 4, characterized in that... The coal-based graphitized porous carbon is prepared from Zhundong coal as a precursor through pre-carbonization and potassium-based activation, and its specific surface area is 1500~3000 m². 2 / g, pore volume 1.0~2.0 cm³ 3 / g.

6. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 3, characterized in that... The titanium source is tetrabutyl titanate, titanium sulfate, or isopropyl titanate; the niobium source is niobium pentachloride, niobium oxalate, or niobium ethanol; and the organic solvent is ethanol, ethylene glycol, or isopropanol.

7. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 6, characterized in that... The titanium source is tetrabutyl titanate; the niobium source is niobium pentachloride; and the organic solvent is anhydrous ethanol.

8. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 3, characterized in that... The solvothermal reaction is carried out at a temperature of 170-190°C for 18-30 hours.

9. The hybrid capacitor with titanium-niobium-oxygen-doped porous carbon material as the negative electrode according to claim 3, characterized in that... The inert atmosphere is argon or nitrogen, and the gas flow rate is 100~300 mL / min; the heating rate of the high-temperature crystallization treatment is 2~10℃ / min, and the temperature is 750~850℃.

10. A hybrid capacitor according to any one of claims 1-9, using titanium niobium oxygen-doped porous carbon material as the negative electrode, can be used in energy storage systems requiring high energy density and high power density output.

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