Preparation method and application of high-energy-density positive electrode material derived from urchin-like lignin carbon intermediate phase

Abstract

The invention discloses a preparation method and application of a high-energy-density positive electrode material derived from a sea urchin-shaped lignin carbon intermediate phase, and belongs to the field of biomass nanomaterials. According to the invention, the industrial by-product lignin is used as a carbon source, the high-energy-density positive electrode material derived from the sea urchin-shaped lignin carbon intermediate phase is successfully constructed through metal salt coordination guided self-assembly, in-situ doping and segmented carbonization strategies, and accurate conversion of lignin from disordered macromolecules to ordered multifunctional nanomaterials is realized. The prepared high-energy-density positive electrode material is used for a zinc ion supercapacitor, high specific capacitance, excellent rate capability and ultra-long cycle life are shown, effective conversion from biomass waste to an energy material is achieved, and a new technical scheme is provided for application of lignin in the field of energy.

Description

Technical Field

[0001] This invention belongs to the field of biomass materials and relates to a method for preparing and applying a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase. Background Technology

[0002] Lignin is the second most abundant natural organic polymer after cellulose, widely found in the cell walls of woody and herbaceous plants, and together with cellulose and hemicellulose, it constitutes the main components of the plant skeleton. Currently, most industrial lignin is directly burned for energy as a byproduct of pulp and paper making and biorefining industries, with only a very small portion being utilized for high-value purposes.

[0003] In recent years, carbon nanomaterials have attracted much attention in various fields. Lignin itself has a high carbon content, is widely available, renewable, and inexpensive. Its molecular structure also contains a large number of active groups such as phenolic hydroxyl groups, carboxyl groups, and methoxy groups, enabling the prepared lignin carbon nanomaterials to combine the high specific surface area and excellent conductivity of carbon nanomaterials with the structural tunability of lignin-derived materials, showing broad application prospects in electrodes, adsorption, catalysis, and other fields. Various methods exist for preparing lignin carbon nanomaterials, including direct high-temperature pyrolysis carbonization, pretreatment modification followed by carbonization activation, and template methods, but these methods have several shortcomings. Among them, materials prepared by direct high-temperature pyrolysis carbonization have small specific surface area, disordered pore structure, limited active sites, and poor electrochemical performance, making it difficult to meet practical needs. Although the method of pretreatment modification such as oxidation and sulfonation followed by carbonization activation can regulate the structure and properties of materials, it has problems such as large amount of activator, cumbersome washing and separation, easy excessive degradation of lignin leading to low carbon yield, and high cost. Although the template method can regulate the size and pore distribution of materials, the template preparation and removal operations are complicated, the experimental conditions are harsh, some templates are expensive and difficult to recycle, which not only increases the complexity of the process and energy consumption, but also easily affects the performance stability due to template residues, and may also cause potential environmental pollution, which is not conducive to green large-scale production. These shortcomings seriously limit the promotion and application of lignin carbon nanomaterials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing high energy density cathode materials derived from sea urchin-like lignin carbon mesophase, which addresses the shortcomings of the existing technology. Through a multi-step synergistic process of "coordination guidance - in-situ doping - segmented carbonization - secondary activation", the method achieves the precise construction of high-performance cathode materials from disordered biomass lignin.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: A high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase is prepared by the following steps: (1) Add lignin, ferric nitrate and zinc sulfate to water, stir evenly and let stand for aging, then filter to obtain filter residue, i.e. Fe coordinated lignin; (2) The filter residue obtained in step (1) is dispersed together with urea and ammonium chloride in solvent water, stirred evenly, and then freeze-dried to obtain Fe-coordinated lignin precursor (brown powder). (3) The brown powder obtained in step (2) is continuously calcined in a tube furnace under nitrogen protection in two stages to obtain Fe-coordinated carbon nanomaterial precursor (black product A). (4) After the black product A obtained in step (3) is thoroughly mixed and ground with potassium bicarbonate, it is calcined in a tube furnace under nitrogen protection to obtain black product B. After repeated washing with hydrochloric acid, it is the Fe-coordinated sea urchin-like lignin carbon mesophase (Fe-NC). (5) The Fe-coordinated sea urchin-like lignin carbon mesophase obtained in step (4) is dispersed together with manganese sulfate, potassium permanganate, and calcium chloride in a solvent water and stirred evenly. Then, a hydrothermal reaction is carried out. After the hydrothermal reaction is completed, the reaction system is filtered, and the resulting filter residue is washed with water and dried to obtain a high energy density cathode material (Ca-MnO) derived from the sea urchin-like lignin carbon mesophase. x @Fe-NC).

[0006] According to the above scheme, in step (1), the ratio between the mass of lignin and the volume of water is preferably 1g:(10~40)mL (solid-liquid ratio), more preferably 1g:(20~30)mL.

[0007] According to the above scheme, in step (1), the concentration range of ferric nitrate and zinc sulfate in water is 15~45 mmol / L, preferably 20~40 mmol / L, and even more preferably 25~35 mmol / L.

[0008] According to the above scheme, in step (1), the stirring temperature is 15~40℃, preferably 20~30℃ for 20~30h.

[0009] According to the above scheme, in step (1), the time for standing and aging after stirring is 8~20h, preferably 10~15h.

[0010] According to the above scheme, in step (1), the filtration uses an aqueous filter membrane with a pore size of 0.22~0.65μm. Further, the pore size of the filter membrane is preferably 0.35~0.55μm.

[0011] According to the above scheme, in step (2), the mass ratio of filter residue to urea and ammonium chloride is 1:(4~6):(2~4). Further, the preferred mass ratio of filter residue to urea and ammonium chloride is 1:(4.5~5.5):(2.5~3.5).

[0012] According to the above scheme, in step (2), the solid-liquid ratio of the total mass of the filter residue, urea, and ammonium chloride to the solvent water is 1g:(2~10)mL. More preferably, the solid-liquid ratio of the total mass of the filter residue, urea, and ammonium chloride to the solvent water is 1g:(4~8)mL.

[0013] According to the above scheme, in step (2), the stirring temperature is 15~40℃, preferably 25~30℃ for 10~60min.

[0014] According to the above scheme, in step (2), the freeze-drying temperature is -60~-50℃ and the drying time is 12~48h.

[0015] According to the above scheme, in step (3), the calcination temperature of the first stage in the continuous two-stage calcination is 500~600℃, and the holding time is 0.5~1.5h; the calcination temperature of the second stage is 750~850℃, and the holding time is 0.5~1.5h. Furthermore, the heating rate in both stages of calcination is 1~5℃ / min.

[0016] According to the above scheme, in step (4), the mass ratio of black product A to potassium bicarbonate is 1:(2~4), and the temperature is raised to the calcination temperature of 750~850℃ at a heating rate of 3~8℃ / min, and the holding time is 0.5~1.5h. Preferably, the mass ratio of black product A to potassium bicarbonate is 1:(2.5~3.5).

[0017] According to the above scheme, in step (4), the concentration of hydrochloric acid used for washing is 0.5~2 mol / L; the pore size of the aqueous filter membrane is 0.20~0.65 μm. Preferably, the pore size of the aqueous filter membrane is 0.3~0.5 μm.

[0018] According to the above scheme, in step (5), the concentration range of the Fe-coordinated sea urchin-like lignin carbon mesophase dispersed in the solvent water is 1~3g / L, preferably 1.5~2.5g / L.

[0019] According to the above scheme, in step (5), the concentration range of manganese sulfate in the solvent water is 3~6 mmol / L, and more preferably 4~5 mmol / L.

[0020] According to the above scheme, in step (5), the molar ratio of manganese sulfate, calcium chloride and potassium permanganate is 1:(1.5~2.5):(4~7); the stirring time is 20~60 min.

[0021] According to the above scheme, in step (5), the temperature of the hydrothermal reaction is 130~150℃ and the reaction time is 8~12h.

[0022] According to the above scheme, in step (5), the vacuum drying temperature is 50~70℃ and the drying time is 8~24h.

[0023] The high-energy-density cathode material derived from the sea urchin-like lignin-carbon mesophase prepared by the above method can be used in zinc-ion supercapacitors. Further, the specific application method is as follows: the high-energy-density cathode material is mixed with a conductive agent and a binder in a solvent and ground, then uniformly coated onto aluminum foil as the cathode, a zinc sheet as the cathode, and a mixed solution of zinc sulfate and manganese sulfate as the electrolyte, assembling a zinc-ion supercapacitor.

[0024] Compared with the prior art, the beneficial effects of the present invention are: This invention uses lignin as a carbon source, first subjecting lignin to co-precipitation treatment with a metal salt solution, utilizing Fe... 3+ / Zn 2 + Coordination with lignin functional groups forms Fe-coordinated lignin, subsequently guiding molecular self-assembly. Then, urea and ammonium chloride are used as N sources and activators to enhance the conductivity and structural stability of carbon nanomaterials, suppressing the collapse of the carbon substrate during energy storage. Subsequently, in segmented carbonization, the low-temperature stage stabilizes the framework, while the high-temperature stage volatilizes Zn to create pores and simultaneously achieve graphitization. Next, secondary activation is achieved by mixing and grinding with KHCO3 followed by calcination, gently expanding pores to optimize ion transport channels without compromising structural integrity, thus constructing a sea urchin-like carbon substrate. This sea urchin-like structure possesses unique three-dimensional network characteristics, offering significant advantages over traditional disordered carbon substrates. Firstly, the sea urchin-like structure is composed of numerous wrinkled carbon nanosheets, providing ample specific surface area and active sites. Secondly, the three-dimensional supporting framework of the sea urchin-like carbon substrate has higher mechanical strength, further enhancing the structural stability of carbon nanomaterials, while mitigating the volume expansion of manganese-based oxides during cyclic charging and discharging, reducing the shedding of active components. Finally, Ca is grown in situ on the sea urchin-like carbon substrate using a hydrothermal method. 2+ Intercalated manganese-based oxides utilize the high conductivity of carbon networks and Ca... 2+ The rapid ion diffusion of the expanded layers and the high capacity of manganese-based oxides enhance the energy storage performance. This invention successfully prepared a cathode material with an energy density as high as 198.5 Wh / kg through the aforementioned multi-step synergistic process of "coordination-guided self-assembly - in-situ doping - segmented carbonization - secondary activation," achieving precise construction from disordered biomass to high-performance composite materials. Attached Figure Description

[0025] Figure 1 The Fe-NC material (left image) and Ca-MnO prepared in Example 1 are shown. x Scanning electron microscope (SEM) image of @Fe-NC material (right figure).

[0026] Figure 2 The material Ca-MnO prepared in Example 1 x XRD characterization of @Fe-NC materials.

[0027] Figure 3 It is the Ca-MnO prepared in Example 1 x XPS characterization of Fe 2p, N 1s, Mn 2p, and Ca 2p in @Fe-NC materials.

[0028] Figure 4 It is Ca-MnO in Example 1 x Constant current charge-discharge test diagram of assembled zinc-ion supercapacitor coin cells using @Fe-NC materials.

[0029] Figure 5 It is Ca-MnO in Example 1 x Current density-specific capacitance-energy density diagram of zinc-ion supercapacitor coin cells assembled with @Fe-NC materials at current densities of 1~10 A / g.

[0030] Figure 6 It is Ca-MnO in Example 1 x Long cycling curves of zinc-ion supercapacitor coin cells assembled with @Fe-NC materials at a current density of 10 A / g. Detailed Implementation

[0031] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0032] Example 1 A method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase includes the following steps: (1) 4g of lignin, 1.212g of ferric nitrate nonahydrate (3mmol) and 0.863g of zinc sulfate heptahydrate (3mmol) were added to 100mL of deionized water. After stirring at room temperature (25℃) for 24h, the mixture was allowed to stand for 12h to age. The mixture was then filtered through a 0.45μm aqueous filter membrane and dried to obtain Fe-coordinated lignin.

[0033] (2) Disperse 1g of Fe-coordinated lignin obtained in step (1) with 5g of urea and 3g of ammonium chloride into 50mL of deionized water, stir for 30min, freeze dry at -55℃ for 1 day to obtain brown powder, i.e. Fe-coordinated lignin composite precursor.

[0034] (3) The brown powder obtained in step (2) was continuously calcined in a tube furnace under nitrogen protection in two stages. The temperature of the first stage was 550℃ and held for 1 hour. The temperature of the second stage was 800℃. The heating rate of both stages was 3℃ / min. The temperature of the second stage was held for 1 hour to obtain black product A, namely Fe coordinated carbon nanomaterial precursor.

[0035] (4) The black product A obtained in step (3) was thoroughly ground with potassium bicarbonate at a mass ratio of 1:3, and then calcined again in a tube furnace under nitrogen protection. The calcination temperature was 800℃, the holding time was 1h, and the heating rate was 5℃ / min. When the tube furnace cooled to room temperature, the product was repeatedly washed with 1mol / L hydrochloric acid and deionized water. When no more bubbles were generated during the washing process and the pH of the solution was neutral, it was filtered with a 0.45μm aqueous filter membrane and dried in an oven at 50℃ for 12h to obtain Fe-coordinated urchin-like lignin carbon mesophase (Fe-NC).

[0036] (5) The 100 mg Fe-coordinated sea urchin-like lignin carbon mesophase obtained in step (4) was mixed with 0.1896 g KMnO4 (1.2 mmol), 0.0338 g MnSO4·H2O (0.22 mmol), and 0.044 g CaCl2 (0.4 mmol) in 50 ml of deionized water and stirred for 30 min. The mixture was then transferred to a Teflon high-pressure reactor and kept at 140 °C for 10 h. After the reactor cooled to room temperature, it was repeatedly washed with deionized water and dried overnight at 60 °C in a vacuum drying oven to obtain the high energy density cathode material (Ca-MnO4) derived from the sea urchin-like lignin carbon mesophase. x @Fe-NC). The molar ratio of manganese sulfate, calcium chloride, and potassium permanganate is approximately 1:1.8:5.5.

[0037] like Figure 2 As shown, the XRD pattern of the high-energy-density cathode material derived from the sea urchin-like lignin carbon mesophase prepared in Example 1 exhibits diffraction peaks at 18.1°, 28.9°, 37.2°, and 59.9°, corresponding to the (200), (310), (211), and (521) crystal planes of MnO2, respectively. Simultaneously, diffraction peaks at 32.4°, 36.1°, 44.5°, and 50.9° correspond to the (103), (202), (220), and (105) crystal planes of Mn3O4, respectively. Therefore, this high-energy-density cathode material is a composite cathode material of sea urchin-like lignin carbon and manganese-based oxides. Figure 3 It can be seen that, Figure 3 a represents the fine spectrum of Fe 2p. Figure 3In the fine N 1s spectrum of b, the Fe-N (399.5 eV) peak, distinct from pyridine N (398.2 eV) and pyrrole N (400.5 eV), can be clearly seen. Figure 3 The fine spectrum of Mn 2p for c shows the +2, +3, and +4 valences of Mn. Figure 3 The absence of zero-valent Ca in the fine Ca 2p spectrum of d indicates the absence of elemental Ca particles, suggesting that Ca was grown in situ on a sea urchin-like lignin-carbon substrate via a hydrothermal method. 2+ Intercalated manganese-based oxides utilize the high conductivity of carbon networks and Ca... 2+ The rapid ion diffusion of the expanded layer and the high capacity of manganese-based oxides enhance the energy storage performance.

[0038] Application Example 1 High-energy-density cathode material derived from sea urchin-like lignin-carbon mesophase (Ca-MnO) x The application of @Fe-NC as the positive electrode of zinc ion supercapacitors, and the specific experimental method are as follows: The Ca-MnO prepared in Example 1 x Fe-NC material, conductive agent (carbon black), and binder (PVDF) were uniformly mixed at a mass ratio of 7:2:1. 1-Methyl-2-pyrrolidone (NMP) was added to prepare a slurry, which was then thoroughly ground and coated onto an aluminum foil current collector at a thickness of 200 μm. After drying and pressing, this slurry served as the positive electrode of the battery. Then, using a zinc sheet as the negative electrode and a mixed solution of 2M ZnSO4 and 0.2M MnSO4 as the electrolyte, a coin cell was assembled with the aforementioned positive electrode. After the battery was allowed to stabilize sufficiently, its energy storage performance was tested using an electrochemical workstation.

[0039] like Figure 4 As shown, Ca-MnO x Constant current charge-discharge curves of zinc-ion supercapacitor coin cells assembled with @Fe-NC material as the positive electrode.

[0040] like Figure 5 As shown, the coin cell achieved specific capacitances of 324, 237, 179, 152, 127, and 114 F / g at current densities of 1, 2, 3, 5, 8, and 10 A / g, respectively, while also exhibiting high energy densities of 198.5, 145.2, 109.6, 92.9, 77.9, and 69.7 Wh / kg, respectively. It also maintained good capacity retention at high current densities.

[0041] like Figure 6As shown, after nearly 20,000 cycles at a high current density of 10 A / g, the capacity retention rate still reaches 85.1%, and there is no significant decay even after 20,000 cycles. This indicates that the material has excellent long-term cycling stability at high rates and minimal loss of energy storage capacity after long-term charge and discharge. At the same time, the coulombic efficiency remains close to 100%, indicating that the material's energy reversibility remains excellent under high current density and long-term cycling conditions, with almost no irreversible energy loss during charge and discharge. Therefore, the battery assembled using the lignin-derived high-energy-density cathode material described in this invention has excellent structural stability, high reversibility, and long cycle life.

[0042] Example 2 A method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase includes the following steps: (1) 4g of lignin, 1.212g of ferric nitrate nonahydrate (3mmol) and 0.863g of zinc sulfate heptahydrate (3mmol) were added to 150mL of deionized water. After stirring at room temperature (25℃) for 24h, the mixture was allowed to stand for 16h to age. The mixture was then filtered through a 0.45μm aqueous filter membrane and dried to obtain Fe-coordinated lignin.

[0043] (2) Disperse 1g of Fe-coordinated lignin obtained in step (1) with 4g of urea and 2g of ammonium chloride into 50mL of deionized water, stir for 30min, and freeze dry at -55℃ for two days to obtain brown powder, i.e. Fe-coordinated lignin precursor.

[0044] (3) The brown powder obtained in step (2) was continuously calcined in a tube furnace under nitrogen protection in two stages. The temperature of the first stage was 550℃ and held for 1 hour. The temperature of the second stage was 800℃. The heating rate of both stages was 4℃ / min. The temperature of the second stage was held for 1 hour to obtain black product A, namely Fe coordinated carbon nanomaterial precursor.

[0045] (4) The black product A obtained in step (3) was thoroughly ground with potassium bicarbonate at a mass ratio of 1:1, and then calcined again in a tube furnace under nitrogen protection. The calcination temperature was 800℃, the holding time was 1h, and the heating rate was 5℃ / min. When the tube furnace cooled to room temperature, the product was repeatedly washed with 1mol / L hydrochloric acid and deionized water. When no more bubbles were generated during the washing process and the pH of the solution was neutral, it was filtered with a 0.45μm aqueous filter membrane and dried in an oven at 50℃ for 12h to obtain Fe-coordinated urchin-like lignin carbon mesophase (Fe-NC).

[0046] (5) The 100 mg Fe-coordinated sea urchin-like lignin carbon mesophase obtained in step (4) was mixed with KMnO4 (1 mmol), 0.0338 g MnSO4·H2O (0.2 mmol), and 0.044 g CaCl2 (0.4 mmol) in 70 ml of deionized water and stirred for 30 min. The mixture was then transferred to a Teflon high-pressure reactor and kept at 145 °C for 8 h. After the reactor cooled to room temperature, it was repeatedly washed with deionized water and dried overnight at 60 °C in a vacuum drying oven to obtain the high energy density cathode material (Ca-MnO4) derived from the sea urchin-like lignin carbon mesophase. x @Fe-NC). The molar ratio of manganese sulfate, calcium chloride, and potassium permanganate is approximately 1:2:5.

[0047] The Ca-MnO prepared in this embodiment x @Fe-NC materials assembled a zinc-ion supercapacitor coin cell according to "Application Example 1" and tested its energy storage performance using an electrochemical workstation. This coin cell exhibited a specific capacitance of 238.3 F / g at a current density of 1 A / g, corresponding to an energy density of 145.9 Wh / kg.

[0048] Example 3 A method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase includes the following steps: (1) 4g of lignin, 1.212g of ferric nitrate nonahydrate (3mmol) and 0.863g of zinc sulfate heptahydrate (3mmol) were added to 80mL of deionized water. After stirring at room temperature (25℃) for 24h, the mixture was allowed to stand for 10h to age. The mixture was then filtered through a 0.45μm aqueous filter membrane and dried to obtain Fe-coordinated lignin.

[0049] (2) Disperse 1g of Fe-coordinated lignin obtained in step (1) with 6g of urea and 4g of ammonium chloride into 50mL of deionized water, stir for 30min, freeze dry at -55℃ for 1 day to obtain brown powder, i.e. Fe-coordinated lignin precursor.

[0050] (3) The brown powder obtained in step (2) was continuously calcined in a tube furnace under nitrogen protection in two stages. The temperature of the first stage was 550℃ and held for 1 hour. The temperature of the second stage was 800℃. The heating rate of both stages was 5℃ / min. The temperature of the second stage was held for 1 hour to obtain black product A, namely Fe coordinated carbon nanomaterial precursor.

[0051] (4) The black product A obtained in step (3) was thoroughly ground with potassium bicarbonate at a mass ratio of 1:2, and then calcined again in a tube furnace under nitrogen protection. The calcination temperature was 800℃, the holding time was 1h, and the heating rate was 5℃ / min. When the tube furnace cooled to room temperature, the product was repeatedly washed with 1mol / L hydrochloric acid and deionized water. When no more bubbles were generated during the washing process and the pH of the solution was neutral, it was filtered with a 0.45μm aqueous filter membrane and dried in an oven at 50℃ for 12h to obtain Fe-coordinated sea urchin-like lignin carbon mesophase (Fe-NC).

[0052] (5) The 50 mg Fe-coordinated carbon nanomaterial obtained in step (4) was mixed with 0.1896 g KMnO4 (1.2 mmol), 0.0338 g MnSO4·H2O (0.22 mmol), and 0.044 g CaCl2 (0.4 mmol) in 40 ml of deionized water and stirred for 30 min. The mixture was then transferred to a Teflon high-pressure reactor and kept at 135 °C for 12 h. After the reactor cooled to room temperature, it was repeatedly washed with deionized water and dried overnight at 60 °C in a vacuum drying oven to obtain a high-energy-density cathode material (Ca-MnO4) derived from a sea urchin-like lignin carbon mesophase. x @Fe-NC).

[0053] The Ca-MnO prepared in this embodiment x @Fe-NC materials assembled a zinc-ion supercapacitor coin cell using "Application Example 1" and tested its energy storage performance using an electrochemical workstation. This coin cell exhibited a specific capacitance of 250.5 F / g at a current density of 1 A / g, corresponding to an energy density of 153.4 Wh / kg.

[0054] In summary, the Ca-MnO prepared in the above embodiments... x The zinc-ion supercapacitor coin cell assembled with @Fe-NC material has an energy density in the range of 145~200 Wh / kg at a current density of 1A / g.

[0055] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the second calcination in step (4) is not performed, and the black product A obtained in step (3) is directly used in step (5).

[0056] The Ca-MnO prepared in this embodiment x @Fe-NC materials assembled a zinc-ion supercapacitor coin cell according to "Application Example 1" and tested its energy storage performance using an electrochemical workstation. This coin cell exhibited a specific capacitance of only 104 F / g at a current density of 1 A / g, corresponding to an energy density of only 63.7 Wh / kg.

[0057] Comparative Example 2 The difference between this comparative example and Example 1 is that CaCl2 is not added in step (5).

[0058] The MnO prepared in this embodiment x @Fe-NC materials assembled a zinc-ion supercapacitor coin cell according to "Application Example 1" and tested its energy storage performance using an electrochemical workstation. This coin cell exhibited a specific capacitance of only 185 F / g at a current density of 1 A / g, corresponding to an energy density of only 102.7 Wh / kg.

[0059] Comparative Example 3 The difference between this comparative example and Example 1 is that zinc sulfate heptahydrate is not added in step (1).

[0060] The Ca-MnO prepared in this embodiment x @Fe-NC materials assembled a zinc-ion supercapacitor coin cell using "Application Example 1" and tested its energy storage performance using an electrochemical workstation. This coin cell exhibits a specific capacitance of 216 F / g at a current density of 1 A / g, corresponding to an energy density of 132.3 Wh / kg.

[0061] Application Example 2 The difference between this application example and Application Example 1 is that: Ca-MnO x The mass ratio of Fe-NC, conductive agent (carbon black), and binder (PVDF) was 8:1:1. After the coin cell assembly was completed and allowed to stand overnight for stabilization, its electrochemical performance was tested using an electrochemical workstation. The coin cell provided a specific capacitance of 295.2 F / g at a current density of 1 A / g, corresponding to an energy density of 180.8 Wh / kg.

[0062] Application Example 3 The difference between this application example and Application Example 1 is that the electrolyte is 2M ZnSO4, while the other steps are the same. After the coin cell was assembled and allowed to stand overnight to stabilize, its electrochemical performance was tested using an electrochemical workstation. This coin cell provided a specific capacitance of 256.8 F / g at a current density of 1 A / g, corresponding to an energy density of 157.3 Wh / kg.

[0063] This invention utilizes Fe 3+ and Zn 2+The coordination and co-precipitation with lignin spontaneously guides lignin molecules to form a two-dimensional precursor, completely avoiding the use of traditional hard or soft templates, simplifying the process and reducing costs. Furthermore, this invention successfully constructs a sea urchin-like structure in carbon materials through the synergistic effects of Zn's pore-forming effect, ammonium chloride's gas activation, and potassium bicarbonate's secondary activation. This structure effectively inhibits the stacking and aggregation of carbon nanosheets, increases the specific surface area of ​​the material, and provides superior channels and sites for ion transport and charge storage, while simultaneously enhancing the material's electrical conductivity during secondary calcination. In addition, this invention successfully introduces highly conductive Fe-N into the carbon framework. x Sites, and on this basis, loaded with Ca 2+ Intercalated manganese-based oxides. Fe-N x The site itself possesses excellent catalytic activity and conductivity, while Ca... 2+ The intercalation can effectively expand the interlayer spacing of manganese-based oxides and improve the ion diffusion rate. The two have a strong synergistic effect with the urchin-like carbon substrate, which greatly improves the performance of the composite material in the electrochemical application of supercapacitors.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase, characterized in that, Includes the following steps: (1) Add lignin, ferric nitrate and zinc sulfate to water, stir evenly and let stand for aging, then filter to obtain filter residue, i.e. Fe coordinated lignin; (2) The filter residue obtained in step (1) is dispersed together with urea and ammonium chloride in solvent water, stirred evenly, and then freeze-dried to obtain a brown powder; (3) The brown powder is continuously calcined in a tube furnace under nitrogen protection in two stages to obtain Fe-coordinated carbon nanomaterial precursor; (4) After the Fe-coordinated carbon material precursor obtained in step (3) is thoroughly mixed and ground with potassium bicarbonate, it is calcined in a tube furnace under nitrogen protection. When the black product obtained is washed to neutral, it is filtered by an aqueous filter membrane and dried to obtain the Fe-coordinated sea urchin-like lignin carbon mesophase. (5) The Fe-coordinated sea urchin-like lignin carbon mesophase obtained in step (4) is dispersed together with manganese sulfate, potassium permanganate and calcium chloride in solvent water and stirred evenly, and then a hydrothermal reaction is carried out; after the hydrothermal reaction is completed, the reaction system is filtered, and the resulting filter residue is washed with water and dried to obtain a high energy density cathode material derived from the sea urchin-like lignin carbon mesophase.

2. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (1), the ratio between the mass of lignin and the volume of water is 1g:(10~40)mL, and the concentrations of ferric nitrate and zinc sulfate in the water are both in the range of 15~45mmol / L.

3. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (1), the time for standing and aging after stirring is 8~20h; the filtration uses an aqueous filter membrane with a pore size of 0.22~0.65μm.

4. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (2), the mass ratio of filter residue to urea and ammonium chloride is 1:(4~6):(2~4); the freeze-drying temperature is -60~-50℃, and the drying time is 12~48h.

5. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (3), the first stage of the continuous two-stage calcination is calcined at 500~600℃ and held for 0.5~1.5h; the second stage is calcined at 750~850℃ and held for 0.5~1.5h.

6. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (4), the mass ratio of Fe-coordinated carbon nanomaterial precursor to potassium bicarbonate is 1:(2~4), and the temperature is raised to calcination temperature of 750~850℃ at a heating rate of 3~8℃ / min, and the holding time is 0.5~1.5h; the concentration of hydrochloric acid used for washing is 0.5~2mol / L; and the pore size of the aqueous filter membrane is 0.20~0.65μm.

7. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, In step (5), the concentration range of Fe-coordinated urchin-like lignin carbon mesophase dispersed in the solvent water is 1~3 g / L, the concentration range of manganese sulfate in the solvent water is 3~6 mmol / L, and the molar ratio of manganese sulfate, calcium chloride and potassium permanganate is 1:(1.5~2.5):(4~7).

8. The method for preparing a high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase according to claim 1, characterized in that, The hydrothermal reaction temperature is 130~150℃, and the reaction time is 8~12h.

9. A high-energy-density cathode material derived from a sea urchin-like lignin-carbon mesophase prepared by any one of claims 1 to 8.

10. The application of the high-energy-density cathode material derived from the sea urchin-like lignin-carbon mesophase of claim 9 in a zinc-ion supercapacitor, characterized in that, The high-energy-density positive electrode material is mixed with a conductive agent and a binder in a solvent and then uniformly coated onto the surface of a metal substrate as the positive electrode. A zinc sheet is used as the negative electrode, and a mixed solution of zinc sulfate and manganese sulfate is used as the electrolyte to assemble a zinc ion supercapacitor.

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