Cellulose-based gel electrolyte and preparation method thereof
By preparing a copper-coated cellulose-based gel electrolyte, the problems of flammability and volatility of liquid electrolytes and poor wettability of solid electrolytes in lithium batteries were solved, achieving high ionic conductivity, wide electrochemical window and high lithium-ion transport number.
Patent Information
- Application Number
- CN202511213283.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2026-01-09
Smart Images
Figure HDA0005569542440000011 
Figure HDA0005569542440000012 
Figure HDA0005569542440000021
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of gel electrolytes, specifically relating to a cellulose-based gel electrolyte and its preparation method. Background Technology
[0002] Lithium batteries have become the main choice for energy storage systems due to their advantages such as long lifespan, high safety and reliability, high energy density, and low self-discharge rate.
[0003] A typical lithium-ion battery consists of four parts: positive electrode material, negative electrode material, electrolyte, and separator. The electrolyte in a lithium-ion battery is the carrier of ions and can be classified into liquid electrolytes, solid electrolytes, and gel electrolytes based on their different states. Liquid electrolytes in lithium-ion batteries generally consist of organic solvents, inorganic salts, and additives. Currently, the most common inorganic salt in liquid electrolytes, i.e., lithium hexafluorophosphate (LiPF6), is the lithium salt. The organic solvents are mainly carbonate compounds. LiPF6-carbonate electrolytes have disadvantages such as flammability, volatility, and lack of self-supporting capacity, requiring an additional separator. Most solid electrolytes, unlike liquid electrolytes, cannot wet the electrode surface, resulting in interfacial porosity and high impedance.
[0004] Cellulose and its derivatives possess excellent electrochemical stability, mechanical properties, low cost, and wide availability, making them ideal materials for lithium-ion battery electrolytes. However, cellulose-based gel electrolytes also have some drawbacks, including low ionic conductivity and poor interfacial properties with electrode materials. Therefore, designing cellulose-based gel electrolytes with high ionic conductivity, a wide electrochemical window, high lithium transference number, and stable cycling performance is of great significance for the development and utilization of natural polymer materials in lithium-ion batteries. Summary of the Invention
[0005] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a cellulose-based gel electrolyte and its preparation method. The present invention involves copper-coordinated cellulose of different types, using a phosphate-based ionic liquid as the solvent for the gel electrolyte, dissolving a lithium salt in the ionic liquid and mixing them uniformly, and then dissolving the copper-coordinated cellulose in the mixed solution of the lithium salt and the ionic liquid to prepare the cellulose-based gel electrolyte. This gel electrolyte is used in lithium batteries, particularly lithium-ion batteries.
[0006] The objective of this invention is achieved through the following technical solution:
[0007] A method for preparing a cellulose-based gel electrolyte includes the following steps:
[0008] 1) Preparation of solutions containing tetrahydroxycuprate complex ions, i.e., tetrahydroxycuprate solutions;
[0009] 2) Cellulose was treated with tetrahydroxycubic acid salt solution, centrifuged, the supernatant was removed, the treatment was repeated, and the cells were freeze-dried to obtain copper-coordinated cellulose.
[0010] 3) Mix lithium salt with phosphate-based ionic liquid to obtain a mixture; dissolve copper-coordinated cellulose in the mixture, place it in a battery, and let it stand to obtain a cellulose-based gel electrolyte.
[0011] Tetrahydroxycuprate solution is prepared by dissolving copper hydroxide or copper oxide in a strong alkaline solution to obtain tetrahydroxycuprate solution; or by stirring copper with a strong alkaline solution in air for 15-30 days to obtain tetrahydroxycuprate solution.
[0012] The concentration of tetrahydroxycuprate in the tetrahydroxycuprate solution is 0.12–1.1 mol / L; the concentration of hydroxyl groups provided by a strong base in the solution is in excess, for example: OH. - The concentration is greater than 4 times the concentration of copper ions.
[0013] The strong alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.
[0014] When tetrahydroxycubic acid salt solution is prepared by the following method: copper is mixed with a strong alkaline solution and stirred at room temperature for 15-30 days to obtain tetrahydroxycubic acid salt solution.
[0015] The strong alkali solution contains 2-30 wt% strong alkali, and the mass-to-volume ratio of copper to the strong alkali solution is 1-2 g: 30-80 mL.
[0016] The mass-to-volume ratio of cellulose to tetrahydroxycubic acid salt solution in step 2) is (1.6–2.4) g : (80–130) mL.
[0017] The cellulose is used in the form of a solution or suspension, wherein the mass fraction of the cellulose solution or suspension is 1 to 3 wt%.
[0018] In step 2), the cellulose includes one or more of unmodified cellulose and modified cellulose; the modified cellulose is one or more of nanocellulose oxidized by 2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO), sulfonated nanocellulose and hydroxyethyl cellulose.
[0019] The unmodified cellulose includes conventional cellulose and nanocellulose, such as homogeneous nanocellulose (5-50 nm in diameter). Conventional cellulose has a diameter greater than 100 nm.
[0020] The repeated treatment is performed 0 to 3 times, preferably 1, 2, or 3 times. The repeated treatment refers to treating the precipitate after removing the supernatant with a tetrahydroxycubic acid salt solution, centrifuging, and then removing the supernatant again, repeating this operation.
[0021] The treatment time for cellulose with tetrahydroxycubic acid salt solution is 2 to 5 hours.
[0022] During the repeated treatment process, the cellulose was treated with tetrahydroxycubic acid salt solution for 2 to 5 hours each time.
[0023] After the final treatment and removal of the supernatant, the precipitate is washed with water to remove the strong alkali, and then freeze-dried.
[0024] In step 3), the mass ratio of the lithium salt, the phosphate-based ionic liquid, and the copper-coordinated cellulose is 1-5:5-50:1-5, or it can be 0.1-0.5:0.5-5:0.1-0.5.
[0025] The phosphate-based ionic liquid is 1-ethyl-3-methylimidazolium methylphosphonate salt [C2MIM][(MeO)RPO2], where R is H, Me, or MeO;
[0026] structure: R is H, Me, or MeO.
[0027] The settling time is 25 to 35 minutes.
[0028] In step 3), the copper-coordinated cellulose dissolves in the ionic liquid at a temperature of 50-150℃ for 10-40 minutes.
[0029] In step 3), lithium salts include LiPF6, LiFSI, LiBF4, and LiTFSI, etc.
[0030] The present invention has the following advantages and beneficial effects:
[0031] This invention prepares a cellulose-based gel electrolyte by uniformly dispersing cellulose in a solution containing tetrahydroxycopper complex ions (i.e., a copper-containing solution), uniformly coordinating copper elements between the fiber molecular chains, dissolving lithium salt in an ionic liquid and mixing them uniformly, and then dissolving the copper-coordinated cellulose in the mixed solution of lithium salt and cellulose. After dissolution and standing, the solution is allowed to stand. Cellulose fibers are rich in oxygen-containing polar groups, providing numerous coordination sites for copper ions. Coordination with copper increases the spacing between fibers, making it easier for ions in the solution to enter the cellulose chains. The method of this invention is simple, and the prepared cellulose-based gel electrolyte exhibits high ionic conductivity, a wide electrochemical window, and a high lithium-ion transference number. Attached Figure Description
[0032] Figure 1 The image shows the appearance of the cellulose-based gel electrolyte prepared in Example 1.
[0033] Figure 2 The electrochemical window of the cellulose-based gel electrolyte prepared in Example 3;
[0034] Figure 3 The lithium-ion transport number of the cellulose-based gel electrolyte prepared in Example 4 is shown in (a) as the chronoamperometry (CA) test curve, and (b) as the lithium-ion transport number calculated by the formula in the left figure. The first measurement of the electrolyte is shown in the left figure, and the second measurement is shown in the right figure. After the current is balanced under a voltage control, the resistance is measured again, and the ion transport efficiency is measured using the formula.
[0035] Figure 4 The images show the EIS and Arrhenius spectra of the cellulose-based gel electrolyte prepared in Example 7; (a) is the EIS spectrum of the prepared cellulose-based gel electrolyte, and (b) is the Arrhenius spectra of the prepared cellulose-based gel electrolyte. Detailed Implementation
[0036] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available products.
[0037] In the examples, the phosphate-based ionic liquid is
[0038] In this embodiment, the coin cell structure consists of a positive electrode, a negative electrode, and an intermediate spacer. The positive electrode material is lithium iron phosphate, and the negative electrode material is lithium foil. The glove box contains less than 0.01 ppm of water and less than 0.1 ppm of oxygen.
[0039] Example 1
[0040] A method for preparing a cellulose-based gel electrolyte includes the following steps:
[0041] 1) Preparation of NaOH-Cu solution: Weigh 7g of copper wire and place it in 350mL of 30% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution or remove the solution; the filtrate is the desired solution.
[0042] 2) Preparation of copper-coordinated cellulose: Weigh 90g of 2% homogenized nanocellulose solution, add 80mL of NaOH-Cu solution, stir evenly at room temperature for 3h, centrifuge to remove the supernatant, add 80mL of NaOH-Cu solution again, centrifuge again to remove the supernatant, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h (pre-freeze at -20℃ to solidify), freeze-dry (dry in a freeze dryer at -40℃ and 10MPa for 24h) to obtain blue powder;
[0043] 3) Preparation of cellulose-based gel electrolytes:
[0044] 0.16 g of LiTFSI was dissolved in 2 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.2 g of copper-coordinated cellulose sample was added to the solution, and the mixture was reacted at 100 °C for 30 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, ensuring a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting cell was allowed to stand for 30 min to obtain the desired gel electrolyte.
[0045] Figure 1 The image shows the appearance of the cellulose-based gel electrolyte prepared in Example 1.
[0046] The gel electrolyte prepared in this embodiment has an ionic conductivity of 1.19 mS / cm at room temperature. -1 The electrochemical window reaches 3.10V, the lithium-ion transference number is 0.71, and the performance at 0.1mA cm⁻¹ is [not specified]. -2 At the current density, the charge-discharge cycle time reaches 450 hours.
[0047] Example 2
[0048] A method for preparing a cellulose-based gel electrolyte includes the following steps:
[0049] 1) Preparation of NaOH-Cu solution: Weigh 9g of copper wire and place it in 400mL of 20% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, dark blue color. Filter the solution or remove the solution; the filtrate is the desired solution.
[0050] 2) Preparation of copper-coordinated cellulose: Weigh 90g of 2% 2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO) oxidized nanocellulose solution, add 80mL of NaOH-Cu solution, stir evenly at room temperature for 3h, centrifuge to remove the supernatant, add 80mL of NaOH-Cu solution again and stir for 3h, centrifuge again to remove the supernatant, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze dry to obtain blue powder;
[0051] 3) Preparation of cellulose-based gel electrolyte: 0.14 g of LiPF6 was dissolved in 1 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.105 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 100 °C for 10 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 2.11 mS / cm at room temperature. -1 The electrochemical window reaches 3.10V, the lithium-ion transference number is 0.65, and the performance at 0.1 mA / cm² is [not specified]. -2 At current density, the charge-discharge cycle time reaches 360 hours.
[0052] Example 3
[0053] A method for preparing a cellulose-based gel electrolyte includes the following steps and process conditions:
[0054] 1) Preparation of NaOH-Cu solution: Weigh 7g of copper wire and place it in 500mL of 20% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution; the filtrate is the desired solution.
[0055] 2) Preparation of copper-coordinated cellulose: Weigh 105g of 2% sulfonated nanocellulose solution, add 95mL of NaOH-Cu solution, stir evenly at room temperature for 3h, centrifuge to remove the supernatant, add 95mL of NaOH-Cu solution again and stir for 2h, centrifuge again to remove the supernatant, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze dry to obtain blue powder;
[0056] 3) Preparation of cellulose-based gel electrolyte: 0.3 g of LiBF4 was dissolved in 3 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.1 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 100 °C for 20 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 1.40 mS / cm at room temperature. -1 The electrochemical window reaches 4.44V, the lithium-ion transference number is 0.70, and the performance at 0.1 mA / cm² is [not specified]. -2 At current density, the charge-discharge cycle time reaches 300 hours.
[0057] Figure 2 The electrochemical window of the cellulose-based gel electrolyte prepared in Example 3 is 4.44 V, which is a relatively wide electrochemical window.
[0058] Example 4
[0059] A method for preparing a cellulose-based gel electrolyte includes the following steps:
[0060] 1) Preparation of NaOH-Cu solution: Weigh 9g of copper wire and place it in 400mL of 20% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution; the filtrate is the desired solution.
[0061] 2) Preparation of copper-coordinated cellulose: Weigh 105g of 2% homogenized nanocellulose solution, add 105mL of NaOH-Cu solution, stir evenly at room temperature for 3h, centrifuge to remove the supernatant, add 105mL of NaOH-Cu solution again and stir for 4h, centrifuge again to remove the supernatant, repeat once more, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze dry to obtain blue powder;
[0062] 3) Preparation of cellulose-based gel electrolyte: 0.1 g of LiTFSI was dissolved in 3 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.3 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 120 °C for 30 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 1.33 mS / cm at room temperature. -1 The electrochemical window reaches 4.45V, the lithium-ion transference number is 0.81, and the performance at 0.1 mA cm⁻¹ is [not specified]. -2 At the current density, the charge-discharge cycle time reaches 420 hours.
[0063] Figure 3 The lithium-ion transport number of the cellulose-based gel electrolyte prepared in Example 4 is shown in (a) and (b) is the chronoamperometry (CA) test curve. The lithium-ion transport number is calculated using the formula in the left figure, and the lithium-ion transport number is 0.81. First measurement: the electrolyte (or battery) was measured for the first time. Second measurement: after current equilibrium was achieved under a controlled voltage, the resistance was measured again, and the ion transport efficiency was measured using the formula.
[0064] Example 5
[0065] A method for preparing a cellulose-based gel electrolyte includes the following steps:
[0066] 1) Preparation of NaOH-Cu solution: Weigh 8g of copper wire and place it in 500mL of 30% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution; the filtrate is the desired solution.
[0067] 2) Preparation of copper-coordinated cellulose: Weigh 85g of 2% hydroxyethyl cellulose solution, add 120mL of NaOH-Cu solution, stir evenly at room temperature for 4h, centrifuge to remove the supernatant, add 110mL of NaOH-Cu solution again, centrifuge again to remove the supernatant, repeat once more, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze dry to obtain blue powder;
[0068] 3) Preparation of cellulose-based gel electrolyte: 0.15 g of LiFSI was dissolved in 2 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.2 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 105 °C for 10 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 1.85 mS / cm at room temperature. -1 The electrochemical window reaches 4.80V, the lithium-ion transference number is 0.56, and the performance at 0.1 mA / cm² is [not specified]. -2 At the current density, the charge-discharge cycle time reaches 410 hours.
[0069] Example 6
[0070] A method for preparing a cellulose-based gel electrolyte includes the following steps and process conditions:
[0071] 1) Preparation of NaOH-Cu solution: Weigh 9g of copper wire and place it in 300mL of 20% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution; the filtrate is the desired solution.
[0072] 2) Preparation of copper-coordinated cellulose: Weigh 110g of 2% sulfonated nanocellulose solution, add 105mL of NaOH-Cu solution, stir evenly at room temperature for 3h, centrifuge to remove the supernatant, add 100mL of NaOH-Cu solution again, stir evenly at room temperature for 4h, centrifuge again to remove the supernatant, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze-dry to obtain blue powder;
[0073] 3) Preparation of cellulose-based gel electrolyte: 0.16 g of LiPF6 was dissolved in 2 g of phosphate-based ionic liquid and stirred until the solution was homogeneous and transparent. 0.4 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 110 °C for 20 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 1.50 mS / cm at room temperature. -1 The electrochemical window can reach 4.30V, the lithium-ion transference number is 0.77, and the charge-discharge cycle time reaches 350h at a current density of 0.1mAcm-2.
[0074] Example 7
[0075] A method for preparing a cellulose-based gel electrolyte includes the following steps and process conditions:
[0076] 1) Preparation of NaOH-Cu solution: Weigh 9g of copper wire and place it in 400mL of 10% sodium hydroxide solution. Stir at 25℃ for 20 days until the solution is a uniform, transparent, deep blue color. Filter the solution; the filtrate is the desired solution.
[0077] 2) Preparation of copper-coordinated cellulose: Weigh 100g of 2% cellulose solution (cotton cellulose dispersed in water), add 100mL of NaOH-Cu solution, stir evenly for 3h at room temperature, centrifuge to remove the supernatant, add 95mL of NaOH-Cu solution again, stir evenly for 3h at room temperature, centrifuge again to remove the supernatant, wash the sample with deionized water several times to remove NaOH, pre-freeze for 12h, freeze-dry to obtain blue powder;
[0078] 3) Preparation of cellulose-based gel electrolyte: 0.34 g of LiBF4 was dissolved in 5 g of the prepared phosphate-based ionic liquid, and the mixture was stirred until the solution was homogeneous and transparent. 0.4 g of copper-coordinated cellulose sample was added to the solution, and the reaction was carried out at 100 °C for 30 min until the copper-coordinated cellulose was completely dissolved. The solution was then directly added to a coin cell. All the above steps were performed in a glove box, with a water content of less than 0.01 ppm and an oxygen content of less than 0.1 ppm. The resulting battery was allowed to stand for 30 min to obtain the desired gel electrolyte. The gel electrolyte prepared in this embodiment has an ionic conductivity of 2.05 mS / cm at room temperature. -1 The ionic conductivity at a high temperature of 65℃ is 3.34 mS / cm. -1 At -15℃, the ionic conductivity is 1.57 mS / cm. -1 The electrochemical window reaches 4.80V, the lithium-ion transference number is 0.65, and the charge-discharge cycle time reaches 400h at a current density of 0.1mAcm-2.
[0079] Figure 4 The images show the EIS and Arrhenius spectra of the cellulose-based gel electrolyte prepared in Example 7; (a) is the EIS spectrum of the prepared cellulose-based gel electrolyte; and (b) is the Arrhenius spectra of the prepared cellulose-based gel electrolyte. Figure 4 The value of b reflects that the cellulose-based gel electrolyte requires a lower activation energy for ion migration, making it easier for ions to migrate.
Claims
1. A method for preparing a cellulose-based gel electrolyte, characterized in that: Includes the following steps: 1) Preparation of solutions containing tetrahydroxycuprate complex ions, i.e., tetrahydroxycuprate solutions; 2) Cellulose was treated with tetrahydroxycubic acid salt solution, centrifuged, the supernatant was removed, the treatment was repeated, and the cells were freeze-dried to obtain copper-coordinated cellulose. 3) Mix lithium salt with phosphate-based ionic liquid to obtain a mixture; dissolve copper-coordinated cellulose in the mixture, place it in a battery, and let it stand to obtain a cellulose-based gel electrolyte; In step 3), the mass ratio of the lithium salt, the phosphate-based ionic liquid, and the copper-coordinated cellulose is 1-5:5-50:1-5. The phosphate-based ionic liquid is 1-ethyl-3-methylimidazolium methylphosphonate salt [C2MIM][(MeO)RPO2], where R is H, Me, or MeO.
2. The method for preparing the cellulose-based gel electrolyte according to claim 1, characterized in that: The concentration of tetrahydroxycuprate in the solution is 0.12–1.1 mol / L; the concentration of hydroxyl groups provided by the strong base in the solution is greater than 4 times the concentration of copper ions; The mass-to-volume ratio of cellulose to tetrahydroxycubic acid salt solution in step 2) is (1.6–2.4) g : (80–130) mL.
3. The method for preparing the cellulose-based gel electrolyte according to claim 1, characterized in that: The repeated treatment is performed 0 to 3 times; the repeated treatment refers to treating the precipitate after removing the supernatant with tetrahydroxycubic acid salt solution, centrifuging, removing the supernatant again, and repeating this operation. During the repeated treatment process, the cellulose was treated with tetrahydroxycubic acid salt solution for 2 to 5 hours each time.
4. The method for preparing the cellulose-based gel electrolyte according to claim 1, characterized in that: The treatment time for cellulose with tetrahydroxycubic acid salt solution is 2–5 hours; In step 3), the copper-coordinated cellulose dissolves in the ionic liquid at a temperature of 50-150℃ for 10-40 minutes.
5. The method for preparing the cellulose-based gel electrolyte according to claim 1, characterized in that: Tetrahydroxycuprate solution is prepared by dissolving copper hydroxide or copper oxide in a strong alkaline solution to obtain tetrahydroxycuprate solution; or by stirring copper with a strong alkaline solution in air for 15-30 days to obtain tetrahydroxycuprate solution.
6. The method for preparing the cellulose-based gel electrolyte according to claim 5, characterized in that: The strong alkali solution is a sodium hydroxide solution or a potassium hydroxide solution; the mass fraction of the strong alkali in the strong alkali solution is 2-30 wt%.
7. The method for preparing the cellulose-based gel electrolyte according to claim 5, characterized in that: When tetrahydroxycuprate solution is prepared by the following method: copper is mixed with a strong alkaline solution and stirred at room temperature for 15-30 days to obtain tetrahydroxycuprate solution; The strong alkali solution contains 2-30 wt% strong alkali, and the mass-to-volume ratio of copper to the strong alkali solution is 1-2 g: 30-80 mL.
8. The method for preparing the cellulose-based gel electrolyte according to claim 1, characterized in that: The cellulose is used in the form of a solution or suspension, wherein the cellulose solution or suspension has a mass fraction of 1 to 3 wt%. In step 2), the cellulose includes one or more of unmodified cellulose and modified cellulose; the modified cellulose is one or more of 2,2,6,6-tetramethylpiperidine-1-oxygen radical oxidized nanocellulose, sulfonated nanocellulose and hydroxyethyl cellulose. The unmodified cellulose includes conventional cellulose and nanocellulose; The diameter of conventional cellulose is greater than 100 nm; The settling time mentioned in step 3) is 25–35 minutes; In step 3), the lithium salt includes one or more of LiPF6, LiFSI, LiBF4, and LiTFSI; Before freeze-drying in step 2), the precipitate needs to be washed with water.
9. A cellulose-based gel electrolyte obtained by the preparation method according to any one of claims 1 to 8.
10. The application of the cellulose-based gel electrolyte according to claim 9, characterized in that: The cellulose-based gel electrolyte is used in lithium batteries.