Preparation method and application of ternary thermoelectric gel electrolyte based on bacterial nanocellulose

Abstract

The present invention discloses a method for preparing a bacterial nanocellulose-based ternary thermoelectric gel electrolyte and its application. The method comprises the following steps: first, potassium ferrocyanide, potassium ferrocyanide, and lithium chloride are stirred and dissolved in deionized water to obtain an electrolyte solution; then, a bacterial nanocellulose hydrogel is immersed in the electrolyte solution for sufficient ion permeation; then, guanidine chloride is added and slowly stirred until uniform crystals form within the gel, thereby obtaining a nanocellulose-based ternary thermoelectric gel electrolyte. The ternary thermoelectric gel electrolyte prepared by the present invention exhibits high thermoelectric performance, excellent mechanical robustness, and antifreeze and anti-drying properties, and can be used to construct high-performance gel thermoelectric batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of gel thermoelectric electrolyte materials, and in particular to a preparation method of a ternary thermoelectric gel electrolyte based on bacterial nanocellulose and application thereof in a gel thermoelectric battery. Background Art

[0002] With the development of industry, human society has been constrained by energy crises and environmental problems for a long time. In the future, these traditional energy sources based on fossil fuels (including coal, oil, and natural gas) will face depletion. In addition, burning these fossil fuels will inevitably produce waste heat, as well as a variety of low-grade heat such as solar heat and human body heat. Therefore, thermoelectric materials that collect low-grade heat and convert it directly into electrical energy have received great attention. Traditional semiconductor thermoelectric generators rely on the electronic Seebeck effect and face challenges such as high cost, potential toxicity, and low Seebeck coefficient (usually less than 400 μV K). -1 ) and other limitations. In contrast, ionic thermoelectric generators not only have a higher thermoelectric coefficient (S i ), usually more than 1mV K -1 , and has a simpler structure and lower cost, which makes it have a wider application prospect.

[0003] Thermal batteries are a type of thermoelectric generator based on redox reactions, which directly convert ionic current into electronic current through redox reactions, thereby achieving continuous operation with higher energy density. However, aqueous thermal batteries are prone to electrolyte leakage and have safety issues. Gel thermal batteries provide a safe, simple and scalable direct thermal-electric energy conversion method by encapsulating liquid electrolytes in a gel matrix, and are expected to become the first choice for emerging thermoelectric generators. With their continuous working mode and adaptability to dynamic human-machine interfaces, gel thermal batteries show great application potential in self-powered wearable electronics, especially in the context of the rapidly expanding Internet of Things (IoT). However, the gel network affects the solvation structure and mass transfer of redox pairs, which usually leads to smaller S e The research team has focused on developing high-performance gel thermal batteries with excellent thermoelectric performance, high stability, and superior mechanical robustness to meet the growing demand for wearable flexible electronic devices. Summary of the Invention

[0004] In response to the above-mentioned problems currently existing in gel thermoelectric battery electrolytes, the present invention provides a method for preparing a ternary thermoelectric gel electrolyte based on bacterial nanocellulose. By adding a thermosensitive crystallizer GdmCl and a supporting electrolyte LiCl to a bacterial nanocellulose hydrogel containing a K3Fe(CN)6 and K4Fe(CN)6 redox couple, the electrolyte material has excellent thermoelectric properties, anti-drying properties, anti-freezing properties and outstanding mechanical properties.

[0005] To achieve the purpose, the present invention adopts the following technical solutions:

[0006] A method for preparing a ternary thermoelectric gel electrolyte based on bacterial nanocellulose comprises the following steps:

[0007] Step 1: Stir potassium ferrocyanide K3Fe(CN)6 and potassium ferrocyanide K4Fe(CN)6 in deionized water until dissolved to obtain solution A; then add lithium chloride LiCl to solution A and stir until completely dissolved to obtain solution B;

[0008] Step 2: Slice the bacterial nanocellulose NC hydrogel and soak it in the solution B prepared in step 1 to obtain a solution C containing the NC hydrogel;

[0009] Step 3: Add guanidine chloride GdmCl to solution C containing NC hydrogel obtained in step 2, slowly stir to form crystalline particles inside the hydrogel, then let it stand at room temperature for aging, take it out and use nitrogen to dry it until the surface moisture is removed to obtain a ternary thermoelectric gel electrolyte based on bacterial nanocellulose.

[0010] Preferably, in solution B, the concentrations of potassium ferrocyanide, potassium ferrocyanide and lithium chloride are 0.25-0.4 mol / L, 0.25-0.4 mol / L and 1-4 mol / L, respectively.

[0011] Preferably, in step 2, the soaking time is 16 to 24 hours to ensure that Fe(CN)6 3- ions, Fe(CN)6 4- ions and Li + Ions can fully penetrate into the interior of the hydrogel.

[0012] As a preference, the molar ratio of guanidine chloride to potassium ferrocyanide in step 3 is 1 to 3:0.4, within which the Fe(CN)6 4- Ions fully crystallize with guanidine chloride without affecting Fe(CN)6 3- ions. If the ratio is higher than 3:0.4, it will cause Fe(CN)6 3- The ions also crystallize, reducing the thermoelectric coefficient.

[0013] Preferably, in step 3, the slow stirring speed is 50-200 rpm and the stirring time is 1-2 hours to ensure that crystallization occurs inside the gel. If there is no stirring or the stirring speed is too high, crystallization will basically appear in the solution phase, resulting in poor crystallization effect inside the gel.

[0014] Preferably, in step 3, the static aging time is 12 to 24 hours, so that the crystal particles in the gel can fully grow and be evenly distributed in the gel.

[0015] Preferably, steps 1 to 3 are carried out in a dark environment to avoid the decomposition of potassium ferrocyanide K3Fe(CN)6 and potassium ferrocyanide K4Fe(CN)6 to produce toxic substances.

[0016] The bacterial nanocellulose-based ternary thermoelectric gel electrolyte prepared by the present invention can be used in gel thermal batteries.

[0017] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0018] The present invention prepares a thermoelectric electrolyte material with high thermoelectric performance, antifreeze and anti-drying properties and high mechanical strength by adding a thermosensitive crystallizer GdmCl and a supporting electrolyte LiCl to a bacterial nanocellulose hydrogel containing a redox couple of K3Fe(CN)6 and K4Fe(CN)6. GdmCl selectively induces K4Fe(CN)6 to form thermosensitive crystals, so that Fe(CN)6 3- / 4- The concentration difference increases, resulting in a higher thermoelectric coefficient. On this basis, LiCl is added as a supporting electrolyte, Li + The strong electronic attraction destroys the hydrogen bond network in the gel system, significantly reducing the minimum operating temperature of the electrolyte and expanding the operating temperature range. It also keeps the gel moist by capturing water molecules in the atmosphere, improving the overall stability. Therefore, the ternary thermoelectric gel electrolyte (denoted as Li-TCNT) prepared by the present invention has excellent thermoelectric performance, antifreeze and anti-drying properties, and excellent mechanical properties. This work helps to understand at the molecular level how the addition of LiCl and GdmCl affects the performance of thermal batteries and provides a simple and effective strategy for the development of high-performance gel thermal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the Fourier transform infrared spectrum of Li-TCNT prepared in Example 1 of the present invention;

[0020] Figure 2 The UV-visible spectra of K3Fe(CN)6 and K4Fe(CN)6 solutions after GdmCl was added respectively in Example 1 of the present invention;

[0021] Figure 3is the X-ray diffraction pattern of the Li-TCNT inner crystalline particles prepared in Example 1 of the present invention;

[0022] Figure 4 is a differential scanning calorimetry spectrum of Li-TCNT prepared in Example 1 of the present invention;

[0023] Figure 5 1 is the steady-state voltage-temperature-time curve of the Li-TCNT prepared in Example 1 of the present invention;

[0024] Figure 6 1 is the current-voltage-power curve of Li-TCNT prepared in Example 1 of the present invention under different temperature gradients;

[0025] Figure 7 is the cycling stability of the Li-TCNT prepared in Example 1 of the present invention at -10°C;

[0026] Figure 8 The TCNT obtained in Comparative Example 1 of the present invention ( Figure 8 (a)) and the Li-TCNT obtained in Example 1 ( Figure 8 (b) Optical photo comparison;

[0027] Figure 9 The weight loss curves of the TCNT obtained in Comparative Example 1 of the present invention and the Li-TCNT obtained in Example 1 are compared;

[0028] Figure 10 The TCNT obtained in Comparative Example 1 of the present invention ( Figure 10 (a)) and the Li-TCNT obtained in Example 1 ( Figure 10 (b)) Raman spectrum comparison;

[0029] Figure 11 1 is a comparison of stress-strain curves of TCNT obtained in Comparative Example 1 of the present invention and Li-TCNT obtained in Example 1;

[0030] Figure 12 The TCNT obtained in Comparative Example 1 of the present invention ( Figure 12 (a)) and the Li-TCNT obtained in Example 1 ( Figure 12 (b)) comparison of job stability;

[0031] Figure 13 The TCNT obtained in Comparative Example 1 of the present invention ( Figure 13 (a)) and the Li-TCNT obtained in Example 1 ( Figure 13 (b) Comparison of optical images at low temperatures. DETAILED DESCRIPTION

[0032] In order to further illustrate the present invention, the preparation method and application of a bacterial cellulose nanocellulose ternary thermoelectric gel electrolyte provided by the present invention are described in detail below in combination with the examples and illustrated in combination with the accompanying drawings, but they should not be understood as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] In this example, a ternary thermoelectric gel electrolyte based on bacterial nanocellulose was prepared according to the following steps, which were performed in a light-proof environment:

[0035] Step 1: Dissolve 2.633g of K3Fe(CN)6 in 20mL of deionized water, then add 2.947g of K4Fe(CN)6 and stir magnetically at room temperature for 20 minutes to completely dissolve it, obtaining Solution A. The solution is dark yellow. Add 2.543g of LiCl to Solution A and stir magnetically at room temperature for 20 minutes to completely dissolve the LiCl, obtaining Solution B.

[0036] Step 2: Cut the NC hydrogel into slices of 15 mm × 15 mm × 2 mm, remove the moisture from the surface of the slices, and soak them in solution B in step 1. Let them stand at room temperature for 24 hours to obtain solution C containing NC hydrogel.

[0037] Step 3: Add 5.732 g of GdmCl powder to solution C containing NC hydrogel obtained in step 2, slowly stir at 200 rpm for 1 hour, and then let it stand at room temperature for 12 hours to allow it to completely crystallize. Take it out and dry it with nitrogen until the surface moisture is removed to obtain Li-TCNT gel electrolyte.

[0038] Figure 1 The Fourier transform infrared spectrum of Li-TCNT obtained in this example is at 3400 cm -1 The strong absorption peak at 1160 cm -1 The absorption peak at 2040 cm is the asymmetric glucose COC stretching vibration. -1 and 2115cm -1 The absorption peaks at 4- and Fe(CN)6 3- C≡N stretching vibration at 3185cm -1 and 1580cm -1 The absorption peak at is attributed to the stretching vibrations of NH and CN, indicating the successful construction of the ternary gel electrolyte.

[0039] To verify the ability of guanidine chloride to induce crystallization, K3Fe(CN)6 and K4Fe(CN)6 solutions with a concentration of 0.4 mol / L were prepared, and then GdmCl was added thereto to different concentrations (1 M to 4 M). Figure 2 The UV-visible spectra of K3Fe(CN)6 and K4Fe(CN)6 solutions after adding GdmCl respectively. As can be seen from the figure, GdmCl selectively induces the crystallization of K4Fe(CN)6.

[0040] Figure 3 This is the X-ray diffraction pattern of the crystalline particles in Li-TCNT obtained in Example 1. Compared with the pure samples of K3Fe(CN)6, K4Fe(CN)6 and GdmCl, it can be seen that the crystalline particles are mainly composed of GdmCl and K4Fe(CN)6.

[0041] Figure 4 This is the differential scanning calorimetry spectrum of the Li-TCNT obtained in this example. As can be seen from the figure, the freezing point of Li-TCNT is -33.1°C, indicating that the minimum operating temperature of the thermal battery is widened to -33.1°C.

[0042] Figure 5 The steady-state voltage-temperature-time curve of Li-TCNT obtained in this example is shown in the figure. As shown in the figure, the thermoelectric coefficient of Li-TCNT reaches 3.42mVK -1 .

[0043] Figure 6 The current-voltage-power curves of the Li-TCNT obtained in this example under different temperature gradients are shown in the figure. As shown in the figure, when the temperature difference is 5, 10, 15 and 20 °C, the power density reaches 0.060, 0.254, 0.630 and 1.102 W m, respectively. -2 .

[0044] Figure 7 This is the cycling stability of the Li-TCNT obtained in this example at -10°C. It can be seen that the voltage remains stable after multiple cycles at low temperature, indicating good low-temperature stability.

[0045] Comparative Example 1

[0046] This comparative example prepared TCNT material according to the following steps, which were carried out in a light-proof environment:

[0047] Step 1: Dissolve 2.633 g of K3Fe(CN)6 in 20 mL of deionized water, then add 2.947 g of K4Fe(CN)6 and stir magnetically at room temperature for 20 minutes to completely dissolve it to obtain solution A. The color of the solution is dark yellow.

[0048] Step 2: Cut the NC hydrogel into slices of 15 mm × 15 mm × 2 mm, remove the moisture from the surface of the slices, and soak them in solution A in step 1. Let them stand at room temperature for 24 hours to obtain solution C containing NC hydrogel.

[0049] Step 3: Add 5.732 g of GdmCl powder to solution C containing NC hydrogel obtained in step 2, slowly stir at 200 rpm for 1 hour, and then let it stand at room temperature for 12 hours to allow it to completely crystallize, thereby obtaining a thermosensitive crystallized nanocellulose-based gel thermal battery, which is recorded as TCNT.

[0050] Figure 8 TCNT obtained in Comparative Example 1 ( Figure 8 (a)) and the Li-TCNT obtained in Example 1 ( Figure 8 Comparison of optical images (b). The TCNT surface appears dry, while the Li-TCNT surface appears wet, indicating that the Li-TCNT can spontaneously capture moisture from the air and exhibits anti-drying properties.

[0051] Figure 9 Comparison of the weight loss curves of the TCNT obtained in Comparative Example 1 and the Li-TCNT obtained in Example 1. After exposure to atmospheric conditions (25°C, RH ~40%) for 48 hours, the Li-TCNT had a mass retention rate of 55%, while the TCNT experienced significant drying, with a mass retention rate of only 20%.

[0052] Figure 10 TCNT obtained in Comparative Example 1 ( Figure 10 (a)) and the Li-TCNT obtained in Example 1 ( Figure 10 (b) Raman spectrum comparison. TCNTs primarily exhibit a large number of ordered tetrahedral hydrogen bonds, while the content of single-donor hydrogen bonds within Li-TCNTs increases significantly, indicating that the addition of LiCl disrupts the ordered hydrogen bond network.

[0053] Figure 11 Comparison of stress-strain curves of TCNT obtained in Comparative Example 1 and Li-TCNT obtained in Example 1. The toughness of TCNT is 302 kJ m -3 The toughness of Li-TCNT is 346 kJ m -3 , indicating the improved mechanical strength of Li-TCNT.

[0054] Figure 12 TCNT obtained in Comparative Example 1 ( Figure 12 (a)) and the Li-TCNT obtained in Example 1 ( Figure 12 (b) Comparison of the working stability of Li-TCNT. Li-TCNT continuously generates a stable voltage of approximately 83 mV for more than 1 hour at a temperature of 25.5 K, while TCNT has difficulty maintaining a stable voltage at a constant temperature.

[0055] Figure 13 TCNT obtained in Comparative Example 1 ( Figure 13 (a)) and the Li-TCNT obtained in Example 1 ( Figure 13(b) Comparison of optical images at low temperatures. Li-TCNT remains unfrozen at -20°C, while TCNT is completely frozen at -20°C.

[0056] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a ternary thermoelectric gel electrolyte based on bacterial nanocellulose, characterized in that: The following steps are involved: Step 1: Stir potassium ferrocyanide K3Fe(CN)6 and potassium ferrocyanide K4Fe(CN)6 in deionized water until dissolved to obtain solution A; then add lithium chloride LiCl to solution A and stir until completely dissolved to obtain solution B; Step 2: Slice the bacterial nanocellulose NC hydrogel and soak it in the solution B prepared in step 1 to obtain a solution C containing the NC hydrogel; Step 3: adding guanidine chloride (GdmCl) to solution C containing NC hydrogel obtained in step 2 at a molar ratio of guanidine chloride to potassium ferrocyanide of 1-3:0.4, stirring slowly to allow crystalline particles to appear inside the hydrogel, then allowing the solution to stand at room temperature for aging, taking it out and drying it with nitrogen until the surface moisture is removed, thereby obtaining a ternary thermoelectric gel electrolyte based on bacterial nanocellulose.

2. The preparation method according to claim 1, wherein: In solution B, the concentrations of potassium ferrocyanide, potassium ferrocyanide, and lithium chloride are 0.25~0.4 mol / L, 0.25~0.4 mol / L, and 1~4 mol / L, respectively.

3. The preparation method according to claim 1, wherein: In step 2, the soaking time is 16 to 24 hours to ensure that Fe(CN)6 3- ions, Fe(CN)6 4- ions and Li + Ions can fully penetrate into the interior of the hydrogel.

4. The preparation method according to claim 1, wherein: In step 3, the slow stirring speed is 50-200 rpm, and the stirring time is 1-2 h.

5. The preparation method according to claim 1, wherein: In step 3, the standing aging time is 12 to 24 hours to allow the crystalline particles in the gel to fully grow and be evenly distributed in the gel.

6. The preparation method according to claim 1, wherein: Steps 1 to 3 are performed in a light-proof environment.

7. A ternary thermoelectric gel electrolyte based on bacterial nanocellulose prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the bacterial nanocellulose-based ternary thermoelectric gel electrolyte according to claim 7 in a gel thermal battery.

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