Wide-temperature polyvinyl alcohol-based hydrogel electrolyte

Abstract

The invention discloses a wide-temperature polyvinyl alcohol-based hydrogel electrolyte, which takes polyvinyl alcohol (PVA) as a hydrogel skeleton, lithium chloride (LiCl) as an electrolyte salt and supramolecular liquid formed by dimethyl sulfoxide (DMSO) and water as a solvent. The core technology of the hydrogel electrolyte is characterized in that the working voltage of the hydrogel electrolyte is linearly increased along with the increase of the molar ratio of DMSO in a H2O-DMSO system, specifically, when the molar ratio of DMSO in the H2O-DMSO system is increased by 0.05, the working voltage of the electrolyte is correspondingly increased by 0.15 V. The linear regulation and control relation is effective only in the interval of the molar ratio of DMSO in the H2O-DMSO system being 0-0.15, and in the interval, the hydrogel electrolyte has a wide working temperature zone of-50 DEG C to 25 DEG C. According to the invention, accurate linear regulation and control of the working voltage of the hydrogel electrolyte are realized, and a wide working temperature zone is maintained.

Description

Technical Field

[0001] This invention relates to the field of wide-temperature electrochemical energy storage technology, specifically to a wide-temperature polyvinyl alcohol-based hydrogel electrolyte. Background Technology

[0002] With the rapid development of wearable electronics, flexible robots, and outdoor emergency energy storage devices, the demand for flexible, wide-temperature-range compatible power systems is becoming increasingly urgent. As a core component of energy storage devices, the performance of the electrolyte directly determines the device's operational stability and applicable scenarios. Hydrogel electrolytes, with their quasi-solid-state characteristics, possess both good flexibility and high ionic conductivity, making them a highly promising electrolyte material for flexible energy storage devices. Among numerous hydrogel electrolyte systems, polyvinyl alcohol (PVA)-based hydrogels have gained widespread research and application in both academia and industry due to their advantages such as non-toxic raw materials, low preparation cost, excellent film-forming properties, and good compatibility with electrode materials. However, existing PVA-based hydrogel electrolytes still face two major technical bottlenecks in practical wide-temperature-range applications: (1) Low working voltage and cannot be precisely linearly controlled: The working voltage of existing polyvinyl alcohol-based hydrogel electrolytes is basically around 1 V, resulting in low energy density. Moreover, it is difficult to precisely linearly control the voltage according to the voltage requirements of different energy storage devices, which further limits its adaptability in flexible energy storage devices of multiple specifications and scenarios.

[0003] (2) Low temperature performance degradation: In low temperature environments below 0 ℃, the migration of electrolyte ions inside the hydrogel becomes difficult, resulting in a sharp drop in ionic conductivity and significant degradation of its electrochemical performance, which cannot meet the working requirements of energy storage devices in low temperature scenarios.

[0004] Therefore, developing a polyvinyl alcohol-based hydrogel electrolyte that combines precise linear control of operating voltage with a wide operating temperature range has become a key direction for breaking through current technological bottlenecks and promoting the development of flexible energy storage devices towards a wider temperature range and more multifunctional applications. Summary of the Invention

[0005] The purpose of this invention is to provide a wide-temperature polyvinyl alcohol-based hydrogel electrolyte to solve the technical bottlenecks of insufficient stability over a wide temperature range and difficulty in precisely controlling the operating voltage of polyvinyl alcohol-based hydrogel electrolytes in the prior art. It provides a wide-temperature polyvinyl alcohol-based hydrogel electrolyte in which the operating voltage increases linearly with the molar ratio of DMSO in the H2O-DMSO system, so as to meet the requirements of flexible energy storage devices for wide temperature adaptability and voltage adjustability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention discloses a wide-temperature polyvinyl alcohol-based hydrogel electrolyte, wherein the wide-temperature polyvinyl alcohol-based hydrogel electrolyte uses polyvinyl alcohol as the hydrogel backbone, lithium chloride as the electrolyte salt, and H2O-DMSO supramolecular liquid formed by dimethyl sulfoxide and water as the solvent.

[0007] Preferably, for the polyvinyl alcohol-based hydrogel electrolyte of the present invention, the mass ratio of lithium chloride, the electrolyte salt serving as an ion carrier, to polyvinyl alcohol constituting the three-dimensional cross-linked network skeleton of the hydrogel is in the range of 0.5 to 8.5:1.

[0008] The electrolyte prepared by the above method exhibits excellent wide-temperature operating performance. When applied to electrochemical energy storage devices, it enables the devices to maintain a relatively stable operating state within a temperature range of -50℃ to 25℃.

[0009] Preferably, in the polyvinyl alcohol-based hydrogel electrolyte of the present invention, the mass ratio of water to polyvinyl alcohol in the electrolyte system is 13.5:1.

[0010] The electrolyte prepared by the above method can ensure sufficient dissociation of electrolyte salt and smooth ion transport through sufficient water, thereby obtaining the ionic conductivity required by energy storage devices. It can also rely on the entanglement of appropriate polyvinyl alcohol molecular chains to form a stable three-dimensional network, avoiding the problems of electrolyte fragility, difficulty in encapsulation, and easy short circuit of devices. At the same time, it also solves the drawbacks of excessive molecular chain entanglement hindering ion migration and causing a significant decrease in electrochemical performance, ensuring that the electrolyte has both reliable practicality and excellent electrochemical performance.

[0011] A wide-temperature polyvinyl alcohol-based hydrogel electrolyte with a working voltage that is linearly adjustable with the proportion of dimethyl sulfoxide can be applied in energy storage devices and electronic devices such as lithium-ion batteries and supercapacitors, where voltage adjustability and wide-temperature stability are required. Preferably, in the polyvinyl alcohol-based hydrogel electrolyte system of the present invention, the molar ratio of dimethyl sulfoxide in the H2O-DMSO system is 0 to 0.15:1.

[0012] With the above-mentioned polyvinyl alcohol-based hydrogel electrolyte formulation, the working voltage of the polyvinyl alcohol-based hydrogel electrolyte increases linearly with the increase of the molar proportion of DMSO in the H2O-DMSO system; at the same time, under the optimal electrolyte salt concentration conditions, the ion transport performance of the polyvinyl alcohol-based hydrogel electrolyte remains relatively stable in a wide temperature range from -50℃ to 25℃.

[0013] In addition, since the energy density of a supercapacitor is proportional to the square of the working voltage, and the energy density of a battery is proportional to the working voltage, and the working voltage of the polyvinyl alcohol-based hydrogel electrolyte described in the present invention increases with the increase of the molar ratio of DMSO in the H2O-DMSO system within the range of 0 to 0.15 of the molar ratio of DMSO in the solvent, and maintains wide-temperature stability under the condition of the optimal electrolyte salt concentration, the electrolyte can synchronously improve the energy density of electrochemical energy storage devices such as supercapacitors and batteries with the increase of the molar ratio of DMSO in the H2O-DMSO system.

[0014] Preferably, the relationship between the working voltage of the polyvinyl alcohol-based hydrogel electrolyte and the molar ratio of DMSO in the H2O-DMSO system satisfies U X = aX + b, where a = 3 V, b = 1.35 V, 0 < X ≤ 0.15; in the formula, U X is the working voltage of the polyvinyl alcohol-based hydrogel electrolyte, with the unit of V; X is the molar ratio of DMSO in the H2O-DMSO system; b is the working voltage of the electrolyte when the molar ratio of DMSO in the H2O-DMSO system is 0.

[0015] Preferably, the polyvinyl alcohol-based hydrogel electrolyte described in the present invention can work stably within the range of -50 °C to 25 °C. The working voltage of this electrolyte increases with the increase of the molar ratio of DMSO in the H2O-DMSO system.

[0016] The beneficial effects of the present invention are as follows: The working voltage of the polyvinyl alcohol-based hydrogel electrolyte described in the present invention linearly increases with the increase of the molar ratio of DMSO in the H2O-DMSO system, and the ion transport performance is relatively stable within the range of -50 °C to 25 °C. This characteristic can greatly expand the application scope of electrochemical energy storage devices such as supercapacitors and batteries using this electrolyte, making them highly adaptable to all-weather and all-season usage scenarios. Even in extreme temperature environments such as polar regions and deserts, they can still maintain stable and excellent performance.

[0017] The polyvinyl alcohol-based hydrogel electrolyte described in the present invention has excellent safety and practical characteristics: in terms of safety, this electrolyte is non-flammable, non-toxic and non-corrosive, avoiding the safety hazards of traditional liquid electrolytes; in terms of process and economy, it has low humidity requirements for the assembly environment, and the raw material cost is controllable and the cost performance is high, which is convenient for large-scale production and application.

[0018] The hydrogel electrolyte of the present invention is applicable to various electrochemical energy storage devices including but not limited to supercapacitors and secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a constant current charge-discharge curve of the supercapacitor in Embodiment 1 of the present invention at -50℃ to 25℃; Figure 2 This is a graph showing the specific capacitance retention rate of the supercapacitor in Embodiment 1 of the present invention at temperatures ranging from -50°C to 25°C. Figure 3 This is a cyclic voltammetry curve of the supercapacitor in Embodiment 1 of the present invention at -50℃ to 25℃. Figure 4 This is a constant current charge-discharge curve of the supercapacitor in Embodiment 2 of the present invention at -50℃ to 25℃; Figure 5 This is a graph showing the specific capacitance retention rate of the supercapacitor in Embodiment 2 of the present invention at temperatures ranging from -50°C to 25°C. Figure 6 This is a cyclic voltammetry curve of the supercapacitor in Embodiment 2 of the present invention at -50℃ to 25℃; Figure 7 The graphs show the constant current charge-discharge curves of the supercapacitors in Examples 1-5 of this invention at 25°C and a current density of 1 A / g. Figure 8 The graphs show the changes in the operating voltage of the supercapacitors in Examples 1-5 of this invention at 25°C and a current density of 1A / g, as a function of the molar percentage of DMSO in the H2O-DMSO system. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Example 1

[0021] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 2.053 g of lithium chloride as the electrolyte salt, and the molar proportion of DMSO in the H2O-DMSO system of the electrolyte was 0.1. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0022] A constant current charge-discharge (CD) test was performed on it in a temperature range of -50 ℃ to 25 ℃ under a current density of 1 A / g, and the results are as follows. Figure 1 As shown, tests indicate that the supercapacitor operates at a voltage of 1.65 V at 25 °C; simultaneously, the specific capacitance retention rate of the supercapacitor at different temperatures was calculated, and the results are as follows. Figure 2As shown in the figure, the test results show that the specific capacitance retention rate decreases slightly as the operating temperature decreases.

[0023] Cyclic voltammetry (CV) tests were performed on the sample at a temperature range of -50 °C to 25 °C and a scan rate of 10 mV / s. The results are as follows: Figure 3 As shown, the CV test results are highly consistent with the CD test conclusions, further verifying the accuracy of the working voltage. Example 2

[0024] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 2.053 g of lithium chloride as the electrolyte salt, and the molar proportion of DMSO in the H2O-DMSO system of the electrolyte was 0.2. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0025] A constant current charge-discharge (CD) test was performed on it in a temperature range of -50 ℃ to 25 ℃ under a current density of 1 A / g, and the results are as follows. Figure 4 As shown, tests indicate that the supercapacitor operates at a voltage of 1.8 V at 25 °C; simultaneously, the specific capacitance retention rate of the supercapacitor at different temperatures was calculated, and the results are as follows. Figure 5 As shown in the figure, the test results show that the specific capacitance retention rate decreases slightly as the operating temperature decreases.

[0026] Cyclic voltammetry (CV) tests were performed on the sample at a temperature range of -50 °C to 25 °C and a scan rate of 10 mV / s. The results are as follows: Figure 6 As shown, the CV test results are highly consistent with the CD test conclusions, further verifying the accuracy of the working voltage. Example 3

[0027] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 2.053 g of lithium chloride as the electrolyte salt, and the molar percentage of DMSO in the H2O-DMSO system of the electrolyte was 0. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0028] Constant current charge-discharge (CD) tests were performed at 25℃ and a current density of 1A / g, and the results are as follows: Figure 7 As shown, the test results indicate that the supercapacitor operates at a voltage of 1.35V at 25℃. Example 4

[0029] A polyvinyl alcohol-based hydrogel electrolyte was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 2.053 g of lithium chloride as the electrolyte salt, with a water-to-polyvinyl alcohol mass ratio of 13.5 and a DMSO molar percentage of 0.05 in the H2O-DMSO system of the electrolyte. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0030] Constant current charge-discharge (CD) tests were performed at 25℃ and a current density of 1A / g, and the results are as follows: Figure 7 As shown, the test results indicate that the supercapacitor operates at a voltage of 1.5V at 25℃. Example 5

[0031] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 2.053 g of lithium chloride as the electrolyte salt, and the molar proportion of DMSO in the H2O-DMSO system of the electrolyte was 0.15. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0032] Constant current charge-discharge (CD) tests were performed at 25℃ and a current density of 1A / g, and the results are as follows: Figure 7 As shown, the test results indicate that the supercapacitor operates at a voltage of 1.8V at 25℃.

[0033] The curves showing the change in operating voltage of the supercapacitors in Examples 1-5 at 25°C and a current density of 1 A / g as a function of the molar percentage of DMSO in the H₂O-DMSO system are shown below. Figure 8 As shown. By Figure 8 It can be seen that as the molar percentage of DMSO in the H2O-DMSO system increases from 0 to 0.15, the corresponding supercapacitor operating voltage increases from 1.35V to 1.8V. However, when the molar percentage of DMSO is further increased to 0.2, the operating voltage no longer shows an increasing trend, and the charging time is extended, indicating that the regulating effect of DMSO on voltage increase has reached the threshold. Example 6

[0034] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 8.5 g of lithium chloride as the electrolyte salt. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0035] Constant current charge-discharge (CD) tests were conducted at 25℃ and 1A / g current density. The test results showed that the supercapacitor's operating voltage was only 0.8 V at 25℃, and its adaptability to wide temperature environments was significantly insufficient, failing to meet the energy storage application requirements in extreme temperature scenarios. Example 7

[0036] A polyvinyl alcohol-based hydrogel electrolyte with a water-to-polyvinyl alcohol mass ratio of 13.5 was prepared using 1 g of polyvinyl alcohol as the hydrogel backbone and 0.636 g of lithium chloride as the electrolyte salt. A supercapacitor was assembled using the above hydrogel electrolyte with activated carbon as the electrode material.

[0037] Constant current charge-discharge (CD) tests were conducted at 25℃ and 1A / g current density. The test results showed that the supercapacitor had an operating voltage of 1.4 V at 25℃ and its wide temperature range adaptability was significantly insufficient, failing to meet the energy storage application requirements in extreme temperature scenarios.

[0038] The specific embodiments of the invention have been described in detail above, but these are merely examples, and the invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of this invention. Therefore, all equivalent transformations, modifications, and improvements made without departing from the spirit and principles of this invention should be included within the scope of this invention.

Claims

1. A wide temperature polyvinyl alcohol-based hydrogel electrolyte, characterized in that, The wide-temperature polyvinyl alcohol-based hydrogel electrolyte takes polyvinyl alcohol as a hydrogel skeleton, lithium chloride as an electrolyte salt, and H2O-DMSO supermolecular liquid formed by dimethyl sulfoxide and water as a solvent.

2. The wide temperature polyvinyl alcohol-based hydrogel electrolyte of claim 1, wherein, The mass ratio of lithium chloride to polyvinyl alcohol is 0.5-8.5:

1.

3. The wide temperature polyvinyl alcohol-based hydrogel electrolyte of claim 1, wherein, The mass ratio of water to polyvinyl alcohol in the polyvinyl alcohol-based hydrogel electrolyte is 13.5:

1.

4. The wide temperature polyvinyl alcohol-based hydrogel electrolyte of claim 1, wherein, The molar ratio of dimethyl sulfoxide in the H2O-DMSO system is 0-0.15:

1.

5. The wide temperature polyvinyl alcohol-based hydrogel electrolyte of claim 1, wherein, The relationship between the working voltage of the polyvinyl alcohol-based hydrogel electrolyte and the mole ratio of dimethyl sulfoxide in the H2O-DMSO system satisfies U X =aX+b, wherein a=3 V, b=1.35 V, 0X≤0.15; in the formula, U X is the working voltage of the polyvinyl alcohol-based hydrogel electrolyte, in V; X is the mole ratio of dimethyl sulfoxide in the H2O-DMSO system; and b is the working voltage of the electrolyte when the mole ratio of dimethyl sulfoxide in the H2O-DMSO system is 0.

6. The wide temperature polyvinyl alcohol-based hydrogel electrolyte of claim 1, wherein, The working temperature range of the polyvinyl alcohol-based hydrogel electrolyte is -50 ℃-25 ℃.

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