Wide-temperature water system neutral electrolyte with working voltage linearly rising along with reduction of working temperature

Abstract

The invention discloses a wide-temperature water system neutral electrolyte with working voltage linearly rising along with reduction of working temperature. The water system neutral electrolyte is a solution formed by dissolving a solute in a solvent, the solute is alkali metal nitrite; the solvent is water. The ion transport performance of the wide-temperature-water-series neutral electrolyte with the working voltage linearly rising along with the reduction of the working temperature is relatively stable in the working temperature range, the highest working voltage of the electrolyte linearly rises along with the reduction of the working temperature, and specifically, the highest working voltage of the electrolyte is increased by 0.01 V every time the working temperature is reduced by 1 DEG C. According to the electrolyte, the applicability of the aqueous neutral electrolyte under all-weather conditions, different seasons and extreme temperature environments can be effectively improved, so that the aqueous neutral electrolyte can play a role more reliably.

Description

Technical Field

[0001] The present invention relates to the technical field of wide-temperature electrochemical energy storage, and in particular to a wide-temperature aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature. Background Art

[0002] With the increasing popularity of electronic devices, people have an increasing demand for electrochemical energy storage devices. Among the many components of electrochemical energy storage devices, electrolyte plays a vital role. Among them, aqueous neutral electrolytes stand out with their significant advantages such as weak corrosion, low cost and environmental friendliness, becoming a type of electrolyte that has attracted much attention. However, as far as the current situation is concerned, common aqueous neutral electrolytes have certain limitations, and their operating temperature range is relatively narrow. In particular, once the temperature drops, their ion transport performance will drop sharply, which will seriously restrict the performance of energy storage devices in low temperature environments. Summary of the invention

[0003] The main purpose of the present invention is to provide a wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature, so as to solve some problems in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] On the one hand, the present invention provides a wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly as the operating temperature decreases. The aqueous neutral electrolyte is a solution formed by dissolving a solute in a solvent; the solute is an alkali metal nitrite; and the solvent is water.

[0006] Preferably, the alkali metal nitrite is lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite or cesium nitrite.

[0007] By adopting the above method, one or more alkali metal nitrites containing lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite or cesium nitrite are dissolved in water to form an aqueous neutral electrolyte with a wide operating temperature range. When applied to an electrochemical energy storage device, the electrochemical energy storage device can operate relatively stably within an operating temperature range of -40°C to 80°C, and the maximum operating voltage increases linearly with decreasing temperature.

[0008] Preferably, the weight percentage of the solute is 50-70wt.%.

[0009] Due to the above method, when the solute concentration is higher, the maximum working voltage of the electrolyte within the working temperature range is higher. And under the condition of the optimal solute concentration, the ion transport performance of the electrolyte is relatively stable within the working temperature range of -40℃ to 80℃.

[0010] In addition, since the energy density of a supercapacitor is proportional to the square of the capacitor's operating voltage and the energy density of a battery is proportional to the battery's operating voltage, it can be seen that the higher the operating voltage of the electrolyte, the higher the energy density of the supercapacitor or battery; the wide-temperature aqueous neutral electrolyte of the present invention, whose operating voltage increases linearly with decreasing operating temperature, can increase the energy density of electrochemical energy storage devices such as supercapacitors and batteries as the operating temperature decreases.

[0011] Preferably, the relationship between the maximum operating voltage and the operating temperature of the electrolyte satisfies U T =aT+b, where a=-10mV / ℃, b=1.2V; where U T is the maximum operating voltage of the aqueous neutral electrolyte, in V; a is the slope of the maximum operating voltage of the electrolyte changing with temperature; T is the operating temperature of the electrolyte, in °C; b is the maximum operating voltage of the electrolyte when the operating temperature is 0 °C.

[0012] Preferably, the aqueous neutral electrolyte can operate within a range of -40°C to 80°C, and the maximum operating voltage of the aqueous neutral electrolyte increases linearly as the operating temperature decreases.

[0013] On the other hand, the present invention provides an application of a wide-temperature aqueous neutral electrolyte in an electrochemical energy storage device, wherein the operating voltage increases linearly as the operating temperature decreases; when the wide-temperature aqueous neutral electrolyte is applied in the electrochemical energy storage device, the aqueous neutral electrolyte can operate in the range of -40°C to 80°C, and the maximum operating voltage of the aqueous neutral electrolyte increases linearly as the operating temperature decreases.

[0014] The beneficial effects of the present invention are:

[0015] 1. The ion transport performance of the aqueous neutral electrolyte of the present invention is relatively stable in the range of -40°C to 80°C, and its operating voltage increases linearly with decreasing operating temperature, which can greatly expand the application scope of electrochemical energy storage devices such as supercapacitors and batteries based on aqueous neutral electrolytes, making them highly adaptable to all-weather and all-season usage scenarios, and even in extreme temperature environments such as polar regions and deserts, they can still maintain stable and excellent performance.

[0016] 2. The aqueous neutral electrolyte of the present invention is non-flammable, has low humidity requirements for the assembly environment, is cost-effective, non-toxic and non-corrosive.

[0017] 3. The aqueous neutral electrolyte of the present invention can be used in electrochemical energy storage devices such as supercapacitors and secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a curve diagram showing the variation of the maximum operating voltage with the operating temperature in Example 1 of the present invention;

[0019] Figure 2 This is a constant current charge and discharge curve diagram of Example 1 of the present invention under different operating temperatures and different charging voltage conditions;

[0020] Figure 3 This is a constant current charge and discharge curve diagram of Example 2 of the present invention under different operating temperatures and different charging voltage conditions;

[0021] Figure 4 The cyclic voltammetry curves of Example 2 of the present invention under different operating temperatures and different voltage windows;

[0022] Figure 5 This is a constant current charge and discharge curve diagram of Example 3 of the present invention under different operating temperatures and different charging voltage conditions; DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] The terms "first", "second" and "third" in this application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second" and "third" can explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. All directional indications in the embodiments of the present application (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0025] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] Embodiment 1:

[0027] A supercapacitor was assembled using a 61wt.% potassium nitrite aqueous solution as the electrolyte and activated carbon as the electrode material. The maximum operating voltage of the electrolyte increases linearly with decreasing operating temperature and satisfies U T =aT+b, where a=-10mV / °C, b=1.2V, and the operating temperature range of the electrolyte is -40°C to 80°C.

[0028] Under the condition of 1A / g current density, the assembled supercapacitor was charged and discharged to obtain the curve of the maximum working voltage of the device with temperature under this condition, as shown in Figure 1 As shown, it can be seen that the maximum operating voltage of the electrolyte increases linearly with decreasing temperature in the operating temperature range of -40°C to 80°C, and at an operating temperature of -40°C it is 0.6V higher than 1.0V at 20°C.

[0029] Correspondingly, under the condition of 1A / g, the constant current charge-discharge curves of the supercapacitor under different operating temperatures and different charging voltages are as follows: Figure 2 As shown, it can be seen that as the operating temperature of the supercapacitor decreases, its maximum operating voltage increases linearly, and the specific capacitance does not decrease significantly.

[0030] Embodiment 2:

[0031] A supercapacitor was assembled using a 65wt.% potassium nitrite aqueous solution as the electrolyte and activated carbon as the electrode material. The maximum operating voltage of the electrolyte increases linearly with decreasing operating temperature and satisfies U T =aT+b, where a=-10mV / °C, b=1.2V, and the operating temperature range of the electrolyte is -40°C to 80°C.

[0032] The assembled supercapacitor was charged and discharged under a current density of 1 A / g. The constant current charge and discharge curves of the supercapacitor under different operating temperatures and different charging voltages are shown in Figure 2. Figure 3 As shown, it can be seen that as the operating temperature of the supercapacitor decreases, its maximum operating voltage increases linearly, and the specific capacitance does not decrease significantly.

[0033] The assembled supercapacitor was subjected to a cyclic voltammetry test at a scan rate of 20 mV / s. The cyclic voltammetry curves of the supercapacitor under different operating temperatures and different voltage windows are shown in FIG. Figure 4 As shown, it can be seen that as the operating temperature of the supercapacitor decreases, its maximum operating voltage increases linearly.

[0034] Embodiment 3:

[0035] A supercapacitor was assembled using a 69wt.% potassium nitrite aqueous solution as the electrolyte and activated carbon as the electrode material. The maximum operating voltage of the electrolyte increases linearly with decreasing operating temperature and satisfies U T =aT+b, where a=-10mV / °C, b=1.2V, and the operating temperature range of the electrolyte is -40°C to 80°C.

[0036] The assembled supercapacitor was charged and discharged under a current density of 1 A / g. The constant current charge and discharge curves of the supercapacitor under different operating temperatures and different charging voltages are shown in Figure 2. Figure 5 As shown, it can be seen that as the operating temperature of the supercapacitor decreases, its maximum operating voltage increases linearly, and the specific capacitance does not decrease significantly.

[0037] Embodiment 4:

[0038] A 65wt.% potassium nitrite aqueous solution was used as the electrolyte, and graphite and lithium cobalt oxide were used as electrode materials to assemble an aqueous neutral secondary battery. Experiments have shown that the maximum operating voltage of the aqueous neutral electrolyte increases linearly with decreasing operating temperature, and the operating temperature range of the electrolyte is: -40℃~80℃.

[0039] Embodiment 5:

[0040] The difference between this embodiment and embodiment 1 is that: in the electrolyte, the weight percentages of lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite and cesium nitrite are 5wt.%, 5wt.%, 30wt.%, 5wt.% and 5wt.%, respectively, and activated carbon is used as the electrode material to assemble a symmetrical aqueous neutral electrochemical supercapacitor. Experiments have shown that when the above aqueous neutral electrolyte is used, the maximum operating voltage increases linearly with the decrease of the operating temperature.

[0041] Embodiment 6:

[0042] The difference between this embodiment and embodiment 1 is that: in the electrolyte, the weight percentages of lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite and cesium nitrite are 5wt.%, 5wt.%, 50wt.%, 5wt.% and 5wt.%, respectively, and activated carbon is used as the electrode material to assemble a symmetrical aqueous neutral electrochemical supercapacitor. Experiments have shown that when the above aqueous neutral electrolyte is used, the maximum operating voltage increases linearly with the decrease of the operating temperature.

[0043] The specific implementation methods of the invention are described in detail above, but they are only examples, and the invention is not limited to the specific implementation methods described above. For those skilled in the art, any equivalent modification or substitution of the invention is also within the scope of the invention, therefore, the equalization, modification, improvement, etc. made without departing from the spirit and principle of the invention should be included in the scope of the invention.

Claims

1. A wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature, characterized in that: The aqueous neutral electrolyte is a solution formed by dissolving a solute in a solvent; the solute is an alkali metal nitrite; and the solvent is water.

2. A wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature as claimed in claim 1, characterized in that: The alkali metal nitrite is lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite or cesium nitrite.

3. A wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature as claimed in claim 1, characterized in that: The weight percentage of the solute is 50-70 wt.%.

4. A wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature as claimed in claim 1, characterized in that: The relationship between the maximum working voltage and working temperature of the aqueous neutral electrolyte satisfies U T =aT+b, where a=-10mV / ℃, b=1.2V; where U T is the maximum operating voltage of the aqueous neutral electrolyte, in V; a is the slope of the maximum operating voltage of the electrolyte changing with temperature; T is the operating temperature of the electrolyte, in °C; b is the maximum operating voltage of the electrolyte when the operating temperature is 0 °C.

5. A wide temperature range aqueous neutral electrolyte whose operating voltage increases linearly with decreasing operating temperature as claimed in claim 4, characterized in that: The aqueous neutral electrolyte can operate within the range of -40°C to 80°C.

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