WO2021004259A1

WO2021004259A1 - Symmetrical aqueous sodium-ion battery

Info

Publication number: WO2021004259A1
Application number: PCT/CN2020/097375
Authority: WO
Inventors: 徐丽; 盛鹏; 李慧; 王博; 薛晴; 赵广耀; 白会涛; 陈新
Original assignee: 全球能源互联网研究院有限公司; 国家电网有限公司
Priority date: 2019-07-08
Filing date: 2020-06-22
Publication date: 2021-01-14
Also published as: CN110380047A

Abstract

The present invention relates to the field of electrochemical energy storage, and in particular, to a symmetrical aqueous sodium ion battery. The electrode material used in a positive electrode material layer and a negative electrode material layer of the battery is Na_xMnO₂ (x=0.22-0.66). The electrolyte of the battery is an aqueous solution of sodium salt, and the concentration of sodium ions in the electrolyte is 0.5-6 mol•L^-1. By selecting Na_xMnO₂ as the electrode material and setting the concentration of sodium ions in the electrolyte to be 0.5-6 mol•L^-1, the symmetrical aqueous sodium-ion battery of the present application has higher energy density which can reach more than 40 Wh/kg.

Description

Symmetrical water-based sodium ion battery

Technical field

This application relates to the field of electrochemical energy storage, for example, to a symmetrical aqueous sodium ion battery.

Background technique

With the integration of solar, wind and other types of renewable energy into the grid and the construction of smart grids, energy storage technology has become the key to optimizing energy utilization. The sodium ion battery is a secondary battery with a reaction principle similar to that of the lithium ion battery. Due to its advantages in raw material reserves and price, it has the potential to be used in energy storage systems.

A sodium ion battery usually includes a positive electrode current collector, a negative electrode current collector, a positive electrode material layer, a negative electrode material layer, and an electrolyte. The positive electrode material layer is coated on the positive electrode current collector, and the negative electrode material layer is coated on the negative electrode current collector. Above, the electrolyte is poured between the positive electrode material layer and the negative electrode material layer, and the electrolyte includes sodium salt and a solvent.

General sodium ion batteries are asymmetric batteries, that is, the electrode material used for the positive electrode material layer and the negative electrode material layer are different, so for asymmetric batteries, the production process involves both positive and negative electrodes. The preparation of the material layer, and the energy storage mechanism of the symmetric battery and the asymmetric battery is the same, and because the positive electrode material is the same as the negative electrode material layer, only one electrode material layer needs to be produced during production. That is, and because the volume change of one electrode during charging and discharging can be offset by the opposite electrode, symmetrical sodium ions have gradually become a research and development hotspot for the sake of cost reduction.

However, the electrolyte solvents in the existing symmetrical sodium ion batteries are usually organic solvents. Although this type of battery has high energy density, organic solvents are flammable and explosive, which can cause deflagration during production and use. Accidents have safety issues, and because organic solvent electrolytes are generally toxic, they are also likely to cause environmental pollution, which is not conducive to environmental protection.

If water is used as the solvent of the electrolyte, the problem of flammability and explosion of organic solvents can be solved. However, due to the limitation of the electrochemical window of water, the choice of electrode materials is greatly restricted. At present, some researchers have reported symmetrical aqueous sodium ions. For batteries, they use Na ₂ VTi(PO ₄ ) ₃ , Na ₃ MnTi(PO ₄ ) ₃ and other materials for research. The positive and negative electrodes use V ⁴⁺ /V ³⁺ and Ti ⁴⁺ /Ti ³⁺ , Mn ^{3+ respectively.} The oxidation-reduction reaction of /Mn ²⁺ and Ti ⁴⁺ /Ti ³⁺ realizes the storage and utilization of electric energy. After testing, the energy densities of the two are 30Wh/kg and 40Wh/kg, respectively. It can be seen that the symmetrical aqueous sodium ion battery has Certain development prospects, but due to the need to have a wide voltage platform and a suitable electrochemical window for electrode materials for forming water-based sodium ion batteries, there are not many electrode materials to choose from.

Summary of the invention

Therefore, the technical problem to be solved by this application includes overcoming the limitation of the electrochemical window of water in the water-based symmetrical sodium ion battery in the prior art, which leads to the defect of low selectivity as the electrode material of the water-based sodium ion battery. , Thereby providing a symmetrical water-based sodium ion battery.

To solve the above technical problems, the technical solution adopted in this application is:

Use of Na _x MnO ₂ (x=0.22-0.66) in symmetrical water-based sodium ion batteries.

Use of Na _x MnO ₂ (x=0.22-0.66) as an electrode material in a symmetrical aqueous sodium ion battery.

A symmetrical water-based sodium ion battery, wherein the electrode materials used for the positive electrode material layer and the negative electrode material layer of the battery are both Na _x MnO ₂ (x=0.22-0.66).

Optionally, both the positive electrode material layer and the negative electrode material layer of the battery are composed of materials including electrode materials, conductive agents, and binders.

Optionally, the mixing ratio of the electrode material, conductive agent, and adhesive is 8:1:1 by mass ratio.

Optionally, the conductive agent is at least one of conductive carbon (super P), conductive graphite, and carbon nanotubes.

Optionally, the adhesive is at least one of polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), sodium polyacrylate (PAAS), and sodium alginate .

Optionally, the battery includes:

A positive electrode sheet, which includes a positive current collector and a positive electrode material layer coated on the positive current collector;

And, a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer coated on the negative electrode current collector; an electrolyte is poured between the positive electrode sheet and the negative electrode sheet.

Optionally, the electrolyte of the battery is an aqueous solution of sodium salt, and the concentration of sodium ions in the electrolyte is 0.5-6 mol·L ^-1 .

Optionally, the sodium salt is at least one of sodium sulfate, sodium hydroxide, sodium chloride or sodium nitrate.

The technical solution of this application has the following advantages:

1. In the symmetrical aqueous sodium ion battery provided by this application, Na _x MnO ₂ has a variety of crystal forms, structures and physical properties, so Na _x MnO ₂ has excellent stability and electrochemical performance, and this type of sodium intercalation compound has Wide working voltage range and multiple charge-discharge voltage platforms, the Na content is highly adjustable (x is 0.22-0.66), Na _x MnO ₂ with different sodium abundance has different electrochemical potential, so by selecting Na _x MnO ₂ constructs a water-based symmetrical sodium-ion battery. During the charging and discharging process, the conversion between manganese and its oxidation state and reduction state will generate several high voltage and low voltage platforms, so that Na _x MnO ₂ located at the positive and negative poles Sodium-poor state Na _x MnO ₂ (0.22≤x≤0.44) and sodium-rich state Na _x MnO ₂ (0.66≤x≤0.44) are formed respectively, and then sodium-poor state Na _x MnO ₂ (0.22≤x≤0.44) can be used and an electrochemical reaction between _{2 (0.66≤x≤0.44)} Na _x MnO sodium rich state potential difference successfully constructed symmetrical aqueous sodium ion battery, the present application selection _{_{Na x MnO 2 (x = 0.22-0.66}} ) constructed fully symmetrical The water-based sodium ion battery expands the selection diversity of electrode materials for symmetrical water-based sodium ion batteries.

2. In the symmetrical aqueous sodium ion battery provided by this application, the electrochemical window of water is only 1.23V due to the narrow electrochemical window of water, and there are many side reactions in the water system, such as hydrogen evolution from water, and electrode materials. Decomposition, side reactions of materials with water and oxygen in water, etc., will directly affect the energy density of the battery. In this application, the sodium ion concentration in the electrolyte is set to 0.5-6mol·L ^-1 and the sodium salt concentration in the electrolyte is determined The increase in the electrochemical activity of the water can reduce the electrochemical activity of the water, which can broaden the electrochemical stability window of the water, thereby improving the electrochemical performance of the electrode material in the aqueous solution and the energy density of the battery. In addition, the increase of the sodium salt concentration will also bring about electrolysis. The conductivity of the liquid is improved, thereby improving the power output performance of the battery. Therefore, this application selects Na _x MnO ₂ as the electrode material and sets the sodium ion concentration in the electrolyte to 0.5-6 mol·L ^-1 , so that the application The installed symmetrical water-based sodium ion battery has a higher energy density and a higher long-cycle cycle capacity retention rate.

3. In the symmetrical water-based sodium ion battery provided by this application, since the positive and negative electrode materials are the same kind of material, only one electrode sheet needs to be prepared during preparation, the preparation process is simple, and large-scale production is easy to realize. Compared with traditional organic batteries, the electrolyte used in this application is an aqueous electrolyte, which has significant advantages such as low cost, clean and efficient, and high safety. Compared with the currently reported batteries of the same system, this application has raw materials With significant advantages such as low price and high energy density, this application provides a new type of energy storage method and a type of symmetrical water-based sodium ion battery electrode material, which provides a reference for the development and utilization of large-scale energy storage in the future.

4. In the symmetrical water-based sodium ion battery provided by this application, the conductive agent and the adhesive are selected from relatively common materials, so the source is relatively wide and easy to obtain, which can reduce the production of symmetrical water-based sodium to a certain extent. The cost of ion batteries.

Description of the drawings

In order to more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the specific embodiments or the description of the prior art. Obviously, the appendix in the following description The drawings are some embodiments of the application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Fig. 1 is a charge-discharge curve diagram of Example 1 of the present application at a current density of 1C;

2 is a cyclic voltammetry curve diagram of Example 2 of the present application at a scanning speed of 0.5 mV/s;

Figure 3 is a long-period cycle curve diagram of Example 3 of the present application at a current density of 10C;

Fig. 4 is a long-period cycle curve diagram of Comparative Example 1 of the present application at a current density of 10C.

Detailed ways

The following examples are provided for a better understanding of this application, and are not limited to the best embodiments, and do not limit the content and protection scope of this application.

If the specific experimental steps or conditions are not indicated in the examples, it can be carried out according to the conventional experimental steps described in the literature in the field. The reagents or instruments used without the manufacturer's indication are all conventional reagent products that are commercially available.

Example 1

This embodiment relates to a symmetrical aqueous sodium ion battery, specifically a three-electrode system battery, including a positive electrode current collector, a negative electrode current collector, a positive electrode material layer, and a negative electrode material layer, wherein the positive electrode material layer is coated on On the positive electrode current collector, the negative electrode material layer is coated on the negative electrode current collector, and electrolyte is filled between the positive electrode material layer and the negative electrode material layer, and the electrolyte includes sodium salt and a solvent.

The battery of this embodiment is a three-electrode system, and Zn ²⁺ /Zn is the reference electrode. Among them, the positive electrode material layer and the negative electrode material layer are made of Na _0.44 MnO ₂ electrode active material, conductive carbon (super P), and polytetrafluoroethylene (PTFE) binder mixed in a mass ratio of 8:1:1 Prepared, the electrolyte is a 2mol/L Na ₂ SO ₄ solution.

Example 2

This embodiment relates to a symmetrical water-based sodium ion battery. The difference between this embodiment and Embodiment 1 is that the electrode active material used in this embodiment is Na _0.22 MnO ₂ , and the electrolyte is a 6 mol/L NaOH solution.

Example 3

This embodiment relates to a symmetrical water-based sodium ion battery. The difference between this embodiment and Embodiment 1 is that the electrode active material used in this embodiment is Na _0.66 MnO ₂ , and the electrolyte is 0.5 mol/L NaNO ₃ Solution.

Comparative example 1

This comparative example relates to a symmetrical water-based sodium ion battery. The difference between this comparative example and implementation 2 is that the electrolyte used in this example is a 7 mol/L NaOH solution.

Comparative example 2

This comparative example relates to a symmetrical water-based sodium ion battery based on Na ₂ VTi(PO ₄ ) ₃ as the material. The difference between this comparative example and Example 1 is that the electrode active material used in this comparative example is Na ₂ VTi (PO ₄ ) ₃ , the electrolyte is 1mol/L Na ₂ SO ₄ , and the reference electrode is Ag/AgCl (0.197V vs. NHE).

Test example 1

The symmetrical sodium ion battery provided in Example 1 was tested, and its charge and discharge curve at a current density of 120mA/g was obtained. As shown in Figure 1, it can be seen that there are multiple charge and discharge of the sodium ion battery of Example 1. Voltage platform, discharge capacity is 68.1mAh/g, average discharge voltage is about 1.40V.

The symmetrical sodium ion battery provided in Example 2 was tested, and its cyclic voltammetry curve at a scanning speed of 0.5 mV/s was obtained. As shown in Figure 2, it can be clearly seen that there are many pairs of redox peaks, indicating that Na _0.22 MnO ₂ undergoes a multi-step phase transition process during the insertion or extraction of Na ⁺ ions.

The symmetrical sodium ion battery provided in Example 3 was tested, and its long-period cycle curve at a current density of 1200mA/g was obtained. As shown in Figure 3, it can be seen that the reversible capacity of the battery in the first week is 35.1 mAh/g. After 500 cycles of cycles, the capacity retention rate was 67%.

The symmetrical sodium ion battery provided by Comparative Example 1 was tested, and its long-period cycle curve at a current density of 1200mA/g was obtained. As shown in Figure 4, it can be seen that the reversible capacity of the battery in the first week is 41.1mAh/g. After 200 weeks of cycling, the capacity retention rate was 49%.

Test example 2

The symmetrical sodium ion batteries provided in Examples 1-3 and Comparative Examples 1-2 were tested, and their energy density and long-cycle cycle performance under different current densities were tested. The test results are shown in Table 1.

Table 1. Test results of each embodiment and comparative example

Obviously, the above-mentioned embodiments are merely examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is unnecessary and impossible to list all the implementation methods here. The obvious changes or changes derived from this are still within the protection scope of this application.

Claims

A symmetrical water-based sodium ion battery, wherein the electrode materials used in the positive electrode material layer and the negative electrode material layer of the battery are both Na x MnO 2 , where x = 0.22-0.66.
The symmetrical water-based sodium ion battery according to claim 1, wherein the battery comprises:

A positive electrode, which includes a positive electrode current collector and a positive electrode material layer coated on the positive electrode current collector;

A negative electrode, which includes a negative current collector and a negative electrode material layer coated on the negative current collector; and

The electrolyte is poured between the positive electrode and the negative electrode.
The symmetrical aqueous sodium ion battery according to claim 2, wherein the electrolyte is an aqueous solution of sodium salt, and the concentration of sodium ions in the electrolyte is 0.5-6 mol·L -1 .
The symmetrical aqueous sodium ion battery according to claim 3, wherein the sodium salt includes at least one of sodium sulfate, sodium hydroxide, sodium chloride, or sodium nitrate.
The symmetrical water-based sodium ion battery according to any one of claims 1 to 4, wherein the positive electrode material layer and the negative electrode material layer of the battery are both composed of the electrode material, the conductive agent and the bonding agent. The material composition of the agent.
The symmetrical water-based sodium ion battery according to claim 5, wherein, in the positive electrode material layer and the negative electrode material layer, the mixing ratio of the electrode material, the conductive agent, and the binder is according to The mass meter is 8:1:1.
The symmetrical aqueous sodium ion battery according to claim 5 or 6, wherein the conductive agent includes at least one of conductive carbon, conductive graphite, and carbon nanotubes.
The symmetrical aqueous sodium ion battery according to any one of claims 5-7, wherein the binder comprises polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, sodium polyacrylate, alginic acid At least one of sodium.
The use of Na x MnO 2 in symmetrical aqueous sodium ion batteries, where x=0.22-0.66.
The use of Na x MnO 2 as an electrode material in a symmetrical aqueous sodium ion battery, where x=0.22-2.66.