CN107256986A - A kind of aqueous electrolyte and Water based metal ion battery - Google Patents

Abstract

The invention provides an aqueous electrolytic solution, which comprises polyethylene glycol, water and inorganic salts. In the present invention, polyethylene glycol is added to the aqueous electrolytic solution using inorganic salt as the electrolyte, which increases the stability of the material in the electrolytic solution. The hydrogen evolution/oxygen evolution side reaction in the electrode reaction process is suppressed to the greatest extent, and it has a good conductive effect, and a high capacity retention rate and Coulombic efficiency are obtained. Experimental results show that the water-based electrolyte provided by the invention is made into a water-based metal-ion battery, charged and discharged at 2C (I=1.091mA), and after 200 cycles, the capacity retention rate of the water-based metal-ion battery is not less than 95.24%. The Coulombic efficiency is not less than 94.23%.

Description

A kind of aqueous electrolyte and aqueous metal ion battery

technical field

The invention relates to the technical field of water-based metal ion batteries, in particular to a water-based electrolyte and a water-based metal-ion battery.

Background technique

With the increasing demand for energy, the continuous consumption of non-renewable energy such as petroleum, and the increasing environmental pollution, it is imperative to develop renewable energy such as solar energy, wind energy, and tidal energy. Secondary batteries have become a research hotspot due to their high energy density, long cycle life, and high voltage. However, traditional secondary batteries (such as lead-acid batteries, nickel-metal hydride batteries) use organic electrolytes, and the batteries have disadvantages such as flammability, toxicity, high production costs, and strict assembly conditions, which are likely to cause environmental pollution and are not conducive to environmental sustainability. develop. The use of aqueous electrolyte instead of organic electrolyte can effectively solve the above problems, and has broad application prospects.

However, due to the low decomposition voltage of water itself (1.23V), its energy density is reduced. At the same time, considering the overpotential of hydrogen and oxygen precipitation, its stable working voltage is difficult to exceed 2.0V, so the working voltage of aqueous metal ion batteries is generally low. In 2.0V, and difficult to improve. In addition, compared with organic electrolytes, the electrode reaction of aqueous metal ion battery electrode materials in aqueous electrolyte solutions is extremely complex, and with the occurrence of side reactions such as hydrogen evolution and oxygen evolution, the pH of the electrolyte is constantly changing. Therefore, The capacity of aqueous lithium-ion batteries decays rapidly during charge-discharge cycles. Although many aqueous lithium-ion batteries have been reported, such as VO ₂ /LiMn ₂ O ₄ , LiV ₃ O ₈ /LiNi _0.81 Co _0.19 O ₂ , TiP ₂ O ₇ /LiMn ₂ O ₄ , LiTi ₂ (PO ₄ ) ₃ /LiMn ₂ O ₄ , LiV ₃ O ₈ /LiCoO ₂ and LiTi ₂ (PO ₄ ) ₃ /LiFePO ₄ , etc., but these batteries generally have defects such as fast capacity decay and easy decomposition of materials.

One of the ways to solve the above problems is to improve the performance of the electrolyte. In 2015, the Wang research group at the University of Maryland proposed the concept of "water-in-salt", that is, using an ultra-high concentration LiTFSI aqueous solution (>20M) as the electrolyte, using Mo ₆ S ₈ as the negative electrode, and LiMn ₂ O ₄ as the positive electrode , constructed an aqueous Li-ion battery with a charging voltage up to 2.3V. In 2012, Watanabe's research group proposed the concept of "Molecular Solvents", which provided a new idea for the development of a new type of aqueous electrolyte. Although the above-mentioned electrolytes have achieved high voltage, there are generally cases of material dissolution and low capacity retention or coulombic efficiency.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide an aqueous electrolyte and an aqueous metal ion battery. The aqueous electrolyte has good electrical conductivity, high capacity retention and Coulombic efficiency.

The invention provides an aqueous electrolytic solution, which comprises polyethylene glycol, water and inorganic salts.

Preferably, the mass ratio of polyethylene glycol, water and inorganic salt is 1-10:1-10:2-14.

Preferably, the mass ratio of polyethylene glycol, water and inorganic salt is 3-7:4-7:5-12.

Preferably, the polyethylene glycol is polyethylene glycol 400, polyethylene glycol 200 or polyethylene glycol 300.

Preferably, the inorganic salt includes one or more of sodium salt, lithium salt and potassium salt.

Preferably, the inorganic salt is selected from one or more of NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ ;

Preferably, the mass ratio of NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ is 0-12:0-8:0-3:0-8:0-6.

The present invention also provides a water-based metal ion battery, which includes a positive electrode, a negative electrode and a water-based electrolyte, and the water-based electrolyte includes: polyethylene glycol, water and inorganic salts.

The invention provides an aqueous electrolytic solution, which comprises polyethylene glycol, water and inorganic salts. In the present invention, polyethylene glycol is added to the aqueous electrolytic solution using inorganic salt as the electrolyte, which increases the stability of the material in the electrolytic solution. The hydrogen evolution/oxygen evolution side reaction in the electrode reaction process is suppressed to the greatest extent, and it has a good conductive effect, and a high capacity retention rate and Coulombic efficiency are obtained. Experimental results show that the water-based electrolyte provided by the invention is made into a water-based metal-ion battery, charged and discharged at 2C (I=1.091mA), and after 200 cycles, the capacity retention rate of the water-based metal-ion battery is not less than 95.24%. The Coulombic efficiency is not less than 94.23%.

Description of drawings

FIG. 1 is a diagram of the situation after 50 cycles of the aqueous electrolyte prepared from the first group of inorganic salts in Example 4 of the present invention and a diagram of the situation after 50 cycles of the aqueous electrolyte prepared from the first group of inorganic salts in Comparative Example 1.

detailed description

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides an aqueous electrolytic solution, which comprises polyethylene glycol, water and inorganic salts.

In the present invention, polyethylene glycol is added to the aqueous electrolytic solution using inorganic salt as the electrolyte, which increases the stability of the material in the electrolytic solution. The hydrogen evolution/oxygen evolution side reaction in the electrode reaction process is suppressed to the greatest extent, and it has a good conductive effect, and a high capacity retention rate and Coulombic efficiency are obtained.

In the present invention, the polyethylene glycol is preferably polyethylene glycol 400 (PEG400), polyethylene glycol 200 (PEG200) or polyethylene glycol 300 (PEG300).

In order to reduce the impact of impurity ions in the water on the electrochemical properties of the electrolyte, the water is preferably deionized water.

The inorganic salt is preferably one or more of sodium salt, lithium salt and potassium salt. More preferably, it is one or more selected from NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ . The mass ratio of NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ is preferably 0-12: 0-8: 0-3: 0-8: 0-6, and does not include Condition. In some embodiments of the present invention, the inorganic salt is NaClO ₄ ; in some embodiments of the present invention, the inorganic salt is LiClO ₄ , KNO ₃ and NaNO ₃ , and the LiClO ₄ , KNO ₃ and The mass ratio of NaNO ₃ is 7:2:5; in some embodiments of the present invention, the inorganic salts are NaClO ₄ , LiClO ₄ and KNO ₃ , and the mass ratio of NaClO ₄ , LiClO ₄ and KNO ₃ is 6:6:2; In some embodiments of the present invention, the inorganic salts are KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ , and the mass ratio of KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ is 4: 7:3; in some embodiments of the present invention, the inorganic salts are KNO ₃ and NaNO ₃ , and the mass ratio of KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ is 1:1; in certain embodiments of the present invention In some embodiments, the inorganic salts are NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ , and the mass ratio of NaClO ₄ , LiClO ₄ , KNO ₃ , NaNO ₃ and NaH ₂ PO ₄ is 7 :2:2:2:1; In some embodiments of the present invention, the inorganic salts are NaClO ₄ , LiClO ₄ , KNO ₃ and NaH ₂ PO ₄ , and the NaClO ₄ , LiClO ₄ , KNO ₃ and NaH The mass ratio of ₂ PO ₄ is 7:3:4:1. The invention further adopts a specific inorganic salt as the electrolyte, which can inhibit the decomposition of the material in the aqueous electrolyte, thereby promoting the acquisition of a higher capacity retention rate and Coulombic efficiency.

In the present invention, the mass ratio of polyethylene glycol, water and inorganic salt is preferably 1-10:1-10:2-14; more preferably 3-7:4-7:11-14. In some embodiments of the present invention, the mass ratio of polyethylene glycol, water and inorganic salt is 7:6:14, 3:4:5, 7:7:12 or 10:10:20.

The preparation method of the water-based electrolyte is not particularly limited in the present invention, and preferably includes the following steps: mixing polyethylene glycol, water and inorganic salts, and stirring to obtain the water-based electrolyte.

The present invention also provides a water-based metal ion battery, which includes a positive electrode, a negative electrode and a water-based electrolyte, and the water-based electrolyte includes: polyethylene glycol, water and inorganic salts.

The present invention has no special restrictions on the types of the positive electrode, negative electrode and separator, preferably: Fe ₄ [Fe(CN) ₆ ] ₃ is used as the positive electrode material, TiP ₂ O ₇ is used as the negative electrode material, and a full battery is assembled without a separator. Wherein, the positive and negative electrode slurries are prepared according to m (active material): m (polyvinylidene fluoride, PVDF): m (acetylene black) = 75:10:15, and the prepared slurry is applied to the Ti grid , the mass of the positive electrode is about 5-8mg, and the mass of the negative electrode is 30%-40% greater than that of the positive electrode. The coated pole pieces were placed in an oven at 80° C. and baked in an air atmosphere for 13 hours to obtain a water-based metal ion battery.

The present invention has no special limitation on the sources of the above-mentioned raw material components, which may be commercially available.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then, the discharge capacity retention rate and Coulombic efficiency of 200 cycles were evaluated. The discharge capacity retention rate is represented by the percentage of the discharge capacity of each cycle relative to the discharge capacity of the first cycle. Coulombic efficiency is expressed as a percentage of discharge capacity per cycle relative to charge capacity. Experimental results show that the capacity retention rate of the aqueous metal ion battery prepared by the invention after 200 cycles is not lower than 95.24%, and the coulombic efficiency is not lower than 94.23%.

The invention provides an aqueous electrolytic solution, which comprises polyethylene glycol, water and inorganic salts. In the present invention, polyethylene glycol is added to the aqueous electrolytic solution using inorganic salt as the electrolyte, which increases the stability of the material in the electrolytic solution. The hydrogen evolution/oxygen evolution side reaction in the electrode reaction process is suppressed to the greatest extent, and it has a good conductive effect, and a high capacity retention rate and Coulombic efficiency are obtained.

In order to further illustrate the present invention, an aqueous electrolyte solution and an aqueous metal ion battery provided by the present invention will be described in detail below in conjunction with examples, but these should not be construed as limiting the protection scope of the present invention.

The reagents used in the following examples are all commercially available.

Example 1

According to the mass ratio of polyethylene glycol, water and inorganic salt being 7:6:14, weigh 7g of PEG400, 6g of water and 14g of inorganic salt, mix and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 1.

Components and quality of 7 groups of inorganic salts selected in table 1 embodiment 1

Then, Fe ₄ [Fe(CN) ₆ ] ₃ is used as the positive electrode material, TiP ₂ O ₇ is used as the negative electrode material, and a full battery is assembled without a separator. Wherein, the positive and negative electrode slurries are prepared according to m (active material): m (polyvinylidene fluoride, PVDF): m (acetylene black) = 75:10:15, and the prepared slurry is applied to the Ti grid , the mass of the positive electrode is about 5-8mg, and the mass of the negative electrode is 30%-40% greater than that of the positive electrode. The coated pole pieces were placed in an oven at 80° C. and baked in an air atmosphere for 13 hours to obtain a water-based metal ion battery.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then evaluate the discharge capacity retention rate and Coulombic efficiency after 200 cycles, and the results are shown in Table 1. It can be seen from Table 1 that the capacity retention rate of the aqueous metal ion battery prepared in this example after 200 cycles is not less than 99.63%, and the Coulombic efficiency is not less than 99.3%.

Example 2

According to the mass ratio of polyethylene glycol, water and inorganic salt as 3:4:5, weigh 3g of PEG400, 4g of water and 5g of inorganic salt, mix and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 2.

Components and quality of 7 groups of inorganic salts selected in table 2 embodiment 2

Then, Fe ₄ [Fe(CN) ₆ ] ₃ is used as the positive electrode material, TiP ₂ O ₇ is used as the negative electrode material, and a full battery is assembled without a separator. Wherein, the positive and negative electrode slurries are prepared according to m (active material): m (polyvinylidene fluoride, PVDF): m (acetylene black) = 75:10:15, and the prepared slurry is applied to the Ti grid , the mass of the positive electrode is about 5-8mg, and the mass of the negative electrode is 30%-40% greater than that of the positive electrode. The coated pole pieces were placed in an oven at 80° C. and baked in an air atmosphere for 13 hours to obtain a water-based metal ion battery.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then evaluate the discharge capacity retention rate and Coulombic efficiency after 200 cycles, and the results are shown in Table 2. It can be seen from Table 2 that the capacity retention rate of the aqueous metal ion battery prepared in this example after 200 cycles is not less than 95.63%, and the Coulombic efficiency is not less than 94.99%.

Example 3

According to the mass ratio of polyethylene glycol, water and inorganic salt being 7:7:12, weigh 7g of PEG400, 7g of water and 12g of inorganic salt, mix and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 3.

Components and quality of 7 groups of inorganic salts selected in table 3 embodiment 3

Then, Fe ₄ [Fe(CN) ₆ ] ₃ is used as the positive electrode material, TiP ₂ O ₇ is used as the negative electrode material, and a full battery is assembled without a separator. Wherein, the positive and negative electrode slurries are prepared according to m (active material): m (polyvinylidene fluoride, PVDF): m (acetylene black) = 75:10:15, and the prepared slurry is applied to the Ti grid , the mass of the positive electrode is about 5-8mg, and the mass of the negative electrode is 30%-40% greater than that of the positive electrode. The coated pole pieces were placed in an oven at 80° C. and baked in an air atmosphere for 13 hours to obtain a water-based metal ion battery.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then evaluate the discharge capacity retention rate and Coulombic efficiency after 200 cycles, and the results are shown in Table 3. It can be seen from Table 3 that the capacity retention rate of the aqueous metal ion battery prepared in this example after 200 cycles is not less than 96.59%, and the Coulombic efficiency is not less than 96.48%.

Example 4

According to the mass ratio of polyethylene glycol, water and inorganic salts being 10:10:20, weigh 7g of PEG400, 6g of water and 14g of inorganic salts, mix and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 4.

Components and quality of 7 groups of inorganic salts selected in table 4 embodiment 4

Then, with Fe ₄ [Fe(CN) ₆ ] ₃ as the working electrode, Ti sheet as the counter electrode, and Ag/AgCl (saturated KCl) as the reference electrode, a half-cell was assembled using a three-electrode system.

Evaluate the electrolyte condition of the half-cell made of the first group of inorganic salts in this example after 50 cycles, and the results are shown in B in FIG. 1 . 1 is a diagram of the situation after 50 cycles of the aqueous electrolyte prepared from the first group of inorganic salts in Example 4 of the present invention and a diagram of the situation after 50 cycles of the aqueous electrolyte prepared in Comparative Example 1. From B in Figure 1, it can be seen that after 50 cycles, the electrolyte solution with PEG added has no obvious change, and the materials in the electrolyte solution are not dissolved. And continue to evaluate the state of the electrolyte of the half-cells made of inorganic salts in the 2-7 groups of this embodiment after 50 cycles. The experimental results show that none of the materials in the electrolyte obtained in this embodiment are dissolved.

Evaluate the potential change of the half-cells prepared in this example during charge-discharge cycles. The experimental results show that the oxidation-reduction potentials obtained in this example are all above 1.1V.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then evaluate the discharge capacity retention rate and Coulombic efficiency after 200 cycles, and the results are shown in Table 4. It can be seen from Table 4 that the capacity retention rate of the aqueous metal ion battery prepared in this example is not lower than 95.24% after 200 cycles, and the Coulombic efficiency is not lower than 94.23%.

Comparative example 1

According to the mass ratio of water and inorganic salt being 6:14, weigh 6g of water and 14g of inorganic salt, mix them, and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 5.

Components and quality of 7 groups of inorganic salts selected in Table 5 Comparative Example 1

Then, with Fe ₄ [Fe(CN) ₆ ] ₃ as the working electrode, Ti sheet as the counter electrode, and Ag/AgCl (saturated KCl) as the reference electrode, a half-cell was assembled using a three-electrode system.

Evaluation of the electrolyte of the half-cell made of the first group of inorganic salts in Comparative Example 1 after 50 cycles, the results are shown in FIG. 1 . From A in Figure 1, it can be seen that after 50 cycles, the electrolyte solution with PEG added has no obvious change, and the materials in the electrolyte solution are not dissolved. And continue to evaluate the electrolyte condition of the half-cells made of inorganic salts in groups 2-7 of this comparative example after 50 cycles. The experimental results show that the materials in the electrolyte obtained in this comparative example are all obviously dissolved.

Evaluate the potential change of the half-cells prepared in this comparative example during charge and discharge cycles. The experimental results show that the oxidation-reduction potentials obtained in this example are all below 1V.

Comparative example 2

According to the mass ratio of ethylene glycol, water, and inorganic salts being 7:6:14, weigh 7g of ethylene glycol, 6g of water, and 14g of inorganic salts, mix them, and stir to obtain an aqueous electrolyte. Among them, 7 groups of inorganic salts were weighed, and the components and quality of the inorganic salts are shown in Table 6.

Components and quality of 7 groups of inorganic salts selected in Table 6 Comparative Example 2

Then, Fe ₄ [Fe(CN) ₆ ] ₃ is used as the positive electrode material, TiP ₂ O ₇ is used as the negative electrode material, and a full battery is assembled without a separator. Wherein, the positive and negative electrode slurries are prepared according to m (active material): m (polyvinylidene fluoride, PVDF): m (acetylene black) = 75:10:15, and the prepared slurry is applied to the Ti grid , the mass of the positive electrode is about 5-8mg, and the mass of the negative electrode is 30%-40% greater than that of the positive electrode. The coated pole pieces were placed in an oven at 80° C. and baked in an air atmosphere for 13 hours to obtain a water-based metal ion battery.

The above water-based metal ion battery was subjected to a constant rate charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). Then evaluate the discharge capacity retention rate and Coulombic efficiency after 200 cycles, and the results are shown in Table 6. It can be seen from Table 6 that the capacity retention rate of the aqueous metal ion battery prepared in this example is lower than 76% after 200 cycles, and the Coulombic efficiency is lower than 87%.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. a kind of aqueous electrolyte, it is characterised in that including：Polyethylene glycol, water and inorganic salts.

2. electrolyte according to claim 1, it is characterised in that the mass ratio of the polyethylene glycol, water and inorganic salts is 1 ~10：1~10：2~14.

3. electrolyte according to claim 2, it is characterised in that the mass ratio of the polyethylene glycol, water and inorganic salts is 3 ~7：4~7：5~12.

4. electrolyte according to claim 1, it is characterised in that the polyethylene glycol is polyethylene glycol 400, polyethylene glycol 200 or Liquid Macrogol.

5. electrolyte according to claim 1, it is characterised in that the inorganic salts are included in sodium salt, lithium salts and sylvite It is one or more of.

6. electrolyte according to claim 1, it is characterised in that the inorganic salts are selected from NaClO₄、LiClO₄、KNO₃、 NaNO₃And NaH₂PO₄In one or more.

7. electrolyte according to claim 6, it is characterised in that the NaClO₄、LiClO₄、KNO₃、NaNO₃With NaH₂PO₄Mass ratio be 0~12：0~8：0~3：0~8：0~6.

8. a kind of Water based metal ion battery, including positive pole, negative pole and aqueous electrolyte, it is characterised in that the water system electrolysis Liquid includes：Polyethylene glycol, water and inorganic salts.