Multifunctional mixed electrolyte for high-magnification long-circulation multi-electron reaction

Abstract

The invention relates to a multifunctional mixed electrolyte for high-magnification long-cycle multi-electron reaction. The electrolyte is an aqueous electrolyte containing zinc salt, iodized salt and bromine salt; wherein the molar concentration of the zinc salt is 1-3 M, the molar concentration of the iodized salt is 0.1-1 M, the molar concentration of the bromine salt is 0.1-1 M, and the molar ratio of bromine ions to iodide ions is 0.1-10. The zinc-double-halogen battery has high ionic conductivity, efficient active substance utilization rate, excellent cycle performance and higher rate capability, and the electrochemical performance of the zinc-double-halogen battery can be remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of zinc ion batteries, and in particular to a multifunctional mixed electrolyte for high-rate, long-cycle multi-electron reactions. Background Art

[0002] Although non-aqueous lithium-ion batteries have dominated the market for decades, their further development is constrained by the uneven distribution of lithium resources and the flammability of organic electrolytes. As a promising alternative to commercial lithium-ion batteries, aqueous zinc-based batteries have attracted extensive attention due to their inherent non-flammability, non-toxicity, and low cost of aqueous electrolytes. In particular, the metallic zinc anode has demonstrated a high charge / discharge rate of 820 mAh g -1 The high theoretical specific capacity lays the foundation for building a high-energy storage system.

[0003] Among many aqueous batteries, rechargeable zinc-iodine batteries have the advantages of multi-electron transfer and rich valence states, and have broad prospects in large-scale energy storage. However, traditional zinc-iodine batteries only rely on I - / I 0 The single electron conversion reaction results in an output voltage platform lower than 1.2 V, and the theoretical capacity is only 211 mAh g -1 , far from realizing the energy storage potential of the iodine cathode. Similarly, zinc-bromine batteries have a storage capacity of 335 mAh g -1 Theoretical capacity, but faced with the common problems of iodine / bromine cathode: high volatility of halogen element (iodine sublimation rate at room temperature is 0.5mg / cm 2 ·h), low conductivity (iodine crystal conductivity <10 -7 S / cm) and polyhalogen intermediates (such as I3 - Br3 - ) shuttling effect, these factors together lead to the obstruction of long-cycle performance.

[0004] Studies have shown that through the coordination of dihalogens in the electrolyte (such as I / Br mass ratio regulation), multivalent, multi-electron composite redox reactions (such as I - / I 0 / I + / Br - / Br 0 Reaction), raising the system voltage to above 1.5V can further improve the energy density of the battery system. Therefore, developing multivalent multi-electron conversion reactions with higher reaction potentials is the key to achieving high specific energy of zinc-dihalogen batteries. However, the challenges faced are: electrochemical hydrogen evolution reaction, corrosion of the zinc negative electrode caused by the shuttle effect of bromine and iodine, and poor reversibility of the zinc negative electrode caused by zinc dendrite growth and the formation of by-products. Therefore, zinc-dihalogen batteries exhibit low coulombic efficiency and short cycle life. In response to the above problems, traditional single-functional additives are obviously insufficient.

[0005] Therefore, there is an urgent need for multifunctional additives that can inhibit hydrogen evolution reaction and zinc dendrite growth and provide dihalogen elements to achieve multivalent multi-electron conversion reactions with higher reaction potentials. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction to improve the electrochemical performance of zinc-double halogen batteries.

[0007] To solve the above problems, the present invention discloses a multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction, characterized in that the electrolyte is an aqueous electrolyte containing zinc salt, iodine salt and bromide salt; wherein the molar concentration of the zinc salt is 1~3M, the molar concentration of the iodine salt is 0.1~1M, the molar concentration of the bromide salt is 0.1~1M, and the molar ratio of bromide ion to iodide ion is 0.1~10.

[0008] The electrolyte dissociates into NH4 in water + , Li + 、Na + , K + , Rb + , Cs + Mg 2+ At least one cation source.

[0009] The zinc salt is one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc perchlorate, zinc bis(trifluoromethanesulfonyl imide), zinc trifluoromethanesulfonate and hydrates thereof.

[0010] The iodized salt is one or more of cesium iodide, sodium iodide, potassium iodide and zinc iodide.

[0011] The bromide salt is one or more of ammonium bromide, cesium bromide, sodium bromide, potassium bromide, zinc bromide, rubidium bromide, lithium bromide and magnesium bromide.

[0012] An aqueous zinc-double halogen battery assembled using the multifunctional mixed electrolyte as described above is characterized in that: the battery is assembled from a positive electrode, a multifunctional mixed electrolyte and a negative electrode using conventional technology; the positive electrode uses activated carbon material; and the negative electrode uses zinc metal.

[0013] The positive electrode loaded activated carbon content is 1-10 mg cm -2 , with a specific surface area of ​​1000~4000 m 2 g -1 .

[0014] Compared with the prior art, the present invention has the following advantages: 1. Due to the halogen ion Br in the electrolyte of the present invention - and I -The molar ratio of is limited to 0.1~10, so the I - / I 0 / I + Four electron conversion, and can be combined with I + Combined to form a halogen compound, achieving a four-electron conversion reaction at the iodine electrode, Br - with I + Formation of [IBr2] - , thereby stabilizing I 0 To I + Conversion; at the same time [IBr2] - Can be further oxidized to form [IBr2] 0 , thus providing additional capacity.

[0015] 2. The electrolyte of the present invention is an aqueous electrolyte containing zinc salt, iodine salt and bromine salt, which is non-volatile, has high ion conductivity and efficient active material utilization, and has excellent cycle performance and higher rate performance.

[0016] 3. The aqueous zinc-dual halogen battery prepared by the electrolyte of the present invention can effectively stabilize I + And Br 0 , thereby realizing the reaction mechanism of multi-electron conversion between halogens and improving the electrochemical performance of zinc-double halogen batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0018] Figure 1 This is the CV curve of Example 1 of the present invention at a scan rate of 2 mV / s.

[0019] Figure 2 This is the CV curve of Example 2 of the present invention at a scan rate of 2 mV / s.

[0020] Figure 3 This is the CV curve of Example 3 of the present invention at a scan rate of 2 mV / s.

[0021] Figure 4 This is the CV curve of Example 4 of the present invention at a scan rate of 2 mV / s.

[0022] Figure 5 This is the CV curve of comparative example 1 of the present invention at a scan rate of 2 mV / s.

[0023] Figure 6 This is the CV curve of comparative example 2 of the present invention at a scan rate of 2 mV / s.

[0024] Figure 7 This is the CV curve of comparative example 3 of the present invention at a scan rate of 2 mV / s. DETAILED DESCRIPTION

[0025] A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction, the electrolyte is an aqueous electrolyte containing zinc salt, iodine salt and bromine salt; wherein the molar concentration of the zinc salt is 1-3M, the molar concentration of the iodine salt is 0.1-1M, the molar concentration of the bromine salt is 0.1-1M, and the molar ratio of bromide ion to iodide ion is 0.1-10.

[0026] The electrolyte dissociates into NH4 in water + , Li + 、Na + , K + , Rb + , Cs + Mg 2+ At least one cation source.

[0027] Wherein: the zinc salt is one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc perchlorate, zinc bis(trifluoromethanesulfonyl)imide, zinc trifluoromethanesulfonate and hydrates thereof.

[0028] The iodized salt is one or more of cesium iodide, sodium iodide, potassium iodide, and zinc iodide.

[0029] The bromide salt is one or more of ammonium bromide, cesium bromide, sodium bromide, potassium bromide, zinc bromide, rubidium bromide, lithium bromide and magnesium bromide.

[0030] The present invention is a mixed multifunctional electrolyte system jointly regulated by iodine and bromine elements, which promotes the generation of stable interhalogen compounds at low potential by combining bromide and iodide to stimulate the four-electron I - / I 0 / I + conversion reaction; and by increasing the voltage window, the two electrons of bromine Br are further increased. - / Br 0 The conversion reaction can realize the aqueous zinc-double halogen battery with multi-electron conversion mechanism; in addition, the capacity and energy density can be regulated by adjusting the ratio of bromide and iodide.

[0031] By designing cations in the electrolyte to form a high-concentration salt electrolyte with bromide and iodide, the zinc metal negative electrode can be protected. A weak hydrogen bond structure is formed by the high-concentration salt to reduce the hydrogen evolution reaction and prevent the formation of zinc dendrites. This effectively controls the polarization reaction of the battery, helps to improve the cycle stability of the battery, and thus improves the electrochemical performance of the zinc-double halogen battery.

[0032] An aqueous zinc-dual halogen battery assembled with the multifunctional mixed electrolyte is assembled with a positive electrode, a multifunctional mixed electrolyte and a negative electrode using conventional technology. The positive electrode uses activated carbon material; the negative electrode uses zinc metal. The content of activated carbon loaded on the positive electrode is 1-10 mg cm -2 , with a specific surface area of ​​1000~4000 m 2 g -1 .

[0033] Working principle: Cations can protect the zinc negative electrode through electrostatic shielding, avoid the formation of zinc dendrites on its surface, prevent zinc dendrites from piercing the diaphragm, improve the cycle stability of the battery, and improve the electrochemical performance of the battery.

[0034] Example 1 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil was used as the negative electrode, the electrolyte was 3M ZnSO4+0.1M CsI+0.2MZnBr2, and glass fiber was used as the separator. The dual halogen battery was assembled and electrochemical tests were performed at room temperature. The ion conductivity was 42.13mS / cm, and the active material utilization rate was 96.0%.

[0035] The CV curve at a scan rate of 2mV / s is as follows Figure 1 As shown in the figure, the four-electron I of iodine is realized. - / I 0 / I + Conversion reaction and the two electrons of bromine Br - / Br 0 Conversion reaction.

[0036] Example 2 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil was used as the negative electrode, the electrolyte was 3M ZnCl2+0.2M CsI+0.3MZnBr2, and glass fiber was used as the diaphragm to assemble a dual halogen battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 41.13mS / cm, and the active material utilization rate was 95.5%.

[0037] The CV curve at a scan rate of 2mV / s is as follows Figure 2 As shown in the figure, the four-electron I of iodine is realized. - / I 0 / I+ Conversion reaction and the two electrons of bromine Br - / Br 0 Conversion reaction.

[0038] Example 3 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil was used as the negative electrode, the electrolyte was 3M Zn(NO3)2+0.1M CsI+0.4MZnBr2, and glass fiber was used as the diaphragm to assemble a dual halogen battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 42.53mS / cm, and the active material utilization rate was 96.2%.

[0039] The CV curve at a scan rate of 2mV / s is as follows Figure 3 As shown in the figure, the four-electron I of iodine is realized. - / I 0 / I + Conversion reaction and the two electrons of bromine Br - / Br 0 Conversion reaction.

[0040] Example 4 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil was used as the negative electrode, the electrolyte was 3M ZnSO4+0.1M CsI+0.2MCsBr, and glass fiber was used as the separator to assemble a dual halogen battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 41.23mS / cm, and the active material utilization rate was 95.1%.

[0041] The CV curve at a scan rate of 2mV / s is as follows Figure 4 As shown in the figure, the four-electron I of iodine is realized. - / I 0 / I + Conversion reaction and the two electrons of bromine Br - / Br 0 Conversion reaction.

[0042] Comparative Example 1 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil as the negative electrode, 2M ZnSO4 as the electrolyte, and glass fiber as the separator to assemble the battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 38.13mS / cm and the active material utilization rate was 90.1%.

[0043] The CV curve at a scan rate of 2mV / s is as follows Figure 5 As shown in the figure, it can be seen that the CV curve of the zinc ion hybrid capacitor.

[0044] Comparative Example 2 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil as the negative electrode, the electrolyte was 3M ZnSO4+ 0.1m KI, and glass fiber was used as the separator to assemble the battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 38.13mS / cm, and the active material utilization rate was 89.2%.

[0045] The CV curve at a scan rate of 2mV / s is as follows Figure 6 As shown in the figure, when the halogen ion Br - and I - The molar ratio of is beyond the limit. The lower limit is a single zinc-iodine battery, where only two electrons of iodine I - / I 0 Conversion reaction, multi-electron reaction cannot occur.

[0046] Comparative Example 3 Battery assembly: After mixing high specific surface area activated carbon positive electrode material with conductive carbon black and PVDF binder in a mass ratio of 8:1:1 (g / g / g), the mixture was coated on carbon cloth and dried in a vacuum oven at 110°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was used as the positive electrode, commercial metal zinc foil was used as the negative electrode, the electrolyte was 3M ZnSO4+ 0.1M ZnBr2, and glass fiber was used as the separator to assemble the battery. Electrochemical tests were performed at room temperature. The ionic conductivity was 37.93mS / cm, and the active material utilization rate was 87.7%.

[0047] The CV curve at a scan rate of 2mV / s is as follows Figure 7 As shown in the figure, when the halogen ion Br - and I -The molar ratio of Br is beyond the range limit. The upper limit is a single zinc-bromine battery, where only the two electrons of bromine Br - / Br 0 Conversion reaction, multi-electron reaction cannot occur.

[0048] The rate performance of Examples 1 to 4 and Comparative Examples 1 to 3 was tested, and the results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 4 exhibit higher rate performance.

[0049] Table 1 Rate performance

Claims

1. A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction, characterized in that: The electrolyte is an aqueous electrolyte containing zinc salt, iodine salt and bromine salt; the molar concentration of the zinc salt is 1-3M, the molar concentration of the iodine salt is 0.1-1M, the molar concentration of the bromine salt is 0.1-1M, and the molar ratio of bromide ion to iodide ion is 0.1-10.

2. A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction as claimed in claim 1, characterized in that: The electrolyte dissociates into NH4 in water + , Li + 、Na + , K + , Rb + , Cs + Mg 2+ At least one cation source.

3. A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction as claimed in claim 1, characterized in that: The zinc salt is one or more of zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc perchlorate, zinc bis(trifluoromethanesulfonyl)imide, zinc trifluoromethanesulfonate and hydrates thereof.

4. A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction as claimed in claim 1, characterized in that: The iodized salt is one or more of cesium iodide, sodium iodide, potassium iodide and zinc iodide.

5. A multifunctional mixed electrolyte for high-rate long-cycle multi-electron reaction as claimed in claim 1, characterized in that: The bromide salt is one or more of ammonium bromide, cesium bromide, sodium bromide, potassium bromide, zinc bromide, rubidium bromide, lithium bromide and magnesium bromide.

6. An aqueous zinc-double halogen battery assembled using the multifunctional mixed electrolyte according to any one of claims 1 to 5, characterized in that: The battery is assembled from a positive electrode, a multifunctional mixed electrolyte and a negative electrode using conventional technology; the positive electrode is made of activated carbon material; and the negative electrode is made of zinc metal.

7. An aqueous zinc-double halogen battery as claimed in claim 6, characterized in that: The positive electrode loaded activated carbon content is 1-10 mg cm -2 , with a specific surface area of ​​1000~4000 m 2 g -1 .

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