Preparation method of zinc bromide / lithium bromide composite electrolyte for zinc ion battery

Abstract

The application relates to a high-concentration aqueous zinc-ion battery electrolyte, aiming to improve the electrochemical performance of the battery, in particular the low-temperature ion transport capacity, the working temperature range and the cycle life. The electrolyte comprises zinc bromide, lithium bromide and deionized water, wherein the concentration of the zinc bromide is 5-12 mol / L, the concentration of the lithium bromide is 10-24 mol / L, and the molar ratio of the two is 1:(0.2-5). By adding lithium bromide as an additive, the long-range ordered local cluster network of zinc bromide is broken, a high-entropy electrolyte is formed, and the ion conductivity and the electrochemical performance are significantly improved. Experimental results show that the electrolyte exhibits excellent ion conductivity and coulomb efficiency at different temperatures, and is suitable for a wide working temperature range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary energy storage batteries, and particularly relates to a water-based zinc ion battery electrolyte and a preparation method thereof. BACKGROUND

[0002] The sustainability of the environment and resources is becoming increasingly important for the development of next-generation battery technologies that need to meet the growing market for renewable energy storage in smart grids and automotive electrification. Lithium-ion battery (LIBs) technology currently dominates the field due to its high energy density and long cycle life. However, as the demand for energy storage capacity continues to increase, the price and resource fluctuations caused by the scarcity of lithium and transition metals are receiving increasing attention. In addition, LIBs require an energy-intensive manufacturing process that often uses toxic and environmentally unfriendly chemicals. The potential safety issues during the operation of LIBs and their tolerance to mechanical abuse have also not been fully resolved.

[0003] Water-based zinc batteries have become one of the promising batteries due to the compatibility of zinc (Zn) with aqueous electrolytes. Zinc is relatively abundant and has a mature recycling infrastructure. The application of "water-in-salt" electrolytes recently has expanded the electrochemical stability window of aqueous electrolytes and enabled new electrochemical properties, including zinc batteries that are currently limited to primary use. However, the advantages of water-in-salt electrolytes for aqueous zinc batteries are not enough to overcome the obstacles to commercialization, as the reversibility of zinc plating / deplating is poor, the energy efficiency is insufficient, and the low-temperature transport capability is weak.

[0004] Unlike simply increasing the salt concentration in a single-salt electrolyte, the addition of a concentrated supporting salt has been shown to be another promising strategy that can largely exclude water from solvating Zn 2+ in aqueous solution. As a result, the hydrolysis ability of this electrolyte is significantly reduced, and the reversibility of zinc plating / deplating is correspondingly improved. Moreover, since all the "free water" in the electrolyte is bound by the concentrated salt, the freezing point of the electrolyte is greatly reduced, thereby enhancing its low-temperature ion transport capability. SUMMARY

[0005] The application aims to provide a water-based zinc ion battery electrolyte containing zinc bromide salt and lithium bromide salt, which reduces the length of zinc solvation structure aggregates and destroys the hydrogen bond network of free water through the synergistic effect of anions and cations, thereby generating a unique high-entropy solvation structure, thereby enhancing the low-temperature ion transport capability, inhibiting dendrite growth, and widening the working temperature range.

[0006] To achieve the above object, the technical scheme of the present application is as follows: A high-concentration aqueous zinc ion battery electrolyte, characterized in that the aqueous zinc ion battery electrolyte comprises zinc bromide, lithium bromide and deionized water, and specifically comprises the following steps:

[0007] (1) At 20 DEG C, 5 mL of deionized water with conductivity less than 18 mu s / cm is taken out by a pipette into a 10 mL glass vial;

[0008] (2) At 20 DEG C, a certain amount of zinc bromide salt is weighed and added to the deionized water, and the mixture is stirred at 10-60 DEG C for 1 h, wherein the concentration of zinc bromide is 5-12 mol / L;

[0009] (3) At 20 DEG C, a certain amount of lithium bromide salt is weighed and added to the zinc bromide solution, and the mixed solution is stirred at 10-60 DEG C for 1 h by a magnetic stirrer, and the aqueous zinc ion battery electrolyte is obtained after stirring; wherein the concentration of lithium bromide is 10-24 mol / L;

[0010] (4) The molar ratio of the added zinc bromide salt to the lithium bromide salt is 1:(0.2-5)

[0011] Further, in the step (2), the concentration of the zinc bromide salt is 6-10 mol / L.

[0012] Further, in the step (3), the concentration of the lithium bromide salt is 10-24 mol / L.

[0013] Further, in the step (4), the molar ratio of the added zinc bromide salt to the lithium bromide salt is 1:(0.5-4).

[0014] Further, in the steps (2) and (3), the temperature range is 20-40 DEG C.

[0015] In the above technical scheme of the present application, the zinc bromide salt is dissolved in pure water solvent as a blank sample electrolyte, and the lithium bromide is added as an additive to improve the electrochemical performance. The electrolyte of a single high-concentration zinc bromide salt dissolved in pure water has a long-range ordered local cluster network, the free solvent network is destroyed, the free solvent is limited in the cluster network, thereby limiting the ion transport capacity, resulting in a substantial reduction in ion conductivity, thereby affecting the electrochemical performance. After adding lithium bromide, the zinc bromide is given additional bromide ions to meet the preferred tetrahedral coordination structure of zinc tetrabromide anions, thereby breaking the long-range ordered local cluster network and becoming a shorter aggregate to form a so-called high-entropy electrolyte.

[0016] The aqueous zinc ion battery electrolyte of the present application comprises zinc bromide, lithium bromide and deionized water; compared with the blank sample electrolyte, it has stronger low-temperature ion transport capacity, wider working temperature range and more excellent cycle life. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the solvation structure of a high-entropy electrolyte.

[0018] Figure 2 This is the coulombic efficiency curve of the aqueous zinc-ion battery electrolyte compared to the blank electrolyte.

[0019] Figure 3 These are the ionic conductivity curves of the aqueous zinc-ion battery electrolyte and the blank electrolyte at different temperatures. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this invention are merely preferred embodiments and are not intended to limit the scope of the invention.

[0021] Example 1

[0022] At room temperature, 5 mL of deionized water was transferred to a 10 mL glass vial using a pipette. Then, 6.76 g of zinc bromide salt and 2.61 g of lithium bromide were weighed and added to the deionized water. The mixture was magnetically stirred for 1 hour to obtain an aqueous zinc-ion battery electrolyte. A CR2025 coin cell battery was assembled using zinc foil as the negative electrode, this aqueous electrolyte, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using a LAND battery testing system, with a test current density of 0.5 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 0.5V, and repeating the charge-discharge cycle. At different temperatures, the conductivity of the blank electrolyte and the aqueous electrolyte was tested using a conductivity meter to compare their ionic conductivity.

[0023] Example 2

[0024] At room temperature, 5 mL of deionized water was transferred to a 10 mL glass vial using a pipette. Then, 7.88 g of zinc bromide salt and 3.03 g of lithium bromide were weighed and added to the deionized water. The mixture was magnetically stirred for 1 hour to obtain an aqueous zinc-ion battery electrolyte. A CR2025 coin cell battery was assembled using zinc foil as the negative electrode, this aqueous electrolyte, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using a LAND battery testing system, with a test current density of 0.5 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 0.5V, and repeating the charge-discharge cycle. At different temperatures, the conductivity of the blank electrolyte and the aqueous electrolyte was tested using a conductivity meter to compare their ionic conductivity.

[0025] Example 3

[0026] At room temperature, 5 mL of deionized water was transferred to a 10 mL glass vial using a pipette. Then, 9 g of zinc bromide salt and 3.47 g of lithium bromide were weighed and added to the deionized water. The mixture was magnetically stirred for 1 hour. After stirring, an aqueous zinc-ion battery electrolyte was obtained. A CR2025 coin cell battery was assembled using zinc foil as the negative electrode, this aqueous electrolyte, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using a LAND battery testing system, with a test current density of 0.5 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 0.5V, and repeating the charge-discharge cycle. At different temperatures, the conductivity of the blank electrolyte and the aqueous electrolyte was tested using a conductivity meter to compare their ionic conductivity.

[0027] Example 4

[0028] At room temperature, 5 mL of deionized water was transferred to a 10 mL glass vial using a pipette. Then, 10.13 g of zinc bromide salt and 3.90 g of lithium bromide were weighed and added to the deionized water. The mixture was magnetically stirred for 1 hour. After stirring, an aqueous zinc-ion battery electrolyte was obtained. A CR2025 coin cell battery was assembled using zinc foil as the negative electrode, this aqueous electrolyte, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using a LAND battery testing system, with a test current density of 0.5 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 0.5V, and repeating the charge-discharge cycle. At different temperatures, the conductivity of the blank electrolyte and the aqueous electrolyte was tested using a conductivity meter to compare their ionic conductivity.

[0029] Example 5

[0030] At room temperature, 5 mL of deionized water was transferred to a 10 mL glass vial using a pipette. Then, 11.26 g of zinc bromide salt and 4.34 g of lithium bromide were weighed and added to the deionized water. The mixture was magnetically stirred for 1 hour to obtain an aqueous zinc-ion battery electrolyte. A CR2025 coin cell battery was assembled using zinc foil as the negative electrode, this aqueous electrolyte, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using a LAND battery testing system, with a test current density of 0.5 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 0.5V, and repeating the charge-discharge cycle. At different temperatures, the conductivity of the blank electrolyte and the aqueous electrolyte was tested using a conductivity meter to compare their ionic conductivity.

[0031] Examples First cycle coulomb efficiency (%) Cycling average coulomb efficiency (%) 1 91.3 99.1 2 93.5 99.3 3 94.8 99.4 4 96.8 99.7 5 97.1 99.7

Claims

1. A high-concentration aqueous zinc-ion battery electrolyte, characterized in that, The aqueous zinc-ion battery electrolyte includes zinc bromide, lithium bromide, and deionized water, and specifically includes the following steps: (1) At 20℃, use a pipette to transfer 5 mL of deionized water with a conductivity of less than 18 μs / cm into a 10 mL glass vial; (2) At 20℃, weigh a certain amount of zinc bromide salt and add it to deionized water. At a temperature range of 10-60℃, add magnetic stirring for 1 hour, wherein the concentration of zinc bromide is 5-12 mol / L. (3) At 20℃, a certain amount of lithium bromide salt was weighed and added to zinc bromide solution. At a temperature range of 10-60℃, magnetic pair was added to mix the solution and stirred for 1 hour. After stirring, an aqueous zinc-ion battery electrolyte was obtained; the concentration of lithium bromide was 10-24 mol / L. (4) The molar ratio of zinc bromide salt to lithium bromide salt is 1:(0.2-5).

2. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, In step (2), the concentration of zinc bromide salt is 6-10 mol / L.

3. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The concentration of lithium bromide salt in step (3) is 10-24 mol / L.

4. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The molar ratio of zinc bromide salt to lithium bromide salt added in step (4) is 1:(0.5-4).

5. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The temperature range in steps (2) and (3) is 20-40℃.

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