Electrolyte and zinc ion battery

Abstract

This invention discloses an electrolyte and a zinc-ion battery. The electrolyte comprises water, Zn(CF3SO3)2, Na2HPO4, NaH2PO4, and MnSO4; wherein the total amount of Na2HPO4 and NaH2PO4 accounts for 0.1-10% of the total mass of the electrolyte, and the total mass of MnSO4 accounts for 0.1-10% of the total mass of the electrolyte. By precisely controlling the concentration of these components, this invention found that adding a specific ratio of mixed sodium phosphate salt and MnSO4 together to Zn(CF3SO3)2 can effectively improve the performance of the electrolyte, thereby positively affecting the overall performance of the zinc-ion battery. A series of electrochemical tests, in-situ X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses confirmed that this novel aqueous zinc-ion battery electrolyte can significantly improve the cycle life of the battery and inhibit the decomposition of the cathode material and the formation of zinc dendrites.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery technology application, and particularly relates to an electrolyte and a zinc-ion battery. Background Technology

[0002] Aqueous zinc-ion batteries, as a type of multivalent battery, possess advantages such as high energy density, low cost, environmental friendliness, and safety, and have seen rapid development in recent years. They are recognized as an ideal battery system for future large-scale energy storage and flexible wearable electronic devices. In recent years, research on aqueous zinc-ion batteries has mainly focused on cathode materials and electrolytes. Optimizing the electrolyte can ensure battery safety, suppress side reactions, and also allow for targeted customization of the cathode material to inhibit its decomposition and improve its electrochemical performance.

[0003] VOPO4 is a good zinc storage material with a high operating voltage, but it suffers from poor solubility in aqueous electrolytes. Common electrolytes used in VOPO4-based zinc-ion batteries are Zn(CF3SO3)2 salt and CF3SO3... – It has a good promoting effect on suppressing the content of free water around Zn ions and can reduce the occurrence of hydrogen evolution side reactions. Chinese patent with publication number CN116759660A discloses a mixed solution prepared by phosphate ester solvent, Zn(CF3SO3)2 and water as an electrolyte, but it is not suitable for VOPO4 system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an electrolyte and a zinc-ion battery. This invention utilizes a phosphate buffer solution and MnSO4 as electrolyte additives to achieve a reverse equilibrium of side reactions. This method effectively suppresses the decomposition of the positive electrode material VOPO4 because PO4... 3- There is competitive adsorption between PO4 and VOPO4, thus reducing the decomposition of VOPO4 (based on the principle of the common ion effect). Meanwhile, PO4... 3- The interconversion process between PO4 and VOPO4 is relatively reversible, which makes PO4... 3- These additives can store protons and buffer local pH levels, helping to maintain system stability and extend battery life. Simultaneously, they can form a Zn3(PO4)2·4H2O protective film on the electrode material surface, inhibiting the dissolution of the cathode material.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] An electrolyte comprising water, Zn(CF3SO3)2, Na2HPO4, NaH2PO4 and MnSO4; wherein the total amount of Na2HPO4 and NaH2PO4 accounts for 0.1 to 10% of the total mass of the electrolyte, and the total mass of MnSO4 accounts for 0.1 to 10% of the total mass of the electrolyte.

[0007] Preferably, the concentration of Zn(CF3SO3)2 in the electrolyte is 2.8~3.2 mol / L.

[0008] Preferably, the concentration of Zn(CF3SO3)2 in the electrolyte is 3 mol / L.

[0009] Preferably, the molar ratio of Na2HPO4 to NaH2PO4 is 1:1.

[0010] Preferably, the concentration of Na2HPO4 in the electrolyte is 0.1~0.15 mol / L.

[0011] Preferably, the concentration of Na2HPO4 in the electrolyte is 0.1 mol / L.

[0012] Preferably, the concentration of MnSO4 in the electrolyte is 0.2~0.5 mol / L.

[0013] A zinc-ion battery comprising the electrolyte.

[0014] Preferably, zinc-ion batteries use zinc metal as the negative electrode.

[0015] Preferably, zinc-ion batteries use phosphate as the positive electrode material.

[0016] Preferably, the phosphate is one of MnVOPO4·2H2O, Li3V2(PO4)3, Na3V2(PO4)3 and Na3V2(PO4)3F3.

[0017] Preferably, the zinc-ion battery uses GF / A glass fiber as the separator.

[0018] Compared with the prior art, the beneficial effects of the present invention include:

[0019] The electrolyte provided by this invention, when used as an electrolyte in an aqueous zinc-ion battery, can effectively suppress the decomposition of the cathode material and the formation of zinc dendrites, and significantly improve the cycle life of the zinc-ion battery. Attached Figure Description

[0020] Figure 1 The graph shows the electrochemical cycling performance of the zinc-ion battery prepared in Example 3.

[0021] Figure 2 The graph shows the electrochemical cycling performance of the zinc-ion battery prepared in Example 4.

[0022] Figure 3 The graph shows the electrochemical cycling performance of the zinc-ion battery prepared for Comparative Example 2.

[0023] Figure 4 Photographs showing the dissolution of MnVOPO4·2H2O powder after it has been placed in the electrolyte of Example 2 and left to stand for 2 months.

[0024] Figure 5 This is a schematic diagram of the electrochemical rate performance of the zinc-ion battery prepared in Example 4.

[0025] Figure 6 The graph shows the cyclic voltammetry test curves of the zinc-ion battery prepared in Example 4.

[0026] Figure 7 The image shows the changes in the in-situ XRD pattern of the (002) crystal plane of the MnVOPO4·2H2O material in the electrolyte of Example 2.

[0027] Figure 8 This is a SEM image of the negative electrode material of the zinc-ion battery in Example 4 after 2000 cycles.

[0028] Figure 9 The image shows the SEM image of the negative electrode material of the zinc-ion battery in Comparative Example 2 after 160 cycles. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] The MnVOPO4·2H2O used in the examples and comparative examples was prepared in-house. For specific synthesis methods, please refer to the following literature: Synthesis and powder data for [Mn(H2O)] 0.25 (VO) 0.75 PO4·2H2O (Powder Diffraction:1, June, 1993, Chemistry).

[0031] Example 1

[0032] An electrolyte is composed of water, Zn(CF3SO3)2, Na2HPO4, NaH2PO4 and MnSO4; wherein the concentration of Zn(CF3SO3)2 in the electrolyte is 3 mol / L, the concentrations of Na2HPO4 and NaH2PO4 in the electrolyte are both 0.1 mol / L, and the concentration of MnSO4 in the electrolyte is 0.2 mol / L.

[0033] Example 2

[0034] An electrolyte is composed of water, Zn(CF3SO3)2, Na2HPO4, NaH2PO4 and MnSO4; wherein the concentration of Zn(CF3SO3)2 in the electrolyte is 3 mol / L, the concentrations of Na2HPO4 and NaH2PO4 in the electrolyte are both 0.1 mol / L, and the concentration of MnSO4 in the electrolyte is 0.5 mol / L.

[0035] Example 3

[0036] A zinc-ion battery is provided, with zinc metal as the negative electrode, MnVOPO4·2H2O as the positive electrode, GF / A glass fiber as the separator, and the electrolyte prepared in Example 1 as the electrolyte, which is assembled into a MnVOPO4·2H2O||Zn battery.

[0037] Example 4

[0038] A zinc-ion battery is provided, with zinc metal as the negative electrode, MnVOPO4·2H2O as the positive electrode, GF / A glass fiber as the separator, and the electrolyte prepared in Example 2 as the electrolyte, which is assembled into a MnVOPO4·2H2O||Zn battery.

[0039] Comparative Example 1

[0040] Zn(CF3SO3)2 with a concentration of 3 mol / L was used as the electrolyte.

[0041] Comparative Example 2

[0042] A zinc-ion battery is provided, with zinc metal as the negative electrode, MnVOPO4·2H2O as the positive electrode, GF / A glass fiber as the separator, and the electrolyte prepared in Comparative Example 1 as the electrolyte, which is assembled into a MnVOPO4·2H2O||Zn battery.

[0043] Test section:

[0044] 1. The zinc-ion batteries prepared in Examples 3 and 4, and Comparative Example 2, were charged and discharged at a current density of 1000 mA / g, with a total time of 20 min for each charge-discharge cycle. Their respective cycle performance is as follows: Figure 1 , Figure 2 and Figure 3 As shown.

[0045] See Figures 1-3 We can see that: Comparative Example 2, which did not use the electrolyte additive described in this invention (e.g., Figure 3 As shown, after 160 cycles, the capacity decayed to 75%. In contrast, Examples 3 and 4, which used electrolyte additives, exhibited better cycle stability. Example 3 (as shown) Figure 1 As shown, after 700 charge-discharge cycles, the battery's capacity retention reached 96%, significantly improving the battery's cycle stability. For Example 4 (as shown...) Figure 2 As shown in the figure, when the concentration of MnSO4 is increased to 0.5 mol / L, after 2160 charge-discharge cycles, the capacity retention rate is 97%, the discharge specific capacity can reach 150 mAh / g, and the battery capacity hardly decays.

[0046] 2. After placing the MnVOPO4·2H2O powder in the electrolyte of Example 2 and letting it stand for 2 months, the dissolution of the powder is shown in the figure. Figure 4 As shown. From Figure 4 It was clearly observed that MnVOPO4·2H2O did not dissolve significantly, demonstrating the excellent ability of the electrolyte in Example 2 to inhibit material dissolution. In fact, the electrolyte prepared in Example 1 of this invention also has excellent ability to inhibit the dissolution of MnVOPO4·2H2O powder, which will not be elaborated here.

[0047] 3. Figure 5 This is a schematic diagram illustrating the electrochemical rate performance of the zinc-ion battery prepared in Example 4. From... Figure 5 It can be seen that the aqueous zinc-ion battery based on the electrolyte described in Example 2 exhibits good rate performance. Even when the current density is increased to 2000 mA / g, the battery still maintains a discharge specific capacity of 124 mAh / g.

[0048] 4. Furthermore, the zinc-ion battery prepared in Example 4 was subjected to cyclic voltammetry testing, and the test results are as follows: Figure 6 As shown. From Figure 6 It can be seen that at a scan rate of 0.2 mV / s, two pairs of redox peaks appeared, both belonging to the redox peaks of vanadium (1.54 / 1.37 V and 1.44 / 1.25 V), which is consistent with the voltage plateau that appeared during charge-discharge cycling. Meanwhile, the cyclic voltammetry curves show that this cathode material has good cycle reversibility in the electrolyte of Example 2.

[0049] 5. Figure 7 This is a non-in-situ XRD pattern of the (002) crystal plane of the MnVOPO4·2H2O material in the electrolyte of Example 2. From... Figure 7The changes can be observed as follows: (a) fully charged state: 2.1 V; (b) discharged state: 1.47 V; (c) discharged state: 1.28 V; (d) fully discharged state: 0.8 V; (e) charged state: 1.47 V; (f) charged state: 1.6 V; (g) fully charged state: 2.1 V. A complete charge-discharge process is the process from point a to point d and then to point g. This result indicates that the interlayer structure of the MnVOPO4·2H2O material in the electrolyte of Example 2 is highly reversible.

[0050] 6. To compare the zinc deposition on the negative electrode of the zinc-ion batteries prepared in Example 4 and Comparative Example 2, the zinc-ion batteries prepared in Example 4 and Comparative Example 2 were charged and discharged at a current density of 1000 mA / g, with a total time of 20 min for each charge-discharge cycle. The SEM image of the negative electrode material of the zinc-ion battery in Example 4 after 2000 cycles is shown below. Figure 8 As shown; the SEM image of the negative electrode material of the zinc-ion battery in Comparative Example 2 after 160 cycles is shown below. Figure 9 As shown. Further, see reference. Figures 8-9 As we can see, after 2000 cycles, the zinc-ion battery in Example 4 has a smooth and dense surface on the zinc anode, indicating that the addition of the electrolyte prepared in this invention has the effect of inhibiting the growth of zinc dendrites. In contrast, after only 160 cycles, a large number of zinc dendrites were generated on the zinc anode of the zinc-ion battery prepared in Comparative Example 2.

[0051] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte contains water, Zn(CF3SO3)2, Na2HPO4, NaH2PO4, and MnSO4; wherein the total amount of Na2HPO4 and NaH2PO4 accounts for 0.1~10% of the total mass of the electrolyte, and the molar ratio of Na2HPO4 to NaH2PO4 is 1:1; the total mass of MnSO4 accounts for 0.1~10% of the total mass of the electrolyte, and the concentration of MnSO4 in the electrolyte is 0.2~0.5 mol / L.

2. The electrolyte according to claim 1, characterized in that, The concentration of Zn(CF3SO3)2 in the electrolyte is 2.8~3.2 mol / L.

3. The electrolyte according to claim 2, characterized in that, The concentration of Zn(CF3SO3)2 in the electrolyte is 3 mol / L.

4. The electrolyte according to claim 1, characterized in that, The concentration of Na2HPO4 in the electrolyte is 0.1~0.15 mol / L.

5. A zinc-ion battery, characterized in that, It includes the electrolyte as described in any one of claims 2 to 4.

6. The zinc-ion battery according to claim 5, characterized in that, The zinc-ion battery uses zinc metal as the negative electrode.

7. The zinc-ion battery according to claim 6, characterized in that, The membrane is made of GF / A glass fiber; the cathode material is phosphate.

8. The zinc-ion battery according to claim 7, characterized in that, The phosphate is one of MnVOPO4·2H2O, Li3V2(PO4)3, Na3V2(PO4)3, and Na3V2(PO4)3F3.

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