A cathode composite material, electrolyte and application thereof for an aqueous zinc-ion battery

Abstract

The present invention discloses a cathode composite material, an electrolyte and their applications for an aqueous zinc-ion battery. The present invention adopts an ion pre-insertion method and a heterostructure design, mixing vanadium pentoxide and zinc citrate and heating them for reaction to form a ZVO@ZVOH composite material. This material has abundant heterointerfaces and active sites. As the cathode material of a zinc-ion battery, it significantly solves the problem of chemical dissolution during the cycling process of vanadium-based compounds. The heterointerfaces in ZVO@ZVOH contribute to electron transport and provide more Zn 2+ storage sites, thus effectively improving the rate performance; ZVOH effectively inhibits the dissolution problem of the cathode during cycling, thereby effectively increasing the cycling stability. The mixed Zn(CF3SO3)2 and ZnSO4 electrolyte can effectively reduce the dissolution of ZVO@ZVOH and inhibit the dendrite growth of the Zn anode.

Description

Technical Field

[0001] The present invention relates to the field of aqueous zinc-ion batteries, and particularly to a cathode composite material, an electrolyte and their applications for aqueous zinc-ion batteries. Background Art

[0002] Aqueous zinc-ion batteries (AZIBs) have received extensive attention due to their unique advantages. Compared with lithium, zinc resources are more abundant and less costly, and aqueous electrolytes have the advantages of being non-flammable, non-explosive, non-toxic and pollution-free. At the same time, multivalent ions in aqueous electrolytes provide a relatively high theoretical capacity and energy density, further enhancing the performance of AZIBs. However, problems still exist in the long-term cycle stability and battery safety of AZIBs, which urgently need to be solved.

[0003] The performance of AZIBs is mainly determined by the selection of the cathode material and the stability of the anode material. Currently, common cathode materials include manganese oxides, vanadium-based compounds, and Prussian blue analogs, etc. Manganese oxides have a relatively high theoretical capacity, but due to irreversible phase changes during charge and discharge processes, their cycle stability is poor; Prussian blue analogs usually have a relatively low specific capacity and poor cycle performance. Therefore, vanadium-based compounds, especially vanadium oxides, due to their rich layered structures and multivalent state characteristics, can achieve more electron transfers in redox reactions and exhibit a relatively high capacity. However, during the electrochemical reaction process, the interaction between free water (H2O) and vanadium (V) atoms causes the cathode material to dissolve, seriously affecting the cycle life and safety of the battery.

[0004] To overcome this problem, researchers have proposed various innovative strategies, such as suppressing vanadium dissolution by surface modification of materials or introducing a new interfacial layer. Mai et al. introduced Zn x (OTf) y (OH) 2x-y ·nH2O into V6O 13 as an artificial cathode-electrolyte interfacial layer, successfully suppressing the dissolution of vanadium during the electrochemical reaction process. In addition, atomic layer deposition technology in-situ prepares a Zn3V2O7(OH)2·2H2O layer on the surface of the V2O5 electrode, which can effectively improve the stability of the vanadium-based cathode and promote the transport ability of Zn 2+ , thereby improving the cycle life of the battery. Although these methods have improved the stability of the cathode to a certain extent, how to further improve the cycle life while maintaining a relatively high capacity is still a technical problem that urgently needs to be solved.

[0005] In addition, the stability of zinc anodes in AZIBs also faces severe challenges. To inhibit the growth of zinc dendrites, researchers have tried to improve the stability of zinc anodes through electrolyte modification and anode protection layer strategies. Although in some electrolytes, such as Zn(CF3SO3)2, it can effectively inhibit the dissolution of vanadium-based cathodes and stabilize the anode, a single electrolyte cannot maintain the stability of both the cathode and the anode simultaneously. Therefore, how to balance the interaction between the cathode and the anode while ensuring their stability and construct an aqueous zinc-ion battery with high stability and long cycle life remains a difficult point and the key in current research. Summary of the Invention

[0006] In view of this, the present invention provides a cathode composite material, an electrolyte and their applications for an aqueous zinc-ion battery, and the main purpose is to provide a cathode composite material that can effectively increase the capacity of the cathode, while enhancing the ion mobility and the battery stability performance.

[0007] To achieve the above object, the present invention mainly provides the following technical solutions:

[0008] On the one hand, the present invention provides a cathode composite material for an aqueous zinc-ion battery, and the cathode composite material is prepared from zinc citrate and vanadium pentoxide through the following steps:

[0009] 1) Weigh zinc citrate and vanadium pentoxide in a mass ratio of (0.03 - 0.8) : 1; add vanadium pentoxide to deionized water and 30wt% hydrogen peroxide as solvents and stir for 1 - 3 h to prepare a vanadium pentoxide solution;

[0010] 2) Add zinc citrate to the vanadium pentoxide solution and stir for 25 - 35 min to form an orange-red mixture;

[0011] 3) Put the orange-red mixture into an autoclave and heat it to react to obtain the cathode composite material.

[0012] In the present invention, the cathode composite material is also called

[0013] ZnV8O 20 ·nH2O (ZVO) @Zn3(OH)2V2O7·2H2O (ZVOH) composite material.

[0014] Preferably, in step 1), the volume ratio of deionized water to 30wt% hydrogen peroxide is 40:1.

[0015] Preferably, the concentration of the vanadium pentoxide solution prepared in step 1) is 0.025 mol / L.

[0016] Preferably, the mass ratio of the zinc citrate and vanadium pentoxide prepared in the step 1) is preferably 0.165:1.

[0017] Preferably, in the step 3), the heating time of the autoclave is 10 h to 14 h, and the heating temperature range is 110 °C to 130 °C.

[0018] Preferably, the step 3) further includes the following steps: repeatedly rinsing the positive electrode composite material with deionized water, and obtaining a powder material after drying treatment.

[0019] Preferably, the drying temperature of the drying treatment is 60 °C to 80 °C, and the drying time is 12 h to 16 h.

[0020] On the other hand, the present invention also provides a mixed electrolyte for an aqueous zinc ion battery, which is used in combination with the above positive electrode composite material. The mixed electrolyte is composed of 2 mol / L Zn(CF3SO3)2 and 1 mol / L ZnSO4 electrolytes.

[0021] Preferably, the concentration of the Zn(CF3SO3)2 electrolyte is 2 mol / L, and the concentration of the ZnSO4 electrolyte is 1 mol / L; the molar ratio of Zn(CF3SO3)2 and ZnSO4 in the mixed electrolyte is (0.1-2):(0.01-1).

[0022] On the other hand, the present invention also provides an aqueous zinc ion battery. The positive electrode material includes any one of the above positive electrode composite materials; the electrolyte is any one of the above mixed electrolytes. Specifically, the positive electrode composite material is applied to the positive electrode material of the zinc ion battery, arranged at the positive electrode of the zinc ion battery, Zn(CF3SO3)2 and ZnSO4 with a molar ratio of (0.1-2):(0.01-1) are used as the electrolyte, and a Zn foil is used as the negative electrode to assemble a full battery.

[0023] Compared with the prior art, the present invention prepares the ZVO@ZVOH composite material by an ion pre-insertion method, and has the following remarkable technical effects:

[0024] 1. A "zinc-rich" ZVO@ZVOH with a biphasic vanadate structure is prepared by a one-step hydrothermal method.

[0025] 2. The rich heterointerfaces in this structure contribute to electron transport and provide more Zn 2+ storage sites, reducing the diffusion impedance in the electrode.

[0026] 3. ZVOH effectively maintains the stability of the positive electrode during cycling, and the composite material exhibits high specific capacity and long cycle life.

[0027] 4. The hybrid Zn(CF3SO3)2 and ZnSO4 electrolyte can effectively reduce the dissolution of ZVO@ZVOH and inhibit the dendritic growth of the Zn anode.

[0028] 5. This material does not require calcination during the preparation process, featuring energy conservation and environmental friendliness.

[0029] Therefore, the present invention provides an efficient and sustainable method for preparing a cathode material and a hybrid electrolyte, significantly enhancing the electrical performance of zinc-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the X-ray diffraction pattern of the ZVO@ZVOH-S2 composite material provided in Example 1 of the present invention;

[0031] Figure 2 It is the scanning electron microscope image of the ZVO@ZVOH-S2 composite material provided in Example 1 of the present invention;

[0032] Figure 3 It is the high-magnification transmission electron microscope image of the ZVO@ZVOH-S2 composite material provided in Example 1 of the present invention;

[0033] Figure 4 It is the cyclic voltammogram of the ZVO@ZVOH-S2 composite material as the cathode material of a zinc-ion battery provided in Example 1 of the present invention;

[0034] Figure 5 It is the cycling performance graph of a zinc-ion battery prepared in Example 1 provided by the present invention;

[0035] Figure 6 It is the cycling performance graph of a zinc-ion battery prepared in Comparative Example 1 provided by the present invention;

[0036] Figure 7 It is the cycling performance graph of a zinc-ion battery prepared in Comparative Example 2 provided by the present invention;

[0037] Figure 8 It is the cycling performance graph of a zinc-ion battery prepared in Comparative Example 3 provided by the present invention;

[0038] Figure 9 It is the cycling performance graph of a zinc-ion battery prepared in Comparative Example 4 provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be further described in detail below with reference to the drawings and examples.

[0040] On the one hand, the embodiments of the present invention provide a composite material, including:

[0041] Zinc citrate and vanadium pentoxide, wherein the mass ratio of the zinc citrate to the vanadium pentoxide is (0.03 - 0.8):1.

[0042] In the ZVO@ZVOH composite material of the present invention, the heterojunction in ZVO@ZVOH helps electron transport and provides more Zn 2+ storage sites, thus effectively improving the rate performance; ZVOH effectively inhibits the dissolution problem of the positive electrode during cycling, thus effectively increasing the cycling stability. The mixed electrolyte of Zn(CF3SO3)2 and ZnSO4 can effectively reduce the dissolution of ZVO@ZVOH and inhibit the dendritic growth of the Zn negative electrode.

[0043] On the other hand, the embodiment of the present invention also provides a preparation method of a composite material, comprising the following steps:

[0044] (1) Weigh zinc citrate and vanadium pentoxide according to the mass ratio; prepare a vanadium pentoxide solution;

[0045] (2) Add zinc citrate to the vanadium pentoxide solution and stir to form an orange-red mixture;

[0046] (3) Put the orange-red mixture into an autoclave and heat it to react to obtain the ZVO@ZVOH composite material.

[0047] Finally, the embodiment of the present invention also provides a mixing method of an electrolyte, wherein the molar ratio of the Zn(CF3SO3)2 and ZnSO4 electrolytes is (0.1 - 2):(0.01 - 1). Assemble the above positive electrode composite material and the mixed electrolyte into a full cell.

[0048] The present invention uses the ion pre-insertion method and heterojunction design to mix vanadium pentoxide and zinc citrate and heat them to react to form the ZVO@ZVOH composite material. The ZVO@ZVOH material with rich boundaries and active sites is used as the positive electrode material of the zinc-ion battery. The heterojunction in ZVO@ZVOH helps electron transport and provides more Zn 2+ storage sites, thus effectively improving the rate performance; ZVOH effectively inhibits the dissolution problem of the positive electrode during cycling, thus effectively increasing the cycling stability. The mixed electrolyte of Zn(CF3SO3)2 and ZnSO4 can effectively reduce the dissolution of ZVO@ZVOH and inhibit the dendritic growth of the Zn negative electrode.

[0049] Example 1

[0050] The embodiment of the present invention provides a preparation method of a composite material, comprising the following steps:

[0051] 100. Weigh zinc citrate and vanadium pentoxide according to a mass ratio of 0.165:1.

[0052] 101. Add 0.182 g of vanadium pentoxide to 40 mL of a solution of deionized water and 30 wt% hydrogen peroxide with a volume ratio of 40:1.

[0053] 102. Stir for 1 h to obtain an orange-red vanadium pentoxide solution with a concentration of 0.025 mol / L.

[0054] 103. Add zinc citrate to the vanadium pentoxide solution and stir for 25 min to form an orange-red mixture.

[0055] 104. Place the orange-red mixture in an autoclave for a heating reaction for 6 h at a heating temperature of 120 °C to obtain a ZVO@ZVOH composite material.

[0056] 105. Wash the composite material repeatedly with deionized water and then perform a drying treatment at a drying temperature of 60 °C for 12 h to obtain a powder material.

[0057] 106. Mix 2 mol / L Zn(CF3SO3)2 and 1 mol / L ZnSO4 electrolytes in a molar ratio of 2:1, and stir to obtain a mixed electrolyte.

[0058] As Figure 1 shown, the composite material is denoted by the code ZVO@ZVOH-S2. The diffraction peaks at 8.3° and 25.62° correspond to the characteristic peaks of CaV8O 20 ·xH2O (PDF#45-1362). The diffraction peaks at 12.3° and 30.16° correspond to the characteristic peaks of Zn3(OH)2V2O7·2H2O (PDF#50-0570).

[0059] As Figure 2 shown, the ZVO@ZVOH sample exhibits a morphology of microsphere aggregation packing, where the smallest microspheres have a diameter of about 0.2 microns and the largest microspheres are 8.0 microns.

[0060] As Figure 3 shown, it can be seen that the ZVO@ZVOH material is composed of uniform nanorods. Heterogeneous interfaces and lattice fringes can be observed in the high-resolution TEM. The lattice fringes of 0.194 nm and 0.125 nm correspond to the (60-1) and (005) crystal planes of ZVO respectively, and the lattice fringe of 0.201 nm corresponds to the (120) lattice fringe of ZVOH.

[0061] In this invention, a CR2032 coin battery is used to test the electrochemical performance of the composite ZVO@ZVOH-S2 material. When preparing the electrode, 70% ZVO@ZVOH-S2 active material, 20% Super P, and 10% polyvinylidene fluoride (PVDF) are mixed and dispersed with N-methylpyrrolidone (NMP) to form a homogeneous slurry. Then, the slurry is coated on a titanium foil and dried in a vacuum environment at 60 °C for 12 h to obtain an electrode with a mass loading of approximately 1.8 mg·cm -2 When assembling the zinc-ion battery, a glass fiber is used as the separator, Zn(CF3SO3)2 and ZnSO4 are used as the electrolyte, and a zinc foil is used as the counter electrode. All components are assembled into a CR2032-type ZIBs in air. A cyclic voltammetry (CV) performance test is carried out using an electrochemical workstation within a scanning voltage range of 0.3 - 1.5 V. In the CV curve, it can be clearly observed that there are two pairs of redox peaks, located at 1.02 V / 0.96 V and 0.62 V / 0.59 V respectively, and two reduction peaks located at 0.45 V and 0.82 V, corresponding to the transformation of V 5+ / V 4+ and V 4+ / V 3+ as shown in Figure 4 At a current density of 0.3 A g -1 , the specific capacity of the battery reaches 340.2 mA h g -1 after 2 cycles. After 200 cycles, the specific capacity still remains at 304.7 mA h g -1 , and the capacity retention rate is approximately 89.6%, as shown in Figure 5 . These data indicate that the battery has excellent cycle stability and electrochemical performance.

[0062] In this embodiment, an ion pre-insertion method and a heterostructure design are adopted. Vanadium pentoxide and zinc citrate are mixed and heated to react to form a ZVO@ZVOH composite material. The ZVO@ZVOH material with rich boundaries and active sites is used as the positive electrode material of the zinc-ion battery. The heterojunction boundaries in ZVO@ZVOH contribute to electron transport and provide more Zn 2+ storage sites, thus effectively improving the rate performance; ZVOH effectively inhibits the dissolution problem of the positive electrode during cycling, thus effectively increasing the cycle stability. The mixed electrolyte of Zn(CF3SO3)2 and ZnSO4 can effectively reduce the dissolution of ZVO@ZVOH and inhibit the dendrite growth of the Zn negative electrode.

[0063] Example 2

[0064] The embodiment of the present invention provides a preparation method for the second composite material, including the following steps:

[0065] 200. Weigh zinc citrate and vanadium pentoxide according to a mass ratio of 0.03:1.

[0066] 201. Add 0.182 g of vanadium pentoxide to 40 mL of a solution of deionized water and 30 wt% hydrogen peroxide with a volume ratio of 40:1.

[0067] 202. Stir for 2 h to obtain an orange-red vanadium pentoxide solution, and the concentration of the vanadium pentoxide solution is 0.025 mol / L.

[0068] 203. Add zinc citrate to the vanadium pentoxide solution and stir for 30 min to form an orange-red mixture.

[0069] 204. Put the orange-red mixture into an autoclave for a heating reaction for 7 h at a heating temperature of 100 °C to obtain a ZVO@ZVOH composite material.

[0070] 205. Repeatedly rinse the composite material with deionized water, and then perform a drying treatment at a drying temperature of 70 °C for 14 h to obtain a powder material.

[0071] 206. Mix 2 mol / L Zn(CF3SO3)2 and 1 mol / L ZnSO4 electrolytes according to a molar ratio of 2:1, and stir to obtain a mixed electrolyte.

[0072] In a high-temperature and high-pressure environment, a mixture of vanadium pentoxide and zinc citrate undergoes a chemical reaction to obtain a ZVO@ZVOH composite material, denoted as ZVO@ZVOH-S1.

[0073] The diffraction peaks of ZVO@ZVOH-S1 are very similar to those of ZVO@ZVOH-S2, and the diffraction peaks of ZVO@ZVOH-S1 are weaker than those of ZVO@ZVOH-S2. Referring to the method of Example 1, using ZVO@ZVOH-S1 as the positive electrode material, Zn(CF3SO3)2 and ZnSO4 as the electrolyte, and a zinc foil as the counter electrode to assemble a zinc-ion battery. The battery operates at a current density of 0.3 A g -1 After running for 10 cycles at a current density, the specific capacity reaches 267.4 mA h g -1 ; after running for 200 cycles, the capacity retention rate relative to the 10th cycle is about 81.2%.

[0074] Example 3

[0075] The embodiment of the present invention provides a preparation method for a third composite material, including the following steps:

[0076] 300. Weigh zinc citrate and vanadium pentoxide according to a mass ratio of 0.8:1.

[0077] 301. Add 0.182 g of vanadium pentoxide to 40 mL of a solution of deionized water and 30 wt% hydrogen peroxide with a volume ratio of 40:1.

[0078] 302. Stir for 3 h to obtain an orange-red vanadium pentoxide solution with a concentration of 0.025 mol / L.

[0079] 303. Add zinc citrate to the vanadium pentoxide solution and stir for 35 min to form an orange-red mixture.

[0080] 304. Place the orange-red mixture in an autoclave for a heating reaction for 6 h at a heating temperature of 130 °C to obtain a ZVO@ZVOH composite material.

[0081] 305. Rinse the composite material repeatedly with deionized water and then perform a drying treatment at a drying temperature of 70 °C for 14 h to obtain a powder material.

[0082] 306. Mix 2 mol / L of Zn(CF3SO3)2 and 1 mol / L of ZnSO4 electrolytes in a molar ratio of 2:1, and stir to obtain a mixed electrolyte.

[0083] In a high-temperature and high-pressure environment, a mixture of vanadium pentoxide and zinc citrate undergoes a chemical reaction to obtain a ZVO@ZVOH composite material, denoted as ZVO@ZVOH-S3.

[0084] Referring to the method of Example 1, using ZVO@ZVOH-S3 as the positive electrode material, Zn(CF3SO3)2 and ZnSO4 as the electrolyte, and a zinc foil as the counter electrode to assemble a zinc-ion battery. After the battery operates at a current density of 0.3 A g -1 After 10 cycles, the specific capacity reaches 246.2 mA h g -1 ; after 200 cycles, the capacity retention rate relative to the first cycle is approximately 75.7%.

[0085] Example 4

[0086] The embodiment of the present invention provides a preparation method for a fourth composite material, including the following steps:

[0087] 400. Weigh zinc citrate and vanadium pentoxide in a mass ratio of 0.6:1.

[0088] 401. Add 0.182 g of vanadium pentoxide to 40 mL of a solution of deionized water and 30 wt% hydrogen peroxide with a volume ratio of 40:1.

[0089] 402. Stir for 3 h to obtain an orange-red vanadium pentoxide solution with a concentration of 0.025 mol / L.

[0090] 403. Add zinc citrate to the vanadium pentoxide solution and stir for 35 min to form an orange-red mixture.

[0091] 404. Place the orange-red mixture in an autoclave for a heating reaction for 10 h at a heating temperature of 110 °C to obtain a ZVO@ZVOH composite material.

[0092] 405. Rinse the composite material repeatedly with deionized water and then perform a drying treatment at a drying temperature of 80 °C for 16 h to obtain a powder material.

[0093] 406. Mix 2 mol / L Zn(CF3SO3)2 and 1 mol / L ZnSO4 electrolytes in a molar ratio of 2:1, and stir to obtain a mixed electrolyte.

[0094] In a high-temperature and high-pressure environment, a mixture of vanadium pentoxide and zinc citrate undergoes a chemical reaction to obtain a ZVO@ZVOH composite material, denoted as ZVO@ZVOH-S4.

[0095] Referring to the method of Example 1, using ZVO@ZVOH-S4 as the positive electrode material, Zn(CF3SO3)2 and ZnSO4 as the electrolyte, and a zinc foil as the counter electrode to assemble a zinc-ion battery. The battery operates at a current density of 0.3 A g -1 After running for 10 cycles, the specific capacity reaches 215.2 mA h g -1 ; after running for 200 cycles, the capacity retention rate relative to the first cycle is approximately 65%.

[0096] Comparative Example 1

[0097] The difference between this Comparative Example 1 and Example 1 is only that the mass ratio of zinc citrate to vanadium pentoxide is 0.01:1, and the obtained composite material is denoted as ZVO.

[0098] Referring to the method of Example 1, using ZVO as the positive electrode material, and performing detailed X-ray diffraction (XRD) tests and zinc-ion battery performance evaluations on it. The diffraction peaks of ZVO at 8.3° and 25.62° correspond to the characteristic peaks of ZnV8O 20 ·xH2O (PDF#45-1362), corresponding to the (001) and (110) crystal planes respectively; in addition, there are no other impurity peaks in the XRD pattern, confirming that ZVO is composed of a single phase. As Figure 6As shown, as the positive electrode material, 2M Zn(CF3SO3)2 and 1M ZnSO4 are used as the electrolyte, and a zinc ion battery is assembled with a zinc foil as the counter electrode. After operating for 2 cycles at a current density of 0.3 A g -1 the specific capacity reaches 291 mA hg -1 ; after operating for 100 cycles, the specific capacity reaches 210 mA h g -1 , and the capacity retention rate relative to the second cycle is about 71.8%. In Example 1, after the battery operates for 2 cycles under the same conditions, the specific capacity reaches 340.2 mA h g - ¹, and the specific capacity still remains at 304.7 mA h g after 200 cycles -1 , and the capacity retention rate relative to the second cycle is about 89.6%. The specific capacity and capacity retention rate of Comparative Example 1 are significantly lower than those of Example 1.

[0099] This significant difference indicates that the electrochemical performance of the ZVO@ZVOH material is superior to that of the ZVO material. The large migration energy and easy solubility of ZVO lead to a significant reduction in its specific capacity and capacity retention rate. Therefore, by pre-embedding ions and introducing heterostructures into vanadium-based compounds, the electrochemical performance of the positive electrode material can be effectively improved, the specific capacity can be increased, and the cycle life can be extended. This comparison result demonstrates the superiority of the ZVO@ZVOH composite material of the present invention in the application of zinc ion batteries.

[0100] Comparative Example 2

[0101] The difference between this Comparative Example 2 and Example 1 is only that the mass ratio of zinc citrate to vanadium pentoxide is 1:1, and the obtained composite material is represented by the code ZVOH.

[0102] Referring to the method of Example 1, ZVOH is used as the positive electrode material, 2 mol / L Zn(CF3SO3)2 and 1 mol / L ZnSO4 are used as the electrolyte, and a zinc ion battery is assembled with a zinc foil as the counter electrode. As Figure 7 shown, after the battery operates for 2 cycles at a current density of 0.3 A g -1 the specific capacity reaches 174 mA h g -1 ; after operating for 100 cycles, its specific capacity drops significantly to 124 mA h g -1 , and the capacity retention rate relative to the first cycle is about 71.3%. The specific capacity and capacity retention rate of Comparative Example 2 are much lower than those of Example 1.

[0103] Comparative Example 3

[0104] The difference between this Comparative Example 3 and Example 1 is only that the molar ratio of Zn(CF3SO3)2 and ZnSO4 as the electrolyte is changed to 2:0.01.

[0105] Referring to the method of Example 1, ZVO@ZVOH was used as the cathode material, and Zn(CF3SO3)2 and ZnSO4 with a molar ratio of 2:0.01 were used as the electrolyte. A zinc-ion battery was assembled with a zinc foil as the counter electrode. As Figure 8 shown, after the battery was operated at a current density of 0.3 A g -1 , the specific capacity reached 301 mA h g -1 after 2 cycles; after 100 cycles, its specific capacity decreased significantly to 232 mAh g -1 , and the capacity retention rate relative to the first cycle was about 76.5%. The specific capacity and capacity retention rate of Comparative Example 3 were lower than those of Example 1.

[0106] Comparative Example 4

[0107] The difference between this Comparative Example 4 and Example 1 was only that the molar ratio of Zn(CF3SO3)2 and ZnSO4 as the electrolyte was changed to 0.1:1.

[0108] Referring to the method of Example 1, ZVO@ZVOH was used as the cathode material, and Zn(CF3SO3)2 and ZnSO4 with a molar ratio of 0.1:1 were used as the electrolyte. A zinc-ion battery was assembled with a zinc foil as the counter electrode. As Figure 9 shown, after the battery was operated at a current density of 0.3 A g -1 , the specific capacity reached 277 mA h g -1 after 2 cycles; after 100 cycles, its specific capacity decreased significantly to 144 mAh g -1 , and the capacity retention rate relative to the first cycle was about 51.9%. The specific capacity and capacity retention rate of Comparative Example 4 were much lower than those of Example 1.

[0109] From the above Examples 1 to 4 and Comparative Examples 1 to 4, it can be seen that in Example 1, through the ion pre-insertion method, heterostructure design, and mixed electrolyte technology, zinc citrate and vanadium pentoxide were mixed and reacted to form the ZVO@ZVOH composite material, and Zn(CF3SO3)2 and ZnSO4 were mixed into the electrolyte. The composite synergistic effect significantly increased the active sites of VOH, thus significantly increasing the capacity of the cathode. After cycling 20 times at a current density of 1 A g -1 , the specific capacity of the battery reached 358 mA h g -1 . In addition, ZVOH effectively enhanced the structural stability of VOH and significantly improved the cycling stability. Zn(CF3SO3)2 and ZnSO4 with a molar ratio of 2:1 effectively inhibited the dissolution of ZVO@ZVOH and reduced the dendrite phenomenon at the negative electrode, and the capacity retention rate was about 89.6%. Therefore, compared with other examples and comparative examples, Example 1 showed higher specific capacity and superior cycling performance, verifying the significant advantages of this technical route in improving battery performance.

[0110] On the other hand, an embodiment of the present invention also provides an application of a composite material. The composite material is applied to the positive electrode material of a zinc-ion battery, is used to be disposed on the positive electrode of the zinc-ion battery, and the mixed electrolyte is used as the electrolyte to assemble a full battery.

[0111] The ZVO@ZVOH composite material prepared by the present invention as the positive electrode material of a zinc-ion battery and the mixed electrolyte of Zn(CF3SO3)2 and ZnSO4 as the electrolyte can have good electrical conductivity, high specific capacity and long cycle life.

[0112] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An aqueous zinc ion battery, characterized in that: The positive electrode material includes a positive electrode composite material; The positive electrode composite material is prepared from zinc citrate and vanadium pentoxide by the following steps: 1) Weighing zinc citrate and vanadium pentoxide in a mass ratio of 0.165:1; adding vanadium pentoxide into a solvent consisting of deionized water and 30 wt% hydrogen peroxide and stirring for 1 hour to prepare a vanadium pentoxide solution; 2) Add zinc citrate to the vanadium pentoxide solution and stir for 25 min to form an orange-red mixture; 3) placing the orange-red mixture into an autoclave for heating and reaction to obtain the positive electrode composite material; In step 3), the heating time of the autoclave is 6 hours, and the heating temperature range is 120° C.; The electrolyte is a mixture of Zn(CF3SO3)2 and ZnSO4 electrolytes; the concentration of the Zn(CF3SO3)2 electrolyte is 2 mol / L, and the concentration of the ZnSO4 electrolyte is 1 mol / L; the molar ratio of Zn(CF3SO3)2 and ZnSO4 in the mixed electrolyte is 2:

1.

2. The aqueous zinc ion battery according to claim 1, characterized in that: In the step 1), the volume ratio of deionized water to 30 wt% hydrogen peroxide is 40:

1.

3. The aqueous zinc ion battery according to claim 1, characterized in that: The concentration of the vanadium pentoxide solution prepared in step 1) is 0.025 mol / L.

4. The aqueous zinc ion battery according to claim 1, characterized in that: The step 3) further comprises the following steps: repeatedly washing the positive electrode composite material with deionized water, and obtaining a powder material after drying.

5. The positive electrode composite material for aqueous zinc ion battery according to claim 4, characterized in that: The drying temperature of the drying treatment is 60° C. to 80° C., and the drying time is 12 h to 16 h.

Images