Aqueous electrolyte and aqueous zn-cl2 battery

Abstract

The application provides a water-based electrolyte and a water-based Zn-Cl2 battery, the water-based Zn-Cl2 battery comprising: an electrolyte, wherein the electrolyte comprises water, a zinc salt, a chlorine salt and a liquid-phase redox adsorbent; a positive electrode for carrying out a Cl2 / Cl ‑ redox reaction with the electrolyte; a negative electrode for carrying out a Zn 2+ / Zn redox reaction with the electrolyte; and the liquid-phase redox adsorbent carries out a redox reaction in the process of charging the battery, and a solid-phase redox adsorbent is generated on the surface of the positive electrode.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to an aqueous electrolyte and an aqueous Zn-Cl2 battery. Background Technology

[0002] With the rapid development of the times and the consumption of vast amounts of resources, energy shortages and the accompanying environmental pollution have become increasingly urgent problems that need to be addressed. The rational development and utilization of new sustainable and clean energy sources such as solar and wind power is an effective means of alleviating energy pressure. However, the effectiveness of these energy sources is currently limited by their intermittent temporal and spatial characteristics. To address the issue of energy fluctuations after conversion into electricity, which can easily damage the power grid, improving grid input patterns and developing large-scale energy storage are imperative. Among all large-scale energy storage devices, batteries are highly anticipated due to their low environmental dependence and high energy density.

[0003] Among various types of batteries, aqueous Zn-Cl2 batteries are considered to have great development potential because they possess a higher theoretical voltage (2.12V) and theoretical capacity than most commercially available aqueous batteries (e.g., vanadium flow batteries at 1.5V, Zn-Br2 batteries at 1.84V), as well as a richer reserve of electrode materials and lower raw material prices. Unfortunately, due to the diffusion of chloride hydrate (Cl2·xH2O) in the electrolyte, as well as material losses and high interfacial charge transfer resistance during Cl2 electrode activation, aqueous static Zn-Cl2 batteries face limitations of low coulombic efficiency (40%-70%) and high overpotential (~100mV). Furthermore, Cl2 entering the electrolyte easily evolves into chlorine byproducts of other valence states, leading to further degradation of electrode stability. At the same time, the dependence of conventional chlorine cathodes on noble metal catalysts also limits the development of this type of battery.

[0004] Therefore, how to avoid the diffusion of chlorine compounds in the electrolyte, reduce material loss during the activation process of the Cl2 electrode, lower the charge transfer impedance at the Cl2 electrode interface, and prevent the positive electrode product Cl2 from entering the electrolyte and generating chlorine byproducts, thereby improving the reaction kinetics and charge-discharge reversibility of the Cl2 electrode, and thus enhancing the coulombic efficiency, discharge potential, and cycle stability of aqueous Zn-Cl2 batteries, are critical technical issues that urgently need to be addressed in the application of aqueous Zn-Cl2 batteries. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the aforementioned technical problems, this invention designs an aqueous electrolyte and an aqueous Zn-Cl2 battery to improve the reaction kinetics and charge-discharge reversibility of the Cl2 electrode, thereby enhancing the coulombic efficiency, discharge potential, and cycle stability of the aqueous Zn-Cl2 battery.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] As one aspect of the present invention, an aqueous Zn-Cl2 battery is provided, comprising:

[0010] Electrolyte, which includes water, zinc salt, chloride salt and liquid-phase redox adsorbent;

[0011] The positive electrode is used for the Cl2 / Cl- redox reaction with the electrolyte;

[0012] The negative electrode is used to react with the electrolyte to form Zn2. + / Zn redox reaction;

[0013] Liquid-phase redox adsorbents undergo redox reactions during battery charging, generating solid-phase redox adsorbents on the positive electrode surface.

[0014] In one embodiment, the zinc salt includes at least one of the following:

[0015] ZnSO4, ZnCl2, Zn(NO3)2, Zn(CH3COO)2, Zn(CF3SO3)2, Zn(TFSI)2;

[0016] In one embodiment, the concentration of the zinc salt is 0.01–30%. mo l / L.

[0017] In one embodiment, the chloride salt includes at least one of the following:

[0018] LiCl, NaCl, KCl, MgCl2, ZnCl2, A1C13;

[0019] In one embodiment, the concentration of the chloride salt is 0.005–12 mol / L.

[0020] In one embodiment, the liquid-phase redox adsorbent includes at least one of the following:

[0021] MnCl2, MnSO4, Mn(NO3)2, Mn(CH3COO)2.

[0022] In one embodiment, the concentration of the liquid-phase redox adsorbent is 0.0025–0.5 mol / L.

[0023] In one embodiment, the solid-phase redox adsorbent includes MnO2.

[0024] In one embodiment, the positive electrode material includes at least one of the following:

[0025] Carbon felt, carbon paper, carbon cloth, carbon nanotube paper, graphene film, carbon nanotube film, mesoporous carbon film, conductive activated carbon film, graphite felt, graphene mesh, conductive graphite mesh, conductive graphite plate.

[0026] In one embodiment, the negative electrode material includes at least one of the following:

[0027] Metallic zinc, metallic copper, metallic nickel, metallic antimony, metallic titanium, stainless steel, metallic organic frameworks, covalent organic frameworks, and Prussian blue analogues.

[0028] In one embodiment, the positive electrode material or negative electrode material further includes: a positive electrode material or negative electrode material obtained by treating the positive electrode or negative electrode by atomic doping, surface coating or modification.

[0029] As another aspect of the present invention, an aqueous electrolyte for the above-mentioned aqueous Zn-Cl2 battery is provided, wherein the electrolyte is:

[0030] Water, zinc salts, chloride salts, and liquid-phase redox adsorbents.

[0031] Based on the above technical solutions, the aqueous electrolyte and aqueous Zn-Cl2 battery provided by the present invention have at least the following beneficial effects:

[0032] 1. According to embodiments of the present invention, a liquid-phase redox adsorbent is introduced into the electrolyte. During battery charging, this liquid-phase redox adsorbent undergoes a redox reaction, generating a solid-phase redox adsorbent on the positive electrode surface. Compared with conventional aqueous Zn-Cl2 batteries, this battery system can produce a solid-phase redox adsorbent by controlling a low concentration of liquid-phase redox adsorbent through an oxidation reaction, providing more adsorption sites for Cl2 adsorption, improving the adsorption efficiency of the positive electrode product Cl2, thereby accelerating reaction kinetics, reducing overpotential polarization loss of the Cl2 electrode, and increasing the activation rate of the Cl2 electrode. Simultaneously, by utilizing the adsorption of Cl2 in the electrolyte by the solid-phase redox adsorbent on the positive electrode surface, the consumption of Cl2 free in the electrolyte is reduced, achieving higher charge-discharge reversibility and coulombic efficiency in the aqueous Zn-Cl2 battery. Furthermore, due to the reduced Cl2 content in the electrolyte, battery side reactions are suppressed, thereby improving the cycle stability of the battery.

[0033] 2. According to an embodiment of the present invention, during the discharge process, the Cl2 enriched at the positive electrode has a stronger oxidizing property and undergoes an electrochemical reaction first, providing discharge capacity for the battery; after the Cl2 is consumed, the solid-phase redox adsorbent products deposited and grown on the surface of the positive electrode undergo an electrochemical reaction during the discharge of the aqueous Zn-Cl2 battery, providing discharge capacity for the battery again. Through the secondary discharge of the battery, the overall energy density, power density and coulombic efficiency of the aqueous Zn-Cl2 battery are improved. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the reaction mechanism of the aqueous Zn-MnO2@Cl2 battery in Embodiment 1 of the present invention;

[0035] Figure 2 These are impedance diagrams of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1 of the present invention.

[0036] Figure 3 The graphs show the response current-time curves of the aqueous Zn-MnO2@C12 battery in Example 1 and the aqueous Zn-C12 battery in Comparative Example 1 at a charging voltage of 2.3V.

[0037] Figure 4 The aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-MnO2@Cl2 battery in Comparative Example 1 are examples of the present invention. n -Cl2 battery discharge curve;

[0038] Figure 5 These are cycle curves of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1 of the present invention.

[0039] Figure 6 This is the first charging curve of an aqueous Zn-Cl2 battery in Embodiment 2 of the present invention, in which the positive electrode is preloaded with different amounts of solid-phase redox adsorbates.

[0040] Figure 7 This is the first discharge curve of an aqueous Zn-C12 battery in Embodiment 2 of the present invention, in which the positive electrode is preloaded with different amounts of solid-phase redox adsorbates. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0042] In the process of developing this invention, it was discovered that preventing the diffusion of chlorine compounds in the electrolyte, reducing material loss during the activation of the Cl2 electrode, lowering the charge transfer impedance at the Cl2 electrode interface, and preventing the positive electrode product Cl2 from entering the electrolyte, thereby reducing the generation of chlorine byproducts, are technical challenges limiting further improvements in the coulombic efficiency, charge-discharge reversibility, discharge potential, and cycle stability of the aqueous Zn-Cl2 battery. This invention introduces a liquid-phase redox adsorbent into the electrolyte of the aqueous Zn-Cl2 battery. Through the redox reaction of this liquid-phase redox adsorbent, a solid-phase redox adsorbent is generated on the positive electrode surface, achieving the adsorption of Cl2, thereby accelerating reaction kinetics, improving the reaction kinetics and activation rate of the Cl2 electrode, and ultimately enhancing the coulombic efficiency, charge-discharge reversibility, and cycle stability of the aqueous Zn-Cl2 battery.

[0043] It should be noted beforehand that, for clarity, in Examples 1 and 2 and Comparative Example 1, the aqueous Zn-Cl2 battery in this invention is defined by a solid-phase redox adsorbent and is thus defined as an aqueous Zn-MnO2@Cl2 battery, to distinguish it from the description in the comparative example. However, this difference in description does not affect the aqueous Zn-Cl2 battery as defined in the claims of this invention.

[0044] Specifically, according to an embodiment of the present invention, an aqueous Zn-Cl2 battery is provided, comprising:

[0045] Electrolyte, which includes water, zinc salt, chloride salt and liquid-phase redox adsorbent;

[0046] The positive electrode is used for Cl2 / Cl reaction with the electrolyte. - Redox reactions;

[0047] The negative electrode is used to react with the electrolyte to form Zn2. + / Zn redox reaction;

[0048] Liquid-phase redox adsorbents undergo redox reactions during battery charging, generating solid-phase redox adsorbents on the positive electrode surface.

[0049] In embodiments of the present invention, for the positive electrode of the aqueous Zn-Cl2 battery, during charging, the liquid-phase redox adsorbent undergoes a redox reaction, generating a solid-phase redox adsorbent on the positive electrode surface. Simultaneously, Cl- in the electrolyte is converted into Cl2. Due to the interaction between Cl2 and the solid-phase redox adsorbent, the generated Cl2 is adsorbed on the positive electrode and hardly enters the electrolyte, increasing the Cl2 concentration at the positive electrode and reducing the consumption of Cl2 free in the electrolyte. This achieves higher charge-discharge reversibility and coulombic efficiency in the aqueous Zn-Cl2 battery, and suppresses side reactions of Cl2 in the aqueous Zn-Cl2 battery, thereby improving cycle stability. Furthermore, the adsorption effect of the solid-phase redox adsorbent helps reduce the interfacial resistance between the positive electrode material surface and the electrolyte, thus contributing to increased charging current. During discharge, the higher Cl2 concentration at the positive electrode is beneficial for increasing the discharge voltage. Simultaneously, the Cl2 at the positive electrode, due to its higher reaction potential, is first reduced by discharge, providing discharge capacity for the battery. After the Cl2 is exhausted, the solid-phase redox adsorbent deposited on the cathode (positive electrode) discharges. This two-stage discharge mechanism of Cl2 and solid-phase redox adsorbent improves the coulombic efficiency of the aqueous Zn-Cl2 battery. In subsequent cycles, due to the reversible conversion between the solid / liquid redox adsorbent, the solid-phase redox adsorbent remains on the positive electrode (continuously depositing / dissolving), providing active sites and adsorption for Cl2, as well as contributing to the secondary discharge capacity.

[0050] For the negative electrode of the aqueous Zn-Cl2 battery of the present invention, during the charging process, Zn 2+ It is reduced to metallic Zn; during the discharge process, the deposited metallic zinc dissolves into Zn. 2+ .

[0051] According to embodiments of the present invention, the zinc salt may be selected from one or more of ZnSO4, ZnCl2, Zn(NO3)2, Zn(CH3COO)2, Zn(CF3SO3)2, and Zn(TFSI)2.

[0052] According to embodiments of the present invention, the concentration of zinc salt in the electrolyte is 0.01 to 30 mol / L, wherein the concentration of zinc salt can be selected from 0.01 mol / L, 1 mol / L, 5 mol / L, 10 mol / L, 15 mol / L, 30 mol / L, etc.

[0053] According to an embodiment of the present invention, the cations in the zinc salt are used to provide zinc ions to the electrolyte of an aqueous Zn-C12 battery, and the anions in the zinc salt undergo changes during charging and discharging. One or two of the reactions.

[0054] According to embodiments of the present invention, the chloride salt may be one or more of LiCl, NaCl, KCl, MgCl2, ZnCl2, and AlCl3.

[0055] According to embodiments of the present invention, the concentration of chloride salt in the electrolyte is 0.005–12 mol / L, wherein the concentration of chloride salt can be selected from 0.005 mol / L, 0.01 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 12 mol / L, etc.

[0056] According to an embodiment of the present invention, the anions in the chloride salt are used to provide chloride ions to the electrolyte of an aqueous Zn-Cl2 battery, and the cations in the chloride salt undergo changes during charging and discharging. One or two of the reactions.

[0057] According to embodiments of the present invention, the liquid-phase redox adsorbent may be one or more of MnCl2, MnSO4, Mn(NO3)2, and Mn(CH3COO)2.

[0058] According to embodiments of the present invention, the concentration of the liquid-phase redox adsorbent in the electrolyte is 0.0025–0.5 mol / L, wherein the concentration of the liquid-phase redox adsorbent can be selected from 0.0025 mol / L, 0.005 mol / L, 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.5 mol / L, etc.

[0059] According to an embodiment of the present invention, the cations in the liquid-phase redox adsorbent are used to provide manganese ions to the electrolyte of the aqueous Zn-Cl2 battery so that a redox reaction occurs during battery charging, thereby generating a solid-phase redox adsorbent on the positive electrode surface.

[0060] According to an embodiment of the present invention, 0.0025–0.5 mol / L Mn is introduced into the electrolyte of an aqueous Zn-Cl2 battery. 2+ This helps reduce the overall impedance of Zn-Cl2 batteries and promotes rapid electron transfer.

[0061] In this embodiment of the invention, because the kinetics of MnO2 are faster than those of Cl2, the manganese salt content should not be too high. When the manganese ion content is too high (e.g., exceeding 0.5 mol / L), the main reaction becomes the precipitation / dissolution reaction of MnO2. Although MnO2 has a higher coulombic efficiency than Cl2, its discharge potential is lower than that of Cl2. When the manganese ion content is too low (e.g., below 0.0025 mol / L), the amount of solid-phase redox adsorbent generated on the positive electrode surface decreases accordingly, making it unable to effectively adsorb Cl2 and unable to improve the charging speed, thus affecting the coulombic efficiency of the battery. Therefore, only a suitable concentration of manganese salt (0.0025–0.5 mol / L) can achieve a bidirectional increase in both voltage and coulombic efficiency.

[0062] According to an embodiment of the present invention, the liquid-phase redox adsorbent undergoes a redox reaction during battery charging, generating a solid-phase redox adsorbent on the positive electrode surface. The solid-phase redox adsorbent includes MnO2.

[0063] In embodiments of the present invention, the liquid-phase redox adsorbent undergoes a redox reaction during charging, generating a solid-phase redox adsorbent, primarily composed of MnO2, at the positive electrode. Simultaneously, Mn3O4 and MnO intermediates may also be generated during the redox reaction, which can also act as solid-phase redox adsorbents deposited on the surface of the positive electrode material, performing the same Cl2 adsorption function as MnO2. Utilizing the adsorption effect of the solid-phase redox adsorbent generated on the surface of the positive electrode material is beneficial for improving the adsorption performance of the positive electrode, increasing the ability to store Cl2 on the positive side, reducing the concentration of Cl2 released into the electrolyte, effectively suppressing side reactions caused by Cl2, and improving battery stability. Furthermore, utilizing the adsorption effect of the solid-phase redox adsorbent generated on the surface of the positive electrode material also reduces the steric hindrance at the solid / liquid interface of the positive electrode surface. This low steric hindrance synergistically enhances the adsorption capacity of MnO2. 2+ The rapid ion conduction facilitated by liquid-phase redox adsorbents accelerates the reaction kinetics of the battery's positive electrode, thereby reducing the overall battery impedance and maintaining a consistently high response current, thus improving charging speed. Simultaneously, the formation of solid-phase redox adsorbents provides secondary discharge capacity for the vn-Cl2 battery, enhancing its overall energy utilization.

[0064] According to embodiments of the present invention, the positive electrode material may be selected from one or more of the following: carbon felt, carbon paper, carbon cloth, carbon nanotube paper, graphene film, carbon nanotube film, mesoporous carbon film, conductive activated carbon film, graphene mesh, conductive graphite mesh, and conductive graphite plate.

[0065] According to embodiments of the present invention, carbon materials have the advantage of a large specific surface area and are commonly used as positive electrode materials. Furthermore, compared to using only carbon materials as the positive electrode, a positive electrode with a solid-phase redox adsorbent deposited on it enhances the adsorption performance of the carbon material positive electrode, promotes the adsorption of Cl2, and thus improves the battery's discharge potential and coulombic efficiency.

[0066] According to embodiments of the present invention, the negative electrode material may be selected from one or more of the following: zinc, copper, nickel, antimony, titanium, stainless steel, metal-organic frameworks, covalent organic frameworks, and Prussian blue analogues.

[0067] According to embodiments of the present invention, the positive electrode material or negative electrode material further includes: a positive electrode material or negative electrode material obtained by treating the positive electrode or negative electrode by atomic doping, surface coating or modification.

[0068] As another aspect of the present invention, an aqueous electrolyte for the above-mentioned aqueous Zn-Cl2 battery is provided.

[0069] According to an embodiment of the present invention, the electrolyte is: water, zinc salt, chloride salt and liquid-phase redox adsorbent.

[0070] According to embodiments of the present invention, the electrolyte needs to be in a mild, weakly acidic environment, i.e., pH ≈ 3–6. In this weakly acidic environment, H+ can help increase the voltage and capacity of the positive electrode, while the weakly acidic environment can help avoid the formation of byproducts such as basic zinc sulfate on the negative electrode side. However, excessive H+ will have adverse effects on the zinc negative electrode side.

[0071] To facilitate a better understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be noted that the specific embodiments listed below are only used to further explain the present invention and are not intended to limit the present invention, nor are the embodiments of the present invention limited thereto.

[0072] Example 1

[0073] Using carbon felt as the positive electrode and zinc sheet as the negative electrode, the electrolyte was 1 mol / L ZnSO4 + 1 mol / L LiCl + 0.005 mol / L MnSO4. The liquid-phase redox adsorbent MnSO4 underwent a redox reaction during battery charging, forming a solid-phase redox adsorbent on the positive electrode surface. This Zn-Cl2 battery was named the Zn-MnO2@Cl2 battery. The electrolyte (providing a mildly acidic environment, pH ≈ 3–6) was 3 mL in volume, immersing 2 × 1 cm (length × width) carbon felt and 2 × 1 cm (length × width) zinc sheet. The carbon felt and zinc sheet were parallel to each other, with a spacing of 0.5 mm.

[0074] The main reaction equations for the positive and negative electrodes of the assembled aqueous Zn-MnO2@Cl2 battery are as follows:

[0075] positive electrode:

[0076] negative electrode:

[0077] Overall reaction:

[0078] Meanwhile, the positive electrode is also accompanied by the following auxiliary reactions:

[0079]

[0080] Figure 1 This is a schematic diagram of the reaction mechanism of the aqueous Zn-MnO2@Cl2 battery in Embodiment 1 of the present invention.

[0081] like Figure 1 As shown, for the positive electrode of a Zn-MnO2@Cl2 battery, during the charging process, the Mn content of the liquid-phase redox adsorbent in the electrolyte... 2+ The MnO2 solid-phase redox adsorbent is converted into Cl- and deposited on the positive electrode surface, while Cl- is converted into Cl2 in the electrolyte. Due to the adsorption effect of the MnO2 solid-phase redox adsorbent, the generated Cl2 is adsorbed near the positive electrode, reducing the amount of Cl2 released into the electrolyte and suppressing its associated side reactions, thus improving battery stability. Furthermore, the low steric hindrance at the solid / liquid interface caused by adsorption synergizes with the MnO2 adsorption process. 2+ The rapid ion conduction facilitated by the liquid-phase redox adsorbent accelerates the reaction kinetics of the MnO2@Cl2 cathode and significantly increases the charging current. During discharge, the higher concentration of Cl2 near the cathode electrode is beneficial for increasing the discharge voltage. Furthermore, the Cl2 near the cathode, due to its strong oxidizing properties, reacts first, providing discharge capacity to the battery; after the Cl2 is depleted, the MnO2 deposited on the cathode discharges. This two-stage discharge mechanism of Cl2 and MnO2 improves the coulombic efficiency. In subsequent cycles, due to the MnO2 / Mn... 2+ This reversible conversion between solid / liquid redox reductants means that MnO2 remains on the electrode throughout, providing active adsorption sites. For the negative electrode of the Zn-MnO2@Cl2 battery, during charging, Zn... 2+ It is reduced to metallic Zn; during the discharge process, the deposited metallic zinc dissolves into Zn. 2+ .

[0082] Comparative Example 1

[0083] A battery was assembled using carbon felt as the positive electrode, zinc sheet as the negative electrode, and 1 mol / L ZnSO4 + 1 mol / L LiCl as the electrolyte. The electrolyte (providing a mildly acidic environment, pH ≈ 3–6) was 3 mL in volume, immersing 2 × 1 cm (length × width) carbon felt and 2 × 1 cm (length × width) zinc sheet. The carbon felt and zinc sheet were parallel to each other, with a spacing of 0.5 mm.

[0084] The main reaction equations for the positive and negative electrodes of the assembled aqueous Zn-Cl2 battery are as follows:

[0085] positive electrode:

[0086] negative electrode:

[0087] Overall reaction:

[0088] Electrochemical impedance spectroscopy was performed on the Zn-MnO2@Cl2 battery prepared in Example 1 and the Zn-Cl2 battery prepared in Comparative Example 1.

[0089] Figure 2 These are impedance diagrams of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1 of the present invention.

[0090] like Figure 2 As shown, compared to Comparative Example 1 without the addition of MnSO4 liquid-phase redox adsorbent in the electrolyte, Example 1, which introduced 0.005 mol / L MnSO4 liquid-phase redox adsorbent, resulted in a Zn-MnO2@Cl2 battery with lower internal resistance. This indicates that the introduction of MnSO4 liquid-phase redox adsorbent helps reduce the electron transfer resistance on the electrode surface, thereby reducing the overall battery impedance and facilitating rapid electron transfer. (The last sentence appears to be incomplete and possibly refers to a separate point about MnSO4.) Figure 2 The electrochemical impedance spectroscopy test conditions are as follows: with an amplitude of 10mV based on the open circuit potential, and a test frequency range of 100kHz to 100mHz.

[0091] The charging curves of the Zn-MnO2@Cl2 battery prepared in Example 1 and the Zn-Cl2 battery prepared in Comparative Example 1 were tested respectively.

[0092] Figure 3 This is a current-time curve of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1 at a charging voltage of 2.3V.

[0093] like Figure 3As shown, both batteries exhibited significant instantaneous current responses at the initial stage, primarily due to the difference between the charging voltage and the open-circuit potential (~1.3V). Furthermore, in Comparative Example 1, the aqueous Zn-Cl2 battery continued to experience a substantial decrease in current after the instantaneous drop in response current, with a charging time approaching 600 seconds. In contrast, the aqueous Zn-MnO2@Cl2 battery in Example 1 maintained a higher current level after the instantaneous drop in response current compared to Comparative Example 1, and its charging time was shortened to approximately 100 seconds. This indicates that during charging, the co-deposited MnO2 solid-phase redox adsorbent exhibits stronger adsorption than the unoptimized cathode material (Comparative Example 1), and the low solid / liquid interfacial steric hindrance resulting from the adsorption synergistically enhances the MnO2 adsorption. 2+ The rapid ion conduction facilitated by the liquid-phase redox adsorbent accelerates the reaction kinetics of the MnO2@Cl2 cathode, thereby helping to maintain the battery's response current at a higher level and shorten the charging time, thus completing the charging process more quickly. (The remaining text appears to be incomplete and requires further context.) Figure 3 The charging curve test conditions were as follows: with a charging voltage of 2.3V, the current-time relationship curves of Zn-MnO2@Cl2 battery and Zn-Cl2 battery were tested before charging to 0.8mAh.

[0094] The discharge curves of the Zn-MnO2@Cl2 battery prepared in Example 1 and the Zn-Cl2 battery prepared in Comparative Example 1 were tested respectively. The test results are shown in the appendix. Figure 4 .

[0095] Figure 4 These are discharge curves of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1 of the present invention.

[0096] like Figure 4 As shown, the median voltage plateau of 2.0V exhibited by the aqueous Zn-MnO2@Cl2 battery prepared in Example 1 is significantly higher than that of the aqueous Zn-Cl2 battery prepared in Comparative Example 1, and the potential is increased by 20mV. It is evident that the introduction of the MnSO4 liquid-phase redox adsorbent increases the discharge voltage, reduces the overpotential polarization loss of the battery, and improves the battery activation rate. This is mainly because, during charging, the MnSO4 liquid-phase redox adsorbent undergoes a redox reaction to generate MnP2 solid-phase redox adsorbent on the surface of the positive electrode material. The co-deposited MnP2 solid-phase redox adsorbent has a stronger adsorption effect than the original positive electrode material, increasing its surface active sites and improving the ability to adsorb and store Cl2 on the positive electrode side, thereby significantly increasing the Cl2 concentration around the positive electrode and increasing the Cl2 discharge voltage, which is consistent with the Nernst equation (Equation 1-1). Furthermore, as... Figure 4As shown, the discharge curve of the aqueous Zn-MnO2@Cl2 battery exhibits two voltage plateaus: the first plateau represents the Cl2 discharge stage, and the second plateau represents the MnO2 discharge stage, with the MnO2 plateau appearing after the Cl2 plateau. In contrast, the aqueous Zn-Cl2 battery only exhibits a Cl2 discharge stage. This demonstrates that the MnP2 solid-phase redox adsorbent participates in the discharge process, and MnO2 participates in subsequent discharges after the Cl2 stage. This two-stage discharge mechanism of Cl2 and MnO2 is beneficial for improving the battery's coulombic efficiency, thereby enhancing the overall energy density, power density, and coulombic efficiency. (Note: The last sentence appears to be incomplete and possibly refers to a separate, unrelated point.) Figure 4 The discharge curve test conditions are as follows: Figure 3 After the battery is fully charged, it is discharged with a current of 5mA and a cutoff potential of 1.4V.

[0097]

[0098] in, Chlorine electrode electromotive force;

[0099] Standard electromotive force of chlorine electrode;

[0100] P(Cl2): The pressure of the mixed gas occupied by chlorine gas inside the electrode in the sealed space of the test device is 0 in the initial state and increases after charging;

[0101] α: The activity of chloride ions in the solution, which can be approximated as concentration for ease of calculation;

[0102] R: gas constant 8.31441 J / (K·mol);

[0103] T: Temperature;

[0104] F: Faraday constant 96.487 kJ / (V·mol)

[0105] The Zn-MnO2@Cl2 battery prepared in Example 1 and the Zn-Cl2 battery prepared in Comparative Example 1 were subjected to cycle performance tests.

[0106] Figure 5 These are cycle curves of the aqueous Zn-MnO2@Cl2 battery in Example 1 and the aqueous Zn-Cl2 battery in Comparative Example 1.

[0107] like Figure 5As shown, both batteries exhibit an activation process, which is due to the inherent properties of C12. The aqueous Zn-MnO2@Cl2 battery in Example 1 achieved a coulombic efficiency of 87.6% at 6.25C, a 17.7% improvement compared to the aqueous Zn-Cl2 battery in Comparative Example 1. Furthermore, compared to Comparative Example 1, the coulombic efficiency change became more stable with increasing cycle number, indicating that the aqueous Zn-MnO2@Cl2 battery in Example 1 possesses superior stability. This also demonstrates that in Example 1, compared to Comparative Example 1, the co-deposited MnO2 solid-phase redox adsorbent has a stronger adsorption effect than the unoptimized cathode material, improving the cathode's ability to store Cl2, limiting the diffusion of chlorine compounds (Cl2·xH2O) in the electrolyte, reducing the release of C12 into the electrolyte, thereby suppressing side reactions, reducing the loss of active material in the Cl2 electrode, and improving the activation rate of Cl2 and the battery's cycle stability. In addition, from Figure 5 It can also be seen that during these 1000 cycles, the average coulombic efficiency of the Zn-MnO2@Cl2 battery in Example 1 reached 91.6%, while the average coulombic efficiency of the Zn-Cl2 battery in Comparative Example 1 was only 66.8%. This demonstrates the significant advantage of introducing MnO2 / Mn... 2+ Solid-phase / liquid-phase redox adsorbents are beneficial for improving the coulombic efficiency of aqueous Zn-Cl2 batteries, as well as their reaction kinetics, charge-discharge reversibility, and cycle stability. Among these, Figure 5 It is a repetition Figure 3 and Figure 4 The corresponding charging and discharging processes, Figure 5 The test conditions and Figure 3 , 4 The cycle is consistent, with 1000 rotations.

[0108] Example 2

[0109] Different amounts of MnO2 (0 mAh cm⁻¹) were pre-electrochemically deposited. -2 0.4mAh cm -2 0.8mAh cm- 2 A battery was assembled using a carbon felt as the positive electrode, a zinc sheet as the negative electrode, and 1 mol / L ZnSO4 + 1 mol / L LiCl as the electrolyte to investigate the effect of MnO2 on the charge and discharge of an aqueous Zn-Cl2 battery. The electrolyte (providing a mildly acidic environment, pH ≈ 3–6) was 3 mL in volume, immersing a 2 × 1 cm (length × width) carbon felt and a 2 × 1 cm (length × width) zinc sheet. The carbon felt and zinc sheet were parallel to each other, with a spacing of 0.5 mm.

[0110] The main reaction equations for the positive and negative electrodes of the assembled aqueous Zn-Cl2 battery are as follows:

[0111] positive electrode:

[0112] negative electrode:

[0113] Overall reaction:

[0114] The Zn-Cl2 battery prepared in Example 2 was subjected to electrochemical tests during charging and discharging.

[0115] Figure 6 This is the first charging curve of an aqueous Zn-Cl2 battery in Embodiment 2 of the present invention, in which the positive electrode is preloaded with different amounts of solid-phase redox adsorbates.

[0116] like Figure 6 As shown, under the same charging potential, the charging response current of the aqueous Zn-Cl2 battery prepared in Example 2 increases with the increase of MnO2 loading on the positive electrode in the initial state. This indicates that compared to the aqueous Zn-Cl2 battery without MnO2 loading on the positive electrode, the aqueous Zn-Cl2 battery with MnO2 loading on the positive electrode surface exhibits a higher charging current. This suggests that MnO2 loading can provide adsorption active sites, thereby improving the kinetics of the aqueous Zn-Cl2 battery. Figure 6 The Zn-Cl2 battery tested at a charging voltage of 2.3V was charged to 0.4mAh cm⁻¹. -2 The previous response current versus time curve.

[0117] Figure 7 This is the first discharge curve of an aqueous Zn-Cl2 battery in Embodiment 2 of the present invention, in which the positive electrode is preloaded with different amounts of solid-phase redox adsorbates.

[0118] like Figure 7 As shown, the discharge curve plateau of the aqueous Zn-Cl2 battery with MnP2 loaded on the positive electrode is significantly higher than that of the aqueous Zn-Cl2 battery without MnP2 loaded on the positive electrode. Furthermore, the discharge voltage during the Cl2 discharge stage is increased by approximately 100 mV, and the overall areal capacity is approximately doubled (0.065 mAh·cm⁻¹). -2 Up to 0.016 mAh·cm -2 This indicates that loading MnO2 onto the positive electrode can enhance the ability of the positive electrode to store Cl2, which is beneficial for increasing the battery's discharge potential. Furthermore, from... Figure 7 It can also be seen that the presence of MnO2 during the discharge phase increases the battery's discharge potential. However, compared to a loading of 0.4 mAh·cm⁻¹, the discharge potential is still lower. 2 The positive electrode of MnO2 has a loading of 0.8 mAh·cm⁻¹. -2While the MnO2 positive electrode achieved higher coulombic efficiency, its overall discharge potential was still somewhat affected. This demonstrates that although MnO2 has a strong adsorption capacity, excessively high MnO2 loading is not conducive to further improving the battery's discharge potential. Figure 7 It is in progress Figure 6 The corresponding discharge curve after the first cycle of the charging process.

[0119] In summary, by comparing the electrochemical impedance, charge-discharge performance, and cycle performance of the battery in Example 1 (containing 0.005 mol / L MnSO4 in the electrolyte) and the battery in Comparative Example 1, it can be seen that adding 0.005 mol / L MnSO4 to the electrolyte as a liquid-phase redox adsorbent can achieve the adsorption of the positive electrode product Cl2 and accelerate reaction kinetics, reduce the formation of chlorine byproducts, and thus improve the battery stability. This, in turn, improves the coulombic efficiency, charge-discharge reversibility, discharge potential, and cycle stability of the aqueous Zn-Cl2 battery. Example 2 shows that loading MnO2 onto the positive electrode can enhance the ability of the positive electrode to store Cl2, which is beneficial for increasing the battery's discharge potential.

[0120] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aqueous Zn-Cl2 battery, comprising: The electrolyte comprises water, zinc salt, chloride salt, and a liquid-phase redox adsorbent; The positive electrode is used for Cl2 / Cl reaction with the electrolyte. - Redox reactions; The negative electrode is used to react with the electrolyte to form Zn. 2+ / Zn redox reaction; The liquid-phase redox adsorbent undergoes a redox reaction during battery charging, generating a solid-phase redox adsorbent on the surface of the positive electrode. The solid-phase redox adsorbent comprises MnO2; the concentration of the liquid-phase redox adsorbent is 0.0025~0.5 mol / L, and the liquid-phase redox adsorbent comprises at least one of the following: MnCl2, MnSO4, Mn(NO3)2, Mn(CH3COO)2.

2. The aqueous Zn-Cl2 battery according to claim 1, wherein, The zinc salt includes at least one of the following: ZnSO4, ZnCl2, Zn(NO3)2, Zn(CH3COO)2, Zn(CF3SO3)2, Zn(TFSI)2; The concentration of the zinc salt is 0.01~30 mol / L.

3. The aqueous Zn-Cl2 battery according to claim 1, wherein, The chloride salt includes at least one of the following: LiCl, NaCl, KCl, MgCl2, ZnCl2, AlCl3; The concentration of the chloride salt is 0.005~12 mol / L.

4. The aqueous Zn-Cl2 battery according to claim 1, wherein, The positive electrode material includes at least one of the following: Carbon felt, carbon paper, carbon cloth, carbon nanotube paper, graphene film, carbon nanotube film, mesoporous carbon film, conductive activated carbon film, graphite felt, graphene mesh, conductive graphite mesh, conductive graphite plate.

5. The aqueous Zn-Cl2 battery according to claim 1, wherein, The negative electrode material includes at least one of the following: Metallic zinc, metallic copper, metallic nickel, metallic antimony, metallic titanium, stainless steel, metallic organic frameworks, covalent organic frameworks, and Prussian blue analogues.

6. The aqueous Zn-Cl2 battery according to claim 4 or 5, wherein, The positive electrode material or negative electrode material further includes: a positive electrode material or negative electrode material obtained by treating the positive electrode or negative electrode through atomic doping, surface coating or modification.

7. An aqueous electrolyte for use in any one of the aqueous Zn-Cl2 batteries according to claims 1-6, wherein, The electrolyte is: Water, zinc salts, chloride salts, and liquid-phase redox adsorbents.

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