Electrolyte additive and application in aqueous zinc-manganese double electrodeless battery electrolyte

Abstract

The invention provides an electrolyte additive and application of the electrolyte additive in an aqueous zinc-manganese double-electrodeless battery electrolyte, and relates to the technical field of batteries, the electrolyte additive is N-octyl pyrrolidone, and belongs to amphoteric organic matters; the invention relates to a hydrophobic polymer, which is an organic matter in a liquid state at room temperature, the molecular structure of the hydrophobic polymer contains an n-octyl alkyl hydrophobic chain and an amide hydrophilic five-membered ring, and the hydrophilic amide group is helpful to be dissolved in an aqueous solution to form an electrolyte with uniform components, has no negative influence on the phase structure of the electrolyte, and only acts on an electrode / electrolyte interface. The hydrophilic group at the interface preferentially adsorbs active sites deposited with zinc and manganese, and the hydrophobic alkyl chain at the tail discharges active water, so that the interface side reaction caused by the interface active water is effectively relieved. In addition, the steric effect can induce uniform deposition of zinc and manganese, the coulombic efficiency of the aqueous zinc-manganese double electrodeless battery is improved, and the cycle life of the aqueous zinc-manganese double electrodeless battery is prolonged. The performance of the zinc-manganese double electrodeless battery is improved by adding the electrolyte additive with low cost, and the application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an electrolyte additive and its application in an aqueous zinc-manganese dual electrode battery electrolyte. Background Technology

[0002] Aqueous zinc-manganese batteries are highly promising for large-scale energy storage due to their inherent safety and low manufacturing cost. In recent years, to further improve energy density and simplify manufacturing processes, a "dual-electrode" (without positive or negative electrode active material coating) zinc-manganese battery architecture has been proposed. In this architecture, the positive and negative electrodes consist only of exposed current collectors during initial assembly, and the charging and discharging process relies entirely on the Zn in the electrolyte. 2+ and Mn 2+ In-situ deposition and stripping on the current collector surface. Although the dual-polar architecture has outstanding theoretical advantages, it faces severe challenges in practical cycling due to low coulombic efficiency and short cycle life.

[0003] Since there are no pre-placed active materials at either the positive or negative electrode, the electrolyte is not only the ion transport medium but also the sole source of active materials. Any irreversible loss during the deposition / stripping process will directly lead to the rapid depletion of effective ions in the electrolyte. Specifically, the degradation of coulombic efficiency and lifespan in dual-electrode zinc-manganese batteries mainly stems from the following two aspects: 1. Dendrites and side reactions on the negative electrode side: Bare current collectors are highly susceptible to inducing uneven zinc deposition, leading to uncontrolled growth of zinc dendrites. Simultaneously, aqueous electrolytes experience severe hydrogen evolution side reactions on the negative electrode surface. This hydrogen evolution not only irreversibly consumes active zinc but also deteriorates the local microenvironment, resulting in dead zinc. 2. Irreversible deposition / stripping on the positive electrode side: The manganese dioxide (MnO2) deposited during charging faces severe kinetic obstacles and structural collapse during the discharge stripping process, with a large amount failing to successfully convert to Mn. 2+ The manganese-based material in the solvent returning to the electrolyte will become "dead manganese" or pulverize and fall off from the current collector. The dead zinc in the negative electrode and the dead manganese in the positive electrode work together to cause the coulombic efficiency of the dual electrodeless battery to drop sharply and the capacity to deplete rapidly after only a few cycles.

[0004] Most existing electrolyte additives are only targeted at a single electrode, such as only suppressing zinc dendrites on the negative electrode, and cannot simultaneously ensure the high reversibility of metal ion deposition / stripping on both bare current collectors.

[0005] Therefore, there is an urgent need to develop a new type of bifunctional or multifunctional electrolyte additive to comprehensively improve the redox reversibility of zinc and manganese ions, fundamentally enhance the coulombic efficiency of aqueous zinc-manganese dual electrode zinc-manganese batteries, and significantly extend their cycle life. Summary of the Invention

[0006] Therefore, this invention proposes an electrolyte additive and its application in an aqueous zinc-manganese dual electrode battery electrolyte.

[0007] The technical solution of this invention is implemented as follows: An electrolyte additive, wherein the additive is N-octylpyrrolidone.

[0008] N-octylpyrrolidone, C 12 H 23 NO, the structural formula is: , N-Octylpyrrolidone is an organic compound that is liquid at room temperature and contains an octylalkyl hydrophobic chain and an amide hydrophilic five-membered ring in its molecular structure.

[0009] Application of an electrolyte additive in aqueous zinc-manganese dual electrode battery electrolyte.

[0010] Furthermore, the content of the electrolyte additive in the aqueous zinc-manganese dual electrode battery electrolyte is 0.02%-0.1%v / v.

[0011] Furthermore, the aqueous zinc-manganese dual electrode electrolyte includes a solute, a solvent, and electrolyte additives.

[0012] Furthermore, the solutes in the aqueous zinc-manganese dual electrode electrolyte are ZnSO4 and MnSO4, with a total concentration of 2 mol / L and a concentration ratio of 1:1 for ZnSO4 and MnSO4.

[0013] Furthermore, the solvent is deionized water.

[0014] Furthermore, the preparation method of the aqueous zinc-manganese dual electrodeless battery electrolyte is as follows: the solute is added to the solvent to prepare a mixture, then electrolyte additives are added, the mixture is shaken and stirred, and ultrasonically mixed evenly to obtain the aqueous zinc-manganese dual electrodeless battery electrolyte.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The electrolyte additive of this invention is N-octylpyrrolidone, an amphoteric organic compound. It is a liquid organic compound at room temperature, and its molecular structure contains a hydrophobic n-octyl alkyl chain and a hydrophilic five-membered amide ring. The hydrophilic amide group facilitates dissolution in aqueous solution, forming a homogeneous electrolyte. It has no negative impact on the electrolyte liquid phase structure and only acts on the electrode / electrolyte interface. At the interface, its hydrophilic group preferentially adsorbs onto the active sites of zinc and manganese deposition, while the hydrophobic alkyl chain at the tail removes active water, thereby effectively mitigating interfacial side reactions caused by active water. Furthermore, its steric hindrance effect can induce uniform deposition of zinc and manganese, improving the coulombic efficiency and cycle life of the aqueous zinc-manganese dual electrodeless battery.

[0016] 2. This invention significantly improves the performance of aqueous zinc-manganese dual electrodeless batteries by adding simple, easy-to-implement, and low-cost electrolyte additives, and has good application prospects. Attached Figure Description

[0017] Figure 1 These are optical photographs of the electrolytes of Examples 1-3 and Comparative Example 1.

[0018] Figure 2 These are Raman diagrams of the electrolytes of Examples 1-3 and Comparative Example 1.

[0019] Figure 3 This is a schematic diagram of the electrolyte assembly of aqueous zinc-manganese dual electrodeless batteries in Examples 1-3 and Comparative Example 1.

[0020] Figure 4 The aqueous zinc-manganese dual electrodeless batteries assembled in Examples 1-3 and Comparative Example 1 were charged at a constant voltage of 2.3 V to 1 mAh·cm⁻¹. -2 At 10 mA•cm -2 Cyclic performance diagram of discharge to 1.0 V at current density.

[0021] Figure 5 The aqueous zinc-manganese dual electrodeless battery assembled in Embodiment 1 and Comparative Example 1 of this invention is charged at a constant voltage of 2.3 V with a capacity of 1 mAh·cm⁻¹. -2 At 10mA•cm -2 Scan image after cycling at current density down to 1.0 V. Detailed Implementation

[0022] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0025] Example 1 The composition of the aqueous zinc-manganese dual electrodeless battery electrolyte (25 mL) in this embodiment is as follows: Solute: 1 mol / L ZnSO4 + 1 mol / L MnSO4 Solvent: Deionized water Additive: 0.06% v / v N-octylpyrrolidone (15 μL) Preparation method of aqueous zinc-manganese dual electrodeless battery electrolyte: Add solute to solvent to prepare mixture, then add additives, shake and stir, sonicate for 30 minutes, mix evenly to obtain aqueous zinc-manganese dual electrodeless battery electrolyte.

[0026] Example 2 The composition of the aqueous zinc-manganese dual electrodeless battery electrolyte (25 mL) in this embodiment is as follows: Solute: 1 mol / L ZnSO4 + 1 mol / L MnSO4 Solvent: Deionized water Additive: 0.02% v / v N-octylpyrrolidone (5 μL) Preparation method of aqueous zinc-manganese dual electrodeless battery electrolyte: Add solute to solvent to prepare mixture, then add additives, shake and stir, sonicate for 30 minutes, mix evenly to obtain aqueous zinc-manganese dual electrodeless battery electrolyte.

[0027] Example 3 The composition of the aqueous zinc-manganese dual electrodeless battery electrolyte (25 mL) in this embodiment is as follows: Solute: 1 mol / L ZnSO4 + 1 mol / L MnSO4 Solvent: Deionized water Additive: 0.1% v / v N-octylpyrrolidone (20 μL) Preparation method of aqueous zinc-manganese dual electrodeless battery electrolyte: Add solute to solvent to prepare mixture, then add additives, shake and stir, sonicate for 30 minutes, mix evenly to obtain aqueous zinc-manganese dual electrodeless battery electrolyte.

[0028] Comparative Example 1 The difference from Example 1 is that no electrolyte additive is added; otherwise, it is the same as Example 1.

[0029] The electrolyte (25 mL) for this comparative example of an aqueous zinc-manganese dual electrodeless battery consists of: Solute: 1 mol / L ZnSO4 + 1 mol / L MnSO4 Solvent: Deionized water Preparation method of aqueous zinc-manganese dual electrode battery electrolyte: The solute is added to the solvent to obtain the aqueous zinc-manganese dual electrode battery electrolyte.

[0030] result See Figure 1 Optical photographs of the electrolytes of Examples 1-3 and Comparative Example 1, and Figure 2 Raman chromatograms of the electrolytes of Examples 1-3 and Comparative Example 1 show that the electrolytes of Examples 1-3 and Comparative Example 1 are all clear and transparent, indicating that the addition of trace amounts of additives has no negative impact on the phase stability of the electrolyte and does not significantly change its microscopic solvation structure.

[0031] Test case The electrolytes prepared in Examples 1-3 and Comparative Example 1 of this invention were used to assemble an aqueous zinc-manganese dual electrodeless battery. The specific process is as follows: See Figure 3 Copper foil and graphite felt with a thickness of 10 micrometers were punched into circular pieces with a diameter of 12 mm, which were used as current collectors for the negative and positive electrodes, respectively. The batteries were assembled using a Swagelok battery mold, with a GF / F glass fiber separator and a electrolyte volume of 1 ml. Battery performance was then tested.

[0032] See Figure 4 The aqueous zinc-manganese dual electrodeless batteries assembled in Examples 1-3 and Comparative Example 1 were charged at a constant voltage of 2.3 V to 1 mAh·cm⁻¹. -2 At 10 mA•cm -2 The cycle performance graphs at current density discharged to 1.0 V show that the aqueous zinc-manganese dual-electrode battery assembled in Comparative Example 1 can only cycle 3 times, with an average coulombic efficiency of only 46.3%. Compared to Comparative Example 1, the aqueous zinc-manganese dual-electrode battery assembled in Example 1 of this invention cycles 120 times, with an average coulombic efficiency of 80.6%. The aqueous zinc-manganese dual-electrode battery assembled in Example 2 of this invention cycles 81 times, with an average coulombic efficiency of 69.3%. The aqueous zinc-manganese dual-electrode battery assembled in Example 3 of this invention cycles 80 times, with an average coulombic efficiency of 62.1%. It is evident that the aqueous zinc-manganese dual-electrode battery assembled in Example 1 (additive: 0.06% v / v N-octylpyrrolidone) exhibits the best performance, with a 40-fold increase in cycle life and a 34.3% increase in coulombic efficiency compared to Comparative Example 1.

[0033] See Figure 5 The aqueous zinc-manganese dual electrodeless batteries assembled in Example 1 and Comparative Example 1 were charged at a constant voltage of 2.3 V to 1 mAh·cm⁻¹. -2 At 10 mA•cm -2 The scan image after cycling at a current density of 1.0 V shows that the manganese oxide deposited in Comparative Example 1 agglomerates, while the deposit in Example 1 is smooth and flat, and has a smaller and more uniform micro-surface, proving that Example 1 improves electrochemical performance.

[0034] The above description is only a preferred embodiment of the present invention and is 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 electrolyte additive, characterized in that, The additive is N-octylpyrrolidone.

2. The application of the electrolyte additive according to claim 1 in the electrolyte of an aqueous zinc-manganese dual electrode battery.

3. The application as described in claim 2, characterized in that, The electrolyte additive has a content of 0.02%-0.1%v / v in the aqueous zinc-manganese dual electrode battery electrolyte.

4. The application as described in claim 3, characterized in that, The aqueous zinc-manganese dual electrode electrolyte includes a solute, a solvent, and electrolyte additives.

5. The application as described in claim 4, characterized in that, The electrolyte of the aqueous zinc-manganese dual electrode battery contains ZnSO4 and MnSO4 as solutes, with a total concentration of 2 mol / L and a concentration ratio of 1:

1.

6. The application as described in claim 4, characterized in that, The solvent is deionized water.

7. The application as described in claim 4, characterized in that, The preparation method of the aqueous zinc-manganese dual electrodeless battery electrolyte is as follows: add the solute to the solvent to prepare a mixture, then add the electrolyte additive, shake and stir, and ultrasonically mix evenly to obtain the aqueous zinc-manganese dual electrodeless battery electrolyte.

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