A zinc-based flow battery structure
By designing an interlaced hole negative electrode structure, the problem of zinc deposition location and morphology limitations in zinc-based flow batteries was solved, achieving high-capacity uniform deposition and effective protection of the separator in zinc-based flow batteries, thereby improving the energy density and reliability of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-05
AI Technical Summary
In zinc-based flow batteries, the deposition location and morphology of zinc during the negative electrode deposition process can lead to membrane blockage and the risk of zinc puncturing the membrane, thus affecting the improvement of energy density.
A cross-hole negative electrode structure is designed, including through holes A and B on the side wall of the negative electrode. Through hole A is connected to the surface of the membrane on the side that contacts the membrane through hole B. The axis of hole B is perpendicular to the contact surface between the negative electrode and the membrane, and through hole A is parallel to the diagonal direction of the electrolyte inflow and outflow angle, thereby increasing the zinc deposition surface capacity and reducing the contact area between the negative electrode and the membrane.
It effectively increases the zinc deposition surface capacity, reduces the risk of membrane blockage, maintains the ion conduction function of the membrane, promotes uniform electrolyte distribution, and achieves high-capacity uniform deposition.
Smart Images
Figure CN122158632A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of zinc-based flow battery technology, specifically a zinc-based flow battery with an interleaved negative electrode. Background Technology
[0002] Zinc has attracted much attention due to its abundant reserves, rapid kinetics, excellent cycle performance, high volumetric and gravimetric specific capacity, and relatively suitable electrode potential. Furthermore, zinc's good compatibility with water makes it a promising candidate for use in aqueous electrolyte battery systems, which offer low cost, high safety, and excellent ionic conductivity. Aqueous zinc-based flow batteries, as a typical example of zinc in battery systems, not only boast high energy density but also excellent safety, showing broad development prospects in distributed energy storage. Improving the energy density of zinc-based flow batteries could significantly reduce their cost, thereby enhancing their market competitiveness. However, the limitations imposed by the deposition location and morphology of zinc during the negative electrode deposition process mean that continuously increasing the areal capacity may lead to membrane blockage and the risk of zinc "puncturing" the membrane, posing a serious challenge to further improving the energy density of zinc-based flow batteries. Therefore, developing more advanced negative electrode structures has become an urgent and challenging task. Summary of the Invention
[0003] This invention provides a cross-hole negative electrode for zinc-based flow batteries. The method aims to increase the negative electrode's areal capacity, thereby reducing the risk of zinc "puncturing" the separator and enhancing the reliability of zinc-based batteries.
[0004] Specifically, the technical solution of the present invention includes:
[0005] A zinc-based flow battery structure, the zinc-based single cell includes a rectangular positive electrode, a separator, and a rectangular negative electrode stacked in sequence, the positive electrode and the negative electrode are respectively placed in an annular electrode frame with a rectangular through hole in the middle, and the negative electrode is a rectangular carbon felt or graphite felt electrode.
[0006] An inlet and an outlet are provided at the two opposite corners of the negative electrode frame, such that the inlet of the negative electrode electrolyte is located at one corner of the rectangular negative electrode, and the outlet is located at the opposite corner of the inlet.
[0007] On the side wall of the negative electrode, two or more through holes A are opened between the side walls of the two sides at the corner where the liquid inlet is located, and two or more through holes A are opened between the side walls of the two sides at the corner where the liquid outlet is located.
[0008] Two or more holes B are provided between the through hole A and the surface of the negative electrode in contact with the diaphragm, so that each through hole A can be connected to the surface of the negative electrode in contact with the diaphragm through the holes B.
[0009] Furthermore, hole B is a circular hole with its axis perpendicular to the surface of the negative electrode that contacts the diaphragm.
[0010] Furthermore, the through hole A is a circular through hole with its axis parallel to the contact surface between the negative electrode and the membrane, and its axis perpendicular to the diagonal line between the angle of electrolyte inflow and outflow from the negative electrode (the boundary line between the angles where the inlet and outlet are located).
[0011] Furthermore, on the axially perpendicular plane of the through hole A on the sidewall of the negative electrode, the opening area of the through hole A accounts for 5 to 40% of the projected area of the electrode on that plane, preferably 10 to 30%.
[0012] The opening area ratio of the hole B on the side surface where the negative electrode contacts the diaphragm is 10-60% of the surface area of the side surface where the negative electrode contacts the diaphragm, preferably 20-40%.
[0013] Furthermore, the thickness of the negative electrode is 3–10 mm, preferably 4–7 mm.
[0014] Furthermore, the diameter of the through hole A is 2-4 mm, the distance between the axis of the through hole A and the contact surface between the negative electrode and the diaphragm is 2-5 mm, and the distance between the axes of adjacent through holes A is 6-9 mm;
[0015] The diameter of the hole B is 2-7 mm, and the distance between the axes of adjacent holes B in the direction of the through hole A is 3-8 mm; the depth of the hole B is 2-8 mm, that is, all or part of the end of the hole B away from the contact surface between the negative electrode and the diaphragm can pass through the through hole A, and / or all or part of the end of the hole B away from the contact surface between the negative electrode and the diaphragm can pass through the through hole A to the negative electrode surface away from the contact surface between the negative electrode and the diaphragm to form a through hole.
[0016] Furthermore, the positive electrode is a rectangular carbon felt or graphite felt electrode; the diaphragm is a polyolefin porous membrane.
[0017] The method provided by this invention can achieve the following beneficial effects:
[0018] 1. By constructing large pores on the surfaces and sides where the electrode contacts the diaphragm, the surface area available for zinc deposition can be effectively increased compared to planar electrodes, thereby increasing the zinc deposition surface capacity.
[0019] 2. It can reduce the direct contact area between the negative electrode and the diaphragm, thereby effectively alleviating the diaphragm blockage and failure caused by the complete coverage of the diaphragm after the formation of dense zinc.
[0020] 3. Since the constructed cross-hole negative electrode zinc deposition does not completely cover the membrane surface, even with an appropriate increase in deposition surface capacity, the membrane still plays a role in ion conduction, allowing the battery to continue operating.
[0021] 4. The channels parallel to the contact surface between the electrode and the diaphragm and perpendicular to the line connecting the inlet and outlet have the function of reducing electrode flow resistance and uniformly distributing electrolyte, which can promote the high-capacity uniform deposition of zinc on the entire electrode. Attached Figure Description
[0022] Figure 1 Schematic diagram of the cross-hole negative electrode of a zinc-based flow battery.
[0023] Wherein: 1: Hole B, 2: Through hole A, 3: Position of negative electrode electrolyte inlet, 4: Position of negative electrode electrolyte outlet. Detailed Implementation
[0024] Example 1:
[0025] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed in annular electrode frames with square through-holes in the center. Inlet and outlet ports are located at opposite corners of the electrode frames, respectively, with the inlet port of the negative electrode electrolyte located at one corner of the rectangular negative electrode, and the outlet port located diagonally opposite the corner containing the inlet port. The positive electrode is a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Perforations are drilled in the negative electrode carbon felt (length × width × thickness, 6cm × 6cm × 0.6cm). On its side wall surface (the thickness surface of the carbon felt), two or more circular through holes A are made between the two side walls of the corner where the liquid inlet is located, and two or more circular through holes A are made between the two side walls of the corner where the liquid outlet is located. The axis of the circular through hole A is perpendicular to the diagonal line between the angles where the electrolyte flows in and out of the electrode (the boundary line between the angles where the liquid inlet and outlet are located). The axis of the circular through hole A is parallel to the contact surface between the electrode and the membrane. The diameter of the through hole A is 3mm. The axial distance between adjacent through holes A is approximately 7.1mm. The axis of the through hole A is 3mm away from the contact surface between the negative electrode and the membrane. On the axially perpendicular plane of the through hole A on the side wall surface of the negative electrode, the opening area of the through hole A accounts for approximately 15.2% of the projected area of the electrode on that plane. Two or more circular holes B are provided between the through-hole A and the surface of the negative electrode contacting the separator, so that each through-hole A can be connected to the surface of the negative electrode contacting the separator through the circular holes B. The axis of the circular holes B is perpendicular to the surface of the negative electrode contacting the separator and is located on the axis of the through-hole A. The diameter of the circular holes B is 5 mm, the distance between the axes of adjacent circular holes B in the direction of the axis of the through-hole A is 7.1 mm, and the hole depth is 6 mm. The end of the circular hole B away from the surface of the negative electrode contacting the separator can pass through the through-hole A to the surface of the negative electrode away from the surface of the negative electrode contacting the separator, forming a through hole. The opening ratio of the holes B on the surface of the negative electrode contacting the separator is approximately 33.8% of the surface area of the side of the negative electrode contacting the separator. Constant current charging and discharging is performed at a current density of 40 mA cm⁻¹. -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 112mAh cm⁻¹. -2 .
[0026] Example 2:
[0027] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed in annular electrode frames with square through-holes in the center. Inlets and outlets are located at opposite corners of the electrode frames, with the inlet for the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode is a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Perforations are drilled in the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). The drilling method for through-hole A is the same as in Example 1; the difference between hole B and Example 1 is that the hole depth is 4mm (i.e., the end of hole B away from the contact surface between the negative electrode and the diaphragm passes through through-hole A, but does not form a through-hole), otherwise it is the same as in Example 1. Constant current charging and discharging is performed at a current density of 40mA / cm². -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 121mAh cm⁻¹. -2 .
[0028] Example 3:
[0029] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed in annular electrode frames with square through-holes in the center. Inlets and outlets are located at opposite corners of the electrode frames, with the inlet for the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode is a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Perforations are drilled in the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). The diameter of through-hole A is 4 mm, the axial spacing between adjacent through-holes A is approximately 7 mm, and the axial distance of through-hole A is 3 mm from the contact surface between the negative electrode and the diaphragm. On the axially perpendicular plane of through-hole A on the sidewall of the negative electrode, the opening area of through-hole A accounts for approximately 30% of the projected area of the electrode on that plane. The drilling method of hole B is the same as in Example 1. Constant current charging and discharging is performed at a current density of 40 mA / cm². -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 118mAh cm⁻¹. -2 .
[0030] Example 4:
[0031] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed in annular electrode frames with square through-holes in the center. Inlets and outlets are located at opposite corners of the electrode frames, with the inlet for the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode is a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Perforations are drilled in the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). The drilling method for through-hole A is the same as in Example 1; the difference between through-hole B and Example 1 is that the hole diameter is 4mm, and the opening ratio of through-hole B on the side of the surface where the negative electrode contacts the separator is approximately 21% of the surface area of that side. The rest is the same as in Example 1. Constant current charging and discharging is performed at a current density of 40mA / cm². -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 129mAh cm⁻¹. -2 .
[0032] Comparative Example 1:
[0033] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed within an annular electrode frame with a square through-hole in the center. An inlet and outlet are located at opposite corners of the electrode frame, with the inlet for the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode uses original carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm), and the negative electrode also uses original carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Constant current charging and discharging is performed at a current density of 40 mA / cm². -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is 78mAh cm⁻¹. -2 The negative electrode structure described in this comparative example has a significantly reduced discharge capacity compared to the comparative example because zinc is mainly deposited at the contact point between the negative electrode and the separator, the effectively utilized electrode surface is nearly planar, and the usable carbon felt thickness is relatively small.
[0034] Comparative Example 2:
[0035] The electrolyte composition of the assembled zinc-iodine flow battery is an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes is 144 mL. The separator is a Daramic membrane (900 μm thick). The positive and negative electrodes are placed in annular electrode frames with square through-holes in the center. Inlets and outlets are located at opposite corners of the electrode frames, with the inlet for the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode is a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Holes are drilled in the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). There are no through-holes A on the side of the negative electrode; only holes B are provided perpendicular to the contact surface between the electrode and the membrane, and these holes have the same diameter, position, and spacing as the through-holes in Example 1. Constant current charge and discharge, current density 40mA cm -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 95mAh cm⁻¹. -2 The absence of through-holes in the negative electrode (A) reduces the uniformity of electrolyte distribution within the electrode and decreases the electrolyte flow rate on the electrode surface where electrochemical reactions occur, thereby leading to a reduction in discharge capacity.
[0036] Comparative Example 3:
[0037] The electrolyte composition of the assembled zinc-iodine flow battery was an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes was 144 mL. The separator was a Daramic membrane (900 μm thick). The positive and negative electrodes were placed within an annular electrode frame with a square through-hole in the center. An inlet and outlet were located at opposite corners of the electrode frame, with the inlet of the negative electrode electrolyte positioned at one corner of the rectangular negative electrode, and the outlet at the opposite corner. The positive electrode was a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Holes were drilled on the side of the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm), with through-hole A drilled in the same manner as in Example 1; there was no hole B perpendicular to the contact surface between the carbon felt and the separator. Constant current charging and discharging was performed at a current density of 40 mA / cm². -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 81mAh cm⁻¹. -2 Although having only pore A on the negative electrode promotes more uniform electrolyte flow inside the electrode, metallic zinc will preferentially deposit on the surface where the membrane contacts the electrode. The effect of the uniformity of electrolyte flow in promoting zinc deposition in the electrode thickness direction is limited, and it cannot significantly increase the battery's discharge capacity.
[0038] Comparative Example 4:
[0039] The electrolyte composition of the assembled zinc-iodine flow battery was an aqueous solution of 4 mol / L KI, 2 mol / L ZnBr2, and 2 mol / L KCl. The electrolyte volume for both the positive and negative electrodes was 144 mL. The separator was a Daramic membrane (900 μm thick). The positive and negative electrodes were placed within an annular electrode frame with a square through-hole in the center. An inlet and outlet were located at opposite corners of the electrode frame, with the inlet of the negative electrode electrolyte positioned at one corner of the rectangular negative electrode and the outlet at the opposite corner. The positive electrode was a raw carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). Holes were drilled in the negative electrode carbon felt (length × width × thickness, 6 cm × 6 cm × 0.6 cm). The axis of hole A was approximately 4.5 mm from the contact surface between the negative electrode and the separator; the remaining drilling method was the same as in Example 1. The drilling method for hole B was the same as in Example 1. Constant current charge and discharge, current density 40mA cm -2 The cutoff voltage during discharge is 0.3V. The discharge capacity is approximately 90mAh / cm³. -2 The axis of the through-hole A is farther from the negative electrode and the diaphragm. Compared with Comparative Example 1, the electrolyte flow rate through the electrochemical reaction surface is lower in this structure, which leads to a reduction in the electrode surface available for zinc deposition.
Claims
1. A zinc-based flow battery structure, the zinc-based single cell comprising a rectangular positive electrode, a separator, and a rectangular negative electrode stacked sequentially, the positive and negative electrodes being respectively placed within an annular electrode frame with a rectangular through hole in the center, wherein the negative electrode is a rectangular carbon felt or graphite felt electrode, characterized in that: An inlet and an outlet are provided at the two opposite corners of the negative electrode frame, such that the inlet of the negative electrode electrolyte is located at one corner of the rectangular negative electrode, and the outlet is located at the opposite corner of the inlet. On the side wall of the negative electrode, two or more through holes A are opened between the side walls of the two sides at the corner where the liquid inlet is located, and two or more through holes A are opened between the side walls of the two sides at the corner where the liquid outlet is located. Two or more holes B are provided between the through hole A and the surface of the negative electrode in contact with the diaphragm, so that each through hole A can be connected to the surface of the negative electrode in contact with the diaphragm through the holes B.
2. The zinc-based flow battery structure according to claim 1, characterized in that: Hole B is a circular hole, and its axis is perpendicular to the surface of the negative electrode that contacts the diaphragm.
3. The zinc-based flow battery structure according to claim 1, characterized in that: Through hole A is a circular through hole with its axis parallel to the contact surface between the negative electrode and the membrane, and its axis perpendicular to the diagonal line between the angle where the electrolyte flows in and out of the negative electrode (the boundary line between the angles where the inlet and outlet are located).
4. The zinc-based flow battery structure according to claim 1, characterized in that: On the axially perpendicular plane of the through hole A on the sidewall of the negative electrode, the opening area of the through hole A accounts for 5 to 40% of the projected area of the electrode on this plane, preferably 10 to 30%. The opening area ratio of the hole B on the side surface where the negative electrode contacts the diaphragm is 10-60% of the surface area of the side surface where the negative electrode contacts the diaphragm, preferably 20-40%.
5. The zinc-based flow battery structure according to claim 1, characterized in that: The thickness of the negative electrode is 3–10 mm, preferably 4–7 mm.
6. The zinc-based flow battery structure according to any one of claims 1-5, characterized in that: The diameter of the through hole A is 2-4 mm, and the distance between the axis of the through hole A and the contact surface between the negative electrode and the diaphragm is 2-5 mm; the distance between the axes of adjacent through holes A is 6-9 mm. The diameter of the hole B is 2-7 mm, and the distance between the axes of adjacent holes B in the direction of the through hole A is 3-8 mm; the depth of the hole B is 2-8 mm, that is, all or part of the end of the hole B away from the contact surface between the negative electrode and the diaphragm can pass through the through hole A, and / or all or part of the end of the hole B away from the contact surface between the negative electrode and the diaphragm can pass through the through hole A to the negative electrode surface away from the contact surface between the negative electrode and the diaphragm to form a through hole.
7. The structure according to any one of claims 1-5, characterized in that: The positive electrode is a rectangular carbon felt or graphite felt electrode; the diaphragm is a polyolefin porous membrane.