A flow battery or battery stack

Abstract

The present invention relates to the field of liquid flow batteries, and in particular to a liquid flow battery or a battery stack structure, comprising a sheet-like porous electrode and a liquid flow frame with a middle band and a through hole of corresponding shape and size, wherein the porous electrode is placed in the middle through hole of the liquid flow frame, and the edges of the porous electrode are all in contact with the inner wall surface of the middle through hole of the liquid flow frame, and a through hole serving as an electrolyte inflow channel and a through hole serving as an electrolyte outflow channel are provided on the liquid flow frame, the through hole of the electrolyte inflow channel is connected with the middle through hole through a groove or a through hole serving as an inlet guide area, and the through hole of the electrolyte outflow channel is connected with the middle through hole through a groove or a through hole serving as an outlet guide area; the characteristic of the invention is that: except for the inner wall surface of the liquid flow frame at the middle through hole where the inlet guide area and the outlet guide area are located, a strip-shaped insulating porous filling layer is provided between the inner wall surface of the middle through hole of the liquid flow frame and the edges of the porous electrode; the insulating porous filling layer separates the porous electrode from the wall surface of the liquid flow frame.

Description

Technical Field

[0001] The present invention relates to the field of liquid flow batteries, and in particular to a liquid flow battery or a battery stack structure. Background Art

[0002] Liquid flow battery technology is an emerging electrochemical energy storage technology. It has attracted widespread attention because of its advantages such as independent design of energy storage capacity and power. During the operation of liquid flow batteries, the active substances dissolved in the electrolyte circulate between the storage tank and the battery (or battery stack). When the electrolyte flows inside the battery stack, the flow velocity near the wall decreases due to the viscosity between the electrolyte and the wall, and the closer to the wall, the smaller the flow velocity, until the flow velocity drops to 0 at the wall. The reduction in the flow rate of the electrolyte will lead to a slowdown in the renewal of the active substances dissolved in the electrolyte, thereby reducing the concentration of the active substances, which in turn leads to a large concentration polarization, reducing the overall performance of the battery (or battery stack), shortening its service life, and increasing the system cost, which is not conducive to the large-scale application of liquid flow batteries. So far, there is no effective solution to this problem. Summary of the invention

[0003] Aiming at the performance degradation problem caused by the decrease of electrolyte flow velocity near the wall in liquid flow batteries, a new type of liquid flow battery or battery stack is proposed. On the basis of the traditional assembly method, an insulating porous filling layer is added to the wall where the electrode frame and the electrode are attached to eliminate the low flow velocity area near the wall, thereby reducing the overall polarization of the battery, improving the utilization rate of the electrolyte, and ultimately reducing the system cost.

[0004] To achieve the above purpose, the specific technical solution provided by the present invention is as follows:

[0005] A liquid flow battery or battery stack comprises a sheet-like porous electrode and a liquid flow frame with a through hole in the middle having a corresponding shape and size, wherein the porous electrode is placed in the middle through hole of the liquid flow frame, and the edges of the porous electrode are all in contact with the inner wall surface of the middle through hole of the liquid flow frame, and a through hole serving as an electrolyte inflow channel and a through hole serving as an electrolyte outflow channel are provided on the liquid flow frame, wherein the through hole of the electrolyte inflow channel is connected to the middle through hole through a groove or through hole serving as an inlet guide area, and the through hole of the electrolyte outflow channel is connected to the middle through hole through a groove or through hole serving as an outlet guide area; the characteristic is that: except for the inner wall surface of the liquid flow frame at the middle through hole where the inlet guide area and the outlet guide area are located, a strip-shaped insulating porous filling layer is provided between the inner wall surface of the middle through hole of the liquid flow frame and the edges of the porous electrode; the insulating porous filling layer separates the porous electrode from the wall surface of the liquid flow frame.

[0006] The design standard of the assembly structure of the present invention is that the insulating porous filling layer is located between the porous electrode and the wall surface of the liquid flow frame.

[0007] Preferably, the insulating porous filling layer has a width of 0.1 to 30 mm; a length greater than or equal to the length of the porous electrode along the electrolyte flow direction; and a thickness that differs from the electrode thickness in the range of 0 to 10 mm.

[0008] Preferably, after assembly, the porosity of the insulating porous filling layer differs from that of the porous electrode by 0 to 0.3.

[0009] The material of the insulating porous filling layer provided by the present invention can be selected from one or more of polyurethane, polytetrafluoroethylene, polybenzimidazole, and polyethersulfone materials, but is not limited thereto.

[0010] Compared with the prior art, the battery or battery stack of the present invention can be rectangular or trapezoidal, which can greatly improve the uniformity of the distribution of reactive substances, thereby ensuring uniform reactions inside the battery and battery stack, reducing local heat release, reducing polarization, and extremely high electrolyte utilization. Especially for high-power battery stacks, it can effectively reduce costs and save materials.

[0011] Beneficial effects brought by the technical solution of the present invention

[0012] The battery or battery stack of the invention is easy to process and simple to operate. By adding an insulating porous filling layer, the distribution uniformity of the active material inside the flow battery is improved, thereby effectively improving the battery performance. Specifically:

[0013] Affected by the fluid, especially the viscosity of the liquid flow itself, when the fluid flows near the wall, within a certain range, the closer to the wall, the smaller the flow rate of the fluid, until the flow rate at the wall drops to 0. Therefore, the electrolyte renewal rate is slow in this area, and as the reaction continues, there is insufficient supply of active substances, which leads to increased polarization, reduced voltage efficiency, and reduced electrolyte utilization, which ultimately reduces the overall performance of the battery.

[0014] By adding a porous insulating filling layer at the junction of the liquid flow frame and the electrode, no electrochemical reaction occurs in the thin liquid layer where the active material is updated more slowly, thereby increasing the concentration of active materials at the edge of the electrode area, making the active materials more evenly distributed, reducing battery polarization, and improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the assembly structure of Example 1.

[0016] Figure 2 Schematic diagram of the assembly structure of Example 2.

[0017] Figure 3 Schematic diagram of the assembly structure of comparative example 3.

[0018] Explanation of symbols:

[0019] 1- electrolyte mainstream inlet, 2- inlet guide area, 3- wall surface, 4- insulating porous filling layer, 5- porous electrode, 6- outlet guide area, 7- electrolyte mainstream outlet

[0020] Figure 4 Distribution diagram of active substance concentration in Example 1 and Comparative Example 2 under the same operating conditions. DETAILED DESCRIPTION

[0021] Example 1

[0022] like Figure 1 As shown, a liquid flow battery assembly structure. The outside of the area shown in the figure is a liquid flow frame, and the figure shows the main area through which the electrolyte flows, including an inlet guide area 2, an insulating porous filling layer 4, a porous electrode 5 and an outlet guide area 6. The inlet guide area is provided with an electrolyte mainstream inlet 1, and the outlet guide area is provided with an electrolyte mainstream outlet 7, and the insulating porous filling layer is placed between the porous electrode 5 and the wall 3. The porous electrode is a trapezoid, with a horizontal bottom width of 30mm and a bottom width of 60mm, and is made of carbon felt; an insulating porous filling layer is provided on each side of the porous electrode, which is a parallelogram, and its horizontal width is 3mm, and is made of polyurethane. The horizontal width of the inlet guide area and the outlet guide area is the sum of the horizontal widths of the porous electrode and the insulating porous filling layer, which are 36mm for the inlet and 66mm for the outlet respectively.

[0023] Example 2

[0024] like Figure 2 As shown, a liquid flow battery assembly structure. The outside of the area shown in the figure is a liquid flow frame, and the figure shows the main area through which the electrolyte flows, including an inlet guide area 2, an insulating porous filling layer 4, a porous electrode 5 and an outlet guide area 6. The inlet guide area is provided with an electrolyte mainstream inlet 1, the outlet guide area is provided with an electrolyte mainstream outlet 7, and the insulating porous filling layer is placed between the porous electrode 5 and the wall 3. The porous electrode is a rectangle with a horizontal width of 30mm and is made of carbon felt; a rectangular insulating porous filling layer is provided on each side of the porous electrode, and the horizontal width is 3mm, and the material is polyurethane. The horizontal width of the inlet guide area and the outlet guide area is the sum of the horizontal widths of the porous electrode and the insulating porous filling layer, which is 36mm.

[0025] Comparative Example 3

[0026] The comparative assembly structure selects the traditional rectangular liquid flow battery assembly structure, such as Figure 3As shown. The outside of the area shown in the figure is the liquid flow frame, and the figure shows the main area through which the electrolyte flows, including the inlet guide area 2, the porous electrode 5 and the outlet guide area 6. The inlet guide area is provided with an electrolyte mainstream inlet 1, and the outlet guide area is provided with an electrolyte mainstream outlet 7. The porous electrode is a rectangle with a horizontal width of 30mm and is made of carbon felt. The inlet guide area and the outlet guide area have a horizontal width of 30mm.

[0027] Taking the all-vanadium liquid flow battery as an example, the commercial software package COMSOL Multiphysics @ Carry out simulation calculations. The mathematical models used in the simulation mainly include:

[0028] Conservation of momentum and continuity equation:

[0029]

[0030] in, and P represent the velocity vector and pressure respectively, μ and μ * They represent the intrinsic viscosity and effective viscosity of the electrolyte respectively, and K represents the permeability of the porous medium (porous electrode), which is obtained by the Carman-Kozeny equation.

[0031] Material conservation equation:

[0032]

[0033] where c i is the concentration of material i, S i is the source term in the conservation equation for material i, is the effective diffusion coefficient in the porous electrode region.

[0034] Boundary conditions and initial conditions:

[0035]

[0036] The inlet pressure is set to 24000Pa and the outlet pressure is set to 0Pa.

[0037] In the model, the concentration of vanadium ions at the inlet is related to the charge and discharge state (SoC) to eliminate the influence of reaction time. Based on the assumption of fully developed flow, the diffusion flux of all materials at the outlet is set to 0. The wall boundary is set to 0 flux. The specific expression is:

[0038]

[0039] and are the initial concentrations of vanadium ions at the positive and negative electrodes, respectively, which are set to 1500 mol m -3The relative error factor of the model convergence is 1×10 -6 .

[0040] At 200mA cm -2 When the current density is charged and the SoC is 50%, the results obtained by simulation calculation of Example 2 and Comparative Example 3 are as follows Figure 4 And the following table shows:

[0041]

[0042] It can be seen that the assembly structure of the present invention significantly improves the uniformity of the distribution of reactive substances, and polarization is also significantly reduced, thereby reducing local heat release, improving the utilization rate of the electrolyte, and reducing costs.

Claims

1. A liquid flow battery, characterized in that: A liquid flow frame comprising a sheet-like porous electrode and a middle band with through holes of corresponding shapes and sizes, wherein the porous electrode is placed in the middle through hole of the liquid flow frame, and the edges of the porous electrode are all in contact with the inner wall surface of the middle through hole of the liquid flow frame. A through hole serving as an electrolyte inflow channel and a through hole serving as an electrolyte outflow channel are provided on the liquid flow frame, wherein the through hole of the electrolyte inflow channel is connected to the middle through hole through a groove or through hole serving as an inlet guide area, and the through hole of the electrolyte outflow channel is connected to the middle through hole through a groove or through hole serving as an outlet guide area; the feature is that: except for the inner wall surface of the liquid flow frame at the middle through hole where the inlet guide area and the outlet guide area are located, a strip-shaped insulating porous filling layer is provided between the inner wall surface of the middle through hole of the liquid flow frame and the edges of the porous electrode; the insulating porous filling layer separates the porous electrode from the wall surface of the liquid flow frame; After assembly, the porosity of the insulating porous filling layer differs from that of the porous electrode in the range of 0 to 0.

3.

2. According to the liquid flow battery of claim 1, the insulating porous filling layer is in the shape of a long strip, and its material is one or more of polyurethane, polytetrafluoroethylene, polybenzimidazole, and polyethersulfone.

3. The liquid flow battery according to claim 1, characterized in that: It includes a quadrilateral sheet-like porous electrode and a liquid flow frame with a corresponding quadrilateral through hole in the middle. The porous electrode is placed in the middle through hole of the liquid flow frame, and the edges of the porous electrode are all in contact with the inner wall surface of the middle through hole of the liquid flow frame.

4. The liquid flow battery according to claim 1, characterized in that: The width of the insulating porous filling layer is 0.1-30 mm; during assembly, the thickness of the insulating porous filling layer differs from the thickness of the electrode in the range of 0-10 mm.

5. The liquid flow battery according to claim 1, characterized in that: The porous electrodes include a positive electrode and a negative electrode.

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