CN111103548B

CN111103548B - Real-time SOC detection method for zinc-bromine flow battery

Info

Publication number: CN111103548B
Application number: CN201811249665.0A
Authority: CN
Inventors: 许鹏程; 李先锋; 张华民; 赖勤志
Original assignee: Yihua Shanghai Investment Co ltd; Dalian Institute of Chemical Physics of CAS
Current assignee: Yihua Shanghai Investment Co ltd; Dalian Institute of Chemical Physics of CAS
Priority date: 2018-10-25
Filing date: 2018-10-25
Publication date: 2021-07-27
Anticipated expiration: 2038-10-25
Also published as: CN111103548A

Abstract

The invention relates to the field of flow batteries, in particular to a zinc-bromine flow battery real-time SOC detection method, wherein the battery real-time SOC is calculated by the following method:

wherein n is₀The initial concentration of the electrolyte before the operation of the zinc-bromine flow battery; n is₁The electrolyte concentration is real-time when the zinc-bromine flow battery operates. The method is simple to operate, convenient to maintain and flexible to use, and can monitor the SOC of the zinc-bromine flow battery in real time.

Description

Real-time SOC detection method for zinc-bromine flow battery

Technical Field

The invention relates to the field of flow batteries, in particular to a flow battery charge state detection method.

Background

The zinc bromine flow battery (ZBB) is a flow energy storage battery with high energy conversion efficiency, high energy density (theoretical energy density 435wh/kg) and low price of key materials (diaphragm and electrolyte), and is widely applied to the fields of power generation of renewable energy sources such as wind energy and solar energy, power grid peak regulation and frequency modulation, communication base stations and the like.

The zinc-bromine redox flow battery realizes the mutual conversion between electric energy and chemical energy through the redox reaction of active substances between a positive electrode and a negative electrode, positive electrode bromide ions are oxidized into bromine simple substances in the charging process and are complexed by quaternary ammonium salts in the solution to generate water-insoluble oil phase complex to be deposited at the bottom of a liquid storage tank, zinc ions in the negative electrode solution are reduced into zinc simple substances to be deposited on the surface of an electrode, and due to the particularity of the redox reaction of the positive electrode and the negative electrode of the zinc-bromine redox flow battery, the charge state, namely SOC, of the battery cannot be accurately reflected through the OCV measurement method. Hyun Ju Lee et al propose a method for detecting SOC of a zinc-bromine battery by on-line Raman spectroscopy, but the method is complex to operate in practical use and is not beneficial to engineering application.

Disclosure of Invention

The invention provides a zinc-bromine flow battery SOC detection method, which is used for rapidly detecting the battery SOC by measuring the conductivity of electrolyte, thereby being beneficial to monitoring the electrolyte state of the whole battery system. In order to achieve the purpose, the invention adopts the technical scheme that:

the real-time SOC of the battery is calculated by the following method:

wherein n is₀The initial concentration of the electrolyte before the operation of the zinc-bromine flow battery;

n₁the electrolyte concentration is real-time when the zinc-bromine flow battery operates;

n₁calculated by measuring the electrolyte conductivity y when the battery is running.

Confirmation of the real-time electrolyte concentration n at this time using the electrolyte conductivity y₁The process of (1) is to substitute the conductivity y of the electrolyte into a linear equation between the concentration and the conductivity of the electrolyte to obtain the electrolyte; the measured electrolyte conductivity in the actual operation process of the battery is substituted into a relation curve equation of the electrolyte conductivity and the concentration obtained according to the fitting curve, and the real-time electrolyte concentration is obtained;

the straight line equation obtaining process: by measuring ZnBr in 0.01M to electrolyte in x MKCl + zM 1-methyl-1-ethyl pyrrolidine bromide (MEP) electrolyte₂Electrolyte conductivity y at initial concentration of at least 3 concentration values, expressed as ZnBr₂And respectively carrying out horizontal and vertical coordinate fitting curves on the molar concentration and the conductivity to obtain a regression linear equation of the relation between the concentration and the conductivity of the electrolyte.

x is the initial concentration of KCl in the electrolyte, and is 2-4M; z is the initial concentration of MEP in the electrolyte, which is 0.4-1M; ZnBr in electrolyte₂The initial concentration was 1-4M.

Advantageous effects

The method is simple to operate, convenient to maintain and flexible to use, and can monitor the SOC of the zinc-bromine flow battery in real time.

Drawings

FIG. 1 is a graph of a regression line equation of the relationship between the concentration of an electrolyte and the conductivity in example 1

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Example 1

The initial electrolyte of the zinc-bromine flow battery is 3MKCl, 0.8MMEP and 2M ZnBr₂Selecting ZnBr in electrolyte₂Measuring the conductivity y at the concentration of 0.1M,0.5M,1M,1.5M,2M, fitting curve, and fitting curve correlation coefficient R²0.99717, the regression equation for the relationship between electrolyte concentration and conductivity is found: 342.40381-55.49393n₁。

The electrolyte of the positive electrode and the electrolyte of the negative electrode are respectively 60ml and 2mol/LZnBr₂+3mol/LKCl +0.8M MEP, positive end plate of single cell in sequence, positive 6x6cm²Graphite plate, carbon felt, diaphragm, carbon felt, negative electrode 6x6cm²Graphite plate, negative pole end plate. The charging and discharging current density is 40mA/cm²And charging for 1 h. After charging for 1h, taking the negative electrolyte to measure the electrolyte conductivity y to be 253mS/cm, and substituting the measured electrolyte conductivity y into a regression linear equation of the relation between the electrolyte concentration and the conductivity to obtain that the zinc bromide concentration in the electrolyte is 1.6mol/L, and n₀＝2，n₁The electrolyte SOC was calculated to be 20% as 1.6.

Claims

1. A zinc-bromine flow battery real-time SOC detection method is characterized in that:

the real-time SOC of the battery is calculated by the following method:

wherein n₀The initial concentration of the electrolyte before the operation of the zinc-bromine flow battery;

n₁the electrolyte conductivity y is obtained by calculation when the battery runs;

confirmation of the real-time electrolyte concentration n at this time using the electrolyte conductivity y₁The process of (1) is that the conductivity y of the electrolyte is substituted into a linear equation between the concentration and the conductivity of the electrolyte to obtain the electrolyte; the measured electrolyte conductivity in the actual operation process of the battery is substituted into a relation curve equation of the electrolyte conductivity and the concentration obtained according to the fitting curve, and the real-time electrolyte concentration is obtained;

the straight line equation obtaining process: the initial electrolyte is ZnBr in the electrolyte containing xM KCl and zM 1-methyl-1-ethyl pyrrolidine bromide and selected from 0.01M₂At least 3 ZnBr between initial concentrations₂Concentration values, respectively determining the different ZnBr selected₂Electrolyte conductivity at concentration value y, ZnBr₂Respectively fitting a horizontal coordinate and a vertical coordinate with the molar concentration and the conductivity to obtain a regression linear equation of the relation between the concentration and the conductivity of the electrolyte;

x is the initial concentration of KCl in the electrolyte, and is 2-4M; z is the initial concentration of 1-methyl-1-ethyl pyrrolidine bromide in the electrolyte, which is 0.4-1M; ZnBr in electrolyte₂The initial concentration was 1-4M.

2. The real-time SOC detection method of the zinc-bromine flow battery according to claim 1, characterized in that:

the straight line equation obtaining process: the initial electrolyte is ZnBr in the electrolyte containing xM KCl and zM 1-methyl-1-ethyl pyrrolidine bromide and selected from 0.01M₂More than 5 ZnBr between initial concentrations₂Concentration values, respectively determining the different ZnBr selected₂Electrolyte conductivity at concentration value y, ZnBr₂And respectively carrying out horizontal and vertical coordinate fitting curves on the molar concentration and the conductivity to obtain a regression linear equation of the relation between the concentration and the conductivity of the electrolyte.