Method and system for on-line monitoring of state of charge of vanadium redox flow battery

Abstract

The invention provides an all-vanadium redox flow battery state-of-charge online monitoring method and system. The monitoring method comprises the steps that the vanadium ion concentration value of each valence state in positive and negative electrode electrolyte in the battery charging and discharging process is acquired and open-circuit voltage is recorded; the state-of-charge of the positive and negative electrode electrolyte is calculated via the vanadium ion concentration value; a relation equation of open-circuit voltage and the corresponding state-of-charge is obtained according to the relational graph of the state-of-charge and open-circuit voltage through fitting; and the state-of-charge of the positive and negative electrode electrolyte of a battery to be measured is obtained according to the relation equation and current open-circuit voltage. The relevant parameters of the positive and negative electrode electrolyte are acquired so that unnecessary error in the calculation process of the battery state-of-charge can be weakened and finally the state-of-charge of the battery electrolyte can be obtained through measurement. According to the method, an existing open-circuit voltage method equation is corrected, and fitting of a negative electrode relation equation and a positive electrode relation equation is respectively performed so that the accurate state-of-charge of the positive and negative electrode electrolyte can be calculated.

Description

technical field [0001] The invention relates to the field of battery charge state monitoring, in particular to an online monitoring method and system for an all-vanadium redox flow battery charge state. Background technique [0002] In the field of existing battery state of charge monitoring, there are mainly the following monitoring methods. Among them, the US patent uses an auxiliary reference battery, or separates a battery at the end of the stack, and determines the relationship between the open circuit voltage OCV and the state of charge SOC. The SOC state of the electrolyte. The premise of this calculation method is that the SOC of the positive and negative electrolytes is equal, and the electrolyte on both sides of the actual vanadium battery system is electrochemically unbalanced due to external oxidation or ion migration, and the electrochemical is not completely reversible. Therefore, this method cannot accurately describe the positive and negative electrolytes. T...

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Problems solved by technology

[0013] However, in this measurement method, the premise is that the charge state of the positive and negative electrolytes is the same, but in fact the charge state of the positive and negative electrodes of the battery is unbalanced. During the charging process, is faster, while V 3+ The reduction of the battery is affected by the air that is not exhausted in the battery, resulting in a slow charging speed; when discharging, V 2+ →V 3+ faster, and Due to the large steric hindrance of the group, the speed of reaching the electrode surface is relatively slow, and the reaction speed is lower than that of the negative electrode. The result of potentiometric titration confirmed this

Since the electrochemical reaction between the positive electrolyte and the negative electrolyte is not completely reversible, the SOC of the positive electrode and the SOC of the negative electrode are not equal or even have a large deviation during the charging and discharging process. The error of the battery SOC calculated by the existing technology is relatively large.

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