Vanadium-Chromium Electrolyte for Room-Temperature Flow Batteries
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Solution Overview
Problem
Existing vanadium electrolytes have low utilization rate, narrow voltage window, and low energy density, while iron-chromium electrolytes suffer from instability and high cost due to chromium aging and ion migration.
Innovation Solution
A vanadium-chromium electrolyte is developed, comprising vanadium and chromium compounds with specific concentrations and ratios, along with a phosphorus compound to enhance stability, and a method for preparing it, allowing operation at room temperature without high-temperature requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vanadium redox flow battery uses pure vanadium as active substance, then high temperature stability can be achieved, but energy density is low and initial investment cost is high
Solution Approach 1:
The patent merges vanadium and chromium electrolytes into a single shared electrolyte system. The electrolyte contains both V2+/V3+ and Cr3+/Cr2+ redox couples, allowing the battery to utilize both vanadium's high temperature stability and chromium's high solubility. This combination enables the system to achieve both reliability (temperature stability) and high energy density simultaneously, resolving the technical contradiction between these two parameters.
Solution Approach 2:
The electrolyte functions as a composite system containing multiple metal ions (vanadium and chromium) with complementary properties. By creating a composite electrolyte formulation with specific concentrations of V2+, V3+, Cr3+, and Cr2+, the patent achieves synergistic effects that provide both the thermal stability of vanadium and the high solubility of chromium, thereby increasing energy density while maintaining temperature stability.
2Productivity
If iron-chromium battery operates at high temperature to improve chromium activity, then battery efficiency increases, but hydrogen evolution reaction occurs and high-temperature resistant fluoroplastics are required
Solution Approach 1:
The patent changes the operating temperature parameter from high temperature (required for iron-chromium batteries) to room temperature (20-25°C). By adjusting the electrolyte composition to include both vanadium and chromium species with appropriate concentrations and pH levels, the system achieves high chromium activity and battery efficiency without requiring elevated temperatures, thereby eliminating hydrogen evolution reactions and the need for special high-temperature resistant materials.
3Quantity of substance
If vanadium electrolyte operates at high charging SOC to improve utilization rate, then more vanadium is utilized, but carbon felts at positive electrode are corroded and hydrogen evolution reaction occurs
Solution Approach 1:
The patent introduces chromium species (Cr3+ and Cr2+) as intermediary redox couples that mediate the charge-discharge process. During charging, chromium species participate in electron transfer reactions, distributing the electrochemical stress away from the vanadium species and carbon electrode. This intermediary mechanism allows the system to operate at high SOC without causing carbon felt corrosion or hydrogen evolution, thereby maintaining electrode stability while achieving high vanadium utilization rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The vanadium-chromium electrolyte increases energy density by 12%, improves utilization rate to 100%, reduces costs, and achieves stable operation with high efficiency, overcoming the limitations of vanadium and iron-chromium electrolytes.
Implementation Method 1
a redox flow battery is a type of battery using liquid to load active substances. It relies on a pump to pump an active liquid into an electrode, where an oxidation-reduction can occur to realize the storage and release of electric energy
Implementation Method 2
the free acid acts as a proton conductive agent after ionization
Data Source
AI summary
A vanadium-chromium electrolyte, a method for preparing the same, and a redox flow battery composed thereof are provided. The vanadium-chromium electrolyte includes active substances and a free acid, the free acid acts as a proton conductive agent after ionization, and the active substances contain at least vanadium ions and chromium ions. The present disclosure further provides the method for preparing the vanadium-chromium electrolyte, which includes the following steps: dissolving a vanadium compound with a free acid, and obtaining a mixed solution of the free acid and vanadium ions through filtering; electrolytically reducing vanadium to an average valence state of 3.5 to 4 valence; adding a chromium compound, dissolving through stirring, and implementing a filtering; and adding pure water and an auxiliary reagent to adjust concentration, and preparing the vanadium-chromium electrolyte.