V-Based Metal Hydride Electrodes with Vanadate Additive
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Solution Overview
Problem
Conventional vanadium-based metal hydride batteries face challenges such as limited cycle stability and capacity due to kinetic limitations and degradation of the metal hydride electrode, leading to significant capacity loss over cycles.
Innovation Solution
The introduction of a negative electrode alloy comprising vanadium and chromium, along with the addition of vanadate ions in the electrolyte, which dissociate to form primary vanadate ions, enhances the chemical stability and capacity retention by mitigating oxidation and degradation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If vanadium-based metal hydride electrodes are used to achieve high theoretical capacity, then electrochemical capacity is improved, but electrode stability and cycle life deteriorate due to oxidation and dissolution of vanadium
Solution Approach 1:
Alkaline earth metal hydroxides (Ca(OH)2, Sr(OH)2, or Ba(OH)2) are introduced as intermediary substances that mediate between the vanadium-based metal hydride electrode and the electrolyte. These hydroxides form protective layers on the electrode surface that prevent direct contact between vanadium and the electrolyte, thereby reducing oxidation and dissolution while maintaining electrochemical capacity.
Solution Approach 2:
The electrode system is transformed from a simple vanadium-based metal hydride into a composite structure containing vanadium-based metal hydride particles dispersed in a matrix of alkaline earth metal hydroxide. This composite material combines the high capacity of vanadium-based hydrides with the protective and stabilizing properties of alkaline earth metal hydroxides, achieving both high capacity and improved cycle stability.
2Use of energy by moving object
If conventional vanadium-based metal hydride batteries are operated to achieve energy storage, then battery function is realized, but capacity is lost over cycles due to kinetic limitations and electrode degradation
Solution Approach 1:
Alkaline earth metal hydroxides serve as intermediary substances that facilitate stable long-term operation by reducing kinetic limitations and preventing electrode degradation. The hydroxides maintain a stable interface between the electrode and electrolyte, enabling sustained energy storage over hundreds of cycles with minimal capacity loss.
Solution Approach 2:
The introduction of alkaline earth metal hydroxides changes the chemical and physical parameters at the electrode-electrolyte interface, including pH, surface composition, and interfacial resistance. These parameter changes create more favorable conditions for hydrogen sorption kinetics and reduce degradation rates, thereby extending cycle life while maintaining energy storage capability.
3Quantity of substance
If vanadium-based metal hydride electrodes are used to achieve high capacity, then theoretical capacity of 1041 mAh/g is possible, but practical capacity is significantly lower due to kinetic limitations
Solution Approach 1:
The addition of alkaline earth metal hydroxides changes the interfacial parameters between the electrode and electrolyte, including surface pH, ionic conductivity, and hydrogen diffusion barriers. These parameter changes reduce kinetic limitations by facilitating faster hydrogen sorption rates, enabling the electrode to approach its theoretical capacity more closely during practical operation.
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
This approach results in a significant increase in discharge-capacity stability, with a reversible capacity of at least 500 mAh/g for up to 300 cycles, comparable to state-of-the-art Li-ion batteries, and improved energy density, addressing the limitations of conventional vanadium-based systems.
Implementation Method 1
an additive is provided in said electrolyte to form primary vanadate ions upon dissociation of said additive in said electrolyte
Implementation Method 2
the electrochemical cells disclosed herein have a negative electrode having an alloy that comprises vanadium and chromium... These, and other approaches discloses here, increase the (electro)chemical stability of the negative electrode by slowing or otherwise limiting the processes that oxidize and/or otherwise degrade V-containing alloy(s) of the negative electrode
Implementation Method 3
the alloy is configured to sorb hydrogen during charging of said electrochemical cell and desorb hydrogen during discharging of said electrochemical cell
Data Source
AI summary
In an aspect, an electrochemical cell comprises: a positive electrode; a negative electrode, said negative electrode having an alloy having a composition comprising V; and an electrolyte; wherein an additive is provided in said electrolyte to form primary vanadate ions upon dissociation of said additive in said electrolyte; and wherein the electrochemical cell is a metal hydride battery. In some embodiments of this aspect, the alloy is configured to sorb hydrogen during charging of said electrochemical cell and desorb hydrogen during discharging of said electrochemical cell. In some embodiments of this aspect, the electrolyte has a pH selected from the range of 13 to 15.