Sulfuric Acid Electrolyzer Pulse Current to Prevent Anode Passivation

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Solution Overview

Problem

Conventional electrolytic methods for dissolving metals like nickel in sulfuric acid solutions face challenges with high anode current density causing passivation, leading to inefficient dissolution and nickel deposition on the cathode, which hampers the production of high-concentration nickel ion solutions required for battery electrodes.

Innovation Solution

The method involves using a chloride ion-containing sulfuric acid solution with a specific chloride ion concentration and applying a pulse current with controlled application and interruption, while maintaining a liquid surface difference between the anode and cathode chambers, to inhibit passivation and enhance metal ion concentration in the anode chamber.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high anode current density is applied to dissolve metal quickly, then dissolution speed is improved, but passivation occurs on the anode surface

Engineering Contradiction:

Improvedissolution speedVSAvoidanode surface stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies periodic pulse current to the anode instead of continuous direct current. The current is applied intermittently with on-time and off-time periods, allowing the anode surface to recover from passivation during the off-period while still achieving high average current density for rapid dissolution during the on-period. This periodic action resolves the contradiction by enabling fast dissolution without sustained passivation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent dynamically adjusts the current application by varying the duty cycle (ratio of on-time to total period) and pulse frequency. This dynamic control allows optimization of dissolution rate while preventing passivation buildup. The system transitions from static continuous current to dynamic pulsed current, enabling adaptability between productivity and reliability requirements.

Inventive Principle:

Principle #15Dynamics

2Productivity

If high current density electrolysis is used to achieve high metal ion concentration, then production efficiency is improved, but metal deposits on the cathode

Engineering Contradiction:

Improveproduction efficiencyVSAvoidmetal deposition on cathode

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The periodic pulse current applied to the anode creates corresponding periodic conditions at the cathode. During the off-period, metal ions that migrated to the cathode during the on-period have time to diffuse back into the bulk solution, reducing deposition. This temporal separation allows high current density operation without proportional increase in cathode deposition losses.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous ion transport and dissolution action through the pulsed regime, ensuring that the useful dissolution process at the anode continues with high efficiency while the cathode deposition is interrupted periodically. The continuous circulation and periodic interruption create a net reduction in unwanted deposition while maintaining productive dissolution.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If conventional electrolytic method is used without chloride ions, then solution purity is maintained, but passivation prevents efficient dissolution

Engineering Contradiction:

Improvedissolution efficiencyVSAvoidsolution quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces chloride ions as an intermediary substance that facilitates the dissolution process. Chloride ions adsorb on the anode surface and prevent oxide film formation, acting as a mediator between the electric current and the metal dissolution. This intermediary enables efficient dissolution while the pulse current regime controls chloride ion concentration to maintain acceptable solution quality for battery applications.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively suppresses passivation, allowing for efficient dissolution of metals at high current densities, achieving high nickel ion concentrations in the sulfuric acid solution, suitable for battery applications, with improved current efficiency and reduced nickel deposition on the cathode.

Implementation Method 1

a method that dissolves a target metal in sulfuric acid by using a metal that is desired to be dissolved as an anode (positive electrode) and a sulfuric acid solution as an electrolyte, and applying a current between the anode and a cathode (negative electrode)

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Implementation Method 2

supplying a pulse current that repeats a periodic application and interruption of the current

Methodology Applied

Scientific EffectPulse current effect:

Data Source

PatentUS11781228B2Method for manufacturing sulfuric acid solution and electrolyzer used thereof

Publication Date: 2023.10.10 SUMITOMO METAL MINING CO LTD

AI summary

A method for manufacturing a sulfuric acid solution includes supplying a chloride ion-containing sulfuric acid solution as an initial electrolyte in an electrolyzer inside of which is divided into an anode chamber and a cathode chamber by a diaphragm; and subsequently taking out a metal dissolved electrolyte in which a metal constituting the anode is dissolved from the anode chamber while supplying a current to an anode and a cathode disposed in the electrolyzer.