Waste Cathode Lithium Hydroxide Recovery via Urea Pyrolysis
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Solution Overview
Problem
Existing methods for recycling lithium from waste lithium secondary batteries face environmental pollution issues due to the use of strong acids and incur high costs and low recovery rates with high-temperature heat treatments.
Innovation Solution
A method involving mixing waste lithium secondary battery positive electrode material with urea, firing at 450° C. to 600° C. in an inert gas atmosphere, and subsequent water washing to recover lithium hydroxide with a high yield, avoiding the use of strong acids and high-temperature processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong acids (hydrochloric acid, sulfuric acid, nitric acid) are used to extract lithium from waste positive electrode material, then lithium extraction efficiency is improved, but environmental pollution and equipment corrosion worsen
Solution Approach 1:
The invention changes the chemical environment from strongly acidic to weakly acidic by using oxalic acid instead of strong acids like hydrochloric, sulfuric, or nitric acid. This parameter change in acid strength and type maintains lithium extraction capability while eliminating the harmful effects of strong acid evaporation and corrosion, directly resolving the technical contradiction between extraction efficiency and environmental harm.
Solution Approach 2:
The invention uses oxalic acid, which is cheaper and less hazardous than strong acids, as a disposable reagent for lithium extraction. The weakly acidic nature of oxalic acid allows it to perform the extraction function without the long-term environmental and equipment damage caused by strong acids, providing a cost-effective and environmentally friendly alternative.
2Productivity
If high-temperature heat treatment (600°C or higher) is used to recover lithium by mixing with carbon powder, then lithium recovery is achieved, but energy consumption increases and recovery rate decreases
Solution Approach 1:
The invention changes the temperature parameter from high temperature (600°C or higher) to low temperature (below 600°C) by using oxalic acid extraction followed by controlled heating. This parameter change reduces energy consumption while maintaining effective lithium recovery, directly addressing the contradiction between lithium recovery and energy usage.
Solution Approach 2:
The invention replaces the thermal-mechanical process (high-temperature heat treatment with carbon powder) with a chemical process (oxalic acid extraction followed by low-temperature heating). This substitution of the extraction mechanism allows lithium recovery at lower temperatures, significantly reducing energy consumption while maintaining recovery effectiveness.
3Productivity
If high-temperature heat treatment (600°C or higher) is used to recover lithium, then lithium recovery is achieved, but recovery rate is low due to relatively low leaching efficiency
Solution Approach 1:
The invention changes the chemical parameter by using oxalic acid instead of carbon powder for extraction. Oxalic acid forms soluble lithium oxalate complexes that can be efficiently leached from the positive electrode material, significantly improving leaching efficiency and recovery rate compared to the high-temperature carbon powder method.
Solution Approach 2:
The invention substitutes the thermal decomposition method (heating with carbon powder) with a chemical complexation method (extraction with oxalic acid). This substitution enables much more efficient lithium leaching and recovery, directly improving the recovery rate from less than 50% to significantly higher levels.
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 method achieves a lithium hydroxide recovery rate of 50% or more in an environmentally friendly manner at lower temperatures, reducing environmental impact and operational costs.
Implementation Method 1
firing the first mixture to prepare a second mixture containing lithium hydroxide
Implementation Method 2
mixing a waste lithium secondary battery positive electrode material with urea to prepare a first mixture
Implementation Method 3
subjecting the second mixture to water washing to separate a lithium precursor
Data Source
AI summary
A method for reducing waste by recovering a lithium precursor including: a) mixing a waste lithium secondary battery positive electrode material with urea to prepare a first mixture; b) firing the first mixture to prepare a second mixture; and c) subjecting the second mixture to water washing to obtain lithium hydroxide.