Lithium Recovery From Cathodes Using Concentrated Formic Acid
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Solution Overview
Problem
Current methods for recycling lithium from lithium-ion battery cathode materials, such as NMC, often result in lithium being contaminated with sodium and other transition metals, making it difficult to obtain high purity lithium due to the use of dilute formic acid leaching solutions that solubilize nickel, manganese, and cobalt along with lithium.
Innovation Solution
A method involving a leaching medium with at least 40 wt% formic acid concentration is used to selectively leach lithium from lithium-ion battery scrap, exploiting the poor solubility of transition metals at high formic acid concentrations while maintaining high solubility of lithium ions, which form soluble lithium formate, thereby achieving high selectivity and efficiency in lithium removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If dilute formic acid is used as leaching medium, then lithium can be leached from cathode material, but nickel, manganese, and cobalt are also solubilized causing contamination
Solution Approach 1:
The patent changes the concentration parameter of formic acid from dilute (conventional) to concentrated (at least 40 wt%, preferably 70-98 wt%). This parameter change fundamentally alters the solubility behavior: concentrated formic acid maintains high lithium leaching efficiency while dramatically reducing the solubility of nickel, manganese, and cobalt, thereby achieving both high quantity of lithium recovery and high purity without contamination
2Manufacturing precision
If high concentration formic acid is used, then transition metals remain insoluble, but process conditions become more stringent
Solution Approach 1:
The patent applies parameter changes by selecting a specific concentration range (at least 40 wt%, preferably 70-98 wt%) that optimizes the balance between selectivity and processability. This concentration range ensures transition metals remain insoluble while lithium is efficiently leached, and the process remains manageable with appropriate temperature control (50-100°C) and solid-liquid ratios
Solution Approach 2:
The patent performs preliminary action by pre-heating the concentrated formic acid before contacting with cathode material. This preliminary heating step facilitates better dissolution kinetics and ensures the leaching process proceeds efficiently under controlled conditions, reducing the complexity of subsequent processing
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 allows for the selective and efficient removal of lithium from lithium-ion battery scrap, reducing contamination from nickel, manganese, and cobalt, and producing high purity lithium, as demonstrated by high leaching selectivity and efficiency in the leachate, even with high formic acid concentrations.
Implementation Method 1
exploiting the poor solubility of transition metals at high formic acid concentrations while maintaining high solubility of lithium ions, which form soluble lithium formate
Implementation Method 2
formic acid acts as a reducing agent to convert insoluble +3 transition metal ions present in the NMC into soluble +2 ions
Implementation Method 3
Hydrogen peroxide is added to assist in this reduction
Data Source
AI summary
A method for selectively removing Li from an input material comprising Li and one or more transition metals, comprising the steps of: contacting said input material with a leaching medium comprising formic acid; and leaching Li from the input material to form a leachate; wherein the concentration of formic acid in the leaching medium is at least 70 wt. %.