Recycled Graphite Purification for Li-Ion Anode Purity
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Solution Overview
Problem
Conventional recycling methods for Li-ion batteries struggle to achieve high purity graphite for anode materials due to residual impurities like aluminum oxide, which affects the performance and physical characteristics of recycled graphite products.
Innovation Solution
A purification process involving acid leaching, heat treatment with NaOH sintering, and subsequent washing with tetrahydrofuran and acidic solutions to achieve a modified recycled graphite with a purity exceeding 99.5%, effectively removing impurities and enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional acid leaching is used to recover graphite from spent Li-ion batteries, then graphite can be recovered from the black mass, but aluminum oxide and residual cathode materials remain as impurities in the recycled graphite
Solution Approach 1:
The purification process is divided into multiple sequential stages: initial acid leaching to remove cathode materials, followed by alkaline treatment to remove aluminum oxide, then filtration and drying steps. Each stage targets specific impurities, progressively separating them from the graphite particles to achieve high purity recovery
Solution Approach 2:
The process extracts and removes specific impurities (aluminum oxide and residual cathode materials) from the recycled graphite through selective chemical treatments. The acid leaching extracts metal salts, while the alkaline treatment extracts aluminum oxide, leaving purified graphite behind
2Manufacturing precision
If multiple purification steps are added to remove impurities from recycled graphite, then graphite purity exceeds 99.5%, but the processing time and complexity increase
Solution Approach 1:
The process utilizes changes in chemical parameters (pH levels, reagent concentrations, temperature) to selectively remove different impurities at different stages. By adjusting these parameters systematically, the process achieves high purity graphite through a series of controlled chemical transformations and separations
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 process results in high-purity recycled graphite with improved coulombic efficiency, cycle stability, and rate performance, meeting or exceeding commercial standards, and enabling extended battery life cycles and energy density.
Implementation Method 1
washing the anode material in an acidic wash solution for removing residual charge material metals
Implementation Method 2
Heat treatment sinters the anode material with NaOH for forming a sintered graphite from the anode material
Implementation Method 3
Heat treatment sinters the anode material with NaOH for forming a sintered graphite from the anode material, which removes a substantial portion of metal salts
Implementation Method 4
A sequence of heating (sintering) and pH adjusted washing further purifies the graphite into a modified, recycled graphite exceeding 99.5% purity
Data Source
AI summary
A purification process for recycled graphite for use as anode material in Li-ion batteries includes a sequence of leaching and heat treatment followed by washing with deionized (DI) water and an acid wash. A graphite source results from a suitable process such as acid leaching of black mass from a battery recycling stream, where the leach removes a substantial portion of metal salts used for cathode materials. Impurities, most notably aluminum oxide and residual cathode materials, are often present in trace amounts in the graphite source. A sequence of heating (sintering) and pH adjusted washing further purifies the graphite into a modified, recycled graphite exceeding 99.5% purity for use in a recycled battery.