Spent Graphite Anode Regeneration via Boric Acid and Sintering
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Solution Overview
Problem
Current lithium-ion battery recycling methods inefficiently dispose of spent graphite anodes, leading to environmental concerns and loss of valuable electrochemical energy, as they either burn or discard this material due to its low cost compared to cathode materials, and existing rejuvenation processes using strong acids pose pollution risks with inferior recycled capacity.
Innovation Solution
A method involving washing, sintering, and pre-treatment with boric acid to remove dead-Li residuals and incorporate boron into the graphite surface, effectively regenerating spent graphite anodes to match or exceed the performance of fresh graphite through a series of steps including boric acid treatment and short annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional washing or sintering is used to treat spent graphite particles, then the processing is simple and low-cost, but the dead-Li residual inside the graphite particles cannot be effectively removed, resulting in inferior regeneration quality
Solution Approach 1:
The patent applies boric acid pre-treatment before sintering to remove dead-Li residual from graphite particles. This preliminary chemical treatment prepares the graphite for subsequent sintering, enabling effective removal of lithium residues that would otherwise remain trapped inside the particle structure, thus achieving high regeneration quality without requiring excessively complex processing
Solution Approach 2:
Boric acid serves as an intermediary substance that facilitates the removal of dead-Li residual from graphite particles. The boric acid reacts with the trapped lithium during pre-treatment, forming compounds that can be subsequently removed during sintering, thereby mediating the complex interaction between the treatment process and the graphite structure
2Manufacturing precision
If strong caustic acids are used to remove SEI from graphite surface, then the surface cleaning effect is improved, but secondary pollution is generated
Solution Approach 1:
The patent changes the chemical parameters of the cleaning process by using boric acid instead of strong caustic acids. This substitution maintains the ability to remove SEI and clean the graphite surface while significantly reducing the environmental harm and secondary pollution associated with aggressive acid treatments
Solution Approach 2:
The patent converts the previously harmful effect of using strong acids into a beneficial approach by employing boric acid, which is much more environmentally friendly. The boric acid pre-treatment followed by sintering achieves effective surface cleaning and dead-Li removal without generating the severe secondary pollution that would result from using conventional strong caustic acids
3Reliability
If extremely high annealing temperature (>1500°C) is used to rejuvenate spent graphite, then the structural restoration is improved, but the capacity remains inferior to pristine graphite and energy consumption increases
Solution Approach 1:
The boric acid pre-treatment removes dead-Li residual and prepares the graphite structure before sintering, eliminating the need for extremely high annealing temperatures. This preliminary chemical treatment enables effective regeneration at moderate temperatures (700-1000°C), significantly reducing energy consumption while achieving structural restoration comparable to or better than pristine graphite
Solution Approach 2:
The patent changes the temperature parameter from extremely high (>1500°C) to moderate (700-1000°C) by introducing the boric acid pre-treatment step. This parameter change, combined with the chemical preparation from boric acid, achieves effective structural restoration at lower temperatures, reducing energy consumption while maintaining or improving regeneration quality
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 eliminates environmental concerns, recovers battery performance, and provides sustainable raw materials by removing bulk defects and enhancing thermal and electrochemical stability, achieving high capacity, rate capability, and stable cycling performance for recycled graphite.
Implementation Method 1
treating the spent graphite particles in a boric acid solution to form borated graphite particles
Implementation Method 2
fast annealing the borated graphite particles
Implementation Method 3
The step of fast annealing may include sintering the borated graphite particles for approximately an hour at a temperature in a range of 750° C. to 1050° C.
Implementation Method 4
the boron is incorporated into the surface of the graphite particle
Implementation Method 5
Prior to the step of treating, the spent graphite particles may be washing in a solvent and dried to form a powder
Implementation Method 6
drying the borated graphite particles
Data Source
AI summary
A method for restoring electrochemical activity and cycling stability to spent graphite anode material for a lithium-ion battery includes exposing powdered graphite anode material to boric acid to form borated material, then sintering the borated material. The processing removes dead lithium from the bulk structure and applies boron doping to surfaces of the graphite material.