Opportunity
The global demand for lithium (Li) has surged due to its critical role in energy storage, particularly in lithium-ion batteries. Traditional lithium extraction methods, such as mining and evaporation ponds, are energy-intensive, environmentally damaging, and geographically limited. Seawater, which contains vast amounts of lithium (~230 billion tons), offers a virtually inexhaustible resource. However, extracting lithium from seawater is challenging due to its low concentration (0.1–0.2 ppm) and the presence of interfering ions (e.g., Na, Mg²). Current membrane-based extraction technologies rely on fossil fuels, exacerbating energy inefficiency and environmental pollution. The need for a sustainable, solar-driven lithium extraction method is urgent to meet the growing demand for green energy solutions.
Technology
The patent introduces a novel photoelectrochemical (PEC) cell and a lithium extraction device that leverages solar energy to extract lithium from seawater efficiently. The PEC cell features a decoupled design, separating the light-absorbing component (photo-absorber) from the catalytic component (catalyst layer) to minimize light-blocking effects. The photo-absorber uses a triple-junction (3J) structure (InGaP/GaAs/Ge) to maximize solar spectrum absorption, while the catalyst layer (e.g., Ru-Ir-TiOx) enables chlorine evolution reactions (CIER) for charge balance. The device integrates a Li-ion selective membrane (LAGP) to achieve high-purity lithium extraction (783.56 ppm, 4,350× enrichment) while co-producing hydrogen and fixing CO₂ as bicarbonate. This innovation addresses key challenges in PEC systems: poor stability in seawater, low photovoltage, and parasitic light absorption.
Advantages
- High Efficiency: Achieves 26.05% solar-to-electricity conversion efficiency with the 3J photo-absorber.
- Selective Extraction: LAGP membrane enables Li/Mg selectivity >50 million and Li/Na selectivity >1.9 million.
- Sustainability: Solar-powered, zero fossil fuel dependency, and co-produces green hydrogen.
- Stability: Operates stably for 840 hours in corrosive seawater conditions.
- Scalability: Potential to extract ~12 kg Li/day (enough for an EV battery) using a 2,800 m² PEC array.
Applications
- Lithium Mining: Direct extraction from seawater or brine with high purity.
- Energy Storage: Couples lithium production with hydrogen generation for renewable energy systems.
- Environmental Remediation: Reduces reliance on land-based mining and associated ecological damage.
- Battery Manufacturing: Provides high-purity LiPO for lithium-ion battery production.
- Carbon Capture: Fixes CO₂ as bicarbonate during the enrichment process.
