The Invention 

An ultra thin surface coating composed of metal oxides that, when applied to granular electrode materials on a large scale, promises to solve the structural instability of electrode materials and the resulting rapid fade of cell capacity at high voltages and high temperatures in lithium-ion batteries. 

Argonne’s innovation, a powder nanocoating technology using metal oxides, has the following features: 

• Gas-phase surface chemical reactions; 
• A layer of extremely uniform metal oxide ultrathin film on granular cathode materials with precisely controlled surface morphology: smooth, conformal, and pin-hole free so that the electrode degradation reactions in the battery can be suppressed; and 
• Film so ultra thin and precisely controlled in its thickness that the transfer of the charge across the electrode/electrolyte interface takes place with a very limited, or even a reduced, interface resistance. 

In developing a surface coating for the electrodes of lithium-ion batteries, Argonne scientists sought to satisfy two requirements simultaneously: 

• Create a uniform coating that will fully isolate electrodes from the electrolyte, and 
• Create an ultra thin film that will allow the lithium ion and electron to easily tunnel without a large increase in impedance. 

Conventional technologies have been unable to fulfill those requirements and have proved incapable of precisely controlling the coating film properties of film thickness and morphology. As a result, battery performance can be unstable.

Benefits 

The new powder coating technology provides: 

• Smooth fluidization of ultrafine powders via non-linear processing control; 
• Online, real-time monitoring of powder fluidization status and surface chemical reaction; 
• Well-controlled properties of the nanocoated film (conformity, thickness, and composition); and 
• A novel process that is scalable, less energy-intensive, and at a lower cost. 

Lithium-ion batteries made of these novel coated materials offer: 

• Isolation of electrode from electrolyte, creating greater structural stability and effectively enhancing capacity retention; 
• Greater stability; 
• Longer lifespan; 
• Higher energy/power densities; 
• Greater safety; and 
• Reduced cost and increased performance (figure 2) reliability. 

Applications and Industries 

• Hybrid electric vehicles 
• Solar cells 
• Ultracapacitors 
• Cosmetics 

Developmental Stage 

Proof of concept. Lab scale has been demonstrated; small pilot scale up is on schedule.