Silicon-based lithium ion batteries may give future mobiles, laptops longer stay

Washington, November 21 : Devices like cell phones, digital cameras, and notebook computers may soon be available with longer running times, thanks to Korean researchers at Hanyang University who have developed a new material for anodes that are used in their batteries to absorb lithium ions.

Research leader Jaephil Cho has revealed that the new material involves three-dimensional silicon structures that are highly porous.

Lithium ion accumulator batteries produce current by moving lithium ions. They usually contain a cathode (positive electrode) made of a mixed metal oxide, such as lithium cobalt oxide, and an anode (negative electrode) made of graphite.

Lithium ions migrate into the anode when the battery is being charged, and get stored between the graphite layers. When the battery is being discharged, these ions migrate back to the cathode.

Cho says that silicon can be used as an anodic material that can store more lithium ions than graphite.

The researcher revealed that the problem before the research team was that silicon expands a great deal while absorbing lithium ions (charging), and shrinks when giving them up (discharging).

Cho adds that after several cycles the required thin silicon layers are pulverized and can no longer be charged.

According to the researcher, the Hanyang University team have now devised a novel way to produce a porous silicon anode that can withstand this strain.

The researchers annealed silicon dioxide nanoparticles with silicon particles whose outermost silicon atoms have short hydrocarbon chains attached to them at 900 degree Celsius under an argon atmosphere.

The silicon dioxide particles were removed from the resulting mass by etching, and what remained were carbon-coated silicon crystals in a continuous, three-dimensional, highly porous structure.

Cho says that anodes made from such highly porous silicon have a high charge capacity for lithium ions.

A research article on this breakthrough work has been published in the journal Angewandte Chemie.

ANI