Waste silicon sawdust recycled into anode for lithium-ion battery

February 21, 2017

Researchers have created a high performance anode material for lithium-ion batteries (LIBs) using waste silicon (Si) sawdust.

It is energy-consuming and expensive to produce Si wafers with high purity (> 99.99%). On top of that, some 50% of Si is actually discarded as industrial waste in the final cutting process. This waste is about 90 thousand tons a year worldwide, an amount large enough to meet the global demands for anodematerials for LIBs.

To make this happen, under the project of "Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials," a joint research team from Tohoku University and Osaka University has developed a practical and mass-producible method of recycling the unwanted Si sawdust into a high-performance anode material for LIBs.

The team found that the pulverization of the Si sawdust into Si nanoflakes (~16 nm in thickness) and the subsequent carbon coating are effective in fabricating high capacity and durable LIBs. So far, a test half-cell has achieved a constant capacity of 1200 mAh/g over 800 cycles. This capacity is 3.3 times as large as that of conventional graphite (ca. 360 mAh/g).

The proposed method of material recycling is applicable for the mass production of high-performance LIB anode materials at a reasonably low cost. The research team expects that it will have great practical use in the battery industry.

Legislation aims to legalize mobile recycling centers in SF

Mobile recycling centers would become legal in San Francisco under legislation introduced by state Sen. Scott Wiener on Thursday.

Senate Bill 458 would allow mobile recycling centers to operate under a pilot program that's meant to relieve small businesses from having to accept recycling for redemption. Wiener said such businesses were especially burdened by having to redeem recycling efforts from customers after the closure of various San Francisco recycling centers in recent years.

"With our ambitious zero waste goals, San Francisco has long been a national leader in recycling and waste reduction efforts," Wiener said in a statement. “Yet, our dense urban environment has evolved over the decades since the Bottle Bill was passed, and we need to be more flexible in finding solutions to maximize our recycling efforts.

He added, "Mobile recycling will allow us to continue to promote smart and effective recycling policies, while relieving a burden on our business owners, particularly our small mom-and-pop corner stores that don't have the capacity or resources to meet the one-size-fits-all obligations of state law."

The legislation, he noted, is meant to alleviate that burden from small businesses.

Under what's known as the "Bottle Bill," the 1986 California Beverage Container Recycling and Litter Reduction Act, any beverage dealer, including supermarkets and corner stores, that aren't within a half-mile of a recycling center must redeem empty bottles and cans in-store or pay an in-lieu fee of $100-per-day.

There are currently seven recycling centers in San Francisco, compared to 35 in 1990.