Technology seen slashing battery recharge time, weight

March 11, 2009
World Science staff

En­gi­neers say they’ve found a way to move en­er­gy faster through a well-known bat­tery ma­te­ri­al, pos­sibly pav­ing the way for smaller, light­er bat­ter­ies that re­charge in sec­onds rath­er than hours.

En­gi­neers say they’ve found a way to move en­er­gy faster through a well-known bat­tery ma­te­ri­al, pos­sibly pav­ing the way for smaller, light­er bat­ter­ies that re­charge in sec­onds rath­er than hours. The ad­vance could also ben­efit car batteries, which usu­ally take hours to charge, ac­cord­ing to en­gi­neers. (Im­age cour­tesy GM)

The work, led by Ger­brand Ced­er of the Mas­sa­chu­setts In­sti­tute of Tech­nol­o­gy, is de­tailed in the March 12 is­sue of the re­search jour­nal Na­ture. Be­cause the ma­te­ri­al in­volved is­n’t new—it’s just made in a new way—Ced­er says the tech­nol­o­gy could reach the mar­ket with­in three years.

Modern lith­i­um re­chargeable bat­ter­ies can pack plen­ty of charge in­to a small space, but are slow to take up and dis­charge that en­er­gy. This draw­back means that, for ex­am­ple, an elec­tric car bat­tery can move the au­to at a mod­er­ate high­way speed for a long time, but ac­cel­er­ation is slug­gish, Ced­er noted.

Sci­en­tists tra­di­tion­ally thought such pokey per­for­mance was due to slow move­ment of the par­t­i­cles that car­ry elec­tric charge across the bat­ter­y—charged atoms and elec­trons. But through a se­ries of com­put­er cal­cula­t­ions, Ced­er and col­leagues found that this was­n’t ex­actly the prob­lem, at least not for a well-known bat­tery ma­te­ri­al, lith­i­um iron phos­phate.

The real dif­fi­cul­ty, the group found, is that the charged atoms can only cross through the ma­te­ri­al through tun­nels ac­cessed from the sur­face. If the par­t­i­cle lies di­rectly at a tun­nel en­trance, it slips right in, but oth­er­wise it gets stuck.

Ced­er and By­oung­woo Kang, a grad­u­ate stu­dent, de­vised a so­lu­tion: a new sur­face struc­ture that lets the par­t­i­cles, called ions, move quickly around the out­side of the ma­te­ri­al. Like a belt­way around a city, this di­verts ions right in­to the tun­nels. The re­sult was a small bat­tery that could be fully charged or dis­charged in 10 to 20 sec­onds. By com­par­i­son, it takes six min­utes to fully charge or dis­charge a cell phone made from the un­pro­cessed ma­te­ri­al.

Ced­er said fur­ther tests showed the new ma­te­ri­al de­grades less than do oth­er bat­tery ma­te­ri­als when re­peat­edly charged and re­charged. This could al­low smaller bat­ter­ies, as less ma­te­ri­al is needed for the same re­sult. The ad­vance “may open up new tech­no­log­i­cal ap­plica­t­ions and in­duce lifestyle changes,” Ced­er and Kang wrote.