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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.


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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 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 thinks the technology could reach the market within three years. State-of-the-art lithium rechargeable batteries 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 the power is low. You can’t accelerate quickly,” Ceder said. Why the sluggishness? Traditionally, scientists thought the particles responsible for carrying electric charge across the battery—charged atoms and electrons—just moved too slowly. 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.