{"id":5300,"date":"2012-03-02T20:55:09","date_gmt":"2012-03-03T03:55:09","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=5300"},"modified":"2012-03-23T10:18:43","modified_gmt":"2012-03-23T17:18:43","slug":"better-batteries-enviable-achievement-from-envia","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/better-batteries-enviable-achievement-from-envia\/","title":{"rendered":"Better Batteries: Enviable Achievement from Envia"},"content":{"rendered":"

Envia<\/a>, a startup battery company in Newark, California, has announced a much-anticipated breakthrough in lithium-polymer storage cell energy density. Although tested to 300 charge\/discharge cycles, the new battery should show at least 1,000 successful cycles before we get too excited.<\/p>\n

Excitement will build, though, as the announced 400 Watt-hours per kilogram doubles the current energy density standard for lithium batteries. This would reduce a Leaf\u2019s battery pack from about 600 pounds to 300 pounds, or keeping the same weight, double the car\u2019s range to about 250 miles. Dr. Brien Seeley points out that the Green Flight Challenge-winning Pipistrel G4 could have traversed 400 miles with a reserve on such batteries.<\/p>\n

According to Envia, quoting from the official report, \u201c\u2019The Naval Surface Warfare Center, Crane Division (NSWC Crane) Test & Evaluation Branch was tasked by Advanced Research Products Agency – Energy (ARPA-E) to perform Verification & Validation testing on two high capacity lithium ion pouch type cells, manufactured by Envia Systems of Newark, California.<\/p>\n

\u201c\u2019…Testing included verification of cell capacity and energy density at C\/10 and C\/3, 100% depth of discharge (DOD), as well as cell capacity and energy density at C\/3, 80% DOD. One cycle at C\/20 was performed at the manufacturer, therefore Crane’s cycling started at cycle 2. Total testing cycles were 23, with 22 of those being performed at Crane (Cycles 2-23).\u2019\u201d<\/p>\n

Testers compared the Envia cells to Panasonic\u2019s NCR18650A, which claims 3,100 milli-Amp hours capacity, an average of 3.6 Volts, and a weight of 45.5 grams. This could give these model cells an energy density of 245 Wh\/kg. Naval testing substantiated the manufacturer\u2019s claim of 400 Wh\/kg, a 63-percent increase over the Panasonic cells.<\/p>\n

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Envia's 45 Amp-hour pouch cells<\/p><\/div>\n

Envia shows a pouch-type cell, while the Panasonic cell is cylindrical, 18.6 millimeters in diameter and 65.2 millimeters in length. Whether these form factors make any difference in output is questionable, but a true apples-apples comparison would remove any doubt about such matters.<\/p>\n

Envia anticipates that commercial production will promote practical electric vehicles. When\u00a0commercialized, \u201cThis 400 Wh\/kg battery is expected to slash the price of a 300\u2010mile range electric vehicle by cutting the cost of the battery pack by more than 50 percent,\u201d with a claimed cost of $125 per kilowatt-hour.\u00a0 Compared to the $400 per kilowatt-hour charged for lithium-ion batteries in late 2010, that would be an even greater differential.<\/p>\n

Such results are partly attributable to Envia\u2019s development of new silicon-carbon anodes, cathodes and their own proprietary electrolyte. This coordinated push on all these technologies gives the resulting product the benefits of improvements in each active part of the battery.\u00a0 Others have taken note.\u00a0 General Motors on January 26 announced it would invest $7 million in Envia\u2019s product development and the Advanced Research Projects Agency\u2014Energy (ARPA\u2013e) has already awarded a $4 million grant to Envia.<\/p>\n

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Envia's battery testing laboratory<\/p><\/div>\n

According to Scientific American<\/a><\/em>, \u201cthe Envia technology builds on work done at Argonne National Laboratory (ANL) that found that including manganese in a mix of materials for the cathode\u2014the electrode to which the lithium ions flock\u2014better energy densities could be achieved. The team then switched focus to the anode\u2014the electrode from which lithium ions flow to produce the electric current\u2014and boosted its performance by incorporating silicon along with the typical graphite.\u201d<\/p>\n

These technologies help the battery resist the swelling and contraction that shorten electrode life, and the thin construction reduces the possibility of \u201cthermal runaway,\u201d in which batteries might overheat to the point of combustion.<\/p>\n