Superior Anode For Lithium-Ion Batteries Developed 77
RogerRoast writes "The anode is a critical component for storing energy in lithium-ion batteries. The Berkeley Lab (D.O.E) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles. According to the research published in Advanced Materials they used a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge."
Re:Subscription access only... (Score:3, Informative)
It's not the Lithium which is expanding. The silicon which stores the lithium expands and breaks into bits and pieces. That's the challenge in using Si as a Grahpite substitute in LIB.
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"Expand" is not a cool choice of words around battery people. Call it "volumetrically challenged" or something.
In lithium-ion batteries, that's exactly what happens though. As lithium fills up the active material, there is a volume expansion. No gases are produced in li-ion batteries unless the electrolyte heats up, the problem with volume expansion is that it can form cracks in the material and reduce its mechanical and electrochemical integrity which usually results in high capacity fade with time (I guess these guys have figured it out though).
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This part here is utterly false: (Score:3, Informative)
(lower density than NiMH, but that technology has severe limitations on longevity that are not going to go away)
This isn't wrong, it's ridiculously wrong. NiMH batteries are used in the Toyota Prius, where almost all of them last for thousands of charge/discharge cycles. The *prototype* of all NiMH batteries lasted 500 c/d cycles and most modern NiMHs last on the order of 4000 cycles or more:
Interest grew in the 1970s with the commercialisation of the Nickel hydrogen battery for satellite applications. Hydride technology promised an alternative much less bulky way to store the hydrogen. Research carried out by Philips Laboratories and France's CNRS developed new high-energy hybrid alloys incorporating rare earth metals for the negative electrode. However, these suffered from the instability of the alloys in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach (using a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1) which kept 84% of its charge capacity after 4000 charge-discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed and modern NiMH cells are based on this design.[9]
For comparison, lithium-ion batteries are often only rated for something like 200 c/d cycles, with the best commercial-grade lithium-ion batteries not rated for longer than 1000 c/d cycles.