Tuesday, October 18, 2011

Battery Electrolyte Breakdown Voltage

I don't usually get into technical discussions on this blog but I thought it might be worth while to continue the topic started on Jack Rickard's EVTV blog.  Simply put Jack has stated that pushing the voltage of a LiFePO4 cell above 4.3 Volts, the breakdown voltage of the electrolyte, will not harm a cell if the cell is not full, and that in fact there is no such thing as electrolyte breakdown voltage.  This of course flies in the face of just about everything I've read on the topic, and even contradicts what battery researcher Jay Whitacre states in his LiFePO4 battery lecture video, a video that Jack actually provided a link to.
Go to the 50 minute mark in Jay's video and listen as he talks about electrolyte solvent breakdown above 4.3 volts, equivalent to water electrolysis at 1.3 volts.  If a cell voltage is held above the breakdown voltage of the electrolyte the components of the electrolyte begin to separate out.  This can happen even if the cell is not yet full.  In normal use this should not be an issue, but it is something to be aware of.
For further technical reading about electrolyte breakdown voltage there is this rather comprehensive review by Kang Xu:  Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries 
The pertinent information starts in section 5.2 page 4325

Saturday, October 15, 2011

EV Subsidies, Why We Need them

Some people complain about the current subsidies that EV's are getting, a $7500 Federal tax credit and some other incentives depending on where you live.  The argument is usually something similar to "Why should I help pay for someone's car, or to help promote a technology I don't agree with?"  On it's surface that seems to be a fair point, until you consider the fact that our tax money is often used for things that some individuals may not necessarily agree with.  The main reason EV's need subsidies is to compete on a level playing field with an established oil industry which still benefits from subsidies that artificially lower the cost of doing business and artificially lowers the cost we pay at the pump.  A recent article exposes the issue:

The IEA estimates that subsidies that artificially lower the cost of fossil fuels – and also impede development of renewables – hit $409 billion in 2010, an increase of nearly $110 billion over 2009 levels. The IEA says that the amount of total worldwide subsidies (assisting with production and consumption) on fossil fuels in 2010 will reach half a trillion dollars. What's even worse is that the IEA predicts that fossil fuel subsidies will soar to $660 billion in 2020.

Oil Subsidies Rise

I'm quite ready to end EV subsidies when the oil and gas industries do the same.