Modified Ohm’s Law in Lithium and Beyond-lithium Battery Electrolytes
Battery electrolytes contain two mobile charged species of opposite charge and thus the traditional Ohm’s law, which applies to one mobile charged species, must be modified. This review uses a modified Ohm’s law to rank order electrolytes.
Significance and Impact
In the limit of low applied potentials, the current passed through an electrolyte is determined by two parameters: conductivity (κ) and a parameter that we call the current ratio. The highly-ranked electrolytes are characterized by low current ratio. Improving this parameter without sacrificing conductivity is a challenging but worthwhile goal.
Published conductivity and current ratio values were aggregated for a variety of electrolytes: homopolymer electrolytes (HPE), gel polymer or cross-linked electrolytes (GPE), multicomponent polymer electrolytes (MCPE), and polymer electrolytes containing a sodium salt (NaPE). All electrolytes, excluding NaPE, contained a lithium salt.
Electrolytes developed thus far are limited by a trade-off between conductivity and current ratio leading to an upper bound that is similar to the permeability-selectivity upper bound that has been found in gas permeation membranes.
Liquid metal battery could lower cost of storing renewable energy
As dreamy as it might be to combine renewable energy sources with storage batteries, there’s a problem: those batteries are expensive. It might take you years to recoup the costs. You’ll be glad to hear, then, that Stanford scientists have a way to make those batteries more cost-effective. They’ve developed a liquid metal-based flow battery that can store electricity at a lower price, even on a large scale. A metal-producing mix of sodium and potassium serves as the negative side of the battery, providing nearly twice the maximum voltage of typical flow batteries (making them high-value) without having to resort to exotic chemicals or extreme temperatures.
It sounds simple, but there was a challenge to making this work. The team had to use a ceramic membrane that combined aluminum oxide and potassium to separate the positive and negative materials while still allowing a current.
There’s still some tweaking left, such as optimizing the membrane to improve the power output and choosing a liquid for the positive side that won’t weaken the membrane. And like many battery experiments, there’s a long road from a successful lab test to something you can buy. There’s a strong incentive to make this a reality, though. If it lowered the price of storage batteries, both homeowners and electrical grid operators might be more likely to switch to solar or wind power knowing that they’d recover their investments that much sooner.
GM has expanded its collaboration with Honda to supply the Japanese automaker with next-generation batteries. These will go in EVs built mainly for the North American market, and though neither company stated when they would start using the new power options, sources toldReuters that they’re expected to begin production in 2021.
GM’s innovations intend to cut electric battery costs in half — which is huge, given their typical pricetag between $10,000 and $12,000, sources told Reuters earlier in the year. The deal will help Honda speed up EV production after 2020. It’s not the automaker’s first collaboration with GM: In early 2017, the pair went in together on a Michigan factory dedicated to producing hydrogen fuel cells to power their vehicles. But given the auto industry’s increasingly expansive investments in electric vehicles — GM included — this is a savvy move to get more EVs on the road.