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Innovative Li-ion Battery Technology: An Interview With Marc Juzkow

Marc Juzkow, Vice President of R&D and Engineering Leyden Energy, talks to AZoM about advances in Li-ion battery technology. Interview conducted by Gary Thomas.

GT: Could you please provide a brief introduction to the industries that Leyden Energy works within and outline the key drivers?

MJ: Leyden Energy is an innovator in lithium-ion (Li-ion) batteries, which power a wide range of consumer, automotive and industrial applications. The global appetite for Li-ion batteries is insatiable; given that there’s one in virtually every cell phone (all six billion of them!), it’s not surprising that more than two billion Li-ion batteries are manufactured every year. The explosive growth of consumer mobility (e.g., smartphones, tablets, ultrabooks) is the main driver of this market.

Electric transportation doesn’t account for anywhere near the volume of mobility batteries, but there’s lively interest in Li-ion for everything from electric bicycles to full electric vehicles (EVs) such as the Tesla Roadster. A good bet for growth here is start-stop vehicles (SSVs). These are cars whose internal-combustion engine starts and stops during travel to save gas and reduce greenhouse gas emissions. According to Kevin See, Senior Analyst at Lux Research, “We forecast that the micro-hybrid market will benefit most from the global trend towards increased fuel economy and lower carbon emissions, reaching 39 million vehicles in 2017, creating a $6.9 billion opportunity for energy storage technologies.”

Our new Li-imide™ chemistry platform offers advantages important for both mobility and transportation applications.

GT: Could you briefly explain how a lithium-ion battery works and how they are different to conventional cells?

MJ: First off, let me note the difference between a battery and a cell. The cell is the fundamental unit of a battery, which may comprise one or more cells. For instance, very thin smartphones are likely to use a single cell battery: a soft Li-ion pouch cell, which is what I’ll use as an example here when talking about batteries.

The fundamental difference to other battery chemistries is the higher voltage of Li-ion cells (currently 3.6 V nominal) compared to nickel-cadmium (NiCd) or nickel-metal hydride (NiMH) at 1.2V, which makes a higher energy density possible. This is the amount of energy delivered by a given size (volumetric) or weight (gravimetric) of cell, and is important for both consumer mobility and transportation applications. Li-ion batteries have twice the energy density, by weight, of nickel-based active materials, and four times that of the lead-acid batteries used in automobiles today. In fact, Li-ion cells can deliver so much energy that protective circuitry is a necessary component to assure safety, in case of short circuits or other conditions.

As in virtually all types of cells, a Li-ion cell comprises a set of anodes and cathodes (the active materials) held apart by separators and electrically connected to the cell terminals by current collectors. In a Li-ion pouch cell, the whole interior of the polymer bag that encases the cell is permeated by a liquid electrolyte, which is not only a source of lithium ions, but the medium through which these ions are exchanged between anode and cathode. This is the basis of the charge-discharge cycle. (The combination of specific active materials and electrolyte is called the “chemistry” of the cell.) During discharge, the anode gives up electrons and lithium ions, while the cathode takes up electrons and lithium ions, a process called intercalation; the result is a current flow between the terminals of the battery in the same direction as the movement of lithium ions inside the battery.

The tendency of an active material to give up or take up electrons is measured by its electromotive force (EMF) in volts; the difference in EMF between the anode and the cathode is the voltage across the terminals, with no load on the cell. This drops when the cell is actually powering something, depending on the current demanded. Putting a higher voltage across the terminals from an outside source in the opposite direction drives the reaction in reverse to charge the cell: the anode takes up electrons (and lithium ions) and the cathode gives up the electrons (and lithium ions). Cells can be put in series to increase the voltage, or in parallel, to increase current capacity.

GT: What are the benefits of using Li-ion cells?

MJ: Their greater energy densities allow for sleeker, smaller mobile device designs, and help to keep vehicle weight down, compared to lead-acid, NiMH, or NiCd. They are also more environmentally friendly, especially in manufacturing; cadmium in particular has a very high environmental cost. Lead’s environmental impact is somewhat mitigated by an extensive recycling industry.

However, current Li-ion chemistries have a common weakness: the instability of the electrolyte used in virtually all Li-ion cells: a solution of lithium hexafluorophosphate (LiPF6) in an organic carbonate-based solvent system. That is the opportunity Leyden Energy’s Li-imide chemistry platform addresses.
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