De-Risking Lithium-Ion Battery Energy Storage Systems – Part 1

Since arriving on the market in the 1990s, a broad swath of products often lumped under the category of “lithium-ion batteries” has wriggled its way into much of our world: our cellphones, tablets, laptops, digital cameras, children’s toys, e-cigarettes, automated vacuums, power tools, lawn care equipment, e-bikes, EVs, and, of course, stationary energy storage. Of particular interest in this article is the last use case, stationary energy storage systems (ESSs). 

Within the United States, deployment of stationary storage is growing and expected to continue:

On our present trajectory, market outlooks project  an increased deployment of lithium-ion batteries, both nationally and internationally:

Are all lithium-ion batteries to be used and regulated similarly? Each lithium-ion battery shares the ability to convert chemical energy into electrical energy and back again through a reduction-oxidation reaction cycle. Each uses a separator with an exchange membrane between electrodes that allows a free flow of positively charged lithium ions and prevents the passage of electrons. Take the Lithium Iron Phosphate (LFP) battery cell:

During discharge, lithium ions pass from the electrolyte on the anode side through the separator to the cathode side spontaneously. At the same time, electrons travel in an external circuit where they are available to do work (supply load) before recombination with the lithium ions at the cathode. The charge mode process is not spontaneous and requires an external voltage source to send the lithium ions and electrons back on their respective paths to recombine at the anode.

A battery’s state of charge (SOC) tracks these two cycles. SOC decreases in discharge mode, and, with an external power source, increases in charge mode. This electrochemical energy conversion is reversible and predictable, provided the lithium-ion batteries are operated within the manufacturer’s recommended ranges for voltage, temperature, C-rates, and/or pressure.

So now we know, generally, how lithium-ion batteries work. But what sets different types of lithium-ion batteries apart? In short, our lithium-ion options differ based on the cathode material. Safety risk assessment can also be tracked, to some extent,  by choice of cathode material. What potential safety impacts does this cathode choice carry? Can we de-risk lithium-ion battery storage systems with this selection, and to what extent?

What’s in a name?

The naming conventions for lithium-ion batteries rely on abbreviations for their electrode materials. With rare exception, like an “LTO” battery with an anode made from lithium titanate oxide rather than graphite or carbon, nearly all lithium-ion chemistries take their common-use name from the cathode materials in play.

LFP Trending

In the past half-decade, we have witnessed a shift toward Lithium Iron Phosphate (LFP) above all the other lithium-ion options. The shift captured here by IDTechEx from 2019 to 2023, has likely deepened through 2024 into 2025 despite LFP’s inferior energy density relative to other lithium-ion technologies like LCO, NCA, and NMC.

LFP’s 2024 cost per kWh is ~20% less than NMC (S&P Global), which may help understand this trend. The reasons why are many: the influence of stationary storage and electric vehicle markets on the total Li+B market, as well as LFP’s preferable thermal stability, longer cycle life, and fewer supply chain concerns relative to rarer earth metals like cobalt.

From Surprise, AZ to Moss Landing, CA

With the increased deployment of lithium-ion-based storage systems of all cathode types, there have been a handful of high-profile fire or explosion incidents involving in this same period.  Communities are understandably concerned.  First responders are looking to evolve their readiness. Test labs aim for improved methods to quantify risks and provide our installers and AHJs with improved recommendations for system design, installation, and O&M.  Manufacturers are eager to maintain trust as they gain market share. The codes & standards bodies are looking to empower all of these fellow stakeholders in our joined efforts for increasingly safe deployment of BESS.  For more on this heterogeneous coalition of stakeholders and the collaboration required, check out  February’s Ask Mayfield Anything.

Ignoring other project-specific details—  BMS choice, enclosure and deflagration venting design, system installation and operation, cell form factor, manufacturer, etc. —  are LFP-based energy storage systems safer than other cathode-based systems?  In some ways, yes,  but not without some trade-offs.

In part two of “De-Risking Lithium-Ion Battery Energy Storage Systems,” we will explore LFP’s relative advantages and disadvantages as they relate to thermal runaway, off-gassing, and toxicity risks. We will also highlight some promising tools and solutions on the horizon to better address some of the potential LFP-based ESS safety risks.

Mayfield Renewables is a technical consultancy specializing in commercial and industrial PV and microgrid engineering. Contact us today for a consultation.