Wang succeeds Judy Jeevarajan, Ph.D., who will remain with UL Research Institutes as vice president and distinguished scientific advisor. In his new role, Wang will direct research strategy and operations at the Electrochemical Safety Research Institute, an organization focused on understanding why electrochemical energy-storage systems fail and how those failures can be prevented. The institute investigates the links between battery chemistry, mechanical design, electrical control, manufacturing quality, and real-world operating conditions. Its work is intended to influence safer products, testing methods, engineering practices, and standards as energy systems become more densely packed and increasingly dependent on rechargeable batteries.

Before joining UL Research Institutes, Wang spent more than three decades at Pennsylvania State University, where he served as the William E. Diefenderfer Chair in Mechanical Engineering, professor of mechanical engineering, chemical engineering, and materials science and engineering, director of the Electrochemical Engine Center, and co-director of the Battery and Energy Storage Technologies Center. His research career has covered the full battery-development chain, from fundamental electrochemical reactions and heat generation to manufacturing, fast charging, system integration, and commercialization. That breadth has made him a prominent figure in a field where the performance of a battery cannot be separated from its thermal behavior, structural integrity, production consistency, and control software.

One of Wang’s most important contributions has been the development of electrochemical-thermal modeling methods for batteries. These models combine the movement of ions and electrons inside a cell with the heat produced by electrochemical reactions, electrical resistance, and transport limitations. As a battery charges or discharges, local variations in current density, temperature, and chemical concentration can create areas of stress that are invisible from the outside. Electrochemical-thermal models allow researchers to predict how these internal conditions evolve, helping engineers design cells and battery packs that operate within safer limits. The approach has influenced battery development across transportation, consumer electronics, defense, and stationary energy storage.

Wang also invented a self-heating, all-climate battery designed to maintain performance in extremely cold conditions. Conventional lithium-ion batteries can lose power at low temperatures because ion transport slows and the internal resistance of the cell rises. Charging a cold battery can be particularly hazardous, as lithium plating may occur on the anode surface instead of lithium ions being safely stored within the electrode structure. Wang’s technology uses the battery’s own electrical energy to generate controlled internal heat, bringing the cell rapidly to an operating temperature at which it can deliver power and accept charge more efficiently. The technology enabled electric buses to operate during the 2022 Winter Olympics and has since been commercialized for transportation, defense, and energy-storage applications.

His work on ultrafast charging also drew international attention after being recognized by The Guardian as one of the world’s leading science stories of 2022. Fast charging is not simply a matter of supplying more electrical current. High charging rates can produce heat, accelerate unwanted chemical reactions, and cause lithium ions to accumulate as metallic deposits on the anode. These deposits can reduce capacity and, in extreme cases, create internal pathways that trigger a short circuit. Wang’s research has explored how electrode architecture, thermal management, charging protocols, and cell chemistry can be coordinated to reduce these risks while shortening the time required to recharge a battery.

More recently, Wang has focused on lithium-metal and solid-state batteries, two technologies widely viewed as possible successors to today’s dominant lithium-ion systems. Lithium-metal anodes can store substantially more charge by replacing conventional graphite, potentially increasing energy density and extending the range of electric vehicles. However, lithium can form needle-like structures known as dendrites during charging. If dendrites penetrate a separator and reach the opposite electrode, they can cause an internal short circuit. Solid-state batteries replace the flammable liquid electrolyte used in many conventional cells with a solid ion-conducting material, but they introduce their own challenges, including interfacial resistance, cracking, contact loss, and mechanical instability. Wang’s research has examined the safety mechanisms behind these emerging systems and contributed to the design of batteries intended to be intrinsically safer rather than merely protected by external controls.

“Dr. Wang is among the world’s foremost authorities on battery technology and electrochemical energy systems,” said James J. Hudgens, Ph.D., president and chief executive officer of UL Research Institutes. Hudgens said Wang’s scientific leadership, entrepreneurial approach, and focus on battery safety made him especially qualified to lead the Electrochemical Safety Research Institute as demand for energy storage accelerates. Wang said batteries are fundamental to the future of transportation, infrastructure, and energy systems, and that he would work with colleagues across UL Research Institutes to advance research that improves the safety, reliability, and sustainability of energy technologies worldwide. His responsibilities will include expanding experimental and computational capabilities and strengthening partnerships with industry, government, universities, and standards-development organizations.

Wang’s appointment also brings an unusually extensive record of invention and technology transfer to a research institute whose findings are intended to inform public safety. He is a fellow of the National Academy of Inventors, the Electrochemical Society, and the American Society of Mechanical Engineers, holds approximately 140 issued patents, and has authored research cited more than 50,000 times. He earned bachelor’s and master’s degrees in mechanical engineering from Zhejiang University and a doctorate in mechanical engineering from the University of Iowa. Throughout his career, he has founded companies and helped move laboratory discoveries into commercial products. At UL Research Institutes, that combination of fundamental science, engineering, and commercialization could help close the gap between promising battery concepts and the safety requirements of technologies deployed at global scale. The institute, part of the nonprofit UL Research Institutes, conducts independent research across electrochemical safety, fire safety, chemical insights, materials discovery, digital safety, and research education, publishing findings openly to support safer standards, policies, products, and communities.

Subject of Research: People

Article Title: Battery Safety Pioneer Chao-Yang Wang Appointed to Lead UL Research Institutes’ Electrochemical Safety Research Institute

Web References: Chao-Yang Wang, Ph.D.; Electrochemical Safety Research Institute; James J. Hudgens, Ph.D.

Image Credits: UL Research Institutes

Keywords

Battery safety, electrochemical energy storage, lithium-ion batteries, lithium-metal batteries, solid-state batteries, ultrafast charging, thermal runaway, battery research, electric vehicles, energy storage safety

Thermal runaway occurs when an internal exothermic reaction within a lithium-ion battery accelerates uncontrollably, generating heat that further fuels chemical reactions in a vicious cycle. This chain reaction often leads to fire or even explosion, posing serious risks particularly in large-scale applications such as electric vehicles and grid storage. Traditionally, research has focused on thermal decomposition of electrolyte solvents, dendrite formation, or mechanical failures as dominant triggers. However, the new findings convincingly establish that the lithium oxidation reaction constitutes the most dangerous initiating process behind thermal runaway.

The study identifies two types of high-energy-density lithium batteries that exhibit extraordinary vulnerability to LOR: all-solid-state batteries with cracked solid separators, and batteries utilizing non-flammable liquid electrolytes. Solid-state batteries have attracted significant attention for their potential to offer enhanced safety and higher energy density by replacing flammable liquid electrolytes with solid ion conductors. Nevertheless, this research reveals a critical caveat—if the solid separator develops cracks due to manufacturing defects, mechanical stress during assembly, or during repeated electrochemical cycling, it creates a pathway for oxygen to traverse directly to the anode.

In these compromised solid-state batteries, oxygen released from oxide-based cathode materials migrates unhindered through the damaged separator to the lithium metal or lithiated anode. At the anode interface, oxygen engages in highly exothermic lithium oxidation reactions. This reaction releases substantial heat, sufficient to trigger thermal runaway. This pathway had previously been underappreciated due to the widely held assumption that solid electrolytes would prevent such crossover of oxygen molecules. The revelation that even minute imperfections in solid separators can facilitate this reaction poses a grave safety concern.

The second vulnerable class involves batteries equipped with non-flammable liquid electrolytes. Non-flammable electrolytes were developed to mitigate risks associated with traditional organic solvents, which are highly flammable and a primary contributor to battery fires. Paradoxically, while these electrolytes reduce flammability, the research shows that they allow oxygen evolved from the cathode to reach the anode with minimal chemical consumption en route. In other words, the protective “fire barrier” effect of flammable electrolytes is lost, leaving the battery susceptible to direct lithium oxidation reactions. Consequently, these seemingly safer electrolyte choices can inadvertently create even more hazardous conditions.

Contrasting sharply with these two risk-prone battery types are conventional lithium-ion batteries that use carbonate- or ether-based liquid electrolytes, the classical formulations that dominate the current market. These traditional electrolytes have an intrinsic safety benefit—they chemically consume or scavenge oxygen molecules transported from the cathode before oxygen can accumulate at the anode. Their oxidation reactions with oxygen are relatively low in exothermicity, meaning the heat generated during these scavenging processes is much less likely to trigger thermal runaway. This dynamic serves as a natural oxygen barrier, limiting the onset of lithium oxidation reactions and improving battery safety.

Importantly, the oxygen scavenging function of conventional electrolytes applies to both lithium metal anodes and lithiated anode materials such as graphite, expanding the relevance of these findings across a broad spectrum of battery chemistries. This universality underscores the importance of electrolyte chemistry in governing battery safety, moving beyond a simplistic binary view of solid versus liquid electrolytes. The chemical interplay between oxygen evolution at the cathode and its subsequent fate within the electrolyte identifies a new axis along which battery developers must innovate.

The implication of these findings is profound for the design and evaluation of new electrolytes and solid-state battery architectures. To ensure robust safety, future solid-state electrolytes must be rigorously engineered to eliminate any oxygen crossover pathways regardless of mechanical or electrochemical stresses during battery operation. Achieving this may require the development of defect-tolerant materials or self-healing solid electrolytes capable of maintaining perfect ionic selectivity throughout hundreds or thousands of battery cycles.

Similarly, the study suggests that liquid electrolytes intended for high-energy-density batteries must either maintain flammability profiles that enable oxygen consumption or incorporate additives and chemistries designed explicitly to scavenge oxygen with mild exothermic reaction pathways. This oxygen scavenging function emerges as a critical performance metric alongside ionic conductivity, electrochemical stability, and cycle life in evaluating and qualifying safe electrolyte formulations.

This research also forces a reconsideration of the trade-offs involved in moving toward safer battery chemistries. While eliminating flammable solvents or replacing liquid electrolytes with solids addresses certain hazards, these benefits may be offset by new failure pathways if oxygen transport and reaction dynamics are not adequately managed. The holistic balance between energy density, safety, longevity, and manufacturability becomes more complex but also clearer with these new mechanistic understandings in hand.

Experimentally, these discoveries were grounded in detailed analysis combining chemical characterization, electrochemical testing, and advanced modeling techniques. The researchers traced oxygen evolution mechanisms at oxide cathodes, quantified oxygen crossover rates through various separator materials, and monitored the energetic signatures of lithium oxidation reactions in realistic battery configurations. This multilayered approach enabled precise identification of the LOR as the primary driver of thermal runaway in these compromised battery systems.

Looking ahead, the advent of predictive metrics for evaluating the oxygen scavenging ability and oxygen crossover resistance of electrolytes offers battery scientists crucial tools for rapid screening and optimization. These metrics translate fundamental chemical insights into actionable engineering guidelines, accelerating development cycles and reducing costly trial-and-error experiments. Industry adoption of these metrics could significantly raise the safety baseline across future lithium battery generations.

The heightened understanding of lithium oxidation reactions also has ramifications for battery diagnostics and failure analysis. Early detection methods focused on identifying minor cracks and defects in separators or tracking oxygen concentration gradients within cells could enable preemptive intervention before thermal runaway initiates. Moreover, novel protective coatings or barrier layers might be introduced to inhibit oxygen migration independently of electrolyte chemistry.

Beyond technical advances, this breakthrough bears immense significance for public perception, regulation, and safety standards of lithium-ion batteries. As electric vehicles, grid-scale storage, and portable electronics proliferate, ensuring that batteries not only deliver high energy but also do so safely is paramount for consumer trust and broad societal acceptance. Regulatory agencies could mandate rigorous testing of oxygen crossover and LOR susceptibility as prerequisites for market entry, setting new industry benchmarks.

This paradigm shift in understanding battery safety mechanisms reinvigorates the quest for the ideal electrolyte and separator materials in lithium-ion technology. Balancing the competing demands of energy density, cycle stability, mechanical integrity, and thermal stability remains challenging, but with clearer knowledge of key reaction pathways, researchers and manufacturers can now target precise chemical vulnerabilities. Ultimately, this work charts a decisive step toward safer, smarter, and more reliable energy storage solutions essential for a sustainable energy future.

In summary, lithium oxidation reaction induced by oxygen crossover from oxide cathodes emerges as the principal trigger for catastrophic thermal runaway in lithium batteries with cracked solid separators or non-flammable electrolytes. Conventional carbonate- and ether-based electrolytes provide a protective oxygen scavenging function, mitigating LOR initiation. The findings propel new metrics and material design criteria focused on oxygen management, demanding tough standards for electrolytes and separators to prevent oxygen transport and promote low-exothermic oxygen consumption. This insight heralds a safer trajectory for the next era of high-energy-density lithium batteries, crucial for electrification and decarbonization worldwide.

Subject of Research: Lithium-ion battery safety mechanisms and electrolyte design.

Article Title: Metrics for evaluating safe electrolytes in energy-dense lithium batteries.

Article References:
Wang, CY., Qin, K., Ge, S. et al. Metrics for evaluating safe electrolytes in energy-dense lithium batteries. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01887-6

Image Credits: AI Generated