#cathodes

Studying battery cycling on the beamline

During his Ph.D. with TUoS, ISIS facility development student Innes McClelland developed a cell for testing battery materials during their operation using muon spectroscopy and used it to study an increasingly vital cathode material.

Understanding what is happening inside a battery material while it is charging and discharging is crucial to improving the performance of existing batteries and developing new materials for use in the batteries of the future.

One cathode material that is proving increasingly vital for future batteries is LiNi0.8Mn0.1Co0.1O2, known as NMC811. This material has a high capacity, but often suffers an irreversible capacity loss between the first charge and discharge. It's thought that this loss of capacity may be due to kinetic barriers to diffusion of the lithium ions in the material. Understanding this issue could lead to insights that inform the design of new and improved alternatives.

Muon spectroscopy is an excellent tool for studying these materials because it can probe the diffusion of ions such as lithium and sodium on a local scale, largely avoiding interfacial or grain boundary effects. Previous muon experiments on battery materials have studied the components individually, outside a battery. Although these are useful for understanding the fundamental properties, they lack an insight into the behavior of the materials during operation.

Elucidation of electrolyte decomposition behavior in all-solid-state lithium-sulfur batteries

A research group of the Department of Electrical and Electronic Information Engineering at Toyohashi University of Technology—consisting of Hirotada Gamo, a doctoral course student; Kazuhiro Hikima, assistant professor; and Atsunori Matsuda, professor—has elucidated the decomposition behavior of electrolytes in the cathode composites of all-solid-state lithium-sulfur batteries (ASSLSB).

It was found that the sulfide solid electrolytes in the ASSLSB's cathode composites were converted into thiophosphates with long-chain cross-linked sulfur through the charging and discharging cycle. These decomposition products govern the overall battery performance of ASSLSBs. The study was published in the journal Chemistry of Materials.

Currently, electric vehicle (EV) market is expanding and thus require the development of better onboard storage batteries. ASSLSBs are expected to become next-generation high-energy-density batteries owing to the use of high-capacity cathode active materials, such as sulfur (S) and lithium sulfide (Li2S).

Researchers at the University of California, Irvine and four national laboratories have devised a way to make lithium-ion battery cathodes without using cobalt, a mineral plagued by price volatility and geopolitical complications.

In a paper published today in Nature, the scientists describe how they overcame thermal and chemical-mechanical instabilities of cathodes composed substantially of nickel -- a common substitute for cobalt -- by mixing in several other metallic elements.

"Through a technique we refer to as 'high-entropy doping,' we were able to successfully fabricate a cobalt-free layered cathode with extremely high heat tolerance and stability over repeated charge and discharge cycles," said corresponding author Huolin Xin, UCI professor of physics & astronomy. "This achievement resolves long-standing safety and stability concerns around high-nickel battery materials, paving the way for broad-based commercial applications."

Cobalt is one of the most significant supply chain risks threatening widespread adoption of electric cars, trucks and other electronic devices requiring batteries, according to the paper's authors. The mineral, which is chemically suited for the purpose of stabilizing lithium-ion battery cathodes, is mined almost exclusively in the Democratic Republic of Congo under abusive and inhumane conditions.

Sulfonamides make robust cathode material for proton batteries

Proton batteries are an innovative and environmentally friendly type of battery in which charge is carried by protons, which are positively charged hydrogen ions. A team of researchers has now developed organic sulfonamides as a robust and flexible material for cathodes in these batteries. As the team explain in the journal Angewandte Chemie International Edition, sulfonamide cathodes also achieve a higher output voltage than conventional cathodes.

In the constant search for alternatives to lithium-ion batteries, proton batteries are proven to have great potential. Rather than storing charge in the form of lithium ions, they transfer light, highly mobile protons instead. As a result, this type of battery does not require the environmentally harmful and unsustainable mining of lithium. In addition, the mobile protons help achieve significantly shorter charging times than for other battery types.

Despite these advantages, the performance of the electrodes in proton batteries still requires improvement. To date, the cathodes (positive electrodes) were only able to achieve a fairly low output voltage, insufficient for most applications. Now, Bingan Lu and his team based at Hunan University in Changsha (China) have improved this voltage by replacing the chemicals making the cathode material. Instead of organic carbonyl compounds or cyanide-based pigments, they used organic sulfonamides.

Researchers unlock potential means to reduce reliance on rare metals

A research group, utilizing inexpensive elements, has demonstrated the feasibility of synthesizing electrode materials for lithium-ion batteries (LIBs). If explored further, this method could reduce industrial reliance on rare metals such as cobalt and nickel.

Details of their results were published in ACS Applied Energy Materials on April 11, 2022.

Rare metals are widely used because they form a suitable crystal structure for LIBs' key component—cathode materials. In these materials, lithium is easily and reversibly extracted/inserted.

Scientists have long sought ways to incorporate other inexpensive elements into the crystal structure. Yet, just like only a certain amount of salt dissolves into water, the solubility of other elements is limited.

Ultrathin Photocathode with High Efficiency

Researchers demonstrate a single-crystal photocathode that can emit electrons with higher efficiency than its predecessors. 

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Scientists use optical microscopes to reveal otherwise invisible worlds, such as those inhabited by wriggling microorganisms and dividing cells. More detailed views of these systems are obtainable via devices such as ultrafast time-resolved electron microscopes, which use electrons rather than photons to image. In these microscopes, the electrons are generated using a photocathode, which emits electrons when illuminated with light. High-performing photocathodes have been around for nearly a century, but scientists have struggled to improve their efficiencies and performance, in part because of the extreme reactivity of the materials from which they are made. Now, a team of researchers from Cornell University has demonstrated a photocathode with an efficiency up to 10 times higher than other photocathode devices [1]. 

America's growing demand for electric vehicles has shed light on the significant challenge of sustainably sourcing the battery technology necessary for the broad shift to renewable electric and away from fossil fuels. In hopes of making batteries that not only perform better than those currently used in EVs, but also are made from readily available materials, a group of Drexel University chemical engineers have found a way to introduce sulfur into lithium-ion batteries -- with astounding results.

With global sales of EVs more than doubling in 2021, prices of battery materials like lithium, nickel, manganese and cobalt surged and supply chains for these raw materials, most of which are sourced from other countries, became bottlenecked due to the pandemic. This also focused attention on the primary providers of the raw materials: countries like Congo and China; and raised questions about the human and environmental impact of extracting them from the earth.

Well before the EV surge and battery material shortage, developing a commercially viable sulfur battery has been the battery industry's sustainable, high-performing white whale. This is because of sulfur's natural abundance and chemical structure that would allow it to store more energy. A recent breakthrough by researchers in Drexel's College of Engineering, published in the journal Communications Chemistry, provides a way to sidestep the obstacles that have subdued Li-S batteries in the past, finally pulling the sought-after technology within commercial reach.

A new type of lithium-metal battery reaches an extremely high energy density of 560 watt-hours per kilogram -- based on the total weight of the active materials -- with a remarkable stability. Researchers used a promising combination of cathode and electrolyte: The nickel-rich cathode enables storage of high energy per mass, the ionic liquid electrolyte ensures largely stable capacity over many cycles.

Currently, lithium-ion batteries represent the most common solution for mobile power supply. In some applications, however, this technology reaches its limits. This especially holds for electric mobility, where lightweight and compact vehicles with large ranges are desired. Lithium-metal batteries may be an alternative. They are characterized by a high energy density, meaning that they store much energy per mass or volume. Still, stability is a problem, because the electrode materials react with conventional electrolyte systems.

Researchers of Karlsruhe Institute of Technology (KIT) and the Helmholtz Institute Ulm for Electrochemical Energy Storage (HIU) have now found a solution. As reported in Joule, they use a promising new combination of materials. A cobalt-poor, nickel-rich layered cathode (NCM88) reaches a high energy density. With the usually applied, commercially available organic electrolyte (LP30), however, stability leaves a lot to be desired. Storage capacity decreases with an increasing number of cycles. Professor Stefano Passerini, Director of HIU and Head of the Electrochemistry for Batteries Group, explains the reason: "In the electrolyte LP30, particles crack on the cathode. Inside these cracks, the electrolyte reacts and damages the structure. In addition, a thick mossy lithium-containing layer forms on the anode." For this reason, the scientists used a non-volatile, poorly-flammable, dual-anion ionic liquid electrolyte (ILE) instead. "With the help of ILE, structural modifications on the nickel-rich cathode can be reduced significantly," says Dr. Guk-Tae Kim from the Electrochemistry for Batteries Group of HIU.