The lithium sulfur (Li-S) battery is promising for next-generation energy storage technologies. However, lithium polysulfide shuttling, sluggish redox kinetics, and uncontrollable lithium dendrite growth limit the cycling stability.
A research group led by Prof. WU Zhongshuai from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences developed niobium (V)-based heterostructure nanosheet for polysulfides-suppressed sulfur cathodes and dendrite-free lithium anodes in long-cycling and lean-electrolyte Li-S batteries.
“We developed a twinborn holey Nb4N5-Nb2O5 heterostructure, serving as dual-functional host for both redox-kinetics-accelerated sulfur cathode and dendrite-inhibited lithium anode simultaneously,” said Prof. WU.
Polysulfide-shutting was alleviated due to the accelerative polysulfides anchoring-diffusion-converting efficiency of Nb4N5-Nb2O5. Meanwhile, the researchers applied lithiophilic nature of holey Nb4N5-Nb2O5 as an ion-redistributor for homogeneous Li-ion deposition.
The Li-S full battery presented a high areal capacity of 5.0 mAh cm-2 at sulfur loading of 6.9 mg cm-2, corresponding to negative to positive capacity ratio of 2.4:1 and electrolyte to sulfur ratio of 5.1 μL mg-1.
This work paves a new avenue for boosting high-performance Li-S batteries toward practical applications.
Featured image: Schematic of bifunctional niobium (V)-based heterostructure nanosheet toward high efficiency lean-electrolyte lithium-sulfur full batteries (Image by SHI Haodong)
Reference: Shi, H. D., Qin, J. Q., Lu, P. F., Dong, C., He, J., X. J, , Das, P., Wang, J. M., Zhang, L. Z., Wu, Z.-S., Interfacial Engineering of Bifunctional Niobium (V)-Based Heterostructure Nanosheet Toward High Efficiency Lean-Electrolyte Lithium–Sulfur Full Batteries. Adv. Funct. Mater. 2021, 2102314. https://doi.org/10.1002/adfm.202102314
A team of researchers designed and manufactured a new sodium-ion conductor for solid-state sodium-ion batteries that is stable when incorporated into higher-voltage oxide cathodes. This new solid electrolyte could dramatically improve the efficiency and lifespan of this class of batteries. A proof of concept battery built with the new material lasted over 1000 cycles while retaining 89.3% of its capacity—a performance unmatched by other solid-state sodium batteries to date.
Researchers detail their findings in the Feb. 23, 2021 issue of Nature Communications.
Solid state batteries hold the promise of safer, cheaper, and longer lasting batteries. Sodium-ion chemistries are particularly promising because sodium is low-cost and abundant, as opposed to the lithium required for lithium-ion batteries, which is mined at a high environmental cost. The goal is to build batteries that can be used in large-scale grid energy storage applications, especially to store power generated by renewable energy sources to mitigate peak demand.
“Industry wants batteries at cell-level to cost $30 to $50 per kWh,” about one-third to one-fifth of what it costs today, said Shirley Meng, a professor of nanoengineering at the University of California San Diego, and one of the paper’s corresponding authors. ‘We will not stop until we get there.”
The work is a collaboration between researchers at UC San Diego and UC Santa Barbara, Stony Brook University, the TCG Center for Research and Education in Science and Technology in Kolkata, India, and Shell International Exploration, Inc.
For the battery described in the Nature Communications study, researchers led by UC San Diego nanoengineering professor Shyue Ping Ong ran a series of computational simulations powered by a machine learning model to screen which chemistry would have the right combination of properties for a solid state battery with an oxide cathode. Once a material was selected as a good candidate, Meng’s research group experimentally fabricated, tested, and characterized it to determine its electrochemical properties.
By rapidly iterating between computation and experiment, the UC SanDiego team settled on a class of halide sodium conductors made up of sodium, yttrium, zirconium and chloride. The material, which they named NYZC, was both electrochemically stable and chemically compatible with the oxide cathodes used in higher voltage sodium-ion batteries. The team then reached out to researchers at UC Santa Barbara to study and understand the structural properties and behavior of this new material.
NYZC is based on Na3YCl6, a well-known material that is unfortunately a very poor sodium conductor. Ong suggested substituting zirconium for yttrium because it would create vacancies and increase the volume of the cell battery unit, two approaches that increase the conduction of sodium ions. Researchers also noted that, in conjunction with the increased volume, a combination of zirconium and chloride ions in this new material undergoes a rotating motion, resulting in more conduction pathways for the sodium ions. In addition to the increase in conductivity, the halide material is much more stable than materials currently used in solid-state sodium batteries.
“These findings highlight the immense potential of halide ion conductors for solid-state sodium-ion battery applications,” said Ong. “Further, it also highlights the transformative impact that large-scale materials data computations coupled with machine learning can have on the materials discovery process.”
Next steps include exploring other substitutions for these halide materials and increasing the battery’s overall power density, along with working to scale up the manufacturing process.
The technology has been licensed by UNIGRID, a startup co-founded by UC San Diego NanoEngineering professor Zheng Chen; Erik Wu, a Ph.D. alumnus from Meng’s research group; and Darren H. S. Tan, one of Meng’s Ph.D. students. Meng is the company’s technical advisor.
Funding to support this work was provided by the Energy & Biosciences Institute through the EBI-Shell program and NSF.
Prof. LIU Zhaoping’s team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS) developed an electrolyte engineering strategy for lithium (Li) metal batteries and thus realized pouch cells with a high energy density of 430 Wh/kg and extended lifespan. The study was published in ACS Energy Letters.
Pursuing next-generation lithium batteries with a high energy density especially beyond 500 Wh kg-1 has become a global research hotspot. However, the unstable interface between the anode or cathode and the electrolyte under a high voltage limits the energy density promotion.
As the electrolyte is the only shared component for both the cathode and anode, electrolyte engineering thus becomes a common and facile strategy to stabilize the electrode/electrolyte interface on both a cathode and an anode simultaneously.
Researchers at NIMTE selected the fluoroether as the electron-withdrawing solvent, and add it into the carbonate-based electrolyte (1.0 M LiPF6 in EC/DMC with 2% wt. LiPO2F2) to weaken the aligned Li+-carbonyl interaction, thus to disturb the balance of Li+-(EC)4 solvation sheath.
As a result, the LiPO2F2 recrystallized from electrolyte and preserved the solid state, realizing concurrent surface protection on both the anode and the cathode.
According to X-ray photoelectron spectroscopy analysis, recrystallized solid LiPO2F2 decomposed into Li3PO4 and LiF, which rebuilt the electrode/electrolyte interfaces and inhibited undesirable side reactions, like the oxidation of carbonate solvent.
By virtue of this electrolyte strategy, the researchers successfully fabricated a 3.62-Ah pouch cell of Li/Li-rich layered oxide with a N/P ratio of 2.0 and an electrolyte injection ratio of 2.49 g/Ah, which exhibits a ultra-high energy density of 430 Wh/kg (based on whole cell) and stable cycling of 50 cycles.
This novel electrolyte engineering strategy may pave the way for future research on the design and utilization of solid sacrificial additives for high-energy Li metal batteries.
The work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, the Key R&D Program of Zhejiang Province, the S&T Innovation 2025 Major Special Programme of Ningbo, and the China Postdoctoral Science Foundation funded Project.
Featured image: Solvation-Induced Concurrent Protection on the Anode and Cathode toward High-Energy-Density Li Metal Batteries (Image by NIMTE)
Reference: Wei Deng, Wenhui Dai, Xufeng Zhou, Qigao Han, Wei Fang, Ning Dong, Bangyi He, and Zhaoping Liu, “Competitive Solvation-Induced Concurrent Protection on the Anode and Cathode toward a 400 Wh kg–1 Lithium Metal Battery”, ACS Energy Lett. 2021, 6, 1, 115–123 https://doi.org/10.1021/acsenergylett.0c02351
In the face of the surging demand for lithium-ion batteries and limited lithium reserves, scientists are searching for alternatives to the lithium technology. Russian researchers from Skoltech, D. Mendeleev University, and the Institute of Problems of Chemical Physics of RAS have synthesized and tested new polymer-based cathode materials for lithium dual-ion batteries. The tests showed that the new cathodes withstand up to 25,000 operating cycles and charge in a matter of seconds, thus outperforming lithium-ion batteries. The cathodes can also be used to produce less expensive potassium dual-ion batteries. The research was published in the journal Energy Technology.
The amount of electricity consumed worldwide grows by the year, and so does the demand for energy storage solutions, since many devices often operate in autonomous mode. Lithium-ion batteries can generate enormous power while showing fairly high discharge and charge rates and storage capacity per unit mass, making them a popular storage device in electronics, electric transport, and global power grids. For instance, Australia is launching a series of large-scale lithium-ion battery storage projects to manage excess solar and wind energy.
If lithium-ion batteries continue to be produced in growing quantities, the world may sooner or later run out of lithium reserves. With Congo producing 60% of cobalt for lithium-ion batteries’ cathodes, cobalt prices may skyrocket. The same goes for lithium, as the water consumption in lithium mining poses a great challenge for the environment. Therefore, researchers are looking for new energy storage devices relying on more accessible materials while using the same operating principle as lithium-ion batteries.
The team used a promising post-lithium dual-ion technology based on the electrochemical processes involving the electrolyte’s anions and cations to attain a manifold increase in the charging rate as compared to lithium-ion batteries. Another plus is that the cathode prototypes were made of polymeric aromatic amines which can be synthesized from various organic compounds.
“Our previous research addressed polymer cathodes for ultra-fast high-capacity batteries that can be charged and discharged in a few seconds, but we wanted more,” says Filipp A. Obrezkov, a Skoltech PhD student and the first author of the paper. “We used various alternatives, including linear polymers, in which each monomeric unit bonds with two neighbors only. In this study, we went on to study new branched polymers where each unit bonds with at least three other units. Together they form large mesh structures that ensure faster kinetics of the electrode processes. Electrodes made of these materials display even higher charge and discharge rates.”
A standard lithium-ion cell is filled with lithium-containing electrolyte and divided into the anode and the cathode by a separator. In a charged battery, the majority of lithium atoms are incorporated in the anode’s crystal structure. As the battery discharges, lithium atoms move from the anode to the cathode through the separator. The Russian team studied the dual-ion batteries in which the electrochemical processes involved the electrolyte’s cations (i.e. lithium cations) and anions that get in and out of the anode and cathode material’s structures, respectively.
Another novel feature is that, in some experiments, the scientists used potassium electrolytes instead of expensive lithium ones to obtain potassium dual-ion batteries.
The team synthesized two novel copolymers of dihydrophenazine with diphenylamine (PDPAPZ) and phenothiazine (PPTZPZ) which they used to produce cathodes. As anodes, they used metallic lithium and potassium. Since the key features of these battery prototypes called half-cells are driven by the cathode, the scientists assemble them in order to quickly assess the capabilities of new cathode materials.
While PPTZPZ half-cells showed average performance, PDPAPZ turned out to be more efficient: lithium half-cells with PDPAPZ were fairly quick to charge and discharge, while displaying good stability and retaining up to a third of their capacity even after 25,000 operating cycles. If a regular phone battery were as stable, it could be charged and discharged daily for 70 years. PDPAPZ potassium half-cells exhibited a high energy density of 398 Wh/kg. For comparison, the value for common lithium cells is 200-250 Wh/kg, the anode and electrolyte weights included. Thus the Russian team demonstrated that polymer cathode materials can be used to create efficient lithium and potassium dual-ion batteries.
New Anode for Aqueous Batteries Allows Use of Cheap, Plentiful Seawater as an Electrolyte.
Lithium-ion batteries are critical for modern life, from powering our laptops and cell phones to those new holiday toys. But there is a safety risk – the batteries can catch fire.
Zinc-based aqueous batteries avoid the fire hazard by using a water-based electrolyte instead of the conventional chemical solvent. However, uncontrolled dendrite growth limits their ability to provide the high performance and long life needed for practical applications.
Now researchers have reported in Nature Communications that a new 3D zinc-manganese nano-alloy anode has overcome the limitations, resulting in a stable, high-performance, dendrite-free aqueous battery using seawater as the electrolyte.
Xiaonan Shan, co-corresponding author for the work and an assistant professor of electrical and computer engineering at the University of Houston, said the discovery offers promise for energy storage and other applications, including electric vehicles.
“It provides a low-cost, high energy density, stable battery,” he said. “It should be of use for reliable, rechargeable batteries.”
Shan and UH PhD student Guangxia Feng also developed an in situ optical visualization technique, allowing them to directly observe the reaction dynamics on the anode in real time. “This platform provides us with the capability to directly image the electrode reaction dynamics in situ,” Shan said. “This important information provides direct evidence and visualization of the reaction kinetics and helps us to understand phenomena that could not be easily accessed previously.”
Testing determined that the novel 3D zinc-manganese nano alloy anode remained stable without degrading throughout 1,000 hours of charge/discharge cycling under high current density (80 mA/cm²).
The anode is the electrode which releases current from a battery, while electrolytes are the medium through which the ionic charge flows between the cathode and anode. Using seawater as the electrolyte rather than highly purified water offers another avenue for lowering battery cost.
Traditional anode materials used in aqueous batteries have been prone to dendrites, tiny growths that can cause the battery to lose power. Shan and his colleagues proposed and demonstrated a strategy to efficiently minimize and suppress dendrite formation in aqueous systems by controlling surface reaction thermodynamics with a zinc alloy and reaction kinetics by a three-dimensional structure.
Shan said researchers at UH and University of Central Florida are currently investigating other metal alloys, in addition to the zinc-manganese alloy.
In addition to Shan and Feng, researchers on the project include Huajun Tian, Zhao Li, David Fox, Lei Zhai, Akihiro Kushima and co-corresponding author Yang Yang, all with the University of Central Florida; Zhenzhong Yang and Yingge Du, both with Pacific Northwest National Laboratory; Maoyu Wang and co-corresponding author Zhenxing Feng, both with Oregon State University; and Hua Zhou with Argonne National Laboratory.
Researchers from Kaunas University of Technology (KTU), Lithuania came up with the idea on how to measure fluctuating blood potassium levels non-invasively, through electrocardiogram.
Researchers from Kaunas University of Technology (KTU), Lithuania came up with the idea on how to measure fluctuating blood potassium levels non-invasively, through electrocardiogram. The researchers claim that their method may become a digital biomarker in the future for managing electrolyte levels. This would be a huge step towards preventing potentially life-threatening conditions among people who suffer from chronic kidney disease.
Electrolytes and especially potassium, are paramount in the conduction of the heart’s cells. When electrolytes are too low or too high, the heart cannot contract normally, leading to dangerous arrhythmias and potentially sudden cardiac death.
“Electrolyte levels are kept within the healthy range by the kidneys. However, the patients with the last stage of chronic kidney disease, who have no renal function left, rely on hemodialysis to keep their electrolyte levels regulated. This means that they are prone to electrolyte imbalance in a 2-day-long hiatus between hemodialysis sessions”, explains Ana Rodrigues, researcher at KTU Biomedical Engineering Institute, one of the authors of the invention.
According to Rodrigues, with today’s aging society, it is estimated that the number of people requiring hemodialysis will markedly increase within 10 years. As people age, so do their kidneys. Research shows that up to 50 percent of seniors over the age of 75 can have kidney disease.
Abnormal electrolyte levels disturb the heart’s natural rhythm; such abnormalities can be reflected in the electrocardiogram. However, identifying electrolyte imbalance using an electrocardiogram is difficult due to confounding factors that mask these expected changes. The task becomes particularly complicated if electrolyte levels start to fluctuate beyond normal, but not reaching levels that require immediate medical attention.
The method proposed by the team of KTU researchers, tackles the problem through mathematical models that enable to quantify subtle changes that are not visible to the naked eye at the early stages of electrolyte imbalance. The method allows to spot potassium – the most arrhythmogenic electrolyte – induced changes in a certain part of the electrocardiogram.
“The initial results are promising. Our method may become a digital biomarker in the future for the management of electrolyte levels”, says Rodrigues.
The method proposed by KTU researchers allows detecting abnormal potassium levels before the onset of life-threatening arrhythmias. Patients could then start hemodialysis sooner, decreasing the chance of hospitalization and even premature death.
Usually, in order to detect the changes in electrolyte balance, a blood sample would be drawn from a patient. However, blood samples are not routinely requested and cannot be drawn outside a clinical environment. Thus, researchers in Lithuania came up with the idea which would allow measuring electrolyte balance noninvasively at home through an electrocardiogram.
“Noninvasive monitoring of electrolyte levels is a very novel concept and is now in its infancy stages. Our paper is one of the first papers published on the topic and, to the best of our knowledge, the first to investigate potassium fluctuations in ambulatory settings between hemodialysis sessions”, says Rodrigues.
The research is the outcome of the close collaboration between KTU, Lithuanian University of Health Sciences (LSMU) and the University of Zaragoza, Spain.
At the moment, clinical studies involving 17 patients have been completed. The researchers are planning on continuing clinical trials with more patients in order to validate their findings. Their next goal is to create an algorithm that would include measuring different electrolyte levels, such as calcium.
Later on, the algorithm could be integrated into wearable wrist-worn device capable of acquiring electrocardiograms. Every once in a while, the patient would record a short electrocardiogram signal (roughly 2-min long) using their fingers, and the system would register the electrolyte levels. If electrolytes were at an alarming level, the clinic would be notified, and the patient would be instructed accordingly.
Recent theoretical research has used the tools of topology, a branch of mathematics that studies the properties of geometric figures that do not depend on their deformations, to analyse electric charge transport in ionic fluids.
A sphere and a cube can be deformed into one another without cuts or stitches. A mug and a glass cannot because, to deform the first into the second, the handle needs to be broken. Topology is the branch of mathematics that formalises this difference between mugs and glasses, extending it also to abstract spaces with many dimensions. A new theory developed by scientists at SISSA in Trieste has succeeded in establishing a new relationship between the presence or absence of “handles” in the space of the arrangements of atoms and molecules that make up a material, and the propensity of the latter to conduct electricity. According to this theory, the insulating materials “equipped with handles” can conduct electricity as well as metals, while retaining typical properties of insulators, such as transparency.
The research, which has just been published in the journal Physical Review X, has thrived in the fascinating world of topology, an abstract discipline that gives a potent handle (pun intended!) to some of the most exotic properties of matter. In this way, scientists at the School of Trieste have investigated how to estimate the charge transport and the currents in generic ionic fluids rigorously, in line with the quantum nature of the material.
They have thus developed a theory to explain physical phenomena which have been known for more than a century but which until now lacked a rigorous interpretative base and predictive framework, thereby laying the foundations for major technological developments, for example in the field of thermoelectric materials.
Metals and mineral water, reflection and transparency
“We usually divide materials into conductors and insulators according to their propensity to conduct electricity or not” explain the research authors Paolo Pegolo, Federico Grasselli and Stefano Baroni. “In a metal, which is a typical conductor, some electrons move freely within the ionic crystal lattice. However, some liquids, such as mineral water, also conduct electricity, thanks to the transport of charged ions that are dissolved in them. In this case, we speak of ionic conductors, which are transparent, while metals are reflective”. Ionic fluids were the focus of the recent study. “We wanted to develop a theory based on the quantum nature of atoms and able to describe charge transport in this type of conductors” explain the scientists. “A sound explanation of the phenomenon could also be useful to create new materials with unprecedented electrical properties”.
Topology at the service of physics
The scholars have borrowed the mathematical tools of topology. Pegolo, Grasselli and Baroni’s theory has thus linked transport in ionic fluids with the existence in an abstract space of structures that present holes or handles. “If these structures exist, it is possible to transport electrons without moving the ions, thus significantly improving the electrical conduction properties of a material while leaving it non-metallic and therefore transparent. In the absence of holes or handles, the electrons remain bound to their atom and the conduction is less efficient”. “These phenomena” continue the researchers “have been known in physics for at least one hundred years. Our research gives them an elegant and powerful mathematical foundation and a reliable theoretical support structure”.
Possible technological developments
This theory finds application in the science of thermoelectric materials, which are all the more efficient the more they are able to guarantee the conduction of electricity without heating up. The researchers conclude, “The materials described in this theory do not have metallic properties and thus favour thermal insulation, but the presence of electrons that are sufficiently mobile to be transported increases their electrical conductivity. Both are important qualities which, at the technological level, could greatly contribute to the development of more efficient and advanced devices”.
The science of electrolyte materials might also benefit from the results of this research, in that better understanding of conduction in absence of metallicity can lead to design batteries that are efficient and electrochemically stable.