Previous research on solid-state batteries is likely toToo one-sided. A review published in the latest issue of Science puts forward this point of view. Because of the desire to achieve solid-state batteries with high performance and high cycle life, most current research is devoted to improving the performance of solid-state batteries.Electrochemical properties. In fact, solid-state batteriesmechanical structureAlso needs to be taken into account.
Why study mechanical structures? How to understand the mechanical structure of solid-state batteries under different materials?
Solid-state batteries fail due to mechanical structure. What are the corresponding solutions?
Five authors from Oak Ridge National Laboratory and Michigan Technological University answered these questions in detail.
The key role of mechanics in solid-state batteries
Since we need to pay attention to the mechanical structure of solid-state batteries, how to evaluate and design them?
The paper provides a framework for understanding and designing mechanically reliable solid-state batteries.
The framework includes three aspects:
1. Identify and understand the sources of local strain in the solid-state battery;
2. Understand this stress, especially at the battery interface, and the response of battery materials to these stresses;
3. Design battery materials and battery cells with required stress and strain evolution.
in,stressis the amount of external force exerted on the material,strainIt refers to the degree of deformation of a material when subjected to external force.
Taking solid electrolytes as an example, it is well known that the key factor why solid lithium batteries are safer than liquid lithium batteries is that the solid electrolytes in solid batteries can effectivelyInhibit the growth of lithium dendrites.
Lithium dendrite
Different solid electrolyte materials also have different inhibitory effects on lithium dendrites. One criterion for evaluating the inhibitory effect is the material'sstress and strain.
If such a solid electrolyte is not prone to elastic deformation even if it is subjected to large stress, such as an oxide electrolyte, this means that this solid electrolyte material can effectively inhibit the growth of lithium dendrites; but at the same time, the hardness and stiffness of the oxide electrolyte are very high, and fractures are more likely to occur, affecting the performance of the solid-state battery.
Stress-strain relationship curve, source reference paper 2
Therefore, when choosing a solid-state electrolyte, choosing a material with more balanced properties will be more conducive to improving the performance and service life of the solid-state battery.
This is why it is necessary to study the mechanical structure of solid-state lithium batteries.
The charge and discharge process of solid-state lithium batteries is accompanied by changes in the volume of the cathode and anode, such as lattice stretching and distortion in the cathode and metallic lithium deposition in the anode.
Corresponding mechanics and transfer phenomena in solid-state lithium batteries
Liquid lithium batteries benefit from liquid electrolytes. Changes in the volume of the cathode and anode will not affect the stress structure inside the battery. However, because of the high solid content in solid-state lithium batteries, changes in the volume of the cathode and anode may affect the stability of the solid-state lithium battery.
If too much lithium is deposited at one place on the anode, it will causestressincrease.
If the stress exceeds the limit of the solid electrolyte, the material deforms too much (i.e.degree of strain), there will be risks such as material breakage and powdering.
Therefore, changes in the mechanical properties of the material will affect the electrochemical properties of the material, leading to battery performance deterioration or even failure.
In addition to the solid electrolyte, the components of the electrode (active material, binder, conductive agent, etc.) and the materials used will also affect the mechanical structure of the battery. This paper provides a framework that can be used to study the mechanical properties of these materials.
The author hopes that this paper will make it easier for researchers to understand the potential causes of solid-state battery failures, and the paper also provides solutions to these problems. include:
Study the stress relief mechanisms of lithium metal in terms of length scale, temperature and strain rate (current density);
Study stress relief mechanisms in ceramics, glasses, and amorphous ceramics as a function of length scale, temperature, and strain rate;
Discuss the engineering ductility of ceramic and glass electrolytes;
Design a lithium metal anode that can not only eliminate uneven deposition and stripping of lithium metal, but also alleviate the stress at the lithium-electrolyte interface;
Design a cathode active material with zero cyclic strain, resistance to fracture, or some ductility;
Design a composite cathode to minimize strain and maximize stress relief;
Detailed modeling is performed to describe the evolution of stress and strain in solid-state batteries, including length-scale effects, friction, adhesion and creep.
So, who completed this paper?
Introduction to the author of the paper
Thesis one actSergiyKalnaus, from Oak Ridge National Laboratory, USA, isDepartment of Computational Science and Engineeringsenior researcher.
Sergiy Kalnaus holds a PhD in mechanical engineering from the University of Nevada and received the Outstanding Contribution to Science and Technology Award from the U.S. Department of Energy. He also holds four patents, three on electrolytes and one on electrode slurry. He has published 34 papers and been cited 3,195 times.
The authors of the paper also includeNancy J.Dudney, also from Oak Ridge National Laboratory, isDepartment of Chemical SciencesAcademician and group leader.
Nancy J. Dudney studied chemistry at the College of William and Mary as an undergraduate. After graduation, she directly entered the School of Ceramic Engineering at the Massachusetts Institute of Technology and completed her Ph.D. He has been awarded the title of Outstanding Inventor by the U.S. Department of Energy, won 13 awards, and holds more than 14 patents. He is currently researching new materials for hybrid car batteries.
The authors of the paper are also fromDepartment of Chemical SciencesofAndrew S. Westover, is a materials scientist in the department.
Andrew S. Westover has published many papers in many journals such as "ACS Energy Letters" and "Materials Chemistry".25 articlesPapers, including one of the three top journals in electrochemistryJournal of the Electrochemical Society JES, the number of citations reached 3292. The goal is to enable next-generation energy storage, including solid-state lithium batteries.
The authors of the paper are alsoErik Herbert, from Oak Ridge National LaboratoryMaterials Science and Technology Department.
Erik Herbert is also an adjunct professor of materials science and engineering at Michigan Technological University and received his PhD in materials science and engineering from the University of Tennessee. A total of 14 papers were published and cited 4288 times.
The last author of the paper isSteveHackney, is a full professor of materials science and engineering at Michigan Technological University.
Steve Hackney studied chemistry at James Madison University for his undergraduate degree, and studied materials science at the University of Virginia for his master's and doctoral degrees. His research interests include lithium-ion batteries, ceramic battery materials, battery thin films and nanostructures.
Starting from the leading research in the field of solid-state batteries, this article systematically proposes the mechanical structure framework of solid-state batteries, focusing onstressMultiple solutions have been proposed for the generation, prevention and mitigation mechanisms.
Most current solid-state battery research is focused on improving the ion transport rate and electrochemical stability of the electrolyte. This paper bridges this gap and is also conducive to the development of solid-state batteries with higher energy density, better performance, safer and more stable.