The M&MS Group contributes to several key DOE programs over areas ranging from electrode modeling, understanding cation and electron transport, active materials development.
Sodium-ion batteries (EERE/VTO/BMR): While lithium-ion systems have become established in several markets, alternative systems based on sodium-ions are under consideration due to advantages including lower materials costs and low state-of-charge safety. Within the M&MS Group our focus is on the development and understanding of next generation materials systems based on new sodium-ion anode and cathode materials.
- Sodium-Ion Anodes: We have been determining new charge storage mechanisms for Na-ion specific anode systems (e.g. NaPb, Na3P) working to identify the role of reversible structural transformations, electrochemical reversibility, stability, and safety in these emerging systems.
- Sodium-ion Cathodes: Structurally sodium-based cathodes are similar to lithium-ion cathodes but with possible significant differences in sodium-ordering, layering schemes, polymorphs, and cation coordination. In these systems, novel electroactive materials have been isolated and the differences in performance can be traced to the differences between sodium-sites, alternative diffusion pathways, and overall materials properties (e.g. conductivity). Recent work:
- “Unraveling the Formation Mechanism of NaCoPO4 Polymorphs” J. Solid State Chemistry, (2020) DOI:10.1016/j.jssc.2020.121766
- “Disrupting the Na+/Vacancy Ordering in P2-type Na(NiMn)O2 Cathodes in Na-Ion Batteries” J. Physical Chemistry C, (2018) DOI:10.1021/acs.jpcc.8b05537
Silicon-Based Anodes (EERE/VTO/SCP): While graphitic carbon is an established anode system for lithium-ion energy storage systems, the next generation of LIB anode materials are projected to contain silicon materials as an active component as a pathway to increase energy density. Within our group we have focused on electrode stability, prelithiation studies, and issues associated with full cell cycling. Recent work:
- Electrodes: Electrode level studies are an important area of research for silicon because of the complex interactions between silicon, binder, electrolyte, and conductive additive. Notably issues associated with blended electrodes (silicon/graphite) are seen due to the different surface chemistry of the electroactive materials.
- “Capacity Fade in High Energy Silicon/Graphite Electrodes of Lithium-Ion Batteries” Chem. Comm. (2018) DOI:10.1039/c8cc00456k
- Prelithiation: An issue associated with silicon-based electrodes has been the large irreversible capacity seen in early cycles due to various break-in processes, slow initial diffusion of lithium into crystalline silicon, and surface reactivity. One way around this problem has been to use a sacrificial lithium source to counter this phenomenon to counter the loss of active lithium to the system.
- “Beneficial Effect of Li5FeO4 Lithium Source for Lithium-ion Batteries with a Layered NMC Cathode and a Silicon Anode” Journal of the Electrochemical Society (2020) DOI:10.1149/1945-7111/abd1ef
- “Liquid Ammonia Chemical Lithiation: An Approach for Higher Energy and High Voltage Silicon/Graphite Li1+x[Ni0.5Mn1.5]O4 Lithium-ion Batteries” ACS Applied Energy Materials (2020) DOI:10.1021/acsaem.9b00695
Electrode Modeling: While the transport and electrochemical properties of materials are a critical aspect of the overall electrodes performance, an understanding of the complex structure that is created when a material is converted to an electrode by addition of binder, current collector, conductive additives, and electrolytes highlights the interplay of these diverse materials and how they must work together to create a viable electrochemical system. Recent work:
Silicon (EERE/VTO/SCP): Next generation anodes, such as silicon, can have significant advantages over graphitic carbon, the state of the art LIB anode, notably in total gravimetric capacity. However at this point issues with lithium transport in the material, electrode design, and degradation mechanisms are not well defined.
- Silicon Anode Design
- “Investigations of Silicon Thins Films as Anodes for Lithium-Ion Batteries” ACS Applied Materials and Interfaces (2018) DOI:10.1021/acsami.7b13980
Fast Charging (EERE/VTO/XCEL): A key aspect of consumer acceptance of electric vehicles is the time necessary to recharge the vehicles battery system while on the road. While significant commercial advances have been made and implemented, identifying the underlying electrochemical cell issues that limit the speed of charging is important to make further advances.
- LIB Cells and Fast Charge
- “Graphite Lithium under Fast Charging Conditions: Atomistic Modeling Insights” J. Physical Chemistry C (2020) DOI:10/1021/acs.jpcc.0c01083
- “Apparent Lithium-Ion Diffusion Coefficient with Applied Current in Graphite” J. Electrochemical Society (2020) DOI:10.1149/1945-7111/abaf9f
- “Fast Charging of Lithium-Ion Cells: Part 2. Non-Linear Contributions to Cell and Electrode Polarization” J. Electrochemical Society (2019) DOI:10.1149/2.0561914jes