New energy storage materials and devices in lithium and sodium ion batteries

1. The suppression of lithium dendrite is critical to the realization of lithium metal batteries. 3D conductive framework, among different approaches, has shown very promising results in dendrite suppression. In our recent work on Advanced Materials Interfaces  (https://doi.org/10.1002/admi.201800807),  a novel cost-effective and versatile dip-coating method is presented here to make 3D conductive framework. Various substrates with different geometries are coated successfully with copper, including electrically insulating glass fiber (GF) or rice paper and conducting Ni foam. In particular, the as-prepared copper coated GF shows promising results to serve as the lithium metal anode by the electrochemical battery tests. The method significantly broadens the candidate materials database for 3D conductive framework to include all kinds of intrinsically insulating 3D substrates with low cost and high scalability. 

3D Cu lithium anode

2. Solid electrolyte is critical to next-generation solid-state lithium-ion batteries with high energy density and improved safety. Sulfide solid electrolytes show some unique properties, such as the high ionic conductivity and low mechanical stiffness. In our recent work on Nature Communications  (https://rdcu.be/8jm2),  we show that the electrochemical stability window of sulfide electrolytes can be improved by controlling synthesis parameters and the consequent core-shell microstructural compositions. This results in a stability window of 0.7–3.1 V and quasi-stability window of up to 5 V for Li-Si-P-S sulfide electrolytes with high Si composition in the shell, a window much larger than the previously predicted one of 1.7–2.1 V. Theoretical and computational work explains this improved voltage window in terms of volume constriction, which resists the decomposition accompanying expansion of the solid electrolyte at the limit of small decomposition fraction. The effect builds up a local energy barrier to prevent the global decompoisiton from happening. Advanced strategies to design the next-generation sulfide solid electrolytes are also discussed based on our understanding.

Editor's Highlight on Nature Communications: Sulfide electrolyte materials offer the opportunity for the development of solid-state batteries. Here the authors further improve the voltage stability of core-shell structured sulfides by modifying the microstructures, and pair the optimized electrolytes with lithium metal anode into battery devices.

LSPS_XRD

 

3. Ceramic-sulfide solid electrolytes are a promising material system for enabling solid-state batteries. However, one challenge that remains is the discrepancy in the reported electrochemical stability. Recent work has sug-gested that it may be due to the sensitivity of ceramic sulfides to mechanically induced stability. Small changes in ceramic-sulfide microstructure, for example, have been shown to cause substantial differences in the electro-chemical stability. In this work on Small (https://onlinelibrary.wiley.com/doi/full/10.1002/smll.201901470), a rigorous theoretical framework is con-structed to enable the simulation of such mechanically induced stability for a generalized constraint mechanism. It is shown that the susceptibility for voltage widening in ceramic sulfides can be significantly influenced by the choice of different decay morphology models. This results in a less intrusive microstructure requirement for improved stability, which stems from the tendency of sulfides to decay via inclusions rather than homogeneously. This predicted decay morphology is experimentally confirmed. Li10GeP2S12 is stabilized by a thin amorphous shell, which prior models predict is too thin for stabilization, and shows the excellent cycling performance in all-solid-state batteries using LiCoO2 as cathode and Li4Ti5O12 as anode.

LGPS core shell

 

4. Sulfide electrolyte based solid state battery shows new possibilities beyond liquid electrolyte based commercial Li-ion battery. We show that it can work with Li metal anode without dendrite issue, using a graphite based covering layer to cycle at 10 mA/cm2 current density on Energy & Environmental Science (https://doi.org/10.1039/C9EE04007B), and further using a multiple-electrolyte-layer design to cycle at 20 mA/cm2 current density on Nature (https://www.nature.com/articles/s41586-021-03486-3), and using a further design of core-shell structure on electrolyte material particles to cycle at 40 mA/cm2 on JACS Au (https://pubs.acs.org/doi/10.1021/jacsau.2c00009). These desgins are guided by our high-throughput and machine learning platform based on mechanical constriciton principle for voltage stabilities with Li metal anode. Computational predictions agree well with experiment on many details. 

Nature

              JACS Au