Metal halide perovskites have generated interest across many fields for the impressive optoelectronic properties achievable in films produced using facile solution-processing techniques. Previous research has revealed the colloidal nature of perovskite precursor inks and established a relationship between the colloid distribution and the film optoelectronic quality. Yet, the identity of colloids remains unknown, hindering our understanding of their role in perovskite crystallization. Here, we investigate precursor inks of the prototypical methylammonium lead triiodide perovskite using cryo-electron microscopy (cryo-EM) and show, for the first time, that the colloids are neither amorphous nor undissolved lead iodide, as previously speculated, but are a crystalline, non-perovskite material. We identify this as a perovskite precursor phase and discuss this as a potential means to understanding the role of chloride in processing. This work establishes cryo-EM as a viable technique to elucidate the nature of colloids in perovskite inks, a vital step toward a fundamental understanding of thin-film crystallization.

The development of high energy density lithium metal batteries requires the successful implementation of thin lithium metal anodes with limited excess lithium. Primary electrodeposition is a strategy for on-site production of thin lithium metal and avoids the costs and challenges of traditional lithium metal foil processing and transport. Herein we explore the interfacial parameters governing deposition of up to 30 μm uniform columnar lithium in LiF-rich environments, by investigating the effects of both the substrate/lithium and electrolyte/lithium interfaces for three common electrolytes: carbonate, fluorinated carbonate, and ether-based. By analyzing the transition to growth heterogeneity at higher current densities and later stage deposition, we confirm that improved growth uniformity is coupled with increasingly stable solid electrolyte interphases, but that this correlation differs for the three electrolytes. In comparison with conventional dimethyl carbonate, fluorinated carbonate and ether-based electrolytes exhibit fewer chemical shifts in the morphological transition region. We pinpoint the chemical origins of growth transitions in conventional dimethyl carbonate and show that close-packed columnar growth can be electrodeposited in ether-based electrolyte at 100-fold higher current densities.

Striking a balance between high theoretical capacity, Earth abundance, and compatibility with existing manufacturing infrastructure, silicon is one of the few materials that meets the requirements for a next-generation anode...

No abstract

Silicon anodes for lithium‐ion batteries (LIBs) have the potential for higher energy density compared to conventionally used graphite‐based LIB anodes. However, silicon anodes exhibit poor cycle and calendar lifetimes due to mechanical instabilities and high chemical and electrochemical reactivity with the carbonate‐based electrolytes that are typically used in LIBs. In this work, we synthesize a pitch carbon‐coated silicon nanoparticle composite active material for LIB anodes that exhibits reduced chemical reactivity with carbonate‐based electrolytes compared to an uncoated silicon anode. Silicon primary particle sizes less than 10 nm diameter minimize micro‐scale mechanical degradation of the anode composite, while conformal coatings of pitch carbon minimize the parasitic reactions between the silicon and the electrolyte. When matched with a high voltage NMC622 (LiNi0.6Mn0.2Co0.2O2) cathode, the pitch carbon‐coated silicon anode retains ≈75 % of its initial capacity at the end of 1000 cycles. Increasing the areal loading of the pitch carbon‐coated silicon anodes to realize energy density improvements over graphite anodes results in severe mechanical degradation on the electrode level, highlighting a remaining challenge to be addressed in future work.