Visualization and Chemical Characterization of the Cathode Electrolyte Interphase Using He-Ion Microscopy and In Situ Time-of-Flight Secondary Ion Mass Spectrometry

Combined Stabilizing of the Solid-Electrolyte Interphase with Suppression of Graphite Exfoliation via Additive-Solvent Optimization in Li-Ion Batteries

Propylene carbonate (PC) is a promising solvent for extending the operating temperature range for lithium-ion batteries (LIBs) because of its high dielectric constant and wide temperature range stability. However, PC can cause graphite exfoliation through cointercalation, leading to electrolyte decomposition and subsequent irreversible capacity loss. This work reports the formulation of a ternary electrolyte with the introduction of an inorganic salt additive, potassium hexafluorophosphate (KPF6), to address the aforementioned concerns. We demonstrate the cumulative effect of solvent and additive on delivering multiple performance benefits and safety of the battery. The faster diffusion rate of K + solvation shell decreases the rate of PC decomposition, thereby reducing its cointercalation. Additionally, the optimum concentration of KPF6, i.e., 0.1 M constructs a robust and insoluble LiF-rich electrode/electrolyte interphase, further suppressing graphite exfoliation and Li dendrite formation. The stable cyclability is achieved by enhanced Li + transportation through the LiF-rich interphase, enabling an exfoliation-free and dendrite-free graphite anode in the ternary electrolyte.

A Critical Review on the Recycling Strategy of Lithium Iron Phosphate from Electric Vehicles

Electric vehicles (EVs) are one of the most promising decarbonization solutions to develop a carbon-negative economy. The increasing global storage of EVs brings out a large number of power batteries requiring recycling. Lithium iron phosphate (LFP) is one of the first commercialized cathodes used in early EVs, and now gravimetric energy density improvement makes LFP with low cost and robustness popular again in the market. Developments in LFP recycling techniques are in demand to manage a large portion of the EV batteries retired both today and around ten years later. In this review, first the operation and degradation mechanisms of LFP are revisited aiming to identify entry points for LFP recycling. Then, the current LFP recycling methods, from the pretreatment of the retired batteries to the regeneration and recovery of the LFP cathode are summarized. The emerging direct recovery technology is highlighted, through which both raw material and the production cost of LFP can be recovered. In addition, the current issues limiting the development of the LIBs recycling industry are presented and some ideas for future research are proposed. This review provides the theoretical basis and insightful perspectives on developing new recycling strategies by outlining the whole-life process of LFP.

Controlling Li Dendritic Growth in Graphite Anodes by Potassium Electrolyte Additives for Li-Ion Batteries

Fast charging promotes Li dendrite formation and its growth on graphite anodes, which affects cell performance in Li-ion batteries (LIBs). This work reports the formation of a robust SEI layer by introducing a KPF₆ inorganic additive into the electrolyte. An optimal concentration of 0.001 M KPF₆ effectively inhibits the growth of Li dendrites at 2C charging rates, compared with a commercial electrolyte. Electrolytes containing a KPF₆ additive are shown here to deliver dual effects to mitigate the growth of dendrites. A thin LiF-rich SEI layer is formed on graphite, which blocks the electron leakage pathways. Additionally, K⁺ resides at defect sites (such as particle boundaries) due to its faster diffusion rate and blocks the incoming Li⁺ and restricts the growth of Li dendrites. The electrolyte with optimum concentration of KPF₆, i.e., 0.001 M, effectively directs Li⁺ transport through the thin, durable, and low resistance LiF-rich SEI layer. This has implications for fast charging through optimization of the electrode/electrolyte interphase by controlling additive concentrations.

npSCOPE: A New Multimodal Instrument for In Situ Correlative Analysis of Nanoparticles

Over the last few decades, nanoparticles have become a key element in a number of scientific and technological fields, spanning from materials science to life sciences. The characterization of nanoparticles or samples containing nanoparticles, in terms of morphology, chemical composition, and other parameters, typically involves investigations with various analytical tools, requiring complex workflows and extending the duration of such studies to several days or even weeks. Here, we report on the development of a new unique in situ correlative instrument, allowing us to answer questions about the shape, size, size distribution, and chemical composition of the nanoparticles using a single probe. Combining various microscopic and analytical capabilities in one single instrument allows a considerable increase in flexibility and a reduction in the duration of such complex investigations. The new instrument is based on focused ion beam microscopy technology using a gas field ion source as a key enabler and combining it with specifically developed secondary ion mass spectrometry and scanning transmission ion microscopy technology. We will present the underlying concept, the instrument and its main components, and proof-of-concept studies performed on this novel instrument. For this purpose, different pure titanium dioxide nanoparticle samples were investigated. Furthermore, the distribution and localization of the nanoparticles in biological model systems were studied. Our results demonstrate the performance and usefulness of the instrument for nanoparticle investigations, paving the way for a number of future applications, in particular, nanotoxicological research.