In Situ Dendrite Suppression Study of Nanolayer Encapsulated Li Metal Enabled by Zirconia Atomic Layer Deposition

Progressing toward the emerging era of high-energy-density batteries, stable and safe employment of lithium (Li) metal anodes is highly desired. The primary concern with Li metal anodes is their uncontrollable dendrites growth and extreme sensitivity to parasitic degradation reactions, raising the alarms for battery safety and shelf life. Nanolayer protection encapsulation, which is conformal and ionically conductive with a high-κ dielectric property, can suppress the degradation and empower stabilization of Li metal. In this work, engineering of a zirconia (ZrO₂) encapsulation layer on Li metal enabled by atomic layer deposition (ALD) was employed and investigated for surface-enhanced dendrite suppression properties using in situ optical observations and electrochemical cycling. The ALD process involved a combination of plasma subcycle activation and thermal subcycle activation in increasing the surface functionalization and chemisorption sites for precursors to obtain highly dense and conformal deposition. The encapsulation of Li with ZrO₂ ALD nanolayer further demonstrated excellent tolerance to atmospheric exposure for at least 1-5 h because of a conformal physical barrier, and excellent heat tolerance up-to 170-180 °C (close to Li melting point) and high rate capability due to thermal resistive property and high ionic transport property, respectively, of the ZrO₂ ceramic. The results establish a technology transferable to other metal anode chemistries and offer a potential insight into carrying out solid-state electrolyte multilayer coatings with high processing temperature flexibility and thereby providing a leap in the advancing of a range of high energy density all-solid-state batteries.

Engineering and Optimization of Silicon-Iron-Manganese Nanoalloy Electrode for Enhanced Lithium-Ion Battery

The electrochemical performance of a battery is considered to be primarily dependent on the electrode material. However, engineering and optimization of electrodes also play a crucial role, and the same electrode material can be designed to offer significantly improved batteries. In this work, Si-Fe-Mn nanomaterial alloy (Si/alloy) and graphite composite electrodes were densified at different calendering conditions of 3, 5, and 8 tons, and its influence on electrode porosity, electrolyte wettability, and long-term cycling was investigated. The active material loading was maintained very high (~2 mg cm^-2) to implement electrode engineering close to commercial loading scales. The densification was optimized to balance between the electrode thickness and wettability to enable the best electrochemical properties of the Si/alloy anodes. In this case, engineering and optimizing the Si/alloy composite electrodes to 3 ton calendering (electrode densification from 0.39 to 0.48 g cm^-3) showed enhanced cycling stability with a high capacity retention of ~100% over 100 cycles.

Nanoscale Porous Lithium Titanate Anode for Superior High Temperature Performance

In this work, nanoscale porous lithium titanate (LTO) anode material was synthesized by using aqueous spray drying method after ball milling. The size of the LTO nanoparticles was optimized to 200 nm because of its considerable moisture absorption levels for stable performance and its cooperation to make good quality electrodes found with testing. The electrochemical performance of the synthesized LTO nanoparticles was found to be very stable at high operating temperature (50 °C) and high current rate (5 C) which was worth noticing than its usual unfavorable behaviors (gas generation and surface phase transitions) at higher temperatures. In the postanalysis on the aged LTO cells, high-resolution-transmission electron microscope (HRTEM) and fast Fourier transform (FFT) measurements reveal that the LTO phase transitions are maintained to very thin surface level (3-5 nm) even after 500 cycles at 50 °C. Moreover, the synthesized LTO material showed stable cycling with a high capacity of 138.74 mA h g(-1) at 1 C rate and 111.53 mA h g(-1) at 5 C rate. Furthermore, high columbic efficiency and excellent capacity retention over 500 cycles at 50 °C was achieved. The enhanced electrochemical properties can be attributed to the increase in surface area and shortened Li(+) diffusion lengths because of the nanoscale primary particles and porous structure of the synthesized LTO particles.