Two New Publication by AMEE Research Group

Debash Teklie, of the AMEE Research Group under Dr. Özgür Çapraz, Associate Professor, CBEE, has 2 new publications in ACS Applied Energy Materials and ACS Applied Materials & Interfaces.

Published in ACS Applied Energy Materials

Title: 
Synergistic Integration of Hierarchical Secondary Si/C Microrod Architecture and Fluorinated Ether Electrolyte for Stable Lithium-Ion Batteries

Authors: 

Sung-Kwang Jung; Esin Aydemir; Debash Teklie; Martin Byung-Guk Jun; Juanjuan Lu; Haiyan Wang; Ömer Özgür Çapraz; Vilas G. Pol

Abstract:

Increasing the energy density of lithium-ion batteries is a central challenge for next-generation electrified technologies. Silicon (Si) is a premier anode candidate due to its high theoretical capacity; yet, its practical use is hindered by extreme volume expansion and subsequent mechanical failure. To address these chronic issues, we demonstrate a comprehensive electrode-electrolyte engineering strategy by synergistically pairing a hierarchical secondary Si/C microrod (μ-rod) architecture with a customized ether-based electrolyte. This approach targets to bridge the gap between nanoscale reaction kinetics and microscale electrode stability without relying on complex, nonscalable particle synthesis. Multiscale structural characterizations confirmed the robust, anisotropic geometry of the secondary micrometer-sized rods consisting of the nanocrystalline Si primary particles. Electrochemical evaluations demonstrate that the integrated μ-rod architecture exhibits superior electromechanical stability when paired with the fluorinated ether electrolyte, outperforming conventional carbonate systems. Consequently, the Li||Si half-cell achieved 76.4% capacity retention after 300 cycles, while practical validation in a Si||NMC622 full cell revealed 71.4% capacity after 100 cycles. Operando strain measurements demonstrate mechanically resilient response of the μ-rod architecture in fluorinated ether electrolyte. These results highlight the synergy between a commercially viable mesoscale structured electrode and a compatible electrolyte in enabling structurally durable and electrochemically stable Si-based anodes.

https://doi.org/10.1021/acsaem.6c02143

Published in ACS Applied Materials & Interfaces

Title: 
The Role of Fluoroethylene Carbonate as an Electrolyte Additive on the Chemomechanical Stabilities of NaCrO2 Cathodes in Na-Ion Batteries

Authors: 

Debash Teklie; Sankalpita Chakrabarty; Sreedeep Sreekumar; Minal Wable; Malachi Noked; Ömer Özgür Çapraz 

Abstract:

Sodium-ion batteries are promising energy storage devices beyond Li-ion batteries; however, their cycling stability is limited by chemomechanical instabilities in transition-metal oxide cathodes. Although electrolyte additives and other surface modification strategies have been widely used to improve electrochemical performance, the mechanisms underlying these improvements remain poorly understood. Here, sodium chromium oxide (NaCrO2) and fluoroethylene carbonate (FEC) were selected as model cathode and electrolyte additive systems, respectively. FEC improved the capacity retention of the NaCrO2 cathode from 66% to 85% after 50 cycles at C/20 rate. Operando digital image correlation (DIC), together with ex situ X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD) techniques, was employed to investigate the mechanical, chemical, and structural evolution of the NaCrO2 cathode. The cathode exhibited nearly identical chemomechanical deformations and phase evolution regardless of FEC except during the first charge, where a distinct deformation response indicated the interfacial reconstruction associated with cathode-electrolyte interphase formation. XPS, FTIR, and HR-TEM measurements demonstrated the formation of a thinner, more uniform NaF-rich cathode-electrolyte interphase with improved preservation of surface Cr3+ species in the presence of FEC. Additional XPS analysis of the Na-metal anode revealed NaF-rich solid-electrolyte interphase formation in the presence of the FEC additive. The enhanced cycling stability of the NaCrO2 cathode against the Na-metal anode is primarily attributed to the cohesive impact of the improvement in chemical stability of the electrodes’ interphases rather than bulk chemomechanical deformations of the cathode alone at a slower rate. The operando mechanical measurements revealed a unique mechanical signature associated with interfacial reconstruction in the presence of FEC, providing a direct mechanistic link between interphase formation and electrochemical performance.

https://doi.org/10.1021/acsami.6c08213