Engineering topics

Xiao, Dongdong

Publications and source records attributed to Xiao, Dongdong.

3 records

DOE OSTI2025

Dual‐Gradient Construction on Li‐Rich Cathodes for High Stability Lithium Battery

Abstract The practical applications of high‐energy Li‐rich layered oxides (LLOs) have been hindered by the severe performance degradation including voltage decay and capacity fading. The gradient construction toward high‐activity interior and high‐stability exterior, typically realized by gradually changed transition metal (TM) gradient in LLOs, can alleviate the performance degradation to certain degrees. In this study, a gradient design of Al/Mg dopants is demonstrated for the TM‐gradient LLOs to further harmonize the high‐activity interior and high‐stability exterior, thereby forming the dual (TM and doping) gradient. As a result, superior capacity retention of 86% and a minor voltage decay of 0.54 mV cycle −1 are achieved at 1 C after 300 cycles. The improved electrochemical stability of the dual‐gradient LLO is attributed to the enhanced surface stability and suppressed bulk structure degeneration of LLOs upon electrochemical cycling. The dual‐gradient design serves as an important approach to fabricate high‐performance bulk LLOs toward applications.

Wu, Tianhao↗

DOE OSTI2024

An orbital strategy for regulating the Jahn–Teller effect

ABSTRACT The Jahn–Teller effect (JTE) arising from lattice–electron coupling is a fascinating phenomenon that profoundly affects important physical properties in a number of transition-metal compounds. Controlling JT distortions and their corresponding electronic structures is highly desirable to tailor the functionalities of materials. Here, we propose a local coordinate strategy to regulate the JTE through quantifying occupancy in the ${{d}_{{{z}^2}}}$ and ${{d}_{{{x}^2} - {{y}^2}}}$ orbitals of Mn and scrutinizing the symmetries of the ligand oxygen atoms in MnO6 octahedra in LiMn2O4 and Li0.5Mn2O4. The effectiveness of such a strategy has been demonstrated by constructing P2-type NaLixMn1–xO2 oxides with different Li/Mn ordering schemes. In addition, this strategy is also tenable for most 3d transition-metal compounds in spinel and perovskite frameworks, indicating the universality of local coordinate strategy and the tunability of the lattice–orbital coupling in transition-metal oxides. This work demonstrates a useful strategy to regulate JT distortion and provides useful guidelines for future design of functional materials with specific physical properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2024

High–Energy Earth–Abundant Cathodes with Enhanced Cationic/Anionic Redox for Sustainable and Long–Lasting Na–Ion Batteries

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na 0.67 Fe 0.3 Mn 0.5 Mg 0.1 Ti 0.1 O 2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210 mAh g –1 at 20 mA g –1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200 mA g –1 , even when operated with a high charge cut-off voltage of 4.5 V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.

25 ENERGY STORAGE↗