微細構造と欠陥のエンジニアリングによるリチウムイオン二次電池の性能向上(Microstructure and Defect Engineering Improves Performance of Lithium-Ion Batteries)

2023-02-08 ノースカロライナ州立大学(NCState)

＜関連情報＞

• https://news.ncsu.edu/2023/02/defects-improve-lithium-ion-battery-performance/
• https://www.sciencedirect.com/science/article/abs/pii/S000862232300009X
• https://pubs.acs.org/doi/10.1021/acsami.2c18918

リチウムイオン電池の高性能化に向けたパルスレーザーアニールによる黒鉛負極の微細構造・欠陥エンジニアリング。 Microstructure and defect engineering of graphite anodes by pulsed laser annealing for enhanced performance of lithium-ion batteries

Author links open overlay panelNayna Khosla a, Jagdish Narayan a, Roger Narayan a b, Xiao-Guang Sun c, Mariappan Parans Paranthaman c
https://doi.org/10.1016/j.carbon.2023.01.009

Abstract

Nanosecond pulsed laser annealing significantly improves cyclability and current carrying capacity of lithium-ion batteries (LIBs). This improvement is achieved by engineering of microstructure and defect contents present in graphite in a controlled way by using pulsed laser annealing (PLA) to increase the number density of Li+ ion trapping sites. The PLA treatment causes the following changes: (1) creates surface steps and grooves between the grains to improve Li+ ion charging and intercalation rates; (2) removes inactive polyvinylidene difluoride (PVDF) binder from the top of graphite grains and between the grains which otherwise tends to block the Li+ migration; and (3) produces carbon vacancies in (0001) planes which can provide Li+ charging sites. From X-ray diffraction data, we find upshift in diffraction peak or reduction in planar spacing, from which vacancy concentration was estimated to be about 1.0%, which is higher than the thermodynamic equilibrium concentration of vacancies. The laser treatment creates single and multiple C vacancies which provide sites for Li+ ions, and it also produces steps and grooves for Li+ ions to enter the intercalating sites. It is envisaged that the formation of these sites enhances Li+ ion absorption during charge and discharge cycles. The current capacity increases from an average 360 mAh/g to 430 mAh/g, and C–V shows significant reduction in SEI layer formation after the laser treatment. If the vacancy concentration is too high and charge-discharge cycles are long, then trapping of electrons by Li+ may occur, which can lead to Li0 formation and Li plating causing reduction in current capacity.

長寿命リチウムイオン電池用高電圧スピネルLiNi0.5Mn1.5O4正極のレーザー支援表面フッ化リチウム化学修飾法 Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode for Long-Life Lithium-Ion Batteries

Zehao Cui, Nayna Khosla, Tianxing Lai, Jagdish Narayan and Arumugam Manthiram
ACS Applied Materials and Interfaces  Published:December 27, 2022
DOI:https://doi.org/10.1021/acsami.2c18918

Abstract

High-voltage spinel LiNi_0.5Mn_1.5O₄ (LNMO) is a promising next-generation cathode material due to its structural stability, high operation voltage, and low cost. However, the cycle life of LNMO cells is compromised by detrimental electrode–electrolyte reactions, chemical crossover, and rapid anode degradation. Here, we demonstrate that the cycling stability of LNMO can be effectively enhanced by a high-energy laser treatment. Advanced characterizations unveil that the laser treatment induces partial decomposition of the polyvinylidene fluoride binder and formation of a surface LiF phase, which mitigates electrode–electrolyte side reactions and reduces the generation of dissolved transition-metal ions and acidic crossover species. As a result, the solid electrolyte interphase of the graphite counter electrode is thin and is composed of fewer electrolyte decomposition products. This work demonstrates the potential of laser treatment in tuning the surface chemistry of cathode materials for lithium-ion batteries.