The Study on Investigating the Structural Determinants of Ion Transport Mechanism and Interfacial Stability in Dual-Ion Battery Cathodes = 듀얼 이온 전지 양극소재의 이온 수송 메커니즘 및 계면 안전성에 관한 구조적 결정 요인 규명 연구

다국어 초록 (Multilingual Abstract)

Sodium dual-ion batteries (SDIBs) represent a promising alternative to lithium-ion batteries for large-scale energy storage applications, leveraging the natural abundance and low cost of sodium. However, their practical deployment is constrained by lower energy density and challenges associated with large anion intercalation into graphite cathodes at elevated voltages, including severe co-intercalation, graphite structural degradation, and substantial electrolyte decomposition. Herein, a unique design strategy employing graphene-coated mesophase carbon microbeads (GCS-MCMB) as a cathode material is presented to address these fundamental limitations. Comprehensive structural characterization reveals that the graphene coating introduces abundant edge plane defects and nanoscale pores while preserving the underlying graphitic crystallinity. The graphene-coated structure facilitates PF6- adsorption at edge sites, inducing a NaF-rich CEI to effectively prevent co-intercalation and graphite degradation. Electrochemical characterization reveals exceptional rate capability, with GCS-MCMB delivering 84.27 mAh g-1 at 60C, substantially surpassing pristine MCMB. Notably, GCS-MCMB maintains stable cycling performance throughout extended operation, achieving a remarkable energy density of 435.2 Wh kg-1 cathode after 1000 cycles at 10C. High-loading electrodes prepared via sustainable dry processing exhibited excellent 2C stability, with GCS-MCMB delivering 87.6 mAh g⁻¹ over 200 cycles—a substantial improvement over pristine MCMB. These comprehensive results demonstrate that the graphene-coated composite cathode architecture synergistically addresses multiple electrochemical challenges intrinsic to SDIBs and establishes a compelling pathway toward high-performance, sustainable, and economically viable sodium dual-ion battery technology for large-scale energy storage applications.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1 High Voltage Cathode Development for Na Based Batteries 1
• 1.2 Emerging rechargeable battery system 5
• 1.3 Issues of Graphite Cathode 8
• 1.4 Strategy for optimizing Anion storage mechanism 11
• Chapter 2. Experimental methods 13
• 2.1 Preparation of graphene core shell MCMB(GCS-MCMB) 13
• 2.2 Preparation of the electrodes 14
• 2.3 Fabrication of 2032-type coin cells 15
• 2.4 Characterization of GCS-MCMB 15
• 2.5 Electrochemical measurement 16
• Chapter 3. Results and discussion 17
• 3.1 Material Characteristics 17
• 3.2 Electrochemical performance evaluation of batteries 22
• 3.3 Optimized formation of the cathode electrolyte interphase 25
• 3.4 Performance evaluation of high-loading batteries 34
• Chapter 4. Conclusion 36
• Reference 38
• Abstract (Korean) 41