Visualization and characterization of nanoscale ionic motion for battery materials using atomic force microscopy원자간력 현미경을 이용한 이차전지 소재의 나노 스케일 이온 거동 영상화 및 특성 평가

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Lithium ion batteries (LIBs), which are representative secondary batteries, possessing high energy density are being used as powerful electric energy storage devices in various applications such as mobile devices such as cellular phones, laptops and electric vehicles, and the developments for high performance have been actively conducted worldwide. Although researches on liquid electrolytes with excellent conductivity as well as electrodes with higher capacity of LIBs have been focused, however, the risk of leakage, ignition and explosion due to decomposition reaction of liquid electrolyte has been pointed out as a problem. As the safety issue of liquid electrolyte has been emerged, LIB using solid-state electrolyte (SSE) is being proposed as an alternative. SSEs have advantages of durability, stability and working without a separator membrane. However, they exhibit lower ionic conductivity than liquid electrolytes, furthermore, incompatibility occurs on the interface between a SSE and an electrode. Therefore, nanoscale analysis in various aspects on the ion channel of SSE and electrode-electrolyte interface is essential for improvement of the low ion conductivity and interface problem, and the research on ion conduction mechanism is required. In this study, we visualized and analyzed the ionic behavior and various properties of anode materials and SSE, which are the core components of all-solid-state lithium batteries (ASSLBs) utilizing atomic force microscopy (AFM) techniques such as electrochemical strain microscopy (ESM), conductive-AFM (C-AFM) and lateral force microscopy (LFM). First, the spatial distribution of ion channels on the commercial lithium silicon titanium phosphate (LSTP) SSE surface was explored. The collective behavior of the ions was confirmed by applying DC voltage through an AFM probe and observing changes in shape and electrochemical strain. Second, the distributions of various components comingled in LSTP-dispersed natural graphite (NG)-based composite anodes were identified using various techniques of AFM, and the sensitivity difference according to the measurement parameters in AFM of each component were confirmed and suggested as a marker for a standard to distinguish the regions of each component. Furthermore, the relation between local ionic behavior and mechanical properties was investigated at the nanoscale through the Pearson’s correlation analysis from the simultaneously acquired images of ESM and LFM. Third, we conducted comparison analysis on the ionic activity and electronic conductivity according to the microstructure and content of lithium lanthanum zirconate (LLZO) lithium ion conductor dispersed NG-based composite anodes utilizing ESM and C-AFM, suggesting the influences on the operation performance when applied to LIBs.
Advisors
Hong, Seungbumresearcher홍승범researcher
Description
한국과학기술원 :신소재공학과,
Publisher
한국과학기술원
Issue Date
2020
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 신소재공학과, 2020.2,[v, 69 p. :]

Keywords

Atomic force microscopy▼aLithium ion batteries▼aNanoscale▼aIonic motion▼aVisualization; 원자간력 현미경▼a리튬이차전지▼a나노스케일▼a이온거동▼a영상화분석

URI
http://hdl.handle.net/10203/283548
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=907059&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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