Toward advanced lithium battery : overcoming facing problems through fusion technology = 차세대 리튬 전지를 위한 연구 : 직면한 문제점의 융합기술을 통한 극복 overcoming facing problems through fusion technology

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1. Spinel-structured lithium manganese oxide ($LiMn_2O_4$) cathodes have been successfully commercialized for various lithium battery applications and are among the strongest candidates for emerging large-scale applications. Despite its various advantages including high power capability, however, $LiMn_2O_4$ chronically suffers from limited cycle life, originating from well-known Mn dissolution. An ironical feature with the Mn dissolution is that the surface orientations supporting Li diffusion and thus the power performance are especially vulnerable to the Mn dissolution, making both high power and long lifetime very difficult to achieve simultaneously. In this investigation, we address this contradictory issue of $LiMn_2O_4$ by developing a truncated octahedral structure in which most surfaces are aligned to the crystalline orientations with minimal Mn dissolution, while a small portion of the structure is truncated along the orientations to support Li diffusion and thus facilitate high discharge rate capabilities. When compared to control structures with much smaller dimensions, the truncated octahedral structure as large as 500 nm exhibits better performance in both discharge rate performance and cycle life, thus resolving the previously conflicting aspects of $LiMn_2O_4$. 2. Wearable electronics represent a significant paradigm shift in consumer electronics since they eliminate the necessity for separate carriage of devices. In particular, integration of flexible electronic devices with clothes, glasses, watches, and skin will bring new opportunities beyond what can be imagined by cur-rent inflexible counterparts. Although considerable progresses have been seen for wearable electronics, lithium rechargeable batteries, the power sources of the devices, do not keep pace with such progresses due to tenuous mechanical stabilities, causing them to remain as the limiting elements in the entire technology. Herein, we revisit the key components of the battery (current collector, binder, and separator) and replace them with the materials that support robust mechanical endurance of the battery. The final full-cells in the forms of clothes and watchstraps exhibited comparable electrochemical performance to those of conventional metal foil-based cells even under severe folding-unfolding motions simulating actual wearing conditions. Furthermore, the wearable textile battery was integrated with flexible and lightweight solar cells on the battery pouch to enable convenient solar-charging capabilities. 3. The demand for lithium ion batteries (LIBs) in various flexible mobile electronic devices is continuously increasing. With this in mind, a vast number of smart approaches, such as implementation of conductive nanomaterials onto paper and textiles, have been recently demonstrated. Most of them were, however, limited to the single-cell level. In the present study, large area flexible battery modules were developed in an attempt to expand the knowledge and design accumulated from the single-cell level approaches to larger-scale applications. A multi-stacked configuration was adopted to produce a high areal energy density in each single-cell. Meanwhile textile-based electrodes on both sides grant mechanical stability, even on the module level, by efficiently releasing the stress generated during aggressive folding and rolling motions. Moreover, the connection between and stacking of the single-cells allow the wide tuning of the overall voltage and capacity of the module. This battery design should be immediately applicable to a broad range of outdoor, building, and military items. 4. The battery community has recently witnessed a considerable progress in the cycle lives of lithium-sulfur (Li-S) batteries, mostly by developing the electrode structures that mitigate fatal dissolution of lithium poly-sulfides. Nonetheless, most of the previous successful demonstrations have been based on limited areal capacities. For realistic battery applications, however, the chronic issues from both the anode (lithium dendrite growth) and the cathode (lithium polysulfide dissolution) need to be readdressed under much higher loading of sulfur active material. To this end, the current study integrates the following three approaches in a systematic manner: 1) the sulfur electrode material with diminished lithium polysulfide dissolution by the covalently bonded sulfur-carbon microstructure, 2)mussel-inspired polydopamine coating onto the separator that suppresses lithium dendrite growth by wet-adhesion between the separator and Li metal, and 3)addition of cesium ions ($Cs^+$) to the electrolyte to repel incoming Li ions and thus prevent Li dendrite growth. This combined strategy resolves the longstanding problems from both electrodes even under the very large sulfur-carbon composite loading of $17 mg cm^{-2}$ in the sulfur electrode, enabling the highest areal capacity ($9 mAh cm^{-2}$) to date while preserving stable cycling performance.
Advisors
Choi, Jang Wookresearcher최장욱researcher
Description
한국과학기술원 :EEWS대학원,
Publisher
한국과학기술원
Issue Date
2015
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : EEWS대학원, 2015.2,[vi, 93 p. :]

Keywords

Lithium ion battery▼amanganese spinel▼aflexible battery▼apolydopamine▼alithium dendrite; 리튬 전지▼a망간 스피넬▼a플렉서블 배터리▼a폴리 도파민▼a리튬 수지상 억제

URI
http://hdl.handle.net/10203/265564
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=849287&flag=dissertation
Appears in Collection
EEW-Theses_Master(석사논문)
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