Electrochemical energy storage system offer enormous potential for meeting future energy demands, such as renewable energy, electric vehicles, uninterruptible power supplies and portable electronic devices. These applications require both high specific energy and high specific power. Lithium ion bat...
Electrochemical energy storage system offer enormous potential for meeting future energy demands, such as renewable energy, electric vehicles, uninterruptible power supplies and portable electronic devices. These applications require both high specific energy and high specific power. Lithium ion batteries and electrochemical capacitors are among the leading electrochemical energy storage systems. Electrical energy can be stored either by a chemical or physical mechanism on the interface between electrolyte and electrode materials. LiCoO2 and activated carbon are the most widely used electrode materials for lithium ion batteries and electrochemical capacitors, respectively. In general, considering their operating principle, lithium ion batteries have a high specific energy but low specific power. In contrast, electrochemical capacitors have a low specific energy but high specific power. Thus, the current technology of electrochemical energy storage systems can not satisfy the future demand. Therefore, great effort have been devoted to identifying alternative and inexpensive electrode materials with high specific energy and power for electrochemical energy storage systems. Manganese oxide is one of the promising electrode materials for lithium ion batteries as well as electrochemical capacitors in terms of its electrochemical behavior, low cost and environmental compatibility. Electrochemical properties of the manganese oxide are related to its intrinsic property and dependent on the nature of the interfaces between the manganese oxide and electrolyte. Tuning the morphology or texture of the manganese oxide to obtain high porosity and high surface area is also very important to improve the specific energy and power of electrochemical energy storage systems. In this thesis, we reported on the synthesis and the electrochemical behaviors of nano-architectured manganese oxide for electrochemical energy storage applications. Nanolayer manganese dioxide was successfully deposited on conductive carbon materials such as acetylene black and carbon nanotube by a spontaneous redox reaction between permanganate ion and carbon surface. The synthesis mechanism of the nano-architectured manganese dioxide on carbon nanotubes was proposed via. the in-situ monitoring of the solution chemistry. Nano-architectured manganese dioxide showed a high specific capacity and high rate capability. This demonstrated that a design of electrode materials, having high electrochemical utilization, high electronic conductivity and large ion supply, is crucial to enable the electrode materials to have high specific capacity and high rate capability. The charge storage mechanism and local/electronic structure change of nano-architectured manganese dioxide on carbon nanotube was investigated by in-situ X-ray absorption spectroscopy during charge/discharge. Novel hybrid capacitor based on manganese oxide materials was designed. Novel hybrid capacitor, which combines commercial lithium manganese oxide (electrode material for lithium ion batteries) and nano-architectured manganese dioxide on carbon nanotubes (electrode material for electrochemical capacitors) as a positive and a negative electrode material, respectively, showed a superior performance in terms of higher specific energy, compared with the hybrid capacitors in literatures. Nano-architectured lithium manganese oxides was successfully synthesized and well dispersed on entangled carbon nanotubes' web by microwave-hydrothermal process for electrochemical energy storage applications. Nano-architectured lithium manganese oxide showed excellent high rate capability and good structural reversibility. The remarkable electrochemical properties of the nano-architectured material were attributed to shorter lithium diffusion length, good dispersion, large ionic supply high electrode/electrolyte interfacial area and high electrical conductivity by introducing the entangled carbon nanotubes' web. The structural stability of nano-architectured lithium manganese oxide on carbon nanotube was investigated by ex-situ X-ray absorption spectroscopy and in-situ X-ray diffraction during charge/discharge. This synthetic strategy opens a new avenue for the synthesis of lithium metal oxides on the entangled carbon nanotubes' web in an effective and facile way.
Electrochemical energy storage system offer enormous potential for meeting future energy demands, such as renewable energy, electric vehicles, uninterruptible power supplies and portable electronic devices. These applications require both high specific energy and high specific power. Lithium ion batteries and electrochemical capacitors are among the leading electrochemical energy storage systems. Electrical energy can be stored either by a chemical or physical mechanism on the interface between electrolyte and electrode materials. LiCoO2 and activated carbon are the most widely used electrode materials for lithium ion batteries and electrochemical capacitors, respectively. In general, considering their operating principle, lithium ion batteries have a high specific energy but low specific power. In contrast, electrochemical capacitors have a low specific energy but high specific power. Thus, the current technology of electrochemical energy storage systems can not satisfy the future demand. Therefore, great effort have been devoted to identifying alternative and inexpensive electrode materials with high specific energy and power for electrochemical energy storage systems. Manganese oxide is one of the promising electrode materials for lithium ion batteries as well as electrochemical capacitors in terms of its electrochemical behavior, low cost and environmental compatibility. Electrochemical properties of the manganese oxide are related to its intrinsic property and dependent on the nature of the interfaces between the manganese oxide and electrolyte. Tuning the morphology or texture of the manganese oxide to obtain high porosity and high surface area is also very important to improve the specific energy and power of electrochemical energy storage systems. In this thesis, we reported on the synthesis and the electrochemical behaviors of nano-architectured manganese oxide for electrochemical energy storage applications. Nanolayer manganese dioxide was successfully deposited on conductive carbon materials such as acetylene black and carbon nanotube by a spontaneous redox reaction between permanganate ion and carbon surface. The synthesis mechanism of the nano-architectured manganese dioxide on carbon nanotubes was proposed via. the in-situ monitoring of the solution chemistry. Nano-architectured manganese dioxide showed a high specific capacity and high rate capability. This demonstrated that a design of electrode materials, having high electrochemical utilization, high electronic conductivity and large ion supply, is crucial to enable the electrode materials to have high specific capacity and high rate capability. The charge storage mechanism and local/electronic structure change of nano-architectured manganese dioxide on carbon nanotube was investigated by in-situ X-ray absorption spectroscopy during charge/discharge. Novel hybrid capacitor based on manganese oxide materials was designed. Novel hybrid capacitor, which combines commercial lithium manganese oxide (electrode material for lithium ion batteries) and nano-architectured manganese dioxide on carbon nanotubes (electrode material for electrochemical capacitors) as a positive and a negative electrode material, respectively, showed a superior performance in terms of higher specific energy, compared with the hybrid capacitors in literatures. Nano-architectured lithium manganese oxides was successfully synthesized and well dispersed on entangled carbon nanotubes' web by microwave-hydrothermal process for electrochemical energy storage applications. Nano-architectured lithium manganese oxide showed excellent high rate capability and good structural reversibility. The remarkable electrochemical properties of the nano-architectured material were attributed to shorter lithium diffusion length, good dispersion, large ionic supply high electrode/electrolyte interfacial area and high electrical conductivity by introducing the entangled carbon nanotubes' web. The structural stability of nano-architectured lithium manganese oxide on carbon nanotube was investigated by ex-situ X-ray absorption spectroscopy and in-situ X-ray diffraction during charge/discharge. This synthetic strategy opens a new avenue for the synthesis of lithium metal oxides on the entangled carbon nanotubes' web in an effective and facile way.
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#전기화학 에너지 저장 장치 전기화학 커패시터 리튬 이온 전지 망간 산화물 리튬 망간 산화물 탄소 나노 튜브 나노 구조 물질 하이브리드 커패시터 X선 흡수 분광법 electrochemical energy storage electrochemical capacitor lithium ion batteries manganese dioxide lithium manganese oxide carbon nanotube nano-architectured material hybrid capacitor X-ray absorption spectroscopy
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