Measurements of the coulombic efficiency as a method for understand the cycle efficiency in Li/FeS2 batteries = Li/FeS2 배터리사이클 수명을 이해하기 위한 쿨롱 효율 측정

다국어 초록 (Multilingual Abstract)

Pyrite FeS2 as an abundant and inexpensive material shows a theoretical capacity of 892 mAh g-1 based in a complete conversion of 4e-/FeS2. The use of pyrite in a battery is a promising candidate for the next generation electrochemical energy storage. The application of FeS2 as a electrode material for lithium secondary batteries, demonstrated the feasibility operating over a high temperature range of 240-500 oC and in an intermediate temperatures range of 90-130 oC, but most of the results in the literature on FeS2 as a negative electrode at room temperature showed a poor initial coulombic efficiency and a unacceptable cycling performance due to the formation of highly soluble lithium polysulfide during the discharge and recharge.
Then in that sense, this work contributes to advancement of pyrite batteries in one aspect, the cycling performance and operates reliability of Li-ion batteries, in other words the lifetime estimation. For the experimental part of this work, the electrochemical performance of negative electrodes based on commercially available FeS2 powder as a reference and four different micrometer-sized samples was investigated. FeS2 electrodes made using large particle show better cycling performance than electrodes made from small particle size. Nevertheless, small particle size electrodes showed considerably uncertainly first discharge capacity with regard to the presence of small particles. In order to understand the cycle efficiency dependent as a function of battery aging, first we investigated the decrement of the specific capacity at different current densities at room temperature, the results obtained was using to compared the voltage profile from 1 to 2.8 V, and the end discharge capacity in different FeS2 milled samples; in general authenticating that variation of particle size is known to disturb the conduction of lithium ion.
In this work with the purpose to verify the reliability of this method we developed detailed classification of the coulumbic efficiency measurement helping us with methods of non linear adjust system for comprehend and verify the fading battery and the reasons during the galvanostatic test.

목차 (Table of Contents)

• Abstract
• Chapter 1 Introduction 1
• Chapter 2 Theoretical Background 3
• Section 1 Lithium Secondary Battery 3
• 1. Definition and history of batteries 3
• 2. Needed for a better batteries 4
• 3. Lithium based batteries 5
• Section 2 The Lithium-FeS2 system 7
• Section 3 Research objectives 11
• Chapter 3 Experiment 12
• Section 1 Manufacture of FeS2 through ball milling 12
• Section 2 Working electrode preparation 13
• Section 3 Coin cell assembly 15
• Section 4 Analysis of electrochemical characterization 17
• Section 5 Agreement for CE measurement and capacity loss rate 18
• Chapter 4 Results and discussion 19
• Section 1 Analysis of FeS2 Active material 19
• 1. Scanning Electron Microscopy analysis after ball milling process 19
• 2. X-ray photoelectron spectroscopy analysis in FeS2 electrodes before and after first cycling 22
• 3. Particle size distribution analysis after ball milling process 24
• 4. X-ray photoelectron spectroscopy analysis in FeS2 electrodes before and after first cycling 29
• Section 2 Electrochemical characteristic of FeS2 as electrode active material 32
• 1. Charge / discharge analysis of active material in electrode manufacturing process 32
• 2. Coulombic efficiency evaluation according cycling in the electrode 36
• Section 3 Validation of results and comparison after long term cycling 37
• 1. Capacity loss rate per cycle of FeS2 milled samples calculated over 60 cycles and non-linear curve fitting report 37
• Chapter 5 Conclusion 41
• References
• Abstract
• Acknowledgments