經由氣氛控制與碳披覆之鈦酸鋰的電化學特性與其在高功率鋰離子電池的應用

隨著各種再生能源的發展，開發鋰離子二次電池作為未來的電力的儲能系統與裝置也日益備受重視，例如應付風能與太陽能等間歇性再生能源輸出之定置型儲電系統以及裝載於電動車的動力鋰電池裝置。鈦酸鋰負極材料由於穩定的結構與安全工作電壓範圍，使其在鋰電池安全性與長循環壽命方面具有相當的優勢。然而鈦酸鋰是絕緣性材料，因此本研究致力於藉由結構缺陷與碳的批覆來提升導電度以改善其快速充放電性能。論文第一部分探究還原性氣氛對於鈦酸鋰的影響，研究結果發現具有氧空缺之鈦酸鋰除了在導電性上的提升，鋰離子擴散速率也因為鈦酸鋰原子結構的些微改變而獲得改善。有鑑於在追求快速充放電性能時，導電度和鋰離子擴散能力須同時促進，因此論文第二部分提出一個結合高分子與還原性氣氛的改良式固態合成法，其合成的鈦酸鋰同時擁有多孔性結構、碳的導電網絡以及利於鋰離子擴散的結構，在5 C快速充放電之下能提供155 mAh/g的電容量(89%的鈦酸鋰理論電容, 175 mAh/g)且具有結構穩定性，在200圈循環測試仍能維持初始的電容量。

關鍵字

鈦酸鋰；高分子熱裂解；氧缺陷；多孔結構；交流阻抗分析

並列摘要

In the society that several alternative energy sources are developing, lithium ion batteries have being designed to meet the raising requirement of electric vehicle (EV) and back-up storage systems. Li4Ti5O12 is a promising anode material for both high-power and high-safety lithium-ion batteries (LIBs). Li4Ti5O12 possesses the advantages of high safety and long cycle life, due to robust spinel structure and no solid electrolyte interface (SEI) formation. However, Li4Ti5O12 is electron insulated. Hence, this study aims to improve the electron conductivity through atmosphere control and carbon-assistance to promote its high-rate performance. Initially, the study probes into the effect of reductive atmosphere. Beyond the enhancement of electron conductivity, it is found that the lithium diffusion is also facilitated due to disorder structure. Furthermore, in view of that both lithium diffusivity and electron conductivity should be promoted for high rate capability, polymer-assisted solid-state method incorporated with reductive atmosphere is proposed. Porous structure, carbon network and disorder structure are synthesized under one-step synthesis, resulting in the outstanding electrochemical performance. The high-rate capacity of 5C reaches 155 mAh/g, 89% of theoretical value, and retained the initial value after 200 discharging/charging cycles.

並列關鍵字

Lithium titanate ； Polymer pyrolysis ； Oxygen vacancy ； Porous structure ； AC impedance

參考文獻

2. C. M. Hayner, X. Zhao and H. H. Kung, "Materials for Rechargeable Lithium-Ion Batteries," Annu. Rev. Chem. Biomol. Eng., 3 (2012) 445-471

3. M. Wakihara and O. Yamamoto, Lithium Ion Batteries: Fundamentals and Performance, Wiley-VCH. (1998)

5. T. Ohzuku, A. Ueda and N. Yamamota, "Zero-Strain Insertion Material of Li[Lil/3Ti5/3]O4 for Rechargeable Lithium Cells," J. Electrochem. Soc., 142 5 (1995) 1431-1435

6. Y. R. Jhan and J. G. Duh, "Electrochemical performance and low discharge cut-off voltage behavior of ruthenium doped Li4Ti5O12 with improved energy density," Electrochim. Acta, 63 (2012) 9-15

7. B. Tian, H. Xiang, L. Zhang, Z. Li and H. Wang, "Niobium doped lithium titanate as a high rate anode material for Li-ion batteries," Electrochim. Acta, 55 (2010) 5453-5458

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經由氣氛控制與碳披覆之鈦酸鋰的電化學特性與其在高功率鋰離子電池的應用

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