Fei zhi zi na li zi dian chi zheng ji cai liao lin suan yan he ceng zhuang jin shu yang hua wu de she ji yu you hua

Ph.D.The ever-growing markets for electric vehicles and smart grids based on renewable energy sources, for example, wind and solar, call for larger scale production of batteries require beyond-lithium-ion technologies to reduce the consume of lithium and cobalt sources. Aprotic sodium ion batteries (NIBs) have been proposed as an alternative technology due to the earth abundant-sodium source. However, NIBs generally deliver low energy density due to the higher weight and higher reversible electrochemical potential of sodium. This thesis focuses on developing high performance SIB by designing and optimizing cathode materials.NASICON-type vanadium phosphate Na₃V₂(PO₄)₃ is firstly investigated due to its preeminent electrochemical property. A sequentially-processed method is developed to enable scalable production of nano-sized, carbon-coated Na₃V₂(PO₄)₃. The sequentially-processed Na₃V₂(PO₄)₃ exhibits a capacity of 113 mAh g⁻¹ with a flat voltage plateau at 3.4 V vs sodium metal. By triggering multi Vᴵᴵ/Vᴵᴵᴵ/Vᴵⱽ redox couples to maximize the achievable capacity, more than 210 mAh g⁻¹ is delivered with the emergence of an additional voltage plateau at 1.6 V. The corresponding energy density at this state reaches to 556 Wh kg⁻¹ with an average potential of 2.57 V. To further enhance the energy density, we explore a fluorinated vanadium phosphate, Na₃V₂(PO₄)₂O₂F. A novel hydrothermal method is developed to prepare the high-quality Na₃V₂(PO₄)₂O₂Fas electrode material. The prepared nano-sized Na₃V₂(PO₄)₂O₂F achieves an energy density of 459 Wh kg⁻¹ with good cyclability within a voltage window of 3 – 4.5 V. By widening the operation voltage window to 1 – 4.5 V, an energy density of 660 Wh kg⁻¹ (average potential, 2.75 V) can be obtained from the nano-sized Na₃V₂(PO₄)₂O₂F electrode at the initial cycles. The multi redox reaction endow vanadium-based phosphates with dramatic energy density. However, it also leads to poor cycling performances. The model of the intercalation reactions as well as the possible reasons of the degraded cycling performance in wide operation voltage windows are discussed based on the battery charging-discharging behavior, electrochemical impedance analysis, ex-situ morphology measurements and previously established material models. Our insights provide a new perspective to design high energy density materials of future.In the last part, we explore another important type of cathode material, layered metal oxide. A composition-based diagram is developed to optimize the Cu-Fe-Mn based layered metal oxides. The addition of Cu can improve the air stability while Fe and Mn can promote the capacity. We find that the low pristine valence state of Mn can dramatically improve the capacity of Naₓ(Cu-Fe-Mn)O₂ by analyzing the electrochemical performances. The champion one with a specific composition of Na₀.₇₅(Cu₀.₁Fe₀.₁Mn₀.₈)O₂ (lowest Mn valence state) delivers a capacity of 190 mAh g⁻¹ (energy density, 499 Wh kg-1; average potential, 2.58 V). The interaction of 3d transition metal cations is analyzed through the composition design and shifts of redox potentials. Based on molecular orbital theory, superexchange and Jahn-Teller effect are proposed to explain the influences of cation interactions. Our exploration about Cu-Fe-Mn based layered metal oxides will promote the design and optimization of energy materials.基於可再生能源（例如風能和太陽能）的電動汽車和智能電網的市場不斷增長，電池的大規模生產的需求急需鋰離子技術以外的其他技術，以減少鋰和鈷源的消耗。非質子鈉離子電池（SIBS）是一種具有豐富地球鈉源的替代技術。然而，由於鈉的重量更大，可逆電化學電位更高，SIBS通常提供低能量密度。本文通過對陰極材料的設計和優化，研制出高性能SIB。首先我們研究了NASICON型磷酸釩鈉 Na₃V₂(PO₄)₃。開發了一種連續處理法，得以實現納米級、碳塗層的 Na₃V₂(PO₄)₃ 的大規模生產。連續處理法的 Na₃V₂(PO₄)₃ 的容量為113 mAh g⁻¹，與金屬鈉相比，電壓平穩在3.4V。通過觸發 Vᴵᴵ/Vᴵᴵᴵ/Vᴵⱽ 多氧化還原對以最大化可實現的容量，在1.6V下出現附加電壓平臺使其容量超過210 mAh g⁻¹，相應的能量密度達到556 Wh kg⁻¹，平均電位為2.57V。為了進一步提高能量密度，我們研究了氟化磷酸釩鈉，Na₃V₂(PO₄)₂O₂F。我們開發了一種水熱法制備高質量電極材料的方法。納米級的 Na₃V₂(PO₄)₂O₂F 在34.5V的電壓窗口內可獲得459 Wh kg⁻¹的能量密度，且具有良好的循環性。通過將操作電壓窗口擴大到14.5V，初始循環可從納米級的 Na₃V₂(PO₄)₂O₂F 電極獲得660 Wh kg⁻¹的能量密度（平均電位，2.75V）。多重氧化還原反應使釩基磷酸鹽具有顯著的能量密度。然而，這也會導致不良的循環性能。從電池充放電行為、電化學阻抗分析、原位形貌測量和已有的研究成果出發，我們討論了插層反應模型以及寬操作電壓窗下循環性能下降的可能原因。我們的見解為未來高能量密度材料的設計提供了一個新的視角。在最後一部分，我們探討了另一種重要的陰極材料，層狀金屬氧化物。為了優化銅鐵錳基層狀金屬氧化物，我們開發了一個基於成分的相圖。銅的加入可以提高空氣的穩定性，而鐵和錳的加入可以提高空氣的穩定性。通過對電化學性能的分析，發現錳的低原價態能顯著提高 Naₓ(Cu-Fe-Mn)O₂ 的容量。最好的樣品的具體成分為 Na₀.₇₅(Cu₀.₁Fe₀.₁Mn₀.₈)O₂（最低錳價態），其容量為190 mAh g⁻¹（能量密度，499 Wh kg⁻¹；平均電位2.58V）。通過我們的設計，我們分析了三維過渡金屬陽離子的相互作用。我們發現鐵和錳的比例可以改變氧化還原電位。基於分子軌道理論，提出了超交換和姜泰勒效應來解釋陽離子相互作用的影響。我們對銅鐵錳基層狀金屬氧化物的探索將有助於能源材料的設計和優化。Xu, Junling.Thesis Ph.D. Chinese University of Hong Kong 2019.Includes bibliographical references.Abstracts also in Chinese.Title from PDF title page (viewed on 20, May 2021).Xu, Junling