Advanced Electrode Materials for Lithium- and Potassium-Based Energy Storage Devices
- Publication Type:
- Thesis
- Issue Date:
- 2021
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With the growing demand for high-energy-density lithium-ion batteries, layered lithium-rich cathode materials with high specific capacity and low cost have been widely regarded as one of the most attractive candidates for next-generation lithium-ion batteries. However, issues such as voltage decay, capacity loss and sluggish reaction kinetics have hindered their further commercialization for decades. Herein, we propose a heterostructured LiAlF₄ coating strategy to overcome those obstacles. The as-developed lithium-rich cathode material shows a high reversible capacity and ultralong cycling stability. The enhanced performances can be attributed to the introduction of the lithium-ion-conductive nanolayer and the generation of nonbonding Oⁿ⁻ species in the active material lattice, which enable rapid and effective lithium ions transport and diffusion.
Considering the increasing cost and uneven distribution of lithium resources, potassium-ion batteries are attracting great interest for emerging large-scale energy storage, owing to their advantages such as low cost and high operational voltage. Herein, the synthesis of hierarchical K₁.₃₉Mn₃O₆ microspheres as cathode materials for potassium-ion batteries is reported. Additionally, an effective AlF₃ surface coating strategy is applied to further improve the electrochemical performance of K₁.₃₉Mn₃O₆ microspheres. The as-synthesized AlF₃ coated K₁.₃₉Mn₃O₆ microspheres show a high reversible capacity, excellent rate capability, and cycling stability. 𝘌𝘹 𝘴𝘪𝘵𝘶 X-ray diffraction measurements reveal that the irreversible structure evolution can be significantly mitigated via surface modification.
As for anode materials, it is reported on carbon-coated K₂Ti₂O₅ microspheres (S-KTO@C) synthesized through a facile spray drying method. Taking advantages of both the porous microstructure and carbon coating, S-KTO@C shows excellent rate capability and cycling stability as an anode material for PIBs. As a proof of concept, a potassium-ion hybrid capacitor shows a high energy density, high power density, and excellent capacity retention.
Phosphorus/oxygen dual-doped porous carbon spheres, which possess expanded interlayer distances, abundant redox active sites and oxygen-rich defects, were also prepared in this thesis. The as-developed anode material shows superior electrochemical performances. 𝘐𝘯 𝘴𝘪𝘵𝘶 Raman spectroscopy and density functional theory calculations further confirm that the formation of P-C and P-O/P-OH bonds not only improves structural stability, but also contributes to a rapid surface-controlled potassium adsorption process. A potassium-ion hybrid capacitor was assembled by a dual-doped porous carbon sphere anode and an activated carbon cathode, which holds great promise as next-generation energy storage devices.
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