Restricted (Penn State Only)
Huang, Qingquan
Graduate Program:
Materials Science and Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
August 06, 2018
Committee Members:
  • Donghai Wang, Dissertation Advisor
  • Donghai Wang, Committee Chair
  • Chao-Yang Wang, Committee Member
  • Adrianus C Van Duin, Committee Member
  • Long-Qing Chen, Outside Member
  • lithium-ion battery
  • silicon anode
  • lithium metal anode
  • gel polymer electrolyte
High-capacity Si-based anode is being considered as promising anode material for next generation of Li-ion battery. The energy density could be increased from 250-260 Wh kg-1 to 300-330 Wh kg-1 via replacing graphite with Si-based anode. However, for high-loading Si-based anode, the huge volume change of Si (400%) or SiO (200%) particles during lithiation/delithiation will arise large electrode thickness change. After repeated electrode expansion and contraction, the electrode integrity is seriously damaged, including large electrode cracking, electrode delamination or peeling-off from Cu current collector, as well as continuous growth of solid electrolyte interphase (SEI) layer. When pairing it with commercial cathode, the damage of electrode integrity results in large amount of irreversible lithium ions loss in each cycle and low full-cell Coulombic efficiency of 99.5-99.7%. Thus the full-cell exhibits fast capacity fading and limited cycle life. Another challenge of SiO anode is its low first cycle Coulombic efficiency of 50-60%, which causes huge irreversible lithium ions loss for the first cycle of full-cell and dramatically decreases the cell capacity. In Chapter 1, we will give an introduction to lithium-ion battery, cell energy density, and advantages and challenges of Si-based anode. The Chapter 2 introduces two strategies to solve the challenges of Si-based anode: including design of nanostructured Si and advanced polymer binder. Also we will also talk about the importance of electrode integrity and the previous work on improving electrode integrity. In Chapter 3, we reported an elastic and stretchable polyurethane-urea (PUU) gel polymer electrolyte (GPE) coating strategy to improve cycling stability of high-areal-capacity SiO anode. The PUU GPE functions as intra-electrode cushion to accommodate the volume change of SiO electrode. It can alleviate electrode thickness change, inhibit electrode cracking, and improve electrode adhesion strength on Cu current collector. The improved electrode structure integrity reduces the continuous growth of SEI layer. The half-cell of SiO electrode with PUU coating shows a reversible capacity of 3.0 mAh cm-2 for 280 cycles. When paring with commercial cathode, the full-cell shows a reversible capacity of 2.1 mAh cm-2 for 200 cycles and 80% capacity retention for 500 cycles with improved full-cell Coulombic efficiency of 99.9%. In Chapter 4, we demonstrate chemical vapor deposition (CVD) growth of carbon layer on SiOx (C-SiOx). The carbon coating is composed of dense graphene layers. It can not only increase the electronic conductivity, but also decrease the amount of electrolyte decomposition. Thus the first cycle Coulombic efficiency increases to 74.1%. Moreover, when blending C-SiOx with graphite anode, the composite anode shows high first cycle CE of 86.4%. In Chapter 5, we report a composite LixSi/gel polymer electrolyte composite protection film on the top of lithium meal via simple cast coating approach. The LixSi functions as seeds for lithium nucleation and it has large surface area, thus it can reduce local current density and prevent lithium dendrite growth. When paring with lithium iron phosphate cathode, the cell with composite protection films shows stable capacity at 2.0 mAh cm-2 for 400 cycles.