Surface Control in Pursuit of Next-generation Batteries

Open Access
Author:
Gordin, Mikhail
Graduate Program:
Mechanical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 16, 2014
Committee Members:
  • Donghai Wang, Dissertation Advisor
  • Chao Yang Wang, Committee Member
  • Hosam Kadry Fathy, Committee Member
  • Sulin Zhang, Committee Member
Keywords:
  • battery
  • energy storage
  • lithium-ion
  • lithium-sulfur
  • sodium-ion
  • electrolyte
  • solid-electrolyte interphase
  • surface analysis
Abstract:
Lithium-ion batteries have had a dramatic impact on the development of technology over the last few decades, enabling new developments like the revolution in mobile devices. However, meeting the needs of today’s technological frontiers, such as electric vehicles and grid-scale energy storage, will require radical new battery designs. Although many factors contribute to the viability of new designs, surface features are often a critical component. With that in mind, the work herein delves into analysis and control of surface features in two promising battery systems: lithium-sulfur batteries and phosphorous anodes for sodium-ion batteries. Lithium-sulfur batteries often suffer from mediocre capacity, poor cycling stability, low efficiency, and high self-discharge caused by the dissolution and diffusion of lithium polysulfides and their side-reactions with the lithium anode. Two approaches for controlling this behavior are thus presented. In Chapter 2, mesoporous nitrogen-doped carbon is shown to have dramatically enhanced ability to adsorb lithium polysulfides compared with undoped mesoporous carbon; this was found to significantly improve both the cyclability and the capacity of the battery. In Chapter 3, a new electrolyte additive, bis(2,2,2-trifluoroethyl) ether, is shown to help form a more robust anode solid-electrolyte interphase (SEI) and thus to mitigate self-discharge over prolonged a rest at an elevated temperature. Phosphorus anodes, in contrast, experience severe volume change (~300%) with cycling, leading to particle fracture and SEI instability. Fluoroethylene carbonate has been shown to be a good electrolyte additive for mitigating the capacity fading caused by these effects. In Chapter 4, the changes in the SEI growth and composition brought about by FEC are investigated in detail by impedance spectroscopy, electron microscopy, and spectroscopic techniques. In addition, it is shown that severe sodium metal deposition can occur on phosphorus electrodes cycled in FEC-free electrolyte. Put together, this work adds to the knowledge of surface behavior in promising battery systems and identifies new directions for future research.