As lithium (Li)‐ion batteries expand their applications, operating over a wide temperature range becomes increasingly important. However, the low‐temperature performance of conventional graphite anodes is severely hampered by the poor diffusion kinetics of Li ions (Li+). Here, zinc oxide (ZnO) nanoparticles are incorporated into the expanded graphite to improve Li+diffusion kinetics, resulting in a significant improvement in low‐temperature performance. The ZnO–embedded expanded graphite anodes are investigated with different amounts of ZnO to establish the structure‐charge storage mechanism‐performance relationship with a focus on low‐temperature applications. Electrochemical analysis reveals that the ZnO–embedded expanded graphite anode with nano‐sized ZnO maintains a large portion of the diffusion‐controlled charge storage mechanism at an ultra‐low temperature of −50 °C. Due to this significantly enhanced Li+diffusion rate, a full cell with the ZnO–embedded expanded graphite anode and a LiNi0.88Co0.09Al0.03O2cathode delivers high capacities of 176 mAh g−1at 20 °C and 86 mAh g−1at −50 °C at a high rate of 1 C. The outstanding low‐temperature performance of the composite anode by improving the Li+diffusion kinetics provides important scientific insights into the fundamental design principles of anodes for low‐temperature Li‐ion battery operation.
Potassium‐ion batteries (KIBs) are considered more appropriate for grid‐scale storage than lithium‐ion batteries (LIBs) due to similar operating chemistry, abundant precursors, and compatibility with low‐cost graphite anodes. However, a larger ion reduces rate capabilities and exacerbates capacity fading from volumetric expansion. Herein, conductive polymer, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), is substituted for standard insulating polyvinylidene fluoride (PVDF). Half‐cells using carbon black (CB) in continuously conductive PEDOT:PSS/CB binder outperforms PVDF/CB by mitigating electrically isolated “dead” graphite, improving 100 cycle capacity retention at C/10 from 63 to 80%. Enhanced electrical contact with PEDOT:PSS/CB also reduces ion impedance and improves rate capabilities. Without CB however, PEDOT:PSS binder performs poorly in electrochemical studies despite promising ex situ electronic conductivity. This discrepancy is mechanistically elucidated through identification of redox activity between PEDOT:PSS and K+which results in high impedances in the anode operating voltage window. Additionally, the impact of conducting binder on mechanical properties and thermal safety of the anode is investigated. Brittleness and poor wettability of PEDOT:PSS are identified as issues, but greater stability against reactive KC8reduces overall heat generation. Binder substitution offers a promising means of mitigating issues with current KIB anodes regardless of active material, and the work herein addresses issues towards further improvement.
more » « less- NSF-PAR ID:
- 10446997
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 12
- Issue:
- 14
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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