posted on 2024-02-23, 09:03authored byHaibin Wang, Jun Liu, Wenting Tai, Guiyang Li
Among composite solid electrolytes,
the addition of fillers could
restrain the crystallization of the molecular chain of poly(ethylene
oxide) (PEO). However, the impact of the spatial distance on the electrochemical
properties remains unstudied. This paper uses linear aldehydes with
carbon chain lengths of 1 and 7 to synthesize polyaminal-formaldehyde
(PAN-FDE) and polyaminal-heptaldehyde (PAN-HDE) with melamine as the
filler, which can reduce the crystallinity of the matrix and improve
the ionic conductivity. Besides, the ionic conductivity of the PAN-FDE
electrolyte membrane can reach 8.433 × 10–5 S·cm–1 at room temperature by adding 1% PAN-FDE
with PEO mass, which increases by 2 orders of magnitude for a poly(ethylene
oxide)-lithium trifluoromethanesulfonimide (PEO-LiTFSI) electrolyte
membrane. In addition, the electrochemical window of PAN-FDE electrolytes
is 0.57 V higher than that of PEO-LiTFSI electrolytes, which can be
attributed to the formation of hydrogen bonds between numerous N–H
groups in PAN-FDE and ether–oxygen in PEO. In symmetric cells,
Li/PAN-FDE/Li cells show a lower initial overpotential of 62 mV and
can cycle steadily for 1600 h without a short-circuit, while PEO-LiTFSI
cells show a high initial overpotential of 457 mV, and short-circuit
occurred at 180 h. In this paper, we contribute another way to optimize
the electrochemical properties of composite solid electrolytes by
changing the spatial distance.