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Room-Temperature Fabrication of a Liquid NaK Alloy-Based Membrane Electrode for Sodium-Ion Batteries
journal contribution
posted on 2020-04-22, 15:06 authored by Junfeng Yang, Xusheng Wang, Shizhi Huang, Xinxiang Zhang, Jitao ChenThe
room-temperature liquid anode is a feasible method for building dendrite-free
alkali-metal-based batteries. The Na–K phase diagram shows
a eutectic point as low as 260.53 K with a long liquid range below
298 K with the molar fraction of potassium ranging from 30.48 to 84.99%.
However, the NaK alloy exhibits a very high surface tension preventing
it from wetting the current collector surface. Herein, a novel homogeneous
dual solid–liquid composite in which the liquid alloy is fixed
by the solid Na15Sn4 phase and perfectly stuffed
into the grid of the mesh has been designed and fabricated. Based
on the liquid range of the NaK alloy, the Na–K–Sn mixture
possesses a theoretical specific capacity of 768 mAh g–1. The symmetric cells of the Na–K–Sn@mesh electrodes
cycled at 2.0 mA cm–2 with 1.0 mAh cm–2 showed little fluctuations with the stable overpotential of ∼200
mV for 550 h, and the full cell coupled with Na3V2(PO4)3 showed an initial discharge capacity
of 103 mAh g–1 at 2 C with a retention of 90% after
800 cycles. When the high-loading Na3V2(PO4)3 electrode is applied in the full cell, a stable
cycling life is still maintained with a good capacity retention of
86% over 190 cycles (2.7 mAh cm–2) and 91% over
60 cycles (5.2 mAh cm–2).