Figure 5. (a) Nyquist plots and (b) linear sweep voltammograms
of PP, cellulose and cellulose/CaCO3 membrane. Ionic
conductivities of (c) cellulose and (d)
cellulose/CaCO3-1 membranes in variable temperatures.
The cycling performances of LiFePO4/Li batteries
assembled with cellulose and cellulose/CaCO3-1 membranes
were evaluated. As shown in Figure 6a , the initial discharge
capacity of LiFePO4/Li batteries assembled with
cellulose/CaCO3-1
membrane reaches 144.2 mAh
g-1, which is higher than that of cellulose membrane
based battery (138.7 mAh g-1). The reason may be
attributed to the higher ionic conductivity of
cellulose/CaCO3-1 membrane. With the formation of solid
electrolyte interface (SEI), the interfacial resistance reduces.
Consequently, the discharge capacity of batteries increases steadily.
For the battery with cellulose/CaCO3-1 membrane, the
stable capacity is 149.0 mAh g-1. Moreover, capacity
retention is as high as 97.4% after 230 cycles. In contrast, the
battery with cellulose membrane has a severe decay and only remains
121.3 mAh g-1 after 100 cycles. The excellent cycle
performance is ascribed to the electrochemically interfacial stability.
The electrode morphology after the battery cycle can reveal the actual
electrochemical reaction condition of the battery. In order to further
analyze the difference in battery performance, the surface of Li anodes
after cycling was observed (Figure 6b ). As for cellulose based
battery, Li anode became black according to the digital photo, which is
caused by the diffusion of active cathodes.[27] As regards the
CaCO3-modified battery, Li anode can retain the original
appearance even after 230 cycles. Besides, the morphologies were
observed by SEM, and corresponding results are supplied inFigure 6b . Notably, the Li structure of cellulose based battery
is broken, while the CaCO3 modified battery is complete.
Furthermore, the electrolyte/electrode interface is damaged by HF
generated by electrolyte decomposition. Conversely, the negative impact
of HF on cellulose/CaCO3-1 based battery can be
eliminated through the neutralization of nano-CaCO3.
With higher thermal and dimensional stability, the battery equipped with
cellulose/CaCO3-1 membrane exhibits high-performance and
great potential application in new energy fields.