Abstract
The pore structure of the separator is crucial to the performance of a lithium-battery as it affects the cell resistance. Herein, a straightforward approach to vary the pore structure of Cladophora cellulose (CC) separators is presented. It is demonstrated that the pore size and porosity of the CC separator can be increased merely by decreasing the thickness of the CC separator by using less CC in the manufacturing of the separator. As the pore size and porosity of the CC separator are increased, the mass transport through the separator is increased which decreases the electrolyte resistance in the pores of the separator. This enhances the battery performance, particularly at higher cycling rates, as is demonstrated for LiFePO4/Li half-cells. A specific capacity of around 100 mAh g−1 was hence obtained at a cycling rate of 2 C with a 10 µm thick CC separator while specific capacities of 40 and close to 0 mAh g−1 were obtained for separators with thicknesses of 20 and 40 µm, respectively. As the results also showed that a higher ionic conductivity was obtained for the 10 µm thick CC separator than for the 20 and 40 µm thick CC separators, it is clear that the different pore structure of the separators was an important factor affecting the battery performance in addition to the separator thickness. The present straightforward, yet efficient, strategy for altering the pore structure hence holds significant promise for the manufacturing of separators with improved performance, as well as for fundamental studies of the influence of the properties of the separator on the performance of lithium-ion cells.
Highlights
Due to their predominant role in energy storage systems (Goodenough and Kim 2011; Goodenough and Park 2013; Sobkowiak et al 2013; Tarascon and Armand 2001; Wang et al 2015; Wei et al 2013; Yang and Hou 2012), lithium-ion batteries (LIBs) have been extensively studied during the past decades
The digital images of the cellulose Cladophora cellulose (CC)-25, CC-50 and CC100 separators shown in Fig. 2 demonstrate that the transparency of the separators decreased with increasing thickness
A surprisingly facile paper-making approach has been described for the manufacturing of stratified Cladophora cellulose (CC) separators with different thicknesses and pore structures
Summary
Due to their predominant role in energy storage systems (Goodenough and Kim 2011; Goodenough and Park 2013; Sobkowiak et al 2013; Tarascon and Armand 2001; Wang et al 2015; Wei et al 2013; Yang and Hou 2012), lithium-ion batteries (LIBs) have been extensively studied during the past decades. We describe a straightforward paper-making filtration process by which CC separators with different thicknesses and pore structures can be manufactured merely by varying the amount of cellulose used.
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