Electrodes areal

To facilitate a demonstration of the advantages of the 3-D architecture, we quantitatively compare metrics related to performance (e.g.. areal energy capacity, active surface area) of a conventional 2-D parallel-plate design with the 3-D interdigitated array cell (Figure 3). We assume a thin-film 2-D battery that comprises a 1-cm -area anode and cathode, each 22.5-/thick electrolyte. The total volume of electrodes and separator is 5 x 10 cm (the cell housing is ignored for simplicity, but is expected to be a comparable... 

Clearly L cannot be increased without limit, as the ohmic resistance of the electrodes will become sufficiently large to offset the advantages of increased areal capacity. While this problem has not been treated systematically, it is clear that the optimized value of L will be determined by the electronic... 

Figure 5. An increase in the height of the interdigitated 3-D battery, L, results in increased areal energy capacity and electrode area, without an increase in transport distances.

Table 5.1 Summaiy of capacity values for ntTi02 with about 600 nm length, which are expressed per electrode area to allow better comparison with literature data for thin-film microbatteries. Reversible and irreversible areal capacities and efficiency on cycling of the ntTi02 layers as electrodes in experimental Li test cells (reprinted from Ref. [86], with permission from Elsevier.]...

Table 5.2 Values of the reversible and irreversible areal capacities and efficiency on q cling of the ntTiOj layers used as electrodes in experimental test cells at different kinetics (reprinted with permission from Ref [35], Copyright 2009 American Chemical Society]...

Recently, Zhang et al. [123] have demonstrated a flexible composite membrane of reduced graphene oxide and pol5T)5n role nanowire [rGO-PPy-NWs] via in situ reduction. A S5mimetric supercapacitor has been fabricated by direct coupling of two membrane electrodes, without the use of any binder or conductive additive. The supercapacitor achieved a large areal capacitance [175 mF/cm ] and excellent cycling stability. The in situ reduction of GO in the composite dispersion with PPy-NWs renders the formation of the rGO-PPy composite foam via self-assembly, as shown in Fig. 7.11. 

In order to evaluate the performance of MFC, the maximum current and power output is normalized to unit electrode area or unit of chamber volume, to get areal or volumetric current/power densities. 

Here R [Q] is the electrical resistance, p is the resistivity [Qm], I is the length [m], and A is the effective area where reaction occurs [m ]. R is directly proportiOTial to 7M thus it is fair to normalize the resistance at a given reaction area. Areal resistivity, r, [Q cm ], denotes the normalized internal resistance at unit of electrode area. 

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