2.1. Na-ion Batteries (NIBs)
Na-based batteries are not new. Back to the 1970s, Na-ion and Li-ion batteries were investigated in parallel.5,6 The investigation of Na-ion batteries significantly decreased after the success of commercial application of Li-ion batteries in the 1990s. Na-ion batteries have a very similar working principle as the Li-ion batteries. As shown in Figure 2.1, each electrochemical cell is basically composed of a positive electrode, a negative electrode, and a membrane separator between the two electrodes. Both electrodes and the separator are immersed in the electrolyte. Each of the two electrodes has active materials on the current collectors. In the Na-ion batteries, the active materials allow Na-ions to be inserted …show more content…
As the demands for and sizes of batteries have increased, the interest in NIBs has resurged particularly for grid-scale ESSs. As shown in Figure 2.2, a remarkable number of new materials have been introduced and evaluated as electrode materials for NIBs in the last few years. Similar to LIB chemistry, layered and polyanionic compounds have been extensively investigated as cathode materials, and carbon based materials, metal oxide compounds, and metals have been studied as anode materials (see Figure 2.2 (b),(c)). Prussian blue and organic materials have also been recently examined as electrode materials for NIBs. As displayed in …show more content…
Sodium insertion into NASICON-type NaTi2(PO4)3 at 2.1 V was reported by Park et al. to undergo a two-phase mechanism.11 The observed capacities for NaTi2(PO4)3 in both non-aqueous and aqueous electrolytes correspond to over 90% of the theoretical capacity of 133 mAhg-1. The polarization observed in the aqueous electrolyte on cycling was substantially smaller as a result of its lower impedance and viscosity. The Na-ion insertion/extraction potential is located at the lower limit of the electrochemical stability window of the aqueous Na2SO4 electrolyte, which makes NaTi2(PO4)3 an attractive negative electrode for aqueous sodium ion batteries.12 Another material, Na2Ti3O7 exhibits a particularly low desirable potential.13 The insertion of two additional sodium atoms (177 mAhg-1) occurs at a reversible plateau around 0.3 V versus Na/Na+, however, to achieve this capacity, a slow cycling rate (C/25) and a composite electrode with 30% super P carbon black are necessary. The large amount of carbon additive decreases the energy density and causes large irreversible capacity, which is of the same order of magnitude as the reversible capacity observed at the first
Na-based batteries are not new. Back to the 1970s, Na-ion and Li-ion batteries were investigated in parallel.5,6 The investigation of Na-ion batteries significantly decreased after the success of commercial application of Li-ion batteries in the 1990s. Na-ion batteries have a very similar working principle as the Li-ion batteries. As shown in Figure 2.1, each electrochemical cell is basically composed of a positive electrode, a negative electrode, and a membrane separator between the two electrodes. Both electrodes and the separator are immersed in the electrolyte. Each of the two electrodes has active materials on the current collectors. In the Na-ion batteries, the active materials allow Na-ions to be inserted …show more content…
As the demands for and sizes of batteries have increased, the interest in NIBs has resurged particularly for grid-scale ESSs. As shown in Figure 2.2, a remarkable number of new materials have been introduced and evaluated as electrode materials for NIBs in the last few years. Similar to LIB chemistry, layered and polyanionic compounds have been extensively investigated as cathode materials, and carbon based materials, metal oxide compounds, and metals have been studied as anode materials (see Figure 2.2 (b),(c)). Prussian blue and organic materials have also been recently examined as electrode materials for NIBs. As displayed in …show more content…
Sodium insertion into NASICON-type NaTi2(PO4)3 at 2.1 V was reported by Park et al. to undergo a two-phase mechanism.11 The observed capacities for NaTi2(PO4)3 in both non-aqueous and aqueous electrolytes correspond to over 90% of the theoretical capacity of 133 mAhg-1. The polarization observed in the aqueous electrolyte on cycling was substantially smaller as a result of its lower impedance and viscosity. The Na-ion insertion/extraction potential is located at the lower limit of the electrochemical stability window of the aqueous Na2SO4 electrolyte, which makes NaTi2(PO4)3 an attractive negative electrode for aqueous sodium ion batteries.12 Another material, Na2Ti3O7 exhibits a particularly low desirable potential.13 The insertion of two additional sodium atoms (177 mAhg-1) occurs at a reversible plateau around 0.3 V versus Na/Na+, however, to achieve this capacity, a slow cycling rate (C/25) and a composite electrode with 30% super P carbon black are necessary. The large amount of carbon additive decreases the energy density and causes large irreversible capacity, which is of the same order of magnitude as the reversible capacity observed at the first