Na-ion Batteries. Laure Monconduit

Na-ion Batteries - Laure Monconduit


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gray box highlights the high voltage region, where O is the active redox process. (b) Galvanostatic charge/discharge curves in 3.0–4.7 V versus Na/Na+ at a rate of C/20. The inset shows a cyclic voltammetry curve at the second cycle at a scan rate of 0.1 mV s−1. Reprinted with permission from Mortemard de Boisse et al. (2018). Copyright 2018, Wiley-VCH. For a color version of this figure, see www.iste.co.uk/monconduit/batteries.zip

      1.3.1.4. O3-NaFeO2

      1.3.1.5. O3-NaCoO2

      Electrochemical properties of O3-NaCoO2 in Na cells were first reported by Braconnier et al. in 1980 (Braconnier et al. 1980) at almost the same time when those of O3-LiCoO2 in Li cells were first reported by (Mizushima et al. 1980). O3-NaCoO2 delivers a reversible capacity of ca. 140 mAh g−1 in the voltage range of 2.5–4.0 V (Figure 1.8) (Yoshida et al. 2013; Lei et al. 2014). As discussed above on O’3-NaMnO2, O3-NaCoO2 represents a stepwise voltage profile that is attributed to multiple phase transitions associated with CoO2-slab gliding and in-plane Na+/vacancy ordering in the interslab spacing as described in section 1.2.2.

      1.3.1.6. O’3-NaNiO2

      Electrochemical properties and phase transitions of O’3-NaNiO2 in Na cells were first reported by Braconnier et al. in 1982 (Braconnier et al. 1982) and re-investigated by Vassilaras et al. in 2013 (Vassilaras et al. 2013). O’3-NaNiO2 delivers a reversible capacity of ca. 100 mAh g−1 with stepwise voltage profile in the voltage range of 1.25–3.75 V (Figure 1.8). Detailed phase transitions during charge-discharge were reported by Han et al. (2014) and Wang et al. (2017a) with operando XRD measurements. The results revealed that O’3-NaNiO2 transforms into at least six phases of O’3 and P’3 during a charging process. Both the authors found that no original O’3 phase was observed on the discharging process and the irreversible phase transition was thought to cause capacity degradation during charge–discharge cycles. Unlike Ti, V, Cr, Mn and Fe, but like Co system, O’3-NaNiO2 delivers a large discharge capacity of ca. 130 mAh g−1 even after charging to the high voltage of 4.5 V versus Na (Vassilaras et al. 2013; Wang et al. 2017a). Wang et al. revealed from in situ synchrotron XRD that the Na-extracted phase of Na0.17NiO2 is irreversibly formed upon charging to 4.5 V and is partly remained in the core of the particles even after discharging to 2.0 V versus Na. Migration of nickel ions into interslab space was often observed for O3-LiNiO2 at the end of charging to 4.45 V versus Li (Croguennec et al. 2001). However, Li et al. mentioned no migration of nickel ions for O’3-NaNiO2 after charging to 4.5 V versus

      These fundamental studies are very helpful to understand the electrochemical properties of the complicated multiple transition metal systems. Transition metals usually dominate redox potential and phase transitions of O3-type layered materials. However, those of multiple 3d transition metal systems are not simple and are influenced by difference in oxygen orbital contribution to the redox reaction (Nanba et al. 2016). Not only nominal valence of transition metals but also hybridization between oxygen 2p and transition metal 3d orbitals plays a critical role in determining the redox potential of layered transition metal oxides in Na batteries. Redox potential and electrochemical activity of nickel ions vary on the other transition metal elements in NaMO2 (Nanba et al. 2016). Selection of the transition metals is, therefore, important to synthesize ternary and quaternary 3d transition metal systems exhibiting excellent electrochemical performance.

      1.3.2. O3-Na[M,M’]O2 (M, M’ = transition metals)

      Cobalt-containing sodium layered oxides often exhibit good rate performance in Na cells. However, the less abundant elemental resources do not meet the demand for Na-ion batteries, and iron and/or manganese-based oxides have been extensively studied as positive electrode materials for Na-ion batteries in the past decade (Yabuuchi and Komaba 2014).

      1.3.2.1. O3-Na[Fe,M]O2


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