Simultaneous Component Ratio and Particle Size Optimization for High‐Performance and High Tap Density P2/P3 Composite Cathode of Sodium‐Ion Batteries

Abstract

The composite structure materials in sodium-ion batteries (SIBs) have received increasing attentions due to the synergistic effect. P2/P3 composite cathode with the advantages of high reversible capacity and superior reaction kinetics was regarded as one of the promising cathodes for SIBs. Crystal phase component ratio and particle morphology of hybrid structures are closely related with the electrochemical performance, especially the energy density. Herein, P2/P3 hybrid structure materials Na 0.6 Mn 1-x Ni x O 2 were synthesized by co-precipitation method. Furthermore, the component ratio and particle size are tuned and realized via simple Ni 2 + content optimization. The targeted sample Na 0.6 Mn 0.75 Ni 0.25 O 2 shows high tap density over 1.2 g cm À 3 and excellent electrical properties with an initial capacity of 101.36 mA h g À 1 at 0.2 C, corresponding to a high volumetric energy density of 512 Wh L À 1 based on the cathode active material. Moreover, the long-term cycling capacity retention can reach 68 % at 1 C after 500 cycles. The present study develops a promising cathode of SIBs that maybe applied in low-speed electric vehicles. And the simultaneous optimization design represents a potential route for the regulation of composite structures to obtain high performance SIBs.

Tailoring P2/P3 Biphases of Layered NaxMnO2 by Co Substitution for High‐Performance Sodium‐Ion Battery

“…Recently, engineering P2/P3 biphases in layered oxides has been reported as an effective strategy for improving the electrochemical performance due to the synergistic effect between phases. [ 12,16–23 ] For example, Guo and co‐workers [ 16 ] demonstrated that the crystalline structure of P2/P3–Na 0.7 Li 0.06 Mg 0.06 Ni 0.22 Mn 0.67 O 2 cathode combines the respective advantages of P2 and P3 phases, and thus exhibits enhanced long‐term cycling performance over 100 cycles and rate capability (≈102 mA h g −1 at 5 C) compared with the pure P2 or P3 phase. Ionic substitution is a feasible method to manipulate the phase composition of Na x MnO 2 layered oxides.…”

“…The superior rate performance of MCA‐3 outperforms state‐of‐the‐art Na x TMO 2 materials with details being summarized in Figure 3d. [ 12,21,31,39–42 ] As shown in Figure S9a (Supporting Information), the MCA‐4 electrode exhibits unsatisfactory rate performance (50 mA h g −1 at 1700 mA g −1 ). The poor rate capability of the MCA‐4 cathode causes by excess Co substitution, which is similar to Na 0.67 Ni 0.33 Mn 0.62 Sn 0.05 O 2 cathode with 94.3% P3 phase but exhibits the worst rate performance than other cathodes with less Sn addition.…”

“…The details are summarized in Table S4 (Supporting Information). [ 12,16,18,20–22,42–44 ] Specific capacities of the MCA samples decrease with increasing P3 content accompanied by improving of cycling stability. However, the P3 cathode (MCA‐4) shows poor electrochemical performance.…”

“…Moreover, the 16.8% P3 phase in the MCA‐2 cathode cannot exert the advantage of synergistic effect, leading to a poor electrochemical property, which is similar to the scenario of the Na 0.6 Mn 0.85 Ni 0.15 O 2 cathode with the 18% P3 phase that exhibits poor electrochemical performance. [ 21 ] To evaluate its practicability when applied to sodium‐ion full batteries, the MCA‐3 cathode was assembled with the hard carbon anode. Hard carbon was precycled to reach a stable platform before assembling the full cell (Figure S12a, Supporting Information).…”

Dual‐Role Surface Modification of Layered Oxide Cathodes for High‐Power Sodium‐Ion Batteries

“…Compared with other P2-type layered oxides reported previously, 0.1 K-NaMCN also exhibits superior high-rate performance (Table S3). [8,9,22] Charge-discharge profiles at different rates of the NaMCN and 0.1 K-NaMCN electrodes are showed in Figure 5e and 5 f, obviously, the NaMCN electrode exhibits a much higher polarization and the voltage plateaus vanish gradually as the rate increases, reflecting a diffusion-limited process at high rates. In comparison, no obvious change in the shape of the curves and severe polarization can be observed in the 0.1 K-NaMCN electrode even at a high rate of 5 C, indicating the favorable Na + diffusion kinetics.…”