A New P2‐Type Layered Oxide Cathode with Extremely High Energy Density for Sodium‐Ion Batteries

Abstract

Herein, a new P2‐type layered oxide is proposed as an outstanding intercalation cathode material for high energy density sodium‐ion batteries (SIBs). On the basis of the stoichiometry of sodium and transition metals, the P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode is synthesized without impurities phase by partially substituting Ni and Fe into the Mn sites. The partial substitution results in a smoothing of the electrochemical charge/discharge profiles and thus greatly improves the battery performance. The P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode delivers an extremely high discharge capacity of 221.5 mAh g−1 with a high average potential of ≈2.9 V (vs Na/Na+) for SIBs. In addition, the fast Na‐ion transport in the P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode structure enables good power capability with an extremely high current density of 2400 mA g−1 (full charge/discharge in 12 min) and long‐term cycling stability with ≈80% capacity retention after 500 cycles at 600 mA g−1. A combination of electrochemical profiles, in operando synchrotron X‐ray diffraction analysis, and first‐principles calculations are used to understand the overall Na storage mechanism of P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2.

Mitigation of Jahn–Teller distortion and Na+/vacancy ordering in a distorted manganese oxide cathode material by Li substitution

“…S7 †. [31][32][33] Notably, at the fully charged states, P In the following discharge of P 0 2-Na x Li 0.05 Mn 0.95 O 2 , the OP4 phase reversibly transforms to the P 0 2 phase, as evidenced by the XRD patterns in Fig. 2b.…”

Shape‐Induced Kinetics Enhancement in Layered P2‐Na0.67Ni0.33Mn0.67O2 Porous Microcuboids Enables High Energy/Power Sodium‐Ion Full Battery

“…are considered as a class of the promising cathode candidates for SIBs due to their high theoretical capacity and facile synthesis process. [17][18][19][20][21] Among these materials, P2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 has recently gained much attention owing to its high operating voltage ascribed to the high redox potential of Ni 2 + /Ni 4 + as well as attracting specific capacity. [22,23] However, the inevitable phase transition process and intrinsically sluggish Na + intercalation kinetics are prone to result in fast capacity decay and inferior rate performance, which severely hinders its practical applications.…”

A Self‐Sodiophilic Carbon Host Promotes the Cyclability of Sodium Anode

“…[ 56 ] In addition, limiting the voltage window to 2.3–4.0 V can further stabilize the cathode materials. [ 57–59 ] As shown in Figure a, the LCNF@Na||NMFT full cell shows good stability up to 390 cycles at 1 C with a 91.2% retention. The same cycling stability can be achieved by the Na foil anode, which maintains 91.0% capacity retention after 390 cycles (Figure 6b and Figure S15a, Supporting Information), indicating the relatively stable bulk structure of NMFT cathode.…”