P3‐Type Layered Sodium‐Deficient Nickel–Manganese Oxides: A Flexible Structural Matrix for Reversible Sodium and Lithium Intercalation

Abstract

Sodium‐deficient nickel–manganese oxides exhibit a layered structure, which is flexible enough to acquire different layer stacking. The effect of layer stacking on the intercalation properties of P3‐NaxNi0.5Mn0.5O2 (x=0.50, 0.67) and P2‐Na2/3Ni1/3Mn2/3O2, for use as cathodes in sodium‐ and lithium‐ion batteries, is examined. For P3‐Na0.67Ni0.5Mn0.5O2, a large trigonal superstructure with 2√3 a×2√3 a×2 c is observed, whereas for P2‐Na2/3Ni1/3Mn2/3O2 there is a superstructure with reduced lattice parameters. In sodium cells, P3 and P2 phases intercalate sodium reversibly at a well‐expressed voltage plateau. Preservation of the P3‐type structure during sodium intercalation determines improving cycling stability of the P3 phase within an extended potential range, in comparison with that for the P2 phase, for which a P2–O2 phase transformation has been found. Between 2.0 and 4.0 V, P3 and P2 phases display an excellent rate capability. In lithium cells, the P3 phase intercalates lithium, accompanied by a P3–O3 structural transformation. The in situ generated O3 phase, containing lithium and sodium simultaneously, determines the specific voltage profile of P3‐NaxNi0.5Mn0.5O2. The P2 phase does not display any reversible lithium intercalation. The P3 phase demonstrates a higher capacity at lower rates in lithium cells, whereas in sodium cells P3‐NaxNi0.5Mn0.5O2 operates better at higher rates. These findings reveal the unique ability of sodium‐deficient nickel–manganese oxides with a P3‐type structure for application as low‐cost electrode materials in both sodium‐ and lithium‐ion batteries.

Synthesis and Electrochemical Study of New P3 Type Layered Na0.6Ni0.25Mn0.5Co0.25O2 for Sodium‐Ion Batteries

“…P3 phase reveals better cycling performance compared to P2 phase. The discharge capacity of 65 and 100 mAh/g delivered up to 15 cycles for P3 phase at C/30 in the voltage window of 2.0‐4.0 and 2.0‐4.5 V, respectively . The substitution of Co 3+ in Li ion battery layered oxide materials have been shown to increase structural stability and electrochemical performance .…”

“…This discharge capacity is similar to observed in the voltage window 1.5‐4.0 V. The performance is stable with a discharge capacity of 92 mAh/g after 35 cycles. The high capacity and stability of this material at voltage window of 2.0‐4.0 and 2.0‐4.4 V may be due to the presence of Co in the structure compared to without cobalt substituted materials like Na x Ni 0.5 Mn 0.5 O 2 , NaFeO 2 ,. The retention capacity 64 % of 2 nd discharge capacity is obtained with coloumbic efficiency of 98 % up to 35 cycles (Figure c) ,.…”

Electrochemistry and Solid‐State Chemistry of NaMeO2 (Me = 3d Transition Metals)

“…The slow Na diffusion increases resistance. Direct synthesis of P3 type materials instead of O3 type ones might mitigate formation of the phase with the narrow interslab distance at sodiated state . Moreover, binary or more 3d transition‐metal systems are estimated to decrease the diffusion barrier .…”

Lithium versus Mono/Polyvalent Ion Intercalation: Hybrid Metal Ion Systems for Energy Storage

“…Both P3‐ and P2 ‐phases are prone to intercalate sodium reversibly within a wide concentration range. The comparison between P 2‐ and P 3‐phases having the same chemical composition shows that the P 2 phase exhibits a better rate capability and cycling stability ,. Furthermore, the P3 ‐structure is preserved even when high amounts of Na + are extracted, which is in opposite of the established P 2‐ O 2 phase transformation ,.…”