Enabling Sodium Batteries Using Lithium‐Substituted Sodium Layered Transition Metal Oxide Cathodes

Abstract

Ambient temperature sodium batteries have the potential to meet growing worldwide demand for electrical energy storage, due in part to sodium's widespread availability and low cost. In moving towards this scenario however, new advanced energy materials are required to enable the technology. In this study, a class of layered oxide materials has been discovered, synthesized, and evaluated as cathodes in rechargeable sodium batteries. Specifi cally, a series of layered Na x Li y Ni 0.25 Mn 0.75 O δ oxides within the range 0.7 ≤ x ≤ 1.2; 0 < y ≤ 0.5 were found to reversibly intercalate sodium at high rates, with negligible structural change. For example, Na 1.0 Li 0.2 Ni 0.25 Mn 0.75 O δ possesses well-ordered layers with hexagonal close-packed oxygen stacking. The transition metal layer contains Li, Ni(II) and Mn(IV) in octahedral coordination. The adjacent layer contains only Na in trigonal prismatic coordination, thus negating the cation disorder commonly observed in lithium-only containing materials. The well ordered metal sites remain intact during cycling and less than 1% crystallographic volume change in the structure is observed during cycling. The average voltage of the sodium cell is 3.4 V exhibiting a stable capacity over 50 cycles with about 95 -100 mAhg − 1 . The electroactivity and structural stability of Na 1.0 Li 0.2 Ni 0.25 Mn 0.75 O δ as a new sodium cathode material should hasten the development of ambient temperature sodium batteries for energy storage applications.Non-aqueous electrolyte ambient temperature sodium batteries have many of the basic qualities associated with lithium batteries. Intercalation reactions, material structural and chemical stability, electronic/ionic conductivity, and the electrode/electrolyte interfacial chemistry all play a pivotal role in battery operation. While the voltage of Na/Na + is only ∼ 300 mV less positive than Li/Li + , sodium's molecular weight of ∼ 23 gmol − 1 is much higher than that of Li ( ∼ 7 gmol − 1 ) which lowers the energy density of the material. To overcome this defi ciency, high-performance cathode and anode materials which are easy to synthesize, safe, non-toxic and low-cost are necessary. Such materials must also have appreciable electrochemical performance characteristics to forward their implementation. Examples in the literature of sodium-ion cathode materials include sodium vanadium phosphate fl uoride type materials (NaVPO 4 F) in sodium-ion cells, [ 1 ] lithium sodium vanadium phosphate fl uoride [ 2 ] (which used a mixed lithium and sodium containing electrolyte), and Na 2 MPO 4 F (M = Fe, Mn).[ 3 ] A Na battery study using NaCrO 2 was recently reported.[ 4 ] However, from a practical and environmental standpoint, NaCrO 2 is diffi cult to handle, and chromium is considered toxic. A recent study by Lu and Dahn demonstrated that the P2-layered oxide Na 2/3 [Ni 1/3 Mn 2/3 ]O 2 could reversibly exchange Na in sodium cells, [ 5 ] but these materials were hard to synthesize as annealing temperatures as high as 900 ° C were combined with liqui...

A zero-strain layered metal oxide as the negative electrode for long-life sodium-ion batteries

“…Recently, several layered Na x MO 2 (M: 3d transition metals, TMs) compounds have been proposed as positive electrode materials for sodium-ion batteries [42][43][44][45][46][47][48][49][50][51][52] . It has also been demonstrated that P2-type materials show better storage performance than that of O3-type materials (Note that the notations of P2 and O3 were defined by Delmas et al 53 , they refer to different ways of the stacking of the oxygen layer, for example, ABBA for P2, ABCABC for O3 and so on) 46 .…”

Anionic redox chemistry in Na-rich Na 2 Ru 1−y Sn y O 3 positive electrode material for Na-ion batteries

“…However, performances of Na-based materials are hindered by the relatively higher atomic weight of Na and its larger atomic radius which limits the variety of materials where sodium can be reversibly extracted and inserted. Most research efforts have been focused on layered Na x MO 2 [1,2] or NASICON [3] type structure that mimic Li-ion batteries positive electrode materials. Recently alkali-rich materials Li 2 MO 3 have shown promising properties [4][5][6][7][8] as their experimental capacities exceed the theoretical value calculated according to the oxidation of the metallic species [6,8].…”

High‐Performance Sodium‐Ion Batteries and Sodium‐Ion Pseudocapacitors Based on MoS2/Graphene Composites

“…These features point to the great potential of sodium-ion batteries for renewable energy and smart grids. [3,4] To date, various cathode materials, including layered transition metal oxides, [5][6][7][8] organic polymers, [3,9,10] and polyanion fluorophosphates, [11][12][13][14][15] have been reported to reversibly accommodate Na ions. Anode research is mainly focused on carbonaceous material, [16][17][18] alloyable metals, [19] alloyable metal oxides/sulfides [20][21][22][23] and non-metal elements.…”