Study on the Reversible Electrode Reaction of Na_1–xNi_0.5Mn_0.5O₂ for a Rechargeable Sodium-Ion Battery

Abstract

Layered NaNi(0.5)Mn(0.5)O(2) (space group: R ̅3m), having an O3-type (α-NaFeO(2) type) structure according to the Delmas' notation, is prepared by a solid-state method. The electrochemical reactivity of NaNi(0.5)Mn(0.5)O(2) is examined in an aprotic sodium cell at room temperature. The NaNi(0.5)Mn(0.5)O(2) electrodes can deliver ca. 105-125 mAh g(-1) at rates of 240-4.8 mA g(-1) in the voltage range of 2.2-3.8 V and show 75% of the initial reversible capacity after 50 charge/discharge cycling tests. In the voltage range of 2.2-4.5 V, a higher reversible capacity of 185 mAh g(-1) is achieved; however, its reversibility is insufficient because of the significant expansion of interslab space by charging to 4.5 V versus sodium. The reversbility is improved by adding fluoroethylene carbonate into the electrolyte solution. The structural transition mechanism of Na(1-x)Ni(0.5)Mn(0.5)O(2) is also examined by an ex situ X-ray diffraction method combined with X-ray absorption spectroscopy (XAS). The staking sequence of the [Ni(0.5)Mn(0.5)]O(2) slabs changes progressively as sodium ions are extracted from the crystal lattice. It is observed that the original O3 phase transforms into the O'3, P3, P'3, and P3" phases during sodium extraction. XAS measurement proves that NaNi(0.5)Mn(0.5)O(2) consists of divalent nickel and tetravalent manganese ions. As sodium ions are extracted from the oxide to form Na(1-x)Ni(0.5)Mn(0.5)O(2), nickel ions are oxidized to the trivalent state, while the manganese ions are electrochemically inactive as the tetravalent state.

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 .…”

A Safer Sodium‐Ion Battery Based on Nonflammable Organic Phosphate Electrolyte

“…Similar to their Li counterparts,1 though sodium‐based system has similar electrochemical reaction characteristics compared to lithium‐based one, the larger ionic radius for sodium ion cause sluggish kinetics and volume change during Na storage, leading to lower capacity, poor cycling and rate properties of the Na storage materials. Recently, major efforts have been devoted to promote the electrochemical performance of Na storage materials, for example, Na x MO 2 ,2, 3, 4, 5, 6, 7, 8, 9, 10 polyanionic framework compounds,11, 12, 13, 14, 15, 16, 17, 18, 19 hexacyanoferrate,20, 21, 22, 23, 24, 25, 26, 27 for the cathode materials, and hard carbons,28, 29, 30, 31, 32, 33 alloys,34, 35, 36, 37, 38, 39, 40, 41 oxides,42, 43 sulfides37, 44, 45, 46 for the anode materials.…”

Radially aligned hierarchical columnar structure as a cathode material for high energy density sodium-ion batteries

“…Recently, several types of insertion materials have been introduced as cathode materials for sodium-ion batteries (SIBs) including P2-types [9][10][11][12][13][14][15][16] , O3-types [17][18][19][20][21][22][23][24][25][26][27][28][29] , pyrophosphates [30][31][32] and organo-compounds [33][34][35] . Owing to the large ionic size of Na þ ions (1.02 Å), their insertion into a spinel framework does not readily occur.…”

“…In contrast, two-dimensional layer structures do favour the insertion of Na þ ions into their structures. Among these, P2-(refs 9-16) and O3-types [17][18][19][20][21][22][23][24][25][26][27][28][29] , which are classified by their sequence of oxygen stacking, are of interest because of their large reversible capacities. For layer-structured compounds, the P2-type usually stabilizes into Na-deficient compositions such as Na 2/3 MO 2 (M: Ni, Co, Mn, Fe and so on).…”