An advanced cathode for Na-ion batteries with high rate and excellent structural stability

Abstract

Layered P2-Na(x)[Ni(1/3)Mn(2/3)]O(2) (0 < x < 2/3) is investigated as a cathode material for Na-ion batteries. A combination of first principles computation, electrochemical and synchrotron characterizations is conducted to elucidate the working mechanism for the improved electrochemical properties. The reversible phase transformation from P2 to O2 is observed. New configurations of Na-ions and vacancy are found at x = 1/3 and 1/2, which correspond to the intermediate phases upon the electrochemical cycling process. The mobility of Na-ions is investigated using the galvanostatic intermittent titration technique (GITT) and the Na diffusion barriers are calculated by the Nudged Elastic Band (NEB) method. Both techniques prove that the mobility of Na-ions is faster than Li-ions in the O3 structure within the 1/3 < x < 2/3 concentration region. Excellent cycling properties and high rate capability can be obtained by limiting the oxygen framework shift during P2-O2 phase transformation, suggesting that this material can be a strong candidate as a sustainable low-cost Na-ion battery cathode.

High-capacity antimony sulphide nanoparticle-decorated graphene composite as anode for sodium-ion batteries

“…Figure 6a shows the charge-discharge profiles of the Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode. A reversible capacity for the cathode of 75mAh g À 1 is obtained between 2.7 and 4.0 versus Na/Na þ , which is consistent with those results from the literature 26,27 . A full cell with a theoretical capacity of 210 mAh was constructed using rGO/Sb 2 S 3 anode and Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode.…”

The NaxMoO2 Phase Diagram (1/2 ≤ x < 1): An Electrochemical Devil’s Staircase

“…The multi-step nature of the corresponding electrochemical curve, presented in Figure 3a, suggest numerous structural transitions in agreement with the observations reported in the literature 24 . In most of the other NaxMO2 systems (M = Co, V, Cr, Ni...) reported in the literature 6,9,10,[33][34][35][36] , the most important voltage drops occur for the Na1/2MO2 and Na2/3MoO2 compositions which are energetically favorable for sodium/vacancy ordering. The initial sodium content in the starting material NaxMoO2 is therefore reevaluated by fitting the 2.5 V and 1.5 V voltage drops at x= 1/2 and 2/3, respectively.…”

Study of Transport Properties and Interfacial Kinetics of Na2/3[Ni1/3MnxTi2/3-x]O2(x = 0,1/3) as Electrodes for Na-Ion Batteries

“…have been shown to exhibit reversible sodium intercalation/de-intercalation while going through multiple monophasic and biphasic regions. Our research interest is on characterizing P-type materials as they have lower activation energy for sodium hopping 12,13 and undergo very little volume change upon sodium exchange. 14,15 The voltage-composition curve of P2-Na x CoO 2 reveals multiple phase transitions as demonstrated by a series of voltage steps and plateaus.…”

“…However, at higher voltages ('x'<1/3), it has a drastic fade mechanism which is linked to the P2-O2 phase transition caused by the gliding of the transition metal layers. 13,19 P2-Na x [Fe 1/2 Mn 1/2 ]O 2 utilizes Fe 3+/4+ redox couple and operates between 'x' = 0.67 (pristine) and 'x' = 0.14 (4.2 V) to achieve high capacity value of 190 mAh/g. 10 The P2 phase is stable till 'x' = 0.4 (3.8 V) and an OP4 intergrowth phase (contains both prismatic and octahedral sites in alternating layers) forms for 'x'<0.…”