Study of Transport Properties and Interfacial Kinetics of Na_2/3[Ni_1/3Mn_xTi_2/3-x]O₂(x = 0,1/3) as Electrodes for Na-Ion Batteries

Abstract

(NMT) layered oxide materials, using three techniques: DC conductivity measurement, potentiostatic intermittent titration technique, and impedance spectroscopy. The measured electronic conductivity (NT: 3.96 × 10 −8 S/cm, NMT: 1.21 × 10 −7 S/cm at 110 • C) was orders of magnitude lower than the ionic conductivity (NT: 4.89 × 10 −3 S/cm, NMT: 8.28 × 10 −3 S/cm at 110 • C) in both materials. Manganese addition improved the charge carrier transport properties by a factor of 2-3. The potential-dependent diffusion coefficients of both materials were in the order of 10 −14 -10 −12 cm 2 /s. The charge transfer resistance was also found to have a strong potential dependency and the interfacial kinetics of NMT were considerably faster than NT. Due to its faster ionic/electronic transport in the pristine/intercalated states and faster interfacial kinetics, NMT was found to exhibit better rate performance than NT. Further performance improvements need to focus on boasting the intrinsic electronic conductivity of these materials. High-performance electrochemical energy storage devices are required for increasing the adoption of intermittent renewable energy supplies, stabilizing the existing electricity grid and enabling smart grid systems, designing portable electronics devices that can last longer, and building extended-range electric/hybrid automobiles. Lithium ion batteries, with their high energy density and cycle life, have been the workhorse for electronic devices. However, they may not be suitable for large-scale applications, such as stationary energy storage, in the light of ongoing debate about geographically constrained resources.1 This has driven researchers into exploring new technologies and Na-ion battery is considered as an attractive alternative chemistry.2-8 Besides being based on earth-abundant resources, this intercalation chemistry can achieve relatively high cell voltage (due to the high electropositive character of sodium) which is essential to realize high energy density.The large size of sodium ions results in the formation of layered oxide materials, i.e. Na x MO 2 , with prismatic sites (P-type) in addition to the octahedral sites (O-type) that are typically seen in Li x MO 2 materials, depending on the overall sodium content/stoichiometry ('x'). Prismatic sites are particularly favorable in sodium deficient compounds. exhibits a solid solution domain when cycled below 4.1 V with stable capacity values of 82 mAh/g at C/5 rate. 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'<0.4. The interlayer prismatic sites in the OP4 phase acts as a buffer zon...

Preparation of intergrown P/O-type biphasic layered oxides as high-performance cathodes for sodium ion batteries

“…These attempts can be categorized into two approaches. 5,[23][24][25][26][27][28] The rst approach makes use of electrochemically inert transition metal (TM) ion doping that appears to be a good strategy to stabilize the structure of the layered oxide. During the sodiation-desodiation process, the valence states of the electrochemically active TM ions change in order to enable charge balance.…”

Commercial Prospects of Existing Cathode Materials for Sodium Ion Storage

“…Moreover, the current anode candidates can deliver more than 200 mA h g −1 capacity, and most of them can show stable cycle life more than 200 cycles through various strategies of structural modification and nanotechnology. Reported cathode materials candidates can be divided into four classes: transition metal (M) oxides (Na x MO 2+y ), phosphates, fluorides, and hexacyanoferrates . Few cathode materials, however, have both high capacity (>100 mA h g −1 ) and long cycle life (capacity retention of 90% over 100 cycles).…”

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

“…P2 type Na 0.74 CoO 2 structural and electrochemical performance has been reported and the discharge capacity of 107 mAh/g was obtained at C/10 rate in the voltage window of 2.2‐3.8 V . P2 type Na 2/3 Ni 2/3 Mn 2/3 O 2 and Na 2/3 Ni 2/3 Mn 1/3 Ti 1/3 O 2 phases were stable during cycling with delivered discharge capacity of 80 mAh/g at C/5 rate in the voltage range between 2.0 and 4.2 V ,. The phase transition from P2 to O2 occurs at above cutoff voltage through gliding mechanism of transition metal layers.…”