Microwave Assisted Ultra-Fast Method to Synthesize Carbonate-Phosphates, Na3MCO3PO4 (M = Mn, Fe, Co, Ni) - Relevant Materials Applied in Sodium-Ion Batteries

Abstract

Although largely used in mobiles and electric vehicles applications, insertion batteries based on Li-ion technology are high-cost devices. These applications require high-performance energy storage systems with high-energy and high-power densities, which are better attained by Li-ion technology. However, stationary applications such as power plants and uninterruptible power supplies (UPS) mainly require low-cost energy storage devices. In this scenario Na-ion insertion batteries feature as a cheaper option for such applications. Among the several compounds for use as cathode in Na-batteries, a largely studied class of compounds are the sodium-carbonate-phosphates, Na 3 MCO 3 PO 4 (M = Mn, Fe, Co or Ni), with structure analogue to the mineral sidorenkite. In this work, it was developed a new microwave-assisted hydrothermal method as an ultra-fast way to prepare sodium-carbonate-phosphate compounds. This methodology results in high-quality materials with general formula Na 3 MCO 3 PO 4 (M = Mn, Fe, Co or Ni) upon only 5 min processing time. Characterization techniques indicate highly ordered materials with sidorenkite-like phase and different morphologies or crystal habits, including plates, rods, and a 'starfruit' shape. As a proof-of-application the Mn-based material was evaluated from electrochemical tests for Na + insertion reactions. The obtained results evidence initial discharge capacity of 107 mA h g-1 with good reversible capacity (65 mA h g-1) after several charge/discharge cycles.

Grüneisen parameters, bulk modulus, and thermal expansion coefficient of Na3MCO3PO4 (M = Mn, Fe, Co, and Ni) carbonophosphates

“…The samples were prepared as described by Costa et al, 6 and they were obtained from a mixture of precursor salts, such as M(C 2 H 3 O 2 ) 2 · 4H 2 O acetates for Mn, Co, and Ni (Synth) and iron chloride FeCl 2 · 4H 2 O (Sigma‐Aldrich) for iron‐containing samples. Quantities of 0.945 g of Na 2 HPO 4 (Neon) and 6.667 g of Na 2 CO 3 (Synth) were dissolved in 45.0 ml of deionized water.…”

“…Depending on the transition metal, the morphology of the samples goes from small plates to local clusters formation, whose typical particle size is about 500 nm for samples with Mn, Fe, and Co and around 4 μm for the nickel‐containing sample 6 …”

“…The measurements were made with CuKα radiation (lambda = 1.5406 Å) in Bragg–Bretano geometry with 2θ ranging from 8 to 80° and a step of 0.02° (0.6 s/step). The Rietveld Refinement for ambient pressure and room temperature is provided in Figure S2 6 …”

“…Research into sodium-ion electrodes and their synthesis 6,7 has shown very encouraging results in recent years. [8][9][10][11] Polyanionic materials such as carbonophosphates present very efficient molecular channels for Na + ions diffusion compared with other similar materials, allowing for shorter recharge times.…”

Progress on Fe‐Based Polyanionic Oxide Cathodes Materials toward Grid‐Scale Energy Storage for Sodium‐Ion Batteries

“…Although it had a considerable initial charge/discharge capacity of 130 mAh g -1 /107 mAh g -1 , it rapidly degraded to 80-90 mAh g -1 due to the decomposition of Na 3 FePO 4 CO 3 throughout the cyclic process. [186] Xie et al prepared Na 3 Fe-PO 4 CO 3 by a simple mechanical ball milling method and counted that the concentration of Fe 2+ and Fe 3+ was 66% and 34% by Moss-Bauer spectroscopy. Moreover, they confirmed that Fe 4+ formed after charging to 4.5 V and Fe 2+ reduced after discharging to 1.5 V (Figure 10e).…”