Theoretical and Experimental Studies of ion Transport in Mixed Polyanion Solid Electrolytes

Abstract

Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on ion transport properties is still debated. Here, we focus on Na1+xZr2SixP3-xO12 (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on Na-transport properties. Although there is a large body of data available on this NASICON system, transport properties extracted from experiments or theory vary by orders of magnitude, signifying the need to bridge the gap between different studies. Here, more than 2,000 distinct ab initio-based kinetic Monte Carlo simulations have been used to map the statistically vast compositional space of NASICON over an unprecedented time range and spatial resolution and across a range of temperatures. We performed impedance spectroscopy of samples with varying Na compositions revealing that the highest ionic conductivity (~ 0.1 S cm–1) is achieved in Na3.4Zr2Si2.4P0.6O12, in line with our predictions (~0.2 S cm–1). Our predictions indicate that suitably doped NASICON compositions, especially with high silicon content, can achieve high Na+ mobilities. Our findings are relevant for the optimization of mixed polyanion solid electrolytes and electrodes, including sulfide-based polyanion frameworks, which are known for their superior ionic conductivities.

Exploration of NaSICON Frameworks as Calcium-ion Battery Electrodes

“…Note that calculating the activation barriers for Ca migration (for example, using the DFT-based nudged elastic band method 85 ) are not trivial within the NaSICON framework. Indeed, some of us have recently completed a set of mobility calculations on Ca cathodes, 28 as well as NaSICONs relevant for Na-ion batteries 86 where we had to endure significant convergence difficulties and computational costs in our calculations.…”

Spectroscopic in-depths of upconverting NaZr2(PO4)3 phosphors for LIR-based thermometry

“…The population densities for Er 3+ ions at the 4 Yb . Whereas s Yb stands for the absorption cross-section between Yb 3+ ions at levels 2 F 7/2 and 2 F 5/2 , s ij stands for the absorption cross-section between Er 3+ ions at the ith and jth levels.…”

“…The population densities for Er 3+ ions at the 4 41 denes radiative decay rates of the 4 F 9/2 , 4 S 3/2 , and 2 H 11/2 levels, respectively. Whereas, the radiative decay rate of 2 F 5/2 of the Yb 3+ ion is represented by W ′ Yb .…”

“…[1][2][3] Lithium-ion batteries face several shortcomings, including high cost, limited energy densities, the low abundance of lithium, and low efficient recycling. [3][4][5] Again, in lithium batteries, liquid electrolytes, such as LiClO 4 dissolved in propylene carbonate, are used, which impart several disadvantages, such as device failure due to electrode corrosion, limited operating temperature range, and unsuitable shapes. 6 Thus, it is important to select a solid electrolyte in order to avoid the above-mentioned problems.…”

“…Currently, research is focused on sodium-ion rechargeable batteries, which can operate at room temperature, owing to their low cost, the natural abundance of sodium, and wide geographical distributions. [3][4][5] The sodium superionic conductor (NASICON) compounds with the structure Na[Ge, Ti, Zr] 2 (PO 4 ) 3 are studied by researchers since the early 60s owing to their unique structure for sodium-ion batteries. NASICON materials possess several interesting features, such as high ionic conductivity at room temperature or elevated temperature, high thermal stability, low thermal expansion coefficient, resistance to radiation damage, low solubility in water, large surface area, and capability to accommodate ions.…”