Nam-Soon Choi

An amorphous red phosphorus/carbon composite as a promising anode material for sodium ion batteries.

An amorphous red phosphorus/carbon composite is obtained through a facile and simple ball milling process, and its electrochemical performance as an anode material for Na ion batteries is evaluated. The composite shows excellent electrochemical performance including a high specific capacity of 1890 mA h g(-1), negligible capacity fading over 30 cycles, an ideal redox potential (0.4 V vs. Na/Na(+)), and an excellent rate performance, thus making it a promising candidate for Na ion batteries.

Charge carriers in rechargeable batteries: Na ions vs. Li ions

We discuss the similarities and dissimilarities of sodium- and lithium-ion batteries in terms of negative and positive electrodes. Compared to the comprehensive body of work on lithium-ion batteries, research on sodium-ion batteries is still at the germination stage. Since both sodium and lithium are alkali metals, they share similar chemical properties including ionicity, electronegativity and electrochemical reactivity. They accordingly have comparable synthetic protocols and electrochemical performances, which indicates that sodium-ion batteries can be successfully developed based on previously applied approaches or methods in the lithium counterpart. The electrode materials in Li-ion batteries provide the best library for research on Na-ion batteries because many Na-ion insertion hosts have their roots in Li-ion insertion hosts. However, the larger size and different bonding characteristics of sodium ions influence the thermodynamic and/or kinetic properties of sodium-ion batteries, which leads to unexpected behaviour in electrochemical performance and reaction mechanism, compared to lithium-ion batteries. This perspective provides a comparative overview of the major developments in the area of positive and negative electrode materials in both Li-ion and Na-ion batteries in the past decade. Highlighted are concepts in solid state chemistry and electrochemistry that have provided new opportunities for tailored design that can be extended to many different electrode materials for sodium-ion batteries.

Sodium Terephthalate as an Organic Anode Material for Sodium Ion Batteries

Disodium terephthalate and its various derivatives are synthesized via simple acid-base chemistry for anode materials in Na ion batteries. They show excellent electrochemical performance, including little capacity fading over 90 cycles, ideal redox potential, and excellent rate performance, making them promising candidates for Na ion batteries.

Tin Phosphide as a Promising Anode Material for Na‐Ion Batteries

Sn4 P3 is introduced for the first time as an anode material for Na-ion batteries. Sn4 P3 delivers a high reversible capacity of 718 mA h g(-1), and shows very stable cycle performance with negligible capa-city fading over 100 cycles, which is attributed to the confinement effect of Sn nanocrystallites in the amorphous phosphorus matrix during cycling.

One dimensional Si/Sn - based nanowires and nanotubes for lithium-ion energy storage materials

There has been tremendous interest in using nanomaterials for advanced Li-ion battery electrodes, particularly to increase the energy density by using high specific capacity materials. Recently, it was demonstrated that one dimensional (1D) Si/Sn nanowires (NWs) and nanotubes (NTs) have great potential to achieve high energy density as well as long cycle life for the next generation of advanced energy storage applications. In this feature article, we review recent progress on Si-based NWs and NTs as high capacity anode materials. Fundamental understanding and future challenges on one dimensional nanostructured anode are also discussed.

Magnesium(II) Bis(trifluoromethane sulfonyl) Imide-Based Electrolytes with Wide Electrochemical Windows for Rechargeable Magnesium Batteries

We present a promising electrolyte candidate, Mg(TFSI)2 dissolved in glyme/diglyme, for future design of advanced magnesium (Mg) batteries. This electrolyte shows high anodic stability on an aluminum current collector and allows Mg stripping at the Mg electrode and Mg deposition on the stainless steel or the copper electrode. It is clearly shown that nondendritic and agglomerated Mg secondary particles composed of ca. 50 nm primary particles alleviating safety concern are formed in glyme/diglyme with 0.3 M Mg(TFSI)2 at a high rate of 1C. Moreover, a Mg(TFSI)2-based electrolyte presents the compatibility toward a Chevrel phase Mo6S8, a radical polymer charged up to a high voltage of 3.4 V versus Mg/Mg(2+) and a carbon-sulfur composite as cathodes.

Recent advances in the electrolytes for interfacial stability of high-voltage cathodes in lithium-ion batteries

Advanced electrolytes with unique functions such as in situ formation of a stable artificial solid electrolyte interphase (SEI) layer on the anode and the cathode, and the improvement in oxidation stability of the electrolyte have recently gained recognition as a promising means for highly reliable lithium-ion batteries with high energy density. In this review, we describe several challenges for the cathode (spinel lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), spinel lithium manganese nickel oxide (LNMO), and lithium-rich layered oxide (Li-rich cathode))-electrolyte interfaces and highlight the recent progress in the use of oxidative additives and high-voltage solvents in high-performance cells.

A multifunctional phosphite-containing electrolyte for 5 V-class LiNi0.5Mn1.5O4 cathodes with superior electrochemical performance

We report a highly promising organophosphorus compound with an organic substituent, tris(trimethylsilyl)phosphite (TMSP), to improve the electrochemical performance of 5 V-class LiNi0.5Mn1.5O4 cathode materials. Our investigation reveals that TMSP alleviates the decomposition of LiPF6 by hydrolysis, effectively eliminates HF promoting Mn/Ni dissolution from the cathode, and forms a protective layer on the cathode surface against severe electrolyte decomposition at high voltages. Remarkable improvements in the cycling stability and rate capability of high voltage cathodes were achieved in the TMSP-containing electrolyte. After 100 cycles at 60 °C, the discharge capacity retention was 73% in the baseline electrolyte, whereas the TMSP-added electrolyte maintained 90% of its initial discharge capacity. In addition, the LiNi0.5Mn1.5O4 cathode with TMSP delivers a superior discharge capacity of 105 mA h g−1 at a high rate of 3 C and an excellent capacity retention of 81% with a high coulombic efficiency of over 99.6% is exhibited for a graphite/LiNi0.5Mn1.5O4 full cell after 100 cycles at 30 °C.

Highly stable Si-based multicomponent anodes for practical use in lithium-ion batteries

We demonstrate a simple process to synthesize silicon-based multicomponents via a high-temperature annealing of bulk silicon monoxide in the presence of sodium hydroxide. The carbon-coated Si-based anodes exhibit a highly stable cycling performance (capacity retention of 99.5% after 200 cycles) with a reversible charge capacity of 1280 mA h g−1.

New polymer electrolytes based on PVC/PMMA blend for plastic lithium-ion batteries

Abstract The electrochemical properties of the polymer electrolytes based on poly(vinyl chloride)/poly(methyl methacrylate) blend with micro-pore structure have been investigated. The introduction of poly(methyl methacrylate) (PMMA) into the poly(vinyl chloride) (PVC) matrix enhanced compatibility between the polymer matrix and the liquid electrolyte (EC/DMC/LiClO4). The addition of silica into the polymer blend generated a micro-pore structure in the polymer matrix and increased the uptake amount of the liquid electrolyte. The ion conductivity of the polymer electrolyte was increased with the increase in the PMMA content in the blend and the room temperature ion conductivity of the polymer electrolyte based on PVC/PMMA (5:5, w/w) blend was 1.1×10−3 S/cm. The charge–discharge behavior of the unit cell was also investigated.