Negative Electrodes For Na-ion Batteries Research Articles

Negative electrodes for Na-ion batteries.

Research interest in Na-ion batteries has increased rapidly because of the environmental friendliness of sodium compared to lithium. Throughout this Perspective paper, we report and review recent scientific advances in the field of negative electrode materials used for Na-ion batteries. This paper sheds light on negative electrode materials for Na-ion batteries: carbonaceous materials, oxides/phosphates (as sodium insertion materials), sodium alloy/compounds and so on. These electrode materials have different reaction mechanisms for electrochemical sodiation/desodiation processes. Moreover, not only sodiation-active materials but also binders, current collectors, electrolytes and electrode/electrolyte interphase and its stabilization are essential for long cycle life Na-ion batteries. This paper also addresses the prospect of Na-ion batteries as low-cost and long-life batteries with relatively high-energy density as their potential competitive edge over the commercialized Li-ion batteries.

Elastic softening of alloy negative electrodes for Na-ion batteries

Accurate description of the mechanical behavior of crystalline Na alloys is essential in establishing their electrochemical performance as well as their viability as anodes in Na-ion batteries. Using first principles simulations, we have investigated the intrinsic elastic properties of crystalline Na–M (M = Sn, Pb, Si and Ge) phases observed during Na intercalation. We have obtained the complete set of concentration-dependent anisotropic elastic constants as well as the average macroscopic elastic moduli of polycrystalline structures. We find that sodiation of pure M phases leads to a remarkable elastic softening that results in up to 75% deterioration of the elastic moduli. Our analysis of the electronic charge distribution demonstrates that the elastic softening during sodiation originates from a transition to weaker ionic interatomic bonding. Our results highlight the significance of the concentration dependence of the elastic moduli for the analysis of deformation behavior of Na alloy anodes of Na-ion batteries during sodiation and desodiation.

High Capacity Negative Electrodes for Na-Ion Batteries: Insertion Mechanism and SEI Layer

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Redox reaction of Sn-polyacrylate electrodes in aprotic Na cell

Sn powder electrodes with polyacrylate binder are examined in aprotic Na cells. The Sn electrodes demonstrate electrochemical redox reaction to reversibly form Sn-Na intermetallic phases, such as Na15Sn4 in the voltage region between 0.0 and 0.7V vs. Na whereas Si, Ge, and Pb electrodes show less or no specific capacity in Na cells. The reversibility of the Sn electrodes is improved by polyacrylate as a binder and restriction of potential range between 0.0 and 0.8V. When fluoroethylene carbonate is added to propylene carbonate solution containing NaClO4, the Sn electrode performance with polyacrylate is further improved. The Sn electrode delivers ca. 500mAh g−1 for more than 20cycles, which is about two times larger reversible capacity compared with a hard-carbon negative electrode for Na-ion batteries.