Effects of fabrication conditions on mechanical properties and microstructure of duplex β''-Al₂O₃ solid electrolyte

Canfield, N.L.,Kim, J.Y.,Bonnett, J.F.,Pearson, R.L.,Sprenkle, V.L.,Jung, K. Elsevier 2015 Materials science and engineering B. Advanced Func Vol.197 No.-

Na-beta batteries are an attractive technology as a large-scale electrical energy storage for grid applications. However, additional improvements in performance and cost are needed for wide market penetration. To improve cell performance by minimizing polarizations, reduction of electrolyte thickness was attempted using a duplex structure consisting of a thin dense electrolyte layer and a porous support layer. In this paper, the effects of sintering conditions, dense electrolyte thickness, and cell orientation on the flexural strength of duplex BASEs fabricated using a vapor phase approach were investigated. It is shown that sintering at temperatures between 1500 and 1550<SUP>o</SUP>C results in fine grained microstructures and the highest flexural strength after conversion. Increasing thickness of the dense electrolyte has a small impact on flexural strength, while the orientation of load such that the dense electrolyte is in tension instead of compression has major effects on strength for samples with a well-sintered dense electrolyte.

A duplex β″-Al₂O₃ solid electrolyte consisting of a thin dense layer and a porous substrate

Kim, Jin Y.,Canfield, Nathan L.,Bonnett, Jeff F.,Sprenkle, Vincent L.,Jung, Keeyoung,Hong, Inchul Elsevier 2015 Solid state ionics Vol.278 No.-

<P><B>Abstract</B></P> <P>To improve the performance of Na-beta batteries at intermediate temperatures (≤200°C) where much improved cyclability and reduced degradation can be achieved, there is a need to lower the resistance/polarization originated from β″-Al<SUB>2</SUB>O<SUB>3</SUB> solid electrolyte (BASE) while maintaining its good strength. In this paper, the concept of a duplex BASE consisting of a thin dense electrolyte and a porous support was proposed as a solution to achieve low area-specific resistance (ASR) with good mechanical strength supported by the porous substrate. The effects of various factors including porosity, composition, and homogeneity of ingredients on the flexural strength of duplex BASEs were examined. In summary, lower porosity, higher YSZ content in the structure, and attrition milling of raw powders resulted in improved strength. The ASR measurement exhibited that the resistance of duplex BASEs was mainly originated from a dense layer. Overall, the maximum strength of 260MPa and the ASR value of 0.31Ωcm<SUP>2</SUP> (at 350°C) was achieved from a duplex BASE consisting of a 50μm thick dense layer (Al<SUB>2</SUB>O<SUB>3</SUB>:YSZ=7:3 in volume) and a 500μm thick porous support (Al<SUB>2</SUB>O<SUB>3</SUB>:YSZ=4:6 in volume with 19% open porosity). The effects of various factors on the properties of duplex BASEs will be discussed in detail.</P> <P><B>Highlights</B></P> <P> <UL> <LI> As a method to lower the ASR, the concept of duplex BASEs is presented. </LI> <LI> A duplex BASEs consists of a thin dense β″-alumina layer and a mechanically strong porous support. </LI> <LI> Processing factors including conversion, porosity, composition, and homogeneity influence the strength of a duplex BASE. </LI> <LI> The minimum ASR value of 0.31Ωcm<SUP>2</SUP> was achieved at 350°C with decent strength of 260MPa. </LI> </UL> </P>

Advanced Na-NiCl₂ Battery Using Nickel-Coated Graphite with Core–Shell Microarchitecture

Chang, Hee-Jung,Canfield, Nathan L.,Jung, Keeyoung,Sprenkle, Vincent L.,Li, Guosheng American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.13

<P>Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earths crust. However, the sodium-nickel chloride (Na-NiCl2) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a coreshell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl2 batteries. An initial energy density of 133 Wh/kg (at similar to C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190 degrees C.</P>

Effect of cathode thickness on the performance of planar Na-NiCl₂ battery

Lu, Xiaochuan,Chang, Hee Jung,Bonnett, Jeff F.,Canfield, Nathan L.,Jung, Keeyoung,Sprenkle, Vincent L.,Li, Guosheng Elsevier 2017 Journal of Power Sources Vol.365 No.-

<P><B>Abstract</B></P> <P>Na-beta alumina batteries (NBBs) are one of the most promising technologies for renewable energy storage and grid applications. Commercial NBBs are typically constructed in tubular designs, primarily because of their ease of sealing. However, planar designs are considered superior to tubular counterparts in terms of power output, cell packing, ease of assembly, and thermal management. In this paper, the performance of planar NBBs has been evaluated at an intermediate temperature. In particular, planar Na-NiCl<SUB>2</SUB> cells with different cathode loadings and thicknesses have been studied at 190 °C. The effects of the cathode thickness, charging current, and discharging power output on the cell capacity and resistance have been investigated. More than 60% of theoretical cell capacity was retained with constant discharging power levels of 200, 175, and 100 mW/cm<SUP>2</SUP> for 1x, 2x, and 3x cathode loadings, respectively. The cell resistance with 1x and 2x cathode loadings was dominated by ohmic resistance with discharging currents up to 105 mA/cm<SUP>2</SUP>, while for 3x cathode loading, it was primarily dominated by ohmic resistance with currents less than 66.67 mA/cm<SUP>2</SUP> and by polarization resistance above 66.67 mA/cm<SUP>2</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Performance of planar Na-NiCl<SUB>2</SUB> cells was primarily limited by the charging current. </LI> <LI> Cells with 1x and 2x cathodes were dominated by ohmic resistance up to 105 mA/cm<SUP>2</SUP>. </LI> <LI> The cell with 3x cathode retained 27% of the capacity at a power output of 200 mW/cm<SUP>2</SUP>. </LI> </UL> </P>

Development of intermediate temperature sodium nickel chloride rechargeable batteries using conventional polymer sealing technologies

Chang, Hee Jung,Lu, Xiaochuan,Bonnett, Jeff F.,Canfield, Nathan L.,Son, Sori,Park, Yoon-Cheol,Jung, Keeyoung,Sprenkle, Vincent L.,Li, Guosheng Elsevier 2017 Journal of Power Sources Vol.348 No.-

<P><B>Abstract</B></P> <P>Developing advanced and reliable electrical energy storage systems is critical to fulfill global energy demands and stimulate the growth of renewable energy resources. Sodium metal halide batteries have been under serious consideration as a low cost alternative energy storage device for stationary energy storage systems. Yet, there are number of challenges to overcome for the successful market penetration, such as high operating temperature and hermetic sealing of batteries that trigger an expensive manufacturing process. Here we demonstrate simple, economical and practical sealing technologies for Na-NiCl<SUB>2</SUB> batteries operated at an intermediate temperature of 190 °C. Conventional polymers are implemented in planar Na-NiCl<SUB>2</SUB> batteries after a prescreening test, and their excellent compatibilities and durability are demonstrated by a stable performance of Na-NiCl<SUB>2</SUB> battery for more than 300 cycles. The sealing methods developed in this work will be highly beneficial and feasible for prolonging battery cycle life and reducing manufacturing cost for Na-based batteries at elevated temperatures (<200 °C).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conventional polymers were adopted as sealing materials for Na-NiCl<SUB>2</SUB> batteries. </LI> <LI> Selected polymers showed excellent compatibility with sodium and melts at 190 °C. </LI> <LI> Batteries with polymer seals showed stable performances over 300 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>