No abstract

A thick (170 μm) LiFePO4 cathode is fabricated through aerosol jet printing. The printed cathode displays a pattern of aligned high aspect ratio needles which, in cross section, produce micron scale channels. These channels surround regions of LiFePO4 that possess submicron pores. When tested in half cell configuration versus a Li‐foil anode, the specific discharge capacity of the printed cathode is 151 mAh g−1 at a C/15 rate and 105 mAh g−1 at 1C. These values correspond to area normalized discharge capacities of 2.5 and 1.7 mAh cm−2 at current densities of 0.2 and 2.4 mA cm−2, respectively. In a 50 cycle constant current charge/discharge test, the discharge capacity is stable, retaining 89% of its initial C/5 capacity. These results suggest that aerosol jet deposition is a promising printing technique for fabricating high capacity, rate capable, Li‐ion battery cathodes.

Battery research has recently diverged into solid-state chemistry and flexible features to address the increasing demands in electric vehicles and novel electronics. In this study, we successfully fabricate 4-inch sized thin freestanding lithium-ion conducting composite electrolyte membrane. The solid electrolytes are made up of polyethylene oxide (PEO) lithiated with lithium bis(trifluoromethylsulphonyl)imide (LiTFSI) in which submicrometer sized crystalline Li 1.4 Al 0.4 Ge 1.6 (PO 4 ) 3 (LAGP) particles are homogeneously distributed. The impacts of the LAGP loading (20-60 wt%) on the thermal, electrical, and mechanical properties of the composite electrolytes are systematically assessed. The composite membranes exhibit similar conducting behavior of dry polymer electrolytes with two distinct ionic conduction mechanisms transitioned around the melting temperature. The conductivities of the composites are marginally lower than the polymer electrolyte with no LAGP. Addition of LAGP, compared with PEO/LiTFSI, has slightly increased thermal transition temperatures (both glass transition temperature and melting temperature) as well as the crystallinity of PEO. Increasing the amount of LAGP ceramic fillers increased the elastic modulus, reduced the strain to failure point, but has less impacts on the yielding strength. The freestanding ceramic/polymer composite electrolytes with optimal LAGP loading can result appropriate electrical, thermal and mechanical properties and hence, have potential applications to flexible all solid-state lithium-based batteries.

Oxygen reduction reaction catalysis on a microwave synthesized Ni(OH) 2 /graphene oxide material was investigated via cyclic voltammetry, rotating disk electrode measurements, chronoamperometry, and electrochemical impedance spectroscopy. Cyclic voltammetry in an 0.5 M alkaline solution indicated that the Ni(OH) 2 /graphene oxide material possesses significant oxygen reduction reaction activity as evidenced by a peak potential of À310 mV vs. Ag/AgCl. This value was a shift of +110 mV as compared to the unsupported Ni(OH) 2 nanoparticles and +90 mV as compared to the graphene oxide support alone. Rotating disk electrode studies show that the limiting current density of the Ni(OH) 2 /GO catalyst is 1.3 mA cm À2 and the electron transfer number is 3.5. Chronoamperometry demonstrates that the current density attributable to the oxygen reduction reaction on the Ni(OH) 2 /graphene oxide material sustained a steady state value of 60% of its initial value. Electrochemical Impedance spectroscopy showed that the charge transfer resistance of the Ni(OH) 2 /graphene oxide catalyst was significantly lower than either the Ni(OH) 2 nanoparticles or the graphene oxide support. The electrocatalytic properties of the Ni(OH )2 /graphene oxide material are discussed in the context of specific chemical interaction between the Ni(OH) 2 nanoparticles and the graphene oxide support.

Progressing toward the emerging era of high-energy-density batteries, stable and safe employment of lithium (Li) metal anodes is highly desired. The primary concern with Li metal anodes is their uncontrollable dendrites growth and extreme sensitivity to parasitic degradation reactions, raising the alarms for battery safety and shelf life. Nanolayer protection encapsulation, which is conformal and ionically conductive with a high-κ dielectric property, can suppress the degradation and empower stabilization of Li metal. In this work, engineering of a zirconia (ZrO) encapsulation layer on Li metal enabled by atomic layer deposition (ALD) was employed and investigated for surface-enhanced dendrite suppression properties using in situ optical observations and electrochemical cycling. The ALD process involved a combination of plasma subcycle activation and thermal subcycle activation in increasing the surface functionalization and chemisorption sites for precursors to obtain highly dense and conformal deposition. The encapsulation of Li with ZrO ALD nanolayer further demonstrated excellent tolerance to atmospheric exposure for at least 1-5 h because of a conformal physical barrier, and excellent heat tolerance up-to 170-180 °C (close to Li melting point) and high rate capability due to thermal resistive property and high ionic transport property, respectively, of the ZrO ceramic. The results establish a technology transferable to other metal anode chemistries and offer a potential insight into carrying out solid-state electrolyte multilayer coatings with high processing temperature flexibility and thereby providing a leap in the advancing of a range of high energy density all-solid-state batteries.