Road vehicles can expend a significant amount of energy in undesirable vertical motions that are induced by road bumps, and much of that is dissipated in conventional shock absorbers as they dampen the vertical motions.Presented in this paper are some of the results of a study aimed at determining the effectiveness of efficiently transforming that energy into electrical power by using optimally designed regenerative electromagnetic shock absorbers. In turn, the electrical power can be used to recharge batteries or other efficient energy storage devices (e.g., flywheels) rather than be dissipated. The results of the study are encouraging -they suggest that a significant amount of the vertical motion energy can be recovered and stored.

LiPON films have been produced by nitrogen ion beam assisted deposition ͑IBAD͒ of thermally evaporated Li 3 PO 4 . This process allowed us to rapidly deposit X-ray amorphous LiPON films with densities close to that of the handbook value for Li 3 PO 4 , high ionic conductivity (1.6 ϫ 10 Ϫ6 S/cm), electronic conductivity smaller than 8 ϫ 10 Ϫ13 S/cm, and an electrochemical stability window of over 6.0 V. These properties, combined with the high deposition rates that can be achieved with this process (Ͼ1.0 nm/s), make it an attractive candidate for industrial production of LiPON thin films for Li-ion batteries.Nitridation of phosphate glasses is known to increase their chemical stability. [1][2][3][4] reported on the production of lithium phosphorus oxynitride ͑LiPON͒ thin films deposited by reactive sputtering of Li 3 PO 4 in a nitrogen atmosphere. These films were both more electrochemically stable ͑5.5 V stability window vs. Li/Li ϩ ) than their non-nitrided counterparts and exhibited a 40 times higher room temperature Li-ion conductivity of 2 ϫ 10 Ϫ6 S/cm. 6 This has led to much interest in using LiPON as an electrolyte for solid-state lithium-ion thin film batteries. [7][8][9] Since the conventional means to deposit LiPON films, sputtering, is a relatively slow process, we decided to explore the use of nitrogen ion beam assisted deposition ͑IBAD͒ of thermally evaporated Li 3 PO 4 as a possible improved process. In this paper, we present a brief description of this process and a summary of our results for two representative films. We show that the process provides for significantly higher deposition rates and gives films with equivalent, if not improved, electrochemical properties. The process has the additional advantage that, at least in principle, it allows one to readily vary the amount of incorporated nitrogen by simply adjusting the ion beam gun current. The main drawback of the process to date is a residual, largely thermal ͑mostly determined by substrate temperature͒, tensile stress that the LiPON films exhibit after their depositions. Cracks arising from this stress have been identified as a major cause of electrical shorts that occasionally are found in asdeposited cells that use LiPON as their electrolyte. 10 ExperimentalThe base pressure of the vacuum chamber in which the films were deposited was 4 ϫ 10 Ϫ7 Torr. Pressed pellets of Li 3 PO 4 ͑Alfa͒ were placed in an electrically heated tungsten boat ͓purchased from Mathis, reference no. S36.010W͔ and were melted during the pump-down and chamber bakeout ͑for Ͼ48 h at approximately 150°C͒ prior to the deposition. The sample holders were part of a planetary system that allowed the substrates to revolve and rotate above the centrally located source to ensure a uniform thickness. The throw distance between the source and the samples was approximately 22 cm. During deposition the substrates were simultaneously bombarded with nitrogen ions provided by a Commonwealth Mark I ion gun, placed to one side of the chamber. The ion gun center was at the same height ...

The chemical stability of phosphate glasses can be improved through the incorporation of nitrogen into the structure. In nitrided amorphous Li 3 PO 4 thin films ͑LiPON͒, the exceptional stability and enhanced Li ϩ conductivity make them particularly attractive for microbattery applications. Reported here are 7 Li, 31 P, and 15 N solid-state nuclear magnetic resonance ͑NMR͒ studies of LiPON thin films fabricated by an ion beam-assisted deposition ͑IBAD͒ process. Variable temperature measurements of the 7 Li resonance yield an activation energy of about 0.2 eV, which is smaller than values obtained from ionic conductivities. 31 P spectra provide direct evidence for at least three phosphate environments: two resonances associated with PO 42Ϫ and PO 4 3Ϫ structures and a third anomalous peak assigned to a nitrided tetrahedral phosphate structural unit of charge Ϫ3. Additional evidence exists for other nitrided phosphate structures of charge Ϫ2. 15 N spectra show evidence for P-NϭP type units and molecular N 2 with relative intensities that vary with the nitrogen ion beam gun voltage. No 15 N peak associated with trigonal NP 3 units is observed. Additional evidence for molecular N 2 is provided by Fourier transform infrared measurements. A structural model of the phosphorus oxynitride host is presented.

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