Reduction of charge-transfer resistance at the solid electrolyte - Electrode interface by pulsed laser deposition of films from a crystalline Li₂PO₂N source

Amorphous films deposited by pulsed laser deposition from a crystalline Li₂PO₂N target in a N₂ ambient atmosphere (LiPON-PLD) have been examined as an approach to reduce the charge-transfer resistance at the electrode-solid electrolyte interface. Despite the relatively low ionic conductivity of ca. 1.5 × 10^-8 S cm^-1 at 25 °C, the amorphous LiPON-PLD films deposited between a LiMn_1.485Ni_0.45Cr_0.05O₄ (LNM) cathode and LiPON electrolyte resulted in sharply improved electrochemical performance in terms of charge-transfer resistance and CV profiles. Cells without a LiPON-PLD film had a charge-transfer resistance of 4470 Ω-cm² compared to 760 and 960 Ω-cm² for the sample with 17 nm and 31 nm thick LiPON-PLD films, respectively. The LiPON-PLD amorphous films show no evidence of the continuous planar -P-N-P-N- backbone characteristic of the crystalline target material, but compared with LiPON prepared from radio frequency magnetron sputtering with Li₃PO₄ in a N₂ atmosphere, the LiPON-PLD films were composed of a higher amount of triply coordinated P-N<PP with relatively lower contributions of P-N=P.