Electrical Characterization of Ultrathin RF-Sputtered LiPON Layers for Nanoscale Batteries

Abstract

Ultrathin lithium phosphorus oxynitride glass (LiPON) films with thicknesses down to 15 nm, deposited by reactive sputtering in nitrogen plasma, were found to be electronically insulating. Such ultrathin electrolyte layers could lead to high power outputs and increased battery energy densities. The effects of stoichiometry, film thickness, and substrate material on the ionic conductivity were investigated. As the amount of nitrogen in the layers increased, the activation energy of the ionic conductivity decreased from 0.63 to 0.53 eV, leading to a maximum conductivity of 1 × 10(-6) S/cm. No dependence of the ionic conductivity on the film thickness or substrate material could be established. A detailed analysis of the equivalent circuit model used to fit the impedance data is provided. Polarization measurements were performed to determine the electronic leakage in these ultrathin films. A 15-nm LiPON layer on a TiN substrate showed electronically insulating properties with electronic resistivity values around 10(15) Ω·cm. To our knowledge, this is the thinnest RF-sputtered LiPON layer shown to be electronically insulating while retaining good ionic conductivity.

Solid and Solid‐Like Composite Electrolyte for Lithium Ion Batteries: Engineering the Ion Conductivity at Interfaces

“…Certain ionic liquid electrolytes (ILE) such as lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI]) in 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) are more stable against these 5 V cathodes but not against Li or carbon anodes . Solid‐state electrolytes can provide the necessary electrochemical window (e.g., lithium phosphate glass doped with nitrogen or LiPON is stable between 0 V and 5.5 V vs Li + /Li) and could thus provide a viable alternative . Unfortunately, the lack of solid electrolyte materials with both sufficiently high Li‐ion conductivity (>10 mS cm −1 ) and wide enough electrochemical window (<0.2 and > 4.5 V) has been the main bottle neck for the introduction of solid‐state electrolytes.…”

Li‐Ion Synaptic Transistor for Low Power Analog Computing

“…[34] Furthermore, the device required a 14 V operating window to overcome a large energy barrier for Li intercalation, limiting applicability to neuromorphic applications that require operation <1 V for energy efficiency gains over CMOS. The LiPON solid electrolyte was chosen for scalability (≈20 nm), [38] a large chemical stability window, and a high electrical resistivity (>10 15 Ω cm). Figure 1a is a false color scanning electron microscopy (SEM) micrograph of a LISTA device in cross section that shows the device structure.…”

“…A 400 nm thick lithium phosphorous oxynitride electrolyte (LiPON) layer (green) separates the channel from a 50 nm Si gate electrode (purple). The LiPON solid electrolyte was chosen for scalability (≈20 nm), [38] a large chemical stability window, and a high electrical resistivity (>10 15 Ω cm). [39] Figure 1b is a diagram illustrating the resistance switching mechanism in a LISTA device.…”

Effects of Mechanical Strain on Ionic Conductivity in the Interface between LiPON and Ni-Mn Spinel

“…24,27,28 Among a wide range of Li x PO y N z (x = 2y + 3z -5) compositions that exhibited acceptable ionic conductivity, 8,14,29,30 we intended to model the one with the highest ionic conductivity. Several experimental demonstrations of the increased ionic conductivity with the N/P ratio [31][32][33] motivated us to choose the stoichiometry of Li 4 PO 3 N, which has a high (and experimentally confirmed 32 ) N/P ratio. A crystalline Li 3 PO 4 was selected as a base frame and modified by adding one Li and substituting one N for an oxygen per formula unit (f.u.…”