Plasma-Assisted ALD of LiPO(N) for Solid State Batteries

Abstract

All solid state 3D batteries are pursued for their increased safety and high power capabilities. At present conformal coating of the solid electrolyte remains one of the key hurdles for the implementation of such devices. In the present work we investigate atomic layer deposition (ALD) as means of conformal deposition of lithium phosphate (Li 3 PO 4 ) and nitrogen doped lithium phosphates (LiPON). These processes are characterized here to obtain the highest possible Li-ion conductivity. Li 3 PO 4 is shown to yield a conductivity of 10 -10 S/cm. On the other hand, an optimized LiPON process gave rise to a Li-ion conductivity of 5⋅10 -7 S/cm. In addition, good conformality of the LiPON process was shown on high aspect ratio pillars. Furthermore, a solid state battery device was fabricated comprising a Li 4 Ti 5 O 12 cathode, a 70 nm thick ALD LiPON solid electrolyte and a metallic lithium anode. The fabricated device is based on the thinnest solid electrolyte used so far as well as on the first ALD deposited solid electrolyte. 10.1149/07520.0061ecst ©The Electrochemical Society ECS Transactions, 75 (20) 61-69 (2017) 61 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.155.145.243 Downloaded on 2017-08-23 to IP

Emerging Role of Non-crystalline Electrolytes in Solid-State Battery Research

“…In concert with this effect, it has also been observed that the conductivity of LiPON films also benefits from the introduction of excess lithium during processing, which presumably increases the concentration of interstitial lithium available for conduction (Xiao et al, 2018). Interestingly, these effects can be realized with the obvious commensurate changes in precursor (i.e., sputtering target) chemistry, but also by changing the processing atmosphere and sputtering parameters (Xiao et al, 2018;Put et al, 2019). With so many possible factors contributing to the conductivity of LiPON, it is perhaps unsurprising that the measured conductivities of LiPON of the same nominal composition can vary up to three orders of magnitude when different processing techniques are employed and the data are collated (Famprikis et al, 2019b).…”

“…Further, the volumetric capacity is often reported rather than specific gravimetric capacity (as is typical in bulk ASSBs) due to the unique configurations of these microbatteries. The presented batteries demonstrate the ability to sputter the cathodes as well, which include LCO, LTO (Put et al, 2019), and LNMO (Yada et al, 2014) thin films. These batteries are typically supported by hard substrates such as SiO 2 or flexible substrates (Song et al, 2010) to impart flexibility to the thin film battery as a whole.…”

Advances in 3D Thin‐Film Li‐Ion Batteries

“…In later work it was shown that the N-content in the films can be controlled by the plasma power, in a similar fashion to the RF-sputter depositions. [86] In addition, plasma enables lower deposition temperatures (down to 100 °C) and reduces the amount of impurities in the film. [84,86] This might open the way for LiPON protectvive coatings on metallic lithium.…”

“…[86] In addition, plasma enables lower deposition temperatures (down to 100 °C) and reduces the amount of impurities in the film. [84,86] This might open the way for LiPON protectvive coatings on metallic lithium. However, the need for a plasma step makes it less straightforward to obtain conformal films.…”

“…However, the need for a plasma step makes it less straightforward to obtain conformal films. [86] Recently, the combination of LiO t Bu and DEPA was evaluated [32] and used in the first full 3D TFB (see below). The combination of DEPA and LiO t Bu yielded layers with a stoichiometry of Li2PO2N (not considering carbon contamination), and was named lithium-phosphazene (LPZ) as the P/N ratio is always 1.…”