Lithium metal is considered to be the most promising anode for next-generation batteries due to its high energy density of 3840 mAh g(-1). However, the extreme reactivity of the Li surface can induce parasitic reactions with solvents, contamination, and shuttled active species in the electrolyte, reducing the performance of batteries employing Li metal anodes. One promising solution to this issue is application of thin chemical protection layers to the Li metal surface. Using a custom-made ultrahigh vacuum integrated deposition and characterization system, we demonstrate atomic layer deposition (ALD) of protection layers directly on Li metal with exquisite thickness control. We demonstrate as a proof-of-concept that a 14 nm thick ALD Al2O3 layer can protect the Li surface from corrosion due to atmosphere, sulfur, and electrolyte exposure. Using Li-S battery cells as a test system, we demonstrate an improved capacity retention using ALD-protected anodes over cells assembled with bare Li metal anodes for up to 100 cycles.

We demonstrate an atomic layer deposition (ALD) process for the solid electrolyte lithium phosphorousoxynitride (LiPON) using lithium tert-butoxide (LiO t Bu), H 2 O, trimethylphosphate (TMP), and plasma N 2 ( P N 2 ) as precursors. We use in-situ spectroscopic ellipsometry to determine growth rates for process optimization to design a rational, quaternary precursor ALD process where only certain substrate−precursor chemical reactions are favorable. We demonstrate via in-situ XPS tunable nitrogen incorporation into the films by variation of the P N 2 dose and find that ALD films over approximately 4.5% nitrogen are amorphous, whereas LiPON ALD films with less than 4.5% nitrogen are polycrystalline. Finally, we characterize the ionic conductivity of the ALD films as a function of nitrogen content and demonstrate their functionality on a model battery electrodea Si anode on a Cu current collector. W hile planar thin film solid-state microbatteries are in commercial production, the push for higher energy and power density necessitates development of 3D device geometries, realized by improvements in device fabrication processes. 1,2 Moving from planar layer structures to high aspect ratio 3D electrode structures holds promise for significant power enhancement without much loss of energy density, or alternatively a tunable optimization and trade-off between power and energy to fit the application.Since its discovery in the early 1990s, 3 LiPON (lithium phosphorus oxynitride) has been one of the most popular solid state electrolytes used for planar lithium ion microbatteries. LiPON thin films are commonly deposited using reactive sputtering of a Li 3 PO 4 target in an N 2 atmosphere. 4−8 Generally, sputtered LiPON films are ∼1 μm thick, but sputtering of much thinner LiPON films (12 nm) has recently been demonstrated. 9 As a physical deposition technique, sputtering is generally unable to deposit high quality films on 3D geometries. 10 Also, the low reactivity of the N 2 gas during the sputtering process makes it difficult to dope these films with >2% N.Highly tunable N doping of LiPON is possible through ebeam evaporation of Li 3 PO 4 coupled with a N 2 plasma discharge above the substrate; 11 however, this technique is also limited to planar substrates.More recently, Kim et al. developed a MOCVD process for LiPON, 12 but the high deposition temperatures reported (500°C ) are undesirable for coprocessing with many battery materials and packaging components, precluding deposition on materials such as (i) Li 2 CoO 3 cathodes without degradation during the deposition process or (ii) metallic Li metal anodes without melting them.ALD has emerged as the premier deposition process for fabrication of uniform, thin, conformal films on high aspect ratio scaffolds, 13−16 and ALD has previously been used to fabricate the solid electrolytes (Utilizing a unique integrated high-vacuum deposition, surface characterization, and battery assembly system, 22 we have developed a quaternary ALD process for the solid electrolyte LiPON. We ...

A single nanopore structure that embeds all components of an electrochemical storage device could bring about the ultimate miniaturization in energy storage. Self-alignment of electrodes within each nanopore may enable closer and more controlled spacing between electrodes than in state-of-art batteries. Such an 'all-in-one' nanopore battery array would also present an alternative to interdigitated electrode structures that employ complex three-dimensional geometries with greater spatial heterogeneity. Here, we report a battery composed of an array of nanobatteries connected in parallel, each composed of an anode, a cathode and a liquid electrolyte confined within the nanopores of anodic aluminium oxide, as an all-in-one nanosize device. Each nanoelectrode includes an outer Ru nanotube current collector and an inner nanotube of V₂O₅ storage material, forming a symmetric full nanopore storage cell with anode and cathode separated by an electrolyte region. The V₂O₅ is prelithiated at one end to serve as the anode, with pristine V₂O₅ at the other end serving as the cathode, forming a battery that is asymmetrically cycled between 0.2 V and 1.8 V. The capacity retention of this full cell (relative to 1 C values) is 95% at 5 C and 46% at 150 C, with a 1,000-cycle life. From a fundamental point of view, our all-in-one nanopore battery array unveils an electrochemical regime in which ion insertion and surface charge mechanisms for energy storage become indistinguishable, and offers a testbed for studying ion transport limits in dense nanostructured electrode arrays.

ABSTRACT:Several active areas of research in novel energy storage technologies, including threedimensional solid state batteries and passivation coatings for reactive battery electrode components, require conformal solid state electrolytes. We describe an atomic layer deposition (ALD) process for a member of the lithium phosphorus oxynitride (LiPON) family, which is employed as a thin film lithium-conducting solid electrolyte. The reaction between lithium tertbutoxide (LiO t Bu) and diethyl phosphoramidate (DEPA) produces conformal, ionically conductive thin films with a stoichiometry close to Li 2 PO 2 N between 250 and 300C. The P/N ratio of the films is always 1, indicative of a particular polymorph of LiPON which closely resembles a polyphosphazene. Films grown at 300C have an ionic conductivity of 6.51 (±0.36) × 10 −7 S/cm at 35C, and are functionally electrochemically stable in the window from 0 to 5.3V vs. Li/Li+. We demonstrate the viability of the ALD-grown electrolyte by integrating it into full solid state batteries, including thin film devices using LiCoO 2 as the cathode and Si as the anode operating at up to 1 mA/cm 2 . The high quality of the ALD growth process allows pinhole-free deposition even on rough crystalline surfaces, and we demonstrate the fabrication and operation of thin film batteries with the thinnest (<100nm) solid state electrolytes yet reported. Finally, we show an additional application of the moderate-temperature ALD process by demonstrating a flexible solid state battery fabricated on a polymer substrate.3

Three-dimensional thin-film solid-state batteries (3D TSSB) were proposed by Long et al. in 2004 as a structure-based approach to simultaneously increase energy and power densities. Here, we report experimental realization of fully conformal 3D TSSBs, demonstrating the simultaneous power-and-energy benefits of 3D structuring. All active battery components-electrodes, solid electrolyte, and current collectors-were deposited by atomic layer deposition (ALD) onto standard CMOS processable silicon wafers microfabricated to form arrays of deep pores with aspect ratios up to approximately 10. The cells utilize an electrochemically prelithiated LiVO cathode, a very thin (40-100 nm) LiPON solid electrolyte, and a SnN anode. The fabrication process occurs entirely at or below 250 °C, promising compatibility with a variety of substrates as well as integrated circuits. The multilayer battery structure enabled all-ALD solid-state cells to deliver 37 μAh/cm·μm (normalized to cathode thickness) with only 0.02% per-cycle capacity loss. Conformal fabrication of full cells over 3D substrates increased the areal discharge capacity by an order of magnitude while simulteneously improving power performance, a trend consistent with a finite element model. This work shows that the exceptional conformality of ALD, combined with conventional semiconductor fabrication methods, provides an avenue for the successful realization of long-sought 3D TSSBs which provide power performance scaling in regimes inaccessible to planar form factor cells.