Gas-phase deposition of di- and tetra-lithium salts of 2,5-dihydroxyterephthalic acid.

Thin films of two ambipolar lithium-organic electrode materials, Li2DHTP and Li4DHTP, are grown from gaseous precursors, Li(thd) (tetramethyl heptanedione) and DHTP (dihydroxyterephthalic acid). These precursors are pulsed into the reactor in a sequential manner like in atomic/molecular layer deposition, but the reaction product, i.e. the di- or the tetra-lithium salt, is controlled by adjusting the precursor pulse lengths.

Atomic and Molecular Layer Deposition of Alkali Metal Based Thin Films.

Atomic layer deposition (ALD) is the fastest growing thin-film technology in microelectronics, but it is also recognized as a promising fabrication strategy for various alkali-metal-based thin films in emerging energy technologies, the spearhead application being the Li-ion battery. Since the pioneering work in 2009 for Li-containing thin films, the field has been rapidly growing and also widened from lithium to other alkali metals. Moreover, alkali-metal-based metal-organic thin films have been successfully grown by combining molecular layer deposition (MLD) cycles of the organic molecules with the ALD cycles of the alkali metal precursor. The current literature describes already around 100 ALD and ALD/MLD processes for alkali-metal-bearing materials. Interestingly, some of these materials cannot even be made by any other synthesis route. In this review, our intention is to present the current state of research in the field by (i) summarizing the ALD and ALD/MLD processes so far developed for the different alkali metals, (ii) highlighting the most intriguing thin-film materials obtained thereof, and (iii) addressing both the advantages and limitations of ALD and MLD in the application space of these materials. Finally, (iv) a brief outlook for the future perspectives and challenges of the field is given.

Benzenedisulfonic Acid as an ALD/MLD Building Block for Crystalline Metal-Organic Thin Films*.

Two new atomic/molecular layer deposition processes for depositing crystalline metal-organic thin films, built from 1,4-benzenedisulfonate (BDS) as the organic linker and Cu or Li as the metal node, are reported. The processes yield in-situ crystalline but hydrated Cu-BDS and Li-BDS films; in the former case, the crystal structure is of a previously known metal-organic-framework-like structure, while in the latter case not known from previous studies. Both hydrated materials can be readily dried to obtain the crystalline unhydrated phases. The stability and the ionic conductivity of the unhydrated Li-BDS films were characterized to assess their applicability as a thin film solid polymer Li-ion conductor.

Electrochemically Active In Situ Crystalline Lithium-Organic Thin Films by ALD/MLD.

Intercalated metal-organic framework (iMOF) type electrochemically active aromatic metal carboxylates are intriguing material candidates for various energy storage devices and microelectronics. In this work, we grow in situ crystalline thin films of such materials through atomic/molecular layer deposition (ALD/MLD); the remarkable benefit of this approach is the possibility to evaluate their electrochemical properties in a simple cell configuration without any additives. Five organic linkers are investigated in combination with lithium: terephthalic acid (TPA), 3,5-pyridinedicarboxylic acid (PDC), 2,6-naphthalenedicarboxylic acid (NDC), 4,4'-biphenyldicarboxylic acid (BPDC), and 4,4'-azobenzenedicarboxylic acid (AZO). In particular, the electrochemical activity of Li-PDC and the crystal structure of Li-AZO are addressed here for the first time. We believe that the in situ gas-phase thin-film deposition is a crucial requirement to benefit from the iMOF-type electrode materials in, e.g., microelectronics and wearable devices.

Atomic/molecular layer deposition and electrochemical performance of dilithium 2-aminoterephthalate.

Control of the redox potential of lithium terephthalate Li2TP anode material is demonstrated by functionalizing its terephthalate backbone with an electron-donating amino group; this lowers - as intended - the redox potential of Li2TP by 0.14 V. The two Li-organic electrode materials, Li2TP and Li2TP-NH2, are fabricated as crystalline thin films from gaseous precursors using the atomic/molecular layer deposition (ALD/MLD) technique. The amino-functionalized material possesses a previously unknown crystal structure, addressed here by applying the USPEX evolutionary algorithm for the structure prediction and then LeBail fitting of the experimental XRD pattern based on the predicted structure model. The ALD/MLD fabrication yields in situ lithiated active electrode materials without any conductive additivies or binders and thus allows a straightforward evaluation of their intrinsic electrochemical properties. Comparison between Li2TP and its amino-functionalized derivative reveals inferior capacity retention and rate capability characteristics for the latter, which somewhat counterveils the pros-and-cons balance between the two Li-organic electrode materials. From galvanostatic cycling experiments and post-mortem XRD and SEM analysis, the issue with Li2TP-NH2 is revealed to be in the morphology changes occurring during the discharge/charge cycling.

CO2-based atomic/molecular layer deposition of lithium ethylene carbonate thin films.

When a conventional lithium-ion battery (LIB) is cycled, a solid electrolyte interphase (SEI) forms on the surface of a negative electrode, passivating it but also depleting the capacity of the battery. Most commercial LIBs utilize a carbonate-based electrolyte, which at least temporarily leads to the formation of lithium alkyl carbonates (ROCO2Li) as the main organic SEI component. Here, we pioneer the use of atomic/molecular layer deposition (ALD/MLD) for the fabrication of lithium ethyl glycoxide (LiEG) and lithium ethylene carbonate (LiEGCO) thin films, to mimic the lithium alkyl carbonate component of the SEI. For the in situ growth of LiEGCO, we employ for the first time CO2 as an ALD/MLD precursor. The films are characterized using XRR, GIXRD, FTIR, AFM and SEM.