Search

Sodium-ion batteries are widely considered as promising energy storage systems for large-scale applications, but their relatively low energy density hinders further practical applications. Developing high-voltage cathode materials is an effective approach to increase the overall energy density of sodium-ion batteries. When cut-off voltage is elevated over 4.3 V, however, the cathode becomes extremely unstable due to structural transformations as well as metal dissolution into the electrolytes. In this work, the cyclic stability of P2-Na0.66(Mn0.54Co0.13Ni0.13)O2 (MCN) electrode at a cut-off voltage of 4.5 V is successfully improved by using ultrathin metal oxide surface coatings (Al2O3, ZrO2, and TiO2) deposited by an atomic layer deposition technique. The MCN electrode coated with the Al2O3 layer exhibits higher capacity retention among the MCN electrodes. Moreover, the rate performance of the MCN electrode is greatly improved by the metal oxide coatings in the order of TiO2 < Al2O3 < ZrO2, due to increased fracture toughness and electrical conductivity of the metal oxide coating layers. A ZrO2-coated MCN electrode shows a discharge capacity of 83 mAh g−1 at 2.4 A g−1, in comparison to 61 mAh g−1 for a pristine MCN electrode. Cyclic voltammetry and electrochemical impedance analysis disclose the reduced charge transfer resistance from 1421 to 760.2 Ω after cycles, suggesting that the metal oxide coating layer can effectively minimize the undesirable phase transition, buffer inherent stress and strain between the binder, cathode, and current collector, and avoid volumetric changes, thus increasing the cyclic stability of the MCN electrode. [ABSTRACT FROM AUTHOR]

Spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising high voltage cathode material for lithium ion batteries (LIBs). However, dissolution of Mn and unwanted side reactions between LNMO and the electrolyte raises several safety issues while also resulting in deteriorated electrochemical performance of LIBs at high working voltages. Here, we report the use of ultrathin atomic layer deposited (ALD) AlPO 4 thin film as a coating material for LNMO electrodes to circumvent the stated issues. The as-prepared AlPO 4 coated LNMO demonstrates excellent capacity retention with prolonged cycle life compared to the bare one. Synchrotron based X-ray spectroscopy was employed to understand how ultrathin coating layer improve the cycle life, and then develop a detailed mechanism for the effect of coating layer. Our studies revealed that using atomic scale coating layer with improved thermal stability effectively impede the side-reactions occurrence at high voltage, resulting in significantly improved safety and electrochemical performances. [ABSTRACT FROM AUTHOR]

Catalysts can play a critical role in the development of sodium-air batteries (SABs). Atomic layer deposition (ALD) technology enables rational design and atomic utilization of catalyst by homogenously distributing catalytically active material on a variety of substrates. Here, a novel hierarchical nanostructured Co3O4 is decorated on carbon nanotubes by ALD (CNT@Co3O4) and used as a catalyst for SABs. CNT@Co3O4 demonstrates better performance and longer cycle life than a mechanically mixed CNT/Co3O4 nanocomposite. Well-dispersed ALD Co3O4 catalyst on CNTs, which serves as functionalized active sites, enables rapid electron exchange and high oxygen reduction/evolution activities. Synchrotron-based X-ray analysis including X-ray absorption near edge structure, extended X-ray absorption fine structure, and scanning transmission X-ray microscopy characterization techniques have been employed to elucidate the activity of Co3O4 and to investigate the nanoscale discharge product distribution found in SABs. This analysis reveals that Co3O4 catalyst can promote the electrochemical decomposition of sodium peroxide, superoxide, and carbonates. The role of the catalyst in SABs is clarified and discussed in detail. [ABSTRACT FROM AUTHOR]

Lithium-rich layered material is one of the most promising candidates of cathode materials for next-generation electric vehicles. However, one of the major issues that pertains to this material is the oxygen release during initial charge, which results in low initial coulombic efficiency (CE), intense electrolyte oxidation and thermal instability. In this study, we have conducted aluminum phosphate (AlPO 4 ) coating via atomic layer deposition (ALD) approach to protect the surface of this cathode material powders. It was found that part of the C2/m Li 2 MnO 3 phase turned into a spinel-like phase during the ALD process. The oxygen release has been effectively suppressed by such transformation, the initial CE increased from 75.2% for the bare electrode to 86.2% for the electrode with only 5 ALD cycles of AlPO 4 coating. Furthermore, AlPO 4 was also found to be more effective in improving the thermal stability of the cathode material comparing to bare or Al 2 O 3 coated samples. Our study has provided a new possible solution towards cathode materials with high thermal resistance via conformal coating. [ABSTRACT FROM AUTHOR]

3D microbatteries hold great promise as on-board energy supply systems for microelectronic devices. The construction of 3D microbatteries relies on the development of film deposition techniques that can enable coatings of uniform electrode and electrolyte materials in high-aspect-ratio substrates. Here, a 3D FePO4 on carbon nanotubes (CNTs@FePO4) structure is fabricated by coating FePO4 on CNTs/carbon paper substrate using atomic layer deposition. Compared to FePO4 on a planar substrate, the 3D CNTs@FePO4 electrode exhibits significantly increased areal capacity and excellent rate capability for lithium-ion and sodium-ion storage. The 3D CNTs@FePO4 maintains areal capacities of 64 and 33 μAh cm−2 after 180 cycles for lithium-ion batteries (LIBs) and sodium-ion batteries, which are 16 and 33 times higher than those of planar FePO4 electrode, respectively. Moreover, hybrid 3D CNTs@FePO4@Li3PO4 structure is fabricated by coating Li3PO4 solid-state electrolyte on 3D CNTs@FePO4. The CNTs@FePO4@Li3PO4 electrode shows stable cycling performance in LIBs. Hard X-ray photoemission spectroscopy analysis demonstrates that the Li3PO4 coating prevents the formation of undesirable LiF in the solid-electrolyte interphase layer, which is believed to be responsible for the performance degradation in CNTs@FePO4. This work paves the way to building reliable 3D nanostructured electrode and electrolyte architectures for high areal capacity microbatteries. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) is considered as a powerful technique to synthesize novel electrode materials for lithium-ion batteries (LIBs), because not only the compositions can be specifically designed to achieve higher battery performances, but also the materials can be deposited on various substrates for different purposes. Herein, a novel design of active material/electrolyte mixture electrode, i.e., titanium dioxide/lithium phosphate (TLPO) nanocomposite, has been successfully developed by ALD and deposited on carbon nanotube substrates (CNTs@TLPO) at 250 °C, by combining the ALD recipes of TiO2 and lithium phosphate (LPO). In the nanocomposite, TiO2 forms anatase nanocrystals, embedded in a matrix of amorphous lithium phosphate. CNTs@TLPO has been examined as an anode material for LIBs, exhibiting a similar electrochemical response as anatase TiO2 in the cyclic voltammetry testing. CNTs@TLPO presents an outstanding capacity of 204 mA h g−1 upon 200 cycles in charge and discharge cycling measurements, as well as a significantly improved rate capability compared with ALD deposited TiO2 on CNTs without LPO ALD cycles. This work shows that the in situ addition of solid-state electrolyte (e.g., lithium phosphate), which introduces higher Li+ ionic conductivity, is an efficient way to achieve high-performance electrode materials for LIBs by ALD. [ABSTRACT FROM AUTHOR]

Single atom catalysts exhibit particularly high catalytic activities in contrast to regular nanomaterial-based catalysts. Until recently, research has been mostly focused on single atom catalysts, and it remains a great challenge to synthesize bimetallic dimer structures. Herein, we successfully prepare high-quality one-to-one A-B bimetallic dimer structures (Pt-Ru dimers) through an atomic layer deposition (ALD) process. The Pt-Ru dimers show much higher hydrogen evolution activity (more than 50 times) and excellent stability compared to commercial Pt/C catalysts. X-ray absorption spectroscopy indicates that the Pt-Ru dimers structure model contains one Pt-Ru bonding configuration. First principle calculations reveal that the Pt-Ru dimer generates a synergy effect by modulating the electronic structure, which results in the enhanced hydrogen evolution activity. This work paves the way for the rational design of bimetallic dimers with good activity and stability, which have a great potential to be applied in various catalytic reactions. Atomically precise control over elemental distributions presents a challenge in the preparation of catalytic nanomaterials. Here the authors report Pt-Ru bimetallic dimer structures through atomic layer deposition process and identify the roles of Pt and Ru in hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Metal-chalcogenide nanomaterials, as compared to their wide bandgap counterparts, are particularly attractive photoelectrocatalytic materials for the conversion of solar energy into chemical energy under visible-light irradiation. In this study, the thin layer of CdTe was deposited on the surface of Au/ITO electrode using electrochemical atomic layer deposition. Deposition process was performed through the alternate under potential deposition of the Te and Cd elements with a monolayer at a time, respectively. The images of scaning electron microscopy (SEM) indicated that nanoparticles of CdTe well dispersed on Au/ITO with an average particle size about 15 nm. The results of energy dispersive analysis by X-rays (EDAX) confirmed the off-stoichiometric CdTe layer, which lead to Cd-rich CdTe because of tellurium vacancies in the deposition potential. The resulting Cd-rich CdTe/Au/ITO electrode was used for preparation of Pt/CdTe/Au/ITO by redox replacement reaction between Pt2+ and Cd excess in CdTe layer to form 1.76 wt% of Pt element which uniformly distributed on the surface of CdTe/Au/ITO. Chronoamperometric tests in sodium sulfide solution exhibited that the Cd-rich CdTe layer had n-type semiconductivity whereas the Pt/CdTe layer showed p-type semiconductivity. The Pt/CdTe/Au/ITO electrode showed higher photoelectrocatalytic activity for the HER as compared to a commercial Pt/C on Au/ITO. The onset potential for HER is almost similar and the overpotential at −10 mA cm−2 is 160 mV more positive on Pt/CdTe/Au/ITO under light illumination with respect to Pt/C/Au/ITO. The long-term stability tests under illumination in acidic solution revealed that Cd-rich CdTe and Pt/CdTe layeres have extremely high stablity for HER compared to Pt/C. The higher photocatalytic activity on Pt/CdTe/Au/ITO electrode for HER is attributed predominantly to the synergistic effect of Pt, which not only serves as co-catalysts for promoting electron transfer to the electrocatalyst-electrolyte interface, but also accelerates the HER. Image 1 • A thin layer of CdTe deposited onto Au/ITO electrode using electrochemical ALD technique. • The Pt/CdTe/Au/ITO electrode prepared by redox replacement of Pt2+ with Cd-rich CdTe layer. • Cd-rich CdTe and Pt/CdTe layers showed n-type and p-type semi conductivity behaviors. • Pt/CdTe/Au/ITO showed excellent electrcatalytic/photoelectrocatalytic activity toward HER. • Compared to Pt/Au/ITO for Pt/CdTe/Au/ITO the overpotintial for HER 160 mV decreased. [ABSTRACT FROM AUTHOR]

A non-aqueous approach was developed to synthesize iron phosphate cathode materials by the atomic layer deposition (ALD) technique. Deposition of iron phosphate thin films was achieved on nitrogen-doped carbon nanotubes (NCNTs) by combining ALD subcycles of Fe 2 O 3 (ferrocene-ozone) and PO x (trimethyl phosphate-water) at 200 – 350 °C. The thickness of iron phosphate thin films depends linearly on the ALD cycle, indicating their self-limiting growth behavior. The growth per cycle of iron phosphate thin films was determined to be ∼ 0.2, 0.4, 0.6, and 0.5 Å, at 200, 250, 300, and 350 °C, respectively. Characterization by SEM, TEM, and HRTEM techniques revealed uniform and conformal coating of amorphous iron phosphates on the surface of NCNTs. XANES analysis confirmed Fe O P bonding in the iron phosphates prepared by ALD. Furthermore, electrochemical measurement verified the high electrochemical activity of the amorphous iron phosphate as a cathode material in lithium-ion batteries. It is expected that the amorphous iron phosphate prepared by this facile and cost-effective ALD approach will find applications in the next generation of lithium-ion batteries and thin film batteries as either cathode materials or surface coating materials. [ABSTRACT FROM AUTHOR]

LiFePO4 is deposited on CNTs (CNT: carbon nanotube) by atomic layer deposition at 300 °C to form LiFePO4/CNT nanocomposite using ferrocene, ozone, trimethylphosphate, water, and LiO-tBu as precursors. [ABSTRACT FROM AUTHOR]