Andrew Lushington

Atomic layer deposition of solid-state electrolyte coated cathode materials with superior high-voltage cycling behavior for lithium ion battery application

LiNi1/3Co1/3Mn1/3O2 (NMC) is a highly promising cathode material for use in lithium ion batteries; unfortunately, its poor cycling performance at high cutoff voltages hinders its commercialization. In this study, for the first time, we employ atomic layer deposition (ALD) to coat lithium tantalum oxide, a solid-state electrolyte, with varying thicknesses on NMC in an attempt to improve battery performance. Our results indicate that utilization of a solid-state electrolyte as a coating material for NMC significantly improves performance at high cutoff voltages but is strongly dependent on coating thicknesses. Our investigation revealed that a thicker coating proved to be beneficial in preventing cathode material dissolution into the electrolyte and aided in maintaining the microstructure of NMC. Consequently, a thicker ALD coating resulted in increased electrochemical impedance of the cathode. The results of this study indicate that an optimized coating thickness is needed in order to strike a balance between maintaining structural stability while minimizing electrochemical impedance. The coating thicknesses are functionally specific, and for the best improvement of a cathode, a particular coating thickness should be sought.

Rational Design of Atomic-Layer-Deposited LiFePO4 as a High-Performance Cathode for Lithium-Ion Batteries

Atomic layer deposition is successfully applied to synthesize lithium iron phosphate in a layer-by-layer manner by using self-limiting surface reactions. The lithium iron phosphate exhibits high power density, excellent rate capability, and ultra-long lifetime, showing great potential for vehicular lithium batteries and 3D all-solid-state microbatteries.

Superior Stable and Long Life Sodium Metal Anodes Achieved by Atomic Layer Deposition

Na-metal batteries are considered as the promising alternative candidate for Li-ion battery beneficial from the wide availability and low cost of sodium, high theoretical specific capacity, and high energy density based on the plating/stripping processes and lowest electrochemical potential. For Na-metal batteries, the crucial problem on metallic Na is one of the biggest challenges. Mossy or dendritic growth of Na occurs in the repetitive Na stripping/plating process with an unstable solid electrolyte interphase layer of nonuniform ionic flux, which can not only lead to the low Coulombic efficiency, but also can create short circuit risks, resulting in possible burning or explosion. In this communication, the atomic layer deposition of Al2 O3 coating is first demonstrated for the protection of metallic Na anode for Na-metal batteries. By protecting Na foil with ultrathin Al2 O3 layer, the dendrites and mossy Na formation have been effectively suppressed and lifetime has been significantly improved. Furthermore, the thickness of protective layer has been further optimized with 25 cycles of Al2 O3 layer presenting the best performance over 500 cycles. The novel design of atomic layer deposition protected metal Na anode may bring in new opportunities to the realization of the next-generation high energy-density Na metal batteries.

Safe and Durable High-Temperature Lithium–Sulfur Batteries via Molecular Layer Deposited Coating

Lithium-sulfur (Li-S) battery is a promising high energy storage candidate in electric vehicles. However, the commonly employed ether based electrolyte does not enable to realize safe high-temperature Li-S batteries due to the low boiling and flash temperatures. Traditional carbonate based electrolyte obtains safe physical properties at high temperature but does not complete reversible electrochemical reaction for most Li-S batteries. Here we realize safe high temperature Li-S batteries on universal carbon-sulfur electrodes by molecular layer deposited (MLD) alucone coating. Sulfur cathodes with MLD coating complete the reversible electrochemical process in carbonate electrolyte and exhibit a safe and ultrastable cycle life at high temperature, which promise practicable Li-S batteries for electric vehicles and other large-scale energy storage systems.

Tailoring interactions of carbon and sulfur in Li-S battery cathodes: significant effects of carbon- heteroatom bonds†

In this study, effects of carbon–heteroatom bonds on sulfur cathodes were investigated. A series of carbon black substrates were prepared using various treatments to introduce nitrogen or oxygen surface species. Our results indicated that nitrogen-doped carbon black significantly improved the electrochemical performance of sulfur cathode materials. Synchrotron-based XPS revealed that the defect sites of nitrogen-doped carbon are favorable for the discharge product deposition, leading to a high utilization and reversibility of sulfur cathodes. Our studies also found that the introduction of oxygen functional groups results in deteriorated performance of Li–sulfur batteries due to the reduced conductivity and unwanted side reactions occurring between sulfur and surface oxygen species.

Highly Stable Na2/3(Mn0.54Ni0.13Co0.13)O2 Cathode Modified by Atomic Layer Deposition for Sodium-Ion Batteries

For the first time, atomic layer deposition (ALD) of Al2 O3 was adopted to enhance the cyclic stability of layered P2-type Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 (MNC) cathodes for use in sodium-ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g(-1) were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2 O3 coating from 2 ALD cycles (MNC-2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC-10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD-coated electrodes could be a result of the protection effects and high band-gap energy (Eg =9.00 eV) of the Al2 O3 coating layer. Additionally, the metal-oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2 O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.

Inorganic–Organic Coating via Molecular Layer Deposition Enables Long Life Sodium Metal Anode

Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al2O3 coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs.

A bifunctional solid state catalyst with enhanced cycling stability for Na and Li–O2 cells: revealing the role of solid state catalysts

Solid state catalysts play a critical role in peroxide alkali metal–O2 cells. However, the underlying mechanism behind the catalytic activity remains controversial due to the different nature of oxygen reduction and evolutions reactions (ORR, OER) in non-aqueous cells compared to those in classic aqueous based reactions. In the present study, we reveal a detailed spectroscopic and electrochemical picture of the mechanism of catalytic activity in Na– and Li–O2 cells. We demonstrate that ORR and OER catalytic activity in alkali metal–O2 cells primarily originates from the stabilization of O2− intermediates on the catalyst surface during the electrochemical reaction. Monitoring the electronic state of the solid state catalyst during the ORR and OER revealed a dynamic interaction occurring between the catalyst and the discharge product. The morphology and composition of discharge products is also illustrated to be influenced by solid state catalysts. The findings of the present study suggest that catalysts with a higher oxygen-bonding capability may exhibit a higher catalytic activity in alkali metal–O2 cells.

Atomically precise growth of sodium titanates as anode materials for high-rate and ultralong cycle-life sodium-ion batteries

Sodium-ion batteries (SIBs) have received increasing attention for applications in large-scale energy storage systems due to their low cost, high energy density, and high abundance of the sodium element. Nanosizing electrode materials becomes a key strategy to overcome the problems resulting from the sluggish kinetics of large sodium ions, thereby achieving good performance in SIBs. Herein, we developed an atomic layer deposition (ALD) approach for atomically precise fabrication of sodium titanate anode materials. This ALD process shows excellent controllability over the growth rate, film thickness, composition of sodium titanates, and high flexibility of coating uniform sodium titanate films onto various dimensions of substrates. Moreover, the amorphous sodium titanate deposited on carbon nanotubes exhibits high specific capacity, excellent rate capability, and ultra-long cycling life (∼100 mA h g−1 after 3500 cycles). It is expected that the ALD approach developed herein can be extended to well-defined fabrication of other sodium-containing electrode materials for SIBs.

Ultrasmall MoS2 embedded in carbon nanosheets-coated Sn/SnOx as anode material for high-rate and long life Li-ion batteries

A Sn/SnOx/MoS2/C composite material with superior performance was developed as an anode for lithium-ion batteries via a facile and scalable ball-milling method using a three-dimensional (3D) self-assembly of NaCl particles as a template. In the constructed architecture, carbon nanosheets avoided the direct exposure of encapsulated Sn/SnOx nanoparticles to the electrolyte and preserved the structural and interfacial stability of the nanoparticles, protecting them from volume expansion during the charge/discharge process. The MoS2 particles, uniformly dispersed on the carbon nanosheets, facilitate an efficient ion transport and ensure structural durability as a particle reinforcing agent. When used as an anode material in lithium-ion batteries, the as-prepared Sn/SnOx/MoS2/C composite exhibit a high rate performance and long cyclic stability, even at a high current density of 3 A g−1 (specific capacity of 725.3 mA h g−1 after 800 cycles). This simple fabrication method and the excellent electrochemical performance demonstrates the potential use of the Sn/SnOx/MoS2/C composite as an anode material for high-performance lithium-ion batteries.