Killian Stokes

SINTEF Industry · Battery Technologies

A persistent obstacle towards the realization of high voltage cathodes is electrolyte instability where oxidation and transition metal dissolution manifest in rapid capacity failure with both issues connected to the presence of ethylene carbonate in the electrolyte. Here, alternative electrolyte co‐solvents are investigated and compared, where the...

Two different types of electrolytes (co-solvent and multi-salt) are tested for use in high voltage LiNi0.5Mn1.5O4||Si/graphite full cells and compared against a carbonate-based standard LiPF6 containing electrolyte (baseline). Ex situ postmortem XPS analysis on both anodes and cathodes over the life span of the cells reveals a continuously growing...

Spinel LiNi0.5Mn1.5O4 as a high-energy positive electrode material for next-generation Li-ion batteries has attracted significant interest due to its economic and environmental advantages. However, the sensitivity of this type of material upon short- to long-term ambient storage conditions and the impact on the electrochemical performances remains...

Silicon is a highly promising electrode material for Li-ion batteries because of its high theoretical capacity, but severe volume changes during cycling leads to pulverization and rapid capacity fading. The use of alternative and water-soluble polymer binders such as poly(vinyl alcohol) (PVA) or poly(acrylic acid) (PAA) can improve the cycling perf...

A scalable and cost‐effective process is used to electroplate metallic Zn seeds on stainless steel substrates. Si and Ge nanowires (NWs) are subsequently grown by placing the electroplated substrates in the solution phase of a refluxing organic solvent at temperatures >430 °C and injecting the respective liquid precursors. The native oxide layer fo...

Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAhg-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13FSI-0.3PYR13TFSI) . We show using post-mortem SEM and TEM, a distinct difference in morphologies of the active...

Two-dimensional (2D) layered materials are a quickly evolving area of scientific exploration, with engineering of these into further constrained dimensions and engineered architectures offering the possibility of unique physical insights. Constructing nanomaterials in dimensionally-constrained 2D network architectures is a viable way for the improv...

CuZnSe2 (CZSe) is an important ternary semiconductor comprised of earth-abundant elements with a suitable bandgap for visible light absorption and structural/stoichiometric versatility that make it a promising candidate for photovoltaic applications. Here we report the controlled synthesis of this compound copper chalcogenide in nanocrystal form us...

Herein, copper silicide (Cu15Si4) nanowires (NWs) grown in high densities from a metallic Cu substrate are utilized as nanostructured hosts for amorphous silicon (aSi) deposition. The conductive Cu15Si4 NW scaffolds offer an increased surface area, versus planar substrates, and enable the preparation of high capacity Li-ion anodes consisting of a n...

Herein, the electrochemical performance of directly grown Ge nanowire anodes in full-cell Li-ion configurations (using lithium cobalt oxide cathodes) are examined. The impacts of voltage window, anode/cathode balancing and anode preconditioning are assessed. The cells had a useable upper cutoff of 3.9 V, with a higher voltage cutoff of 4.2 V shown...

Herein, textured Cu foil is presented as an attractive current collector substrate for directly grown Ge nanowire (NW) anodes. Compared to planar stainless steel (SS) current collectors, textured Cu led to an increase in achievable mass loading, removal of the requirement for a catalyst deposition step, improved adhesion of the active material and...

Interactions between hydrophobic drugs and endogenous gastrointestinal substances have the potential to manipulate drug concentration in the human gastrointestinal system, and thus likely play an important role in determining the rate of absorption for hydrophobic drugs. The effects of phospholipids, bile salts and digestive proteins on the solutio...

Highly aligned Copper Zinc Tin Sulfide (CZTS) nanorods (NRs) electrophoretically deposited directly on the current collector are tested for suitability as Li-ion battery (LIB) anodes in both half cell (HC) and full cell (FC) configurations. This facile fabrication process offers several advantages for high-performance nanostructured battery electro...

Here, we report the application of axially heterostructured nanowires consisting of alternating segments of silicon and germanium, with a tin seed, as lithium-ion battery anodes. During repeated lithiation and delithiation, the heterostructures completely rearrange into a porous network of homogenously alloyed Si1-xGex ligaments. The transformation...

Herein, we report the formation of silicon, germanium and more complex Si-SixGe1-x and Si-Ge axial 1D heterostructures, at low temperatures in solution. These nanorods/nanowires are grown using phenylated compounds of silicon and germanium as reagents, with precursor decomposition achieved at substantially reduced temperatures (200 °C -for single c...

Li‐ion batteries containing cost‐effective, environmentally benign cathode materials with high specific capacities are in critical demand to deliver the energy density requirements of electric vehicles and next‐generation electronic devices. Here, the phase‐controlled synthesis of copper sulfide (CuxS) composites by the temperature‐controlled sulfu...

Here we report the formation of high capacity Li-ion battery anodes from Si1-xGex alloy nanowire arrays that are grown directly on stainless steel current collectors, in a single step synthesis. The direct formation of these Si1-xGex nanowires (ranging from Si0.20Ge0.80 to Si0.67Ge0.33) represents a simple and efficient processing route for the pro...

Here we report the rational design of a high-capacity Li-ion anode material comprising of Ge nanowires with Si branches. The unique structure provides an electrode material with tunable properties, allowing the performance to be tailored for either high capacity or high rate capability by controlling the mass ratio of Si to Ge. The binder free Si-G...