Recent progress and emerging application areas for lithium-sulfur battery technology

Electrification is progressing significantly within the present and future vehicle sectors such as large commercial vehicles (e. g. trucks and busses), high altitude long endurance (HALE), high altitude pseudo satellites (HAPS), and electric vertical take‐off and landing (eVTOL). The battery systems performance requirements differ across these applications in terms of power, cycle life, system cost, etc. However, the need for high gravimetric energy density, 400 Wh kg−1 and beyond, is common across them all, since it will enable vehicles to achieve extended range, longer mission duration, lighter weight or increased payload. The system level requirements of these emerging applications can be broken down into the component level developments required to integrate Li‐S technology as the power system of choice. In order to adapt the batteries’ properties, such as energy and power density, to the respective application, the academic research community has a key role to play in component level development. However, materials and component research must be conducted within the context of a viable Li‐S cell system. Herein, the key performance benefits, limitations, modelling and recent progress of the Li‐S battery technology and its adaption towards real world application are discusse

Confocal Microscopy for Process Monitoring and Wide-Area Height Determination of Vertically-Aligned Carbon Nanotube Forests

Confocal microscopy is introduced as a new and generally applicable method for the characterization of the vertically-aligned carbon nanotubes (VACNT) forest height. With this technique process control is significantly intensified. The topography of the substrate and VACNT can be mapped with a height resolution down to 15 nm. The advantages of confocal microscopy, compared to scanning electron microscopy (SEM), are demonstrated by investigating the growth kinetics of VACNT using Al2O3 buffer layers with varying thicknesses. A process optimization using confocal microscopy for fast VACNT forest height evaluation is presented

Nanostructured networks for energy storage: Vertically aligned carbon nanotubes (VACNT) as current collectors for high-power Li4Ti5O12(LTO)//LiMn2O4(LMO) lithium-ion batteries

As a concept for electrode architecture in high power lithium ion batteries, self-supported nanoarrays enable ultra-high power densities as a result of their open pore geometry, which results in short and direct Li+-ion and electron pathways. Vertically aligned carbon nanotubes (VACNT) on metallic current collectors with low interface resistance are used as current collectors for the chemical solution infiltration of electroactive oxides to produce vertically aligned carbon nanotubes decorated with in situ grown LiMn2O4 (LMO) and Li4Ti5O12 (LTO) nanoparticles. The production processes steps (catalyst coating, VACNT chemical vapor deposition (CVD), infiltration, and thermal transformation) are all scalable, continuous, and suitable for niche market production to achieve high oxide loadings up to 70 wt %. Due to their unique transport structure, as-prepared nanoarrays achieve remarkably high power densities up to 2.58 kW kg\u1000001, which is based on the total electrode mass at 80 C for LiMn2O4//Li4Ti5O12 full cells. The tailoring of LTO and LMO nanoparticle size (~20–100 nm) and VACNT length (array height: 60–200 m) gives insights into the rate-limiting steps at high current for these kinds of nanoarray electrodes at very high C-rates of up to 200 C. The results reveal the critical structural parameters for achieving high power densities in VACNT nanoarray full cells

Designing room temperature sodium sulfur batteries with long cycle-life at pouch cell level

The successful transfer of room temperature sodium sulfur (RT-Na-S) technology from coin cell to pouch cell level is demonstrated. The general cell design is based on a previously developed RT-Na-S concept implementing hard carbon based anodes. Scalable technologies known from lithium ion battery production are utilized for electrode production. The electrolyte composition, the voltage window as well as the balancing is evaluated on coin cell level leading to optimized parameters. For scaled electrodes and electrolytes, a specific capacity of 418 mAh gS −1 coupled with a high coulombic efficiency of 95.3% can be still obtained in RT-Na-S coin cells after a total of 549 cycles. Residual carbonates in the HC-anode were found to deteriorate the cycling performance. An increased cut-off voltage (1.5 V) significantly raises the coulombic efficiency. Finally, the design is successfully transferred to a 10-layered pouch cell leading to a high energy efficiency of 88.6% and a capacity of 387 mAh gS −1 after a total of 937 cycles. Hence, the present work shows the principle feasibility of a stationary energy storage technology based on RT-Na-S pouch cell technology

Enabling electrolyte compositions for columnar silicon anodes in high energy secondary batteries

Columnar silicon structures are proven as high performance anodes for high energy batteries paired with low (sulfur) or high (nickel-cobalt-aluminum oxide, NCA) voltage cathodes. The introduction of a fluorinated ether/sulfolane solvent mixture drastically improves the capacity retention for both battery types due to an improved solid electrolyte interface (SEI) on the surface of the silicon electrode which reduces irreversible reactions normally causing lithium loss and rapid capacity fading. For the lithium silicide/sulfur battery cycling stability is significantly improved as compared to a frequently used reference electrolyte (DME/DOL) reaching a constant coulombic efficiency (CE) as high as 98%. For the silicon/NCA battery with higher voltage, the addition of only small amounts of fluoroethylene carbonate (FEC) to the novel electrolyte leads to a stable capacity over at least 50 cycles and a CE as high as 99.9%. A high volumetric energy density close to 1000 Wh l−1 was achieved with the new electrolyte taking all inactive components of the stack into account for the estimation