High Power Battery Systems Research Articles

Electrode/electrolyte interface adjustment through adding mannitol into the solution to improve the re-discharge performance of alkaline Al-air batteries

As a high-power battery system, Al-air batteries exhibit a wide range of potential applications. However, Al-air batteries are susceptible to significant open-circuit corrosion of the aluminum electrodes when removed from the electrolyte during standby, resulting in the formation of a dense film of corrosion products on the aluminum electrode surface. This, in turn, impedes the re-discharge performance of Al-air batteries. Based on an electrode/electrolyte interface adjustment strategy, mannitol is used as the additive to be added into 4 M KOH solution to improve re-discharge performance. Experimental analyses and theoretical calculations reveal that the inclusion of mannitol enhances the re-discharge performance of Al-air batteries through a combination of hydrogen bonding and adsorption. Importantly, it is noted that mannitol has minimal impact on the battery power density. The reason for the improvement is explained reasonably by a proposed mechanism. These findings offer valuable insights for the development of Al-air batteries with high performance.

Analysis of Interfacial Effects in All-Solid-State Batteries with Thiophosphate Solid Electrolytes.

All-solid-state batteries (ASSBs) present a promising route toward safe and high-power battery systems in order to meet the future demands in the consumer and automotive market. Composite cathodes are one way to boost the energy density of ASSBs compared to thin-film configurations. In this manuscript, we investigate composites consisting of β-Li3PS4 (β-LPS) solid electrolyte and high-energy Li(Ni0.6Mn0.2Co0.2)O2 (NMC622). The fabricated cells show a good cycle life with a satisfactory capacity retention. Still, the cathode utilization is below the values reported in the literature for systems with liquid electrolytes. The common understanding is that interface processes between the active material and solid electrolyte are responsible for the reduced performance. In order to throw some light on this topic, we perform 3D microstructure-resolved simulations on virtual samples obtained via X-ray tomography. Through this approach, we are able to correlate the composite microstructure with electrode performance and impedance. We identify the low electronic conductivity in the fully lithiated NMC622 as material inherent restriction preventing high cathode utilization. Moreover, we find that geometrical properties and morphological changes of the microstructure interact with the internal and external interfaces, significantly affecting the capacity retention at higher currents.

Overlap joining of aluminium and copper using laser micro welding with spatial power modulation

The rising demand for high power battery systems for the electric mobility requires the connection of a large number of cells. Due to the functionality of the cell chemistry, a combination of copper and aluminium is necessary. The differing material properties like thermal conductivity as well as the formation of intermetallic phases are challenging for welding processes. This study contains the results for overlap joints of copper and aluminium using a laser beam welding process with spatial power modulation. With a parameter variation, the cross-sectional shape of the weld seams and therefore, the ratio of depth to width can be adjusted. With additional longitudinal cross sections and an energy-dispersive X-ray spectroscopy analysis, the different mixing behaviour of the dissimilar material depending on the top layer is investigated.

Factors Determining Ionic Mobility in Ion Migration Pathways of Polypropylene (PP) Separator for Lithium Secondary Batteries

To clarify the primary ion-transport factors in separator membranes, we evaluated the effects of pathway tortuosity and width on the mobilities (Dca and Dan) and microviscosities (η, α, and βca) of ions in a PP separator. Ionic diffusivities in different directions, along and inclined to the straight pathway composed of aligned pores, were compared to understand the effect of the geometrical pathway tortuosity. For cations in a specific solution moving along the straight pathway (tortuosity ∼ 1), the βca value attributable to cation–membrane interaction was around zero, which was different than the positive values of βca of cations of the same solution in random-network pathways with higher tortuosity. When cations diffuse in the direction inclined to the straight pathway, which corresponds to ion migration in a pathway of tortuosity > 1, βca was larger than both η and α attributed to the interactions between the ions and surrounding species. On the other hand, α and η were almost independent of pathway tortuosity and depended on the pathway width instead. These results suggest that reducing the geometrical pathway tortuosity of the separator, which assumes an ideal form with straight pathways, is key to designing separators for high ionic mobility in a high-power battery system.

Nanomanufacturing of graphene nanosheets through nano-hole opening and closing

Abstract Facile and scalable fabrication of highly dense and high-quality graphene films and articles is extremely attractive for a range of electronic and mechanical applications. Pristine, high-quality graphene with its inherent impermeability poses challenges in fabricating dense films and thick parts with high electrical conductivity due to the difficulty in removing trapped air and/or solvents used in various fabrication methods. To overcome this deficiency, nano-holes were intentionally created in pristine graphene (“holey graphene”) with an average diameter of approximately 15 nm. The holes serve as pathways for the rapid removal of gases or liquids and enable the fabrication of dense holey graphene nanostructures. Subsequently, a high-temperature process is applied to effectively repair the nano-holes and recover the high-quality graphene conjugated network. Through the creation and repair of the nano-holes, dense graphene articles that exhibited an ultrahigh conductivity of 2209 S/cm and superior thermal conductivity of 863 W/mK were created. This unique processing methodology enables the facile and scalable fabrication of high-quality graphene constructs, which can be easily integrated into the next generation of electronic circuits and high-power battery systems for highly efficient and lightweight thermal management.

Nanostructured Anode Material for High‐Power Battery System in Electric Vehicles

A new MSNP-LTO anode is developed to enable a high-power battery system that provides three times more power than any existing battery system. It shows excellent cycle life and low-temperature performance, and exhibits unmatched safety characteristics.

High power battery systems for hybrid vehicles

Pure electric and hybrid vehicles have differing demands on the battery system of a vehicle. This results in correspondingly different demands on the battery management of a hybrid vehicle. Examples show the differing usage patterns. The consequences for the battery cells and the battery management are discussed. The importance of good thermal management is underlined.

Advanced bipolar lead–acid battery for hybrid electric vehicles

A large size 80 V bipolar lead acid battery was constructed and tested successfully with a drive cycle especially developed for a HEV. The bipolar battery was made using the bipolar plate developed at TNO and an optimised paste developed by Centurion. An empirical model was derived for calculating the Ragone plot from the results from a small size 12 V bipolar lead–acid battery. This resulted in a specific power of 340 W/kg for the 80 V module. The Ragone plot was calculated at t=5 and t=10 s after the discharge started for current densities varying from 0.02 to 1.2 A/cm 2. A further development of the bipolar lead–acid battery will result in a specific power of 500 W/kg or more. From the economic analysis we estimate that the price of this high power battery will be in the order of 500 US$/kWh. This price is substantially lower than for comparable high power battery systems. This makes it an acceptable candidate future for HEV.