Holger Hain

Future high-energy density anode materials from an automotive application perspective

Ramping up the full-electric vehicle market share heavily relies on the extension of electrical driving range, as well as on the reduction of charging time and cost. New Li-batteries should, at the same time, offer at least the same levels of power, lifetime and safety as the one nowadays available on the market. The achievement of these goals requires the development of new electrode materials with improved capacity, operating voltage, transport properties together with cycling and temperature stability. Several new anode materials have been proposed over the last decade. In this contribution we critically evaluate their chance to find application in the future automotive batteries. First, we discuss their properties at the materials level, subsequently, the energy density for selected candidates is calculated at the automotive battery cell level using an in-house developed software. If available, literature results concerning power capability and lifetime are also discussed with reference to the automotive targets.

Systematic control of α-Fe2O3 crystal growth direction for improved electrochemical performance of lithium-ion battery anodes

α-Fe2O3 nanomaterials with an elongated nanorod morphology exhibiting superior electrochemical performance were obtained through hydrothermal synthesis assisted by diamine derivatives as shape-controlling agents (SCAs) for application as anodes in lithium-ion batteries (LIBs). The physicochemical characteristics were investigated via XRD and FESEM, revealing well-crystallized α-Fe2O3 with adjustable nanorod lengths between 240 and 400 nm and aspect ratios in the range from 2.6 to 5.7. The electrochemical performance was evaluated by cyclic voltammetry and charge–discharge measurements. A SCA test series, including ethylenediamine, 1,2-diaminopropane, 2,3-diaminobutane, and N-methylethylenediamine, was implemented in terms of the impact on the nanorod aspect ratio. Varied substituents on the vicinal diamine structure were examined towards an optimized reaction center in terms of electron density and steric hindrance. Possible interaction mechanisms of the diamine derivatives with ferric species and the correlation between the aspect ratio and electrochemical performance are discussed. Intermediate-sized α-Fe2O3 nanorods with length/aspect ratios of ≈240 nm/≈2.6 and ≈280 nm/≈3.0 were found to have excellent electrochemical characteristics with reversible discharge capacities of 1086 and 1072 mAh g−1 at 0.1 C after 50 cycles.