In this issue, J. Janek et al. review LiNiO₂ as an active cathode material in Li-ion batteries. What is the effect of lithium off-stoichiometry, how can instability issues be overcome? In a further Review, F. Glorius et al. discuss selective arene hydrogenation for direct access to saturated carbo- and heterocycles. The Minireviews deal with organic photoacid and photobase generators for polymerizations (H. Sardon et al.) and peptide assemblies in complex environments (B. Xu et al.). H.-J. Werner et al. comment on a recent Communication by K.-i. Shudo et al. on core electron topologies in chemical compounds, a case study of carbon vs. silicon, and the latter reply.

In the original research section, J. Cho et al. describe oxygen vacancy diffusion and condensation in lithium-ion battery cathode materials (see picture). S.-L. You et al. elaborated an iridium-catalyzed asymmetric allylic aromatization reaction. H. Schönherr et al. investigate the propagation and purification of human induced pluripotent stem cells with selective homopolymer release surfaces. H. G. Börner et al. learned from peptides to access functional precision polymer sequences.

• Angewandte Chemie 31/2019: Learning,
  Angew. Chem. Int. Ed. 2019, 58 (31).