Their functioning mechanism is the electrochemical intercalation of ions from the electrolyte into the solid-state host structure of the electrode materials. Layered transition metal oxides (TMOs) are common intercalation hosts utilized as cathode materials, but also as alternatives for carbon-based anode materials in both lithium-and sodium-ion batteries. Among them, titanate-based materials have attracted interest due to their relative abundance, low toxicity and structural/chemical tunability. They can often serve as host structures for both lithiumand sodium-ions making them highly versatile. Hydrogen titanates are a family of metastable materials derived from layered alkali titanates. They are typically synthesized in acidic solution by etching and topotactic exchange of the alkali ion in the interlayer space by protons and/or water. This provides them with a high degree of structural/chemical tunability of their nanoconfined interlayer composition, comparable to two-dimensional Ti3C2Tx MXenes derived via a similar selective etching approach. These materials' nanoconfinement environment, in turn, can have an effect on their electrochemical ion intercalation properties. In the layered hydrogen titanate H2Ti3O7, it was found that confined interlayer protons are the determining structural feature to enable electrochemical H + intercalation. This is because they separate the titanate layers, allowing to effectively compensate electrochemically induced strain by contraction/expansion without altering intralayer structure. Interlayerexpansion of layered titanate hollow spheres by confined Mg 2+ ions was demonstrated as a design strategy for electrochemical Na + intercalation hosts. An investigation into different types of confined alkali ions (Li + , Na + , K + , Cs + ) within lepidocrocite-type layered titanates revealed that the interlayer spacing is expanded with increasing ion size (0.68 to 0.85 nm). However, sodium-modified titanate showed the highest capacity for electrochemical Na + intercalation hosts (153 mAh g -1 ), even though this material has a smaller interlayer spacing than the cesium-modified titanate (95 mAh g -1 ), demonstrating the importance of nanoconfinement chemistry in addition to just geometrical considerations. In the layered hydrogen titanate H2Ti2O5 system, it was found that K + intercalation can be accomplished most efficiently, especially at low temperatures (-40 °C), for the material with confined interlayer water (H2Ti2O5•H2O, "HTO"), compared to its dehydrated form with additional interlayer defects ("QTO") that also exhibits smaller interlayer spacing (0.78 nm for QTO vs. 0.84 nm for HTO). The authors attribute this to ion-solvent cointercalation from the organic electrolyte into HTO, which is enabled by strong K + /1,2-dimethoxyethane binding energy (electrolyte effect) and a charge shielding effect of confined interlayer H2O (electrode effect). These results motivate us to explore the structural motifs that enable such favorable electrochemical cointercalation effects in titanates. Besides interlayer modification of layered titanates with simple cations or crystal water, the introduction of organic pillar molecules like alkylamines offers an even wider materials design space, with the potential to induce effective cointercalation phenomena. However, no clear materials design rules for host materials on how to control cointercalation have emerged so far. Specifically, there is an urgent need to identify how electrochemically induced strain is compensated in strongly expanded / pillared titanates and whether layerseparating or cross-linking pillaring approaches favor electrochemical kinetics.