Self-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity.

Inorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C 6 H 10 N 2 ] 2 [Mo 8 O 26 ] ⋅ 6 H 2 O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C 6 H 9 N 2 ] 4 [NH 4 ] 2 [Mo 7 O 24 ] ⋅ 3 H 2 O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g -1 at 100 mA g -1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li 2 MoO 4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.