Development of Quaternized Chitosan Integrated with Nanofibrous Polyacrylonitrile Mat as an Anion-Exchange Membrane

A two-phase anion-exchange membrane was prepared from quaternized chitosan (QCS) integrated with an electrospun polyacrylonitrile (PAN) scaffold by spin coating. To synthesize QCS, glycidyltrimethylammonium chloride in various amounts was introduced into the structure of CS. The characterization of the cast cross-linked QCS (CQCS) membranes by impedance spectroscopy revealed the ionic conductivity (IC) in the range of 2.8 × 10–4 to 8.2 × 10–4 S cm–1 and the degree of quaternization (DQ) of 26.4–51.0%, where the CQCS film with the DQ of 51.0% showed excellent performance. When CQCS was reinforced with a PAN fiber mat, the newly developed composite membrane demonstrated the highest IC of 34 × 10–4 S cm–1 at 80 °C, low swelling, and an almost eightfold increase in tensile strength at a fully hydrated state compared to pristine materials. Moreover, the CQCS/PAN membrane was chemically stable and revealed increasing hydroxide transport during 1 month immersion in alkaline media

Li_2.0Ni_0.67N, a Promising Negative Electrode Material for Li-Ion Batteries with a Soft Structural Response

The layered lithium nitridonickelate Li_2.0(1)Ni_0.67(2)N has been investigated as a negative electrode in the 0.02–1.25 V vs Li⁺/Li potential window. Its structural and electrochemical properties are reported. Operando XRD experiments upon three successive cycles clearly demonstrate a single-phase behavior in line with the discharge–charge profiles. The reversible breathing of the hexagonal structure, implying a supercell, is fully explained. The Ni²⁺/Ni⁺ redox couple is involved, and the electron transfer is combined with the reversible accommodation of Li⁺ ions in the cationic vacancies. The structural response is fully reversible and minimal, with a maximum volume variation of 2%. As a consequence, a high capacity of 200 mAh g^–1 at C/10 is obtained with an excellent capacity retention, close to 100% even after 100 cycles, which makes Li_2.0(1)Ni_0.67(2)N a promising negative electrode material for Li-ion batteries