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Variation of the MnO2 Birnessite Structure upon Charge/Discharge in an Electrochemical Supercapacitor Electrode in Aqueous Na2SO4 Electrolyte

“…Metal cations can easily move into or out of the interlayer region, which allows for example partial cations intercalations from an electrolyte in its lamellar structure. Several kinds of birnessite have been reported depending on the nature of the metal cations and their properties are dependent on the preparation conditions due to the facile change in the manganese oxidation state and in the occurrence of Mn(III) sites in the compound. ,, Synthesis of birnessite can be achieved by the oxidation of Mn 2+ in basic solution, the reduction of MnO 4 - in acidic solutions, or the redox reaction between Mn 2+ and MnO 4 - (redox precipitation processes) − ,,,− ,− by a sol−gel process ,,,− or by an hydrothermal treatment from a manganese oxide compound ,,− or more recently by electrochemical deposition from a manganese sulfate solution. ,,, …”

High-performance carbon-coated mesoporous LiMn2O4 cathode materials synthesized from a novel hydrated layered-spinel lithium manganate composite

“…[25][26][27] and R-MnO 2 . 28 Among them, birnessite-type lithium manganese oxide (d-type or Libirnessite) possesses a hydrated layered structure containing Li ions and crystal water between the layers, [29][30][31] contributing to the exotic properties in many elds. [32][33][34] Moreover, the layered phase is prone to generate the lamellar nanostructure 32,33 which can reduce the Li + diffusion pathway in the thickness direction and further improve the rate performance.…”