A facile and surfactant-free synthesis of porous hollow λ-MnO2 3D nanoarchitectures for lithium ion batteries with superior performance

A direct Li2O2 mediated solution-based synthesis is successfully applied to produce self-assembled 3D architectures of porous hollow λ-MnO2 structures. In general, λ-MnO2 can be obtained by the extraction of lithium from LiMn2O4 using traditionally applied complex chemical methods such as electrochemical or acid leaching. Due to its 3D spinel structure, λ-MnO2 can be applied in various applications, for example, as a catalyst, or an electrode material for capacitors. However, only a few research groups have applied λ-MnO2 as an anode material for rechargeable lithium ion batteries because of its complex preparation, especially in nanoscale. Here, we developed a surfactant-free synthesis method to obtain randomly arranged porous hollow λ-MnO2 nanostructures. Each hollow particle is accompanied with meso/nanoporous shell with a nanosized wall thickness (∼80 nm) while the outer wall of each particle is decorated with nanoflakes with a wall thickness of ∼10 nm. Due to its unique morphology, the electrochemical properties regarding specific capacity, cycleability, and rate capability of λ-MnO2 are significantly improved. Electrodes made with porous hollow λ-MnO2 deliver high capacities of ∼1400 mAh g−1 at 100 mA g−1 and ∼749 mAh g−1 at 1000 mA g−1, showing the highest reversible capacity and rate capability among reported nanostructured MnO2 materials. The distinctive morphology of porous hollow λ-MnO2 facilitates the reaction kinetics of the reversible conversion reaction, which enhances the electrochemical performance. •Hollow porous λ-MnO2 is synthesized by a surfactant free solution based method.•Li2O2 plays a dual role as a host template and as an oxidizing agent.•Hollow porous λ-MnO2 has large surface area with mesoporous nature.•The distinctive structure offers superior rate capability and cycleability.