Tracking the pyrolysis process from 2D Mn2n polymer to high-rate anode materials for lithium ion batteries

By manipulating the pyrolysis of multidimensional precursors, excellent energy storage materials can be obtained. On the molecular level, however, the pyrolysis tracking and evolution of two-dimensional (2D) precursors require additional study. Here, we designed a 2D layered Mn-based polymer ( Mn _2n, [Mn ₂L ₂(CH ₃OH) ₂] _n, L = 3-ethoxylsalicylate iso-nicotinyl hydrazone) bridged with L as a precursor, and obtained a 2D porous nanosheet N-doped carbon skeleton embedded with Mn ²⁺O (Mn ²⁺ O/NC) through controlled pyrolysis under an inert atmosphere. The pyridine nitrogen coordination of isoniazid is astonishingly essential for the formation of 2D layered Mn _2n polymers. The formation of Mn-N(pyridine) bonds serves as a bridge between the basic units of Mn ₂ . Thermogravimetric mass spectrometry (TG-MS) could track the pyrolysis process and provide a potential evolutionary from a 2D Mn _2n precursor to a 2D porous nanosheet Mn ²⁺O/NC structure. The specific capacity of Mn ²⁺O/NC-800 electrode reaches up to 614.1 mAh g ⁻¹ after 600 cycles at 200 mA g ⁻¹ current density when the pyrolysis product is used as the anode material of lithium ion battery. Dynamic analysis indicates that the 2D porous nanosheet structure of Mn ²⁺ O/NC has a high pseudocapacitance contribution and charge transfer efficiency, which effectively improves the performance of lithium ion batteries. This work will provide a useful guidance for the design of new electrode materials.