Development of Novel Cathode with Large Lithium Storage Mechanism Based on Pyrophosphate‐Based Conversion Reaction for Rechargeable Lithium Batteries

Abstract

A conversion‐reaction‐based nanosized Cu2P2O7–carbon composite is investigated as a novel cathode material with superior capacity for lithium‐ion batteries. To overcome the sluggish kinetics of the conversion reaction, the nanosized Cu2P2O7–carbon composite is prepared by high‐energy ball‐milling of Cu2P2O7 and conductive carbon to achieve simultaneous nanosizing and carbon mixing. The nanosized Cu2P2O7–carbon composite exhibits a large specific capacity of ≈355 mAh g−1 with an average operation voltage of ≈2.8 V (vs Li+/Li). Moreover, even at 10C (1C = 355 mA g−1), the composite delivers a capacity of ≈215 mAh g−1, corresponding to ≈60% of its theoretical capacity. For 400 cycles at 1C, the nanosized Cu2P2O7–carbon composite exhibits capacity retention of ≈72% compared with the initial capacity as well as high Coulombic efficiency of more than 99%. The reversible conversion reaction mechanism of the nanosized Cu2P2O7–carbon composite under the Li‐cell system is confirmed using various techniques, including operando/ex situ X‐ray diffraction, X‐ray absorption near edge structure spectroscopy, extended X‐ray absorption fine structure spectroscopy, and transmission electron microscopy. It is verified that Cu2P2O7 is converted into Li4P2O7 and metallic Cu0 on discharge and reversibly recovered to Cu2P2O7 on charge.

Recent Developments of Two-Dimensional Anode Materials and Their Composites in Lithium-Ion Batteries

“…Following the development of graphene, monatomic layer 2D materials of B, Si, P, Ge, As, and other elements adjacent to C were also developed in succession. This series of materials was named Xenes (X = B, Si, P, Ge, As). − The surface atoms of these single-layer Xenes are almost completely exposed. Compared with bulk materials, the atom utilization rate is greatly improved.…”

Synthesis and Applications of Nanostructured Hollow Transition Metal Chalcogenides

“…[157] The material can also undergo a reversible conversion reaction, which provides a higher specific capacity, rather than irreversibly inserting lithium ions into the main crystal structure of the structural change. [158] A common method of combining carbon and sulfur is through physical mixing or chemical hybridization. [159,160] TMC are usually bonded to carbon because their polar positions have better interactions with polysulfides, which can significantly reduce polysulfide shuttles.…”

Similarity between the redox potentials of 3d transition-metal ions in polyanionic insertion materials and aqueous solutions

“…The relationship between these potentials is then discussed from the thermodynamic point of view. Polyanionic materials composed of LiMPO 4 -olivine (M = 3d transition metal) [14][15][16] and Li x M 2 (XO 4 ) 3 -sodium superionic conductors (NASICON) 17 and their analogues [18][19][20] have been extensively investigated, and the development of these materials has shown remarkable progress. The electrochemical insights gained from this study could be used to tailor the electrode potential of transition-metal ions and stimulate the development of novel polyanionic materials.…”