▎ 摘　　要

NOVELTY - Carbon quantum dot or its derivatives coated phosphoric acid pyrophosphoric acid iron magnesium sodium composite material comprises phosphoric acid pyrophosphoric acid iron magnesium sodium particle as core and a surface carbon coating layer, where the chemical formula of phosphoric acid pyrophosphoric acid iron magnesium sodium is Na4Fe3-xMgx(PO4)2P2O7, where x = 0-1. USE - The composite material is useful for preparing anode material or anode sheet of ion batteries (claimed). ADVANTAGE - The material: has high specific capacity, stable working voltage, excellent rate, cycle stability, simple preparation method, and large-scale production. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: preparing the carbon quantum dot or its derivative coated phosphoric acid magnesium iron phosphate composite material; an anode material prepared by the composite material; an anode sheet prepared by using the composite material; and a sodium-ion battery assembled by the anode sheet.