Abstract: A continuous reaction system for preparing a ferromanganese oxalate precursor may comprise a first dissolution reactor, a second dissolution reactor, a first reactor, a second reactor, a material storage tank, and an ultrasonic reactor; the first dissolution reactor may be configured to accommodate a metal salt solution required for preparing the ferromanganese oxalate precursor, and the second dissolution reactor may be configured to accommodate a precipitant solution required for preparing the ferromanganese oxalate precursor; the first reactor may include a first feed port and a first overflow port, and the first feed port of the first reactor may be interconnected to a first discharge port of the first dissolution reactor and a second discharge port of the second dissolution reactor respectively through two pipelines.

Abstract: A lithium manganese iron phosphate positive electrode active material, preparation method, a positive electrode plate, a secondary battery and an electrical apparatus are disclosed. The method comprises: mixing and grinding an iron source, a solid base and optionally a source of doping element M After grinding, impurities are removed to obtain a nanoscale iron-containing oxide; mixing the obtained nanoscale iron-containing oxide with a solvent, a lithium source, a manganese source, a phosphorus source, optionally a source of doping element N, optionally a source of doping element Q and optionally a source of doping element R in a predetermined ratio and then grinding. After grinding, granulating to obtain a powder; and sintering the powder to obtain the lithium manganese iron phosphate positive electrode active material. A lithium manganese iron phosphate positive electrode active material having both good electrochemical performance and high tap density can be obtained.