An energy storage composition can be used as a new Na-ion battery cathode material. The energy storage composition with an alluaudite phase of A.sub.xT.sub.y(PO4).sub.z, Na.sub.xT.sub.y(PO4).sub.z, Na.sub.1.702Fe.sub.3(PO4).sub.3 and Na.sub.0.872Fe.sub.3(PO4).sub.3, is described including the hydrothermal synthesis, crystal structure, and electrochemical properties. After ball milling and carbon coating, the compositions described herein demonstrate a reversible capacity, such as about 140.7 mAh/g. In addition these compositions exhibit good cycling performance (93% of the initial capacity is retained after 50 cycles) and excellent rate capability. These alluaudite compounds represent a new cathode material for large-scale battery applications that are earth-abundant and sustainable.

An energy storage composition can be used as a new Na-ion battery cathode material. The energy storage composition with an alluaudite phase of A.sub.xT.sub.y(PO4).sub.z, Na.sub.xT.sub.y(PO4).sub.z, Na.sub.1.702Fe.sub.3(PO4).sub.3 and Na.sub.0.872Fe.sub.3(PO4).sub.3, is described including the hydrothermal synthesis, crystal structure, and electrochemical properties. After ball milling and carbon coating, the compositions described herein demonstrate a reversible capacity, such as about 140.7 mAh/g. In addition these compositions exhibit good cycling performance (93% of the initial capacity is retained after 50 cycles) and excellent rate capability. These alluaudite compounds represent a new cathode material for large-scale battery applications that are earth-abundant and sustainable.

Disclosed are a method for preparing lithium iron manganese phosphate precursor and a method for preparing lithium iron manganese phosphate. The method for preparing lithium iron manganese phosphate precursor comprises the following steps: (1) preparing liquid material A and liquid material B, wherein the liquid material A is a mixed solution of manganese salt and iron salt, and the liquid material B is oxalic acid or phosphoric acid solution; (2) subjecting liquid material A and liquid material B to a co-precipitation reaction in a rotary packed bed (100) to obtain a first slurry; (3) washing and filtering the first slurry to obtain a filter cake; (4) mixing the filter cake with water, adding a carbon source, and stirring until uniform to obtain a second slurry; (5) homogenizing the second slurry; (6) drying the homogenized second slurry, to obtain the lithium iron manganese phosphate precursor. The particle size of the lithium iron manganese phosphate precursor prepared by the method is finer and more uniform than that of a precursor prepared by a traditional method using a reaction kettle, the preparation speed is increased, and the carbon coating is more uniform. FIG. 1: : lithium iron manganese phosphate precursor FIG. 2: : lithium iron manganese phosphate FIG. 3: (V): Voltage (V) (mAh/g): Specific capacity (mAh/g) : charge curve : discharge curve FIG. 4: (mAh/g): Discharge specific capacity (mAh/g) METHOD FOR PREPARING LITHIUM IRON MANGANESE PHOSPHATE PRECURSOR AND METHOD FOR PREPARING LITHIUM IRON MANGANESE PHOSPHATE