Cation energy storage device and methods
AssigneeBrown University
InventorsG. Tayhas R. Palmore, Dan Liu
Life of this patent
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Abstract
An energy storage composition can be used as a new Na-ion battery cathode material. The energy storage composition with an alluaudite phase of AxTy(PO4)z, NaxTy(PO4)z, Na1.702Fe3(PO4)3 and Na0.872Fe3(PO4)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.
Claims18
A composition comprising a material having an alluaudite crystal structure;
- wherein the alluaudite crystal structure is made by a method comprising the steps of:
- (1) dissolving reactants (A) (NH4)2Fe(SO4)2-6H2O, (B) H3PO4, and (C) NaOH in water with a 1:1:3 molar ratio (A:B:C), thereby forming a cathode solution;
- and
- (2) heating the cathode solution, whereby said reactants crystallize in a monoclinic C 2/c space group consisting of pure alluaudite crystal;
- and
- wherein the alluaudite crystal structure comprises formula (I):
- Na1.702Fey(PO4)z (formula I);
- wherein y is greater than or equal to 3 and less than or equal to 3.5, and wherein z is greater than or equal to 1 and less than or equal to 3.
A method of making a material having an alluaudite crystal structure capable of providing an energy storage capacity of up to about 160 mAh/g, the method comprising the steps of:
- (1) dissolving reactants (A) (NH4)2Fe(SO4)2-6H2O, (B) H3PO4, and (C) NaOH in water with a 1:1:3 molar ratio (A:B:C), thereby forming a cathode solution;
- and
- (2) heating the cathode solution, whereby said reactants crystallize in a monoclinic C 2/c space group consisting of pure alluaudite crystal;
- and
- wherein the alluaudite crystal structure comprises formula (I):
- Na1.702Fey(PO4)z (formula I);
- wherein y is greater than or equal to 3 and less than or equal to 3.5, and wherein z is greater than or equal to 1 and less than or equal to 3.
Dependencies are inferred from the claim text.