Patent
Olivine-type compounds, their preparation and use in cathode materials for sodium-ion batteries. The olivine-type compounds may be obtained by a direct synthesis embodying a hydrothermal method. The method may include preparing an aqueous mixture including a M-containing compound, a M′-containing compound and a M″-containing compound to obtain a M-M′-M″ mixture; adding a P-containing compound to the mixture M-M′-M″ mixture to obtain a M-M′-M″-P mixture; adding a Na-containing compound to the M-M′-M″-P mixture to obtain a Na-M-M′-M″-P mixture; and introducing the Na-M-M′-M″-P mixture into an autoclave to perform crystal growth and obtain the compound of general formula Na h M i M′ j M″ k PO 4 .
1. A method of preparing a cathode material comprising a compound of general formula Na h M i M′ j M″ k PO 4 , wherein: 0<h≤1, 0<i≤1, 0<j≤1 and 0<k≤1, and wherein M, M′ and M″ are each independently a metal, the method comprising the steps of:
(a) preparing an aqueous mixture comprising a M-containing compound, a M′-containing compound and a M″-containing compound to obtain a M-M′-M″ mixture;
(b) adding a P-containing compound to the M-M′-M″ mixture to obtain a M-M′-M″-P mixture;
(c) adding a Na-containing compound to the M-M′-M″-P mixture to obtain a Na-M-M′-M″-P mixture;
(d) introducing the Na-M-M′-M″-P mixture into an autoclave to perform crystal growth and obtain the compound of general formula Na h M i M′ j M″ k PO 4 ;
(e) fast-cooling the crystals; and
(f) drying the cooled crystals.
2. The method of claim 1 , wherein step (f) is performed at a temperature of about 50-85° C. for a period of about 6-12 hours.
3. The method of claim 1 , wherein step (f) is performed at a temperature of about 60-75° C. for a period of about 8-10 hours.
4. The method of claim 1 , wherein step (a) comprises preparing separate aqueous solutions of the M-containing compound, the M′-containing compound and the M″-containing compound, first mixing two of the three solutions and then adding the third solution to obtain the M-M′-M″ mixture.
5. The method of claim 1 , wherein each of steps (a)-(c) is performed under stirring.
6. The method of claim 1 , wherein step (c) comprises preparing an aqueous solution of the Na-containing compound and adding the solution to the M-M′-M″-P mixture.
7. The method of claim 1 , wherein step (d) is performed under an atmosphere of O 2 , N 2 or a combination thereof.
8. A method of preparing a cathode material comprising a compound of general formula Na h M i M′ j M″ k PO 4 , wherein: 0<h≤1,0<i≤1,0<j≤1 and 0<k≤1, and wherein M, M′ and M″ are each independently a metal, the method comprising the steps of:
(a) preparing an aqueous mixture comprising a M-containing compound, a M′-containing compound and a M″-containing compound to obtain a M-M′-M″ mixture;
(b) adding a P-containing compound to the M-M′-M″ mixture to obtain a M-M′-M″-P mixture;
(c) adding a Na-containing compound to the M-M′-M″-P mixture to obtain a Na-M-M′-M″-P mixture; and
(d) introducing the Na-M-M′-M″-P mixture into an autoclave to perform crystal growth and obtain the compound of general formula Na h M i M′ j M″ k PO 4 , wherein step (d) is performed at a temperature of about 150-250° C. for a period of about 2-6 hours under a pressure of about 1.5-2.5 MPa.
9. The method of claim 8 , wherein step (d) is performed at a temperature of about 200° C. for a period of about 4 hours under a pressure of about 2 MPa.
10. The method of claim 8 , wherein the aqueous mixture comprises deionized water bubbled under N 2 .
11. The method of claim 8 , wherein the M-containing compound, the M′-containing compound and the M″-containing compound are each independently selected from the group consisting of MnSO 4 , LiOH, FeSO 4 and MgSO 4 .
12. The method of claim 8 , wherein the compounds are each independently a hydrated compound.
13. A method of preparing a cathode material comprising a compound of general formula Na h M i M′ j M″ k PO 4 , wherein: 0<h≤1,0<i≤1,0<j≤1 and 0<k≤1, and wherein M, M′ and M″ are each independently a metal, the method comprising the steps of:
(a) preparing an aqueous mixture comprising a M-containing compound, a M′-containing compound and a M″-containing compound to obtain a M-M′-M″ mixture;
(b) adding a P-containing compound to the M-M′-M″ mixture to obtain a M-M′-M″-P mixture;
(c) adding a Na-containing compound to the M-M′-M″-P mixture to obtain a Na-M-M′-M″-P mixture; and
(d) introducing the Na-M-M′-M″-P mixture into an autoclave to perform crystal growth and obtain the compound of general formula Na h M i M′ j M″ k PO 4 , wherein the P-containing compound is H 3 PO 4 .
14. The method of claim 13 , wherein the Na-containing compound is NaOH.
15. The method of claim 13 , wherein the Na-containing compound is used in an excess amount.
16. The method of claim 13 , wherein, in the general formula Na h M i M′ j M″ k PO 4 , h=1 and 0≤i≤0.2 and 0≤j≤0.8 and 0.85≤i+j+k≤1.