Modified positive electrode active material, method for preparing the same and electrochemical energy storage device
The disclosure provides a modified positive electrode active material, a preparation method thereof, and an electrochemical energy storage device. The modified positive electrode active material comprises positive electrode active material substrate; first oxide layer, coated on the surface of the positive electrode active material substrate and selected from one or more of oxides of element M being selected from the group of one or more of Li, Al, Zr, Mg, Ti, Y, Si, Ca, Cr, Fe, Zn, Nb, Sn, Ba, and Cd; and second oxide layer having a continuous layered structure, coated on the surface of the first oxide layer and selected from one or more of oxides of element M′ being selected from one or more of Li, B, P, As, Pb, V, Mo, and Sn. High temperature storage performance and cycling performance of electrochemical energy storage device are improved by the modified positive electrode active material.
1. A modified positive electrode active material, comprising:
a positive electrode active material substrate, wherein, the positive electrode active material substrate is lithium-nickel-manganese-cobalt-based oxide ternary material LiNi 0.8 Co 0.1 Mn 0.1 O 2 ;
a first oxide layer, coated on the surface of the positive electrode active material substrate and selected from one or more of oxides of element M, wherein the element M is Al, and the one or more of oxides is Al 2 O 3 ; and
a second oxide layer having a continuous layered structure, coated on the surface of the first oxide layer and selected from one or more of oxides of element M′, wherein the element M′ is B, and one or more of oxides is B 2 O 3 ;
wherein based on the mass of the positive electrode active material substrate, the element M is present in an amount of 0.01% to 2% in the first oxide layer and the element M′ is present in an amount of 0.01% to 1% in the second oxide layer; and
wherein the positive electrode active material substrate comprises primary particles and secondary particles formed by agglomeration of primary particles; and wherein the primary particles have a particle diameter of 0.2 μm to 1 μm and the secondary particles have a particle diameter of 5 μm to 18 μm.
2. The modified positive electrode active material according to claim 1 , wherein the first oxide layer coated on the surface of the positive electrode active material substrate has an island-like shape.
3. The modified positive electrode active material according to claim 1 , wherein based on the mass of the positive electrode active material substrate, the element M and the element M′ are present in the following amounts:
(i) the element M is present in an amount of 0.3%, and the element M′ is present in an amount of 0.2%;
(ii) the element M is present in an amount of 0.01%, and the element M′ is present in an amount of 0.1%;
(iii) the element M is present in an amount of 2%, and the element M′ is present in an amount of 0.01%; or
(iv) the element M is present in an amount of 2%, and the element M′ is present in an amount of 1%.
4. A method for preparing the modified positive electrode active material according to claim 1 , comprising the steps of:
(i) mixing homogeneously a positive electrode active material substrate with first oxide layer substance itself or the precursor thereof, followed by sintering, to coat the surface of the positive electrode active material substrate with the first oxide layer selected from one or more of the oxides of element M, wherein the element M is Al, and the one or more of oxides is Al 2 O 3 ;
(ii) mixing homogeneously the substance obtained in step (i) with second oxide layer substance itself or the precursor thereof, followed by sintering, so that the formed second oxide layer is coated on the surface of the first oxide layer and has a continuous layered structure, wherein the second oxide layer is selected from one or more of the oxides of element M′, wherein the element M′ is B, and one or more of oxides is B 2 O 3 , thus yielding the modified positive electrode active material;
wherein based on the mass of the positive electrode active material substrate, the element M is present in an amount of 0.01% to 2% in the first oxide layer and the element M′ is present in an amount of 0.01% to 1% in the second oxide layer; and
wherein the positive electrode active material substrate comprises primary particles and secondary particles formed by agglomeration of primary particles; and wherein the primary particles have a particle diameter of 0.2 μm to 1 μm and the secondary particles have a particle diameter of 5 μm to 18 μm;
wherein the positive electrode active material substrate is lithium-nickel-manganese-cobalt-based oxide ternary material LiNi 0.8 Co 0.1 Mn 0.1 O 2 .
5. The method for preparing the modified positive electrode active material according to claim 4 , wherein melting point of the first oxide layer substance is higher than melting point of the precursor of the second oxide layer substance, so that the second oxide layer after sintering is uniformly coated on the surface of the first oxide layer; and wherein the formed second oxide layer has a continuous layered structure.
6. The method for preparing the modified positive electrode active material according to claim 4 , wherein melting point of the first oxide layer substance is higher than melting point of the second oxide layer substance itself, so that the second oxide layer after sintering is uniformly coated on the surface of the first oxide layer; and wherein the formed second oxide layer has a continuous layered structure.
7. The method for preparing the modified positive electrode active material according to claim 5 , wherein
the temperature of sintering in step (ii) is lower than that in step (i) and is equal to or greater than the melting point of the precursor of the second oxide layer substance;
the temperature of sintering in step (i) is 600° C. to 750° C.;
the temperature of sintering in step (ii) is 400° C. to 600° C.
8. The method for preparing the modified positive electrode active material according to claim 6 , wherein
the temperature of sintering in step (ii) is lower than that in step (i) and is equal to or greater than the melting point of the second oxide layer substance itself;
the temperature of sintering in step (i) is 600° C. to 750° C.;
the temperature of sintering in step (ii) is 400° C. to 600° C.
9. An electrochemical energy storage device, comprising the modified positive electrode active material, wherein the modified positive electrode active material comprises:
a positive electrode active material substrate, wherein the positive electrode active material substrate is lithium-nickel-manganese-cobalt-based oxide ternary material LiNi 0.8 Co 0.1 Mn 0.1 O 2 ;
a first oxide layer, coated on the surface of the positive electrode active material substrate and selected from one or more of oxides of element M, wherein the element M is Al, and the one or more of oxides is Al 2 O 3 ; and
a second oxide layer having a continuous layered structure, coated on the surface of the first oxide layer and selected from one or more of oxides of element M′, wherein the element M′ is B, and one or more of oxides is B 2 O 3 ;
wherein based on the mass of the positive electrode active material substrate, the element M is present in an amount of 0.01% to 2% in the first oxide layer and the element M′ is present in an amount of 0.01% to 1% in the second oxide layer; and
wherein the positive electrode active material substrate comprises primary particles and secondary particles formed by agglomeration of primary particles; and wherein the primary particles have a particle diameter of 0.2 μm to 1 μm and the secondary particles have a particle diameter of 5 μm to 18 μm.