Sagger for sintering lithium composite transition metal oxide and preparation method thereof

1 . A sagger for sintering lithium composite transition metal oxide, wherein the sagger includes a substrate layer and a shallow layer on a surface of the substrate layer, and a coating layer;

the substrate layer is prepared from the following raw materials: silicon carbide, magnesia-alumina spinel, aluminum oxide-magnesium oxide-yttrium oxide composite fiber, zircon powder and a binding agent;

the shallow layer is prepared from the following raw materials: silicon carbide, magnesia-alumina spinel, aluminum oxide-titanium oxide composite fiber, yttrium oxide-zirconium oxide composite fiber and a binding agent; and

the coating layer is prepared from the following raw materials: silicon carbide, magnesia-alumina spinel, magnesium oxide, zirconium oxide fiber, lithium composite transition metal oxide powder and a binding agent; wherein, the substrate layer is prepared from the following raw materials in parts by weight: 40-85 parts of silicon carbide, 2-10 parts of magnesia-alumina spinel, 5-15 parts of aluminum oxide-magnesium oxide-yttrium oxide composite fiber, 5-10 parts of zircon powder and 2-10 parts of the binding agent; the shallow layer is prepared from the following raw materials in parts by weight: 30-50 parts of silicon carbide, 10-30 parts of magnesia-alumina spinel, 5-20 parts of aluminum oxide-titanium oxide composite fiber, 5-20 parts of yttrium oxide-zirconium oxide composite fiber and 5-10 parts of the binding agent; and the coating layer is prepared from the following raw materials in parts by weight: 5-20 parts of silicon carbide, 5-20 parts of magnesia-alumina spinel, 6-10 parts of magnesium oxide, 3-10 parts of zirconium oxide fiber, 5-25 parts of lithium composite transition metal oxide powder and 10-20 parts of the binding agent; and the binding agent is at least one selected from a group consisting of dextrin, polyvinyl alcohol, polyether modified polydimethylsilane, and silica alumina sol.

2 . The sagger of claim 1 , wherein the magnesium oxide in the coating layer comprises magnesium oxide fiber and micro/nano magnesium oxide with a mass ratio of magnesium oxide fiber to micro/nano magnesium oxide of (3-10):(3-10).

3 . The sagger of claim 1 , wherein the lithium composite transition metal oxide powder is one or more selected from a group consisting of powders of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide and lithium nickel-cobalt manganate.

4 . The sagger of claim 1 , wherein the aluminum oxide-magnesium oxide-yttrium oxide composite fiber is prepared through stirring and compounding aluminum oxide fiber, magnesium oxide fiber and yttrium oxide fiber at 50° C.-100° C.; the aluminum oxide-titanium oxide composite fiber is prepared through stirring and compounding aluminum oxide fiber and titanium oxide fiber at 50° C.-200° C.; and the yttrium oxide-zirconium oxide composite fiber is prepared through stirring and compounding yttrium oxide fiber and zirconium oxide fiber at 100° C.-200° C.

5 . A preparation method of the sagger of claim 1 , wherein the preparation method comprises steps of:

step (1): mixing and slurrying raw materials of a substrate layer to obtain a first slurry, and subjecting the first slurry to staling treatment and compression moulding to obtain a primary green body;

step (2): mixing and slurrying raw materials of a shallow layer to obtain a second slurry, coating the second slurry on a surface of the primary green body, and then subjecting the primary green body coated with the second slurry to compression moulding again to obtain a green body;

step (3): subjecting the green body to drying and sintering to obtain an intermediate sagger; and

step (4): mixing and slurrying raw materials of a coating layer into a third slurry to obtain a coating agent, spraying the coating agent on an inner surface of the intermediate sagger, and then performing micro-fire treatment to obtain a finished sagger.

6 . A preparation method of the sagger of claim 2 , wherein the preparation method comprises steps of:

step (1): mixing and slurrying raw materials of a substrate layer to obtain a first slurry, and subjecting the first slurry to staling treatment and compression moulding to obtain a primary green body;

step (2): mixing and slurrying raw materials of a shallow layer to obtain a second slurry, coating the second slurry on a surface of the primary green body, and then subjecting the primary green body coated with the second slurry to compression moulding again to obtain a green body;

step (3): subjecting the green body to drying and sintering to obtain an intermediate sagger; and

step (4): mixing and slurrying raw materials of a coating layer into a third slurry to obtain a coating agent, spraying the coating agent on an inner surface of the intermediate sagger, and then performing micro-fire treatment to obtain a finished sagger.

7 . A preparation method of the sagger of claim 3 , wherein the preparation method comprises steps of:

step (1): mixing and slurrying raw materials of a substrate layer to obtain a first slurry, and subjecting the first slurry to staling treatment and compression moulding to obtain a primary green body;

step (2): mixing and slurrying raw materials of a shallow layer to obtain a second slurry, coating the second slurry on a surface of the primary green body, and then subjecting the primary green body coated with the second slurry to compression moulding again to obtain a green body;

step (3): subjecting the green body to drying and sintering to obtain an intermediate sagger; and

step (4): mixing and slurrying raw materials of a coating layer into a third slurry to obtain a coating agent, spraying the coating agent on an inner surface of the intermediate sagger, and then performing micro-fire treatment to obtain a finished sagger.

8 . A preparation method of the sagger of claim 4 , wherein the preparation method comprises steps of:

step (1): mixing and slurrying raw materials of a substrate layer to obtain a first slurry, and subjecting the first slurry to staling treatment and compression moulding to obtain a primary green body;

step (2): mixing and slurrying raw materials of a shallow layer to obtain a second slurry, coating the second slurry on a surface of the primary green body, and then subjecting the primary green body coated with the second slurry to compression moulding again to obtain a green body;

step (3): subjecting the green body to drying and sintering to obtain an intermediate sagger; and

step (4): mixing and slurrying raw materials of a coating layer into a third slurry to obtain a coating agent, spraying the coating agent on an inner surface of the intermediate sagger, and then performing micro-fire treatment to obtain a finished sagger.

9 . The preparation method of claim 5 , wherein water is used as a medium when the raw materials of the substrate layer, the shallow layer and the coating layer are mixed and slurried; water is used in the substrate layer in an amount of 4%-10% of total mass of the raw materials of the substrate, water is used in the shallow layer in an amount of 4%-10% of total mass of the raw materials of the shallow layer; and water is used in the coating layer in an amount of 50%-80% of total mass of the raw materials of the coating layer.

10 . The preparation method of claim 5 , wherein the binding agent is used in the shallow layer in an amount of 4%-6% of total mass of the raw material of the shallow layer, and the binding agent is used in the coating layer in an amount of 12%-20% of total mass of the raw material of the coating layer.

11 . The preparation method of claim 5 , wherein in step (4), a procedure of repeatedly performing spraying and micro-fire treatment is further comprised after the micro-fire treatment, and the spraying and micro-fire treatment is performed at least 2 times.