Positive electrode sheet, secondary battery, battery module, battery pack and electrical apparatus

A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector;

• at least one of the positive electrode film layers is of a multi-layer structure, and any positive electrode film layer having a multi-layer structure respectively comprises a first positive electrode active material having a core-shell structure and a second positive electrode active material in different layers;
• the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer;
• wherein the inner core comprises Li1+xMn1-yAyP1-zRzO4, the first coating layer comprises pyrophosphate MP2O7 and phosphate XPO4, and the second coating layer comprises carbon element;
• wherein,
• A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge;
• R is selected from one or more elements of B, Si, N and S;
• x is selected from −0.100-0.100;
• y is selected from 0.001-0.500;
• z is selected from 0.001-0.100;
• M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al;
• the second positive electrode active material is selected from one or more of LiNiaCobMn(1-a-b)O2, LiNiaCobAl(1-a-b)O2 and LiCoO2;
• wherein a is independently selected from any value in the range of 0.3-0.9, and the sum of a and b is independently selected from any value in the range of 0.3-0.9;
• and
• optionally, any of the positive electrode film layers having a multi-layer structure respectively comprises the first positive electrode active material and the second positive electrode active material in adjacent layers.

A positive electrode sheet, comprising a positive electrode current collector as well as a positive electrode film layer A and a positive electrode film layer B respectively provided on both surfaces of the positive electrode current collector;

• the positive electrode film layer A and the positive electrode film layer B are each independently of a single-layer structure or a multi-layer structure;
• at least one layer of the positive electrode film layer A comprises a first positive electrode active material having a core-shell structure, while at least one layer of the positive electrode film layer B comprises a second positive electrode active material;
• the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer;
• wherein the inner core comprises Li1+xMn1-yAyP1-zRzO4, the first coating layer comprises pyrophosphate MP2O7 and phosphate XPO4, and the second coating layer comprises carbon element;
• wherein,
• A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge;
• R is selected from one or more elements of B, Si, N and S;
• x is selected from −0.100-0.100;
• y is selected from 0.001-0.500;
• z is selected from 0.001-0.100;
• M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al;
• and
• the second positive electrode active material is selected from one or more of LiNiaCobMn(1-a-b)O2, LiNiaCobAl(1-a-b)O2 and LiCoO2;
• wherein a is independently selected from any value in the range of 0.3-0.9, and the sum of a and b is independently selected from any value in the range of 0.3-0.9.