An electrode comprising: an electrode mixture layer comprising active material particles comprising Li and at least one transition metal selected from the group consisting of Fe, Mn, Co and Ni; and a current collector comprising at least one surface on which the electrode mixture layer is supported, wherein: the electrode mixture layer comprises a first surface being in contact with the current collector and a second surface separated by a thickness of the electrode mixture layer from the first surface; the electrode mixture layer comprises: a first portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the first surface; and a second portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the second surface; in the first portion of the electrode mixture layer, a first oxide layer is formed on surfaces of the active material particles, the first oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of more than 0.5 nm and 100 nm or less; in the second portion of the electrode mixture layer, a second oxide layer is formed on surfaces of the active material particles, the second oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of 0.5 nm or more and less than 100 nm; and the thickness of the first oxide layer is more than the thickness of the second oxide layer. an electrode mixture layer comprising active material particles comprising Li and at least one transition metal selected from the group consisting of Fe, Mn, Co and Ni; and a current collector comprising at least one surface on which the electrode mixture layer is supported, wherein: the electrode mixture layer comprises a first surface being in contact with the current collector and a second surface separated by a thickness of the electrode mixture layer from the first surface; the electrode mixture layer comprises: a first portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the first surface; and a second portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the second surface; in the first portion of the electrode mixture layer, a first oxide layer is formed on surfaces of the active material particles, the first oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of more than 0.5 nm and 100 nm or less; in the second portion of the electrode mixture layer, a second oxide layer is formed on surfaces of the active material particles, the second oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of 0.5 nm or more and less than 100 nm; and the thickness of the first oxide layer is more than the thickness of the second oxide layer. the electrode mixture layer comprises a first surface being in contact with the current collector and a second surface separated by a thickness of the electrode mixture layer from the first surface; the electrode mixture layer comprises: a first portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the first surface; and a second portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the second surface; a first portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the first surface; and a second portion having a thickness of at least 20% of the thickness of the electrode mixture layer and comprising the second surface; in the first portion of the electrode mixture layer, a first oxide layer is formed on surfaces of the active material particles, the first oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of more than 0.5 nm and 100 nm or less; in the second portion of the electrode mixture layer, a second oxide layer is formed on surfaces of the active material particles, the second oxide layer comprising at least one element selected from the group consisting of Li, Mg, Ca, B, Al, Si, P, Fe, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, and W, and having a thickness of 0.5 nm or more and less than 100 nm; and the thickness of the first oxide layer is more than the thickness of the second oxide layer.