A positive electrode active material for a secondary battery includes a lithium metal composite oxide having a crystal structure based on a rock-salt structure belonging to a space group Fm-3m. The lithium metal composite oxide contains a first metal element other than Li, and a second metal element other than Li and the first metal element. The first metal element is at least one selected from the group consisting of Gd, Ce, Eu, Sm, and Yb.

A positive-electrode active material contains a compound that has a crystal structure belonging to a space group FM3-M and that is represented by the composition formula (1) and a lithium ion conductor,

Li.sub.xMe.sub.yO.sub.F.sub.(1)

wherein Me denotes one or two or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr, and the following conditions are satisfied.

17x2.2

0.8y1.3

12.5

0.52

A composite exhibiting a thermoelectric effect is provided. The composite comprises a metal sulphosalt, an electrically conductive polymer, and fibres. A method of making a composite material is also provided, comprising mixing the components. The three components work together to provide a low-cost thermoelectric composite that utilises readily available materials. A friction material and a thermoelectric device comprising the composite of the invention are also discussed. Preferably a copper sulphosalt is used, such as tetrahedrite. Preferably man-made vitreous fibres and a binder are used.

A positive-electrode active material containing a compound that has a crystal structure belonging to the space group FM-3M and is represented by the composition formula (1):

Li.sub.xMe.sub.yO.sub.F.sub.p (1)

wherein Me denotes one or two or more elements selected from the group consisting of Mn, Co, Ni, Fe, and Al, and the following conditions are satisfied.

1.3x2.2

0.8y1.3

12.93

0.072

A positive-electrode active material contains a compound that has a crystal structure belonging to the space group FM3-M and that is represented by the composition formula (1):

Li.sub.xMe.sub.yO.sub.F.sub.(1) wherein Me denotes one or two or more elements selected from the group consisting of B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, and solid solutions thereof, and the following conditions are satisfied.

1.8x2.2

0.8y1.3

1.22.5

0.51.8

A battery includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolytic solution including a nonaqueous solvent. The positive electrode active material includes a compound having a crystal structure belonging to a space group FM3-M and represented by Compositional Formula (1): Li.sub.xMe.sub.yO.sub.F.sub., where, Me is one or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr; and subscripts x, y, , and satisfy the following requirements: 1.7x2.2, 0.8y1.3, 12.5, and 0.52. The nonaqueous solvent includes a solvent having at least one fluoro group.

A positive-electrode active material contains a compound that has a crystal structure belonging to a space group FM3-M and contains is represented by the composition formula (1) and an insulating compound,

Li.sub.xMe.sub.yO.sub.F.sub.(1) wherein Me denotes one or two or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr, and the following conditions are satisfied.

1.7x2.2

0.8y1.3

12.5

0.52

A positive-electrode active material contains a compound that has a crystal structure belonging to a space group FM3-M and that is represented by the composition formula (1):

Li.sub.xA.sub.yMe.sub.zO.sub.F.sub.(1) wherein A denotes Na or K, Me denotes one or two or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr, and the following conditions are satisfied.

1.7x+y2.2

0y0.2

0.8z1.3

12.5

0.52

Mixed-metal oxides and lithiated mixed-metal oxides are disclosed that involve compounds according to, respectively, Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub. and Li.sub.1+Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub.. In these compounds, Me is selected from B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Ag, In, and combinations thereof; 0x1; 0y1; 0z<1; x+y+z>0; 00.5; and x+y+>0. For the mixed-metal oxides, 15. For the lithiated mixed-metal oxides, 0.11.0 and 1.93. The mixed-metal oxides and the lithiated mixed-metal oxides include particles having an average density greater than or equal to 90% of an ideal crystalline density.

Mixed-metal oxides and lithiated mixed-metal oxides are disclosed that involve compounds according to, respectively, Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub. and Li.sub.i+Ni.sub.xMn.sub.yCo.sub.zMe.sub.O.sub.. In these compounds, Me is selected from B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Ag, In, and combinations thereof; 0x1; 0y1; 0z1; x+y+z>0; 00.5; and x+y+>0. For the mixed-metal oxides, 15. For the lithiated mixed-metal oxides, 0.11.0 and 1.93. The mixed-metal oxides and the lithiated mixed-metal oxides include particles having an average density greater than or equal to 90% of an ideal crystalline density.