(Ⅰ)函数f(x)为减函数,
∵f(-x)=
=
2?x?1
2?x+1
=-1?2x
1+2x
=-f(x),
2x?1
2x+1
∴函数f(x)为减函数;
(Ⅱ)设x1<x2,
则f(x1)-f(x2)=
-
2x1?1
2x1+1
=
2x2?1
2x2+1
=(2x1?1)(2x2+1)?(2x2?1)(2x1+1) (2x1+1)(2x2+1)
,
2(2x1?2x2) (2x1+1)(2x2+1)
∵x1<x2,
∴2x1<2x2,
则f(x1)-f(x2)=
<0,
2(2x1?2x2) (2x1+1)(2x2+1)
即f(x1)<f(x2),
即函数在其定义域上的单调递增;
(Ⅲ)若不等式f(1-m)+f(1-m2)<0恒成立,
则等价为f(1-m)<-f(1-m2),
∵f(x)为奇函数且为增函数,
∴不等式等价为f(1-m)<f(m2-1),
即1-m<m2-1,
则m2+m-2>0,
解得m>1或m<-2,
即m的取值范围是{m|m>1或m<-2}.