issue is with varchar value 'z' in data ('2013-10-29 22:59:00Z) and you are converting it to datetime or datetime2.
you can convert it after removing that value from data.
use this.
SELECT TOP 10 key_value
,convert(datetime2,PV.key_value) as DT2
,convert(datetime,CONVERT(DATETIME2, left(PV.key_value,19))) AS DT
FROM parameter_value PV
WHERE PV.datatype = 'D'
and CONVERT(DATETIME,LEFT(PV.key_value,19)) BETWEEN GETDATE() and DATEADD(d, 10, GETDATE())