Update folder names using Power Shell in SharePoint

#Get the Web
$Web = Get-SPWeb "http://yourSharePointSite"

#New Name for the Folder
$NewFolderName = "PagesLibSubFolderNewName";

#Get the Folder to Rename by its path
$folder = $Web.GetFolder("http://yourSharePointSite/pages/CurrentFolderName");

if ($folder.Exists)
{
   #Set the New Name and Update
   $folder.Item["Name"] = $NewFolderName;
   $folder.Item.Update();
}