Hi, here is an example of how I did it using controllers.

Here 'phone.reputation' is a custom model I developed. You can give 'account.invoice', and

give which all fields you want to be printed in the csv file. "name" is the actual field name and "label" is the label how you want that field to have in the csv file. "ids" is the list of ids of records that you want to be printed in the csv  file.

@api.multi
def download_phone_reputation_data(self):
    for intel in self:
        str_dic = """{"model":"phone.reputation",
                            "fields":[{"name":"phone_number","label":"Phone Number"},
                                            {"name":"country_code","label":"Country Code"},
                                            {"name":"country_calling_code","label":"Country Calling Code"},
                                            {"name":"reputation_level","label":"Reputation Level"}, 
                                            {"name":"score","label":"Score"},
                                            {"name":"type","label":"Type"},
                                            {"name":"category","label":"Category"},
                                            {"name":"volume_score","label":"Volume Score"}, 
                                            {"name":"report_count","label":"Report Count"},
                                            {"name":"error","label":"Error"},
                                            {"name":"warnings","label":"Warnings"}],
                                "ids":%s,
                                "domain":[],
                                "context":{},
                                "import_compat":0}""" % intel.phone_reputation_ids.ids
        return {
                'type': 'ir.actions.act_url',
                'url': '/web/export/csv?data=%s&token=' % (str_dic),
                'target': 'current',
                    }

Thanks