You can manipulate recipients just before sending out the emails with the hook wpcf7_before_send_mail.
Here is a simple script that adds an extra recipient:
add_action( 'wpcf7_before_send_mail', 'add_my_second_recipient', 10, 1 );
function add_my_second_recipient($instance) {
$properites = $instance->get_properties();
// use below part if you want to add recipient based on the submitted data
/*
$submission = WPCF7_Submission::get_instance();
$data = $submission->get_posted_data();
*/
$additional_recipent="[email protected]";
$properites['mail']['recipient'] .= ', ' . $additional_recipent;
$instance->set_properties($properites);
return ($instance);
}