Firstly, as the importer, it’s highly unlikely your liability for any safety issues occurring due to batteries in your products would be nil.
However, testing the batteries at the battery supplier’s factory (this qualifies them before production even starts) and then during production on samples from the right batch, if their standard is clear and their results are documented, it would definitely help you in case you are sued for a problem the test was aiming at detecting. You will probably have covered yourself against the accusation of negligence which would hurt you in a court of law if proven correct.
Note: It’s important for the samples to be selected randomly from production by your representative (rather than picked by the manufacturer). That’s a plus since this usually prevents a dishonest manufacturer from gaming the system by, say, swapping out the batteries you’re expecting for cheaper versions in order to increase their profit margin.
As ever, in this situation, it’s best to consult with a lawyer to get guidance on your liabilities