You need a reliable method that you can reduce to writing, as some kind of log book or diary. I don't know what that would be for EV use. Certainly if you use a commercial charge station that costs money, you will have a receipt. For home charging, you can get your electricity rate from your utility bill, but how would you reliably determine how much you are being billed? Does your charging station have a separate meter? Could you get one installed after-market? Otherwise, you would have to know that Monday you used 100kWh, Tuesday 80kWh, Wednesday 50kWh, and so on, for the entire year (365 days of charging). And of course, your electric rate may change day to day or even at different times of the day, if your utility has demand pricing.
Remember that with the actual mileage method, you track all your business and personal miles for the year, and you track all your vehicle expenses, and you take the percentage. The IRS does not have to allow any deduction that you can't prove with adequate, reliable records.
Also, remember that the standard mileage rate includes allowances for fuel, maintenance, repairs and depreciation. It may not be so far off after all, and it's a lot easier to administer, since you only need a mileage diary and not also an expense diary.
