There are a lot of scare stories out there, especially in tabloids (including the Daily Mail and Telegraph). Don't believe the clickbait. I bet the article cited a specific model or a specific case. Overall if you look at the average of many vehicles the depreciation on an electric vehicle is perfectly good.
Also keep in mind that it makes perfect sense however for EVs to depreciate faster since they are giving you more value.
Example:
Buy EV (second hand) for £20k
spend £10k on electricity and maintenance and other costs over some years
sell for £10k
Total cost £20k to have a car for some years
Buy Petrol car (second hand) for £10k
spend £15k on petrol and maintenance and other costs over some years
sell for £5k
Total cost £20k to have a car for some years
The EV depreciated faster but it gave more value in fuel savings over that time, so it worked out the same.