It's a normal metabolic process for cats to have their nails split, and the blackening of the gaps between the splits is because the nails are dirty. When cats play around, they get dirt under their nails, and if it's not cleaned in time, the nails will turn black.
Reasons for cracked and blackened gaps in cat nails
It's a normal metabolic process for cats to have split nails. During nail shedding, the nails grow outwards layer by layer, causing the old nails to split and peel off. The gaps between the split nails may turn black because the nails are dirty. When cats play around, dirt gets into their nails, and if it's not cleaned in time, it will cause them to turn black. Another reason could be a skin disease in the cat, causing abnormal nail conditions. In this case, the owner needs to carefully observe the skin around the nails for any other abnormalities and take the cat to the vet promptly. 
How to treat cracked and blackened gaps in cat's nails
Owners should trim their cats' nails regularly to reduce the likelihood of cracking. In dry weather, apply a lubricating oil around the nails to prevent cracking. After playing outside, wipe the cat's paws with a clean cloth to keep them clean and dry.
