My oppo phone has been dead for half a year 1%, is it normal to have 99% left?

Normal.

According to oppo official website, under normal circumstances, the battery loss 1% of oppo mobile phones after half a year's use is normal. This data can not fully reflect the service life and performance of mobile phone batteries, because the service life and performance of batteries not only depend on the length of use, but also on the frequency of use, charging method, environmental temperature and other factors.