I bought my wife a new phone for her self employed business but also uses it for personal. Is the cost of the physical phone deducible under De Minimis Expense Threshold?

I bought my wife a new iPhone for her business but she uses it for personal use as well. Quickbooks is telling me this is a business asset that falls under the safe harbor De Minimis Expense Threshold. If the phone was $800, is all $800 deductible as a business asset or only a portion because there is some personal use as well? All the questions I could find regarding this were questions about cell phone "costs" which most questions are referring to you month bill. I want to know about the actual physical phone cost, not the bill.