The pyrolysis of 1,2-diphosphinobenzene at 800 °C gives a phosphorus-doped graphite (P-DG) with an unprecedented high phosphorus content, ca. 20 at%. In contrast with previously studied boron and nitrogen doped graphite materials, thorough characterisation and analysis of this material demonstrates that it is extensively disordered and contains substitutional P-atoms along with PO units in the host graphitic lattice, as well as P₄ molecules trapped between the graphitic sheets. This represents a stabilised form of P₄, which has been shown to covalently bind to lithium as Li₃P in this material.