A SnP3 anode material with a theoretical volumetric capacity of 6890 mAh cm−3 is investigated for Na-ion batteries. The SnP3/C can deliver a reversible capacity of 810 mAh g−1 at a current density of 150 mA g−1 for 150 cycles. The superior performance is attributed to the strong bonding interaction of P and Sn after desodiation. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.