High energy density lithium metal batteries enabled by a porous graphene/MgF2 framework

The big challenge for practical lithium metal batteries is how to make full and reversible utilization of lithium anode. The preformed three-dimensional (3D) porous framework with numerous lithium nucleation sites is able to guide the lithium deposition in the cavity of 3D framework, suppressing the dendrite growth and dimensional change. Herein, we design a nanocapsule structure for lithium metal anodes consisting of 3D graphene with Mg x Li y seeds inside. The 3D composite anode not only can be prepared in a simple and scalable process, but also can meet the requirements for both high energy density and long cycle life in the practical cells. During the observation of lithium deposition by transmission electron microscope, it was found that lithium metal was mainly deposited around the Mg x Li y seeds within 3D graphene. Thereafter, when the composite anodes are well paired with the commercial LiFePO 4 cathodes in coil cells and NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) cathodes in pouch batteries, they are able to deliver the energy density exceeding 350 ​Wh·kg −1 and long cycle life (>150 cycles) with high energy retention (>85%). The 3D lithium metal/graphene composite anode in the present work provides a promising new avenue for the fabrication of high energy density Li-metal batteries.