Electromechanical Probing of Li/Li₂CO₃ Core/Shell Particles in a TEM

We provide a detailed electromechanical study of individual core/shell structure – Li metal/Li₂CO₃ particles by utilizing an in-situ probing technique in the transmission electron microscope (TEM). This technique allows us to concurrently monitor the mechanical and electrical response of single Li/Li₂CO₃ core/shell structures in real time. The pressure on the Li/Li₂CO₃ core/shell particle was measured to be ∼15 MPa at the initiation of fracture and the conductivity of the Li₂CO₃ shell is estimated to be ∼10⁻⁶ S/cm. To simulate the application of the core-shell particles in a real battery, we assembled coin cells with Li metal as a counter electrode. Prior to the cell assembly, the electrode was compressed in order to break the Li₂CO₃ shells to expose the fresh lithium metal to the graphite. When the electrolyte is added to wet the electrode, an electrochemical reaction spontaneously occurs between the exposed Li and graphite particles to produce a partially lithiated graphite anode. This lithiation occurs prior to the initial charging process, therefore compensating for the irreversible capacity loss due to the lithium consummation events during standard formation^. Our results demonstrate a new pathway for the utilization of non-lithiated cathode material in future Li-ion batteries