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capabilities of state-of-the-art batteries, such as lithium-ion batteries (LIBs) based on the commercial graphite anode with a limited theoretical specific capacity of ≈372 mAh g −1 . [1] Rechargeable lithium metal batteries (LMBs) are considered to be the key to next generation highenergy-density batteries, since Li metal anode presents a theoretical gravimetric specific capacity up to 3860 mAh g −1 and a low reduction potential of -3.04 V versus standard hydrogen electrode (SHE). [2] However, the applicability of LMBs is severely hindered by a series of bottlenecks caused by lithium anode, including dendritic lithium growth, unstable solidelectrolyte interphase (SEI), and almost infinite volume change during cycling. Among these, the inevitable dendrite formation and growth is one of the most serious issues, which aggravates the adverse side-reaction and the formation of "dead Li". Consequently, it leads to low Coulombic efficiency (CE), limited life span, and severe safety risks. [2] To seize the "holy grail" of Li metal anode, the research community significantly focuses on how to maintain the flat surface morphology and dense structure of the metallic Li deposition without apparent dendrites during the electrochemical plating/stripping processes. Practical lithium metal batteries (LMBs) are still far from market readiness, as a result of the severe Li degradation and safety issues caused by Li dendrites. Herein, by studying the thermodynamic behavior of lithium deposition, it is unveiled that the tip area of Li metal has an increasing heat generation rate as a function of the deposition time and overpotential. This triggers the emergence of the accumulated overpotential heat and local temperature "hotspots" due to poor local thermal diffusion, which exacerbates the undesirable irregular Li deposition and dendrite growth. To address this issue, a thermally conductive graphene-coated separator is constructed to eliminate these local hotspots. The graphene layer affords timely diffusion of local heat generated by irregular Li growth and incipient dendrite formation, achieving the stable and uniform lithium deposition to deter further degradation. As a result, the Li metal, suffering a drastic Coulombic efficiency (CE) decay to ≈60% using a conventional separator, can be recovered for continual cycling with a high CE of >95%. Notably, the corresponding Li||LiNi 0.8 Mn 0.1 Co 0.1 O 2 cells present high capacity retention and recovery. This study highlights the thermodynamic factor of Li dendrite-induced local heat and its elimination to preclude Li anode deterioration, which provides insight into Li metal protection strategies for high performance LMBs.

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