The realization of large‐capacity, high‐energy‐density Li metal battery technology is seriously impeded by dendrite growth and massive dead lithium formation upon cycling. Here, a stable flexible electrostatic self‐adapting polymer (poly(1‐benzyl‐3‐vinylimidazolium), (PBM)) interface is reported to regulate lithium‐ion deposition for dendrite‐free lithium metal batteries. The cationic PBM interlayer can adaptively tune the surface current density near the lithium/electrolyte interface, inducing a uniform distribution of current density and lithium ions and thus achieving dendrite‐free Li deposition under harsh conditions (lean electrolyte 8.75 µL mAh−1, high areal capacity >4 mAh cm−2). Moreover, the tethered phenyl groups endow PBM with a low reduction potential of −3.7 V versus standard hydrogen electrode by decreasing Hirshfeld charge at the reductive site. This avoids electrochemical reduction and therefore ensures the long‐term stability of the PBM interface. Consequently, the Li|PBM@Cu asymmetric cells deliver a high average Coulombic efficiency of 99.38% at 8 mAh cm−2 with lean electrolyte. Notably, the 5.1 Ah LiNi0.8Co0.1Mn0.1O2|PBM@Li pouch cell exhibits excellent cycling stability (0.011% decay/cycle) and high energy density (418.7 Wh kg−1) under realistic conditions (lean electrolyte 2.5 g Ah−1, high areal capacity 5.7 mAh cm−2, and high current density 2.7 mA cm−2).

Under realistic conditions especially for high-energy-density LMBs (>400 Wh kg −1 ), these phenomena will be exacerbated, thereby leading to poor electrochemical performance.Extensive efforts have been devoted to tackling the issues mentioned above, including the modification of surface with protective layers, [7][8][9][10][11] design of current collector structures, [12][13][14][15] introduction of functional electrolyte additives, [16][17][18][19] and application of solid-state electrolytes. [20][21][22] Despite the considerable success achieved in preventing dendrite growth to a certain extent at low Li plating capacities (<2 mAh cm −2 ), challenges still exist at high deposition capacities (>4 mAh cm −2 ). [23] Fundamentally, the formation of Li dendrites undergoes two steps involving nucleation and growth of the Li crystals. [24] As with other metal anodes, Li metal grows continuously on its early-formed nuclei during cycling. The final deposition morphology tightly relies on the preferential crystallographic orientation of Li-metal crystal. [25,26] Intrinsically, Li metal is a body-centered cubic structure, and ( 110), (200), and (211) crystal planes are normally the dominant crystallographic features. Among them, the (110) crystal plane is the most densely packed and thus has the lowest-energy surface, which is regarded as the preferential growth crystal plane of Li-metal anode. [27] Thermodynamically, Li dendrites will eventually be formed if the Li metal keeps growing along the (110) crystal plane. [28,29] Therefore, regulating Li metal's preferential growth orientation is essential. Recently, biomacromolecules have been proven effective in modulating inorganic crystal orientation and inhibiting Li dendrites. [30] Besides, a lateral growth model of Li deposition on single crystal Cu substrates was reported, and the acquired planar Li-metal layer exhibited improved cycle stability and high CE. [31] However, most of the approaches reported to date mainly operated at relatively low Li deposition capacities (<2 mAh cm −2 ), which are insufficient to boost the specific energy beyond 400 Wh kg −1 . To achieve the specific energy up to 400 Wh kg −1 , realistic conditions, including high areal capacity of both anode and cathode (>4 mAh cm −2 ) and lean electrolyte (<3 g Ah −1 ), are necessary. [32,33] Whereas, conditions of current investigations are low mass loading cathode (<3 mAh cm −2 ) and flooded electrolyte (>3 g Ah −1 ), which are far from realizing high cell-level energy Lithium (Li) metal, a promising anode for high-energy-density rechargeable batteries, typically grows along the low-surface energy (110) plane in the plating process, resulting in uncontrollable dendrite growth and unstable interface. Herein, an unexpected Li growth behavior by lanthanum (La) doping is reported: the preferred orientation turns to (200) from (110) plane, enabling 2D nuclei rather than the usual 1D nuclei upon Li deposition and thus forming a dense and dendrite-free morphology even at an ultrahigh areal capacity of 10 mAh...