energy density, and cost effective. Albertus et al. have advocated for the use of limited lithium (≤30 µm) to ensure early identification of technical challenges associated with stable and dendrite-free cycling and a more rapid transition to commercially relevant designs. [7] And recently, Liu et al. [8] re-emphasized the importance of limited lithium and announced that 50 µm Li anode was required to reach a high energy of 300 Wh kg −1. Therefore, for practical lithium-metal batteries (LMBs), the utilization of thin Li metal anode with thicknesses <30 µm (<6 mAh cm −2) is extremely necessary. [6-10] In other words, the negative to positive electrode capacity ratio (N/P ratio) must be strictly restricted. Limiting the amount of Li metal anode is a great challenge, since it is highly reactive. The continuous reaction of Li metal with electrolyte to generate a solid electrolyte interphase (SEI) as well as the uneven Li platting to form dendrite growth and pulverized Li metal, which cause fast consumptions of Li metal and electrolyte, low Coulombic efficiency (CE), and short lifespan of LMBs. To improve cycling stability of Li metal anode in organic liquid electrolyte, various attempts have already been made, including highly concentrated electrolyte, [11] electrolyte additives, [12,13] external pressure, [14,15] Li host, [16,17] and surface coating. [18,19] While most of the above strategies use unlimited Li foil, only a few studies focus on limiting the amount of Li metal for LMBs. [6,9,20,21] For example, Niu et al. reported a self-smoothing Li-carbon anode based on the host of mesoporous carbon nanofibers and a high-energy LMB with a low N/P ratio of ≤2. [6] Archer's group and Cho's group achieved stable operations of LMBs composed of a high-loading cathode and a thin Li anode (20 µm) with Langmuir-Blodgett artificial SEIs. [9] While, compared with liquid electrolyte, some types of solid electrolytes are less reactive with Li metal, which may be good candidates for LMBs with low N/P ratios. [22] Additionally, the safety of LMBs can be greatly improved by replacing flammable liquid electrolyte with solid electrolyte. [23] But, up to now, there are only a few researches about all-solidstate lithium-metal batteries (ASSLMBs) using limited amount of Li metal anode. A recent work reported an ASSLMB with Li 6 PSCl sulfide electrolyte and Ag-C composite anode with no excess Li. [24] Besides, the studies of LiPON-based thin-film batteries with limited Li metal have been reported, which are Metallic lithium (Li), considered as the ultimate anode, is expected to promise high-energy rechargeable batteries. However, owing to the continuous Li consumption during the repeated Li plating/stripping cycling, excess amount of the Li metal anode is commonly utilized in lithium-metal batteries (LMBs), leading to reduced energy density and increased cost. Here, an all-solid-state lithium-metal battery (ASSLMB) based on a garnet-oxide solid electrolyte with an ultralow negative/positive electrode capacity ratio (N/P ratio) is reported...
