Important Role of Ion Flux Regulated by Separators in Lithium Metal Batteries

Polyolefin separators are the most common separators used in rechargeable lithium (Li)-ion batteries. However, the influence of different polyolefin separators on the performance of Li metal batteries (LMBs) has not been well studied. By performing particle injection simulations on the reconstructed three-dimensional pores of different polyethylene separators, it is revealed that the pore structure of the separator has a significant impact on the ion flux distribution, the Li deposition behavior, and consequently, the cycle life of LMBs. It is also discovered that the homogeneity factor of Li-ion toward Li metal electrode is positively correlated to the longevity and reproducibility of LMBs. This work not only emphasizes the importance of the pore structure of polyolefin separators but also provides an economic and effective method to screen favorable separators for LMBs.

Cu-Doped Alloy Layer Guiding Uniform Li Deposition on a Li-LLZO Interface under High Current Density

Li₇La₃Zr₂O₁₂(LLZO)-based ceramics as promising solid-state electrolytes (SSEs) have received much attention for use in high-energy lithium (Li) metal batteries. However, the Li growth through the solid garnet electrolyte under a low current density hinders its practical application. In this work, the Cu doped Li₃Zn was designed to guide uniform Li deposition by magnetron cosputtering and an in situ alloying reaction on Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) pellets. After introducing the composite layer, a small interfacial area specific resistance (∼30 Ω·cm²) can be obtained. Improved lithium plating/stripping performance, including a long-life span of 450 h (under a current density of 0.8 mA cm^-2 without short circuit) and a high critical current density (CCD) of 2.8 mA cm^-2 is performed by the composite interlayer with a Zn:Cu ratio of 10:1. And the Li/Cu-Li₃Zn SSEs/LFP full cell exhibits good electrochemical performance. Accordingly, the Li deposited behavior in the Li plating/stripping process at the intermediate layer is discussed in detail. This work provides a new sight for the alloy interface designed on the solid-state garnet SSEs for high performance lithium metal batteries under high current density.

Early Lithium Plating Behavior in Confined Nanospace of 3D Lithiophilic Carbon Matrix for Stable Solid-State Lithium Metal Batteries

Considerable efforts are devoted to relieve the critical lithium dendritic and volume change problems in the lithium metal anode. Constructing uniform Li⁺ distribution and lithium "host" are shown to be the most promising strategies to drive practical lithium metal anode development. Herein, a uniform Li nucleation/growth behavior in a confined nanospace is verified by constructing vertical graphene on a 3D commercial copper mesh. The difference of solid-electrolyte interphase (SEI) composition and lithium growth behavior in the confined nanospace is further demonstrated by in-depth X-ray photoelectron spectrometer (XPS) and line-scan energy dispersive X-ray spectroscopic (EDS) methods. As a result, a high Columbic efficiency of 97% beyond 250 cycles at a current density of 2 mA cm^-2 and a prolonged lifespan of symmetrical cell (500 cycles at 5 mA cm^-2 ) can be easily achieved. More meaningfully, the solid-state lithium metal cell paired with the composite lithium anode and LiNi_0.5 Co_0.2 Mn_0.3 O₂ (NCM) as the cathode also demonstrate reduced polarization and extended cycle. The present confined nanospace-derived hybrid anode can further promote the development of future all solid-state lithium metal batteries.