Green in Situ Growth Solid Electrolyte Interphase Layer with High Rebound Resilience for Long-Life Lithium Metal Anodes

Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

In-situ cross-linked multifunctional polymer electrolyte buffer layers for high-performance garnet solid-state lithium metal batteries

The garnet Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZTO) is one of the most promising electrolytes for commercial application since of its high ionic conductivity and good stability to Li. Nevertheless, the poor electrolyte/electrode interface contact enlarges the interface impedance of all-solid-state battery (ASSB). Herein, a multifunctional polymer electrolyte (MPE) interface buffer layers are formed on both sides of LLZTO surface through an in-situ crosslinking strategy to improve the interface contact with electrodes, which can facilitate uniform Li⁺ deposition/exfoliation and inhibit the growth of lithium dendrites as evidenced by the reduced interface impedance (103.4 Ω cm²), the increased critical current density (CDD, 1.2 mA cm^-2) and 950 h stable cycle of Li symmetric cells at 0.7 mA cm^-2, 0.7 mA h cm^-2. Besides, the MPE layer can reduce the magnitude of electric field at the interface and widen the electrochemical window (0∼5.2 V). The stable interface of the LLZTO@MPE/cathode enables the full cells matching with the LiFePO₄ (LFP) and LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathodes to deliver superior electrochemical performances. Specifically, the Li/MPE@LLZTO@MPE/LFP delivers a capacity retention rate of 87% after 200 cycles at 1 C. When it's matched with the NCM523 cathode, a capacity retention rate of 98% is retained after 100 cycles at 1 C. This work provides an effective and simple way to build good-interface-contact and long-lifespan garnet solid-state lithium metal batteries (SSLMBs).

Polymer Zwitterion-Based Artificial Interphase Layers for Stable Lithium Metal Anodes

Lithium (Li) metal batteries are promising future rechargeable batteries with high-energy density as the Li metal anode (LMA) possesses a high specific capacity and the lowest potential. However, the commercial application of the LMA has been hindered by a low Coulombic efficiency and dendrite growth, which are related to the unstable interphase with poor Li⁺ ion transport. Herein, we report novel polymer zwitterion-based artificial interphase layers (AILs) with improved Li⁺ ion transport and high stability for long-life LMAs. Benefitting from the unique zwitterion effect within the polymer zwitterion-based AILs, a high Li⁺ ion transference number (0.81) and a good ionic conductivity (0.75 × 10^-4 S cm^-1) can be realized simultaneously at the interface. By regulating the weight ratio of the sulfonate group and the phosphate group in polymer zwitterion-based AILs, the modified LMA enables long-term Li plating/stripping for 1400 h at 1 mA cm^-2 and stable cycling in a full cell. This interfacial engineering concept could shed light on the development of safe LMAs.

Advanced Electrolyte Design for High-Energy-Density Li-Metal Batteries under Practical Conditions

Given the limitations inherent in current intercalation-based Li-ion batteries, much research attention has focused on potential successors to Li-ion batteries such as lithium-sulfur (Li-S) batteries and lithium-oxygen (Li-O₂ ) batteries. In order to realize the potential of these batteries, the use of metallic lithium as the anode is essential. However, there are severe safety hazards associated with the growth of Li dendrites, and the formation of "dead Li" during cycles leads to the inevitable loss of active Li, which in the end is undoubtedly detrimental to the actual energy density of Li-metal batteries. For Li-metal batteries under practical conditions, a low negative/positive ratio (N/P ratio), a electrolyte/cathode ratio (E/C ratio) along with a high-voltage cathode is prerequisite. In this Review, we summarize the development of new electrolyte systems for Li-metal batteries under practical conditions, revisit the design criteria of advanced electrolytes for practical Li-metal batteries and provide perspectives on future development of electrolytes for practical Li-metal batteries.

Covalent Organic Frameworks with Low Surface Work Function Enabled Stable Lithium Anode

Uniform deposition and distribution of lithium ion (Li⁺ ) on the surface of lithium metal anode is crucial for long-life and high-safety lithium metal batteries. However, the preparation of stable solid-electrolyte interphase (SEI) is mostly based on trial and error in the absence of guideline. Herein, covalent organic framework (COF) with high Young's modulus and low surface work function is in situ synthesized on Li anode to stabilize Li|electrolyte interface. Notably, Young's modulus, mechanical index for Li dendrite resistance, and surface work function, electrical index for Li⁺ distribution, can be regarded as macroscopically detectable indicators to evaluate the artificial SEI before battery assembly. The COF_TpPa modified Li metal anodes delivered stable cycling over 1000 (2000) h at high current density of 5 (2) mA cm^-2 in the ether-based electrolyte, and the full cells with commercial LiFePO₄ electrode (mass loading of 16.5 mg cm^-2 ) demonstrate remarkably enhanced cycling performance with a high reversible capacity of 152.3 mAh g^-1 (retention of 96.8%) after 300 cycles.

Planar Fully Stretchable Lithium-Ion Batteries Based on a Lamellar Conductive Elastomer

Stretchable lithium-ion batteries (LIBs) have attracted great attention as a promising power source in the emerging field of wearable electronics. Despite the recent advances in stretchable electrodes, separators, and sealing materials, building stretchable full batteries remains a big challenge. Herein, a simple strategy to prepare stretchable electrodes and separators at the full battery scale is reported. Then, electrostatic spraying is used to make the anode and cathode on an elastic current collector. Finally, a polyvinylidene fluoride/thermoplastic polyurethane nanofiber separator is hot-sandwiched between the cathode and anode. The fabricated battery shows stable electrochemical performance during repeatable release-stretch cycles. In particular, a stable capacity of 6 mA•h/cm² at the current rate of 0.5 C can be achieved for the fully stretchable LIB. More importantly, over 70% of the initial capacity can be maintained after 100 cycles with ∼150% stretch.