Anion-tethered Single Lithium-ion Conducting Polyelectrolytes through UV-induced Free Radical Polymerization for Improved Morphological Stability of Lithium Metal Anodes

Decreased Electrically and Increased Ionically Conducting Scaffolds for Long-Life, High-Rate and Deep-Capacity Lithium-Metal Anodes

Lithium (Li) metal batteries are deemed as promising next-generation power solutions but are hindered by the uncontrolled dendrite growth and infinite volume change of Li anodes. The extensively studied 3D scaffolds as solutions generally lead to undesired "top-growth" of Li due to their high electrical conductivity and the lack of ion-transporting pathways. Here, by reducing electrical conductivity and increasing the ionic conductivity of the scaffold, the deposition spot of Li to the bottom of the scaffold can be regulated, thus resulting in a safe bottom-up plating mode of the Li and dendrite-free Li deposition. The resulting symmetrical cells with these scaffolds, despite with a limited pre-plated Li capacity of 5 mAh cm-2, exhibit ultra-stable Li plating/stripping for over 1 year (11 000 h) at a high current density of 3 mA cm-2 and a high areal capacity of 3 mAh cm-2. Moreover, the full cells with these scaffolds further demonstrate high cycling stability under challenging conditions, including high cathode loading of 21.6 mg cm-2, low negative-to-positive ratio of 1.6, and limited electrolyte-to-capacity ratio of 4.2 g Ah-1.

Zwitterionic Cellulose-Based Polymer Electrolyte Enabled by Aqueous Solution Casting for High-Performance Solid-State Batteries

Polyethylene oxide (PEO)-based solid-state batteries hold great promise as the next-generation batteries with high energy density and high safety. However, PEO-based electrolytes encounter certain limitations, including inferior ionic conductivity, low Li+ transference number, and poor mechanical strength. Herein, we aim to simultaneously address these issues by utilizing one-dimensional zwitterionic cellulose nanofiber (ZCNF) as fillers for PEO-based electrolytes using a simple aqueous solution casting method. Multiple characterizations and theoretical calculations demonstrate that the unique zwitterionic structure imparts ZCNF with various functions, such as disrupting PEO crystallization, dissociating lithium salts, anchoring anions through cationic groups, accelerating Li+ migration by anionic groups, as well as its inherent reinforcement effect. As a result, the prepared PL-ZCNF electrolyte exhibits remarkable ionic conductivity (5.37×10-4 S cm-1) and Li+ transference number (0.62) at 60 °C without sacrificing mechanical strength (9.2 MPa), together with high critical current density of 1.1 mA cm-2. Attributed to these merits of PL-ZCNF, the LiFePO4|PL-ZCNF|Li solid-state full-cell delivers exceptional rate capability and cycling performance (900 cycles at 5 C). Notably, the assembled pouch-cell can maintain steady operation over 1000 cycles with an impressive 93.7 % capacity retention at 0.5 C and 60 °C, highlighting the great potential of PL-ZCNF for practical applications.

Cation-Conduction Dominated Hydrogels for Durable Zinc-Iodine Batteries

Zinc-iodine batteries have the potential to offer high energy-density aqueous energy storage, but their lifetime is limited by the rampant dendrite growth and the concurrent parasite side reactions on the Zn anode, as well as the shuttling of polyiodides. Herein, a cation-conduction dominated hydrogel electrolyte is designed to holistically enhance the stability of both zinc anode and iodine cathode. In this hydrogel electrolyte, anions are covalently anchored on hydrogel chains, and the major mobile ions in the electrolyte are restricted to be Zn2+. Specifically, such a cation-conductive electrolyte results in a high zinc ion transference number (0.81) within the hydrogel and guides epitaxial Zn nucleation. Furthermore, the optimized Zn2+ solvation structure and the reconstructed hydrogen bond networks on hydrogel chains contribute to the reduced desolvation barrier and suppressed corrosion side reactions. On the iodine cathode side, the electrostatic repulsion between negative sulfonate groups and polyiodides hinders the loss of the iodine active material. This all-round electrolyte design renders zinc-iodine batteries with high reversibility, low self-discharge, and long lifespan.

Making Plasticized Polymer Electrolytes Stable Against Sodium Metal for High-Energy Solid-State Sodium Batteries

Solid polymer electrolytes based on plastic crystals are promising for solid-state sodium metal (Na0) batteries, yet their practicality has been hindered by the notorious Na0-electrolyte interface instability issue, the underlying cause of which remains poorly understood. Here, by leveraging a model plasticized polymer electrolyte based on conventional succinonitrile plastic crystals, we uncover its failure origin in Na0 batteries is associated with the formation of a thick and non-uniform solid electrolyte interphase (SEI) and whiskery Na0 nucleation/growth. Furthermore, we design a new additive-embedded plasticized polymer electrolyte to manipulate the Na0 deposition and SEI formulation. For the first time, we demonstrate that introducing fluoroethylene carbonate (FEC) additive into the succinonitrile-plasticized polymer electrolyte can effectively protect Na0 against interfacial corrosion by facilitating the growth of dome-like Na0 with thin, amorphous, and fluorine-rich SEIs, thus enabling significantly improved performances of Na//Na symmetric cells (1,800 h at 0.5 mA cm-2) and Na//Na3V2(PO4)3 full cells (93.0 % capacity retention after 1,200 cycles at 1 C rate in coin cells and 93.1 % capacity retention after 250 cycles at C/3 in pouch cells at room temperature). Our work provides valuable insights into the interfacial failure of plasticized polymer electrolytes and offers a promising solution to resolving the interfacial instability issue.