Organic-Inorganic Composite Electrolytes Optimized with Fluoroethylene Carbonate Additive for Quasi-Solid-State Lithium-Metal Batteries

Ultrathin, Mechanically Robust Quasi-Solid Composite Electrolyte for Solid-State Lithium Metal Batteries

Herein, we present the preparation and properties of an ultrathin, mechanically robust, quasi-solid composite electrolyte (SEO-QSCE) for solid-state lithium metal battery (SLB) from a well-defined polystyrene-b-poly(ethylene oxide) diblock copolymer (SEO), Li6.75La3Zr1.75Ta0.25O12 nanofiller, and fluoroethylene carbonate plasticizer. Compared with the ordered lamellar microphase separation of SEO, the SEO-QSCE displays bicontinuous phases, consisting of a Li+ ion conductive poly(ethylene oxide) domain and a mechanically robust framework of the polystyrene domain. Therefore, the 12 μm-thick SEO-QSCE membrane exhibits an exceptional ionic conductivity of 1.3 × 10-3 S cm-1 at 30 °C, along with a remarkable tensile strength of 5.1 MPa and an elastic modulus of 2.7 GPa. The high mechanical robustness and the self-generated LiF-rich SEI enable the SEO-QSCE to have an extraordinary lithium dendrite prohibition effect. The SLB of Li|SEO-QSCE|LiFePO4 reveals superior cycling performances at 30 °C for over 600 cycles, maintaining an initial discharge capacity of 145 mAh g-1 and a remarkable capacity retention of 81% (117 mAh g-1) after 400 cycles at 0.5 C. The high-voltage SLB of Li|SEO-QSCE|LiNi0.5Co0.3Mn0.2O2 displays good cycling stability for over 150 cycles at 30 °C. Moreover, the exceptional robustness of SEO-QSCE enables the high-voltage solid-state pouch cell of Li|SEO-QSCE|LiNi0.5Co0.3Mn0.2O2 with high flexibility and excellent safety features. The current investigation delivers a promising and innovative approach for preparing quasi-solid electrolytes with features of ultrathin design, mechanical robustness, and exceptional electrochemical performance for high-voltage SLBs.

In situ electrochemical modification of the Li/Li1.3Al0.3Ti1.7(PO4)3 interface in solid lithium metal batteries via an electrolyte additive

Solid-state Li batteries employing Li-metal anodes and solid Li/Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) electrolytes have emerged as promising next-generation energy storage devices due to their high energy density and safety. However, their performance is seriously limited by the irreversible reactivity of LATP with the Li-metal anode and the poor solid-solid interfacial contact between them, which result in relatively low ionic conductivity at the interface. The present work addresses these issues by presenting a method for modifying the Li/LATP interface in situ by applying 2-(trimethylsilyl) phenyl trifluoromethanesulfonate (2-(TMS)PTM) as a new type of electrolyte additive between the Li anode and the LATP electrolyte when assembling the battery, and then forming a uniform and thin interfacial layer via redox reactions occurring during the application of multiple charge-discharge cycles to the resulting battery. As a result of the significantly improved chemical compatibility between the Li anode and the LATP electrolyte, an as-assembled battery delivers a high reversible capacity of 165.7 mAh g^-1 and an outstanding capacity retention of 86.2% after 300 charge-discharge cycles conducted at a rate of 0.2C and a temperature of 30 °C. Accordingly, this work provides a new strategy for developing advanced solid-state Li metal batteries by tailoring the interface between the Li anode and the solid electrolyte.

Negatively Charged Holey Titania Nanosheets Added Electrolyte to Realize Dendrite-Free Lithium Metal Battery

Electrolyte modulation and electrode structure design are two common strategies to suppress dendrites growth on Li metal anode. In this work, a self-adaptive electrode construction method to suppress Li dendrites growth is reported, which merges the merits of electrolyte modulation and electrode structure design strategies. In detail, negatively charged titania nanosheets with densely packed nanopores on them are prepared. These holey nanosheets in the electrolyte move spontaneously onto the anode under electrical field, building a mesoporous structure on the electrode surface. The as-formed porous electrode has large surface area with good lithiophilicity, which can efficiently transfer lithium ion (Li⁺ ) inside the electrode, and induce the genuine lithium plating/stripping. Moreover, the negative charges and nanopores on the sheets can also regulate the lithium-ion flux to promote uniform deposition of Li metal. As a result, the symmetric and full cells using the holey titania nanosheets containing electrolyte, show much better performance than the ones using electrolyte without holey nanosheets inside. This work points out a new route for the practical applications of Li-metal batteries.

Enhancement of the Electrochemical Performances of Composite Solid-State Electrolytes by Doping with Graphene

With high safety and good flexibility, polymer-based composite solid electrolytes are considered to be promising electrolytes and are widely investigated in solid lithium batteries. However, the low conductivity and high interfacial impedance of polymer-based solid electrolytes hinder their industrial applications. Herein, a composite solid-state electrolyte containing graphene (PVDF-LATP-LiClO4-Graphene) with structurally stable and good electrochemical performance is explored and enables excellent electrochemical properties for lithium-ion batteries. The ionic conductivity of the composite electrolyte membrane containing 5 wt% graphene reaches 2.00 × 10^-3 S cm^-1 at 25 °C, which is higher than that of the composite electrolyte membrane without graphene (2.67 × 10^-4 S cm^-1). The electrochemical window of the composite electrolyte membrane containing 5 wt% graphene reaches 4.6 V, and its Li⁺ transference numbers reach 0.84. Assembling this electrolyte into the battery, the LFP/PVDF-LATP-LiClO4-Graphene /Li battery has a specific discharge capacity of 107 mAh g^-1 at 0.2 C, and the capacity retention rate was 91.58% after 100 cycles, higher than that of the LiFePO₄/PVDF-LATP-LiClO₄/Li (LFP/PLL/Li) battery, being 94 mAh g^-1 and 89.36%, respectively. This work provides a feasible solution for the potential application of composite solid electrolytes.