Ceramic-in-Polymer Hybrid Electrolytes with Enhanced Electrochemical Performance

Abstract

Polymer electrolytes are attractive candidates to boost the application of rechargeable lithium metal batteries. Single-ion conducting polymers may reduce polarization and lithium dendrite growth, though these materials could be mechanically overly rigid, thus requiring ion mobilizers such as organic solvents to foster transport of Li ions. An inhomogeneous mobilizer distribution and occurrence of preferential Li transport pathways eventually yield favored spots for Li plating, thereby imposing additional mechanical stress and even premature cell short circuits. In this work, we explored ceramic-in-polymer hybrid electrolytes consisting of polymer blends of single-ion conducting polymer and PVdF-HFP, including EC/PC as swelling agents and silane-functionalized LATP particles. The hybrid electrolyte features an oxide-rich layer that notably stabilizes the interphase toward Li metal, enabling single-side lithium deposition for over 700 h at a current density of 0.1 mA cm–2. The incorporated oxide particles significantly reduce the natural solvent uptake from 140 to 38 wt % despite maintaining reasonably high ionic conductivities. Its electrochemical performance was evaluated in LiNi0.6Co0.2Mn0.2O2 (NMC622)||Li metal cells, exhibiting impressive capacity retention over 300 cycles. Notably, very thin LiNbO3 coating of the cathode material further boosts the cycling stability, resulting in an overall capacity retention of 78% over more than 600 cycles, clearly highlighting the potential of hybrid electrolyte concepts.

External Pressure in Polymer-Based Lithium Metal Batteries: An Often-Neglected Criterion When Evaluating Cycling Performance?

“…The voltage noise often results from Li dendritic growth and the occurrence of micro short circuits. , The vulnerability of PEO-based polymers to microshorts depends on several parameters, e.g., molecular weight and thickness of the polymer membrane. Also, adjusting the cell setup has been reported to realize battery cell systems based on PEO electrolytes paired with high-voltage cathodes, suggesting to look at this strategic parameter more carefully. − One mitigating strategy relies on the introduction of more rigid materials such as ceramics to physically delay or block Li dendrite penetration. , Another approach involves the formation of a polymer network by cross-linking the polymer chains. , Figure a displays the voltage profiles of cells utilizing either PEO or cross-linked PEO (xPEO) as the SPE.…”

“… 34 − 36 One mitigating strategy relies on the introduction of more rigid materials such as ceramics to physically delay or block Li dendrite penetration. 37 , 38 Another approach involves the formation of a polymer network by cross-linking the polymer chains. 36 , 39 Figure 1 a displays the voltage profiles of cells utilizing either PEO or cross-linked PEO (xPEO) as the SPE.…”

Enhancing the Electrochemical Performance of Blended Single-Ion Conducting Polymers by Smart Modification of the Polymer Structure

“…Prior to cycling, as previously reported, PAES-2 was drop-coated into the cathodes to enhance internal contacts and Li + transport properties. 70,71 In NMC622-PCr||Li cells, the initial discharge capacity for membranes containing EC/DMC is 152.0 mAh g −1 at 0.5C (cycle 11), surpassing that of membranes with EC/PC, which yield an initial discharge capacity of ≈140.0 mAh g −1 (Figure 9a). The higher ionic conductivity of PAES-2b with the plasticizer EC/DMC diminishes polarization phenomena and, consequently, augments the discharge capacity.…”

Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes

“…21 Depending on the ratio of polymers to ceramics, CSEs are further classified into "ceramic-inpolymer" (CIP) and "polymer-in-ceramic" (PIC) forms. 22,23 The former exhibits poor dendrite resistance due to inadequate mechanical strength caused by low ceramic component content (∼20 wt %). The latter incorporates a weight loading of ceramics larger than 50 wt %, significantly enhancing their safety and sufficient mechanical strength to counter lithium dendrite formation, and is therefore more suitable for practical applications, such as electric vehicles and grid-energy storage.…”

“…They combine the advantages of polymer solid electrolytes in wettability with electrodes (particularly the stability against lithium metal) and in flexibility as well as the advantages of ceramic solid electrolytes in ionic conductivity, (electro)­chemical stability, and mechanical strength . Depending on the ratio of polymers to ceramics, CSEs are further classified into “ceramic-in-polymer” (CIP) and “polymer-in-ceramic” (PIC) forms. , The former exhibits poor dendrite resistance due to inadequate mechanical strength caused by low ceramic component content (∼20 wt %). The latter incorporates a weight loading of ceramics larger than 50 wt %, significantly enhancing their safety and sufficient mechanical strength to counter lithium dendrite formation, and is therefore more suitable for practical applications, such as electric vehicles and grid-energy storage. , Sun et al developed a hierarchical “CIP” and “PIC” CSE featuring a PIC interlayer sandwiched between two CIP layers, which shows superiority in dendrite suppression and interfacial contact against Li metal .…”