Supramolecular Self-Assembly of Methylated Rotaxanes for Solid Polymer Electrolyte Application

Li+-conducting solid polymer electrolytes (SPEs) obtained from supramolecular self-assembly of trimethylated cyclodextrin (TMCD), poly(ethylene oxide) (PEO), and lithium salt are investigated for application in lithium-metal batteries (LMBs) and lithium-ion batteries (LIBs). The considered electrolytes comprise nanochannels for fast lithium-ion transport formed by CD threaded on PEO chains. It is demonstrated that tailored modification of CD beneficially influences the structure and transport properties of solid polymer electrolytes, thereby enabling their application in LMBs. Molecular dynamics (MD) simulation and experimental data reveal that modification of CDs shifts the steady state between lithium ions inside and outside the channels, in this way improving the achievable ionic conductivity. Notably, the designed SPEs facilitated galvanostatic cycling in LMBs at fast charging and discharging rates for more than 200 cycles and high Coulombic efficiency

Grafted polyrotaxanes as highly conductive electrolytes for lithium metal batteries

Hyperbranched polymers comprised of polyrotaxanes as mechanically stable backbone and grafted polycaprolactone (PCL) side chains are utilized as solid polymer electrolyte for application in lithium metal (LMBs) and lithium ion batteries (LIBs). The polyrotaxanes were obtained from self-assembly of Cyclodextrin (CD) host molecules threading onto polyethylenoxide (PEO) chains. In particular, CD serves as initiator for a ring-opening-polymerization of PCL affording pendant side chains with merely a few monomer unit lengths that foster enhanced lithium ion transport, as mediated by well-defined lamellar morphology of the PCL side chains. An impressive ionic conductivity of 1 mS cm−1 of the solid polymer electrolyte at 60 °C and more than 0.1 mS cm-1 at room temperature in addition to a superior oxidative electrochemical stability of up to 4.7 V vs. Li/Li+ allows for robust galvanostatic cycling in LiFePO4|Li cells, even at reduced temperatures not accessible by commonly utilized PEO-based electrolytes. The hyperbranched polymers can be readily up-scaled and further modified, thereby demonstrating the versatility of the introduced class of solid-state polymer electrolytes, as reflected by its interfacial stability against the high-capacity Lithium metal anode

Trimethylsiloxy based metal complexes as electrolyte additives for high voltage application in lithium ion cells

Previous studies have shown that electrolyte additives based on metals and semimetals (LiBOB, Mg(TFSI)2, Al(TFSI)3) as well as additives containing trimethylsiloxyl (TMS) groups as ligands can have positive impact on the cycling performance of lithium ion battery cells due to solid electrolyte interphase (SEI) and/or cathode electrolyte interphase (CEI) film forming properties and/or scavenging properties towards acidic impurities. In this study, both active functionalities (metal core and trialkylsiloxy based ligands) were combined into one using Al, Ti and B as metal cores combined with TMS ligands (M(TMS)x). All investigated additives M(TMS)x were able to improve the cycling performance regarding Coulombic efficiency, energy efficiency and capacity retention of LiNi1/3Co1/3Mn1/3O2 (NCM111)/Li half-cells and NCM111/graphite full-cells at high potentials (>4.3 V vs. Li/Li+). The formed CEI was studied by means of electrochemical impedance spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The obtained results indicate that the investigated additives are either actively incorporated into the formed CEI layer (in case of Al, Ti as metal core) or interacting with decomposition products (in case of B as metal core) resulting in lower charge-transfer impedance and hence improved long-term cycling behavior

Supramolecular Self-Assembly of Methylated Rotaxanes for Solid Polymer Electrolyte Application

Li⁺-conducting solid polymer electrolytes (SPEs) obtained from supramolecular self-assembly of trimethylated cyclodextrin (TMCD), poly­(ethylene oxide) (PEO), and lithium salt are investigated for application in lithium-metal batteries (LMBs) and lithium-ion batteries (LIBs). The considered electrolytes comprise nanochannels for fast lithium-ion transport formed by CD threaded on PEO chains. It is demonstrated that tailored modification of CD beneficially influences the structure and transport properties of solid polymer electrolytes, thereby enabling their application in LMBs. Molecular dynamics (MD) simulation and experimental data reveal that modification of CDs shifts the steady state between lithium ions inside and outside the channels, in this way improving the achievable ionic conductivity. Notably, the designed SPEs facilitated galvanostatic cycling in LMBs at fast charging and discharging rates for more than 200 cycles and high Coulombic efficiency