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1. Highly‐Cyclable Room‐Temperature Phosphorene Polymer Electrolyte Composites for Li Metal Batteries

   https://doi.org/10.1002/adfm.201910749  

   Rojaee, Ramin; Cavallo, Salvatore; Mogurampelly, Santosh; Wheatle, Bill K.; Yurkiv, Vitaliy; Deivanayagam, Ramasubramonian; Foroozan, Tara; Rasul, Md Golam; Sharifi‐Asl, Soroosh; Phakatkar, Abhijit H.; et al (June 2020, Advanced Functional Materials)

   Despite significant interest toward solid-state electrolytes owing to their superior safety in comparison to liquid-based electrolytes, sluggish ion diffusion and high interfacial resistance limit their application in durable and high-power density batteries. Here, a novel quasi-solid Li+ ion conductive nanocomposite polymer electrolyte containing black phosphorous (BP) nanosheets is reported. The developed electrolyte is successfully cycled against Li metal (over 550 h cycling) at 1 mA cm(-2) at room temperature. The cycling overpotential is dropped by 75% in comparison to BP-free polymer composite electrolyte indicating lower interfacial resistance at the electrode/electrolyte interfaces. Molecular dynamics simulations reveal that the coordination number of Li+ ions around (trifluoromethanesulfonyl)imide (TFSI-) pairs and ethylene-oxide chains decreases at the Li metal/electrolyte interface, which facilitates the Li+ transport through the polymer host. Density functional theory calculations confirm that the adsorption of the LiTFSI molecules at the BP surface leads to the weakening of N and Li atomic bonding and enhances the dissociation of Li+ ions. This work offers a new potential mechanism to tune the bulk and interfacial ionic conductivity of solid-state electrolytes that may lead to a new generation of lithium polymer batteries with high ionic conduction kinetics and stable long-life cycling. 

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2. Ion Coordination and Transport in Magnesium Polymer Electrolytes Based on Polyester-co-Polycarbonate

   https://doi.org/10.34133/2021/9895403  

   Park, Bumjun; Andersson, Rassmus; Pate, Sarah G; Liu, Jiacheng; O’Brien, Casey P; Hernández, Guiomar; Mindemark, Jonas; Schaefer, Jennifer L (January 2021, Energy Material Advances)

   Magnesium-ion-conducting solid polymer electrolytes have been studied for rechargeable Mg metal batteries, one of the beyond-Li-ion systems. In this paper, magnesium polymer electrolytes with magnesium bis(trifluoromethane)sulfonimide (Mg(TFSI)₂) salt in poly(ε-caprolactone-co-trimethylene carbonate) (PCL-PTMC) were investigated and compared with the poly(ethylene oxide) (PEO) analogs. Both thermal properties and vibrational spectroscopy indicated that the total ion conduction in the PEO electrolytes was dominated by the anion conduction due to strong polymer coordination with fully dissociated Mg²⁺. On the other hand, in PCL-PTMC electrolytes, there is relatively weaker polymer–cation coordination and increased anion–cation coordination. Sporadic Mg- and F-rich particles were observed on the Cu electrodes after polarization tests in Cu|Mg cells with PCL-PTMC electrolyte, suggesting that Mg was conducted in the ion complex form (Mg_xTFSI_y) to the copper working electrode to be reduced which resulted in anion decomposition. However, the Mg metal deposition/stripping was not favorable with either Mg(TFSI)₂in PCL-PTMC or Mg(TFSI)₂in PEO, which inhibited quantitative analysis of magnesium conduction. A remaining challenge is thus to accurately assess transport numbers in these systems. 

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3. Novel Zwitterionic Polyurethane‐in‐Salt Electrolytes with High Ion Conductivity, Elasticity, and Adhesion for High‐Performance Solid‐State Lithium Metal Batteries

   https://doi.org/10.1002/aenm.202405676  

   Wang, Kun; Koverga, Volodymyr; Maslekar, Namrata; Wu, Fukang; Kuphl, Robert; Lyu, Xingyi; Deshpande, Piyush; Guo, Hanzeng; Seol, Hyang; Degraff, Wade; et al (May 2025, Advanced Energy Materials)

   This study presents a novel polymer‐in‐salt (PIS) zwitterionic polyurethane‐based solid polymer electrolyte (zPU‐SPE) that offers high ionic conductivity, strong interaction with electrodes, and excellent mechanical and electrochemical stabilities, making it promising for high‐performance all solid‐state lithium batteries (ASSLBs). The zPU‐SPE exhibits remarkable lithium‐ion (Li⁺) conductivity (3.7 × 10⁻⁴ S cm⁻¹at 25 °C), enabled by exceptionally high salt loading of up to 90 wt.% (12.6 molar ratio of Li salt to polymer unit) without phase separation. It addresses the limitations of conventional SPEs by combining high ionic conductivity with a Li⁺transference number of 0.44, achieved through the incorporation of zwitterionic groups that enhance ion dissociation and transport. The high surface energy (338.4 J m⁻²) and elasticity ensure excellent adhesion to Li anodes, reducing interfacial resistance and ensuring uniform Li⁺flux. When tested in Li||zPU||LiFePO₄ and Li||zPU||S/C cells, the zPU‐SPE demonstrated remarkable cycling stability, retaining 76% capacity after 2000 cycles with the LiFePO₄cathode, and achieving 84% capacity retention after 300 cycles with the S/C cathode. Molecular simulations and a range of experimental characterizations confirm the superior structural organization of the zPU matrix, contributing to its outstanding electrochemical performance. The findings strongly suggest that zPU‐SPE is a promising candidate for next‐generation ASSLBs. 

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4. Improved interfacial li-ion transport in composite polymer electrolytes via surface modification of LLZO

   https://doi.org/10.20517/energymater.2024.195  

   Counihan, Michael J; Lee, Jungkuk; Mirmira, Priyadarshini; Barai, Pallab; Burns, Meghan E; Amanchukwu, Chibueze V; Srinivasan, Venkat; Zhang, Yuepeng; Tepavcevic, Sanja (January 2025, Energy Materials)

   Composite polymer electrolytes that incorporate ceramic fillers in a polymer matrix offer mechanical strength and flexibility as solid electrolytes for lithium metal batteries. However, fast Li+ transport between polymer and Li+-conductive filler phases is not a simple achievement due to high barriers for Li+ exchange across the interphase. This study demonstrates how modification of Li7La3Zr2O12 (LLZO) nanofiller surfaces with silane chemistries influences Li+ transport at local and global electrolyte scales. Anhydrous reactions covalently link amine-functionalized silanes [(3-aminopropyl)triethoxysilane (APTES)] to LLZO nanoparticles, which protects LLZO in air. APTES functionalization lowers the poly (ethylene oxide) (PEO)-LLZO interphase resistance to half that of unmodified LLZO and increases effective Li+ transference number, while insulating Al2O3 completely blocks ion exchange and lowers transference number and conductivity in PEO-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-LLZO composites. Modeling an inner resistive interphase between LLZO and PEO surrounded by an outer conductive interphase explains non-linear conductivity trends. Solid-state 7Li & 6Li nuclear magnetic resonance shows Li+ only exchanges between PEO-LiTFSI and some LLZO interphase, with no appreciable Li+ transport through bulk LLZO. Surface functionalization is a promising path toward lowering the polymer-ceramic interphase resistance. This work demonstrates that local changes in Li+ transport affect macroscopic performance, highlighting the intricate relationships between all interfaces in inherently heterogeneous composite polymer electrolytes. 

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5. Non-solvating, side-chain polymer electrolytes as lithium single-ion conductors: synthesis and ion transport characterization

   https://doi.org/10.1039/c9py01035a  

   Liu, Jiacheng; Pickett, Phillip D.; Park, Bumjun; Upadhyay, Sunil P.; Orski, Sara V.; Schaefer, Jennifer L. (January 2020, Polymer Chemistry)

   Solid-state single-ion conducting polymer electrolytes have drawn considerable interest for secondary lithium batteries due to their potential for high electrochemical stability and safety, but applications are limited by their low ionic conductivities. Specifically, poly(ethylene oxide) (PEO) based electrolytes have the highest reported Li + conductivities for these materials; however, their potential is limited due to the ion transport mechanism being coupled to segmental relaxations of the cation solvating polymer chain. To investigate the potential of single-ion conducting polymer electrolytes lacking polar matrices, we synthesized three para -polyphenylene-based, side-chain polymer electrolytes with various pendent anion chemistries (–SO 3 − , –PSI − , and –TFSI − ) with differing binding affinities to Li + . Compared with the previously reported lithium poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide) (LiPSTFSI), the side-chain polymers showed at least 3 orders of magnitude higher conductivity with the same –TFSI − anion (6.7 × 10 −6 S cm −1 compared with 1.2 × 10 −10 S cm −1 at 150 °C). We found that the side-chain electrolyte showed a dielectric relaxation dominated transport mechanism through use of dielectric spectroscopy analysis. The conductivity is highly dependent on the charge delocalization and size of the pendent anion, which provides a pathway forward for the engineering of polymeric ion conductors for electrochemical applications. 

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