Elimination of “Voltage Noise” of Poly (Ethylene Oxide)-Based Solid Electrolytes in High-Voltage Lithium Batteries: Linear versus Network Polymers

Self Cite

100

Solid polymer electrolytes (SPEs) are promising candidates for the realization of lithium metal batteries. However, the popular SPE based on poly(ethylene oxide) (PEO) reveals a "voltage noise"-failure during charge, for example, with high energy/high voltage electrodes like LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622), which can be attributed to short-circuits via penetrating Li dendrites. This failure disappears when integrating PEO-based SPE in a semi interpenetrating network, which mainly consists of PEO units, as well. In this work, it is shown that this SPE allows performance improvement via elimination of the crystalline domains without significant sacrifice of mechanical integrity. Hence, a highly amorphous SPE can be obtained by a simple increase of plasticizing Li salts, which overall is beneficial, not only for the ionic conductivity, but also the homogeneity, while remaining mechanically stable and solid in its original shape even after storage at 60 °C for 7 days. These aspects are crucial for the performance of the modified SPE as they can suppress the failure-causing Li dendrite penetration while the electrochemical aspects, that is, anodic stability, are rather unaffected by the modification and remain stable (4.6 V vs Li│Li +). Overall, this optimized SPE enables stable cycling performance in NMC622│SPE│Li cells, even at 40 °C operation temperature.

Section: Methodsmentioning

confidence: 88%

Section: Semi Interpenetrating Network Poly(ethylene Oxide)-based Solmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effective Optimization of High Voltage Solid‐State Lithium Batteries by Using Poly(ethylene oxide)‐Based Polymer Electrolyte with Semi‐Interpenetrating Network

Homann

Stolz

Neuhaus

et al. 2020

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100

Towards All‐Solid‐State Polymer Batteries: Going Beyond PEO with Hybrid Concepts

Chen

Lennartz

Liu

et al. 2023

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To go beyond polyethylene oxide in lithium metal batteries, a hybrid polymer/oligomer cell design is presented, where an ester oligomer provides high ionic conductivity of 0.2 mS cm−1 at 40 °C within thicker composite cathodes with active mass loadings of up to 11 mg cm−2 (LiNbO3‐coated) LiNi0.6Mn0.2Co0.2 (NMC622), while a 30 µm thin scaffold‐supported polymer electrolyte affords mechanical stability. Corresponding discharge capacities of the hybrid cells exceed 170 mAh g−1 (11 mg cm−2) or 160 mAh g−1 (6 mg cm−2) at rates of either 0.1 or 0.25 C. Multilayer pouch cells are projected to enable energy densities of 235 Wh L−1 (6 mg cm−2) and even up to 356 Wh L−1 (11 mg cm−2), clearly superior to other reported polymer‐based cell designs. Polyester electrolytes are environmentally benign and safer compared to common liquid electrolytes, while the straightforward synthesis and affordability of precursors render hybrid polyester electrolytes suitable candidates for future application in solid‐state lithium metal batteries.

Assessment of “Inverse” Cross‐Talk (Anode to Cathode) in High‐Voltage Li/Mn‐Rich Layered Oxide || Li Cells

Arifiadi,

Demelash,

Abke

et al. 2024

Li/Mn‐rich layered oxide (LMR) offers high practical discharge capacity originating from both cationic and anionic redox, but its operation is practically challenging as full capacity utilization at high cathode potentials (> 4.6 V vs Li|Li+) is intertwined with phase transformation, oxygen release, and transition metal dissolution. Dissolved TMs in particular, can deposit and damage the anode via a process known as electrode cross‐talk that decreases Li inventory due to Li plating. Given the excess in active lithium, Li‐metal anode (LMA) is frequently paired with LMR for a systematic cathode R&D, though is believed to cause inverse cross‐talk, i.e., diffusion of LMA degradation products from the solid electrolyte interphase (SEI) toward the cathode, triggering bulid‐up of resistive cathode electrolyte interphase (CEI). Indeed, a thicker, more organic‐based, and slightly resistive CEI is proven in Li‐ compared to “SEI‐poor” Li4Ti5O12 (LTO)‐based cells via X‐ray photoelectron spectroscopy, time‐of‐flight secondary ion mass spectrometry, and electrochemical techniques, which likely even decreases metal dissolution from LMR, though their practical impact on overpotential is shown to be less relevant. The capacity recovery after transferring cycled (“old”) LMR from Li cells to fresh Li cells rather points to other meaningful contributions to capacity fading than the inverse crosstalk.