Frontier Orbital Energy-Customized Ionomer-Based Polymer Electrolyte for High-Voltage Lithium Metal Batteries

Abstract

The development of gel polymer electrolytes (GPEs) is considered to be an effective strategy to drive practical applications of high-voltage lithium metal batteries (HLMBs). However, rare GPEs that can satisfy the demands of HLMBs have been developed because of the limited compatibility with lithium anodes and high-voltage cathodes simultaneously. Herein, a novel strategy for constructing polymer matrixes with a customized frontier orbital energy for GPEs is proposed. The as-investigated polymer matrix (P­(CUMA-NPF6))-based GPE (P­(CUMA-NPF6)-GPE) obtained via in situ random polymerization delivers a wide voltage window (0–5.6 V vs Li+/Li), large lithium-ion transference number (t Li +, 0.61), and superior electrode/electrolyte interface compatibility. It is to be noted that such a t Li + of P­(CUMA-NPF6)-GPE, which is one of the largest t Li + among high-voltage GPEs in a fair comparison, results from the high dissociation of lithium salts and effective anion immobilization abilities of P­(CUMA-NPF6). Ultimately, the as-assembled HLMB delivers more enhanced cycle performance than its counterpart of commercial liquid electrolytes. It is also demonstrated that P­(CUMA-NPF6) can scavenge the active PF5 intermediate generated in the electrolyte at the anode side, thus suppressing the PF5-mediated decomposition reaction of carbonates. This work will enlighten the rational structure design of GPEs for HLMBs.

In Situ Characterization of Over-Lithiation of Organosulfide-Based Lithium Metal Anodes

“…Comparing the results of the in situ Raman spectra with those of ex situ 13 C solid-state nuclear magnetic resonance (SS-NMR) and Fourier transform infrared (FT-IR) spectroscopy (Figures 1c, S1, and S2) allows us to understand the chemical evolution of SPAN in detail. The chemical structure of SPAN, as shown in the inset of Figure 1c, contains polymeric pyridine rings and polysulfide chains attached to the polymer backbone.…”

“…Compared with the commercial graphite anode, LMAs suffer from the less uniform Li-ion (Li + ) deposition and a more fragile solid electrolyte interphase (SEI), which usually leads to disordered dendrite growth and low lithium reversibility . Many strategies have been proposed to solve the above problems, including the design of a structured current collector to homogenize Li + flux, − building an artificial protective layer to improve interface stability, − employing a gel/inorganic solid electrolyte to inhibit the growth of dendrites, − optimizing electrolyte composition to increase the Li plating/stripping Coulombic efficiency (CE). − …”

Advances in host selection and interface regulation of polymer electrolytes

“…The P(CUMA‐NPF 6 )‐PE not only exhibits superior oxidation stability (>5.6 V), high lithium‐ion conductivity (1.02 × 10 −3 S cm −1 , 25°C) and t Li+ (0.61), but also traps the generated PF 5 intermediate, thereby efficiently suppressing the decomposition of the liquid plasticizer (1 M LiPF 6 ‐EC/DMC). Hence, the as‐assembled Li/LiNi 0.5 Mn 1.5 O 4 batteries show better cycling performance than conventional LE‐based cells with a capacity retention of 75% after 250 cycles 74 …”

Lithium-Rich Anti-perovskite Li2OHBr-Based Polymer Electrolytes Enabling an Improved Interfacial Stability with a Three-Dimensional-Structured Lithium Metal Anode in All-Solid-State Batteries

“…Solid polymer electrolytes are one of the highly likely successors of solid-state electrolytes due to their high ionic conductivity, high flexibility, and good interfacial compatibility with electrodes, and hence, they are promising solid-state electrolytes toward 3D-structured electrodes. − Among all the solid polymer electrolytes reported to date, poly­(ethylene oxide) (PEO)-based polymer electrolytes are currently the leading candidates for application in lithium-metal batteries because of their sufficient ether coordination sites for lithium ion diffusion and good stability toward lithium metal. , Their main disadvantages are the semicrystallization of PEO at room temperature that resulted from the presence of long and ordered EO chains, hindering the migration of lithium ions, and the lack of strong mechanical strength to withstand the possible puncture by the sharp lithium dendrites as well as the burrs on the ragged and rigid electrode interface. Using inorganic fillers (e.g., SiO 2 , Li 1.4 Al 0.4 Ge 1.6 (PO 4 ) 3 , and Li 7 La 3 Zr 2 O 12 ) as a PEO-based polymer electrolyte modification method can effectively improve the lithium ion conductivity and mechanical strength. − Although substantial progress has been made, the exploration of more filler candidates to realize the full potential of the PEO-based polymer electrolytes and the understanding of the synergistic effects of the filler with the solid polymer electrolyte are priority research areas.…”