An Efficient Route to Polymeric Electrolyte Membranes with Interparticle Chain Microstructure Toward High‐Temperature Lithium‐Ion Batteries

Abstract

The application of current polymer lithium‐ion batteries is still challenged with the limited electrochemical performance and thermal stability of polymeric electrolyte membranes as battery separators. In this report, an efficient route to polymeric polyvinylidene fluoride‐hexafluoropropylene electrolyte membranes with interparticle chain microstructure is presented. The structure is capable of hosting sufficient electrolyte for efficient migration of electrolyte salts. The electrolyte uptake ratio is up to 188.4% and the highest ionic conductivity reaches 1.08 mS cm−1 at room temperature. In particular, the membrane exhibits higher thermal resistance compared with traditional separators, only giving rise to a subtle shrinkage at 175 °C and allows for efficient battery operation for a record number of charge/discharge cycles at 110 °C. The electrolyte membrane through such a single‐step method shows promising application potentials in electric vehicles and wearable electronics, especially in extreme operation conditions.

High‐Performance PE‐BN/PVDF‐HFP Bilayer Separator for Lithium‐Ion Batteries

“…The most commonly used separators in LIBs are polyolefin separators predominantly polypropylene (PP), polyethylene (PE), and their multilayer formations like PE/PP or PP/PE/PP owing to their high tensile strength and shutdown ability. Nevertheless, the polyolefin separators suffer from severe dimensional instability at elevated temperatures and poor compatibility with liquid electrolytes due to hydrophobic surface character, and have poor capability to retain electrolyte . Conventionally, polyolefin separators are prepared through dry or wet processes and their tensile strength, porosity, or Gurley number vary with respect to methods of preparation .…”

Recent Development in Separators for High‐Temperature Lithium‐Ion Batteries

“…However, the electrochemical performances of Li/separator‐anode batteries deliver the remarkable discharge capacity with 100% capacity retention after 300 cycles at 37.2 mA g −1 as given in Figure d. Ye et al prepared PVDF‐HFP separator through phase inversion method with interparticle chain structure. The prepared PVDF‐HFP structure hosts more electrolyte owing to the high porosity and polar nature of undissolved PVDF‐HFP particles in a structure that absorbs electrolyte so efficiently and improves the overall performances.…”

“…The interparticle chain structure of separator further enhances the thermal and mechanical stabilities of separator, as given in Figure a–d. Liu et al used a similar concept of interparticle chain structure of PVDF‐HFP separator as reported by Ye et al, but using two solvent (N‐methyl pyrrolidone (NMP) and acetone) during the preparation of separator, as shown in Figure e,f. The use of bisolvents formed the hierarchical interbond structure with high porosity, which leads toward the high electrolyte uptake and enhanced ionic conductivity.…”

“…a) SEM image of PVDF‐HFP separator with interparticle chain structure, b) tensile strength graphs of I – C and phase inversion PVDF‐HFP separator, and c,d) thermal shrinkage images of Celgard 2325, phase inversion PVDF‐HFP, and I – C separators before and after annealing at 150 °C for 1 h. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

A Highly Stable Separator from an Instantly Reformed Gel with Direct Post‐Solidation for Long‐Cycle High‐Rate Lithium‐Ion Batteries

“…[3,18,19] As shown in Figure 1i,j,t he contacta ngle of Celgard 2320 is 458 whereas M-0.5 shows al ower contact angle of 188 in the early stage of electrolyte contacting (t = 2s), which verifies that M-0.5 shows better wettability owing to its strong cross-linked, inner-bound, and tortuous porous structure. [20] High electrolyte uptake,c aused by high porosity and electrolyte wettability of the separator,improves the rate capability and long-term stabilityb yf acilitating ionic shuttling across the separator and reducing electrode/electrolyte interfacial resistance. [21][22][23] The electrolyte uptake ratios of the separators (M-0, M-0.5, M-1, M-1.5,and Celgard 2320) are 180.58, 114.81, 108.63, 106.43, and 86.67 %, respectively.T he PVDF-HFP separators absorb more electrolytes than Celgard2320.…”