Improvement in LiFePO4–Li battery performance via poly(perfluoroalkylsulfonyl)imide (PFSI) based ionene composite binder

Abstract

Lithiated poly(perfluoroalkylsulfonyl)imide (PFSILi) ionene is synthesized and blended with poly(vinylidene) difluoride (PVDF) to serve as binder for the electrode of a lithium ion battery. The incorporation of the PFSILi ionene adds ionic conducting channels inside the electrodes and prevents electrolyte depletion during rapid charging-discharging. The small composition change results in an increase in the battery performance, including a better reversibility, lower polarization or internal resistance and an improved discharge capacity, as well as a higher energy density at high rates or elevated temperatures. At the rate of 2 C and 60 C, the discharge plateau potential for the cell with the ionene based binder is 0.29 V higher than that for the cell with a PVDF only cathode binder. At a 4 C rate, the discharge capacity and energy density of a LiFePO 4 -Li half-cell with the ionic binder are 50% and 66%, respectively, higher than those of the cell using the nonionic PVDF binder at room temperature. Thus, the ionene polymer offers a new route, rather than just altering the active materials, to overcome the limitations of capacity and power density for rechargeable lithium batteries.

Synthesis and Application of a Conjugated Polydianion‐Based Single‐Ion Conducting Polymer for High‐Performance Solid Lithium‐Ion Batteries

“…However, the PEO‐LiPFSDI‐5 and −10 membranes cannot be formed since the dried mixture had poor mechanical properties and the viscosity was too high to take the dry mixture off the Teflon™ plate with a membrane shape. For comparison, PEO based electrolyte blended with LiPFSI and the classical LiTFSI were also prepared in EO/Li + ratios of 20 : 1 (referred to as PEO‐LiPFSI‐20 and PEO‐LiTFSI‐20, respectively), because this ratio provides a high electrochemical performance for both of these composites in the previous reports ,…”

“…For comparison, PEO based electrolyte blended with LiPFSI and the classical LiTFSI were also prepared in EO/Li + ratios of 20 : 1 (referred to as PEO-LiPFSI-20 and PEO-LiTFSI-20, respectively), because this ratio provides a high electrochemical performance for both of these composites in the previous reports. [48,49] 19 F NMR spectra of the compounds in synthetic process of the LiPFSDI are shown in Figure 2. The ICF (b) 2 CF (c) 2 OCF (d) 2 CF (e) 2 SO 2 F (a) shows 5 obvious peaks ( 19 F NMR, CD 3 CN, ppm: (a) 43.89, (b) À 70.51, (c) À 83.88, (d) À 86.98, (e) À 113.75).…”

Advances in the Synthesis and Application of Tetrafluoroethylene‐ and 1,1,2,2‐Tetrafluoroethyl‐Containing Compounds

“…Another example by Hallac et al shows a single fluorinated lithium sulfonimide attached to poly(ethylene glycol) ( 148 , Scheme ) . Watanabe and co‐workers developed polyanion LiPPI (Scheme ), which they alloyed with polyethers, and a similar polyanion, LiPFSI (Scheme ), was synthesized as a blend with polyvinylidene fluoride and poly(ethylene glycol) . All mentioned polymers were examined for their electrochemical properties.…”

Design and Preparation of a Lithium‐rich Layered Oxide Cathode with a Mg‐Concentration‐Gradient Shell for Improved Rate Capability

“…The technical obstacles are mainly attributed to the limited electrochemical properties of cathode materials, [5] such as low capacity (layered LiCoO 2 ), [6,7] structural vulnerability (spinel LiMn 2 O 4 ), [8,9] and poor conductivity of electron/lithium-ion diffusivity (olivine LiFePO 4 ). [10,11] Among all the cathodem aterials reported so far,l ithium-rich layered oxide materials[ xLi 2 MnO 3 ·(1-x)LiMO 2 ], as as olid solution between layers of Li 2 MnO 3 and LiMO 2 (M = Mn, Ni, Co, and so forth, 0 < x < 1), are recognizedasone of the most promising candidates, because of their low cost and low toxicity,a nd characteristic high specificc apacities ( % 250 mAh g À1 )w hen charged to ah igh upperc utoff voltage (> 4.5 V). [12][13][14] Although this cathode materialc an provideanumber of advantages over traditional materials, its widespread practical use has so far been hindered by severald rawbacks, such as large irreversible capacity loss in the first cycle (low initial coulombic efficiency), relativelyp oor rate capability,a nd significant capacity fade during high long-term cycling at high voltages.…”