Enhanced Electrochemical Properties of LiFePO₄ Cathode Using Waterborne Lithiated Ionomer Binder in Li-Ion Batteries with Low Amount

Abstract

The poor conductivity of olivine structure LiFePO4 led to inevitable hindered electrochemical performances and restricted their uses in Li-ion batteries. To overcome the problem, introduction of conductive agents that bind with LiFePO4 active material is a universal solution. In this paper, a novel waterborne lithiated ionomer binder (PSBA-Li)for Li-ion batteries was originally designed and assembled with the low addition of 1.5% of a LiFePO4 cathode, showing a high areal capacity of 2.0 mAh cm–2. During lithiation/delithiation processes, PSBA-Li provided more Li+ ions, resulting in enhanced conductivity, which led to better performances. After 200 cycles, the PSBA-Li cathode based battery maintained stable cycling performances with retentions of 108.5%, 103.6%, and 114.9% at rates of 0.5C, 1C, and 2C, respectively, in contrast with a commercially used PVDF-cathode with a retention of only 7% (0.5C). The rate performance of the PSBA-Li cathode is higher than that of the PVDF-cathode, which shows almost no capacity at high rates. For contrastive analysis, SEM indicates a well integrity PSBA-Li cathode structure after cycling. On the contrary, active materials of PVDF-cathode separate from the aluminum foil after cycling. It is believed that the PSBA-Li has significant potential for further application for LiFePO4 cathodes in Li-ion batteries.

An environment-friendly crosslinked binder endowing LiFePO4 electrode with structural integrity and long cycle life performance

“…The attached Li + on the binder chains could help shorten the pathway of the free Li + to the particles' surface and enhance the Li + conductivity. 24 Additionally, the introduction of some specic polar functional groups into the 3D crosslinked binder were proved to effectively enhance the transport of Li + and e À . 11 For instance, Zhang et al prepared a double-helix-structure water-based binder consisting of abundant charged functional groups (hydroxyl and carboxylate), which were benecial to wrap binder chains tightly on the surfaces of the particles and conductive additives, and to contribute a compact interconnected electric network.…”

Partially lithiated ternary graft copolymer with enhanced elasticity as aqueous binder for Si anode

“…14 Recently, the lithiated polymers have been developed as effective binders to improve the electrochemical performances of LIBs ether for LiFePO 4 and LiMn 2 O 4 cathode or graphite/Si anode. 15,[16][17][18][19][20][21][22][23] These lithiated polymers can provide extra lithium-ion, which facilitates the ion transport and thus promotes the high rate performances of the cells. In summary, most of these polymers are the lithiated sulfonate polymers, including perfluorosulfonate, poly(etherether-ketone) and poly(vinylidenefluoride hexafluoro propylene).…”

“…[16][17][18][19][20][21] Additionally, Yuan et al reported the lithiated carboxylate polymer binders with different functions, such as, self-healing and crosslinking. 15,[22][23] Although the lithiated polymers can improve the rate performance of LIBs ether cathode or anode, they also exhibit brittle property due to the metal salt on polymer chain. [24][25][26] Previously, we reported a composite of lithiated PAA and terpene resin as a water soluble binder for LiFePO 4 cathode, 27 which demonstrates some advantages of lithiated PAA, such as, extra lithium-ion compensation for lithiumion loss, and strong adhesion capability due to the carboxylate functional groups.…”

“…Recently, the lithiated polymers have been developed as effective binders to improve the electrochemical performances of LIBs ether for LiFePO 4 and LiMn 2 O 4 cathode or graphite/Si anode 15,16–23 . These lithiated polymers can provide extra lithium‐ion, which facilitates the ion transport and thus promotes the high rate performances of the cells.…”

“…In summary, most of these polymers are the lithiated sulfonate polymers, including perfluorosulfonate, poly(ether‐ether‐ketone) and poly(vinylidenefluoride hexafluoro propylene) 16–21 . Additionally, Yuan et al reported the lithiated carboxylate polymer binders with different functions, such as, self‐healing and crosslinking 15,22–23 . Although the lithiated polymers can improve the rate performance of LIBs ether cathode or anode, they also exhibit brittle property due to the metal salt on polymer chain 24–26 …”