A Lithium‐Ion Pump Based on Piezoelectric Effect for Improved Rechargeability of Lithium Metal Anode

Abstract

Lithium metal is widely studied as the “crown jewel” of potential anode materials due to its high specific capacity and low redox potential. Unfortunately, the Li dendrite growth limits its commercialization. Previous research has revealed that the uniform Li‐ion flux on electrode surface plays a vital role in achieving homogeneous Li deposition. In this work, a new strategy is developed by introducing a multifunctional Li‐ion pump to improve the homogenous distribution of Li ions. Via coating a β‐phase of poly(vinylidene fluoride) (β‐PF) film on Cu foil (Cu@β‐PF), a piezoelectric potential across such film is established near the electrode surface because of its piezoelectric property, which serves as a driving force to regulate the migration of Li ions across the film. As a result, uniform Li‐ion distribution is attained, and the Cu@β‐PF shows coulombic efficiency around 99% throughout 200 cycles. Meanwhile, the lithium‐sulfur full cell paired with Li‐Cu@β‐PF anode exhibits excellent performance. This facile strategy via regulating the Li‐ion migration provides a new perspective for safe and reliable Li metal anode.

Stabilizing lithium metal anode by octaphenyl polyoxyethylene-lithium complexation

“…Issues resulted from dendritic lithium deposition, infinite volume change, and unstable solid-electrolyte interface (SEI) layers all contribute to the impracticality of lithium metal batteries [2][3][4] . Over the past several decades, researchers have developed various strategies to counteract these obstacles, including replacing Li metal with a LiX alloy 5 , developing new solid electrolytes or optimizing electrolyte components [6][7][8][9] , modifying separators [10][11][12][13] , constructing an artificial upper interfacial layer for Li metal anodes [14][15][16][17][18] , designing two-dimensional/three-dimensional (2-D/3-D) Lihosting materials 4,[19][20][21] , and various other techniques 22 .…”

Mechanistic understanding of the role separators playing in advanced lithium‐sulfur batteries

“…Uniform electric field/ion flux achieved by the separator also contributes to uniform lithium electrodeposition. Thus, strenuous efforts have been made under the guidance of this purpose . Kim et al used a polydopamine (PD)‐modified separator to facilitate uniform Li + flux and enhance the separator‐lithium contraction to diminish lithium surface tension (Figure B) .…”

“…Besides rejecting the polysulfides, this electronegative coating layer suppresses lithium dendrite growth by regulating uniform Li + fluxes, leading to highly stable cycling performance of 1000 cycles with greatly reduced dendrite inhibition for 1000 hours. Xiang et al introduced a Li + pump to the separator with β‐phase poly(vinylidene fluoride) in which piezoelectric potential is established near the electrode surface and serves as a driving force to regulate the migration of Li + . With this pump effect, the Li + transfer number was greatly increased from 0.19 of PP/PE to 0.59.…”

Synergistic improvement of the overall performance of lithium-sulfur batteries

“…PDDA-TFSI@Li/NMC811 和 Li/NMC811 在 0.5~8 C 下的倍率性能 [100] 。(e) 不同处理方 法在铜箔上沉积 Li 的示意图：(上)未加保护，沉积后在铜箔上形成多孔 Li 枝晶和缺锂 层；(下)用 β-PF 膜修饰，该膜可作为锂离子泵调节锂离子的均匀分布 [101] 。(f) 以 Li 箔 (蓝色)、Li@α-PF(红色)和 Li@β-PF(黑色)为负极的 Li-S 全电池在 0.2 C 下的循环性能对 比图 [101] on (a) the bare Cu and (b)PDDA-TFSI@Cu electrodes at 1 mA cm −2 . Scale bar, 20 μm [100] .…”

“…(d) Rate performance of PDDA-TFSI@Li/NMC811 and Li/NMC811 at various rates from 0.5 to 8 C [100] . (e) Schematic illustration of Li deposition on Cu foil with different treatments: (upper) without protection, leading to the formation of porous Li dendrite and Li-ion deficient layer on the Cu foil after deposition; (lower) with β-PF film modification, serving as the Li-ion pump to regulate the uniform distribution of Li ions [101] . (f) Cycle performances of Li-S full cells with Li foil (blue), Li@α-PF (red), and…”