Suppressing Dendrite Growth of a Lithium Metal Anode by Modifying Conventional Polypropylene Separators with a Composite Layer

Abstract

Lithium metal is a promising candidate anode for next generation high energy density batteries. However, the Li dendrite growth results in electrode degradation and safety hazards, obstructing its practical applications. Herein, we propose a facile and effective method to build a robust ion conductive layer on the lithium metal surface. A thin coating layer containing nano-Si and poly­(acrylic acid) on the surface of the conventional separator would react with lithium metal after adding electrolytes, forming a protective layer composed of the Li–Si alloy and LiPAA, which is a good Li-ion conductor. Both the Li–Li symmetric and full cells (Li-LiFePO4 and Li–S) using this modified separator exhibited much better cycle stability than those using an unmodified one. The dendrite suppression and electrochemical performance enhancement should be attributed to the unique interfacial structure modification for uniform and accelerated Li+ flux and rich lithium deposition sites. These findings suggest that the lithium interfacial properties have a huge effect on lithium stripping/plating and that the proposed strategy would provide new insights toward high energy lithium metal batteries.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

“…Nanoscale coatings on conventional polypropylene separators help in the formation of a protective SEI layer. The systematic coating of Si nanoparticles and polyacrylic acid (PAA) over the separator surface yields a stable, highly conductive passivation layer comprising Li-Si alloy and LiPAA [356]. Various functional modifications and catalyst additions to the separator reinforce the stability of the separator-electrolyte species interface, contributing to higher efficiency and reduced dendrite evolution [357,358].…”

Safer Lithium‐Ion Batteries from the Separator Aspect: Development and Future Perspectives

“…(Reproduced with permission. [ 143 ] Copyright 2019, American Chemical Society.) k) The morphology illustration of the Li metal after 200 cycles with pristine PP separator and the SrF 2 microsphere‐modified PP separator.…”

“…[ 141,142 ] Zhang et al. [ 143 ] decorated the PP separator with a composite layer containing nano‐Si and poly(acrylic acid) (PAA). The coating layer would react with Li metal to form an inorganic/organic composite layer consisting of Li‐Si alloy and polymer ion conductors (LiPAA), with both flexibility and high strength, which serves as a robust protective layer to efficiently restrain the dendrite growth (Figure 10e‐j).…”

Strategies to anode protection in lithium metal battery: A review

“…Further, the growing Li dendrites may puncture the unstable SEI and then fresh Li metal is exposed, which would react with electrolyte, leading to continuous consumption of electrolyte and consequently deviling a high overpotential and low CE 28‐31 . In response to these issues, a number of approaches have been developed to restrain the formation of Li dendrites, including artificial SEI layer construction (inorganic or organic SEI layer), 32‐37 separator modification, 38‐42 current collector modification, 43‐48 additives of electrolyte, 49‐53 solid‐state electrolyte, and so on 54‐60 …”