Delamination‐Free Multifunctional Separator for Long‐Term Stability of Lithium‐Ion Batteries

Abstract

Next‐generation lithium‐ion batteries (LIBs) that satisfy the requirements for an electric vehicle energy source should demonstrate high reliability and safety for long‐term high‐energy‐density operation. This inevitably calls for a novel approach to advance major components such as the separator. Herein, a separator is designed and fabricated via application of multilayer functional coating on both sides of a polyethylene separator. The multilayer‐coated separator (MCS) has a porous structure that does not interfere with lithium ion diffusion and exhibits superior heat resistance, high electrolyte uptake, and persistent adhesion with the electrode. More importantly, it enables high capacity retention and reduced impedance build up during cycling when used in a coin or pouch cell. These imply its promising application in energy sources requiring long‐term stability. Fabrication of the MCS without the use of organic solvents is not only environmentally beneficial but also effective at cost reduction. This approach paves the way for the separator, which has long been considered an inactive major component of LIBs, to become an active contributor to the energy density toward achieving longer cycle stability.

Nanopile Interlocking Separator Coating toward Uniform Li Deposition of the Li Metal Anodes

“…To address the Li dendrite issues associated with Li metal anodes, researchers have investigated various approaches, − including introducing stable hosts, − modifying structures of current collectors, − constructing artificial solid electrolyte interphase (SEI), − separator modification, − and optimizing electrolyte composition. − As an important component in batteries, separator plays a critical role in determining the diffusion of Li ions and safety issues of Li-ion batteries. − Due to its chemical stability, relatively low price, no requirement to change either electrode or electrolyte systems, commercial polyolefin separator modification is a convenient alternative to regulate the Li deposition behavior . Also recently, a growing number of works have demonstrated that surface modification of separator is a promising route to avoid Li dendritic growth, , their schemes including improving separator wettability, regulating Li ionic flux, − and lithiophilic modifications. , However, due to huge Young’s modulus difference between the coating layer and the substrate, the intrinsic low surface energy of polyolefin separator, and continuous immersion in the polar electrolyte during charge/discharge cycles, the drop-dregs phenomenon of the coating layer desquamated from polyolefin separator extensively exists in traditional separator modification methods. − Unfortunately, these detached points would act as defects that cause a nonuniform Li ionic flux and increase in separator impedance, finally resulting in the generation of Li dendrite, significantly diminished practical performance, and even serious safety concerns of Li metal batteries. − Hence, the drop-dregs issue is still a big hurdle for separator modification methods toward long-term stable Li metal anodes because of potential failure at interface connection, especially between the soft separator and the rigid inorganic coating layer.…”

Intercalated Montmorillonite Reinforced Polyimide Separator Prepared by Solution Blow Spinning for Lithium-Ion Batteries

“…Superior thermal dimensional stability is desirable for the separator, striving to avoid serious safety hazards such as internal short circuiting of the electrode, even battery combustion or explosion caused by overheating. , Accordingly, we conducted a hot oven test for various separators. Figure represents the thermal shrinkage of Celgard 2400 and different contents of OMMT-incorporated PI/OMMT separators after subjected to elevated temperature.…”

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

“…The wettability between the separator and liquid electrolyte is important because it would influence the interfacial resistance . Thus, the contact angle and wettability of the PP or PP@PS separators have been examined.…”