Tandem Design of Functional Separators for Li Metal Batteries with Long‐Term Stability and High‐Rate Capability

Abstract

The lithium (Li) dendrite growth seriously hinders the applications of lithium metal batteries (LMBs). Numerous methods have been proposed to restrict the formation of Li dendrites by improving the Li‐ion transference number (tLi+) through separator modification according to Sand's time equation. However, ignoring the positive contribution of anion motion to solid electrolyte interphase (SEI) formation will result in insufficient inorganic components, which impedes practical implementation of LMBs. Herein, a “tandem” separator is constructed (ZSM‐5‐Poly dimethyl diallyl ammonium chloride (PDDA)/Polyethylene (PE)/SbF3), which anchored anions and built an inorganic‐rich SEI at the same time. The resulting SEI from SbF3 (SBF) coating on side facing Li is rich in Li‐Sb alloy (Li3Sb) and LiF. Li3Sb can significantly reduce the migration energy barrier of Li ion (Li+) and facilitate Li+ transport. Simultaneously, ZSM‐5‐PDDA (Z5P) coating at the other side can effectively immobilize anions and increase the tLi+. Moreover, the regular pore structure is conducive to homogenizing Li+ flux and also capable to uniform temperature distribution, significantly improving safety. Hence, the lifespan of Li|Li and Li|Cu cells assemble with Z5P/PE/SBF separator is significantly extended. In addition, full cells with LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiFePO4 (LFP) cathodes show excellent cycle stability and superior rate performance.

Synergetic impact of nitrate-based additives for enhanced solid electrolyte interphase performance

“…To address the challenges associated with interfacial impedance and Li dendrite growth, efforts have been directed at application of structured hosts, 23–25 deployment of artificial SEI, 26–28 design of functionalized separators, 29–31 and optimization of the electrolyte. 32–34 Amongst them, regulating the electrolyte formulation is the most effective approach for facilitating an intrinsically more stable SEI growth.…”

A Deeper Understanding of Metal Nucleation and Growth in Rechargeable Metal Batteries Through Theory and Experiment

“…[84][85] Sand's time theory clearly has large relevance to metal batteries and has been applied in several works. [85][86][87][88][89] Bai, et al observed rapid onset dendritic growth and a spike in potential in capillary Li cells which corresponded to Sand's time when the current density was sufficiently high (see Figure 14a and b). [85] The apparent diffusion coefficient of the electrolyte (D app ) was calculated following Equation 11below, where t Sand is Sand's time, z c is the charge number of the metal cation, c 0 is the bulk salt concentration, F is Faraday's constant, J is the current density, and t a = 0.62 is the transference number of anions in the system.…”

“…Sand's time theory clearly has large relevance to metal batteries and has been applied in several works [85–89] . Bai, et al.…”

A Li+-flux-homogenizing separator for long-term cycling of Li metal anodes

“…25 These materials are well-suited for improving wettability and tuning the Li-ion flux. Unfortunately, both the pore structure construction and surface modification strategies usually occupy extra volume in the batteries, 14,19,24,26 and the synthesis methods of the coating materials and the coating process involve time-consuming and complex manufacturing processes that are not economically and industrially viable for large-scale production. 22,27 Therefore, a practicable separator modification strategy that is economically feasible and capable of tuning Li-ion transfer behavior is needed, even if the pore distribution is imperfect.…”