Protecting lithium metal anodes in lithium–sulfur batteries: A review

Abstract

Lithium–sulfur (Li–S) batteries are considered as one of the most promising next-generation energy storage devices because of their ultrahigh theoretical energy density beyond lithium-ion batteries. The cycling stability of Li metal anode largely determines the prospect of practical applications of Li–S batteries. This review systematically summarizes the current advances of Li anode protection in Li–S batteries regarding both fundamental understanding and regulation methodology. First, the main challenges of Li metal anode instability are introduced with emphasis on the influence from lithium polysulfides. Then, a timeline with 4 stages is presented to afford an overview of the developing history of this field. Following that, 3 Li anode protection strategies are discussed in detail in aspects of guiding uniform Li plating/stripping, reducing polysulfide concentration in anolyte, and reducing polysulfide reaction activity with Li metal. Finally, 3 viewpoints are proposed to inspire future research and development of advanced Li metal anode for practical Li–S batteries.

Towards durable practical lithium–metal batteries: advancing the feasibility of poly-DOL-based quasi-solid-state electrolytes via a novel nitrate-based additive

“…23 Electrolyte additives are commonly used to regulate the SEI composition and structure. 24 In particular, LiNO 3 is often used to form a stable nitrogen-rich SEI that effectively protects the LMA. 1,25 The utilization of LiNO 3 has been observed as an effective strategy to address the issue of the “shuttle effect” in lithium-sulfur batteries, leading to enhanced coulombic efficiencies and significantly improved battery performance.…”

Adjusting Interfacial Reactions for Achieving Highly Stable Operation in Lithium Metal Batteries

“…Owing to their low reduction potential (−3.04 V vs SHE) and high theoretical specific capacity (3860 mA h g –1 ), − lithium-metal batteries (LMBs) are known as the most promising candidate for next-generation energy storage devices. However, the challenges of lithium metal anodes are still a matter of great urgency. − The foremost is the poor cycling stability and low Coulombic efficiency (CE), which is attributed to unstable interface behaviors such as lithium dendrite growth, volumetric change, the accumulation of “dead” Li, and consumption of active materials. − The savage growth of lithium dendrites may lead to cracking of the solid electrolyte interphase (SEI) film and an internal short circuit, which brings about the consumption of active material, thermal runaway, and explosions . Significant efforts have been made to stabilize the lithium metal anode, such as the modification of separator, the design of the anode structure based on the 3D framework and unique lithiophilic structures, surface modifications, including the reconstruction of SEI film, − surface alloying, − and electrolyte optimization. − However, elaborate processing steps are usually required for the structural construction due to the high reaction activity of lithium metal.…”

Scalable Metal Phosphides as a Dual-Function Catalyst and Lithium–Metal Stabilizer for Lithium–Sulfur Batteries

“…To resolve issues on the anode side, researchers have sought to passivate the highly reactive lithium metal and prevent the growth of dendrites by forming favorable solid–electrolyte interface (SEI) compositions. Many methods have been proposed to attain a favorable SEI in situ, such as Li-metal coatings or electrolyte additives. − In particular, LiNO 3 has been routinely added to the electrolyte of Li–S batteries to form a nitrogen-rich SEI, which provides superior conductivity and reduces the formation of dead lithium. , Additionally, phosphide-based additives, such as P 2 S 5 , have been shown to effectively passivate the anode while forming highly conductive Li 3 PS 4 species in the SEI. , While such methods improve the SEI formation on lithium, they do not fundamentally address the infinite relative expansion of lithium, which can introduce internal stresses that fracture the SEI. Additional methods for stabilizing lithium metal include integrating it into a three-dimensional (3D) host material to alleviate its volume expansion; in particular, carbonaceous materials have been widely considered as suitable 3D hosts because of their high surface area and good conductivity. − However, owing to the lithiophobic nature of carbon, lithiophilic seeds must be planted within the material to enable uniform lithium deposition onto the host, such seeds can be designed to further optimize the SEI. − Thus, the lithium–metal anode should be stabilized by a rationally designed 3D lithiophilic host.…”