Review of Emerging Concepts in SEI Analysis and Artificial SEI Membranes for Lithium, Sodium, and Potassium Metal Battery Anodes

Abstract

Lithium metal batteries (LMBs), sodium metal batteries (SMBs), and potassium metal batteries (KMBs) are receiving extensive attention in scientific literature. [1,2] The specific capacity of lithium, sodium, and potassium metal anodes is 3861 − , 1165 − , and 678 mAh g −−1 , which is substantially higher than that of graphite or hard carbons employed for ion battery anodes. For all three metal battery systems, achieving long-term stable and safe metal anode performance would be potentially transformative. However, growth of dendrites is a ubiquitous problem for each system, to date inhibiting wide scale commercial application of LMBs, SMBs, and KMBs in rechargeable cells. [3-6] The well-known risk is that dendrites will penetrate the separator and reach the cathode, resulting in a short circuit, potentially causing thermal runaway, burning, and even explosions. This is largely why Li metal anodes were originally abandoned in favor of graphite. [2,7] Less dramatically, dendrites result in a severe cell impedance increase, pouch swelling, as well as electrolyte drying. [3,8] The science around Li, Na, and K metal anodes is rapidly advancing. It is recognized that the structure of the solid electrolyte interface (SEI) plays a crucial role in determining the cyclability of metal anodes. [4,5] The SEI serves multiple roles, including limiting further side-reactions between the metal and the electrolyte, as well as promoting uniform metal deposition by regulating the solid-state ion flux. An ideal SEI layer has properties along the following: High cation conductance but also high electrical resistance, stable thickness close to a few nanometers, high mechanical toughness (combination of strength and ductility) leading to a tolerance to charginginduced volumetric changes, insolubility in the electrolyte, and stability over a wide range of operating temperatures and voltages. A stable SEI is an accepted prerequisite for safe battery performance, be it with a metal or an ion insertion anode. [6] The characteristics of SEI growth, gradual and uniform versus rapid and heterogeneous, is a key indicator whether or not dendrites form. [9-11] The dominant focus of many reports is on the spatially averaged SEI chemistry. [12,13] However recent progress brings fourth site-specific concepts in the SEI analysis, Anodes for lithium metal batteries, sodium metal batteries, and potassium metal batteries are susceptible to failure due to dendrite growth. This review details the structure-chemistry-performance relations in membranes that stabilize the anodes' solid electrolyte interphase (SEI), allowing for stable electrochemical plating/stripping. Case studies involving Li, Na, and K are presented to illustrate key concepts. "Classical" versus "modern" understandings of the SEI are described, with an emphasis on the new structural insights obtained through novel analytical techniques, including in situ liquid-secondary ion mass spectroscopy, titration gas chromatography, and tip-enhanced Raman spectroscopy. This Review highlights diver...

Stabilizing metal battery anodes through the design of solid electrolyte interphases

“…The variations in physical-chemical performance and surface information point out the different strategies to design the SEI in these metals. In general, Na and K share similar physical-chemical properties with lithium but exhibit more electronegative properties, 94 which results in the different solubility and modulus in the recipes of SEI. Meanwhile, K and Na are softer than metallic Li when comparing the shear modulus, bulk modulus, and Mohs hardness, indicating that the dendrite growth is more easily suppressed by physical means.…”

“…Understanding the composition, morphologies, and mechanical properties of SEI is important to direct further design of interphases on the metal anode. 94 Because of the elusory and highly dynamic properties, various approaches need to join hands together to thoroughly recognize SEI at the atomic level. Previous studies mainly focus on spectroscopic techniques, such as FTIR, Raman, XPS, which is sensitive enough to study the functional groups on the surface of the electrode.…”

Rational Design of a ZIF‐67/Cobalt‐Glycolate Heterostructure with Improved Conductivity for High Cycling Stability and High‐Capacity Lithium Storage

“…[37] Therefore, a stable SEI film gradually forming on the surface of ZIF-67 benefit for stability during the long cycle. [38] In addition, the capacity retention of four electrodes after 100 cycles is 108, 85, 81 and 79 %, respectively for ZIF-67, Co-glycolate/ZIF-67-60, Co-glycolate/ZIF-67-80, and Co-glycolate. Therefore, Co-glycolate demonstrates the worst cycling stability.…”

Molecular Engineering Approaches to Fabricate Artificial Solid‐Electrolyte Interphases on Anodes for Li‐Ion Batteries: A Critical Review

“…Some excellent recent reviews summarize the current development, design and improvement of Art-SEIs. [26,27,28,99,[108][109][110][111][112][113][114] In contrast, our present review mainly focuses on the reality check of Art-SEI materials and methods toward real-world applications. Specifically, in this chapter, Art-SEI engineering approaches are reviewed from a practical perspective, divided into top-down and bottom-up methods.…”

“…This provides a holistic view on the different approaches, allowing science and industry to assess their suitability. While most of the existing Art-SEI concepts as well as recent reviews [26][27][28][29] on the topic are focusing on scientific novelty, we understand this section as a reality check toward real-world applications.…”