Battery-operated electric vehicles (BEVs) are gaining popularity due to their eco-friendly nature, but their energy capacity needs improvement. Lithium-air batteries (LABs) are considered promising with their high theoretical energy density.
However, challenges such as sluggish kinetics and poor stability hinder their practical implementation. This study focuses on the solvent effect on LAB intermediates using dimethyl sulfoxide (DMSO) as the solvent. The researchers investigate the adsorption properties of LAB intermediates on the Li2O2(100) surface and analyze the effects of DMSO on the electrochemical performance.
- Battery-operated electric vehicles (BEVs) are being commercialized due to their eco-friendly nature.
- Lithium-air batteries (LABs) have high theoretical energy density but face challenges in practical implementation.
- LABs suffer from large discharge/charge overpotentials, poor stability of cathode materials, short cycle life, and poor electrolyte stability.
- The growth of Li2O2 discharge product on the cathode surface can occur through two modes: solution model growth and surface model growth.
- The solubility and desorption of LiO2 from the cathode surface depend on the nature of the solvent.
- Dimethyl sulfoxide (DMSO) is a potential solvent for LABs due to its stability and high donor number (DN = 29.8).
- The explicit solvation model is important for studying solvent-intermediate interactions accurately.
With the increasing concerns about climate change and environmental pollution, the commercialization of battery-operated electric vehicles (BEVs) has become widespread due to their eco-friendly nature. However, the current energy density of lithium-ion batteries (LIBs) is insufficient to meet the energy demands of up-scaling devices like electric cars. As a result, heavy batteries are required, leading to reduced energy efficiency. To improve BEVs, the development of battery designs is crucial.
Lithium-air batteries (LABs) have garnered significant attention as next-generation candidates for high-energy-density batteries. LABs have the potential to offer energy densities up to 10 times higher than LIBs by utilizing abundant O2 at the cathode. However, practical implementation faces challenges such as large discharge/charge overpotentials, poor stability of cathode materials, short cycle life, and poor electrolyte stability. These challenges arise mainly from the sluggish kinetics of the oxygen reduction reaction (ORR). To address these issues, various cathode materials with good stability and ORR catalytic activity have been reported.
The growth of Li2O2 on the cathode surface during discharging plays a crucial role in determining the capacity of LABs. Two modes of Li2O2 growth have been observed in experiments: solution model growth and surface model growth. The solubility and desorption of LiO2 from the cathode surface depend on the nature of the solvent, specifically its Lewis basicity (donor number). Solvents with higher donor numbers have higher solubility. Dimethyl sulfoxide (DMSO) has emerged as a potential solvent due to its chemical stability toward oxygen-containing species and high donor number.
In this study, the researchers focused on investigating the solvent effect on LAB intermediates using a pristine Li2O2(100) surface and a Li2O2(100)-DMSO surface-solvent interphase system. They examined the ORR/OER activity trend on the Li2O2(100) surface in the gas phase and with the presence of DMSO. Additionally, the feasibility of Li2O2 decomposition to solvated LiO2 and its impact.
Challenges in Developing Li-Air Batteries
The development of Li-air batteries (LABs) is limited by challenges such as large discharge/charge overpotentials, poor stability of cathode materials, short cycle life, and poor electrolyte stability. To improve the eco-friendly nature of battery-operated electric vehicles (BEVs), it is crucial to develop better batteries. LABs with high theoretical energy density and abundant O2 at the cathode have attracted great attention. However, the practical implementation of LABs still faces several obstacles.
First Principles Thermodynamic Analysis of LAB Reactions
In this study, a first principles thermodynamic analysis for LAB reactions on the Li2O2 (100) cathode surface, considering the effect of explicit dimethyl sulfoxide (DMSO) solvent, is carried out. The mechanistic pathways, thermodynamic overpotentials, and influence of the DMSO environment on configurations of intermediate adsorptions resulting in free energy changes are investigated. An improved overpotential of discharging is reported, signifying the importance of considering the surface−solvent interphase model. The explicit solvation model enables a more accurate investigation of solvent−intermediate interactions.
Examination of Li-O2 Battery Intermediates and the Influence of DMSO Solvent
The researchers examined the adsorption configurations and adsorption energies of Li-O2 battery intermediates using computational methods. The adsorption of intermediates involved the formation of Li2O2 via the addition of Li to LiO2 in a superoxo manner. Smaller intermediates formed during the discharging process were not affected by the explicit DMSO environment, while higher intermediates were significantly affected. The equilibrium potential and discharging overpotential of the system were lower in the presence of DMSO, indicating improved catalytic activity. The formation of toroidal-shaped Li2O2 in DMSO solvent benefits battery longevity.
Insights into Li-O2 Battery Systems and Charging/Discharging Mechanisms
Overall, this study provides insights into the intermediates and mechanisms involved in Li-O2 battery systems, potential improvements in catalytic activity, and battery longevity in the presence of solvents. The research explores the charging and discharging mechanisms of LABs by studying the Li2O2(100) surface and Li2O2(100)-DMSO surface-solvent interphase model. The discharging pathway involves Li2O2 adsorption, the second Li adsorption, and LiO2* intermediate formation. Overpotential values of charging and discharging correspond to the rate-determining step (RDS) in the respective process. The study offers valuable information on discharge and charging mechanisms in LABs, opening up new possibilities for designing efficient cathode catalysts.
Q: What is climate change?
A: Climate change refers to long-term shifts in weather patterns and average temperatures on Earth, primarily caused by human activities such as burning fossil fuels, deforestation, and industrial processes. It leads to various environmental and ecological impacts, including rising sea levels, extreme weather events, and changes in ecosystems.
Q: What is environmental pollution?
A: Environmental pollution refers to the contamination of the natural environment by harmful substances or excessive amounts of waste, resulting in negative effects on ecosystems, human health, and the overall well-being of the planet. Pollution can occur in various forms, such as air pollution (emissions from industries and vehicles), water pollution (contamination of rivers, lakes, and oceans), and soil pollution (chemicals and waste materials).
Q: What are battery-operated electric vehicles (BEVs)?
A: Battery-operated electric vehicles (BEVs) are vehicles that use electricity as their primary source of power. They are propelled by electric motors and are powered by rechargeable batteries instead of internal combustion engines. BEVs offer a cleaner and more sustainable alternative to traditional gasoline or diesel-powered vehicles, contributing to reducing greenhouse gas emissions and dependence on fossil fuels.
Q: What are lithium-ion batteries (LIBs)?
A: Lithium-ion batteries (LIBs) are rechargeable batteries that use lithium ions to store and release electrical energy. They are commonly used in portable electronic devices, electric vehicles, and renewable energy systems. LIBs have a high energy density, long cycle life, and relatively low self-discharge rate, making them popular for various applications.
Q: What are lithium-air batteries (LABs)?
A: Lithium-air batteries (LABs) are a type of rechargeable battery that uses oxygen from the air as the cathode material, interacting with lithium at the anode to generate electrical energy. LABs have the potential to provide significantly higher energy densities compared to lithium-ion batteries, which could lead to longer-lasting and more efficient energy storage solutions.
Q: What is Li2O2 growth?
A: Li2O2 growth refers to the formation of lithium peroxide (Li2O2) on the surface of a lithium-air battery’s cathode during the discharge process. Li2O2 is a byproduct of the electrochemical reaction that occurs in LABs and plays a crucial role in their operation. Understanding and controlling Li2O2 growth is important for improving the performance and stability of lithium-air batteries.
Q: What is a solution model?
A: In the context of scientific research, a solution model refers to a computational approach or simulation that represents a system or phenomenon using mathematical equations and algorithms. It allows researchers to study and analyze complex processes by simulating them in a simplified and computationally tractable manner. In the case of battery research, a solution model may be used to simulate the behavior and properties of various components and materials within a battery system.
Q: What is a surface model?
A: A surface model, in the context of scientific research, typically refers to a representation or simulation of the surface properties and interactions of a material or system. It focuses on the characteristics and behaviors occurring at the interface between different materials or phases. Surface models are commonly used in studying chemical reactions, catalysis, and electrochemical processes, such as those involved in battery systems.