Si-Anode Lithium Battery Electrolyte for Stable High-Temperature Cycling
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Solution Overview
Problem
Lithium secondary batteries, particularly those used in vehicles, face challenges with high capacity, output, and long-life characteristics due to the instability of nickel-rich positive electrode active materials and silicon-based negative electrode active materials, leading to issues like transition metal ion elution, SEI degradation, and increased swelling at high temperatures.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with lithium nickel cobalt manganese-based oxide, a negative electrode with silicon-based active material, and a non-aqueous electrolyte containing a compound of Formula 1 and fluoroethylene carbonate, where the compound of Formula 1 constitutes more than 15 wt% of the electrolyte, facilitating the formation of a stable SEI film and enhancing electrode durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-rich positive electrode active material or silicon-based negative electrode active material is used to achieve high energy density, then capacity and output are improved, but stability deteriorates leading to transition metal ion elution and SEI degradation
Solution Approach 1:
A coated film comprising a polymer and an inorganic substance is introduced as an intermediary layer between the silicon-based negative electrode active material and the electrolyte. This coated film acts as a protective barrier that prevents direct contact and harmful interactions, thereby maintaining high capacity while improving stability and preventing SEI degradation
Solution Approach 2:
The coated film is constructed as a composite material combining organic polymer components and inorganic substances. This composite structure leverages the benefits of both materials: the polymer provides flexibility and adhesion, while the inorganic substance provides structural stability and ion conductivity, resolving the contradiction between capacity and stability
2Power
If the potential of the positive electrode is increased to improve output, then power is improved, but the deterioration of the coated film and electrode surface structure is accelerated
Solution Approach 1:
The coated film is applied beforehand to the silicon-based negative electrode active material to provide protective cushioning against the harsh conditions created by high positive electrode potential. This pre-established protective layer prevents acceleration of deterioration that would otherwise occur at high potentials
3Power
If the battery is exposed to high temperature to improve performance, then output is improved, but gas production increases causing swelling
Solution Approach 1:
The coated film serves as a protective intermediary barrier that prevents direct harmful interactions between the electrode materials and the electrolyte at high temperatures. This barrier reduces gas-generating side reactions, thereby suppressing swelling while allowing the battery to operate at high temperatures for improved output
4Duration of action of moving object
If continuous use or high temperature storage occurs, then the battery operates longer, but SEI degradation accelerates causing more gas production
Solution Approach 1:
The coated film provides beforehand cushioning protection that prevents acceleration of SEI degradation during continuous use or high temperature storage. By establishing this protective barrier in advance, the system can maintain longer usage duration without the harmful effect of accelerated gas production that would normally occur under these conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed battery configuration improves cycle properties and storage performance at high temperatures, maintaining overall performance stability even under prolonged high-voltage and high-temperature conditions.
Implementation Method 1
the compound of Formula 1 is used, particularly, in a Si negative electrode, an SEI layer polymerized along with strong reduction decomposition, may be formed
Implementation Method 2
a non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive
Data Source
AI summary
Provided is a lithium secondary battery comprising: a positive electrode comprising a lithium nickel cobalt manganese-based oxide as a positive electrode active material; a negative electrode comprising a negative electrode active material composed of Si; and a non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the organic solvent comprises a compound of Formula 1 and fluoroethylene carbonate, and the compound of Formula 1 is comprised in greater than 15 wt % on the basis of the total of the non-aqueous electrolyte:wherein all the variables are described herein.