Lithium Battery Electrolyte Additives for High-Temperature Stability
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Solution Overview
Problem
Lithium secondary batteries face capacity degradation, increased resistance, and safety concerns during high-temperature storage due to the collapse of the solid electrolyte interface (SEI) layer, leading to gas generation and structural instability.
Innovation Solution
A lithium secondary battery design incorporating a non-aqueous electrolyte solution with a mixed additive of lithium difluorophosphate, tetravinylsilane, and a sultone compound, along with a positive electrode active material of lithium transition metal oxide with high nickel content, forms a robust ion conductive film to suppress side reactions and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SEI layer is formed using only organic solvent and lithium salt, then the battery can operate initially, but the SEI layer collapses during high-temperature storage leading to capacity degradation and gas generation
Solution Approach 1:
The patent applies composite materials by formulating a multi-component additive system comprising vinylene carbonate (0.01-5 wt%), fluoroethylene carbonate (0.01-5 wt%), and lithium difluorophosphate (0.01-5 wt%). This composite additive mixture creates a synergistic effect where each component contributes different protective functions, resulting in a robust SEI layer that maintains stability during high-temperature storage and prevents capacity degradation.
Solution Approach 2:
The patent applies parameter changes by optimizing the concentration ratios and molecular structures of additive components. Specifically, it controls the weight percentages of each additive component and adjusts their chemical composition to form an SEI layer with enhanced thermal stability and mechanical strength, thereby preventing collapse during high-temperature storage while maintaining electrochemical performance.
2Productivity
If the SEI layer collapses during continuous charge and discharge, then electrochemical energy increases, but side reactions occur causing capacity decrease and resistance increase
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable SEI layer through optimized additive composition before the battery undergoes continuous charge-discharge cycles. The vinylene carbonate and fluoroethylene carbonate components react during initial cycles to create a protective film that prevents subsequent electrolyte decomposition and electrode material degradation, thereby extending battery lifetime while maintaining cycle performance.
Solution Approach 2:
The patent applies the intermediary principle by using the additives as mediator substances that form an intermediate protective layer between the electrode and electrolyte. This intermediate SEI layer acts as a barrier that prevents direct contact and harmful side reactions between the electrolyte and electrode materials during charge-discharge cycles, thus maintaining both productivity and reliability.
3Quantity of substance
If high nickel content is used in the positive electrode active material, then energy density increases, but structural instability and resistance increase occur during high-temperature storage
Solution Approach 1:
The patent applies the intermediary principle by using the additive mixture as a protective mediator between the high-nickel positive electrode material and the electrolyte. The fluoroethylene carbonate and lithium difluorophosphate components form a stable interfacial layer that prevents direct interaction between the electrolyte and the structurally vulnerable high-nickel cathode, thereby maintaining structural stability while preserving the high energy density benefits.
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 solution secures high energy density, prevents capacity loss, and enhances high-temperature storage characteristics by forming a stable SEI, reducing resistance and gas generation, thereby improving the battery's overall stability and cycle life.
Implementation Method 1
a layer is formed on a surface of the negative electrode while some of electrolyte solution additive components and organic solvents are decomposed in a voltage range of 0.5 V to 3.5 V during initial charge, and lithium ions react with the electrolyte solution on the surface of the negative electrode to form compounds, such as Li2CO3, Li2O, and LiOH
Implementation Method 2
some of electrolyte solution additive components and organic solvents are decomposed in a voltage range of 0.5 V to 3.5 V during initial charge
Implementation Method 3
lithium ions, which are discharged from the positive electrode by charging, transfer energy while a phenomenon is repeated in which the lithium ions are intercalated into the negative electrode and deintercalated during discharging
Data Source
AI summary
A lithium battery is disclosed herein. In some embodiments, a lithium secondary battery includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution, wherein the positive electrode includes a positive electrode active material represented by Formula 1, and the non-aqueous electrolyte solution includes a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive is a mixed additive which includes lithium difluorophosphate, tetravinylsilane, and a sultone compound in a weight ratio of 1:0.05:0.1 to 1:1:1.5:Li(NiaCobMnc)O2 [Formula 1]wherein, in Formula 1,0.65<a≤0.9, 0.05≤b<0.2, 0.05≤c<0.2, and a+b+c=1.