Non-Aqueous Electrolyte Additives for Stable SEI at High Charge
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Solution Overview
Problem
Lithium secondary batteries face degradation due to the collapse of the solid electrolyte interface (SEI) layer during high-temperature storage, leading to increased internal pressure, resistance, and reduced cycle life, especially when stored fully charged at elevated temperatures.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, organic solvent, and specific additives represented by Formulas 1 and 2, which form a stable passivation layer on electrodes, stabilizing anions and suppressing side reactions, thereby enhancing high-temperature durability and cycle capacity characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lithium secondary battery is stored fully charged at high temperature, then the initial charge capacity is maximized, but the SEI layer collapses and causes continuous side reactions leading to increased internal pressure and reduced cycle life
Solution Approach 1:
The patent applies preliminary action by forming a stable SEI layer through initial charge reactions before storage. The SEI layer is created in advance to prevent subsequent harmful reactions during high-temperature storage, thereby protecting the battery during the storage period when it is most vulnerable to degradation
Solution Approach 2:
The SEI layer acts as an intermediary between the electrolyte and the negative electrode. It mediates the interaction by allowing lithium ion transport while blocking harmful direct contact between the electrolyte and electrode, thus preventing continuous side reactions and gas generation during high-temperature storage
2Reliability
If the SEI layer is formed during initial charge, then irreversible capacity is consumed, but the battery maintains stable charge and discharge without further decomposition
Solution Approach 1:
The SEI layer formation is performed as a preliminary action during initial charge. This one-time consumption of lithium ions creates a protective barrier that prevents further irreversible reactions, ensuring stable charge-discharge cycles for the remaining battery life while minimizing total lithium ion loss
3Temperature
If the SEI layer collapses during high-temperature storage, then the battery structure is exposed, but continuous side reactions occur leading to gas generation and increased internal pressure
Solution Approach 1:
The patent converts the potentially harmful high-temperature storage condition into a beneficial opportunity by designing an SEI layer that is specifically stabilized for high-temperature conditions. The additives in the electrolyte promote formation of a more thermally stable SEI composition that actually improves upon the baseline SEI structure, turning the harsh storage condition into a test that validates the enhanced stability
Solution Approach 2:
The SEI layer serves as an intermediary barrier that prevents direct contact between the electrolyte and electrode during high-temperature storage. This mediation blocks the pathway for continuous side reactions and gas generation, even when the battery is stored in a fully charged state at elevated temperatures
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 effectively forms a robust SEI layer that prevents electrode decomposition, reduces gas generation, and improves overall battery performance by maintaining capacity and suppressing resistance increase during high-temperature storage, ensuring stable cycle life and performance.
Implementation Method 1
a carbon-based negative electrode capable of intercalating and deintercalating lithium ions
Implementation Method 2
Highly reactive lithium ions discharged from the positive electrode during initial charge of the lithium secondary battery react with the carbon-based negative electrode to form an organic material and Li2CO3, Li2O, or LiOH
Implementation Method 3
The layer is denoted as a solid electrolyte interface (SEI) layer... may act as an ion tunnel that only passes the lithium ions between the electrolyte solution and the negative electrode
Implementation Method 4
Since the SEI layer blocks organic solvents of the electrolyte solution having a high molecular weight from moving to the carbon-based negative electrode by an effect of the ion tunnel, it prevents the collapse of a structure of the carbon-based negative electrode
Implementation Method 5
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, for example, carbon particles, and deintercalated during discharging
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, and particularly, to a non-aqueous electrolyte solution includes a lithium salt, an organic solvent, a first additive, and a second additive, wherein the first additive is a compound represented by Formula 1 and the second additive is a compound represented by Formula 2.