Lithium Battery Electrolyte Additive for Storage Stability
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Solution Overview
Problem
Nonaqueous electrolyte lithium secondary batteries face issues with organic solvent reductive decomposition on the negative electrode, leading to increased impedance and capacity degradation over time, which existing additives like vinylene carbonate and pyridine derivatives fail to adequately address for higher energy density demands.
Innovation Solution
Incorporating a compound with boron and a carbon-carbon double bond in the electrolyte, which forms an insoluble polymer film on the negative electrode, reducing impedance and enhancing storage properties by trapping lithium ions and providing a higher decomposition potential than the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing additives like vinylene carbonate and pyridine derivatives are used to suppress reductive decomposition, then the decomposition of organic solvent is reduced, but the battery storage properties cannot meet higher capacity demands
Solution Approach 1:
The invention changes the chemical composition parameter of the electrolyte by introducing a boron-containing compound with specific molecular structure (formula 1) having different functional groups (carboxyl, hydroxyl, amino, etc.). This parameter change enables the formation of a protective film with superior properties that simultaneously suppresses decomposition and maintains high capacity, resolving the contradiction between reliability and quantity of substance
Solution Approach 2:
The invention creates a composite protective film on the negative electrode surface consisting of the boron-containing compound and reductive decomposition products. This composite structure combines the benefits of decomposition suppression with enhanced capacity retention, achieving both improved reliability and maintained quantity of substance
2Reliability
If conventional electrolyte additives are added to suppress reductive decomposition, then the negative electrode impedance increases over time, but the battery capacity degradation cannot be adequately prevented
Solution Approach 1:
The boron-containing compound performs preliminary action by forming a stable protective film on the negative electrode surface before significant decomposition occurs. This pre-formed film prevents subsequent impedance increases and capacity degradation, maintaining both reliability and composition stability over extended storage periods
Solution Approach 2:
The boron-containing compound acts as an intermediary substance between the negative electrode and the organic solvent. It forms a mediating protective layer that prevents direct harmful interactions, thereby suppressing decomposition while maintaining low and stable impedance characteristics
3Quantity of substance
If the battery is designed for higher energy density, then the capacity demand increases, but the storage properties deteriorate due to reductive decomposition and gas generation
Solution Approach 1:
The invention modifies the electrolyte composition parameter by adding the boron-containing compound at optimized concentrations (0.01-5% by weight). This parameter change enables the system to achieve both high energy density and excellent storage properties by forming a protective film that prevents capacity loss during storage
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 use of the boron-containing compound with a carbon-carbon double bond improves the coating performance on the negative electrode, leading to better high-temperature storage properties and increased discharge capacity retention, outperforming batteries without this additive.
Implementation Method 1
a compound having boron and a carbon-carbon double bond is converted into an insoluble polymeric substance on negative electrode surfaces because of a reduction reaction in the initial cycle, so that a film is formed
Implementation Method 2
a compound having boron and a carbon-carbon double bond is converted into an insoluble polymeric substance on negative electrode surfaces because of a reduction reaction in the initial cycle
Implementation Method 3
reducing impedance and enhancing storage properties by trapping lithium ions
Data Source
AI summary
The present invention provides a battery that experiences a small degree of temporal change from the initial battery properties over the long term storage period of the battery. Specifically, the present invention provides a lithium secondary battery, in which a positive electrode capable of storing and releasing lithium and a negative electrode capable of storing and releasing lithium are formed via an electrolyte, wherein: the electrolyte comprises a cyclic solvent and a chain-type solvent and contains a compound having a boron-oxygen bond (B—O) and a carbon-carbon double bond (C═C).