Lithium Cobalt Oxide Battery Electrolyte Additive for High Voltage Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with lithium cobalt oxide as the positive electrode active material face degradation and swelling issues when charged to higher voltages due to increased oxidation and electrolyte decomposition, leading to reduced storage characteristics, especially at high temperatures.
Innovation Solution
Incorporating a non-aqueous electrolyte with 0.1 to 10 volume % of a compound having an ether group, along with a lithium cobalt oxide positive electrode active material and a graphite negative electrode, to form a surface film that prevents side reactions and maintains battery integrity, while optimizing the charge capacity ratio and adding zirconium and magnesium to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the end-of-charge voltage is increased to improve battery capacity and energy density, then the positive electrode capacity utilization is improved, but the structure of LiCoO2 deteriorates and the electrolyte solution decomposes
Solution Approach 1:
A compound having an ester group (such as vinylene carbonate or fluoroethylene carbonate) is introduced as an intermediary substance in the electrolyte solution. This compound preferentially reacts with the positive electrode surface to form a protective film that mediates between the high-voltage operation and the electrode stability, preventing direct harmful reactions while allowing lithium ion transport.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte solution by incorporating specific ester group-containing compounds at controlled concentrations (0.1-10 volume%). This parameter change enables the formation of a stable surface film that allows the battery to operate at higher voltages (4.4-4.5 V vs. Li/Li+) without causing electrode deterioration.
2Reliability
If the battery is stored in a charged state at high temperature, then the storage capacity is maintained, but the battery thickness increases and charge-discharge performance degrades due to gas generation and electrode disintegration
Solution Approach 1:
The ester group-containing compound performs preliminary action by reacting with the positive electrode surface during initial charging cycles to form a stable protective film before high-temperature storage occurs. This pre-formed film prevents subsequent gas generation and electrode disintegration during storage, maintaining both capacity and structural integrity.
Solution Approach 2:
The invention converts the potentially harmful high reactivity of ester group compounds into a beneficial protective mechanism. These compounds initially appear to be unstable at high temperatures, but they actually react preferentially to form stable protective films that prevent more severe degradation, thus converting the potential harm into a protective benefit.
3Reliability
If a compound having an ester group is added to the electrolyte solution to improve high-temperature storage characteristics, then storage stability is improved, but battery swelling and performance deterioration still occur at charge voltages higher than 4.2 V
Solution Approach 1:
The invention uses a composite electrolyte system combining ester group-containing compounds (0.1-10 volume%) with conventional electrolyte components. This composite approach creates a synergistic effect where the ester compound forms a protective surface film while the conventional electrolyte maintains bulk ionic conductivity, preventing both swelling and performance deterioration at high voltages.
Solution Approach 2:
The ester group-containing compound provides local quality improvement by concentrating its protective effect specifically at the positive electrode surface where voltage-induced degradation occurs. This localized protection allows the bulk electrolyte to maintain its conventional composition and properties while the electrode interface gains enhanced stability.
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 approach significantly improves storage characteristics by preventing battery thickness increase and capacity degradation, maintaining performance even at elevated temperatures and higher charge voltages, as demonstrated by reduced swelling and retained capacity.
Implementation Method 1
the non-aqueous electrolyte contains 0.1 to 10 volume % of a compound having an ether group... to form a surface film that prevents side reactions
Data Source
AI summary
The storage characteristics in a charged state are improved in a non-aqueous electrolyte secondary battery containing a lithium cobalt oxide as a positive electrode active material. The non-aqueous electrolyte secondary battery includes a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material other than metallic lithium; and a non-aqueous electrolyte. The positive electrode active material contains a lithium cobalt oxide as its main component. The non-aqueous electrolyte contains 0.1 to 10 volume % of a compound having an ether group. The positive electrode active material and the negative electrode active material are contained so that the charge capacity ratio of the negative electrode to the positive electrode is from 1.0 to 1.2 when the battery is charged until the potential of the positive electrode reaches 4.4 to 4.5 V (vs. Li/Li+)