Electrolyte Composition for Lithium Secondary Battery
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining stability and performance at high voltages and high-rate charge/discharge characteristics due to variations in electrode composition, particularly with the use of cyclic carbonate and linear solvents in the electrolyte, which can lead to electrolyte decomposition and reduced lifespan.
Innovation Solution
A lithium secondary battery using a non-aqueous electrolyte with a cyclic carbonate content within the range of 1 wt% to 30 wt% based on the total weight, specifically with a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as solvents, enhances stability and rate characteristics by optimizing ion conductivity and reducing anode reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of cyclic carbonate in the non-aqueous electrolyte is increased to improve ion conductivity and rate characteristics, then the battery's rate characteristics improve, but electrolyte decomposition and cathode component elution increase, reducing battery lifespan
Solution Approach 1:
The patent applies parameter changes by precisely controlling the cyclic carbonate content within 1-30 wt% range. This quantitative parameter optimization balances the competing requirements: sufficient cyclic carbonate to maintain ion conductivity and rate characteristics, while limiting it enough to prevent electrolyte decomposition and cathode component elution, thereby resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent uses a composite electrolyte system combining cyclic carbonate and linear carbonate solvents. This composite approach leverages the high ion conductivity and electrochemical stability of linear carbonates to compensate for the decomposition issues of cyclic carbonates, while cyclic carbonates provide necessary rate characteristics. The synergistic combination resolves the contradiction by distributing functions across different material components
2Reliability
If the cyclic carbonate content is kept low to prevent electrolyte decomposition, then battery lifespan improves, but ion conductivity decreases, reducing rate characteristics
Solution Approach 1:
The patent applies parameter changes by setting the cyclic carbonate content lower bound at 1 wt%, ensuring sufficient ion conductivity and rate characteristics are maintained even with limited cyclic carbonate. This parameter optimization prevents the electrolyte from becoming too stable and losing its rate performance, while still benefiting from improved lifespan compared to high cyclic carbonate formulations
Solution Approach 2:
The composite electrolyte system combines cyclic carbonate (providing rate characteristics) with linear carbonate (providing ion conductivity and stability). This composition allows the battery to achieve good rate characteristics through the cyclic carbonate component while the linear carbonate component ensures sufficient ion conductivity, resolving the contradiction between reliability and productivity
3Ease of manufacture
If conventional electrolyte compositions are used to simplify manufacturing, then manufacturing complexity is reduced, but the battery cannot maintain stability at high voltages with new electrode materials
Solution Approach 1:
The patent applies parameter changes by specifying a cyclic carbonate content range (1-30 wt%) that is optimized for high voltage stability with spinel-structure lithium metal oxides. This parameter adjustment adapts the electrolyte composition to work effectively with new electrode materials, maintaining reliability while keeping the manufacturing process relatively simple through a straightforward compositional specification
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 optimized electrolyte composition improves the battery's lifespan and rate characteristics by suppressing electrolyte decomposition and elution of cathode components, while maintaining high ionic conductivity and stability, especially when used with spinel-structure lithium metal oxides as active materials.
Implementation Method 1
the non-aqueous electrolyte acts as a medium through which lithium ions migrate between the anode and the cathode
Implementation Method 2
lithium ions of the cathode active material are deintercalated and then are intercalated into a carbon layer of the anode
Implementation Method 3
the lithium ions of the carbon layer are deintercalated and then are intercalated into the cathode active material
Data Source
AI summary
Disclosed are an electrolyte for a lithium secondary battery which includes a non-aqueous solvent and a lithium salt, wherein the non-aqueous solvent includes a cyclic carbonate and a linear solvent, wherein an amount of the cyclic carbonate in the non-aqueous solvent is in the range of 1 wt% to 30 wt% based on a total weight of the non-aqueous solvent and a lithium secondary battery including the same.