Over-Lithiated Cathode Electrolyte Balance for High-Voltage Cycling
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Solution Overview
Problem
Lithium secondary batteries with over-lithiated cathode active materials face challenges in maintaining capacity and operational stability due to high voltage operations, which degrade their lifespan and increase resistance during repeated charging and discharging.
Innovation Solution
A lithium secondary battery design incorporating a cathode with lithium metal oxide particles having a lithium-to-metal ratio of 1.05 or more, a non-aqueous electrolyte solution containing a fluorine-based organic solvent within a specific volume range, and a lithium salt, enhancing capacity and stability by improving oxidation resistance and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If over-lithiated cathode active material is used to achieve high capacity, then capacity property is improved, but operational stability and lifespan are degraded due to high voltage operation
Solution Approach 1:
The patent modifies the chemical composition parameters of the cathode active material by controlling the lithium content ratio (a/(x+y+z)) to be 1.05 or more, and adjusting transition metal ratios (Co:Ni:Mn = 1:3.5:6.5) to achieve high capacity while maintaining stability through compositional optimization
Solution Approach 2:
The patent uses a composite cathode active material containing multiple transition metals (Co, Ni, Mn) in specific ratios combined with excess lithium, creating a composite structure that balances high capacity with operational stability through synergistic material properties
2Power
If high voltage operation is applied to over-lithiated cathode active material, then capacity is improved, but resistance increases during repeated charging and discharging
Solution Approach 1:
The patent operates the battery at high voltage (4.3V or higher) while maintaining stability by optimizing the cathode material composition with specific lithium excess ratio (a/(x+y+z) ≥ 1.05) and transition metal ratios, allowing high power operation without excessive resistance increase
Solution Approach 2:
The patent pre-optimizes the cathode material composition with excess lithium and specific transition metal ratios before operation, creating a stable structure that cushions against resistance increase during high voltage repeated charging and discharging cycles
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 battery exhibits improved capacity retention and reduced resistance increase, maintaining performance over multiple charge-discharge cycles, especially in high voltage environments, thereby extending its lifespan and suitability for eco-friendly applications.
Implementation Method 1
improving oxidation resistance and ion conductivity
Implementation Method 2
improving oxidation resistance and ion conductivity
Data Source
AI summary
A lithium secondary battery includes a cathode including a cathode active material that contains lithium metal oxide particles, an anode facing the cathode, and a non-aqueous electrolyte solution including a non-aqueous organic solvent that contains a fluorine-based organic solvent and a lithium salt. A ratio of the number of moles of lithium contained in each of the lithium metal oxide particles to the total number of moles of metals excluding lithium contained in each of the lithium metal oxide particles is 1.05 or more. A content of the fluorine-based organic solvent is in a range from 5 vol % to 60 vol % based on a total volume of the non-aqueous organic solvent.