Positive Electrode Alkaline Earth Carbonate for High Voltage Stability
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Solution Overview
Problem
Current lithium ion secondary batteries face issues with the stability of positive electrode active materials, leading to transition metal elution, internal short circuits, and reduced cycle life, especially at high temperatures, and existing solutions either provide insufficient effects or introduce new problems such as increased impedance and gas generation.
Innovation Solution
Incorporating an alkaline earth metal carbonate with a fixed shape, such as calcium carbonate, into the positive electrode active material layer to enhance chemical stability and prevent transition metal elution, while maintaining high workability and electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium ion secondary battery uses lithium cobaltate for a positive electrode and operates at high voltage (4.2V to 4.5V) to increase energy density, then the energy density is improved, but the positive electrode active material becomes unstable, causing transition metal elution, internal short circuits, and reduced cycle life
Solution Approach 1:
The patent applies composite materials by combining lithium cobaltate with lithium iron phosphate to create a positive electrode active material that leverages the high capacity of lithium cobaltate while the lithium iron phosphate component provides structural stability and suppresses transition metal elution, thereby maintaining both high energy density and long cycle life at elevated temperatures and high voltages
2Use of energy by moving object
If the charge voltage is increased to 4.2V or higher to enhance energy density, then the energy density is improved, but the nonaqueous electrolyte undergoes oxidative decomposition, generating gas and causing battery defects such as blister, rupture, and liquid leakage
Solution Approach 1:
The patent converts the harmful oxidative decomposition of the nonaqueous electrolyte into a beneficial effect by utilizing the decomposition products to form a protective film on the positive electrode surface. This protective film prevents further electrolyte decomposition and suppresses gas generation, allowing the battery to operate safely at high voltages (4.2V or higher) while maintaining high energy density
3Reliability
If a metal oxide coating is applied to the positive electrode surface to suppress transition metal elution and improve cycle characteristics, then the cycle life is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the functions of the positive electrode active material and the protective coating into a single composite material system. By combining lithium cobaltate with lithium iron phosphate, the material inherently provides both high capacity and surface stability without requiring separate coating steps, thereby simplifying manufacturing while maintaining improved cycle characteristics
4Reliability
If a compound is added to the nonaqueous electrolyte to form a protective coating on the electrodes, then the battery characteristics at high temperature are improved, but the impedance increases and the energy efficiency decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material by combining lithium cobaltate with lithium iron phosphate in specific ratios. This compositional change creates a material with inherently stable surface properties that reduce impedance and improve high-temperature characteristics without requiring additional electrolyte additives, thereby maintaining high energy efficiency
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 alkaline earth metal carbonate with a fixed shape effectively suppresses positive electrode corrosion and deterioration, improving battery cycle characteristics and energy density without increasing impedance, even at elevated temperatures and high voltages.
Implementation Method 1
a method in which a compound having a special function imparted thereto is added in a nonaqueous electrolyte, thereby forming a minute coating on either one of a positive electrode or a negative electrode or both of them and preventing deterioration of a battery capacity especially at a high temperature
Implementation Method 2
in the case of repeating charge and discharge at a high capacity, in particular, in a high-temperature region, a nonaqueous electrolyte coming into physical contact with a positive electrode is oxidatively decomposed, and a gas is generated to cause defectives such as blister, rupture, liquid leakage and the like of the battery
Data Source
AI summary
A positive electrode includes: a positive electrode collector; and a positive electrode active material layer provided on the positive electrode collector and containing a positive electrode active material and an alkaline earth metal carbonate having a fixed form.