Mixed Positive Electrode Active Material for Secondary Battery
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Solution Overview
Problem
Current lithium secondary batteries face challenges with high voltage stability, limited mass production applicability, and reduced service life due to issues with LiCoO2, LiMnO2, and LiNiO2-based oxides, particularly concerning cycle characteristics and high-temperature storage.
Innovation Solution
A mixed positive electrode active material comprising large-grain and small-grain particles coated with lithium boron oxide-based and metal oxide compositions, respectively, to enhance voltage stability and service life, with specific embodiments using lithium·nickel·manganese·cobalt complex oxides and thermal treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode active material, then excellent cycle characteristic is achieved, but high voltage stability deteriorates and price increases
Solution Approach 1:
The patent uses a composite material system consisting of LiCoO2 positive electrode active material combined with specific electrolyte additives (fluorinated cyclic carbonates and chain carbonates) to achieve both excellent cycle characteristics and high voltage stability. The composite approach allows the LiCoO2 to provide cycle stability while the electrolyte composition prevents decomposition at high voltages up to 4.3V or higher.
2Quantity of substance
If LiNiO2 is used to increase discharge capacity, then capacity exceeds LiCoO2, but crystal structure stability deteriorates and gas generation increases
Solution Approach 1:
The patent introduces fluorinated cyclic carbonate and chain carbonate electrolyte additives as intermediary substances that mediate between the LiNiO2 positive electrode and the electrolyte. These intermediary additives form protective films on the electrode surface, preventing direct harmful interactions while allowing Li ion transport, thus maintaining crystal structure stability and reducing gas generation during high-capacity operation.
3Use of energy by moving object
If high voltage operation is implemented, then energy density increases, but service life at high temperature deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by incorporating specific ratios of fluorinated cyclic carbonate (10-40 wt%) and chain carbonate (60-90 wt%). This parameter modification allows the electrolyte to maintain stable performance at high voltages (4.3V or higher) and high temperatures, thereby extending service life while preserving high energy density. The specific compositional parameters create a stable electrochemical window that prevents degradation.
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 solution provides a secondary battery with improved output characteristics and high-temperature service life, achieving enhanced energy density and stability through the combination of heterogeneous active materials.
Implementation Method 1
a coating layer which includes a lithium boron oxide-based composition or a metal oxide on each of the large-grain positive electrode active material and the small-grain positive electrode active material
Implementation Method 2
a coating layer which includes a lithium boron oxide-based composition or a metal oxide on each of the large-grain positive electrode active material and the small-grain positive electrode active material
Implementation Method 3
specific embodiments using lithium·nickel·manganese·cobalt complex oxides and thermal treatment processes
Data Source
AI summary
Provided is a mixed positive electrode active material comprising a large-grain positive electrode active material with an average diameter of 10 μm or greater and a small-grain positive electrode active material with an average diameter of 5 μm or smaller, in which the large-grain positive electrode active material and the small-grain positive electrode active material are coated with different materials between a lithium boron oxide-based composition and metal oxide, respectively.