Lithium-Ion Cathode Roughness and Electrolyte for Stable Cycling
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Solution Overview
Problem
Lithium ion secondary batteries using monolithic positive electrode active materials face challenges in maintaining good cycle characteristics at high temperatures and preventing a decrease in rate performance at low temperatures.
Innovation Solution
A lithium ion secondary battery with a positive electrode active material layer surface roughness (Ra) of less than 1.0 × 10^4 Å and a nonaqueous electrolyte solution containing specific compounds, such as those in Formulas (1) to (10), which enhance both high-temperature cycle stability and low-temperature rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monolithic positive electrode active material is used, then cycling stability is improved, but rate performance at low temperature deteriorates
Solution Approach 1:
The patent applies local quality by creating a dual-structure positive electrode active material where monolithic particles (providing stability) are coated with a porous layer (providing rate performance). The porous coating layer with specific pore size (0.5-5 μm) and porosity (30-70%) provides local pathways for lithium ion transport while the monolithic core maintains structural stability during cycling.
Solution Approach 2:
The patent uses composite materials by combining monolithic positive electrode active material particles with a porous coating layer to create a hybrid structure. This composite structure integrates the advantages of both monolithic materials (high stability) and porous materials (high rate performance), achieving both good cycling stability and maintained rate performance at low temperatures.
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 cycle characteristics under severe conditions exceeding 50°C and maintains rate performance at 0°C by preventing microcracks and forming a conductive path for lithium ions.
Implementation Method 1
surface roughness (Ra) of a surface of a positive electrode active material layer containing a positive electrode active material is less than 1.0 × 10^4 Å
Implementation Method 2
nonaqueous electrolyte solution containing specific compounds, such as those in Formulas (1) to (10), which enhance both high-temperature cycle stability and low-temperature rate performance
Data Source
Figure 1~2
Figure 3
AI summary
The present disclosure provides a lithium ion secondary battery, in which surface roughness (Ra) of a surface of a positive electrode active material layer containing a positive electrode active material is less than 1.0 × 104 Å, and the lithium ion secondary battery includes a nonaqueous electrolyte solution containing at least one selected from the group consisting of compounds of Formulas (1) to (10) described in the specification.