Single-Layer Positive Electrode Mixture for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face a tradeoff between high energy density and high security due to the heat generation risk of lithium composite oxides and the low energy density of polyanionic compounds, and the manufacturing complexity and low productivity of two-layered positive electrode structures.
Innovation Solution
A single positive electrode mixture layer containing a lithium composite oxide with a layered structure and a polyanionic compound with an olivine type structure, where the average secondary particle diameter of the first material is larger than the second, and the weight ratio and area occupation ratio are optimized to balance energy density and security, improving production efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium composite oxide with a layered structure is used as the positive electrode active material to achieve high energy density, then the energy density is improved, but heat generation occurs at high temperature causing security deterioration
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of a lithium composite oxide with a layered structure (providing high energy density) and a polyanionic compound with an olivine type structure (providing thermal stability). This composite material combines the advantages of both materials to achieve high energy density while maintaining security by suppressing heat generation.
2Reliability
If a polyanionic compound with an olivine type structure is used as the positive electrode active material to achieve high security, then the thermal stability is improved, but the energy density deteriorates
Solution Approach 1:
The patent creates a composite positive electrode active material where the polyanionic compound with an olivine type structure (providing thermal stability and security) is combined with a lithium composite oxide with a layered structure (providing high energy density). The composite structure allows the polyanionic compound to suppress heat generation while the lithium composite oxide maintains high energy density.
3Reliability
If a two-layered structure positive electrode mixture layer is formed to achieve both high security and high energy density, then the security and energy density are improved, but the manufacturing complexity increases and productivity deteriorates
Solution Approach 1:
The patent merges the first positive electrode active material (lithium composite oxide with layered structure) and the second positive electrode active material (polyanionic compound with olivine type structure) into a single positive electrode mixture layer. This single-layer structure contains both materials in a mixed arrangement, eliminating the need for separate application and drying processes for two layers, thereby maintaining both security and energy density while significantly improving productivity.
4Reliability
If a two-layered structure positive electrode mixture layer is formed to achieve both high security and high energy density, then the security and energy density are improved, but the device complexity increases
Solution Approach 1:
The patent combines both positive electrode active materials (lithium composite oxide with layered structure and polyanionic compound with olivine type structure) into a single positive electrode mixture layer with a mixed structure. This eliminates the complexity of forming and managing two separate layers, while still achieving the dual goals of high security and high energy density through the synergistic combination of materials within the single layer.
Data Source
AI summary
A positive electrode for a lithium ion secondary battery includes a positive electrode current collector and a positive electrode mixture layer formed on one surface or both surfaces of the positive electrode current collector, wherein the positive electrode mixture layer contains a positive electrode active material, and conductive agent material, and a binder, the positive electrode active material is a mixture of a first positive electrode active material which is a lithium composite oxide with a layered structure and a second positive electrode material which is a polyanionic compound with an olivine type structure.