Multilayer Cathode Composition for Easier Battery SOC Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium nickel metal oxide batteries face degradation in structural stability and thermal stability due to high nickel content, making it difficult to estimate the state of charge (SOC) and manage power, while lithium iron phosphate batteries have minimal voltage change during charging and discharging, making SOC estimation challenging and reducing energy density when high solid content is used in positive electrode manufacturing.
Innovation Solution
A lithium secondary battery with a positive electrode comprising multiple layers, including an iron phosphate compound and a lithium composite metal oxide, where the second positive electrode active material's concentration increases towards the outer layers, and particle size decreases from the first to the nth layer, allowing for a significant voltage change per SOC percentage, enabling reliable SOC estimation and high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickel metal oxide with high nickel content is used as positive electrode active material, then energy density is improved, but structural stability and thermal stability deteriorate
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of lithium nickel metal oxide (providing high energy density) and lithium iron phosphate (providing structural stability and thermal stability). This composite structure allows the battery to achieve high energy density while maintaining reliability through the stabilizing effect of the lithium iron phosphate component.
2Reliability
If lithium iron phosphate is used as positive electrode active material, then structural stability and safety are improved, but voltage change during charging and discharging becomes minimal, making SOC estimation difficult
Solution Approach 1:
The patent combines lithium iron phosphate (providing structural stability) with lithium nickel metal oxide (providing significant voltage change during charging/discharging). This composite allows SOC estimation to be performed accurately while maintaining the structural stability benefits of lithium iron phosphate.
3Use of energy by moving object
If solid content in positive electrode slurry is increased to 80 wt% or more, then energy density is improved, but viscosity becomes excessively high, making coating difficult
Solution Approach 1:
The patent optimizes the solid content parameter of the positive electrode slurry to a specific range that balances energy density and manufacturability. By carefully controlling the solid content and slurry composition, the patent achieves high energy density while maintaining coating properties that allow for successful electrode manufacturing.
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 achieves easy and reliable SOC estimation with a large voltage deviation, improving output performance and energy density by controlling the composition and particle size of the positive electrode layers, enhancing thermal stability and manufacturing efficiency.
Implementation Method 1
a first positive electrode mixture layer contacting a surface of the positive electrode current collector contains a first positive electrode active material comprising an iron phosphate compound... second to nth positive electrode mixture layers disposed on the first positive electrode mixture layer comprise the first positive electrode active material... and a second positive electrode active material comprising a lithium composite metal oxide
Data Source
AI summary
Disclosed herein relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, and since the positive electrode contains a first positive electrode active material including an iron phosphate compound and a second positive electrode active material including a lithium composite metal oxide in a multi-layered positive electrode mixture layer, it is possible to display a large voltage deviation for each state of charge (SOC) of a secondary battery. Therefore, when applying a secondary battery, there is an advantage in that the state of charge (SOC) can be easily estimated and/or measured with high reliability. In addition, the positive electrode for a lithium secondary battery has an advantage in terms of the output performance of the secondary battery being excellent because the energy density of the battery can be increased by containing a lithium composite metal oxide in a positive electrode mixture layer spaced apart from a positive electrode current collector among a plurality of positive electrode mixture layers.