Layered Positive Electrode Structure for Stable Lithium Batteries
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving improved capacity, efficiency, lifespan, output properties, and thermal stability, particularly with lithium nickel composite metal oxides due to issues such as poor thermal stability, decomposition during internal shorts, and increased cycle resistance.
Innovation Solution
A positive electrode for lithium secondary batteries is designed with a two-layered structure, where the first layer includes large-diameter and small-diameter particles of specific nickel, cobalt, and manganese-based lithium composite transition metal oxides, and the second layer includes similar particles with different diameters and forms, optimized for particle aggregation and conductive material distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode is used, then the battery can operate, but the battery swells due to gas generation during charging and discharging
Solution Approach 1:
An alumina coating layer is introduced as an intermediary between the positive electrode active material and the electrolyte. This coating layer acts as a mediator that suppresses gas generation reactions while maintaining ionic conductivity, thereby preventing battery swelling without compromising electrochemical performance
Solution Approach 2:
The alumina coating layer is designed with porous structure having specific surface area and pore volume characteristics. The porous structure allows lithium ion transport while providing large surface area for suppressing gas-generating side reactions between the electrolyte and electrode materials
2Object-generated harmful factors
If the positive electrode is coated with alumina to suppress gas generation, then battery swelling is prevented, but electrochemical performance deteriorates
Solution Approach 1:
The alumina coating layer parameters (thickness, surface area, pore volume, average pore diameter) are precisely controlled within specific ranges. By optimizing these parameters, the coating suppresses gas generation while maintaining sufficient ionic conductivity and electrochemical activity
Solution Approach 2:
The porous structure of the alumina coating provides pathways for lithium ion diffusion while the controlled pore size and distribution ensure adequate ionic conductivity. The porosity allows the coating to function as both a protective barrier and a conductive medium
3Duration of action of stationary object
If the positive electrode is coated with alumina to improve cycle stability, then cycle life is extended, but manufacturing complexity increases
Solution Approach 1:
The alumina coating is applied to the positive electrode before assembly into the battery, preparing the electrode in advance with the desired coating characteristics. This preliminary coating step ensures consistent gas suppression and electrochemical performance while simplifying the overall manufacturing process
Solution Approach 2:
The coating process parameters (alumina particle size, coating thickness, surface area, pore volume) are controlled within specific ranges to achieve the desired balance between gas suppression and electrochemical performance. This parameter control ensures repeatable manufacturing results
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 two-layered structure enhances capacity, efficiency, lifespan, and thermal stability by improving heat transfer, reducing cracking, and optimizing conductive pathways, resulting in a more stable and high-performance battery.
Implementation Method 1
a coating layer comprising alumina is formed on the positive electrode
Implementation Method 2
the coating layer has a pore volume of 0.003 mL/g or more and an average pore diameter of 3 nm or less, thereby facilitating diffusion of lithium ions from the electrolyte to the positive electrode
Data Source
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AI summary
The present invention relates to a positive electrode for a lithium secondary, the positive electrode having improved capacity, efficiency, lifespan, output properties, and thermal stability, and including a positive electrode current collector, and a first positive electrode active material layer and a second positive electrode active material layer sequentially stacked on the positive electrode current collector, wherein the first positive electrode active material layer and the second positive electrode active material layer include a bimodal positive active material, the first positive electrode active material layer includes small-diameter particles in the form of a single particle, and the second positive electrode active material layer includes small-diameter particles in the form of a secondary particle.