Cathode Active Material for Secondary Battery and Lithium Secondary Battery Including the Same
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Solution Overview
Problem
Lithium secondary batteries face issues with reduced output characteristics and lifespan due to side reactions between the cathode active material and electrolyte, necessitating improved stability and efficiency.
Innovation Solution
A cathode active material with a cobalt concentration gradient is developed, where the surface portion has a higher cobalt content than the central portion, maintaining a controlled cobalt content gradient to minimize lattice structure deformation and reduce side reactions, thereby enhancing structural stability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content in cathode active material is increased to achieve high capacity, then battery capacity is improved, but structural stability deteriorates due to lattice deformation
Solution Approach 1:
The patent applies local quality by creating a non-uniform cobalt distribution within the cathode active material particles. The surface portion contains higher cobalt content (1-10 mol%) while the central portion contains lower cobalt content (3-9 mol%), forming a concentration gradient that provides different local properties: the cobalt-rich surface stabilizes the lattice structure and reduces side reactions, while the nickel-rich center maintains high capacity. This spatial variation in composition resolves the contradiction between high nickel content for capacity and structural stability.
2Reliability
If cobalt content is increased to reduce side reactions with electrolyte, then lifespan is improved, but manufacturing cost increases
Solution Approach 1:
The patent reduces manufacturing cost while maintaining lifespan improvement by applying local quality: cobalt is concentrated only in the surface portion (1-10 mol%) where it is needed to prevent side reactions with the electrolyte, rather than uniformly distributing cobalt throughout the entire particle. This gradient distribution minimizes the total cobalt content required while still achieving the protective effect at the particle surface, thereby reducing material costs.
Solution Approach 2:
The patent changes the concentration parameter of cobalt from a uniform value to a gradient distribution, with the surface concentration (1-10 mol%) being higher than the center concentration (3-9 mol%). This parameter change optimizes the balance between lifespan characteristics and manufacturing cost by placing cobalt strategically where it provides maximum benefit for reducing side reactions.
3Ease of manufacture
If uniform cobalt distribution is used to simplify manufacturing, then manufacturing complexity is reduced, but structural stability deteriorates due to insufficient surface protection
Solution Approach 1:
The patent achieves structural stability through local quality by concentrating cobalt in the surface portion (1-10 mol%) where it is most effective at preventing side reactions and stabilizing the lattice structure. This non-uniform distribution provides superior surface protection compared to uniform distribution, while the gradient design (higher at surface, lower at center) can be achieved through controlled synthesis methods.
Solution Approach 2:
The patent changes the spatial distribution parameter of cobalt from uniform to gradient, creating a concentration profile where surface cobalt content (1-10 mol%) exceeds center cobalt content (3-9 mol%). This parameter change ensures adequate surface protection for structural stability while allowing manufacturing through controlled precipitation or doping processes that naturally create gradient distributions.
Data Source
AI summary
According to the present disclosure, there is provided a cathode active material for a secondary battery, which includes lithium transition metal oxide particles containing nickel in a content of 80 mol % or more, based on a total number of moles of elements excluding lithium and oxygen, and cobalt. An average content of cobalt in a surface portion of the particle, based on the total number of moles of elements excluding lithium and oxygen is higher than an average content of cobalt in a central portion of the particle, based on the total number of moles of elements excluding lithium and oxygen.