Nickel Cathode Material Structure for Residual Lithium Control
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Solution Overview
Problem
Lithium secondary batteries using nickel-based active materials face reliability issues due to unreacted residual lithium at the surface, leading to decreased performance and lifespan, including increased resistance and crack formation during charging and discharging.
Innovation Solution
A cathode active material with a radial arrangement structure and an irregular porous structure, where a lithium fluoride-based compound is present on the surface, is developed. This material is synthesized through a process involving a first heat treatment of a lithium source and metal hydroxide, followed by a second heat treatment with a fluoride precursor, to reduce residual lithium and enhance lithium diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based active material is used to achieve high capacity, then battery capacity is improved, but residual lithium remains on the surface causing reliability deterioration
Solution Approach 1:
The patent removes residual lithium from the surface of nickel-based active material particles through a washing process using organic solvents, directly extracting the harmful substance that causes reliability deterioration while preserving the high-capacity nickel-based material
Solution Approach 2:
The patent applies different treatments to different parts of the material: the interior maintains high-nickel composition for capacity, while the surface is cleaned of residual lithium and coated with protective layers to ensure reliability, creating local quality differentiation between core and surface regions
2Quantity of substance
If nickel-based active material is used to achieve high capacity, then battery capacity is improved, but cracks occur during charging and discharging
Solution Approach 1:
The patent divides the particle structure into multiple layers: an inner high-nickel region for capacity and an outer protective layer that accommodates volume changes during charging/discharging, preventing crack propagation through structural segmentation
Solution Approach 2:
The patent creates a composite structure combining nickel-based active material with protective coating materials, forming a core-shell type composite where the outer layer provides mechanical strength and crack resistance while the inner core delivers high capacity
3Quantity of substance
If nickel-based active material is used to achieve high capacity, then battery capacity is improved, but resistance increases over time
Solution Approach 1:
The patent performs preliminary surface treatment including washing to remove residual lithium and applying protective coatings before battery assembly, preventing subsequent resistance increase by addressing surface issues in advance
Solution Approach 2:
The patent changes surface chemical parameters by removing residual lithium and applying protective coatings, transforming the surface composition to reduce resistance and improve long-term electrical stability while maintaining bulk capacity
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 solution effectively reduces residual lithium, improves lithium ion conductivity, and enhances the battery's capacity and lifespan by minimizing surface resistance and gas generation during high-temperature storage.
Implementation Method 1
a lithium fluoride-based compound is present on a surface of the nickel-based active material
Implementation Method 2
the primary particles are aligned such that a (003) plane of each of the primary particles is perpendicular to an outermost plane of the secondary particle
Implementation Method 3
performing a first heat treatment on a mixture comprising a lithium source and a metal hydroxide in an oxidative gas atmosphere
Data Source
AI summary
Provided are a cathode active material for a lithium secondary battery, a method of preparing the same, and a lithium secondary battery including a cathode including the cathode active material. The cathode active material includes: a secondary particle of a nickel-based active material, wherein the secondary particle including a plurality of primary particles, wherein the secondary particle includes a radial arrangement structure and an irregular porous structure, the radial arrangement structure is located closer to a surface of the secondary particle than the irregular porous structure, and a lithium fluoride-based compound is present on a surface of the nickel-based active material.