Nickel Active Material Precursor Porous Core Dense Intermediate Layer
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Solution Overview
Problem
Lithium secondary batteries face issues with the long-term lifespan and capacity due to cracking of positive active materials caused by repeated charging and discharging, leading to increased resistance and unsatisfactory capacity characteristics.
Innovation Solution
A nickel-based active material precursor for lithium secondary batteries is developed, comprising a porous core, a dense intermediate layer, and a porous shell, which facilitates lithium ion intercalation and deintercalation, reducing stress from volumetric expansion and enhancing the utilization rate and lifespan by optimizing the porosity and structure of the active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a dense positive active material is used to increase capacity, then energy density is improved, but cracking occurs during repeated charging and discharging leading to reduced lifespan
Solution Approach 1:
The patent employs a porous core structure within the positive active material particles, which provides internal void space to accommodate volumetric expansion and contraction during lithium ion intercalation and deintercalation. This porous architecture prevents crack formation while maintaining high capacity, thus resolving the contradiction between energy density and lifespan by allowing the material to withstand repeated charge-discharge cycles without structural degradation.
Solution Approach 2:
The patent creates a composite structure consisting of a porous core, a dense intermediate layer, and an outer shell. This multi-layer composite design combines the benefits of high capacity (dense regions) with stress resistance (porous core), enabling the material to achieve both high energy density and extended lifespan by distributing mechanical stresses during electrochemical cycling.
2Productivity
If the positive active material structure is optimized for high capacity, then utilization rate increases, but stress from volumetric expansion reduces structural stability
Solution Approach 1:
The porous core structure provides internal buffer space that absorbs volumetric expansion stresses during lithium ion insertion, preventing structural degradation. This allows the material to maintain high utilization rate while preserving structural stability over repeated cycles, as the porous architecture accommodates dimensional changes without compromising integrity.
Solution Approach 2:
The porous core acts as a pre-designed cushioning structure that anticipates and absorbs expansion stresses before they can cause damage. By incorporating this buffer space in advance, the material can undergo high-utilization charge-discharge cycles without suffering from stress-induced structural failure.
3Speed
If lithium ion diffusion distance is reduced to improve rate capability, then charging speed increases, but particle size must be reduced which limits capacity
Solution Approach 1:
The patent segments the particle into a porous core and an outer shell region. This segmentation creates multiple internal pathways for lithium ion diffusion through the porous core, effectively reducing diffusion distance without requiring overall particle size reduction. The segmented structure allows fast charging while maintaining adequate capacity through the distributed pore network.
Solution Approach 2:
The porous core provides a three-dimensional network of diffusion pathways that shorten the effective distance lithium ions must travel to reach active material sites. This porous architecture enables rapid ion transport throughout the particle interior while maintaining sufficient material volume for high capacity, resolving the trade-off between charging speed and 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 nickel-based active material precursor improves lithium diffusion and stress relief, resulting in increased capacity and extended lifespan of lithium secondary batteries by reducing cracking and maintaining structural stability during charge-discharge cycles.
Implementation Method 1
diffusion of lithium at an interface between a positive active material and an electrolytic solution may be facilitated
Implementation Method 2
relief of stress caused by volumetric expansion due to intercalation and deintercalation of lithium ions may be facilitated
Data Source
AI summary
Provided are a nickel-based active material precursor for a lithium secondary battery including a porous core and a porous shell, wherein a porosity of the porous shell may be greater than a porosity of the porous core, and a dense intermediate layer may be disposed between the porous core and the porous shell, wherein a porosity of the dense intermediate layer may be lower than the porosity of the porous core and the porosity of the porous shell; a method of preparing the same; a nickel-based active material for a lithium secondary battery formed therefrom; and a lithium secondary battery containing a positive electrode including the same.