Core-Shell Positive Electrode Material with Buffer Layer
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Solution Overview
Problem
Lithium secondary batteries face issues with rapid lifespan degradation due to electrolyte degradation and active material deterioration, especially at high temperatures, limiting their capacity and thermal stability, and existing positive electrode materials like LiCoO2 have structural stability limitations and high production costs.
Innovation Solution
A positive electrode active material with a core-shell structure and a three-dimensional network buffer layer made of lithium composite metal oxide, optimized for specific surface area, porosity, and particle size, which enhances lithium ion intercalation and deintercalation, reducing material decomposition and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode active material, then lifespan and charge/discharge efficiency are improved, but structural stability deteriorates and application to high capacity battery is limited
Solution Approach 1:
The patent applies a core-shell structure where a buffer layer is constructed between the core (conductive additive) and shell (positive electrode active material). This nested structure allows the buffer layer to absorb expansion stress and prevent structural degradation of the LiCoO2 shell, thereby maintaining both high reliability and structural stability during charge/discharge cycles.
Solution Approach 2:
The patent creates a composite structure combining conductive additives (core), buffer layer materials, and LiCoO2 (shell). This composite approach leverages the electrical conductivity of the core, the mechanical buffering capability of the intermediate layer, and the electrochemical performance of the LiCoO2 shell, achieving both structural stability and high reliability simultaneously.
2Quantity of substance
If LiNiO2 is synthesized to achieve high discharge capacity, then battery characteristic of high discharge capacity is improved, but thermal stability and cycle characteristic deteriorate
Solution Approach 1:
The buffer layer nested between the core and shell provides a protective interface that enhances thermal stability. This intermediate layer acts as a thermal barrier and stress buffer, preventing direct exposure of the high-capacity LiNiO2 to harsh conditions, thereby maintaining both high discharge capacity and thermal stability.
Solution Approach 2:
The patent applies different materials with specific properties to different regions: the core provides conductivity, the buffer layer provides thermal and mechanical protection, and the shell provides electrochemical activity. This local differentiation allows the high-capacity material to function optimally while being protected in critical regions.
3Temperature
If LiMn2O4 is used to achieve excellent thermal stability and cheap price, then thermal stability is improved, but lifespan characteristic deteriorates due to structural deformation
Solution Approach 1:
The buffer layer nested within the core-shell structure prevents Jahn-Teller distortion by providing mechanical support and accommodating volume changes during lithium insertion/extraction. This protects the LiMn2O4 shell from structural degradation, thereby extending lifespan while maintaining thermal stability.
Solution Approach 2:
The buffer layer is pre-positioned between the core and shell to provide cushioning against structural deformation before it occurs. This preventive measure absorbs expansion stresses and prevents Jahn-Teller distortion from developing, thereby preserving both thermal stability and lifespan characteristic.
4Stability of the object's composition
If LiFePO4 is used to achieve low price and excellent stability, then stability is improved, but conductivity deteriorates making it difficult to be used for other applications
Solution Approach 1:
The patent merges LiFePO4 with conductive additives in a core-shell structure. The conductive core and buffer layer compensate for the inherent low conductivity of LiFePO4, enabling it to achieve both stability and adequate conductivity for broader applications.
Solution Approach 2:
The patent creates a composite structure where LiFePO4 is combined with conductive materials. This composite approach overcomes the conductivity limitation of pure LiFePO4 while preserving its stability, making it suitable for various battery applications beyond hybrid electric vehicles.
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 optimized positive electrode active material improves charge/discharge characteristics, lifespan, and thermal stability, enabling high-capacity and long-lasting batteries suitable for applications like electric vehicles, while minimizing performance deterioration at high temperatures.
Implementation Method 1
a buffer layer which is located between the core and the shell and includes a three-dimensional network structure connecting the core and the shell and a pore
Implementation Method 2
a buffer layer which is located between the core and the shell and includes a three-dimensional network structure connecting the core and the shell and a pore
Data Source
AI summary
The present invention provides a positive electrode active material for a secondary battery and a secondary battery including the same, which includes a core; a shell located to surround the core; and a buffer layer located between the core and the shell, and including a three-dimensional network structure connecting the core and the shell and a pore. The decomposition of the active material may be minimized by a rolling process in the manufacture of an electrode by controlling the specific surface area, average particle diameter and porosity of the active material particles as well as the specific structure, the reactivity with an electrolyte solution may be maximized, and the output and lifespan characteristics of the secondary battery may be improved since the particles forming the shell have crystal structure with orientation which facilitates intercalation and deintercalation of lithium ions.