Monolithic Cathode Active Material for High-Temperature Capacity Retention
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Solution Overview
Problem
Current positive electrode active materials for lithium secondary batteries face challenges in maintaining high-temperature stability and capacity characteristics due to decomposition of electrolytes and surface impurities formation.
Innovation Solution
A positive electrode active material with a monolithic structure, composed of a lithium composite metal oxide (Li a Ni 1-x-y Co x M1 y M3 z M2 w O 2), is developed, featuring an average particle size of 2 µm to 8 µm and a specific surface area of 0.15 m 2/g to 0.5 m 2/g, which minimizes surface impurities and maintains structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as a positive electrode active material to achieve high discharge capacity, then battery capacity is improved, but thermal stability and cycle characteristics deteriorate
Solution Approach 1:
The patent uses LiNi0.8Co0.1Mn0.1O2 as a composite material that combines multiple transition metals (Ni, Co, Mn) in specific ratios. This composite structure leverages the high capacity of Ni while Co and Mn provide structural stability and thermal resistance, resolving the contradiction between high discharge capacity and thermal stability/cycle characteristics
Solution Approach 2:
The patent optimizes the atomic ratios of transition metals (Ni:Co:Mn = 8:1:1) and controls synthesis parameters (sintering temperature, atmosphere, time) to achieve a specific crystal structure with refined grain size. These parameter changes enable the material to simultaneously achieve high capacity and improved thermal stability
2Reliability
If LiMn2O4 is used as a positive electrode active material to achieve excellent thermal stability and low cost, then thermal stability is improved, but capacity and high-temperature characteristics deteriorate
Solution Approach 1:
The patent creates a composite material LiNi0.8Co0.1Mn0.1O2 that combines Mn (providing thermal stability) with Ni (providing high capacity) and Co (providing structural stability). This composite approach allows the material to overcome the low capacity limitation of pure LiMn2O4 while maintaining its thermal stability advantages
Solution Approach 2:
The patent creates a concentration gradient structure where the surface region has different compositional characteristics than the core region. The surface is enriched with elements that provide thermal stability and form protective layers, while the core maintains high capacity characteristics, achieving both thermal stability and high-temperature performance
3Quantity of substance
If secondary particle structure is used to increase battery capacity, then capacity is improved, but surface impurity formation increases due to lithium ion reaction with moisture and CO2
Solution Approach 1:
The patent performs preliminary surface treatment during the sintering process by controlling the atmosphere and temperature to form a stable surface layer before the material is exposed to ambient conditions. This preliminary action prevents subsequent reaction with moisture and CO2, reducing surface impurity formation while maintaining high capacity
Solution Approach 2:
The patent conducts sintering and surface treatment in an inert or controlled atmosphere (oxygen or nitrogen environment) to prevent lithium ions from reacting with moisture and CO2. This inert environment protection during critical processing stages minimizes surface impurity formation while preserving the high-capacity secondary particle structure
4Reliability
If LiCoO2 is used as a positive electrode active material to achieve excellent lifespan characteristics and charge/discharge efficiency, then lifespan and efficiency are improved, but structural stability deteriorates limiting capacity increase
Solution Approach 1:
The patent creates a composite material LiNi0.8Co0.1Mn0.1O2 where Co (10 atom%) provides structural stability and excellent lifespan characteristics similar to LiCoO2, while Ni (80 atom%) provides high capacity. This composite structure maintains the charge/discharge efficiency and lifespan of LiCoO2 while enabling higher capacity through the Ni content
Data Source
Figure 1
AI summary
The present invention provides a positive electrode active material for a secondary battery, the positive electrode active material being a primary particle having a monolithic structure that includes a lithium composite metal oxide of Formula 1 below, wherein the primary particle has an average particle size (D50) of 2 µm to 20 µm and a Brunauer-Emmett-Teller (BET) specific surface area of 0.15 m2/g to 1.9 m2/g, and a secondary battery including the same. [Formula 1] LiaNi1-x-yCoxM1yM3zM2wO2 (In Formula 1, M1 to M3, a, x, y, z, and w are the same as those defined in the specification) According to the present invention, a positive electrode active material for a secondary battery has a monolithic structure and thus maintains a stable crystal structure even during charging and discharging such that thereby is no concern about a sharp decrease in capacity due to a change in the crystal structure and the generation of surface impurities is minimized, thereby being capable of exhibiting excellent high-temperature stability and capacity characteristic when the positive electrode active material is applied to a battery.