Glassy-Coated High-Ni NCM Cathode for Heat and Rolling Stability
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Solution Overview
Problem
High-Ni NCM-based lithium composite transition metal oxides for secondary batteries face limitations in thermal stability and particle strength, leading to reduced battery lifetime and stability due to increased nickel content and lithium by-products, as well as particle breakage during electrode rolling.
Innovation Solution
A positive electrode active material with a lithium composite transition metal oxide containing nickel, cobalt, and manganese, coated with a glassy layer composed of boron, aluminum, or silicon compounds, which improves thermal stability and particle strength, reducing lithium by-products and preventing particle breakage during electrode rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in NCM-based lithium composite transition metal oxide is increased to secure high capacity, then the capacity characteristics are improved, but thermal stability is rapidly reduced
Solution Approach 1:
The patent applies local quality by creating a dual-composition structure where the particle interior maintains high nickel content (60-80 mol%) for high capacity, while the particle surface is enriched with manganese (greater than cobalt content) to provide thermal stability. This spatial differentiation of composition allows each region to optimize its function: the core provides capacity while the surface provides stability.
Solution Approach 2:
The patent employs composite materials by combining multiple transition metals (nickel, cobalt, manganese) in a lithium composite oxide structure with specific compositional ratios. The composite nature allows synergistic effects where nickel provides capacity, cobalt provides structural stability, and manganese enhances thermal stability, achieving a balance that single-metal oxides cannot achieve.
2Reliability
If the concentration of manganese is increased to improve thermal stability of high-Ni positive electrode active material, then thermal stability is improved, but particle strength is reduced causing particle breakage during electrode rolling
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters within specific ranges: nickel content at 60-80 mol%, manganese content greater than cobalt but optimized to avoid excessive values, and overall maintaining the sum of nickel, cobalt, and manganese at 95 mol% or more. These parameter optimizations ensure thermal stability while preserving sufficient particle strength.
3Quantity of substance
If the nickel content in the active material is increased, then capacity characteristics are improved, but lithium by-products (LiOH and Li2CO3) on the surface are increased causing swelling phenomenon
Solution Approach 1:
The patent applies the extraction principle by removing excess lithium from the crystal structure through controlled lithium deficiency (0.95 ≤ p < 1.0 in Li1+pNi1−(x1+y1+z1)Cox1Mnym1M2z1M3q1O2). This prevents the formation of lithium by-products like LiOH and Li2CO3 on the surface that would otherwise cause swelling, while maintaining the high nickel content necessary for 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 glassy coating enhances thermal stability and particle strength, improving high-temperature life characteristics and reducing gas generation during storage, while maintaining high capacity and stability of the battery.
Implementation Method 1
since lithium by-products present in the form of LiOH and Li2CO3 on the surface of the positive electrode active material are increased as the nickel content in the active material is increased
Implementation Method 2
a glassy coating layer formed on surfaces of particles of the lithium composite transition metal oxide
Data Source
AI summary
A positive electrode active material for a secondary battery includes a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), and a glassy coating layer formed on surfaces of particles of the lithium composite transition metal oxide, wherein, in the lithium composite transition metal oxide, an amount of the nickel (Ni) in a total amount of transition metals is 60 mol % or more, and an amount of the manganese (Mn) is greater than an amount of the cobalt (Co), and the glassy coating layer includes a glassy compound represented by Formula 1.LiaM1bOc [Formula 1]wherein, M1 is at least one selected from the group consisting of boron (B), aluminum (Al), silicon (Si), titanium (Ti), and phosphorus (P), and 1≤a≤4, 1≤b≤8, and 1≤c≤20.