Gradient Ni-Co-Mn Cathode Material for High-Temperature Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high voltage and high-energy density characteristics, especially when used in high-temperature applications like electric vehicles, due to limitations in discharge capacity and lifespan.
Innovation Solution
A positive electrode active material comprising nickel, cobalt, and manganese with a core and surface part composition gradient, where manganese is higher than 25 mol% in both parts, and nickel and cobalt concentrations vary to create a concentration gradient from the core to the surface, enhancing structural stability and facilitating lithium ion movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage and high-energy density characteristics are pursued in lithium secondary batteries, then energy density is improved, but discharge capacity and lifespan deteriorate under high-temperature conditions
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface part has different composition (higher Mn, lower Ni) compared to the core part (higher Ni, lower Co). This gradient composition allows the surface to provide stability against electrolyte decomposition while the core maintains high capacity, resolving the contradiction between energy density and reliability under high-temperature conditions.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (Ni, Co, Mn) in a gradient distribution within the same compound structure (LiNi0.8Co0.1Mn0.1O2 core to LiNi0.6Co0.2Mn0.2O2 surface). This composite approach enables simultaneous achievement of high energy density from Ni-rich core and high reliability from Mn-rich surface, particularly under high-temperature operation.
2Quantity of substance
If nickel content is increased to improve capacity, then discharge capacity is improved, but structural stability deteriorates due to side reactions with electrolyte
Solution Approach 1:
The patent implements local quality by concentrating high nickel content (0.8-0.85) in the core part where it provides high discharge capacity, while reducing nickel content (0.6-0.65) in the surface part where it would otherwise cause structural instability. The surface is enriched with manganese to provide protective stability, thus allowing high overall capacity while maintaining structural integrity.
Solution Approach 2:
The patent uses manganese-rich surface layer as an intermediary between the high-nickel core and the electrolyte environment. This Mn-rich surface acts as a protective barrier that prevents direct contact between the Ni-rich core and electrolyte, reducing side reactions and structural degradation while allowing the high-capacity Ni core to function effectively.
3Ease of manufacture
If uniform composition is used throughout the positive electrode active material, then manufacturing is simplified, but lithium ion movement and charge balance are hindered
Solution Approach 1:
The patent applies local quality by creating a gradient composition where the core and surface have different metal ratios optimized for different functions. The core (higher Ni, lower Co) is optimized for capacity and lithium ion insertion/extraction, while the surface (lower Ni, higher Mn) is optimized for structural stability and charge balance. This spatial variation in composition enhances overall battery performance despite increased manufacturing complexity.
Data Source
AI summary
A positive electrode active material for a lithium secondary battery, a method of preparing the same, and a lithium secondary battery, the positive electrode active material including nickel, cobalt, and manganese, wherein the positive electrode active material has a core part and a surface part, an amount of manganese in the core part and the surface part is higher than 25 mol %, and amounts of nickel and cobalt in the positive electrode active material vary such that a concentration gradient of the nickel and the cobalt in a direction from the core part to the surface part is present in the positive electrode active material.