Gradient NCM Cathode Composition for Capacity and Cycle Stability
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Solution Overview
Problem
Existing lithium-ion battery positive electrode materials, particularly ternary nickel cobalt manganese materials, face challenges in achieving high initial discharge specific capacity, cycle, and rate performance, with complex synthesis processes and high production costs, limiting their suitability for large-scale energy storage applications.
Innovation Solution
A full-gradient nickel cobalt manganese positive electrode material with a chemical formula of LiNixCoyMn(1-x-y)O2, where the nickel content decreases and manganese content increases from the core to the surface, and cobalt is uniformly distributed, is synthesized using a method involving coprecipitation and sintering, with optional ruthenium oxide coating to enhance electronic conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coprecipitation and sintering methods are used to prepare nickel cobalt manganese positive electrode material, then the material can be synthesized, but the initial discharge specific capacity is low (189 mAh/g) and capacity is not well maintained at high rates
Solution Approach 1:
The patent applies local quality by creating a full-gradient concentration distribution where nickel content decreases from core to surface while manganese content increases accordingly. This gradient structure optimizes different regions for different functions: the nickel-rich core provides high capacity, while the manganese-rich surface enhances stability and rate performance, resolving the contradiction between initial capacity and cycle/rate performance.
Solution Approach 2:
The patent uses parameter changes by systematically varying the concentration of metal ion solutions during coprecipitation. By controlling the feeding rates and concentrations of nickel, cobalt, and manganese salt solutions, the method achieves a continuous gradient composition without requiring complex multi-step sintering processes, thus improving both capacity and performance while simplifying synthesis.
2Reliability
If high temperature sintering (1000°C) and complex synthesis procedures are employed, then material performance can be improved, but the synthesis process becomes cumbersome and production cost increases
Solution Approach 1:
The patent merges the composition control and structure formation into a single coprecipitation step followed by a simplified sintering process. By adjusting the concentration gradient during coprecipitation rather than through multiple sintering stages, the method combines what would otherwise be separate process steps, reducing overall complexity while maintaining performance.
Solution Approach 2:
The patent changes the approach from temperature-based control (high temperature multi-stage sintering) to concentration-based control (gradient coprecipitation). This parameter substitution allows the formation of the desired gradient structure at lower temperatures with simpler processing, resolving the contradiction between performance and ease of manufacture.
3Reliability
If conventional uniform composition methods are used, then synthesis is simpler, but the material cannot achieve both high initial capacity and excellent cycle/rate performance
Solution Approach 1:
The patent implements local quality by creating spatial variation in composition throughout the material. The full-gradient structure has different nickel and manganese concentrations at different radial positions, with the core being nickel-rich for high capacity and the surface being manganese-rich for stability. This local differentiation enables simultaneous optimization of capacity and performance without requiring complex external structures.
Solution Approach 2:
The coprecipitation process inherently creates the gradient structure through controlled diffusion and precipitation kinetics. The system self-organizes into a gradient composition based on the feeding rates and solubility products of the metal ions, without requiring external intervention or complex processing steps to impose the gradient, thus achieving complex internal structure through a relatively simple process.
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 approach results in improved cycle and rate performance, maintaining high discharge specific capacity and capacity retention rates, while simplifying the production process and reducing costs, making it suitable for industrial production and large-scale energy storage.
Implementation Method 1
preparing a precursor of the nickel cobalt manganese ternary material by coprecipitation using a soluble salt of nickel, cobalt and manganese, and a hydroxide as a precipitating agent
Implementation Method 2
yielding the gradient positive ternary material by using different feeding sequences
Implementation Method 3
the precursor is ball milled and sintered using lithium carbonic acid, magnesium acetate and lithium fluoride
Data Source
AI summary
The present invention discloses a full-gradient nickel cobalt manganese positive electrode material, a ruthenium oxide coated material and a preparation method thereof. The material has a chemical formula of LiNixCoyMn(1-x-y)O2, wherein, 0.5≤x≤0.9, 0.05≤y≤0.40, 1-x-y>0. A content of the nickel element is gradually decreased from a core portion to an outer surface of the full-gradient nickel cobalt manganese positive electrode material. A content of the manganese element is gradually increased from the core portion to the outer surface of the full-gradient nickel cobalt manganese positive electrode material. And, a content of the cobalt element is uniformly distributed in the full-gradient nickel cobalt manganese positive electrode material. The present invention also discloses a preparation method of the full-gradient nickel cobalt manganese positive electrode material. The present invention also discloses a preparation method of the ruthenium oxide coated material.