Ni-Mn Cathode Material for High-Rate Lithium Battery Stability
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Solution Overview
Problem
Conventional lithium secondary battery cathode active materials face challenges such as high cost, limited structural stability, and poor electrochemical properties due to the use of cobalt and manganese oxides, which affect their performance under high-rate charge/discharge conditions.
Innovation Solution
A lithium transition metal oxide cathode active material with a layered crystal structure, where the transition metal is a blend of Ni and Mn, and the average oxidation number of transition metals is greater than +3, ensuring a stable crystal structure and improved electrochemical properties by maintaining a higher nickel content than manganese and adjusting the oxidation number to enhance ion mobility and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium cobalt composite oxide (LiCoO2) is used as cathode active material, then long life span and good charge/discharge characteristics are achieved, but structural stability is low and cost is high
Solution Approach 1:
The patent uses composite materials by combining lithium nickel composite oxide and lithium manganese composite oxide in specific ratios (0.1≤x≤0.9 for Li1−xNixMn3−xO4 spinel structure and LiyMn2−yO3 layered structure). This composite approach leverages the high capacity of nickel-based materials while the manganese component provides structural stability, resolving the contradiction between charge/discharge characteristics and structural stability.
Solution Approach 2:
The patent optimizes composition parameters (x and y values) and oxidation states to achieve the desired balance. By controlling the ratio of Ni to Mn and adjusting the oxidation number of transition metals to greater than +3, the material achieves both good electrochemical performance and enhanced structural stability without relying on cobalt.
2Temperature
If lithium manganese composite oxides (LiMnO2, LiMn2O4) are used as cathode active material, then thermal stability is superior and cost is low, but capacity is low and low-temperature characteristics are poor
Solution Approach 1:
The patent creates a composite system where lithium manganese oxide provides thermal stability and cost advantages, while lithium nickel oxide contributes higher capacity. The synergistic combination in the spinel-layered structure composite (0.1≤x≤0.9) allows the material to achieve both thermal stability and enhanced capacity, overcoming the limitations of pure manganese-based materials.
3Quantity of substance
If lithium nickel composite oxide (LiNiO2) is used as cathode active material, then capacity is high, but structural stability is poor
Solution Approach 1:
The patent combines lithium nickel composite oxide (high capacity) with lithium manganese composite oxide (high structural stability) in a composite spinel-layered structure. The manganese component acts as a structural scaffold that maintains stability, while the nickel component provides high capacity, effectively resolving the contradiction between capacity and structural stability.
Solution Approach 2:
The patent creates different local structures within the composite material: the spinel phase (Li1−xNixMn3−xO4) provides a stable framework, while the layered phase (LiyMn2−yO3) provides high capacity pathways. This local differentiation allows each region to perform its optimal function, with the spinel providing stability and the layered structure enabling high capacity.
Data Source
AI summary
Provided is a cathode active material which is lithium transition metal oxide having an α-NaFeO2 layered crystal structure, wherein the transition metal is a blend of Ni and Mn, an average oxidation number of the transition metals except lithium is more than +3, and lithium transition metal oxide satisfies the Equation m(Ni)≧m(Mn) (in which m (Ni) and m (Mn) represent an molar number of nickel and manganese, respectively). The lithium transition metal oxide has a uniform and stable layered structure through control of oxidation number of transition metals to a level higher than +3, thus advantageously exerting improved overall electrochemical properties including electric capacity, in particular, superior high-rate charge/discharge characteristics.