Lithium Secondary Battery Positive Electrode Active Material
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium secondary batteries using lithium-containing composite metal oxides as positive electrode active materials fail to achieve high power output at high current rates, particularly in applications such as automobiles and power tools.
Innovation Solution
A positive electrode active material for lithium secondary batteries is developed, comprising lithium-containing composite metal oxide secondary particles with a specific α-NaFeO2 type crystal structure, a coating layer of Li and M2 metals, and optimized particle size and density, which enhances the battery's power output at high current rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel composite oxide is used as positive electrode active material, then discharge capacity is improved, but heat stability during charging deteriorates
Solution Approach 1:
The patent uses a composite material structure where lithium-nickel composite oxide particles are coated with lithium-manganese composite oxide. This composite structure combines the high discharge capacity of lithium-nickel oxide with the superior heat stability of lithium-manganese oxide, resolving the contradiction between capacity and thermal stability.
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where the inner core (lithium-nickel composite oxide) provides high capacity while the outer shell (lithium-manganese composite oxide coating layer) provides heat stability. Different regions of the material have different compositions optimized for different functions.
2Reliability
If conventional lithium-containing composite metal oxide is used, then thermal stability is improved, but power output at high current rate deteriorates
Solution Approach 1:
The patent segments the positive electrode active material into discrete particles with controlled size (3 μm to 20 μm). This segmentation increases the surface area to volume ratio, improving ion transport kinetics and enabling higher power output at high current rates while maintaining the thermal stability benefits of the composite oxide structure.
Solution Approach 2:
The patent changes physical parameters including particle size (3-20 μm), specific surface area (0.03 to 0.30 m²/g), and compositional ratios to optimize both power output and thermal stability. By carefully controlling these parameters, the material achieves high rate capability without sacrificing safety.
Data Source
AI summary
A positive electrode active material for a lithium secondary battery, comprising a lithium-containing composite metal oxide in the form of secondary particles formed by aggregation of primary particles capable of being doped and undoped with lithium ions, each of the secondary particles having on its surface a coating layer, the positive electrode active material satisfying the following requirements (1) to (3):(1) the metal oxide has an α-NaFeO2 type crystal structure of following formula (A):Lia(NibCocM11-b-c)O2 (A)wherein 0.9≤a≤1.2, 0.9≤b<1, 0<c≤0.1, 0.9<b+c≤1, and M1 represents at least one optional metal selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In and Sn;(2) the coating layer comprises Li and M2, wherein M2 represents at least one optional metal selected from Al, Ti, Zr and W; and(3) the active material has an average secondary particle diameter of 2 to 20 μm, a BET specific surface area of 0.1 to 2.5 m2/g, and a value of 1.0 to 2.0 as a tamped density/untamped density ratio of the active material.