LiNiMn Composite Oxide for HEV Battery Power and Efficiency
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Solution Overview
Problem
Lithium-ion secondary batteries for HEV applications face challenges with high-cost positive electrode materials like Co-based compounds, leading to high battery voltage and low input power, necessitating the development of low-cost, low-voltage batteries with improved power characteristics and charge-discharge efficiency.
Innovation Solution
A non-aqueous electrolyte secondary battery using a lithium-nickel-manganese composite oxide with a hexagonal layered rock-salt structure, represented by the molecular formula Li[LixNiyMnz]O2-a, where 0<x<0.4, 0.12<y<0.5, 0.3<z<0.62, and 0≦a(1−2y)/3, ¼≦y/z≦1.0, which balances input and output power and enhances initial charge-discharge efficiency and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Li(Li-Ni-Mn) composite oxide is used to reduce charge-discharge potential, then input power increases, but initial charge-discharge efficiency becomes poor due to high irreversible capacity
Solution Approach 1:
The patent optimizes the compositional parameters of the Li(Li-Ni-Mn)O2 material by precisely controlling the ratios of Li, Ni, and Mn elements and the amount of lithium in 3b sites. This parameter optimization reduces irreversible capacity during initial charge while maintaining the low charge-discharge potential, thereby improving initial charge-discharge efficiency without sacrificing input power characteristics
Solution Approach 2:
The patent creates local structural differences within the composite oxide by placing lithium in specific crystallographic sites (3b sites) alongside Ni and Mn elements. This local quality differentiation allows selective lithium extraction during initial charge, reducing irreversible capacity and improving charge-discharge efficiency while maintaining the overall low-voltage, high-input-power characteristics
2Reliability
If costly metal elements like Co are used in positive electrode materials, then battery performance is maintained, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive cobalt-based materials with a composite oxide containing more abundant and cheaper elements (Li, Ni, Mn). The Li(Li-Ni-Mn)O2 composite oxide achieves comparable or superior performance to conventional LiCoO2 materials while using lower-cost elements, directly addressing the cost reduction requirement for HEV battery applications
Solution Approach 2:
The patent develops a composite oxide material combining Li, Ni, and Mn elements in optimized proportions. This composite approach leverages the advantages of each element: Li provides high capacity, Ni contributes to voltage and power characteristics, and Mn offers structural stability and cost-effectiveness, achieving a balance between performance and manufacturing cost
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 battery achieves a good balance between input and output power, exhibits excellent power characteristics, and has high initial charge-discharge efficiency and discharge capacity, addressing the limitations of conventional lithium-ion batteries.
Implementation Method 1
lithium extraction from the 3b sites occurs during an initial charge at 4.45 V (vs. Li/Li+) or higher
Implementation Method 2
the capacity originating from the oxidation-reduction reaction of Mn3+/Mn4+ is obtained at 3.5 V (vs. Li/Li+) or lower
Implementation Method 3
non-aqueous electrolyte secondary battery comprising: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; and a non-aqueous electrolyte
Data Source
AI summary
A non-aqueous electrolyte secondary battery has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte. The positive electrode active material includes a lithium-nickel-manganese composite oxide having a hexagonal layered rock-salt structure that belongs to the space group R-3m, and contains lithium in 3b sites that contain transition metals. The lithium-nickel-manganese composite oxide is represented by the molecular formula Li[LixNiyMn2Mb]O2-a, where: 0.2<x<0.4, 0.12<y<0.5, 0.3<z<0.62, and 0≦a<0.5; M is at least one of Mg, Al, Zr, Ti, Nb, W, and Mo; and variables x, y, z, and b satisfy the expressions x>(1−2y)/3, ¼≦y/z≦1.0, 0<b/(y+z)≦0.1, and 1.0≦x+y+z+b≦1.1.