Lithium Mixed Metal Oxide High-Temperature Cycle Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using conventional lithium mixed metal oxides exhibit inadequate cycle characteristics, particularly at high temperatures, limiting their performance in applications requiring high output and durability.
Innovation Solution
A lithium mixed metal oxide with a specific composition and structure, represented by Li x (Mn 1-y-z Ni y Fe z )O 2, where x is between 0.9 and 1.3, y is between 0.46 and 0.5, and z is between 0 and 0.1, with controlled particle sizes and a preferred α-NaFeO 2 crystal structure, is used as a positive electrode active material, along with a heat-resistant porous separator, to enhance cycle stability and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium mixed metal oxide is used as positive electrode active material, then the battery can be manufactured with existing materials, but the cycle characteristics particularly at high temperature operation are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters (x, y, z) of the lithium mixed metal oxide Li x (Mn 1-y-z Ni y Fe z )O 2 to optimize cycle characteristics. By adjusting the stoichiometric ratios and elemental composition within specific ranges, the material maintains stability at high temperatures while improving overall cycle performance.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (Mn, Ni, Fe) in a mixed metal oxide structure. This composite approach leverages the complementary properties of each element: Mn provides structural stability, Ni enhances capacity, and Fe improves rate capability, resulting in a material that performs well under high temperature conditions.
2Power
If the lithium mixed metal oxide composition is optimized for high output, then the battery delivers high output at high electric current rate, but the cycle characteristics may deteriorate
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the compositional parameters (x, y, z) within specific ranges. The balanced composition enables the material to deliver high output at high electric current rates while maintaining good cycle characteristics, avoiding the trade-off between power and reliability.
3Productivity
If the particle size is reduced to improve electrochemical performance, then the surface area increases for better reaction kinetics, but the particle strength decreases leading to potential degradation
Solution Approach 1:
The patent applies parameter changes by controlling particle size parameters within optimal ranges. This ensures sufficient surface area for good electrochemical performance while maintaining adequate particle strength to prevent degradation during cycling.
Data Source
AI summary
Disclosed is a lithium mixed metal oxide which is useful for a positive electrode active material that is capable of providing a nonaqueous electrolyte secondary battery having more excellent cycle characteristics, in particular, more excellent cycle characteristics during high-temperature operation at 60 DEG C or the like. Specifically disclosed is a lithium mixed metal oxide represented by the following formula (A). Lix(Mn1-y-zNiyFez)O2 (A) (In the formula, x is not less than 0.9 and not more than 1.3; y is 0.46 or more and less than 0.5; and z is 0 or more and less than 0.1.) Also disclosed are: a positive electrode active material which comprises the lithium mixed metal oxide; a positive electrode which comprises the positive electrode active material; and a nonaqueous electrolyte secondary battery which comprises the positive electrode.