Mn Composite Oxide Positive Electrode for High-Rate Lithium Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity and improved charge-discharge cycle life, particularly due to low ionic and electronic conductivity of existing positive electrode materials, which limits their performance at high charge-discharge rates and temperatures.
Innovation Solution
A positive electrode comprising a Mn composite oxide with a tetragonal structure and a composite oxide with a layered structure, specifically designed to compensate for irreversible capacity and enhance cycle characteristics, is used. The Mn composite oxide is represented by Lia(MxMn2-x-yYy)(O4-wZw) and the composite oxide by Li(LixM1-x-yYy)O2, where M includes Co, Ni, Fe, and Mn, and Y includes Li, B, Na, Mg, Al, Ti, and Zn, allowing for efficient lithium compensation and improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li rich layered compounds are used as positive electrode active materials to achieve high energy density and high charge termination voltage (4.8 V), then capacity of 200 mAh/g or more can be obtained under high temperature (45°C) or low charge-discharge rate (0.025 C), but capacity is little exhibited under high charge-discharge rate (1 C or more) at 20°C due to low ionic conductivity and electronic conductivity
Solution Approach 1:
The patent uses a composite material system consisting of Li rich layered compound particles combined with spinel structure particles (LiMn2O4 or LiNi0.5Mn1.5O4). The spinel component provides high ionic and electronic conductivity to compensate for the conductivity deficiencies of the Li rich layered compound, enabling the composite to deliver high capacity (200 mAh/g or more) even at high charge-discharge rates (1 C or more) at 20°C, while maintaining the high energy density benefits of the Li rich layered compound
2Reliability
If spinel structure materials such as LiMn2O4 or LiNi0.5Mn1.5O4 are used as positive electrode active materials to achieve high ionic conductivity and wide temperature range performance, then energy density of 90% or more can be obtained even at low temperature (−20°C), but initial charge capacity is smaller than that of layered structure materials
Solution Approach 1:
The patent merges Li rich layered compound particles (providing high initial charge capacity of 200 mAh/g or more) with spinel structure particles (providing high ionic conductivity and wide temperature performance). The resulting composite material combines the advantages of both structures, achieving high capacity that can be effectively utilized across a wide temperature range including low temperatures (−20°C), while the spinel component ensures high rate capability
Data Source
AI summary
The present invention relates to a positive electrode comprising a Mn composite oxide having a tetragonal structure represented by formula (1): Lia(MxMn2-x-yYy)(O4-wZw)(wherein 1<a≤2.6, 0≤x≤1.2, 0≤y, x+y<2, 0≤w≤1; M is at least one selected from the group consisting of Co, Ni, Fe, Cr and Cu; Y is at least one selected from the group consisting of Li, B, Na, Mg, Al, Ti, Si, K and Ca; Z is at least one of F or Cl; and a composite oxide having a layered structure represented by formula (2): Li(LixM1-x-yYy)O2 (wherein 0≤x<0.3, 0≤y<0.3; M is at least one selected from the group consisting of Co, Fe, Ni and Mn; Y is at least one selected from the group consisting of Mg, Al, Zr, Ti and Zn. According to the present invention, a lithium secondary battery having a high capacity and being excellent in cycle life can be provided.