Multiphase Positive Electrode Material for Higher Li-Ion Capacity
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Solution Overview
Problem
Existing lithium-ion batteries face limitations in capacity due to the use of single-phase crystal structures, which either compromise cycle characteristics, rate performance, or capacity, as each structure type has inherent drawbacks such as low Li content, diffusibility, or stability.
Innovation Solution
A lithium composite oxide active material comprising a multiphase mixture with crystal structures belonging to monoclinic, hexagonal, and cubic phases, enhancing capacity through synergistic effects, increased Li insertion and release, and improved diffusibility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-phase crystal structure is used in lithium-ion batteries, then the manufacturing process is simple, but the battery capacity is limited due to inherent drawbacks of each structure type
Solution Approach 1:
The patent applies composite materials by creating a multiphase mixture containing monoclinic phase (C2/m space group), hexagonal phase (R-3m space group), and cubic phase (Fm-3m or Fd-3m space group) in specific proportions. This composite structure combines the advantages of each phase: monoclinic phase provides high Li content, hexagonal phase ensures good diffusibility, and cubic phase offers high stability, thereby achieving high battery capacity while maintaining manufacturing feasibility through controlled synthesis processes
2Quantity of substance
If a monoclinic crystal structure is used, then the Li content is high, but the cycle characteristics deteriorate
Solution Approach 1:
The patent applies local quality by distributing different crystal phases in specific proportions within the composite material. The monoclinic phase (C2/m) comprising 10-50 mass% provides high Li content locally, while the cubic phase (Fm-3m or Fd-3m) comprising 10-50 mass% provides high stability locally. This spatial distribution of different phase qualities allows the material to simultaneously achieve high Li content and good cycle characteristics
3Speed
If a hexagonal crystal structure is used, then the diffusibility is good, but the capacity is reduced
Solution Approach 1:
The patent merges multiple crystal phases into a composite structure where the hexagonal phase (R-3m) comprising 10-50 mass% provides good Li diffusibility, while the monoclinic phase (C2/m) comprising 10-50 mass% contributes high Li content. The synergistic combination of these phases allows the material to achieve both high diffusibility and high capacity, overcoming the limitations of using hexagonal phase alone
4Stability of the object's composition
If a cubic crystal structure is used, then the stability is high, but the Li insertion and release is limited
Solution Approach 1:
The patent applies local quality by incorporating cubic phase (Fm-3m or Fd-3m) comprising 10-50 mass% into the composite structure, where this phase provides high structural stability locally. Simultaneously, the monoclinic phase (C2/m) comprising 10-50 mass% provides high Li content and good Li insertion/release capability locally. This phase distribution strategy allows the material to achieve both high stability and high Li insertion/release performance
Data Source
AI summary
A positive electrode active material according to the present disclosure includes a lithium composite oxide that is a multiphase mixture including a first phase having a crystal structure belonging to a monoclinic crystal (e.g., space group C2/m), a second phase having a crystal structure belonging to a hexagonal crystal (e.g., space group R-3m), and a third phase having a crystal structure belonging to a cubic crystal (e.g., space group Fm-3m or space group Fd-3m). In addition, a battery according to an aspect of the present disclosure includes a positive electrode containing the positive electrode active material, a negative electrode, and an electrolyte. The positive electrode active material according to the present disclosure improves the capacity of the battery.