Layered Rock-Salt Cathode Particles for High-Capacity Li-Ion Cells
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in increasing capacity per volume and weight, achieving high energy density, maintaining stable battery reactions at high potentials, preventing capacity degradation in charge and discharge cycles, and requiring high ionic and electrical conductivity, while also being cost-effective.
Innovation Solution
A lithium-manganese composite oxide particle with distinct regions, including a first region with a layered rock-salt structure and a second region with a different crystal structure, optionally with a spinel structure, is used as a positive electrode active material, coated with a carbon layer to enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-ion secondary battery uses conventional positive electrode active materials, then the battery structure is simple and manufacturing is easy, but the capacity per volume and weight is limited
Solution Approach 1:
The positive electrode active material is divided into multiple regions with different crystal structures: a first region with layered rock-salt structure and a second region with spinel structure. This segmentation allows each region to contribute differently to battery performance, increasing capacity per volume and weight while managing structural complexity through functional differentiation.
Solution Approach 2:
The patent employs a composite material consisting of lithium-manganese composite oxide with multiple crystal structures within the same particle. The combination of layered rock-salt structure (providing high capacity) and spinel structure (providing stability and conductivity) creates a composite active material that achieves high capacity per volume and weight while maintaining manufacturability.
2Use of energy by moving object
If the positive electrode active material operates at high potential to increase energy density, then the energy density increases, but the battery reaction becomes unstable and capacity degrades in charge and discharge cycles
Solution Approach 1:
Different regions of the active material particle are assigned different crystal structures with specific local qualities: the layered rock-salt structure region provides high capacity for energy density, while the spinel structure region provides structural stability and electrochemical stability. This local quality differentiation allows the material to operate at high potential while maintaining reaction stability during charge and discharge cycles.
Solution Approach 2:
The spinel structure region acts as a stabilizing framework that prevents structural degradation before it occurs during cycling. The spinel phase, being inherently more stable, provides a cushioning effect that protects the high-capacity layered rock-salt regions from degradation, ensuring long-term battery reaction stability at high potentials.
3Productivity
If the positive electrode active material requires high ionic conductivity and electrical conductivity for optimal performance, then the battery efficiency improves, but the manufacturing cost increases
Solution Approach 1:
The patent achieves high ionic conductivity and electrical conductivity by optimizing the composition parameters of the lithium-manganese composite oxide, specifically controlling the ratio of lithium to (manganese + element M) to be 0.95 or more. This parameter optimization enables the material to inherently provide high conductivity without requiring expensive additional conductive additives or complex manufacturing processes, thus improving battery efficiency while maintaining cost-effectiveness.
Data Source
AI summary
To increase capacity per weight of a power storage device, a particle includes a first region, a second region in contact with at least part of a surface of the first region and located on the outside of the first region, and a third region in contact with at least part of a surface of the second region and located on the outside of the second region. The first and the second regions contain lithium and oxygen. At least one of the first region and the second region contains manganese. At least one of the first and the second regions contains an element M. The first region contains a first crystal having a layered rock-salt structure. The second region contains a second crystal having a layered rock-salt structure. An orientation of the first crystal is different from an orientation of the second crystal.