Core-Shell Positive Electrode Active Material for Lithium Batteries
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Solution Overview
Problem
Current lithium secondary batteries face challenges in achieving high energy density and long cycle life due to limitations in the design and composition of positive electrode active materials, particularly in providing efficient charge/discharge performance and thermal safety.
Innovation Solution
The development of a positive electrode active material comprising secondary particles with a core-shell structure, where primary particles have a rod shape with a concentration gradient in the seed element and constant concentration in the maintain element, enhancing the flow channel for metal ions and electrolyte, thereby improving charge/discharge efficiency and thermal safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional positive electrode active material is used, then the battery can operate, but the energy density and cycle life are insufficient
Solution Approach 1:
The positive electrode active material is divided into primary particles that aggregate to form secondary particles. Each primary particle has a specific composition ratio that optimizes both capacity and stability, while the secondary particle structure provides mechanical integrity and facilitates ion transport, thereby achieving high energy density and long cycle life simultaneously
Solution Approach 2:
The invention specifies different composition ratios for different regions within the primary particles. By controlling the local composition (Ni:Co:Mn ratio) within specific ranges, the material achieves optimal balance between high capacity (from Ni-rich regions) and structural stability (from Co and Mn), resolving the contradiction between energy density and cycle life
2Power
If the charge/discharge rate is increased to improve power output, then the power increases, but the thermal safety deteriorates
Solution Approach 1:
The invention optimizes the composition parameters (Ni:Co:Mn ratio within specific ranges) of the positive electrode active material to reduce heat generation during high-rate charge/discharge. By adjusting these compositional parameters, the material achieves lower resistance and reduced thermal runaway risk, enabling high power output with maintained thermal safety
Data Source
Figure 1~2
Figure 3
Figure 4~5a
AI summary
Positive electrode active materials are provided. The positive electrode active materials includes a primary particle formed of a plurality of metals including a first metal and a secondary particle formed of at least one of the primary particle. The secondary particle (E2) includes a core part (210), a shell part (220), a seed region (310) where the primary particle having concentration gradient of the first metal is disposed and a maintain region (330) where the primary particle having constant concentration of the first metal is disposed, the seed region adjacent to the core part and a maintain region adjacent to the shell part, and length of the seed region in a direction (230) from the core part to the shell part is 1 µm.