Hollow Cathode Active Material for Power-Cycle Battery Trade-Off
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Solution Overview
Problem
Existing nickel-containing positive electrode active materials, such as lithium nickel cobalt manganese oxide ternary materials, face a trade-off between improved power performance and cycling stability, where enhancing power performance often compromises cycling performance, and vice versa.
Innovation Solution
A positive electrode active material with hollow secondary particles and specific elements M and A distributed at grain boundaries, along with controlled residual alkali content, to enhance bonding strength and ion transport, thereby stabilizing the structure and improving both power and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nickel-containing positive electrode active materials are used to improve power performance, then power performance is improved, but cycling performance deteriorates
Solution Approach 1:
The patent applies local quality by creating hollow secondary particles with specific structural characteristics. The hollow structure is formed by controlling the aggregation of primary particles, creating a core-shell like structure where the hollow cavity provides space for volume expansion while the outer shell maintains structural integrity. This local structural modification allows the material to achieve both high power performance through improved ion transport and good cycling stability through structural reinforcement.
Solution Approach 2:
The patent employs composite material strategy by combining multiple elements (Li, Ni, Co, Mn, Al, B) in a specific composition ratio within the hollow secondary particle structure. The composite nature of the material, with different elements serving specific functions (Ni for capacity, Co for stability, Mn for safety, Al and B for surface modification), enables simultaneous improvement of power performance and cycling performance that cannot be achieved with single-element materials.
2Power
If the internal resistance is reduced to improve power performance, then ion transmission is accelerated, but structural stability may be compromised
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material into primary particles that aggregate to form hollow secondary particles. This segmented structure creates multiple internal pathways for ion transmission, reducing internal resistance and accelerating ion transport. Simultaneously, the segmented structure allows each primary particle to maintain its structural integrity independently, preventing catastrophic failure and enhancing overall structural stability during cycling.
Solution Approach 2:
The patent utilizes porous material strategy by creating hollow secondary particles with internal cavities and a porous structure formed by primary particle aggregation. This porous architecture provides numerous channels for rapid ion diffusion, significantly reducing internal resistance and improving power performance. At the same time, the porous structure maintains sufficient mechanical strength through the interconnected framework of primary particles, ensuring structural stability during repeated charging and discharging cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed material achieves improved power performance by reducing internal resistance and accelerating ion transmission, while maintaining cycling stability by stabilizing the crystal structure and reducing particle cracking, thus enhancing overall battery performance.
Implementation Method 1
shortening the lithium ion diffusion path, and accelerating the transmission of ions inside the particles
Implementation Method 2
stabilize the crystal structure of the primary particles, improve the bonding strength between the primary particles
Implementation Method 3
the element M mainly distributed at the grain boundaries can better coordinate with residual alkali of the positive electrode active material, which is conducive to strengthening the bonding strength of element M to the grain boundaries, thereby further stabilizing the structure
Data Source
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AI summary
A positive electrode active material and a preparation method therefor, a positive electrode sheet, a secondary battery, and an electric device, wherein the positive electrode active material comprises hollow secondary particles, the hollow secondary particles comprising LiaNixCoyMnzAqMpOb, 0.2≤a≤1.2, 1.8≤b≤2, 0.3≤x≤0.6, 0≤y≤0.4, 0<z≤0.4, 0≤q≤0.02, and 0<p≤0.02, the atomic percentage of element M at grain boundaries being greater than or equal to the atomic percentage of element M in bulk phase parts of primary particles, and element A being distributed in the hollow secondary particles in the form of bulk phase doping. The positive electrode active material comprises the hollow secondary particles, element M is mainly distributed at the grain boundary of the hollow secondary particles, and element A can be optionally doped, thereby keeping good cycle performance while effectively improving the power performance.