Core-Shell Positive Electrode Material for Battery Rate Capability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high output and long life characteristics due to the limitations of large particle-sized active materials, which have a low surface area, leading to reduced rate capability and initial capacity.
Innovation Solution
A positive electrode active material with a core-shell structure, featuring a lithium nickel manganese cobalt-based composite metal oxide with a buffer layer that includes pores and a three-dimensional network structure, where the concentration of nickel, cobalt, and manganese gradually changes across the material, enhancing reactivity with the electrolyte and facilitating lithium ion intercalation and deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If large particle size active material is used to increase packing density and energy per unit volume, then packing density is improved, but surface area decreases leading to reduced rate capability and initial capacity
Solution Approach 1:
The active material is divided into multiple particles with sizes of 3 μm to 20 μm, creating a distribution of particle sizes that increases overall surface area while maintaining high packing density. The segmented structure allows more particles to contact the electrolyte simultaneously, improving rate capability without sacrificing energy density
Solution Approach 2:
The surface of each particle is modified with a coating layer containing lithium phosphate and/or lithium pyrophosphate, creating a localized region with enhanced properties. This coating improves surface area utilization and electrochemical activity at the particle-electrolyte interface, directly addressing the rate capability issue while preserving the bulk particle's energy storage capacity
2Use of energy by moving object
If large particle size active material is used to increase packing density, then energy per unit volume is improved, but active area in contact with electrolyte solution decreases
Solution Approach 1:
By segmenting the active material into multiple smaller particles (3-20 μm), the total surface area increases significantly, creating more active contact areas with the electrolyte. This segmentation maintains high energy per unit volume through efficient packing while providing sufficient active area for electrochemical reactions
Solution Approach 2:
The coating layer contains lithium phosphate and lithium pyrophosphate compounds that create a porous or highly textured surface structure. This increases the effective active area available for electrolyte contact and lithium ion insertion/extraction, enhancing both energy utilization and rate capability
3Quantity of substance
If large particle size active material is used, then packing density is improved, but kinetics are negatively affected resulting in low rate capability
Solution Approach 1:
Segmenting the active material into particles of 3-20 μm reduces the diffusion distance for lithium ions within each particle, significantly improving kinetics. The segmented structure allows faster lithium ion transport while maintaining high packing density through optimized particle size distribution
Solution Approach 2:
The surface coating of lithium phosphate and lithium pyrophosphate creates a conductive pathway and reduces interfacial resistance at the particle surface. This local modification enhances electron and ion transport kinetics without affecting the bulk composition, directly improving rate capability while preserving packing density
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 solution minimizes material destruction during electrode preparation, maximizes reactivity with the electrolyte, and improves output and life characteristics of the battery, making it suitable for high-capacity and long-lifetime applications such as automotive batteries.
Implementation Method 1
a buffer layer which is disposed between the core and the shell and includes pores and a three-dimensional network structure connecting the core and the shell
Data Source
AI summary
The present invention provides a method of preparing a positive electrode active material for a secondary battery including preparing a first transition metal-containing solution including a nickel raw material, a cobalt raw material, and a manganese raw material and a second transition metal-containing solution including a nickel raw material, a cobalt raw material, and a manganese raw material in a concentration different from that of the first transition metal-containing solution; preparing a reaction solution, in which nickel manganese cobalt-based composite metal hydroxide particles are formed, by adding an ammonium cation-containing complexing agent and a basic compound as well as the second transition metal-containing solution to the first transition metal-containing solution and performing a co-precipitation reaction in a pH range of 11 to 13.