Method for evaluating a characteristic of a nonaqueous electrolyte secondary battery positive electrode active material
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Solution Overview
Problem
Conventional techniques for non-aqueous electrolyte secondary batteries face challenges in achieving high output characteristics while preventing gelation during paste preparation, due to issues with lithium elution and crystallinity of the positive electrode active material.
Innovation Solution
A lithium-metal composite oxide powder with a specific particle size and structure is used, formed by pulverizing lithium compounds and mixing with metal composite hydroxides, followed by a controlled firing process to maintain reactivity and prevent excessive lithium elution, resulting in a positive electrode active material with improved output characteristics at low temperatures without water washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water washing is performed on lithium-metal composite oxide to remove excessive lithium, then initial discharge capacity and thermal stability are improved, but the surface is damaged and required lithium is eluted deteriorating output characteristic
Solution Approach 1:
The patent extracts and removes excessive lithium from the surface of lithium-metal composite oxide particles through controlled water washing, separating the harmful excessive lithium while preserving the required lithium in the crystal structure. This resolves the contradiction by selectively removing only the unwanted component without damaging the functional structure.
Solution Approach 2:
The patent applies different treatments to different parts of the material: the surface undergoes controlled water washing to remove excessive lithium, while the internal crystal structure maintains its required lithium content. This local differentiation allows simultaneous improvement of thermal stability (surface) and output characteristic (internal structure).
2Power
If fine particles are used as positive electrode active material to increase specific surface area, then output characteristic is improved, but large amount of conductive agent is required reducing energy density
Solution Approach 1:
The patent creates a porous structure on the surface of the lithium-metal composite oxide particles, increasing the specific surface area and reaction sites for improved output characteristic. The porous structure provides high surface area without requiring excessive conductive agents, as the porosity itself enhances electrolyte access and reaction efficiency.
Solution Approach 2:
The patent changes the surface morphology parameter from smooth to porous, fundamentally altering how the material interacts with electrolyte and conductive agents. This parameter change increases effective surface area and reaction sites while reducing the absolute amount of conductive agent needed.
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 approach enhances the high output characteristics of lithium-ion secondary batteries at low temperatures, suppresses soluble lithium generation, and prevents gelation during paste preparation, leading to improved industrial applicability for energy storage devices.
Implementation Method 1
the active materials of the positive electrode and the negative electrode include a material in which lithium extraction/insertion is possible
Implementation Method 2
By using such fine particles as the positive electrode active material powder, it is possible to increase the specific surface area corresponding to the reaction area with the electrolyte solution
Implementation Method 3
a positive electrode active material having a surface with a porous structure and a specific surface area of 1,800 to 2,500 [m2/g], and being subjected to a thermal treatment at a temperature of 700 [° C.] or less
Data Source
AI summary
The present invention provides a method of evaluating a characteristic of a positive electrode active material for non-aqueous electrolyte secondary batteries, including a lithium-metal composite oxide powder including a secondary particle configured by aggregating primary particles containing lithium, nickel, manganese, and cobalt, or a lithium-metal composite oxide powder including both the primary particles and the secondary particle. The secondary particle has a porous internal structure. The characteristic being evaluated is a slurry pH, a soluble lithium content rate, or a porosity.