Amorphous-Coated Spinel Cathode for Low-Resistance Solid-State Batteries
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Solution Overview
Problem
The interfacial resistance between the 5 V-class positive electrode active substance and the solid electrolyte in all solid-state lithium secondary batteries is high, leading to poor rate and cycle characteristics, despite the use of lithium ion-conducting oxide layers like LiNbO3.
Innovation Solution
A positive electrode active substance composed of spinel-type composite oxide particles coated with an amorphous compound containing Li, A (A represents Ti, Zr, Ta, Nb, Zn, W, or Al) is used, with specific particle size and coating characteristics to reduce contact resistance and enhance ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as the positive electrode active substance to achieve high output, then the battery capacity increases, but structural stability deteriorates and safety issues arise
Solution Approach 1:
The patent uses LiCoO2 as the core material combined with LiMn2O4 as a shell layer, creating a composite structure that leverages the high capacity of LiCoO2 while the LiMn2O4 shell provides structural stability and safety, preventing the deterioration issues of pure LiCoO2
Solution Approach 2:
The patent applies different materials to different regions of the positive electrode: LiCoO2 in the core for high capacity and LiMn2O4 in the outer shell for stability. This spatial differentiation of material properties allows each region to perform its specialized function, resolving the contradiction between capacity and stability
2Reliability
If LiMn2O4 is used as the positive electrode active substance to improve safety and structural stability, then reliability increases, but output and battery capacity deteriorate
Solution Approach 1:
The composite structure combines LiMn2O4 shell (providing stability) with LiCoO2 core (providing high capacity), allowing the system to achieve both safety and high output simultaneously by integrating the advantages of both materials
Solution Approach 2:
The patent merges two different positive electrode active substances (LiMn2O4 and LiCoO2) into a single composite structure, combining the safety advantages of LiMn2O4 with the high capacity advantages of LiCoO2 to achieve both reliability and high output
3Reliability
If a coating layer is formed on the positive electrode to improve safety, then reliability increases, but manufacturing complexity increases
Solution Approach 1:
Instead of forming a separate coating layer on an existing electrode, the patent creates a composite positive electrode active substance where LiMn2O4 forms an integral shell around LiCoO2 particles during the sintering process, achieving safety improvement while minimizing manufacturing complexity by combining material synthesis into a single step
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 solution effectively reduces interfacial resistance, maintains high operating voltage during discharge, and improves rate and cycle characteristics of the battery.
Implementation Method 1
all solid-state lithium secondary battery which uses a lithium ion diffusion-type positive electrode active substance
Implementation Method 2
a lithium ion diffusion-type positive electrode active substance for all solid-state lithium secondary batteries
Data Source
Figure 1~2
AI summary
Provided is, with respect to a 5 V-class spinel, a spinel-type lithium manganese-containing composite oxide that can improve rate characteristics and cycle characteristics by suppressing resistance while improving ion conductivity. Proposed is a positive electrode active substance for an all solid-state lithium secondary battery having an operating potential of 4.5 V or more at a metal Li reference potential, wherein the surface of the present core particles composed of a spinel-type lithium manganese-containing composite oxide containing at least Li, Mn, O, and two or more elements other than these is coated with an amorphous compound containing Li, A (A represents one element or a combination of two or more elements selected from the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al), and O; and primary particles of the present core particles are composed of a polycrystal; and wherein the D50 is 0.5 to 9 µm, the value of ((|mode diameter - D50|/mode diameter) × 100) is 0 to 25%, the value of ((|mode diameter - D10|/mode diameter) × 100) is 20 to 58%, and the value of the average primary particle diameter/D50 is 0.20 to 0.99.