Positive electrode active material and all-solid-state secondary battery comprising same
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Solution Overview
Problem
The pressing process in lithium secondary battery manufacturing, particularly in all-solid-state secondary batteries, causes particle breakage due to high pressure, leading to deterioration of battery characteristics, as the solid electrolyte requires stronger interfacial contact, exacerbating the issue of particle breakage.
Innovation Solution
A cathode active material is developed that satisfies specific conditions in particle size and volume distribution before and after pressing, defined by Equations 1, 2, and 3, to minimize particle breakage and maintain high particle strength, using a secondary particle structure or non-aggregated one-body particle structure, and adjusting synthesis conditions like pH and doping with elements like Al or Ti.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure is applied during pressing to improve interfacial contact in all-solid-state secondary batteries, then interfacial contact is improved, but particle breakage increases
Solution Approach 1:
The patent changes the physical-chemical parameters of the cathode active material particles, specifically controlling particle size distribution (D10-D90 range of 7-15 μm) and morphology, to enhance particle strength and resistance against breakage during the pressing process while maintaining effective interfacial contact
2Quantity of substance
If pressing is performed to improve energy density, then energy density is improved, but particle breakage increases
Solution Approach 1:
The patent optimizes particle size distribution parameters (D10-D90 of 7-15 μm) and particle morphology to achieve a balance between energy density and particle strength, allowing effective pressing without excessive breakage
Solution Approach 2:
The patent employs composite particle structures with specific compositions including Li-rich layered oxides and doping elements (Al, Ti, Zr, Nb, Ta) to create particles with enhanced mechanical strength that can withstand pressing while maintaining high energy density
3Reliability
If particle size is reduced to improve battery characteristics, then battery characteristics are improved, but particles become more susceptible to breakage
Solution Approach 1:
The patent identifies and controls critical particle size parameters (D10-D90 distribution in 7-15 μm range) to achieve optimal balance between battery performance and particle strength, preventing excessive breakage while maintaining good electrochemical characteristics
Data Source
AI summary
Disclosed is a cathode active material for an all-solid-state secondary battery, wherein, when comparing volume versus particle size distribution (PSD) graphs before and after pressing under the following pressing condition, the condition of the following Equation 1 is satisfied at point A corresponding to a diameter of particles having a maximum occupied volume before pressing on an X-axis of the graph.Z=(volume % of particles at point A after pressing/volume % of particles at point A before pressing)×100[Equation 1]Z≥70% [Pressing condition]The active material is pressed at 4.5 tons per unit area (cm2).