Lanthanum-Modified Cathode Material for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face reduced battery capacity due to conductive oxides on the surface of cathode active materials not exhibiting lithium ion conductivity, hindering lithium ion transmission.
Innovation Solution
A method involving mixing transition metal-containing composite compound particles with lanthanum, followed by calcination and main firing processes to create a cathode active material with lanthanum compound particles dispersed on surfaces and in gaps, enhancing electron conductivity while maintaining lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive oxide is used to cover particle surfaces, then cathode resistance is reduced, but battery capacity decreases
Solution Approach 1:
The patent applies local quality by concentrating conductive oxide at specific locations (surfaces and grain boundaries) where electron conductivity is most needed, rather than uniformly distributing it throughout the particle structure. This localized approach reduces cathode resistance effectively while minimizing the blocking of lithium ion transmission pathways, thereby preserving battery capacity.
Solution Approach 2:
The patent introduces lithium compound as an intermediary substance that fills the gaps between primary particles. This intermediary material serves dual purposes: it maintains lithium ion transmission pathways that would otherwise be blocked by conductive oxide, and it allows the conductive oxide to perform its resistance-reducing function at the surfaces without sacrificing battery capacity.
2Stability of the object's composition
If high temperature firing is used to synthesize cathode active material, then crystallinity is improved, but particle aggregation increases
Solution Approach 1:
The patent applies preliminary action by performing a first firing treatment before the main sintering process. This preliminary firing initiates crystallization and forms the basic crystal structure at a lower temperature, reducing the degree of aggregation that would occur during subsequent high-temperature firing. This staged approach allows high crystallinity to be achieved while minimizing excessive particle aggregation.
Solution Approach 2:
The patent segments the firing process into two distinct stages: a first firing treatment and a main sintering process. This segmentation allows each stage to be optimized for its specific purpose - the first firing for initial crystallization with minimal aggregation, and the main sintering for achieving high crystallinity. The separation of these functions resolves the contradiction between crystallinity improvement and particle aggregation.
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
This approach improves electron conductivity and reduces cathode resistance without lowering discharge capacity, resulting in enhanced performance for lithium ion secondary batteries.
Implementation Method 1
lanthanum compound particles each having a perovskite-type structure are dispersed on surfaces of the secondary particles and/or in gaps or grain boundaries between the primary particles
Implementation Method 2
a calcination process of firing the lithium mixture at a temperature equal to or lower than the melting point of the lithium compound; and a main firing process of firing the lithium mixture at a temperature higher than the melting point of the lithium compound
Data Source
AI summary
The cathode active material is capable of reducing cathode resistance of a secondary battery by enhancing electron conductivity thereof without reducing discharge capacity of the secondary battery. The method for manufacturing a cathode active material includes: mixing transition metal-containing composite compound particles containing lanthanum with a lithium compound to obtain a lithium mixture; calcinating the lithium mixture at a temperature equal to or lower than the melting point of the lithium compound; and then subjecting the lithium mixture to main firing at a firing temperature within a range of 725° C. to 1000° C. Lithium carbonate is preferably used as the lithium compound, and in this case, the calcination temperature is within a range of 600° C. to 723° C. It is preferable to obtain the transition metal-containing composite compound particles containing lanthanum by a coprecipitation method and to uniformly disperse a lanthanum element in the particles.