Cathode Active Material Surface Modification for Low-Temperature Sintering
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Solution Overview
Problem
High-temperature sintering of lithium-containing composite oxide particles in oxide solid-state batteries often results in chemical reactions with the oxide solid electrolyte, forming high resistance layers, and the cathode active material may decompose if excessively deficient in lithium, leading to energy inefficiencies and reduced battery performance.
Innovation Solution
A cathode active material with a layered rock-salt crystalline phase that is partially deficient in lithium, particularly at the surface, and a cathode mixture including a lithium compound with a lower melting point than the cathode active material, allowing for low-temperature sintering without decomposition, is used. This involves acid-treating the cathode active material to create a surface with a higher lithium deficiency and mixing it with a lithium compound like lithium nitrate or lithium hydroxide to facilitate lithium diffusion and suppress chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature sintering is used to join cathode and oxide solid electrolyte layer, then joining strength is improved, but chemical reaction with electrolyte occurs forming high resistance layer
Solution Approach 1:
The invention changes the sintering temperature parameter from high temperature (800-880°C as in prior art) to low temperature (400-600°C), thereby achieving both adequate joining strength and suppression of harmful chemical reactions between the cathode and oxide solid electrolyte layer
Solution Approach 2:
The invention applies preliminary acid treatment to the cathode active material surface before sintering, which modifies the surface properties to enable low-temperature sintering and prevent chemical reactions with the electrolyte during the joining process
2Object-generated harmful factors
If sintering temperature is lowered to prevent chemical reaction, then harmful factors are reduced, but joining strength decreases
Solution Approach 1:
The invention changes the sintering temperature parameter to an optimized low range (400-600°C) that simultaneously achieves adequate joining strength while preventing chemical reactions, rather than simply reducing temperature without optimization
Solution Approach 2:
The acid treatment performed before sintering modifies the cathode surface to enhance sintering efficiency at lower temperatures, ensuring adequate joining strength is achieved even at 400-600°C where chemical reactions are suppressed
3Use of energy by moving object
If acid treatment is applied to lower sintering temperature, then energy efficiency is improved, but cathode decomposition may occur
Solution Approach 1:
The invention optimizes the acid treatment parameters (acid type, concentration, treatment time) to achieve the desired surface modification without excessive lithium removal, thereby enabling low-temperature sintering while maintaining cathode material stability and preventing decomposition
Solution Approach 2:
The acid treatment creates a localized modified layer on the cathode surface with different properties from the bulk material, allowing low-temperature sintering at the surface while maintaining the stability and composition of the interior cathode material
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 enables efficient sintering at lower temperatures, reducing the formation of high resistance layers and preventing cathode decomposition, thereby enhancing battery capacity and energy density while maintaining high lithium ion and electronic conductivity.
Implementation Method 1
mixing it with a lithium compound like lithium nitrate or lithium hydroxide to facilitate lithium diffusion
Implementation Method 2
sintering particles of such a composite oxide... heating the layers while pressurizing the layers
Implementation Method 3
it is effective to acid-treated cathode active material with a lithium compound whose melting point is lower than that of the cathode active material
Data Source
AI summary
Disclosed is a cathode active material that can lower sintering temperature, the cathode active mated al including a particle of a lithium containing composite oxide having a layered rock-salt crystalline phase, wherein the layered rock-salt crystalline phase is partially deficient in lithium, a percentage of deficient lithium in the layered rock-salt crystalline phase in a surface portion of the particle is higher than that in the layered rock-salt crystalline phase inside the particle, and the particle includes two phases that are different in lattice constant as the layered rock-salt crystalline phase.