Cathode Active Material Composite With Diffused Ion-Conductor Interface
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Solution Overview
Problem
All solid-state batteries face high internal resistance and inadequate charge-discharge capacity at room temperature due to insufficient interface formation between the positive electrode active material and the solid electrolyte, leading to limited charge transfer and ion availability during high-rate charging and discharging.
Innovation Solution
A positive electrode active material composite body is developed, comprising a transition metal element with a particulate shape and an ion conductor containing Li, Zr, and at least one of Nb, Sb, or Ta, where the transition metal element is partially diffused into the ion conductor, with a specific average content ratio gradient to enhance adhesion and charge transfer at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interface formation techniques are used to decrease charge transfer resistance between solid electrolyte and positive electrode active material, then charge transfer efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming a coating layer on the positive electrode active material particles before assembly. This coating layer, containing lithium ion conductive inorganic solid electrolyte particles and electric conductive agent particles bound together, is prepared in advance to ensure proper interface formation and prevent lithium ion deficiency at the interface during charge transfer operations.
Solution Approach 2:
The patent employs composite materials by creating a coating layer that combines lithium ion conductive inorganic solid electrolyte particles with electric conductive agent particles. This composite structure simultaneously provides both ionic conductivity for lithium ion transport and electronic conductivity for charge transfer, resolving the contradiction between charge transfer efficiency and manufacturing complexity.
2Reliability
If molding methods are used to decrease resistance by making the positive electrode composite material thin, then internal resistance decreases, but charge transfer capacity is limited
Solution Approach 1:
The patent applies local quality by creating a specialized coating layer with specific properties (lithium ion conductivity and electric conductivity) only at the interface region between the positive electrode active material and solid electrolyte. This localized enhancement of interfacial properties improves charge transfer efficiency without requiring the entire material to be thin, thus maintaining charge transfer capacity while reducing internal resistance.
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 significantly reduces internal resistance and improves charge-discharge characteristics, enabling better performance at room temperature by optimizing the interface between the positive electrode active material and the solid electrolyte, thus enhancing the battery's energy density and output performance.
Implementation Method 1
the transition metal element is partially diffused in the ion conductor, and an average decrease ratio of a content ratio of the transition metal element until a point where the content ratio of the transition metal element in the ion conductor to be determined by a characteristic X-ray has reached 12% of the content ratio of the transition metal element at an interface between the positive electrode active material and the ion conductor based on a substance amount is 0.5% or more and 6.1% or less per 1 nm thickness from the interface
Data Source
AI summary
A positive electrode active material composite body according to the present disclosure includes a positive electrode active material containing a transition metal element and having a particulate shape, and an ion conductor provided in contact with a surface of the positive electrode active material, wherein the ion conductor is constituted by a material containing Li, Zr, and M which is at least one type of element selected from the group consisting of Nb, Sb, and Ta, the transition metal element is partially diffused in the ion conductor, and an average decrease ratio of a content ratio of the transition metal element until a point where the content ratio of the transition metal element in the ion conductor to be determined by a characteristic X-ray has reached 12% of the content ratio of the transition metal element at an interface between the positive electrode active material and the ion conductor based on a substance amount is 0.5% or more and 6.1% or less per 1 nm thickness from the interface.