Layered Cathode Coating for Sulfide Solid-State Battery Interfaces
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Solution Overview
Problem
Existing positive electrode active materials for all-solid lithium ion batteries suffer from high resistance and insufficient output characteristics due to the presence of carbon oxides and hydroxides in the coated layer, which also reduces the effectiveness of suppressing the reaction with sulfide-based solid electrolytes.
Innovation Solution
A positive electrode active material is developed with a core composition of Li a Ni b Co c M d O 2, where M is selected from Mn, V, Mg, Ti, and Al, coated with a layer of lithium niobate followed by a layer of elemental carbon. This structure suppresses the formation of high-resistivity layers and enhances electron conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coated layer containing carbon (including oxides and hydroxides) is used to cover the positive electrode active material, then the surface is protected, but the resistance increases and output characteristics deteriorate
Solution Approach 1:
The coated layer is segmented into two distinct functional layers: an inner layer containing lithium niobate and the positive electrode active material, and an outer layer containing carbon. This segmentation allows the inner layer to provide protection while the outer layer provides conductivity, resolving the contradiction between protection and power output.
Solution Approach 2:
Different regions of the coated layer are assigned different compositions and functions: the inner layer near the positive electrode active material surface contains lithium niobate for protection and interface stability, while the outer layer contains carbon for electron conductivity. This local quality differentiation allows simultaneous achievement of protection and high power characteristics.
2Reliability
If a coated layer containing carbon is used to cover the positive electrode active material, then the surface is protected, but the reaction suppression with sulfide-based solid electrolyte is reduced
Solution Approach 1:
The coated layer is divided into an inner layer and an outer layer, where the inner layer contains lithium niobate that directly contacts the positive electrode active material and sulfide-based solid electrolyte interface. This segmentation places the reaction-suppressing function in the inner layer while allowing carbon in the outer layer to provide conductivity without interfering with interface stability.
Solution Approach 2:
Lithium niobate acts as an intermediary substance between the positive electrode active material and the sulfide-based solid electrolyte. The inner layer containing lithium niobate mediates the interface interaction, suppressing harmful reactions while the outer carbon layer provides electrical conductivity.
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 proposed solution effectively reduces the resistance and improves the output characteristics of all-solid lithium ion batteries by suppressing the formation of high-resistivity layers and enhancing both ionic and electronic conductivity at the interface with the solid electrolyte.
Implementation Method 1
suppresses the formation of high-resistivity layers at an interface with a sulfide-based solid electrolyte
Implementation Method 2
enhances both ionic and electronic conductivity at the interface with the solid electrolyte
Implementation Method 3
enhances both ionic and electronic conductivity at the interface with the solid electrolyte
Data Source
AI summary
Provided are a positive electrode active material for all-solid lithium ion batteries, which suppresses generation of ahigh-resistivity layer at an interface with a sulfide-based solid electrolyte, has improved electron conductivity, and exhibits good output characteristics when applied to all-solid lithium ion batteries; a positive electrode for all-solid lithium ion batteries using the same; an all-solid lithium ion battery; and a method for producing a positive electrode active material for all-solid lithium ion batteries. A positive electrode active material for all-solid lithium ion batteries includes: a core positive electrode active material having a composition represented by the following formula: LiaNibCocMdO2 in which M is at least one element selected from Mn, V, Mg, Ti and Al, 1.00 ≤ a ≤ 1.02, 0.8 ≤ b ≤ 0.9, and b + c + d = 1; and a coated portion formed on a surface of the core positive electrode active material, wherein the coated portion comprises a layer of lithium niobate and a carbon layer in this order, from the surface of the core positive electrode active material.