Coated High-Ni Cathode Material for Solid-State Battery Interfaces
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Solution Overview
Problem
The use of positive electrode active materials with high Ni ratios in all-solid-state lithium ion secondary batteries does not achieve the expected energy density or battery capacity due to interfacial reactions with solid electrolytes, leading to increased resistance and reduced performance.
Innovation Solution
A lithium-nickel composite oxide particle with a specific crystal structure and a coating layer composed of certain elements is used, along with a manufacturing process that includes mixing, firing, and coating steps to form a composite oxide layer on the particle surface, enhancing battery capacity and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfide solid electrolyte is used to achieve high lithium ion conductivity, then lithium ion conductivity is improved, but a high resistance phase is generated at the interface with the positive electrode active material due to interfacial reactions
Solution Approach 1:
A coating layer comprising LiNbO3 and a lithium phosphate glass layer is introduced as an intermediary between the sulfide solid electrolyte and the positive electrode active material. This intermediate structure prevents direct contact and interfacial reactions while maintaining lithium ion conductivity, thereby resolving the contradiction between achieving high conductivity and preventing harmful interfacial resistance.
Solution Approach 2:
The patent employs a composite coating structure combining LiNbO3 (an oxide with stable crystal structure) and lithium phosphate glass (a glassy material with high ionic conductivity). This composite approach leverages the advantages of both materials: LiNbO3 provides structural stability and reaction barrier, while the lithium phosphate glass layer ensures high lithium ion conductivity at the interface.
2Object-affected harmful factors
If a coating layer made of LiNbO3 is formed to prevent contact between solid electrolyte and positive electrode active material, then interfacial reactions are suppressed, but lithium ion conductivity may be reduced due to the coating layer
Solution Approach 1:
The patent combines LiNbO3 coating with a lithium phosphate glass layer to create a composite structure where LiNbO3 provides reaction suppression and the lithium phosphate glass layer compensates for potential conductivity loss by providing high ionic conductivity pathways at the interface.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of the coating layers. By controlling the thickness of LiNbO3 and lithium phosphate glass layers within specific ranges, and adjusting the composition of the positive electrode active material (including adding Nb element), the patent achieves a balance between preventing interfacial reactions and maintaining high lithium ion conductivity.
3Quantity of substance
If a positive electrode active material with high Ni ratio is used to increase energy density, then charge and discharge capacity is improved, but interfacial reactions with solid electrolyte increase leading to higher resistance
Solution Approach 1:
The dual-layer coating structure (LiNbO3 + lithium phosphate glass) acts as a protective intermediary that allows high Ni ratio materials to be used without suffering from severe interfacial reactions. The coating prevents direct contact between the reactive high-Ni material and the sulfide solid electrolyte, enabling the high capacity material to function at its full potential.
Solution Approach 2:
The patent modifies the composition parameters of the positive electrode active material by adding Nb element and optimizing the Ni ratio within specific ranges. Combined with optimized coating layer thickness and composition, this allows achieving high energy density while suppressing interfacial resistance through parameter optimization.
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 improves battery capacity and manufacturing efficiency by reducing interfacial resistance and optimizing the interaction between the positive electrode active material and solid electrolyte, resulting in higher energy density and better performance.
Implementation Method 1
forming a coating layer made of LiNbO3 on a surface of a positive electrode active material (oxide) in order to prevent contact between a solid electrolyte and the positive electrode active material to suppress generation of a high resistance phase
Implementation Method 2
a lithium-nickel composite oxide particle... in which the lithium-nickel composite oxide particle has a crystal structure belonging to a space group R-3m, contains at least Li, Ni, an element M, and Nb
Data Source
AI summary
A positive electrode active material includes a lithium-nickel composite oxide particle and a coating layer. The particle has a crystal structure belonging to a space group R-3m, contains at least Li, Ni, an element M, and Nb, wherein Li:Ni:M:Nb=a:(1-x-y):x:y (0.98≤a≤1.15, 0<x≤0.5, 0<y≤0.03, 0<x+y≤0.5, and the element M is at least one of Co, Al, Mn, Zr, Si, Zn, and Ti), has a crystallite diameter of 140 nm or less, and has an eluted lithium ion amount of 0.30% by mass or more and 1.00% by mass or less. The coating layer is a composite oxide containing Li and at least one of Al, Si, Ti, V, Ga, Ge, Zr, Nb, Mo, Ta, and W.