Solid-State Battery Cathode Material With Buffer Layer for Ion Conduction
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Solution Overview
Problem
All-solid-state rechargeable batteries face challenges with low ionic conductivity, interfacial resistance, and poor ion conduction due to solid-to-solid bonding, necessitating the development of positive electrode active materials that enhance capacity and cycle-life characteristics.
Innovation Solution
A positive electrode active material comprising lithium nickel-cobalt-aluminum-based and lithium nickel-cobalt-aluminum-manganese-based composite oxides with radial primary particle arrangement and a buffer layer, prepared through a co-firing process that diffuses aluminum into the smaller particles, forming a unique composition and structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte is used instead of liquid electrolyte, then safety is improved, but ionic conductivity deteriorates
Solution Approach 1:
A buffer layer comprising a lithium compound and a metal oxide is introduced as an intermediary between the solid electrolyte and the positive electrode active material particles. This buffer layer mediates the interface between solid electrolyte and solid electrode material, improving ion conduction performance by preventing depletion layer formation while maintaining the safety benefits of solid electrolyte.
Solution Approach 2:
The invention changes the physical and chemical parameters of the interface between solid electrolyte and electrode material by introducing the buffer layer with specific composition (lithium compound and metal oxide). This parameter change optimizes the interface for ion transport while maintaining the solid-state structure, thereby improving ionic conductivity without sacrificing safety.
2Device complexity
If solid-to-solid bonding is used, then device complexity is reduced, but ion conduction performance deteriorates due to depletion layer formation
Solution Approach 1:
The buffer layer acts as a mediator between the solid electrolyte and solid electrode particles, preventing direct solid-to-solid contact that causes depletion layer formation. This intermediary layer maintains the simplicity of solid-state structure while enabling efficient ion conduction by eliminating the harmful depletion layer effect.
3Productivity
If interfacial resistance is reduced, then initial charge/discharge efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The buffer layer formation is merged with the existing battery manufacturing process by coating the positive electrode active material particles with lithium compound and metal oxide before assembly. This combined approach reduces interfacial resistance to improve initial charge/discharge efficiency while avoiding significant increases in manufacturing complexity.
Solution Approach 2:
The invention changes the surface composition parameters of the positive electrode active material particles by coating them with specific lithium compounds and metal oxides. This parameter change reduces interfacial resistance and improves initial charge/discharge efficiency through a relatively simple coating process.
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 material achieves high capacity, high initial charge/discharge efficiency, and excellent cycle-life characteristics by optimizing lithium diffusion paths and reducing interfacial resistance.
Implementation Method 1
a co-firing process that diffuses aluminum into the smaller particles
Implementation Method 2
optimizing lithium diffusion paths
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3
AI summary
Disclosed are a positive electrode active material for an all-solid-state rechargeable battery, a preparation method thereof and a rechargeable lithium battery, the positive electrode active material which includes a first positive electrode active material including secondary particles including a lithium nickel-cobalt-aluminum-based composite oxide and formed by agglomerating a plurality of primary particles wherein at least a portion of the primary particles are oriented radially, and a buffer layer disposed on the surface of the secondary particles and including a lithium compound and a metal oxide; and a second positive electrode active material including secondary particles including a lithium nickel-cobalt-aluminum-manganese-based composite oxide and formed by agglomerating a plurality of primary particles, and a buffer layer disposed on the surface of the secondary particles and including a lithium compound and a metal oxide, wherein an average particle diameter of secondary particles of the first positive electrode active material is larger than an average particle diameter of the secondary particles of the second positive electrode active material.