Composite Positive Electrode for All-Solid-State Battery
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Solution Overview
Problem
Existing all-solid-state secondary batteries face challenges in maximizing charge and discharge capacity due to high electrical resistivity and insufficient contact between positive electrode active materials and solid electrolytes, leading to suboptimal ion conductivity and reduced charge/discharge performance.
Innovation Solution
A composite positive electrode active material is developed with a sulfide-based solid electrolyte layer coating the surface of particles, enhancing ion conductivity and charge/discharge efficiency by increasing the average roundness of the composite material and optimizing the contact ratio and area occupancy of the solid electrolyte layer, achieved through a dry particle blending process in an inert gas atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If positive electrode active materials are individually dispersed and surface is in contact with solid electrolyte, then ion conductivity is improved, but the proportion of solid electrolyte increases and charge/discharge capacity decreases
Solution Approach 1:
The invention applies local quality by creating a core-shell structure where the inner core maintains high positive electrode active material content for capacity, while the outer surface layer provides smooth solid electrolyte coating for ion conductivity. This spatial differentiation of material properties resolves the contradiction between maximizing capacity and ensuring ion transport.
Solution Approach 2:
The invention uses composite materials by combining positive electrode active material particles with solid electrolyte coating to form a composite structure. The composite positive electrode active material integrates both materials with optimized proportions, achieving high ion conductivity through the solid electrolyte layer while maintaining high charge/discharge capacity through the active material core.
2Quantity of substance
If proportion of solid electrolyte is decreased and proportion of positive electrode active material is increased, then charge/discharge capacity increases, but contact between active material and solid electrolyte is reduced and ion conductivity decreases
Solution Approach 1:
The invention ensures that the outer surface region (where ion transport occurs) has high solid electrolyte content for conductivity, while the inner core region (where capacity is stored) has high active material content. This local optimization resolves the contradiction by having different material compositions in different spatial regions.
Solution Approach 2:
The solid electrolyte forms a thin film coating on the surface of the positive electrode active material particles. This thin film structure provides sufficient ion conductivity while occupying minimal volume, allowing high proportion of active material to be maintained for high capacity.
3Quantity of substance
If rough surface of positive electrode active material is used, then more solid electrolyte can be accommodated, but contact area and ion transfer efficiency are reduced
Solution Approach 1:
The invention smooths the surface of the composite positive electrode active material particles, creating a more spherical and uniform outer surface. This smooth surface with appropriate curvature facilitates better contact between particles and solid electrolyte, improving ion transfer efficiency while the core-shell structure ensures sufficient solid electrolyte is present for 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 solution significantly improves the charge and discharge properties of all-solid-state secondary batteries by increasing the charge/discharge capacity, maintaining ion conductivity, and extending the battery's cycle life, while ensuring safety by reducing the use of flammable non-aqueous solvents.
Implementation Method 1
The solid electrolyte in the positive electrode reduces an electrical resistivity between the positive electrode active materials to facilitate transfer of metal ions
Implementation Method 2
achieved through a dry particle blending process in an inert gas atmosphere
Data Source
Figure 1(a)~1(e)
Figure 2(a)~2(b)
Figure 3(a)~3(c)
AI summary
A composite positive electrode active material for an all-solid-state secondary battery containing particles of a positive electrode active material and a sulfide-based solid electrolyte layer coating surfaces of the particles, wherein the composite positive electrode active material has an average roundness that is 1.3 times or more of that of a positive electrode active material at an inner core of the composite positive electrode active material.