Nb-W Shell Cathode Material for Sulfide Solid-State Batteries
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Solution Overview
Problem
All-solid-state batteries using sulfide-based solid electrolytes face issues with low ion conductivity, interfacial side reactions, and non-uniform charge distribution, leading to capacity degradation and poor charging/discharging characteristics, particularly when using lithium composite metal oxides like Li(NiCoMn)O2, which can degrade due to cobalt-sulfur reactions.
Innovation Solution
A positive electrode active material is developed with a lithium metal oxide core coated by a shell containing niobium (Nb) and tungsten (W), enhancing ion mobility and reducing side reactions by controlling the content and distribution of these elements on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium composite metal oxide with high cobalt content is used as positive electrode active material, then overcharging characteristics and thermal safety are improved, but discharge capacity and charge/discharge efficiency are degraded
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains high-cobalt lithium composite metal oxide for safety and the shell contains low-cobalt or cobalt-free lithium composite metal oxide for high discharge capacity. This spatial differentiation of composition allows each region to optimize its function locally.
Solution Approach 2:
The patent uses composite materials by combining two different lithium composite metal oxide compositions into a single electrode active material system. The core-shell structure integrates materials with different cobalt contents to simultaneously achieve thermal safety and high discharge capacity.
2Reliability
If coating technique is applied to passivate surface of positive electrode active material, then interfacial side reactions are reduced, but charging/discharging characteristics remain poor
Solution Approach 1:
The patent employs composite materials by creating a core-shell structure where both core and shell are lithium composite metal oxides with specific compositions. This composite approach provides better interfacial compatibility and electrochemical performance compared to conventional coating with unrelated materials.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the composition parameters (metal ratios, oxidation states) and structural parameters (shell thickness, particle size) of the core-shell structure to optimize both interfacial stability and charging/discharging characteristics simultaneously.
3Reliability
If contact area between electrode active material and solid electrolyte is increased, then ion conductivity is improved, but interfacial resistance and space-charge layer formation cause non-uniform charge distribution
Solution Approach 1:
The patent applies local quality by designing the shell with specific composition and thickness to locally optimize the interface with solid electrolyte. The shell creates a favorable local environment for ion transport while maintaining uniform charge distribution through controlled composition gradients.
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 core-shell structure improves discharge capacity and reduces interfacial resistance, enhancing the electrical performance and stability of all-solid-state batteries by minimizing shell detachment and side reactions.
Implementation Method 1
The reason why ion conductivity is low in batteries using solid electrolytes is that a contact area between an electrode active material and the solid electrolyte is small compared to the conventional liquid electrolyte system and the inherent ion conductivity of the solid electrolyte is low.
Implementation Method 2
a coating technique capable of passivating the surface of a conventional positive electrode active material has been proposed. Passivation is treatment of the surface of any material so that the inherent properties thereof are not changed even by external conditions or stimuli.
Data Source
AI summary
The present technology relates to a positive electrode active material for an all-solid-state battery, and the positive electrode active material is effective for enhancing lithium ion mobility, reducing a side reaction between the positive electrode active material and a solid electrolyte, and thus enhancing the discharge performance of a battery by including a lithium metal oxide of Chemical Formula 1, which has a high nickel content and includes a certain amount or less of cobalt, as a core and a shell containing niobium and tungsten on the surface of the core.