NOx-Coated Positive Electrode for Low-Resistance Solid-State Batteries
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Solution Overview
Problem
All-solid-state batteries with sulfide-based solid electrolytes face increased resistance due to degradation when in direct contact with positive electrode active material particles, and existing coating solutions like lithium niobate may not adequately prevent moisture adsorption, leading to resistance issues.
Innovation Solution
A positive electrode with a coating film containing lithium-ion-conductive oxides and NOx, where the NOx content is above 1000 ppm, inhibits moisture adsorption and reduces resistance by maintaining a low moisture content, achieved through a specific NOx content range and moisture-to-NOx ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film of lithium-ion-conductive oxide (e.g., lithium niobate) is formed on the positive electrode active material particles, then direct contact between the active material and sulfide-based solid electrolyte is inhibited, but the coating film has relatively high resistance which increases battery resistance
Solution Approach 1:
The patent introduces nitrogen atoms into the lithium niobate coating film to change its chemical composition and electronic structure. This parameter change reduces the resistance of the coating film while maintaining its protective function, thereby resolving the contradiction between protection and resistance.
Solution Approach 2:
The patent creates a composite coating film by combining lithium niobate with nitrogen-containing compounds. This composite structure provides both the protective properties of lithium niobate and the low-resistance characteristics of nitrogen-containing materials, simultaneously achieving protection and low resistance.
2Object-affected harmful factors
If drying treatment is carried out to reduce moisture content of the active material, then resistance can be reduced, but during storage or inside the battery the active material can re-adsorb moisture causing resistance increase
Solution Approach 1:
The nitrogen-containing coating film is applied in advance to the active material surface before the material is exposed to moisture during storage or battery operation. This preliminary protective layer prevents moisture adsorption from occurring in the first place, maintaining low resistance without requiring continuous drying treatment.
Solution Approach 2:
The nitrogen-containing coating film acts as an intermediary barrier between the active material and moisture in the environment. It prevents direct interaction between moisture and the active material, thereby stabilizing moisture content and maintaining low resistance during storage and operation.
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 high NOx content in the coating film effectively decreases the moisture adsorption on the active material, thereby reducing the battery's resistance and maintaining a low resistance state, even during charge and discharge cycles.
Implementation Method 1
the sulfide-based solid electrolyte may degrade. When the sulfide-based solid electrolyte (an ion conduction path) degrades, battery resistance may increase. To address this problem, forming a coating film on the surface of the positive electrode active material particles is suggested.
Implementation Method 2
NOx tends not to adsorb water 22, the high NOx content leads to a decrease of the amount of moisture adsorbed on the active material
Implementation Method 3
forming a coating film on the surface of the positive electrode active material particles is suggested. The coating film may inhibit direct contact between the positive electrode active material particles and the sulfide-based solid electrolyte to reduce degradation of the sulfide-based solid electrolyte.
Data Source
Figure 1~1(b)
Figure 2
Figure 3
AI summary
A positive electrode for an all-solid-state battery that comprises a sulfide-based solid electrolyte and a covered active material. The covered active material includes a positive electrode active material particle and a coating film covering at least part of a surface of the positive electrode active material particle. The coating film includes a lithium-ion-conductive oxide, and also includes NOx at at least a surface thereof. A NOx content at the surface of the coating film is more than 1000 ppm.