NOx-Coated Positive Electrode for Low-Resistance Solid-State Batteries
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Solution Overview
Problem
In all-solid-state lithium batteries with sulfide-based solid electrolytes, direct contact between the electrolyte and positive electrode active material particles leads to electrolyte degradation, increasing battery resistance, which is not effectively addressed by existing coating films like lithium niobate due to moisture re-adsorption issues.
Innovation Solution
A positive electrode with a coating film containing lithium-ion-conductive oxides and NOx, where the NOx content exceeds 1000 ppm, reducing moisture adsorption and thereby minimizing resistance, with a specific NOx content range of 1050 to 1500 ppm and a moisture-to-NOx ratio of 0.7 to 1.8, ensuring low and stable resistance.
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 sulfide-based solid electrolyte and active material is inhibited, but the coating film has relatively high resistance and does not effectively prevent moisture re-adsorption
Solution Approach 1:
The patent applies composite materials by combining lithium-ion-conductive oxide with nitrogen-containing compounds to form a composite coating film. This composite structure integrates the protective function of the oxide barrier with the moisture-absorbing capability of nitrogen compounds, achieving both electrolyte protection and moisture control simultaneously.
Solution Approach 2:
The patent changes the chemical composition parameters of the coating film by introducing nitrogen-containing compounds with specific properties (nitrogen content, basicity). By adjusting these compositional parameters, the coating film gains enhanced moisture adsorption capacity while maintaining lithium-ion conductivity and protective functions.
2Object-affected harmful factors
If drying treatment is carried out to reduce moisture content of the active material, then resistance can be reduced, but the active material can re-adsorb moisture during storage or inside the battery, causing resistance increase
Solution Approach 1:
The nitrogen-containing compounds in the coating film provide self-service functionality by automatically adsorbing moisture that attempts to re-enter the active material during storage or battery operation. This self-active moisture adsorption mechanism maintains low resistance without requiring external intervention.
Solution Approach 2:
The coating film with nitrogen-containing compounds provides preliminary anti-action by preemptively capturing moisture before it can re-adsorb onto the active material surface. This preventive mechanism counteracts the natural tendency of dried materials to re-absorb moisture from the environment.
3Object-affected harmful factors
If the NOx content at the surface of the coating film is increased to reduce moisture adsorption, then resistance decreases, but excessive NOx content can create resistance at the time of charge and discharge
Solution Approach 1:
The patent optimizes the NOx content parameter within a specific range (1000-1500 ppm) to achieve the best balance between moisture adsorption capability and charge-discharge performance. This parameter optimization ensures sufficient moisture protection while avoiding excessive resistance generation during electrochemical operations.
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 inhibits moisture adsorption, resulting in a positive electrode with reduced resistance, effectively addressing the degradation issue and maintaining low resistance during charge and discharge cycles.
Implementation Method 1
the active material can re-adsorb moisture to cause resistance increase
Data Source
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.