Carbon-Coated Lithium Cathodes Without High-Temperature Treatment
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Solution Overview
Problem
Lithium secondary battery positive electrodes face challenges with thermal stability and electrical conductivity due to the use of materials like LiNiO2, which are prone to decomposition and ignition upon external pressure, and Co-less or Ni-rich materials have low conductivity and are vulnerable to moisture, necessitating a method to form a uniform carbon coating layer without high-temperature heat treatment.
Innovation Solution
A method involving mechanofusion of lithium transition metal oxides with carbon-based materials of low density to form a uniform carbon coating layer, eliminating the need for high-temperature treatment and reducing the use of conductive materials, thereby enhancing electrical conductivity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon coating layer is formed using conventional high-temperature heat treatment, then electrical conductivity is improved, but the oxidation number of the positive electrode material changes and performance deteriorates
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature heat treatment to low-temperature processing (below 200°C), and changes the method parameter from thermal treatment to plasma treatment, thereby achieving carbon coating formation without altering the oxidation number of the positive electrode material
Solution Approach 2:
The patent replaces the thermal field (heat treatment) with a plasma field (low-temperature plasma treatment), using plasma activation to form the carbon coating layer instead of high-temperature thermal processes, thus avoiding oxidation number changes
2Quantity of substance
If Co-less or Ni-rich positive electrode materials are used to reduce cost, then manufacturing cost is reduced, but electrical conductivity decreases and moisture vulnerability increases
Solution Approach 1:
The patent creates a composite structure by forming a carbon coating layer on the surface of Co-less or Ni-rich positive electrode materials, combining the low-cost advantage of reduced cobalt content with the high conductivity advantage of the carbon coating layer
Solution Approach 2:
The patent applies carbon coating locally on the surface of the positive electrode material particles, providing enhanced conductivity and moisture resistance at the surface interface while maintaining the bulk material composition for cost efficiency
3Reliability
If pitch-based carbon coating is applied to improve conductivity, then electrical properties are enhanced, but high-temperature heat treatment is required causing material oxidation
Solution Approach 1:
The patent replaces the thermal field (heat treatment) with a plasma field (low-temperature plasma treatment), using plasma activation to form the carbon coating layer instead of high-temperature thermal processes, thus avoiding oxidation number changes
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 method achieves a thin and uniform carbon coating on lithium transition metal oxides, improving the electrical conductivity and lifespan of positive electrodes while maintaining performance, and allows for a dry electrode process without solvent use, reducing manufacturing costs and environmental impact.
Implementation Method 1
mixing a lithium transition metal oxide and a carbon-based material having a density of 0.05 g/cc or less in a mechanofusion manner to form a positive electrode active material including a carbon coating layer
Data Source
AI summary
A method for manufacturing a positive electrode for a lithium secondary battery includes i) mixing a lithium transition metal oxide and a carbon-based material having a density of 0.05 g/cc or less in a mechanofusion manner to form a positive electrode active material including a carbon coating layer, ii) dry mixing the positive electrode active material and a binder to form a dry mixture, and iii) applying the dry mixture on a positive electrode current collector. A positive electrode for a lithium secondary battery manufactured by the method is also provided.