Carbon-Coated Fast-Ionic Cathode Coating to Balance Ion and Electron Flow
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Solution Overview
Problem
The safety issues in lithium-ion batteries, particularly in large batteries for automobiles and energy storage, are exacerbated by the volatile organic electrolytic solution, and the use of fast-ionic conductors as a coating faces challenges due to poor electronic conductivity, hindering their commercialization in all-solid-state batteries.
Innovation Solution
A carbon-coated fast-ionic conductor-modified positive electrode material is developed, where the surface of the carbon-coated fast-ionic conductor is coated with boric acid to prevent carbon escape and enhance both ionic and electronic conductivity, using a chemical formula of Li a Ni x Co y Mn z O 2 ·cA·dB, with A being a carbon-coated fast-ionic conductor and B being a carbon escape-prevention compound like boric acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a fast-ionic conductor is coated on the surface of positive electrode material to improve ionic conductivity and safety, then ionic conductivity is improved, but electronic conductivity deteriorates due to the insulating nature of fast-ionic conductors
Solution Approach 1:
The patent applies a composite coating structure consisting of a fast-ionic conductor layer (LATP or LLZO) combined with a carbon coating layer. This composite structure allows the fast-ionic conductor to provide high ionic conductivity while the carbon layer compensates for electronic conductivity losses, effectively resolving the contradiction between improved ionic conductivity and maintained electronic conductivity.
Solution Approach 2:
The patent introduces localized carbon coating specifically on the fast-ionic conductor surface where electronic conductivity is needed, while maintaining the fast-ionic conductor properties in the bulk. This local modification approach allows different regions of the coating to have different functions: the fast-ionic conductor provides ionic conductivity and the carbon layer provides electronic conductivity.
2Reliability
If carbon coating is applied to fast-ionic conductor to improve electronic conductivity, then electronic conductivity is improved, but carbon escape occurs during sintering process
Solution Approach 1:
The patent applies carbon coating to the fast-ionic conductor before the final sintering process. By performing the carbon coating operation in advance, the carbon layer is already in place to provide electronic conductivity pathways before any potential carbon loss during subsequent high-temperature treatment. This preliminary action ensures that even if some carbon escapes during sintering, sufficient carbon remains to maintain electronic conductivity.
Solution Approach 2:
The patent uses a relatively thick carbon coating layer (0.1-2.0 wt% relative to positive electrode material) that acts as a cushion against carbon loss during sintering. This excess carbon provides a buffer that compensates for the carbon that may escape during the high-temperature sintering process, ensuring that the final product still has adequate carbon for electronic conductivity.
3Stability of the object's composition
If conventional sintering process is used to stabilize fast-ionic conductor coating, then coating stability is improved, but carbon escape occurs and coating quality deteriorates
Solution Approach 1:
The patent optimizes the sintering parameters including temperature (900-1100°C), time (1-12 hours), and atmosphere (air or oxygen) to achieve a balance between coating stability and carbon retention. By carefully controlling these parameters, the fast-ionic conductor coating is stabilized while minimizing carbon escape, thus improving both coating stability and coating quality simultaneously.
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 carbon-coated fast-ionic conductor-modified positive electrode material improves ionic and electronic conductivity, enhancing the safety and performance of lithium-ion batteries by preventing carbon escape and stabilizing the fast-ionic conductor.
Implementation Method 1
the surface of the carbon-coated fast-ionic conductor is coated with boric acid due to the glassy property
Implementation Method 2
The fast-ionic conductor is a good ion-conducting material
Implementation Method 3
the ionic conductivity and the electronic conductivity of the positive electrode material are synchronously improved
Data Source
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AI summary
The present disclosure provides a carbon-coated fast-ionic conductor-modified positive electrode material and a preparation method therefor. The positive electrode material has a chemical general formula of LiaNixCoyMnzO2·cA·dB, where 1.00 ≤ a ≤ 1.20, 0.00 < c ≤ 0.01, 0.00 < d ≤ 0.02, 0.00 ≤ x < 1.00, 0.00 ≤ y < 0.2, 0.00 ≤ z < 0.4, and x + y + z = 1; A is a first coating material, and B is a second coating material; and the first coating material A is a carbon-coated fast-ionic conductor, and the second coating material B is a carbon escape-prevention compound. According to the present disclosure, a fast-ionic conductor modified through carbon coating is used to modify a positive electrode material, such that the ionic conductivity and the electronic conductivity of the positive electrode material are synchronously improved. In addition, the surface of the carbon-coated fast-ionic conductor is coated with boric acid due to the glassy property, such that the escape of carbon in the carbon-coated fast-ionic conductor is effectively prevented. Therefore, the present disclosure synchronously improves the ionic conductivity and the electronic conductivity of the positive electrode material, and also improves the safety of the battery.