Outer Positive Electrode Coating for Higher-Density Lithium Batteries
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Solution Overview
Problem
The use of a positive electrode with a high-capacity non-reversible additive, such as Li2O2, in secondary lithium batteries leads to a decrease in energy density due to the formation of voids and a reduction in positive electrode density after the first charge.
Innovation Solution
An electrode assembly is configured with a non-reversible material coating layer, including lithium oxide, on the outermost surface of the positive electrodes, instead of a positive active material layer, to enhance charging/discharging efficiency and maintain energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a positive electrode with high-capacity non-reversible additive (Li2O2) is used to increase energy density, then the charging/discharging efficiency is improved, but voids form and positive electrode density decreases after first charge
Solution Approach 1:
The positive electrode is segmented into two distinct layers: a bulk layer containing the non-reversible additive (Li2O2) for high capacity, and a surface layer without the additive to maintain structural integrity. This segmentation allows the electrode to achieve high charging/discharging efficiency while preventing void formation and density degradation after first charge.
2Quantity of substance
If non-reversible material coating layer is applied on outermost surface instead of positive active material layer, then energy density is increased, but electrode structure complexity increases
Solution Approach 1:
The non-reversible material (Li2O2) is extracted from the bulk positive active material layer and relocated to form a separate coating layer on the outermost surface of the positive electrode. This extraction increases energy density by concentrating the high-capacity material at the surface while simplifying the overall electrode structure compared to a fully mixed composition.
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
This configuration increases the energy density of the battery by preventing the degradation of the positive electrode density and maintaining high charging/discharging efficiency, even after the first charge.
Implementation Method 1
as Li2O2 is decomposed to discharge oxygen gas through first charging
Data Source
AI summary
Disclosed are an electrode assembly, and a secondary lithium battery including the same. The electrode assembly is configured by alternately stacking two or more positive electrodes and one or more negative electrodes using a separator as a boundary therebetween, outermost positive electrodes are positioned on outermost opposite surfaces of the electrode assembly, respectively, each of the outermost positive electrodes includes a positive electrode current collector, a positive active material layer formed on one surface of the positive electrode current collector, and a non-reversible material coating layer formed on the other surface of the positive electrode current collector and including lithium oxide, and the non-reversible material coating layer is positioned on an outermost surface of the electrode assembly.