Coated Cathode Active Material for High-Rate Solid-State Batteries
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Solution Overview
Problem
Conventional lithium-ion-conductive oxide-coated active materials for all-solid-state batteries suffer from significant discharge capacity loss under high-rate conditions and have inadequate cycle life characteristics.
Innovation Solution
A positive electrode active material for all-solid-state batteries is developed, comprising a layered lithium transition metal oxide core coated with a lithium-ion-conductive oxide, with specific diffraction peak intensity ratios, crystallite size, and molar lithium-to-transition metal ratios to enhance discharge capacity and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium-ion-conductive oxide coating is applied to prevent interfacial reactions, then initial capacity and cycle life are improved, but discharge capacity decreases significantly under high-rate conditions
Solution Approach 1:
The patent applies different coating materials to different regions of the cathode particle surface. A first lithium-ion-conductive oxide coating is applied to the entire particle surface to prevent interfacial reactions, while a second coating of carbon material or conductive polymer is applied specifically to regions where lithium-ion-conductive oxide coating thickness exceeds a predetermined value. This local differentiation ensures both protection against interfacial reactions and maintenance of electrical conductivity under high-rate conditions.
Solution Approach 2:
The patent creates a composite coating structure combining two different materials: lithium-ion-conductive oxide and carbon material or conductive polymer. This composite approach leverages the protective properties of the lithium-ion-conductive oxide while the carbon or polymer component maintains electrical conductivity, resolving the contradiction between protection and conductivity under high-rate conditions.
2Quantity of substance
If electrode loading level is increased to improve energy density, then battery capacity increases, but discharge capacity decreases due to interfacial reaction effects
Solution Approach 1:
By applying the second coating (carbon material or conductive polymer) specifically to regions where the first lithium-ion-conductive oxide coating is thick, the patent locally compensates for conductivity losses. This allows increased electrode loading while maintaining sufficient conductivity in critical regions, thereby preserving discharge capacity even as overall battery capacity increases.
Solution Approach 2:
The patent changes the coating thickness parameter of the lithium-ion-conductive oxide and compensates by applying a second coating in specific regions. This parameter adjustment allows the system to achieve both high loading levels and maintained discharge capacity by optimizing the distribution and thickness of different coating layers.
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 material improves discharge capacity and cycle life under high-rate conditions by minimizing interfacial resistance and optimizing lithium-ion transport paths, resulting in enhanced performance.
Implementation Method 1
a coating layer disposed on the core and comprising a lithium-ion-conductive oxide
Implementation Method 2
a solid electrolyte is applied as a secondary electrolyte inside the positive electrode to form a lithium-ion conduction pathway
Data Source
Figure 1
AI summary
The present invention relates to a positive electrode active material for an all-solid-state battery, comprising: a core comprising a layered lithium transition metal oxide; and a coating layer disposed on the core, wherein a ratio of the diffraction peak intensity of the (003) plane to the diffraction peak intensity of the (104) plane, I(003)/I(104), as measured by X-ray diffraction analysis, is from 1.20 to 1.40, and a molar ratio of lithium to transition metal (Li/Me) in the lithium transition metal oxide is from 1.02 to 1.05.