Dual-Layer Cathode Coating for Stable Solid-State Battery Interfaces
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Solution Overview
Problem
Current battery technologies face challenges in reducing interfacial resistance, particularly when a sulfide solid electrolyte undergoes oxidative decomposition during battery charging, leading to variations in battery characteristics and pore distribution changes after coating with a solid electrolyte.
Innovation Solution
A coated active material is developed with a dual-layer coating system, comprising a first coating layer with a halide solid electrolyte and a second coating layer of lithium-containing oxide or oxide solid electrolyte, which inhibits direct contact between the positive electrode active material and the solid electrolyte, thereby reducing interfacial resistance by controlling pore volume distribution changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfide solid electrolyte is used to coat the positive electrode active material, then the battery can achieve high ionic conductivity, but the sulfide solid electrolyte undergoes oxidative decomposition during charging leading to increased interfacial resistance
Solution Approach 1:
The coating is divided into two distinct layers: a first coating layer containing an oxide solid electrolyte that provides oxidation resistance, and a second coating layer containing a sulfide solid electrolyte that provides high ionic conductivity. This segmentation allows each layer to perform its specific function without the sulfide layer being directly exposed to oxidizing conditions during charging.
Solution Approach 2:
The first coating layer of oxide solid electrolyte acts as an intermediary protective barrier between the positive electrode active material and the sulfide solid electrolyte in the second coating layer. This intermediary layer prevents direct contact and oxidation of the sulfide electrolyte during charging while still allowing ionic transport.
2Ease of manufacture
If a single-layer coating is applied to the positive electrode active material, then the manufacturing process is simple, but the coating cannot simultaneously provide both oxidation resistance and controlled pore distribution
Solution Approach 1:
The coating structure is segmented into two functional layers with distinct properties. The first layer controls oxidation resistance and provides a base pore structure, while the second layer optimizes ionic conductivity with a specific pore distribution. This segmentation enables precise control over both oxidation resistance and pore distribution that cannot be achieved with a single-layer coating.
Solution Approach 2:
The invention uses a composite coating structure combining two different solid electrolyte materials with complementary properties. The oxide solid electrolyte in the first layer provides chemical stability and oxidation resistance, while the sulfide solid electrolyte in the second layer provides high ionic conductivity. The composite structure allows simultaneous optimization of multiple properties.
3Object-affected harmful factors
If the coating layer completely seals the pores of the positive electrode active material, then oxidation resistance is maximized, but ionic transport is hindered leading to increased interfacial resistance
Solution Approach 1:
The coating structure implements local quality differentiation through its two-layer design. The first coating layer has a pore structure optimized for oxidation resistance, while the second coating layer has a different pore structure optimized for ionic transport. Each layer locally provides the specific quality needed for its function, allowing both oxidation resistance and ionic transport to be optimized simultaneously.
Solution Approach 2:
The invention utilizes porous structures in both coating layers, but with different characteristics. The first layer's pores are designed to resist oxidation while the second layer's pores are optimized for ion transport. The controlled porosity in the sulfide electrolyte layer allows ionic transport without compromising the oxidation protection provided by the oxide electrolyte layer.
Data Source
AI summary
A coated active material including: a positive electrode active material; a second coating layer; and a first coating layer outside the second coating layer, in which a percentage of change from S1 to S2 is −78.0% or greater and −15.0% or less and/or a percentage of change from S3 to S4 is −77.0% or greater and −12.0% or less, where S1 is a sum of dV/dD over a range of pore diameters of 2 nm to 100 nm of the active material coated with the second coating layer; S2 is a sum of dV/dD over a range of pore diameters of 2 nm to 100 nm of the coated active material; S3 is dV/dD at a pore diameter of 3 nm of the active material coated with the second coating layer; and S4 is dV/dD at a pore diameter of 3 nm of the coated active material.