Solid-State Li-Ion Cathode Oxide Coating for Electrolyte Stability
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Solution Overview
Problem
Lithium-ion batteries face issues with undesired reactions on the cathode surface, leading to electrolyte decomposition and compatibility problems with solid electrolytes, particularly with nickel-containing cathode materials, which impede reversible operation and cycling performance.
Innovation Solution
The development of all-solid-state lithium-ion electrochemical cells with a cathode comprising a particulate electrode active material coated with a continuous layer of tungsten or molybdenum oxide, and a solid electrolyte made of lithium, sulfur, and phosphorus, which enhances oxidative stability and lithium-ion conductivity, preventing direct contact between the cathode and electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nickel-containing cathode material is used to achieve high capacity, then the battery capacity is improved, but undesired reactions occur on the cathode surface leading to electrolyte decomposition
Solution Approach 1:
A coating layer comprising metal fluoride and metal oxide is applied to the surface of the nickel-containing cathode material. This intermediary layer prevents direct contact between the reactive cathode surface and the electrolyte, thereby eliminating undesired decomposition reactions while preserving the high capacity characteristics of nickel-based materials.
2Reliability
If the cathode material is coated with protective material to prevent reactions, then electrolyte stability is improved, but lithium ion exchange may be hindered
Solution Approach 1:
The coating layer is designed with spatially differentiated composition and properties: metal fluoride provides chemical stability and protection against electrolyte decomposition, while metal oxide regions maintain high lithium ion conductivity. This local differentiation allows the coating to simultaneously provide protective function and facilitate ion transport.
Solution Approach 2:
The coating comprises a composite of metal fluoride and metal oxide materials. The metal fluoride component provides chemical stability and protection against electrolyte decomposition, while the metal oxide component maintains high lithium ion conductivity. This composite structure resolves the contradiction between protection and ion exchange efficiency.
3Stability of the object's composition
If the cathode surface is protected with coating material, then oxidative stability is improved, but manufacturing complexity increases
Solution Approach 1:
The coating process utilizes controlled deposition parameters to form the metal fluoride and metal oxide layer. By optimizing deposition temperature, pressure, and material ratios, the process achieves protective coating formation with manageable complexity, balancing surface stability improvement against manufacturing complexity.
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 solution results in improved cycling performance and capacity retention, with low capacity fading, even after multiple cycles, and maintains high lithium-ion conductivity while avoiding electrolyte decomposition.
Implementation Method 1
a particulate electrode active material according to general formula Li1+xTM1-xO2... wherein said electrode active material is coated with a continuous layer containing an oxide compound of Mo or W
Implementation Method 2
a solid electrolyte comprising lithium, sulphur and phosphorus
Data Source
AI summary
Disclosed herein is an all-solid-state lithium-ion electrochemical cells including:(A) a cathode including(a) particulate electrode active material according to general formula Li1+xTM1-xO2, where TM is Ni and, optionally, at least one of Co and Mn, and, optionally, at least one element selected from the group consisting of Al, Mg, and Ba, transition metals other than Ni, Co, and Mn, and x is in the range of from zero to 0.2, wherein at least 50 mole-% of the transition metal of TM is Ni, where said electrode active material is coated with a continuous layer containing an oxide of W or Mo and where said particulate electrode active material has an average particle diameter (D50) in the range of from 2 to 20 μm,(B) an anode, and(C) a solid electrolyte including lithium, sulphur and phosphorus.