Reactive Coated Positive Electrode for Sulfide Battery Interface
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Solution Overview
Problem
Lithium ion secondary batteries with sulfide-containing solid electrolytes face increased interface resistance due to reactions between positive active material particles and solid electrolyte particles, leading to decreased conductivity and battery output.
Innovation Solution
A positive electrode with a coated particle featuring a reactive layer containing a highly reactive element, such as aluminum or magnesium, is used to inhibit reactions at the interface between the positive active material and sulfide-containing solid electrolyte particles, with the reactive layer's thickness optimized to between 0.0010 and 0.25 times the particle diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfide-containing solid electrolyte is used, then lithium ion conductivity is improved, but interface resistance increases due to reactions at the interface between positive active material particles and solid electrolyte particles
Solution Approach 1:
A coating layer comprising a metal element with higher reactivity to sulfur than the transition metal element is introduced as an intermediary between the positive active material particle and the sulfide-containing solid electrolyte. This coating layer acts as a mediator that preferentially reacts with sulfur, preventing direct reaction between the transition metal element and sulfur, thereby reducing interface resistance while maintaining lithium ion conductivity.
Solution Approach 2:
The positive electrode active material is constructed as a composite structure with a core positive active material particle containing a transition metal element and an outer coating layer comprising a metal element. This composite material design combines the high lithium ion conductivity of the sulfide-containing solid electrolyte with the protective function of the reactive metal coating, resolving the contradiction between conductivity and interface stability.
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 reactive layer effectively reduces interface resistance, as evidenced by higher initiation temperatures for exothermic reactions and improved lithium ion conductivity, thereby enhancing the battery's performance and output.
Implementation Method 1
the reactive element has a reactivity with the sulfide-containing solid electrolyte particle which is greater than a reactivity of the reactive element with a transition metal element included in the positive active material particle
Implementation Method 2
Due to the increase in the interface resistance, the conductivity of lithium ions decreases, and thus output of the lithium ion secondary battery may be deteriorated
Data Source
AI summary
A positive electrode for a lithium ion secondary battery, the positive electrode including: a coated particle including a positive active material particle and a reactive layer on the surface of the positive active material particle; and a sulfide-containing solid electrolyte particle which is in contact with the coated particle, wherein the reactive layer includes a reactive element other than lithium and oxygen, wherein the reactive element has a reactivity with the sulfide-containing solid electrolyte particle which is greater than with a reactivity of the reactive element with a transition metal element included in the positive active material particle, and wherein a ratio of a thickness of the reactive layer to a particle diameter of the positive active material particle is in a range of about 0.0010 to about 0.25.