Composite Cathode Material With Sub-10 Nm M2S for Solid-State Batteries
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Solution Overview
Problem
Lithium batteries with liquid electrolytes pose risks of overheating and fires due to their high likelihood of igniting, necessitating the development of safer alternatives like all-solid secondary batteries with solid electrolytes, which require improved cathode active materials for enhanced safety and performance.
Innovation Solution
A composite cathode active material comprising M2S, an alkali metal salt, and a carbon-based material is developed, where M is Li or Na, with M2S crystallites of reduced size (less than 9.9 nm) to enhance ionic and electronic conductivity, thereby improving specific capacity, cycle characteristics, and safety of all-solid secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid electrolyte is used in lithium batteries, then high energy density can be achieved, but safety deteriorates due to high ignition risk and overheating
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to solid, fundamentally altering the safety characteristics while maintaining energy density. The solid electrolyte eliminates ignition risks associated with liquid electrolytes while preserving the high energy density required for battery performance.
Solution Approach 2:
The patent employs composite materials in the cathode structure, combining M2S crystallites with carbon-based materials and conductive additives to create a composite cathode active material that achieves both high energy density and improved safety when paired with solid electrolytes.
2Productivity
If M2S crystallite size is reduced to less than 9.9 nm, then specific capacity and cycle characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystallite size parameter to be less than 9.9 nm, which optimizes the balance between specific capacity and cycle characteristics while managing the manufacturing precision requirements through defined size thresholds.
Solution Approach 2:
The patent implements local quality by creating uniform distribution of ultra-fine M2S crystallites throughout the cathode structure, ensuring consistent electrochemical performance and cycle characteristics while maintaining controlled crystallite sizes through localized synthesis conditions.
3Reliability
If solid electrolyte is implemented instead of liquid electrolyte, then safety improves by reducing fire and explosion risk, but internal resistance increases
Solution Approach 1:
The patent uses composite materials combining M2S crystallites with carbon-based conductive materials to create a composite cathode active material that reduces internal resistance when used with solid electrolytes, thereby mitigating the harmful effect of increased internal resistance while preserving safety benefits.
Solution Approach 2:
The patent applies local quality by optimizing the interface characteristics between the solid electrolyte and the composite cathode active material, ensuring low interfacial resistance and efficient ion transport at critical interfaces while maintaining the overall safety advantages of solid electrolyte implementation.
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 composite cathode active material reduces internal resistance, increases specific capacity, and improves the cycle and high-rate characteristics of all-solid secondary batteries, enhancing their safety and energy density while minimizing the risk of thermal runaway.
Implementation Method 1
with M2S crystallites of reduced size (less than 9.9 nm) to enhance ionic and electronic conductivity
Implementation Method 2
with M2S crystallites of reduced size (less than 9.9 nm) to enhance ionic and electronic conductivity
Implementation Method 3
a size of an M2S crystallite obtained from an X-ray diffraction (XRD) spectrum of the composite
Implementation Method 4
a size of an M2S crystallite obtained from an X-ray diffraction (XRD) spectrum of the composite
Data Source
AI summary
A composite cathode active material, a cathode including the same, and an all-solid secondary battery are provided. The composite cathode active material includes a composite of M2S, an alkali metal salt, and a carbon-based material, wherein M is an alkali metal, the alkali metal is Li or Na, a size of an M2S crystallite obtained from an X-ray diffraction (XRD) spectrum of the composite is less than 9.9 nm, and the composite includes a solid solution of the M2S and the alkali metal salt.