Solid-State Battery Cathode Composite for Stable Ion Conduction
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Solution Overview
Problem
Existing lithium batteries with liquid electrolytes are susceptible to overheating and flammability, posing safety risks, particularly in applications like vehicles. Solid secondary batteries with solid electrolytes offer improved safety but require enhancements in initial efficiency, specific capacity, energy density, and lifespan.
Innovation Solution
A solid secondary battery design incorporating a positive electrode with a composite positive active material. This composite includes M2S (where M is Li or Na), an alkali metal salt, a two-dimensional carbonaceous nanostructure, and a fibrous carbonaceous material with an aspect ratio of 2 or more, enhancing electronic conduction and ion conduction paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid electrolyte is used in a lithium battery, then high ionic conductivity is achieved, but safety risks increase due to overheating and flammability
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to solid, specifically using a sulfide-based solid electrolyte. This parameter change eliminates the flammability and overheating risks associated with liquid electrolytes while maintaining ionic conductivity through the solid state material properties
Solution Approach 2:
The patent employs a composite material system consisting of sulfide-based solid electrolyte combined with specific positive active materials (such as Li2SiO3, Li2SiO2, Li4SiO4) and conductive additives. This composite structure achieves both safety improvement and maintained electrochemical performance
2Reliability
If a solid electrolyte is used to improve safety, then initial efficiency, specific capacity, and energy density decrease
Solution Approach 1:
The patent optimizes parameters including the particle size distribution of the solid electrolyte (D10, D50, D90 values), the composition ratios of positive active materials, and the density of the electrode structure to enhance initial efficiency and specific capacity while maintaining the safety benefits of solid electrolytes
Solution Approach 2:
The patent uses composite positive active materials combining sulfide-based solid electrolyte with specific lithium-containing compounds (Li2SiO3, Li2SiO2, Li4SiO4) and conductive carbon materials. This composite approach improves electronic conductivity and ionic transport, thereby enhancing initial efficiency and specific capacity
3Reliability
If a solid electrolyte is used to improve safety, then lifespan is reduced
Solution Approach 1:
The patent optimizes parameters such as the particle size distribution of solid electrolyte particles, the compression density of electrodes, and the composition ratios of active materials to improve structural stability during cycling, thereby extending battery lifespan while maintaining safety
Solution Approach 2:
The patent employs composite materials with sulfide-based solid electrolyte combined with stable lithium-containing compounds and conductive additives. This composite structure provides both safety improvement and enhanced structural stability during charge-discharge cycling, leading to extended lifespan
4Quantity of substance
If M2S is used as positive active material, then energy density increases, but electronic conduction and ion conduction paths are insufficient
Solution Approach 1:
The patent creates a composite positive active material combining M2S (such as Li2S) with sulfide-based solid electrolyte, lithium-containing compounds (Li2SiO3, Li2SiO2, Li4SiO4), and conductive carbon materials. This composite structure provides both high energy density from M2S and improved electronic/ionic conduction pathways from the other components
Solution Approach 2:
The patent introduces conductive carbon materials and optimizes the local distribution of lithium-containing compounds around M2S particles to create localized conduction pathways. This ensures efficient electron and ion transport at critical interfaces while maintaining the high energy density of the M2S bulk material
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 battery achieves improved initial efficiency, specific capacity, energy density, and extended lifespan due to the enhanced electronic and ion conduction networks, reducing internal resistance and preventing discontinuity in the ion conduction path during charging and discharging.
Implementation Method 1
enhancing electronic conduction and ion conduction paths
Implementation Method 2
enhancing electronic conduction and ion conduction paths
Data Source
AI summary
A solid secondary battery including a positive electrode layer, a negative electrode layer, and an electrolyte layer provided between the positive electrode layer and the negative electrode layer is provided. The positive electrode layer includes a positive current collector, and a positive active material layer provided on at least one side of the positive current collector, the positive active material layer includes a composite positive active material that includes M2S, an alkali metal salt, a two-dimensional carbonaceous nanostructure, and a fibrous carbonaceous material with an aspect ratio of 2 or more, where M is Li or Na. The two-dimensional carbonaceous nanostructure includes graphene, a graphene oxide, a reduced graphene oxide, or a combination thereof, and the composite positive active material includes a solid solution of M2S and the alkali metal salt.