Halide Solid Electrolyte Composite Cathodes for All-Solid-State Batteries
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Solution Overview
Problem
All-solid-state batteries face challenges such as cathode instability due to oxidative degradation of solid electrolytes and reactivities between uncoated cathode active materials, as well as mechanical integrity loss, which hinder their development and cycle life.
Innovation Solution
The use of composite cathodes featuring a halide solid electrolyte with high oxidative stability and single-crystal cathode materials to eliminate intergranular cracking and facilitate lithium transport, enabling stable cycling without the need for coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide solid electrolytes are used to achieve high ionic conductivity, then ionic conductivity is improved, but chemical reactions occur during high-temperature sintering that degrade battery performance
Solution Approach 1:
A coating layer is introduced as an intermediary between the oxide solid electrolyte and the cathode active material. This coating prevents direct chemical reactions during high-temperature sintering while allowing ionic conductivity to be maintained, thus resolving the contradiction between achieving high ionic conductivity and maintaining chemical stability.
Solution Approach 2:
The sintering temperature parameter is reduced to below 900°C to prevent chemical reactions between the oxide solid electrolyte and cathode materials, while still achieving adequate contact and ionic conductivity through optimized processing conditions at these lower temperatures.
2Reliability
If sulfide solid electrolytes are used to achieve high ionic conductivity and good ductility, then ionic conductivity and contact quality are improved, but electrochemical stability deteriorates due to decomposition at 2.6 V
Solution Approach 1:
An electronically insulating coating such as LiNbO3 or LiNb0.5Ta0.5O3 is applied to the cathode active material as an intermediary layer. This coating prevents oxidation of the sulfide solid electrolyte by blocking electron transport while maintaining ionic conductivity pathways, thus resolving the electrochemical stability issue.
Solution Approach 2:
A thin film coating is applied to the cathode particles to provide protection against sulfide electrolyte oxidation. The thin film structure maintains intimate contact with the sulfide electrolyte while preventing harmful chemical reactions, balancing conductivity and stability requirements.
3Ease of manufacture
If polycrystalline cathode materials are used, then ease of manufacture is improved, but mechanical integrity is lost due to intergranular cracking from volume changes
Solution Approach 1:
The cathode particles are designed with internal segmentation through a core-shell structure, where a buffer layer is introduced between the active material core and the outer surface. This segmentation accommodates volume changes during lithium insertion/extraction, preventing intergranular cracking while maintaining particle integrity.
Solution Approach 2:
A composite structure is created by combining the cathode active material with a buffer material that has different mechanical properties. This composite approach provides both the electrochemical functionality of the active material and the mechanical stability of the buffer layer, preventing cracking during cycling.
4Device complexity
If uncoated cathode active materials are used to simplify the structure, then device complexity is reduced, but reactivity between the cathode material and solid electrolyte increases
Solution Approach 1:
A thin coating layer is introduced as an intermediary between the cathode active material and solid electrolyte. This coating prevents direct harmful chemical reactions while allowing ionic transport, thus resolving the contradiction between simplicity and reactivity control.
Solution Approach 2:
The coating thickness parameter is optimized to be thin enough to maintain simplicity and allow ionic transport, yet thick enough to prevent harmful reactions. This parameter optimization balances the contradiction between structural simplicity and reactivity control.
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
This configuration achieves nearly 90% capacity retention after 1000 cycles at a C/2 rate, outperforming polycrystalline counterparts by maintaining mechanical integrity and intimate contact with the solid electrolyte, thereby enhancing the stability and performance of all-solid-state batteries.
Implementation Method 1
a halide SE with high oxidative stability to enable direct use of uncoated 4 V-class CAM
Implementation Method 2
single-crystal (SC) CAM to eliminate intergranular cracking associated with volume changes and to facilitate Li transport
Implementation Method 3
sulfide SEs, such as glass-, glass-ceramic-, and argyrodite-, they can perform 10−2 ̃10−3 S·cm−1 class high ionic conductivity and good ductility which enables to establish intimate contact to CAMs
Data Source
AI summary
This disclosure provides systems, methods, and apparatus related to composite cathodes for all solid-state batteries. In one aspect, an all solid-state battery comprises a composite cathode, a separator, and an anode. The composite cathode comprises LiNixMnyCo1-x-yO2, x≥0.33, with about 80% or more of the LiNixMnyCo1-x-yO2 comprising single crystals of LiNixMnyCo1-x-yO2. The LiNixMnyCo1-x-yO2 is embedded in a matrix of a first lithium metal halide solid electrolyte comprising Li6-3aMaX6, 0<a<2. M is an element from a group of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), indium (In), zirconium (Zr), niobium (Nb), hafnium (Hf), tantalum (Ta), yttrium (Y), lanthanum (La), samarium (Sm), bismuth (Bi), holmium (Ho), erbium (Er), ytterbium (Yb), and combinations thereof. X is a halide from a group of chlorine (Cl), bromine (Br), iodine (I), and combinations thereof.