MXene-Coated Composite Cathode for High-Loading Solid-State Batteries
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Solution Overview
Problem
Solid-state lithium-ion batteries face challenges in achieving high energy density due to difficulties in cathode material loading, which hinders lithium ion transport and accelerates chemical side reactions, leading to reduced discharge capacity and shortened service life.
Innovation Solution
A composite cathode material comprising a cathode active material coated with an MXene-coated fast ionic conductor is developed, enhancing both ionic and electronic conductivity, and protected by functional atoms or groups in MXene to prevent electrolyte corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the loading amount of cathode material is increased to achieve high energy density, then the energy density is improved, but the thickness of the cathode sheet increases causing hindered lithium ion transport and reduced discharge capacity
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the cathode material particles have a different composition at the core versus the shell. The core contains the high-capacity cathode material while the shell contains fast lithium ion conductor material, allowing different regions to serve different functions: the core provides high energy density while the shell ensures efficient lithium ion transport even at high loading amounts.
Solution Approach 2:
The patent uses composite materials by combining cathode active material with fast lithium ion conductor material in a core-shell configuration. This composite structure allows the system to simultaneously achieve high energy density from the cathode material and high ionic conductivity from the fast ion conductor shell, resolving the contradiction between energy density and lithium ion transport efficiency.
2Use of energy by moving object
If the loading amount of cathode material is increased to achieve high energy density, then the energy density is improved, but chemical side reactions between cathode and electrolyte are accelerated reducing service life
Solution Approach 1:
The patent introduces fast lithium ion conductor material as an intermediary layer between the cathode active material and the electrolyte. This intermediary shell prevents direct contact and harmful chemical reactions between the cathode and electrolyte, while still allowing efficient lithium ion transport. This protective barrier extends service life even when high loading amounts are used to achieve high energy density.
Solution Approach 2:
The composite core-shell structure combines cathode material with fast ion conductor material, where the shell component specifically addresses the reliability issue by preventing harmful side reactions while the core component provides high energy density. This composite approach allows both high energy density and long service life to be achieved simultaneously.
3Reliability
If fast ionic conductors are incorporated to improve lithium ion transport and protect cathode material, then cycling stability is enhanced, but the proportion of active materials is reduced lowering specific discharge capacity
Solution Approach 1:
The patent applies local quality by concentrating the fast ionic conductor material specifically in the shell region rather than uniformly distributing it throughout the entire particle. This allows the core region to be densely packed with high-capacity cathode material for high specific discharge capacity, while the shell region provides the necessary ionic conductivity and protective functions for cycling stability.
Solution Approach 2:
The patent uses a thin shell structure of fast ionic conductor material that provides sufficient protective and conductive functions without excessive thickness. This thin film approach ensures that the shell provides adequate protection and ionic transport pathways for cycling stability while minimizing the volume occupied by non-active material, thereby preserving high specific discharge capacity.
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 material achieves high ionic conductivity (up to 7.555×10 -3< S/cm) and electronic conductivity (up to 4.761×10 -5< S/cm), resulting in a first-cycle specific discharge capacity of 211.22 mAh/g and capacity retention of over 96% after 150 cycles at 0.5C, demonstrating high discharge capacity and cycling stability.
Implementation Method 1
The incorporated fast ionic conductors can not only establish rapid and stable lithium-ion transport channels to facilitate the transmission of lithium ions to the cathode
Implementation Method 2
the formed coating layers can protect the cathode material, enhancing the cycling stability of batteries
Data Source
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AI summary
Provided are a composite cathode material and a preparation method thereof, and a solid-state lithium-ion battery (SSLIB), belonging to the technical field of cathode materials for lithium-ion batteries. The composite cathode material includes a cathode active material and an MXene-coated fast ionic conductor. Introducing the fast ionic conductor into the cathode active material increases the ionic transport capability of the cathode material. Coating the fast ionic conductor with the MXene having high electronic conductivity improves the electronic conductivity and specific discharge capacity of the composite cathode material, while significantly increasing the long-term cycling stability of the cathode material. The composite cathode material exhibits an ionic conductivity up to 7.555×10-3 S/cm and an electronic conductivity up to 4.761×10-5 S/cm. An SSLIB fabricated using this composite cathode material exhibits a first-cycle specific discharge capacity up to 211.22 mAh/g, and a capacity retention over 96% after 150 cycles at 0.5C.