Composite Oxide Cathode for All-Solid-State Battery Interface Resistance
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Solution Overview
Problem
Current all-solid-state lithium batteries with solid electrolytes face issues such as interface resistance and capacity deterioration when using cathode active materials like nickel cobalt aluminum acid or lithium cobalt oxide, and they have limited charging voltage, necessitating a material with improved discharge capacity and cycle characteristics.
Innovation Solution
A cathode active material comprising a composite oxide of vanadium pentoxide and lithium phosphoric acid, with a molar ratio of vanadium pentoxide to lithium phosphate controlled between 2:1 and 10:1, is used to reduce capacity deterioration and enhance lithium ion conductivity, along with optional lithium metal oxide compounds and a coating layer to improve interface resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cathode active materials like nickel cobalt aluminum acid or lithium cobalt oxide are used with solid electrolytes, then the battery can operate with solid electrolyte benefits, but interface resistance is produced and lithium ion conductivity deteriorates
Solution Approach 1:
The patent applies an intermediary coating layer comprising lithium phosphate on the cathode active material surface. This coating layer acts as a mediator between the cathode active material and the solid electrolyte, preventing direct harmful reactions while maintaining lithium ion conductivity. The coating layer specifically addresses the interface resistance problem by providing a stable intermediate interface that facilitates ion transport without the detrimental reactions that occur between the bare cathode material and solid electrolyte.
Solution Approach 2:
The patent creates a composite structure by coating the cathode active material (such as vanadium pentoxide or lithium cobalt oxide) with lithium phosphate. This composite material approach combines the high capacity benefits of the cathode active material with the protective and conductive properties of the lithium phosphate coating, thereby maintaining reliability while reducing the harmful interface resistance effect.
2Duration of action of moving object
If conventional cathode active materials are used in all-solid-state batteries, then the battery structure is simplified, but capacity deterioration occurs during repeated charge/discharge processes
Solution Approach 1:
The lithium phosphate coating layer serves as a protective intermediary that prevents direct contact and harmful reactions between the cathode active material and the solid electrolyte during charge/discharge cycles. This intermediary layer maintains capacity retention by preventing degradation reactions while allowing sustained cycling operation, thereby improving both cycle life and capacity retention simultaneously.
Solution Approach 2:
The patent changes the surface chemical composition and structure of the cathode active material by applying a lithium phosphate coating. This parameter change at the material surface level modifies the electrochemical stability and reaction characteristics, enabling the material to withstand repeated charge/discharge processes without significant capacity deterioration.
3Use of energy by moving object
If the charging voltage is limited to 4.0 V or less to avoid reactions, then interface stability is maintained, but energy density needs to be improved
Solution Approach 1:
The lithium phosphate coating layer enables higher charging voltages by serving as a protective intermediary that prevents harmful reactions between the cathode active material and solid electrolyte. This intermediary protection allows the battery to operate at elevated voltages (above 4.0 V) that would otherwise cause interface instability, thereby improving energy density while maintaining 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 composite oxide cathode active material significantly improves discharge capacity and cycle characteristics, maintaining high capacity and lifespan, and when coated, further enhances ion conductivity and capacity retention in all-solid-state secondary batteries.
Implementation Method 1
sulfide solid electrolytes provide lithium ion conductivity
Implementation Method 2
An interface resistance is thus produced and lithium ion conductivity deteriorates
Data Source
AI summary
A cathode active material including a first composite oxide represented by Formula (1):xV2O5.Li3PO4 (1)wherein, in Formula 1, x satisfies 2<x≤10.