Nickel-Rich Cathode Composition With Spinel Grain-Boundary Protection
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Solution Overview
Problem
Nickel-based cathode active materials in lithium batteries suffer from poor lifespan characteristics and thermal stability due to high residual surface lithium and side reactions, necessitating a method to prevent battery performance deterioration.
Innovation Solution
A composite cathode active material is developed, comprising a core of nickel-containing first lithium transition metal oxide with a layered crystal structure and a grain boundary of spinel crystal structure, surrounded by a shell of second lithium transition metal oxide with a spinel crystal structure, which suppresses side reactions and enhances lithium ion conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nickel-based cathode active material is used to achieve high capacity, then the battery capacity increases, but the lifespan characteristics and thermal stability deteriorate due to high residual surface lithium and side reactions
Solution Approach 1:
A coating layer comprising lithium fluoride (LiF) and lithium hydroxide (LiOH) is introduced as an intermediary substance between the nickel-based cathode active material and the electrolyte. This coating layer acts as a protective barrier that suppresses side reactions while maintaining lithium ion conduction, thereby resolving the contradiction between high capacity and reliability.
Solution Approach 2:
The surface composition and chemical state of the cathode active material are modified by forming a specific coating layer with controlled stoichiometry (Li-rich composition). This parameter change transforms the reactive nickel-based surface into a stable LiF-LiOH composite structure that prevents degradation while preserving electrochemical performance.
2Quantity of substance
If the nickel content in the cathode active material is increased to improve capacity, then more lithium residue remains on the surface, but side reactions increase causing performance deterioration
Solution Approach 1:
The harmful lithium residue on the nickel-based cathode surface is converted into a beneficial protective coating layer. By treating the Li-rich surface with a fluorinating agent to form LiF and LiOH, the originally harmful substance becomes a protective barrier that suppresses side reactions and improves battery reliability.
Solution Approach 2:
The LiF-LiOH coating layer serves as an intermediary that separates the nickel-based cathode material from the electrolyte, preventing direct contact and side reactions while allowing lithium ion transport. This intermediary layer effectively blocks harmful interactions.
3Reliability
If a coating layer is formed on the cathode active material to suppress side reactions, then thermal stability improves, but the complexity of the manufacturing process increases
Solution Approach 1:
The coating layer is formed in advance during the cathode manufacturing process, before battery assembly. By incorporating the coating formation step into the existing manufacturing workflow, the process complexity is minimized while achieving the desired thermal stability and performance enhancement.
Solution Approach 2:
The coating layer composition and thickness are optimized to achieve maximum protective effect with minimal processing complexity. By controlling the fluorinating treatment parameters (temperature, time, reagent concentration), a sufficient coating is formed without requiring complex multi-step processes.
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 improves cycle characteristics, reduces lithium residue, decreases gas occurrence, and enhances thermal stability, leading to a lithium battery with increased capacity and prolonged lifespan.
Implementation Method 1
a grain boundary disposed between adjacent primary particles among the plurality of primary particles; and a shell on the core, the shell including a second lithium transition metal oxide having a spinel crystal structure, wherein the grain boundary includes a first composition having a spinel crystal structure
Implementation Method 2
enhances lithium ion conduction
Data Source
AI summary
A composite cathode active material and a cathode and a lithium battery including the composite cathode active material. The composite cathode active material has a core including a plurality of primary particles including a nickel-containing first lithium transition metal oxide having a layered crystal structure; a grain boundary disposed between adjacent primary particles of the plurality of primary particles; and a shell on the core, the shell including a second lithium transition metal oxide having a spinel crystal structure, wherein the grain boundary includes a first composition having a spinel crystal structure.