Ternary Li-Ion Cathode Porosity and Coating Against Electrolyte Erosion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ternary materials used as positive electrode materials in lithium ion batteries suffer from poor cycle performance and severe gas production due to side reactions with the electrolyte, leading to particle degradation and reduced battery performance.
Innovation Solution
A positive electrode material with an intrinsic specific surface area and pore size within specific ranges, achieved through a method involving lithiation of a precursor with a nickel cobalt manganese active material, followed by programmed calcining and optional doping and coating, to enhance particle strength and resistance to electrolyte erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ternary materials are used as positive electrode materials, then battery capacity is improved, but cycle performance deteriorates due to particle degradation from side reactions with electrolyte
Solution Approach 1:
A coating layer comprising at least one of oxide, nitride, carbide, or boride is applied to the surface of the positive electrode material particles. This coating layer acts as an intermediary barrier between the ternary material and the electrolyte, preventing direct contact and side reactions that cause particle degradation, while allowing lithium ion transport to maintain capacity.
Solution Approach 2:
The positive electrode material is designed as a composite structure combining ternary material (LiNixCoyM1-x-yO2) with a protective coating layer. This composite structure integrates the high capacity characteristics of ternary materials with the protective and stable surface properties of the coating layer, achieving both high capacity and good cycle performance.
2Use of energy by moving object
If ternary materials contact with electrolyte, then electrochemical reactions occur, but side reactions cause particle strength to decrease and cracks to increase
Solution Approach 1:
The coating layer serves as a protective intermediary that allows beneficial electrochemical reactions (lithium insertion/extraction) to occur while blocking harmful side reactions between the ternary material and electrolyte that would otherwise weaken the particle structure.
Solution Approach 2:
The coating layer is applied in advance to the positive electrode material surface before battery operation. This preliminary protective action prevents direct contact between the electrolyte and the ternary material, thereby preventing the formation of cracks and degradation of particle strength before they can occur.
3Speed
If particle size is reduced to improve rate performance, then Li ion transference is enhanced, but particle strength decreases and resistance to electrolyte erosion worsens
Solution Approach 1:
A thin coating layer is formed on the surface of the positive electrode material particles. This thin film provides mechanical strength and chemical protection to the particles, compensating for the reduced strength that comes with smaller particle size, while still allowing efficient lithium ion diffusion for high rate performance.
Solution Approach 2:
The structure combines small-sized ternary material particles with a protective coating layer, creating a composite where the core provides high surface area for fast ion transport and the shell provides mechanical strength and chemical stability.
4Stability of the object's composition
If doping is performed to enhance particle strength, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of complex doping processes that require multiple steps and precise control of dopant concentrations, a simpler coating process is used where a coating layer is applied to the particle surface. This intermediary approach achieves particle strengthening and stabilization with a more straightforward manufacturing process.
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 resulting positive electrode material exhibits excellent rate performance and cycle stability, maintaining a controlled pore configuration and preventing capacity loss and side reactions, with a discharge capacity of up to 223.8 mAh/g and 93.6% capacity retention after 80 cycles.
Implementation Method 1
subjecting a precursor of the positive electrode material to lithiation by: mixing the precursor with a lithium source
Implementation Method 2
subjecting to programmed calcining under an oxygen atmosphere, wherein the programmed calcining comprises: subjecting to a first calcining at 300-500°C to obtain the first calcined product; and subjecting to a second calcining to obtain the second calcined product
Implementation Method 3
The positive electrode material in accordance with the present disclosure has an intrinsic specific surface area and an intrinsic pore size within the required ranges... good resistance to electrolyte erosion
Data Source
AI summary
The present disclosure relates to a positive electrode material for a lithium ion battery and its preparation. The positive electrode material in accordance with the present disclosure has an intrinsic specific surface area of 5-13 m2/g. The positive electrode material in accordance with the present disclosure has an intrinsic specific surface area and an intrinsic pore size within the required ranges. In this regard, the positive electrode material in accordance with the present disclosure has excellent particle strength, excellent Li ion transference ability, and good resistance to electrolyte erosion. When used in lithium batteries, it may impart the batteries with excellent rate performance and cycle performance. The present disclosure also relates to a method for preparing the positive electrode material.