Ternary Cathode Material Grain-Boundary Oxides Against Particle Cracking
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Solution Overview
Problem
Existing methods for modifying ternary positive electrode materials in lithium ion secondary batteries are ineffective in achieving desired electrical and mechanical properties, particularly for polycrystalline structures, leading to issues like particle cracking and reduced cycle stability.
Innovation Solution
A positive electrode material comprising polycrystalline particles of a ternary material with a modifying material of tungsten oxide, niobium oxide, or molybdenum oxide on the surface and at grain boundary interfaces, which improves mechanical strength and high-temperature cycle stability by refining the microstructure and reducing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ternary positive electrode material is used to achieve high energy density and power density, then capacity is improved, but mechanical strength is insufficient causing particle breakage
Solution Approach 1:
The patent uses a composite structure where a core ternary positive electrode material (LiNixCoyMn1-x-yO2) is combined with a shell layer of modifying material (tungsten oxide, niobium oxide, or molybdenum oxide). This composite structure allows the core to provide high energy density while the shell provides mechanical strength and structural stability, preventing particle breakage during cycling.
Solution Approach 2:
The modifying material is selectively positioned at the surface and grain boundary interfaces of the ternary positive electrode material particles. This local modification provides enhanced mechanical strength and structural stability precisely where needed (at grain boundaries and surfaces) without compromising the bulk energy density of the ternary material.
2Strength
If modifying material is deposited on ternary positive electrode material to improve mechanical strength, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the modifying material with the ternary positive electrode material precursors into a single mixture before sintering. This merging of materials into one homogeneous mixture simplifies the manufacturing process by eliminating the need for separate deposition steps, while still achieving the desired core-shell structure and grain boundary modification during the sintering process.
3Reliability
If high temperature sintering is used to obtain monocrystalline structure, then electrochemical properties are improved, but energy consumption increases
Solution Approach 1:
The patent optimizes the sintering temperature parameter to a specific range (700-900°C) that is sufficient to form the desired monocrystalline structure and achieve good electrochemical properties, but not excessively high to waste energy. The presence of modifying materials in the precursor mixture also facilitates structure formation at these optimized temperatures.
4Shape
If secondary sintering process is used to add tungsten source, then coating is achieved, but improvement of electrochemical properties is not obvious
Solution Approach 1:
The patent incorporates the modifying material (tungsten oxide, niobium oxide, or molybdenum oxide) into the precursor mixture before the first sintering process. This preliminary incorporation ensures that the modifying material is uniformly distributed and properly integrated into the structure during the main sintering process, leading to significant improvements in electrochemical properties rather than just surface coating.
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 solution effectively enhances the mechanical strength and structural stability of the ternary positive electrode material, improving high-temperature cycle stability and reducing impedance increase during battery cycles, thereby extending the battery's lifespan and performance.
Implementation Method 1
The method comprises: step S1, subjecting a lithium source, a ternary positive electrode material precursor and a modifying material to primary sintering; and step S2, grinding the product after the primary sintering, and subjecting the ground product to secondary sintering
Data Source
AI summary
The present application provides a positive electrode material for a lithium ion secondary battery and a preparation method therefor. The positive electrode material for a lithium ion secondary battery comprises polycrystalline particles of a ternary positive electrode material and a modifying material. The polycrystalline particles comprise a plurality of primary particles. The modifying materials are located on the surface of the polycrystalline particles and/or at the grain boundary interfaces between the primary particles, wherein the modifying material comprises an oxide of a positive pentavalent or positive hexavalent transition metal. By using the positive electrode material for a lithium ion secondary battery and the preparation method therefor of the present application, the problem of cracking of secondary particles of the material during the circulation process is avoided. Thus, the mechanical strength and structural stability of the ternary positive electrode material are effectively improved, and at the same time, the high-temperature cycle stability of the ternary positive electrode material is significantly improved, and the impedance increase during the cycle of the lithium ion secondary battery prepared thereby is effectively reduced.