Ni-Rich Cathode Material Crystallinity for Longer Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium transition metal composite oxides with higher molar content ratios of Ni to transition metal elements in LiMeO2-type positive active materials experience significant volume expansion and contraction during charge-discharge cycles, leading to cracking and poor charge-discharge cycle performance, despite efforts to enhance crystallinity and add sintering agents.
Innovation Solution
A lithium transition metal composite oxide with an α-NaFeO2 structure, containing Ni, Co, and Mn, exhibiting a specific X-ray diffraction pattern and crystallite size ratio, is produced using a method involving an aqueous solution with halogen and ammonium ions, followed by firing to achieve improved charge-discharge cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the molar content ratio of Ni to transition metal elements is increased to enhance discharge capacity, then the discharge capacity is improved, but the charge-discharge cycle performance deteriorates due to volume expansion and contraction
Solution Approach 1:
The invention changes the chemical composition parameters by introducing Zn elements and adjusting the molar ratios of Ni, Co, Mn, and Zn in the LiMeO2-type composite oxide. This compositional parameter adjustment reduces the volume expansion and contraction during charge-discharge cycles while maintaining high discharge capacity, thereby improving charge-discharge cycle performance
Solution Approach 2:
The invention creates a composite material system by combining multiple transition metal elements (Ni, Co, Mn, Zn) in specific ratios within the LiMeO2-type structure. This composite approach leverages the beneficial properties of each element: Ni for high capacity, Co for stability, Mn for structural integrity, and Zn for reduced volume change, achieving both high discharge capacity and improved cycle performance
2Stability of the object's composition
If sintering agents are added and crystallinity is enhanced to improve structural stability, then the structural stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention changes the firing temperature parameter to a specific range (900-1100°C) to achieve optimal crystallinity and structural stability without requiring additional sintering agents. This parameter optimization simplifies the manufacturing process by eliminating the need for extra chemical additives while maintaining structural integrity
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 active material demonstrates enhanced charge-discharge cycle performance with reduced anisotropy and increased discharge capacity, maintaining structural integrity and energy density.
Implementation Method 1
supplying an aqueous solution containing halogen ions, ammonium ions, and Ni, Co, and Mn as transition metals (Me) to a reaction tank to precipitate a carbonate precursor containing Ni, Co, and Mn
Implementation Method 2
firing the mixture to produce a lithium transition metal composite oxide
Implementation Method 3
the lithium transition metal composite oxide having an α-NaFeO2 structure
Implementation Method 4
a ratio of the full width at half maximum of a diffraction peak of the (003) plane to the full width at half maximum of a diffraction peak of the (104) plane in X-ray diffraction measurement
Implementation Method 5
X-ray diffraction pattern attributable to R3-m
Data Source
AI summary
Provided is a positive active material for a nonaqueous electrolyte secondary battery which contains a lithium transition metal composite oxide, the lithium transition metal composite oxide having an α-NaFeO2 structure, containing Ni, Co and Mn as a transition metal (Me), and having an X-ray diffraction pattern attributable to a space group R3-m, in which a ratio of the full width at half maximum of a diffraction peak of the (003) plane to the full width at half maximum of a diffraction peak of the (104) plane, (003)/(104) at a Miller index hkl in X-ray diffraction measurement using a CuKα ray is 0.810 to 0.865, and a crystallite size is 410 Å or more.