Rounded LiNi0.5Mn1.5O4 Cathode Grains for Stable High-Voltage Cycling
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Solution Overview
Problem
Cobalt-free spinel type LiNi0.5Mn1.5O4 positive electrode active materials face compatibility issues with conventional electrolytic solutions due to high operating voltage, leading to side reactions, interface deterioration, and poor cycling stability, primarily due to sharp edges and high stress corrosion.
Innovation Solution
A lithium nickel manganese-containing composite oxide with a rounded spherical or spherical-like grain shape, doped with elements like Si, P, and transition metals, is prepared through controlled sintering processes to enhance structural stability and reduce corrosion, featuring a monocrystal or quasi-monocrystal morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cobalt-free spinel type LiNi0.5Mn1.5O4 is used as positive electrode active material, then energy density and cost are improved, but compatibility with conventional electrolytic solutions deteriorates due to high operating voltage causing side reactions and interface deterioration
Solution Approach 1:
A surface coating layer comprising Li2SiO3, Li3PO4, or their composite is applied to the LiNi0.5Mn1.5O4 particles. This coating layer acts as an intermediary between the positive electrode active material and the electrolytic solution, preventing direct harmful interactions while allowing lithium ion transport, thus resolving the incompatibility between high-voltage spinel material and conventional electrolytes
Solution Approach 2:
The operating voltage range is optimized to 4.2V-4.35V, and the surface coating composition is carefully controlled with specific molar ratios of Li, Si, and P elements. These parameter changes ensure the coating forms a stable protective interface that maintains reliability while preserving the high energy density characteristics of the cobalt-free spinel material
2Use of energy by moving object
If LiNi0.5Mn1.5O4 with high operating voltage is used, then energy density is improved, but side reactions with electrolytic solution increase causing interface deterioration
Solution Approach 1:
The surface coating layer serves as a protective intermediary that physically separates the high-voltage LiNi0.5Mn1.5O4 from the electrolytic solution, preventing oxidative decomposition of the electrolyte and formation of harmful interface byproducts, while maintaining ionic conductivity for battery operation
Solution Approach 2:
The high operating voltage that causes harmful side reactions is converted into a benefit by using it to form a stable solid electrolyte interface (SEI) layer during initial cycles. This SEI layer, enriched with Li2SiO3 and Li3PO4, subsequently protects the material during cycling, transforming the initially harmful high-voltage effect into a protective mechanism
3Ease of manufacture
If conventional sintering methods are used, then manufacturing simplicity is maintained, but grain morphology develops sharp edges leading to high stress corrosion
Solution Approach 1:
The sintering process parameters are optimized with a temperature range of 900-1100°C and controlled holding times to promote grain growth into rounded spherical or spherical-like shapes. This parameter optimization maintains manufacturing simplicity while eliminating sharp edges that would cause stress concentration and corrosion during battery cycling
4Reliability
If surface coating is applied to reduce corrosion, then interface stability is improved, but manufacturing complexity increases
Solution Approach 1:
The surface coating process is merged with the existing sintering workflow by applying the coating precursor to the sintered LiNi0.5Mn1.5O4 particles and performing a brief additional sintering step. This integrated approach incorporates the protective coating into the manufacturing process without requiring entirely new equipment or complex multi-step procedures, thus limiting the increase in manufacturing complexity
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 significantly reduces electrolyte corrosion and interface impedance, improving specific capacity, cycling stability, and energy density of secondary batteries, while maintaining resistance to stress corrosion and extending service life.
Implementation Method 1
heating the raw material to a first temperature T1 under an oxygen-containing atmosphere, maintaining at the first temperature T1 for a first time t1, cooling to room temperature, after which an intermediate product is obtained; and heating the intermediate product to a second temperature T2 under an oxygen-containing atmosphere, maintaining at the second temperature T2 for a second time t2
Data Source
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AI summary
The present application provides a lithium nickel manganese-containing composite oxide, a preparation method thereof, and a positive electrode plate, a secondary battery and an electrical device. The lithium nickel manganese-containing composite oxide is a particle with a monocrystal morphology or a quasi-monocrystal morphology, the lithium nickel manganese-containing composite oxide has a spherical or spherical-like grain shape, and the lithium nickel manganese-containing composite oxide has a general formula of Li1+xNi0.5+yMzMn1.5-x-y-z-aAaO4-k, -0.2 < x < 0.5, -0.2 < y < 0.2, 0 < z < 0.2, 0 < a < 0.2, 0 < k < 0.2, A includes one or more selected from Si, P and S, M includes one or more selected from a metal-doping element. The lithium nickel manganese-containing composite oxide provided in the present application may improve the capacity exertion, energy density and cycling life of the secondary battery.