Positive Electrode Material With Oxygen Defects for High-Voltage Stability
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Solution Overview
Problem
Lithium-ion batteries face issues with surface oxygen release and structural phase changes under high voltage and lithium extraction, leading to cycling performance degradation and gas production, which are not effectively addressed by current optimizations such as nano-oxide coatings that hinder lithium-ion transport.
Innovation Solution
A positive electrode material with internal oxygen defects and specific doping of elements like Na, Ni, and Mn, which enhances energy density and kinetic performance by regulating oxygen defects and lithium-oxygen interlayer spacing, reducing gas production and improving high-temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the voltage and lithium extraction amount are increased to achieve higher energy density, then the energy density is improved, but surface oxygen release and structural phase change occur leading to cycling performance degradation and gas production
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode material by doping with elements such as Ni, Co, Mn, and Al, and adjusting the Li content to achieve a formula of Li1+x□1-yNi1-a-bCobMncO2−z. This compositional parameter change allows the material to maintain structural stability at high voltages (4.2-4.5V) while achieving high energy density, resolving the contradiction between energy density improvement and cycling performance degradation
Solution Approach 2:
The patent creates a composite positive electrode material by combining multiple transition metal elements (Ni, Co, Mn, Al) in specific ratios within the layered oxide structure. This composite approach leverages the advantageous properties of each element: Ni for high capacity, Co for stability, Mn for structural support, and Al for surface protection, achieving both high energy density and good cycling performance simultaneously
2Object-generated harmful factors
If the surfaces of positive electrode materials are coated with nano-oxides to reduce gas production, then gas production is reduced, but lithium-ion migration is hindered affecting extractable capacity
Solution Approach 1:
Instead of coating the surface with nano-oxides, the patent changes the intrinsic surface properties by doping the positive electrode material with Al and controlling the Li content (x and y parameters). This creates a surface composition of Li1+x□1-yNi1-a-bCobMncO2−z that inherently resists oxygen release and forms stable surface structures, reducing gas production without adding external coating layers that would block lithium-ion transport
Solution Approach 2:
The patent removes the need for external nano-oxide coating layers by integrating protective functionality directly into the positive electrode material's crystal structure through doping. The Al doping and Li content adjustment create intrinsic surface protection that eliminates the harmful gas production without requiring separate coating layers, thus avoiding the trade-off between protection and lithium-ion transport
3Object-generated harmful factors
If oxidation-resistant electrolytes with long molecular chain solvent molecules are used to reduce gas production, then gas production is reduced, but lithium-ion transport kinetics worsen leading to lower rate performance and higher temperature rise
Solution Approach 1:
The patent changes the positive electrode material's surface chemistry through Al doping and controlled Li deficiency (y parameter), creating a surface that is inherently resistant to oxidation and gas production. This allows the use of standard electrolytes with good lithium-ion transport kinetics without the need for long-chain oxidation-resistant electrolytes, thus maintaining both low gas production and high rate performance
Solution Approach 2:
The doped positive electrode material surface acts as an intermediary layer that provides oxidation resistance and gas production suppression without requiring external electrolyte modifications. The Al-doped surface composition (Li1+x□1-yNi1-a-bCobMncO2−z) serves as a protective interface between the electrode and electrolyte, enabling the use of fast-transport electrolytes while preventing harmful gas generation
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 positive electrode material exhibits high energy density, good structural stability, and improved kinetic performance, with reduced gas production during high-temperature storage, enabling better lithium-ion diffusion and electron conductivity.
Implementation Method 1
the positive electrode material has a reversible charge/discharge capacity in the high voltage range of 4.2 V to 4.5 V due to the presence of internal oxygen defects
Implementation Method 2
enabling better lithium-ion diffusion and electron conductivity
Data Source
AI summary
A positive electrode material, when an electrode including such positive electrode material is assembled with lithium metal to form a button cell and the button cell is charged and discharged at a current of 0.04 C in the voltage range of 2.8 V to 4.5 V, a differential capacity versus voltage dQ/dV curve obtained has a first oxidation peak and a first reduction peak in a range of 4.2 V to 4.5 V. The positive electrode material has high energy density as well as improved kinetic performance and high-temperature stability.