LiMO2 Cathode Dopants Stabilize Bulk and Surface Chemistry
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Solution Overview
Problem
Lithium-ion batteries face challenges with Ni-rich layered oxides due to bulk and surface structural instability, leading to capacity fading and impedance buildup, especially at high voltages, and cobalt-free alternatives struggle with phase transformations and electrolyte oxidation, resulting in limited cycle life and energy density.
Innovation Solution
The use of electrochemically active materials with specific dopants such as Mg and Ti in LiMO2 structures, which stabilize both the bulk and surface chemistry, reducing phase transformations and enhancing cycle life, energy density, and thermal stability, while minimizing Ni dissolution and oxygen release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Ni-rich layered oxides are used to achieve high energy density, then specific energy is improved, but bulk and surface structural stability deteriorates leading to capacity fading and impedance buildup
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties than the bulk. A Li-rich surface layer is formed through controlled delithiation, creating a gradient structure that stabilizes the surface while maintaining high-nickel bulk composition for energy density. This local differentiation resolves the contradiction by protecting the unstable surface without compromising the energy-rich bulk.
Solution Approach 2:
The patent employs composite materials by combining high-nickel LiNi1-x-yMxO2 bulk material with a Li-rich surface layer formed through electrochemical delithiation. The composite structure integrates the high energy density of Ni-rich bulk with the structural stability of Li-rich surface, creating a multi-phase composite that simultaneously achieves both high specific energy and improved structural stability.
2Use of energy by moving object
If high voltage operation is implemented to increase energy density, then specific energy is improved, but interfacial reactions increase causing capacity fading and impedance buildup
Solution Approach 1:
The patent uses the Li-rich surface layer as an intermediary between the high-voltage cathode and the electrolyte. This surface layer acts as a protective mediator that reduces direct contact between the unstable high-nickel bulk and the electrolyte, thereby suppressing interfacial reactions, oxygen release, and impedance buildup while allowing high-voltage operation for energy density improvement.
Solution Approach 2:
The patent converts the harmful effect of surface instability into a beneficial protective layer. By deliberately inducing controlled surface reconstruction and Li depletion at the surface, the patent transforms what would normally be a degradation mechanism into a protective surface layer that stabilizes the interface and reduces harmful interfacial reactions during high-voltage operation.
3Ease of manufacture
If cobalt-free LiNiO2 is used to reduce cost and toxicity, then manufacturing cost and environmental impact are improved, but phase transformations and electrolyte oxidation increase reducing cycle life
Solution Approach 1:
The patent applies local quality by creating a compositional gradient where the surface region differs from the bulk. The Li-rich surface layer formed through delithiation provides local structural stability and reduced reactivity at the critical interface, while the bulk maintains the desired cobalt-free high-nickel composition for cost-effectiveness. This local differentiation enables both cost reduction and improved cycle life.
4Reliability
If surface coating is applied to improve structural stability, then reliability is improved, but manufacturing complexity increases due to difficulty achieving conformal coating
Solution Approach 1:
The patent employs self-service by utilizing electrochemical delithiation to automatically form the protective surface layer during normal battery charging cycles. The surface modification occurs in-situ through electrochemical reactions, eliminating the need for separate coating processes. The battery itself performs the surface engineering function during its normal operation, greatly simplifying manufacturing while achieving the desired surface stability.
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 introduction of Mg and Ti dopants in LiMO2 materials results in improved specific energy, cycle life, rate capability, self-discharge resistance, and thermal stability, leading to more efficient and durable lithium-ion battery cathodes.
Implementation Method 1
The use of electrochemically active materials with specific dopants such as Mg and Ti in LiMO2 structures, which stabilize both the bulk and surface chemistry
Implementation Method 2
electrochemically active materials with specific dopants such as Mg and Ti in LiMO2 structures
Data Source
AI summary
In one aspect, the disclosure relates to electrochemically active materials for use in constructing cathodes in lithium ion batteries. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure. In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, the disclosure, in one aspect, relates to electrochemically active materials for use as cathodes in lithium-ion batteries, methods of introducing dopants into the electrochemically active materials, and electrochemical cells and batteries comprising the same. Cathodes made using the electrochemically active materials disclosed herein exhibit smoother voltage profiles as well as enhanced specific energy, cycle life, rate capability, self-discharge resistance, and thermal stability compared to conventional cathodes.