Delithiated Core-Shell Cathode Reduces Formation Losses
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Solution Overview
Problem
Lithium ion batteries experience significant formation losses during the first charging operation due to the formation of the solid electrolyte interface (SEI) on the anode, which reduces the battery's capacity and energy density, especially when using layered oxide cathodes like NMC.
Innovation Solution
An active cathode material with a core-shell structure is developed, where the core is made of layered oxides and the shell is composed of a delithiated olivine compound, allowing for stable processing and reduced formation losses by enabling lithium ions to be intercalated uniformly, thus enhancing specific energy and energy density without increasing the use of costly nickel and cobalt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layered oxide cathode (e.g., NMC) is used with a graphite anode, then the battery achieves high capacity, but formation losses increase to 6%-20% due to SEI formation and incomplete lithium intercalation
Solution Approach 1:
The cathode material is pre-delithiated before battery assembly, so that lithium ions are removed from the cathode in advance. This preliminary action ensures that during the first charging operation (formation), fewer lithium ions are needed for SEI formation on the anode, thereby reducing formation losses while maintaining high battery capacity.
Solution Approach 2:
The lithiation level of the cathode material is changed from a fully lithiated state to a delithiated state (reducing x in LixMO2). This parameter change optimizes the battery's energy density and reduces formation losses by adjusting the initial lithium content in the cathode to match the anode's lithium acceptance capacity.
2Loss of energy
If the cathode material is delithiated to reduce formation losses, then energy density improves, but the material may become less stable
Solution Approach 1:
The cathode material undergoes a controlled preliminary delithiation process before battery assembly, where lithium ions are removed to an optimal extent (reducing x in LixMO2 to 0.95-1.05). This preliminary action stabilizes the cathode structure in advance, preventing excessive structural changes during battery formation and cycling, thereby maintaining material stability while reducing formation losses.
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 core-shell structure reduces formation losses, stabilizes the cathode material, and allows for environmentally friendly aqueous processing, resulting in improved energy density and safety without the need for toxic solvents, while maintaining high energy performance.
Implementation Method 1
allowing for stable processing and reduced formation losses by enabling lithium ions to be intercalated uniformly
Implementation Method 2
the shell is composed of a delithiated olivine compound, allowing for stable processing
Data Source
AI summary
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