Boron-Carbon Coated Lithium-Rich Cathode for Low Gas Generation
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Solution Overview
Problem
Lithium-rich oxides used in positive electrodes of lithium secondary batteries face issues with irreversible capacity loss and gas generation due to structural changes during high-voltage operation, leading to reduced efficiency and stability.
Innovation Solution
A positive electrode active material is developed with a lithium-rich transition metal oxide coated with boron and carbon, meeting specific X-ray photoelectron spectroscopy (XPS) conditions, and prepared through dry-mixing and heat treatment processes to enhance performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-rich oxide is used as positive electrode active material to achieve high capacity, then discharge capacity is improved, but irreversible capacity loss occurs and efficiency deteriorates during first formation process
Solution Approach 1:
A coating layer comprising boron and carbon is applied to the surface of the lithium-rich transition metal oxide particles. This coating layer acts as an intermediary between the active material and the electrolyte, preventing direct harmful interactions while allowing beneficial electrochemical reactions. The coating reduces irreversible capacity loss during the first formation process by suppressing oxygen release and stabilizing the surface structure, thereby improving initial charging-discharging efficiency without significantly reducing discharge capacity.
2Power
If lithium-rich oxide operates at high voltage to improve energy density, then output is improved, but O2 gas is generated and voltage fading occurs
Solution Approach 1:
The coating layer comprising boron and carbon transforms the harmful high-voltage operation conditions into beneficial effects. By stabilizing the surface structure, the coating prevents oxygen release that would otherwise occur during high-voltage charging. The boron and carbon elements form a protective barrier that suppresses the formation of rock-salt structure and prevents O2 gas generation, allowing the battery to operate at high voltages (>3.5 V vs. Li/Li+) without the associated harmful effects, thereby maintaining high output and energy density.
3Duration of action of moving object
If lithium-rich oxide undergoes charge and discharge cycles to maintain layered structure, then capacity is maintained, but structure changes to spinel and then rock-salt causing voltage fading
Solution Approach 1:
The coating layer comprising boron and carbon is applied in advance to the surface of the lithium-rich transition metal oxide particles before cycling. This preliminary action stabilizes the surface structure and prevents the phase transformation from layered to spinel to rock-salt structure that occurs during charge and discharge cycles. By pre-protecting the surface, the coating maintains the layered structure integrity throughout cycling, preventing voltage fading and ensuring long-term capacity retention.
4Reliability
If coating layer is formed on lithium-rich transition metal oxide to improve stability, then efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The coating layer comprising boron and carbon is formed through a self-service mechanism where the coating materials are applied to the lithium-rich transition metal oxide particles, and upon heat treatment, the coating forms autonomously on the particle surfaces. The boron and carbon elements react with the surface to create a stable coating structure without requiring complex external equipment or multi-step processes. This self-forming coating approach improves stability while minimizing manufacturing complexity by utilizing the inherent reactivity of the materials involved.
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 coated material improves discharge capacity, efficiency, and resistance characteristics of lithium secondary batteries, reducing gas generation and enhancing energy density.
Implementation Method 1
dry-mixing the lithium-rich transition metal oxide and a boron-containing raw material and performing a heat treatment to form a coating layer on the lithium-rich transition metal oxide
Data Source
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AI summary
The present invention relates to a positive electrode active material which may consequently improve performance of a battery including the same by improving performance and stability of a lithium-rich oxide, wherein the present invention relates to a positive electrode active material which includes a layer-structured lithium-rich transition metal oxide including both a Li2MnO3 phase and a LiMO2 phase (where M is an element including at least one selected from nickel (Ni), cobalt (Co), and manganese (Mn)); and a coating layer including boron and carbon which is formed on the lithium-rich transition metal oxide, and satisfies at least one of conditions (1) to (3), a method of preparing the same, and a positive electrode and a lithium secondary battery which include the same. - Condition (1): An atomic ratio (B/Mn) of boron (B) to manganese (Mn) present on a surface, which is analyzed by X-ray photoelectron spectroscopy (XPS), is in a range of 1 to 5 - Condition (2): An intensity ratio (ICarbonate,1:IC-C) of a peak (ICarbonate,1) at 287.5 eV to 288.5 eV to a peak (IC-C) at 284 eV to 285 eV in an XPS spectrum of the surface is in a range of 0.05:1 to 0.15:1 - Condition (3): An intensity ratio (ICarbonate,2:IC-C) of a peak (ICarbonate,2) at 288.6 eV to 290.5 eV to the peak (IC-C) at 284 eV to 285 eV in the XPS spectrum of the surface is in a range of 0.05:1 to 0.15:1