NiO-Like Coated Cathode Material for Low-Damage Lithium Removal
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high capacity, initial efficiency, and cycle life due to issues such as oxidation, electrolyte depletion, and surface damage during the washing process.
Innovation Solution
A cathode active material is developed comprising secondary particles with a NiO-like crystalline phase coating, prepared through a method involving heat-treatment, washing with a weakly acidic or neutral organic buffer, and secondary heat-treatment to enhance surface coating and reduce residual lithium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional washing process is used to remove residual lithium, then residual lithium is removed, but surface damage and formation of resistive NiO-like phases occur
Solution Approach 1:
The patent changes the chemical parameters of the washing process by using a weakly acidic or neutral organic buffer solution instead of conventional aqueous solutions. This parameter change prevents surface damage and resistive NiO-like phase formation while effectively removing residual lithium, thereby improving battery life characteristics without causing surface damage.
Solution Approach 2:
The patent introduces a weakly acidic or neutral organic buffer solution as an intermediary substance between the cathode active material and the washing process. This intermediary buffer solution mediates the removal of residual lithium while preventing harmful surface damage and NiO-like phase formation, resolving the contradiction between effective cleaning and surface protection.
2Quantity of substance
If high nickel content is used to increase capacity, then capacity is improved, but oxidation and electrolyte depletion occur
Solution Approach 1:
The patent applies local quality by creating a differentiated surface layer with specific chemical composition and properties. The weakly acidic or neutral organic buffer treatment creates a surface layer that is chemically distinct from the bulk material, providing localized protection against oxidation and electrolyte depletion while maintaining high nickel content for capacity in the bulk material.
Solution Approach 2:
The patent creates a composite structure where the cathode active material with high nickel content is combined with a surface layer formed through weakly acidic or neutral organic buffer treatment. This composite structure allows the bulk material to provide high capacity while the surface layer provides protection against oxidation and electrolyte depletion, resolving the contradiction between capacity and initial efficiency.
3Manufacturing precision
If conventional heat treatment is applied to form surface coating, then surface coating is formed, but resistive NiO-like phases are formed
Solution Approach 1:
The patent applies preliminary action by performing the weakly acidic or neutral organic buffer treatment before final heat treatment. This preliminary treatment prepares the surface in a controlled manner, creating a surface layer that is resistant to forming harmful NiO-like phases during subsequent heat treatment, while still achieving uniform surface coating.
Solution Approach 2:
The patent changes the chemical parameters of the surface treatment process by using weakly acidic or neutral organic buffers instead of conventional treatments. This parameter change modifies the surface chemistry to prevent resistive NiO-like phase formation during heat treatment while maintaining uniform surface coating, resolving the contradiction between coating quality and harmful phase formation.
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 proposed cathode active material improves the initial efficiency, capacity, and life characteristics of lithium secondary batteries by reducing surface damage, suppressing the formation of resistive NiO-like phases, and effectively removing residual lithium.
Implementation Method 1
washing a resulting product of the primary heat treatment using a solvent comprising a weakly acidic or neutral organic buffer
Implementation Method 2
washing a resulting product of the primary heat treatment using a solvent comprising a weakly acidic or neutral organic buffer
Implementation Method 3
primarily heat-treating a mixture comprising a transition metal precursor and a lithium source
Implementation Method 4
a first coating layer disposed on the plurality of primary particles to have a thickness of about 2.5 nm or less and comprising a NiO-like crystalline phase
Data Source
AI summary
This application relates to a cathode active material for a lithium secondary battery, a method of preparing the cathode active material, a cathode employing the cathode active material, and a lithium secondary battery employing the cathode. The cathode active material may include a secondary particle in which primary particles are aggregated and a first coating layer disposed on the plurality of primary particles to have a thickness of about 2.5 nm or less and including a NiO-like crystalline phase belonging to a Fm3-m space group. The cathode active material may prevent surface deterioration through a washing process using a weakly acidic or neutral organic buffer, thereby improving the initial efficiency characteristic and life characteristics of the lithium secondary battery while maintaining the initial capacity of the lithium secondary battery.