LNMO Phosphate Coating for Low-Gas Positive Electrode Materials
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Solution Overview
Problem
Lithium nickel manganese oxide (LNMO) in lithium ion secondary batteries generates gas due to the decomposition of nonaqueous electrolytic solution because of its high operating voltage and exposure to an oxidizing atmosphere, and existing coatings like LATP result in non-uniform layers with locally varying thicknesses.
Innovation Solution
A positive electrode composite active substance is developed with a lithium manganese-based oxide having a spinel-type crystal structure coated by a phosphate-based compound (Li\_aA\_bD\_cPO4) with a thickness of 5 nm to 20 nm, forming a uniform and amorphous layer to reduce contact with the electrolyte and alleviate dielectric polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LNMO is used as positive electrode active substance, then high energy density is achieved, but gas is generated due to decomposition of nonaqueous electrolytic solution
Solution Approach 1:
A phosphate-based compound coating layer is introduced as an intermediary between the LNMO active substance and the nonaqueous electrolytic solution. This coating layer prevents direct contact between the electrolyte and LNMO surface, thereby suppressing decomposition reactions and gas generation while maintaining the high energy density benefits of LNMO.
Solution Approach 2:
A thin film coating layer with controlled thickness (5-50 nm) is applied to the LNMO surface. This thin film acts as a protective shell that prevents electrolyte decomposition while minimizing resistance loss, achieving both gas suppression and maintained energy density.
2Object-generated harmful factors
If LATP coating layer is formed to suppress gas generation, then gas amount is reduced, but coating layer becomes non-uniform with locally different thickness
Solution Approach 1:
The coating method is changed from conventional coating to a sol-gel process using phosphate-based compound precursors. By controlling parameters such as sol concentration, drying temperature, and heating conditions, a uniform coating layer with consistent thickness (5-50 nm) is achieved across the entire LNMO particle surface, eliminating local thickness variations.
Solution Approach 2:
The coating layer is designed to form uniformly across the entire surface of LNMO particles rather than creating localized thick or thin regions. The sol-gel process ensures homogeneous distribution of the phosphate-based compound, creating consistent protective properties across all areas of the active substance.
3Object-generated harmful factors
If coating layer thickness is increased to suppress gas generation, then gas generation is reduced, but resistance loss increases
Solution Approach 1:
The coating thickness is precisely controlled within the range of 5-50 nm through optimization of the sol-gel process parameters. This thin but sufficient thickness provides effective protection against electrolyte decomposition while minimizing the additional resistance introduced by the coating layer, achieving optimal balance between gas suppression and electrical performance.
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 solution effectively suppresses gas generation and maintains high energy density by ensuring a uniform, thin coating that reduces resistance loss and interface resistance, enhancing the battery's stability and capacity retention.
Implementation Method 1
a coating layer covering a surface of the oxide active substance... the coating layer includes a phosphate-based compound... the coating layer has a thickness of 5 nm or more and 20 nm or less
Implementation Method 2
the coating layer is amorphous in a range of 2 nm from an interface with the oxide active substance
Data Source
AI summary
The present invention provides a positive electrode composite active substance which includes a uniform coating layer as compared with the related art and can suppress generation of gas due to decomposition of a nonaqueous electrolytic solution, and a method of manufacturing the positive electrode composite active substance. An oxide active substance, and a coating layer covering a surface of the oxide active substance are provided, the oxide active substance includes a lithium manganese-based oxide having a spinel-type crystal structure, the coating layer includes a phosphate-based compound represented by Formula (1), and the coating layer has a thickness of 5 nm or more and 20 nm or less,LiaAbDcPO4 (1)where a, b, and c satisfy 0.9<a<1.1, 0<b≤1, 0≤c<1, 0.9<b+c<1.1, A is at least one selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr, and D is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, and Y.