B- and Sn-Doped Ni-Rich NCM Cathode for Cycle Stability
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Solution Overview
Problem
Ni-rich NCM cathode active materials in lithium secondary batteries experience rapid capacity decrease due to crystal structure collapse, oxygen release, and microcracks caused by anisotropic lattice stress, leading to reduced battery performance over charging and discharging cycles.
Innovation Solution
Doping boron (B) and tin (Sn) heteroatoms into the cathode active material to stabilize the crystal structure, prevent oxygen release, and reduce lattice stress, thereby maintaining the material's integrity and performance over multiple cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Ni content is increased to achieve high energy density, then energy density is improved, but crystal structure stability deteriorates leading to rapid capacity decrease
Solution Approach 1:
The patent applies local quality by doping B and Sn heteroatoms at specific sites within the NCM crystal structure. The heteroatoms are incorporated into the layered structure at controlled concentrations (B: 0.01-0.05 mol ratio relative to Li, Sn: 0.01-0.05 mol ratio relative to Li), creating localized regions that stabilize the crystal structure without compromising the overall high Ni content (0.8-0.96) required for energy density. This localized modification allows the bulk material to maintain high energy density while specific doped regions prevent structure collapse.
Solution Approach 2:
The patent creates a composite cathode material by combining NCM with heteroatom dopants B and Sn. The composite structure Li(Ni0.8-x-yCoxMn1-x-y)1-zBzSnnO2 integrates multiple elements with different properties: Ni provides high capacity, Co provides structural stability, Mn provides spinel structure stability, B provides strong bonding with oxygen, and Sn provides additional structural stabilization. This composite approach allows the material to achieve both high energy density and improved structural stability simultaneously.
2Use of energy by moving object
If Ni content is increased to achieve high energy density, then energy density is improved, but oxygen release increases leading to capacity degradation
Solution Approach 1:
The patent converts the potentially harmful oxygen release phenomenon into a beneficial effect by using B and Sn heteroatoms that have strong affinity for oxygen. The heteroatoms preferentially bind with oxygen atoms in the crystal structure, forming strong B-O and Sn-O bonds that prevent oxygen release during charging cycles. This transforms the oxygen that would otherwise be released as a harmful byproduct into a stabilized component of the doped crystal structure, thereby maintaining high energy density while eliminating oxygen release degradation.
3Use of energy by moving object
If Ni content is increased to achieve high energy density, then energy density is improved, but lattice stress increases causing microcracks and particle destruction
Solution Approach 1:
The patent applies beforehand cushioning by incorporating B and Sn heteroatoms into the NCM crystal structure prior to battery operation. These heteroatoms create a pre-stabilized framework that cushions against the anisotropic lattice stress that occurs during charging and discharging cycles. The strong B-O and Sn-O bonds formed during doping create a rigid yet flexible structure that absorbs and distributes mechanical stress, preventing the formation of microcracks and particle destruction that would otherwise occur in high-Ni materials under repeated cycling.
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 doping of B and Sn heteroatoms in the lithium secondary battery cathode active material results in a capacity retention rate of 80% or more after 150 cycles, enhancing the battery's service life by stabilizing the crystal structure and preventing transition metal leakage.
Implementation Method 1
The technique uses the principle of maintaining the stable crystal structure during charging and discharging, based on strong bonding energy with oxygen
Implementation Method 2
Tin ions, which are high-valent cations, strongly pull the electrons of oxygen when combined with oxygen
Data Source
AI summary
Proposed are a lithium secondary battery cathode active material doped with B and Sn and a lithium secondary battery including the cathode active material. The B and Sn doping enables a cathode capable of solving problems occurring in a high-nickel cathode, such as (1) an electrolyte side reaction on the surface, 2) a crystal structure collapse, 3) oxygen release, 4) inert Ni4+ generation; 5) cation mixing, and 6) transition metal elution. This improves the life span of a lithium secondary battery.