High-Nickel Li-Ion Cathode Coating for Low Resistance Stability
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Solution Overview
Problem
The depletion of cobalt (Co) in lithium ion secondary batteries poses a challenge, leading to increased initial resistance and resistance over time, especially when the cobalt content in the positive electrode active material is reduced.
Innovation Solution
A lithium ion secondary battery design featuring a positive electrode with a high nickel-containing lithium-transition metal complex oxide having a layered structure, a boron chemical compound covering part, and a negative electrode with a specific silicon content, which together suppress the increase in initial resistance and storage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cobalt content in the positive electrode active material is decreased, then the cost and resource sustainability are improved, but the initial resistance and storage resistance are significantly increased
Solution Approach 1:
The invention changes the chemical composition parameters of the positive electrode active material by incorporating specific ratios of nickel, cobalt, and manganese elements, along with surface modification using boron-containing compounds. This parameter optimization allows reducing overall cobalt content while maintaining resistance stability through the synergistic effect of high-nickel core composition and boron-based surface coating that prevents degradation.
Solution Approach 2:
The invention uses a composite material structure where the positive electrode active material consists of multiple elements (Ni, Co, Mn) in specific ratios, with further surface modification by boron-containing compounds. This composite approach creates a multi-functional material that reduces cobalt dependency while maintaining electrochemical stability and resistance properties through the combined effects of the core composite and surface coating.
2Use of energy by moving object
If the nickel containing rate is increased to 75 mol% or more, then the energy density is improved, but the structural stability and resistance control become more difficult
Solution Approach 1:
The invention optimizes the compositional parameters by setting nickel content at 75 mol% or more while precisely controlling cobalt and manganese ratios. Additionally, surface modification with boron-containing compounds at controlled concentrations changes the surface chemical properties, enabling high energy density from the nickel-rich core while the surface modification stabilizes resistance by preventing cation mixing and surface degradation.
Solution Approach 2:
The invention applies local quality modification by treating the surface of the high-nickel positive electrode active material with boron-containing compounds. This creates a differentiated structure where the core provides high energy density through high nickel content, while the surface layer provides structural stability and resistance control, allowing each region to fulfill its specific function optimally.
Data Source
AI summary
In a disclosed lithium ion secondary battery, a positive electrode active material includes a lithium-transition metal complex oxide, containing Li, Ni, and Mn and being formed in a layered structure, and includes a covering part, a lithium-transition metal complex oxide has a Ni containing rate being equal to or more than 75 mol % with respect to the total of metal elements other than Li and is a secondary particle, an average void rate of the secondary particle is equal to or more than 2% and not more than 10%, and a covering part contains a boron chemical compound. A negative electrode active material contains a carbon material and a Si containing material, and a containing ratio of a Si element in the negative electrode active material is equal to or more than 5 mass % and not more than 10 mass % of a total amount of the negative electrode active material.