Core-Shell Cathode Material to Prevent Ni Cation Mixing
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Solution Overview
Problem
High-nickel cathode active materials in lithium secondary batteries face instability due to nickel trivalent ions (Ni3+) being reduced to nickel divalent ions (Ni2+), leading to cation mixing and surface resistance issues, which affect capacity and energy density.
Innovation Solution
A core-shell structured cathode active material doped with boron (B) and aluminum (Al) is developed, featuring a nickel-rich core and cobalt-doped shell, maintaining high nickel concentrations and preventing cation mixing through a specific composition and heat treatment process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel cathode active material is used to increase capacity and energy density, then battery capacity and energy density are improved, but Ni3+ ions become unstable and are reduced to Ni2+, causing cation mixing and surface resistance
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high-nickel content (LiNixCo1-xO2 where x≥0.8) for high capacity, while the shell region has different composition to stabilize the structure. This allows different parts of the material to have different functions: the core provides capacity while the shell prevents degradation
Solution Approach 2:
The patent uses composite materials by combining nickel-rich and cobalt-rich regions in a core-shell structure. The composite nature allows the material to simultaneously achieve high capacity (from nickel) and structural stability (from cobalt), resolving the contradiction between capacity and stability
2Use of energy by stationary object
If high-nickel cathode active material is used to increase capacity, then energy density is improved, but cation mixing occurs where Li+ is replaced with Ni2+ and pushed outward, forming NiO resistance layer
Solution Approach 1:
The patent creates local quality differences by having a nickel-rich core for high energy density and a cobalt-rich shell that prevents cation mixing. The shell region's different composition locally suppresses the harmful cation mixing effect while preserving the high-nickel core's energy density benefits
Solution Approach 2:
The patent converts the potential harm of nickel instability into a benefit by using the core-shell structure where the nickel-rich core provides high capacity while the cobalt-rich shell captures and stabilizes any migrated nickel ions, preventing them from forming resistive NiO layers on the surface
3Productivity
If nickel content is increased to improve capacity, then battery performance is enhanced, but NiO forms on surface acting as strong resistance component
Solution Approach 1:
The patent applies local quality by concentrating the high-nickel content in the core region where it provides capacity without direct exposure to electrolyte, while the shell region has lower nickel content and higher cobalt content to prevent surface resistance formation. This spatial separation resolves the contradiction between capacity and surface resistance
Solution Approach 2:
The cobalt-rich shell acts as an intermediary between the high-nickel core and the electrolyte environment. It mediates by preventing direct interaction between the nickel-rich core and external conditions that would cause NiO formation, thus protecting the core's capacity while preventing surface resistance
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 stabilizes Ni3+ ions, enhancing the battery's capacity recovery, high-rate charging and discharging capabilities, and extending battery life by preventing cation mixing and shell infiltration into the core.
Implementation Method 1
a cathode active material for a lithium secondary battery having a core-shell structure doped with B and Al
Implementation Method 2
a core-shell structured cathode active material doped with boron (B) and aluminum (Al) for a lithium secondary battery
Implementation Method 3
F) heat-treating the mixed powder
Data Source
AI summary
Proposed is a lithium secondary battery cathode active material doped with B and Al. The cathode active material has a high specific capacity upon charging and discharging, a high capacity resilience, and a high capacity retention rate.