Lithium Ion Battery Cathode Gradient and CNT Conductive Network
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Solution Overview
Problem
Lithium secondary batteries face challenges with unstable thermal characteristics and lower output due to internal resistance, particularly with lithium transition metal oxides, which have a uniform metal concentration gradient only in the external area, limiting their performance.
Innovation Solution
A secondary battery design incorporating a cathode active material with a concentration gradient of metals throughout the entire region from the central portion to the surface, combined with a conductive material mixture of carbon nanotubes and carbon black at specific ratios to enhance stability, output, and low-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium transition metal oxide with uniform metal concentration is used as cathode active material, then thermal stability is improved, but output characteristic deteriorates due to large internal resistance
Solution Approach 1:
The cathode active material employs a concentration gradient structure where metal element concentration varies from the particle center to surface. Specifically, the ratio of Ni/(Co+Mn) is higher at the center (0.8-0.9) and lower at the surface (0.6-0.7), creating locally optimized properties: high-capacity Ni-rich core for power output and stable LiCoO2-like surface for thermal stability
Solution Approach 2:
The invention uses composite lithium transition metal oxide combining multiple metal elements (Ni, Co, Mn) with specific concentration distribution. The composite structure integrates high-capacity Ni-rich regions with stable Co/Mn-containing regions, achieving both high output characteristic and good thermal stability through material composition optimization
2Ease of manufacture
If conventional conductive materials are used, then manufacturing simplicity is maintained, but low temperature characteristic and output characteristic deteriorate
Solution Approach 1:
The conductive material uses a composite of carbon nanotubes and carbon black in a weight ratio of 1:9 to 4:6. This composite structure combines the high aspect ratio and conductivity of carbon nanotubes with the spherical nanoparticle characteristics of carbon black, creating an efficient conductive network that improves electron transport at low temperatures while remaining compatible with existing manufacturing processes
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 battery exhibits improved stability, output characteristics, and low-temperature performance by forming an effective conductive path between the cathode active material and conductive materials, maintaining high capacity and lifespan while reducing internal resistance.
Implementation Method 1
a conductive material mixture in which carbon nanotube is mixed with carbon black at an appropriate ratio
Implementation Method 2
a lithium secondary battery uses a principle in which electrical energy is generated by a change in chemical potential when lithium ions are inserted into and desorbed from a cathode and an anode
Data Source
AI summary
Provided is a secondary battery, specifically, a secondary battery having excellent stability and improved output characteristic and low temperature characteristic by including a cathode active material in which at least one of metals forming the cathode active material has a concentration gradient in an entire region from a central portion up to a surface portion; and a conductive material mixture in which carbon nanotube is mixed with carbon black at an appropriate ratio, the carbon black being a spherical nanoparticle.