Fluorinated Carbon Coated Cathode for High Voltage Lithium Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional cathode active materials for lithium ion secondary batteries (LIBs) fail to maintain high energy density and favorable cycle characteristics when charged at high voltages, as increasing the proportion of cathode active material in the cathode leads to decreased cycle characteristics.
Innovation Solution
A cathode active material comprising a composite oxide with Li and transition metals, combined with particles and fluorinated carbon material on its surface, which includes specific metal oxides and fluorinated carbon fibers or particles, enhancing energy density and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the proportion of cathode active material in the cathode is increased to increase energy density, then energy density is improved, but cycle characteristics are lowered
Solution Approach 1:
A fluorinated carbon material is introduced as an intermediary substance between the cathode active material and the electrolyte. This intermediate layer protects the cathode active material surface from direct contact with the electrolyte, reducing side reactions and maintaining cycle characteristics even when the cathode active material proportion is high (90 mass% or more).
Solution Approach 2:
The carbon material is fluorinated to change its chemical properties. The fluorination modifies the surface characteristics of the carbon material, enhancing its ability to protect the cathode active material while maintaining electrical conductivity, thus enabling high cathode active material content without sacrificing cycle life.
2Quantity of substance
If LiCoO2 is charged at high voltage to achieve high initial energy density, then initial energy density is improved, but cycle characteristics are lowered
Solution Approach 1:
The fluorinated carbon material is applied beforehand to the surface of the LiCoO2 cathode active material as a protective cushioning layer. This pre-formed protective layer prevents direct exposure of the LiCoO2 surface to the electrolyte during high-voltage charging, cushioning against degradation and maintaining cycle characteristics while enabling high initial energy density.
Solution Approach 2:
The high voltage charging condition, which normally causes degradation of LiCoO2, is converted into a beneficial operating mode. The fluorinated carbon material enables the system to tolerate and even utilize high voltage charging by protecting the LiCoO2 surface, transforming what would be a harmful condition into a means of achieving higher energy density.
Data Source
AI summary
To provide a cathode active material with which a lithium ion secondary battery having favorable cycle characteristics and having a high energy density even when discharged at a high voltage can be obtained; a cathode comprising the cathode active material; and a lithium ion secondary battery having the cathode.A cathode active material comprising a composite oxide (A) containing Li and at least one transition metal element selected from the group consisting of Ni, Co and Mn, and the following particles (B) and the following fluorinated carbon material (C) present on the surface of the composite oxide (A):particles (B): particles containing an oxide of at least one metal element selected from the group consisting of Ti, Sn, Si, Al, Ce, Y, Zr, Co, W, V, Nb, Ta, La and Mg; andfluorinated carbon material (C): a fluorinated carbon material in the form of particles or fibers.