Lithium Carbonate-Coated Cathode Material for Low-Impedance Li-Ion Cells
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Solution Overview
Problem
The limited solubility of lithium difluorophosphate in electrolytes leads to a sharp increase in viscosity when added in excess, reducing the performance improvement of lithium ion batteries.
Innovation Solution
Coating lithium carbonate on the surface of positive electrode active substances to generate lithium difluorophosphate in situ, forming a stable solid electrolyte film that reduces impedance and enhances cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium difluorophosphate is added to improve electrode/electrolyte interface properties, then cycle stability and impedance reduction are improved, but electrolyte viscosity increases sharply
Solution Approach 1:
Lithium carbonate serves as an intermediary substance that reacts with lithium difluorophosphate to generate the desired coating in situ, avoiding direct addition of large amounts of lithium difluorophosphate to the electrolyte. This mediator approach allows controlled generation of the active component without the harmful side effect of viscosity increase
Solution Approach 2:
The invention applies lithium difluorophosphate locally on the positive electrode surface through in situ generation, rather than distributing it uniformly throughout the entire electrolyte. This localized application achieves the interface improvement effect while minimizing the overall amount of additive needed, thus avoiding bulk electrolyte viscosity increase
2Reliability
If lithium difluorophosphate is added to form solid electrolyte film, then oxidative decomposition inhibition is improved, but electrolyte solubility limit is exceeded
Solution Approach 1:
Lithium carbonate is pre-coated on the positive electrode surface before battery operation. During initial charging cycles, this pre-applied lithium carbonate reacts with lithium difluorophosphate to generate the protective solid electrolyte film in situ, avoiding the need to dissolve large amounts of lithium difluorophosphate in the electrolyte
3Reliability
If lithium carbonate is coated on positive electrode active substance, then in-situ generation of lithium difluorophosphate is achieved, but coating process complexity increases
Solution Approach 1:
The lithium carbonate coating on the positive electrode automatically reacts with lithium difluorophosphate during the initial charging cycles to generate the protective film in situ. The system uses its own operating conditions (charging process, presence of lithium difluorophosphate in electrolyte) to create the desired effect, eliminating the need for separate complex coating equipment or 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 in-situ generation of lithium difluorophosphate improves battery performance by inhibiting oxidative decomposition and reducing electrode/electrolyte interface impedance, resulting in higher energy density and cycle stability.
Implementation Method 1
the lithium carbonate is coated on the surface of the positive electrode active substance... lithium carbonate may react with the lithium hexafluorophosphate in the electrolyte to generate a coating layer of lithium difluorophosphate in situ
Implementation Method 2
lithium difluorophosphate may be oxidized and decomposed on the surface of the positive electrode to form a layer of thermodynamically and mechanically stable solid electrolyte film
Data Source
AI summary
A positive electrode material and a preparation method thereof, a positive electrode slurry, a positive electrode plate, a lithium ion battery and a preparation method thereof are provided. The battery comprises an electrolyte, the electrolyte comprises lithium hexafluorophosphate and an organic solvent, the positive electrode material comprises a positive electrode active substance and lithium carbonate, the lithium carbonate is coated on the surface of the positive electrode active substance, and a mass ratio of the positive electrode active substance to the lithium carbonate is 1:(0.001-0.03).