LiCoO2 Cathode Coating and Electrolyte Additives for High Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithium-ion batteries with LiCoO2 cathodes face challenges in achieving high energy density and stability when charged to voltages above 4.35V due to structural instability and impedance growth, especially during high-temperature storage.
Innovation Solution
The development of lithium secondary cells with a doped LiCoO2 cathode material and a specific electrolyte composition including succinonitrile (SN) and lithium bis(oxalato)borate (LiBOB) additives, which stabilize the cathode and reduce impedance build-up at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge voltage is increased to improve specific capacity and energy density, then the specific capacity increases, but the structural stability of LiCoO2 deteriorates and side reactions with electrolyte accelerate
Solution Approach 1:
A coating layer comprising at least one of a lithium phosphate compound, a lithium silicate compound, and a lithium aluminate compound is formed on the surface of the LiCoO2 particles. This coating layer acts as an intermediary barrier between the LiCoO2 cathode material and the electrolyte, preventing direct contact and reducing side reactions while enabling stable operation at high charge voltages (4.35V or higher), thereby resolving the contradiction between achieving high specific capacity and maintaining structural stability
2Quantity of substance
If the charge voltage is increased to improve energy density, then the energy density increases, but impedance growth and capacity fading accelerate during cycling and storage
Solution Approach 1:
The coating layer serves as a protective intermediary that reduces impedance growth by preventing parasitic reactions between the LiCoO2 surface and electrolyte components. This allows the battery to operate at high voltages (4.35V or higher) that enable high energy density while maintaining low impedance during cycling and storage
Solution Approach 2:
The coating layer modifies the surface chemistry parameters of LiCoO2 by introducing phosphate, silicate, or aluminate compounds. These parameter changes create a more stable surface that resists oxidation and reduces electrolyte decomposition, thereby suppressing impedance growth even at elevated charge voltages and temperatures
3Quantity of substance
If the charge voltage is increased to improve specific capacity, then the specific capacity increases, but Co dissolution in electrolyte and anode degradation accelerate
Solution Approach 1:
The coating layer comprising lithium phosphate, silicate, or aluminate compounds acts as a physical and chemical barrier that prevents cobalt ions from dissolving into the electrolyte. This intermediary layer maintains structural integrity at high voltages, enabling high specific capacity operation while minimizing cobalt loss and preventing anode degradation from deposited cobalt
4Quantity of substance
If LiCoO2 is used as cathode material to achieve high gravimetric density, then the gravimetric density is improved, but storage stability at high temperature deteriorates
Solution Approach 1:
The coating layer acts as a thermal and chemical buffer between the LiCoO2 particles and the electrolyte during high-temperature storage. This intermediary protection reduces the reactivity of the LiCoO2 surface at elevated temperatures, maintaining storage stability while preserving the high gravimetric density characteristics of LiCoO2 cathodes
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 enables lithium-ion batteries to operate stably at high voltages with reduced impedance growth, maintaining performance and capacity retention even during temperature fluctuations, thus addressing the limitations of existing LiCoO2-based batteries.
Implementation Method 1
addition of a first electrolyte additive which forms, on a surface of the cathode, a film reducing side reactions between the cathode and the electrolyte
Implementation Method 2
The active material is doped by at least 0.5 mole % of either one or more of Mn, Mg and Ti
Data Source
AI summary
A lithium secondary cell having an operating voltage ≥4.35 sV, comprising a cathode comprising a doped L1CoO2 active material, an anode comprising graphite, and an electrolyte comprising a carbonate-based solvent, a lithium salt and both a succinonitrile (SN) and a lithium bis(oxalato)borate (LiBOB) additive wherein during the discharge at 45° C. from a state of charge (SOC) of 100% at 4.5V to a SOC of 0 at 3V at a C/10 rate the difference of the SOC at 4.42V and 4.35V is at least 7% but less than 14%, and wherein the active material is doped by at least 0.5 mole % of either one or more of Mn, Mg and Ti.