Lithium Battery Amorphous Carbon Coating for Fast Charging
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Solution Overview
Problem
Lithium secondary batteries struggle to discharge at large currents, especially at -30 degrees Celsius, and charge at high currents, which limits their performance in idling stop systems, and altering the negative electrode material to amorphous carbon compromises weight savings and capacity.
Innovation Solution
The battery employs a metal foil with through-holes, specific positive and negative electrode materials coated with amorphous carbon, a mixed electrolyte of LiPF6 and LiFSI, and a separator with a high heat resistance and hydrophilic groups, enhancing current collection and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the negative electrode material is altered from graphite to amorphous carbon to prevent lithium precipitation, then the battery can be charged at large current, but the weight increases and capacity decreases
Solution Approach 1:
The patent applies local quality by coating only the surface of graphite particles with amorphous carbon material, rather than using amorphous carbon throughout. This creates a hybrid structure where the core graphite maintains low density and high capacity, while the surface coating prevents lithium precipitation during fast charging. The coating thickness is controlled to be 1-10 nm, optimizing both fast charging capability and weight efficiency.
Solution Approach 2:
The patent uses composite materials by combining graphite and amorphous carbon in a core-shell structure. The graphite core provides high capacity and low weight, while the amorphous carbon shell prevents lithium precipitation. This composite approach allows the battery to achieve both fast charging capability (39 improvement) and weight savings (1 worsening mitigation).
2Weight of moving object
If the battery is designed for high capacity, then the weight increases, but using amorphous carbon for the negative electrode would save weight while compromising capacity
Solution Approach 1:
The patent applies local quality by coating only the surface of graphite particles with amorphous carbon material, rather than using amorphous carbon throughout. This creates a hybrid structure where the core graphite maintains low density and high capacity, while the surface coating prevents lithium precipitation during fast charging. The coating thickness is controlled to be 1-10 nm, optimizing both fast charging capability and weight efficiency.
Solution Approach 2:
The patent uses composite materials by combining graphite and amorphous carbon in a core-shell structure. The graphite core provides high capacity and low weight, while the amorphous carbon shell prevents lithium precipitation. This composite approach allows the battery to achieve both fast charging capability (39 improvement) and weight savings (1 worsening mitigation).
3Productivity
If the battery resistance is decreased by thinning electrodes and applying carbon coating, then the battery can be discharged at large current, but the low-temperature discharge performance deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the carbon coating thickness on the aluminum current collector to 1-10 nm, and controlling the porosity and pore size distribution of the separator. These parameter optimizations reduce battery resistance for high current discharge while maintaining low-temperature performance through improved ion transport pathways.
Solution Approach 2:
The patent uses porous materials by controlling the separator structure with specific porosity and pore size distribution. The porous structure facilitates ion transport at low temperatures while the overall electrode and separator design maintains low resistance for high current discharge capability.
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 achieves twice the lifespan of lead acid batteries, enabling discharge at 20 ItA at -30 degrees Celsius and charge at 50 ItA, with improved low-temperature performance and regenerative charging efficiency.
Implementation Method 1
a metal foil having a plurality of through-holes, formed therethrough, each having a projected portion on one surface thereof
Implementation Method 2
The positive electrode material occludes and discharges lithium ions
Implementation Method 3
The negative electrode material of the battery contains the graphite-based carbon material particles (soft carbon) whose surfaces are coated with the amorphous carbon material
Implementation Method 4
The organic electrolytic solution thereof consists of the lithium hexafluorophosphate, serving as the supporting electrolyte, which is dissolved in the organic solvent
Data Source
Figure 1
AI summary
The present invention provides a lithium secondary battery for an ISS which can be discharged at not less than 20 ItA when temperature is -30 degrees centigrade and can be charged at not less than 50 ItA. The positive electrode material consists of a mixture of lithium-containing metal phosphate compound particles whose surfaces are coated with an amorphous carbon material and a conductive carbon material, in which atoms of the surface carbon materials are chemically bonded to one another. The negative electrode material contains at least one kind of particles selected from among graphite particles whose surfaces are coated with an amorphous carbon material, having a specific surface area of not less than 6m2/g and soft carbon particles. A mixed electrolyte contains lithium hexafluorophosphate and lithium bis fluorosulfonyl imide.