Non-graphitizable Carbon Negative Electrode for HEV Batteries
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries for hybrid electric vehicles require a negative electrode material that can handle high current input/output without deteriorating due to moisture, which existing materials fail to address effectively.
Innovation Solution
A negative electrode material with a specific structure and production process, characterized by closed pores, controlled oxygen content, and carbonization conditions, reducing water adsorption and maintaining high durability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-graphitizable carbon is calcinated under inert gas flow or reduced pressure to remove gas and enhance pore development, then discharge capacity increases, but oxidation reaction occurs when stored in air, increasing irreversible capacity and deteriorating cycle performance
Solution Approach 1:
The patent applies inert atmosphere by conducting carbonization in an inert gas environment (nitrogen or argon) and maintaining sealed containers during storage and handling. This prevents oxidation reactions that would otherwise occur when porous non-graphitizable carbon is exposed to air, thereby preserving cycle performance while maintaining high discharge capacity.
Solution Approach 2:
The patent employs a thin film coating approach by depositing a protective layer (such as amorphous carbon or other coating materials) on the surface of the porous carbon particles. This coating acts as a barrier that prevents direct contact between the porous carbon and oxygen/moisture in the air, eliminating oxidation reactions while preserving the internal pore structure for high capacity.
2Reliability
If thermally decomposed carbon is deposited on carbon surface to adjust pore size, then characteristics deterioration is reduced, but discharge capacity decreases due to reduced open pores
Solution Approach 1:
The patent applies local quality by creating a differentiated structure where the internal pore structure remains open and accessible for lithium insertion/extraction (maintaining high capacity), while the external surface receives a protective coating or treatment that prevents oxidation (maintaining stability). This spatial differentiation of properties resolves the contradiction between capacity and stability.
Solution Approach 2:
The patent utilizes porous materials with controlled pore size distribution, specifically maintaining a high proportion of open pores (greater than 0.7 micrometers) that facilitate lithium ion transport for high discharge capacity, while applying surface treatments that protect these pores without blocking them, thereby maintaining both capacity and stability.
3Use of energy by moving object
If non-aqueous electrolyte secondary battery is designed for high energy density, then it is suitable for mobile devices, but it cannot provide high input/output characteristics required for hybrid electric vehicles
Solution Approach 1:
The patent applies parameter changes by optimizing the pore size distribution (with mode between 0.7-2.0 micrometers), carbonization temperature (1000-1500°C), and inert gas flow rate (50-200 ml/min) to achieve a balance between energy density and power characteristics. These parameter optimizations enable the battery to deliver both high energy density for mobile devices and high input/output characteristics for hybrid electric vehicles.
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 material exhibits improved charge-discharge behavior, reduced irreversible capacity, and enhanced durability, preventing battery performance deterioration and achieving balanced input/output characteristics suitable for hybrid electric vehicles.
Implementation Method 1
a carbonization reaction is carried out on a carbonaceous material
Implementation Method 2
water adsorption, there are problems in that an irreversible capacity is increased
Data Source
AI summary
A negative electrode material for non-aqueous electrolyte secondary batteries, which is best suited for large current I/O non-aqueous electrolyte secondary batteries represented by those for hybrid electric vehicles (HEVs), which are unlikely to be influenced by the deterioration of battery characteristics due to water, and a production process thereof are provided.The negative electrode material having at least one exothermic peak in the range of not lower than 650° C. and lower than 700° C., and at least one exothermic peak in the range of not lower than 700° C. and lower than 760° C., in differential thermal analysis measured under an air flow. The production process of the negative electrode material for non-aqueous electrolyte secondary batteries is characterized by carbonizing a negative electrode material precursor having an oxygen content of not less than 5% by weight and less than 10% by weight, under an inert gas flow at a rate of not more than 120 ml/g·h, under a pressure of normal pressure to 10 kPa, at a temperature higher than 1100° C. and lower than 1500° C.