Non-graphitic Carbon Anode for High-capacity Li-ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current non-aqueous electrolyte secondary batteries face limitations in achieving high energy density due to the theoretical lithium storage capacity of graphitic materials and the degradation of electrolyte solutions, with existing carbonaceous materials either having low doping and de-doping capacities or inefficient lithium utilization.
Innovation Solution
A carbonaceous material with specific surface area, atomic ratio, and diffraction intensity characteristics is developed, impregnated with an alkali metal compound and subjected to heat treatment, followed by pyrolytic carbon coating, to enhance lithium storage and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphitic material is used as anode material, then lithium storage capacity is limited to theoretical value of 372 Ah/kg, but energy density cannot be increased further
Solution Approach 1:
The invention changes the fundamental parameter of carbon structure from graphitic (ordered) to non-graphitic (disordered) form. This structural parameter change enables lithium storage capacity to exceed the theoretical limit of graphitic materials, achieving higher energy density by utilizing both interlayer spacing and internal pore structures for lithium doping.
Solution Approach 2:
The invention utilizes porous non-graphitic carbon materials with controlled pore structures to enhance lithium storage capacity. The porous structure provides additional pathways and sites for lithium doping beyond the limitations of graphitic interlayer spacing, thereby increasing both capacity and energy density.
2Quantity of substance
If advanced graphite structure is used, then lithium doping causes repeated increase and return of interlayer spacing, but this leads to breakdown of graphite crystals and poor charging/discharging characteristics
Solution Approach 1:
Instead of using ordered graphitic carbon structures that suffer from crystal breakdown during lithium doping cycles, the invention inverts to disordered non-graphitic carbon structures. This inversion eliminates the crystal structure stability problem while maintaining high lithium doping capacity through alternative mechanisms such as pore filling and surface adsorption.
Solution Approach 2:
The invention accepts that non-graphitic carbon may have less structural stability but compensates by designing a system where the carbon structure serves its primary function of lithium storage without requiring long-term structural integrity, similar to disposable components that fulfill their function efficiently before replacement.
3Stability of the object's composition
If phenol resin is heat treated at high temperature (1900°C or higher), then carbon structure is formed, but doping and de-doping capacity of lithium becomes small
Solution Approach 1:
The invention changes the heat treatment temperature parameter from conventional high temperatures (1900°C or higher) to a lower range (800-1500°C). This parameter change produces a non-graphitic carbon structure that retains higher lithium doping capacity while achieving sufficient structural stability for battery application.
Solution Approach 2:
Instead of applying excessive heat treatment to achieve complete graphitization, the invention applies partial heat treatment that is sufficient to form a stable carbon structure but stops before creating the highly ordered graphitic structure that would reduce lithium doping capacity. This partial action optimizes the balance between structural stability and doping capacity.
4Quantity of substance
If phenol resin is heat treated at relatively low temperature (480-700°C), then lithium doping amount is large, but lithium cannot be completely de-doped and remains in anode carbon
Solution Approach 1:
The invention optimizes the heat treatment temperature parameter to a specific range (800-1500°C) that is higher than the low temperature range (480-700°C) but lower than conventional high temperature treatment (1900°C or higher). This optimized parameter range creates a carbon structure that allows both high lithium doping and complete de-doping, eliminating irreversible lithium consumption.
Solution Approach 2:
The invention employs a feedback mechanism in the heat treatment process where the temperature is controlled to achieve the desired carbon structure characteristics. The heat treatment conditions are adjusted based on the required balance between lithium doping capacity and de-doping completeness, creating an optimized process that prevents irreversible lithium retention.
5Quantity of substance
If alloy-based anode materials containing tin or silicon are used, then large capacity is achieved, but durability is insufficient and use is limited
Solution Approach 1:
The invention uses composite carbonaceous materials that combine the advantages of different carbon forms. The composite structure incorporates non-graphitic carbon with high capacity characteristics while maintaining the durability and stability of carbon-based materials, avoiding the durability problems of alloy-based materials like tin and silicon.
Solution Approach 2:
The invention replaces expensive and durable alloy materials (tin, silicon) with more economical carbonaceous materials that achieve comparable capacity. The carbon-based solution provides sufficient durability for battery applications without the structural instability and volume expansion problems inherent in alloy-based anode materials.
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 carbonaceous material achieves high doping and de-doping capacities, leading to improved energy density and charge/discharge efficiency in non-aqueous electrolyte secondary batteries, with reduced irreversible capacity and efficient lithium utilization.
Implementation Method 1
subjected to heat treatment
Implementation Method 2
followed by pyrolytic carbon coating
Data Source
AI summary
An object of the present invention is to provide a non-aqueous electrolyte secondary battery which has a large charge/discharge capacity, has a small irreversible capacity, and is capable of effectively using an active material.This object can be achieved by a material for a non-aqueous electrolyte secondary battery anode; a specific surface area determined by a BET method being not greater than 30 m2/g; an atomic ratio (H/C) of hydrogen atoms to carbon atoms determined by elemental analysis being not greater than 0.1; an average particle size being not greater than 50 μm; and a diffraction intensity ratio (R-value) determined by Equation (1) being not greater than 1.25: (wherein Imax is a maximum value of a 002 diffraction intensity of carbon measured at an angle of diffraction (2θ) within a range of from 20 to 25° as determined by powder X-ray diffraction measured using CuKα rays; Imin is a minimum value of a diffraction intensity measured at an angle of diffraction (2θ) within a range of from 15 to 20° as determined by powder X-ray diffraction; and I35 is a diffraction intensity at an angle of diffraction (2θ) of 35° as determined by powder X-ray diffraction).