Hard Carbon Anode Doping for Capacity-Conductivity Balance
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Solution Overview
Problem
Current secondary batteries face limitations in energy density, cycle performance, fast charge and discharge performance, and safety, particularly with commercial graphite nearing its performance limits and hard carbon requiring optimal sintering temperatures to balance gram volume and conductivity.
Innovation Solution
A negative electrode active material composed of hard carbon with doped nitrogen and transition metal elements, optimized in terms of mass percentages and distribution, along with a conductive carbon shell, to enhance reversible capacity, electronic conductivity, and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hard carbon is used as negative electrode active material, then reversible gram volume is improved, but electronic conductivity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of hard carbon by doping nitrogen elements and transition metal elements at specific concentrations. The nitrogen content is controlled at 0.1-12.0 mass% and transition metal elements at 0.2-5.0 mass%, which modifies the electronic structure and improves conductivity while preserving the high reversible gram volume characteristic of hard carbon.
Solution Approach 2:
The patent creates a composite material system by combining hard carbon with nitrogen-doped structures and transition metal element compounds. This composite approach leverages the high capacity of hard carbon while the nitrogen and transition metal components provide enhanced electronic conductivity pathways, resolving the contradiction between capacity and conductivity.
2Reliability
If sintering temperature is increased to improve electronic conductivity, then conductivity is improved, but reversible gram volume deteriorates
Solution Approach 1:
The patent introduces chemical composition parameters (nitrogen doping at 0.1-12.0 mass% and transition metal elements at 0.2-5.0 mass%) as alternative levers to improve conductivity without relying solely on thermal sintering. This allows achieving good conductivity at lower sintering temperatures where reversible gram volume is better preserved.
Solution Approach 2:
The nitrogen elements and transition metal elements act as intermediaries that facilitate electronic conduction in the hard carbon structure. Instead of directly increasing sintering temperature to improve conductivity, these dopant elements serve as intermediate conduits for electron transport, enabling conductivity enhancement at milder processing conditions that preserve reversible gram volume.
3Reliability
If nitrogen element content is increased to improve electronic conductivity, then conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates nitrogen sources and transition metal element sources into the precursor mixture before the sintering process. This preliminary incorporation ensures uniform distribution of dopant elements throughout the hard carbon matrix during a single sintering step, avoiding the need for subsequent complex doping treatments or multiple processing stages.
Solution Approach 2:
The patent combines the sintering process with the doping process into a single integrated manufacturing step. By merging the incorporation of nitrogen and transition metal elements with the thermal treatment that forms the hard carbon structure, the patent simplifies manufacturing while achieving the desired compositional control for improved conductivity.
4Reliability
If transition metal elements are doped to improve electronic conductivity, then conductivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary mixing of transition metal element sources with carbon precursors before sintering, ensuring homogeneous distribution at the molecular level. This preliminary action allows for precise compositional control (0.2-5.0 mass% transition metals) to be achieved through simple mixing ratios rather than requiring complex in-situ doping control during sintering.
Solution Approach 2:
The patent defines specific parameter ranges for transition metal element content (0.2-5.0 mass%) that balance conductivity improvement with manufacturing feasibility. These parameter specifications provide clear manufacturing targets that simplify quality control while ensuring the dopant concentration is sufficient to enhance electronic conductivity effectively.
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 proposed material achieves improved reversible capacity, electronic conductivity, and reduced platform voltage, leading to enhanced energy density and cycle performance in secondary batteries.
Implementation Method 1
appropriate amounts of nitrogen element and transition metal elements are doped into the hard carbon material
Implementation Method 2
the effect of reducing band gap energy by nitrogen atoms may be fully exerted, so that the hard carbon material provided by this application may have good electronic conductivity
Implementation Method 3
performing primary sintering treatment on the first intermediate product obtained in S30 at a second temperature T2 to obtain a hard carbon material
Data Source
AI summary
A negative electrode active material includes a hard carbon material, the hard carbon material includes a carbon element, a hydrogen element, a nitrogen element, and transition metal elements. Based on a total mass of the hard carbon material, a mass percentage of the carbon element is A %, a mass percentage of the hydrogen element is B %, a mass percentage of the nitrogen element is C %, and a mass percentage of the transition metal elements is D %, and 0.003≤B/A≤0.050, 0<C≤12.0, and 0<D≤5.0.