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Introduction and Synthesis of Lithiumion Batteries Negative Material
Canrd March 3, 2026 159
With the rapid development of new energy industries such as electric vehicles and portable electronic devices, lithium-ion batteries have become the core energy storage equipment due to their high energy density, long cycle life, and environmental friendliness. The negative electrode material, as a key component of lithium-ion batteries, directly determines the battery’s capacity, cycle performance, and safety. This article systematically introduces the requirements for lithium-ion battery negative electrode materials, focuses on the classification, lithium intercalation characteristics, and synthesis of carbon-based negative materials, briefly describes non-carbon negative materials, and summarizes the development status and future trends of negative electrode materials, providing a reference for related research and industrial applications.
1. Requirements for Lithium-Ion Battery Negative Electrode Materials
1.1 Core Performance Requirements for Negative Electrode Materials
At present, the negative materials used in lithium-ion batteries are generally carbon materials, such as graphite, soft carbon (such as coke), hard carbon, etc. The negative electrode materials under exploration include nitrides, PAS, tin oxides, tin alloys, and nano-negative electrode materials.
As negative electrode materials for lithium-ion batteries, they must meet the following key properties:
(1) We need the redox potential for lithium-ion intercalation in the negative matrix to be as low as possible, close to that of metallic lithium, to ensure a high battery output voltage.
(2) The matrix should reversibly insert and extract a large amount of lithium to achieve high capacity density, that is, a large reversible x value.
(3) During the insertion/extraction process, the lithium intercalation/deintercalation should be highly reversible, and the host structure should remain unchanged or only slightly change.
(4) The redox potential variation with x should be minimal, so that the battery voltage remains stable during charging and discharging.
(5) The intercalated compound should have good electrical conductivity and ionic conductivity to reduce polarization and enable high-rate charging and discharging.
(6) The host material should have a favorable surface structure and can form a stable and high-quality SEI film with the liquid electrolyte.
(7) The intercalated compound must be chemically stable over the full operating voltage range and should not react with the electrolyte or the formed SEI film.
(8) The lithium-ion diffusion coefficient in the host material should be large to facilitate fast charging and discharging.
(9) From a practical perspective, the host material should be low-cost and environmentally friendly to meet industrial mass production needs.
2. Carbon Negative Materials
2.1 Overview of Carbon-Based Negative Materials
Carbon-based negative electrodes exhibit excellent safety and cycle life. Carbon materials are also low-cost and non-toxic, making them widely used in commercial lithium-ion batteries. In recent years, with in-depth research on carbon materials, researchers have realized surface modification and structural regulation of graphite and other carbon materials. By partially disordering graphite or introducing nanopores, voids, and channels, lithium can intercalate/deintercalate not only in the stoichiometric form of LiC₆ but also in a non-stoichiometric manner. This has greatly improved the specific capacity from the theoretical value of 372 mAh/g (LiC₆) to 700–1000 mAh/g, significantly enhancing the specific energy of lithium-ion batteries.
2.2 Main Types of Carbon Negative Materials
Currently, the main carbon negative materials include graphite, petroleum coke, carbon fiber, pyrolytic carbon, mesophase pitch-based carbon microspheres (MCMB), carbon black, and glassy carbon. Among them, graphite and petroleum coke have the highest application value in commercial production.
3. Lithium Intercalation Characteristics of Graphite
3.1 Key Lithium Intercalation Properties of Graphite
(1) Graphite has a low and flat intercalation potential, with most capacity delivered between 0.00–0.20 V (vs. Li⁺/Li), which provides a high and stable working voltage for lithium-ion batteries.
(2) It has a high lithium intercalation capacity, with a theoretical capacity of 372 mAh/g for LiC₆.
(3) Graphite has poor compatibility with organic electrolytes and is prone to solvent co-intercalation, which degrades its lithium intercalation performance.
4. Lithium Intercalation/Deintercalation Characteristics of Petroleum Coke
4.1 Core Performance of Petroleum Coke as Negative Material
(1) Petroleum coke has no obvious potential plateau during initial lithiation.
(2) It forms intercalation compounds LiₓC₆ with x ≈ 0.5; its lithium intercalation capacity depends on the heat treatment temperature and surface state.
(3) It has good solvent compatibility and excellent cycling performance, making it suitable for large-scale industrial applications.
5. Classification of Carbon Negative Materials by Graphitization Degree
5.1 Graphite
Graphite has high conductivity, high crystallinity, and a well-defined layered structure suitable for lithium insertion/extraction, forming lithium-graphite intercalation compounds. Its charge-discharge capacity can reach above 300 mAh/g, coulombic efficiency over 90%, and irreversible capacity below 50 mAh/g.
Lithium intercalation/deintercalation in graphite shows a stable plateau near 0–0.25 V, making it compatible with cathode materials such as LiCoO₂, LiMn₂O₄, and LiNiO₂. It is the most widely used negative material for commercial lithium-ion batteries.
Graphite mainly includes artificial graphite and natural graphite.
5.1.1 Artificial Graphite
Artificial graphite is produced by high-temperature graphitization of graphitizable carbon (e.g., pitch coke) at 1900–2800 °C under N₂ atmosphere. Typical types are mesocarbon microbeads (MCMB) and graphite fibers.
MCMB has a highly ordered lamellar structure derived from coal tar pitch or petroleum residues. After pyrolysis below 700 °C, its lithium intercalation capacity exceeds 600 mAh/g but with high irreversible capacity. After heat treatment above 1000 °C, graphitization improves; at >2800 °C, the reversible capacity reaches ~300 mAh/g with irreversible capacity<10%.
Vapor-deposited graphite fibers have a tubular hollow structure, delivering ~320 mAh/g capacity and 93% initial coulombic efficiency, enabling high-rate discharge and long cycle life. However, their preparation process is complex and cost is high.
5.1.2 Natural Graphite
Natural graphite is a high-performance negative material with a theoretical capacity of 372 mAh/g (LiC₆ structure), high reversible capacity, coulombic efficiency, and stable operating voltage. It shows clear charge-discharge plateaus at very low potentials, resulting in high battery output voltage.
Amorphous graphite has low impurities but low reversible capacity (~260 mAh/g) and high irreversible capacity (>100 mAh/g).
Flake graphite delivers 300–350 mAh/g reversible capacity with irreversible capacity <50 mAh/g.
Natural graphite has high capacity due to its complete structure and abundant lithium storage sites. However, it is sensitive to electrolytes and shows poor high-rate performance. An SEI film forms on the surface during cycling, and volume expansion/contraction may cause graphite pulverization, leading to relatively high irreversible capacity and requiring further cycle life improvement.
5.1.3 Modified Graphite
Researchers can modify graphite by surface oxidation, polymer-derived carbon coating, or core-shell composite structure to enhance its electrochemical performance.
Surface oxidation reduces irreversible capacity and improves cycle life, with reversible capacity reaching up to 446 mAh/g (Li₁.₂C₆). Common oxidants include HNO₃, O₃, H₂O₂, NO⁺, NO₂⁺, etc. Fluorination can produce (CF)ₙ, (C₂F)ₙ, or CₓFₙ. Both oxidation and fluorination can effectively improve lithium storage capacity.
5.1.4 Graphitized Carbon Fiber
Vapor-grown carbon fiber (VGCF) is derived from hydrocarbons and shows high capacity and stable structure after 2800 °C treatment.
Mesophase pitch-based carbon fiber (MCF) treated at 3000 °C has a radial crystalline layered structure, similar to disordered pyrolytic graphite, with high specific capacity and coulombic efficiency.
Graphite exhibits only ~10% volume expansion at full lithiation (LiC₆), enabling stable electrode dimensions and good cycling performance.
However, graphite has limitations: high electrolyte selectivity, poor overcharge/overdischarge tolerance, and low Li⁺ diffusion coefficient, which hinder fast charging. Modifications such as MCMB, amorphous carbon coating, and composite graphite have effectively improved its performance.
5.2 Soft Carbon
Soft carbon refers to easily graphitizable carbon, which can be graphitized at temperatures above 2500 °C. It has low crystallinity, small crystallite size, large interlayer spacing, and good electrolyte compatibility.
Typical soft carbon materials include petroleum coke, needle coke, carbon fiber, and carbon microspheres.
5.3 Hard Carbon
Hard carbon is difficult-to-graphitize carbon, usually obtained from polymer pyrolysis. It remains non-graphitizable even above 2500 °C.
Typical hard carbon materials include resin carbon (phenolic, epoxy, PFA-C), organic polymer pyrolysis carbon (PVA, PVC, PVDF, PAN), and carbon black (acetylene black).
Hard carbon shows high lithium storage capacity (500–1000 mAh/g) but suffers from low initial coulombic efficiency, lack of obvious voltage plateaus, large potential hysteresis, and high irreversible capacity due to residual heteroatoms (e.g., H).
6. Non-Carbon Negative Electrode Materials
6.1 Nitrides
Lithium transition metal nitrides have high ionic and electronic conductivity and good chemical stability. They typically show discharge voltages above 1.0 V.
Li₃FeN₂ has a capacity of ~150 mAh/g, discharge potential ~1.3 V (vs. Li/Li⁺), flat curve, and no discharge lag, but it has obvious capacity fading.
Li₃₋ₓCoₓN can reach up to 900 mAh/g, discharge potential ~1.0 V, but it has an unstable curve, large potential lag, and serious capacity decay.
Nitride systems often have antifluorite (CaF₂) or Li₃N-type structures with high ionic conductivity and potential close to metallic lithium.
Li₇MnN₄ and Li₃FeN₂ show good reversibility and high capacities (210 and 150 mAh/g, respectively). Li₃₋ₓCoₓN (M = Co, Ni, Cu) has extremely high capacity but requires further mechanistic and performance optimization.
6.2 Tin-Based Negative Materials
Tin-based negative materials have higher theoretical capacity than graphite, making them one of the most promising non-carbon negative materials.
6.2.1 Tin Oxides
SnO and SnO₂ exhibit higher capacity than graphite (>500 mAh/g) but have large initial irreversible capacity and rapid capacity fading.
Their discharge potential is relatively low (0.4–0.6 V vs. Li/Li⁺). Electrochemical performance varies greatly with the synthesis method.
Amorphous tin-based composite oxides (ATCO) doped with B, Al, Ge, Ti, Mn, Fe show reversible capacity >600 mAh/g and volumetric capacity >2200 mAh/cm³, more than twice that of conventional carbon materials.
6.2.2 Tin Composite Oxides
Researchers can prepare Sn–B–P–O amorphous composites by sintering and rapid quenching. Their cycle life is greatly improved compared to pure SnO/SnO₂ but still below industrial requirements.
6.2.3 Tin Alloys
Metals such as Sn, Si, Al can form high-lithium-content alloys. Sn has a theoretical volumetric capacity ~990 mAh/cm³, nearly 10 times that of graphite.
Alloys such as 25% Sn₂Fe + 75% SnFe₃C combine active alloying components and inactive structural skeletons, achieving high capacity and improved stability.
The major challenges of tin-based negative materials include low initial efficiency, poor cycle stability, and severe volume expansion-induced structural degradation.
6.3 Lithium Titanium Composite Oxide
The main lithium-titanium negative material is Li₄Ti₅O₁₂, which researchers prepare by high-temperature solid-state reaction or sol-gel method. It has good cycle stability but low capacity.
6.4 Carbon Nanotubes
Carbon nanotubes are novel nanocarbon materials with nanoscale hollow tubular structures. They show extremely high initial lithium uptake capacity but also very high irreversible capacity and low initial coulombic efficiency.
Common preparation methods include DC arc discharge and catalytic pyrolysis.
Nanoscale negative materials can alleviate volume expansion effects and improve cycling performance. However, nanoparticle agglomeration during cycling and high production cost limit their practical application.
7. Common Questions (FAQs)
7.1 Why is graphite the most widely used negative material in commercial lithium-ion batteries?
Graphite has the advantages of low cost, abundant resources, high conductivity, stable lithium intercalation potential, and good cycle performance. Its theoretical capacity of 372 mAh/g can meet the basic needs of most commercial batteries, and its volume expansion rate is only ~10%, which ensures the structural stability of the electrode during charging and discharging. These characteristics make it the first choice for commercial lithium-ion battery negative materials.
7.2 What are the main differences between soft carbon and hard carbon?
The core difference lies in the graphitization degree: soft carbon can be graphitized at temperatures above 2500 °C, with low crystallinity and large interlayer spacing; hard carbon cannot be graphitized even at temperatures above 2500 °C, usually derived from polymer pyrolysis. In terms of performance, hard carbon has higher lithium storage capacity (500–1000 mAh/g), while soft carbon has better electrolyte compatibility and cycling stability.
7.3 What problems need to be solved for non-carbon negative materials to achieve industrialization?
Non-carbon negative materials (such as tin-based, nitride-based materials) mainly face three key problems: first, large initial irreversible capacity and low initial coulombic efficiency, which affect battery energy density; second, severe volume expansion during lithium intercalation/deintercalation, leading to electrode pulverization and poor cycle stability; third, high preparation cost, which is difficult to meet large-scale industrial production needs. Solving these problems is the key to their industrialization.
7.4 How does surface modification improve the performance of graphite negative materials?
Surface modification can improve graphite’s performance in three aspects: first, surface oxidation or fluorination can reduce irreversible capacity and improve lithium storage capacity; second, polymer-derived carbon coating can form a stable protective layer, prevent solvent co-intercalation, and reduce volume expansion; third, core-shell composite modification can integrate the advantages of different materials, improving both capacity and cycle stability.
7.5 What are the development trends of lithium-ion battery negative materials?
The future development trend mainly focuses on high-capacity carbon/non-carbon composite materials. These composites integrate the advantages of carbon materials (good cycle stability, low cost) and non-carbon materials (high capacity), aiming to achieve higher energy density and longer cycle life. At the same time, researchers are also exploring novel modification technologies and low-cost preparation methods to promote the industrialization of high-performance negative materials.
8. Conclusion
Lithium-ion battery negative electrode materials are crucial to the performance and application of lithium-ion batteries. Carbon-based negative materials, especially graphite, have become the dominant type in commercial batteries due to their abundant resources, low cost, and stable performance. Modified graphite, soft carbon, and hard carbon have further expanded the application scope of carbon-based materials by optimizing their structure and performance.
Non-carbon negative materials, such as tin-based materials, nitrides, and lithium-titanium composite oxides, have shown great potential in high-capacity applications, but they still face challenges such as poor cycle stability, high irreversible capacity, and high cost, which limit their large-scale industrialization.
In the future, the development of negative electrode materials will focus on carbon/non-carbon composite systems, combining the advantages of both types of materials to achieve a balance between high capacity, long cycle life, and low cost. With the continuous advancement of modification technologies and preparation processes, negative electrode materials will further promote the development of high-performance lithium-ion batteries, meeting the growing demand for energy storage in new energy fields.
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