CN1268015C - A modified bamboocarbon lithium-ion battery cathode material and method for making same - Google Patents

Abstract

The present invention relates to a modified bamboo carbon lithium-ion battery cathode material which comprises the components of the following weight percentage: 0.5 to 6.0 wt% of Si, 0.2 to 4.0 wt% of B, 0.12 to 3.0 wt% of P and the balance of bamboo carbon in which moisture and ash content are eliminated. The cathode material has a preparation method that the bamboo carbon which is burnt from natural bamboo is pulverized by a machine to be sieved to 50 meshes to 300 meshes, the bamboo carbon powder is put in water, nitric acid is added, the mixture is stirred and filtrated at 60 DEG C to 80 DEG C, the mixture is washed repeatedly by deionized water, then the mixture is dried, the bamboo carbon, silicon powder, boron powder and phosphorus powder are uniformly mixed mechanically in proportion, and then, the mixture is ground or milled in a ball milling mode. The modified bamboo carbon lithium-ion battery cathode material of the present invention has the characteristics of high electrochemical capacity, good circulation performance, safety, no pollution, wide material source, etc.

Description

A kind of modified bamboo carbon lithium ion battery negative electrode material and preparation method thereof

technical field

The invention relates to a lithium ion battery negative electrode material and a preparation method thereof.

Background technique

Since the 1990s, the "bamboo charcoal craze" has emerged. It is the product of high-temperature pyrolysis of bamboo and processing residues. The production and research of bamboo charcoal are mainly in Japan, South Korea, India, Indonesia and other countries. my country is the distribution center of bamboo in the world, and bamboo resources are very rich. Since 1995, my country has started to burn bamboo charcoal, and it has a considerable scale at present. Bamboo, as a forest resource with a short growth cycle, rapid growth, easy regeneration and strong regeneration ability, is easy to sustainably manage, and is increasingly valued by people. As an important product of bamboo, bamboo charcoal is mainly used in fuel, environmental protection, food preservation, agricultural production, etc. At present, many experts and scholars at home and abroad have conducted a lot of research work on the processing and utilization of bamboo charcoal, hoping to develop many new applications. field.

In 1991, Sony Corporation of Japan replaced the metallic lithium negative electrode with graphite-structured carbon materials and developed a lithium-ion battery. After that, a wave of research and industrialization of lithium-ion batteries was set off worldwide. In recent years, due to the rapid development of portable electrical appliances and the potential advantages of lithium-ion batteries in electric vehicles (EVs), the demand for lithium-ion batteries in the world is increasing and the performance requirements are becoming higher and higher. Carbon materials, as the most commonly used negative electrode materials for lithium-ion batteries, have very broad development prospects. At present, the carbon anode materials used in commercial lithium-ion batteries are mainly graphite, petroleum coke, mesophase pitch-based carbon microspheres (MCMB), carbon fibers, and pyrolytic carbon. Among them, natural graphite, petroleum coke, MCMB, etc. are primary resources and are not renewable. Moreover, the heat treatment temperature of most carbon materials is higher than 2000 ° C, and the process control in production is relatively difficult. As a low-temperature pyrolysis amorphous carbon material, bamboo charcoal has high carbon content. However, the cycle performance of general amorphous carbon is not ideal, and the reversible lithium storage capacity generally decays faster with the cycle. In addition, there is hysteresis in the voltage. When lithium is inserted, it is mainly carried out below 0.3V, and when it is extracted, a considerable part is above 0.8V. And generally speaking, the low-temperature amorphous carbon materials have relatively low charge and discharge efficiency for the first time, and the reversible capacity is not high.

Contents of the invention

The purpose of the present invention is to provide a modified bamboo carbon lithium ion battery negative electrode material with high electrochemical capacity, good cycle performance, safety and pollution-free, and a wide range of materials and a preparation method thereof.

The invention uses the modified bamboo carbon as a negative electrode material for a lithium ion battery. The modified bamboo carbon lithium ion battery negative electrode material provided by the invention contains (by weight): 0.5-6.0% Si, 0.2-4.0% B, 0.12-3.0% P, and the remainder is bamboo carbon for removing water and ash.

The preparation method of the modified bamboo carbon lithium-ion battery negative electrode material of the present invention, the steps are as follows: after the bamboo carbon mechanically pulverized that natural bamboo is fired and passed through 50～300 mesh sieves, put into water, add nitric acid, in 60～80 Stir at ℃, filter, wash repeatedly with deionized water, and then dry to remove the moisture and ash in the bamboo charcoal, mechanically mix the bamboo charcoal with silicon powder, boron powder, and phosphorus powder in proportion, and then grind or ball mill, The obtained product is the negative electrode material of the lithium ion battery after the bamboo carbon is modified by silicon, boron and phosphorus.

Mix the prepared modified bamboo carbon as electrode active material with acetylene black and polyvinylidene fluoride (PVDF) solution dissolved in dimethylpyrrolidone (NMP) in a certain ratio, and then coat it on a copper foil of a certain size. , dried in a drying oven for 4 hours, then pressed into 0.05-0.15mm thin sheets on a double-roll machine, and dried in a vacuum oven at 120°C for 12 hours to make electrode sheets.

With the bamboo carbon made by doping silicon, boron, and phosphorus modification of the present invention as the negative electrode material of the lithium ion battery, during the charging and discharging process, silicon can reversibly interact with lithium atoms, and its electrochemical capacity remains the same after many cycles. There is no attenuation. Due to the addition of boron, the binding energy between lithium and carbon materials is increased, which can improve the reversible capacity of bamboo carbon. Phosphorus doping increases the interlayer spacing of carbon materials, which is beneficial to the insertion and extraction of lithium. Doping silicon, boron, and phosphorus into bamboo carbon can improve the reversible lithium intercalation capacity and charge-discharge cycle performance of bamboo carbon as the negative electrode material of lithium-ion batteries. The material of the invention has the characteristics of high electrochemical capacity, good cycle performance, safety and pollution-free, wide selection of materials and the like.

Detailed ways

Example:

The modified bamboo carbon lithium ion battery negative electrode material contains (by weight): 1.4% Si, 0.53% B, 0.32% P, and the remainder is bamboo carbon for removing water and ash.

The preparation method comprises the following steps: burning natural bamboo into bamboo charcoal, the bamboo charcoal contains (by weight): 85% carbon, 4% ash, and the rest is moisture; mechanically pulverize the bamboo charcoal through a 100-mesh sieve, put Pour into water, add nitric acid, stir at 60°C, filter, wash repeatedly with deionized water, then dry to remove moisture and ash in bamboo charcoal; mix bamboo charcoal with silicon powder, boron powder, and phosphorus powder according to the above weight content Mix evenly than mechanically, and then ball mill for 15 hours to obtain the product.

After the prepared modified bamboo carbon product is mixed uniformly with the ratio of 85:7.5:7.5 (weight ratio) with acetylene black and polyvinylidene fluoride (PVDF) solution dissolved in dimethylpyrrolidone (NMP) as electrode active material , coated on a copper foil with a diameter of 14mm, dried in a drying oven for 4 hours, and then pressed into a 0.05-0.15mm sheet on a roller machine, and dried in a vacuum oven at 120°C for 12 hours to make an electrode sheet.

The prepared electrode sheet was used as the negative electrode of the lithium-ion battery and the counter electrode to form a double-electrode simulated battery. The counter electrode is metal lithium sheet (purity greater than 99.9%), and the amount of lithium electrode is excessive. The electrolyte is DEC+EC containing 1mol/L LiPF ₆ (weight ratio DEC:EC=1:1), and the diaphragm is made of polypropylene Celgard2400. The simulated battery assembly process was done in a dry glove box with a relative humidity below 1%. After the assembled simulated battery was placed for 12 hours, it was charged and discharged with a constant current (current density 1mA/cm ² ), and the charge and discharge voltage was 0.005-3V. The change of the reversible lithium intercalation capacity and the charge-discharge cycle performance of the electrode sheet made of the negative electrode material of the lithium ion battery of the present invention is measured repeatedly at normal temperature.

Bamboo carbon that removes water and ash is modified by doping silicon, boron, and phosphorus, and silicon can reversibly interact with lithium atoms during charge and discharge, especially between 0.1 and 0.6V. Still no decay. The electron deficiency of boron can increase the binding energy of lithium and carbon materials, which can improve the reversible capacity of bamboo carbon. The addition of phosphorus increases the interlayer spacing of carbon materials, which is beneficial to the insertion and extraction of lithium. After adding silicon, boron and phosphorus to bamboo carbon, the electrochemical performance of bamboo carbon is greatly improved.

The test results show that the prepared bamboo carbon modified lithium ion battery negative electrode material has the following advantages:

1) High electrochemical capacity. The bamboo carbon after the modified treatment in this example, the first lithium intercalation capacity of the electrode material has been greatly improved. The discharge capacity after the first charge-discharge cycle reaches 403mAh/g, and the efficiency of lithium intercalation and deintercalation remains at a very high level after multiple cycles, and the phenomenon of voltage hysteresis in the process of lithium intercalation and deintercalation is significantly improved. Bamboo carbon without any treatment has a lithium insertion capacity of less than 200mAh/g for the first time, a large irreversible capacity for the first time, and a lithium insertion and removal efficiency of less than 50%.

2) Good charge and discharge cycle performance. Under the conditions of charging and discharging current density 1mA/cm ² and the voltage range of the simulated battery being 0.005～3.0V, compared with the electrochemical performance of bamboo carbon without any treatment, the negative electrode material of bamboo carbon modified lithium ion battery of the present invention The cycle performance has been significantly improved. After the first charge-discharge cycle, the capacity has basically not faded after many cycles. And the bamboo carbon modified lithium ion battery negative electrode material of the present invention has good cycle performance under the condition of high current charge and discharge.

Claims (3)

1. a modified bamboo carbon lithium ion battery negative electrode material is characterized in that containing: 0.5～6.0% Si, 0.2～4.0%B, 0.12～3.0%P, surplus is the bamboo carbon that removes moisture and ash. 2. modified bamboo carbon lithium ion battery negative electrode material according to claim 1 is characterized in that containing: 1.4% Si, 0.53% B, 0.32% P, surplus is the bamboo carbon that removes moisture and ash. 3. according to the preparation method of the described modified bamboo carbon lithium ion battery negative electrode material of claim 1 or 2, it is characterized in that after the bamboo carbon mechanically pulverizing that natural bamboo burns is crossed 50～300 mesh sieves, put into water , add nitric acid, stir at 60-80°C, filter, wash repeatedly with deionized water, then dry, mechanically mix bamboo carbon with silicon powder, boron powder, and phosphorus powder in proportion, and then grind or ball mill.