# Improved Technology for Rounding Graphite: Machine Structure and Industrial Test
## 1 Introduction  
The lithium-ion battery has become an indispensable electrochemical energy storage device in people's lives and production activities [1]. Especially with the dramatic increasing development of the electric vehicle industry, the global demand for lithium-ion batteries is rising sharply [2]. Improving the performance and safety, as well as reducing the manufacturing cost of lithium-ion batteries, have long been the goal of the sustainable energy industry [3]. Up to now, many kinds of materials, mainly including LiMxO\({}_{2}\) (M is one of or a combination of Co, Mn and Ni) and LiMxPO\({}_{4}\) (M = Fe, Mn), have been developed as the cathode material to satisfy different requirements [4, 5]. It is worth mentioning that, for all of the above cathode materials, graphite is their common anode material, which plays an important role in the performance and manufacturing cost of lithium-ion batteries [6]. Natural graphite occupies an important position in the anode material market due to its advantages of low cost, wide resource distribution, easy obtaining and suitable charge-discharge characteristics, and its usage is expected to grow continuously in the future [7]. The raw material for the preparation of graphite anode is usually in a flaky shape, which cannot be used directly in lithium-ion batteries [8]. Spheroidization is generally an essentialprocess to obtain anode-active materials from the raw material of graphite in prior art processes [9], which affects many important characteristics impacting the electrochemical performance, such as the shape, tap density and particle size distribution of graphite products [10]. Excellent processing technology is the key to cost-effectively and efficiently obtaining high-quality graphite anode products from the raw material of natural graphite [11]. However, there are a few kinds of literature that have been reported focusing on graphite rounding, which is dominantly limited to the approach and a lab scale [11]. For an industrial production scale in practice, the research on equipment design and key structure improvement is still lacking. In general, there are two main methods for particle surface modification treatment: jet milling and rotational impact blending. Jet milling is also employed in rounding treatment. In this process, the particles that need to be rounded are drafted by the high-speed airflow jetted by the nozzles. The particles are rounded via the actions of collision and grinding each other. This method is mainly used in the morphology modification of materials with high hardness, such as diamond, silicon carbide, etc., The processing cost is high, and graphite, which has high toughness, is suitable for mechanical shaping equipment. The rotational impact blending mainly uses the impact and shear of the hammer on the particles to achieve the surface modification of the particles. This method is popularly adopted for spheroidization of graphite, which is also the method adopted in this study. This method is more suitable for surface modification of graphite, a material particle with high toughness, and has the advantages of high yield and low energy consumption. At present, the rotational impact blending for spheroidization of graphite mainly contains two ways: continuous method and intermittent method [12]. The continuous shaping machine has many advantages, but it also has the problem that the shaping time is not easy to control. However, shaping time is one of the most important factors in the final product morphology control. Batch shaping equipment is, therefore, more and more popular, and it is also the main equipment used in production. Through practical experience, we found that, at present, the intermittent shaping machine most worth improving is the increase of the output of a single machine, which is directly related to the decline of production costs.