## 1 Introduction  
The lead-acid battery has a history of over 150 years and has a dominant position in electrochemical power supplies due to its low price, easy availability of raw materials and its full reliability in use, which is suitable for a wide range of environmental temperatures [1; 2; 3; 4; 5]. In the past decade, the electric bike industry has been unprecedentedly prosperous and electric bikes (e-bikes) have been gaining increasing attention in China [6]. In 2017, the total output of e-bikes in China was 29.96 million and the social ownership of e-bikes reached 250 million. However, poor cycle performance restricts the service life of valve-regulated lead -acid (VRLA) batteries for e-bikes. The e-bike batteries operate in the deep cycle duty and experience short charge and discharge pulses with high currents. The irreversible lead sulfate crystals grow on the negative electrode and form a barrier layer on the surface of the electrode, which further impedes electrolyte transfer and the charging and discharging process of the battery [7; 8; 9; 10; 11].  
To suppress the sulfation phenomenon of the negative plate, many researchers have found that different carbon materials (such as graphite [12; 13; 14; 15], carbon black [7; 16; 17], activated carbon [12; 15], or graphene [18; 19; 20]) can be added to the negative active material (NAM). The addition of the carbon material can increase the specific surface area (SSA) and overall conductivity of the NAM [21; 22], promote the uniform spread of the lead sulfate on the surface of the negative plate, store excess charge and build a conductive network between the lead sulfate particles [8; 20].  
The carbon material can effectively extend the cycle life of the battery by suppressing the growth of lead sulfate in negative plates, but the effect of extending the service life differs according to their SSA. [PERSON] et al. [15] reported that the SSA of the carbon material to the NAM is an important factor that affects the electrochemical performance of negative plates. [PERSON] [23] found that carbon black with a higher SSA at a high-rate partial-state-of-charge (HRPSoC) was more conducive to prolonging the cycle life of hybrid electric vehicle (HEV) batteries than carbon black with a lower SSA. [PERSON] et al. [7] pointed out that under HRPSoC conditions, the addition of 0.5 wt % carbon black to the NAM of HEV batteries increased the utilization of the active material and thus boosted the cycle life by more than 255.5% at 1 C rate discharge. [PERSON] et al. [24] reported that adding a certain amount of carbon black to the NAM of HEV batteries operating in partial-state-of-charge (PSoC) conditions effectively suppressed the accumulation of PbSO\({}_{4}\) and improved the cycle life performance due to the conductive network of carbon particles formed on the PbSO\({}_{4}\) particles. However, most studies have added carbon black to the negative plate for VRLA batteries in HEV applications [7; 23; 24]. Therefore, it is quite advantageous to add high performance carbon black in the NAM to further improve the charge acceptance and deep-cycling performance of batteries for e-bike applications.  
In the present work, we report, that high performance carbon black as a negative additive can significantly increase the performance of e-bike VRLA batteries. When the batteries are cycled at a C\({}_{2}\) rate discharge under a 100% depth-of-discharge (100% DoD) condition, the cycle life of the batteries with a higher SSA of carbon black is prolonged by more than 86.9% compared to that of the control batteries with acetylene black. Moreover, both the charge acceptance and larger current discharge performance of carbon black as a negative electrode additive are improved.