Sodium ion battery (SIB) technology is considered as an attractive alternative to lithium ion batteries for the large scale energy storage systems due to vast availability of sodium resource. Up to now, much research effort has been devoted to the exploration of advanced electrode materials for SIBs. In order to promote the industrialization of sodium ion batteries, we scale up the synthesis of layered oxides Na_xMO₂ (M: Fe, Mn, Ni, Cu, Ti) using facile hydroxide co-precipitation combined with following calcination method. The obtained cathode materials showed good rate performance and excellent cycling stability even at low temperature. The Na_x(Fe_0.5Mn_0.5)O₂ cathode showed excellent reversibility between 2.0 V and 4.0 V with reversible capacity of 100 mAh g^-1 (0.1 C). After Ni doping, the Na_x(Fe_0.5Ni_0.3Mn_0.2)O₂ cathode showed good rate performance and excellent cycling stability with an initial capacity of 130 mAh g^-1 at 1C. When hard carbon was used as anode, we designed soft-packed batteries with capacities ranging from 0.5Ah to 5Ah. Electrochemical behaviors of the batteries at different temperatures were studied and thermal stability of these batteries was also evaluated.

     A 0.1KWh sodium ion battery pack was fabricated and evaluated as shown in Fig.1. The sodium ion packs can be assembled and used in portable energy storage device, household electrical energy storage, smart grid and low-speed electric vehicle, etc.

     The authors are grateful for the financial support of this work by the Natural Science Foundation of China (21573147, 21506123, 21336003) and the 973 Program of China (2014CB239700).