Study Of Carbon Microsphere/tin Based Composite Core-shell Structure Anode Materials For Lithium-ion Batteries

In recent years,wit h the improve ment of sc ience and techno logy,more and more electronic products appear in our daily life.Popular izat ion and civilizat io n of electronic products put forward higher require ments of energy storage equip ments,lit hium-ion batter ies have been t he most popular energy storage equip ments e ven more it w ill be one of the most mat ure energy storage equip ments due to the advanta ges of t he excelle nt c irculat ion per forma nce and none of me mory e ffect.Anode,as the one of co mponents o f lit hium-io n batteries,the characterist ics o f it can affect the performa nce direct ly.C arbon-based materia ls have been the most successful commerc ia lizat ion of anode materia ls,but the inevitab le shortcomings like the theoretica l spec ific capacit y limited they deve lopme nt.Nowadays,Tin-based anode mater ia ls due to the high theoretica l specific capacit y become the main research object for lit hium-io n battery anode mater ia ls,but t in-based anode mater ia ls may cause vo lume expans ion/contraction in t he process of charge-discharge cyc le,whic h leads to poor cyc le stability and low capac ity retent io n.Therefore,the key of research are solving the proble ms of low specific capacit y of carbon-based cathode and severely volume changes of t in-based cathode in cycle process.In this paper,we can get the carbon materia ls of high capacity by us ing hydrother ma l/solvother ma l method.We can improve the cyc le perfor mance of t in based anode materia ls thro ugh the way of comb inat ion w ith nanocrysta llizat ion and comb inat ion.So the carbon microspheres/tin-based materia ls w it h core-she ll struct ures were synt hes ize to improve t he cyc le perfor mance of t in-based anode materia ls.The specific research contents and experimental results are as follows:?1?The micron-sized carbon microspheres?C s?were successfully synt hesized by one-step hydrother ma l method wit h the sucrose as carbon source.XRD characterizat ion showed that the synt hesized C s is composed by amorphous structure carbon wit h high pur ity and no other impur it ies.Through SEM and partic le size analys is we fo und that the synthes ized C s has narrow shape,unifor m partic le and excellent mo nodies iersit y.The average part ic le s ize were 1.84?m and1.2?m at temperature of 180?and 160?,and the C s yie ld can reach to 35%.The for mat ion mecha nis m of C s was stud ied by furt her exp loring the synthet ic exper imenta l conditions of ideal Cs.?2?The submicron-sized and nano-sized C s which have high conduct ivity were modified by t herma l treat ment and sur factant.The different s ized C s were used as the anode of lit hium-ion batteries to research e lectroche mica l performa nce.Tho ugh the XRD characterizat ion we found that t he degree of gr aphit izat ion o f micron-sized C s were increased rapidly after ther mal treatme nt.It demo nstrated that the therma l treatment can effect ive ly improve the conduct ivity of carbon mater ia ls.From the SEM and EDS ana lys is,we can de monstrate that t he 0.2 g C TAB and PVA contro lled the growth of C s effect ive ly and the partic le size of C s was the sub-micron of 400 nm grade and nanoscale grade of 90 nm.A fter the t herma l treat ment C s which were used as cathode materia ls o f the lit hium-ion batteries showed better specific capacit y and cycle perfor mance tha n the C s wit hout ther ma l treat ment.A fter 50 times charge and discharge c irculat ion,t he d ischarge specific capacity of C s whic h were modified by ther mal treat ment were 250 mA h/g and the y showed a good cyc le perfor manc e.The lit hium storage properties of different partic le s ize showed that the sma ller of carbon mater ia ls can lead to the higher specific capacit y a nd better cyc le performa nce.Reversib le dischar ge specific capacit y of na no-sized carbon mater ia ls have been 580mA h/g.After 50 times cyc les of 100mA/g,the d ischarge specific capac ity re ma ined498.6 mA h/g.The size of carbon materia ls has been effective ly contro lled by adding surfactant and the carbon cathode have high capacity after adding surfactant.?3?As-prepared monodisperse micron-sized carbon microspheres were used as carr iers,the core-she ll structure C@SnS₂ anode materia ls was synt hesized on its smooth sur face co mposite tin sulfide?SnS₂?nanosheets by solvot her mal.The XRD characterizat ion s howed that C@SnS₂ core-she ll struct ure anode mater ia ls have high purit y a nd well crysta llizat ion.There were no influences for crysta l struct ure of SnS ₂after addit io n of C s.The SEM and TEN demo nstrated that C@SnS₂ have stable structure and the sur face of core-she ll for med network struct ure which used the SnS₂nanosheets as primit ive for the se lf-assemb led crosslink growt h.The she ll layer cons isted wit h SnS₂ nanosheets was 200 nm.C ompared with pure SnS₂ as the anode mater ia ls of lithium-ion batteries,the core-shell struct ure C@SnS₂ have higher specific capacit y and nice cyc le perfor mance and the reversib le d ischarge specific capacity re mained 500 mA h/g after 50 times charge/discharge cyc les,while the discharge specific capacit y of pure SnS ₂ decayed to 243 mA h/g.It demonstrated the addit io n of C s and the preparation o f core-shell str ucture ha ve improved the lithium storage property of pure SnS₂ effect ive ly.The init ia l dischar ge curve and C V test showed that lit hium storage mec hanis m of C@Sn S₂ was allo ying.It was cons istent with other literature?4?The core-she ll C@SnO₂ composites were successfully synthes ized by one-step high te mperature calc inatio n of t he C@SnS₂ core-shell str ucture.The XRD characterizat ion s howed C@SnS₂ has oxid ized to the C@SnO₂ compos ites enough.The SEM showed that the sur face of core-shell str ucture cons isted wit h the 50 nm nanopartic les.When the y were used as cathode mater ials of lit hium-io n batteries through t he lit hium storage properties we found that the materia ls ha ve highly reversib le discharge specific capacit y for the first time?900 mA h/g?,while the cycle perfor mance was poor.It demo nstrated that in t he process of mult ip le cyc les the mater ia ls has yie ld large volume change whic h destroyed the structure of mater ials.Ultimately the destroyed structure influenced the cycle performance severely.